Phosphorus pentachloride → 4-(2-tert-butyl-4-nitro-1H-pyrrole-5-carbonyl)-3,3-dimethylpiperazin-2-one

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The previously prepared 5-tert-butyl-3-nitro-1H-pyrrole-2-carboxylic acid (0.203 g, 1.11 mmol) and PCl5 (0.232 g, 1.11 mmol) were dissolved in dichloromethane (4 mL) and stirred at room temperature for 5 minutes. The resulting solution was added in one portion to a solution of 3,3-dimethylpiperazin-2-one (0.214 g, 1.67 mmol) and DIEA (0.288 g, 2.23 mmol) in dichloromethane (3 mL) and stirred at room temperature for 5 minutes. The reaction mixture was diluted with dichloromethane and washed sequentially with 1N aqueous HCl, saturated sodium bicarbonate, dried and the solvent removed under vacuum. The crude product was purified by chromatographic column (silica gel, dichloromethane:methanol, 95:5) to afford 0.190 g of expected 4-(2-tert-butyl-4-nitro-1H-pyrrole-5-carbonyl)-3,3-dimethylpiperazin-2-one.

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