The Construction Of C-N Bonds Through Nitrogen-centered Radicals Or Aryl Radical Cationic Intermediates Generated From Electrochemical Oxidation

Organic electrosynthesis is a"green synthetic tool".By using electrons as a"clean rea-gent"to replace traditional redox agents,the reactants undergo redox reaction by gaining or losing electrons at the interface between electrode and solution.This process can avoid the use of exogenous chemical oxidants or reductants,reducing the consumption of chemicals and environmental pollution.Due to the mild,green and sustainable conditions,organic elec-trosynthesis has attracted more and more attention from synthetic chemists in recent years.The reaction of constructing C-N bonds is widely used in the synthesis of nitro-gen-containing drug molecules,bioactive molecules and functional materials.Therefore,or-ganic chemists have been committed to finding simple,efficient,green and environmentally friendly synthetic methods to construct C-N bonds in recent decades.Organic electrosynthesis,as a novel green synthetic method,provides an ideal strategy for the construction of C-N bonds.The thesis reviewed the progress on the C-N bonds formation under electrochemical conditions over the last decade.Subsequently,the studies on the construction of C-N bonds by electrochemical strategy to generate active intermediates such as nitrogen radical,aryl radical cation,etc.,were carried out,achieving the synthesis of indoloquinolines,N-（2-alkoxyethyl）sulfoximines,and spirooxazolidinones.The detailed studies are listed be-low:Chapter two described the synthesis of indoloquinolines by using indoles containingα-imino-oxy acid moiety as reaction substrates.This approach used n Bu₄NBr as the redox medium and exploited the strategy of indirect anodic oxidative decarboxylation to produce the iminyl radical,and then intramolecular cyclization to construct the C-N bond.Notable fea-tures of this strategy are mild reaction conditions,no need for external chemical oxidants and metal catalysts,broad substrate scope.The gram-scale experiment could be successfully com-pleted.In addition,this method can also be applied to the construction of other nitro-gen-containing heterocycles,such as benzofuroquinolines,pyrroloquinolines,phenanthridines and other valuable nitrogen-containing heterocyclic compounds.Chapter three described the synthesis of N-（2-alkoxyethyl）sulfoximines via the sul-foximido-alkoxygenation of alkenes under electrochemical conditions.This method used al-kenes,NH-sulfoximines and alcohols as reaction substrates,and the N-centered sulfoximidoyl radicals were generated through electrochemical oxidation of NH-sulfoximines with the cleavage of N-H,followed by a tandem reaction between the three components to give a se-ries of N-（2-alkoxyethyl）sulfoximines.Notable features of this strategy are simple operation,no additional pre-activation step,high atom economy,good regioselectivity and easy to scale-up.Chapter four described the synthesis of spirooxazolidinones by exploiting the electro-chemical oxidation strategy to activate phenol derivatives to generate aryl radical cations,followed by intramolecular dearomatizative amination reactions.Notable features of this strategy are mild reaction conditions,wide substrate scopes and diverse functional group compatibility.Moreover,the yield was up to quantitative,and hydrogen gas was the only by-product,which is environmentally friendly.This electrochemical method was successfully scaled up to the gram-scale,and was applied to the derivatization of valdecoxib and poma-lidomide and the synthesis of a compound with antineoplastic activity.In addition,by tunning the reaction conditions,the alcohols can be afforded from phenol derivatives,which is a good strategy for the deprotection of para-methoxyphenyl（PMP）group to recover the alcohol function.The research work in chapter five is a further development of our group’s previous work on electrochemical synthesis of vinyl thioethers.This chapter described the synthesis of oxa-zolyl vinyl thioethers by the reaction of acetonitrile with oxazolyl thiols.This electrochemical process used tetramethylammonium bromide as the redox catalyst,and the Csp³-H bonds of acetonitrile and the S-H bond of oxazolyl thiols were activated via indirect anodic oxidation.A tandem reaction between one molecule of oxazolyl thiol and two molecules of acetonitrile was achieved to obtain a series of vinyl thioethers containing 1,3-oxazole or 1,3,4-oxadiazole moiety.