Intramolecular Aza-Michael Addition of Indoles

Significance

Indole alkaloids are a common core structure in natural products. Herein, the authors report the enantioselective intramolecular aza-Michael additions of C2-substituted indoles 2 to N-alkylated products 3 catalyzed by phosphoric acid 1 (er up to 96.5:3.5). Various aryl enones are tolerated in the reaction and give good enantio­selectivity with high chemoselectivity. Moreover, substrates 2 can be prepared in situ by olefin cross-metathesis using catalyst 4 in the presence of phosphoric acid catalyst 1 to afford the desired products in good enantioselectivity.