Synthesis of triptoquinone H and its C-5 epimer via efficient asymmetric dearomative cyclization

Enantioselective syntheses of triptoquinone H and its C-5 epimer were accomplished for the first time in seven linear steps and 33% overall yield from aldehyde 6 and Wittig salt 5 via a key palladium-catalyzed asymmetric dearomative cyclization. The P-chiral biaryl monophosphorus ligand AntPhos was proved to be efficient for the asymmetric dearomative cyclization to provide the tricyclic compound 8 bearing a chiral all-carbon quaternary center in 85% ee and 87% yield.