反应详情

Seventy percent nitric acid (3.4 ml) was added to dropwise to acetic anhydride (35 ml) with stirring at room temperature. The mixture was then cooled in an ice bath and 7-chloroindole-2-carboxylic acid (EP 0 622 356 A1, 1.71 g, 8.74 mmol) was added carefully. After stirring for an additional 1.5 h, the suspension was filtered and the filter cake washed with hexane and air-dried. The yield of 7-chloro-3-nitroindole-2-carboxylic acid , yellow solids, was 283 mg (14%). 1H-NMR (DMSO-d6) δ: 13.66 (1H, br s), 8.04 (1H, dd, J=1.1, 8.1 Hz), 7.53 (1H, dd, J=1.1, 7.7 Hz), 7.42 (1H, dd, J=7.7, 8.1 Hz).

1. temperatureThe mixture was then cooled in an ice bath
2. stirringAfter stirring for an additional 1.5 h
3. filtrationthe suspension was filtered
4. washthe filter cake washed with hexane
5. customair-dried