GB2111054A

GB2111054A - Preparation of formyl-butyric acid derivatives

Info

Publication number: GB2111054A
Application number: GB08234520A
Authority: GB
Inventors: Hans-George Schmidt
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1981-12-05
Filing date: 1982-12-03
Publication date: 1983-06-29
Also published as: JPS58105942A; DE3148155A1; GB2111054B; FR2517669B1; DK525582A; CH651539A5; FR2517669A1

Abstract

Formyl-butyric acids of the general formula <IMAGE> wherein R<1>, R<2> and R<3> stand for hydrogen and/or alkyl groups with 1 to 10 carbon atoms and R<4> is hydrogen or an alkyl residue with 1 to 4 carbon atoms and their dialkyl ester acetals in which the alkyl groups are the same as esterifying group R<4> are produced by ring opening of 3,4-dihydro- alpha -pyrones of the general formula <IMAGE> wherein R<1>, R<2> and R<3> have the aforesaid meanings in the presence of water, an alcohol or an alcohol and water used simultaneously or subsequently, according to the character of the reaction product to be obtained. The dialkyl acetals are novel substances.

Description

SPECIFICATION Process for the preparation of formyl-butyric acid derivatives This invention relates to the preparation of formyl-butyric acid derivatives of the general formula

wherein R1, R2 and R3 are alkyl groups containing from 1 to 10 carbon atoms and R4 is hydrogen or an alkyl group containing from 1 to 4 carbon atoms, and dialkyl acetal derivatives of esters within said general formula. The alkyl-substituted formyl-butyric acid ester-dialkyl acetals obtainable by the process of the present invention are novel substances.

Alkyl-substituted formyl-butyric acid esters are described for example in German Offenlegungsschrift No.

28 10 031. These esters find use in the preparation of pest control agents based on substituted hexene carboxylic acid esters. The preparation of these esters is described in the indicated Offenlegungsschrift in which it is stated in particular that these formyl-butyric acid esters required as intermediate products in the production of pest control agents can be obtained by ozonolysis of the corresponding 3,3-dialkyl-hexene-5carboxylic acid esters. The process described there has the disadvantage of requiring additional special apparatus and it is carried out with starting compounds whose production is likewise very expensive.

According to one aspect of this invention, there is provided a process for the preparation of a compound of the general formula

in which R1, R2 and R3 which can be the same or different stand for hydrogen and/or alkyl groups with 1 to 10 carbon atoms and R4 is hydrogen or an alkyl residue containing 1 to 4 carbon atoms, in which a 3,4-dihydro-a-pyrone of the general formula

in which R1, R2 and R3 have the above-indicated meaning is reacted with water, with an alcohol of the formula R40H wherein R4 is alkyl containing 1 to 4 carbon atoms in the presence of water or with a said alcohol followed by reaction with water under conditions sufficiently mild to avoid hydrolysis of the ester group of the said compound which has been formed.

This invention also provides according to a second aspect a variant of the first aspect wherein, when ring opening of the a-pyrone is carried out using an alcohol, reaction with water is omitted and the aforementioned dialkyl acetal which is itself a novel substance is obtained in the reaction mixture from which it may be isolated by fractional distillation.

The ring splitting to which the dihydro-a-pyrones are subject, whether operating in accordance with the first or the second aspect of the invention preferably takes place in the presence of acid compounds. Lewis and Brönsted acids are preferably used for this purpose. Examples of Lewis acids which may be used are AlCI2, ZnCl2, BF3 and FeCI3. Brönsted acids which may be used include H2S04, H3P04, p-toluenesulphonic acid and trichloro-acetic acid, and acid ion exchangers.

The amounts of the acid compounds which are employable may be varied within wide limits. Amounts of 0.0001% by weight related to the a-pyrone already show a catalytic effect. In general, however, amounts of from 0.001 to 0.1% by weight related to the a-pyrone are employed.

If water is present as a reaction partner, the substituted formyl-butyric acid is obtained directly. If, in contrast, water is absent and an alcohol is present as sole reaction partner, the above-indicated dialkyl acetal of the substituted formyl-butyric acid ester is obtained. The acetal residues and the ester residue (designated by R4 in the above-indicated formula) will therefore be like residues. If the acetal is not to be isolated, it may be converted in known manner into the corresponding formal by treatment with water. In the hydrolysis of the acetal into the formal, the ester grouping generally remains on the carboxylic acid residue if mild hydrolysis conditions are adhered to. Hence hydrolysis is preferably carried out at temperatures of from 0 to 50"C as well as in the presence of the above-indicated amounts of acid.

The ring splitting of the a-pyrones with water or alcohols generally takes place at temperatures in the range of from 20 to 200"C. It is preferred to work in the temperature region between 20"C and the boiling point of the water, alcohol or water/alcohol mixture which is employed.

The 3,4-dihydro-cr-pyrones employed as starting materials can be prepared for example by thermolysis of substituted dihydro-5-hydroxymethyl-(3H)-furanones as described in German Offenlegungsschrift No. 29 52 068.

The following Examples illustrate this invention.

Example 1 12.6 g of 3,4-dihydro-4,4-dimethyl-a-pyrone were mixed with 9 g of water and the mixture obtained was boiled under reflux and a nitrogen atmosphere in the presence of 0.1 g of p-toluenesulphonic acid for four hours. Excess water and unreacted starting material were separated off distillatively and the residue obtained was recrystallised from carbon tetrachloride. 11.0 g (75.2%) of 4-formyl-3,3-dimethyl-butyric acid (melting point 59"C) were obtained.

Example 2 11.0 g of 3,4-dihydro-4,4-dimethyl-a-pyrone were boiled under reflux for four hours with 18.3 g of methanol and 0.1 g of H2SO4 (96%). Unreacted methanol was then distilled off and 13.3 g of 4-formyl-3,3-dimethyl-butyric acid methyl ester-dimethyl acetal obtained were isolated. The crude acetal was stirred for 6 hours with 18 g of H20 under an atmosphere of nitrogen at ambient temperature. Then the organic phase was separated off and distillation was carried out. The 4-formyl-3,3-dimethylbutyric acid methyl ester thus obtained distilled over at 138 to 140"C at 16 x 10-3 bar (yield 7.1 g).

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

Claims

1. A process for the preparation of a compound of the general formula:

in which R', R2 and R3 have the above-indicated meaning is reacted with water, with an alcohol of the formula R40H wherein R4 is alkyl containing 1 to 4 carbon atoms in the presence of water or with a said alcohol followed by reaction with water under conditions sufficiently mild to avoid hydrolysis of the ester group of the said compound which has been formed.

2. A process for the preparation of an acetal of the general formula

wherein R', R2 and R3 which can be the same or different stand for hydrogen and/or alkyl groups containing 1 to 10 carbon atoms and R4 stand for alkyl containing 1 to 4 carbon atoms, which comprises reacting a 3,4-dihydro-a-pyrone of the general formula

in which R1, R2 and R3 have the above-indicated meaning with an alcohol of the formula R40H wherein R4 has the above-indicated meaning.

3. A process as claimed in claim 1 or 2, in which reaction is carried out in the presence of an acid catalyst.

4. A process as claimed in claim 3, wherein the acid catalyst is a Lewis or a Brönsted acid.

5. A process as claimed in claim 4, wherein the Brönsted acid is p-toluene sulphonic acid.

6. A process as claimed in any one of claims 3 to 5, wherein the acid catalyst is employed in an amount of from 0.001 to 0.1% by weight related to the a-pyrone.

7. A process as claimed in claim 1 or any one of claims 3 to 6, wherein reaction of said ester with water takes place at a temperature in the range of from 0 to 50"C.

8. A process for the preparation of a formyl-butyric acid derivative, substantially as described in either of the foregoing Examples 1 and 2.

9. A process for the preparation of an acetal of a formyl-butyric acid, substantially as described in the foregoing Example 2.

10. An alkyl substituted 4-formyl-butyric acid alkyl ester acetal of the formula

wherein R1, R2 and R3 which can be the same or different stand for alkyl residues with 1 to 10 carbon atoms and all of the radicals R4 stand for the same alkyl residue, being an alkyl residue containing from 1 to 4 carbon atoms.