Studies on a new route to (±)-copaene and (±)-ylangene

Abstract

Elaboration of the perhydroazulene ring system formed by the intramolecular cycloaddition of a dienyl-substituted 3-oxidopyrylium has generated key intermediates used in the total synthesis of the α- and β-series of the copaene and ylangene sesquiterpene hydrocarbons. During the synthesis of the β-series of compounds selective protection of an olefinic bond was achieved by thiol addition; protection in this manner preventing migration of the double bond from an exocyclic to endocyclic position during the perhydroazulene to decalone rearrangement.