Copper(II) mediated homo-coupling of 1,2-difluorovinyl stannanes

The reaction of substituted 1,2-difluorovinylstannanes with anhydrous Cu(OA c)(2) in dimethylformamide, under an oxygen atmosphere, at room temperature stereospecifically gives the corresponding symmetrical 1,3-dienes in goad to excellent yields. Moisture drastically reduces the yield of home-coupled product and produces significant amounts of RCF=CFH. The Cu(II) promoted h ome-coupling of the fluorinated vinylstannanes is superior to the Cu(I)Cl m ediated home-coupling of the corresponding hydrocarbon vinylstannanes. When 1,2-difluorovinylstannanes are treated with Cu(I)Cl, the reaction is slugg ish and significant amounts of RCF=CFH are formed.