Stereoselective and regioselective synthesis of azepane and azepine derivatives via piperidine ring expansion

Abstract

Diastereomerically pure azepane derivatives 5, 13 were prepared by piperidine ring expansion with exclusive stereoselectivity and regioselectivity and in excellent yield. The structure and stereochemistry of 5 were confirmed via X-ray crystallographic analysis. The ring expansion strategy was applied to the construction of an azepine backbone 22 of a potential biologically active compound. The regiochemistry and stereochemistry of the piperidine ring expansion process were investigated by semiempirical molecular orbital calculations.