用硫酸或甲酸作溶剂,用氮气稀释的F2能直接对苯环发生亲电取代,生成氟代苯,不过由于用到F2,其操作不方便。
前面列出的大多数试剂,都能对活化的芳环发生亲电取代,得到相应的氟化合物。如下所示,但反应的选择性不是很好,产物主要是邻对位取代的混合物:
反应实例
To the solutionof phenol (0.94 g,10 mmol) in dry CH2Cl2 (20 mL) was addedN-fluoropyridinium salt (2.54 g,10 mmol), the mixture was stirred under reflux for 24 h. The reaction was monitored by TLC. Then 20 mL of water was added to the reactionmixture, the resulting mixture was extracted with CH2Cl2,the organic phase was dried over Na2SO4, the solvent wasevaporated under reduced pressure, the residue was purified by flash column chromatography on silica gel to give themixture of two ismers (1.05 g, 94%, o:p = 84: 10) as a colorless oil.
【Umemoto, T; Fukami, S. J. Am. Chem Soc. 1990, 112, 8563】