3,5-Dimethyl-4-nitro-1H-pyrrole-2-carbaldehyde

2199-58-8

40236-20-2

General procedure for the synthesis of 3,5-dimethyl-4-nitropyrrole-2-carbaldehyde from 3,5-dimethyl-2-pyrrolecarboxaldehyde: 2-Formyl-3,5-dimethyl-1-hydroxypyrrole (5.0 g, 1.0 eq.) was added in batches to concentrated sulfuric acid (60 ml), and the reaction temperature was maintained at 0 to -5 °C. The reaction mixture showed a reddish brown transparent liquid state. Subsequently, potassium nitrate (4.35 g, 1.05 eq.) was added in batches and the reaction temperature was maintained at -8 to -2 °C. After the addition was completed, the reaction mixture was continued at about -7 °C for 20 min, then slowly warmed up to room temperature and continued the reaction for 20 min. The progress of the reaction was monitored by TLC and after confirming the completion of the reaction, the reaction solution was slowly poured into 1500 ml of ice water and a yellow solid precipitated. The precipitate was collected by filtration, washed with water to neutrality and dried to give 6.7 g of gray product in 98% yield.