2,2,2-Trifluoroethanol → (2R,3S)-3-acetamido-2-allyl-N-tert-butyltetrahydrofuran-3-carboxamide

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A solution of 2-allyldihydrofuran-3(2H)-one (1.2 g, 9.5 mmol) and ammonium acetate (4.39 g, 57.0 mmol) in 2,2,2-trifluoroethanol (5 mL) was treated with tert-butyl isocyanide (2.37 g, 3.23 mL, 28.5 mmol). After stirring at room temperature for 5 days, the reaction mixture diluted with water (50 mL) and extracted using ethyl acetate (2×50 mL). The combined organic layers were washed with saturated aqueous sodium chloride, dried over MgSO4, filtered and concentrated. Purification by flash column chromatography (silica gel, 50% ethyl acetate in methylene chloride) gave (2R 3S)-3-acetamido-2-allyl-N-tert-butyltetrahydrofuran-3-carboxamide as a colorless oil (930 mg, 36%) and (2S,3S)-3-acetylamido-2-allyl-N-tert-butyltetrahydrofuran-3-carboxamide as a colorless oil (650 mg, 26%). Analytical data for (2R,3S)-3-acetylamido-2-allyl-N-tert-butyltetrahydrofuran-3-carboxamide: 1H NMR (CDCl3, 300 MHz) δ 6.65 (s, NH, 1 H), 6.06 (s, NH, 1 H), 5.86 (m, 1 H), 5.16 (m, 2 H), 4.20 (dd, J1=9 Hz, J2=4 Hz, 1 H), 3.82 (m, 2 H), 2.54 (m, 2 H), 2.20-2.40 (m, 2 H), 2.03 (s, 3 H), 1.32 (s, 9 H); MS (+CI): m/z for C14H24N2O3: expected 268.2; found 269.2 (M+H)+.

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