Synthesis Of Nitrogen-containing Heterocyclic Derivatives From Aromatic Amine Compounds Based On Free Radical Chemistry

Because of their unique structures and properties,nitrogen-containing heterocycles are widely used in various fields,so the efficient construction of C-N bond is particularly important.In recent years,many researchers have used the nucleophilicity of amino groups in substrates containing amino group to construct C-N bonds,providing an important method for synthesis of nitrogen-containing heterocycles.This paper introduces synthesis of a variety of nitrogen-containing heterocycles via free radical reaction of various substrates containing amino group.On this basis,we chose two kinds of aromatic amines as substrates to explore more convenient and efficient methods for obtaining free radicals,through the radical tandem and the intramolecular nucleophilic cyclization to form nitrogen-containing heterocycles.The main contents of this paper include the following two parts:1.Construction of fluorinated pyrrolo[1,2-d]benzodiazepine derivatives via free radical reaction of 2-?1H-pyrrol-1-yl?anilinesA new photoredox-catalyzed cascade reaction is described to access fluorinated pyrrolo[1,2-d]benzodiazepine derivatives under mild conditions.In this process,single electron transfer?SET?between the excited state photocatalyst fac-Ir?ppy?₃ and ethyl bromodifluoroacetate initiated the regioselective radical addition to a wide range of 2-?1H-pyrrol-1-yl?anilines or indol-substituted anilines,followed by another SET process and intramolecular amidation.2.Construction of quinoline-fused imidazopyridines via free radical reaction of 2-?imidazo[1,2-a]pyridin-2-yl?anilinesA NH₄I-catalyzed cross-dehydrogenative coupling reaction of ethers with 2-?imidazo[1,2-a]pyridin-2-yl?anilines cascade cyclization under transition-metal-free conditions has been developed.Cheap,commercially available ethers were used as both reagents and solvents,and green aqueous H₂O₂ was used as an oxidizing agent.A series of substituents on 2-?2-aminoaryl?imidazo[1,2-a]pyridines were tolerated,and the reaction gave quinoline-fused imidazopyridines in moderate to good yields.