CH651539A5 - METHOD FOR PRODUCING FORMYL BUTTERIC ACID DERIVATIVES. - Google Patents

Description

The present invention relates to a process for the preparation of formylbutyric acid derivatives of the general formula I:

and then reacted with water.

In the procedure according to the invention, in which the di-hydro-a-pyrone is reacted with alcohols, the dialkylacetal of the desired Alde-40 hydes is formed as an intermediate. This intermediate is a previously unknown substance; if necessary, it can easily be isolated by fractional distillation. It has the following formula IV:

CH - CH,

4th

, / \

R2 R3

CH— COOR [IV]

Alkyl substituted formyl butyric acid esters are e.g. described in DE-OS 2 810 031. They are used to manufacture pesticides based on substituted hexane carboxylic acid esters. The preparation of these esters is described in the protective right mentioned and it is stated that the formylbutyric acid esters required as intermediates can be obtained by ozonolysis of the corresponding 3,3-dialkylhexene-5-carboxylic acid esters. The process described there has the disadvantage that considerable equipment requirements are required and is carried out with starting compounds, the production of which is also very complex.

The object was therefore to produce the formyl butyric acid derivatives mentioned in a simple manner and

The inventive ring cleavage of the dihydro-a-pyrone is preferably carried out in the presence of acidic compounds both in the reaction with water and in the reaction with the alcohols mentioned. Lewis and Brönsted acids are the main acidic compounds. Examples of Lewis acids that can be used include A1C13, ZnCl2, BF3, FeCl3. Brönsted acids may be mentioned: H2S04, H3P04, p-toluenesulfonic acid, 60 trichloroacetic acid or acidic ion exchangers.

The amount of acidic compounds that can be used can vary within wide limits. Even amounts of 0.0001% by weight, based on the a-pyrone, show a catalytic effect. In general, however, amounts between 65 0.001 and 0.1% by weight, based on the a-pyrone, are used.

If water is used as the reactant, the substituted formylbutyric acid is obtained directly. On the other hand, if you use alcohol as a reaction partner,

the above-mentioned acetal of the substituted formylbutyric acid ester is formed. The ester and acetal residues (designated R4 in the above formula) are residues with the same number of carbon atoms. The acetal obtained as an intermediate is then converted into the corresponding formal in a manner known per se by treatment with water, it generally not being necessary to isolate the acetal if it is to be converted directly into the aldehyde. When the acetal is hydrolysed into the aldehyde, the ester grouping on the carboxylic acid residue is generally retained if mild hydrolysis conditions are maintained. This hydrolysis is therefore preferably carried out at temperatures between 0 and 50 ° C. in the presence of the abovementioned amounts of acid.

The a-pyrones are generally cleaved with water or alcohols at temperatures between 20 and 200 ° C. Is preferably carried out in the temperature range between 20 ° C and the boiling point of the alcohol used.

The 3,4-dihydro-a-pyrones used as starting materials can, for. B. are produced by thermolysis of substituted dihydro-5-hydroxymethyl- (3H) -furano-nen (DE-OS 2 952 068).

651 539

example 1

12.6 g of 3,4-dihydro-4,4-dimethyl-a-pyrone were mixed with 9 g of H20 and this mixture was refluxed in the presence of 0.1 g of p-toluenesulfonic acid for 4 hours under nitrogen. Excess water and unreacted starting product were separated by distillation and the residue obtained was recrystallized from carbon tetrachloride. 11.0 g (75.2%) of 4-formyl-3,3-dimethyl-butyric acid (mp. 59 ° C.) were obtained.

Example 2

11.0 g of 3,4-dihydro-4,4-dimethyl-a-pyrone were refluxed with 18.3 g of methanol and 0.1 g of H2S04 (96%) for 4 hours. The methanol was then distilled off. 13.3 g of 4-formyl-3,3-dimethylbutyric acid methyl ester-dimethylacetal were obtained. The crude acetal was stirred for 6 hours with 18 g H20 under N2 at room temperature. Then the org. Phase separated and distilled. The 4-formyl-3,3-dimethylbutyric acid methyl ester distilled at 138 to 140 ° C at 16 • 10-3 bar (yield 7.1 g).

NMR spectrum of 4-formyl-3,3-dimethylbutyric acid methyl ester-dimethylacetal (CC14, 30 MHZ): S = 1.05 (6 H); 1.65 (d, 2H); 2.25 (2H); 3.30 (6H); 3.65 (3H); 4.5 (t, 1H).

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Claims (3)

651 539 2nd PATENT CLAIMS 1. Process for the preparation of formylbutyric acid derivatives of the formula I: HC CH, O , A -CH COOR 2 k3 in which the radicals R1, R2 and R3 represent hydrogen or alkyl groups having 1 to 10 carbon atoms and R4 can be hydrogen or an alkyl radical having 1 to 4 carbon atoms, characterized in that a 3,4-dihydro-a-pyrone Formula II: R 1 R to use starting products that are more easily accessible than the above-mentioned dimethylhexenecarboxylic acid esters. In fulfilling this task, a method 5 for the preparation of formylbutyric acid derivatives of the formula I has now been achieved: COOR 4th [13 in which R1, R2 and R3 represent hydrogen and / or alkyl groups having 1 to 10 carbon atoms and R4 15 is hydrogen or an alkyl radical having 1 to 4 carbon atoms, which is characterized in that a 3,4-dihydro a-pyrone of the formula II: C R " [II] HC \ ^ 0 in which R1, R2 and R3 have the meaning given above, either with water or with an alcohol of the formula III: R4OH (R4 = CM alkyl) (III) and then reacted with water. 2. The method according to claim 1, characterized in that the reaction is carried out in the presence of an acid catalyst. 3. The method according to claim 2, characterized in that Lewis or Brontsted acids are used as acid catalysts. 20th 25th HC CH, H I. -C .COOR ' R 2 13 'R R [I] [II] 30 in which R1, R2 and R3 have the meaning given above, preferably in the presence of acidic substances, either with water or with an alcohol of the formula III: R40H (R4 = C, _4-alkyl) (III)