Catalytic Dehalogenation of Aryl Halides Mediated by a Palladium/Imidazolium Salt System

Abstract

A convenient and efficient catalytic aryl halide dehalogenation protocol has been developed using an imidazolium salt/palladium/base system. The use of the ligand precursor SIMes·HCl ((2,4,6-trimethylphenyl)dihydroimidazolium chloride) in conjunction with Pd(dba)2 was found to be most effective for the dehalogenation of aryl chlorides, bromides, and polyhalogenated aromatic hydrocarbons. Strong bases having β-hydrogens both perform deprotonation of the imidazolium salt and are hydrogen sources for the dehalogenation process. The oxidative addition of the imidazolium salt to the palladium(0) precursor generating a carbene palladium hydride species may also be involved in the dehalogenation process. This oxidative-addition reaction may have fundamental implications in low-valent metal carbene mediated transformations.