反应详情

Ethyl 5-chlorothiophene-2-carboxylate (2.7 g, 14.1 mmol) was added in portions to concentrated sulfuric acid (5 mL) and the stirred solution was cooled to below 0° C. with a methanol/ice bath. Fuming nitric acid (1.78 g, 1.2 mL, 28.3 mmol) was added slowly, keeping the temperature below 0° C. throughout the addition. On completion of addition the stirred mixture was removed from the cold bath and warmed to ambient temperature for 2 hours. The reaction was quenched by addition to ice/water (100 mL) resulting in formation of a sticky solid. The product was extracted into dichloromethane (2×100 mL). The combined organic extracts were dried (MgSO4), filtered and the solvent was removed to afford an orange oil. The crude material was purified by silica gel chromatography using a 95:5 mixture of hexane and ethyl acetate as eluent to afford the title product as a solid (2.23 g, 67% yield). 1H NMR (CDCl3) δ: 8.14 (1H, s), 4.37 (2H, q, J=7.11 Hz), 1.37 (3H, t, J=7.11 Hz).

1. temperaturethe stirred solution was cooled to below 0° C. with a methanol/ice bath
2. customthe temperature below 0° C.
3. additionthroughout the addition
4. additionOn completion of addition the stirred mixture
5. customwas removed from the cold bath
6. customThe reaction was quenched by addition to ice/water (100 mL)
7. customresulting in formation of a sticky solid
8. extractionThe product was extracted into dichloromethane (2×100 mL)
9. dry with materialThe combined organic extracts were dried (MgSO4)
10. filtrationfiltered
11. customthe solvent was removed
12. customto afford an orange oil
13. customThe crude material was purified by silica gel chromatography
14. additiona 95:5 mixture of hexane and ethyl acetate as eluent