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, Re2O7/Al2O3 catalyses the self-metathesis of Z-stilbene and its cross-metathesis with ethene. Additionally, reaction of Re2O7/Al2O3 with Z-2-butene followed by C-13 di-labelled ethene shows that it contains only 2% of active sites.