Remarkable Effect of N-Substituent on Enantioselective Ruthenium-Catalyzed Propargylation of Indoles with Propargylic Alcohols

Ruthenium-catalyzed enantioselective propargylation of indoles with propargylic alcohols affords the corresponding β-propargylated indoles in good yields with a high enantioselectivity (up to 95% ee). A remarkable effect of the nature of the N-substituent of indoles is observed for the enantioselectivity of the propargylated indoles. The preparative method described in this paper may provide a novel protocol for asymmetric Friedel−Crafts alkylation of indoles using propargylic alcohols as a new type of electrophiles.