Electrochemical Synthesis Of Vinyl Sulfones And Epoxides

Vinyl sulfones and epoxides both are important intermediates in organic synthesis, which are widely applied in organic, pharmaceutical and the other fields. It is of great significance to develop new methods for the synthesis of two types of compounds.In the first part, a simple and efficient electrochemical method has been developed for the synthesis of vinyl sulfones from sodium sulfinates and olefins. The effect of electrolytic time, supporting electrolytes, solvents and electrode materials on the electrosynthesis was investigaeted. According to the experimental results, an appropriate electrochemical system is composed of Na I supporting electrolyte, DMSO solvent, Ni cathode and graphite anode, electrolysis with constant current for 1 h and then continuously stirring for 4 h at room temperature. In this optimized condition, styrene with sodium 4-methylbenzene sulfinate could be successfully converted to the target product vinyl sulfones in an excellent yield 90%. In order to test the scope of the reaction, our investigation was extended to different olefins and sodium sulfinates under the optimized conditions. The results show that various styrene derivers, including ortho-, meta- or para-methyl styrene, and para-(methoxyl, halogen or trifluoromethyl) styrene, could afford satisfactory yields. However, when styrene was replaced by vinyloxybenzene, the target product was not observed at all, indicating that the conjugated effect of olefins is very important for this transformation. In addition, the reaction mechanism was further studied and a plausible mechanism was proposed.In the second part, an efficient electrochemical route toward the synthesis of epoxides from olefins has been developed. Similarly, we investigated the effect of supporting electrolytes, solvents, electrode materials, electrolytic time and water on the electrochemical synthesis of epoxides. According to the experimental results, an electrochemical system which is composed of NH4 I supporting electrolyte, DMSO solvent, Ni cathode and graphite anode, 0.05 g of water, electrolysis with constant current for 6 h at room temperature, should be preferentially considered. In the optimized conditions, both aromatic and aliphatic olefins could be converted to the target product epoxides in high to excellent yields(55%~95%). Moreover, the electrochemical reaction mechanism of olefins epoxidation was investigated.In this paper, studies on the sulfone and epoxidation reactions of olefins via electrochemical synthesis are discussed in detail. Our studies provide a new synthetic route for vinyl sulfones and epoxides.