Study On Visible-Light-Mediated C-H Bond Activation For Functionalization Of Azaheterocycles

Azaheterocyclic compounds,such as pyridine,quinoline,pyrazole,and their derivatives,are widely found in nature,drugs,and organic functional materials.The exploration of the functionalization of nitrogen heterocyclic compounds holds immense importance in the advancement of synthetic chemistry,materials science,and medicinal chemistry.In recent years,visible light,as an environmentally friendly,gentle,and easily accessible renewable energy source,has made significant progress in the study of photochemical reactions.The investigation of photochemical reactions catalyzed by visible light has witnessed remarkable advancements,particularly in the realm of visible light-induced C-H bond activation.This technique offers innovative paths,concepts,and methodologies for the functionalization of nitrogen heterocyclic compounds.Against this background,we are committed to exploring the use of visible light to promote C-H bond activation under gentle conditions,thereby directly synthesizing heterocyclic compounds with specific functional groups.Through in-depth research and continuous experiments,we have achieved this goal and obtained certain results.The specific research content and results are as follows:1.Visible-light-promoted selective silylation of azaheterocyclic compounds.The reaction is based on the use of cheap and readily available fluorine reagent(Selectfluor)as an additive and tert-butyldimethylsilane as a silicon source,and the silylation of C2 sites of nitrogen heterocyclic compounds has been achieved under room-temperature illumination.This reaction process,which abandons the use of transition metals,exhibits many significant advantages,such as mild reaction conditions,easy operation steps,high yields,and a wide range of substrates.It provides an efficient and practical route for the silylation of aziridines.2.Site-selective C-H fluorination of heteroarenes under visible light.Siteselective C-H fluorination of heteroaromatics is a great challenge.We develope a novel strategy for visible-light-promoted C-H fluorination of heteroaromatic hydrocarbons via the combination of Selectfluor and silanes.The method features metal-free,photocatalyst-free and high positional selectivity under mild reaction conditions(ambient temperature,visible light irradiation,water resistance).This strategy enables the first visible-light-induced selective fluorination of the C2 position of azaheterocycles.Quinoline,isoquinoline and pyridine analogues were obtained as corresponding fluorinated products.3.Visible light promoted C-H bond methylation reaction of azacyclic compounds.The reaction is carried out under visible light irradiation at room temperature,and the most common simple alcohol methanol is used as the methyl source to react with the azacyclic ring to obtain the azacyclic methylation product.The method is also applicable to other simple alkane alcohols,such as ethanol,propanol,butanol,etc.,demonstrating good reaction compatibility.The reaction is simple and mild with wide functional group tolerance.4.N-Allylation of azoles with hydrogen evolution enabled by visible-light Photocatalysis.The direct N-allylation and hydrogenolysis of azoles was achieved by the co-catalysis of an organic photocatalyst and cobalt.The scheme eliminates the need for additional oxidants and pre-functionalisation of olefins and produces only hydrogen as a by-product.This transformation highlights atom economy,step efficiency,and functional group tolerance for further derivatisation,which opens new pathways for C-N bond formation in heterocyclic chemistry.