Study On The Reaction Of C(sp~2)-H Thioetherification And Selenoetherification Of Imidazopyridine Derivatives Catalyzed By Cobalt And Nickel

C-S bond and C-Se bond are two kinds of important chemical bonds in organic synthesis,and they are found in many candidate drugs,bioactive molecules and organic functional materials.Therefore,the development of simple and efficient synthesis strategies to construct new C-S and C-Se bond is one of the hot research directions.Considering unique chemical and biological functions of organosulfides and selenides,the development of new reaction methods to directly introduce sulfur and selenium elements into the drug skeletal molecules via C-H functionalization is welcomed.It is of great significance to study the combination of the sixth main group element chemistry with drug molecules.It is well-known that imidazopyridines are dominant drug scaffolds and have a variety of biological activities.Therefore,here we used imidazopyridines as reactants,and one-pot multicomponent strategy was used to construct C-S bond and C-Se bond under the action of transition metal catalysts,a series of novel thioether-substituted or selenide-substituted imidazopyridine derivatives were obtained.The main work of this paper includes the following two parts:Part I:we use imidazopyridine molecules and arylboronic acids as reactants,cheap and readily available sulfur powder as sulfur source,cobalt chloride hexahydrate as a catalyst,DABCO as a base,and DMF as a reaction solvent,the reaction was carried out at 130~oC for 20 hrs and give arylsulfide-substituted derivatives.All the reaction gave the expected products in good yields.Part II:We continued previous research work,first we used nickel catalysts to obtain structurally functional selenide-substituted imidazopyridine derivatives through multi-component reactions.In experimental part of aryl selenide,we use imidazopyridine and arylboronic acid as reactants,selenium powder,which is economically available was used as selenium source,nickel bromide as a catalyst,and2,2'-bipyridyl as a ligand,tripotassium phosphate is used as base,DMSO is used as reaction solvent.Aryl selenide-substituted imidazopyridine derivatives are obtained after 20 hrs by reacting at 135~oC.In alkyl selenide experimental part,we used imidazopyridine molecules and alkyl reagents as reactants,selenium powder that are stable and tasteless as selenium source,nickel bromide as a catalyst,2,2'-bipyridyl as a ligand,sodium carbonate as a base and DMF as a reaction solvent.The reaction is carried out at 135~oC for 20 hrs,alkyl selenide-substituted imidazopyridine derivatives can be obtained in good yields.In this thesis,we developed two methods for efficient synthesis of C-S and C-Se bonds on imidazopyridine derivatives by transition metal catalysts.These two types of catalysts have the advantages of wide substrate applicability,economic availability of raw materials and high atomic utilization.