Pd(ii)/LA-catalyzed acetanilide olefination with dioxygen†

Transition-metal-catalyzed aromatic olefination through direct C–H activation represents an atom and step-economic route for versatile pharmaceutical syntheses, and in many cases, different stoichiometric oxidants are frequently employed for achieving a reasonable catalytic efficiency of the transition metal ions. Herein, we report a Lewis acid promoted Pd(ii)-catalyzed acetanilide olefination reaction with atmospheric dioxygen as the oxidant source. The linkage of the Lewis acid to the Pd(ii) species through a diacetate bridge significantly improved its catalytic efficiency, and independent kinetic studies on the olefination step revealed that adding the Lewis acid significantly accelerated the olefination rate as well as the C–H activation step. A strong basicity of the internal base in the Pd(ii) salt also benefited the olefination reaction plausibly through base-assisted β-hydride elimination.