Ethyl Acetoacetate → Ethyl 2-acetyl-5-chlorohex-4-enoate

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Reaction Steps

To a solution of 46 g sodium (2 g atom) in 500 ml ethanol at reflux, in a 2-liter flask equipped with mechanical stirrer, and addition funnel, was added 325 g ethyl acetoacetate (2.5 mole) over 30 minutes. The resulting solution of enolate was refluxed for 15 minutes, and then 250 g (2.0 mole) 1,3-dichlorobut-2-ene (nD20 1.4675) was added dropwise at such a rate as to maintain reflux with gentle heating towards the end of the addition. After addition, refluxing and stirring were maintained for 4 hours, the condenser converted for distillation, and ethanol removed as 500 ml distillate. The residual product was cooled, water and 1.2 N hydrochloric acid were added and the organic layer separated. The aqueous portion was extracted with ether, the organic layers combined, washed with water and brine, filtered through sodium sulfate and evaporated in vacuo to give 485 g. dark yellow oil (96%, based on dichlorobutene). Vpc showed 73% of trans plus cis product, together with 20% ethyl acetoacetate and other volatiles, and 7% dialkylated product at long retention time. A small sample was purified by TLC on silica gel (1:3 ethyl acetate:pentane) Rf 0.27, followed by distillation at 100° C./0.1 mm. 3-Carboethoxy-6-chlorohept-5-en-2-one was obtained as a colorless oil, nD20 1.4640.

Provenance & Evidence