Regio- and Stereoselective Enyne Cross Metathesis of Silylated Internal Alkynes

Cross metathesis between silylalkynes and various functionalized alkenes catalyzed by Grubbs carbene complex produced, in most cases, single regio- and stereoisomers of the resultant 1,3-dienes. Polar heteroatom substituents at the propargylic site are important for high reactivity and selectivity. An important mechanistic insight regarding the initiation event and the key propagating alkylidene in this reaction was obtained by employing a tandem cross metathesis ring-closing metathesis between a terminal alkene and a silylated alkyne possessing an alkene tether.