Fluoro-imidazopyridinylidene Ruthenium Catalysts for Cross Metathesis with Ethylene

Abstract

A series of ruthenium metathesis catalysts bearing fluorinated imidazo­[1,5-a]­pyridin-3-ylidene carbenes (F-ImPy) were developed for ethenolysis (cross metathesis with ethylene) of methyl oleate. X-ray crystal structure analysis shows Ru–F interaction, and this fluorine substitution appears to be pivotal to have stable ImPy-Ru precatalysts. Ligand structure was varied for high catalyst activity and cross metathesis selectivity in ethenolysis reaction. F-ImPy-Ru catalysts showed high selectivity in ethenolysis of methyl oleate and thermal robustness under an ethylene atmosphere.

Highly Efficient Ethenolysis and Propenolysis of Methyl Oleate Catalyzed by Abnormal N-Heterocyclic Carbene Ruthenium Complexes in Combination with a Phosphine–Copper Cocatalyst

“…Furthermore, the fluorine substituent at the C8 position seemed to play a crucial role in stabilizing the ruthenium catalyst, as the unsubstituted H- a ImPy–Ru complex was unstable. The same trend was observed with normal ImPy ruthenium catalyst 9 . F- a ImPy–Ru complexes 10 were characterized by NMR spectroscopy, elemental analysis, high-resolution mass spectrometry, and X-ray crystallography analysis.…”

“…Examples of a NHC–Ru complexes, fluorinated ImPy–Ru complex 9 (ref ), and fluorinated a ImPy–Ru complexes 10 .…”

Origin of the Breakthrough Productivity of Ruthenium–Cyclic Alkyl Amino Carbene Catalysts in Olefin Metathesis

“…Striking, therefore, is the extraordinary productivity demonstrated for metathesis catalysts bearing a cyclic alkyl amino carbene (CAAC; Chart ) in place of an NHC ligand. − Even in ethenolysis (that is, generation of α-olefins from unsaturated internal olefins of plant or algal origin ,− under an atmosphere of ethylene), turnover numbers (TONs) as high as 340 000 could be achieved using a CAAC catalyst . This represents a level of efficiency 2 orders of magnitude higher than that attained with leading H 2 IMes catalysts under standard conditions of metathesis.…”

Syntheses and activities of indol-2-ylidene-ligated ruthenium-based olefin metathesis catalysts

“…The inferior performance of 2f was mainly due to the strong steric effect. 11,13,18 Ring flip of the cyclohexyl group effectively covered the Ru center and hindered the facile binding of the substrate to 2f. This tendency was also discovered in the case of sterically demanding Ru−CAAC-6, which exhibited low performance (TON: 1720) as compared to that of less bulky Ru−CAAC-5 (TON: 24180).…”