Photoinduced Zinc-Catalyzed Synthesis Of 2-Quinolinone Derivatives

The quinolinone structural motifs are frequently found in the frameworks of various natural products and pharmacologically active compounds.In addition,quinolinone derivatives have been applied in the fields of antibacterial,anti-malarial,insecticidal,anti-tumor,anti-diuretic,anti-arrhythmia and sedation.Photocatalytic organic synthesis has the advantages of mild reaction conditions,renewable energy and high reaction efficiency.Therefore,the development of convenient,economical and environment-friendly method for synthesis of quinolinones has attracted widespread attention.In this paper,zinc-catalyzed reaction of quinoline-N-oxide derivatives under irradiation conditions for the synthesis of2-quinolinone derivatives is describedThe reaction with quinoline-N-oxide was chosen as a model to optimize the reaction conditions.The effects of different wavelengths of light,transition metal catalysts,solvents,and reaction time were investigated.The optimal reaction conditions were as follows:zinc chloride（ZnCl₂）as catalyst（5 mol%,）,full-spectrum illumination,acetonitrile（CH₃CN）as solvent,and reaction in air for 3 h.Under optimized conditions,quinoline-N-oxide can be successfully converted to 2-quinolinone in 90%yields.It was found that various functional group-substituted quinoline-N-oxides are suitable for the present method to produce the corresponding 2-quinolinones in satisfactory to good yields.The reaction with iso quinoline-N-oxide also proceed smoothly to produce isoquinolinone in good yield.However,the reaction of quinoline-N-oxide bearing a nitro-group at 8-position resulted in no reaction.Furthermore,the yields of the substrates containing the electron-donating groups are higher than that bearing electron-withdrawing groups on quinoline-N-oxide.Finally,proton nuclear magnetic resonance^（1）H-NMRand carbon nuclear magnetic resonance(¹³C-NMR)spectra are used to characterize the resulting 2-quinolinone compounds.