Chiral Brønsted Acid Catalyzed Enantioconvergent Synthesis of Chiral Tetrahydrocarbazoles with Allenylsilanes from Racemic Indolylmethanols

An efficient method for the synthesis of chiral tetrahydrocarbazoles (THCs) containing an allene moiety is disclosed, which was established by an enantioconvergent substitution reaction catalyzed by a chiral phosphoric acid. Racemic indolylmethanols bearing the THC motif reacted with N-methylpyrrole in the presence of the SPINOL-derived chiral phosphoric acid to give the corresponding chiral THCs with allenylsilanes in good yields with high enantioselectivities.