Hydrogenative Cyclopropanation and Hydrogenative Metathesis.

The unusual geminal hydrogenation of a propargyl alcohol derivative with [CpX RuCl] as the catalyst entails formation of pianostool ruthenium carbenes in the first place; these reactive intermediates can be intercepted with tethered alkenes to give either cyclopropanes or cyclic olefins as the result of a formal metathesis event. The course of the reaction is critically dependent on the substitution pattern of the alkene trap.