Metal-and Oxidant-Free Electrochemistry For The Construction Of C-S Bonds

Sulfur-containing compounds have received more and more attention in medicine due to their unique physiological and pharmacological activities.Till now,many methods have been developed to construct C-S bonds and synthesize sulfur-containing compounds for drugs or their intermediates.Therein,traditional organic synthesis methods are the most widely used which utilize cross-coupling of aryl halide and mercaptan with the catalysis of transition metals such as palladium,copper,nickel,cobalt,and iron to generate sulfur-containing compounds.However,these methods suffer from some drawbacks.For example,the catalysts are expensive and difficult to recovery,complicated ligands with special structures to form complexes with the above-mentioned metals need to designed and synthesized,a large number of oxidants,high-temperature conditions and is long reaction time are necessary,and therefore a large amount of environmental waste are generated.Compared with traditional organic synthesis methods,electrochemical synthesis does not require chemical redox agents which uses electrons as redox agents directly and therefore is environmentally friendly.Moreover,the efficiency can be significantly improved by optimizing electrode type,current/voltage,and electrolyte solution etc.In recent years,electrochemical synthesis methods have also been used for the construction of C-S bonds.However,metal catalysts are still needed and the reactions are usually carried out at high temperatures in previous reports.Especially,the often used substrates are thiophenols and sulfinic acids which are chemically active,malodorant and highly toxic.It is still a big challenge for chemists to construct C-S bonds with much greener substrates in mild reaction conditions.So,this thesis is aimed at preparing a series of sulfur-containing compounds with disulfide as a substrate under mild conditions.The detail is described as follow:1.A series of aryl sulfides were synthesized by electrochemical methods using electron-rich aromatic hydrocarbons and disulfides as substrates.It processed successfully under room temperature and air atmosphere.Importantly,no extra metallic catalyst and no exogenous oxidants were needed.A total of 21 target compounds were prepared with yields among 25% ～ 81% through this electrochemical synthesis method.And it can be conducted successfully with the gram scale.Additionally,the possible reaction mechanism was proposed by combing free radical capture and cyclic voltammetry experiments with literature.2.An amount of 9 3-sulfide indole and its derivatives were synthesized with N-methylindole and its derivatives as substrates using the similar electrochemical synthesis method with 50% ～ 85% yield.And it also can carry out successfully with the gram scale.Moreover,the possible reaction mechanism was explored by combing cyclic voltammetry experiment with literature.