Triphenylphosphine → HCID 86679978, compound

Participants

Reaction Conditions

Reaction Steps

To a solution of 5-azido-1-(1-methyl-4-nitro-1H-pyrazol-5-yl)azepan-3-ol, Intermediate 18 (3.4 g, 16 mmol) in THF (40 mL) and water (8 mL) was added triphenylphosphine (1.89 g, 7.2 mmol) and the mixture was heated at 65° C. behind a blast screen for 16 hr. The solvents were removed under reduced pressure to afford 5-amino-1-(1-methyl-4-nitro-1H-pyrazol-5-yl)azepan-3-ol (contaminated with triphenylphosphine oxide) as a viscous oil. To this amine in DCM (40 mL) was added di-tert-butyl dicarbonate (4.49 g, 20.6 mmol) and DIPEA (4.78 mL, 27.4 mmol) and the mixture was stirred at room temperature for 60 hr. The solvent was removed under reduced pressure and the residue purified via silica gel column chromatography (0-100% EtOAc/isohexane) to give tert-butyl 6-hydroxy-1-(1-methyl-4-nitro-1H-pyrazol-5-yl)azepan-4-ylcarbamate as a yellow oil (1.2 g). To a solution of this oil (1.2 g) in DCM (25 mL) was added portionwise Dess-Martin periodinane (1.72 g, 1.51 mmol). After stirring at room temperature for 16 hr, the mixture was diluted with DCM (25 mL) and quenched with saturated aqueous NaHCO3 (40 mL) followed by 20% aqueous sodium thiosulphate (40 mL). The resulting mixture was stirred for 20 min. The organic layer was separated, dried over Na2SO4 and the solvent removed under reduced pressure. Purification via silica gel column chromatography (0-60% EtOAc/isohexane) gave tert-butyl 1-(1-methyl-4-nitro-1H-pyrazol-5-yl)-6-oxoazepan-4-ylcarbamate (0.56 g) as a yellow oil. To a solution of this oil (0.51 g, 1.46 mmol) in DCM (15 mL) was added deoxo-Fluor® (50% in THF, 1.85 mL, 5.1 mmol) and the mixture was stirred at room temperature for 16 hr. The mixture was diluted with DCM (30 mL), cooled in an ice/water bath and quenched by dropwise addition of saturated aqueous NaHCO3 (30 mL). The resulting mixture was stirred for 10 min. The organic layer was separated, dried over Na2SO4 and the solvent removed under reduced pressure. Purification via silica gel column chromatography (0-50% EtOAc/isohexane) gave tert-butyl 6,6-difluoro-1-(1-methyl-4-nitro-1H-pyrazol-5-yl)azepan-4-ylcarbamate (510 mg, 64% over four steps) as an oil. 1H NMR (400 MHz, CDCl3) δ 8.04 (s, 1H), 4.18-4.01 (m, 1H), 3.84 (s, 3H), 3.79-3.19 (m, 4H), 2.56-2.42 (m, 1H), 2.38-1.99 (m, 4H), 1.46 (s, 9H).

Provenance & Evidence