Cross-metathesis s. silylative coupling of vinyl alkyl ethers with vinylsilanes catalyzed by a ruthenium–carbene complex (Grubbs catalyst)

Abstract

Grubbs complex, (PCy₃)₂Cl₂RuCHPh (I) is a very effective catalyst of the cross-disproportionation of vinyl-trisubstituted silanes H₂CCHSiR₃ [where R₃=Me₃, PhMe₂, (OEt)₃] with vinyl alkyl ethers H₂CCHOR′ [where R′=ethyl, propyl, butyl, t-butyl, t-pentyl, 2-(ethyl)hexyl, cyclohexyl, trimethylsilyl] to yield a mixture of (E+Z) 1-silyl-2-alkoxyethenes. The reaction occurs quantitatively under milder conditions (60°C) than the analogous one catalyzed by Ru–H and/or Ru–Si complexes reported previously (80°C). The stoichiometric reaction of (I) and (PCy₃)₂Cl₂RuCH₂ (III) with vinyl ethyl ether leads to the formation of (PCy₃)₂Cl₂RuCH(OEt) (II), inactive in the stoichiometric reaction with vinylsilanes but very active in the catalytic process. Experiments with the use of deuterated vinylsilanes indicate the non-metallacarbene mechanism of the reaction and provide evidence for the initiation of Ru–H bond formation ia the hydrovinylation with vinylsilanes.