反应详情

Route A: To a solution of 3-(2-bromo-5-nitropyridin-4-yl)-2-oxopropionic acid ethyl ester (Preparation 25, 3.38 g, 10.7 mmol) in THF (50 mL) and ethanol (100 mL) was added saturated ammonium chloride solution (50 mL) and iron powder (3.57 g, 64.0 mmol) and the reaction heated under reflux for 2 h. The reaction mixture was filtered through celite and washed several times with ethyl acetate. The solvent was removed in vacuo and the remainder partitioned between saturated sodium hydrogen carbonate solution (100 mL) and ethyl acetate (3×150 mL). The combined organic fractions were dried (MgSO4) and concentrated in vacuo to give the title compound as a brown solid. δH (CD3OD): 1.42 (3H, t), 4.43 (2H, q), 7.14 (1H, s), 7.85 (1H, s), 8.58 (1H, s); m/z (ES+)=269 [M+H]+. Route B: To a solution of 2-bromo-4-methyl-5-nitropyridine (Preparation 24, 5.7 g, 26.3 mmol) in diethyl oxalate (17.9 mL) under argon was added 1,8-diazabicyclo[5,4,0]undec-7-ene (4.5 mL, 30.2 mmol) to give a dark red precipitate. Reaction mixture was stirred at rt for 4.5 h and concentrated in vacuo. Acetic acid (140 mL) was added to the residue under argon and heated to 60° C. Iron (2.94 g, 52.6 mmol) was added in small portions over a period of 1 h. The reaction mixture was heated at 80° C. for 4 h. The reaction mixture was cooled to rt and poured into water (300 mL) which gave a beige precipitate. The precipitate was isolated and washed with water. The solid obtained was dissolved in ethyl acetate (700 ml) and filtered. The filtrate was concentrated in vacuo to give the title compound. m/z (ES+)=269 [M+H]+; RT=3.39 min.

1. customto give a dark red precipitate
2. customReaction mixture
3. concentrationconcentrated in vacuo
4. additionAcetic acid (140 mL) was added to the residue under argon
5. temperatureheated to 60° C
6. temperatureThe reaction mixture was heated at 80° C. for 4 h
7. temperatureThe reaction mixture was cooled to rt
8. customgave a beige precipitate
9. customThe precipitate was isolated
10. washwashed with water
11. customThe solid obtained
12. filtrationfiltered
13. concentrationThe filtrate was concentrated in vacuo