Electrochemical Dehydrogenative Coupling Of S-H/N-H To Synthesis Sulfenamide

S-N bonds are important structural units in organic chemistry and have a very wide range of applications,especially in the industrial,agricultural and pharmaceutical fields.The conventional method to form S-N bond is by reacting sulfonyl chloride/sulfenyl chloride with amine.However,the stability of the sulfenyl chloride/sulfonyl chloride is poor,and the preparation process is complicated.There are many reactions in the reported literature for non-metal-related S-N bond construction,but it is difficult to avoid the usage of excess oxidant or chlorinating reagent.Metal-catalyzed S-N coupling also has drawbacks such as expensive and toxic transition metal catalyst,and various ligands that require long steps to prepare.In this context,the development of novel synthetic tools to construct S-N bonds to fulfill the criteria of green chemistry,atom economy,great efficiency,is highly desired.As an efficient and environment-friendly synthetic tool,electrochemical oxidation process has received increasing attention.The electrochemical synthesis process avoids using other catalysts and oxidants.Therefore,a protocol for electrochemically oxidation S-H/N-H coupling to construct S-N bonds was designed.By optimizing the electrolyte,solvent,electrode material,reaction time and other reaction parameters,the optimal reaction conditions for the synthesis of S-H/N-H electrochemical dehydrogenation coupling to sulfenamide were determined.Ammonium tetrabutylammonium tetrafluoroborate?0.1 mol/L?was used as the supporting electrolyte,acetonitrile was used as the solvent,and foamed nickel was used as the anode/cathode of the electrolytic cell,and electrolysis was carried out for 6 h at room temperature.This electrochemical reaction condition tolerates a wide range of substrates,and a total number of 20sulfenamide compounds was obtained.The yields of compounds are 10-95%,with most of the substrates achieving medium to high yields.All of the target products were characterized by melting point,LR-MS or HR-MS,¹H NMR and ¹³C NMR.Experiments have shown that the method can be scaled up to a 50 g scale with a yield of 94%.The possible reaction mechanism was proposed by cyclic voltammetry and free radical trapping experiments.In this paper,a new,efficient and extensive versatility method for the direct synthesis of sulfenamide by electrochemical oxidative coupling of thiol and amine was developed.This oxidant-and catalyst-free electrochemical process enables S-N bond formation with inexpensive nickel electrodes in an undivided cell.It has the characteristics of simple,cheap and scalable,showing a good application prospect.