Asymmetric N-aminoalkylation of 3-substituted indoles by N-protected N,O-acetals: an access to chiral propargyl aminals.

A direct enantioselective N1 aminoalkylation of 3-substituted indoles is efficiently catalyzed by a phosphoric acid catalyst under mild conditions to afford diverse enantioenriched propargyl aminals. The strategy could be applied to the modification of tryptophan containing oligopeptides. Additionally, structurally diverse and multifunctional transformations of the propargyl aminal products reveal the potential synthetic utility of this protocol.