Carbene reactions of alpha-oxacyclo- and alpha-azacyclo-N-aziridinylimines: Effect of heteroatom and ring size in the ring expansion reaction

Carbenes, generated from thermolysis of alpha-oxacyclo- and alpha-azacyclo- N-aziridinylimines in refluxing toluene, underwent ring expansions via inse rtion of alkyl carbenes into carbon-carbon bonds and intramolecular ammoniu m ylide formations, respectively. Ring expansion reaction of alpha-oxetanyl -N-aziridinylimines occurred via alkylidenecarbene intermediates, whereas t hermal reaction of alpha-azetidinyl-N-aziridinylimines afforded alpha-amino acetylene compounds via 1,2-H migration of alkylidenecarbene intermediates.