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

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.

Graphical AbstractA new strategy has been developed for the sequential Cu-catalyzed asymmetric propargylic alkylation and DDQ-mediated dehydrogenation of indolines using a bulky and structurally rigid ketimine P,N,N-ligand. This reaction allowed for the enantioselective synthesis of optically active N-propargylindoles.Figure optionsDownload full-size imageDownload as PowerPoint slide