Study Of The Design, Synthesis And Application Of Benzimidazole Carbene Ligands Containing Oxazoline Ring

In this paper, a new class of oxazoline ligands have been designed and synthesized and the chiral amino acids were used as starting materials. The main contents include: Chapter I: Literature ReviewFirst, chiral compands which play an important role of the production and life were reviewed in this paper. The latest progress, research results and outstanding achievements in the field in asymmetric catalysis of the oxazoline ligands which included N, N, N, O, N, S, N, P oxazoline ligands such as single-and double-oxazoline ligands were also reviewed.Chapter II Ligand Design and synthesisSix excellent ligands were designed and the synthetic methods under more moderate conditions were studied in this paper. The optimal synthetic conditions were gained. The characterization of all the compounds was successfully performed using a variety of characterization methods, including 1H NMR, 13C NMR, COSY, DEPT 135, HMBC and HMQC, etc. As a result, the target ligands were successfully afforded through simple and efficient synthetic route. In the synthesis, the reduction of amino acids, the protection of amino group using acetyl chloride which reacted with benzimidazole and the cross-coupling with oxazoline were putforword. The key intermediate 5 was successfully achieved, in which the quantitative yield were gained in two of the above steps. It is the first time to identify the absolute structure of the importand intermediates 5. Finally, six new target ligands were obtained in high yield in the solvent of acetonitrile and the different aryl bromides were used in different temperature conditions. The highest yield reached 87.7 %. In the synthesis of the new ligands, 27 compounds were successfully synthesized, of which 7 compounds were first synthesized and six catalytic products were also afforded. In the six ligands , there are five compounds with a single oxazoline ring and one compound with a double-oxazoline ring. The ligand with two-oxazoline ring has a C2 axis which was the hotspot in catalytic field. Chapter III catalytic reactionsIn the application of the designed ligands for the catalytic reaction, the ligands were used in allylic alkylation reaction, Friedel-Crafts alkylation reacton and Michael addition reaction. In the AAA reaction, when 1, 3-diphenyl-2-allyl acetate were the substrate, ligand A had the optimal yield of 73.5 %. In the Friedel-Crafts alkylation reacton, when indole and ethtyl-2-oxoacetate were the bubstrate, ligand F had the optimal yield of 91 %,. In the Michael addition reaction, ligands can reacted the reaction.