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.