An unusual substitution reaction directed by an intramolecular re-arrangement

Secondary amines and thiols undertake a substitution reaction on the side chain of 2-bromoethyl-pyridinium derivatives ‘directed’ by an intramolecular re-arrangement. Experimental investigations strongly indicate that the reaction is initiated by an alpha addition of the nucleophile onto the iminium moiety of the N-heteroaromatic cation, followed by a cyclisation and an oxidative ring opening. This novel substitution process is able to occur with less reactive nucleophiles that would not undergo conventional substitution with ‘isolated’ bromoethyl moieties.