Synthesis of some new benzimidazole-5(6)-carboxylic acids

The title compounds, 1,2-dialkyl-benzimidazole-5(6)-carboxylic acids 34–45 were prepared at four steps; 1) preparation of mono amide derivatives 1–11 by the reaction of methyl 3,4-diaminobenzoate and substituted phenyl or phenoxyacetic acid chlorides; 2) preparation of the methyl benzimidazolecarboxyl-ates 12–22 , with zinc chloride and dry hydrogen chloride gas; 3) alkaline hydrolysis of the esters 23–33 ; and 4) substitution of the imidazole ring with benzyl or p-fluorobenzyl bromide, in alkali medium. 2-Aryl-benzimidazole-5(6)-carboxylic acids 50–53 were prepared via the oxidative condensation of 3,4-diaminobenzoic acid and aromatic aldehydes with cupric ion.