Regioselective synthesis of α-(2-indolyl) ketone with arylaldehydes via tandem reaction of 2-alkynylanilines

A base-promoted synthesis of α-(2-indolyl) ketones (or 2-(α-aryl benzyl ketone) indoles) is developed via 5-endo-dig cyclization of 2-alkynylanilines, followed by aroylation of the resulting carbanion. This transition metal-free reaction proceeded with high regioselectivity and a wide substrate scope (46 examples, up to 93% yield). Among the syntheses of 2-substituted indoles, this tandem process is straightforward and convenient.