Synthesis of 1,2-disubstituted benzimidazole-5(6)-carboxamides and evaluation of their antimicrobial activity

A series of 14, N'-(N,N-dialkylaminoethyl)-benzimidazole-5(6) or 5-carboxyamides (1-14), having several substituents on the azole and benzene nuclei, were prepared and evaluated in vitro for antimicrobial activity. The precursor benzimidazolecarboxylic acids (15-27) were prepared via oxidative condensation of diaminobenzoic acids and several aldehydes with cupric ion. Compounds 11-14 were prepared by selective regioisomer synthesis. All carboxamides were prepared from the corresponding acids and N,N-dialkylethylenediamine. Antibacterial and antifungal activities were determined as MIC values. Of the synthesized compounds 1-10, 6 and 10 were found to be the most favourable. In order to clarify the effect of the substituents at N1 on antimicrobial activity, 12 was prepared by p-chlorobenzyl substitution of compound 6, and increased activity was shown. Compounds 13 and 14, which were prepared by replacement with more bulky alkyl groups on the tert-N atom than 12, gave the best results.