ACTIVATION OF GRUBBS-HOVEYDA SECOND-GENERATION CATALYSTS EMPLOYING AROMATIC LIGANDS BEARING A WIDESPREAD ARYL SUBSTITUENT

In this study, an activation strategy for Grubbs-Hoveyda second-generation-type catalysts by utilizing the intramolecular steric strain on the ligands is described. The variant, which is expected to exhibit intramolecular steric strain, containing extensively spread aromatic and alkoxy groups in the ligand structure was prepared and examined. The combination of tricyclic anthracenyl and isopropoxy groups are observed to exhibit the highest catalytic activity among these synthetic catalysts. The activated catalyst was successfully used in a ring-closing metathesis reaction depicting a catalyst loading of the order of 20 mol ppm in dry benzene. The X-ray crystallographic analysis suggests the existence of an intramolecular CH/pi interaction between the sp(2) carbon of the anthracenyl group and the methyne hydrogen of the isopropoxy group.