Sterically demanding Csp 2 ( ortho -substitution)-Csp 3 (tertiary) bond formation via carboxylate-directed Mizoroki-Heck reaction under extra-ligand-free conditions.

Construction of the sterically demanding Csp 2 ( o S)-Csp 3 (T) bond was achieved by carrying out the Pd-catalyzed carboxylate-directed Mizoroki-Heck reaction under extra-ligand-free aqueous conditions. The cooperative role of the presence of water with the absence of phosphine ligand was proposed to accelerate the migratory insertion process considerably, delivering a broad substrate scope.