AgSbF₆-catalyzed C3 aza-Friedel-Crafts alkylation of N, O-acetals with indoles for the synthesis of N-α indole substituted pyrrolidine and piperidine derivatives

An efficient approach to access chiral N-α indole substituted pyrrolidine and piperidine skeletons has been developed through a AgSbF₆-catalyzed N-α aza-Friedel-Crafts alkylation of N,O-acetals 6a, 6b, 9, and 11a-11d with indoles. As a result, a series of 2,3-trans N-α indole substituted pyrrolidines 8a-8x and piperidines 10a-10j were prepared in moderate to excellent yields and with excellent diastereoselectivities (dr up to 99 : 1). Moreover, several 2,5-cis-N-α indole substituted pyrrolidine derivatives 12a-12k were synthesized according to this strategy with moderate to good yields and diastereoselectivities (dr up to 99 : 1).