Chiral Holmium Complex-Catalyzed Diels–Alder Reaction of Silyloxyvinylindoles: Stereoselective Synthesis of Hydrocarbazoles

The catalytic and asymmetric cycloaddition between 3-[1-(silyloxy)vinyl]indoles and electron-deficient olefins gave substituted hydrocarbazoles in up to 99% yield and 94% ee. This reaction was catalyzed by a novel chiral holmium(III) complex. Alkylation of the cycloadduct gave a tricyclic compound with four continuous chiral centers, one of which was a quaternary carbon.