Liquid/solid phase transfer activation of Grubbs-type alkene metathesis catalysts; application of silver salts of sulfonated polystyrene

Abstract

Alkene metatheses catalyzed by (H₂IMes)(Cy₂PCH₂CH₂N(CH₃)₃⁺)(Cl)₂Ru(CHPh) Cl⁻, an analog of Grubbs' second generation catalyst with an ammonium-salt containing phosphine, are dramatically accelerated when conducted in the presence of the insoluble resin PS-SO₃Ag (PS = polystyrene). A mechanism involving ionic and covalent phosphine binding (PS-SO₃Ag·PCy₂CH₂CH₂N(CH₃)₃⁺ PS-SO₃⁻) with concomitant formation of AgCl is proposed. Grubbs' second generation catalyst exhibits a modest rate enhancement, believed to reflect the generation of PS-SO₃Ag·PCy₃.