The homogeneous catalysed isomerization of 2-allylphenol and of (Z)-2-propenylphenol in the presence of a palladium catalyst

Abstract

The isomerization of 2-allylphenol (ap) in the presence of bis(benzonitrile)-dichloropalladium(II) displays kinetics which differ in certain respects from the normal isomerization of olefins catalysed homogeneously by transition metal complexes. The most unusual feature is that the rate increases continuously so long as a detectable concentration of ap remains. The behaviour is believed to be due to a concentration of active catalyst which increases with time and with concentration of the product, 2-propenylphenol (pp). The participation of the phenolic hydroxyl group, resulting in chelation of pp to palladium is considered to be responsible for the difference in behaviour between ap and, for example, allylbenzene. The isomerization of (Z)-pp also displays unusual characteristics which are explained within the framework of this hypothesis.