Enantioselective N-propargylation of indoles via Cu-catalyzed propargylic alkylation/dehydrogenation of indolines

Abstract

The synthesis of optically active N-propargylindoles has been accomplished via the Cu-catalyzed asymmetric propargylic alkylation of indolines with propargylic esters, followed by the dehydrogenation of the resulting N-substituted indolines with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The reaction proceeded in good yield with high enantioselectivity under mild conditions using a bulky and structurally rigid tridentate ketimine P,N,N-ligand, and exhibited a broad substrate scope.