Synthesis of 1,2-disubstitued benzimidazoles using SiO2/ZnCl2

Biomass into chemicals: One-pot two- and three-step synthesis of quinoxalines from biomass-derived glycols and 1,2-dinitrobenzene derivatives using supported gold nanoparticles as catalysts

“…At the beginning of the reaction, only the α-hydroxycarbonyl compound (4), formed by oxidation of the diol 2g, and benzaldehyde (6) which comes from the oxidative cleavage of 2g were observed as primary products. However, after one hour reaction, their concentration decreases probably by reaction of the α-hydroxycarbonyl compound (4) with a molecule of phenylenediamine 1a to afford 2-phenylquinoxaline 3 and, in a much lesser degree, the benzimidazole derivatives (8, 9, 10 and 11) [55]. Since this consecutive reaction is very fast, product 3 appears as a pseudo primary product.…”

Indion 190 resin: efficient, environmentally friendly, and reusable catalyst for synthesis of benzimidazoles, benzoxazoles, and benzothiazoles

“…A number of methods are in vogue for the synthesis of these heterocycles by using different catalysts such as Pd-catalyzed oxidative cyclization (12); ionic-liquid-mediated synthesis (13); baseassisted reaction of 1,1-dibromoethanes (14), SiO 2 / ZnCl 2 (15), ZrOCl 2 ×8H 2 O (16), In(OTF) 3 (17), polyethylene-glycol-mediated catalysts (18), and different heteropolyacid catalysts (19), which include condensation of orthoesters 20Á22, nitriles (23), aldehydes (24), carboxylic acids (25), acid chlorides (26), amides (27), and esters (28) with o-substituted aminoaromatics in the presence of different acids or catalysts; Beckmann rearrangement of o-acylphenol oximes (29); photocyclization of phenolic Schiff bases (30); and benzimidazole synthesis in solvent-free conditions (15). More recently, Germin et al (31) have developed cleaner protocols for alkoxybenzimidazole synthesis via S N Ar reaction, and our group developed benzimidazole, benzoxazole, and benzothiazole from condensation of aldehydes with o-substituted aminoaromatics in the presence of phosphorus trichloride (32).…”

A Green Route for the One‐Pot Synthesis of 1,2‐Disubstituted Benzimidazoles Using Iron(III) Phosphate under Solventless Conditions

“…Finally, 1,3-hydridetransfer followed to produce 1,2-disubstituted benzimidazoles. [20] Recently Jacob and et al [27] proved when the reaction in the presence of deuterated solvents such as D 2 O and CH 3 OD was performed; any amount deuterated benzimidazole was detected. The mechanism can be enhanced that the reaction probably occurs according to Scheme 2.…”