Sodium hydride (60% suspension in mineral oil, 1.60 mmol) was added to a mixture of tert-butyl ethyl malonate (300 mg) in 1-methyl-2-pyrrolidinone (3 mL) and was followed by 1,5-dichloro-2,4-dinitrobenzene (0.45 g). The reaction mixture was stirred for 15 minutes and was then quenched by addition of a diluted aqueous solution of hydrochloric acid. The resulting mixture was extracted with ethyl acetate; the combined organic extracts were washed with brine, dried over anhydrous sodium sulfate, filtered and evaporated under reduced pressure. The residue was purified by flash chromatography (EtOAc/hexane, 5/95 to 15/85) to give 0.4 g of 2-(5-chloro-2,4-dinitro-phenyl)-malonic acid tert-butyl ester ethyl ester.
