Metal triflate-catalyzed cyclization of arylvinylcarbinols: formal synthesis of (±)-dichroanone and (±)-taiwaniaquinone H

A formal synthesis of diterpenoids viz. the taiwaniaquinoids (±)-dichroanone (1a) and (±)-taiwaniaquinone H (1b) possessing an all carbon quaternary stereocenter has been reported. The key step involves a metal triflate-catalyzed cyclization of arylvinylcarbinols, prepared from β-cyclocitral. The reaction possibly follows a stepwise mechanism via the intermediacy of arylallyl carbocationic species.