The cross-metathesis reaction between cyclic olefins and ethylene (ethenolysis) yields highly valuable terminal dienes.1 While ethenolysis of ethyl oleate has been widely studied with Grubbs-type Ru metathesis catalysts,2 there are currently no reports on ethenolysis of cyclic olefins with Ru catalysts. This is presumably due to the high activity of Ru metathesis initiators in the ring opening metathesis polymerization, a competing reaction that would severely deplete the selectivity towards terminal dienes. Furthermore, it is well known that supporting ligands can greatly influence the selectivity of Ru catalysts.3 For instance, we have recently reported on the synthesis of ruthenium metathesis catalysts containing unsymmetrical N-trifluoromethyl NHC ligands. These catalysts display an unusually high selectivity (80–90%) for terminal olefins in ethenolysis of ethyl oleate by avoiding competing homodimerization of primary terminal olefins.4 That being said, the identification of a specific supporting ligand for the Grubbs-type catalyst could be a tedious, empirical endeavor if the parent Grubbs catalyst fails to furnish the desired product in high yield, as it is the case for the ethenolysis of cyclic olefins.5 We therefore set about to systematically evaluate the influence of a vast array of various NHC ligands on the ethenolysis of cis-cyclooctene (Scheme 1). To rationalize the experimental structure-activity results, a computational study was conducted that explained the observed dependence via the univariate correlations of activity to selected physical-chemical properties of the supporting ligand.

Structure-activity relationship of ruthenium metathesis catalysts in ethenolysis of cyclic olefins

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.