FR2588862A1 - PROCESS FOR THE PREPARATION OF 2E, 4E-CARBOXYLIC ACIDS - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO A PROCESS FOR PREPARING 2E, 4E-CARBOXYLIC ACIDS. THESE ACIDS CORRESPOND TO GENERAL FORMULA I (CF DRAWING IN BOPI) IN WHICH X REPRESENTS A HYDROGEN ATOM, A HYDROXY OR ALCOXY GROUP IN CA C. APPLICATION: THESE COMPOUNDS ARE USEFUL AS AN INTERMEDIATE FOR THE PREPARATION OF ESTERS OF FORMULA II (CF DRAWING IN BOPI) IN WHICH ESTERS CONSTITUTE EXTREMELY ACTIVE SELECTIVE INSECTICIDES.

Description

The present invention relates to a new and improved process for

  preparation of carboxylic acids of general formula I (1) having a stereoconfiguration 2E, 4E (o X represents a

  hydrogen atom, hydroxy group or C1-C4 alkoxy).

  The compounds of general formula I are useful

  intermediates in the preparation of esters of general formula

  II having a stereoconfiguration 2Z, 2E, 4E (where X is as defined above and R is a group

  saturated or unsaturated straight or branched chain alkyl).

  The esters of the general formula II inhibit the metamorphosis of insects and are extremely selective insecticides.

  assets that do not harm the environment.

  Many processes are described in Art

  prior art, for the preparation of compounds of general formula

  According to UK Patent No. 1,368,266, the compound of the general formula I (where X is hydrogen) is prepared from the dihydrocitronellal of the formula III which is conditioned with a phosphonate anion of the general formula IV lE 0

## STR5 ##

  ## STR2 ## in which R 1 and R 2 are alkyl groups), followed by the mixture of the ester 2E, 4E of the general formula V COOR ((y) and of the ester 2Z, 4E of the general formula VI

OO4 (VI)

/ CO0J

  thus obtained (where R 1 is as defined above) is converted into a mixture of acids of general formulas I and VII

(VII)

COOW

  by alkaline hydrolysis (where X is a hydrogen atom).

  According to this patent, the acids of general formulas I and

  VII are separated by crystallization from the salts of S-

  benzyl isothiorunium. The yield and melting point of the pure acid of general formula I, however, are not indicated in this U.K. Patent. The above process is accompanied by several

  disadvantages. On the one hand, the preparation of the compound of formula

  the general IV is complicated, while on the other hand, the separation of the unsaturated acid 2E, 4E of the general formula I

  and 2Z, 4E acid of the general formula VII depends on the

  steadiness and this significantly decreases the yield.

  According to another process described in this patent, the unsaturated ketone of formula VIII

/ (VIII)

  is treated with a carbanion prepared from a phosphonic ester of the general formula IX iDu Ro o - (IX) ".-1, s-43 -O

00/0

  (Where R and R are as defined above), or with a ilide of general formula X, where R 1 and R 2 are as defined above, then the mixture of unsaturated esters of general formulas V and VI is hydrolysed into a mixture of unsaturated acids of general formulas I and VII (o X

is a hydrogen atom).

  The disadvantage of the above process lies in

  that a mixture of isomers is formed and that the ketone

  turkey of general formula VIII is hardly available.

  According to another process described in this patent, the dihydro-citronellal of formula III is condensed with an acetylide of general formula XI

C% - C 3 C-- R. (XI)

  in which R 3 is a lithium, sodium, potassium or magnesium atom, and the acetylene derivative of formula XII (XII) thus obtained is treated with an ortho ester in the presence of a weak acid as a catalyst for providing an ester of general formula XIII / k4V'N / vc0k COû4 (XIII) (wherein R1 is as defined above), and the product is then converted in an alkaline medium into a mixture of the esters of general formulas V and VI. During this transformation, however, the stereoconfiguration of the C4-C5 double bond is partially modified, and thus the compounds of the general formulas XIV 1COO 4 (XIv) (2Z, 4Z) and XV / "ó00o97, (XV ) (2E, 4Z), which makes the isolation of the compounds of the formula

general V even more difficult.

  The mixture of the acids of general formulas I and VII (where X is a hydrogen atom) is prepared by hydrolysis

  esters of general formulas V and VI.

  The disadvantage of the above method is

  in that a mixture of multi-component isomers is formed

  sants, from which the desired acid of the general formula I (where X is a hydrogen atom) can be isolated, but

complicated way.

  According to UK Patent No. 1,368,267, compounds of general formula I (where X is hydroxy or alkoxy) are prepared by condensing citronellal of formula XVI (XVI) with a phosphonate anion of general formula IV (o R1 and R2 represent an alkyl group), the conversion of the ester mixture 2E, 4E of the general formula XVII

(XVII)

  and ester 2Z, 4E of general formula XVIII

(XVIII)

  COSR (where R1 is as defined above) in a mixture of acid 2E, 4E of general formula XIX COO w (XIX) and of acid 2Z, 4E of formula XX (xx) coou and then the addition of water or alcohol corresponding to these acids to provide a mixture of acids of general formulas I and VII (where X represents a hydroxy or alkoxy group) and the separation of the desired acid 2E, 4E of general formula I to from this mixture. According to another variant of this process, water or the corresponding alcohol is added directly to the mixture of esters of general formulas XVII and XVIII. This gives a mixture of esters of general formulas XXI (xx :) and XXII

(XXII)

  wherein R 3 represents a hydrogen atom or a C 1 -C 4 alkyl group and R 1 is as defined above), which is subjected to an alkaline hydrolysis to provide the mixture of acids of general formulas I and VII (o X represents

a hydroxy or alkoxy group).

  The above process has the disadvantage that, on the one hand, the compounds of the general formula IV are hardly available and that on the other hand the

  Isomeric acid separation is delicate.

  According to another process described in this patent, the unsaturated ketone of formula XXIII is reacted

0 (XXIII)

  with a carbanion prepared from a phosphonic ester of general formula IX or with a ilide of general formula X

'R (0

  then the mixture of esters of general formulas XXIV (xxiv> and XXV cooxp.4 (x (o R1 is as defined above) is hydrolyzed in an alkaline medium into a mixture of acids of formulas XIX and XX, to which add water or the corresponding alcohol to provide a

  mixture of acids of general formulas I and VII (where X represents

a hydroxy or alkoxy group).

  According to another variant of the above process, water or the corresponding alcohol is added to a mixture of esters of general formulas XXIV and XXV and then hydrolyzed.

  in an alkaline medium the mixture of esters of general formulas

  XXI and XXII thus obtained to provide a mixture of acids of general formulas I and VII (where X is a hydroxy group

or alkoxy).

  The disadvantage of this process lies in the formation of the isomeric mixture and the fact that the unsaturated ketone

  of formula XXIII is hardly available.

  According to another method described in this patent, citronellal of formula XVI is condensed with an acetylide of general formula XI (where R 3 represents a lithium, potassium, sodium or magnesium atom), and then the acetylene derivative of formula XXVI is reacted. 1 04 (xxvi) with an ortho ester in the presence of a weak acid as a catalyst, the allenyl ester of the general formula XXVII is treated, where R 1 is as defined. above) in an alkaline medium to give an ester mixture of general formulas XVII

  and XVIII. During this treatment, however, the configuration

  The spatial distribution of the C4-C5 double bond is partially changed and this gives rise to the formation of the esters of the general formulas XXVIII / j. / C0OO'4 (XXVIII) and XXIX

G (XXIX)

  also (o R1 is as defined above).

  The mixture of the acids of general formulas I and VII (where X represents a hydroxyl or alkoxy group) is prepared as described above from the mixture of esters of formulas XVII and XVIII. The disadvantage of the above process is that the desired compound of general formula I (where X is hydroxy or alkoxy) can be isolated and separated from the

  reaction mixture, but in a complex manner.

  According to another process described in this patent, water or the alcohol corresponding to the citronellal of formula XVI is added, then the aldehyde of general formula XXX is reacted.

M (& O 0 (XXX)

  thus obtained (wherein R is a hydrogen atom or an alkyl group) with a phosphonate anion of general formula IV and then the mixture of esters of general formulas XXI and XXII thus obtained is treated in the manner which

is described above.

  According to another method, water or the alcohol corresponding to the unsaturated ketone of formula XIII is added, and then the unsaturated ketone of general formula XXXI is reacted.

0 (XXXI)

  thus obtained (o R3 is as defined above) with a carbanion prepared from a phosphonic ester of general formula IX or with a ilide of general formula X to give a mixture of esters of general formulas XXI and

  XXII which is then treated in the manner indicated above.

  According to U.K. Patent No. 1,409,321, the reaction is

  a ketone of formulas VIII, XXIII or XXXI with an organic salt

  zinc compound prepared from a haloacetate of the general formula XXXII X Cz-OOIR4 (Xxxii) (wherein X is a chlorine or bromine atom and R1 is

  as defined above), then the hydroxide is dehydrated

  ester of general formula XXXIII Cf Z c 001. c 4 (XXXIII) (where Z1 represents a hydrogen atom or -OR3, R3 is as defined above and Z2 is a hydrogen atom or Z1 and Z2 together form a double bond) to obtain a mixture of esters of general formulas V and VI, or XVII or XVIII, or XXI and XXII, respectively, from which the acids of general formula I can be prepared in the manner

indicated above.

  The disadvantage of the above methods lies in the complicated separation of isomeric mixtures and

  the difficult availability of starting ketones.

  According to U.K. Patent No. 3,873,586, the reaction is

  an aldehyde of formulas III, XVI or XXX with a salt of

  lithium of general formulas XXXIVa or XXXIVb LJ-C .CC.-COOLiLiC14-CwCW-COOLi C14LsCg, = C-COOL; Mid-

XX IV c, XXXIm V r.

  the carboxylic acid of the general formula XXXV or COO

(XXXV)

  thus obtained (where R4 is a hydrogen atom and Z1 and z2 are as defined above) to a thermal isomerization to provide hydroxy acids of general formulas XXXVIa and XXXVIb Z c, -

XX XVI o ..

XX'XV b.

  (in which Z 1 and Z 2 are as defined above and R 4 is a hydrogen atom) from which a mixture of the acids of the general formulas I and VII or a mixture of the acids of the general formulas XIX and XX is obtained by dehydration and the compound of general formula I is isolated from these mixtures according to a method described above.

above.

  The above method is accompanied by a number of disadvantages. Thus, a very low temperature (-80 C) is applied, a lithium salt dC it be used and during the dehydration, it can also be formed the unwanted isomers of general formulas XXXVII coda

(XXXVII)

  ## STR2 ## (wherein Z 1 and Z 2 are as defined above and R 4 is a hydrogen atom). The separation and isolation of the desired compounds of general formula I are therefore difficult

and complicated.

  According to another variant of this patent, an aldehyde of general formulas III, XVI or XXX is reacted with a lithium ester salt of general formulas XXXIXa or XXXIXb

C C

LIC 1- CH- Coo%

XXX IX s. XXXIX b.

  (where R1 represents an alkyl group) to obtain a hydroxyl

  ester of the general formula XXXV which is treated in the manner

described above.

  According to another variant of the process above, an aldehyde of general formulas III, XVI or XXX is condensed with a lithium ester salt of general formulas XXXIXa or XXXIXb at -80 ° C., the reaction mixture is heated to provide in situ. a mixture of hydroxy-esters of general formulas XXXVIa and XXXVIb and of lactone of general formula XL o0 2k (XL)

  (wherein z1 and z2 are as defined above).

  The mixture is separated by chromatographic methods.

  The hydroxy esters of the general formulas XXXVIa and-XXXVIb (where R is an alkyl group) are treated and subjected to subsequent reactions as described above, whereas the lactone of the general formula XL is converted into salts of the hydroxy acids of the formulas XXXVIa and XXXVIb (where z1 and z2 are as defined above and R4 is an alkali metal atom), from which the hydroxy acids of general formulas XXXVIa and XXXVIb (o Z1 and Z2 are as defined above and R4 is a hydrogen atom) are obtained by acidification. The acids thus obtained are

  treated as described above.

  The disadvantage of the above methods lies in the use of lithium salts and the separation

  various isomers provided in the reaction.

  According to another process described in this patent, an aldehyde of formulas III, XVI or XXX is reacted with an acrylic ester of general formula XLI (XLI) (where Y is a halogen atom and R1 is an alkyl group) in the presence of zinc, and then the hydroxy-esters of general formulas XXXVIa and XXXVIb are dehydrated to provide a mixture of the esters of general formulas V and VI, or XVII and XVIII, or XXI and XXII, respectively, and these mixtures are treated. converts later as described above. The disadvantage of the above method is that the separation of the various undesired isomers formed during the alien arrangement is complicated.

and depends on the circumstances.

  According to U.K. Pat. No. 3,911,025, an aldehyde of the general formula XXX is reacted with an acetylene derivative of the general formula XI, the hydroxyacetylene derivative of the general formula XLII 0M is treated.

(XLII)

  thus obtained (o R4 is as defined above) with a trialkyl orthoacetate, the allene ester of general formula XLIII is rearranged

01

  (XLIII) thus obtained (where R is as defined above and R1 is an alkyl group) by treating them with hydroxide of

  sodium to provide a mixture of esters of general formulas

  XXI and XXII, and then treat the mixture in the way that

is described above.

  The disadvantage of the above method is that the isolation of the desired compound of general formula I is difficult (where X is hydroxy or alkoxy)

  and that the rearrangement is not stereoselective.

  According to the Soviet Patent No. 727,624, the unsaturated ketone of formula VIII or a ketone of general formula XXXI (where R is as defined above) is reacted with ethoxyacetylene of formula XLIV in the presence of boron trifluoride etherate. , then the mixture of esters of the general formulas II and XLV EtO-CrCH (XLV) is hydrolyzed

(XLIV) COOP

  thus obtained (o X is as defined above and R is

  an alkyl group) to obtain a mixture of

General I and VII.

  The patent does not indicate any method for separating

  the isomeric acids of the general formulas I and VII.

  According to Soviet Patent No. 654,606, the E-

  hydroxy-dihydro-citronellal of formula XLVI Op 0 (XLVI) is treated with a phosphoric ester of general formula IX,

  the reaction mixture is acylated with acetic anhydride.

  There is thus obtained a mixture of an ester of formula XLVII locrus Ck-COo: t,

(XLVII)

and a lactone of formula XLVIII

(XLVIII)

  firstly converted - without prior separation - into a salt formed with potassium tert-butoxide, then treated successively with thionyl chloride and an alcohol to give a mixture of esters of general formulas V and VI, which are hydrolyzed by one of the methods described above to provide a mixture of the acids of the general formulas I and VII (where X is an atom

  hydrogen). There is no description concerning the separation

ration of the mixture.

  According to U.K. Patent No. 1,399,196, an aldehyde of formula III or XXX is condensed with an ester of general formula LVII

O 0 (LVII)

  Embedded image in an alkaline medium, then the dicarboxylic salt of the general formula LVIII (where M is an alkali metal) is acidified to give the dicarboxylic acid. corresponding of general formula LVIII mn M

X COOM (LVIII)

  (where X is as defined above and M is a

hydrogen atom).

  The dicarboxylic acid thus obtained is converted using a tertiary amine in the presence or absence of copper ions or copper son, via a lactone of general formula LIX o

I / \, (LIX)

  (o X is as defined above), in the corresponding acid

of general formula VII.

  The acid of general formula VII thus obtained (where X is as defined above) is treated in a solvent-free medium with diphenyl disulfide, thioacetic acid or thiophenol at a lower temperature in the presence of 2, 2-azo-bis-iso-butyronitrile (radical inducer), or the radical reaction is induced at a higher temperature to give a mixture of the acids, in which the ratio is as follows: I: VII = -65: 40 -35. The radical nature of the reaction is confirmed in a later publication of the Authors / J. Org. Chem. 40, 3 (1975) 7. The sulfur compounds used for radical isomerization and the radical inducer are carefully removed from the reaction mixture to avoid unwanted polymerization reactions, and then the mixture of the acids of general formulas I and VII is dissolved in diethyl ether. , dichloromethane, chloroform

  or hexane and ammonia is introduced into the solution.

  tion, so that the ammonium salt of the desired acid of

  general formula I precipitates as crystalline salt.

  Thus, according to Example 24 of this patent, 130 g of the ammonium salt of general formula I (where X is a methoxy group) is obtained from 242.5 g of an isomeric mixture and this corresponds to a yield of 50.4%. According to this patent, the highest yield is in principle 65% because of the equilibrium of cis: trans isomers which is 65:35 (the value of 50.4% indicated above corresponds to 77.7%

of this balance).

  The most serious drawback of this method lies in the isomerization of the acids of general formula VII. This reaction is carried out in a solvent-free medium at a higher temperature in order to induce

  radicals or in the presence of an inductor of radicals (the 2,2'-

  bis-isobutyronitrile) which contaminates the reaction mixture.

  The removal of the agents used in the isomerization of the radical inducer with Soltrol 130 is particularly disadvantageous because it results in an additional destructive heat load for the highly heat-sensitive reaction mixture (e.g. , decarboxylation reactions, polymerization, oxidation, cleavage of the terminal XH group may take place) and it

  results in a further decrease in yield.

  The object of the present invention is to overcome the disadvantages of the known methods and to provide an improved process for the preparation of the acids of general formula I.

  It has surprisingly been found that the isomeric

  The addition of the acid of the general formula VII to the acid of the general formula I is not a reaction of the radical type; moreover, it can be accomplished in the presence of hydroquinone as a radical trapping agent as well. It follows from this unexpected finding that no free radical is required to induce isomerization, but that it can

  be carried out in a solvent as well.

  So the reaction can be accomplished in

  a temperature range of 0 to 130 C because no inductive

  thermal radicals is not necessary. Recognition

  The non-radical nature of the reaction leads to the practical advantage that not only the acids of the general formula VII but also their alkali metal or ammonium salts undergo isomerization. For the same reason, it is quite disadvantageous to remove the catalyst from the reaction mixture after isomerization,

  since the ammonium salt of the desired acid of general formula

  I separates by precipitating in crystalline form at

  from the equilibrium mixture of acids of general formulas

  I and VII (I: VII = 60-65: 40-35), whereby the ammonium salt of the undesired salt of the general formula VII is enriched in the mother liquor and the presence of the catalyst induces the subsequent isomerization. of it, the yield in

  The desired acid of general formula I is thus increased.

  There is another positive factor in that the reaction mixture

  is not subjected to a thermal treatment carried out to remove the catalyst, so that no undesirable destructive decomposition appears and this increases even further.

the yield.

  The present invention relates to a process for the preparation of the 2E, 4E carboxylic acids of general formula I (where X is a hydrogen atom, a hydroxy group or a C1-C4 alkoxy group) from 2Z, 4E carboxylic acids of formula general VII (where X is as defined above) by isomerization in the presence of a catalyst, which comprises the isomerization of a 2Z, 4E acid of general formula VII (where X is as defined above) or of an alkali metal or ammonium salt thereof in the molten state or in the presence of an inert solvent in the presence of a catalyst comprising a free electron pair and then separating, from the mixture of isomers of the carboxylic acids of the general formulas I and VII or the alkali metal or ammonium salts thereof, the carboxylic acid of the general formula I in the form of an ammonium salt thereof

without removing the catalyst.

  A preferred embodiment of the process of

  The present invention is discussed below.

  The isomerization of an acid of general formula VII (where X is as defined above) or of a metal salt

  alkaline or ammonium content thereof, is carried out in the

  or in a suitable solvent. the solvent used is, for example, an aliphatic or aromatic hydrocarbon (for example, gasoline, hexane, cyclohexane, benzene, toluene), a

  halogenated hydrocarbon (for example, dichloromethane, chloro

  benzene) or an ester or an ether (for example, ethyl acetate,

  butyl acetate) or a polar solvent (preferably water).

  The isomerization of the acid of general formula VII or an alkali metal or ammonium salt thereof may be carried out preferably at a temperature of 0 to 1300C,

preferably from 20 to 100 C.

  The catalyst comprising a pair of electrons

  free may be preferably selected from compounds containing

  sulfur, in particular thiophenol.

  According to a preferred embodiment of the process of the present invention, an acid of general formula VII is isomerized in the molten state by thiophenol as catalyst,

  then the reaction mixture is dissolved in a suitable solvent.

  the catalyst, and the desired acid of general formula I is precipitated from the solution thus obtained in the form of the ammonium salt by introduction.

ammonia gas.

  According to another preferred embodiment of the process of the present invention, the isomerization of the acid of general formula VII is carried out using thiophenol as a catalyst in a solution formed from a suitable solvent, then the acid of the general formula I is precipitated from the solution in the form of an ammonium salt by

introduction of ammonia gas.

  According to another embodiment of the process of the present invention, thiophenol catalyst is added to the solution of the ammonium salt of an acid of general formula VII, so that the ammonium salt of the acid

  of general formula I is precipitated from the solution.

  The process of the present invention offers the following advantages: 1) Since the isomerization is not a reaction of the radical type, as the Applicant has found, it can be carried out both in a solvent serving

of middle.

  2) The reaction can be carried out at a temperature

  also lower, that is to say at room temperature. 3) Not only free acid can be used

  of general formula VII, but also a salt thereof.

  4) It is not necessary to eliminate the catalyst

  isomerization of the reaction mixture.

  Since the isomerization catalyst is present in the reaction mixture throughout the course of

  the reaction, the ratio of I: VII = 65:35 determined by the equi-

  free thermodynamic, can be moved.

  6) The ammonium salt of the desired acid of the general formula I is precipitated while the ammonium salt of the acid of the general formula VII remains in the solution and is subjected to additional isomerization in the presence

isomerizing agent.

  7) As a result of the foregoing, one can increase the theoretical yield of 65% of UK Patent No. 1,399,196 (yields of 50% are shown in the Examples) up to a value as high as 100% in principle. (According to Example 11 of the present invention, the yield

at 75%).

  The following nonlimiting examples illustrate

further the present invention.

Example 1

  Process for the preparation of 11-methoxy-3,7,11-trimethyl-

2E, 4E-dodécadiènoique

  11-Methoxy-3,7,11-trimethyl-2Z, 4E-

  dodecadienoic are added 1 g of thiophenol and the mixture is stirred at 100 C for one hour. The melt thus obtained is cooled and dissolved in 300 ml of ether, the solution is saturated with gaseous ammonia and stirred for one hour, then the precipitated ammonium salt is filtered off. The ammonium salt thus obtained is added to a mixture of a solution of 16 g of concentrated sulfuric acid, 63 ml of water and 300 ml of toluene. The mixture is stirred at 25 ° C. until the ammonium salt is dissolved. The phases are separated, the organic layer is washed three times with 50 ml

  of water each time and the solvent is distilled off. 53 g of the desired compound are thus obtained with a yield of 53% and a

  96.8% purity (chromatography in phase

gas).

Example 2

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

dodécadiènoique

  The procedure is as described in the Exem-

  1, except that after cooling, the melt is dissolved in cyclohexane in place of the ether. 54 g of the desired compound resembling honey are thus collected with a yield of 54% and a purity of 97% (chromatography

in the gas phase).

Example 3

  Preparation of 11-hydroxy-3,7,11-trimethyl-2E, 4E-

  dodecadienic The procedure of Example 1 is followed, except that

  11-hydroxy-3,7,11-trimethyl-2Z, 4E-dodecanate is used

It is used as a starting material and the isomers are separated after isomerization using dichloromethane instead of ether. Thus, 55 g of the desired honey-like compound was recovered with 85% yield and purity.

  97.8% (gas chromatography).

Example 4

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 1 is followed except that the melt is dissolved, after cooling, in toluene instead of ether. 54 g of the desired compound are thus collected in a yield of 54% and a purity of

  96.8% (gas chromatography).

Example 5

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 4 is followed except that the reaction mixture is stirred at 30 ° C. for 3 hours instead of 1 hour. 61 g of the desired compound are thus collected.

  with a yield of 61% and a purity of 97.2% (chromato-

gas phase graph).

Example 6

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  dodecadienic The procedure of Example 5 is followed except that after

  cooling, the melt is dissolved in acetylene

  ethyl acetate instead of ether. 60 g of the desired compound resembling honey are thus collected with a yield of

  %. Purity of 97.9% (gas chromatography).

Example 7

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

dodécadiènoique

  11-Methoxy-3,7,11-trimethyl-2Z, 4E-

  dodecadienoic are dissolved in 300 ml of cyclohexane, then 2 g of thiophenol are added. The reaction mixture is stirred at 20 ° C. for one day, the solution thus obtained is saturated with gaseous ammonia at 25 ° C. and stirred for additional hours. The ammonium II-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate thus precipitated is filtered and treated as indicated in Example 1. 67 g of the desired compound are thus collected in a yield of 67% and

  a purity of 98.7% (gas chromatography).

Example 8

  Preparation of 11-methoxy-3,7,1i-trimethyl-2E, 4E-

  The procedure of Example 7 is followed except that ethyl acetate is used in place of cyclohexane as a solvent. 66 g of the honey-like compound are thus collected with a yield of 66% and a purity of 98.5%.

(gas chromatography).

Example 9

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 8 is followed except that 2 g of hydroquinone is used in addition to 2 g of thiophenol. 67 g of the desired compound resembling honey are thus collected with a yield of 67% and a purity of 98% (chromatography

in the gas phase).

Example 10

  Preparation of 3,7,11-trimethyl-2E, 4E-dodecadienoic acid The procedure of Example 7 is followed except that 100 g of 3,7,11-trimethyl-2Z, 4E-dodecadienoic acid is used as the material. starting and the isomerization is carried out at 800C for 4 hours. 63 g of the compound are thus collected.

  resembling honey with a purity of 97.8% (chromato-

gas phase graph).

Example 11 -

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 7 is followed except that the cyclohexane is replaced by toluene and the reaction mixture is stirred under a slight overpressure of ammonia for 12 hours rather than for 5 hours. Thus, 75 g of the desired honey-like compound is collected with a yield of 75% and a purity of 99.1% (gas chromatography).

Example 12

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  dodecadienic The procedure of Example 7 is followed, except that the

  cyclohexane is replaced by toluene and isomerisation

  It is carried out at 100 ° C. for 2 hours. 63 g of the desired compound are thus collected in a yield of 63% and

  a purity of 97.9% (gas chromatography).

Example 13

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 7 is followed except that the cyclohexane is replaced by ethyl acetate and

  that isomerization is carried out at 100 C for 2 hours.

  61 g of the desired honey-like compound are thus collected with a yield of 61% and a purity of 98.7%.

(gas chromatography).

Example 14

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 7 is followed except that the cyclohexane is replaced by ethyl acetate. 68 g of the desired compound are thus recovered with a yield of 68% and a purity of 99.3% (chromatography in phase

gas).

Example 15

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  Dodecadienoic The procedure of Example 7 is followed except that the cyclohexane is replaced by dichloromethane. 64 g of the desired compound resembling honey are thus collected with a yield of 64% and a purity of 98.3% (chromatography

in the gas phase).

Example 16

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoic acid

  11-Methoxy-3,7,11-trimethyl-2Z, 4E-

  dodecadienoic are dissolved in 300 ml of cyclohexane, the solution is saturated with ammonia, 5 g of thiophenol are added and the mixture is stirred at 20 C for 2 days under a slight overpressure of ammonia. The precipitated ammonium salt is filtered off and then treated in the same manner as described in Example 1. 53 g of the desired honey-like compound are thus recovered with a yield of

  53% and purity of 97.6% (gas chromatography).

Example 17

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  dodecadienic The procedure of Example 16 is followed except that

  cyclohexane is replaced by toluene and isomerisation

  This is done for 3 days instead of 2 days. 60 g of the desired compound are thus collected in a yield of 60% and a purity of 98.2% (gas chromatography).

Example 18

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  Dodecadienoic The procedure of Example 16 is followed except that the cyclohexane is replaced with ether. 48 g of the desired compound resembling honey are thus collected with a yield of 48% and a purity of 98% (chromatography

in the gas phase).

Example 19

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  The procedure of Example 16 is followed except that the cyclohexane is replaced by dichloromethane. 47 g of the desired compound resembling honey are thus collected with a yield of 47% and a purity of 97.9% (chromatography

in the gas phase).

Example 20

  Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-

  dodecadienoic 2 g of thiophenol are added to a solution of 108.5 g of 11-methoxy-3,7,11-trimethyl-2Z, 4E-dodecadienoate

  of sodium and 300 ml of water and the reaction mixture is stirred

  at 20 C for one day. the pH is adjusted to 2 by the addition of 20% sulfuric acid. The mixture is extracted twice with 150 ml portions of cyclohexane, the organic layer is washed three times with 1 ml portions of water and the solution is saturated with ammonia. The mixture

  The reaction is treated in the manner described in

  7. This gives 56 g of the desired honey-like compound with a yield of 56% and a purity of 98.4%.

(gas chromatography).

Claims (7)

  1) Process for the preparation of the 2E, 4E carboxylic acids of general formula I (in which X represents a hydrogen atom, a hydroxyl group or a C1-C4 alkoxy group) starting from the 2Z, 4E carboxylic acids of general formula VII ( VII)   (where X is as defined above) by isomerization   in the presence of a catalyst, which comprises the isomerization of a 2Z, 4E-carboxylic acid of general formula VII (where X is as defined above) or an alkali metal or ammonium salt of that in the molten state or in the presence of an inert solvent, in the presence of a catalyst comprising a pair of free electrons and then the separation, from the mixture of isomers of the carboxylic acids of general formulas I and VII or alkali metal or ammonium salts thereof, the carboxylic acid of general formula I in the form of the ammonium salt thereof, without removal of the catalyst.   2) Process according to claim 1, which comprises   takes the achievement of isomerization in an aliphatic or aromatic hydrocarbon, a halogenated hydrocarbon, an ester or an ether.   3) Process according to claim 2, which comprises   takes the achievement of isomerization in toluene, cyclohexane, dicoromethane, diethyl ether,   ethyl acetate or water.   4) Process according to any one of the claims   1 to 3, which comprises precipitating the ammonium salt of the carboxylic acid of general formula I in the same   solvent that is used in the isomerism reaction.   tion. A process as claimed in any one of claims 1 to 4 which comprises using a sulfur-containing compound comprising a pair of free electrons as a catalyst. The method of claim 5, which comprises   the use of thiophenol as a catalyst.   7) Process according to any one of the claims   1 to 6, which comprises performing the isomerization to   presence of an agent trapping radicals.   The method of claim 7, which comprises using hydroquinone as a scavenger. radicals.   9) Process according to any one of the claims   1 to 8, which comprises carrying out the reaction at a temperature between 0 and 100 C, preferably between 20 and 1000 C. 10) A method according to claim 9, which comprises   carrying out the reaction at 20-30 C.