Amine oxidation. Part X. The oxidation of some 4-substituted NN-dimethylbenzylamines and a selection of other amines with 1-chlorobenzotriazole

Abstract

1-Chlorobenzotriazole in benzene converts substituted NN-dimethylbenzylamines into NN-disubstituted aminoalkylbenzotriazoles and a product containing positive chlorine. Hydrolytic work-up gives substituted benzaldehydes and benzylmethylamines. Kinetic studies show that the consumption of 1-chlorobenzotriazole, corrected for the positive chlorine in the product, obeys the rate law –d[chlorobenzotriazole]/dt=k₂′[amine][chlorobenzotriazole]. Correlation of the logarithm of the second-order rate constants for oxidation of the NN-dimethylbenzylamines using the Hammett and Brönsted relationships gives ρ–0.71 and α 0.63 respectively. Comparative kinetic measurements with NN-dimethylbenzylamine and NN-dimethyl[α-²H₂]benzylamine give k₂′H/k₂′D = 1·3. Product studies reveal information about the factors that control the direction of the oxidative dealkylation. The identity of the active chlorine product although not conclusively established is assigned as the NN-dimethylbenzylchloroammonium ion.

In the suggested mechanism the predominant role of 1-chlorobenzotriazole involves an initial one-electron abstraction from the amine followed by a product-determining deprotonation of the resulting aminium radical. Chlorine transfer is a minor route.

Information obtained from the reaction of a selection of other amines supports the dual nature of these oxidations.