[Ru(p-cymene)Cl2]2-catalyzed 1,4-addition reactions between arylboronic acids and butyl acrylate and acrylamide in the presence of phenols were investigated, good to excellent yields were obtained. The addition of phenols remarkably promoted the protonolysis and inhibited the β-H elimination of the 1,4-addition intermediates, and also efficiently suppressed the protonolysis of arylboronic acids.