2-Amino-5-fluoro-3',4'-dichlorobenzene is an important intermediate of succinate dehydrogenase inhibitor(SDHI)fungicide,bixafen.Based on microchannel technology,3,4-dichloroaniline was used as raw material to obtain 2-amino-5-fluoro-3',4'-dichlorobiphenyl through diazotization,neutralization,and coupling with p-fluoroaniline.The system investigated the effects of the three steps of diazotization,neutralization,and coupling on the reaction,and obtained optimized conditions:hydrochloric acid and 3,4-dichloroaniline equivalent 6︰1,sodium nitrite and 3,4-dichloroaniline equivalent 1.1︰1,salt formation reaction temperature 60℃,diazotization reaction temperature 25℃,sodium hydroxide equivalent 6.5︰1,neutralization temperature 25℃,optimal coupling temperature 120℃,and p-fluoroaniline equivalent 10︰1.Under these optimized conditions,2-amino-5-fluoro-3',4'-dichlorobiphenyl was synthesized with a crude content of 85% .After refinement,the content can reach 98.5%,and the total yield of the two steps is 65% .
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