Palladium–diphosphine complexes as catalysts for allylations with allyl alcohol

Abstract

Several palladium complexes with bidentate phosphine ligands were tested for their activity in the O-allylation of phenols with allyl alcohol. The use of C 3-bridged bidentate phosphine ligands results in very high selectivity for O-allylation. The reactions do not require stoichiometric amounts of additives to control the chemoselectivity. Especially, catalysts with gem-dialkyl substituted C 3-bridged bidentate phosphine ligands perform very well, resulting in a (equilibrium) conversion of ∼50% of phenol with a selectivity of 99% for O-allylation. The use of diallyl ether as the allylating agent results in a significant increase in phenol conversion while maintaining high selectivity for O-allylation. Apart from Pd(OAc) 2 as catalyst precursor, Pd(dba) 2 was also employed, making it possible to use other types of phosphine or phosphite ligands. With the palladium catalytic system not only phenol, but also aliphatic alcohols can be allylated, as well as aromatic and aliphatic amines.