Combined Lewis Acid Catalyzed Diastereoselective Halogenative Cascade Annulation of Enone-Tethered Cyclohexadienones.

The cascade difunctionalization of α,β -unsaturated carbonyls by nucleophilic halogenation followed by enolate trapping with other electrophiles is highly challenging in synthetic organic chemistry. Herein, we report a chemo- and diastereoselective cascade annulation of enone-tethered cyclohexadienones by using an unconventional combined Lewis acid catalyzed halogenation reaction in the presence of an In(III)-catalyst and trimethylsilyl halide. The reaction provides highly functionalized bicyclic enones with four contiguous stereocenters.