24425-13-6Relevant articles and documents
Synthesis of benzimidazoles by phosphine-mediated reductive cyclisation of ortho-nitro-anilides
Duchek, Jan,Vasella, Andrea
experimental part, p. 977 - 986 (2011/08/05)
Heating ortho-nitro-anilides 1-3 and 2-methyl-N-(3-nitropyridin-2-yl) propanamide (5) with 4 equiv. of a phosphine led to the 2-substituted benzimidazoles 6-8 and to the imidazo[4,5-b]pyridine 10, respectively, in yields between 45 and 85%. Heating 1 with (EtO)3P effected cyclisation and N-ethylation, leading to the 1-ethylbenzimidazole 6b. The slow cyclisation of the N-pivaloylnitroaniline 2b allowed isolation of the intermediate phosphine imide 11 that slowly transformed into the 1H-benzimidazole 7b. The structure of 11 was established by crystal-structure analysis. While the N-methylated ortho-nitroacetanilide 3 cyclised to the 1,2-dimethyl-1H-benzimidazole (8), the 2-methylpropananilide 4 was transformed into 1-methyl-3-(1-methylethyl)-2H- benzimidazol-2-one (9).
Conversion of sterically hindered diacylated 1,2-phenylenediamines into 2-substituted benzimidazoles
Charton, Julie,Girault-Mizzi, Sophie,Sergheraert, Christian
, p. 492 - 497 (2007/10/03)
A series of bulky 2-substituted benzimidazoles was designed in order to find new leads for several biological targets. Formation by cyclodehydration from their monoacylated counterparts was shown to be strongly dependent upon the nature of the acyl group. In the case of a dicyclohexylmethyl group, cycllzation was only observed in a p-toluenesulfonic acid/toluene mixture from the symmetrical diacylated precursor. Analysis of the mechanism was begun starting from mixed diacylated derivatives.