Preparation of An 8-Membered Ring via Intramolecular Photocycloadduct: Formal Total Synthesis of (+/-)-Precapnelladiene

Article abstract of DOI:10.1246/bcsj.66.324

Irradiation of 4,4-dimethyl-3-<(2-cyclopentenyl)methoxy>-2-cyclohexen-1-one, prepared from 4,4-dimethyl-3-phenylthio-2-cyclohexen-1-one and (2-cyclopentenyl)methanol, gave a tetracyclic intramolecular <2+2>-photocycloadduct 7.Treatment of 7 with iodotrimethylsilane followed with tributyltin hydride afforded 3,3,11-trimethylbicyclo<6.3.0>undecane-2,6-dione (12).Methylenation of 12 afforded 6-methylene-3,3,11-trimethylbicyclo<6.3.0>undecan-2-one, the known intermediate to precapnelladiene.