Sulfuric Acid → 3-Amino-2,4-difluorophenol

Participants

Reaction Steps

To a solution of 2,6-difluoro-3-triisopropylsilyloxy-benzoic acid (18.4 g, 0.056 mol, 1.0 eq) in DCM (180 mL) and DMF (3 drops) at 0° C. was added (COCl)2 (21.19 g, 0.167 mmol, 3.0 eq) dropwise. The mixture was warmed to room temperature and stirred for 1 h. The reaction mixture was evaporated in vacuo and the residue obtained dissolved in acetone (100 mL). The resultant solution was added dropwise to a cooled solution of NaN3 (14.5 g, 0.223 mol, 4.0 eq) in acetone (160 mL) and water (100 mL) at 0° C. The reaction was stirred for 1 h at 0° C. Further water was then added (200 mL) and the reaction heated at 70° C. overnight. The acetone was removed under reduced pressure and the aqueous layer extracted with EtOAc. The combined organic extracts were washed with water and brine, dried (Na2SO4), filtered and evaporated in vacuo. The residue obtained dissolved in EtOH (94 mL) and water (30 mL). Concentrated H2SO4 (30 mL) was added and the reaction heated at 110° C. overnight. The ethanol was removed under reduced pressure and the aqueous layer extracted with EtOAc. The combined organic extracts were dried (Na2SO4), filtered and evaporated in vacuo. The residue was purified by column chromatography (petroleum ether: EtOAc, 20:1 to 6:1) to give the title compound as a white solid (4.0 g, 50%).

Provenance & Evidence