A Hydrogen Bonding Catalyzed Asymmetric Cascade to Tetrahydrocarbazoles

Significance

The authors report the hydrogenbonding catalyst 1 promoted catalytic asymmetric synthesis of tetrahydrocarbazoles from 2-pro­penylindoles and nitroolefins. The reaction is ­assumed to proceed via a Michael-Michael ­aromatization pathway rather than a concerted [4+2] cycloaddition. The described method uses a commercially available disulfonamide catalyst and gives rapid access to tetrahydrocarbazoles with three contiguous stereocenters in high yields and enantioselectivities.