N → N′ intramolecular acyl transfer in acid media for alkylenediamine derivatives

Abstract

Intramolecular N → N′ benzoyl migrations in acid media at 25° are reported for N′-aryl-N-benzoyl-N-methyl-ethylene- and trimethylene-diamine derivatives. Kinetic studies were performed on N → N′ benzoyl transfer for N-benzoyl-N-methyl-N′-phenylethylenediamine (1) in acid solutions over the H₀–pH range –2.28 to 2.30. The existence of a maximum in the pH–rate profile and chromatographic experiments provide evidence for a tetrahedral addition intermediate. Compound (1) undergoes acyl transfer to give N-benzoyl-N-phenyl-N′-methyl-ethylenediamine (4) by a mechanism which involves the formation and rate-determining catalysed decomposition of the addition intermediate over the pH range 0.24–2.30. Below H₀–0.54 the reaction involves the rate-determining formation of the intermediate and observed rate constants become pH independent. Some factors influencing the rearrangement such as the number of methylene groups, basicity of the attacking nucleophile, and importance of the N-methyl group, are analysed. Two reaction schemes are proposed to explain the results.