| Sulfur-containing heterocyclic structural units are widely found in natural products,functional materials,drugs,and other functional molecules.Visible light-catalyzed reactions have received much attention from synthetic chemists in recent years due to their unique role in chemical bond construction and the high efficiency and cleanliness of the reactions,among which the synthesis of heterocyclic compounds has become one of the hot spots in the research of organic synthesis methods.In this thesis,the efficient synthesis of dihydrothiophene and thiobicyclo[3.2.0]heptane was developed around two catalytic modes,namely single-electron redox catalysis and triplet energy transfer catalysis,in visible light catalysis.This thesis consists of three parts as follows:Chapter 1: This chapter focuses on photocatalytic tandem reactions based on trilinear state energy transfer catalysis,including SET/ En T catalytic tandem,En T/En T catalytic tandem and the progress of research on En T catalytic tandem catalytic reactions with other catalytic modes.Chapter 2: This chapter describes the visible light-catalyzed [3+2]-annulation reactions of pyridinium 1,4-zwitterionic thiolates with olefins.The reaction of pyridinium 1,4-zwitterionic thiolates with styrene,alkenamines and enols under the catalysis of Eosin Y gives [3+2]-annulation products,and the synthesis of dihydrothiophene to thiophene and sulfonates can be achieved by an oxidation strategy.Chapter 3: Based on the idea of sequential tandem catalysis by SET-En T,a single photocatalyst-catalyzed [3+2+2]-annulation reaction of pyridinium 1,4-zwitterionic thiolates with two molecules of alkenes was developed.This method provided a new method for the efficient synthesis of thiobicyclo[3.2.0]heptane compounds.Mechanistic experiments showed that the reaction first undergoes a SET-catalyzed[3+2]-cycloaddition followed by an En T-catalyzed [2+2]-cycloaddition. |
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