Skeletal contraction: A novel strategy to access multisubstituted cyclobutane

Abstract

The polysubstituted and spirocyclic cyclobutanes were efficiently constructed by the utilization of a novel skeletal contraction strategy which only took one-step synthesis from the readily accessible pyrrolidines. The mechanistic studies indicated that a key intermediate N-aminated pyrrolidine was formed initially and subsequent extrusion of a nitrogen via a radical pathway completed the transformation. This practical methodology was further highlighted by the concise, formal synthesis of the cytotoxic natural product piperarborenine B.