Study On Synthesis Of Sufur-Containing Heterocyclic Compounds Using Potassium Sulfide As Sulfuration Agent

The sulfur-containing benzene fused heterocyclic compounds, such as benzothiazoles and benzothiophenes, are an important class of Sulfur-containing heterocyclic compounds. These compounds have a wide range of applications in medicine, agriculture, material and other fields. Thus, development of general methods for the construction of these compounds is valuable.Potassium sulfide is a common inorganic sulfide. Recently, potassium sulfide has been widely investigated for introducing sulfur atoms into organic molecules via C-S bond construction. Compared with organic sulfides, it has obvious advantages of low cost, low toxicity, relatively stability and easy operation. In this paper, general methods were developed for the formation of the sulfur-containing benzoheterocycles compounds using potassium sulfide as sulfuration agent. The contents of this thesis are summarized as follow:Chapter one:briefly introduction about the methods for synthesis of sulfur-containing benzoheterocycles are demonstrated, which a wide variety of sulfuration agents are utilized in synthetic transformations to afford organosulfur compounds.Chapter two:copper-catalyzed synthesis of benzothiazoles via double C-S bond formation. A novel, highly efficient procedure for the synthesis of benzothiazoles from easily available N-benzyl-2-iodoaniline and potassium sulfide has been developed. Two C-S bonds are formed via a copper-catalyzed traditional cross-coupling reaction and an oxidative cross-coupling reaction. Finally, the desired products were obtained in an oxidative dehydrogenation procedure.Chapter three:The transition-metal-free approach to synthesis of benzothiophenes. A new, highly efficient procedure for the synthesis of benzothiophenes from easily available o-halovinylbenzenes and potassium sulfide has been developed. Functional groups were tolerated under the optimized reaction conditions and various2-substituted benzothiophenes are provided in the high yields in the absence of a transition metal catalyst.Chapter four:catalyst-free approach to2-aryl benzothiazoles using metal sulfides as coupling partners. This is the first successful example for the use of potassium sulfide as coupling partners to synthesize2-aryl benzothiazoles under catalyst-free conditions. This synthetic strategy has the advantages of environmental-friendly, easy operation, mild reaction conditions and good selectivity toward halogen atom.