Brønsted Acid Catalyzed Cascade Reactions of 2-[(2-Aminophenyl)ethynyl]phenylamine Derivatives with Aldehydes: A New Approach to the Synthesis of 2,2′-Disubstituted 1<i>H</i>,1′<i>H</i>-3,3′-Biindoles
An unusual Brønsted acid catalyzed cascade reaction of 2-[(2-aminophenyl)ethynyl]phenylamine derivatives with aryl(heteroaryl)aldehydes to afford an efficient alternative entry into 2,2′-disubstituted-1H,1′H-3,3′-biindoles under metal-free conditions is reported.
A new one-pot approach was developed to construct the 11H-indolo[3,2-c]quinoline scaffold through a gold-catalysed reaction of 2-[(2-aminophenyl)ethynyl]phenylamine derivatives with aldehydes. The broad scope and the high regioselectivity of this new protocol as well as the mild and neutral reaction conditions make it a viable alternative to the previously reported procedures.