Syntheses of N-Alkyl 2-Arylindoles from Saturated Ketones and 2-Arylethynylanilines via Cu-Catalyzed Sequential Dehydrogenation/Aza-Michael Addition/Annulation Cascade.

We describe here a Cu-catalyzed and 4-OH-TEMPO-mediated sequential dehydrogenation/aza-Michael addition/annulation cascade reaction for the construction of N-alkyl 2-arylindoles from facilely available saturated ketones and 2-arylethynylanilines. This reaction shows high regioselectivity and tolerates a variety of functional groups. Moreover, 3-alkyl-substituted indoles can also be achieved when using 2-alkylethynylanilines as starting materials.