Cobalt-catalyzed dimerization of alkenes

In the presence of CoX2(PPh3)2/3 PPh3 and zinc metal conjugated alkenes (CH2CHCOOR, CH2CHCN, CH2CHSO2Ph and CH2CHCONEt2) undergo reductive tail-to-tail dimerization to yield the corresponding saturated linear products. Under similar reaction conditions, vinylarenes (ArCHCH2) give stereoselective head-to-tail dimerization products, trans-1,3-diarylbut-1-ene, in good to excellent yields.