The Study On Photocatalyzed Coupling Reactions With Sulfonium Salts

Sulfonium salt compound is one kind of the important reactants and intermediates in organic synthesis due to its structure and valence change.Moreover,sulfonium salts tend to undergo single-electron reduction because it carries a positive charge,thus,it also plays an important role in the synthesis of natural products and drug molecules.Radical intermediates produced by light-induced C-S bond cleavage could be used in the construction of various chemical bonds.This paper mainly focus on the utilization of sulfonium salts(including alkenyl and aryl ones)in photocatalysis chemistry.In these work,the sulfonium salts acted as a radical acceptor or a radical donor to realize the formation of C-C bond.The work included is as follows:(1)Visible light catalyzed vinylation reaction using alkenyl-sulfonium salts as Michael acceptor.In chapter 2,the first photocatalytic vinylation reaction using alkenyl-sulfonium salts as coupling reagents has been realized without the participation of transition metals.Under photocatalytic reduction,alkyl radicals,generating from the active esters of primary,secondary and tertiary acids,react with alkenyl-sulfonium salts(which was treated as Michael acceptors)to obtain alkenylation products.This reaction shows good functional group tolerance.(2)Radical addition reaction using aryl-sulfonium salts as a radical donorChapter 3 developed a methodology in which aryl radical was initiated from arylsulfonium salts in the presence of photocatalysis,followed by the radical addition with pyridine olefin substrates to construct C-C bond.This protocol could tolerate various functional groups and provide a convenient approach to synthesize ligands,drug molecules and amino acids containing heterocycles.It is worth noting that the arenes could be treated as the substrate to give the corresponding radical addition product using a one-pot method which eliminates the need for isolation of aryl-sulfonium salts.