DE1643195C - - Google Patents

Description

Example 2.

With the appropriate implementation of diketene with an ethanolic sodium chloroacetate solution (0.25 g / l) the temperature rose at the end of the reaction at 132 ° C. The yield of ethyl acetoacetate, based on the diketene used, was 94.5 · / ο.

Example 3

In the analogous implementation of diketene with an ethanolic potassium chloroacetate solution (1.5 g / l) were 94.1% ethyl acetoacetate (based on the diketene used) was obtained. The temperature at The end of the reaction was 132 ° C.

Example 4

The above reaction could also be catalyzed by a mixture of sodium chloride, sodium bromide and sodium sulfate (0.4 g / l each). The temperature at the end of the diketene addition was 108 ° C. The yield of ethyl acetoacetate, based on the diketene used, was 95.5 · / ·.

Example 5

The following ίο procedure was used for the continuous tests: Using a Normados dosing pump
the alcohol-catalyst-diketene mixture (100 ml of raw diketene and 72 ml of ethanol were premixed) was pumped into a 2-1 flask (overflow at 1000 ml) not quite sufficient, with electric heating to 135 to 14O ⁰ C. The test results obtained are summarized in the table below.

g / l catalyst

Dwell time hours

Yield of * Ethyl acetoacetate

Debris flooding

(· / · The theory)

O- and C-Acet-

ethyl acetate (Vo) *

0.3 sodium acetate (comparative example)

0.3 sodium chloroacetate

0.6 sodium chloroacetate

* Based on the diketene used.

3.5
3.5
3.5

93.44
95.68
96.70

11.5
0
3.9

2.3

0.62

1.5

Example 6

When the process was carried out on an industrial scale, in the case of methyl acetoacetate the yield from 90% (Na acetate as catalyst) to 96% (Na chloroacetate) under otherwise identical conditions improved.

Claims (1)

Ί / is worked under increased pressure. The patent claim: driving is characterized by the fact that one is the implementation in the presence of alkali salts of acids Process for the preparation of acetoacetic acid with a pk value below 3.0 or mixtures thereof acid esters carried out by reacting diketene with 5 as catalysts Alcohols, in particular aliphatic Aiko- Alkali halides are suitable as catalysts get that contain the catalyst dissolved, and / or alkali sulfates, z. B. sodium chloride, Nabei Temperatures between the boiling point of trium bromide and sodium sulfate but also alkali used Alcohol and the boiling point of the salts formed by α-chlorocarboxylic acids, e.g. Acetoacetic acid ester at normal pressure io res sodium or a-chloroacetic acid potassium as well or work is carried out under increased pressure, disulfonic acid salts can be used with success characterized by that one will be around. Settlement in the presence of alkali salts of Sau- As alcohols are particularly suitable aliphatic Ren with a pk value below 3.0 individually or alcohols such as methanol, ethanol, butanol, 2-ethyl mixtures 15 of these are catalyzed by hexanol. The alcohol component is preferred used in a slight excess, usually less than 15 ° / o. The heat of reaction is sufficient for maintenance the reaction temperature and optionally also for ao distilling off the volatile constituents such as Acetone, alcohol, acetic acid and ethyl acetate. The conversion of diketene with alcohols to It was by no means foreseeable that the addition Acetoacetic acid esters are known. of alcohols on diketene by the invention In the usual processes, alkaline or practically neutral salts are catalyzed acidic catalysts applied. Because Diketen can do an ace. * represents an extremely reactive compound, are a number of side reactions possible, carried out both by procedures as follows:
acidic as well as basic catalysts favored In one with a reflux condenser, dropping funnel will. 1-1 flasks equipped with a stirrer became the The basic catalysts are, for. B. tertiary 30 alcohol and the catalyst submitted to boiling Amines such as triethylamine and pyridine, also heated to sodium and dropwise with stirring within acetate, sodium stearate, sodium silicate, borax and eight hours with 94% of the sodium methylate calculated on the alcohol applied. These lead to seconds of diketene being offset. According to the dietary supplements, the most important of which was the O-acetyl or the reaction mixture would continue for 45 minutes C-acetyl acetic acid esters are. 35 heated and fractionated in vacuo after 16 hours. Furthermore, the acetoacetic ester is obtained by diketene. The raw diketene used consisted of 84.5% acylated. This results in condensation and diketene, 5.5% acetic anhydride and 9.5% reverse polymerisation reactions higher gumming rate. products that can no longer be separated by distillation and Vf ^ ipiphehpisniei λ back as a brownish-black residue in the bladder- 40 vergieicnsoeispiei a remain. Following the procedure described above If, on the other hand, acidic catalysts are used, a methanolic solution of sodium such as sulfuric acid or sulfonic acid is converted into acetate (0.5 g / l) with diketene. At the end of the main secondary product / S-alkoxycroten- of the diketene feed, the temperature in the flask acid ester rose. This has compared to the above 45 to 102 ° C. The reaction mixture had the disadvantage of fractionated water jet vacuum in the by-products described. The yield of that it cannot economically be separated from acetoacetic acid methyl ester, based on the. put diketene, was 95.1%. In the reference "Organic Syntesis", vol. 42, an increase in the amount of sodium acetate to 1.0 g / l 1962, pp. 28/29, the implementation of diketene with 50 has a reduction in the yield result. Tertiary butanol in the presence of sodium acetate as bp ₁₂ = 60 ° C.
Catalyst described. Now sodium acetate is a ice cream 1 1 alkaline catalyst. Practically all ^p alkaline reacting substances the reaction of In the analogous reaction with diketene with a Diketen with alcohol. But they also catalyze SS methanolic solution of sodium chloroacetate side reactions, e.g. B. the dehydracetic acid and (1 g / 1) the temperature in the flask rose at the end of the polyketene formation from diketene. Therefore the reaction to 120 ° C results. The yield of acetoacetic acid when using these catalysts, lower acid methyl esters, was 97.63% (based on the one yield than with the diketene according to the invention. This set diketene).
do not catalyze these side reactions or do so to 60. at least much weaker. Comparative experiment B A process has now been found for producing the procedure described above Position of acetoacetic acid esters by reaction, an ethanolic sodium acetate solution (0.3 g / l) of diketene with Alkoii ^ n, in particular aliphatic with diketene, was implemented. The final temperature in the Cologne alcohols containing the dissolved catalyst was 137 ° C. The yield of acetoacetic acid, at temperatures between the boiling ethyl ester after the fractional distillation at the point of the alcohol used and the boiling point of the water jet vacuum, based on the of the acetoacetic ester formed at normal pressure or diketene was 92.41%. Bp ₁₂₅ = 71 ° C.