Pyrrole → 5-[(4-chlorophenyl)(methylimino)methyl]-4-methyl-1H-pyrrole-2-acetic acid

Participants

Reaction Steps

N-Methyl 4-chlorobenzimidoyl chloride (2.37 g, 12.6 mmole) was placed in a dry 50 ml round bottom flask and treated with alcohol free chloroform and chlorosulfonic acid (0.15 g, 1.3 mmole). The reaction was placed under a nitrogen atmosphere and stirred at room temperature while ethyl 4-methyl-1H-pyrrole-2-acetate (2.11 g, 12.6 mmole) was added dropwise over a five-minute period. Upon addition of the pyrrole, the reaction mixture turned dark brown and the reaction temperature rose. The reaction was stirred overnight at room temperature, then quenched with saturated aqueous sodium bicarbonate. The phases were separated and the organic phase was extracted with saturated aqueous sodium bicarbonate, washed with water, dried over sodium sulfate, filtered, and concentrated. The residue was dissolved in absolute ethanol, treated with 70% perchloric acid (2.0 g, 14 mmole) cooled and diluted with ether. A brown viscous liquid separated which was suspended in methylene chloride and treated with saturated aqueous sodium bicarbonate. The solution was dried over sodium sulfate, filtered, and concentrated. The residue was placed on a silica gel column and eluted with methylene chloride/methanol (99/1) to remove nonpolar impurities. The silica gel was extracted with methanol to yield 0.47 g (12%) of the title compound as a dark brown solid, m.p. 79°-80° C. (dec).

Provenance & Evidence