反应详情

10.0 g (48 mmol) of 2-nitro-6-acetyl-benzoic acid (cf. Horii et al., Yakugaku Zasshi, 1954, 466, and Baker et al., J. Org. Chem. 1952, 17, 164) are dissolved at 40° C. in 50 ml of 2N sodium hydroxide solution and treated with 1.87 g (48 mmol) of sodium borohydride in portions. After 40 minutes, the reaction mixture, which has been cooled, is acidified and the precipitated crystals are filtered off and dried in vacuo; the product consists of 8.4 g of a product mixture of 82% of 2-nitro-6-(1-hydroxyethyl)-benzoic acid; 1H-NMR (DMSO-D6): 8.00 ppm, m, 2H; 7.68 ppm, t, 1H; 5.6 ppm, b, OH; 4.92 ppm, q, 1H; 1.32 ppm, d, 3H; and 18% of 3-methyl-7-nitro-3H-isobenzofuran-1-one; 1H-NMR (DMSO-D6): 8.02 ppm, m, 2H; 7.68 ppm, t, 1H; 5.80 ppm, q, 1H; 1.62 ppm, d, 3H. The acid aqueous phase is then also extracted with ethyl acetate, combined with the crystals obtained above, dried thoroughly over magnesium sulfate and concentrated completely to dryness by evaporation. 9.14 g (98.6%) of pure 3-methyl-7-nitro-phthalide (3-methyl-7-nitro-3H-isobenzofuran-1-one) are thereby obtained; 1H-NMR (CDCl3): 7.92 ppm, d, 1H; 7.88 ppm, t, 1H; 7.72 ppm, d, 1H; 5.63 ppm, q, 1H; 1.72 ppm, d, 3H.

1. temperaturethe reaction mixture, which has been cooled
2. filtrationthe precipitated crystals are filtered off
3. customdried in vacuo
4. additionthe product consists of 8.4 g of a product mixture of 82% of 2-nitro-6-(1-hydroxyethyl)-benzoic acid
5. extractionThe acid aqueous phase is then also extracted with ethyl acetate
6. customobtained above,
7. dry with materialdried thoroughly over magnesium sulfate
8. concentrationconcentrated completely to dryness by evaporation