Study On C-S Bond Formation Initiated By Electron Donor-acceptor Complex

The construction of C-S bond is not only an important branch in the field of organic synthesis and catalysis,but also an effective way to synthesize organic sulfur compounds.As an important part of organic sulfides,the application of thioesters covers drug synthesis,perfume manufacturing,material polymerization and antioxidant development,which has made great contributions to the development of modern industry.The use of visible light participation and electron donor-acceptor(EDA)complex initiation is an important method to realize the construction of C-S bonds.It has the characteristics of many controllable conditions,green environmental protection and sustainability.Therefore,it is of great significance to develop C-S bond construction reactions based on electron donor-acceptor complexes for the synthesis of thioesters.Based on the above research background,we designed and realized the synthesis of a series of disulfide esters by using thiocarboxylic acid anions as electron donors and 1,1-diphenylethylene as electron acceptors to form electron donor-acceptor complexes under visible light in air atmosphere.In the process of condition optimization,thiobenzoic acid and 1,1-diphenylethylene were used as model substrates,and the conditions such as solvent,light source,type and amount of alkali were investigated.Finally,the dithioester product was obtained with a separation yield of 52 %.At the same time,the mechanism of the reaction was preliminarily discussed,and the possible mechanism was speculated by ultraviolet-visible absorption spectroscopy and control experiments.It was found that1,1-diphenylethylene was not only used to form electron donor-acceptor complexes with thiobenzoic acid anions during the reaction,but also used as a carbon source for the synthesis of disulfides.Different from the traditional thermally initiated dihaloalkanes to obtain dithioesters by substitution reaction,the reaction not only avoids the use of metal and sulfur transfer reagents,but also achieves the use of visible light without adding photosensitizers,which provides a mild,efficient and green method for the synthesis of dithioesters.