Reactions of N-Halobenzylalkylamines with Sodium Methoxide in Methanol

Reactions of N-halobenzylmethylamines 1 and 2 (X = Cl and Br) with MeONa-MeOH have been investigated. Eliminations from 1 were quantitative, producing only benzylidenemethylamines. Reaction of 2 with MeONa-MeOH produced benzylidenemethylamines and benzylmethylamines. The yield of benzylidenemethylamine increased with electron-withdrawing aryl substituents and increased base concentration and became quantitative when pentane was used as a solvent. The results are interpreted as competing bimolecular elimination and nucleophilic substitution by methoxide on bromine. Product studies for reaction of NN-halobenzyl-tert-butylamines with MeONa-MeOH and EtSNa-MeOH establish that the substitution reaction is a general reaction pathway available for the N-haloamines. Transition states for eliminations from 1 and 2 are characterized by Hammett p and primary deuterium isotope effect values.