Simple Synthesis of Benzazoles by Substrate-Promoted CuI-Catalyzed Aerobic Oxidative Cyclocondensation of o-Thio/Amino/Hydroxyanilines and Amines under Air

Simple practical method for synthesis of trisubstituted imidazoles: an efficient copper catalyzed multicomponent reaction

“…Aer that, intermediate C gets converted into E by loss of water which further converts into intermediate F via oxidation in the presence of CuI catalyst. [43][44][45][46][47][48] The same F intermediate formation takes place from intermediate D by loss of water. At the end, the desired product 4a formation takes place from common intermediate F via [1,5]-Htransfer.…”

Recent Advances in the Synthesis of Benzimidazole Derivatives from the Oxidative Coupling of Primary Amines

“…Xu and co-workers have reported a similar action of CuI (5 mol%) for the catalyzed oxidative cyclocondensation of benzylic amines (2 equiv) and o-phenylenediamines (1 equiv) in toluene at 100 °C under air for 48 hours. 19 The yields of isolated 2-substituted benzimidazole derivatives were acceptable, ranging from 41 to 83%. Noteworthy, variously substituted benzothiazoles and benzoxazoles were also prepared through this protocol.…”

“…20 Xu and co-workers have proposed an alternative route in which the CuI-catalyzed aerobic oxidation of amines under air produces the homocoupled imine intermediate, which then reacts with o-phenylenediamine to give the cross-coupled imine through a transimination step (path C). 19 Because of the presence of benzaldehyde as the byproduct in reactions with low conversion, Xu and co-workers also envisage that benzylimine can hydrolyze into benzaldehyde and then afford the cross-coupled imine by condensation reaction (path B). The final steps of the process leading to the target benzimidazole heterocycle involve intramolecular cyclization and subsequent oxidation as reported in Scheme 1.…”

Sodium dichloroiodate promoted C-C bond cleavage: An efficient synthesis of 1,3-Benzazoles via condensation of $${\varvec{o}}$$ o -amino/mercaptan/hydroxyanilines with $${\varvec{\beta }}$$ β -diketones

“…A range of methods are available for synthesis of these heterocycles, including condensation of ophenylenediamine, o-aminophenol, or o-aminobenzenethiol, with aldehydes/carboxylic acids or their equivalents including acid chlorides, amides, nitriles, orthoesters, and β-ketoesters. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] All these methods involve the use of strong oxidative conditions, high temperature, strong proton acids, and/or microwave irradiation for high yields. Another method involves the transition-metal-catalyzed intramolecular cyclization of 2-haloanilides analogues.…”