Reactivation of a Ruthenium-Based Olefin Metathesis Catalyst

First-generation Hoveyda–Grubbs olefin metathesis catalyst was purposely decomposed in the presence of ethylene, yielding inorganic species that are inactive in the ring-closing metathesis (RCM) of the benchmark substrate diethyl diallylmalonate (DEDAM). The decomposed catalyst was treated with 1-(3,5-diisopropoxyphenyl)-1-phenylprop-2-yn-1-ol (<b>3</b>) to generate an olefin metathesis active ruthenium indenylidene-ether complex in 43% yield. This complex was also prepared independently by reacting RuCl₂(<i>p</i>-cymene)­(PCy₃) with the organic precursor <b>3</b>. The activity of the isolated reactivated catalyst in the RCM of DEDAM is similar to that of the independently prepared complex