Ethyl bromodifluoroacetate → (4R,5S)-5-ethyl-3,3-difluoro-4-hydroxypyrrolidin-2-one

Beteiligte Stoffe

Reaktionsschritte

tert-Butyl[(1S)-1-formylpropyl]carbamate (24.00 g) and ethyl bromodifluoroacetate (77.0 g) were dissolved in tetrahydrofuran (220 mL), and to a suspension of a zinc powder (25.4 g) in tetrahydrofuran (50 mL) was added dropwise the solution at room temperature. After heating under reflux for 1 hr, the mixture was cooled to room temperature, 1 mol/L aqueous potassium hydrogen sulfate solution (400 mL) was added, and the mixture was extracted with ethyl acetate. The extracted organic layer was washed with water and saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=10→40%), the obtained oil was dissolved in 4 mol/L hydrogen chloride/ethyl acetate solution (150 mL), and the mixture was stirred at room temperature for 2 hr. The reaction solution was concentrated under reduced pressure, and the residue was dissolved in tetrahydrofuran (600 mL). Diisopropylethylamine (32.8 mL) was added, and the mixture was heated under reflux for 4 hr. The reaction solution was concentrated under reduced pressure, the residue was filtered through silica gel, and the filtrate was concentrated under reduced pressure. The obtained residue was recrystallized from ethyl acetate/hexane to give the title compound as a white powder (yield: 7.20 g, 54%).

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