Synthesis of Cinnolines and Cinnolinium Salt Derivatives by Rh(III)-Catalyzed Cascade Oxidative Coupling/Cyclization Reactions

A novel method for the synthesis of cinnolines and cinnolinium salt derivatives via Rh­(III)-catalyzed cascade oxidative coupling/cyclization reaction from Boc-arylhydrazines and alkynes has been developed. The reactions have a broad substrate scope and high stereoselectivity with readily available starting materials and provides an efficient synthetic route for this kind of compounds. A catalytically competent five-membered rhodacycle has been isolated, thus revealing a key intermediate in the catalytic cycle.