| This study subjected the 4,4-disubstituted-2-carboxamide-2-cyclohexenone Birch-Cope products to carbon nucleophile conjugate additions to enantioselectively generate vicinal quaternary-tertiary stereocenters. Intermolecular conjugate additions were studied extensively but were unfortunately limited in scope. It is hypothesized that steric congestion around the enone from the chiral auxiliary and the vicinal quaternary carbon contributed to these difficulties. Because our lab has previously reported on ring forming intramolecular conjugate addition reactions with oxygen, nitrogen, and carbon nucleophiles, intramolecular Friedel-Crafts alkylations were explored. These conjugate additions have enantioselectively formed 6-6-6 and 6-5-6 tricarbocyclic ring systems. The framework of multiple tetracyclic diterpenes has also been achieved through chiral auxiliary removal on the Friedel-Crafts products followed by regioselective enol silane formation and palladium-catalyzed cycloalkenylation to form the bicyclo[3.2.1]octane core. |
