acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis has been found. Ring-closing enyne metathesis of terminalalkynes possessing an allylic hydroxy group proceeded smoothly without the ethylene atmosphere generally necessary to promote the reaction. The synthesis of (+)-isofagomine with the aid of this efficient reaction has been demonstrated. Mechanistic studies of the acceleration
The intramolecular 1,3-dipolar cycloaddition of silacarbonyl ylides derived from a silylene and unsaturated aldehydes tethered to unactivated olefinic or acetylenicdipolarophiles successfully proceeded to directly afford bicyclosilaoxolane derivatives in good yields.