Cu-Catalyzed Acylation of Quinoline-<i>N</i>-oxides with <i>gem</i>-Difluorostyrenes via the Tandem Cycloaddition/Elimination/Oxidation Process

The copper-catalyzed defluorination and decarbonization cross-coupling reaction between quinoline-<i>N</i>-oxides and <i>gem</i>-difluorostyrenes via key 2-arylmethylquinoline intermediates to access 2-aroylquinolines is described. Versatile 2-aroylquinolines were obtained in up to 83% yield with exclusive regioselectivity. The detailed reaction mechanism investigation shows that it undergoes a tandem [3 + 2] cycloaddition/elimination of formyl difluoride/oxidation of 2-arylmethylquinolines. This copper-catalyzed transformation proceeds efficiently at 90 °C, eliminating the necessity for exogenous oxidants or hazardous reagents, while maintaining excellent functional group tolerance.