Cobalt catalysed, copper assisted C(sp2)–P cross coupling
An efficient protocol for the cross coupling of styrenyl/aryl halides and H-phosphinate has been developed using a unique Co/Cu catalytic system in the absence of any additional ligand for the first time. A library of diversely functionalised styrenyl/aryl phosphonates has been synthesized using this procedure. The advantages offered using this procedure are operational simplicity, the use of inexpensive and relatively benign metals as a catalyst, wide tolerance to functionality including electron withdrawing and releasing substituents, excellent stereoselectivity and high yields. The mechanism has also been established. The unique feature of this Co/Cu system is that, it primarily involves Co in the catalytic cycle and Cu in the transmetalation process.