Studies On S-X Bonds Formation Via Catalytic Oxidative Dehydrogenation Coupling Reaction

Sulfur compounds are of great importance among organic compounds,which are widely found in natural products,pharmaceuticals,pesticides and other bioactive molecules.In recent years,catalytic oxidation dehydrogenation coupling to construct S-X?X=C,N,P,S,etc.?bonds develop rapidly,playing an increasingly crucial role in the synthesis of natural products and drugs.However,there are many problems in such poor methods,such as the high costs of catalysts and ligands,base or too much oxidant added in the reaction process.Therefore,it is of significant scientific and application value to study a new method for efficient construction of S-X bond.On the basis,the forming of S-N bond and S-C bonds through catalytic dehydrogenation coupling is systematically studied in this paper.The methods of constructing S-X bonds by catalytic oxidative dehydrogenation coupling using thiol as sulfur source are reviewed by this paper in recent years.They can be divided into two categories:The first is constructing S-X bonds through free-catalytic dehydrogenation coupling,which require excess amounts of bases or oxidants,owning a threat to the environment and poor economics;the second is the catalytic oxidative dehydrogenation coupling to construct S-X bonds,which is more economical and greener than free-catalytic methods.Various types of metal and free-metal catalysts have been studied.Some important molecules were effectively prepared,such as disulfide,phosphite,sulfenamide,sulfinate,etc.Although great progress has been made in the construction of S-X bonds through catalytic oxidative dehydrogenation,there are still many problems.We are committed to searching for new methods to construct S-X bonds,which improve the green,high-atom economic and step economic methods to synthesize the high value-added compounds.1.A new I₂-KMnO₄ catalytic system was established and successfully applied to form S-N bonds through oxidative dehydrogenation coupling reaction of thiols and amines.Preliminary studies on the reaction mechanism show that the real catalytic manganese species is the active MnO₂ produced by the thermal decomposition of KMnO₄,which acts as an electron transfer bridge and assist iodine to complete the catalytic cycle.All kinds of thiols and amines with different substituents can adapt to the catalytic system,and obtain moderate to good yields.In addition,this method can used be for synthesize a drug with an S-N bond skeleton and has potentially antihypertensive.2.DTBP is used the oxidant and catalytic amount of nickel complex promoted to gain a series of alkyl sulfide compounds via oxidative dehydrogenation coupling reaction of thiols and alkanes.The reaction system can be used to synthesize Pyridaben and Chlorbenside,as well as the drug Modafinil?Provigil?for treating central nervous system diseases.Preliminary studies on the reaction mechanism show that disulfide compounds are possible intermediates,and nickel catalysts can accelerate the formation of disulfide,thereby accelerating the formation of products.The detailed mechanism of this catalytic system is being studied.