The Pd-Catalyzed Alder-Ene Reactions of N-Protected and Propargylated 1-Amino-2-aryl-2-cyclohexenes as a New Route to C3a-Arylhexahydroindoles: Towards the Total Synthesis of Tazettine

A series of N-protected and propargylated 1-amino-2-aryl-2-cyclohexenes (4) has been prepared. Several of these have been shown to undergo an intramolecular Alder-ene reaction in the presence of palladium acetate and the ligand BBEDA to afford C3a-arylhexahydroindoles of the general form 1. Certain of these products may serve as precursors to the alkaloid tazettine (2).