Succinimidation by N-bromosuccinimide of N,N-dimethylamido and N,N-dimethylamino groups

N,N-Dimethylamides (1)–(6) and N,N-dimethylamines (7)–(10) are converted by the action of N-bromosuccinimide (NBS) in carbon tetrachloride and in the presence of a catalytic amount of benzoyl peroxide into the corresponding succinimido derivatives (11)–(23). The reaction involves two steps: (i) a radical bromination of the N-methyl moiety; and (ii) subsequent reaction of the resulting N-bromo-methyl derivatives (24) with NBS. The latter step occurs via electrophilic substitution of the bromine atom of NBS by stabilized azacarbonium ions of which the N-bromomethyl derivatives (24) are effective sources. Proof of the suggested ionic mechanism is obtained from the conversion of independently synthesized N-bromomethylamides (25) and (26) and N-bromomethyl-N,N-dimethylamine (27) into the succinimido derivatives (11), (15), and (28) respectively by reaction with NBS in carbon tetrachloride. Bromomethylphthalimide (29), in which the two carbonyl groups destabilize the charge in the corresponding imidocarbonium ion, reacts only when a more solvolytic solvent such as nitrobenzene is used.