Trichloroacetyl chloride → 2-(Trichloroacetyl)pyrrole

Participants

Reaction Steps

Preparation of4-nitro-2-trichloroacetyl-1-methylpyrrole(15). To a well stirred solution of trichloroacetylchloride (1 kg, 5.5 mole) in 1.5 liters of ethyl ether was added dropwise over a period of 3 hours a solution of N-methylpyrrole (14) (0.45 kg, 5.5 mole) in 1.5 liters of anhydrous ethyl ether. The reaction was allowed to stir for an additional 3 hours and quenched by the dropwise addition of a solution of 400 g of potassium carbonate in 1.5 liters of water. The layers were separated and the ether layer was concentrated in vacuo to provide 2-trichloroacetyl pyrrole (1.2 kg, 5.1 mole) as a yellow crystalline solid. which can be purified by recrystallization from benzene, but is sufficiently pure to be used without further purification. To a cooled (−40° C.) solution of 2-trichloroacetyl pyrrole (1.2 kg, 5.1 mole) in acetic anhydride (6 liters) flask equipped with a mechanical stirrer was added 440 ml of filming nitric acid over a period of I hour while maintaining a temperature of −40° C. The reaction was carefully allowed to warm to room temperature and stirred an additional 4 hours after which the mixture was cooled to −30° C. and isopropyl alcohol (6 liters) was added. The solution was stirred at −20° C. for 30 minutes during which time a white precipitate formed. The solution was allowed to stand for 15 minutes and the resulting precipitate collected by vacuum filtration to provide (15) (0.8 kg, 54% yield). TLC (7:2 benzene/ethyl acetate) Rf 0.7; 1H NMR (DMSO-d6) δ8.55 (d, 1 H, J=1.7 Hz), 7.77 (d, 1 H, J=1.7 Hz), 3.98 (s, 3 H); 13C NMR (DMSO-d6) δ173.3, 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