Sonogashira Coupling with UC Pd under Copper-Free Conditions

Abstract

A novel form of Pd/C (UC Pd) was prepared by ultrasonication of Pd(NO3)2 with activated charcoal in water (eq. 1). UC Pd catalyzed the Sonogashira coupling of aryl bromides 1 with terminal alkynes 2 in the presence of XPhos and K2CO3 to give the corresponding internal alkynes 3 in 55-96% yield (eq. 2, 17 examples). The catalyst was recovered by simple filtration and reused three times without significant loss of its catalytic activity for the formation of 3a (3rd reuse: 87% yield).