Studies on Synthesis of Chiral β-Amino Alcohols and Their Application in Asymmetric Henry Reactions
|School||Zhejiang University of Technology|
|Keywords||Chiral β-amino alcohols Asymmetric Catalysis Henry Reaction Asymmetric Reduction|
Asymmetric synthesis is one of today's organic chemistry frontier, the development of efficient and selective synthesis method is the hot issue of modern synthetic chemistry research. Henry reaction is a very important class of organic reactions, building a carbon-carbon bond chiral ligand-catalyzed asymmetric Henry reaction has become one of the important means of the synthesis of carbon-carbon bond, the chiral β-nitro alcohol obtained in this way has a high ee values. The product is an important intermediate for organic synthesis, can be a lot of useful conversion further reduced to β-amino alcohols, the dehydration nitroolefin oxidized carbonyl compounds. Chiral β-amino alcohols have important uses in organic synthesis. They are an ideal chiral building blocks, can be used for synthesis of adrenergic drugs, although a variety of chiral drugs receptor blockers, and amino acids, etc.; organic catalyst, they are also excellent for the catalytic dialkylzinc and aldehyde symmetrical addition reaction, asymmetric epoxidation reaction, asymmetric Henry reaction and prochiral ketones asymmetric reduction of a variety of asymmetric catalytic reactions. Therefore, we glycine to L-phenylalanine and L-phenylalanine as the raw material, the two types of chiral β-amino alcohols are synthesized by simple methods; while in turn they are applied to the catalytic asymmetric Henry reaction and catalytic asymmetric reduction of prochiral ketones. This research work has the following three parts: (1) the synthesis of chiral β-amino alcohols (1) L-phenylalanine as raw material, by esterification, Grignard reaction, and finally restore aldehyde condensation, simple and efficient synthesis of chiral β-amino alcohol of the eight kinds of the literature has not been reported. Mass spectrometry, infrared spectroscopy, 1 sup> H NMR and 13 sup> CNMR verify their structure. (2) L-phenylglycine as raw materials, so the carboxyl reduced to hydroxyl NaBH 4 / I 2 and aldehyde condensation last restore simple and efficient synthesis of 5 chiral β-amino alcohols, the structure of the product were confirmed by mass spectrometry, infrared spectroscopy, 1 sup> HNMR verification. 2 will be L-phenylalanine and L-phenylglycine synthesized two types of chiral β-amino alcohols used in catalytic nitromethane, a series of chiral aromatic nitro asymmetric Henry reaction of aldehyde alcohol compounds. Affect product enantioselectivity of the catalyst structure, the amount of catalyst, the different metals copper salt, solvent and reaction temperature and other factors were investigated. When the amount of catalyst is 10%, the amount of 10% of CuCl, ethanol as solvent and a temperature of 18 ° C to LBG-3 as catalyst, the resulting β-nitro-alcohol enantiomer excess up to 89%, the chemical yield was 95 %. Based on the experimental results, we propose a possible mechanism of the catalytic asymmetric Henry reaction. 3 the NaBH 4 / I 2 -reduction system, the synthesis of chiral β-amino alcohols used for the asymmetric reduction reaction of Acetophenone Catalyzed explore. The chemical yield of 80% -89% can be obtained, but unfortunately product enantioselectivity generally low and 5%, and this reaction is still further study.