Copper-Catalyzed Denitrogenative Radical Cyclization of 3-Aminoindazoles with -Cyanoarylacrylamides: Synthesis of Cyanoarylated Quinoline-2,4(1,3)-diones.

A copper-catalyzed denitrogenative radical cyclization of 3-aminoindazoles with -cyanoarylacrylamides has been developed, enabling the efficient synthesis of a variety of cyanoarylated quinoline-2,4(1,3)-diones in moderate to good yields at room temperature. Notably, this strategy overcomes the traditional challenge of the low reactivity of nitrile groups toward radical addition by utilizing cyanoaryl radicals generated from 3-aminoindazoles as reactive intermediates. Mechanism studies indicate that 2-cyanophenyl radicals, generated through the cleavage of two C-N bonds of 3-aminoindazoles, served as the key intermediates initiating the cyclization process. This transformation features mild conditions, broad substrate scope, and the simultaneous formation of two new C-C bonds in a single operation.