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Search for "Heck" in Full Text gives 159 result(s) in Beilstein Journal of Organic Chemistry.
Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones
- Jan Bartáček,
- Jan Svoboda,
- Martin Kocúrik,
- Jaroslav Pochobradský,
- Alexander Čegan,
- Miloš Sedlák and
- Jiří Váňa
Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84
- in the presence of water, it is selectively converted to the 1,4-addition product instead of undergoing a β-hydride elimination leading to an oxidative Heck product [3][26][35]. In 2005, one month after the very first report of the addition of aryltrifluoroborates to enones by Miyaura [32], the
- oxidative Heck-type product. The authors stated that as a result of the coordination with PPh3, there is a steric hindrance disfavouring the β-hydride elimination [43]. Catalytic systems based on NHC ligands Historically, the second type of ligands used were N-heterocyclic carbenes (NHC). The first use was
- was chosen DMF, although the use of polar aprotic solvents usually leads to products of the oxidative Heck reaction. The authors noticed a significant reduction of Pd(II) to Pd(0) (by secondary processes such as oxidative homocoupling or oxidation of boronic acid to the corresponding phenol). The Pd(0
Graphical Abstract
Scheme 1: Synthesis of optically pure 4-phenylchroman-2-one [34].
Scheme 2: Synthesis of (R)-tolterodine [3].
Scheme 3: Catalytic cycle of the Pd(II)-catalysed 1,4-addition of organoboron reagents to enones [3,26,35].
Scheme 4: Enantioselective β-arylation of cyclohexanone [38].
Scheme 5: Application of L2/Pd(OAc)2 in the total synthesis of terpenes [8].
Scheme 6: Plausible catalytic cycle for the addition of phenylboronic acid to 2-cyclohexenone catalysed by L3...
Scheme 7: Microwave-assisted addition of phenylboronic acid to 2-cyclohexenone catalysed by L4/Pd2(dba)3·CHCl3...
Scheme 8: Plausible catalytic cycle of the addition of phenylboronic acid to 2-cyclohexenone catalysed by pal...
Scheme 9: Proposed catalytic cycle for the addition of phenylboronic acids to 2-cyclohexenone catalysed by Pd...
Scheme 10: Usage of addition reactions of boronic acids to various chromones in the syntheses of potentially a...
Scheme 11: Multigram-scale synthesis of ABBV-2222 [6].
Scheme 12: Application of the asymmetric addition of phenylboronic acid to a chromone derivative for the total...
Scheme 13: Plausible catalytic cycle for the addition of phenylboronic acid to 3-methyl-2-cyclohexenone cataly...
Scheme 14: Total syntheses of naturally occurring terpenoids [10,11].
Scheme 15: Use of the L9/Pd(TFA)2 catalytic system for the synthesis of intermediates of biologically active c...
Scheme 16: Usage of a Michael addition catalysed by L9/Pd(TFA)2 in the total synthesis of (–)-ar-tenuifolene [12].
Scheme 17: Synthesis of terpenoids by Michael addition to 3-methyl-2-cyclopentenone [13].
Scheme 18: Rh-catalysed isomerisation of 3-alkyl-3-arylcyclopentanones to 1-tetralones [53].
Scheme 19: Addition reaction of phenylboronic acid to 3-methyl-2-cyclohexenone catalysed by L9/Pd(TFA)2 in wat...
Scheme 20: Micellar nanoreactor PdL10c for the synthesis of flavanones [58].
Scheme 21: Plausible catalytic cycle for the desymmetrisation of polycyclic cyclohexenediones by the addition ...
Scheme 22: Attempt to use the catalytic system L2/Pd(TFA)2 for the addition of phenylboronic acid to 3-methyl-...
Scheme 23: Ring opening of an enantioenriched tetrahydropyran-2-one derivative as alternative strategy to line...
Scheme 24: Synthesis of biologically active compounds from addition products [14-16].
Scheme 25: Chiral 1,10-phenantroline derivative L15 as ligand for the Pd-catalysed addition reactions of pheny...
Scheme 26: The Rh-catalysed addition reaction of phenylboronic acid to a 3-substituted enone [20].
Scheme 27: Underdeveloped methodologies [14,15,65-67].
Scheme 28: Flowchart for the selection of the proper catalytic system.
Synthetic accesses to biguanide compounds
- Oleksandr Grytsai,
- Cyril Ronco and
- Rachid Benhida
Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82
- catalysts in various organic reactions [1] such as the Ullmann coupling, Suzuki coupling, Suzuki–Miyaura coupling, and the Heck reaction. Aside from being useful synthetic agents, biguanides gained particular interest from the perspective of medicinal chemistry. For the first time, the biological activity
Graphical Abstract
Figure 1: Tautomeric forms of biguanide.
Figure 2: Illustrations of neutral, monoprotonated, and diprotonated structures biguanide.
Figure 3: The main approaches for the synthesis of biguanides. The core structure is obtained via the additio...
Scheme 1: The three main preparations of biguanides from cyanoguanidine.
Scheme 2: Synthesis of butylbiguanide using CuCl2 [16].
Scheme 3: Synthesis of biguanides by the direct fusion of cyanoguanidine and amine hydrochlorides [17,18].
Scheme 4: Synthesis of ethylbiguanide and phenylbiguanide as reported by Smolka and Friedreich [14].
Scheme 5: Synthesis of arylbiguanides through the reaction of cyanoguanidine with anilines in water [19].
Scheme 6: Synthesis of aryl- and alkylbiguanides by adaptations of Cohn’s procedure [20,21].
Scheme 7: Microwave-assisted synthesis of N1-aryl and -dialkylbiguanides [22,23].
Scheme 8: Synthesis of aryl- and alkylbiguanides by trimethylsilyl activation [24,26].
Scheme 9: Synthesis of phenformin analogs by TMSOTf activation [27].
Scheme 10: Synthesis of N1-(1,2,4-triazolyl)biguanides [28].
Scheme 11: Synthesis of 2-guanidinobenzazoles by addition of ortho-substituted anilines to cyanoguanidine [30,32] and...
Scheme 12: Synthesis of 2,4-diaminoquinazolines by the addition of 2-cyanoaniline to cyanoguanidine and from 3...
Scheme 13: Reactions of anthranilic acid and 2-mercaptobenzoic acid with cyanoguanidine [24,36,37].
Scheme 14: Synthesis of disubstituted biguanides with Cu(II) salts [38].
Scheme 15: Synthesis of an N1,N2,N5-trisubstituted biguanide by fusion of an amine hydrochloride and 2-cyano-1...
Scheme 16: Synthesis of N1,N5-disubstituted biguanides by the addition of anilines to cyanoguanidine derivativ...
Scheme 17: Microwave-assisted additions of piperazine and aniline hydrochloride to substituted cyanoguanidines ...
Scheme 18: Synthesis of N1,N5-alkyl-substituted biguanides by TMSOTf activation [27].
Scheme 19: Additions of oxoamines hydrochlorides to dimethylcyanoguanidine [49].
Scheme 20: Unexpected cyclization of pyridylcyanoguanidines under acidic conditions [50].
Scheme 21: Example of industrial synthesis of chlorhexidine [51].
Scheme 22: Synthesis of symmetrical N1,N5-diarylbiguanides from sodium dicyanamide [52,53].
Scheme 23: Synthesis of symmetrical N1,N5-dialkylbiguanides from sodium dicyanamide [54-56].
Scheme 24: Stepwise synthesis of unsymmetrical N1,N5-trisubstituted biguanides from sodium dicyanamide [57].
Scheme 25: Examples for the synthesis of unsymmetrical biguanides [58].
Scheme 26: Examples for the synthesis of an 1,3-diaminobenzoquinazoline derivative by the SEAr cyclization of ...
Scheme 27: Major isomers formed by the SEAr cyclization of symmetric biguanides derived from 2- and 3-aminophe...
Scheme 28: Lewis acid-catalyzed synthesis of 8H-pyrrolo[3,2-g]quinazoline-2,4-diamine [63].
Scheme 29: Synthesis of [1,2,4]oxadiazoles by the addition of hydroxylamine to dicyanamide [49,64].
Scheme 30: Principle of “bisamidine transfer” and analogy between the reactions with N-amidinopyrazole and N-a...
Scheme 31: Representative syntheses of N-amidino-amidinopyrazole hydrochloride [68,69].
Scheme 32: First examples of biguanide syntheses using N-amidino-amidinopyrazole [66].
Scheme 33: Example of “biguanidylation” of a hydrazide substrate [70].
Scheme 34: Example for the synthesis of biguanides using S-methylguanylisothiouronium iodide as “bisamidine tr...
Scheme 35: Synthesis of N-substituted N1-cyano-S-methylisothiourea precursors.
Scheme 36: Addition routes on N1-cyano-S-methylisothioureas.
Scheme 37: Synthesis of an hydroxybiguanidine from N1-cyano-S-methylisothiourea [77].
Scheme 38: Synthesis of an N1,N2,N3,N4,N5-pentaarylbiguanide from the corresponding triarylguanidine and carbo...
Scheme 39: Reactions of N,N,N’,N’-tetramethylguanidine (TMG) with carbodiimides to synthesize hexasubstituted ...
Scheme 40: Microwave-assisted addition of N,N,N’,N’-tetramethylguanidine to carbodiimides [80].
Scheme 41: Synthesis of N1-aryl heptasubstituted biguanides via a one-pot biguanide formation–copper-catalyzed ...
Scheme 42: Formation of 1,2-dihydro-1,3,5-triazine derivatives by the reaction of guanidine with excess carbod...
Scheme 43: Plausible mechanism for the spontaneous cyclization of triguanides [82].
Scheme 44: a) Formation of mono- and disubstituted (iso)melamine derivatives by the reaction of biguanides and...
Scheme 45: Reactions of 2-aminopyrimidine with carbodiimides to synthesize 2-guanidinopyrimidines as “biguanid...
Scheme 46: Non-catalyzed alternatives for the addition of 2-aminopyrimidine derivatives to carbodiimides. A) h...
Scheme 47: Addition of guanidinomagnesium halides to substituted cyanamides [90].
Scheme 48: Microwave-assisted synthesis of [11C]metformin by the reaction of 11C-labelled dimethylcyanamide an...
Scheme 49: Formation of 4-amino-6-dimethylamino[1,3,5]triazin-2-ol through the reaction of Boc-guanidine and d...
Scheme 50: Formation of 1,3,5-triazine derivatives via the addition of guanidines to substituted cyanamides [92].
Scheme 51: Synthesis of biguanide by the reaction of O-alkylisourea and guanidine [93].
Scheme 52: Aromatic nucleophilic substitution of guanidine on 2-O-ethyl-1,3,5-triazine [95].
Scheme 53: Synthesis of N1,N2-disubstituted biguanides by the reaction of guanidine and thioureas in the prese...
Scheme 54: Cyclization reactions involving condensations of guanidine(-like) structures with thioureas [97,98].
Scheme 55: Condensations of guanidine-like structures with thioureas [99,100].
Scheme 56: Condensations of guanidines with S-methylisothioureas [101,102].
Scheme 57: Addition of 2-amino-1,3-diazaaromatics to S-alkylisothioureas [103,104].
Scheme 58: Addition of guanidines to 2-(methylsulfonyl)pyrimidines [105].
Scheme 59: An example of a cyclodesulfurization reaction to a fused 3,5-diamino-1,2,4-triazole [106].
Scheme 60: Ring-opening reactions of 1,3-diaryl-2,4-bis(arylimino)-1,3-diazetidines [107].
Scheme 61: Formation of 3,5-diamino-1,2,4-triazole derivatives via addition of hydrazines to 1,3-diazetidine-2...
Scheme 62: Formation of a biguanide via the addition of aniline to 1,2,4-thiadiazol-3,5-diamines, ring opening...
Figure 4: Substitution pattern of biguanides accessible by synthetic pathways a–h.
Synthetic reactions driven by electron-donor–acceptor (EDA) complexes
- Zhonglie Yang,
- Yutong Liu,
- Kun Cao,
- Xiaobin Zhang,
- Hezhong Jiang and
- Jiahong Li
Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67
- -metal catalysts, such as in the Suzuki–Miyaura and Heck coupling reactions. Methodologies for forming different C–C bonds have recently been developed in the field of single-electron chemistry [63][64][65]. Considering that EDA-complex-initiated free-radical reactions are carried out under mild
Graphical Abstract
Scheme 1: The electron transfer process in EDA complexes.
Scheme 2: Synthesis of benzo[b]phosphorus oxide 3 initiated by an EDA complex.
Scheme 3: Mechanism of the synthesis of quinoxaline derivative 7.
Scheme 4: Synthesis of imidazole derivative 10 initiated by an EDA complex.
Scheme 5: Synthesis of sulfamoylation product 12 initiated by an EDA complex.
Scheme 6: Mechanism of the synthesis of sulfamoylation product 12.
Scheme 7: Synthesis of indole derivative 22 initiated by an EDA complex.
Scheme 8: Synthesis of perfluoroalkylated pyrimidines 26 initiated by an EDA complex.
Scheme 9: Synthesis of phenanthridine derivative 29 initiated by an EDA complex.
Scheme 10: Synthesis of cis-tetrahydroquinoline derivative 32 initiated by an EDA complex.
Scheme 11: Mechanism of the synthesis of cis-tetrahydroquinoline derivative 32.
Scheme 12: Synthesis of phenanthridine derivative 38 initiated by an EDA complex.
Scheme 13: Synthesis of spiropyrroline derivative 40 initiated by an EDA complex.
Scheme 14: Synthesis of benzothiazole derivative 43 initiated by an EDA complex.
Scheme 15: Synthesis of perfluoroalkyl-s-triazine derivative 45 initiated by an EDA complex.
Scheme 16: Synthesis of indoline derivative 47 initiated by an EDA complex.
Scheme 17: Mechanism of the synthesis of spirocyclic indoline derivative 47.
Scheme 18: Synthesis of cyclobutane product 50 initiated by an EDA complex.
Scheme 19: Mechanism of the synthesis of spirocyclic indoline derivative 50.
Scheme 20: Synthesis of 1,3-oxazolidine compound 59 initiated by an EDA complex.
Scheme 21: Synthesis of trifluoromethylated product 61 initiated by an EDA complex.
Scheme 22: Synthesis of indole alkylation product 64 initiated by an EDA complex.
Scheme 23: Synthesis of perfluoroalkylation product 67 initiated by an EDA complex.
Scheme 24: Synthesis of hydrotrifluoromethylated product 70 initiated by an EDA complex.
Scheme 25: Synthesis of β-trifluoromethylated alkyne product 71 initiated by an EDA complex.
Scheme 26: Mechanism of the synthesis of 2-phenylthiophene derivative 74.
Scheme 27: Synthesis of allylated product 80 initiated by an EDA complex.
Scheme 28: Synthesis of trifluoromethyl-substituted alkynyl product 84 initiated by an EDA complex.
Scheme 29: Synthesis of dearomatized fluoroalkylation product 86 initiated by an EDA complex.
Scheme 30: Mechanism of the synthesis of dearomatized fluoroalkylation product 86.
Scheme 31: Synthesis of C(sp3)–H allylation product 91 initiated by an EDA complex.
Scheme 32: Synthesis of perfluoroalkylation product 93 initiated by an EDA complex.
Scheme 33: Synthesis of spirocyclic indolene derivative 95 initiated by an EDA complex.
Scheme 34: Synthesis of perfluoroalkylation product 97 initiated by an EDA complex.
Scheme 35: Synthesis of alkylated indole derivative 100 initiated by an EDA complex.
Scheme 36: Mechanism of the synthesis of alkylated indole derivative 100.
Scheme 37: Synthesis of arylated oxidized indole derivative 108 initiated by an EDA complex.
Scheme 38: Synthesis of 4-ketoaldehyde derivative 111 initiated by an EDA complex.
Scheme 39: Mechanism of the synthesis of 4-ketoaldehyde derivative 111.
Scheme 40: Synthesis of perfluoroalkylated olefin 118 initiated by an EDA complex.
Scheme 41: Synthesis of alkylation product 121 initiated by an EDA complex.
Scheme 42: Synthesis of acylation product 123 initiated by an EDA complex.
Scheme 43: Mechanism of the synthesis of acylation product 123.
Scheme 44: Synthesis of trifluoromethylation product 126 initiated by an EDA complex.
Scheme 45: Synthesis of unnatural α-amino acid 129 initiated by an EDA complex.
Scheme 46: Synthesis of thioether derivative 132 initiated by an EDA complex.
Scheme 47: Synthesis of S-aryl dithiocarbamate product 135 initiated by an EDA complex.
Scheme 48: Mechanism of the synthesis of S-aryl dithiocarbamate product 135.
Scheme 49: Synthesis of thioether product 141 initiated by an EDA complex.
Scheme 50: Mechanism of the synthesis of borate product 144.
Scheme 51: Synthesis of boronation product 148 initiated by an EDA complex.
Scheme 52: Synthesis of boration product 151 initiated by an EDA complex.
Scheme 53: Synthesis of boronic acid ester derivative 154 initiated by an EDA complex.
Scheme 54: Synthesis of β-azide product 157 initiated by an EDA complex.
Scheme 55: Decarboxylation reaction initiated by an EDA complex.
Scheme 56: Synthesis of amidated product 162 initiated by an EDA complex.
Scheme 57: Synthesis of diethyl phenylphosphonate 165 initiated by an EDA complex.
Scheme 58: Mechanism of the synthesis of diethyl phenylphosphonate derivative 165.
Scheme 59: Synthesis of (Z)-2-iodovinyl phenyl ether 168 initiated by an EDA complex.
Scheme 60: Mechanism of the synthesis of (Z)-2-iodovinyl phenyl ether derivative 168.
Scheme 61: Dehalogenation reaction initiated by an EDA complex.
Progress in the total synthesis of inthomycins
- Bidyut Kumar Senapati
Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7
- . Therefore, the synthesis of inthomycin A was advanced in the racemic form. Treatment of compound (rac)-17 with aqueous ammonia gave the corresponding amide (rac)-18 in 96% yield. Heck coupling between (rac)-18 and vinylboronate pinacol ester [31] using Pd(PPh3)4/Et3N conditions provided stereoselective
Graphical Abstract
Figure 1: The inthomycins A–C (1–3) and structurally closely related compounds.
Figure 2: Syntheses of inthomycins A–C (1–3).
Scheme 1: The first total synthesis of racemic inthomycin A (rac)-1 by Whiting.
Scheme 2: Moloney’s synthesis of the phenyl analogue of inthomycin C ((rac)-3).
Scheme 3: Moloney’s synthesis of phenyl analogues of inthomycins A (rac-1) and B (rac-2).
Scheme 4: The first total synthesis of inthomycin B (+)-2 by R. J. K. Taylor.
Scheme 5: R. J. K. Taylor’s total synthesis of racemic inthomycin A (rac)-1.
Scheme 6: The first total synthesis of inthomycin C ((+)-3) by R. J. K. Taylor.
Scheme 7: The first total synthesis of naturally occurring inthomycin C ((–)-3) by Ryu et al.
Scheme 8: Preparation of E,E-iododiene (+)-84 and Z,E- iododiene 85a.
Scheme 9: Hatakeyama’s total synthesis of inthomycin A (+)-1 and inthomycin B (+)-2.
Scheme 10: Hatakeyama’s total synthesis of inthomycin C ((–)-3).
Scheme 11: Maulide’s formal synthesis of racemic inthomycin C ((rac)-3).
Scheme 12: Hale’s synthesis of dienylstannane (+)-69 and enyne (+)-82b intermediates.
Scheme 13: Hale’s total synthesis of inthomycin C ((+)-3).
Scheme 14: Hale and Hatakeyama’s resynthesis of (3R)-inthomycin C (−)-3 Mosher esters.
Scheme 15: Reddy’s formal syntheses of inthomycin C (+)-3 and inthomycin C ((−)-3).
Scheme 16: Synthesis of the cross-metathesis precursors (rac)-118 and 121.
Scheme 17: Donohoe’s total synthesis of inthomycin C ((−)-3).
Scheme 18: Synthesis of dienylboronic ester (E,E)-128.
Scheme 19: Synthesis of the alkenyl iodides (Z)- and (E)-130.
Scheme 20: Burton’s total synthesis of inthomycin B ((+)-2).
Scheme 21: Burton’s total synthesis of inthomycin C ((−)-3).
Scheme 22: Burton’s total synthesis of inthomycin A ((+)-1).
Scheme 23: Synthesis of common intermediate (Z)-(+)-143a.
Scheme 24: Synthesis of (Z)-and (E)-selective fragments (+)-145a–c.
Scheme 25: Kim’s total synthesis of inthomycins A (+)-1 and B (+)-2.
Scheme 26: Completion of total synthesis of inthomycin C ((–)-3) by Kim.
Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring
- Daria I. Tonkoglazova,
- Anna V. Gulevskaya,
- Konstantin A. Chistyakov and
- Olga I. Askalepova
Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2
- sp. and displaying inhibitory activities towards telomerases. The classical synthetic approach for carbohelicenes is the oxidative photocyclization of stilbene derivatives [1][2][3][4][5][6][7][8][9][10][11]. The latter are generally available via the Wittig, Heck-type or McMurry couplings. It is
Graphical Abstract
Scheme 1: Overview of the synthetic methods for the carbazole-based heterohelicenes. i) Pd2dba3, xantphos, K3...
Scheme 2: Synthetic strategy for the carbazole-based [6]helicenes fused with an azine ring.
Scheme 3: Sonogashira coupling of compound 4b with phenylacetylene. i) Pd(PPh3)2Cl2, CuI, iPr2NH, DMSO, 80 °C...
Figure 1: Molecular structure of carbazole-based [6]helicenes 10a (a), 10b (b) and 10c (c) (X-ray data).
Figure 2: Crystal packing of carbazole-based [6]helicenes 10a (a, b), 10b (c,d) and 10c (e). Hydrogen atoms a...
Palladium nanoparticles supported on chitin-based nanomaterials as heterogeneous catalysts for the Heck coupling reaction
- Tony Jin,
- Malickah Hicks,
- Davis Kurdyla,
- Sabahudin Hrapovic,
- Edmond Lam and
- Audrey Moores
Beilstein J. Org. Chem. 2020, 16, 2477–2483, doi:10.3762/bjoc.16.201
- Mining and Materials Engineering, McGill University, Montreal, Quebec H3A 0E9, Canada 10.3762/bjoc.16.201 Abstract In this report, chitin and chitosan nanocrystals were used as biomass-based supports for Pd nanoparticles (NPs) used as a heterogeneous catalyst for the Heck coupling reaction. By using a
- one-pot fabrication method, a Pd salt precursor was directly reduced and deposited onto these nanocrystal catalysts. Characterization of these nanocomposites showed disperse Pd NPs on the surfaces of the chitinous nanocrystals. Heck coupling model reactions revealed full product yield in relatively
- benign conditions, outcompeting the use of other catalysts supported on biomass-based nanomaterials, including cellulose nanocrystals. These initial results show the potential for using chitinous nanomaterials as effective catalyst supports in cross-coupling reactions. Keywords: chitin; chitosan; Heck
Graphical Abstract
Scheme 1: Pathway for the formation of ChNC and subsequently ChsNCs from bulk chitin.
Figure 1: TEM micrographs of (a) ChNCs and (b) ChsNCs. Both samples were stained and prepared on glow-dischar...
Scheme 2: Catalyst fabrication method for the deposition of Pd NPs onto chitin (PdNP@ChNC) and chitosan (PdNP...
Figure 2: TEM micrographs of (a) PdNP@ChNCs and (b) PdNP@ChsNCs. The samples were placed on glow discharged T...
Figure 3: High-resolution X-ray photoelectron spectroscopy of the Pd 3d region of (a) PdNP@ChNC and (b) PdNP@...
Syntheses of spliceostatins and thailanstatins: a review
- William A. Donaldson
Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166
- Scheme 10. Very recently, the groups of Nimura and Arisawa reported the synthesis of a phenyl C-glucoside derivative of spliceostatin beginning from ᴅ-glucal (Scheme 12) [35]. A Heck coupling of the tris(trimethylsilyl) ether of 74 with phenylboronic acid in the presence of Pd(OAc)2 and benzoquinone (BQ
Graphical Abstract
Figure 1: Structures of spliceostatins/thailanstatins.
Scheme 1: Synthetic routes to protected (2Z,4S)-4-hydroxy-2-butenoic acid fragments.
Scheme 2: Kitahara synthesis of the (all-cis)-2,3,5,6-tetrasubstituted tetrahydropyran.
Scheme 3: Koide synthesis of (all-cis)-2,3,5,6-tetrasubstituted tetrahydropyran.
Scheme 4: Nicolaou synthesis of the (all-cis)-2,3,5,6-tetrasubstituted tetrahydropyran.
Scheme 5: Jacobsen synthesis of the (all-cis)-2,3,5,6-tetrasubstituted tetrahydropyran.
Scheme 6: Unproductive attempt to generate the (all-cis)-tetrahydropyranone 50.
Scheme 7: Ghosh synthesis of the C-7–C-14 (all-cis)-tetrahydropyran segment.
Scheme 8: Ghosh’s alternative route to the (all-cis)-tetrahydropyranone 50.
Scheme 9: Alternative synthesis of the dihydro-3-pyrone 58.
Scheme 10: Kitahara’s 1st-generation synthesis of the C-1–C-6 fragment of FR901464 (1).
Scheme 11: Kitahara 1st-generation synthesis of the C-1–C-6 fragment of FR901464 (1).
Scheme 12: Nimura/Arisawa synthesis of the C-1-phenyl segment.
Scheme 13: Ghosh synthesis of the C-1–C-6 fragment of FR901464 (1) from (R)-glyceraldehyde acetonide.
Scheme 14: Jacobsen synthesis of the C-1–C-7 segment of FR901464 (1).
Scheme 15: Koide synthesis of the C-1–C-7 segment of FR901464 (1).
Scheme 16: Ghosh synthesis of the C-1–C-5 segment 102 of thailanstatin A (7).
Scheme 17: Nicolaou synthesis of the C-1–C-9 segments of spliceostatin D (9) and thailanstatins A (7) and B (5...
Scheme 18: Ghosh synthesis of the C-1–C-6 segment 115 of spliceostatin E (10).
Scheme 19: Fragment coupling via Wittig and modified Julia olefinations by Kitahara.
Scheme 20: Fragment coupling via cross-metathesis by Koide.
Scheme 21: The Ghosh synthesis of spliceostatin A (4), FR901464 (1), spliceostatin E (10), and thailanstatin m...
Scheme 22: Arisawa synthesis of a C-1-phenyl analog of FR901464 (1).
Scheme 23: Jacobsen fragment coupling by a Pd-catalyzed Negishi coupling.
Scheme 24: Nicolaou syntheses of thailanstatin A and B (7 and 5) and spliceostatin D (9) via a Pd-catalyzed Su...
Scheme 25: The Ghosh synthesis of spliceostatin G (11) via Suzuki–Miyaura coupling.
When metal-catalyzed C–H functionalization meets visible-light photocatalysis
- Lucas Guillemard and
- Joanna Wencel-Delord
Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147
- , thus rendering this methodology well suitable for the synthesis of a variety of indole derivatives. Subsequently, the panel of oxidative Heck coupling reactions via a photoredox catalytic system combined with C–H activation using Rh [74] or Ru [75] was extended by Rueping’s group. In 2014, Rueping
Graphical Abstract
Figure 1: Concept of dual synergistic catalysis.
Figure 2: Classification of catalytic systems involving two catalysts.
Figure 3: General mechanism for the dual nickel/photoredox catalytic system.
Figure 4: General mechanisms for C–H activation catalysis involving different reoxidation strategies.
Figure 5: Indole synthesis via dual C–H activation/photoredox catalysis.
Figure 6: Proposed mechanism for the indole synthesis via dual catalysis.
Figure 7: Oxidative Heck reaction on arenes via the dual catalysis.
Figure 8: Proposed mechanism for the Heck reaction on arenes via dual catalysis.
Figure 9: Oxidative Heck reaction on phenols via the dual catalysis.
Figure 10: Proposed mechanism for the Heck reaction on phenols via dual catalysis.
Figure 11: Carbazole synthesis via dual C–H activation/photoredox catalysis.
Figure 12: Proposed mechanism for the carbazole synthesis via dual catalysis.
Figure 13: Carbonylation of enamides via the dual C–H activation/photoredox catalysis.
Figure 14: Proposed mechanism for carbonylation of enamides via dual catalysis.
Figure 15: Annulation of benzamides via the dual C–H activation/photoredox catalysis.
Figure 16: Proposed mechanism for the annulation of benzamides via dual catalysis.
Figure 17: Synthesis of indoles via the dual C–H activation/photoredox catalysis.
Figure 18: Proposed mechanism for the indole synthesis via dual catalysis.
Figure 19: General concept of dual catalysis merging C–H activation and photoredox catalysis.
Figure 20: The first example of dual catalysis merging C–H activation and photoredox catalysis.
Figure 21: Proposed mechanism for the C–H arylation with diazonium salts via dual catalysis.
Figure 22: Dual catalysis merging C–H activation/photoredox using diaryliodonium salts.
Figure 23: Direct arylation via the dual catalytic system reported by Xu.
Figure 24: Direct arylation via dual catalytic system reported by Balaraman.
Figure 25: Direct arylation via dual catalytic system reported by Guo.
Figure 26: C(sp3)–H bond arylation via the dual Pd/photoredox catalytic system.
Figure 27: Acetanilide derivatives acylation via the dual C–H activation/photoredox catalysis.
Figure 28: Proposed mechanism for the C–H acylation with α-ketoacids via dual catalysis.
Figure 29: Acylation of azobenzenes via the dual catalysis C–H activation/photoredox.
Figure 30: C2-acylation of indoles via the dual C–H activation/photoredox catalysis.
Figure 31: Proposed mechanism for the C2-acylation of indoles with aldehydes via dual catalysis.
Figure 32: C2-acylation of indoles via the dual C–H activation/photoredox catalysis.
Figure 33: Perfluoroalkylation of arenes via the dual C–H activation/photoredox catalysis.
Figure 34: Proposed mechanism for perfluoroalkylation of arenes via dual catalysis.
Figure 35: Sulfonylation of 1-naphthylamides via the dual C–H activation/photoredox catalysis.
Figure 36: Proposed mechanism for sulfonylation of 1-naphthylamides via dual catalysis.
Figure 37: meta-C–H Alkylation of arenes via visible-light metallaphotocatalysis.
Figure 38: Alternative procedure for meta-C–H alkylation of arenes via metallaphotocatalysis.
Figure 39: Proposed mechanism for meta-C–H alkylation of arenes via metallaphotocatalysis.
Figure 40: C–H borylation of arenes via visible-light metallaphotocatalysis.
Figure 41: Proposed mechanism for C–H borylation of arenes via visible-light metallaphotocatalysis.
Figure 42: Undirected C–H aryl–aryl cross coupling via dual gold/photoredox catalysis.
Figure 43: Proposed mechanism for the undirected C–H aryl–aryl cross-coupling via dual catalysis.
Figure 44: Undirected C–H arylation of (hetero)arenes via dual manganese/photoredox catalysis.
Figure 45: Proposed mechanism for the undirected arylation of (hetero)arenes via dual catalysis.
Figure 46: Photoinduced C–H arylation of azoles via copper catalysis.
Figure 47: Photo-induced C–H chalcogenation of azoles via copper catalysis.
Figure 48: Decarboxylative C–H adamantylation of azoles via dual cobalt/photoredox catalysis.
Figure 49: Proposed mechanism for the C–H adamantylation of azoles via dual catalysis.
Figure 50: General mechanisms for the “classical” (left) and Cu-free variant (right) Sonogoshira reaction.
Figure 51: First example of a dual palladium/photoredox catalysis for Sonogashira-type couplings.
Figure 52: Arylation of terminal alkynes with diazonium salts via dual gold/photoredox catalysis.
Figure 53: Proposed mechanism for the arylation of terminal alkynes via dual catalysis.
Figure 54: C–H Alkylation of alcohols promoted by H-atom transfer (HAT).
Figure 55: Proposed mechanism for the C–H alkylation of alcohols promoted by HAT.
Figure 56: C(sp3)–H arylation of latent nucleophiles promoted by H-atom transfer.
Figure 57: Proposed mechanism for the C(sp3)–H arylation of latent nucleophiles promoted by HAT.
Figure 58: Direct α-arylation of alcohols promoted by H-atom transfer.
Figure 59: Proposed mechanism for the direct α-arylation of alcohols promoted by HAT.
Figure 60: C–H arylation of amines via dual Ni/photoredox catalysis.
Figure 61: Proposed mechanism for the C–H arylation of amines via dual Ni/photoredox catalysis.
Figure 62: C–H functionalization of nucleophiles via excited ketone/nickel dual catalysis.
Figure 63: Proposed mechanism for the C–H functionalization enabled by excited ketones.
Figure 64: Selective sp3–sp3 cross-coupling promoted by H-atom transfer.
Figure 65: Proposed mechanism for the selective sp3–sp3 cross-coupling promoted by HAT.
Figure 66: Direct C(sp3)–H acylation of amines via dual Ni/photoredox catalysis.
Figure 67: Proposed mechanism for the C–H acylation of amines via dual Ni/photoredox catalysis.
Figure 68: C–H hydroalkylation of internal alkynes via dual Ni/photoredox catalysis.
Figure 69: Proposed mechanism for the C–H hydroalkylation of internal alkynes.
Figure 70: Alternative procedure for the C–H hydroalkylation of ynones, ynoates, and ynamides.
Figure 71: Allylic C(sp3)–H activation via dual Ni/photoredox catalysis.
Figure 72: Proposed mechanism for the allylic C(sp3)–H activation via dual Ni/photoredox catalysis.
Figure 73: Asymmetric allylation of aldehydes via dual Cr/photoredox catalysis.
Figure 74: Proposed mechanism for the asymmetric allylation of aldehydes via dual catalysis.
Figure 75: Aldehyde C–H functionalization promoted by H-atom transfer.
Figure 76: Proposed mechanism for the C–H functionalization of aldehydes promoted by HAT.
Figure 77: Direct C–H arylation of strong aliphatic bonds promoted by HAT.
Figure 78: Proposed mechanism for the C–H arylation of strong aliphatic bonds promoted by HAT.
Figure 79: Direct C–H trifluoromethylation of strong aliphatic bonds promoted by HAT.
Figure 80: Proposed mechanism for the C–H trifluoromethylation of strong aliphatic bonds.
Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole
- Carlos H. Escalante,
- Eder I. Martínez-Mora,
- Carlos Espinoza-Hicks,
- Alejandro A. Camacho-Dávila,
- Fernando R. Ramos-Morales,
- Francisco Delgado and
- Joaquín Tamariz
Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113
- - and pyrrolo-fused polycyclic indoles is herein described, starting from 2-formylpyrrole and employing Diels–Alder and Heck arylation reactions. 3-(N-Benzyl-2-pyrrolyl)acrylates and 4-(pyrrol-2-yl)butenones underwent a highly endo-Diels–Alder cycloaddition with maleimides to furnish octahydropyrrolo
- [3,4-e]indoles, which served as precursors in the regioselective synthesis of aza-polycyclic skeletons via an intramolecular Heck arylation reaction. Through the latter reaction, the 3-(N-benzyl-2-pyrrolyl)acrylates give rise to 3-(pyrrolo[2,1-a]isoindol-3-yl)acrylates. A further oxidative
- in governing the endo stereocontrol. Keywords: endo-Diels–Alder stereocontrol; 2-formylpyrrole; intramolecular Heck arylation reaction; non-covalent interactions; pyrroloindoles; pyrroloisoindoles; Introduction Pyrrolizines [1][2] and pyrrolizidines [3][4], abundant in nature [4][5], are among the
Graphical Abstract
Figure 1: Fused aza-hetero polycyclic frames and natural pyrrolizine- and isoindole-containing alkaloids.
Scheme 1: Synthetic approaches for the preparation of pyrrolo-fused aza-hetero polycyclic frames.
Scheme 2: Preparation of 1,2-substituted pyrroles 8a–f and 8i,j.
Scheme 3: Diels–Alder cycloadditions of pyrroles 8a–j and 16a–b with maleimides 7b–c.
Figure 2: Structures of 9m (a) and 10m (b) as determined by single-crystal X-ray diffraction crystallography ...
Scheme 4: Pd(0)-catalyzed intramolecular Heck cross-coupling reaction of 2-vinylpyrroles 8c,d and 8g.
Scheme 5: Synthesis of 2-vinylpyrroles 8k,l and their Pd(0)-catalyzed intramolecular Heck cross-coupling to p...
Scheme 6: Diastereoselective Diels–Alder reaction of pyrrolo[2,1-a]isoindole 18a with 7c.
Scheme 7: Synthetic approach to the fused aza-heterocyclic pentacycle 12.
Figure 3: M06-2X/6-31+G(d,p) Optimized geometry for each of the SCs (a and d), TSs (b and e) and ADs (c and f...
Figure 4: M06-2X/6-31+G(d,p) Optimized geometry for each of the TSs of the Diels–Alder reactions of dienes 8b...
Figure 5: M06-2X/6-31+G(d,p) Optimized geometry of the endo SCs (a) and TSs (b) for the Diels–Alder reaction ...
Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions
- Xiaoming Ma,
- Suzhi Meng,
- Xiaofeng Zhang,
- Qiang Zhang,
- Shenghu Yan,
- Yue Zhang and
- Wei Zhang
Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106
- Two kinds of [3 + 2] cycloaddition intermediates generated from the three-component reactions of 2-bromobenzaldehydes and maleimides with amino esters or amino acids were used for a one-pot N-allylation and intramolecular Heck reactions to form pyrrolidinedione-fused hexahydropyrrolo[2,1-a
- ]isoquinolines. The multicomponent reaction was combined with one-pot reactions to make a synthetic method with good pot, atom and step economy. MeCN was used as a preferable green solvent for the reactions. Keywords: [3 + 2] cycloaddition; Heck reaction; hexahydropyrrolo[2,1-a]isoquinoline; one-pot reactions
- via sequential 1,3-dipolar cycloaddition, N-allylation, and intramolecular Heck cyclization reactions [50][51][52][53][54] (Scheme 2, K). Both stabilized and non-stabilized azomethine ylides could be used for the initial [3 + 2] cycloaddition. A multicomponent reaction was combined with one-pot
Graphical Abstract
Figure 1: Bioactive pyrrolo[2,1-a]isoquinolines and hexahydropyrrolo[2,1-a]isoquinolines.
Scheme 1: [3 + 2] Cycloaddition with amino esters or amino acids.
Scheme 2: Scaffolds derived from the initial [3 + 2] adducts.
Scheme 3: [3 + 2] Cycloaddition with amino esters or amino acids. Conditions: 1:3:4 (1.2:1:1.1), Et3N (1.5 eq...
Scheme 4: Synthesis of pyrrolo[2,1-a]isoquinolines 9. Reaction conditions: 5 (0.5 mmol, 1 equiv), 7 (3 equiv)...
Scheme 5: Synthesis of pyrrolo[2,1-a]isoquinolines 11. Reaction conditions: 6 (0.5 mmol, 1 equiv), 7 (3 equiv...
Scheme 6: Synthesis of pyrrolo[2,1-a]isoquinolines 12. Reaction conditions: 5 or 6 (0.5 mmol, 1 equiv), cinna...
Scheme 7: Plausible mechanism for the synthesis of 9a.
Suzuki–Miyaura cross coupling is not an informative reaction to demonstrate the performance of new solvents
- James Sherwood
Beilstein J. Org. Chem. 2020, 16, 1001–1005, doi:10.3762/bjoc.16.89
- the key fundamental principles of boron and palladium speciation and the role of the base in the Suzuki–Miyaura reaction. For researchers developing safer solvents, the Mizoroki–Heck reaction is a more suitable cross-coupling methodology to demonstrate solvent performance [28]. The reaction kinetics
- of Mizoroki–Heck reactions have a strong dependence on the dipolarity of the reaction medium, and the rate determining step can be controlled by the equivalents of ligand added, thereby eliminating one variable [8]. Reprotoxic solvents such as N,N-dimethylformamide (DMF) are routinely used in the
- Mizoroki–Heck reaction and hence there is also a motivation to investigate safer alternative solvents that the Suzuki–Miyaura reaction lacks. If researchers are still compelled to study the utility of solvents in the Suzuki–Miyaura reaction, I encourage future studies to be directed at challenging
Graphical Abstract
Scheme 1: (a) Case study 1, reaction of 4-bromotoluene; (b) case study 2, reaction of 4-bromophenylacetic aci...
Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules
- Valerian Dragutan,
- Ileana Dragutan,
- Albert Demonceau and
- Lionel Delaude
Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68
- to build the desired 1,3-dienic units. The advantageous association of this approach with name reactions like Grignard, Wittig, Diels–Alder, Suzuki–Miyaura, Heck cross-coupling, etc. is illustrated. Examples unveil the generality of such tandem reactions in providing not only the intricate structures
- ][39][40][41][42][43]. In ingeniously elaborated procedures, olefin metathesis has been frequently employed as such or associated with name reactions like Grignard, Wittig, Diels–Alder, Suzuki–Miyaura, Heck, etc., resulting in the assembly of diverse intricate building blocks of the targeted structures
- other memory impairments, namely (−)-galanthamine (13), has attracted great interest for its structural complexity and specific bioactivity. The total synthesis of compound 13, described by Brown et al. [81], involved an enyne ring-closing metathesis and a Heck cross-coupling as the key reactions for
Graphical Abstract
Scheme 1: Intramolecular (A) and intermolecular (B) enyne metathesis reactions.
Scheme 2: Ene–yne and yne–ene mechanisms for intramolecular enyne metathesis reactions.
Scheme 3: Metallacarbene mechanism in intermolecular enyne metathesis.
Scheme 4: The Oguri strategy for accessing artemisinin analogs 1a–c through enyne metathesis.
Scheme 5: Access to the tetracyclic core of nanolobatolide (2) via tandem enyne metathesis followed by an Eu(...
Scheme 6: Synthesis of (−)-amphidinolide E (3) using an intermolecular enyne metathesis as the key step.
Scheme 7: Synthesis of amphidinolide K (4) by an enyne metathesis route.
Scheme 8: Trost synthesis of des-epoxy-amphidinolide N (5) [72].
Scheme 9: Enyne metathesis between the propargylic derivative and the allylic alcohol in the synthesis of the...
Scheme 10: Synthetic route to amphidinolide N (6a).
Scheme 11: Synthesis of the stereoisomeric precursors of amphidinolide V (7a and 7b) through alkyne ring-closi...
Scheme 12: Synthesis of the anthramycin precursor 8 from ʟ-methionine by a tandem enyne metathesis–cross metat...
Scheme 13: Synthesis of (−)‐clavukerin A (9) and (−)‐isoclavukerin A (10) by an enyne metathesis route startin...
Scheme 14: Synthesis of (−)-isoguaiene (11) through an enyne metathesis as the key step.
Scheme 15: Synthesis of erogorgiaene (12) by a tandem enyne metathesis/cross metathesis sequence using the sec...
Scheme 16: Synthesis of (−)-galanthamine (13) from isovanilin by an enyne metathesis.
Scheme 17: Application of enyne metathesis for the synthesis of kempene diterpenes 14a–c.
Scheme 18: Synthesis of the alkaloid (+)-lycoflexine (15) through enyne metathesis.
Scheme 19: Synthesis of the AB subunits of manzamine A (16a) and E (16b) by enyne metathesis.
Scheme 20: Jung's synthesis of rhodexin A (17) by enyne metathesis/cross metathesis reactions.
Scheme 21: Total synthesis of (−)-flueggine A (18) and (+)-virosaine B (19) from Weinreb amide by enyne metath...
Scheme 22: Access to virgidivarine (20) and virgiboidine (21) by an enyne metathesis route.
Scheme 23: Enyne metathesis approach to (−)-zenkequinone B (22).
Scheme 24: Access to C-aryl glycoside 23 by an intermolecular enyne metathesis/Diels–Alder cycloaddition.
Scheme 25: Synthesis of spiro-C-aryl glycoside 24 by a tandem intramolecular enyne metathesis/Diels–Alder reac...
Scheme 26: Pathways to (−)-exiguolide (25) by Trost’s Ru-catalyzed enyne cross-coupling and cross-metathesis [94].
A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions
- Pezhman Shiri and
- Jasem Aboonajmi
Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52
- reactions, Ugi–Smiles reactions, Mizoroki–Heck reactions, aldol reactions, oxidation and dehydration reactions, Mannich reactions, and multicomponent reactions. Because of the mentioned reasons as well as due to the low toxicity of silica nanoparticles, they are often a good option [24]. For this review
- multitask nanocatalyst was used for one-pot Sonogashira-“click”/“click”-Heck sequences [87]. Palladium(II) acetate, copper(II) acetate, and charcoal were dispersed in methanol. In order to remove oxygen from the reaction mixture, hydrogen gas was passed through the medium. Then, the solution was stirred at
Graphical Abstract
Scheme 1: Chemical structure of the catalysts 1a and 1b and their catalytic application in CuAAC reactions.
Scheme 2: Synthetic route to the catalyst 11 and its catalytic application in CuAAC reactions.
Scheme 3: Synthetic route of dendrons, illustrated using G2-AMP 23.
Scheme 4: The catalytic application of CuYAu–Gx-AAA–SBA-15 in a CuAAC reaction.
Scheme 5: Synthetic route to the catalyst 36.
Scheme 6: Application of the catalyst 36 in CuAAC reactions.
Scheme 7: The synthetic route to the catalyst 45 and catalytic application of 45 in “click” reactions.
Scheme 8: Synthetic route to the catalyst 48 and catalytic application of 48 in “click” reactions.
Scheme 9: Synthetic route to the catalyst 58 and catalytic application of 58 in “click” reactions.
Scheme 10: Synthetic route to the catalyst 64 and catalytic application of 64 in “click” reactions.
Scheme 11: Chemical structure of the catalyst 68 and catalytic application of 68 in “click” reactions.
Scheme 12: Chemical structure of the catalyst 69 and catalytic application of 69 in “click” reactions.
Scheme 13: Synthetic route to, and chemical structure of the catalyst 74.
Scheme 14: Application of the cayalyst 74 in “click” reactions.
Scheme 15: Synthetic route to, and chemical structure of the catalyst 78 and catalytic application of 78 in “c...
Scheme 16: Synthetic route to the catalyst 85.
Scheme 17: Application of the catalyst 85 in “click” reactions.
Scheme 18: Synthetic route to the catalyst 87 and catalytic application of 87 in “click” reactions.
Scheme 19: Chemical structure of the catalyst 88 and catalytic application of 88 in “click” reactions.
Scheme 20: Synthetic route to the catalyst 90 and catalytic application of 90 in “click” reactions.
Scheme 21: Synthetic route to the catalyst 96 and catalytic application of 96 in “click” reactions.
Scheme 22: Synthetic route to the catalyst 100 and catalytic application of 100 in “click” reactions.
Scheme 23: Synthetic route to the catalyst 102 and catalytic application of 23 in “click” reactions.
Scheme 24: Synthetic route to the catalysts 108–111.
Scheme 25: Catalytic application of 108–111 in “click” reactions.
Scheme 26: Synthetic route to the catalyst 121 and catalytic application of 121 in “click” reactions.
Scheme 27: Synthetic route to 125 and application of 125 in “click” reactions.
Scheme 28: Synthetic route to the catalyst 131 and catalytic application of 131 in “click” reactions.
Scheme 29: Synthetic route to the catalyst 136.
Scheme 30: Application of the catalyst 136 in “click” reactions.
Scheme 31: Synthetic route to the catalyst 141 and catalytic application of 141 in “click” reactions.
Scheme 32: Synthetic route to the catalyst 144 and catalytic application of 144 in “click” reactions.
Scheme 33: Synthetic route to the catalyst 149 and catalytic application of 149 in “click” reactions.
Scheme 34: Synthetic route to the catalyst 153 and catalytic application of 153 in “click” reactions.
Scheme 35: Synthetic route to the catalyst 155 and catalytic application of 155 in “click” reactions.
Scheme 36: Synthetic route to the catalyst 157 and catalytic application of 157 in “click” reactions.
Scheme 37: Synthetic route to the catalyst 162.
Scheme 38: Application of the catalyst 162 in “click” reactions.
Scheme 39: Synthetic route to the catalyst 167 and catalytic application of 167 in “click” reactions.
Scheme 40: Synthetic route to the catalyst 169 and catalytic application of 169 in “click” reactions.
Scheme 41: Synthetic route to the catalyst 172.
Scheme 42: Application of the catalyst 172 in “click” reactions.
Copper-catalyzed remote C–H arylation of polycyclic aromatic hydrocarbons (PAHs)
- Anping Luo,
- Min Zhang,
- Zhangyi Fu,
- Jingbo Lan,
- Di Wu and
- Jingsong You
Beilstein J. Org. Chem. 2020, 16, 530–536, doi:10.3762/bjoc.16.49
- the carbonyl oxygen to I gives intermediate II, which undergoes an aryl-transfer reaction via a Heck-like four-membered-ring transition state III to form the intermediate IV with Cu(III) and aryl group added at the C8- and C7-positions of the naphthalene ring, respectively. Finally, the breakdown of
Graphical Abstract
Scheme 1: Direct C–H arylation of PAHs.
Scheme 2: Scope of aryliodonium salts. Reaction conditions: 1a (0.2 mmol), 2 (0.3 mmol) in DCE (1 mL) at 70 °...
Scheme 3: Scope of PAHs. Reaction conditions: 1 (0.2 mmol), 2a (0.3 mmol) in DCE (1 mL) at 70 °C under N2 for...
Scheme 4: Proposed catalytic cycle.
Figure 1: a) UV-visible absorption spectra of 4k, 4n and 4o in toluene (1 × 10−5 mol/L). b) Emission spectra ...
Room-temperature Pd/Ag direct arylation enabled by a radical pathway
- Amy L. Mayhugh and
- Christine K. Luscombe
Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36
- majority of experimental evidence supporting this pathway [22][23][24][25][26]. In this case, C2 selectivity is often observed, theoretically from a C3/C2 Pd migration. A third possible mechanism that has had little experimental evidence but cannot be ruled out, is a Heck-type carbopalladation. This
Graphical Abstract
Scheme 1: A high yielding, highly selective room-temperature direct arylation reaction between indole and iod...
Figure 1: 1H NMR (500 MHz, CDCl3) of (a) 5-iodo-1-octylindole monomer (b) PIn prepared according to condition...
Figure 2: MALDI–TOF MS of PIn, indicating octylindole repeat units with three different types of end groups. ...
Scheme 2: Commonly discussed mechanisms for C2 selective direct arylation, none containing radical intermedia...
Scheme 3: Proposed mechanism for palladium radical involved reaction between indole and iodobenzene.
Scheme 4: Radical trap effects on literature methods for the direct arylation at room temperature. A) From re...
Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds
- Vuyisa Mzozoyana,
- Fanie R. van Heerden and
- Craig Grimmer
Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22
- , numerous methods for the synthesis of these compounds have been developed, examples are the Pechmann condensation [10][11], Stille coupling reaction [12], Knoevenagel condensation [13], Heck coupling reaction [14], Kostanecki reaction, Baylis–Hillman reaction [15], Michael reaction [16], Suzuki–Miyaura
Graphical Abstract
Scheme 1: Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin (6).
Figure 1: 1H NMR spectra for the “aromatic” region of coumarin 6; comparison of 1H spectrum and 1H-{19F} spec...
Figure 2: 13C NMR spectra for coumarin 5 and 6; showing the splitting of the signal corresponding to C5.
Figure 3: 19F,1H-HOESY NMR spectrum for coumarin 6 illustrating two through-space interactions.
Figure 4: Superposition of single-crystal X-ray structure (red) and DFT-optimized structure (green); RMSD 0.3...
Figure 5: DFT-optimized structure for coumarin (6).
Figure 6: Plots of relative energy (black trace, no units), interatomic distance F–H5 (red trace, Å), interat...
Figure 7: Short contacts within the single-crystal X-ray structure of coumarin 6.
Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst
- Abhijit Paul,
- Debnath Chatterjee,
- Srirupa Banerjee and
- Somnath Yadav
Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16
- Pd-catalysed Fujiwara–Moritani or oxidative dehydrogenative Heck reaction via dual C–H activation [21][22][23][24]. One of the early examples of this reaction, reported by Gaunt and co-workers, involved the regioselective, solvent-controlled C3 alkenylation of indoles with alkenes containing electron
Graphical Abstract
Figure 1: Biologically and medicinally important 3-alkenylindoles.
Scheme 1: a) Previous and b) present work related to the synthesis of 3-alkenylindoles.
Scheme 2: Substrate scope for the C–H alkenylation of the indoles 1. Reaction conditions: 1 (1 mmol), 2 (2 mm...
Scheme 3: a) Three-phase test to determine a homogeneous or heterogeneous catalytic mechanism of action for t...
Scheme 4: Probable catalytic mechanism for the transformation of 1a by the RuNC.
Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction
- Damian Kusy,
- Agata Wojciechowska,
- Joanna Małolepsza and
- Katarzyna M. Błażewska
Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3
- ]pyridine ring has been synthesized via the microwave-assisted Mizoroki–Heck reaction. The efficient modification of the imidazo[1,2-a]pyridine ring has been achieved as late-stage functionalization, enabling and accelerating the generation of a library of compounds from a common precursor. Keywords: α
- -phosphonoacrylates; α-phosphonopropionates; imidazo[1,2-a]pyridine; microwave-assisted reaction; Mizoroki–Heck reaction; Introduction In the last few decades, the Mizoroki–Heck reaction has become one of the main tools in organic synthesis. Its use for the functionalization of a wide range of compounds cannot be
- confirmed by the presence in a number of pharmaceuticals [2][3]. The imidazo[1,2-a]pyridine-ring modification via Pd-catalyzed reactions is broadly reported in the literature [3], however, such functionalizations for more complex molecules are not very common. On the other hand, the Mizoroki–Heck reaction
Graphical Abstract
Figure 1: Substrates used for the Mizoroki–Heck reaction in this study.
Figure 2: Structures of the identified side products 4 and 5.
Scheme 1: Scope of the method for analogs derived from 1 and 2. The ratio of isomers is given (E/Z or β/α) in...
Scheme 2: Dealkylation of fluorinated analog 23 under the Mizoroki–Heck reaction conditions.
Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids
- Benedikt C. Melzer,
- Alois Plodek and
- Franz Bracher
Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222
- synthesis via an Heck-type palladium-catalysed reaction according to the method of Harayama [30] (Pd(II)acetate/tri(o-tolyl)phosphine/K2CO3) did not lead to the expected alkaloid 3. Also the radical procedure published by Markgraf et al. [31] using AIBN and Bu3SnH and a photochemical cyclization protocol we
Graphical Abstract
Figure 1: Marine pyridoacridine alkaloids amphimedine (1), ascididemin (2), kuanoniamine A (3), styelsamine D...
Figure 2: A–C): Published methods for the synthesis of 4,5-disubstituted benzo[c][2,7]naphthyridines; D) New ...
Scheme 1: Regioselective metalation of 4-bromobenzo[c][2,7]naphthyridine (9d) and subsequent conversion into ...
Scheme 2: Outcome of a D2O quenching experiment after metalation of 4-bromobenzo[c][2,7]naphthyridine (9d).
Scheme 3: Synthesis of 5-substituted 4-bromobenzo[c][2,7]naphthyridines via regioselective metalation of 9d u...
Scheme 4: Attempted synthesis of kuanoniamine A (3).
Scheme 5: Synthesis of pyrido[4,3,2-mn]acridone 22 starting from 20a via bromine–magnesium exchange reaction ...
Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups
- Xiaowei Li,
- Xiaolin Shi,
- Xiangqian Li and
- Dayong Shi
Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218
Graphical Abstract
Scheme 1: The main three strategies of fluorination: nucleophilic, electrophilic and radical fluorination.
Scheme 2: Doyle’s Pd-catalyzed fluorination of allylic chlorides.
Scheme 3: Allylic fluorination of 2- and 3-substituted propenyl esters.
Scheme 4: Regioselective allylic fluorination of cinnamyl phosphorothioate esters.
Scheme 5: Palladium-catalyzed aliphatic C–H fluorination reported by Doyle.
Scheme 6: Pd-catalyzed enantioselective fluorination of α-ketoesters followed by stereoselective reduction to...
Scheme 7: Pd-catalyzed C(sp3)–H fluorination of oxindoles.
Scheme 8: C–H fluorination of 8-methylquinoline derivatives with F− reagents.
Scheme 9: Fluorination of α-cyano acetates reported by van Leeuwen.
Scheme 10: The catalytic enantioselective electrophilic C–H fluorination of α-chloro-β-keto phosphonates.
Scheme 11: Fluorination of unactivated C(sp3)–H bonds directed by the bidentate PIP auxiliary.
Scheme 12: Fluorination of C(sp3)–H bonds at the β-position of carboxylic acids.
Scheme 13: Enantioselective benzylic C–H fluorination with a chiral transient directing group.
Scheme 14: Microwave-heated Pd-catalyzed fluorination of aryl alcohols.
Scheme 15: Fluorination of aryl potassium trifluoroborates.
Scheme 16: C(sp2)–F bond formation using precatalyst [L·Pd]2(cod).
Scheme 17: Pd-catalyzed fluorination of (hetero)aryl triflates and bromides.
Scheme 18: The Pd-catalyzed C–H fluorination of arenes with Selectfluor/NFSI.
Scheme 19: Pd(II)-catalyzed ortho-monofluorination protocol for benzoic acids.
Scheme 20: Pd-catalyzed C(sp2)–H bond fluorination of 2-arylbenzothiazoles.
Scheme 21: Nitrate-promoted fluorination of aromatic and olefinic C(sp2)–H bonds and proposed mechanism.
Scheme 22: Fluorination of oxalyl amide-protected benzylamine derivatives.
Scheme 23: C–H fluorination of benzaldehydes with orthanilic acids as transient directing group.
Scheme 24: Pd(II)-catalyzed aryl C–H fluorination with various directing groups.
Scheme 25: Cu-catalyzed aliphatic, allylic, and benzylic fluorination.
Scheme 26: Cu-catalyzed SN2 fluorination of primary and secondary alkyl bromides.
Scheme 27: Copper-catalyzed fluorination of alkyl triflates.
Scheme 28: Cu-catalyzed fluorination of allylic bromides and chlorides.
Scheme 29: Synthetic strategy for the fluorination of active methylene compounds.
Scheme 30: Fluorination of β-ketoesters using a tartrate-derived bidentate bisoxazoline-Cu(II) complex.
Scheme 31: Highly enantioselective fluorination of β-ketoesters and N-Boc-oxindoles.
Scheme 32: Amide group-assisted site-selective fluorination of α-bromocarbonyl compounds.
Scheme 33: Cu-mediated aryl fluorination reported by Sanford [77].
Scheme 34: Mono- or difluorination reactions of benzoic acid derivatives.
Scheme 35: Cu-catalyzed fluorination of diaryliodonium salts with KF.
Scheme 36: Copper(I)-catalyzed cross-coupling of 2-pyridylaryl bromides.
Scheme 37: AgNO3-catalyzed decarboxylative fluorination of aliphatic carboxylic acids.
Scheme 38: The Mn-catalyzed aliphatic and benzylic C–H fluorination.
Scheme 39: Iron(II)-promoted C–H fluorination of benzylic substrates.
Scheme 40: Ag-catalyzed fluorodecarboxylation of carboxylic acids.
Scheme 41: Vanadium-catalyzed C(sp3)–H fluorination.
Scheme 42: AgNO3-catalyzed radical deboronofluorination of alkylboronates and boronic acids.
Scheme 43: Selective heterobenzylic C–H fluorination with Selectfluor reported by Van Humbeck.
Scheme 44: Fe(II)-catalyzed site-selective fluorination guided by an alkoxyl radical.
Scheme 45: Fluorination of allylic trichloroacetimidates reported by Nguyen et al.
Scheme 46: Iridium-catalyzed fluorination of allylic carbonates with TBAF(t-BuOH)4.
Scheme 47: Iridium-catalyzed asymmetric fluorination of allylic trichloroacetimidates.
Scheme 48: Cobalt-catalyzed α-fluorination of β-ketoesters.
Scheme 49: Nickel-catalyzed α-fluorination of various α-chloro-β-ketoesters.
Scheme 50: Ni(II)-catalyzed enantioselective fluorination of oxindoles and β-ketoesters.
Scheme 51: Scandium(III)-catalyzed asymmetric C–H fluorination of unprotected 3-substituted oxindoles.
Scheme 52: Iron-catalyzed directed C–H fluorination.
Scheme 53: Electrophilic silver-catalyzed Ar–F bond-forming reaction from arylstannanes.
Figure 1: Nucleophilic, electrophilic and radical CF3 sources.
Scheme 54: Cu(I)-catalyzed allylic trifluoromethylation of unactivated terminal olefins.
Scheme 55: Direct copper-catalyzed trifluoromethylation of allylsilanes.
Scheme 56: Cupper-catalyzed enantioselective trifluoromethylation of five and six-membered ring β-ketoesters.
Scheme 57: Cu-catalyzed highly stereoselective trifluoromethylation of secondary propargyl sulfonates.
Scheme 58: Remote C(sp3)–H trifluoromethylation of carboxamides and sulfonamides.
Scheme 59: Trifluoromethylation of allylsilanes with photoredox catalysis.
Scheme 60: Ag-catalyzed decarboxylative trifluoromethylation of aliphatic carboxylic acids in aqueous CH3CN.
Scheme 61: Decarboxylative trifluoromethylation of aliphatic carboxylic acids via combined photoredox and copp...
Scheme 62: Palladium-catalyzed Ar–CF3 bond-forming reaction.
Scheme 63: Palladium-catalyzed trifluoromethylation of arenes with diverse heterocyclic directing groups.
Scheme 64: Pd-catalyzed trifluoromethylation of indoles as reported by Liu.
Scheme 65: Pd-catalyzed trifluoromethylation of vinyl triflates and vinyl nonaflates.
Scheme 66: Pd(II)-catalyzed ortho-trifluoromethylation of aromatic C–H bonds.
Scheme 67: Visible-light-induced Pd(OAc)2-catalyzed ortho-trifluoromethylation of acetanilides with CF3SO2Na.
Scheme 68: CuI-catalyzed trifluoromethylation of aryl- and alkenylboronic acids.
Scheme 69: Cu-catalyzed trifluoromethylation of aryl- and vinylboronic acids.
Scheme 70: Copper-catalyzed trifluoromethylation of α,β-unsaturated carboxylic acids.
Scheme 71: Formation of C(sp2)–CF3 bond catalyzed by copper(I) complex.
Scheme 72: Loh’s Cu(I)-catalyzed trifluoromethylation of enamides and electron-deficient alkenes.
Scheme 73: Copper and iron-catalyzed decarboxylative tri- and difluoromethylation.
Scheme 74: Cu-catalyzed trifluoromethylation of hydrazones developed by Bouyssi.
Scheme 75: Cu(I)-catalyzed trifluoromethylation of terminal alkenes.
Scheme 76: Cu/Ag-catalyzed decarboxylative trifluoromethylation of cinnamic acids.
Scheme 77: Copper-catalyzed direct alkenyl C–H trifluoromethylation.
Scheme 78: Copper(I/II)-catalyzed direct trifluoromethylation of styrene derivatives.
Scheme 79: Regioselective trifluoromethylation of pivalamido arenes and heteroarenes.
Scheme 80: Synthesis of trifluoromethylquinones in the presence of copper(I).
Scheme 81: Oxidative trifluoromethylation of imidazoheterocycles in ionic liquid/water.
Scheme 82: A mild and fast continuous-flow trifluoromethylation of coumarins using a CuI/CF3SO2Na/TBHP system.
Scheme 83: Copper-catalyzed oxidative trifluoromethylation of various 8-aminoquinolines.
Scheme 84: PA-directed copper-catalyzed trifluoromethylation of anilines.
Scheme 85: Trifluoromethylation of potassium vinyltrifluoroborates catalyzed by Fe(II).
Scheme 86: Alkenyl trifluoromethylation catalyzed by Ru(phen)3Cl2 as photocatalyst.
Scheme 87: Ru-catalyzed trifluoromethylation of alkenes by Akita’s group.
Scheme 88: Ir-catalyzed Cvinyl–CF3 bond formation of α,β-unsaturated carboxylic acids.
Scheme 89: Ag(I)-catalyzed denitrative trifluoromethylation of β-nitrostyrenes.
Scheme 90: Photocatalyzed direct trifluoromethylation of aryl and heteroaryl C–H bonds.
Scheme 91: Rhenium (MTO)-catalyzed direct trifluoromethylation of aromatic substrates.
Scheme 92: Trifluoromethylation of unprotected anilines under [Ir(ppy)3] catalyst.
Scheme 93: Oxidative trifluoromethylation of imidazopyridines and imidazoheterocycles.
Scheme 94: Ruthenium-catalyzed trifluoromethylation of (hetero)arenes with trifluoroacetic anhydride.
Scheme 95: Phosphovanadomolybdic acid-catalyzed direct C–H trifluoromethylation.
Scheme 96: Picolinamide-assisted ortho-trifluoromethylation of arylamines.
Scheme 97: A nickel-catalyzed C–H trifluoromethylation of free anilines.
Scheme 98: Cu-mediated trifluoromethylation of terminal alkynes reported by Qing.
Scheme 99: Huang’s C(sp)–H trifluoromethylation using Togni’s reagent.
Scheme 100: Cu-catalyzed methods for trifluoromethylation with Umemoto’s reagent.
Scheme 101: The synthesis of alkynyl-CF3 compounds in the presence of fac-[Ir(ppy)3] under visible-light irradi...
Scheme 102: Pd-catalyzed Heck reaction reported by Reutrakul.
Scheme 103: Difluoromethylation of enamides and ene-carbamates.
Scheme 104: Difluoromethylation of α,β-unsaturated carboxylic acids.
Scheme 105: Copper-catalyzed direct C(sp2)–H difluoroacetylation reported by Pannecoucke and co-workers.
Scheme 106: Difluoroalkylation of aldehyde-derived hydrazones with functionalized difluoromethyl bromides.
Scheme 107: Photoredox-catalyzed C–H difluoroalkylation of aldehyde-derived hydrazones.
Scheme 108: Synergistic ruthenium(II)-catalyzed C–H difluoromethylation reported by Ackermann.
Scheme 109: Visible-light photocatalytic decarboxylation of α,β-unsaturated carboxylic acids.
Scheme 110: Synthesis of difluorinated ketones via S-alkyl dithiocarbamates obtained from acyl chlorides and po...
Scheme 111: Synthesis of aryl and heteroaryl difluoromethylated phosphonates.
Scheme 112: Difluoroalkylation of secondary propargyl sulfonates using Cu as the catalyst.
Scheme 113: Ru(II)-mediated para-selective difluoromethylation of anilides and their derivatives.
Scheme 114: Bulky diamine ligand promoted cross-coupling of difluoroalkyl bromides.
Scheme 115: Copper-catalyzed C3–H difluoroacetylation of quinoxalinones.
Scheme 116: Copper(I) chloride-catalyzed trifluoromethylthiolation of enamines, indoles and β-ketoesters.
Scheme 117: Copper-boxmi-catalyzed asymmetric trifluoromethylthiolation of β-ketoesters.
Scheme 118: Direct Cu-catalyzed trifluoromethylthiolation of boronic acids and alkynes.
Scheme 119: Cu-catalyzed synthesis of α-trifluoromethylthio-substituted ketones.
Scheme 120: Trifluoromethylthiolation reactions promoted by diazotriflone and copper.
Scheme 121: Halide activation of N-(trifluoromethylthio)phthalimide.
Scheme 122: The visible light-promoted trifluoromethylthiolation reported by Glorius.
Scheme 123: Synthesis of α-trifluoromethylthioesters via Goossen’s approach.
Scheme 124: Photoinduced trifluoromethylthiolation of diazonium salts.
Scheme 125: Ag-mediated trifluoromethoxylation of aryl stannanes and arylboronic acids.
Scheme 126: Catalytic (hetero)aryl C–H trifluoromethoxylation under visible light.
Scheme 127: Photoinduced C–H-bond trifluromethoxylation of (hetero)arenes.
Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors
- Christoph W. Grathwol,
- Nathalie Wössner,
- Sören Swyter,
- Adam C. Smith,
- Enrico Tapavicza,
- Robert K. Hofstetter,
- Anja Bodtke,
- Manfred Jung and
- Andreas Link
Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214
- available naphthalene-2-ylboronic acid or (3,4-dihydronaphthalen-2-yl)boronic acid (Scheme 1). The latter was synthesized according to a literature procedure [36]. Formation of compounds 2b–h was accomplished through Heck coupling of aryl bromides with the appropriate styrenes (Scheme 2) [37]. Compounds 2b
- and 2e were obtained in moderate yield using 3a as the aryl halide in the Heck reaction. The use of 3b in the Heck reaction resulted in a substantial improvement of yield in the synthesis of 2g but not for 2c. Interchanging the roles by using 5-vinylnicotinamide (5a) or methyl 5-vinylnicotinate (5b
Graphical Abstract
Figure 1: Selisistat (1) and hit compound GW435821X (2a).
Scheme 1: Reagents and conditions: a) appropriate boronic acid, Pd(PPh3)4, Na2CO3, DMF, H2O, microwave, 15 mi...
Scheme 2: Reagents and conditions: a) Pd2(dba)3 or Pd(OAc)2, P(o-tol)3, TEA, DMF, 120–140 °C, 0.7–24 h, 11–75...
Figure 2: (Left) UV–vis spectrum of 2b 50 µM in 5% DMSO (v/v) in assay buffer after varying durations of irra...
Figure 3: (Left) LC chromatogram of the LC–HRMS analysis of 2b after varying durations of irradiation with 25...
Scheme 3: Photocyclization and oxidation reaction of 2b upon UV irradiation.
Figure 4: Calculated and experimental absorption spectra of compounds (E)-2b-B (A), (Z)-2b-A (B), and product...
Scheme 4: Reagents and conditions: a) 4-fluoroaniline, oxone, HAc, 60 °C, 14 d, 42%; b) NH3, MeOH, rt, 3 d, 9...
Figure 5: (Left) UV–vis spectrum of 11, 50 µM in 5% DMSO (v/v), in assay buffer at the thermal equilibrium an...
Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage
- Gagandeep Kour Reen,
- Ashok Kumar and
- Pratibha Sharma
Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165
- Suzuki, Sonogashira and Heck coupling reactions (Scheme 48). The reaction proceeded by the formation of 1-iodoalkyne 142 which was characterized by mass and 1H NMR spetra. This iodoalkyne then formed a complex of Cu(I) with 2-AP. This was followed by migratory insertion of haloalkyne to form reactive Cu
Graphical Abstract
Figure 1: Various drugs having IP nucleus.
Figure 2: Participation percentage of various TMs for the syntheses of IPs.
Scheme 1: CuI–NaHSO4·SiO2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 2: Experimental examination of reaction conditions.
Scheme 3: One-pot tandem reaction for the synthesis of 2-haloimidazopyridines.
Scheme 4: Mechanistic scheme for the synthesis of 2-haloimidazopyridine.
Scheme 5: Copper-MOF-catalyzed three-component reaction (3-CR) for imidazo[1,2-a]pyridines.
Scheme 6: Mechanism for copper-MOF-driven synthesis.
Scheme 7: Heterogeneous synthesis via titania-supported CuCl2.
Scheme 8: Mechanism involving oxidative C–H functionalization.
Scheme 9: Heterogeneous synthesis of IPs.
Scheme 10: One-pot regiospecific synthesis of imidazo[1,2-a]pyridines.
Scheme 11: Vinyl azide as an unprecedented substrate for imidazo[1,2-a]pyridines.
Scheme 12: Radical pathway.
Scheme 13: Cu(I)-catalyzed transannulation approach for imidazo[1,5-a]pyridines.
Scheme 14: Plausible radical pathway for the synthesis of imidazo[1,5-a]pyridines.
Scheme 15: A solvent-free domino reaction for imidazo[1,2-a]pyridines.
Scheme 16: Cu-NPs-mediated synthesis of imidazo[1,2-a]pyridines.
Scheme 17: CuI-catalyzed synthesis of isoxazolylimidazo[1,2-a]pyridines.
Scheme 18: Functionalization of 4-bromo derivative via Sonogashira coupling reaction.
Scheme 19: A plausible reaction pathway.
Scheme 20: Cu(I)-catalyzed intramolecular oxidative C–H amidation reaction.
Scheme 21: One-pot synthetic reaction for imidazo[1,2-a]pyridine.
Scheme 22: Plausible reaction mechanism.
Scheme 23: Cu(OAc)2-promoted synthesis of imidazo[1,2-a]pyridines.
Scheme 24: Mechanism for aminomethylation/cycloisomerization of propiolates with imines.
Scheme 25: Three-component synthesis of imidazo[1,2-a]pyridines.
Figure 3: Scope of pyridin-2(1H)-ones and acetophenones.
Scheme 26: CuO NPS-promoted A3 coupling reaction.
Scheme 27: Cu(II)-catalyzed C–N bond formation reaction.
Scheme 28: Mechanism involving Chan–Lam/Ullmann coupling.
Scheme 29: Synthesis of formyl-substituted imidazo[1,2-a]pyridines.
Scheme 30: A tandem sp3 C–H amination reaction.
Scheme 31: Probable mechanistic approach.
Scheme 32: Dual catalytic system for imidazo[1,2-a]pyridines.
Scheme 33: Tentative mechanism.
Scheme 34: CuO/CuAl2O4/ᴅ-glucose-promoted 3-CCR.
Scheme 35: A tandem CuOx/OMS-2-based synthetic strategy.
Figure 4: Biomimetic catalytic oxidation in the presence of electron-transfer mediators (ETMs).
Scheme 36: Control experiment.
Scheme 37: Copper-catalyzed C(sp3)–H aminatin reaction.
Scheme 38: Reaction of secondary amines.
Scheme 39: Probable mechanistic pathway.
Scheme 40: Coupling reaction of α-azidoketones.
Scheme 41: Probable pathway.
Scheme 42: Probable mechanism with free energy calculations.
Scheme 43: MCR for cyanated IP synthesis.
Scheme 44: Substrate scope for the reaction.
Scheme 45: Reaction mechanism.
Scheme 46: Probable mechanistic pathway for Cu/ZnAl2O4-catalyzed reaction.
Scheme 47: Copper-catalyzed double oxidative C–H amination reaction.
Scheme 48: Application towards different coupling reactions.
Scheme 49: Reaction mechanism.
Scheme 50: Condensation–cyclization approach for the synthesis of 1,3-diarylated imidazo[1,5-a]pyridines.
Scheme 51: Optimized reaction conditions.
Scheme 52: One-pot 2-CR.
Scheme 53: One-pot 3-CR without the isolation of chalcone.
Scheme 54: Copper–Pybox-catalyzed cyclization reaction.
Scheme 55: Mechanistic pathway catalyzed by Cu–Pybox complex.
Scheme 56: Cu(II)-promoted C(sp3)-H amination reaction.
Scheme 57: Wider substrate applicability for the reaction.
Scheme 58: Plausible reaction mechanism.
Scheme 59: CuI assisted C–N cross-coupling reaction.
Scheme 60: Probable reaction mechanism involving sp3 C–H amination.
Scheme 61: One-pot MCR-catalyzed by CoFe2O4/CNT-Cu.
Scheme 62: Mechanistic pathway.
Scheme 63: Synthetic scheme for 3-nitroimidazo[1,2-a]pyridines.
Scheme 64: Plausible mechanism for CuBr-catalyzed reaction.
Scheme 65: Regioselective synthesis of halo-substituted imidazo[1,2-a]pyridines.
Scheme 66: Synthesis of 2-phenylimidazo[1,2-a]pyridines.
Scheme 67: Synthesis of diarylated compounds.
Scheme 68: CuBr2-mediated one-pot two-component oxidative coupling reaction.
Scheme 69: Decarboxylative cyclization route to synthesize 1,3-diarylimidazo[1,5-a]pyridines.
Scheme 70: Mechanistic pathway.
Scheme 71: C–H functionalization reaction of enamines to produce diversified heterocycles.
Scheme 72: A plausible mechanism.
Scheme 73: CuI-promoted aerobic oxidative cyclization reaction of ketoxime acetates and pyridines.
Scheme 74: CuI-catalyzed pathway for the formation of imidazo[1,2-a]pyridine.
Scheme 75: Mechanistic pathway.
Scheme 76: Mechanistic rationale for the synthesis of products.
Scheme 77: Copper-catalyzed synthesis of vinyloxy-IP.
Scheme 78: Regioselective product formation with propiolates.
Scheme 79: Proposed mechanism for vinyloxy-IP formation.
Scheme 80: Regioselective synthesis of 3-hetero-substituted imidazo[1,2-a]pyridines with different reaction su...
Scheme 81: Mechanistic pathway.
Scheme 82: CuI-mediated synthesis of 3-formylimidazo[1,2-a]pyridines.
Scheme 83: Radical pathway for 3-formylated IP synthesis.
Scheme 84: Pd-catalyzed urea-cyclization reaction for IPs.
Scheme 85: Pd-catalyzed one-pot-tandem amination and intramolecular amidation reaction.
Figure 5: Scope of aniline nucleophiles.
Scheme 86: Pd–Cu-catalyzed Sonogashira coupling reaction.
Scheme 87: One-pot amide coupling reaction for the synthesis of imidazo[4,5-b]pyridines.
Scheme 88: Urea cyclization reaction for the synthesis of two series of pyridines.
Scheme 89: Amidation reaction for the synthesis of imidazo[4,5-b]pyridines.
Figure 6: Amide scope.
Scheme 90: Pd NPs-catalyzed 3-component reaction for the synthesis of 2,3-diarylated IPs.
Scheme 91: Plausible mechanistic pathway for Pd NPs-catalyzed MCR.
Scheme 92: Synthesis of chromenoannulated imidazo[1,2-a]pyridines.
Scheme 93: Mechanism for the synthesis of chromeno-annulated IPs.
Scheme 94: Zinc oxide NRs-catalyzed synthesis of imidazo[1,2-a]azines/diazines.
Scheme 95: Zinc oxide-catalyzed isocyanide based GBB reaction.
Scheme 96: Reaction pathway for ZnO-catalyzed GBB reaction.
Scheme 97: Mechanistic pathway.
Scheme 98: ZnO NRs-catalyzed MCR for the synthesis of imidazo[1,2-a]azines.
Scheme 99: Ugi type GBB three-component reaction.
Scheme 100: Magnetic NPs-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 101: Regioselective synthesis of 2-alkoxyimidazo[1,2-a]pyridines catalyzed by Fe-SBA-15.
Scheme 102: Plausible mechanistic pathway for the synthesis of 2-alkoxyimidazopyridine.
Scheme 103: Iron-catalyzed synthetic approach.
Scheme 104: Iron-catalyzed aminooxygenation reaction.
Scheme 105: Mechanistic pathway.
Scheme 106: Rh(III)-catalyzed double C–H activation of 2-substituted imidazoles and alkynes.
Scheme 107: Plausible reaction mechanism.
Scheme 108: Rh(III)-catalyzed non-aromatic C(sp2)–H bond activation–functionalization for the synthesis of imid...
Scheme 109: Reactivity and selectivity of different substrates.
Scheme 110: Rh-catalyzed direct C–H alkynylation by Li et al.
Scheme 111: Suggested radical mechanism.
Scheme 112: Scandium(III)triflate-catalyzed one-pot reaction and its mechanism for the synthesis of benzimidazo...
Scheme 113: RuCl3-assisted Ugi-type Groebke–Blackburn condensation reaction.
Scheme 114: C-3 aroylation via Ru-catalyzed two-component reaction.
Scheme 115: Regioselective synthetic mechanism.
Scheme 116: La(III)-catalyzed one-pot GBB reaction.
Scheme 117: Mechanistic approach for the synthesis of imidazo[1,2-a]pyridines.
Scheme 118: Synthesis of imidazo[1,2-a]pyridine using LaMnO3 NPs under neat conditions.
Scheme 119: Mechanistic approach.
Scheme 120: One-pot 3-CR for regioselective synthesis of 2-alkoxy-3-arylimidazo[1,2-a]pyridines.
Scheme 121: Formation of two possible products under optimization of the catalysts.
Scheme 122: Mechanistic strategy for NiFe2O4-catalyzed reaction.
Scheme 123: Two-component reaction for synthesizing imidazodipyridiniums.
Scheme 124: Mechanistic scheme for the synthesis of imidazodipyridiniums.
Scheme 125: CuI-catalyzed arylation of imidazo[1,2-a]pyridines.
Scheme 126: Mechanism for arylation reaction.
Scheme 127: Cupric acetate-catalyzed double carbonylation approach.
Scheme 128: Radical mechanism for double carbonylation of IP.
Scheme 129: C–S bond formation reaction catalyzed by cupric acetate.
Scheme 130: Cupric acetate-catalyzed C-3 formylation approach.
Scheme 131: Control experiments for signifying the role of DMSO and oxygen.
Scheme 132: Mechanism pathway.
Scheme 133: Copper bromide-catalyzed CDC reaction.
Scheme 134: Extension of the substrate scope.
Scheme 135: Plausible radical pathway.
Scheme 136: Transannulation reaction for the synthesis of imidazo[1,5-a]pyridines.
Scheme 137: Plausible reaction pathway for denitrogenative transannulation.
Scheme 138: Cupric acetate-catalyzed C-3 carbonylation reaction.
Scheme 139: Plausible mechanism for regioselective C-3 carbonylation.
Scheme 140: Alkynylation reaction at C-2 of 3H-imidazo[4,5-b]pyridines.
Scheme 141: Two-way mechanism for C-2 alkynylation of 3H-imidazo[4,5-b]pyridines.
Scheme 142: Palladium-catalyzed SCCR approach.
Scheme 143: Palladium-catalyzed Suzuki coupling reaction.
Scheme 144: Reaction mechanism.
Scheme 145: A phosphine free palladium-catalyzed synthesis of C-3 arylated imidazopyridines.
Scheme 146: Palladium-mediated Buchwald–Hartwig cross-coupling reaction.
Figure 7: Structure of the ligands optimized.
Scheme 147: Palladium acetate-catalyzed direct arylation of imidazo[1,2-a]pyridines.
Scheme 148: Palladium acetate-catalyzed mechanistic pathway.
Scheme 149: Palladium acetate-catalyzed regioselective arylation reported by Liu and Zhan.
Scheme 150: Mechanism for selective C-3 arylation of IP.
Scheme 151: Pd(II)-catalyzed alkenylation reaction with styrenes.
Scheme 152: Pd(II)-catalyzed alkenylation reaction with acrylates.
Scheme 153: A two way mechanism.
Scheme 154: Double C–H activation reaction catalyzed by Pd(OAc)2.
Scheme 155: Probable mechanism.
Scheme 156: Palladium-catalyzed decarboxylative coupling.
Scheme 157: Mechanistic cycle for decarboxylative arylation reaction.
Scheme 158: Ligand-free approach for arylation of imidazo[1,2-a]pyridine-3-carboxylic acids.
Scheme 159: Mechanism for ligandless arylation reaction.
Scheme 160: NHC-Pd(II) complex assisted arylation reaction.
Scheme 161: C-3 arylation of imidazo[1,2-a]pyridines with aryl bromides catalyzed by Pd(OAc)2.
Scheme 162: Pd(II)-catalyzed C-3 arylations with aryl tosylates and mesylates.
Scheme 163: CDC reaction for the synthesis of imidazo[1,2-a]pyridines.
Scheme 164: Plausible reaction mechanism for Pd(OAc)2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 165: Pd-catalyzed C–H amination reaction.
Scheme 166: Mechanism for C–H amination reaction.
Scheme 167: One-pot synthesis for 3,6-di- or 2,3,6-tri(hetero)arylimidazo[1,2-a]pyridines.
Scheme 168: C–H/C–H cross-coupling reaction of IPs and azoles catalyzed by Pd(II).
Scheme 169: Mechanistic cycle.
Scheme 170: Rh-catalyzed C–H arylation reaction.
Scheme 171: Mechanistic pathway for C–H arylation of imidazo[1,2-a]pyridine.
Scheme 172: Rh(III)-catalyzed double C–H activation of 2-phenylimidazo[1,2-a]pyridines and alkynes.
Scheme 173: Rh(III)-catalyzed mechanistic pathway.
Scheme 174: Rh(III)-mediated oxidative coupling reaction.
Scheme 175: Reactions showing functionalization of the product obtained by the group of Kotla.
Scheme 176: Mechanism for Rh(III)-catalyzed oxidative coupling reaction.
Scheme 177: Rh(III)-catalyzed C–H activation reaction.
Scheme 178: Mechanistic cycle.
Scheme 179: Annulation reactions of 2-arylimidazo[1,2-a]pyridines and alkynes.
Scheme 180: Two-way reaction mechanism for annulations reaction.
Scheme 181: [RuCl2(p-cymene)]2-catalyzed C–C bond formation reaction.
Scheme 182: Reported reaction mechanism.
Scheme 183: Fe(III) catalyzed C-3 formylation approach.
Scheme 184: SET mechanism-catalyzed by Fe(III).
Scheme 185: Ni(dpp)Cl2-catalyzed KTC coupling.
Scheme 186: Pd-catalyzed SM coupling.
Scheme 187: Vanadium-catalyzed coupling of IP and NMO.
Scheme 188: Mechanistic cycle.
Scheme 189: Selective C3/C5–H bond functionalizations by mono and bimetallic systems.
Scheme 190: rGO-Ni@Pd-catalyzed C–H bond arylation of imidazo[1,2-a]pyridine.
Scheme 191: Mechanistic pathway for heterogeneously catalyzed arylation reaction.
Scheme 192: Zinc triflate-catalyzed coupling reaction of substituted propargyl alcohols.
Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams
- Edorta Martínez de Marigorta,
- Jesús M. de Los Santos,
- Ana M. Ochoa de Retana,
- Javier Vicario and
- Francisco Palacios
Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104
- comprising three palladium-catalysed reactions: Sonogashira, Heck and Suzuki–Miyaura (Scheme 37) [113][114][115]. In this methodology, N-arylpropiolamides 128 reacted with aryl iodides 129 and aryl- or styrylboronic acids 130 under microwave activation to yield 3-(diarylmethylene)oxindoles 131 or 3-(1,3
- Heck cyclization reaction between the substituted alkyne and aryl bromide in 133 takes place to form a cyclic palladium intermediate 134 with E-configuration, resulting from a syn-addition mechanism of this step. The addition of a silver salt reduces the probability of isomerization of the double bond
Graphical Abstract
Figure 1: γ-Lactam-derived structures considered in this review.
Figure 2: Alkaloids containing an isoindolinone moiety.
Figure 3: Alkaloids containing the 2-oxindole ring system.
Figure 4: Drugs and biological active compounds containing an isoindolinone moiety.
Figure 5: Drugs and biologically active compounds bearing a 2-oxindole skeleton.
Scheme 1: Three-component reaction of benzoic acid 1, amides 2 and DMSO (3).
Scheme 2: Copper-catalysed three-component reaction of 2-iodobenzoic acids 10, alkynylcarboxylic acids 11 and...
Scheme 3: Proposed mechanism for the formation of methylene isoindolinones 13.
Scheme 4: Copper-catalysed three-component reaction of 2-iodobenzamide 17, terminal alkyne 18 and pyrrole or ...
Scheme 5: Palladium-catalysed three-component reaction of ethynylbenzamides 21, secondary amines 22 and CO (23...
Scheme 6: Proposed mechanism for the formation of methyleneisoindolinones 24.
Scheme 7: Copper-catalysed three-component reaction of formyl benzoate 29, amines 2 and alkynes 18.
Scheme 8: Copper-catalysed three-component reaction of formylbenzoate 29, amines 2 and ketones 31.
Scheme 9: Non-catalysed (A) and phase-transfer catalysed (B) three-component reactions of formylbenzoic acids ...
Scheme 10: Proposed mechanism for the formation of isoindolinones 36.
Scheme 11: Three-component reaction of formylbenzoic acid 33, amines 2 and fluorinated silyl ethers 39.
Scheme 12: Three-component Ugi reaction of 2-formylbenzoic acid (33), diamines 41 and isocyanides 42.
Scheme 13: Non-catalysed (A, B) and chiral phosphoric acid promoted (C) three-component Ugi reactions of formy...
Scheme 14: Proposed mechanism for the enantioselective formation of isoindolinones 46.
Scheme 15: Three-component reaction of benzoic acids 33 or 54, amines 2 and TMSCN (52).
Scheme 16: Several variations of the three-component reaction of formylbenzoic acids 33, amines 2 and isatoic ...
Scheme 17: Proposed mechanism for the synthesis of isoindoloquinazolinones 57.
Scheme 18: Three-component reaction of isobenzofuranone 61, amines 2 and isatoic anhydrides 56.
Scheme 19: Palladium-catalysed three-component reaction of 2-aminobenzamides 59, 2-bromobenzaldehydes 62 and C...
Scheme 20: Proposed mechanism for the palladium-catalysed synthesis of isoindoloquinazolinones 57.
Scheme 21: Four-component reaction of 2-vinylbenzoic acids 67, aryldioazonium tetrafluoroborates 68, DABCO·(SO2...
Scheme 22: Plausible mechanism for the formation of isoindolinones 71.
Scheme 23: Three-component reaction of trimethylsilylaryltriflates 77, isocyanides 42 and CO2 (78).
Scheme 24: Plausible mechanism for the three-component synthesis of phthalimides 79.
Scheme 25: Copper-catalysed three-component reaction of 2-formylbenzonitriles 85, arenes 86 and diaryliodonium...
Scheme 26: Copper-catalysed three-component reaction of 2-formylbenzonitriles 85, diaryliodonium salts 87 and ...
Scheme 27: Proposed mechanism for the formation of 2,3-diarylisoindolinones 88, 89 and 92.
Scheme 28: Palladium-catalysed three-component reaction of chloroquinolinecarbaldehydes 97 with isocyanides 42...
Scheme 29: Palladium-catalysed three-component reaction of imines 99 with CO (23) and ortho-iodoarylimines 100....
Scheme 30: Palladium-catalysed three-component reaction of amines 2 with CO (23) and aryl iodide 105.
Scheme 31: Three-component reaction of 2-ethynylanilines 109, perfluoroalkyl iodides 110 and carbon monoxide (...
Scheme 32: Ultraviolet-induced three-component reaction of N-(2-iodoaryl)acrylamides 113, DABCO·(SO2)2 (69) an...
Scheme 33: Proposed mechanism for the preparation of oxindoles 115.
Scheme 34: Three-component reaction of acrylamide 113, CO (23) and 1,4-benzodiazepine 121.
Scheme 35: Multicomponent reaction of sulfonylacrylamides 123, aryldiazonium tetrafluoroborates 68 and DABCO·(...
Scheme 36: Proposed mechanism for the preparation of oxindoles 124.
Scheme 37: Three-component reaction of N-arylpropiolamides 128, aryl iodides 129 and boronic acids 130.
Scheme 38: Proposed mechanism for the formation of diarylmethylene- and diarylallylideneoxindoles 131 and 132.
Scheme 39: Three-component reaction of cyclohexa-1,3-dione (136), amines 2 and alkyl acetylenedicarboxylates 1...
Scheme 40: Proposed mechanism for the formation of 2-oxindoles 138.
Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase
- Robert J. Kempton,
- Taylor A. Kidd-Kautz,
- Soizic Laurenceau and
- Stefan Paula
Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94
- Abstract In this study, we explored Heck- and Suzuki-coupling methodology to modify the template 2,5-di-tert-butylhydroquinone (BHQ, 2), an inhibitor of the enzyme sarco/endoplasmic reticulum calcium ATPase (SERCA). We found that by utilizing Suzuki coupling, we could successfully attach a six-carbon
- convey specificity for prostate cancer cells. Keywords: calcium ATPase inhibitors; Heck- and Suzuki-coupling reactions; hydroquinones; prostate cancer; tethered amino acid; Introduction Sarco/endoplasmic reticulum calcium ATPase (SERCA) is an integral protein that resides in the membrane of the
- at C-8 of TG, replacing the natural butanoyl group at that position with an ester moiety terminating in a primary amine. Here, we describe our efforts to use transition metal cross-coupling reactions (Suzuki [10] and Heck [11]) to modify BHQ with a side chain terminating with a free primary amine
Graphical Abstract
Figure 1: Thapsigargin- and hydroquinone-based SERCA inhibitors.
Scheme 1: Friedel–Crafts alkylation of 4.
Scheme 2: Heck cross-coupling reactions.
Scheme 3: Suzuki approach to a tethered hydroquinone.
The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives
- Tilman Lechel,
- Roopender Kumar,
- Mrinal K. Bera,
- Reinhold Zimmer and
- Hans-Ulrich Reissig
Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61
- . The reduction of OX7 followed by elimination to OX21 proceeded smoothly and as subsequent transformation a Heck reaction with alkenyl nonaflate 10 was performed delivering OX22. The conversion of OX7 to alkyne OX23 applied the protocol of Lyapkalo et al. [59] using Schwesinger’s base [60] as crucial
Graphical Abstract
Scheme 1: Discovery of the LANCA three-component reaction. The reaction of pivalonitrile (1) with lithiated m...
Scheme 2: Proposed mechanism of the LANCA three-component reaction to β-ketoenamides KE and pyridin-4-ol deri...
Scheme 3: One-pot preparation of pyridin-4-ols PY and their subsequent transformations to highly substituted ...
Scheme 4: Synthesis of β-ketoenamides KE by the LANCA three-component reaction of alkoxyallenes, nitriles and...
Scheme 5: β-Ketoenamides KE36–43 derived from enantiopure components.
Scheme 6: Bis-β-ketoenamides KE44–46 derived from aromatic dicarboxylic acids.
Scheme 7: Conversion of alkyl propargyl ethers E into aryl-substituted β-ketoenamides KEAr and selected produ...
Scheme 8: Condensation of LANCA-derived β-ketoenamides KE with ammonium salts to give 5-alkoxy-substituted py...
Scheme 9: Synthesis of PM31–35 from β-ketoenamides KE37, KE38, KE40, KE41 and KE78 obtained by method A (NH4O...
Scheme 10: Synthesis of bis-pyrimidine derivatives PM36, PM39 and PM40 from β-ketoenamides KE44–46 by method A...
Scheme 11: Functionalization of pyrimidine derivatives PM through selenium dioxide oxidations of PM5, PM9, PM15...
Scheme 12: Conversion of 2-vinyl-substituted pyrimidine PM7 into aldehyde PM50; (NMO = N-methylmorpholine N-ox...
Scheme 13: Deprotection of 5-alkoxy-substituted pyrimidines PM2, PM20 and PM29 and conversion into nonaflates ...
Scheme 14: Palladium-catalyzed coupling reactions of PM54 and PM12 giving rise to new pyrimidine derivatives P...
Scheme 15: Synthesis of pyrimidyl-substituted pyridyl nonaflate PM60.
Scheme 16: Condensation of LANCA-derived β-ketoenamides KE with hydroxylamine hydrochloride leading to pyrimid...
Scheme 17: Reactions of β-ketoenamides KE15 and KE7 with hydroxylamine hydrochloride leading to pyrimidine N-o...
Scheme 18: Structures of pyrimidine N-oxides PO30–33 derived from β-ketoenamides KE43, KE45, KE78 and KE80.
Scheme 19: Reduction of PO4 to PM5 and Boekelheide rearrangements of PO13, PO14, PO4 and PO30 to 4-acetoxymeth...
Scheme 20: Deprotection of 4-acetoxymethyl-substituted pyrimidine derivatives PM61 and PM63, oxidations to for...
Scheme 21: Synthesis of pyrimidinyl-substituted alkyne PM74 and conversion into furopyrimidine PM75 and Sonoga...
Scheme 22: Trifluoroacetic acid-promoted conversion of LANCA-derived β-ketoenamides KE into oxazoles OX and 1,...
Scheme 23: Conversion of β-ketoenamide KE79 into oxazole OX16 and transformation into 5-styryl-substituted oxa...
Scheme 24: Mechanisms of the formation of 1,2-diketones DK and of acetyl-substituted oxazole derivatives OX.
Scheme 25: Hydrogenolyses of benzyloxy-substituted β-ketoenamides KE52 and KE54 to 1,2-diketone DK14 and to di...
Scheme 26: Conversions of 2,4-dicyclopropyl-substituted oxazole OX7 into oxazole derivatives OX18–20 (PPA = po...
Scheme 27: Syntheses of vinyl and ethynyl-substituted oxazole derivatives OX21 and OX23 and their palladium-ca...
Scheme 28: Synthesis of C3-symmetric oxazole derivative OX28 and the STM current image of its 1-phenyloctane s...
Scheme 29: Condensation of 1,2-diketones DK with o-phenylenediamine to quinoxalines QU1–7 (CAN = cerium ammoni...
Scheme 30: The LANCA three-component reaction leading to β-ketoenamides KE and the structure of functionalized...
