Palladium complexes with chiral imidazole ligands as potential catalysts for asymmetric C-C coupling reactions

Two palladium complexes of the type [Pd(im)2Cl2] containing chiral imidazole ligands (im = 1-bornyloxymethylene imidazole, 1-fenchyloxymethylyne imidazole) were synthesized and structurally characterized. The square planar structure of one of the complexes was confirmed by the X-ray analysis. The new palladium complexes were tested as catalysts in various C-C bond forming reactions, namely Suzuki–Miyaura, carbonylative Suzuki–Miyaura, asymmetric Heck-type coupling reactions and asymmetric conjugate addition of phenylboronic acid to heterocyclic acceptors. In all the reactions the cross-coupling products were obtained with high yield and selectivity under mild conditions. In case of coupling of 2,3-dihydrofuran with phenylboronic acid ee value ca. 10 was observed.