Research On Visible Light-induced CS Bond Construction

C-S bonds are widespread in bioactive drugs,natural products,and advanced functional materials.Therefore,the development of efficient methods for constructing C-S bonds is particularly important in the fields of synthetic chemistry and medicinal chemistry.In general,the C-S bond formation reaction involves the following methods:(a)Transition-metal catalyzed cross-couplings of thiols or disulfides with arylboronic acids or organic halides;(b)Nucleophilic substitution reaction in polar solvents at high temperature;(c)Click reaction of thiol-ene and thiol-alkyne.In recent years,visible light catalysis has become an attractive synthetic strategy in organic chemistry.In particular,this catalytic method,which is different from traditional organic transformations,could generate various active free radical intermediates by photo-cracking different chemical bonds,opening a new avenue for the construction of C-C and C-heteroatom bonds.Recently,organic dyes,copper complexes,iridium,ruthenium and other efficient photocatalysts have been widely used to construct C-C and C-heteroatom bonds through organic transformation induced by visible light.Compared with traditional methods,photoredox catalysis has the advantages of cheap,environmentally friendly,easy to operate,and mild reaction conditions.However,the promotion of C-C and C-heteroatom bonding by visible light in the absence of photocatalysts are rather limited.Therefore,the development of photochemical conversion in the absence of photocatalysts is of great significance.In this paper,we have successfully developed some efficient methods for the construction of C-S bonds under visible light conditions.The detailed resarch works are as follows:(1)We describe the successful development of a novel and efficient C(sp~2)-H thiocyanation reaction of electron-rich heteroarenes and arenes with readily available ammonium thiocyanate under visible light exposure.Most importantly,the reaction proceeded smoothly without addition of any photocatalyst or strong oxidant,ultimately minimizing the production of chemical waste.The advantages of this reaction met the requirements of green and sustainable synthetic chemistry and may be widely used in organic synthesis and pharmaceutical chemistry.(2)We have successfully developed a green and efficient MCRs protocol to synthesize S-aryl dithiocarbamates under visible light conditions.Most attractively,the reaction can proceed smoothly without adding any transition-metal catalyst,ligand,and photocatalyst,and minimize chemical wastes and metal residues in the end products.The advantages of this developed method meet the requirements of sustainable and green synthesis chemistry and provides a straightforward way to construct valuable S-aryl dithiocarbamates.