To a solution of 5-amino-2-dimethylamino-N-[3-(2-oxo-pyrrolidin-1-yl)-propyl]-4-(4-o-tolyl-piperazin-1-yl)-benzamide 7c (91.7 mg, 0.19 mmol, 100 mol %) and N,N-diisopropylethylamine (0.10 ml, 0.58 mmol, 300 mol %) in dichloromethane (4.0 ml) was added furan-2-carbonyl chloride (0.02 ml, 0.23 mmol, 120 mol %) and a catalytic amount of N,N-dimethylaminopyridine. The reaction was stirred for 16 h at room temperature and then diluted with water and extracted three times with dichloromethane. The combined organics were dried over sodium sulfate and concentrated to a residue that was purified by column chromatography (dichloromethane to 10% methanol/dichloromethane) to afford furan-2-carboxylic acid [4-dimethylamino-5-[3-(2-oxo-pyrrolidin-1-yl)-propylcarbamoyl]-2-(4-o-tolyl-piperazin-1-yl)-phenyl]-amide 7d (50.0 mg; 0.09 mmol, 45.6%) as an off-white solid.
