Construction Of C-S Bond Via C-H Functionalization Under Metal-free Conditions

Many natural products and drugs contain carbon-sulfur(C-S)bonds.Thus,the construction of C-S bond is an important research content in the fields of chemistry,materials and medicine.The early methods to construct C-S bond mainly focused on the coupling reaction between thiols and organic halide,and the addition reaction of thiols to unsaturated carbon-carbon bond or carbon-heteroatom bond.These methods usually required the use of transition metal catalysts and prefunctionalized substrates,which limited their application.Due to the avoidance of metal residues and prefunctionalization of substrate,the construction of C-S bond via C-H bond functionalization under metal-free conditions has gradually become a research highlights.Based on the oxidative coupling strategy,the conversion of C-H bond to C-S bond was developed by using ammonium thiocyanate or elemental sulfur as sulfur source under metal-free conditions.This thesis contains three parts.In the first part,the recent progress of C-S bond construction by electrochemical synthesis is reviewed.In the second part,organic thiophosphates are synthesized by one pot reaction involing construction of C-S-P bonds through organic electrochemical synthesis strategy.In the third part,the C=S bond and C=O bond can be selectively constructed in S8/DMSO system to synthesize thioamides and amides by adjusting the temperature.The main research contents are as follows:1.Regioselective C-H phosphorothiolation of(hetero)arenes enabled by the synergy of electrooxidation and ultrasonic irradiationBased on the C-H bond functionalization strategy,the three component coupling reaction of(hetero)arenes,ammonium thiocyanate and phosphite was developed by combining electrochemical strategy with ultrasonic irradiation,and arylthiophosphite compounds could be synthesized in one-pot.Imidazo[1,5-a]pyridines,indoles,1,3,5-trimethoxybenzene and N,N-dimethylaniline were suitable substrates for the reaction.The reaction is distinguished by its wide substrate scope,transition-metal-free and external oxidant-free conditions.It provides an alternative method for phosphorothiolation of aromatics or heteroaromatics.2.Temperature-controlled oxidative coupling of methylhetarenes with amines promoted by S8/DMSO:synthesis of thioamides and amidesThe temperature-controlled oxidative coupling of methylhetarenes with amines was realized in S8/DMSO system.Thioamides were obtained at 80? and amides were obtained at 130?.Both aliphatic and aromatic amines were found to be competent substrates.This reaction provided a green method for the synthesis of thioamides and amides in the absence of oxidants and catalysts,and expanded the application scope of S8/DMSO system in organic synthesis.Figure[41]table[16]reference[127]...