Asymmetric synthesis of carbocycles: use of intramolecular conjugate displacement

Intramolecular conjugate displacement (ICD), the process illustrated in eqn (1), has been applied to the Morita–Baylis–Hillman adducts formed from (5S)-5-(L-menthyloxy)-2(5H)-furanone and aldehydes that are substituted in the γ- or δ-position by geminal phenylthio groups. When the initial Morita–Baylis–Hillman alcohols are acetylated and oxidized to geminal sulfones, deprotonation causes ring closure by ICD (2.5→2.6). Hydrogenation, DIBAL-H reduction and desulfonylation releases an optically pure carbocycle.