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

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 RuC(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.