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Search for "amidation" in Full Text gives 131 result(s) in Beilstein Journal of Organic Chemistry.
Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review
- Nosheen Beig,
- Varsha Goyal and
- Raj K. Bansal
Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102
- carboxylation, C(sp2)–H alkenylation and allylation, C(sp2)–H arylation, C(sp2)–H amidation, and C(sp2)–H thiolation. Preceding the section of applications, a brief description of the structure of NHCs, nature of NHC–metal bond, and methods of preparation of NHC–Cu complexes is provided. Keywords: conjugate
- conversion occurred using either Pd–NHC or Cu–NHC alone. 2.9 C(sp2)–H amidation Chang and co-workers [96] reported an NHC–Cu-catalyzed direct amidation of C–H bonds by using N-chlorocarbamates or N-chloro-N-sodiocarbamates as amino source. In this mechanism, a copper–aryl intermediate reacts with the
- amidating reagent leading to the isolation of copper–arylcarbamato species and the desired product. The developed amidation protocol works highly efficiently and selectively over a broad range of substrates including polyfluorobenzenes, azoles, and quinoline N-oxides (Scheme 74). 2.10 C(sp2)–H thiolation
Graphical Abstract
Scheme 1: In situ generation of imidazolylidene carbene.
Scheme 2: Hg(II) complex of NHC.
Scheme 3: Isolable and bottlable carbene reported by Arduengo [3].
Scheme 4: First air-stable carbene synthesized by Arduengo in 1992 [5].
Figure 1: General structure of an NHC.
Figure 2: Stabilization of an NHC by donation of the lone pair electrons into the vacant p-orbital (LUMO) at ...
Figure 3: Abnormal NHC reported by Bertrand [8,9].
Figure 4: Cu(d) orbital to σ*C-N(NHC) interactions in NHC–CuX complexes computed at the B3LYP/def2-SVP level ...
Figure 5: Molecular orbital contributions to the NHC–metal bond.
Scheme 5: Synthesis of NHC–Cu(I) complexes by deprotonation of NHC precursors with a base.
Scheme 6: Synthesis of [NHC–CuX] complexes.
Scheme 7: Synthesis of [(ICy)CuX] and [(It-Bu)CuX] complexes.
Scheme 8: Synthesis of iodido-bridged copper–NHC complexes by deprotonation of benzimidazolium salts reported...
Scheme 9: Synthesis of copper complexes by deprotonation of triazolium salts.
Scheme 10: Synthesis of thiazolylidene–Cu(I) complex by deprotonation with KOt-Bu.
Scheme 11: Preparation of NHC–Cu(I) complexes.
Scheme 12: Synthesis of methylmalonic acid-derived anionic [(26a,b)CuCl]Li(THF)2 and zwitterionic (28) heterol...
Scheme 13: Synthesis of diaminocarbene and diamidocarbene (DAC)–Cu(I) complexes.
Scheme 14: Synthesis of the cationic (NHC)2Cu(I) complex 39 from benzimidazolium salts 38 with tetrakis(aceton...
Scheme 15: Synthesis of NHC and ADC (acyclic diamino carbenes) Cu(I) hexamethyldisilazide complexes reported b...
Scheme 16: Synthesis of NHC–copper(I) complexes using an acetylacetonate-functionalized imidazolium zwitterion...
Scheme 17: Synthesis of NHC–Cu(I) complexes through deprotonation of azolium salts with Cu2O.
Scheme 18: Synthesis of NHC–CuBr complex through deprotonation with Cu2O reported by Kolychev [31].
Scheme 19: Synthesis of chiral NHC–CuBr complexes from phenoxyimine-imidazolium salts reported by Douthwaite a...
Scheme 20: Preparation of linear neutral NHC–CuCl complexes through the use of Cu2O. For abbreviations, please...
Scheme 21: Synthesis of abnormal-NHC–copper(I) complexes by Bertrand, Cazin and co-workers [35].
Scheme 22: Microwave-assisted synthesis of thiazolylidene/benzothiazolylidene–CuBr complexes by Bansal and co-...
Scheme 23: Synthesis of NHC–CuX complexes through transmetallation.
Scheme 24: Preparation of six- or seven-membered NHC–Cu(I) complexes through transmetalation from Ag(I) comple...
Scheme 25: Synthesis of 1,2,3-triazolylidene–CuCl complexes through transmetallation of Ag(I) complexes genera...
Scheme 26: Synthesis of NHC–copper complexes having both Cu(I) and Cu(II) units through transmetalation report...
Scheme 27: Synthesis of new [(IPr(CH2)3Si(OiPr)3)CuX] complexes and anchoring on MCM-41.
Scheme 28: Synthesis of bis(trimethylsilyl)phosphide–Cu(I)–NHC complexes through ligand displacement.
Scheme 29: Synthesis of silyl- and stannyl [(NHC)Cu−ER3] complexes.
Scheme 30: Synthesis of amido-, phenolato-, thiophenolato–Cu(NHC) complexes.
Scheme 31: Synthesis of first isolable NHC–Cu–difluoromethyl complexes reported by Sanford et al. [44].
Scheme 32: Synthesis of NHC–Cu(I)–bifluoride complexes reported by Riant, Leyssens and co-workers [45].
Scheme 33: Conjugate addition of Et2Zn to enones catalyzed by an NHC–Cu(I) complex reported by Woodward in 200...
Scheme 34: Hydrosilylation of a carbonyl group.
Scheme 35: NHC–Cu(I)-catalyzed hydrosilylation of ketones reported by Nolan et al. [48,49].
Scheme 36: Application of chiral NHC–CuCl complex 104 for the enantioselective hydrosilylation of ketones.
Scheme 37: Hydrosilylation reactions catalyzed by NHC–Cu(Ot-Bu) complexes.
Scheme 38: NHC–CuCl catalyzed carbonylative silylation of alkyl halides.
Scheme 39: Nucleophilic conjugate addition to an activated C=C bond.
Figure 6: Molecular electrostatic potential maps (MESP) of two NHC–CuX complexes computed at the B3LYP/def2-S...
Scheme 40: Conjugate addition of Grignard reagents to 3-alkyl-substituted cyclohexenones catalyzed by a chiral...
Scheme 41: NHC–copper complex-catalyzed conjugate addition of Grignard reagent to 3-substituted hexenone repor...
Scheme 42: Conjugate addition or organoaluminum reagents to β-substituted cyclic enones.
Scheme 43: Conjugate addition of boronates to acyclic α,β-unsaturated carboxylic esters, ketones, and thioeste...
Scheme 44: NHC–Cu(I)-catalyzed hydroboration of an allene reported by Hoveyda [63].
Scheme 45: Conjugate addition of Et2Zn to cyclohexenone catalyzed by NHC–Cu(I) complex derived from benzimidaz...
Scheme 46: Asymmetric conjugate addition of diethylzinc to 3-nonen-2-one catalyzed by NHC–Cu complexes derived...
Scheme 47: General scheme of a [3 + 2] cycloaddition reaction.
Scheme 48: [3 + 2] Cycloaddition of azides with alkynes catalyzed by NHC–Cu(I) complexes reported by Diez-Gonz...
Scheme 49: Application of NHC–CuCl/N-donor combination to catalyze the [3 + 2] cycloaddition of benzyl azide w...
Scheme 50: [3 + 2] Cycloaddition of azides with acetylenes catalyzed by bis(NHC)–Cu complex 131 and mixed NHC–...
Figure 7: NHC–CuCl complex 133 as catalyst for the [3 + 2] cycloaddition of alkynes with azides at room tempe...
Scheme 51: [3 + 2] Cycloaddition of a bulky azide with an alkynylpyridine using [(NHC)Cu(μ-I)2Cu(NHC)] copper ...
Scheme 52: [3 + 2] Cycloaddition of benzyl azide with phenylacetylene under homogeneous and heterogeneous cata...
Scheme 53: [3 + 2] Cycloaddition of benzyl azide with acetylenes catalyzed by bisthiazolylidene dicopper(I) co...
Figure 8: Copper (I)–NHC linear coordination polymer 137 and its conversion into tetranuclear (138) and dinuc...
Scheme 54: An A3 reaction.
Scheme 55: Synthesis of SiO2-immobilized NHC–Cu(I) catalyst 141 and its application in the A3-coupling reactio...
Scheme 56: Preparation of dual-purpose Ru@SiO2–[(NHC)CuCl] catalyst system 142 developed by Bordet, Leitner an...
Scheme 57: Application of the catalyst system Ru@SiO2–[Cu(NHC)] 142 to the one-pot tandem A3 reaction and hydr...
Scheme 58: A3 reaction of phenylacetylene with secondary amines and aldehydes catalyzed by benzothiazolylidene...
Figure 9: Kohn–Sham HOMOs of phenylacetylene and NHC–Cu(I)–phenylacetylene complex computed at the B3LYP/def2...
Figure 10: Energies of the FMOs of phenylacetylene, iminium ion, and NHC–Cu(I)–phenylacetylene complex compute...
Scheme 59: NHC–Cu(I) catalyzed diboration of ketones 147 by reacting with bis(pinacolato)diboron (148) reporte...
Scheme 60: Protoboration of terminal allenes catalyzed by NHC–Cu(I) complexes reported by Hoveyda and co-worke...
Scheme 61: NHC–CuCl-catalyzed borylation of α-alkoxyallenes to give 2-boryl-1,3-butadienes.
Scheme 62: Regioselective hydroborylation of propargylic alcohols and ethers catalyzed by NHC–CuCl complexes 1...
Scheme 63: NHC–CuOt-Bu-catalyzed semihydrogenation and hydroborylation of alkynes.
Scheme 64: Enantioselective NHC–Cu(I)-catalyzed hydroborations of 1,1-disubstituted aryl olefins reported by H...
Scheme 65: Enantioselective NHC–Cu(I)-catalyzed hydroboration of exocyclic 1,1-disubstituted alkenes reported ...
Scheme 66: Markovnikov-selective NHC–CuOH-catalyzed hydroboration of alkenes and alkynes reported by Jones et ...
Scheme 67: Dehydrogenative borylation and silylation of styrenes catalyzed by NHC–CuOt-Bu complexes developed ...
Scheme 68: N–H/C(sp2)–H carboxylation catalyzed by NHC–CuOH complexes.
Scheme 69: C–H Carboxylation of benzoxazole and benzothiazole derivatives with CO2 using a 1,2,3-triazol-5-yli...
Scheme 70: Use of Cu(I) complex derived from diethylene glycol-functionalized imidazo[1,5,a] pyridin-3-ylidene...
Scheme 71: Allylation and alkenylation of polyfluoroarenes and heteroarenes catalyzed by NHC–Cu(I) complexes r...
Scheme 72: Enantioselective C(sp2)–H allylation of (benz)oxazoles and benzothiazoles with γ,γ-disubstituted pr...
Scheme 73: C(sp2)–H arylation of arenes catalyzed by dual NHC–Cu/NHC–Pd catalytic system.
Scheme 74: C(sp2)–H Amidation of (hetero)arenes with N-chlorocarbamates/N-chloro-N-sodiocarbamates catalyzed b...
Scheme 75: NHC–CuI catalyzed thiolation of benzothiazoles and benzoxazoles.
Synthesis of ether lipids: natural compounds and analogues
- Marco Antônio G. B. Gomes,
- Alicia Bauduin,
- Chloé Le Roux,
- Romain Fouinneteau,
- Wilfried Berthe,
- Mathieu Berchel,
- Hélène Couthon and
- Paul-Alain Jaffrès
Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96
Graphical Abstract
Figure 1: Chemical structure of some natural ether lipids (ELs).
Figure 2: Synthesis of lyso-PAF and PAF from 1-O-alkylglycerol [64].
Figure 3: Synthesis of lyso-PAF from 1,3-benzylideneglycerol 3.1 [69].
Figure 4: A) Synthesis of the two enantiomers of octadecylglycerol (4.6 and 4.10) from ᴅ-mannitol (4.1); B) s...
Figure 5: Four-step synthesis of PAF 5.6 from (S)-glycidol [73].
Figure 6: Synthesis of 1-O-alkylglycerol A) from solketal, B) from ᴅ- or ʟ-tartaric acid and the intermediate ...
Figure 7: Synthesis of EL building blocks starting from substituted glycidol 7.1a–c [82].
Figure 8: Synthesis of PAF 8.5 by using phosphoramidite 8.2 [86].
Figure 9: Synthesis of oleyl-PAF 9.7 from ʟ-serine [88].
Figure 10: Synthesis of racemic analogues of lyso-PAF 10.8 and PAF 10.9 featuring a phenyl group between the g...
Figure 11: Synthesis of racemic deoxy-lyso-PAF 11.7 and deoxy-PAF 11.8 [91].
Figure 12: Synthesis of racemic thio-PAF 12.8 [93].
Figure 13: Racemic synthesis of 13.6 to illustrate the modification of the glycerol backbone by adding a methy...
Figure 14: Racemic synthesis of 14.5 as an illustration of the introduction of methyl substituents on the glyc...
Figure 15: Synthesis of functionalized sn-2-acyl chains of PC-EL; A) Steglich esterification or acylation reac...
Figure 16: Synthesis of racemic mc-PAF (16.3), a carbamate analogue of PAF [102].
Figure 17: A) Synthesis of (R)-17.2 and (S)-17.6 starting from (S)-solketal (17.1); B) synthesis of N3-PAF (17...
Figure 18: Modification of the phosphocholine polar head to produce PAF analogues [81].
Figure 19: Racemic PAF analogues 19.3 and 19.5 characterized by the absence of the phosphate group [107].
Figure 20: Synthesis of PIP3-PAF (20.7) [108].
Figure 21: Large-scale synthesis of C18-edelfosine (21.8) [116].
Figure 22: Synthesis of C16-edelfosine (22.10) starting from isopropylidene-ʟ-glyceric acid methyl ester (22.1...
Figure 23: Phosphocholine moiety installation by the use of chlorophosphite 23.2 as key reagent [119].
Figure 24: Synthesis of rac-1-alkyl-2-O-methylglycerol (AMG) [120].
Figure 25: Synthesis of stereocontrolled 1-alkyl-2-O-methyl glycerol 25.9 (AMG) from dimethyl ᴅ-tartrate [81].
Figure 26: A) Racemic synthesis of thioether 26.4 [129,130], B) structure of sulfone analogue 26.5 [129].
Figure 27: Stereocontrolled synthesis of C18-edelfosine thioether analogue 27.8 [118].
Figure 28: Synthesis of thioether 28.4 that include a thiophosphate function [134].
Figure 29: Synthesis of ammonium thioether 29.4 and 29.6 [135].
Figure 30: Synthesis of the N-methylamino analogue of edelfosine 30.6 (BN52211) [138].
Figure 31: Synthesis of 1-desoxy analogues of edelfosine; A) with a saturated alkyl chain; B) synthesis of the...
Figure 32: Stereocontrolled synthesis of edelfosine analogue (S)-32.8 featuring a C18:1 lipid chain [142].
Figure 33: Synthesis of edelfosine analogues with modulation of the lipid chain; A) illustration with the synt...
Figure 34: Synthesis of phospholipid featuring a carbamate function to link the lipid chain to the glycerol un...
Figure 35: Synthesis of sesquiterpene conjugates of phospho glycero ether lipids [148].
Figure 36: Racemic synthesis of methyl-substituted glycerol analogues 36.7 and 36.10: A) synthesis of diether ...
Figure 37: Racemic synthesis of ilmofosine (37.6) [155,156].
Figure 38: A) Stereoselective synthesis of 38.5 via a stereoselective hydroboration reaction; B) synthesis of ...
Figure 39: Racemic synthesis of SRI62-834 (39.6) featuring a spiro-tetrahydrofurane heterocycle in position 2 ...
Figure 40: Racemic synthesis of edelfosine analogue 40.5 featuring an imidazole moiety in sn-2 position [160].
Figure 41: Racemic synthesis of fluorine-functionalized EL: A) Synthesis of 41.6 and B) synthesis of 41.8 [161-163].
Figure 42: A) Synthesis of the β-keto-ester 42.6 that also features a decyl linker between the phosphate and t...
Figure 43: Synthesis of phosphonate-based ether lipids; A) edelfosine phosphonate analogue 43.7 and B) thioeth...
Figure 44: Enantioselective synthesis of phosphonates 44.3 and 44.4 [171].
Figure 45: Racemic synthesis of phosphinate-based ether lipid 45.10 [172].
Figure 46: Racemic synthesis of edelfosine arsonium analogue 46.5 [173].
Figure 47: Synthesis of edelfosine dimethylammonium analogue 47.2 [118].
Figure 48: Synthesis of rac-C18-edelfosine methylammonium analogue 48.4 [176].
Figure 49: A) Synthesis of edelfosine N-methylpyrrolidinium analogue 49.2 or N-methylmorpholinium analogue 49.3...
Figure 50: A) Synthesis of edelfosine’s analogue 50.4 with a PE polar group; B) illustration of a pyridinium d...
Figure 51: A) Synthesis of 51.4 featuring a thiazolium cationic moiety; B) synthesis of thiazolium-based EL 51...
Figure 52: Synthesis of cationic ether lipids 52.3, 52.4 and 52.6 [135,183].
Figure 53: Synthesis of cationic carbamate ether lipid 53.5 [184].
Figure 54: Synthesis of cationic sulfonamide 54.5 [185].
Figure 55: Chemical structure of ONO-6240 (55.1) and SRI-63-119 (55.2).
Figure 56: Synthesis of non-ionic ether lipids 56.2–56.9 [188].
Figure 57: Synthesis of ether lipid conjugated to foscarnet 57.6 [189].
Figure 58: A) Synthesis of ether lipid conjugated to arabinofuranosylcytosine; B) synthesis of AZT conjugated ...
Figure 59: Synthesis of quercetin conjugate to edelfosine [191].
Figure 60: Synthesis of 60.8 (Glc-PAF) [194].
Figure 61: A) Synthesis of amino ether lipid 61.7 functionalized with a rhamnose unit and its amide analogue 6...
Figure 62: A) Synthesis of glucose ether lipid 62.4; B) structure of ether lipid 62.5 possessing a maltose uni...
Figure 63: A) Synthesis of glucuronic methyl ester 63.8; B) structure of cellobiose 63.9 and maltose 63.10 ana...
Figure 64: A) Synthesis of maltosyl glycerolipid 64.7; B) structure of lactose analogue 64.8 prepared followin...
Figure 65: A) Asymmetric synthesis of the aglycone moiety starting from allyl 4-methoxyphenyl ether; B) glycos...
Figure 66: A) Synthesis of ohmline possessing a lactose moiety. B) Structure of other glyco glycero lipids pre...
Figure 67: A) Synthesis of lactose-glycerol ether lipid 67.5; B) analogues possessing a maltose (67.6) or meli...
Figure 68: Synthesis of digalactosyl EL 68.6, A) by using trityl, benzyl and acetyl protecting groups, B) by u...
Figure 69: A) Synthesis of α-ohmline; B) structure of disaccharide ether lipids prepared by using similar meth...
Figure 70: Synthesis of lactose ether lipid 70.3 and its analogue 70.6 featuring a carbamate function as linke...
Figure 71: Synthesis of rhamnopyranoside diether 71.4 [196].
Figure 72: Synthesis of 1-O-hexadecyl-2-O-methyl-3-S-(α-ᴅ-1'-thioglucopyranosyl)-sn-glycerol (72.5) [225].
Figure 73: A) Preparation of lipid intermediate 73.4; B) synthesis of 2-desoxy-C-glycoside 73.10 [226].
Figure 74: Synthesis of galactose-pyridinium salt 74.3 [228].
Figure 75: Synthesis of myo-inositol derivative Ino-C2-PAF (75.10) [230].
Figure 76: A) Synthesis of myo-inositol phosphate building block 76.7; B) synthesis of myo-inositolphosphate d...
Figure 77: A) Synthesis of phosphatidyl-3-desoxy-inositol 77.4; B) synthesis of phosphono-3-desoxyinositol 77.9...
Figure 78: A) Structure of diether phosphatidyl-myo-inositol-3,4-diphosphate 78.1; B) synthesis of phosphatidy...
Figure 79: A) Synthesis of diether-phosphatidyl derivative 79.4 featuring a hydroxymethyl group in place of a ...
Figure 80: Synthesis of Glc-amine-PAF [78].
Figure 81: Synthesis of glucosamine ether lipid 81.4 and its analogues functionalized in position 3 of the ami...
Figure 82: Synthesis of fully deprotected aminoglucoside ether lipid 82.5 [246].
Figure 83: Synthesis of C-aminoglycoside 83.12 using Ramberg–Bäcklund rearrangement as a key step [250].
Figure 84: A) List of the most important glyco lipids and amino glyco lipids included in the study of Arthur a...
Figure 85: Synthesis of mannosamine ether lipid 85.6 [254].
Figure 86: A) Synthesis of glucosamine ether lipids with a non-natural ʟ-glucosamine moiety; B) synthesis of e...
Figure 87: A) Structure of the most efficient anticancer agents 87.1–87.4 featuring a diamino glyco ether lipi...
Figure 88: A) Synthesis of diamino glyco ether lipid 87.4; B) synthesis of bis-glycosylated ether lipid 88.10 [256]....
Figure 89: Synthesis of triamino ether lipid 89.4 [260].
Figure 90: Synthesis of chlorambucil conjugate 90.7 [261].
Figure 91: Three main methods for the preparation of glycerol ether lipid 91.3; A) from solketal and via a tri...
Figure 92: Four different methods for the installation of the phosphocholine polar head group; A) method using...
Figure 93: Illustration of two methods for the installation of saccharides or aminosaccharides; A) O-glycosyla...
Photoredox catalysis harvesting multiple photon or electrochemical energies
- Mattia Lepori,
- Simon Schmid and
- Joshua P. Barham
Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81
- conditions. In 2020, the Polyzos group also demonstrated the carbonylative amidation of aryl halides in continuous flow with the in situ-generated [Ir2]0 (Figure 19A) [79]. This multi-photon tandem photocatalysis protocol provides an elegant alternative to established classical procedures for condensing
- carboxylic acids with amines that typically generate stochiometric amounts of harmful byproducts released [80][81], while simultaneously operating under milder reaction conditions than those applied in transition metal-catalyzed carbonylative amidation protocols [82][83]. Following the same distinct, yet
- . Notably, carbonylative amidation of a borylated aryl bromide to 26d proceeded well, where a Pd-catalyzed carbonylative amidation reaction would be plagued by undesired Suzuki coupling. Several secondary cyclic and acyclic amines, as well as primary amines were successfully employed as amine coupling
Graphical Abstract
Figure 1: Oxidative and reductive activations of organic compounds harvesting photoredox catalysis.
Figure 2: General catalytic cycles of radical ion conPET (left) and radical ion e-PRC (right).
Figure 3: “Beginner’s guide”: comparison between advantages, capacities, and prospectives of conPET and PEC.
Figure 4: A) conPET reductive dehalogenation of aryl halides with PDI. B) Reductive C–H arylation with pyrrol...
Figure 5: A) Chromoselective mono- and disubstitution or polybrominated pyrimidines with pyrroles. B) Sequent...
Figure 6: A) Synthesis of pyrrolo[1,2-a]quinolines. B) Synthesis of ullazines.
Figure 7: A) Reductive phosphorylation of aryl halides via conPET. B) Selected examples from the substrate sc...
Figure 8: A) Reductive dehalogenation of aryl halides via conPET and selected examples from the substrate sco...
Figure 9: A) Reductive C–H arylation of aryl halides via conPET (top) and selected examples from the substrat...
Figure 10: A) Reductive hydrodehalogenation of aryl halides with Mes-Acr-BF4. B) Selected examples from the su...
Figure 11: A) Reductive hydrodechlorination of aryl chlorides with 4-DPAIPN. B) Proposed formation of CO2•−. C...
Figure 12: A) Reductive conPET borylation with 3CzEPAIPN (top) and selected examples from the substrate scope ...
Figure 13: Scale-up of conPET phosphorylation with 3CzEPAIPN.
Figure 14: A) Borylation of 1d. B) Characteristics and structure of PC1 with green and red parts showing the l...
Figure 15: A) Reductive C–H arylation scope with polysulfide conPET (top) and selected examples from the subst...
Figure 16: Scale-up of A) C–H arylation and B) dehaloborylation with polysulfide photocatalysis in continuous-...
Figure 17: A) Formation of [Ir1]0 and [Ir2]0 upon PET between [Ir1]+ and Et3N. B) Mechanism of multi-photon ta...
Figure 18: A) Reductive hydrodehalogenation of aryl halides via multi-photon tandem photocatalysis. B) Selecte...
Figure 19: A) Carbonylative amidation of aryl halides in continuous flow. B) Selected examples from the substr...
Figure 20: A) General scheme for reductive (RQ) and oxidative quenching (OQ) protocols using [FeIII(btz)3](PF6)...
Figure 21: A) Carbonylative amidation of alkyl iodides with [IrIII(ppy)2(dtbbpy)]PF6. B) Selected examples fro...
Figure 22: A) Carboxylative C–N bond cleavage in cyclic amines. B) Selected examples from the substrate scope....
Figure 23: A) Formal reduction of alkenes to alkanes via transfer hydrogenation. B) Selected examples from the...
Figure 24: A) Birch-type reduction of benzenes with PMP-BPI. B) Selected examples from the substrate scope (sc...
Figure 25: Proposed mechanism of the OH− mediated conPET Birch-type reduction of benzene via generation of sol...
Figure 26: Reductive detosylation of N-tosylated amides with Mes-Acr-BF4. B) Selected examples from the substr...
Figure 27: A) Reductive detosylation of N-tosyl amides by dual PRC. B) Selected examples from the substrate sc...
Figure 28: A) Mechanism of the dual PRC based on PET between [Cu(dap)2]+ and DCA. B) Mechanism of the dual PRC...
Figure 29: A) N–O bond cleavage in Weinreb amides with anthracene. B) N–O bond cleavage in Weinreb amides rely...
Figure 30: A) Pentafluorosulfanylation and fluoride elimination. B) Mechanism of the pentafluorosulfanylation ...
Figure 31: A) α-Alkoxypentafluorosulfanylation (top) and selected examples from the substrate scope (bottom). ...
Figure 32: A) Oxidative amination of arenes with azoles catalyzed by N-Ph PTZ. B) Selected examples from the s...
Figure 33: A) C(sp3)–H bond activation by HAT via chloride oxidation by *N-Ph PTZ•+. B) Proposed mechanism for...
Figure 34: A) Recycling e-PRC C–H azolation of electron-rich arenes with pyrazoles using Mes-Acr+ as a photoca...
Figure 35: A) Radical ion e-PRC direct oxidation of unactivated arenes using TAC+ as an electro-activated phot...
Figure 36: A) Radical ion e-PRC direct oxidation of unactivated arenes using TPA as an electro-activated photo...
Figure 37: Proposed mechanism (top) and mode of preassembly (bottom).
Figure 38: A) Possible preassemblies of reactive (left) vs unreactive (right) arenes. B) Calculated spin densi...
Figure 39: A) Recycling e-PRC C(sp2 )–H acetoxylation of arenes using DDQ as a photocatalyst. B) Proposed cata...
Figure 40: Gram scale hydroxylation of benzene in a recirculated flow setup.
Figure 41: A) Radical ion e-PRC vicinal diamination of alkylarenes using TAC+ as an electro-activated photocat...
Figure 42: A) Sequential oxygenation of multiple adjacent C–H bonds under radical ion e-PRC using TAC+ as an e...
Figure 43: A) Enantioselective recycling e-PRC cyanation of benzylic C–H bonds using ADQS as photocatalyst. B)...
Figure 44: Proposed tandem mechanism by Xu and co-workers.
Figure 45: A) Enantioselective recycling e-PRC decarboxylative cyanation using Cu(acac)2, Ce(OTf)3 and a box l...
Figure 46: A) Enantioselective recycling e-PRC benzylic cyanation using Cu(MeCN)4BF4, box ligand and anthraqui...
Figure 47: A) Radical ion e-PRC acetoxyhydroxylation of aryl olefins using TAC+ as an electro-activated photoc...
Figure 48: Selected examples from the substrate scope.
Figure 49: Photoelectrochemical acetoxyhydroxylation in a recirculated flow setup.
Figure 50: A) Radical ion e-PRC aminooxygenation of aryl olefins using TAC+ as an electro-activated photocatal...
Figure 51: A) Recycling e-PRC C–H alkylation of heteroarenes with organic trifluoroborates using Mes-Acr+ as p...
Figure 52: A) Recycling e-PRC decarboxylative C–H alkylation of heteroarenes using CeCl3·7H2O as catalyst. B) ...
Figure 53: A) Recycling e-PRC decarboxylative C–H alkylation of heteroarenes using Fe(NH4)2(SO4)2·6H2O as cata...
Figure 54: A) Recycling e-PRC C–H alkylation of heteroarenes with alkyl oxalates and 4CzIPN as photocatalyst. ...
Figure 55: A) Recycling e-PRC decarboxylative C–H carbamoylation of heteroarenes using 4CzIPN as photocatalyst...
Figure 56: A) Photoelectrochemical HAT-mediated hydrocarbon activation via the chlorine radical. B) Proposed m...
Figure 57: A) Selected examples from the substrate scope. B) Gram and decagram scale semi-continuous flow PEC ...
Figure 58: A) Photoelectrochemical HAT-mediated dehydrogenative coupling of benzothiazoles with aliphatic C–H ...
Figure 59: A) Photoelectrochemical HAT activation of ethers using electro-activated TAC+ as photocatalyst. B) ...
Figure 60: Selected examples from the substrate scope.
Figure 61: A) Photoelectrochemical HAT-mediated synthesis of alkylated benzimidazo-fused isoquinolinones using...
Figure 62: A) Decoupled photoelectrochemical cerium-catalyzed oxydichlorination of alkynes using CeCl3 as cata...
Figure 63: Proposed decoupled photoelectrochemical mechanism.
Figure 64: A) Decoupled photoelectrochemical ring-opening bromination of tertiary cycloalkanols using MgBr2 as...
Figure 65: A) Recycling e-PRC ring-opening functionalization of cycloalkanols using CeCl3 as catalyst. B) Prop...
Figure 66: Selected examples from the substrate scope of the PEC ring-opening functionalization.
Figure 67: A) Radical ion e-PRC reduction of chloro- and bromoarenes using DCA as catalyst and various accepto...
Figure 68: A) Screening of different phthalimide derivatives as catalyst for the e-PRC reduction of aryl halid...
Figure 69: Screening of different organic catalysts for the e-PRC reduction of trialkylanilium salts.
Figure 70: A) e-PRC reduction of phosphonated phenols and anilinium salts. B) Selected examples from the subst...
Figure 71: A) ConPET and e-PRC reduction of 4-bromobenzonitrile using a naphthalene diimide (NDI) precatalyst ...
Figure 72: A) Radical ion e-PRC reduction of phosphinated aliphatic alcohols with n-BuO-NpMI as catalyst. B) C...
Figure 73: Selected examples from the substrate scope.
Figure 74: A) Recycling e-PRC reductive dimerization of benzylic chlorides using a [Cu2] catalyst. B) Proposed...
Figure 75: A) Decoupled photoelectrochemical C–H alkylation of heteroarenes through deamination of Katritzky s...
Figure 76: Proposed mechanism by Chen and co-workers.
Strategies in the synthesis of dibenzo[b,f]heteropines
- David I. H. Maier,
- Barend C. B. Bezuidenhoudt and
- Charlene Marais
Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51
- ) [77][78]. The allyl moiety in 144 allows for facile further functionalization. Amidation of the dihydrodibenzo[b,f]azepine (2a) derivatives with acyl halides 145 allowed for the introduction of variable length amide linkers by Kastrinsky et al. [3] (Scheme 33B). An industrial synthesis of opipramol (5
Graphical Abstract
Figure 1: Dibenzo[b,f]azepine (1a), -oxepine (1b) and -thiepine (1c) as examples of dibenzo[b,f]heteropines (1...
Figure 2: Selected pharmaceuticals with the dibenzo[b,f]azepine skeleton.
Figure 3: Examples of 10,11-dihydrodibenzo[b,f]azepine-based ligands.
Figure 4: The dibenzo[b,f]azepine moiety in dyes with properties suitable for the use in organic light emitti...
Figure 5: Selective bioactive natural products (13–18) containing the dibenzo[b,f]oxepine scaffold and Novart...
Scheme 1: Retrosynthetic approach to 5H-dibenzo[b,f]azepine (1a) from nitrotoluene (22).
Scheme 2: Oxidative coupling of o-nitrotoluene (22) and reduction of 2,2'-dinitrobibenzyl (21) to form 2,2'-d...
Scheme 3: Synthesis of 10,11-dihydro-5H-dibenzo[b,f]azepine (2a) via amine condensation.
Scheme 4: Catalytic reduction of 10,11-dihydro-5H-dibenzo[b,f]azepine (2a).
Scheme 5: The Wagner–Meerwein rearrangement of acridin-9-ylmethanol (23) into 5H-dibenzo[b,f]azepine (1a).
Scheme 6: Oxidative ring expansion of 2-(9-xanthenyl)malonates 24.
Scheme 7: Ring expansion via C–H functionalisation.
Scheme 8: The synthesis of fluorinated 5H-dibenzo[b,f]azepine 38 from isatin (32).
Scheme 9: The synthesis of substituted dibenzo[b,f]azepines 43 from indoles 39.
Scheme 10: Retrosynthetic pathways to dibenzo[b,f]azepines via Buchwald–Hartwig amination.
Scheme 11: Synthesis of dibenzo[b,f]oxepine 54 and -azepine 55 derivatives via (i) Heck reaction and (ii) Buch...
Scheme 12: Double Buchwald–Hartwig amination and thioetherification in the synthesis of tricyclic azepines 60 ...
Scheme 13: Double Buchwald–Hartwig amination towards substituted dibenzoazepines 62.
Scheme 14: Double Buchwald–Hartwig amination towards 10,11-dihydro-5H-dibenzo[b,f]azepine derivatives 71.
Scheme 15: One-pot Suzuki coupling–Buchwald–Hartwig amination.
Scheme 16: One-pot Rh/Pd-catalysed synthesis of dihydropyridobenzazepines.
Scheme 17: A retrosynthetic pathway to dibenzo[b,f]azepines via Mizoroki–Heck reaction.
Scheme 18: One-pot domino Pd-catalyzed Mizoroki–Heck–Buchwald–Hartwig synthesis of dibenzo[b,f]azepines.
Scheme 19: Dibenzo[b,f]thiapine and -oxepine synthesis via SNAr (thio)etherification, Wittig methylenation and...
Scheme 20: A retrosynthetic pathway to dibenzo[b,f]oxepines via Ullmann coupling.
Scheme 21: Ullmann-type coupling in dibenzo[b,f]oxepine synthesis.
Scheme 22: Wittig reaction and Ullmann coupling as key steps in dihydrobenz[b,f]oxepine synthesis.
Scheme 23: Pd-catalysed dibenzo[b,f]azepine synthesis via norbornene azepine intermediate 109.
Scheme 24: A simple representation of olefin metathesis resulting in transalkylidenation.
Scheme 25: Ring-closing metathesis as key step in the synthesis of dibenzo[b,f]heteropines.
Scheme 26: Alkyne–aldehyde metathesis in the synthesis of dibenzo[b,f]heteropines.
Scheme 27: Hydroarylation of 9-(2-alkynylphenyl)-9H-carbazole derivatives.
Scheme 28: Oxidative coupling of bisphonium ylide intermediate to give pacharin (13).
Scheme 29: Preparation of 10,11-dihydrodibenzo[b,f]heteropines via intramolecular Wurtz reaction.
Scheme 30: Phenol deprotonation and intramolecular etherification in the synthesis of bauhinoxepine J.
Figure 6: Functionalisation of dibenzo[b,f]azepine.
Scheme 31: Palladium-catalysed N-arylation of dibenzo[b,f]azepine.
Scheme 32: Cu- and Ni-catalysed N-arylation.
Scheme 33: N-Alkylation of dibenzo[b,f]azepine (1a) and dihydrodibenzo[b,f]azepine (2a).
Scheme 34: Preparation of methoxyiminosilbene.
Scheme 35: Synthesis of oxcarbazepine (153) from methoxy iminostilbene 151.
Scheme 36: Ring functionalisation of dihydrodibenzo[b,f]azepine.
An efficient metal-free and catalyst-free C–S/C–O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides
- Shubham Sharma,
- Dharmender Singh,
- Sunit Kumar,
- Vaishali,
- Rahul Jamra,
- Naveen Banyal,
- Deepika,
- Chandi C. Malakar and
- Virender Singh
Beilstein J. Org. Chem. 2023, 19, 231–244, doi:10.3762/bjoc.19.22
- , metal-free and easy to perform reaction conditions. Moreover, the pyrazole C-3/5-linked amide conjugates were also synthesized via an oxidative amination of pyrazole carbaldehydes and 2-aminopyridines using hydrogen peroxide as an oxidant. Keywords: C–S/O bond formation; metal-free; oxidative amidation
- oxidative amidation reaction of pyrazole-3-carbaldehyde 1 and 2-aminopyridine (F) in the presence of TBHP in DMSO as a solvent at 130 °C (entry 1, Table 2). However, the reaction required longer time (20 h) for the completion, and afforded a product in 29% yield only. It was realized that the isolated
- yield was observed (entries 2–5, Table 2). The oxidant TBHP (10 equiv) failed to deliver the anticipated product in good yield (36%, entry 6, Table 2). Similar results were obtained with H2O2 (25.0 equiv) under neat reaction conditions (entry 7, Table 2). Next, we performed the oxidative amidation
Graphical Abstract
Figure 1: Representative drug molecules based on pyrazole, thioamide, and amide derivatives.
Figure 2: Previous and present findings for the synthesis of thioamide derivatives.
Scheme 1: Synthesis of pyrazole C-3-tethered thioamides.
Scheme 2: Synthesis of pyrazole C-4-tethered thioamides.
Scheme 3: Metal- and catalyst-free preparation of pyrazole C-5-linked thioamide conjugates.
Scheme 4: Synthesis of 4-iodopyrazole C-3-tethered thioamides.
Scheme 5: Gram-scale scope of the current protocol.
Scheme 6: Control experiment.
Scheme 7: H2O2-mediated synthesis of pyrazole-pyridine conjugates with amide tethers.
Scheme 8: Synthesis of pyrazole-pyridine conjugates 9F and 10F having amide tethers.
Scheme 9: A tentative mechanism for the formation of pyrazole conjugates with thioamide and amide linkage.
Solid-phase total synthesis and structural confirmation of antimicrobial longicatenamide A
- Takumi Matsumoto,
- Takefumi Kuranaga,
- Yuto Taniguchi,
- Weicheng Wang and
- Hideaki Kakeya
Beilstein J. Org. Chem. 2022, 18, 1560–1566, doi:10.3762/bjoc.18.166
- 29. Then, five rounds of DIC/Oxyma-mediated amidation [22] and Nα-deprotection with piperidine led to resin-bound peptide 5. Treatment of 5 with TFA/CH2Cl2 1:99 released 30 into the solution without unmasking the acid-labile protecting groups of the side chains. Subsequently, peptide 30 was cyclized
Graphical Abstract
Figure 1: Structures of longicatenamides A–D (1–4).
Scheme 1: Retrosynthesis of longicatenamycin A (1).
Scheme 2: Synthesis of building block 10.
Scheme 3: Synthesis of building block 7.
Scheme 4: Total synthesis of longicatenamycin A (1).
Figure 2: LC–MS extracted ion chromatograms (EICs) of synthesized and natural 1. Column: Imtakt Cadenza CD-C1...
Vicinal ketoesters – key intermediates in the total synthesis of natural products
- Marc Paul Beller and
- Ulrich Koert
Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129
- mesoxalic ester amide 102 in a Friedel–Crafts reaction followed by a spontaneous lactamization to give (rac)-cladoniamide G (103). The mesoxalic ester amide 102 was synthesized from malonyl chloride 104 through amidation and Regitz diazotransfer, yielding diazo compound 105. Subsequent oxidation and
Graphical Abstract
Scheme 1: Structures of vicinal ketoesters and examples for their typical reactivity.
Scheme 2: Doyle’s diastereoselective intramolecular aldol addition of α,β-diketoester.
Scheme 3: Synthesis of euphorikanin A (16) by intramolecular, nucleophilic addition [6].
Scheme 4: Ketoester cycloisomerization for the synthesis of preussochromone A (24) [10].
Scheme 5: Diastereoselective, intramolecular aldol reaction of an α-ketoester 28 in the synthesis of (−)-preu...
Scheme 6: Synthesis of an α-ketoester through Riley oxidation and its use in an α-ketol rearrangement in the ...
Scheme 7: Azomethine imine cycloaddition towards the synthesis of the proposed structure of palau’amine (44) [19]....
Scheme 8: Intramolecular diastereoselective carbonyl-ene reaction of an α-ketoester in the synthesis of jatro...
Scheme 9: Grignard addition to an α-ketoester and subsequent Friedel–Crafts cyclization in the synthesis of (...
Scheme 10: Diastereoselective addition to an auxiliary modified α-ketoester in the formal synthesis of (+)-cam...
Scheme 11: Intramolecular photoreduction of an α-ketoester in the synthesis of (rac)-isoretronecanol (69) [26].
Scheme 12: α-Ketoester as nucleophile in a Tsuji–Trost reaction in the synthesis of (rac)-corynoxine (76) [27].
Scheme 13: Mannich reaction of an α-ketoester in the synthesis of (+)-gracilamine (83) [28].
Scheme 14: Enantioselective aldol reaction using an α-ketoester in the synthesis of (−)-irofulven (87) [29].
Scheme 15: Allylboration of a mesoxalic acid ester in the synthesis of (+)-awajanomycin (92) [30,31].
Scheme 16: Condensation of a diamine with mesoxolate in the synthesis of (−)-aplaminal (96) [32].
Scheme 17: Synthesis of mesoxalic ester amide 102 and its use in the synthesis of (rac)-cladoniamide G (103) [33].
Scheme 18: The thermodynamically controlled, intramolecular aldol addition of a vic-tricarbonyl compound in th...
First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell
- Daniele Rocco,
- Ana A. Folgueiras-Amador,
- Richard C. D. Brown and
- Marta Feroci
Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98
- atom is reversed (umpolung) from electrophilic to nucleophilic (Scheme 3). This approach can be exploited in many organic reactions, such as: the benzoin condensation [16][17], esterification and amidation of benzaldehydes and cinnamaldehydes [18][19], synthesis of γ-butyrolactones [20], synthesis of
- electrochemistry, NHC instability (and anodic electroactivity) prevented its cathodic generation and subsequent use as catalyst or reagent. Instead, the NHC was generated by chemical deprotonation using a strong base (DBU) and then applied in anodic esterification [30][31][32], and amidation of aromatic aldehydes
Graphical Abstract
Scheme 1: Electrochemical generation of NHC.
Scheme 2: Transformation of electrochemically generated NHC into the corresponding thione by its reaction wit...
Scheme 3: Umpolung of the aldehyde carbonyl carbon atom. Formation of the Breslow intermediate using NHCs.
Figure 1: Schematic representation of a plane-parallel plate flow electrochemical reactor.
Figure 2: C/PVDF anode before (A) and after (B) the first experiment (Table 1, entry 1).
Scheme 4: Electrogenerated NHC-catalyzed self-annulation of cinnamaldehyde.
Scheme 5: Byproduct obtained from the reaction between methanol and the Breslow intermediate.
Figure 3: Expanded view of the electrochemical cell components: (a) Aluminium end plates; (b) insulating PTFE...
Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides
- Jiaxi Xu
Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90
- (Scheme 5) [25]. The metal-free intramolecular oxidative C–H bond amidation of methyl and ethyl 2,6-dimethylphenylphosphonamidates 24, 26, and 28 is an interesting strategy for the synthesis of 1-methoxy/ethoxy-7-methyl-2-hydrobenzo[c][1,2]azaphosphol-3-one 1-oxide derivatives 25, 27, and 29 in
Graphical Abstract
Figure 1: Biologically active 1,2-azaphospholine 2-oxide derivatives.
Figure 2: Diverse synthetic strategies for the preparation of 1,2-azaphospholidine and 1,2-azaphospholine 2-o...
Scheme 1: Synthesis of 1-phenyl-2-phenylamino-γ-phosphonolactam (2) from N,N’-diphenyl 3-chloropropylphosphon...
Scheme 2: Synthesis of 2-ethoxy-1-methyl-γ-phosphonolactam (6) from ethyl N-methyl-(3-bromopropyl)phosphonami...
Scheme 3: Synthesis of 2-aryl-1-methyl-2,3-dihydrobenzo[c][1,2]azaphosphole 1-oxides 13 from N-aryl-2-chlorom...
Scheme 4: Synthesis of 2,3-dihydrobenzo[c][1,2]azaphosphole 1-oxides from alkylarylphosphinyl or diarylphosph...
Scheme 5: Synthesis of 3-arylmethylidene-2,3-dihydrobenzo[c][1,2]azaphosphole 1-oxides via the TBAF-mediated ...
Scheme 6: Synthesis of 2-hydrobenzo[c][1,2]azaphosphol-3-one 1-oxides via the metal-free intramolecular oxida...
Scheme 7: Synthesis of 1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides 42 and 44 from ethyl/benzyl 2-bromobenzy...
Scheme 8: Synthesis of azaphospholidine 2-oxides/sulfide from 1,2-oxaphospholane 2-oxides/sulfides and 1,2-th...
Scheme 9: Synthesis of 1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides/sulfides from 2-aminobenzyl(phenyl)phosp...
Scheme 10: Synthesis of 1,3-dihydrobenzo[d][1,2]azaphosphole 2-sulfide (59) from zwitterionic 2-aminobenzyl(ph...
Scheme 11: Synthesis of 1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides from 2-aminobenzyl(methyl/phenyl)phosphi...
Scheme 12: Synthesis of ethyl 2-methyl-1,2-azaphospholidine-5-carboxylate 2-oxide 69 from 2-amino-4-(hydroxy(m...
Scheme 13: Synthesis of 2-methoxy-1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxide 71 from dimethyl 2-(methylamino...
Scheme 14: Synthesis of tricyclic γ-phosphonolactams via formation of the P–C bond.
Scheme 15: Synthesis of γ-phosphonolactams 85 from ethyl 2-(3-chloropropyl)aminoalkanoates with diethyl chloro...
Scheme 16: Synthesis of N-phosphoryl- and N-thiophosphoryl-1,2-azaphospholidine 2-oxides 90/2-sulfides 91 from...
Scheme 17: Synthesis of 1-methyl-1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides 56a and 93 from P-(chloromethyl...
Scheme 18: Synthesis of 2-allylamino-1,5-dihydro-1,2-azaphosphole 2-oxides from N,N’-diallyl-vinylphosphonodia...
Scheme 19: Diastereoselective synthesis of 2-allylamino-1,5-dihydro-1,2-azaphosphole 2-oxides from N,N’-dially...
Scheme 20: Synthesis of 1-alkyl-3-benzoyl-2-ethoxy-1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides 106 from ethy...
Scheme 21: Synthesis of cyclohexadiene-fused γ-phosphinolactams from diphenyl-N-benzyl-N-methylphosphinamide (...
Scheme 22: Synthesis of cyclohexadiene-fused γ-phosphinolactams from diphenyl-N-alkyl-N-benzylphosphinamides.
Scheme 23: Synthesis of cyclohexadiene-fused γ-phosphinolactams from diphenyl-N-methyl-N-(1-phenylethyl)phosph...
Scheme 24: Synthesis of benzocyclohexadiene-fused γ-phosphinolactams from dinaphth-1-yl-N-alkyl-N-benzylphosph...
Scheme 25: Synthesis of benzocyclohexadiene-fused γ-phosphinolactams from dinaphth-1-yl-N-benzyl-N-methylphosp...
Scheme 26: Synthesis of carbonyl-containing benzocyclohexadiene-fused γ-phosphinolactams from dinaphth-1-yl-N-...
Scheme 27: Synthesis of benzocyclohexadiene-fused γ-phosphinolactams from dinaphthyl-N-benzyl-N-methylphosphin...
Scheme 28: Synthesis of cyclohexadiene-fused 1-(N-benzyl-N-methyl)amino-γ-phosphinolactams from aryl-N,N’-dibe...
Scheme 29: Synthesis of bis(cyclohexadiene-fused γ-phosphinolactam)s from bis(diphenyl-N-benzylphosphinamide)s....
Scheme 30: Synthesis of bis(hydroxymethyl-derived cyclohexadiene-fused γ-phosphinolactam)s from tetramethylene...
Scheme 31: Synthesis of 2-aryl/dimethylamino-1-ethoxy-2-hydrobenzo[c][1,2]azaphosphol-3-one 1-oxides from ethy...
Scheme 32: Synthesis of ethyl 2-ethoxy-1,2-azaphospholidine-4-carboxylate 2-oxides from ethyl 2-((chloro(ethox...
Scheme 33: Synthesis of (1S,3R)-2-(tert-butyldiphenylsilyl)-3-methyl-1-phenyl-2,3-dihydrobenzo[c][1,2]azaphosp...
Scheme 34: Synthesis of 2,3,3a,9a-tetrahydro-4H-1,2-azaphospholo[5,4-b]chromen-4-one (215) from 3-(phenylamino...
Scheme 35: Synthesis of quinoline-fused 1,2-azaphospholine 2-oxides from 2-azidoquinoline-3-carbaldehydes and ...
Scheme 36: Synthesis of 1-hydro-1,2-azaphosphol-5-one 2-oxide from cyanoacetohydrazide with phosphonic acid an...
Scheme 37: Synthesis of chromene-fused 5-oxo-1,2-azaphospolidine 2-oxides.
Scheme 38: Synthesis of (R)-1-phenyl-2-((R)-1-phenylethyl)-2-hydrobenzo[c][1,2]azaphosphol-3-one 1-oxide (239)...
Scheme 39: Synthesis of dihydro[1,2]azaphosphole 1-oxides from aryl/vinyl-N-phenylphosphonamidates and aryl-N-...
Scheme 40: Synthesis of 1,3-dihydro-[1,2]azaphospholo[5,4-b]pyridine 2-oxides.
DDQ in mechanochemical C–N coupling reactions
- Shyamal Kanti Bera,
- Rosalin Bhanja and
- Prasenjit Mal
Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64
- the presence of DDQ, the intramolecular C(sp2)–H amidation of N-(2-(arylideneamino)phenyl)-p-toluenesulfonamides leads to 1,2-disubstituted benzimidazoles and the one-pot coupling of 2-aminobenzamides with aryl/alkyl aldehydes resulted in substituted quinazolin-4(3H)-one derivatives in high yields
- . Keywords: ball mill; 1H-benzo[d]imidazole; C(sp2)–H amidation; DDQ; mechanochemistry; quinazolin-4(3H)-one; Introduction The reawakening approaches to use solvent-free and environmentally benign conditions in organic synthesis have facilitated new opportunities [1][2][3][4]. The research area of
- mechanochemical C–N coupling reactions using DDQ. The newly formed C–N bonds are shown as red lines for clarity. a) The intramolecular C(sp2)-H amidation leading to 1,2-disubstituted benzimidazoles. b) One-pot coupling to synthesize substituted quinazolin-4(3H)-ones. Scope of the mechanochemical synthesis of
Graphical Abstract
Figure 1: Our work on mechanochemical C–N coupling reactions using DDQ. The newly formed C–N bonds are shown ...
Figure 2: Scope of the mechanochemical synthesis of substituted benzimidazoles.
Figure 3: Synthesis of quinazolin-4(3H)-one derivatives.
Figure 4: The substrate scope for the synthesis of quinazolin-4(3H)-one derivatives.
Figure 5: a) Control experiment and b) Plausible mechanism.
Figure 6: Large-scale synthesis. a) 1,2-Disubstituted benzimidazoles. b) Substituted quinazolin-4(3H)-ones. R...
Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions
- José G. Hernández,
- Karen J. Ardila-Fierro,
- Dajana Barišić and
- Hervé Geneste
Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20
- solution, the mechanochemical reactions were accomplished in the absence of solvents, in short reaction times, and in yields comparable to or higher than their solvent-based counterparts. Keywords: amidation; ball mill; fluorination; in situ monitoring; mechanochemistry; NFSI; Raman monitoring
- -milling conditions. NFSI is a colorless crystalline powder (mp 114–116 °C), bench-stable, and an easy-to-handle reagent, which, due to its commercial availability, has been extensively used as a fluorinating agent in solution [7][8][9]. Additionally, NFSI has also been explored as an oxidant, amidation
- functionalizations [22][23]. In particular, efficient fluorination protocols are long sought after in several areas of science, including medicinal chemistry [24]. Next to fluorination, in this work, we also have investigated NFSI as a source for mechanochemical sulfonylation of imidazoles and amidation reactions
Graphical Abstract
Scheme 1: Examples of mechanochemical reactions using NFSI.
Scheme 2: Mechanochemical fluorination of arenes 1 with NFSI. (a) Product distributions and reaction conditio...
Figure 1: Time-resolved 2D plots of the mechanochemical reaction of: (a) 1c (0.59 mmol), NFSI (1.0 equiv), an...
Scheme 3: (a–f) Reactions of substrates 3 with NFSI. Reaction conditions: Substrates 3 (0.734 mmol) were mill...
Scheme 4: Regioselective C-3 mechanochemical amidation of 5 with NFSI.
Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction
- Irina Kuznetcova,
- Felix Bacher,
- Daniel Vegh,
- Hsiang-Yu Chuang and
- Vladimir B. Arion
Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15
- batch of 1a was reduced. It is likely that 2a can be cyclized by base catalysis, or by using common peptide coupling reagents (e.g., EDCI, HATU) upon saponification of the ester group. However, we opted for a trimethylaluminum-mediated amidation reaction [4][39] to give rise to 8-benzyl-7-hydroindolo
Graphical Abstract
Figure 1: Paullone related indolobenzazepinone isomers. 7,12-Dihydroindolo[3,2-d][1]benzazepin-6(5H)-one or p...
Scheme 1: Investigated retrosynthetic pathways to scaffold C.
Scheme 2: Attempted synthesis of scaffold C by route (a).
Scheme 3: Attempted synthesis of C by route (b).
Scheme 4: Attempted synthesis of N-benzylated indole-2-acetic acid.
Scheme 5: Attempt to obtain open-chain precursor N-(2-bromophenyl)-2-(1H-indol-2-yl)acetamide.
Scheme 6: Synthesis of scaffold C and analogues by route (c).
Figure 2: ORTEP view of 1a with thermal ellipsoids drawn at the 50% probability level.
Figure 3: ORTEP view of 3a with thermal ellipsoids drawn at the 50% probability level.
Scheme 7: Attempted Ullmann cross-coupling of 23 with o-bromo-nitrobenzene.
Chemoselective N-acylation of indoles using thioesters as acyl source
- Tianri Du,
- Xiangmu Wei,
- Honghong Xu,
- Xin Zhang,
- Ruiru Fang,
- Zheng Yuan,
- Zhi Liang and
- Yahui Li
Beilstein J. Org. Chem. 2022, 18, 89–94, doi:10.3762/bjoc.18.9
- transthioesterification of aryl halides for the synthesis of thioethers and thioesters [17] (Scheme 1, C). In addition, we also used this reagent to trap alkylcopper(I) intermediates and to form C−S bonds [18]. To the best of our knowledge, thioesters have not been developed as indole N-amidation reagent. Based on our
- substrates to establish this procedure. As shown in Table 1, different bases were tried to improve the amidation reaction, and Cs2CO3 was found the most suitable choice (Table 1, entry 1). NaOt-Bu can also be used in this reaction and 82% yield could be obtained. In addition, NaOH and K2CO3 were not suitable
Graphical Abstract
Figure 1: Representative pharmaceuticals containing N-acylindole moieties.
Scheme 1: A) Strategies for the synthesis of N-acylindoles; B) thioester as dicarbonylation reagent; C) recen...
Scheme 2: Reactions of thioesters and indoles. Reaction conditions: 1 (0.2 mmol, 1.0 equiv), 2 (0.6 mmol, 3.0...
Scheme 3: Gram-scale experiment.
Scheme 4: Control experiments.
Scheme 5: Proposed mechanism.
Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes
- Nicolai Wippert,
- Martin Nieger,
- Claudine Herlan,
- Nicole Jung and
- Stefan Bräse
Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187
- accessible 3,6-substituted-4,6-dihydro-3H-pyrazolo[3,4-d][1,2,3]triazines as nitrogen-rich heterocycles. The target compounds were obtained in five steps, including an amidation and a cyclative cleavage reaction as key reaction steps. The introduction of two side chains allowed a variation of the pyrazolo
Graphical Abstract
Scheme 1: Synthesis of 3,6-dihydro-4H-pyrazolo[3,4-d][1,2,3]triazin-4-ones 2a,b by diazotization of 3-amino-1H...
Figure 1: Structural differences of several known (2–4) and so far unknown (5 and 6) pyrazolo[3,4-d][1,2,3]-3H...
Scheme 2: Synthesis of 3,4-dihydrobenzo[d][1,2,3]triazine derivatives 8 from triazene-containing precursors 7 ...
Scheme 3: Planned retrosynthesis to obtain 4,6-dihydropyrazolo[3,4-d][1,2,3]-3H-triazines 5 and 4,7-dihydropy...
Figure 2: Molecular structures of compounds 12h (A) and 13c (B) representing both possible regioisomers of th...
Scheme 4: Cleavage of the triazene protective group and cyclization of the resulting diazonium intermediate y...
Figure 3: Graphical overview about selected pyrazolo[1,2,3]triazines 5 and intermediates 9, 12, and 13 and th...
Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines
- Zhen-Sheng Jia,
- Qiang Yue,
- Ya Li,
- Xue-Tao Xu,
- Kun Zhang and
- Bing-Feng Shi
Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165
- groups. Kumar and co-workers developed a Cu-mediated C–H chalcogenation and sulfonation of ferrocenes [27][28][29]. The use of a bidentate 1,10-phenathroline ligand was critical to achieve mono-selectivity in the chacogenation reactions [28]. Meanwhile, Co(III)-catalyzed ortho-C–H amidation of ferrocene
Graphical Abstract
Scheme 1: 3d-Transition-metal-catalyzed C–H functionalization to access functionalized ferrocenes.
Scheme 2: Scope of ferrocenes with morpholine.
Scheme 3: Scope of various amines with 1a.
Scheme 4: Synthetic applications.
Scheme 5: Mechanistic experiments.
Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives
- Yi Liu,
- Puying Luo,
- Yang Fu,
- Tianxin Hao,
- Xuan Liu,
- Qiuping Ding and
- Yiyuan Peng
Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163
- structural motifs to provide the functionalized pyridine and pyrrole derivatives. The functionalization reactions cover iodination, bromination, trifluoromethylation, azidation, carbonylation, arylation, alkylation, selenylation, sulfenylation, amidation, esterification, and hydroxylation. We also briefly
Graphical Abstract
Scheme 1: Ag/I2-mediated electrophilic annulation of 2-en-4-ynyl azides 1.
Scheme 2: The proposed mechanism of Ag-catalyzed aza-annulation.
Scheme 3: The proposed mechanism of I2-mediated aza-annulation.
Scheme 4: Copper-catalyzed amination of (E)-2-en-4-ynyl azides 1.
Scheme 5: The proposed mechanism of copper-catalyzed amination.
Scheme 6: The derivatization of sulfonated aminonicotinates.
Scheme 7: Copper-catalyzed chalcogenoamination of (E)-2-en-4-ynyl azides 1.
Scheme 8: The possible mechanism of chalcogenoamination.
Scheme 9: The derivatization of 5‑selenyl- and 5-sulfenyl-substituted nicotinates.
Scheme 10: The tandem reaction of nitriles, Reformatsky reagents, and 1,3-enynes.
Scheme 11: Nickel-catalyzed [4 + 2]-cycloaddition of 3-azetidinones with 1,3-enynes.
Scheme 12: Electrophilic iodocyclization of 2-nitro-1,3-enynes to pyrroles.
Scheme 13: Electrophilic halogenation of 2-trifluoromethyl-1,3-enynes to pyrroles.
Scheme 14: Copper-catalyzed cascade cyclization of 2-nitro-1,3-enynes with amines.
Scheme 15: Tandem cyclization of 2-nitro-1,3-enynes, Togni reagent II, and amines.
Scheme 16: Tandem cyclization of 2-nitro-1,3-enynes, TMSN3, and amines.
Scheme 17: Cascade cyclization of 6-hydroxyhex-2-en-4-ynals to pyrroles.
Scheme 18: Au/Ag-catalyzed oxidative aza-annulation of 1,3-enynyl azides.
Scheme 19: The plausible mechanism of Au/Ag-catalyzed oxidative aza-annulation.
Scheme 20: Synthesis of 2-tetrazolyl-substituted 3-acylpyrroles from enynals.
Scheme 21: CuH-catalyzed coupling reaction of 1,3-enynes and nitriles to pyrroles.
Scheme 22: The mechanism of CuH-catalyzed coupling of 1,3-enynes and nitriles to pyrroles.
On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets
- Renato L. Carvalho,
- Amanda S. de Miranda,
- Mateus P. Nunes,
- Roberto S. Gomes,
- Guilherme A. M. Jardim and
- Eufrânio N. da Silva Júnior
Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126
- Streptomyces lasaliensis cultures [195]. The synthesis succeeded in five steps, each one of them in good yields, including the cobalt-catalyzed C–H bond addition (Scheme 37D). One year later, the same group described a unique cobalt-Cp* catalyzed C(sp2)–H amidation technique [196] applied to thiostrepton (125
- same year, Wu, Li and co-workers described a successful cobalt-Cp*-catalyzed C–H amidation of benzaldehyde derivatives (Scheme 39B), in which the aldehyde portion works as the directing group [198]. After an acid workup using diluted hydrochloric acid, the desired ortho-amidated products were obtained
Graphical Abstract
Scheme 1: Schematic overview of transition metals studied in C–H activation processes.
Scheme 2: (A) Known biological activities related to benzimidazole-based compounds; (B and C) an example of a...
Scheme 3: (A) Known biological activities related to quinoline-based compounds; (B and C) an example of a sca...
Scheme 4: (A) Known biological activities related to sulfur-containing compounds; (B and C) an example of a s...
Scheme 5: (A) Known biological activities related to aminoindane derivatives; (B and C) an example of a scand...
Scheme 6: (A) Known biological activities related to norbornane derivatives; (B and C) an example of a scandi...
Scheme 7: (A) Known biological activities related to aniline derivatives; (B and C) an example of a titanium-...
Scheme 8: (A) Known biological activities related to cyclohexylamine derivatives; (B) an example of an intram...
Scheme 9: (A) Known biologically active benzophenone derivatives; (B and C) photocatalytic oxidation of benzy...
Scheme 10: (A) Known bioactive fluorine-containing compounds; (B and C) vanadium-mediated C(sp3)–H fluorinatio...
Scheme 11: (A) Known biologically active Lythraceae alkaloids; (B) synthesis of (±)-decinine (30).
Scheme 12: (A) Synthesis of (R)- and (S)-boehmeriasin (31); (B) synthesis of phenanthroindolizidines by vanadi...
Scheme 13: (A) Known bioactive BINOL derivatives; (B and C) vanadium-mediated oxidative coupling of 2-naphthol...
Scheme 14: (A) Known antiplasmodial imidazopyridazines; (B) practical synthesis of 41.
Scheme 15: (A) Gold-catalyzed drug-release mechanism using 2-alkynylbenzamides; (B and C) chromium-mediated al...
Scheme 16: (A) Examples of anti-inflammatory benzaldehyde derivatives; (B and C) chromium-mediated difunctiona...
Scheme 17: (A and B) Manganese-catalyzed chemoselective intramolecular C(sp3)–H amination; (C) late-stage modi...
Scheme 18: (A and B) Manganese-catalyzed C(sp3)–H amination; (C) late-stage modification of a leelamine deriva...
Scheme 19: (A) Known bioactive compounds containing substituted N-heterocycles; (B and C) manganese-catalyzed ...
Scheme 20: (A) Known indoles that present GPR40 full agonist activity; (B and C) manganese-catalyzed C–H alkyl...
Scheme 21: (A) Examples of known biaryl-containing drugs; (B and C) manganese-catalyzed C–H arylation through ...
Scheme 22: (A) Known zidovudine derivatives with potent anti-HIV properties; (B and C) manganese-catalyzed C–H...
Scheme 23: (A and B) Manganese-catalyzed C–H organic photo-electrosynthesis; (C) late-stage modification.
Scheme 24: (A) Example of a known antibacterial silylated dendrimer; (B and C) manganese-catalyzed C–H silylat...
Scheme 25: (A and B) Fe-based small molecule catalyst applied for selective aliphatic C–H oxidations; (C) late...
Scheme 26: (A) Examples of naturally occurring gracilioethers; (B) the first total synthesis of gracilioether ...
Scheme 27: (A and B) Selective aliphatic C–H oxidation of amino acids; (C) late-stage modification of proline-...
Scheme 28: (A) Examples of Illicium sesquiterpenes; (B) first chemical synthesis of (+)-pseudoanisatin (80) in...
Scheme 29: (A and B) Fe-catalyzed deuteration; (C) late-stage modification of pharmaceuticals.
Scheme 30: (A and B) Biomimetic Fe-catalyzed aerobic oxidation of methylarenes to benzaldehydes (PMHS, polymet...
Scheme 31: (A) Known tetrahydroquinolines with potential biological activities; (B and C) redox-selective Fe c...
Scheme 32: (A) Known drugs containing a benzofuran unit; (B and C) Fe/Cu-catalyzed tandem O-arylation to acces...
Scheme 33: (A) Known azaindolines that act as M4 muscarinic acetylcholine receptor agonists; (B and C) intramo...
Scheme 34: (A) Known indolinones with anticholinesterase activity; (B and C) oxidative C(sp3)–H cross coupling...
Scheme 35: (A and B) Cobalt-catalyzed C–H alkenylation of C-3-peptide-containing indoles; (C) derivatization b...
Scheme 36: (A) Cobalt-Cp*-catalyzed C–H methylation of known drugs; (B and C) scope of the o-methylated deriva...
Scheme 37: (A) Known lasalocid A analogues; (B and C) three-component cobalt-catalyzed C–H bond addition; (D) ...
Scheme 38: (A and B) Cobalt-catalyzed C(sp2)–H amidation of thiostrepton.
Scheme 39: (A) Known 4H-benzo[d][1,3]oxazin-4-one derivatives with hypolipidemic activity; (B and C) cobalt-ca...
Scheme 40: (A and B) Cobalt-catalyzed C–H arylation of pyrrole derivatives; (C) application for the synthesis ...
Scheme 41: (A) Known 2-phenoxypyridine derivatives with potent herbicidal activity; (B and C) cobalt-catalyzed...
Scheme 42: (A) Natural cinnamic acid derivatives; (B and C) cobalt-catalyzed C–H carboxylation of terminal alk...
Scheme 43: (A and B) Cobalt-catalyzed C–H borylation; (C) application to the synthesis of flurbiprofen.
Scheme 44: (A) Benzothiazoles known to present anticonvulsant activities; (B and C) cobalt/ruthenium-catalyzed...
Scheme 45: (A and B) Cobalt-catalyzed oxygenation of methylene groups towards ketone synthesis; (C) synthesis ...
Scheme 46: (A) Known anticancer tetralone derivatives; (B and C) cobalt-catalyzed C–H difluoroalkylation of ar...
Scheme 47: (A and B) Cobalt-catalyzed C–H thiolation; (C) application in the synthesis of quetiapine (153).
Scheme 48: (A) Known benzoxazole derivatives with anticancer, antifungal, and antibacterial activities; (B and...
Scheme 49: (A and B) Cobalt-catalyzed C–H carbonylation of naphthylamides; (C) BET inhibitors 158 and 159 tota...
Scheme 50: (A) Known bioactive pyrrolo[1,2-a]quinoxalin-4(5H)-one derivatives; (B and C) cobalt-catalyzed C–H ...
Scheme 51: (A) Known antibacterial cyclic sulfonamides; (B and C) cobalt-catalyzed C–H amination of propargyli...
Scheme 52: (A and B) Cobalt-catalyzed intramolecular 1,5-C(sp3)–H amination; (C) late-stage functionalization ...
Scheme 53: (A and B) Cobalt-catalyzed C–H/C–H cross-coupling between benzamides and oximes; (C) late-state syn...
Scheme 54: (A) Known anticancer natural isoquinoline derivatives; (B and C) cobalt-catalyzed C(sp2)–H annulati...
Scheme 55: (A) Enantioselective intramolecular nickel-catalyzed C–H activation; (B) bioactive obtained motifs;...
Scheme 56: (A and B) Nickel-catalyzed α-C(sp3)–H arylation of ketones; (C) application of the method using kno...
Scheme 57: (A and B) Nickel-catalyzed C(sp3)–H acylation of pyrrolidine derivatives; (C) exploring the use of ...
Scheme 58: (A) Nickel-catalyzed C(sp3)–H arylation of dioxolane; (B) library of products obtained from biologi...
Scheme 59: (A) Intramolecular enantioselective nickel-catalyzed C–H cycloalkylation; (B) product examples, inc...
Scheme 60: (A and B) Nickel-catalyzed C–H deoxy-arylation of azole derivatives; (C) late-stage functionalizati...
Scheme 61: (A and B) Nickel-catalyzed decarbonylative C–H arylation of azole derivatives; (C) application of t...
Scheme 62: (A and B) Another important example of nickel-catalyzed C–H arylation of azole derivatives; (C) app...
Scheme 63: (A and B) Another notable example of a nickel-catalyzed C–H arylation of azole derivatives; (C) lat...
Scheme 64: (A and B) Nickel-based metalorganic framework (MOF-74-Ni)-catalyzed C–H arylation of azole derivati...
Scheme 65: (A) Known commercially available benzothiophene-based drugs; (B and C) nickel-catalyzed C–H arylati...
Scheme 66: (A) Known natural tetrahydrofuran-containing substances; (B and C) nickel-catalyzed photoredox C(sp3...
Scheme 67: (A and B) Another notable example of a nickel-catalyzed photoredox C(sp3)–H alkylation/arylation; (...
Scheme 68: (A) Electrochemical/nickel-catalyzed C–H alkoxylation; (B) achieved scope, including three using na...
Scheme 69: (A) Enantioselective photoredox/nickel catalyzed C(sp3)–H arylation; (B) achieved scope, including ...
Scheme 70: (A) Known commercially available trifluoromethylated drugs; (B and C) nickel-catalyzed C–H trifluor...
Scheme 71: (A and B) Stereoselective nickel-catalyzed C–H difluoroalkylation; (C) late-stage functionalization...
Scheme 72: (A) Cu-mediated ortho-amination of oxalamides; (B) achieved scope, including derivatives obtained f...
Scheme 73: (A) Electro-oxidative copper-mediated amination of 8-aminoquinoline-derived amides; (B) achieved sc...
Scheme 74: (A and B) Cu(I)-mediated C–H amination with oximes; (C) derivatization using telmisartan (241) as s...
Scheme 75: (A and B) Cu-mediated amination of aryl amides using ammonia; (C) late-stage modification of proben...
Scheme 76: (A and B) Synthesis of purine nucleoside analogues using copper-mediated C(sp2)–H activation.
Scheme 77: (A) Copper-mediated annulation of acrylamide; (B) achieved scope, including the synthesis of the co...
Scheme 78: (A) Known bioactive compounds containing a naphthyl aryl ether motif; (B and C) copper-mediated eth...
Scheme 79: (A and B) Cu-mediated alkylation of N-oxide-heteroarenes; (C) late-stage modification.
Scheme 80: (A) Cu-mediated cross-dehydrogenative coupling of polyfluoroarenes and alkanes; (B) scope from know...
Scheme 81: (A) Known anticancer acrylonitrile compounds; (B and C) Copper-mediated cyanation of unactivated al...
Scheme 82: (A) Cu-mediated radiofluorination of 8-aminoquinoline-derived aryl amides; (B) achieved scope, incl...
Scheme 83: (A) Examples of natural β-carbolines; (B and C) an example of a zinc-catalyzed C–H functionalizatio...
Scheme 84: (A) Examples of anticancer α-aminophosphonic acid derivatives; (B and C) an example of a zinc-catal...
[2 + 1] Cycloaddition reactions of fullerene C60 based on diazo compounds
- Yuliya N. Biglova
Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55
- methanofullerene-appended dicarboxylic acid 85 synthesized from 10 is a versatile synthon for conversion into numerous derivatives (Scheme 25). The reactivity of compound 85 was studied under DCC-promoted esterification conditions (see adducts 8 and 86) and amidation conditions (see adducts 21 and 22). Hummelen
Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines
- Geetanjali S. Sontakke,
- Rahul K. Shukla and
- Chandra M. R. Volla
Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42
- secondary amines as the nucleophiles [49]. In their protocol, the regioselectivity is controlled by PyBroP catalyst, which acts as the N-oxide activator. Manley and Bilodeau reported the amidation of heterocyclic N-oxides at the C2-position using oxalyl chloride for activating the N-oxides [50]. In addition
- to amination and amidation, there are few reports on metal-free C2-heteroarylation of pyridine N-oxides. In 1984, Rogers demonstrated the synthesis of 2-triazolylpyridines from 2-azidopyridines and phenylacetylene [51]. Along the same lines, Keith reported methodologies for the C2-imidazolylation and
Graphical Abstract
Figure 1: Bioactive molecules containing the 2-aminoquinoline motif.
Scheme 1: C2-selective C–N bond formation of N-oxides.
Scheme 2: Substrate scope of N-sulfonyl-1,2,3-triazoles. Reaction conditions: 1a (0.2 mmol), 2 (0.24 mmol) an...
Scheme 3: Substrate scope of quinoline N-oxides. Reaction conditions: 1 (0.2 mmol), 2a (0.24 mmol) and DCE (2...
Scheme 4: Late-stage modification of natural products.
Scheme 5: Substrate scope for the reaction of substituted triazoles with isoquinoline N-oxide.
Scheme 6: Gram-scale and one-pot synthesis.
Scheme 7: Proposed mechanism.
Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders
- David Straßburger,
- Svenja Herziger,
- Katharina Huth,
- Moritz Urschbach,
- Rainer Haag and
- Pol Besenius
Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10
- -mediated amidation of Boc-protected tri-ʟ-phenylalanine, as β-sheet directing peptide sequence, afforded the peptide amphiphile in good yields. After deprotection of the N-terminus with TFA, molecule 4 was suitable for coupling to the branching unit to obtain the desired dendritic peptide amphiphiles. In
- case of the C3-symmetric amphiphile I, the readily available benzene-1,3,5-tricarboxylic acid (trimesic acid) was chosen as the branching unit. In the final amidation reaction, the efficient PyBOP-mediated coupling was carried out using an excess of the peptide amphiphile. Finally, the target compound
Graphical Abstract
Scheme 1: The synthesis of the C3-symmetrical tetraethylene glycol-decorated peptide amphiphile I and the azi...
Scheme 2: Synthesis of the sulfated peptide amphiphile II by copper-catalyzed azide–alkyne cyclization.
Figure 1: Analysis of the self-assembly behavior of I by A: CD-spectra of 5, 10, 25 or 50 µM aqueous solution...
Figure 2: Analysis of the supramolecular polymerization of II by A: CD-spectra of a 25 µM solution in TRIS bu...
Figure 3: Concentration-dependent relative L-selectin binding of the supramolecular polymers I and II in HEPE...
Progress in the total synthesis of inthomycins
- Bidyut Kumar Senapati
Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7
- % yield. Finally, compound (+)-76 underwent amidation and deacetylation to give an 11.1:1 mixture of geometrical isomers of inthomycin C ((−)-3) in 77% yield over two steps (Scheme 17) [50]. The (3R) stereochemistry of (−)-3 was confirmed by MTPA ester derivatization, which supports the recent work by
- (+)-147a followed by Pinnick oxidation afforded the acid (+)-148a. Finally, the EDCl-mediated amidation of unstable acid (+)-148a followed by debenzoylation produced inthomycin A ((+)-1). Similarly, compound (+)-146b was converted into inthomycin B ((+)-2) (Scheme 25). To complete the total synthesis of
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.
Syntheses of spliceostatins and thailanstatins: a review
- William A. Donaldson
Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166
- -methyl-3-buten-1-yl tosylate in the presence of Grubbs’ 2nd generation catalyst yielded 59, which, upon elimination with potassium tert-butoxide led to the diene 50. The reductive amination of 50 afforded an inseparable mixture of the C-14 amines (6:1 ratio). However, the amidation of this mixture with
- transformations, prior to the cleavage of the Boc amide protecting group. The free amine 118 underwent an amidation with the TBS-protected (2Z,4S)-4-hydroxy-2-butenoic acid 12b to give 119. The modified Julia olefination of the aldehyde 73 with the anion derived from 119 proceeded with a high E-selectivity to
- the use of a Ru-catalyzed olefin cross-metathesis for the generation of the dienyl segment joining the two tetrahydropyranyl segments (Scheme 20) [12][13]. The cleavage of the Boc amide of 31 and the eventual amidation with (2Z,4S)-4-acetoxy-2-butenoic acid (12c) gave 121. The construction of the
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.
Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review
- Alessandra Del Tito,
- Havall Othman Abdulla,
- Davide Ravelli,
- Stefano Protti and
- Maurizio Fagnoni
Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123
- oxidative C–H amidation, offering a straightforward access to phenanthridones (Scheme 18). The process took place upon blue LED irradiation (20–24 h at 60 °C were required) of the chosen substrates (e.g., 18.1a–d) in the presence of the Ir-based photoredox catalyst Ir[dF(CF3)ppy]2(bpy)PF6 (2.5 mol %) and a
- -cyanobiaryl)acrylamides 17.1a–d. The direct oxidative C–H amidation involving amidyl radicals for the synthesis of phenanthridones. Funding Havall Othman Abdulla is grateful to the Chemistry Department, College of Science, Salahaddin University‐Erbil (Iraq) for financial support.
Graphical Abstract
Figure 1: Bioactive phenanthridine and phenanthridinium derivatives.
Scheme 1: Synthesis of phenanthrenes by a photo-Pschorr reaction.
Scheme 2: Synthesis of phenanthrenes by a benzannulation reaction.
Scheme 3: Photocatalytic cyclization of α-bromochalcones for the synthesis of phenanthrenes.
Figure 2: Carbon-centered and nitrogen-centered radicals used for the synthesis of phenanthridines.
Scheme 4: General scheme describing the synthesis of phenanthridines from isocyanides via imidoyl radicals.
Scheme 5: Synthesis of substituted phenanthridines involving the intermediacy of electrophilic radicals.
Scheme 6: Photocatalyzed synthesis of 6-β-ketoalkyl phenanthridines.
Scheme 7: Synthesis of 6-substituted phenanthridines through the addition of trifluoromethyl (path a), phenyl...
Scheme 8: Synthesis of 6-(trifluoromethyl)-7,8-dihydrobenzo[k]phenanthridine.
Scheme 9: Phenanthridine syntheses by using photogenerated radicals formed through a C–H bond homolytic cleav...
Scheme 10: Trifluoroacetimidoyl chlorides as starting substrates for the synthesis of 6-(trifluoromethyl)phena...
Scheme 11: Synthesis of phenanthridines via aryl–aryl-bond formation.
Scheme 12: Oxidative conversion of N-biarylglycine esters to phenanthridine-6-carboxylates.
Scheme 13: Photocatalytic synthesis of benzo[f]quinolines from 2-heteroaryl-substituted anilines and heteroary...
Scheme 14: Synthesis of noravicine (14.2a) and nornitidine (14.2b) alkaloids.
Scheme 15: Gram-scale synthesis of the alkaloid trisphaeridine (15.3).
Scheme 16: Synthesis of phenanthridines starting from vinyl azides.
Scheme 17: Synthesis of pyrido[4,3,2-gh]phenanthridines 17.5a–d through the radical trifluoromethylthiolation ...
Scheme 18: The direct oxidative C–H amidation involving amidyl radicals for the synthesis of phenanthridones.
Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches
- Rodrigo Costa e Silva,
- Luely Oliveira da Silva,
- Aloisio de Andrade Bartolomeu,
- Timothy John Brocksom and
- Kleber Thiago de Oliveira
Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83
- thermal decomposition of urea at 550 °C for 2 h afforded the CN polymer, which possesses abundant –NH2 functional groups. The heterogeneous photocatalyst carbon nitride-hemin (CNH) was prepared after an amidation reaction between a carboxyl group of Fe(III) protoporphyrin IX and an amino group of the CN
Graphical Abstract
Figure 1: Chemical structures of the porphyrinoids and their absorption spectra: in bold are highlighted the ...
Figure 2: Photophysical and photochemical processes (Por = porphyrin). Adapted from [12,18].
Figure 3: Main dual photocatalysts and their oxidative/reductive excited state potentials, including porphyri...
Scheme 1: Photoredox alkylation of aldehydes with diazo acetates using porphyrins and a Ru complex. aUsing a ...
Scheme 2: Proposed mechanism for the alkylation of aldehydes with diazo acetates in the presence of TPP.
Scheme 3: Arylation of heteroarenes with aryldiazonium salts using TPFPP as photocatalyst, and corresponding ...
Scheme 4: A) Scope with different aryldiazonium salts and enol acetates. B) Photocatalytic cycles and compari...
Scheme 5: Photoarylation of isopropenyl acetate A) Comparison between batch and continuous-flow approaches an...
Scheme 6: Dehalogenation induced by red light using thiaporphyrin (STPP).
Scheme 7: Applications of NiTPP as both photoreductant and photooxidant.
Scheme 8: Proposed mechanism for obtaining tetrahydroquinolines by reductive quenching.
Scheme 9: Selenylation and thiolation of anilines.
Scheme 10: NiTPP as photoredox catalyst in oxidative and reductive quenching, in comparison with other photoca...
Scheme 11: C–O bond cleavage of 1-phenylethanol using a cobalt porphyrin (CoTMPP) under visible light.
Scheme 12: Hydration of terminal alkynes by RhIII(TSPP) under visible light irradiation.
Scheme 13: Regioselective photocatalytic hydro-defluorination of perfluoroarenes by RhIII(TSPP).
Scheme 14: Formation of 2-methyl-2,3-dihydrobenzofuran by intramolecular hydro-functionalization of allylpheno...
Scheme 15: Photocatalytic oxidative hydroxylation of arylboronic acids using UNLPF-12 as heterogeneous photoca...
Scheme 16: Photocatalytic oxidative hydroxylation of arylboronic acids using MOF-525 as heterogeneous photocat...
Scheme 17: Preparation of the heterogeneous photocatalyst CNH.
Scheme 18: Photoinduced sulfonation of alkenes with sulfinic acid using CNH as photocatalyst.
Scheme 19: Sulfonic acid scope of the sulfonation reactions.
Scheme 20: Regioselective sulfonation reaction of arimistane.
Scheme 21: Synthesis of quinazolin-4-(3H)-ones.
Scheme 22: Selective photooxidation of aromatic benzyl alcohols to benzaldehydes using Pt/PCN-224(Zn).
Scheme 23: Photooxidation of benzaldehydes to benzoic acids using Pt or Pd porphyrins.
Scheme 24: Photocatalytic reduction of various nitroaromatics using a Ni-MOF.
Scheme 25: Photoinduced cycloadditions of CO2 with epoxides by MOF1.
Figure 4: Electronic configurations of the species of oxygen. Adapted from [66].
Scheme 26: TPP-photocatalyzed generation of 1O2 and its application in organic synthesis. Adapted from [67-69].
Scheme 27: Pericyclic reactions involving singlet oxygen and their mechanisms. Adapted from [67].
Scheme 28: First scaled up ascaridole preparation from α-terpinene.
Scheme 29: Antimalarial drug synthesis using an endoperoxidation approach.
Scheme 30: Photooxygenation of colchicine.
Scheme 31: Synthesis of (−)-pinocarvone from abundant (+)-α-pinene.
Scheme 32: Seeberger’s semi-synthesis of artemisinin.
Scheme 33: Synthesis of artemisinin using TPP and supercritical CO2.
Scheme 34: Synthesis of artemisinin using chlorophyll a.
Scheme 35: Quercitol stereoisomer preparation.
Scheme 36: Photocatalyzed preparation of naphthoquinones.
Scheme 37: Continuous endoperoxidation of conjugated dienes and subsequent rearrangements leading to oxidized ...
Scheme 38: The Opatz group total synthesis of (–)-oxycodone.
Scheme 39: Biomimetic syntheses of rhodonoids A, B, E, and F.
Scheme 40: α-Photooxygenation of chiral aldehydes.
Scheme 41: Asymmetric photooxidation of indanone β-keto esters by singlet oxygen using PTC as a chiral inducer...
Scheme 42: Asymmetric photooxidation of both β-keto esters and β-keto amides by singlet oxygen using PTC-2 as ...
Scheme 43: Bifunctional photo-organocatalyst used for the asymmetric oxidation of β-keto esters and β-keto ami...
Scheme 44: Mechanism of singlet oxygen oxidation of sulfides to sulfoxides.
Scheme 45: Controlled oxidation of sulfides to sulfoxides using protonated porphyrins as photocatalysts. aIsol...
Scheme 46: Photochemical oxidation of sulfides to sulfoxides using PdTPFPP as photocatalyst.
Scheme 47: Controlled oxidation of sulfides to sulfoxides using SnPor@PAF as a photosensitizer.
Scheme 48: Syntheses of 2D-PdPor-COF and 3D-Pd-COF.
Scheme 49: Photocatalytic oxidation of A) thioanisole to methyl phenyl sulfoxide and B) various aryl sulfides,...
Scheme 50: General mechanism for oxidation of amines to imines.
Scheme 51: Oxidation of secondary amines to imines.
Scheme 52: Oxidation of secondary amines using Pd-TPFPP as photocatalyst.
Scheme 53: Oxidative amine coupling using UNLPF-12 as heterogeneous photocatalyst.
Scheme 54: Synthesis of Por-COF-1 and Por-COF-2.
Scheme 55: Photocatalytic oxidation of amines to imines by Por-COF-2.
Scheme 56: Photocyanation of primary amines.
Scheme 57: Synthesis of ᴅ,ʟ-tert-leucine hydrochloride.
Scheme 58: Photocyanation of catharanthine and 16-O-acetylvindoline using TPP.
Scheme 59: Photochemical α-functionalization of N-aryltetrahydroisoquinolines using Pd-TPFPP as photocatalyst.
Scheme 60: Ugi-type reaction with 1,2,3,4-tetrahydroisoquinoline using molecular oxygen and TPP.
Scheme 61: Ugi-type reaction with dibenzylamines using molecular oxygen and TPP.
Scheme 62: Mannich-type reaction of tertiary amines using PdTPFPP as photocatalyst.
Scheme 63: Oxidative Mannich reaction using UNLPF-12 as heterogeneous photocatalyst.
Scheme 64: Transformation of amines to α-cyanoepoxides and the proposed mechanism.
Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid
- Dong Cai,
- ZhiHua Zhang,
- Yufan Meng,
- KaiLi Zhu,
- LiYi Chen,
- ChangXiang Yu,
- ChangWei Yu,
- ZiYi Fu,
- DianShen Yang and
- YiXia Gong
Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73
- for the construction of important intermediate 8 are discussed. One procedure involves the amidation of 1-Boc-piperazine with 3-acetyl-18β-glycyrrhetinic acid, prepared by the reaction of 18β-glycyrrhetinic acid with acetic anhydride without any solvent at 130 °C. The other procedure to prepare
- compound 8 involves the amidation of 18β-glycyrrhetinic acid followed by the esterification with acetic anhydride. Finally, compound 8 underwent N-Boc deprotection to prepare product 4. To ascertain the scope of the reaction, another C-3 ester derivative 17 was tested under the optimized reaction
- two methods are complicated through the side formation of bisamide, obviously, due to the competitive attack on the N atoms of the symmetric diamine. An alternative method [12] to prepare such piperazinyl amides (c) involves the amidation of 18β-glycyrrhetinic acid with 4-substituted phenylpiperazines
Graphical Abstract
Figure 1: Chemical structure of 18β-glycyrrhetinic acid and known derivatives.
Scheme 1: Synthesis of compound 4. Reagents and conditions: (a) Ac2O, NEt3, DMF (cat.), DCM, 25 °C, 1 day; (b...
Scheme 2: Synthesis of compound 4. Reagents and conditions: (a) Ac2O, 130 °C, 1 h; (b) 1-Boc-piperazine, CH3C...
Figure 2: a) Estimated structure of the intermediate 6; b) Possible aminolysis process.
Scheme 3: Synthesis of byproduct 11. Reagents and conditions: (a) chloroacetic anhydride, 130 °C, 1 h.
Scheme 4: Synthesis of compound 17. Reagents and conditions: (a) chloroacetic anhydride, 130 °C, 1 h; (b) mor...
Figure 3: Crystal structure of conpound 18.
