Synthesis of N-& beta;-aminoacrylate substituted indoles via(t)BuOK catalyzed addition of indoles to ketenimines

Catalytic functionalization of indoles has been one of the most flourishing topics in organic chemistry. However, most known methods for the synthetic modifications of indoles take place at the C3 or C2 position. The direct functionalization of indole N-H remains a challenge owing to the weak nucleophilicity. Herein, we report a rare example of a (BuOK)-Bu-t catalyzed aza-Mannich-type addition of indole N-H bonds to ketenimines. The reaction gave the corresponding N-& beta;-aminoacrylate substituted indoles in moderate to excellent yields (37-99%). DFT calculation results explain the experimentally observed exclusive chemoselectivity.