Zinc‐Catalyzed [4+2] Annulation of 2‐Aminoarylnitriles with Ynamides: An Easy Access to Polysubstituted Quinolines

Abstract

AbstractThe zinc‐catalyzed [4+2] annulation of 2‐aminoarylnitriles with ynamides offers an easy one‐step access to polysubstituted quinolines. In this new protocol, inexpensive ZnCl2 is used for the first time as an efficient alternative of noble‐metal catalysts. This zinc catalytic system offers the desired polysubstituted quinolines in yields up to 87% with a broad substrate scope and good functional group tolerance. The large‐scale experiment proves the practical utility of this method. Interestingly, the newly synthesized product decorated with an o‐fluorophenyl substituent is transformed to 11‐aminoindolo[2,3‐b]quinoline by deprotection of the benzenesulfonyl group and subsequent regioselective aromatic nucleophilic substitution in combined yield of 62%.