Study On The Radial Type Ring Opening Of Sulfonium Salts For The Construction Of Csp~3-Csp~3 Bond And C-Se Bond By Visible Light/Copper Catalysis

Csp~3-Csp~3 bond and C-Se bond are very important organic structures,which are ubiquitous in a wide range of pesticides,medicine and materials.The traditional strategies to construct Csp~3-Csp~3 bond are as follows:nucleophilic substitution reactions between carbon anions and alkyl halides;Michael addition reaction between carbon anions and activated olefins;metal-catalyzed traditional cross-couplings or radical-type cross-couplings between alkyl-metallic reagents and alkyl halides;reductive cross-coupling between two different alkyl halides.The construction of C-Se bond is usually through transition metal catalyzed coupling reaction of halogenated aromatic hydrocarbons with selenides/C-H bond functionalization and free radical reaction.Most of these methods have some shortcomings,such as high cost of reactants,harsh reaction conditions and excessive use of strong oxidants.Therefore,significant space and challenges still exist for the construction of Csp~3-Csp~3 bond and C-Se bond with regard to generality,reaction conditions,and catalytic efficiency.It is very important to find general alkylation reagents and efficient and green synthesis methods to construct Csp~3-Csp~3 bond and C-Se bond.In recent years,visible-light-promoted organic transformation has been developed as a convenient and powerful tool for the formation of C-C bonds and C-heteroatom bonds.Visible-light-driven organic dyes photocatalysts and noble metal catalysts such as iridium and ruthenium have some disadvantages,such as high price,difficult to obtain and short lifetime of excited state.Compared with these photocatalysts,copper photosensitizers are cheap and environmentally friendly,green and non-toxic chemical reagent,and has good absorption in the visible region.In recent years,the reaction catalyzed by metal copper photosensitizers has become an effective method for the construction of Csp~3-Csp~3 bonds and C-heteroatom bonds and has attracted wide attention in the field of catalytic synthesis.Sulfonium salt is a kind of important alkylation reagents,which is widely used in the conversion process of organic synthetic chemistry.Traditionally,the chemical transformation of sulfonium salts can be classified as follows:serving as precursors to sulfur ylides for the formation of ring-sized compounds,nucleophilic ring-opening reactions with nucleophiles and transition metal-catalyzed desulfurization reactions for the synthesis of C-Se and Csp~3-Csp~3bonds.But the application of sulfonium salts as precursors of free radicals in reactions in which radicals participate is rarely explored,and there are disadvantages of using noble metal catalysis and harsh reaction conditions.Therefore,there is still a great challenge to develop a cheaper,universal,green and efficient methods to build Csp~3-Csp~3 bond and C-Se bond.Based on the research of our group on sulfonium salts and copper photosensitizers,we explored the new methods of copper photosensitizers-catalyzed radial ring opening of sulfonium salts to construct Csp~3-Csp~3 bond and C-Se bond.The detailed resarch works are as follows:(1)A new method for the construction of Csp~3-Csp~3 bond based on visible light induced copper photosensitizer catalyzed sulfonium radical ring opening was developed.Enabled by the copper(I)photocatalysis,the C-S bond of arylsulfonium salts can be efficiently cleaved to deliver C-centered radicals,which provides straightforward access to utilize arylsulfonium salts as the sulfur source for the synthesis of aryl alkyl thioethers.It provides a new idea for the reaction types of sulfonium salts,and has a wide application prospect in pharmaceutical chemistry and synthetic chemistry.(2)A new method for the construction of Csp~3-Se bond based on visible light induced copper photosensitizer catalyzed sulfonium radical ring opening was developed.This process shows a broad substrate scope and high functional group tolerance,providing practical access to valuable alkyl chalcogenide/alkyl selenide/alkyl telluride compounds.This strategy breaks the limitation that only Lewis bases and Br(?)nsted bases can promote C-C bond and C-heteroatom bond construction through the nucleophilic ring-opening reaction of sulfonium salts,which will inspire further applications of sulfonium salts in visible-light-driven organic transformations.