Ring-closing enyne metathesis is generally considered a "mature" catalytic reaction, despite the fact that little detailed mechanistic information is available. In the course of synthesizing unnatural carbocyclic nucleosides, we found that certain 1,6-enynes are resistant to ring-closing metathesis (see graphic). To promote the reaction, we elected to trigger the ring-closing by including a more reactive, external alkene. The external alkene instigates the reaction via the vinyl carbene intermediate shown. This technique should be useful to promote difficult ring-closing enyne metatheses and offers new insight into the role of ethylene. Our results in the promoted ring-closing metathesis and mechanistic studies on the reactivity of alkenes as it pertains to this process will also be discussed.