反应详情

Sulfuric acid (50 ml) was added to (2Z)-2-(2-bromo-4-methoxyphenoxy)-2-butenedioic acid (24.3 g, 86.6 mmol; as prepared in Reference Example 2b above). After heating the mixture with a heat gun for 5-10 min a clear deep brown solution was obtained. This solution was slowly added to refluxing absolute ethanol (250 ml). After the addition the reaction was refluxed for 30 min then allowed to cool. Crystals started to form after 20 min and the reaction was put in the refrigerator overnight. The solid was filtered, washed with cold ethanol/water 9:1 and dried to give ethyl 8-bromo-6-methoxy-4-oxo-4H-chromene-2-carboxylate as an off-white solid (12.3 g, 50% yield, mp 159-161° C.).

1. temperatureAfter heating the mixture with a heat gun for 5-10 min a clear deep brown solution
2. customwas obtained
3. additionThis solution was slowly added
4. additionAfter the addition the reaction
5. temperaturewas refluxed for 30 min
6. temperatureto cool
7. customto form after 20 min
8. customwas put in the refrigerator overnight
9. filtrationThe solid was filtered
10. washwashed with cold ethanol/water 9:1
11. customdried