N-Monobenzoylation (acetylation, arylsulfonation), N-, C- di- and N-, C-, O- tribenzoylation of 5H(chloro, nitro)-2-methyl(ethyl)benzimidazoles

Abstract

The interaction of 2­methyl(ethyl)­5H(chloro, nitro)benzimidazoles with benzoyl (acetyl) chloride, and p­toluenesulfonyl chloride in the presence of triethylamine in tetrahydrofuran or chloroform was studied. It was found that the reaction proceeds in three stages with the formation of N­ monobenzoyl (acetyl, p­toluenesulfonyl), N­, C­dibenzoyl­ and N­, C­, O­tribenzoyl benzimidazoles depending on the ratio of reagents, the nature of the substituent in the aromatic ring, α­methylene group, and acid chlorides. It was revealed that in the case of acetyl, p­toluenesulfonyl chloride reaction is stopped at the first stage with formation of N­monoacetyl (p­toluenesulfonyl) derivatives. The method for HPLC analysis for separation, identification and determination of the ratio of obtained compounds was developed. It was found that 1­acetyl (benzoyl)­2­methylbenzimidazoles Original Research Article Shakhidoyato et al.; ACSj, 6(4): 192-204, 2015; Article no.ACSj.2015.051 193 were decomposed at the standing. The crystalline form of 1­acetyl­2­methylbenzimidazole is decomposed to the 2­methylbenzimidazole: 25% (7 days), 50% (15 days), 100% (30 days) and decomposition of 1­benzoyl­2­methylbenzimidazole to the 2­methylbenzimidazole (50%) occurs within 2 months.