Alkaline hydrolysis of 1,2,3-trisubstituted cyclic amidinium salts. Kinetic study of N → N′ acyl migration in alkaline solution in an ethylenediamine derivative

Abstract

The alkaline hydrolysis of 1,2-diphenyl-3-methylimidazolinium iodide (1) affords N-benzoyl-N-phenyl-N′-methylethylenediamine (2). An intermediate of the reaction, probably 1,2-diphenyl-2-hydroxy-3-methylimidazolidine (8), was isolated by thick layer chromatography. Compound (2) in neutral or alkaline media undergoes intramolecular aminolysis affording N-benzoyl-N-methyl-N′-phenylethylenediamine (3) by benzoyl transfer. Kinetic studies were performed on this reaction over the pH range 11.65–12.80. Compound (2) appears to rearrange by a mechanism which involves the formation and catalysed decomposition of a tetrahedral addition intermediate. This intermediate is the same as that isolated by alkaline hydrolysis of (1). Pseudo-first-order rate constants show a first-order dependence on hydroxide ion activity all over the pH range studied indicating that the contribution of the anionic species of the intermediate is negligible under the experimental conditions. The alkaline hydrolysis of the 1,2-diphenyl-1,4,5,6-tetrahydropyrimidinium iodide (9) allowed the isolation of only the rearranged product N-benzoyl-N-methyl-N′-phenyltrimethylenediamine (10).