Catalytic Asymmetric N‐Alkylation of Indoles and Carbazoles through 1,6‐Conjugate Addition of Aza‐para‐quinone Methides

Catalytic asymmetric N‐alkylation of indoles and carbazoles represents a family of important but underdeveloped reactions. Herein, we describe a new organocatalytic strategy in which in situ generated aza‐para‐quinone methides are employed as the alkylating reagent. With the proper choice of a chiral phosphoric acid and an N‐protective group, the intermolecular C−N bond formation with various indole and carbazole nucleophiles proceeded efficiently under mild conditions with excellent enantioselectivity and functional‐group compatibility. Control experiments and kinetic studies provided important insight into the reaction mechanism. An organocatalytic strategy for the asymmetric N‐alkylation of indoles and carbazoles was developed in which in situ generated aza‐para‐quinone methides are employed as the alkylating reagent. With the proper choice of a chiral phosphoric acid and N‐protective group (P), the intermolecular C−N bond formation with various indole and carbazole nucleophiles proceeds under mild conditions with excellent efficiency and enantioselectivity.