Acetaldehyde → Ethyl 2-ethylidene-4-chloro-3-oxobutyrate

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50 parts by weight of ethyl 4-chloroacetoacetate and 76 parts by volume of ethyl acetate are taken, covered with a layer of nitrogen and cooled to -75° C. 33 parts by weight of acetaldehyde are added to the cold solution and a solution of 0.43 part by volume of piperidine in 3 parts by volume of ethyl acetate is then allowed to run in over a period of 50 minutes. The solution is now warmed to 0° C. in the course of 40 minutes and is stirred at this temperature for 2 hours. After addition of 121 parts by volume of 1N hydrochloric acid and 16 parts by weight of sodium chloride, the mixture is worked up. The organic phase is separated off and the aqueous phase is extracted again with 45 parts by volume of ethyl acetate. The combined organic phases are extracted twice with a solution of in each case 16 parts by weight of sodium chloride in 55 parts by volume of water and dried. After the solvent has been stripped off, 51.9 parts by weight of product remain, which can be further processed in the crude form.

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