Electro-oxidative Coupling With H₂ Evolution For C-N Construction

In recent years,electrochemically induced C-H direct functionalization initiated by free radicals has been an effective means to construct C-N bonds and nitrogen-containing compounds.As the reaction intermediate,nitrogen radical can react with various?systems to construct C-N bond,which plays an important role in the synthesis of nitrogen-containing compounds.Compared with the nitrogen free radicals generated by N-X(X=Cl,O,S,etc.)bond breaking,the strategy of direct oxidation of N-H bond to generate nitrogen free radicals has higher atomic economy and step economy.After a large number of literature research and discussion,combined with our research interest in the field of oxidative coupling,final research project focused on by electrochemical oxidation coupling,the synthesis of organic nitrogen compounds and through the related mechanism research techniques,has carried on the exploration to the reaction mechanism and the main content of the thesis are as follows:(1)Compared with the reported intramolecular electro-oxidative cyclization of alkenyl amines or vinyl anilines for the preparation of indolines,the intermolecular version is less studied.In this study,we synthesized 2-substituted indolinoids with high regional-selectivity by electrochemical oxidation(3+2)cyclization,using the strategy of anodic oxidation of N-arylsulfonamide N-H bond to produce nitrogen radicals and olefin as free radical acceptor in absence of additional chemical oxidant and the only by-product is hydrogen.In addition,the reaction can be carried out in an electrochemical flow cell without the addition of supporting electrolyte,which shows the potential application value of this method.The cyclic voltammetry experiments suggested that the reaction may be initiated by the oxidation of sulfamide.(2)In this study,the intermolecular oxidation amination reaction between N-alkyl sulfonamide and alkyl alkene under the condition of no metal and no chemical oxidant was realized,and a series of allyl amines were synthesized with high selectivity.It is worth noting that the suitable amine source was selected through the strategy of experimental screening and comparison of p Ka values,which reacted with alkyl alkenes to selectively construct C=C double bond.In addition,internal,terminal,tri-and tetra-substituted alkenes,cycloalkene and aromatic olefins can be converted.The gram-scale experiments show that this method has potential application value.(3)In this study,the intramolecular C(sp~2)-H/N-H coupling of 2-amino-biphenyl compounds was realized by electrochemical oxidation of metal C-H bond activation to synthesize carbazole compounds.This method can be carried out in an electrochemical cell.By adjusting the current density and using appropriate additives,the precipitation of palladium can be slowed down effectively,which provides a simple and efficient strategy for the synthesis of carbazole compounds due to mild reaction conditions and easy preparation of substrate.