DE1276021B - Process for the preparation of ª ‡, ª ‡ '-tetrasubstituted AEtherdicarboxylic acids, their mononitriles, esters or salts - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C 07c

German class: 12 ο -11

Number: 1276 021

File number: P 12 76 021.3-42 (L 50820)

Filing date: May 31, 1965

Opening day: August 29, 1968

The invention relates to the preparation of α, α'-tetrasubstituted Ether dicarboxylic acids and their derivatives. α, α'-tetrasubstituted oil dicarboxylic acids and the corresponding a-mononitrile-a'-monocarboxylic acid ethers form esters that are difficult to saponify and serve as intermediates that were previously difficult to access for the production of polyesters and polyamides, formaldehyde resins, α-oxycarboxylic acid and their esters, which in turn are valuable starting materials for the production of methacrylic acid, ίο represent their higher homologues and esters.

The invention relates to a process for the production of α, α'-tetrasubstituted ether dicarboxylic acids, its mononitriles, esters or salts, which is characterized in that a-oximation products of 2,2,5,5-tetrasubstituted 4-oxotetrahydrofurans of the general formula

HON = C

(3)

(4)

CO

(D -O'

in which R ¹ , R ² , R ³ , R ^{4 are} alkyl radicals, are treated with an inert or reactive solvent which dissolves the oximation product in the presence of equimolecular amounts of basic agents.

Such oximation products are obtained by reacting the corresponding «, a'-tetrasubstituted 4-Oxotetrahydrofurans made with nitrous acid or its derivatives. (Bulletin de la Societe Chimique de France [1947] pp. 693 to 699).

Carboxyl and / or nitrile groups which have a dissolving effect on the oximation product inert agents are organic solvents with a boiling point above 75 ° C; z. B. aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, gasoline, higher ketones, ζ. Β. Methyl ethyl ketone; Carboxamides, ζ. Β. Dimethylformamide, α, α'-dicarboxamide diisopropyl ether or pyridine and homologues.

Carboxyl and / or nitrile groups which have a dissolving effect on the oximation product reactive agents which react with the named groups with saponification or esterification can, are z. B. water or mono- or polyhydric alcohols with a saturated or unsaturated one Hydrocarbon radical, which can be aliphatic or aromatic.

Process for the preparation of α, α'-tetrasubstituted ether dicarboxylic acids, their Mononitriles, esters or salts

Applicant:

LONZA A. G., Basel (Switzerland)

Representative:

Dr. G. W. Lotterhos

and Dr.-Ing. H. W. Lotterhos, Patent Attorneys, 6000 Frankfurt, Annastr. 19th

Named as inventor:

Dr. Theodor Völker,

Klaus Hering, Friborg (Switzerland)

Claimed priority:

Switzerland of June 12, 1964 (7699)

The basic agents used are saponification, esterification or transesterification catalysts, such as alkali or alkaline earth hydroxides, oxides, alcoholates, for use.

The type and amount of the catalyst to be used depends on whether the first to be formed Mononitrile monocarboxylic acid is to be isolated or whether its conversion into its corresponding derivatives carried out by reaction of the carboxyl and / or nitrile group in the same reaction medium shall be. If the mononitrile monocarboxylic acid is to be isolated, it is advisable to proceed as follows: that the starting product in an inert solvent, e.g. B. toluene, or one opposite the Carboxyl and / or nitrile group reactive solvents, such as alcohol or water, distributed and an alkali hydroxide is used as a catalyst. It is expedient for each mole of oxime 1 mole of alkali hydroxide is used. In addition to its effect as a catalyst, the alkali hydroxide also serves at the same time as a stabilizer for the mononitrile monocarboxylic acid, which can be isolated as an alkali salt. It should be noted that after completed Annular cleavage the salt bath must be isolated. When the salt is formed in the reaction medium left, the corresponding dicarboxylic acid is formed by hydrolysis of the nitrile group.

809 598/577

The time at which the ring cleavage has ended is indicated by the start of ammonia evolution. In water as the solvent, the end of the reaction is indicated by a color change from intense red to yellow. '.

The preparation of the a-oximation products of 2,2,5,5 - tetrasubstituted 4 - oxotetrahydrofurans can in a known manner by adding 2 mol Ketone to 1 mole of acetylene, rearrangement of the resulting tetrasubstituted hexynediol in the presence of soluble mercury (II) catalysts into the water-insoluble 2,2,5,5-tetrasubstituted 4-oxotetrahydrofuran and finally by its a-oximation with nitrous acid, its esters, chlorides or Anhydrides.

The known preparation of the α-oximation product and its further implementation according to the invention can also be carried out in the same reaction vessel be carried out (see. Example 2).

The formulaic sequence of the process is reminiscent of the well-known "Beckmann rearrangement", which leads from ketoximes to substituted carboxamides (H Ό üben - Weyl, "Methods of Organic Chemistry", 4th edition, Vol. VIII [1952], p. 669 bis 671). In the practical implementation of the "Beckmann rearrangement" on the one hand and the method of the invention on the other hand, one encounters essential differences between the two reactions. To trigger the "Beckmann rearrangement", strongly acidic or acidic substances such as H ₂ SO ₄ , SO ₃ , P ₂ O ₅ , SOCl ₂ , PCl _{5 are} required. Under the action of the acids mentioned, cations are formed from the oximes and, after the elimination of water, the "Beckmann rearrangement" is carried out. Completely contrary to these results is the fact that in the case of the process according to the invention not only can the use of acids be dispensed with, but also with strong alkalis in excess a substantial acceleration of the reaction is achieved and high yields of the desired reaction products are achieved.

The new process is limited to the oximation products, which are yellow crystals 2,2,5,5-tetrasubstituted 4-oxotetrahydrofurans as starting compounds. Are the analogously a-oximated tri-, di-, monosubstituted or unsubstituted 4-oxotetrahydrofurane conditions subject, in which the new procedure runs smoothly, one arrives not or with hardly recognizable Yields of the corresponding mononitrile monocarboxylic acids and their derivatives. For the new procedures seem to be the particular steric ones

example 1

0.3 moles of 4-nitroso-2,2,5,5-tetramethyl-4-oxotetrahydrofuran with the equimolar amount of 25% potassium hydroxide solution in the cold in the corresponding Transferred to the potassium salt of the oxime. The intense red aqueous solution of the oxime salt is heated to boiling under reflux. After about 10 to For 15 minutes, the completed rearrangement is shown by a sharp change in the color of the Reaction solution clearly recognizable from intense red to pale yellow. It is immediately cooled. Then the reaction solution is shaken out with ether to remove impurities and the aqueous layer slowly mixed with the equimolar amount of hydrochloric acid while cooling. For isolation the carboxylic acid is shaken out again with ether and the dried essential extract evaporated in the cold in a weak vacuum. There are 41.5 g of a-nitrile-a'-carboxylic acid diisopropyl ether obtained, which corresponds to a yield of 81% of theory. This crude product melts at 69 to 71'C and corresponds to its Purity meets most requirements (acid number found 327, calculated 328). With recrystallizations Significant losses (up to 60%) occur due to the formation of secondary products. Obtained from gasoline an acid with the following data:

Acid number: found 330, calculated 328; N: found 8.25%, calculated 8.18%; Q: 72.5 ⁰ C.

By reacting the potassium salt of this monocarboxylic acid mononitrile with excess dimethyl sulfate in a benzene-aqueous slurry at the boiling point the diisopropylether nitrile-a'-carboxylic acid methyl ester becomes obtained as a colorless liquid. This connection has the following metrics:

Saponification number: found: 575, calculated: 605; Refractive index at 20 ⁰ C: 1.4262; Boiling point at 0.3 to 0.4 mm: 38 to 40 ⁰ C.

Example 2

For the representation of the starting material 4-nitroso-2,2,5,5-tetramethyl-4-oxotetrahydrofuran, which is not claimed, 0.2 mol of 2,2,5,5-tetramethyl-4-oxotetrahydrofuran with 0.22 mol of amyl nitrite are added with stirring 40 to 50 ⁰ C implemented in the presence of 7.5 ml of concentrated hydrochloric acid. Over 65% of the theoretical amount of α-oximation product already precipitates during the reaction. This can be recrystallized from dimethyl ether

Relationships with the a-oxotetrahydrofurans the

essential prerequisite to be that a levy 55 den (F. 127 ° C; N: found 8.07%, calculated 8.18%).

tion from the fully substituted 5-ring When adding 1 mol of the reaction mixture

Oxygen compounds in the apparently more relaxed open-chain or 6-membered compounds favor. This is also an essential difference to the well-known "Beckmann rearrangement", after the technical rearrangement of the 6-membered cyclohexanone oxime to the 7-membered caprolactam he follows.

The ether compounds obtainable by the process of the invention can be separated by cleavage of the Convert ether bond with concentrated acids into the correspondingly substituted a-oxycarboxylic acids.

30% aqueous sodium hydroxide solution immediately causes ring splitting. Becomes the formed mononitrile monocarboxylic acid not immediately isolated as in Example 1, but left in the reaction medium, occurs a strong ammonia development. With water vapor and with warming it is descending over a The ammonia released and the amyl alcohol resulting from the oximation cooler expelled. The reaction mixture is colored reddish brown at the moment the alkali is added brightens up during implementation. The reaction is complete as soon as the distillate has been reduced to ammonia

poor. For conversion of the sodium salt of Ätherdicarbonsäure in the free acid is neutralized with concentrated hydrochloric acid at about 90 ⁰ C gradually with a total of 1 mole of HCl. Rapidly the α, α'-Dicarbonsäurediisopropyläther theory crystallized from the now slightly yellow-colored reaction solution as a colorless product in a yield of about 80% and is extracted with hot 6O ⁰ C. The acid can be freed from the enclosed alkali metal chloride by recrystallization from water or benzene or by washing with water. Their melting point is 158 ° C.

Acid number: found 580, calculated 590;
C: found 50.5%, calculated 50.5%;
H: found 7.4%, calculated 7.4%;
N content: 0.03%.

If instead of caustic soda the corresponding amount of caustic potash solution with a concentration of approx 40% is used, the yield of dicarboxylic acid increases to just under 90% of theory.

The corresponding ether dicarboxylic acids are obtained with at least as good yields when using more highly substituted a-Oximierungsprodukien, such. B. from the a-oximation product of 2,5-dimethyl-2,5-diethyl-4-oxotetrahydrofuran the corresponding α, α'-dicarboxylic acid secondary butyl ether. It melts at 151 ⁰ C.

Claims (1)

Claim: Process for the preparation of α, α'-tetrasubstituted Ether dicarboxylic acids, their nitriles, esters or salts, characterized in that that a-oximation products of 2,2,5,5 - tetrasubstituted 4 - oxotetrahydrofurans the general formula HON = C, (3) St. CO in which R ¹ , R ² , R ³ , R ^{4 are} alkyl radicals, are treated with an inert or reactive solvent which dissolves the oximation product, in the presence of equimolecular amounts of basic agents. 809 SM / 577 8.68 O Bundesdruckerei Berlin