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.