Dimethylformamide → HCID 21071903, compound

Participants

Reaction Conditions

Reaction Steps

Dimethylformamide (7.5 g) and 45 mL of dichloromethane were cooled to 6° C. and 7.3 mL of phosphorus oxychloride were added with stirring. 4-(2,4-Dimethyl-1H-pyrrol-3-yl)-benzoic acid (11.1 g) was slowly added. The mixture was refluxed for 30 minutes. Thin layer chromatography (ethyl acetate:hexane:acetic acid 4:6:0.5) showed no starting material at Rf 0.5 and a new spot at the origin. The mixture was cooled to 5° C. and 50 mL of ice water were added. Potassium hydroxide (9 N, 60 mL total) was slowly added with cooling. The final pH was 12–13. The maximum temperature reached was 48° C. Water (100 mL) was added along with 15 mL of dichloromethane, some of which had boiled off. The aqueous phase was isolated at a temperature of about 35° C. to prevent precipitation. The aqueous phase was adjusted to pH 3 by slow addition of about 21 mL of 10 N hydrochloric acid with stirring and cooling in an ice bath. The solids were collected by vacuum filtration and washed 3 times with 15 mL of water each time to give 5.6 g (50% yield) of 4-(5-formyl-2,4-dimethyl-1H-pyrrol-3-yl)-benzoic acid as a tan solid. 1H-NMR (dimethylsulfoxide-d6) δ 2.23, 2.27 (2×s, 2×3H, 2×CH3), 7.40, 7.95 (multiplets, 4H, aromatic), 9.56 (s, 1H, CHO), 11.85 (br s, 1H, NH), 12.90 (br s, 1H, COOH). MS m/z 244 [M+1].

Provenance & Evidence