4-amino-3,5-difluorophenol

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 4-amino-3,5-difluorophenol (580 mg), imidazole (354 mg), triisopropylsilane chloride (848 mg) and DMF (12 mL) was stirred at room temperature overnight. The solvent was evaporated under reduced pressure, water was added to the residue, and the mixture was extracted with ethyl acetate. The separated aqueous layer was extracted again with ethyl acetate. The combined organic layer was washed with saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate) to give the title compound as a pale-brown oil (1.0 g). The solvent was evaporated under reduced pressure, water was added to the residue the mixture was extracted with ethyl acetate The separated aqueous layer was extracted again with ethyl acetate The combined organic layer was washed with saturated brine dried over anhydrous magnesium sulfate the solvent was evaporated under reduced pressure The residue was purified by silica gel column chromatography (hexane/ethyl acetate)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 20.4 g (0.09 mol) of 3,5-difluoro-4-(phenyldiazenyl)phenol from Example 1 and 0.5 g of Pd/C (10%) were initially charged in 120 ml of methanol. The solution was degassed and aerated with hydrogen. The mixture was stirred at room temperature under a 1 bar hydrogen atmosphere for 16 hours. On completion of hydrogen uptake, the catalyst was filtered off and the filtrate concentrated on a rotary evaporator. The residue was chromatographed on silica gel (n-hexane/ethyl acetate, 3:1). The resulting solid was stirred with n-hexane and dried. 7.6 g (60%) of 4-amino-3,5-difluorophenol were obtained as a yellow-brown solid. The solution was degassed On completion of hydrogen uptake, the catalyst was filtered off the filtrate concentrated on a rotary evaporator The residue was chromatographed on silica gel (n-hexane/ethyl acetate, 3:1) The resulting solid was stirred with n-hexane dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: This compound was prepared from 1,2,3-trifluoro-4-nitrobenzene (5.0 g, 28 mmol) in the manner described for 4-amino-3,5-difluorophenol, affording 0.60 g (84%) of 4-amino-2,3-difluorophenol. 1H-NMR (DMSO-d6) δ 9.19 (s, 1H), 6.59 to 6.53 (m, 1H), 6.48 to 6.41 (m, 1H), 4.85 (s, 2H); TLC (12% DCM/Hex), Rf=0.08.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: This compound was prepared from 1,2,3-trifluoro-4-nitrobenzene (5.0 g, 28 mmol) in the manner described for 4-amino-3,5-difluorophenol, affording 0.60 g (84%) of 4-amino-2,3-difluorophenol. 1H-NMR (DMSO-d6) δ 9.19 (s, 1H), 6.59 to 6.53 (m, 1H), 6.48 to 6.41 (m, 1H), 4.85 (s, 2H); TLC (12% DCM/Hex), Rf=0.08.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: This compound was prepared from 1,2,4-trifluoro-5-nitrobenzene (5.0 g, 28 mmol) in the manner described for 4-amino-3,5-difluorophenol, affording 3.0 g (72.3%) of 4-amino-2,5-difluorophenol. 1H-NMR (DMSO-d6) δ 9.04 (s, 1H), 6.67 to 6.46 (m, 2H), 4.64 (s, 2H); MS GC-MS M+=146.1, RT=1.04 min.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 4-amino-3,5-difluorophenol (580 mg), imidazole (354 mg), triisopropylsilane chloride (848 mg) and DMF (12 mL) was stirred at room temperature overnight. The solvent was evaporated under reduced pressure, water was added to the residue, and the mixture was extracted with ethyl acetate. The separated aqueous layer was extracted again with ethyl acetate. The combined organic layer was washed with saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate) to give the title compound as a pale-brown oil (1.0 g). The solvent was evaporated under reduced pressure, water was added to the residue the mixture was extracted with ethyl acetate The separated aqueous layer was extracted again with ethyl acetate The combined organic layer was washed with saturated brine dried over anhydrous magnesium sulfate the solvent was evaporated under reduced pressure The residue was purified by silica gel column chromatography (hexane/ethyl acetate)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 20.4 g (0.09 mol) of 3,5-difluoro-4-(phenyldiazenyl)phenol from Example 1 and 0.5 g of Pd/C (10%) were initially charged in 120 ml of methanol. The solution was degassed and aerated with hydrogen. The mixture was stirred at room temperature under a 1 bar hydrogen atmosphere for 16 hours. On completion of hydrogen uptake, the catalyst was filtered off and the filtrate concentrated on a rotary evaporator. The residue was chromatographed on silica gel (n-hexane/ethyl acetate, 3:1). The resulting solid was stirred with n-hexane and dried. 7.6 g (60%) of 4-amino-3,5-difluorophenol were obtained as a yellow-brown solid. The solution was degassed On completion of hydrogen uptake, the catalyst was filtered off the filtrate concentrated on a rotary evaporator The residue was chromatographed on silica gel (n-hexane/ethyl acetate, 3:1) The resulting solid was stirred with n-hexane dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: This compound was prepared from 1,2,3-trifluoro-4-nitrobenzene (5.0 g, 28 mmol) in the manner described for 4-amino-3,5-difluorophenol, affording 0.60 g (84%) of 4-amino-2,3-difluorophenol. 1H-NMR (DMSO-d6) δ 9.19 (s, 1H), 6.59 to 6.53 (m, 1H), 6.48 to 6.41 (m, 1H), 4.85 (s, 2H); TLC (12% DCM/Hex), Rf=0.08.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: This compound was prepared from 1,2,4-trifluoro-5-nitrobenzene (5.0 g, 28 mmol) in the manner described for 4-amino-3,5-difluorophenol, affording 3.0 g (72.3%) of 4-amino-2,5-difluorophenol. 1H-NMR (DMSO-d6) δ 9.04 (s, 1H), 6.67 to 6.46 (m, 2H), 4.64 (s, 2H); MS GC-MS M+=146.1, RT=1.04 min.