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Search for "pyridinium salt" in Full Text gives 25 result(s) in Beilstein Journal of Organic Chemistry.
Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles
- Yumei Wang,
- Guangzhu Wang,
- Yanping Zhu and
- Kaiwu Dong
Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20
- mechanism of the CPA-catalyzed transfer hydrogenation reaction was proposed (Figure 2). The activation of 3,3-difluoro-substituted 3H-indole 1 by protonation through the Brønsted acid generates the iminium A. Subsequent hydrogen transfer from the Hantzsch ester gives the chiral amine 2 and pyridinium salt B
Graphical Abstract
Figure 1: Structures of bioactive fluorinated indole derivatives.
Scheme 1: Synthesis of chiral indolines via asymmetric reduction.
Scheme 2: Substrate scope of 3,3-difluoro-3H-indoles.
Scheme 3: Experiment at 2 mmol scale.
Figure 2: Proposed mechanism for the transfer hydrogenation reaction.
Facile access to pyridinium-based bent aromatic amphiphiles: nonionic surface modification of nanocarbons in water
- Lorenzo Catti,
- Shinji Aoyama and
- Michito Yoshizawa
Beilstein J. Org. Chem. 2024, 20, 32–40, doi:10.3762/bjoc.20.5
- technology. We here report pyridinium-based, bent aromatic amphiphiles PA-R, featuring a pyridinium salt (Py-R+·Cl−) as the key motif, capable of providing both a cationic hydrophilic hinge and a variety of nonionic side-chains (i.e., CH3 and CH2CH2(OCH2CH2)2–Y (Y = OCH3, OH, and imidazole); Figure 1b). The
Graphical Abstract
Figure 1: a) Previous methods for the water-solubilization and modification of nanocarbons (NCs). b) Bent aro...
Figure 2: a) Synthetic route toward prePA and PA-CH3, including the optimized structure (DFT) of PA-CH3. b) S...
Figure 3: 1H NMR spectra (500 MHz, rt, 0.5 mM and 1.0 mM based on PA-CH3 and PA-OCH3, respectively, TMS in CD...
Figure 4: a) General protocol for the noncovalent encircling of C60 and s-CNT by PA-R. b) UV–visible spectra ...
Figure 5: 1H NMR spectra (500 MHz, D2O, rt, 0.5 mM based on PA-Im) of (PA-Im)n·(C60)m a) before and b) after ...
Figure 6: a) Protocol for the noncovalent encircling of g-C3N4 by PA-OCH3 and subsequent deposit of g-C3N4 on...
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...
Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings
- Ivan P. Mosiagin,
- Olesya A. Tomashenko,
- Dar’ya V. Spiridonova,
- Mikhail S. Novikov,
- Sergey P. Tunik and
- Alexander F. Khlebnikov
Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105
- compounds are more expensive and less accessible than bromo-substituted analogs, we tried to accomplish the cyclization of pyridinium salt 1a using another radical mediator, tris(trimethylsilyl)silane (TTMSS) [31][32], which, moreover, is much less toxic than tributylstannane. Fortunately, free-radical
Graphical Abstract
Scheme 1: Retrosynthetic analysis of heterocycles A and B.
Figure 1: Molecular structure of compound 3a, displacement parameters are drawn at 50%.
Scheme 2: Free-radical cyclization of N-protected and N-unprotected pyrroles 1a and 2.
Scheme 3: Synthesis of 2H-pyrido[2,1-a]pyrrolo[3,4-c]isoquinolin-4-ium bromide 8.
Scheme 4: Free-radical cyclization of dihalogeno-substituted salts 9 and 12.
Figure 2: Molecular structure of compound 13, displacement parameters are drawn at 50% probability level.
Scheme 5: N-alkylation of the base 6a.
Figure 3: Molecular structure of compound 17a, displacement parameters are drawn at 50% probability level.
Scheme 6: Isomerization of compounds 17a and 18a.
Scheme 7: N-Alkylation of compounds 18a and 19.
A metal-free approach for the synthesis of amides/esters with pyridinium salts of phenacyl bromides via oxidative C–C bond cleavage
- Kesari Lakshmi Manasa,
- Yellaiah Tangella,
- Namballa Hari Krishna and
- Mallika Alvala
Beilstein J. Org. Chem. 2019, 15, 1864–1871, doi:10.3762/bjoc.15.182
- functional group tolerance, broad substrate scope and operational simplicity are the prominent advantages of the current protocol. Keywords: amidation; benzoylation; benzylamines; pyridinium salt of phenacyl bromides; Introduction Amidation and esterification are fundamental transformations in synthetic
- electron-donating groups on both the aryl moieties of the pyridinium salt of phenacyl bromides and benzylamines were well tolerated and delivered the corresponding products in good yields. The electron-rich pyridinium salts of phenacyl bromides reacted smoothly with the amines and furnished the
- ) the yield of the product was decreased. The product was not detected in the reaction with water as solvent (Scheme 5c). And finally, the pyridinium salt was replaced with phenacyl bromide (I) as a starting material and the reaction was performed under standard optimized conditions, but the expected
Graphical Abstract
Scheme 1: Comparison of our work with previous studies.
Scheme 2: Scope of pyridinium salts and benzylamine substrates. Reaction conditions: 1 (1 mmol), 2 (1 mmol), ...
Scheme 3: Scope of pyridinium salts and benzyl alcohol substrates. Reaction conditions: 1 (1 mmol), 4 (1 mmol...
Scheme 4: Scope of pyridinium salts, primary and secondary amine substrates. Reaction conditions: 1 (1 mmol), ...
Scheme 5: Control experiments for the oxidative cleavage of C–C bonds.
Scheme 6: Plausible reaction mechanism for the synthesis of N-alkylated benzamides 3.
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.
Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives
- Mikhail V. Makarov and
- Marie E. Migaud
Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36
- corresponding deprotected NR+ salt in good yields and free of admixtures, removal of acetate groups from 3-(carbamoyl)-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyridinium salt (NR+ triacetate) should be conducted under specifically controlled conditions (e.g., using ammonia in anhydrous methanol at −3 to −5 °C
Graphical Abstract
Figure 1: Structural formulas of Nam, NA, NR+, NMN, and NAD+.
Figure 2: Main synthetic routes to nicotinamide riboside (NR+X−).
Scheme 1: Synthesis of NR+Cl− based on the reaction of peracylated chlorosugars with Nam.
Figure 3: Predominant formation of β-anomer over α-anomer of NR+X−.
Scheme 2: Synthesis of NR+Cl− by reacting 3,5-di-O-benzoyl-D-ribofuranosyl chloride (5) with Nam (1a).
Figure 4: Mechanism of the formation of the β-anomer of the glycosylated product in the case of the reaction ...
Scheme 3: Synthesis of NR+Br− by reacting bromosugars with Nam (1a).
Scheme 4: Synthesis of NR+OTf− based on the glycosylation of Nam (1a) with tetra-O-acetyl-β-D-ribofuranose (2a...
Scheme 5: Improved synthesis of NR+OTfˉ and NAR+OTfˉ based on the glycosylation of pre-silylated Nam or NA wi...
Scheme 6: Synthesis of triacetylated NAR+OTf− by glycosylation of nicotinic acid trimethylsilyl ester with te...
Scheme 7: Synthesis of NR+Cl− from NR+OTf− by means of ion exchange with sodium chloride solution.
Scheme 8: Synthesis of acylated NR+OTf− by means of ion exchange with sodium chloride.
Scheme 9: Synthesis of triacetylated derivatives of NAR+ by glycosylation of nicotinic acid esters with ribos...
Scheme 10: Synthesis of NR+OTf− from the triflate salt of ethyl nicotinate-2,3,5-triacetyl-β-D-riboside in met...
Scheme 11: Reaction of 2,3,5-tri-O-acetyl-β-phenyl nicotinate riboside triflate salt with secondary and tertia...
Scheme 12: Synthesis of NMN based on the Zincke reaction of N-(2,4-dinitrophenyl)-3-carbamoylpyridinium chlori...
Scheme 13: Synthesis of NMN based on the Zincke reaction of N-(2,4-dinitrophenyl)-3-carbamoylpyridinium chlori...
Scheme 14: Efficacious protection of 2′,3′-hydroxy groups of NR+X−.
Scheme 15: Protection of the 2′,3′-hydroxy groups of NR+Cl– with a mesitylmethylene acetal group.
Figure 5: Reduction of derivatives of NR+Xˉ into corresponding 1,2-; 1,4-; 1,6-NRH derivatives.
Figure 6: Mechanism of the reduction of the pyridinium core with dithionite as adapted from [67].
Scheme 16: Reduction of triacylated NR+OTf– derivatives by sodium dithionite followed by complete removal of a...
Figure 7: Structural formulas of iridium and rhodium catalysts (a)–(d) for regeneration of NAD(P)H from NAD(P)...
Figure 8: Two approaches to synthesis of 5′-derivatives of NR+.
Scheme 17: Synthesis of NMN starting from NR+ salt.
Scheme 18: Efficient synthesis of NMN by phosphorylation of 2′,3′-O-isopropylidene-NR+ triflate followed by re...
Scheme 19: Synthesis of a bisphosphonate analogue of β-NAD+ based on DCC-induced conjugation of 2′,3′-O-isopro...
Scheme 20: Synthesis of 5′-acyl and 2′,3′,5′-triacyl derivatives of NR+.
Figure 9: Structural formulas of NMN analogues 39–41.
Scheme 21: Synthesis of 5′-phosphorylated derivatives of NR+ using a “reduction–modification–oxidation” approa...
Scheme 22: Synthesis of 5′-phosphorylated derivatives of NR+ using a “reduction–modification–reoxidation” appr...
Figure 10: Structural formulas of 5′-phosphorylated derivatives of NR+.
Scheme 23: Synthesis of 5′-phosphorylated derivatives of NR+ using a direct NR+ phosphorylation approach.
Figure 11: Structural formulas of amino acid NR+ conjugates.
Scheme 24: Synthesis of amino acid NR+ conjugates using NRH and protected amino acid under CDI-coupling condit...
Figure 12: Chemical structures of known isotopically labelled NR+ analogues and derivatives.
Scheme 25: Synthesis of [2′-3H]-NR+ and [2′-3H]-NMN.
Scheme 26: Synthesis of α- and β-anomers of [1′-2H]-NMN.
Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines
- Olga A. Storozhenko,
- Alexey A. Festa,
- Delphine R. Bella Ndoutoume,
- Alexander V. Aksenov,
- Alexey V. Varlamov and
- Leonid G. Voskressensky
Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287
- single crystal X-ray diffraction study (Figure 2). The sequential domino reaction presumably starts with the Knoevenagel condensation of o-hydroxybenzaldehyde and N-(cyanomethyl)pyridinium salt forming styryl derivative A, which undergoes intramolecular cyclization to give 2-iminochromene salt 3
Graphical Abstract
Figure 1: Biologically relevant imidazo[1,2-a]pyridines and chromenes.
Scheme 1: Domino formation of imidazopyridines and current work.
Scheme 2: Scope of the reaction between N-(cyanomethyl)pyridinium chloride, o-hydroxybenzaldehydes, and nitro...
Scheme 3: Scope of the reaction of o-hydroxybenzaldehydes with N-(cyanomethyl)pyridinium chloride and indoles...
Scheme 4: Scope of the nucleophiles in the reaction of o-hydroxyarylaldehydes with N-(cyanomethyl)pyridinium ...
Scheme 5: N-(Cyanomethyl)thieno[2,3-c]pyridinium chloride (15) and 6-(cyanomethyl)-1-methyl-1H-pyrrolo[2,3-c]...
Figure 2: General view of the molecule 7b in the crystal state (CCDC 1849215). Anisotropic displacement param...
Scheme 6: The presumed mechanism for the formation of target chromenoimidazopyridines (reaction 1) and additi...
Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors
- Mukta Shaw,
- Yogesh Kumar,
- Rima Thakur and
- Amit Kumar
Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236
- trichloroacetimidate donors using a synergistic catalytic system of electron-deficient pyridinium salts/aryl thiourea derivatives at room temperature is demonstrated. The acidity of the adduct formed by the 1,2-addition of alcohol to the electron-deficient pyridinium salt is increased in the presence of an aryl
- in the 1H NMR spectra. However, when the mixture of electron-deficient pyridinium salt 3a and glycosyl acceptor 2a (1:1) was dissolved in CD2Cl2 and investigated by 1H NMR, an upfield shift of the -CH2- peak of 3a from δ 6.17 to δ 4.03 (Figure 2c) was observed. This result clearly supports the
- , as envisaged, was indeed interesting and encouraging, which clearly indicates the ability of the electron-deficient pyridinium salt to activate the trichloroacetimidate donor. However, it took longer reaction time and required higher catalyst loading (up to 25 mol %). This outcome can be attributed
Graphical Abstract
Scheme 1: Mechanistic hypothesis for work.
Figure 1: 1H NMR (a) glycosyl donor 1α and (b) a mixture of 1α and 10 mol % 3a in CD2Cl2 at room temperature.
Figure 2: 1H NMR (a) glycosyl acceptor 2a, (b) pyridinium salt 3a (in DMSO-d6) and (c) a mixture of 2a and 3a...
Figure 3: 1H NMR (a) glycosyl acceptor 2a, (b) pyridinium salt 3a (in DMSO-d6), (c) aryl thiourea and (d) a m...
Scheme 2: Synergistic electron-deficient pyridinium salt/aryl thiourea-catalyzed regioselective O-glycosylati...
Figure 4: Plausible reaction mechanism.
Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles
- Johannes Schörgenhumer,
- Maximilian Tiffner and
- Mario Waser
Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170
- anions can control Pd-catalysed α-fluorinations [84]). Very interestingly, however, the authors clearly proved that the nature of the F-transfer reagent is crucial to obtain high selectivities. While NFSI or SelectfluorTM did not give reasonable enantioselectivities [81], the pyridinium salt 6 turned out
Graphical Abstract
Scheme 1: Generally accepted ion-pairing mechanism between the chiral cation Q+ of a PTC and an enolate and s...
Scheme 2: Reported asymmetric α-fluorination of β-ketoesters 1 using different chiral PTCs.
Scheme 3: Asymmetric α-fluorination of benzofuranones 4 with phosphonium salt PTC F1.
Scheme 4: Asymmetric α-fluorination of 1 with chiral phosphate-based catalysts.
Scheme 5: Anionic PTC-catalysed α-fluorination of enamines 7 and ketones 10.
Scheme 6: PTC-catalysed α-chlorination reactions of β-ketoesters 1.
Scheme 7: Shioiri’s seminal report of the asymmetric α-hydroxylation of 15 with chiral ammonium salt PTCs.
Scheme 8: Asymmetric ammonium salt-catalysed α-hydroxylation using oxygen together with a P(III)-based reduct...
Scheme 9: Asymmetric ammonium salt-catalysed α-photooxygenations.
Scheme 10: Asymmetric ammonium salt-catalysed α-hydroxylations using organic oxygen-transfer reagents.
Scheme 11: Asymmetric triazolium salt-catalysed α-hydroxylation with in situ generated peroxy imidic acid 24.
Scheme 12: Phase-transfer-catalysed dearomatization of phenols and naphthols.
Scheme 13: Ishihara’s ammonium salt-catalysed oxidative cycloetherification.
Scheme 14: Chiral phase-transfer-catalysed α-sulfanylation reactions.
Scheme 15: Chiral phase-transfer-catalysed α-trifluoromethylthiolation of β-ketoesters 1.
Scheme 16: Chiral phase-transfer-catalysed α-amination of β-ketoesters 1 using diazocarboxylates 38.
Scheme 17: Asymmetric α-fluorination of benzofuranones 4 using diazocarboxylates 38 in the presence of phospho...
Scheme 18: Anionic phase-transfer-catalysed α-amination of β-ketoesters 1 with aryldiazonium salts 41.
Scheme 19: Triazolium salt L-catalysed α-amination of different prochiral nucleophiles with in situ activated ...
Scheme 20: Phase-transfer-catalysed Neber rearrangement.
New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation
- Pavel Nagorny and
- Zhankui Sun
Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283
- attributed to their ability to form a hydrogen bond with the oxygen of epoxide. In 2015 Shirakawa and Maruoka demonstrated that ammonium salts L5 and L6 could serve as effective catalysts for isoquinolinium and pyridinium salt Mannich reactions (Scheme 7) [50]. Catalysts L5 and L6 were selected due to their
Graphical Abstract
Figure 1: Electrophile Activation by Hydrogen Bond Donors [1-16].
Figure 2: Early examples of C–H hydrogen bonds and their recent use in supramolecular chemistry [18,19,32-34].
Scheme 1: Design of 1,2,3-triazole-based catalysts for trityl group transfer through chloride anion binding b...
Scheme 2: Examples of chiral triazole-based catalysts for anion activation designed by Mancheno and co-worker...
Scheme 3: Application of chiral triazole-based catalysts L3 and L4 for counterion activation of pyridinium, q...
Scheme 4: Ammonium salt anion binding via C–H hydrogen bonds in solid state [40-45,50,51].
Scheme 5: Early examples of ammonium salts being used for electrophilic activation of imines in aza-Diels–Ald...
Scheme 6: Ammonium salts as hydrogen bond-donor catalysts by Bibal and co-workers [53,54].
Scheme 7: Tetraalkylammonium catalyst (L6)-catalyzed dearomatization of isoquinolinium salts [50].
Scheme 8: Tetraalkylammonium catalyst L6 complexation to halogen-containing substrates [51].
Scheme 9: Tetraalkylammonium-catalyzed aza-Diels–Alder reaction by Maruoka and co-workers [52].
Scheme 10: (A) Alkylpyridinium catalysts L13-catalyzed reaction of 1-isochroman and silyl ketene acetals by Be...
Scheme 11: Mixed N–H/C–H two hydrogen bond donors L14 and L15 as organocatalysts for ROP of lactide by Bibal a...
Scheme 12: Examples of stable complexes based on halogen bonding [68,69].
Scheme 13: Interaction between (−)-sparteine hydrobromide and (S)-1,2-dibromohexafluoropropane in the cocrysta...
Scheme 14: Iodine-catalyzed reactions that are computationally proposed to proceed through halogen bond to car...
Scheme 15: Transfer hydrogenation of phenylquinolines catalyzed by haloperfluoroalkanes by Bolm and co-workers ...
Scheme 16: Halogen bond activation of benzhydryl bromides by Huber and co-workers [82].
Scheme 17: Halogen bond-donor-catalyzed addition to oxocarbenium ions by Huber and co-workers [89].
Scheme 18: Halogen bond-donor activation of α,β-unsaturated carbonyl compounds in the [2 + 4] cycloaddition re...
Scheme 19: Halogen bond donor activation of imines in the [2 + 4] cycloaddition reaction of imine and Danishef...
Scheme 20: Transfer hydrogenation catalyzed by a chiral halogen bond donor by Tan and co-workers [91].
Scheme 21: Allylation of benzylic alcohols by Takemoto and co-workers [92].
Scheme 22: NIS induced semipinacol rearrangement via C–X bond cleavage [93].
Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics
- Kevin Lafaye,
- Cyril Bosset,
- Lionel Nicolas,
- Amandine Guérinot and
- Janine Cossy
Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241
- metathesis Formation of pyridinium/imidazolium salt prior to metathesis Most of the examples of RCM involving substrates that possess a pyridine ring relied on the pre-requisite formation of a pyridinium salt. In 2004, Vaquero et al. reported the synthesis of dihydroquinolizium cations through RCM of dienic
Graphical Abstract
Figure 1: Some ruthenium catalysts for metathesis reactions.
Scheme 1: Decomposition of methylidenes 1 and 2.
Scheme 2: Deactivation of G-HII in the presence of ethylene.
Scheme 3: Reaction between GI/GII and n-BuNH2.
Scheme 4: Reaction of GII with amines a–d.
Scheme 5: Amine-induced decomposition of GII methylidene 2.
Scheme 6: Amine-induced decomposition of GII in RCM conditions.
Scheme 7: Deactivation of methylidene 2 in the presence of pyridine.
Scheme 8: Reaction of G-HII with various amines.
Scheme 9: Formation of olefin 22 from styrene.
Scheme 10: Hypothetic deactivation pathway of G-HII.
Scheme 11: RCM of dienic pyridinium salts.
Scheme 12: Synthesis of polycyclic scaffolds using RCM.
Scheme 13: Enyne ring-closing metathesis.
Scheme 14: Synthesis of (R)-(+)-muscopyridine using a RCM strategy.
Scheme 15: Synthesis of a tris-pyrrole macrocycle.
Scheme 16: Synthesis of a bicyclic imidazole.
Scheme 17: RCM using Schrock’s catalyst 44.
Scheme 18: Synthesis of 1,6-pyrido-diazocine 46 by using a RCM.
Scheme 19: Synthesis of fused pyrimido-azepines through RCM.
Scheme 20: RCM involving alkenes containing various N-heteroaromatics.
Scheme 21: Synthesis of dihydroisoquinoline using a RCM.
Scheme 22: Formation of tricyclic compound 59.
Scheme 23: RCM in the synthesis of normuscopyridine.
Scheme 24: Synthesis of macrocycle 64.
Scheme 25: Synthesis of macrocycles possessing an imidazole group.
Scheme 26: Retrosynthesis of an analogue of erythromycin.
Scheme 27: Retrosynthesis of haminol A.
Scheme 28: CM involving 3-vinylpyridine 70 with 71 and vinylpyridine 70 with 73.
Scheme 29: Revised retrosynthesis of haminol A.
Scheme 30: CM between 78 and crotonaldehyde.
Scheme 31: Hypothesized deactivation pathway.
Scheme 32: CM involving an allyl sulfide containing a quinoline.
Scheme 33: CM involving allylic sulfide possessing a quinoxaline or a phenanthroline.
Scheme 34: CM between an acrylate and a 2-methoxy-5-bromo pyridine.
Scheme 35: Successful CM of an alkene containing a 2-chloropyridine.
Scheme 36: Variation of the substituent on the pyridine ring.
Scheme 37: CM involving alkenes containing a variety of N-heteroaromatics.
The simple production of nonsymmetric quaterpyridines through Kröhnke pyridine synthesis
- Isabelle Sasaki,
- Jean-Claude Daran and
- Gérard Commenges
Beilstein J. Org. Chem. 2015, 11, 1781–1785, doi:10.3762/bjoc.11.193
- accomplished through the simple synthesis of 6-acetyl-2,2’:6’,2”-terpyridine. After the preparation of the corresponding pyridinium salt, the subsequent condensation with enones led to the desired quaterpyridines. The methyl groups on the pyridine ring are potential grafting points, which can be used without
Graphical Abstract
Scheme 1: Synthesis of the quaterpyridines 6–8 and of the platinum complex 9.
Figure 1: Molecular view of compound 8 with the atom labelling scheme. Ellipsoids are drawn at the 50% probab...
Figure 2: Molecular view of compound 9 using the atom labelling scheme. Selected values of bonds (Å) and angl...
Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity
- Louis P. Sandjo,
- Victor Kuete and
- Maique W. Biavatti
Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183
- imine formation and aromatization, occurred presumably due to the presence of an acidic solvent. Styelsamine B (4) was obtained with an overall yield of 35%. This pyridinium salt was treated with an ampholyte to afford its neutral form cystodytin J (Scheme 1) [58]. This biomimetic synthetic strategy is
Graphical Abstract
Figure 1: Fragments produced by the FAB–MS of dehydrokuanoniamine B (20) [42].
Figure 2: Fragments produced by the EIMS of sagitol (26) [55].
Figure 3: Fragments produced by the EIMS of styelsamine B (4) [45].
Figure 4: Fragments produced by the EIMS of styelsamine D (6) [45].
Figure 5: Fragments produced by the EIMS of subarine (37) [40].
Scheme 1: Synthesis of styelsamine B (4) and cystodytin J (1) [58].
Scheme 2: Synthesis of sebastianine A (38) and its regioisomer 39 [59].
Scheme 3: Synthesis route A of neoamphimedine (12) [61].
Scheme 4: Synthesis route B of neoamphimedine (12) [62].
Scheme 5: Synthesis of arnoamines A (40) and B (41) [63].
Scheme 6: Synthesis of ascididemin (42) [65].
Scheme 7: Synthesis of subarine (37) [66,67].
Scheme 8: Synthesis of demethyldeoxyamphimedine (9) [68].
Scheme 9: Synthesis of pyridoacridine analogues related to ascididemin (42) [70].
Scheme 10: Synthesis of analogues of meridine (56) [71].
Scheme 11: Synthesis of bulky pyridoacridine as eilatin (58) [72].
Scheme 12: Synthesis of AK37 (59), analogue of kuanoniamine A (60) [73].
Figure 6: Biosynthesis pathway I [74].
Figure 7: Reaction illustrating catechol and kynuramine as possible biosynthetic precursors [75].
Figure 8: Biosynthesis pathway B deduced from the feeding experiment A using labelled precursors [76].
Figure 9: Proposed biosynthesis pathway [47].
Figure 10: 4H-Pyrido[2,3,4-kl]acridin-4-one as a cytotoxic pharmacophore.
Figure 11: 7H-Pyrido[2,3,4-kl]acridine as a cytotoxic pharmacophore.
Figure 12: 9H-Quinolino[4,3,2-de][1,10]phenanthrolin-9-one as a cytotoxic pharmacophore.
Figure 13: 8H-Benzo[b]pyrido[4,3,2-de][1,7]phenanthrolin-8-one as a cytotoxic pharmacophore.
Figure 14: Pyrido[4,3,2-mn]pyrrolo[3,2,1-de]acridine as a cytotoxic pharmacophore.
Figure 15: 9H-Pyrido[4,3,2-mn]thiazolo[4,5-b]acridin-9-one and 8H-pyrido[4,3,2-mn]thiazolo[4,5-b]acridine: cyt...
Figure 16: 9H-quinolino[4,3,2-de][1,10]phenanthrolin-9-one as an anti-mycobacterial pharmacophore.
Figure 17: 9H-Quinolino[4,3,2-de][1,10]phenanthrolin-9-one as an antibacterial pharmacophore.
Figure 18: Saturated and less saturated pyridine moieties as aspartyl inhibitor cores.
Figure 19: Iminobenzoquinone and acridone cores as intercalating and TOPO inhibitor motifs found in pyridoacri...
Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF5-substituted phenylboronic esters and iodobenzenes
- George Iakobson,
- Junyi Du,
- Alexandra M. Z. Slawin and
- Petr Beier
Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162
- tetrafluoroborate radical giving dihydrofuran (11) and pyridinium salt. Conclusion In conclusion, a novel dediazoniation–borylation methodology was developed based on the reaction of aryldiazonium tetrafluoroborates with pyridine and B2pin2 to give arylpinacolborates. Particular emphasis was on the synthesis of SF5
Graphical Abstract
Scheme 1: Borylation of aryldiazonium tetrafluoroborates 3. Reaction conditions: 3 (1 mmol), B2pin2 (1 mmol),...
Scheme 2: Proposed reaction mechanism.
Scheme 3: Reaction of diazonium salt 3i under borylation conditions.
Scheme 4: Suzuki–Miyaura reaction of boronates 2a and 2b with aryl iodides. Reaction conditions: 2 (1 mmol), ...
Scheme 5: Syntesis of boronic acid 8b and trifluoroborates 9. Reaction conditions for the synthesis of 8b: 2 ...
Scheme 6: Iodination of aryldiazonium tetrafluoroborates 3. Reaction conditions: 3 (1 mmol), I2 (1.1 mmol), p...
Synthesis of the calcilytic ligand NPS 2143
- Henrik Johansson,
- Thomas Cailly,
- Alex Rojas Bie Thomsen,
- Hans Bräuner-Osborne and
- Daniel Sejer Pedersen
Beilstein J. Org. Chem. 2013, 9, 1383–1387, doi:10.3762/bjoc.9.154
- (Scheme 2). Reduction of 7 was easily achieved on multigram scale by using LiAlH4 to provide amine 8 in excellent yield and purity after work-up. According to the method of Katritzky et al. [16] amine 8 was activated as the corresponding pyridinium salt 10 upon treatment with triphenylpyrylium salt 9 in
- ethanol under reflux. Subsequently, the crude pyridinium salt 10 was exposed to the sodium salt of 2-nitropropane (11) to give nitro compound 12. Reduction of the nitro group in 12 by catalytic hydrogenation at atmospheric pressure to produce amine 6 has previously been described by Kamal and Chouhan [17
Graphical Abstract
Figure 1: Marketed calcium-sensing receptor agonist cinacalcet (1), and CaSR antagonists Calhex 231 (2) and N...
Scheme 1: Strategy for assembling (R)-3 from fragments 4, 5 and 6. m-Ns = m-nitrobenzenesulfonyl.
Scheme 2: Synthesis of amine building block 6 by using Katritzky’s pyrylium chemistry [16].
Scheme 3: Synthesis of phenol 4 from commercially available aryl fluoride 13.
Scheme 4: Synthesis of rac-3 and (R)-3 from commercially available racemic- and (S)-glycidol 15, respectively...
Figure 2: Determination of the optical purity for (R)-3 by chiral HPLC on a Daicel AD-H column. Top: Opticall...
Figure 3: Characterisation of concentration-dependent (R)-3 inhibition of 3.5 mM calcium-stimulated IP1 respo...
Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts
- Mostafa Kiamehr,
- Firouz Matloubi Moghaddam,
- Satenik Mkrtchyan,
- Volodymyr Semeniuchenko,
- Linda Supe,
- Alexander Villinger,
- Peter Langer and
- Viktor O. Iaroshenko
Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124
- proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive
- screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product. Keywords: cyclization; density functional calculations; heterocycles; nucleophilic addition; pyridinium salt; Introduction The nucleophilic addition to pyridinium salts has recently
- -mentioned study we discovered an interesting reaction that represents an external dinucleophilic addition of the dimedone molecule to the pyridinium salt 2a, taken as a random example, delivering 8-oxa-10-aza-tricyclo[7.3.1.02,7]trideca-2(7),11-diene (3a) in modest yield (Scheme 1). Previously, we have
Graphical Abstract
Scheme 1: Reagents and conditions: (i) CH3CN, K2CO3, rt, 24 h.
Scheme 2: Synthesis of compounds 3–8. Reagents and conditions: (i): CH3CN, K2CO3, rt, 24 h. In the case of 3-...
Figure 1: Synthesized compounds 3, 4, 6, 7.
Figure 2: Plausible reaction mechanism.
Scheme 3: The influence of K+ on the product free energy.
Facile synthesis of functionalized spiro[indoline-3,2'-oxiran]-2-ones by Darzens reaction
- Qin Fu and
- Chao-Guo Yan
Beilstein J. Org. Chem. 2013, 9, 918–924, doi:10.3762/bjoc.9.105
- , the reactions of various substituted isatins with pyridinium salt in the presence of base were examined under different conditions. We were disappointed that the reactions produced much complicated mixtures and no acceptable results were obtained. Thus, our attention was turned toward the development
Graphical Abstract
Scheme 1: Synthesis of spiro-epoxyoxindole with pyridinium ylide.
Figure 1: Molecular structure of spiro compound 3c.
Figure 2: Molecular structure of spiro compound 4a.
Figure 3: Molecular structure of spiro compound 5o.
Control over molecular motion using the cis–trans photoisomerization of the azo group
- Estíbaliz Merino and
- María Ribagorda
Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119
- fluorescence emitted by the pyridinium salt free cyclophane. The azobenzene trans-10 is conveniently replaced with electron donor units, so that when it is associated, as azo-10∙11, the fluorescence is completely inhibited by charge-transfer interactions. The photoexcitation carried out by irradiation with
Graphical Abstract
Figure 1: Photoisomerization process of azobenzene.
Figure 2: Representative example of an UV spectrum of an azocompound of the azobenzene type (blue line: trans...
Figure 3: Mechanistic proposals for the isomerization of azobenzenes.
Figure 4: Representation of the photocontrol of a K+ channel in the cellular membrane based on the isomerizat...
Figure 5: (a) MAG interaction with iGluR; (b) photocontrol of the opening of the ion channel by trans–cis iso...
Figure 6: Photocontrol of the structure of the α-helix in the polypeptide azoderivative 2. Reprinted (adapted...
Figure 7: Recognition of a guanidinium ion by a cis,cis-bis-azo derivative 3.
Figure 8: Recognition of cesium ions by cis-azo derivative 4.
Figure 9: Photocontrolled formation of an inclusion complex of cyclodextrin trans-azo 5+6.
Figure 10: Pseudorotaxane-based molecular machine.
Figure 11: Molecular hinge. Reprinted (adapted) with permission from Org. Lett. 2004, 6, 2595–2598. Copyright ...
Figure 12: Molecular threader. Reprinted (adapted) with permission from Acc. Chem. Res. 2001, 34, 445–455. Cop...
Figure 13: Molecular scissors based on azobenzene 12. Reprinted (adapted) with permission from J. Am. Chem. So...
Figure 14: Molecular pedals. Reprinted by permission from Macmillan Publishers Ltd: Nature, 2006, 440, 512–515...
Figure 15: Design of nanovehicles based on azo structures. Reprinted (adapted) with permission from Org. Lett. ...
Figure 16: Light-activated mesostructured silica nanoparticles (LAMs).
Figure 17: Molecular lift.
Figure 18: Conformational considerations in mono-ortho-substituted azobenzenes.
Scheme 1: Synthesis and photoisomerization of sulfinyl azobenzenes. Reprinted (adapted) with permission from ...
Figure 19: Photoisomerization of azocompound 22 and its application as a photobase catalyst.
Figure 20: Effect of irradiation with linearly polarized light on azo-LCEs. Reprinted by permission from Macmi...
Figure 21: Chemically and photochemically triggered memory switching cycle of the [2]rotaxane 25.
Figure 22: Unidirectional photoisomerization process of the azobenzene 26.
Recent advances towards azobenzene-based light-driven real-time information-transmitting materials
- Jaume García-Amorós and
- Dolores Velasco
Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113
- -azobenzene derivatives. This notable red-shift of the absorption wavelength arises from the strong charge transfer from the alkoxy group to the positively-charged nitrogen atom of the pyridinium salt. Figure 8 shows the transient absorption generated upon pulsed laser irradiation of ethanol solutions of azo
- electron transfer from the alkoxy group to the pyridinium salt produces a partial breaking of the double N–N bond of the azo moiety, thereby facilitating the rotation around this bond to recover the more stable initial trans configuration in a quick fashion [56]. Type-II azoderivatives: photochromic
Graphical Abstract
Figure 1: Some important families of photochromic compounds and their photochromic reactions.
Figure 2: Photochromism of azobenzene derivatives and energetic profile for the switching process.
Figure 3: General overview of the different types of azoderivatives presented in this review.
Figure 4: Changes in the electronic spectrum of a 3 cis-to-trans isomerising ethanol solution at 45 °C (Δt = ...
Figure 5: Chemical structure and thermal relaxation time in ethanol at 298 K, τ, for the slow thermally-isome...
Figure 6: Rotation and inversion mechanisms proposed for the thermal cis-to-trans isomerisation processes of ...
Figure 7: Effect of the presence of the electron-withdrawing cyano and nitro groups on the thermal relaxation...
Figure 8: Transient absorption generated by UV irradiation (λ = 355 nm) for azo-dyes 8 (right) and 9 (left) i...
Figure 9: Effect of the presence of a positively charged nitrogen as an electron-withdrawing group on the the...
Figure 10: Mechanism proposed for the thermal cis-to-trans isomerisation process for the push–pull azopyridini...
Figure 11: Comparison between the thermal relaxation time at 298 K, τ, for the azoderivative 4 (type-I) and th...
Figure 12: Solvent effect on the thermal relaxation time at 298 K, τ, for the type-II azophenols 11–13.
Figure 13: Transient generated by irradiation with UV-light (λ = 355 nm) for the type-II azophenol 12 in ethan...
Figure 14: Proposed isomerisation mechanisms for the thermal cis-to-trans isomerisation of the alkoxy-substitu...
Figure 15: Solvent effect on the thermal relaxation time at 298 K, τ, for the type-II ortho-substituted azophe...
Figure 16: Cooperative effect of the para- and ortho-hydroxyl groups in azophenol 17.
Figure 17: Effect of the poly-hydroxylation of the azobenzene core on the thermal relaxation time at 298 K, τ,...
Figure 18: Transients generated by irradiation with UV-light (λ = 355 nm) for the poly-substituted azophenol 18...
Figure 19: Effect of the introduction of electron-withdrawing groups in the position 4’ of the azophenol struc...
Figure 20: Transient absorptions generated by UV irradiation (λ = 355 nm) of azo-dyes 11 (type-II), 19 (type-I...
Figure 21: Effect of the introduction of the hydroxyl group in the position 2’ of the push–pull azo-dye on the...
Figure 22: Effect of the substitution of a benzene ring by a pyridine one on the thermal relaxation time in et...
Figure 23: Influence of the introduction of additional electron-withdrawing nitro groups in the pyridine ring ...
Figure 24: Chemical structure and thermal relaxation time in ethanol at 298 K, τ, for the type-III azoderivati...
Figure 25: Oscillation of the optical density of an ethanol solution of azo-dye 26 generated by UV-light irrad...
Hybrid super electron donors – preparation and reactivity
- Jean Garnier,
- Douglas W. Thomson,
- Shengze Zhou,
- Phillip I. Jolly,
- Leonard E. A. Berlouis and
- John A. Murphy
Beilstein J. Org. Chem. 2012, 8, 994–1002, doi:10.3762/bjoc.8.112
- protonation, then it should undergo easy fragmentation to 45, featuring a pyridinium salt and an imidazolylidene, and in these circumstances, it would be difficult to understand why this electron-donor system works well. However, if isomeric compound 44 is the product of protonation, then its fragmentation to
Graphical Abstract
Figure 1: Super-electron-donors and related compounds.
Scheme 1: Preparation of the oxidised disalts.
Figure 2: Cyclic voltammograms in DMF of 8/4 (red) and 21/11 (blue). Current plotted vs V (relative to Fc/Fc+...
Scheme 2: Reductive reactions of donor 11 [17,18].
Figure 3: Cyclic voltammograms in DMF of 8/4 (red), 6/1 (green) and 22/9 (blue). Current plotted vs V relativ...
Scheme 3: Reductive reactions of donor 9.
Figure 4: (a) c.v. in DMF of 7/2 (red), 6/1 (green) and 27/10 (blue); (b) c.v. in DMF of 27/10 at different s...
Scheme 4: Use of hybrid donor 10 in reduction of iodoarenes.
Scheme 5: Reductive chemistry from disalt 15.
Scheme 6: Rationalisation of effect of excess NaH base.
Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines
- Jérôme Husson and
- Michael Knorr
Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41
- these with pyridinium salt 8 afforded 1,5-diketo-derivatives 9–11 through Michael addition. These derivatives are generally not isolated, but undergo in situ ring closure performed in the presence of an ammonia source, such as ammonium acetate, leading to terpyridines 12–14 (Scheme 1) [4][15]. In the
- sodium hydroxide without solvent, thus yielding 1,5-diketo-derivatives. Ring closure was then carried out in methanol in the presence of ammonium acetate, according to Scheme 2. In addition to reducing the amount of solvent , this one-pot two-steps procedure avoids preparation of pyridinium salt 8
- synthesis starts with 6-carboxy-2-acetylpyridine (20), which is reacted with furfural (1), thus providing chalcone 21. This is then reacted with di-pyridinium salt 22 in the presence of ammonium acetate to afford quinquepyridine 23 (Scheme 4). Another possibility to access the key intermediate “1,5-diketone
Graphical Abstract
Figure 1: Structure and atomic numbering of 2,2’:6’,2’’-terpyridines.
Scheme 1: Synthesis of furanyl-substituted terpyridines 12–14 by using Kröhnke’s method.
Scheme 2: Synthesis of terpyridines under solvent-free conditions.
Scheme 3: Preparation of 4,4′,4′′-trisubstituted terpyridine containing carboxylate moieties.
Scheme 4: Synthetic pathway for the preparation of a furanyl-functionalised quinquepyridine.
Scheme 5: Utilization of an iminium salt in the preparation of a furanyl-substituted tpy.
Figure 2: Chemical structure of U- and S-shaped isomers.
Scheme 6: Preparation of an asymmetric furanyl-substituted terpyridine.
Scheme 7: Synthesis of tpy by Stille cross-coupling reaction.
Scheme 8: Oxidation of the furan ring of furanyl-substituted terpyridines.
Scheme 9: Direct oxidation of a furan ring attached on Ru(II) tpy complexes.
Figure 3: Example of polyoxometalate frameworks functionalised with tpy ligands and tpy-complex (reprinted wi...
Scheme 10: Synthetic pathway to europium(III) and samarium(III) chelates 56 and 57.
Scheme 11: Synthetic pathway to prepare thiocyanato-functionalised tpys as potential biomolecule-labelling age...
Scheme 12: Synthetic sequence envisioned for biomolecules labelling by click-chemistry.
Figure 4: Structure of pyrrolyl (66), thienyl (67) and bithienyl (68)-substituted complexes analogous to comp...
Pyridinium based amphiphilic hydrogelators as potential antibacterial agents
- Sayanti Brahmachari,
- Sisir Debnath,
- Sounak Dutta and
- Prasanta Kumar Das
Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101
- dry DCM) added dropwise with stirring and ice cooling. The solution was stirred for 3–4 h, the DCM removed and the residue dissolved in ethyl acetate. The solution was washed with NaOH to remove excess acid and to convert the pyridinium salt to the free pyridine base. The organic layer was washed with
Graphical Abstract
Figure 1: Structure of amphiphiles 1–5.
Scheme 1: Synthetic procedure of the amphiphiles.
Figure 2: Variation of the Tgel with concentration of amphiphiles 1 and 2.
Figure 3: (a, b) FESEM images of the dried gels of 1 and 2, respectively at their MGC. (c, d) Two- and three-...
Figure 4: Luminescence spectra of 2 in water (λex = 330 nm) at various concentrations and room temperature.
Figure 5: FTIR spectra of (a) 1 and (b) 2 in CHCl3 solution (dashed line) and in D2O at the gel state (solid ...
Figure 6: 2D-NOESY spectra of 2 (2%, w/v) in DMSO-d6 with 70% water.
Figure 7: XRD diagram of the dried gel of 2.
Figure 8: Schematic representation of the possible arrangement of molecules during hydrogelation of 2.
Figure 9: MTT assay based percent NIH3T3 cell viability as a function of concentration of amphiphile 2.
The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts
- Kari Raatikainen,
- Massimo Cametti and
- Kari Rissanen
Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4
- strong hydrogen bond donor [N+–H···] moiety is envisaged to disrupt or severely hinder the strong halogen bonding interactions manifested in the non-HB pyridinium salt 9. Slow diffusion of ethyl acetate into the ethanol solution of 3-iodopyridinium chloride gave an X-ray-quality crystal of 10. The
Graphical Abstract
Scheme 1: The chemical structures of the salts 1–13.
Figure 1: X-ray structure of 4-IPhNH3Cl (1) with numbering for selected atoms (a) and the packing scheme view...
Figure 2: Interaction contacts in 4-IPhNH3Cl (1; a), 4-BrPhNH3Cl (2; b), 4-ClPhNH3Cl (3; c) and 4-FPhNH3Cl (4...
Figure 3: X-ray structure of 4-IPhNH3Br (5) with selected numbering scheme (a) and the packing scheme viewed ...
Figure 4: X-ray structure of 4-IPhNH3H2PO4 (6) with selected numbering scheme of the asymmetric unit and the ...
Figure 5: X-ray structure of 3-IPyBnCl (9) with the selected numbering scheme of the asymmetric unit (a) and ...
Figure 6: X-ray structure of 3-IPyHCl (10) with the selected numbering scheme of the asymmetric unit (a) and ...
Figure 7: X-ray structure of 3-IPyH-5-NIPA (13) with selected numbering scheme of the asymmetric unit (a). A ...
Convenient method for preparing benzyl ethers and esters using 2-benzyloxypyridine
- Susana S. Lopez and
- Gregory B. Dudley
Beilstein J. Org. Chem. 2008, 4, No. 44, doi:10.3762/bjoc.4.44
- these new conditions (Method A), as well as results obtained under the previously reported conditions using pre-formed pyridinium salt 1 and trifluorotoluene as the solvent (Method B, entries 2, 4, and 6). Benzylations of monoglyme (3a) and Roche ester (3b) were accomplished with similar efficiency
Graphical Abstract
Figure 1: Benzyl bromide, benzyl trichloroacetimidate, and 2-benzyloxy-1-methylpyridinium triflate (1).
Scheme 1: Published syntheses of benzyl esters from alcohols using neutral reagent 1; other benzylation proce...
Scheme 2: Preparation of 2-benzyloxypyridine (2).
Scheme 3: Synthesis of a benzyl ester from a carboxylic acid.
Scheme 4: Representative synthesis of a halobenzyl ether under neutral conditions.
