反应详情

A solution of 5 (25.5 g, 71.73 mmol) in THF (300 mL) and water (75 mL) under Ar is cooled to 0° C. To this is added via syringe H2O2 (30% in water, 30.6 mL, 0.300 mol) gradually over a period of 15 minutes. LiOHH2O (4.92 g, 0.12 mol) in water (150 mL) is added via syringe. The mixture is stirred for 3 h after which the septum is removed and Na2SO3 (37.8 g, 0.300 mol) in water (225 mL) is added slowly. The bulk of the THF is removed by rotavap at a bath temperature between 25-30° C. The residue is extracted with CH2Cl2 (100 ml×3). The combined organic layer is washed consecutively with 0.5 N HCl (100 mL), sat. NaHCO3 (100 mL), water (100 mL) and brine ( 100 mL). The solution is then dried over Na2SO4 and concentrated in vacuo. The residue is recrystallized in hexane/ethyl acetate to afford the Evan's chiral auxiliary 2 as white needles. The aqueous layer from the first extraction was acidified to pH 1 and extracted with ethyl acetate (100 mL×3). The combined organic layer is washed with 0.5 N HCl (100 mL) and then brine (100 mL). It is then dried over Na2SO4 and concentrated to yield 6 as a colorless oil (17.198 g, 70.39 mmol, 98%). 1H NMR (400 MHz, CDCl3) δ0.88 (t, J=6.8 Hz, 3 H), 1.21-1.37 (m, 6 H), 1.43 (s, 9 H), 1.40-1.70 (m, 2 H), 2.61 (dd, J=9.3 Hz, 1 H), 2.38 (dd, J=16.4, 5.1, 1 H), 2.61 (dd, J=16.4, 9.3, 1 H), 2.78 (m, 1 H); 13C NMR (100 MHz, CDCl3) δ13.9, 17.5, 17.9, 22.3, 26.5, 27.9, 31.5, 37.0, 41.3, 94.9, 80.0, 171.1, 181.1. HRMS calcd for C13H25O4 (MH+): 245.1752. Found (DCI): 245.1766 (Δ=5.2 ppm).

1. customis removed
2. customThe bulk of the THF is removed by rotavap at a bath temperature between 25-30° C
3. extractionThe residue is extracted with CH2Cl2 (100 ml×3)
4. washThe combined organic layer is washed consecutively with 0.5 N HCl (100 mL), sat. NaHCO3 (100 mL), water (100 mL) and brine ( 100 mL)
5. dry with materialThe solution is then dried over Na2SO4
6. concentrationconcentrated in vacuo
7. customThe residue is recrystallized in hexane/ethyl acetate