Synthesis Of Chiral Organocatalysts And Their Application In Asymmetric Reactions

1.Synthesis and Application of Chiral Quaternary Ammonium Salts in Enantioselective Epoxidation of Chalcone ReactionA new chiral quaternary ammonium salt Catâ… was synthesized by the reaction of cinchonine and 2,4,6-trimethyl benzyl chloride. Etherification of Catâ… was achieved by reaction with benzyl bromide, allyl bromide, and methyl iodide, to give the corresponding etherified quaternary ammonium salts Catâ…¡, Catâ…¢, and Catâ…£, respectively. In the presence of Catâ…¡, Catâ…¢, or Catâ…£(5 mol%), chalcone was stereoselectively epoxidized by sodium hypochlorite in the yields between 89% and 92%, with the ee ranged from 58% to 63%.2. Synthesis of Novel Chiral Thiourea/Urea Catalysts and their Application in the Asymmetric Michael Addition ReactionsNew chiral thiourea Catâ…¤and chiral urea Catâ…¥derived from L-proline have been synthesized and determined by 1HNMR, MS. The crystal of thiourea picric salt has been brought up and its crystal structure has been determined by single crystal X-ray diffraction. The direct Michael reaction of cyclohexanone/aldehyde with nitroolefins, catalyzed by a new pyrrolidine-thiourea/urea catalyst Catâ…¤/ Catâ…¥, is described. When Catâ…¤was used ( 20mol% ), the desired 1,4-adducts are obtained in moderate yield with enantioselectivities up to 99% ee and dr up to 100:1.