tert-butyl 3,5-difluorobenzoate

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a stirred solution of diisopropylamine (5 mL, 35.5 mmol, 1.2 eq) in THF (100 mL, anhyd) was slowly added BuLi (1.6M in hexanes, 20 mL, 32.3 mmol, 1.1 eq) at below 0° C. After addition was completed, the solution was cooled to −78° C. and then charged dropwise with a solution of tert-butyl 3,5-difluorobenzoate (6.3 g, 29 mmol) in THF (50 mL, anhyd) over 1 h. The resulting solution was stirred for another 2 h at −78° C. Next anhyd DMF (2.5 mL, 32.3 mmol, 1.1 eq) was added dropwise and, after 30 min, AcOH (4 mL) and water were added successively to quench the reaction. The reaction mixture was warmed to room temperature and diluted with EtOAc (100 mL). The organic layer was washed with brine, dried over MgSO4 and concentrated in vacuo. The residue was purified by flash column chromatography (Hex/EtOAc=4:1) to give tert-butyl 3,5-difluoro-4-formylbenzoate (5.8 g, 83%) as a white solid. at below 0° C After addition to quench the reaction The reaction mixture was warmed to room temperature The organic layer was washed with brine dried over MgSO4 concentrated in vacuo The residue was purified by flash column chromatography (Hex/EtOAc=4:1)

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

Procedure: Concentrated H2SO4 (1.74 mL, 31.6 mmol) was added to a vigorously stirred suspension of MgSO4 (15.2 g, 126.4 mmol, 4 eq) in toluene (100 mL). The mixture was stirred for 15 minutes, after which 3,5-difluorobenzoic acid (5 g, 31.6 mmol) and t-BuOH (14.9 mL, 158 mmol, 5 eq) were added successively. The mixture was stoppered tightly and stirred at room temperature until the reaction was complete by TLC analysis. The reaction mixture was then quenched with saturated NaHCO3 solution and stirred until all MgSO4 had dissolved. The organic layer was washed with brine, dried over MgSO4 and concentrated to afford the crude product. The residue was purified by chromatography (silica, Hex) to give tert-butyl 3,5-difluorobenzoate (5.3 g, 78%) as a colorless oil. stirred at room temperature until the reaction The reaction mixture was then quenched with saturated NaHCO3 solution stirred until all MgSO4 had dissolved The organic layer was washed with brine dried over MgSO4 concentrated to afford the crude product The residue was purified by chromatography (silica, Hex)

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a stirred solution of diisopropylamine (5 mL, 35.5 mmol, 1.2 eq) in THF (100 mL, anhyd) was slowly added BuLi (1.6M in hexanes, 20 mL, 32.3 mmol, 1.1 eq) at below 0° C. After addition was completed, the solution was cooled to −78° C. and then charged dropwise with a solution of tert-butyl 3,5-difluorobenzoate (6.3 g, 29 mmol) in THF (50 mL, anhyd) over 1 h. The resulting solution was stirred for another 2 h at −78° C. Next anhyd DMF (2.5 mL, 32.3 mmol, 1.1 eq) was added dropwise and, after 30 min, AcOH (4 mL) and water were added successively to quench the reaction. The reaction mixture was warmed to room temperature and diluted with EtOAc (100 mL). The organic layer was washed with brine, dried over MgSO4 and concentrated in vacuo. The residue was purified by flash column chromatography (Hex/EtOAc=4:1) to give tert-butyl 3,5-difluoro-4-formylbenzoate (5.8 g, 83%) as a white solid. at below 0° C After addition to quench the reaction The reaction mixture was warmed to room temperature The organic layer was washed with brine dried over MgSO4 concentrated in vacuo The residue was purified by flash column chromatography (Hex/EtOAc=4:1)

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

Procedure: Concentrated H2SO4 (1.74 mL, 31.6 mmol) was added to a vigorously stirred suspension of MgSO4 (15.2 g, 126.4 mmol, 4 eq) in toluene (100 mL). The mixture was stirred for 15 minutes, after which 3,5-difluorobenzoic acid (5 g, 31.6 mmol) and t-BuOH (14.9 mL, 158 mmol, 5 eq) were added successively. The mixture was stoppered tightly and stirred at room temperature until the reaction was complete by TLC analysis. The reaction mixture was then quenched with saturated NaHCO3 solution and stirred until all MgSO4 had dissolved. The organic layer was washed with brine, dried over MgSO4 and concentrated to afford the crude product. The residue was purified by chromatography (silica, Hex) to give tert-butyl 3,5-difluorobenzoate (5.3 g, 78%) as a colorless oil. stirred at room temperature until the reaction The reaction mixture was then quenched with saturated NaHCO3 solution stirred until all MgSO4 had dissolved The organic layer was washed with brine dried over MgSO4 concentrated to afford the crude product The residue was purified by chromatography (silica, Hex)

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

Procedure: 3,5-Difluorobenzoic acid (25 g, 0.158 mol) was dissolved in DCM (150 mL) and dioxane (50 mL). The mixture was transferred into a stainless steel autoclave. Concentrated sulfuric acid (3.6 mL) was added, followed by isobutene (100 mL). The mixture was kept in the autoclave for 5 days. Excess isobutene and the solvents were removed under reduced pressure, the mixture diluted with EtOAc and washed with water, saturated aqueous sodium hydrogen carbonate and brine. Drying and evaporation gave a dark-yellow oil, which was purified by kugelrohr distillation (80–100° C., 1.0 mbar) to give tert-butyl-3,5-difluorobenzoate (27.51, g, 81% ) as a colorless solid. Excess isobutene and the solvents were removed under reduced pressure the mixture diluted with EtOAc washed with water, saturated aqueous sodium hydrogen carbonate and brine Drying evaporation gave a dark-yellow oil, which was purified by kugelrohr distillation (80–100° C., 1.0 mbar)