Synthesis
Add 70g of water and 26g of concentrated sulfuric acid to the 250mL reaction flask (pay attention to exothermic, add concentrated sulfuric acid to water slowly, the same below), add 17.5g of 4-fluoro-2-methylaniline at room temperature while stirring, a white solid was produced, raise the temperature to 100~105 , completely dissolved, and reduce the temperature to 0 ; slowly add 44.5g of nitrosyl sulfuric acid dropwise, control the temperature at -5~5 , hold the heat after dropwise The reaction solution was clarified for 2h to obtain the diazo solution. In another 250mL reaction bottle add 66g of water and 19g of concentrated sulfuric acid, warming to 110 , drop into the above prepared diazo liquid, control the drop acceleration, drop and add the side of water vapor distillation, so that the oil droplets continue to evaporate, the temperature is controlled at 110 ~ 115 ; drop and add the completion of the distillation continued for 2 hours, until no oil droplets evaporated; separation of the oil layer, add 11.1g content of 1% aqueous sodium hydroxide solution to wash, and the oil layer, the top temperature of 80 , and then the oil layer, the top temperature is 0 , the top temperature of 80 , the top temperature is 0 . Separate the oil layer, the top temperature of 80 ~ 90 _x000D _
10mmHg distillation, the product 4-fluoro-2-methylphenol 14.8g, GC: 99.5%, yield 83%.
References
[1] Tetrahedron Letters, 2011, vol. 52, # 41, p. 5338 - 5341
