pH-Dependent conjugate addition of arylboronic acids to α,β-unsaturated enones catalyzed by a reusable palladium(II)/cationic 2,2′-bipyridyl system in water under air

A reusable Pd(NH3)(2)Cl-2/cationic 2,2'-bipyridyl system for the catalysis of the conjugate addition of arylboronic acids to alpha,beta-unsaturated enones in water under air was developed. Addition of arylboronic acids to both cyclic and acyclic enones progressed smoothly, providing the products in good to high yields, the best result being obtained when HBF4 was used to adjust the pH value to 1.0. After the reaction, the residual aqueous solution could be reused several times, making the reaction greener and reducing wastage of precious metals. Copyright (C) 2010 John Wiley & Sons, Ltd.