Pyridine Mediated Palladium Acetate-Catalysed Dehalogenation of Biaryl Halides in Ionic Liquid System:

The palladium acetate-catalysed dehalogenation of biaryl halides has been investigated in room temperature ionic liquids with pyridine acting as a co-solvent. The significant effect of pyridine in conjunction with Pd(OAc)2 in [bmim][PF6] gave excellent results in the dehalogenation of biaryl iodines and bromides. The pyridine activated the C2-H of the imidazolium salt to be the source of hydrogen. The separation of desired product was easily performed by extraction with diethyl ether and the Pd(OAc)2–[bmim][PF6] system could be recycled five times with only a small decrease in activity. This procedure represents an environmentally friendly method for the preparation of biaryl compounds without the use of complex ligands.