Reactions of N-halogenobenzylmethylamines with triethylamine in acetonitrile. Effect of leaving group upon the imine-forming transition state

Abstract

Reactions of N-halogenobenzylmethylamines (1) and (2) with Et₃N–MeCN have been investigated kinetically. Eliminations from (1) and (2) were quantitative and regiospecific, producing only benzylidenemethylamines. For the elimination reaction of (1) with Et₃N, k_H/k_D 5.7, p 0.88, ΔH^‡ 9.1 kcal mol^–1, and ΔS^‡–42.4 cal mol^–1K^–1 were determined. The transition-state structure is assessed as being highly symmetric with similar extents of C_β–H and N_α–Cl bond cleavage, little carbanionic character, and significant π-bond formation. The structure of the transition state changes only slightly with the change in the leaving group from Cl to Br.