Synthesis of functionalized benzimidazoles and quinoxalines catalyzed by sodium hexafluorophosphate bound Amberlite resin in aqueous medium
作者:Pranab Ghosh、Amitava Mandal
DOI:10.1016/j.tetlet.2012.09.045
日期:2012.11
for the selective synthesis of 1,2-disubstitutedbenzimidazoles and quinoxalines in water–methanol (1:1) mixture with the aid of resin bound hexafluorophosphate ion as catalyst is reported. The method is also effective for the incorporation of quinoxaline nucleus at the A ring of pentacyclic triterpenoid, friedelin. A plausible mechanism for the formation of disubstituted benzimidazole has also been suggested
Selectivity control during the solid supported protic acids catalysed synthesis of 1,2-disubstituted benzimidazoles and mechanistic insight to rationalize selectivity
作者:Dinesh Kumar、Damodara N. Kommi、Rajesh Chebolu、Sanjeev K. Garg、Raj Kumar、Asit K. Chakraborti
DOI:10.1039/c2ra21994h
日期:——
Selectivity control during the formation of 1,2-disubstituted benzimidazoles has been achieved for the reaction of o-phenylenediamine with aldehydes in the presence of solid supported protic acids as catalysts and choosing an appropriate reaction medium. Perchloric acid adsorbed on silica-gel (HClO4–SiO2) was found to be the most effective catalyst system for the synthesis of 1,2-disubstituted benzimidazoles in EtOH at rt. Apart from the catalyst and solvent, the electronic and steric factors of the aldehyde and the electronic factor of the o-phenylenediamine are also significant contributory factors in dictating the selectivity. An understanding of the mechanistic course of the formation of the 1,2-disubstituted benzimidazoles has been outlined that would rationalise the origin of selectivity control under the set experimental parameters.
Catalytic role of sodium dodecyl sulfate: Selective synthesis of 1, 2-disubstituted benzimidazoles in water
作者:Pranab Ghosh、Amitava Mandal
DOI:10.1016/j.catcom.2011.01.005
日期:2011.3
A simple and efficient procedure for the synthesis of 1, 2-disubstituted benzimidazoles has been developed by a one-pot reaction of o-phenylenediamine with both aromatic and aliphatic aldehydes in the presence of sodiumdodecylsulfate in aqueousmedium at roomtemperature in open air without any organic solvent. The surfactant is recycled. A plausible mechanistic approach has also been suggested.
o-phenylenediamine and carbonyl compounds by Brønstedacid/base assisted titanocene dichloride. Mechanism research including NMR and ESI-MS analyses and control experiments elucidated the new catalytic species formed by Cp2TiCl2 and the combination of titanocene Lewis acid with Brønstedacid/base was responsible for selective transformations of aldehyde and ketone with o-phenylenediamine into benzimidazole
Highly selective synthesis of libraries of 1,2-disubstituted benzimidazoles using silica gel soaked with ferric sulfate
作者:Susmita Paul、Basudeb Basu
DOI:10.1016/j.tetlet.2012.05.129
日期:2012.8
An efficient and highly selective synthesis of functionalized 1,2-benzimidazoles has been developed under solvent-free conditions at ambient temperature using eco-friendly ferric sulfate soaked with silica [iron(III)sulfate–silica]. Recycling of the solid support up to six runs was investigated with appreciable yield and selectivity of the product.