R)-Hydroxy-(S)-proline was N-protected by reaction with di-tert-butyl pyrocarbonate to give N-Boc-(4R)-hydroxy-(S)-proline, which was treated with NaH in anhydrous tetrahydrofuran and followed by etherification with P...R)-Hydroxy-(S)-proline was N-protected by reaction with di-tert-butyl pyrocarbonate to give N-Boc-(4R)-hydroxy-(S)-proline, which was treated with NaH in anhydrous tetrahydrofuran and followed by etherification with PhCH 2Br to form the N-Boc-(4R)-benzyloxy-(S)-proline, which, after removal of the protecting group with CF 3COOH gave the title compound. As an efficient catalyst for the direct asymmetryic aldol reaction the compound gave products in yield ranged from 58% to 77% with enantiomeric excess up to 88%.展开更多
Chiral Mn Ⅲ (salen) (Jacobsen's catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different lin...Chiral Mn Ⅲ (salen) (Jacobsen's catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different linkage lengths and evaluated as catalysts for the epoxidation of unfunctionalized olefins. The results demonstrated that the prepared catalysts exhibited moderate to good activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the immobilized catalysts were relatively stable and could be conveniently separated from the reaction system by simple precipitation in hexane. Moreover, higher enantioselectivity was obtained with catalyst 2c than that of homogeneous counterpart catalyzed even after eight times. The excellent recycling of the catalyst was attributed to its structure feature of ZPS-IPPA which is different from either pure polystyrene or pure zirconium phosphates.展开更多
It is one of the most attractive types of asymmetric synthesis that chiral commpounts are generated under the influence of chiral catalysts. In recent years catalytic asymmetric Michael addition by chiral metal comple...It is one of the most attractive types of asymmetric synthesis that chiral commpounts are generated under the influence of chiral catalysts. In recent years catalytic asymmetric Michael addition by chiral metal complexes has been recognized as an efficient method for obtaining asymmetric products. In this work we reported that using potassium thiazolidine -2-thione-4-carboxylate [(R)-TTCA·K] as the chiral catalyst, the addition reaction of cyclohexanone with acrylonitrile was carried out and optically active (S)-(+)-2-cyanoethyl cyclohexanone 1 ([α] 20 D=+2.8°, e.e. 19%) and hydrolysis product of 1, (S)-(-)-2-oxocyclohexanepropionic acid 2 ([α] 20 D=-2.95°, e.e. 19%), were obtained. Enantiomeric excess of compound 1 was determined by resolution of (R,S)-2-oxocyclohexanepropionic acid with (-)-quinine. Compounds 1 and 2 were easily racemized at a long time for laying aside and in the presence of dil H 2SO 4 or dil base. When (S)-(+)-2-cyanoethyl cyclohexanone reacts with ethylene glycol in the presence of toluene sulfonic acid as the catalyst the racemic 2-ethylendioxy cyclohexyl propionitrile was obtained. The mechanism of the reaction of cyclohexanone with acrylonitrile would be a complicated catalysis process.展开更多
文摘R)-Hydroxy-(S)-proline was N-protected by reaction with di-tert-butyl pyrocarbonate to give N-Boc-(4R)-hydroxy-(S)-proline, which was treated with NaH in anhydrous tetrahydrofuran and followed by etherification with PhCH 2Br to form the N-Boc-(4R)-benzyloxy-(S)-proline, which, after removal of the protecting group with CF 3COOH gave the title compound. As an efficient catalyst for the direct asymmetryic aldol reaction the compound gave products in yield ranged from 58% to 77% with enantiomeric excess up to 88%.
基金grateful to Southwest University of China for financial supportthe Natural Science Foundation Project of CQ CSTS(2011jjA50003) for the financial support
文摘Chiral Mn Ⅲ (salen) (Jacobsen's catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different linkage lengths and evaluated as catalysts for the epoxidation of unfunctionalized olefins. The results demonstrated that the prepared catalysts exhibited moderate to good activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the immobilized catalysts were relatively stable and could be conveniently separated from the reaction system by simple precipitation in hexane. Moreover, higher enantioselectivity was obtained with catalyst 2c than that of homogeneous counterpart catalyzed even after eight times. The excellent recycling of the catalyst was attributed to its structure feature of ZPS-IPPA which is different from either pure polystyrene or pure zirconium phosphates.
文摘It is one of the most attractive types of asymmetric synthesis that chiral commpounts are generated under the influence of chiral catalysts. In recent years catalytic asymmetric Michael addition by chiral metal complexes has been recognized as an efficient method for obtaining asymmetric products. In this work we reported that using potassium thiazolidine -2-thione-4-carboxylate [(R)-TTCA·K] as the chiral catalyst, the addition reaction of cyclohexanone with acrylonitrile was carried out and optically active (S)-(+)-2-cyanoethyl cyclohexanone 1 ([α] 20 D=+2.8°, e.e. 19%) and hydrolysis product of 1, (S)-(-)-2-oxocyclohexanepropionic acid 2 ([α] 20 D=-2.95°, e.e. 19%), were obtained. Enantiomeric excess of compound 1 was determined by resolution of (R,S)-2-oxocyclohexanepropionic acid with (-)-quinine. Compounds 1 and 2 were easily racemized at a long time for laying aside and in the presence of dil H 2SO 4 or dil base. When (S)-(+)-2-cyanoethyl cyclohexanone reacts with ethylene glycol in the presence of toluene sulfonic acid as the catalyst the racemic 2-ethylendioxy cyclohexyl propionitrile was obtained. The mechanism of the reaction of cyclohexanone with acrylonitrile would be a complicated catalysis process.
