反应详情

To a solution of dimethylformamide (21 mL, 0.27 mol) in 75 mL of dichloroethane was added a solution of phosphorus oxychloride (25 mL, 0.27 mol) in 75 mL of dichloroethane at 0° C. The mixture was stirred at room temperature for 30 minutes and cooled to 0–20 C. To the mixture was added a solution of ethyl pyrrole-2-carboxylate (25 g, 0.18 mol) in 50 mL of dichloroethane dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then at 40° C. for 1 hour. The mixture was poured into ice and basified to pH 11 with 5 N sodium hydroxide solution. The mixture was extracted with ethyl acetate and the extract washed with water and brine and dried over anhydrous sodium sulfate. The two products were separated by column chromatography (1:3 ethyl acetate:hexane) to give 15 g (50% yield) of 5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester and 2 g (7% yield) of 4-formyl-1H-pyrrole-2-carboxylic acid ethyl ester. 1H-NMR (300 MHz, dimethylsulfoxide) δ 13.02 (br s, 1H, NH), 9.69 (s, 1H, CHO), 6.95 (d, 1H), 6.86 (d, 1H), 4.27 (q, 2H, CH3), 1.28 (t, 3H, CH3). MS m/z 167 [M+].

1. temperaturecooled to 0–20 C
2. stirringThe resulting mixture was stirred at room temperature for 30 minutes
3. waitat 40° C. for 1 hour
4. extractionThe mixture was extracted with ethyl acetate
5. washthe extract washed with water and brine
6. dry with materialdried over anhydrous sodium sulfate
7. customThe two products were separated by column chromatography (1:3 ethyl acetate:hexane)