Electrochemical Synthesis Of Indolines,Oxazolones,Imidazolidones And Photoelectrochemical C-H Amination Of Arenes And C-H Alkylation Of Heteroarenes

Nitrogen-containing compounds are very important class of organic compounds and are widely existed in natural products,agrochemicals and pharmaceuticals.Because of their good physiological activity and medicinal value,new methods,new reactions and new strategies for the synthesis of nitrogen-containing compounds have been the research focus of organic chemistry.However,the methods reported in the literature often require noble metal reagents or oxidants,which reduce the sustainability of the methods by producing byproducts,wastes and bringing safety issues.Therefore,it is a very indispensable and challenging task to develop a sustainable and efficient method for constructing nitrogen-containing compounds without relying on noble metal catalysts or oxidants.Organic electrosynthesis as a green synthesis technology can efficiently generate many active intermediates such as radicals,positive ions,and negative ions.It not only provides the basis for the construction of C-N bonds,but also furnishs a powerful tool for the C-H functionalization of heteroarenes.This dissertation is divided into the following sections mainly:In the first part,we have reported an electrochemical method for the synthesis of functionalized(aza)indolines through dehydrogenative[3+2]annulation of arylamines with tethered alkenes.This transformation employs the easily available and inexpensive ferrocene as a mild and selective redox catalyst and is compatible with di-,tri-and even tetrasubstituted alkenes to construct indolines as well as the more challenging azaindolines without overoxidation,which obviates the need for noble-metal catalysts and oxidants.In addition,employing the newly developed electrochemical synthesis of indolines as a key step,the total synthesis of marine alkaloid(±)-hinckdentine A has been achieved successfully.#12In the second part,an electrochemical approach to the 5-exo-dig cyclization of amidyl radicals with tethered internal alkynes has been developed.The cyclized radical intermediate can be trapped by 2,2,6,6-tetramethylpiperidine-N-oxyl radical(TEMPO),affording isomerized oxazol-2-ones and imidazol-2-ones with excellent product selectivity.The electrosynthesis relies on the dual role of TEMPO as both a redox mediator and a radical trap,avoids the use for transition-metal reagents,and demonstrates broad substrate scope and compatibility.#12In the thrid part,we have described a green photoelectrochemical method for the C-H amination of arenes.The arenes scope of the reaction comprises electron-rich,electron-deficient and heterocyclic aromatic compounds.The photoelectrosynthesis has a broad substrate scope without the use of external oxidants.(?)In the fourth part,a photoelectrochemical strategy for the C-H alkylation of heteroarenes with organotrifluoroborates has been developed.The merger of electrocatalysis and photoredox catalysis provides a chemical oxidant-free approach for the generation and functionalization of alkyl radicals from organotrifluoroborates.A variety of heteroarenes are functionalized using primary,secondary,and tertiary alkyltrifluoroborates with excellent regio-and chemoselectivity.Under the photoelectrochemical conditions,alkyl radicals are efficiently participate readily in intermolecular oxidative transformations without passivation electrode,polymerization and overoxidation.