反应详情

2-Hydroxy-7-nitro-2,3-dihydro-benzofuran-4-carboxylic acid methyl ester prepared above was heated in phosphoric acid (60 mL) at 100° C. for one hour. The reaction mixture was poured into ice water and the aqueous solution was extracted with ethyl acetate. The organic phase was washed with brine, dried (anhydrous sodium sulfate) and concentrated under reduced pressure. The residue was purified by flash column chromatography over silica gel eluting with 15% ethyl acetate in hexane to give 7-nitro-benzofuran-4-carboxylic acid methyl ester as solid (2.3 g, 40%). 1H (CDCl3) δ: 4.04 (s, 3H), 7.54 (d, 1H, J=2.0 Hz), 7.95 (d, 1H, J=1.9 Hz), 8.07 (d, 1H, J=8.5 Hz), 8.17 (d, 1H, J=8.5 Hz).

1. extractionthe aqueous solution was extracted with ethyl acetate
2. washThe organic phase was washed with brine
3. dry with materialdried (anhydrous sodium sulfate)
4. concentrationconcentrated under reduced pressure
5. customThe residue was purified by flash column chromatography over silica gel eluting with 15% ethyl acetate in hexane