Studies On The Free Radical Reactions Of Organic Azides And Halogenated Aromatic Compounds

Free radical reactions have found important applications in modern organic synthesis.This thesis deals with the studies on the free radical reactions of organic azides and halogenated aromatic compounds.It includes the following two aspects.In the first aspect,the free radical reactions of organic azides and halogenated aromatic compounds,particularly the new progress made in recent years,are briefly reviewed in the first chapter.The main contents are:(1)the free radical method for the preparation of organic azides,(2)the free radical reactions of organic azides,and(3)the free radical reactions of photo-induced halogenated aromatic compounds.The second aspect introduces my research work during PhD's study,which includes the following three chapters:The second chapter describes a new finding that visible light irradiation of N-bromosuccinimide serves as an effective means to convert 3-aryl allylazides to the corresponding iminyl radicals via ?-hydrogen abstraction and subsequent extrusion of dinitrogen.Thus formed iminyl radicals then undergo intramolecular ortho attack on the aryl ring,affording 3-electron withdrawing group-substituted quinolines.This reaction provides a new protocol for the synthesis of quinoline-3-carboxylic acid derivatives.In the work of the third chapter,the aforementioned NBS-based protocol was extended to the the free radical reaction of the organic azides containing azido group at the alpha position of nitrogen atom.It was found that 2-azido-l-benzoylpyrrolidines could be transformed to the corresponding iminyl radicals by the treatment of visible light irradiation in the presence of NBS.Further cyclization of the iminyl radicals delievered 2,3-dihydropyrrolo[2,1-b]quinazolin-9(1 H)-one derivatives.The fourth chapter describes a photo-induced chloride atom transfer cyclization reaction of 5-acetyl-2-chloropyrroles bearing an acetylenyl side chain.Under the UV light irradiation in dichloromethane,5-acetyl-2-chloropyrroles underwent tandem free radical cylization/halogen atom transfer reaction,giving both the endo-and exo-cyclization products in good yield.The formation of endo-cyclization products was favored in all the cases.When the reactions were performed in the solvent of acetone-5%aqueous Na2CO3,some of the endo-type products were further converted to cyclic ketone derivatives.This investigation helps to further extend the photo-induced atom transfer cyclization reaction of halogenated aromatic compounds in organic synthesis.