Stereospecific synthesis of (E)-α,β-difluorostyrenes

Isomerically pure (Z)-HFCCFZnI undergoes Pd(PPh3)4/CuBr co-catalyzed cross-coupling reactions with aryl iodides in DMAC to give the title compounds in good yields, under mild conditions. In the absence of CuBr, the reaction is sluggish, requires more vigorous reaction conditions, and gives lower yields.