Acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis of terminal alkynes: scope, application, and mechanistic insights.

An interesting acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis has been found. Ring-closing enyne metathesis of terminal alkynes 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.