Efficient synthesis of benzo[c]cinnolines and azoarenes via dual C–N coupling of phthalhydrazide and trivalent halogen reagents

Abstract

Phthalhydrazide has been proven to be an elegant NN source to undergo tandem dual-C–N coupling/deprotection/oxidation with not only cyclic/linear diaryliodoniums but also rarely explored diarylbromoniums, giving benzo[c]cinnolines (up to 99% yields) and azoarenes (mostly >90% yields) with broad scope. 3,3′,4,4′-Tetraphenyl-1,1′-biisoquinoline serves as a privileged ligand for Cu-catalyzed C–N coupling for the first time. This method features base-mediated auto-deprotection of phthaloyl after Cu-catalyzed N,N′-diarylation in one pot, without extra steps for deprotection.