Isomerisation of allyl phenyl ethers and allylphenols with transition metal catalysts

Abstract

Isomerisation of allyl phenyl ethers with PdCl₂(PhCN)₂ in boiling benzene gives quantitatively phenyl prop-1-enyl ethers with the cis-isomer predominating. Varying the substituents in all three positions of the allyl group shows that the reaction is sensitive to steric effects and the results are discussed in terms of an intermediate π-allyl(hydrido)palladium complex and also a sigmatropic [1,3] hydrogen shift within a π-olefinpalladium complex. The effect of other transition metals on the isomerisation is summarised. The isomerisation of allylphenols to trans-(prop-1-enyl)phenols is discussed in terms of these mechanisms and conformations of the side chains.