反应详情

Methyl 4-hydroxy-5-(methoxycarbonyl)thiophene-2-carboxylate (5 g, 23.14 mmol) was added slowly for 15 min at 0 to −5° C. to concentrated sulfuric acid (25 mL). Then concentrated nitric acid (3.2 mL, 70%, 34.7 mmol) was added to the above reaction mixture for 10 min and stirred at the same temperature for 1 h. The mixture was poured into ice cooled water and extracted with ethyl acetate (3×100 mL). The combined organic layer was washed with water, brine and dried over sodium sulfate. The solution was filtered and evaporated the solvent. The residue was chromatographed over silica gel column using chloroform-methanol (95:5) as eluents to give the product as a yellow color semi-solid (1.2 g, 20%).

1. additionThe mixture was poured into ice
2. extractionextracted with ethyl acetate (3×100 mL)
3. washThe combined organic layer was washed with water, brine
4. dry with materialdried over sodium sulfate
5. filtrationThe solution was filtered
6. customevaporated the solvent
7. customThe residue was chromatographed over silica gel column