Synthesis of <i>N</i>-Vinyl Cinnamaldehyde Nitrones through Atropisomeric Quinoxaline-Derived <i>N</i>,<i>N</i>,<i>O</i>-Ligand-Promoted Chan-Lam Reaction

A type of quinoxaline-derived tridentate N,N,O-ligand was synthesized in good to excellent yields over three steps through iodination of 2-aryl indoles, sequential Kornblum-type oxidation with DMSO, and capture by 1,2-diaminobenzenes. The prepared atropisomeric N,N,O-ligand was successfully applied in the synthesis of N-vinyl cinnamaldehyde nitrones as only Z-isomers in good yields through the Chan-Lam reaction. The method features an easily accessed tunable tridentate N,N,O-ligand, broad substrate scope, good functional group tolerance, and high Z-isomer for N-vinyl nitrones.