Total Synthesis of (±)-Taiwaniaquinol F and Related Taiwaniaquinoids.

Total synthesis of (±)-taiwaniaquinol F (1a) has been accomplished via an efficient Lewis acid-catalyzed Nazarov-type cyclization of aryldiallylcarbinols (±)-2e derived from safranal 7. The methodology works under mild conditions using only 2 mol % of metal triflate as catalyst to afford a previously unknown carbotricyclic core sharing an olefin functionality in excellent yield. The aforementioned methodology also offers enough flexibility to complete the total syntheses of various taiwaniaquinoids, including (±)-taiwaniaquinone H (1d), (±)-dichroanone (1e), (±)-5-epi-taiwaniaquinone G (ent-1h), and (±)-taiwaniaquinol B (1b).