Study On Visible-Light-Mediated Amination Of Heterocyclic Compounds With N-Aminopyridinium Salts

Visible light,as a sustainable,green and environment-friendly energy,has broad development prospects.Visible-light-induced reactions mainly realized by photoinduced electron transfer(PET),hydrogen atom transfer(HAT)and energy transfer(En T)have become a hot subject in recent years.This dissertation focuses on the PET process,including the single electron transfer(SET)process initiated by photoredox or EDA(Electron-Donor-Acceptor)complex paths under visible-light irradiation.N-Aminopyridinium salts,precursor of nitrogen radicals,could generate corresponding nitrogen radicals via single electron transfer,which is applied to the amination of various compounds.The purpose of this study is to employ N-aminopyridinium salt to realize the selective amination of imidazo [1,2-a] pyridines and indoles under visible-light irradiation.In the first part,we accomplished visible-light selective amination of imidazo [1,2-a]pyridine compounds in aqueous phase by merging the micellar effect of surfactants and the photoredox of photocatalysts.In the research process,we screened the best reaction conditions and expanded a total of 33 related substrates.Finally,the reaction mechanism was put forward according to the results of radical capture experiments and control experiments.In the second part,we employed electron-donor indole compounds and electron-acceptor N-aminopyridinium salts to form colored EDA complex,and intermolecular single electron transfer occurred under visible-light irradiation,so as to realize the amination of indole compounds at positions C2 and C3.In this research work,we carried out a series of experiments including cyclic voltammetry,UV-vis spectrophotometry,Job’s plot,fluorescence quenching and nuclear magnetic titration to prove the existence of EDA complex.In addition,the optimal reaction condition was selected,and 33 related substrates and gram-scale experiments were compatible with this strategy.Finally,the mechanism was given according to the radical capture experiment and light on-off experiment.