Cobalt-Catalyzed Allylic Substitution Reaction of Allylic Ethers with Phenyl and Trimethylsilylmethyl Grignard Reagents

Treatment of cinnamyl methyl ether with phenylmagnesium bromide in ether in the presence of CoCl2[1,5-bis (diphenylphosphino)pentane] affords 1,3-diphenylpropene in good yield. Similar allylic substitution reaction with trimethylsilylmethylmagnesium chloride proceeded smoothly to yield homoallylsilanes. (alpha),(beta)-Unsaturated aldehyde acetal also underwent allylic substitution.