Denitration Halogenation Synthesis Of Aromatic Halides

Haloaromatic compounds have comprehensive purposes as important intermediates in the preparation of Pharmaceuticals, pesticides and dyes. It plays an important role in studying the synthetic methods of haloaromatic compounds. Fine selectivity, few by-reactions and high yield of chlorodenitration reaction can be obtained and because of its strong electron-withdrawing, leaving ofNO2 is easy.This paper concerns with the study of the chlorodenitration and fluorodenitration reactions with comprising -X, -NO2, -CF3 electron-withdrawing nitroaromatic compounds. On the study of chlorodenitration reaction through six kinds of haloaromatic compounds such o-fluoronitrobenzene,p-fluoronitrobenzene, m-dinitrobenzene, 2,4-dinitrochlorobenzene, 3,5-dinitro-4-chlorobenzotrifluoride, 3,5-dinitro-4-fluorobenzotrifluoride as start materials, the effects of temperature, time, amount of activator, flow rate of chlorine, the kind of substituent group and so on were studied particularly. Except for p-fluoronitrobenzene, the yields of other five kinds of compounds were from 75% to 95% around. The conditions of reactions were studied by reaction-rectification method, time was reduced, yields were improved, tube shape reaction equipments were avoided and reaction equipments were simpled. Denitration of p-fluorochlorobenzene was difficult, yield was only 20%. Furthermore, fluorodenitrations of five kinds nitroaromatic compounds such m-dinitrobenzene, m-nitrobenzotrifluoride, 2,4-dinitrochlorobenzene, 3-nitro-4-chlorobenzo-trifluoride and 2-chloro-5-nitrobenzotrifluoride as start materials were studied. During fluorodenitration of m-dinitrobenzene, the effects of catalysts, temperature, time, solvents, PDC and substitutent groups and so on were studied. The effect of phase transfer catalyst tetraphenylphosphonium bromide showed good catalytic activity and selectivity. The equilibrium was moved rightward by adding PDC.