| Green catalytic technology is an important way to achieve green chemistry.Using of renewable,environmentally friendly resources as a catalyst will play a key role in chemical reactions.As green and sustainable bio-catalysts,enzymes can catalyze different chemical transformations of natural or non-natural substrates.Today,many examples of enzyme catalytic promiscuies have been reported successfully.Visible light has always been considered a cheap,rich,renewable and non-polluting energy.Using it as a energy of the chemical reaction,has successfully applied to synthesis a variety of organic compounds.The research on enzyme catalytic promiscuity and photocatalysis are the important content of green chemical research and consistent with the research direction of green chemistry.In this paper,we reported bio-catalytic asymmetric Mannich reaction of ketimines using wheat germ lipase for the synthesis of ?-amino ketone derivatives,metal-free visible-light-promoted intermolecular [2+2]-cycloaddition of 3-ylideneoxindoles for the synthesis of spirocyclic oxindoles and Rose Bengal-photosensitized oxidation of tertiary amines for the synthesis of bis-1,3-dicarbonyl compounds in divided sections.Asymmetric Mannich reactions of ketimines provide a useful method for synthesizing ?-amino ketone derivatives with biological activity and pharmacological activity.In the second chapter of this thesis,asymmetric Mannich reaction between 3-substituted-2H-1,4-benzoxazines and acetone catalyzed by lipase from wheat germ Type I(WGL)is described.The desirable products were obtained in excellent enantioselectivities.The influence of several factors,including water content,solvent,amount of substrate,enzyme loading,solvent volume,and temperature was systematically investigated.Under the optimal reaction conditions,we performed 16 examples,the desired products were obtained in excellent enantioselectivities(up to 95% ee).Although the yields are not good enough at present,the lipase from wheat germ was used for the first time in asymmetric Mannich reaction of ketamine.It provides the basis for the application of enzyme catalysis in organic synthesis.Light-promoted intermolecular [2+2]-cycloaddition of allenoates provide a powerful method for synthesizing spirocyclic oxindoles which are common structural units in the bioactive alkaloids and pharmacologically important compounds.In the third chapter of this thesis,Rose Bengal was used as a triplet sensitizer for the first time in the intermolecular [2+2]-cycloaddition of 3-ylideneoxindoles for the synthesis of spirocyclic oxindoles.Substrate scope was tested,and 11 new cycloaddition products were obtained in good yields(up to 93%)with excellent diastereoselectivity and regioselectivity by using a low loading of Rose Bengal(0.125 mol%).This work demonstrates the potential benefits of Rose Bengal as an inexpensive,low-toxic,and widely available metal-free photosensitizer in visible light-promoted intermolecular [2+2]-cycloaddition reaction.The addition reations between nucleophiles with iminium ions have been extensively studied as an efficient method for C-H functionalization,which can provide new reaction protocols for synthesis bis-1,3-dicarbonyl compounds.Bis-1,3-dicarbonyl compounds are valuable intermediates or precursors for organic synthesis and transition metal complexes.In the fourth chapter of this thesis,we report the first example of Rose Bengal-photosensitized oxidation of tertiary amines with various ?-ketoesters and aryl 1,3-diketones for synthesis of bis-1,3-dicarbonyl compounds.The substrate scope was tested,and the reactions are very efficient with a wide range of substrates.11 new products were obtained in this reaction.This protocol expanded the application of Rose Bengal as a photosensitizer in the field of visible-light catalysis. |
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