Dimethylformamide → 1,2-Dimethyl 4-oxo-2-cyclopentene-1,2-dicarboxylate

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Reaction Conditions

Reaction Steps

(1R,2S)-4-oxo-cyclopentane-1,2-dicarboxylic acid dimethyl ester (4.8 g, 23.8 mmol) and CuBr2 (11.9 g, 53.2 mmol) were dissolved in dry THF (70 ml) and the mixture was refluxed for two hours at 90° C. The formed CuBr was filtrated off and the organic phase was concentrated. CaCO3 (2.7 g, 27.2 mmol) and DMF (70 mL) were added and the mixture was held at 100° C. for one hour. The dark brown mixture was poured over ice (35 g) and the formed precipitate was filtrated off. The aqueous layer was extracted with ethyl acetate (1×300 ml+3×150 ml). The organic phases were dried, filtrated and concentrated. Purification by flash chromatography (toluene/EtOAc 9:1) gave the title compound (2.1 g, 45%) as yellow crystals

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