Search results
Search for "N-heterocycles" in Full Text gives 77 result(s) in Beilstein Journal of Organic Chemistry.
Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom
- Giovanna Zanella,
- Martina Petrović,
- Dina Scarpi,
- Ernesto G. Occhiato and
- Enrique Gómez-Bengoa
Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255
- substrates. Keywords: DFT calculations; gold catalysis; Nazarov reaction; N-heterocycles; Introduction In the development of new and effective catalysts, step economy is surely one of the major goals. A reduction of the number of steps in the synthesis of complex compounds can be attained by cascade
- first step [1][9][10][11][12]. In the framework of our studies on gold(I)-catalyzed reactions of propargyl alcohol derivatives [13][14][15], we have recently reported that the pentannulation of N-heterocycles [16] can be efficiently achieved by a cascade gold-catalyzed [3,3]-rearrangement/Nazarov
- piperidine derivatives 1 because of the accelerating effect of the nitrogen atom that stabilizes the oxyallyl cation intermediate 4 formed upon the ring closure. This was in analogy to that found for the classical Brønsted or Lewis acid-catalyzed Nazarov reaction involving N-heterocycles [27][28][29][30][31
Graphical Abstract
Figure 1: Tandem acetate rearrangement/Nazarov cyclization of different substrates.
Figure 2: DFT-computed energy profile of the tandem Au(I)-catalyzed [3,3]-rearrangement/Nazarov reaction of 3...
Figure 3: DFT-computed energy profile of the tandem Au(I)-catalyzed [3,3]-rearrangement/Nazarov reaction of 2...
Figure 4: Computed comparison of the NBO charges of 2- and 3-substituted substrates.
Figure 5: Single-step transformation of IV to IX.
Figure 6: Triflate-promoted hydrogen abstraction and protodeauration with HOTf.
Figure 7: Triflate-mediated abstraction of the hydrogen atom Ha and protodeauration.
Scheme 1: Synthesis of the enynyl acetate starting material 14.
Scheme 2: Synthesis and cyclization of enynyl acetate 20.
Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation
- Kumar Godugu,
- Venkata Divya Sri Yadala,
- Mohammad Khaja Mohinuddin Pinjari,
- Trivikram Reddy Gundala,
- Lakshmi Reddy Sanapareddy and
- Chinna Gangi Reddy Nallagondu
Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156
- reaction times, and excellent isolated yields. The products do not require chromatographic purification, and the catalyst can be reused seven times. Therefore, the catalyst is a greener alternative for the synthesis of the above N-heterocycles compared to the existing reported catalysts. Keywords
- aforesaid nitrogen-containing heterocycles. Benzimidazoles are an important class of N-heterocycles due to their potential applications in both biology and medicinal chemistry [10][11][12][13]. These compounds are used in the treatment of diseases, such as obesity, ischemia-reperfusion injury, hypertension
- . Further, dolomite is used as a heterogeneous green catalyst in very few organic transformations, such as Knoevenagel, Michael–Henry, and transesterification reactions [73][74]. To the best of our knowledge, there are no reports on the NDL-catalyzed synthesis of aforesaid N-heterocycles under ultrasonic
Graphical Abstract
Figure 1: The benzimidazoles I–IV, dihydropyrimidinones/-thiones V–VIII, and 2-amino-4-aryl-3,5-dicarbonitril...
Scheme 1: NDL-catalyzed synthesis of i) 1,2-disubstituted benzimidazoles 3, ii) dihydropyrimidinones/-thiones ...
Figure 2: XRD pattern of the NDL catalyst.
Figure 3: FTIR spectrum of the NDL catalyst.
Figure 4: Raman spectrum of the NDL catalyst.
Figure 5: SEM images of the NDL catalyst.
Figure 6: EDAX analysis of the NDL catalyst.
Scheme 2: Unexpected formation of the bisimine I, 3h, from o-phenylenediamine (1) and salicylaldehyde (2h).
Figure 7: 1H NMR spectrum of 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis (methanylylidene))diphenol (...
Figure 8: XRD pattern of a) the fresh NDL catalyst; b) the recovered NDL catalyst after the 7th cycle of the ...
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
- et al., allowing the synthesis of N-heterocycles such as indoles and pyrroles. The targeted heterocyclic products were obtained by cyclization of acetanilides with alkyne derivatives via a direct ortho-metalation pathway (Figure 17) [79]. Acetyl substituents acted as DG in this transformation
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.
Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes
- Grzegorz Mlostoń,
- Mateusz Kowalczyk,
- André U. Augustin,
- Peter G. Jones and
- Daniel B. Werz
Beilstein J. Org. Chem. 2020, 16, 1288–1295, doi:10.3762/bjoc.16.109
- )ethylene-1,2-dicarbonitrile (R = CF3) [8]. Both five-membered spirotetrahydrothiophenes 3 and seven-membered S,N-heterocycles (ketene imines) 4 were observed in the course of these reactions (Scheme 1). The latter products were trapped with suitable nucleophiles (R = CO2Me) or even isolated and identified
Graphical Abstract
Scheme 1: Synthesis of spirotetrahydrothiophenes 3 via non-concerted [3 + 2]-cycloadditions of thiocarbonyl y...
Scheme 2: Formal [3 + 2]-cycloadditions of thioketones and [4 + 3]-cycloadditions of thiochalcones with donor...
Scheme 3: Formal [3 + 2]-cycloadditions of dimethyl 2-substituted cyclopropane-1,1-dicarboxylates 5a–g with f...
Figure 1: Thermal ellipsoid plots of the molecular structures of cis-9c and trans-9d drawn using 50% probabil...
Scheme 4: Plausible mechanism for the formal [3 + 2]-cycloadditions of ferrocenyl thioketones 8 with D–A cycl...
Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis
- Stephanie G. E. Amos,
- Marion Garreau,
- Luca Buzzetti and
- Jerome Waser
Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103
- -Acr+ scaffold. In 2015, they developed a site-selective C–H amination of arenes (Scheme 25) [110]. The arenes 25.1 could be aminated by various N-heterocycles 25.2 for the synthesis of the C–H functionalization products 25.3 with fine-tuned Mes-di(t-Bu)Acr+ (OD4) as a photocatalyst. In this
- oxidation of 29.1 was achieved using Mes-Acr-Me+ (OD2) and a cobalt cocatalyst, ensuring an efficient dehydrogenation. Various N-heterocycles 29.3 were accessed via a radical cyclization cascade with the alkyne derivatives 29.2. Amidyl radical generation The oxidation of amides is more difficult compared to
Graphical Abstract
Figure 1: Selected examples of organic dyes. Mes-Acr+: 9-mesityl-10-methylacridinium, DCA: 9,10-dicyanoanthra...
Scheme 1: Activation modes in photocatalysis.
Scheme 2: Main strategies for the formation of C(sp3) radicals used in organophotocatalysis.
Scheme 3: Illustrative example for the photocatalytic oxidative generation of radicals from carboxylic acids:...
Scheme 4: Illustrative example for the photocatalytic reductive generation of C(sp3) radicals from redoxactiv...
Figure 2: Common substrates for the photocatalytic oxidative generation of C(sp3) radicals.
Scheme 5: Illustrative example for the photocatalytic oxidative generation of radicals from dihydropyridines ...
Scheme 6: Illustrative example for the photocatalytic oxidative generation of C(sp3) radicals from trifluorob...
Scheme 7: Illustrative example for the photocatalytic reductive generation of C(sp3) radicals from benzylic h...
Scheme 8: Illustrative example for the photocatalytic generation of C(sp3) radicals via direct HAT: the cross...
Scheme 9: Illustrative example for the photocatalytic generation of C(sp3) radicals via indirect HAT: the deu...
Scheme 10: Selected precursors for the generation of aryl radicals using organophotocatalysis.
Scheme 11: Illustrative example for the photocatalytic reductive generation of aryl radicals from aryl diazoni...
Scheme 12: Illustrative examples for the photocatalytic reductive generation of aryl radicals from haloarenes:...
Scheme 13: Illustrative example for the photocatalytic reductive generation of aryl radicals from aryl halides...
Scheme 14: Illustrative example for the photocatalytic reductive generation of aryl radicals from arylsulfonyl...
Scheme 15: Illustrative example for the reductive photocatalytic generation of aryl radicals from triaryl sulf...
Scheme 16: Main strategies towards acyl radicals used in organophotocatalysis.
Scheme 17: Illustrative example for the decarboxylative photocatalytic generation of acyl radicals from α-keto...
Scheme 18: Illustrative example for the oxidative photocatalytic generation of acyl radicals from acyl silanes...
Scheme 19: Illustrative example for the oxidative photocatalytic generation of carbamoyl radicals from 4-carba...
Scheme 20: Illustrative example of the photocatalytic HAT approach for the generation of acyl radicals from al...
Scheme 21: General reactivity of a) radical cations; b) radical anions; c) the main strategies towards aryl an...
Scheme 22: Illustrative example for the oxidative photocatalytic generation of alkene radical cations from alk...
Scheme 23: Illustrative example for the reductive photocatalytic generation of an alkene radical anion from al...
Figure 3: Structure of C–X radical anions and their neutral derivatives.
Scheme 24: Illustrative example for the photocatalytic reduction of imines and the generation of an α-amino C(...
Scheme 25: Illustrative example for the oxidative photocatalytic generation of aryl radical cations from arene...
Scheme 26: NCR classifications and generation.
Scheme 27: Illustrative example for the photocatalytic reductive generation of iminyl radicals from O-aryl oxi...
Scheme 28: Illustrative example for the photocatalytic oxidative generation of iminyl radicals from α-N-oxy ac...
Scheme 29: Illustrative example for the photocatalytic oxidative generation of iminyl radicals via an N–H bond...
Scheme 30: Illustrative example for the photocatalytic oxidative generation of amidyl radicals from Weinreb am...
Scheme 31: Illustrative example for the photocatalytic reductive generation of amidyl radicals from hydroxylam...
Scheme 32: Illustrative example for the photocatalytic reductive generation of amidyl radicals from N-aminopyr...
Scheme 33: Illustrative example for the photocatalytic oxidative generation of amidyl radicals from α-amido-ox...
Scheme 34: Illustrative example for the photocatalytic oxidative generation of aminium radicals: the N-aryltet...
Scheme 35: Illustrative example for the photocatalytic oxidative generation of nitrogen-centered radical catio...
Scheme 36: Illustrative example for the photocatalytic oxidative generation of nitrogen-centered radical catio...
Scheme 37: Illustrative example for the photocatalytic oxidative generation of hydrazonyl radical from hydrazo...
Scheme 38: Generation of O-radicals.
Scheme 39: Illustrative examples for the photocatalytic generation of O-radicals from N-alkoxypyridinium salts...
Scheme 40: Illustrative examples for the photocatalytic generation of O-radicals from alkyl hydroperoxides: th...
Scheme 41: Illustrative example for the oxidative photocatalytic generation of thiyl radicals from thiols: the...
Scheme 42: Main strategies and reagents for the generation of sulfonyl radicals used in organophotocatalysis.
Scheme 43: Illustrative example for the reductive photocatalytic generation of sulfonyl radicals from arylsulf...
Scheme 44: Illustrative example of a Cl atom abstraction strategy for the photocatalytic generation of sulfamo...
Scheme 45: Illustrative example for the oxidative photocatalytic generation of sulfonyl radicals from sulfinic...
Scheme 46: Illustrative example for the photocatalytic generation of electronically excited triplet states: th...
Scheme 47: Illustrative example for the photocatalytic generation of electronically excited triplet states: th...
Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents
- Yafei Guo and
- Syuzanna R. Harutyunyan
Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90
- oxabicyclic substrates with organolithium reagents (selected examples). Copper-catalysed ring opening of polycyclic meso hydrazines. Copper-catalysed ACA of Grignard reagents to alkenyl-substituted aromatic N-heterocycles. Copper-catalysed ACA of Grignard reagents to β-substituted alkenylpyridines. Copper
Graphical Abstract
Scheme 1: Copper-catalysed ACA of organometallics to piperidones. A) addition of organozinc reagents; B) addi...
Scheme 2: Copper-catalysed ACA of alkenylalanes to N-substituted-2,3-dehydro-4-piperidones.
Scheme 3: Copper-catalysed asymmetric addition of dialkylzinc reagents to N-acyl-4-methoxypyridinium salts fo...
Scheme 4: Copper-catalysed ACA of organozirconium reagents to N-substituted 2,3-dehydro-4-piperidones and lac...
Scheme 5: Copper-catalysed ACA of Grignard reagents to chromones and coumarins and further derivatisation of ...
Scheme 6: Copper-catalysed ACA of Grignard reagents to N-protected quinolones.
Scheme 7: Copper-catalysed ACAs of organometallics to conjugated unsaturated lactams.
Scheme 8: Copper-catalysed ACA of Et2Zn to 5,6-dihydro-2-pyranone.
Scheme 9: Copper-catalysed ACA of Grignard reagents to pyranone and 5,6-dihydro-2-pyranone.
Scheme 10: Copper-catalysed AAA of an organozirconium reagent to heterocyclic acceptors.
Scheme 11: Copper-catalysed ring opening of an oxygen-bridged substrate with trialkylaluminium reagents.
Scheme 12: Copper-catalysed ring opening of oxabicyclic substrates with organolithium reagents (selected examp...
Scheme 13: Copper-catalysed ring opening of polycyclic meso hydrazines.
Scheme 14: Copper-catalysed ACA of Grignard reagents to alkenyl-substituted aromatic N-heterocycles.
Scheme 15: Copper-catalysed ACA of Grignard reagents to β-substituted alkenylpyridines.
Scheme 16: Copper-catalysed ACA of organozinc reagents to alkylidene Meldrum’s acids.
Asymmetric synthesis of CF2-functionalized aziridines by combined strong Brønsted acid catalysis
- Xing-Fa Tan,
- Fa-Guang Zhang and
- Jun-An Ma
Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60
- or fluoroalkyl groups into three-membered N-heterocycles has emerged as an attractive direction due to the unique fluorine effect in pharmaceuticals and biology [7][8][9][10][11]. In this context, it is not surprising that the syntheses of trifluoromethylaziridines have been pursued from versatile
Graphical Abstract
Scheme 1: Preparation of chiral aziridines from fluorinated diazo reagents.
Scheme 2: Substrate scope of chiral CF2-substituted aziridines from PhSO2CF2CHN2. General reaction conditions...
Scheme 3: Scale-up experiment to 4a and further synthetic transformations.
Architecture and synthesis of P,N-heterocyclic phosphine ligands
- Wisdom A. Munzeiwa,
- Bernard Omondi and
- Vincent O. Nyamori
Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35
- , Pietermaritzburg 3201, South Africa 10.3762/bjoc.16.35 Abstract Diverse P,N-phosphine ligands reported to date have performed exceptionally well as auxiliary ligands in organometallic catalysis. Phosphines bearing 2-pyridyl moieties prominently feature in literature as compared to phosphines with five-membered N
- -heterocycles. This discussion seeks to paint a broad picture and consolidate different synthetic protocols and techniques for N-heterocyclic phosphine motifs. The introduction provides an account of P,N-phosphine ligands, and their structural and coordination benefits from combining heteroatoms with different
Graphical Abstract
Scheme 1: Synthesis of pyridylphosphine ligands.
Figure 1: Pyridylphosphine ligands.
Scheme 2: Synthesis of piperidyl- and oxazinylphosphine ligands.
Scheme 3: Synthesis of linear multi-chelate pyridylphosphine ligands.
Scheme 4: Synthesis of chiral acetal pyridylphosphine ligands.
Scheme 5: Synthesis of diphenylphosphine-substituted triazine ligands.
Scheme 6: Synthesis of (pyridine-2-ylmethyl)phosphine ligands.
Scheme 7: Synthesis of diphosphine pyrrole ligands.
Scheme 8: Synthesis of 4,5-diazafluorenylphosphine ligands.
Scheme 9: Synthesis of thioether-containing pyridyldiphosphine ligands starting from ethylene sulfide and dip...
Scheme 10: Synthesis of monoterpene-derived phosphine pyridine ligands.
Scheme 11: Synthesis of N-phenylphosphine-substituted imidazole ligands.
Scheme 12: Synthesis of triazol-4-ylphosphine ligands.
Scheme 13: Synthesis of phosphanyltriazolopyridines and product selectivity depending on the substituents’ eff...
Scheme 14: Synthesis of PTA-phosphine ligands.
Scheme 15: Synthesis of isomeric phosphine dipyrazole ligands by varying the reaction temperature.
Scheme 16: Synthesis of N-tethered phosphine imidazolium ligands (route A) and diphosphine imidazolium ligands...
Scheme 17: Synthesis of {1-[2-(pyridin-2-yl)- (R = CH) and {1-[2-(pyrazin-2-yl)quinazolin-4-yl]naphthalen-2-yl...
Scheme 18: Synthesis of oxazolylindolylphosphine ligands 102.
Scheme 19: Synthesis of pyrrolylphosphine ligands.
Scheme 20: Synthesis of phosphine guanidinium ligands.
Scheme 21: Synthesis of a polydentate aminophosphine ligand.
Scheme 22: Synthesis of quinolylphosphine ligands.
Scheme 23: Synthesis of N-(triazolylmethyl)phosphanamine ligands.
Figure 2: Triazolylphosphanamine ligands synthesized by Wassenaar’s method [22].
Scheme 24: Synthesis of oxazaphosphorines.
Scheme 25: Synthesis of paracyclophane pyridylphosphine ligands.
Scheme 26: Synthesis of triazolylphosphine ligands.
Figure 3: Click-phosphine ligands.
Scheme 27: Ferrocenyl pyridylphosphine imine ligands.
Scheme 28: Synthesis of phosphinooxazolines (PHOX).
Scheme 29: Synthesis of ferrocenylphosphine oxazoles.
Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations
- Rafia Siddiqui and
- Rashid Ali
Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26
- enormous range of applications in biology [121][122][123]. Inspired by other C–H arylation methods for N-heterocycles [124][125][126], recently, Guo and co-workers reported a dual photoredox-catalyzed C–H arylation of 6-arylpurine using photoredox catalyst 12a in the presence of a Pd cocatalyst [127]. With
Graphical Abstract
Figure 1: List of photoredox catalysts used for C–H bond functionalizations.
Figure 2: List of metal-based photoredox catalysts used in this review article.
Figure 3: Jablonski diagram.
Figure 4: Photoredox catalysis via reductive or oxidative pathways. D = donor, A = acceptor, S = substrate, P...
Figure 5: Schematic representation of the combination of photoredox catalysis and transition metal catalysis.
Scheme 1: Weinreb amide C–H olefination.
Figure 6: Mechanism for the formation of 21 from 19 using photoredox catalyst 11.
Scheme 2: C–H olefination of phenolic ethers.
Scheme 3: Decarboxylative acylation of acetanilides.
Figure 7: Mechanism for the formation of 30 from acetanilide derivatives.
Scheme 4: Synthesis of fluorenone derivatives by intramolecular deoxygenative acylation of biaryl carboxylic ...
Figure 8: Mechanism for the photoredox-catalyzed synthesis of fluorenone derivatives.
Scheme 5: Synthesis of benzothiazoles via aerobic C–H thiolation.
Figure 9: Plausible mechanism for the construction of benzothiazoles from benzothioamides.
Scheme 6: Synthesis of benzothiazoles via oxidant-free C–H thiolation.
Figure 10: Mechanism involved in the synthesis of benzothiazoles via oxidant-free C–H thiolation.
Scheme 7: Synthesis of indoles via C–H cyclization of anilides with alkynes.
Scheme 8: Preparation of 3-trifluoromethylcoumarins via C–H cyclization of arylpropiolate esters.
Figure 11: Mechanistic pathway for the synthesis of coumarin derivatives via C–H cyclization.
Scheme 9: Monobenzoyloxylation without chelation assistance.
Figure 12: Plausible mechanism for the formation of 71 from 70.
Scheme 10: Aryl-substituted arenes prepared by inorganic photoredox catalysis using 12a.
Figure 13: Proposed mechanism for C–H arylations in the presence of 12a and a Pd catalyst.
Scheme 11: Arylation of purines via dual photoredox catalysis.
Scheme 12: Arylation of substituted arenes with an organic photoredox catalyst.
Scheme 13: C–H trifluoromethylation.
Figure 14: Proposed mechanism for the trifluoromethylation of 88.
Scheme 14: Synthesis of benzo-3,4-coumarin derivatives.
Figure 15: Plausible mechanism for the synthesis of substituted coumarins.
Scheme 15: Oxidant-free oxidative phosphonylation.
Figure 16: Mechanism proposed for the phosphonylation reaction of 100.
Scheme 16: Nitration of anilines.
Figure 17: Plausible mechanism for the nitration of aniline derivatives via photoredox catalysis.
Scheme 17: Synthesis of carbazoles via intramolecular amination.
Figure 18: Proposed mechanism for the formation of carbazoles from biaryl derivatives.
Scheme 18: Synthesis of substituted phenols using QuCN.
Figure 19: Mechanism for the synthesis of phenol derivatives with photoredox catalyst 8.
Scheme 19: Synthesis of substituted phenols with DDQ (5).
Figure 20: Possible mechanism for the generation of phenols with the aid of photoredox catalyst 5.
Scheme 20: Aerobic bromination of arenes using an acridinium-based photocatalyst.
Scheme 21: Aerobic bromination of arenes with anthraquinone.
Figure 21: Proposed mechanism for the synthesis of monobrominated compounds.
Scheme 22: Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2).
Figure 22: Mechanism for the synthesis of 131 from 132.
Scheme 23: Chlorination of arenes with 4CzIPN (5a).
Figure 23: Plausible mechanism for the oxidative photocatalytic monochlorination using 5a.
Scheme 24: Monofluorination using QuCN-ClO4 (8).
Scheme 25: Fluorination with fluorine-18.
Scheme 26: Aerobic amination with acridinium catalyst 3a.
Figure 24: Plausible mechanism for the aerobic amination using acridinium catalyst 3a.
Scheme 27: Aerobic aminations with semiconductor photoredox catalyst 18.
Scheme 28: Perfluoroalkylation of arenes.
Scheme 29: Synthesis of benzonitriles in the presence of 3a.
Figure 25: Plausible mechanism for the synthesis of substituted benzonitrile derivatives in the presence of 3a....
Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles
- Hoang Huy Do,
- Saif Ullah,
- Alexander Villinger,
- Joanna Lecka,
- Jean Sévigny,
- Peter Ehlers,
- Jamshed Iqbal and
- Peter Langer
Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276
- results were rationalized based on docking studies. Keywords: Buchwald–Hartwig reaction; cyclization; N-heterocycles; palladium; Suzuki–Miyaura reaction; Introduction Furoindoles and their derivatives have received a lot of attention based on their versatile pharmaceutical activities. Furoindols were
Graphical Abstract
Figure 1: Pharmacologically relevant furoindoles.
Scheme 1: Synthesis of benzo[4,5]furo[3,2-b]indoles 5a–j. Conditions: (i) 1.2 equiv 2-bromophenylboronic acid...
Figure 2: Ortep of 5c (propability of ellipsoids: 45%).
Figure 3: Diindolofurans 6a–e.
Figure 4: Illustration of binding poses of selected inhibitors for the ENPP1 homology model: (a): suramin, (b...
Figure 5: 3D poses of docked selected inhibitors inside homology model of ENPP3. (a): suramin, (b): 5e, (c): ...
Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation
- Andreas Boelke,
- Yulia A. Vlasenko,
- Mekhman S. Yusubov,
- Boris J. Nachtsheim and
- Pavel S. Postnikov
Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223
- high Tpeak but also higher ΔHdec values for the latter ones. NHIs bearing N-heterocycles with a high N/C-ratio such as triazoles show among the lowest Tpeak and the highest ΔHdec values. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal
- promising properties in terms of reactivity and stability. However, iodanes stabilized by nitrogen-based ligands, in particular N-heterocycles are still underexplored [22][23][24][25][26][27][28]. Recently, our groups investigated systematically cyclic and pseudocyclic N-heterocycle-stabilized iodanes (NHIs
- ). We demonstrated that the N-heterocycle significantly influences the important I–L1 bond length and subsequently has a profound impact on the reactivity of the iodane in oxygen transfer reactions [29][30]. Since the combination of a highly oxidized hypervalent iodine species with N-heterocycles with a
Graphical Abstract
Figure 1: General structure of aryl-λ3-iodanes.
Figure 2: Tpeak and ΔHdec-values for a range of N- and O-substituted iodanes.
Figure 3: TGA/DSC curves of (a) benziodoxolone 1, (b) triazole 2 and (c) pyrazole 6.
Figure 4: Decomposition enthalpy (ΔHdec) scale for pseudocyclic tosylates 1–15 and cyclic iodoso species 16 a...
Figure 5: Correlation between the relative reactivity for pseudocyclic NHIs based on the reaction time in the...
Figure 6: Tpeak and ΔHdec values for a range of N- and O-substituted iodanes.
Figure 7: Decomposition enthalpy (ΔHdec) scale for (pseudo)cyclic mesitylen(phenyl)- λ3-iodanes 18–33.
Figure 8: TGA/DSC curves for the benzimidazole based diaryliodonium salt 25.
Figure 9: TGA/DSC curves for the cyclic triazole 32.
Scheme 1: The thermal decomposition of (pseudo)cyclic N-heterocycle-stabilized mesityl(aryl)-λ3-iodanes 25 an...
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
- ]. Additionally, a diverse range of N-heterocycles, amides and motifs commonly encountered in medicinal chemistry were used as handles to direct C–H fluorination for the synthesis of pharmaceutical drugs (Scheme 24) [25]. Copper catalysis Despite the success of Pd-catalyzed fluorinations, the more widespread use
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.
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
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.
Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts
- Grzegorz Mlostoń,
- Małgorzata Celeda,
- Katarzyna Urbaniak,
- Marcin Jasiński,
- Vladyslav Bakhonsky,
- Peter R. Schreiner and
- Heinz Heimgartner
Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43
- ; nucleophilic carbenes; sulfur transfer reaction; Introduction Imidazole N-oxides constitute a practically valuable class of five-membered aromatic N-heterocycles [1][2][3][4][5]. The subclass of 2-unsubstituted imidazole N-oxides 1 with diverse substituents located at N(1), C(4), and C(5) is of special
- in monomeric form in the case of sterically crowded parent amines such as 1-aminoadamantane or tert-butylamine or, alternatively, as trimeric hexahydro-1,3,5-triazines 3’ in the case of sterically less crowded amines [7]. In analogy to other azoles and in contrast to six-membered aromatic N
- -heterocycles, N-oxides 1 cannot be prepared via oxidation of the parent imidazoles by treatment with an oxidizing agent, e.g., with a percarboxylic acid [6]. Imidazole N-oxides are versatile substrates for the preparation of diverse imidazole derivatives and the most characteristic feature is their 1,3-dipolar
Graphical Abstract
Scheme 1: Synthesis of 2-unsubstituted imidazole N-oxides 1 from α-hydroxyiminoketones 2 and formaldimines 3.
Scheme 2: Preparation of adamantyloxyamine (4) and its conversion into N-(adamantyloxy)formaldimine (6a); Ad ...
Scheme 3: Synthesis of 1-(adamantyloxy)imidazole 3-oxides 7a–e and 1-adamantylimidazole 3-oxides 7f,g in acet...
Scheme 4: Deoxygenation of 1-(adamantyloxy)imidazole 3-oxides 7a–d and isomerization of 7b into imidazole-2-o...
Scheme 5: Conversions of imidazole 3-oxides 7a–d into 1-(adamantyloxy)imidazole-2-thiones 10a–d via sulfur tr...
Scheme 6: Syntheses of the non-symmetric 1,3-dialkoxyimidazolium bromides 13a–c and 1-alkyl-3-alkoxyimidazoli...
Scheme 7: Attempted O-adamantylation of imidazole N-oxide 7a with adamantan-1-yl trifluoroacetate and subsequ...
Scheme 8: Synthesis of the symmetric 1,3-di(adamantyloxy)imidazolium bromide (15) and its transformation to 1...
Molecular iodine-catalyzed one-pot multicomponent synthesis of 5-amino-4-(arylselanyl)-1H-pyrazoles
- Camila S. Pires,
- Daniela H. de Oliveira,
- Maria R. B. Pontel,
- Jean C. Kazmierczak,
- Roberta Cargnelutti,
- Diego Alves,
- Raquel G. Jacob and
- Ricardo F. Schumacher
Beilstein J. Org. Chem. 2018, 14, 2789–2798, doi:10.3762/bjoc.14.256
- -phenylselanyl-1H-pyrazoles through reaction of α,β-alkynic hydrazones with phenylselenyl chloride [11]. In this context, pyrazoles are one of the most important N-heterocycles found in natural products including formycin, pyrazofurin and withasomnine, for example. Still, pyrazole unities are present in several
- antidepressive activity [14][15][16][17]. Moreover, they have been extensively used as synthons to prepare a wide variety of fused N-heterocycles of synthetic and pharmacological importance [18][19][20]. Thus, an effective strategy for the design and the preparation of new pharmacologically promising drugs that
Graphical Abstract
Scheme 1: Synthesis of selanyl-pyrazoles and their derivatives previously described.
Scheme 2: Multicomponent reaction proposed in this work.
Scheme 3: Direct selanylation reaction of 5-amino-pyrazole 5a with diphenyl diselenide (3a) under the optimiz...
Scheme 4: Proposed reaction mechanism.
Scheme 5: Synthesis of diazo pyrazole derivative 6.
Figure 1: Molecular structure of compound 6. The hydrogen atoms are omitted for clarity [27].
A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines
- Katherine E. Jolley,
- Michael R. Chapman and
- A. John Blacker
Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196
- are known to react with N-haloamines to form aziridines and other N-heterocycles. Typically, the reactions require a catalyst (e.g., Cu, I2) [17][18][27], whilst more active reagents such as chloramine-T with osmate catalysts have been used to make 1,2-aminoalcohols and diamines [28][29][30][31][32
Graphical Abstract
Figure 1: Continuous-flow process to produce and react N-chloramines.
Figure 2: Left: Laboratory scale CSTR developed by our group [8]. Right: 5-stage CSTR configuration using co-fee...
Figure 3: Continuous-flow amide 18 formation using 1-stage CSTR. Blue squares: FeCl3 included; red circles: F...
Scheme 1: Continuous-flow transfer hydrogenation of in situ generated imines.
β-Hydroxy sulfides and their syntheses
- Mokgethwa B. Marakalala,
- Edwin M. Mmutlane and
- Henok H. Kinfe
Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143
- enantioselectivities (Scheme 14) [44]. The reaction was also found to be compatible with aromatic N-heterocycles and alcohol nucleophiles to afford the corresponding products in moderate to good yields with high to excellent enantioselectivities [44]. The use of water as a solvent by Kobayashi and co-workers is
Graphical Abstract
Figure 1: Some sulfur-containing natural products.
Figure 2: Some natural products incorporating β-hydroxy sulfide moieties.
Figure 3: Some synthetic β-hydroxy sulfides of clinical value.
Scheme 1: Alumina-mediated synthesis of β-hydroxy sulfides, ethers, amines and selenides from epoxides.
Scheme 2: β-Hydroxy sulfide syntheses by ring opening of epoxides under different Lewis and Brønsted acid and...
Scheme 3: n-Bu3P-catalyzed thiolysis of epoxides and aziridines to provide the corresponding β-hydroxy and β-...
Scheme 4: Zinc(II) chloride-mediated thiolysis of epoxides.
Scheme 5: Thiolysis of epoxides and one-pot oxidation to β-hydroxy sulfoxides under microwave irradiation.
Scheme 6: Gallium triflate-catalyzed ring opening of epoxides and one-pot oxidation.
Scheme 7: Thiolysis of epoxides and one-pot oxidation to β-hydroxy sulfoxides using Ga(OTf)3 as a catalyst.
Scheme 8: Ring opening of epoxide using ionic liquids under solvent-free conditions.
Scheme 9: N-Bromosuccinimide-catalyzed ring opening of epoxides.
Scheme 10: LiNTf2-mediated epoxide opening by thiophenol.
Scheme 11: Asymmetric ring-opening of cyclohexene oxide with various thiols catalyzed by zinc L-tartrate.
Scheme 12: Catalytic asymmetric ring opening of symmetrical epoxides with t-BuSH catalyzed by (R)-GaLB (43) wi...
Scheme 13: Asymmetric ring opening of meso-epoxides by p-xylenedithiol catalyzed by a (S,S)-(salen)Cr complex.
Scheme 14: Desymmetrization of meso-epoxide with thiophenol derivatives.
Scheme 15: Enantioselective ring-opening reaction of meso-epoxides with ArSH catalyzed by a C2-symmetric chira...
Scheme 16: Enantioselective ring-opening reaction of stilbene oxides with ArSH catalyzed by a C2-symmetric chi...
Scheme 17: Asymmetric desymmetrization of meso-epoxides using BINOL-based Brønsted acid catalysts.
Scheme 18: Lithium-BINOL-phosphate-catalyzed desymmetrization of meso-epoxides with aromatic thiols.
Scheme 19: Ring-opening reactions of cyclohexene oxide with thiols by using CPs 1-Eu and 2-Tb.
Scheme 20: CBS-oxazaborolidine-catalyzed borane reduction of β-keto sulfides.
Scheme 21: Preparation of β-hydroxy sulfides via connectivity.
Scheme 22: Baker’s yeast-catalyzed reduction of sulfenylated β-ketoesters.
Scheme 23: Sodium-mediated ring opening of epoxides.
Scheme 24: Disulfide bond cleavage-epoxide opening assisted by tetrathiomolybdate.
Scheme 25: Proposed reaction mechanism of disulfide bond cleavage-epoxide opening assisted by tetrathiomolybda...
Scheme 26: Cyclodextrin-catalyzed difunctionalization of alkenes.
Scheme 27: Zinc-catalyzed synthesis of β-hydroxy sulfides from disulfides and alkenes.
Scheme 28: tert-Butyl hydroperoxide-catalyzed hydroxysulfurization of alkenes.
Scheme 29: Proposed mechanism of the radical hydroxysulfurization.
Scheme 30: Rongalite-mediated synthesis of β-hydroxy sulfides from styrenes and disulfides.
Scheme 31: Proposed mechanism of Rongalite-mediated synthesis of β-hydroxy sulfides from styrenes and disulfid...
Scheme 32: Copper(II)-catalyzed synthesis of β-hydroxy sulfides 15e,f from alkenes and basic disulfides.
Scheme 33: CuI-catalyzed acetoxysulfenylation of alkenes.
Scheme 34: CuI-catalyzed acetoxysulfenylation reaction mechanism.
Scheme 35: One-pot oxidative 1,2-acetoxysulfenylation of Baylis–Hillman products.
Scheme 36: Proposed mechanism for the oxidative 1,2-acetoxysulfination of Baylis–Hillman products.
Scheme 37: 1,2-Acetoxysulfenylation of alkenes using DIB/KI.
Scheme 38: Proposed reaction mechanism of the diacetoxyiodobenzene (DIB) and KI-mediated 1,2-acetoxysulfenylat...
Scheme 39: Catalytic asymmetric thiofunctionalization of unactivated alkenes.
Scheme 40: Proposed catalytic cycle for asymmetric sulfenofunctionalization.
Scheme 41: Synthesis of thiosugars using intramolecular thiol-ene reaction.
Scheme 42: Synthesis of leukotriene C-1 by Corey et al.: (a) N-(trifluoroacetyl)glutathione dimethyl ester (3 ...
Scheme 43: Synthesis of pteriatoxins with epoxide thiolysis to attain β-hydroxy sulfides. Reagents: (a) (1) K2...
Scheme 44: Synthesis of peptides containing a β-hydroxy sulfide moiety.
Scheme 45: Synthesis of diltiazem (12) using biocatalytic resolution of an epoxide followed by thiolysis.
Atom-economical group-transfer reactions with hypervalent iodine compounds
- Andreas Boelke,
- Peter Finkbeiner and
- Boris J. Nachtsheim
Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108
- atom-economical biphenylation of N-heterocycles was developed [33]. This method involved a direct N-arylation of pyrazoles or triazoles 12 under basic conditions, followed by a ruthenium-catalysed C–H arylation with the emerging aryl iodide (Scheme 8). Due to the fact that the first step of this
- dithiocarbamates 7 and 7’ from one equivalent of diaryliodonium salt 1. Synthesis of substituted isoindolin-1-ones 9 from 2-formylbenzonitrile 8 and the postulated reaction mechanism. Domino C-/N-arylation of indoles 10. Domino modification of N-heterocycles 12 via in situ-generated directing groups. Synthesis of
Graphical Abstract
Scheme 1: Overview of different types of iodane-based group-transfer reactions and their atom economy based o...
Scheme 2: (a) Structure of diaryliodonium salts 1. (b) Diarylation of a suitable substrate A with one equival...
Scheme 3: Synthesis of biphenyls 3 and 3’ with symmetrical diaryliodonium salts 1.
Scheme 4: Synthesis of diaryl thioethers 5.
Scheme 5: Synthesis of two distinct S-aryl dithiocarbamates 7 and 7’ from one equivalent of diaryliodonium sa...
Scheme 6: Synthesis of substituted isoindolin-1-ones 9 from 2-formylbenzonitrile 8 and the postulated reactio...
Scheme 7: Domino C-/N-arylation of indoles 10.
Scheme 8: Domino modification of N-heterocycles 12 via in situ-generated directing groups.
Scheme 9: Synthesis of triarylamines 17 through a double arylation of anilines.
Scheme 10: Selective conversion of novel aryl(imidazolyl)iodonium salts 1b to 1,5-disubstituted imidazoles 18.
Scheme 11: Selected examples for the application of cyclic diaryliodonium salts 19.
Scheme 12: Tandem oxidation–arylation sequence with (dicarboxyiodo)benzenes 20.
Scheme 13: Oxidative α-arylation via the transfer of an intact 2-iodoaryl group.
Scheme 14: Tandem ortho-iodination/O-arylation cascade with PIDA derivatives 20b.
Scheme 15: Synthesis of meta-N,N-diarylaminophenols 28 and the postulated mechanism.
Scheme 16: (Dicarboxyiodo)benzene-mediated metal-catalysed C–H amination and arylation.
Scheme 17: Postulated mechanism for the amination–arylation sequence.
Scheme 18: Auto-amination and cross-coupling of PIDA derivatives 20c.
Scheme 19: Tandem C(sp3)–H olefination/C(sp2)–H arylation.
Scheme 20: Atom efficient functionalisations with benziodoxolones 36.
Scheme 21: Atom-efficient synthesis of furans 39 from benziodoxolones 36a and their further derivatisations.
Scheme 22: Oxyalkynylation of diazo compounds 42.
Scheme 23: Enantioselective oxyalkynylation of diazo compounds 42’.
Scheme 24: Iron-catalysed oxyazidation of enamides 45.
Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue
- Romain Sallio,
- Stéphane Lebrun,
- Frédéric Capet,
- Francine Agbossou-Niedercorn,
- Christophe Michon and
- Eric Deniau
Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46
- incorporate α-methylbenzylamine-type chiral auxiliaries, which have been extensively used by Davies et al. to gain access to a wide range of chiral N-heterocycles via intermolecular aza-Michael reactions [34][47][48][49][50][51]. The starting unsaturated benzoic acids 14a–e and 15 were readily prepared via a
Graphical Abstract
Figure 1: Examples of synthetic pharmacologically active chiral 3-substituted isoindolinones.
Scheme 1: Retrosynthetic analysis of NH free chiral 3-substituted isoindolinones (3S)-1 and (3S)-2.
Scheme 2: Synthesis of parent benzamides 6–8.
Figure 2: Esters 12a–e, 13 prepared, isolated yield.
Figure 3: Benzamides 6a–d, 7a–e, 8 prepared, isolated yield.
Figure 4: Phase transfer catalysts (PTC) used in this study.
Scheme 3: Synthesis of isoindolinones 3a–d, 4a–e, 5; isolated yield, de by HPLC and 1H NMR. aAfter flash chro...
Scheme 4: Removal of the chiral auxiliary. Synthesis of isoindolinones 1a–c, 1e, 2; isolated yield, ee by HPL...
Figure 5: ORTEP plot of isoindolinone (2R,3S)-3a (CCDC 1590565) [68].
Scheme 5: Synthesis of pazinaclone analogue (3S)-27.
Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline
- Benedikt C. Melzer,
- Jan G. Felber and
- Franz Bracher
Beilstein J. Org. Chem. 2018, 14, 130–134, doi:10.3762/bjoc.14.8
- of the direct methylation of electron-deficient N-heterocycles have been reviewed [9]. In a project aimed at the synthesis of tri- and tetracylic alkaloids containing the isoquinoline scaffold, we were interested in isoquinoline building blocks which bear a methyl group at C1, since this group should
Graphical Abstract
Figure 1: Previously published total syntheses of alkaloid 1 [11,12].
Scheme 1: Total synthesis of alkaloid 1 via direct ring metalation and methylation.
Scheme 2: Total synthesis of alkaloid 1 via the aminomethyl intermediate 5 and selectivity’s found in debenzy...
Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole
- Martina Tireli,
- Silvija Maračić,
- Stipe Lukin,
- Marina Juribašić Kulcsár,
- Dijana Žilić,
- Mario Cetina,
- Ivan Halasz,
- Silvana Raić-Malić and
- Krunoslav Užarević
Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232
- synthesis of 5–8 Based on the recently obtained 1,2,3-triazole-appended N-heterocycles, as promising lead compounds with efficient and selective cytostatic activities [8][9], our research groups share an interest in derivatization of target compounds by a triazole bridge [33]. Quinoline is an important
Graphical Abstract
Scheme 1: Synthetic procedures for preparation of p-halogen-substituted and non-substituted phenyl-1,2,3-tria...
Figure 1: Experimental Raman spectra of the alkyne 4 and triazole products 5–8. Bands attributed to the vibra...
Figure 2: In situ Raman monitoring of a) mechanochemical formation of triazole 5 using copper(II) acetate mon...
Figure 3: a) In situ Raman monitoring for mechanochemical synthesis of 5 using brass balls and PMMA reaction ...
Figure 4: ESR spectra of samples obtained after milling by methods 2a (black), 2b (red) and 2c (blue). The in...
Figure 5: X-ray structure of the triazole compounds. (a) Molecular structure of 5, with the atom-numbering sc...
Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains
- Layal Hariss,
- Kamal Bou Hadir,
- Mirvat El-Masri,
- Thierry Roisnel,
- René Grée and
- Ali Hachem
Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208
- , Lebanon Université de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226, Avenue du Général Leclerc, 35042 Rennes Cedex, France 10.3762/bjoc.13.208 Abstract Using an aerobic oxidative coupling, different new imidazo[1,2-a]-N-heterocycles with gem-difluroroalkyl side chains have been
- coupling reactions as well as nucleophilic substitutions have been performed successfully in order to increase the molecular diversity. Keywords: aerobic oxidative coupling; imidazo[1,2-a]-N-heterocycles; gem-difluoroalkyl derivatives; propargylic fluorides; Introduction Nitrogen-containing heterocyclic
- fluorinated propargylic derivatives [21]. Thus, taking into account the known biological properties of the imidazo-fused N-heterocycles, we became interested in the preparation of new derivatives of this type possessing gem-difluorinated side chains as indicated in Figure 1. Such new fluorinated heterocycles
Graphical Abstract
Figure 1: Representative examples of bioactive imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, imidazopyr...
Scheme 1: Retrosynthetic scheme for the preparation of our target molecules A.
Scheme 2: Synthesis of enones 6 with a gem-difluoroalkyl side chain.
Scheme 3: Synthesis of 7a.
Figure 2: Structures of 7a and 7e by X-ray crystallography analysis.
Scheme 4: One-pot synthesis of 7a.
Pd(OAc)2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles
- Dominik Kellner,
- Maximilian Weger,
- Andrea Gini and
- Olga García Mancheño
Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175
- - and N-heterocycles The different dimers of isoprene can be transformed into a large number of derivatives such as terpene-alcohols or ethers [38]. Moreover, some isoprene dimers have been submitted to Diels–Alder reactions with olefins such as maleic acid anhydride or methacrolein to form products
- isoprene. Functionalization of the isoprene-dimer 2-TT to substituted O- and N-heterocycles. Optimization of the dimerization reaction of isoprene.a Supporting Information Supporting Information File 244: 1H NMR and 13C NMR spectra collection of the products and GC–FID analysis of the isoprene dimer’s
Graphical Abstract
Figure 1: Isoprene as chemical building block in nature and organic synthesis.
Scheme 1: Pd-catalyzed dimerization of isoprene.
Scheme 2: Putative mechanism for the Pd(OAc)2-catalyzed dimerization of isoprene.
Scheme 3: Functionalization of the isoprene-dimer 2-TT to substituted O- and N-heterocycles.
Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds
- Santanu Hati,
- Ulrike Holzgrabe and
- Subhabrata Sen
Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162
- ]. Encouraged by these results a variety of functionalized N-heterocycles were oxidatively dehydrogenated with IBX, to afford their aromatic counterpart. For example imidazoles 11, dihydroisoquinoline 12, pyridine 13, and pyrrole 14 were obtained from their corresponding heterocyclic precursors 7–10 in
- dehydrogenation of N-heterocycles [31][32][33][34]. IBX-mediated room temperature one-pot condensation–oxidative dehydrogenation of o-aminobenzylamines. Anhydrous cerium chloride-catalyzed, IBX-mediated oxidative dehydrogenation of various heterocycles at room temperature. Oxidative dehydrogenation of
Graphical Abstract
Figure 1: Representative bioactive heterocycles.
Scheme 1: The concept of oxidative dehydrogenation.
Scheme 2: IBX-mediated oxidative dehydrogenation of various heterocycles [31-34].
Scheme 3: Potential mechanism of IBX-mediated oxidative dehydrogenation of N-heterocycles [31-34].
Scheme 4: IBX-mediated room temperature one-pot condensation–oxidative dehydrogenation of o-aminobenzylamines....
Scheme 5: Anhydrous cerium chloride-catalyzed, IBX-mediated oxidative dehydrogenation of various heterocycles...
Scheme 6: Oxidative dehydrogenation of quinazolinones with I2 and DDQ [37-40].
Scheme 7: DDQ-mediated oxidative dehydrogenation of thiazolidines and oxazolidines.
Scheme 8: Oxone-mediated oxidative dehydrogenation of intermediates from o-phenylenediamine and o-aminobenzyl...
Scheme 9: Transition metal-free oxidative cross-dehydrogenative coupling.
Scheme 10: NaOCl-mediated oxidative dehydrogenation.
Scheme 11: NBS-mediated oxidative dehydrogenation of tetrahydro-β-carbolines.
Scheme 12: One-pot synthesis of various methyl(hetero)arenes from o-aminobenzamide in presence of di-tert-buty...
Scheme 13: Oxidative dehydrogenation of 1, 4-DHPs.
Scheme 14: Synthesis of quinazolines in the presence of MnO2.
Scheme 15: Selenium dioxide and potassium dichromate-mediated oxidative dehydrogenation of tetrahydro-β-carbol...
Scheme 16: Synthesis of substituted benzazoles in the presence of barium permanganate.
Scheme 17: Oxidative dehydrogenation with phenanthroline-based catalysts. PPTS = pyridinium p-toluenesulfonic ...
Scheme 18: Oxidative dehydrogenation with Flavin mimics.
Scheme 19: o-Quinone based bioinspired catalysts for the synthesis of dihydroisoquinolines.
Scheme 20: Cobalt-catalyzed aerobic dehydrogenation of Hantzch 1,4-DHPs and pyrazolines.
Scheme 21: Mechanism of cobalt-catalyzed aerobic dehydrogenation of Hantzch 1,4-DHPs.
Scheme 22: DABCO and TEMPO-catalyzed aerobic oxidative dehydrogenation of quinazolines and 4H-3,1-benzoxazines....
Scheme 23: Putative mechanism for Cu(I)–DABCO–TEMPO catalyzed aerobic oxidative dehydrogenation of tetrahydroq...
Scheme 24: Potassium triphosphate modified Pd/C catalysts for the oxidative dehydrogenation of tetrahydroisoqu...
Scheme 25: Ruthenium-catalyzed polycyclic heteroarenes.
Scheme 26: Plausible mechanism of the ruthenium-catalyzed dehydrogenation.
Scheme 27: Bi-metallic platinum/iridium alloyed nanoclusters and 5,5’,6,6’-tetrahydroxy-3,3,3’,3’-tetramethyl-...
Scheme 28: Magnesium iodide-catalyzed synthesis of quinazolines.
Scheme 29: Ferrous chloride-catalyzed aerobic dehydrogenation of 1,2,3,4-tetrahydroquinolines.
Scheme 30: Cu(I)-catalyzed oxidative aromatization of indoles.
Scheme 31: Putative mechanism of the transformation.
Scheme 32: Oxidative dehydrogenation of pyrimidinones and pyrimidines.
Scheme 33: Putative mechanisms (radical and metal-catalyzed) of the transformation.
Scheme 34: Ferric chloride-catalyzed, TBHP-oxidized synthesis of substituted quinazolinones and arylquinazolin...
Scheme 35: Iridium-catalyzed oxidative dehydrogenation of quinolines.
Scheme 36: Microwave-assisted synthesis of β-carboline with a catalytic amount of Pd/C in lithium carbonate at...
Scheme 37: 4-Methoxy-TEMPO-catalyzed aerobic oxidative synthesis of 2-substituted benzazoles.
Scheme 38: Plausible mechanism of the 4-methoxy-TEMPO-catalyzed transformation.
Scheme 39: One-pot synthesis of 2-arylquinazolines, catalyzed by 4-hydroxy-TEMPO.
Scheme 40: Oxidative dehydrogenation – a key step in the synthesis of AZD8926.
Scheme 41: Catalytic oxidative dehydrogenation of tetrahydroquinolines to afford bioactive molecules.
Scheme 42: Iodobenzene diacetate-mediated synthesis of β-carboline natural products.
N-Propargylamines: versatile building blocks in the construction of thiazole cores
- S. Arshadi,
- E. Vessally,
- L. Edjlali,
- R. Hosseinzadeh-Khanmiri and
- E. Ghorbani-Kalhor
Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61
- biologically important compounds. Keywords: 6-endo-dig cyclization; 5-exo-dig cyclization; N-heterocycles; N-propargylamines; thiazoles; Introduction Thiazoles are an important class of azole compounds that have attracted considerable attention due to the fact that they exhibit a wide variety of
- patterns. It is well known that they can undergo a number of cyclization reactions to produce various N-heterocycles and complex natural products. In this context we recently reviewed their role in the syntheses of pyrrole [65], pyridine [66], quinoline [67], pyrazine [68], 1,4-oxazepane, and 1,4-diazepane
Graphical Abstract
Figure 1: Selected examples of bioactive thiazole derivatives.
Figure 2: Some natural sources of thiazoles.
Figure 3: Some important thiazole-based compounds derived from N-propargylamines.
Scheme 1: The synthesis of thiazole-2-thiones 3 through the thermal cyclocondensation of N-propargylamines 1 ...
Scheme 2: (a) One-pot synthesis of 2-benzylthiazolo[3,2-a]benzimidazoles 6 through a base-catalyzed cascade r...
Scheme 3: (a) Synthesis of 2-iminothiazolidines 11 from N-propargylamines 9 and isothiocyanates 10. (b) Synth...
Scheme 4: (a) Synthesis of 2-aminothiazoles 17 through the reaction of ethyl 4-aminobut-2-ynoate salts 15 wit...
Scheme 5: Synthesis of 5-(iodomethylene)-3-methylthiazolidines 27 described by Zhou.
Scheme 6: Mechanism that accounts for the formation of 27.
Scheme 7: Clausen’s synthesis of fluorescein thiazolidines 30.
Scheme 8: Synthesis of multiply substituted thiazolidines 33 from N-propargylamines 32 and blocked N-isothioc...
Scheme 9: (a) Microwave-assisted cyclization of N-propargyl thiocarbamate 34. (b) Synthesis of thiazoles 39 t...
Scheme 10: Synthesis of thiazolidines 42 (42’) from the reaction of β-oxodithioesters 40 (40’) with N-propargy...
Scheme 11: Synthesis of 5-(dibromomethyl)thiazoles 44 via halocyclization of N-propargylamines 43 described by...
Scheme 12: Synthesis of dihydrothiazoles 46 through the treatment of N-propargylamides 45 with Lawesson’s reag...
Scheme 13: Synthesis of thiazoles 49 by treatment of silyl-protected N-propargylamines 47 with benzotriazolylt...
Scheme 14: Mechanism proposed to explain the synthesis of 2,5-disubstituted thiazoles 49 developed by Sasmal.
Scheme 15: Mo-catalyzed cyclization of N-propargylthiocarbamate 50.
Scheme 16: (a) DABCO-mediated intramolecular cyclization of N-(propargylcarbamothioyl)amides 53 to the corresp...
Scheme 17: Proposed mechanism for the generation of the iodine-substituted 4H-1,3-thiazines 56 and 4,5-dihydro...
Scheme 18: Au(III)-catalyzed synthesis of 5-alkylidenedihydrothiazoles 58 developed by Stevens.
