The Study On Selective Synthesis Of Nitrobiphenyl

The regioselectivityfor the synthesis of nitrobiphenyls and dibromonitrobipheny-ls was present in this paper. In the presence of zeolite and iron exchanged zeolites,4,4′-dibromobiphenyl could be region-selectively nitrated by action of nitrogen dioxideand nitric acid in organic solvent. Superior selectivity for production of4,4’-dibromo-2-nitrobiphenyl was achieved in the yieid of90%with nitric acid ornitrogen dioxide as nitrating agent over FeZSM-5catalyst. The ratio of4,4′-dibromo-2-nitrobiphenyl to4,4′-dibromo-3-nitrobiphenyl could reach14.polyphosphoric acid facilitated reaction of dinitration of4,4′-dibromobiphenyl.HZSM-5could enhance the yield of2-nitrobiphenyl in the nitration process using95%nitric acid as nitrating agent. CdZSM-5promoted dinitration of biphenyl using molarratio of nitrogen dioxide to4,4′-dibromobiphenyl of4:1and gave a high yield of2,4′-dinitrobiphenyl. BEA-25appeared to play a positive role in selective synthesis of4-nitrobiphenyl, whereas LaZSM-5could improve the yield of2-nitrobiphenyl.The conversion and yield would be improved when the substrates were nitratedwith nitrogen dioxide and molecular oxygen. The ratio of4,4′-dibromo-2-nitrobiphen-yl to4,4′-dibromo-3-nitrobiphenyl could reach14in a high yield of90%when reactionwas carried out in dichloromethane with1.0mmol4,4’-dibromobiphenyl,6mmolnitrogen dioxide and0.2g FeZSM-5under molecular oxygen atmosphere at5℃. Thezeolite could be easily regenerated by heating and reused four times to give the resultssimilar to those obtained with fresh catalyst.As an extension, a similar nitration of other aromatic compounds wereinvestigated. The catalyst FeZSM-5was ineffective towards o-xylene and thecorresponding nitro products were obtained in poor yield. However, m-xylene andnapthalene underwent regioselective nitration under the same conditions.