Studies On The Sodium Nitrite-Catalyzed Aerobic Oxybromination And Oxychlorination Of Aromatic Compounds

Simple, mild, efficient and high selective methods for aerobic oxybromination and oxychlorination of aromatic compounds catalyzed by sodium nitrite were developed in the paper.Initial experiment showed that the aromatic compounds were brominated to corresponding bromides with hydrobromic acid or bromine as brominating agent in the presence of sodium nitrite under the mild conditions. The effect of various conditions on the reaction, such as solvent, temperature, the amount of catalyst, the concentration of hydrobromic acid, oxygen/air and so on, was studied. Under optimum condition, aryl ether and arene and phenol were efficient and high selective brominated to corresponding bromides, which the hydrogen atom of aromatic ring was substituted by bromine undergoing the mechanism of electrophilic aromatic substitution in HBr(or Br₂)/NaNO₂/O₂/CH₃CN system. However, in HBr(or Br₂)/NaNO₂/O₂/CH₃CH₂OH system aryl ketones were efficient and high selective brominated to correspondingα-bromine ketones. The yields are from good to excellent. On the base of experiments the plausible mechanism was proposed.The aromatics were chlorinated to corresponding chloride with hydrochloric acid as chlorinating agent and trichloroisocyanuric acid(TCCA) as co-catalyst in the presence of sodium nitrite under mild conditions. The effect of various conditions on the reaction, such as solvent, temperature, the amount of catalysts,the concentration of hydrochloric acid, the amount of hydrochloric acid, oxygen/air and so on, was studied. Under optimum condition, aryl ether and arene were efficient and high selective chlorinated to corresponding chlorides, which the hydrogen atom of aromatic ring was substituted by chlorine undergoing the mechanism of electrophilic aromatic substitution in HCl/TCCA/NaNO₂/O₂/ CH₃COOH system. The yields are from good to excellent. On the base of experiments the plausible mechanism was proposed.