Rhenium(VII) Oxide/Aluminum Oxide: More Experimental Evidence for an Oxametallacyclobutane Intermediate and a Pseudo‐Wittig Initiation Step in Olefin Metathesis

Reactivity studies of the rhenium( VII ) oxide/aluminum oxide olefin metathesis catalyst with various olefins show that initiation does not require an olefin with an allylic CH bond, and therefore probably takes place via a pseudo‐Wittig reaction. While it does not react with ethene in the absence of propene, Re 2 O 7 /Al 2 O 3 catalyses the self‐metathesis of Z ‐stilbene and its cross‐metathesis with ethene. Additionally, reaction of Re 2 O 7 /Al 2 O 3 with Z ‐2‐butene followed by 13 C di‐labelled ethene shows that it contains only 2 % of active sites.