反应详情

2-Hydroxyimino-N-(4-methoxy-3-methylphenyl)acetamide (0.5 g, 2.4 mmol) was added portionwise to concentrated methanesulfonic acid (1.5 mL). The 2-hydroxyimino-N-(4-methoxy-3-methylphenyl)acetamide was added over a period of 45 min in order to keep the reaction temperature between 65 to 70° C. After addition, the mixture was stirred for 10 min and then poured onto ice (10 g). The resulting aqueous solution was extracted with ethyl acetate (3×50 mL). Combined organic layers were dried (Na2SO4), filtered and concentrated in vacuo. The crude product was purified by column chromatography on silica gel with petroleum ether:ethyl acetate (20:1, v/v) as eluent to afford 5-methoxy-6-methyl-1H-indole-2,3-dione (350 mg, 1.8 mmol, 77%).

1. custombetween 65 to 70° C
2. additionAfter addition
3. additionpoured onto ice (10 g)
4. extractionThe resulting aqueous solution was extracted with ethyl acetate (3×50 mL)
5. dry with materialCombined organic layers were dried (Na2SO4)
6. filtrationfiltered
7. concentrationconcentrated in vacuo
8. customThe crude product was purified by column chromatography on silica gel with petroleum ether:ethyl acetate (20:1