Three-Component Domino Reactions for Regioselective Formation of Bis-indole Derivatives

A microwave-assisted regioselective reaction dealing with arylglyoxal monohydrate, diverse N-aryl enaminones, and indoles to achieve 3,2′- and 3,3′-bis-indoles by varying a substituted indole substrate is reported. The 2-unsubstituted indoles resulted in the 3,2′-bis-indole skeleton, whereas indoles bearing a methyl or phenyl group at C2 led to the 3,3′-bis-indoles with simultaneous formation of three sigma-bonds. The procedures feature excellent regioselectivity, short reaction times, convenient one-pot manner, and operational simplicity.