Anionic cyclization of N-aziridinyl imines

Abstract

Anionic cyclization, widely utilized for the construction of carbocycles, primarily involve stabilized anionic intermediates, although much attention has recently been devoted to the cyclization of reactive anionic intermediates onto unactivated alkenes. A conceptually novel anionic cyclization has been studied using N-aziridinylimines as 1,1-dipoles. Anionic cyclization reaction of N-aziridinylimines was achieved, involving the formation of consecutive carbon-carbon bonds at the same carbon, which has considerable synthetic potential for the construction of carbocycles. In order to find proper nucleophiles which can reductively alkylate N-aziridinylimine, several nucleophiles were studied and found that vinylmagnesium bromide and allyl lithium gave most satisfactory results. The addition of organometallic reagents such as vinylmagnesium bromide and allyllithium onto N-aziridinylimines generates allyl and homoallyl anions which undergo anionic cyclizations for ring formations. With the evolution of nitrogen and styrene, successive carbon-carbon bond formations at the iminyl carbon of aldehydeaziridinylimine resulted in carbocycle in good yield. Next, tandem anionic cyclization of N-aziridinylimines could be achieved using allyl lithium and vinyl lithium to afford polycarbocycles.