Preparation of hydrindenones from 2-methylcyclopent-2-enone and the carbanion of (E)-but-2-enyldiphenylphosphine oxide: Efficient enolate trapping with β-sulphonylvinyl ketones

The β-sulphonylvinyl ketones (5), (7), (9), and (10), easily prepared from β-(phenylthio)propionyl chloride or from methyl vinyl ketone, react efficiently with the enolate produced by the conjugate addition of the carbanion of (E)-but-2-enyldiphenylphosphine oxide to 2-methylcyclopent-2-enone to provide in highly stereoselective fashion vinylogous β-diketones, two of which upon hydrogenation and aldol ring closure have been converted into hydrindenones in high yields.