Using L-valine, L-leucine, L-phenylalanine as starting materials, the imidazole ring was condensed by ring fragments and hydroxyl group was induced by the reduction of carboxyl of the amino acids. And then through chlorination and subsequent substitution by thiols, chiral imidazole thioethers were synthesized and their structures were characterized by ¹H NMR, ¹³C NMR, IR and HRMS. Using SiO₂ as a carrier, chiral imidazole thioethers were loaded and they were characterized by the DTA and elemental analysis. The results showed that the covalent bond was formed between thioether and silica. SiO₂-supported chiral imidazole thioether ligands were separately coordinated to PdCl₂ and the catalysts were characterized by XPS. The results showed that the palladium was coordinated with SiO₂-supported chiral imidazole thiother ligand which can stabilize the catalyst, and the carbene might participate in the coordination with Pd. The activity of the catalysts was studied in the Suzuki coupling reaction. Under the optimum reaction conditions, which the reaction temperature was 80 ℃ and the amount of the catalyst was 0.75% of the substrate, the conversion of brombenzene was 95% for 5 h.

Key words: chiral midazole thioether ligand, supported Pd catalyst, Suzuki reaction