Regioselective generation of iminium cation by PET processes: Its in situ trapping by intramolecular nucleophiles and synthesis of some biologically active heterocycles

Article abstract of DOI:10.1016/S0040-4020(01)80497-X

Efficient, mild and direct route for regiospecific iminium cation is developed by sequential two electron oxidation of several N-alkylated tertiary amines by photoinduced electron transfer processes. The regiospecificity of iminium cation arises from the deprotonation step of amine radical cation to generate α-amino radical which depends on the stereoelectronic factor subject to kinetic acidity of amine radical cation. Iminium cation is efficiently trapped in situ by internal nucleophiles to give cyclic compounds 14-18 and 22a-c. Stereoselective synthesis of cis α,α'-dialkylated piperidines and pyrrolidines 30a-c is achieved by nucleophilic opening of tetrahydro-1,3-oxazines 22a-c.