Lewis-acid assisted cross metathesis of acrylonitrile with functionalized olefins catalyzed by phosphine-free ruthenium carbene complex

The exchange of the PPh₃ ligand in the complex [1,3-bis(2,6-dimethylphenyl)4,5-dihydroimidazol-2-ylidene](PPh₃)(Cl)₂RuCHPh (7) for a pyridine ligand at ambient temperature leads to the formation of the stable phosphine-free carbene ruthenium complex [1,3-bis(2,6-dimethylphenyl)4,5-dihydroimidazol-2-ylidene](C₅H₅N)₂(Cl)₂ RuCHPh (8). The resulted ruthenium complex exhibits highly catalytic activity for the cross metathesis of acrylonitrile with various functionalized olefins under mild conditions, and its activity can be further improved by the addition of a Lewis acid such as Ti(OⁱPr)₄. In the mixture products, the Z-isomer predominates.