反应详情

A mixture of 1-ethoxycarbonylmethylpyridinium bromide 5 (1 g, 4.1 mmol), 1,1-bismethylthio-2-nitroethene (1.2 g; 8.1 mmol) and Et3N (4.1 g, 40.6 mmol) in ethanol (30 mL) was heated at reflux for 12 h. The solvents and the triethylamine were then evaporated under vacuum. The oil obtained was extracted with water (50 mL) and toluene (3×50 mL). The combined extracts were dried over anhydrous magnesium sulphate, filtered and then concentrated under vacuum. The residue was chromatographed on a column of silica with an elution gradient of 1/1 to 4/1 of ethyl acetate/petroleum ether. This gave 0.5 g of ethyl 2-methylaminoindolizine-3-carboxylate 6 in the form of an oil. 1H NMR (DMSO-d6) δ: 9.11 (br s, 1H), 7.32 (d, J=8.8 Hz, 1H), 7.07-7.01 (m, 1H), 6.71-6.66 (m, 1H), 5.88 (br s, 1H), 5.85 (s, 1H), 4.32 (q, J=7.0 Hz, 2H), 2.85 (d, J=5.1 Hz, 3H), 1.34 (t, J=7.0 Hz, 1H), 13C NMR (CDCl3) δ: 161.0, 148.9, 138.2, 127.0, 123.4, 115.8, 109.9, 98.6, 84.3, 58.7, 31.0, 14.7.

1. temperaturewas heated
2. temperatureat reflux for 12 h
3. customThe solvents and the triethylamine were then evaporated under vacuum
4. customThe oil obtained
5. extractionwas extracted with water (50 mL) and toluene (3×50 mL)
6. dry with materialThe combined extracts were dried over anhydrous magnesium sulphate
7. filtrationfiltered
8. concentrationconcentrated under vacuum
9. customThe residue was chromatographed on a column of silica with an elution gradient of 1/1 to 4/1 of ethyl acetate/petroleum ether