Amidines. IV. : Hydrolysis of N¹-Acyl Derivatives of N¹, N²-Diarylamidine in Carboxylate Buffer Solution

Abstract

In the hydrolysis of N¹-benzoyl-N¹, N²-diphenylacetamidine (1) in carboxylate buffer solutions, nucleophilic attack of the catalytic acid was proved to take place at the amide carbonyl carbon (pathway d) and presumably also at the amidine central carbon (pathway e) in parallel to the normal hydrolysis processes. Mixed acid anhydride and N¹, N²-diphenylacetamidine were formed by pathway d, and the former reacted with aniline formed by further hydrolysis of the latter to give two N-acylanilines. In parallel with this process, the mixed anhydride reacts with water to give two carboxylic acids. In this case, carboxylic acid acts as a nucleophilic catalyst.The reaction of 1 and p-methoxybenzoic acid under anhydrous conditions gave products derived from the attack of p-methoxybenzoate ion at both amide carbonyl and amidine central carbons.Hydrolysis of N¹-benzoyl-N-¹, N²-diphenylformamidine (7) in acetate buffer solution proceeded mainly through the ordinary hydrolysis pathway. Formation of a small amount of acetanilide implies that the reaction proceeds through pathway d or e to a small extent.In hydrolysis of N¹-tosyl-N¹, N²-di(p-methylphenyl)acetamidine (6b) in glycolate buffer solution, a small amount of N-(acetoxyacetyl)-p-toluidine was formed together with the ordinary hydrolysis products. This implies that the reaction proceeds through pathway e to a small extent.