Study On A New Reagent System For Bromination Using LDHs As The Precursor

A new reagent system for bromination was built on the carrier of Zn/Al-BrO3--LDHs cooperating with appropriate reductant, such as bromide ion. The Zn/Al-BrO3--LDHs was synthesised by different methods and its structure was characterized by X-ray diffraction, TG analysis and Fourier transform infrared spectrometer. To achieve a well controlled release of bromine in practical application, the release behavior of BrO3-was also investigated. Furthermore, the impacts put by synthesis methods, temperature, the type of ion exchangers and pH value were studied. The results indicated that the LDHs synthesized by co-precipitation showed a better controlled release performance than the one synthesized by anion exchange method, the release rate became more rapidly as the temperature rises or the anionic exchanging capacity enhanced, the Br O3- released more quickly in a pH=9.0 phosphate buffer solution than in a p H=4.0 phosphate buffer solution. To get a better understanding of the release property of BrO3-, the release profiles were fitted by four theoretical models, Peppas Equation, Higuchi Equation, First order Equation and Bhaskar Equation. The fitting results indicated that the release behavior showed a better match with the Bhaskar equation.This bromination reagent system has been applied successfully for synthesizing 3,5-dibromine-2-amino methyl benzoate in a green path. Futhermore, the effects of reaction parameters such as n(BrO3-):n(Methyl anthranilate), reaction solvents, reaction temperature and reaction time were investigated. The results showed that this new bromination reagent takes the advantages of mild reaction conditions, less corrosion and more enviromental. In the condition of n(BrO3-):(Methyl anthranilate)=2.5: 3, CH2Cl2: H2O(10 ml: 5 ml), 30°C react 6 h, the yield of 3,5-dibromine-2-amino methyl benzoate reached to 91.43%. We further applied this bromination reagent to more aromatic substrates under the optimal conditions. The results showed that this reaction is a mild, environmental friendly and new method in the bromination of arylamines.