Recyclable Pd(OAc)/2P(3-tol)/PEG-400 System for Regio- and Stereoselective Addition of Boronic Acids to Ynamides

Pd(OAc)/2P(3-tol) in poly(ethylene glycol) (PEG-400) is shown to be a highly efficient catalyst for the regio- and stereoselective addition of boronic acids to ynamides. The reaction proceeds smoothly at 70 °C with NaCO as base, delivering a variety of (Z)-α, β-disubstituted enamides in good to excellent yields with high regio- and stereoselectivity. The isolation of the crude products can be facilely performed by extraction with diethyl ether and more importantly, the Pd(OAc)/2P(3-tol)/PEG-400 system could be readily recycled and reused more than six times without any significant loss of its catalytic efficiency.