Diethyl Malonate → Diethyl 2,5-dimethylcyclopentane-1,1-dicarboxylate

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Reaction Steps

Sodium metal (16 g, 0.7 mole) was dissolved in absolute ethanol (500 ml) under argon with cooling as necessary to maintain a temperature of <70° C. The solution was cooled and redistilled diethyl malonate (54.3 g, 0.362 mole) was added dropwise, with cooling as necessary, followed by 2,5-dibromohexane (85 g, 0.348 mole) in a single portion. The reaction mixture was stirred overnight at room temperature and then refluxed for 2 hours. The mixture was then concentrated to approximately half the volume under reduced pressure, water (500 ml) added and the mixture extracted with ether (3×200 ml). The combined extracts were dried (Na2SO4), filtered, and evaporated under reduced pressure. The residue was fractionated in vacuo to yield diethyl 2,5-dimethylcyclopentane-1,1-dicarboxylate (35 g), which was homogeneous by GC.

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