A Preferred Intramolecular ‘Ene’ Reaction Between Ketene and Olefin

Abstract

Aplysin (1), a marine sesquiterpene was isolated from ‘aplysia kurodai’ and its structure was ellucidated by Hirata-et-al¹. They also reported the synthesis of racemic aplysin². Their synthetic route involved cyclopentanone (2) as a well-characterized intermediate. We visualized the synthesis of cyclobutanone (3) and its subsequent conversion to (2) as an attractive alternative. But during our attempts to synthesize the said cyclobutanone, we have come across a very facile intramolecular ‘ene’ reaction between ketene and olefin. We report our unexpected observations in this communication.