Visible-Light-Catalyzed Amidation Reaction Based On Aminopyridinium Salts

Amide derivatives are widely utilized in natural products,agriculture,pharmaceuticals and functional chemicals,and the exploration of their synthetic methods has always been a key area of concern.On the other hand,visible-light-catalysis,as a green and environmentally friendly synthesis method,has made great strides in the field of organic chemistry.Therefore,this thesis mainly explored the reaction of N-benzamidopyridine salt to generate amide radicals under visible light irradiation.The first part focuses on the photoinduced direct C-H amidation of aromatic hydrocarbons,heteroaromatic hydrocarbons with N-benzamidopyridine salt.Firstly,the model reaction of N-benzamidopyridinium salt with mesitylene in the presence of Ru（bpy）₃Cl₂ was preliminarily explored.We screened the the types of photocatalyst,reaction times,and the equivalent ratios of the reaction substrate and the optimal conditions were obtained:Ru（bpy）₃Cl₂ was used as the photocatalyst,the equivalent ratio of pyridinium salt to mesitylene was 1:10,acetonitrile acted as the solvent,maintained under argon atmosphere for 24 h at room temperature.The ap-plicability of the reaction was then investigated,and the results displayed that most of the electron-rich aromatics,fused ring compounds,and heteroaromatics exhibited excellent reac-tivity.This protocol possessed simple operation,concise synthesis and stability of the substrate,thus opening a new avenue for the synthesis of benzamide derivatives with free NH.The second part mainly studies the[3+2]cyclization of N-benzamidopyridinium salt,styrene and acetonitrile to offer imidazolines,which are biologically active molecules,organic synthesis intermediates and organic catalysts.Under the excitation of blue light,the expected benzamide-substituted imidazoline products were successfully received with Ru（bpy）₃（PF₆）₂ as the photocatalyst.By optimizing the reaction of synthesizing imidazoline,the optimal condi-tions are determined as:the photosensitizer was Ru（bpy）₃（PF₆）₂,1:1 equivalent ratio,stirred at room temperature for 24 h under argon atmosphere.In addition,the reaction conditions were mild and no additional Lewis acids were required,which was a promising scheme for the synthesis of imidazolines.