Sulfanilic acid → 4-((3,5-Difluoro-4-hydroxyphenyl)diazenyl)benzenesulfonic acid

Beteiligte Stoffe

Reaktionsschritte

Sulfanilic acid (0.767 g, 4.43 mmol) was dissolved in hot mixture of 20 mL of water and 10 mL of conc. HCl. The solution was cooled in ice/NaCl bath to 0° C. giving a suspension of HCl salt. The solution of sodium nitrite (0.367 g, 5.32 mmol in 5 mL of water) was added dropwise to the suspension of ammonium salt, maintaining the temperature below +5° C. All solid dissolved and the resulting solution was stirred for 20 min. After that white precipitate formed again and the resulting suspension was added dropwise to the mixture of 2,6-difluorophenol (0.576 g, 4.43 mmol) in 10 mL of dioxane and KOH (10 g) in 15 mL of water, cooled in ice/water bath. The reaction mixture was stirred for 30 min in ice/water bath and then extracted with ethyl acetate (3×30 mL). The aqueous solution was acidified with 10% HCl to pH 2-3 and the formed yellow precipitate was collected, washed with water and dried in vacuum to give phenol 2 as a yellow powder (1.1 g, 79%).

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