Cross Metathesis Allowing the Conversion of a Ruthenium Indenylidene Complex into Grubbs' Catalyst

Abstract

The active metathesis catalyst (PCy 3 ) 2 Cl 2 Ru(3-phenylinden-1-ylidene) (4) was obtained in high yield using a simple one-pot procedure. The initial reaction of RuCl 2 (PPh 3 ) 3 with 1,1-diphenyl-2-propyn-1-ol gave (PPh 3 ) 2 Cl 2 Ru(3-phenylinden-1-ylidene) (6). In situ exchange of PPh 3 with PCy 3 led to the isolation of 4 in > 90% yield. Whereas complex 6 did not show any activity in the cross metathesis reaction with styrene, reaction of compound 4 with excess styrene gave Grubbs× catalyst, (PCy 3 ) 2 Cl 2 Ru ¼ C(H)Ph (1), dichloro(phenylmethylene)bis-(tricyclohexylphosphane)ruthenium(II), in nearly quantitative yield. This two-step procedure yielded complex 1 in 88% overall yield starting from inexpensive and commercially available materials. The widely used metathesis catalyst 1 was also obtained in good yield in one single step, that is, without isolation of compound 4, making this a simple and safe synthetic route to Grubbs× catalyst.

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

“…[47] Nolan and co-workers further refined the concept by devising a one-pot procedure for the synthesis of Grubbs catalyst 1a starting from [RuCl 2 A C H T U N G T R E N N U N G (PPh 3 ) 3 ] and 1,1-diphenylpropargyl alcohol, followed by phosphine exchange with PCy 3 , and cross-metathesis with excess styrene. [48] In a slightly less efficient variation, Fürstner et al converted a tricyclohexylphosphine-bearing indenylidene complex into a Hoveyda-type catalyst via enyne metathesis with 1-ethynyl-2-isopropoxybenzene in the presence of silver(I) chloride as phosphine scavenger. [49] Since the reaction of homobimetallic ruthenium-indenylidene complex 11 with excess styrene afforded the highly unstable methylidene complex 16 that eventually decomposed into ethylene complex 7a rather than the corresponding benzylidene complex 3a (vide supra), we chose to react complex 11 with a two-fold excess of 2-isopropoxystyrene, reasoning that the styrenyl ether would stabilize the alkylidene cross-metathesis product via oxygen chelation.…”

Olefin metathesis in air

“…Again, these complexes showed similar activity to the Grubbs 2 nd generation catalysts [ 77 – 78 ], and are stable when stored under air. Nolan reported the synthesis of Grubbs’ 2 nd generation catalyst ( 15 ) from indenylidene complexes 84 , by simple reaction with styrene, avoiding the use of hazardous diazo compound 7 [ 82 ].…”

Imidazol(in)ium‐2‐Carboxylates as N‐Heterocyclic Carbene Ligand Precursors for Ruthenium Metathesis Initiators

“…To complement our investigations on ruthenium‐benzylidene complexes, we decided to prepare second generation ruthenium‐indenylidene catalysts using imidazol(in)ium‐2‐carboxylate zwitterions as NHC ligand precursors (Scheme ) 21. The reaction of diphosphine complex 11 28 with SIMes · CO 2 was investigated in refluxing THF. After 1.5 h, 31 P NMR analysis showed that the starting material had been fully consumed.…”