Studies on stereoselective Sonogashira coupling of 1,1-dibromo-1-alkene

The stereoselective Sonogashira coupling of 1,1-dibromo-1-alkene was described. The use of PdCl2(dppf) as a catalyst with trialkylsilylacetylene in benzene selectively gave the (Z)-bromoenyne (2a) along with small amounts of the enediyne (3a). Based on the experimental results, a mechanism of the selectivity was proposed. The bromoenyne was coupled with some electrophiles to give the substituted (Z)-bromoenynes after deprotection of the terminal silyl group.