Visible Light-promoted Synthesis Of Aromatic Azo Compounds

Aromatic azo compounds are widely used in organic synthesis,medicine,dyes,food additives and other fields.Traditional methods for synthesizing aromatic azo compounds have some drawbacks such as requiring stoichiometric and toxic oxidants,harsh reaction conditions and environmentally related problems,which is inconsistent with the requirements green chemistry and sustainable development.Therefore,the development of green and efficient methods for the synthesis of aromatic azo compounds has attracted much attention.In this dissertation,the visible light-promoted synthesis of aromatic azo compounds via oxidation reaction of aryl amines is described.This new oxidation reaction will be performed to provide a mild pathway for the synthesis of aromatic azo compounds.The oxidation coupling reaction of 4-methylaniline was selected as model reaction to optimize the reaction conditions such as photosensitizer,catalyst,solvent,and reaction time.The optimal reaction conditions were as follows:tris（2,2’-bipyridine）ruthenium dichloride[（bpy）₃Ru]Cl₂ as photosensitizer（1 mol%）,CuI（15 mol%）as catalyst,pyridine（0.6 mmol）as additive,acetonitrile as solvent,room temperature 36 W in air Blue LED light for 12 h.Under the optimal reaction conditions,4,4’-dimethylazobenzene was formed in 92%yield.It was found substituted aryl amines with methyl and methoxyl groups on the phenyl ring provided the corresponding products in high yields,and the steric hindrance effect on the substituted phenyl ring had an effect on the reaction yield.On the other hand,the aromatic ring of aryl amines contains halogen was also suitable for present method.The obtained aromatic azo compounds were characterized by ¹H-NMR and ¹³C-NMR.