Nitric Acid → 2,2,2-Trichloro-1-(1-methyl-4-nitro-1H-pyrrol-2-yl)ethan-1-one

Participants

Reaction Conditions

Reaction Steps

To a well stirred solution of trichloroacetyl chloride (1 kg, 5.5 mole) in 1.5 liter ethyl ether in a 12 liter flask was added dropwise over a period of 3 h a solution of N-methylpyrrole (0.45 kg, 5.5 mole) in 1.5 liter anhydrous ethyl ether. The reaction was stirred for an additional 3 hours and quenched by the dropwise addition of a solution of 400 g potassium carbonate in 1.5 liters water. The layers were separated and the ether layer concentrated in vacuo to provide 2-(trichloroacetyl)pyrrole (1.2 kg, 5.1 mol) as a yellow crystalline solid sufficiently pure to be used without further purification. To a cooled (−40° C.) solution of 2-(trichloroacetyl) pyrrole (1.2 kg, 5.1 mol) in acetic anhydride (6 L) in a 12 L flask equipped with a mechanical stirrer was added 440 mL fuming nitric acid over a period of 1 hour while maintaining a temperature of (−40° C.). The reaction was carefully allowed to warm to room temperature and stir an additional 4 h. The mixture was cooled to −30° C., and isopropyl alcohol (6 L) added. The solution was stirred at −20° C. for 30 min during which time a white precipitate forms. The solution was allowed to stand for 15 min and the resulting precipitate collected by vacuum filtration to provide 4-nitro-2-trichloroacetyl-1-methylpyrrole, shown as compound B-1 in Scheme B (0.8 kg, 54% yield) TLC (7:2 benzene/ethyl acetate) Rf 0.7; 1H NMR (DMSO-d6) δ 8.55 (d, 1H, J=1.7 Hz), 7.77 (d, 1H, J=1.7 Hz), 3.98 (s, 3H); 13C NMR (DMSO-d6) δ 173.3, 134.7, 133.2, 121.1, 116.9, 95.0, 51.5; IR (KBr) 1694, 1516, 1423, 1314, 1183, 1113, 998, 750. FABMS m/e 269.936 (M+H 269.937 calc. for C7H5N2O3Cl3).

Provenance & Evidence