Rapid microwave-promoted cross-coupling reaction of aryl bromides with aryl boronic acids and sodium tetraphenylborate catalyzed by a reusable polymer-supported palladium complex

A variety of biaryls were prepared in a rapid and highly efficient manner via the cross-coupling reaction of aryl bromides with aryl boronic acids or sodium tetraphenylborate in toluene, aqueous potassium carbonate and in the presence of a polymer-supported palladium(II) catalyst under microwave irradiation condition. The supported catalyst was prepared directly from a commercial Merrifield resin and ultrasound dramatically accelerated the preparation of the catalyst. The polymeric catalyst can be easily separated from a reaction mixture and reused five times without decrease in activity. This suggests that a comparatively stable palladium phosphine complex is the reacting species in this special case. The reaction can be performed equally well using microwave and conventional heating, showing that microwave irradiation accelerates the reaction tremendously and in higher yields.