Oxidatively Intercepting Heck Intermediates:  Pd-Catalyzed 1,2- and 1,1-Arylhalogenation of Alkenes

This communication describes the development of two Pd-catalyzed reactions for the arylchlorination of diverse α-olefins by oxidatively intercepting Heck intermediates. Depending on the nature of the oxidant and the reaction conditions, these transformations can afford synthetically useful 1,1- or 1,2-arylchlorinated products in good yields and with good to excellent selectivities. Preliminary mechanistic investigations show that the selectivity of these reactions can be rationally tuned (i) by controlling the relative rates of oxidative functionalization versus β-hydride elimination from equilibrating PdII−alkyl species and (ii) by π-benzyl stabilization of Pd intermediates.