Copper catalyzed oxidative coupling of ortho-vinylanilines with N-tosylhydrazones: Efficient synthesis of polysubstituted quinoline derivatives

Efficient and general copper catalyzed oxidative cyclization of ortho-vinylaniline has been accomplished employing N-tosylhydrazone as coupling partner. Various substituted quinoline derivatives of biological importance were achieved in good to excellent yield. The important features are the high functional group tolerates, up-gradation to gram scale synthesis and possible one-pot synthesis of quinoline from corresponding carboxaldehyde. Synthetic potential of the obtained quinoline derivatives was demonstrated through C-H bond functionalization reaction. Furthermore, preliminary mechanistic investigation revealed the possible generation of non-stabilized diazo compound and imine derivative as potential intermediates as well as copper catalyzed electrocyclic reaction and oxidative aromatization. (C) 2018 Elsevier Inc. All rights reserved.