反应详情

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0 °C

0.5 Parts of benzyl trimethylammonium hydroxide were added dropwise to a mixture of 156.6 parts of 4-chloro-3, 5-xylenol, 149.1 parts of dimethyl acetylene dicarboxylate and 30 parts of dioxan. The reaction mixture was heated for 1/2 hour on the steam bath, cooled, and basified with 320 parts of 25% aqueous sodium hydroxide solution. After addition of 100 parts of methanol the red solution was heated at reflux for 3 hours on the steam bath, cooled, and acidified with excess dilute sulphuric acid. The precipitated yellow solid was filtered, washed with a little water, and dried. The solid was added portionwise to 850 parts of stirred chlorosulphonic acid cooled to 0°C. When all the solid had dissolved, the dark red solution was added cautiously dropwise to excess ice-water. The precipitated solid was filtered, washed with water, and recrystallised from a dioxan aqueous ethanol mixture to give 157.1 parts of 6-chloro-5,7-dimethyl-4-oxo-4H-1-benzopyran-2-carboxylic acid as a colourless solid, melting point 289°-290°C.

1. temperatureThe reaction mixture was heated for 1/2 hour on the steam bath
2. temperaturecooled
3. temperaturewas heated
4. temperatureat reflux for 3 hours on the steam bath
5. temperaturecooled
6. filtrationThe precipitated yellow solid was filtered
7. washwashed with a little water
8. customdried
9. additionThe solid was added portionwise to 850 parts of stirred chlorosulphonic acid
10. dissolutionWhen all the solid had dissolved
11. additionthe dark red solution was added cautiously dropwise to excess ice-water
12. filtrationThe precipitated solid was filtered
13. washwashed with water
14. customrecrystallised from a dioxan aqueous ethanol mixture