反应详情

To a solution of racemic (R/S)-1-(5-methoxy-2-nitrophenyl)-2,2-dimethyl-1-propanol (1.75 g, 7.3 mmol) and DMAP (2.92 g, 23.9 mmol) in anhydrous CH2Cl2 (10 mL), (1S)-camphanic chloride (Corrie et al., 1992), which is incorporated by reference) (2.6 g, 12 mmol) was added, and the mixture was stirred overnight at room temperature under a nitrogen atmosphere. The reaction mixture was diluted with CH2Cl2 (50 mL) and washed with saturated NaHCO3 solution (50 mL). The organic phase was dried over Na2SO4, concentrated in vacuo, and the residue was purified by silica gel column chromatography to yield (R/S)-1-(5-methoxy-2-nitrophenyl)-2,2-dimethyl-1-propyl (1S)-camphanate (2.5 g, 85%, 1:1 mixture of diastereomers). The camphanate was dissolved in ethyl acetate (30 mL) followed by slow addition of hexane (120 mL) with stirring. Needle crystals formed gradually from the solution over a two-hour period. The crystals were collected by filtration to yield pure single diastereomer (S)-1-(5-methoxy-2-nitrophenyl)-2,2-dimethyl-1-propyl (1S)-camphanate. The filtrate was concentrated in vacuo, and the crystallization process was repeated twice to provide additional (S)-1-(5-methoxy-2-nitrophenyl)-2,2-dimethyl-1-propyl (1S)-camphanate (total 1.08 g, 43%). 1H NMR (400 MHz, CDCl3): δ 8.04 (d, 1H, J=9.2 Hz, Ph-H), 7.27 (d, 1H, J=2.8 Hz, Ph-H), 6.88 (dd, 1H, J=2.8 and 8.8 Hz, Ph-H), 6.81 (3, 1H, Ph-CH), 3.87 (s, 3H, OCH3), 2.36 (m, 1H, CH), 1.92 (m, 2H, CH2), 1.66 (m, 1H, CH), 1.12 (s, 3H, CH3), 1.06 (s, 3H, CH3), 1.02 (s, 3H, CH3), 0.95 (s, 9H, C(CH3)3).

1. additionwas added
2. washwashed with saturated NaHCO3 solution (50 mL)
3. dry with materialThe organic phase was dried over Na2SO4
4. concentrationconcentrated in vacuo
5. customthe residue was purified by silica gel column chromatography