Trisubstituted alkenes from alkynes and aryl iodides by boron-to-zinc transmetallation and palladium(0) catalysed cross coupling

Alkenylethylzincs, obtained from the corresponding trialkenylboranes by transmetallation with diethylzinc, couple with aryl iodides in the presence of Pd(PPh 3 ) 4 , 0.19–0.28 mol%, to produce trisubstituted alkenes in good isolated yields. Both the transmetallation and subsequent coupling occur with complete retention of stereochemistry.