The Synthesis And Application Of Chiral Phase-transfer Catalysts In Asymmetric Catalytic Reactions

Eight new chiral quaternary ammonium salts, starting from naturaly occuring proline and hydroxyproline, were designed and synthesized. These compounds are stereogenic both at N and at C. Also, two phase-transfer catalysts from cinchonine were prepared.These new catalysts have been tested in a number of known enantio-selective phase-transfer catalytic(PTC) reactions, such as reduction of ke-tones with sodium hydroborate, alkylation of imines and epoxidation of chalcone. The epoxidation of chalcone has been studied systematically. The structure of these catalysts, oxidants and solvents can all affect the asymmetric epoxidation reaction. Only very moderate e.e.s were observed. The asymmetric-induction results of the catalysts derived from cinchonine are better than those derived from proline or hydroxyproline.