反应详情

温度

0 °C

51.2 g of 3-fluorocatechol and 36.8 g of glyoxylic acid were dissolved at 20° C. in 160 ml of water and 34.8 g of sodium hydroxide in solution in 400 ml of water were added to this solution cooled to 0° C. The mixture was heated for 4 hours at 46° C., then cooled to 0° C. and the pH was brought to 4.6 by the addition of concentrated hydrochloric acid. Extraction was carried out with ethyl ether (after evaporation 14.7 g of the starting 9-fluorocatechol were collected) and the aqueous phase was acidified with concentrated hydrochloric acid until a pH of 1.8 was obtained. Extraction was carried out with ethyl acetate and after evaporation of the solvent, 47.7 g of the desired product were obtained (mixture of isomers, 2,3-bis-hydroxy-4-fluoro; 3,4-bis-hydroxy-5-fluoro; 2-fluoro-3,4-bis-hydroxy) which was used as is in Step A of Example 16.

1. temperatureThe mixture was heated for 4 hours at 46° C.
2. temperaturecooled to 0° C.
3. extractionExtraction
4. customwas carried out with ethyl ether (after evaporation 14.7 g of the starting 9-fluorocatechol were collected)
5. customwas obtained
6. extractionExtraction
7. customafter evaporation of the solvent