Copper(0)/PPh3-Mediated Bisheteroannulations of o-Nitroalkynes with Methylketoximes Accessing Pyrazo-Fused Pseudoindoxyls.

A copper(0)/PPh3-mediated cascade bisheteroannulation reaction of o-nitroalkynes with methylketoximes has been developed that provides viable access to a diverse range of pyrazo-fused pseudoindoxyl compounds. Synthetically useful functional groups including sensitive C-I bonds are compatible with this system. Mechanistic studies suggest a reaction cascade involving sequential PPh3-mediated deoxygenative cycloisomerization and copper-catalyzed [3 + 2] pyrazo-annulation.