Stannylation of unsaturated carbon–carbon bonds by tin tetrachloride

The reactions of tin tetrachloride and four terminal alkynes (PhCtriple bond; length of mdashCH, tBuCtriple bond; length of mdashCH, nBuCtriple bond; length of mdashCH, HOCH2Ctriple bond; length of mdashCH), norbornene, and norbornadiene in dichloromethane or chloroform solution lead to the formation of stannylation products, which were characterized by 1H, 13C and 119Sn NMR spectroscopy. Virtually complete α-regioselectivity was obtained in reaction of all four alkynes without any effect of the relative steric bulk of the substituent R at the triple bond of alkyne RCβtriple bond; length of mdashCαH. The reaction of norbornene and norbornadiene with SnCl4 is stereoselective, giving an exo stannylation product.