Dimethylformamide → Ethyl 5-formyl-4-methyl-1H-pyrrole-2-carboxylate

Participants

Reaction Steps

Dimethylformamide (3 mL, 6 equivalents) was cooled with stirring in an ice bath. To this was added phosphorus oxychloride (1.1 equivalents, 0.67 mL). After 30 minutes, a solution of 4-methyl-2-pyrrolecarboxylic acid ethyl ester (1 g, 6.53 mmol) in dimethylformamide (2M, 3 mL) was added to the reaction and stirring continued. After 1 hour, the reaction was warmed to room temperature. After another 2.5 hours, the reaction mixture was diluted with water (100 mL) and basified to pH 11 with 1 N sodium hydroxide solution. The precipitate was collected by vacuum filtration, washed with water and dried to afford 0.8 g (68% yield) 5-formyl-4-methyl-1H-pyrrole-2-carboxylic acid ethyl ester as a white solid. 1H-NMR (360 MHz, dimethylsulfoxide-d6) δ 12.6 (br s, 1H, NH), 9.78 (s, 1H, CHO), 6.68 (s, 1H, CH), 4.26 (q, 2H, OCH2), 2.28 (s, 3H, CH3), 1.28 (t, 3H, CH3). MS m/z 181 [M+].

Provenance & Evidence