Application Of Visible Light Catalyst In The Synthesis Of Tetrahydroisoquinoline Derivatives

Tetrahydroisoquinoline alkaloids exist widely in nature and are recognized as classic and effective drug precursor molecules.Modification and transformation of the tetrahydroisoquinoline skeleton has become a hot field for new drug research and development.Among many synthetic methods,visible light catalysis is favored by many chemists due to its green and high-efficiency characteristics.This Thesis investigates the research progress of visible light-catalyzed cross-dehydrogenative coupling（CDC）reaction.For the issues that homogeneous catalysts are difficult to separate from the catalytic system,relevant works have been done on the design and preparation of visible light catalysts.First,starting from the inorganic semiconductor visible light catalyst graphite phase carbon nitride（g-C₃N₄）,protonated carbon nitride（P-g-C₃N₄）was prepared by means of protonation treatment.And use SEM（scanning electron microscope）,UV-Vis（ultraviolet-visible diffuse reflectance spectrophotometer）,FT-IR（Fourier infrared spectrometer）and other characterization methods for qualitative analysis The results showed that the protonation treatment peeled off the originally agglomerated g-C₃N₄ sheets,increased the specific surface area of the catalyst,and improved the light absorption intensity of the catalyst.Subsequently,CDC reaction of N-phenyltetrahydroisoquinoline and its derivatives with nitroalkanes and acetone were used to verify its catalytic activity.The results showed that the catalytic activity of P-g-C3N4 visible light catalyst was improved compared with g-C₃N₄,And the stability of the catalyst is good.After 6 times of recycling,the reaction yield can still reach 93%.Subsequently,due to the time-consuming operation of the separation and recovery of the above-mentioned catalysts,we designed and synthesized a macroscopic composite photocatalyst.It was proposed to grow a silane coupling agent on the surface of the cotton cloth to introduce amino groups.The intermolecular dehydration condensation between amino groups and Rose Bengal（RB）carboxyl groups formed an amide bond,and finally the organic photocatalyst RB was anchored on the cotton cloth by a covalent manner to obtain the Bengal Rose Red-Cotton Cloth（RB-Cotton Cloth）visible light catalyst.This new type of composite RB-Cotton Cloth photocatalyst exhibits excellent CDC reaction catalytic activity.All reactions can be catalyzed within1.5 hours.After the reaction,the catalyst was directly separated from the reaction system simply by tweezers,saving post-treatment costs significantly.The catalyst would be applied to the flow reactor in the future,and has potential commercial value in industry.