The Enzyme-catalyzed Michael Addition Reaction And Multi-component Reactions

Enzymes have been more and more widely used in organic chemistry. The catalytic promiscuity of enzyme in organic medium has provided a large number of alternative methods for organic synthesis. With the development of enzymology, enzyme catalysis has received great attention as an efficient and green tool. This thesis focuses on TLIM-catalyzed asymmetric C-C Michael addition, enzyme-catalyzed Biginelli reaction to prepare 3,4-dihydropyrimidin-2-(1H)-ones and other some multicomponent reactions in organic medium.C-C bond forming reactions are one of the mainstays of organic chemistry. In this thesis, we investigated that Lipozyme TLIM (immobilized lipase from Thermomyces lanuginosus) catalyzed asymmetric C-C Michael addition in organic medium in the presence of water. This biocatalysis is applicable to the Michael additions of a wide range of substrates including 1,3-dicarbonyl compounds and cyclohexanone as Michael donors and aromatic and heteroaromatic nitroolefins and cyclohexenone as accepters. The effects of organic solvents, temperature and water content on the enzymatic Michael addition were evaluated in details. The enantioselectivity up to 83% ee and yield up to 90% were achieved. The enzyme can be reused for three cycles.The enzyme-catalyzed Biginelli reaction had been investigated in this thesis. The Biginelli reaction is considered as an important multi-component reaction for generating dihydropyrimidinone and derivates. The interest in the synthesis of Biginelli products has increased tremendously because of their diverse therapeutic and pharmacological properties such as antibacterial, antitumour and antihypertensive activities. The effects of organic solvents, temperature, water content and enzyme amounts on the enzymatic Biginelli reaction were evaluated in details.Multicomponent reactions (MCRs) are powerful tools for the synthesis of complex, biologically relevant molecules. MCRs can be efficiently used in the synthesis of chiral compounds controlled by chiral catalysts. The enzyme A-catalyzed multi-component reaction, such as the Ugi reaction and the Passerini reaction had been studied in this thesis. The effects of organic solvents, water content on the reactions were evaluated in details. The results of the study showed that the best yield was 75% when water content achieved 15% in ethanol solution for the Ugi reaction. The best yield of 94% was obtained for Passerini reaction catalyzed by enzyme A. In addition, different enzyme screen was performed for the Ugi reaction, the best yield of 94% was achieved using lipase from Penicilium camemberti.