Aerobic C(sp~3)-H Oxidation And Oxygenation Of Quaternized Quinolines And Pyridines By Visible-Light-Induced Photocatalysis

Visible light,as a sustainable,clean energy in line with modern green chemistry concepts,has greatly solved the increasingly serious energy problem.In recent years,visible light-induced photoredox catalysis featured the advantages of mild conditions,simple operation,and high efficiency,which has attracted great attention of scientists and has been widely used in organic synthesis.This thesis introduces the latest research progress on visible light catalysis in the field of aerobic organic synthesis,and then includes a series of original researches on the visible light-induced aerobic C?sp³?-H oxygenations of quaternized N-heterocycles.Nitrogen-containing heterocycles are structurally privileged frameworks to constitute a large number of biologically active molecules and thus have wide applications in medicines,dyes,pesticides,and materials science.While quaternized N-heterocycles were mainly accessed by direct quaternization of functionalized heterocycles,the chemical site-selective modification of them has been rarely studied.The possible reason is that the quaternized N-heterocycle is unstable to heat and alkali.Amphoteric substances affect the activity of the catalyst.The weak solubility of amphoteric substances brings a series of problems such as difficulty in separation.Therefore,we report herein the site-selective oxidation of alkylpyridinium under mild aerobic photocatalysis under visible light.A visible light-catalyzed carboxylation reaction of C?sp³?-H bond with oxygen has been reported.In this reaction,Ru?bpy?₃Cl₂·6H₂O was used as a photocatalyst,and a series of carboxylation products from quaternized quinolines and pyridines were obtained in moderate to high yields under an oxygen atmosphere.The control experiments,isotope experiments,and fluorescence quenching experiments were conducted to verify the possible reaction mechanism.The reaction has the characteristics of mild conditions,environmentally benign oxidant,and high atomic economy,and provides a new idea for the aerobic C-H modification of quaternized N-heterocycles.This article also developed a catalyst-free,oxidative hydroxylation strategy of C?sp³?-H bonds with oxygen participation under light conditions.Under room temperature conditions,a variety of alcohol compounds with widely compatible functional groups of quaternized quinolines and pyridines by aerobic oxidation were obtained by visible light irradiation in modest to excellent yields.Through UV-visible absorption experiments and intermediate-trapping experiments,it was verified that the reaction was driven by the photochemical activity of the electron donor-acceptor?EDA?complex.The reaction has the characteristics of mild conditions,environmentally friendly oxidant,and high efficiency.