Complex Alkaloid-Type Polycycles via Aza-Michael/Epoxidation of Indole-7-Carbaldehydes with Vinyl Sulfonium Salts and Alkenyl Thianthrenium Salts.

Abstract

An efficient synthesis of pyrroloquinolines has been developed via the aza-Michael/epoxidation cascade process in a diastereospecific manner. The domino reaction occurred properly to afford the desired tetracyclic indoles in 50->99% isolated yields. This synthetic protocol displayed especially broad substrate generality with respect to both indole-7-carbaldehydes and vinylsulfonium salts. Alkenyl thianthrenium salts were also tolerated by this protocol, affording a range of structurally distinct pyrroloquinolines. Indole-2-carbaldehydes were suitable reaction partners, as well, yielding epoxide-fused pyrrolo[1,2-a]indole with good isolated yields.