CS266596B2 - Method of unsaturated carboxyl acid's esters production with 2e, 2z stereoconfiguration - Google Patents

Abstract

Unsaturated carboxylic acid esters <IMAGE> having a 2E,4E stereoconfiguration (wherein X stands for hydrogen, C1-4 alkoxy or hydroxy and R represents C1-4 alkyl), may be prepared by reacting a salt <IMAGE> (wherein M stands for a metal ion or an ammonium ion substituted by one or more alkyl and/or aralkyl group(s) and X has the same meaning as stated above) with an alkyl halide R-Y (wherein Y stands for halogen and R is as stated above) in a polar solvent. The process provides end-products free of isomers in excellent yields, and is readily feasible on an industrial scale. The compounds of the general Formula I are known insecticides.

Description

The present invention relates to a novel and improved process for the preparation of unsaturated carboxylic acid esters of the stereoconfiguration 2E, 2Z of formula I wherein:

is hydrogen or (C 1 -C 4) alkoxy and is (C 1 -C 4) alkyl.

The unsaturated carboxylic acid esters of the stereoconfiguration 2E, 2Z of the general formula I, in which R and X are as defined above, are known selective insecticides which are highly effective and are based on a novel mechanism of action. Said known compounds inhibit the insect metamorphosis and are suitable insecticides because they do not have harmful effects on the environment.

A number of methods are known for the preparation of the compounds of formula (I).

According to British Patent No. 1,368,266, esters of formula I wherein X is hydrogen and R is C1 -C4 alkyl are prepared from the starting dihydrocitronellal of formula II

This starting material is reacted with a phosphonate anion of formula III

(III), in which it has the meaning given above, and

R

represents an alkyl group, to form a mixture of esters of formulas I and IV

(IV), wherein they are as defined above.

This method has serious drawbacks. On the one hand, the phosphonate anion of formula III is difficult to separate, and on the other hand, the synthesis of the 2E, 4E ester of formula I produced with the isomeric 2Z, 4E ester of formula IV is obtained. Separation of the two isomers is difficult and significant losses occur.

CS 266 596 B2

According to another method described in said British patent specification, an unsaturated ketone of formula V (V) is reacted with a carbanion prepared from a phosphoric acid ester of formula VI

0

II II

P-CH-C-OR (VI)

in which

R @ ¹ and R @ ¹ are as defined above, or with an ylide of formula (VII) (VII) wherein

R and R ¹ are as defined above.

Said reaction yields a mixture of the ester (I) to be produced with an isomeric ester (IV).

This process has the same drawbacks as the previous process, i.e. separating the individual isomers from their mixture is difficult. Another drawback is that the unsaturated ketone of formula V is difficult to sever.

According to another method described in British Patent Specification No. 1,368,266, dihydrocitronellal of formula II is condensed with acetylide of formula VIII

CH ₃ -CeC-R ² (VIII) wherein

means lithium, sodium, potassium or magnesium, the resulting acetylene derivative of formula IX

OH is converted to the allene ester of formula X

COOR (IX) in which

CS 266 596 B2 has the above meaning.

the ortho-ester double bonds in the presence of a weak acid catalyst, whereupon the resulting product is converted to a mixture of isomeric esters of formulas I and IV in which X is hydrogen and R is as defined above. During the transformation, the spatial configuration Сд-С ^ is partially changed, thus also forming esters of formulas XI (2E, 4Z) and XII

(XI) (XII) (2Z, 4Z).

hydrogen; and

This makes the isolation of the pure ester of formula R as defined above substantially more difficult.

I, in which

X stands for

According to British Patent No. 1,368,267, esters of the general formula are hydroxyl or alkoxy and R is as defined above, of formula XIII

I, in preparing from which

X is citronellal

(XIII).

Citronellal is condensed with the phosphonate anion of formula III to give a mixture of the 2E, 4E ester of formula XIV

(XIV), wherein it is as defined above, with the 2Z, 4E ester of formula XV

(XV),

COOR as defined above, followed by the addition of water or an appropriate alcohol. This gives a mixture of isomeric esters of formulas XVI

(XVI) and XVII

CS 266 596 B (XVII)

COOR in which

R is as defined above and

R ³ is hydrogen or C 1 -C 4 alkyl.

The above-described method has several disadvantages. On the one hand, phosphonic acid esters are difficult to obtain, and on the other hand, the separation of the resulting mixture of isomers is difficult and complex.

According to yet another method described in said British patent specification, an unsaturated ketone of formula XVIII '

(XVIII) is reacted with a carbanion prepared from a phosphonic acid ester of formula (VI) or an ylide of formula (VII) to give a mixture of isomeric esters of formulas (XIV) and (XV), followed by addition of water or an appropriate alcohol as described above. This gives a mixture of isomeric esters of formulas I and IV in which X is a hydroxyl or alkoxy group and R is as defined above.

The disadvantage of this method is the difficult availability of the unsaturated ketone of formula XVIII and the distribution of the resulting mixture of isomers.

According to yet another method described in said formula (XIII), it is condensed with an acetylide of formula (VIII), acetylene of formula (XIX) rather than citrellellal to form the derivative formed

(XIX) acts with an orthoester in the presence of a weak acid as ester of formula (XX) of the catalyst.

The resulting allen

COOR (XX) in which it is as defined above is converted into a mixture of isomeric esters of formulas XIV and XV under basic conditions.

In the course of the transformation, however, the spatial configuration of the C _{4 -} C ₅ double bond is partially altered, thereby also forming the isomeric esters of formulas XXI.

COOR (XXI) and XXII

CS 266 596 B2 (XXII) in which

COOR is as defined above.

A disadvantage of the above-described process is that the ester of formula (I) produced can be obtained from said mixture of isomers only by a complex and difficult process.

According to yet another process described in said patent, water or the corresponding alcohol is added to the citricellal of formula XIII, followed by the aldehyde of formula XXIII thus obtained.

(XXIII), in which it is hydrogen or an alkyl group, is condensed with a phosphonate anion of formula III to give a mixture of isomeric esters of formulas XVI and XVII.

The disadvantages of the above-described process are similar to the disadvantages of the aforementioned processes, namely the complex separation of the mixture of isomers.

According to British Patent No. 1,409,321 a ketone of formula V or XVIII or XXIV is allowed

(XXIV), in which it has the foregoing, to react with an organometallic zinc salt prepared from a haloacetate of formula XXV

x-ch ₂ -coor (XXV), in which R is as defined above, and X means chlorine or bromine, and arose hydroxy ester XXVI zkl 1 .COOR (XXVI) of ² < ) H

in which

CS 266 596 B2

is as defined above and is hydrogen or -OR ³ , wherein R ³ is as defined above and is hydrogen, or together form a double bond, is hydrated to form a mixture of esters of formulas I and IV, XIV and XV or XVI and XVII.

This method is characterized by similar drawbacks to the previously mentioned methods, namely the difficult availability of the starting ketone compound and the difficult separation of the mixture of isomers obtained.

According to U.S. Pat. No. 3,873,586, esters of formula I may be prepared by reacting an aldehyde of formula II or XIII or XXIII with a dilithium salt of formula XXVII or XXVIII. i “ ³

Li-CH ₂ -C = CH-COOL 1

Г ³

CH ₂ = C-CH-COOLi Li (XXVII) (XXVIII), whereupon the resulting carboxylic acid of formula XXIX is formed

COOR ⁴ (XXIX), from ^{1 to 2} are as defined above and is hydrogen, isomerized, the resulting product is dehydrated to form a mixture of acids of formulas XXX and XXXI in which:

(XXXI), as defined above, which is then reacted sequentially with thionyl chloride and an alcohol to give a mixture of esters of formulas XXXII.

of ¹ of ² 1 XOOR ^Z V ^{/ 2} k AND AND 1 Ί of ² 1 COOR

(XXXII) and XXXIII (XXXIII),

CS 266 596 B2 has the meaning given above.

deficiencies. It is operated at a very low temperature (-80 ° C), during the dehydration is the possibility of formation of undesirable in which

Z ¹ , Z ² and R

The above-described process has several uses of the lithium salt and in addition

(XXXIV) (XXXV)

Z ¹ and Z ² are as defined above and are hydrogen which are esterified to the undesired esters of formulas XXXIV and XXXV, in which Z ¹ and

4

Z is as defined above and R is C1-C4alkyl. This makes it even more difficult to isolate the produced ester of formula (I) from the reaction mixture.

According to another variation described in the aforementioned patent specification, an aldehyde of formula II, XIII or XXIII is reacted with a lithium ester of formula XXXVI or XXXVII

CH-.

I ³

Li-CH ₂ -C = CH-COOR c ^h 3

CH _O = C-CH-C00R ² I

Li (XXXVI) (XXXVII) in which

has the above meaning,

the mixture of hydroxy esters thus formed of formulas XXXVIII of' of ² OH 1, COOR ⁴ (XXXVIII) and XXXIX * 4 1 OH 1 i 1 T (XXXIX) in which of ² COOR ⁴

and Z ² are as defined above and is an alkyl group,

CS 266 596 B2 and a lactone of formula XL

in which

2

Z and Z are as defined above, chromatographically separated. The obtained hydroxy esters of formulas XXXVIII and XXXIX are then worked up as described above.

The lactone of formula XL sp is treated with an alkali metal hydroxide to form an alkali metal salt of the hydroxy acids of formulas XXXVIII and XXXIX, wherein R ⁴ is an alkali metal, from which salts the acids are liberated by acidification. The resulting free acids of the general formulas XXXVIII and XXXIX in which R is hydrogen are then treated as described above.

A disadvantage of the above-described process is the need to use a lithium salt and the very difficult separation of the resulting mixture of isomers.

According to yet another variation of the described process, an aldehyde of formula II, XIII or XXIII is reacted with an acrylic ester of formula XLI

CH,

I ³

Y-CH ₂ -C = CH-COOR (XLI) wherein

Y is halogen and

R is as defined above, in the presence of zinc, whereupon the resulting hydroxy esters of formulas XXXVIII and XXXIX dehydrate are formed to form a mixture of esters of formulas XXXII and XXXIII in which Z, Z and R are as defined above and R is alkyl having 1; up to 4 carbon atoms.

This process is also characterized by difficult and time-consuming separation from the undesired isomers.

According to U.S. Pat. No. 3,911,025, an aldehyde of formula XXIII is reacted with an acetylene derivative of formula VIII to form the acetylene hydroxy derivative of formula XLII formed.

(XLII), as defined above, is treated with a trialkyl orthoacetate, followed by formation of the allene ester of formula XLIII

(XLIII),

CS 266 596 B2 has the above meaning in which:

R ³ and R undergoes rearrangement by treatment with sodium hydroxide to give the esters of the formulas XVI, XVII а.

A disadvantage of this process is the complex isolation of the ester of formula (I) in which X is a hydroxy or alkoxy group.

According to US-A-727 624, an unsaturated ketone of formula V or a ketone of formula XXIII is reacted with ethoxyacetylene of formula XLIV

CH ₃ -CH ₂ -OC = CH (XLIV) in the presence of boron trifluoride etherate to give a mixture of isomeric esters of formulas I and IV, wherein X is as defined above and R ³ is ethyl.

Said USSR patent does not mention or describe the separation of the resulting mixture of isomeric esters of formulas I and IV.

According to U.S. Pat.

654,606 is reacted with beta-hydroxydihydrocitronellyl acetone of formula XLV

a phosphonic acid ester of the formula III in which R and R ¹ are each ethyl, the reaction mixture is acylated with acetic anhydride and the mixture obtained ester of formula XLVII XLVII with a lactone of formula

(XLVI) (XLVII) is converted without isolation into a salt by treatment with potassium tert-butoxide, then the resulting salt is reacted sequentially with thionyl chloride and an alcohol to form a mixture of isomeric esters of formulas I and IV wherein X is hydrogen and R is as above this meaning. However, the separation of the resulting mixture of isomers is not mentioned in said patent.

According to British Patent No. 1,399,196 an aldehyde of formula II or XXIII is condensed with an ester of formula LVI

O

II

R OC-CH ₂

CH.

I ^{0 1} H 2

-C = CH-C-OR (LVI), as defined above, in an alkaline medium, whereupon the formed alkali metal dicarboxylate of formula LVII

CS 266 596 B2

(LVII) in which

M is an alkali metal ion and

X is as defined above, converted by acidification to the corresponding free dicarboxylic acid of formula LVII, wherein M is hydrogen. The thus obtained free dicarboxylic acid of formula LVII is treated with a tertiary amine in the presence or absence of copper ions or shavings to convert to the acid of formula XXXI in which Z 2 is hydrogen or alkoxy;

Z is hydrogen, via a lactone of formula LVIII in which

(LVIII) has the above meaning.

The acid of formula XXXI is subjected to isomerization to form a mixture of acids

2 'XXXI and XXX formulas, in which Z and Z are as defined above. Ammonia is added to a solution of this mixture in a suitable solvent to give the pure ammonium salt of Formula LIX

(LIX) in which

X is as defined above and

M is an ammonium ion.

The isolated pure ammonium salt is acidified and then treated successively with thionyl chloride and the appropriate alcohol to produce the ester of formula (I) wherein X and R are as defined above.

A disadvantage of the above process is that even the most pure acid of formula LIX, in which R is as defined above and M is hydrogen, always forms the undesired 2Z, 4E isomer of formula IV in which X and R are as defined above in amounts. 2 to 8%, and a small amount of the ester of formula LX is also formed

(LX) in which

is as defined above, and an ester of formula LXI

CS 266 596 B2

(LXI) in which

R is as defined above.

Thus, the process described above is suitable only for the preparation of an ester of formula I wherein R and X are as defined above, having a purity of at most 90%. Another disadvantage of the above-described process is that the use of strongly corrosive starting materials (oxalyl chloride, thionyl chloride) and the formation of by-products causing environmental pollution (hydrochloric acid, sulfur dioxide) in industrial scale production results in serious problems.

According to U.S. Pat. No. 3,917,662, esters of formula I wherein R and X are as defined above are prepared by heating an ammonium salt of formula LIX, wherein X is as defined above and 11 is an ammonium ion, with a tetraalkoxytitanate of formula LXII

STEED

AND

RO - Ti - OR

Ir (LXII), where defined above.

However, the implementation of the above-described process on an industrial scale is doubtful because the titanium compounds used are highly toxic and their complete separation from the compound produced is virtually impossible.

It is therefore an object of the invention to overcome the drawbacks of the known processes described above and to provide a process that allows the preparation of compounds of formula I wherein R and X are as defined above by a simple process without side reactions with good yields and high purity.

The process according to the invention for the preparation of unsaturated carboxylic acid esters of stereoconfiguration 2E, 2Z of the general formula I, in which X represents hydrogen or C1 -C4 alkoxy and R represents C1 -C4 alkyl, is characterized in that a salt of formula LIX

(LIX) wherein a metal ion, an ammonium ion, or an ammonium ion substituted with at least one alkyl and / or aralkyl radical is as defined above, and

is 1, 2 or 3, reacted with an alkyl halide of formula LXIII

CS 266 596 B2

R-Y (LXIII) wherein

Y is halogen and

R is as defined above, in a polar solvent, in particular a dipolar aprotic solvent, preferably dimethylformamide, dimethylsulfoxide, hexamethylphosphoric triamide, methanol, butanol or acetone.

Mixtures thereof or mixtures thereof containing 1 to 25%, preferably 5 to 10% water, may also be used as solvents.

Salts of formula LIX are preferably salts formed with alkali metals, especially sodium or potassium, or alkaline earth metals, such as calcium, or other metal cations, such as aluminum or iron. Compounds of formula LIX in which M is an ammonium ion optionally substituted by at least one alkyl or aralkyl group such as methylammonium, ethylammonium, benzylammonium, dimethylammonium, dibenzylammonium, trimethylammonium, triethylammonium, tribenzylammonium, benzyldimethylammonium ammonium, benzyldimethylammonium ammonium, benzyldimethylammonium ammonium, benzyldimethylammonium, group.

According to a preferred embodiment of the process of the invention, the salts of formula LIX, wherein X is as defined above and M is a metal ion or an ammonium ion optionally substituted with at least one alkyl or aralkyl group, are prepared in situ in a reaction mixture from an acid of formula LIX wherein X is as defined above and M is hydrogen.

As the alkyl halide of general formula LXIII, for example, methyl bromide, methyl iodide, ethyl bromide, ethyl iodide, propyl chloride, propyl bromide, propyl iodide, isopropyl chloride, isopropyl bromide, isopropyl iodide or butyl bromide, etc. can be used.

The process according to the invention is carried out at a temperature of 10 ° C to 100 ° C, preferably at 20 ° C to 40 ° C.

The acids and salts of Formula LIX are known compounds and can be prepared by known methods. A preferred process for the preparation of these compounds is described in German Published Patent Publication No. 3,635,613. The alkyl halides of formula LXIII are readily available commercial products.

The process according to the invention is illustrated in more detail by the following non-limiting examples.

He did

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

5.8 g of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate are dissolved in 50 ml of hexamethylphosphoric triamide, 10 g of isopropyl bromide are added and the reaction mixture is stirred at room temperature for 3 days. 50 ml of water are then added to the reaction mixture while cooling, and the mixture is extracted twice with 50 ml of ether each time. The pH of the ether phase is adjusted to 9 by addition of 8% aqueous sodium hydroxide solution, after which the ether phase is freed from alkali by washing with water. The solvent was removed by evaporation. Thus, 5.75 g of the title compound are obtained (yield 93%) with a purity of 99% (determined by gas chromatography).

CS 266 596 B2

Example 2

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

5.1 g of ammonium 3,7,11-trimethyl-2E, 4E-dodecadienoate are dissolved in 50 ml of hexamethylphosphoric triamide and 2.2 g of triethylamine are added. The mixture was stirred at room temperature for 1 hour and 10 g of ethyl bromide and 0.2 g of potassium iodide were added. The reaction mixture was then stirred at 40 ° C for 24 hours, 50 ml of water were added under cooling, and the mixture was extracted twice with 50 ml of ether each time. The ether phase is treated with an 8% aqueous potassium hydroxide solution and the aqueous phase is washed with water to pH 7. The ether phase is then evaporated. This yields 4.95 g of the title compound (93% yield) with a purity of 98% (determined by gas chromatography).

Example 3

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

To 5.7 g of ammonium 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate was added 50 ml of dimethylformamide and 1.57 g of potassium carbonate. After stirring for 1 hour, 10 g of isopropyl bromide was added and the mixture was stirred at room temperature for 2 days. Water (50 ml) was added to the mixture under cooling, and the mixture was extracted with ether (2 x 50 ml). The ether phase is treated with 8% aqueous sodium hydroxide solution until the pH reaches 9 and then the excess alkali is washed with water. The ether phase is then evaporated. This gave 4.5 g of the title compound (yield 73%) with a purity of 97% (determined by gas chromatography).

Example 4

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

To 5.7 g of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate ammonium, 50 ml of dimethylsulfoxide and 3.2 g of 25% aqueous sodium hydroxide solution are added, and the mixture is stirred at room temperature for 1 hour. After addition of 10 g of isopropyl bromide, the reaction mixture was stirred at room temperature for 3 days. Thereafter, the reaction mixture was worked up analogously to Example 1. This gave 5.85 g (94.5% yield) of the title compound with a purity of 99% (determined by gas chromatography).

Example 5.

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

5.35 g of 11-methoxy-3,7,11-triemethyl-2E, 4E-dodecadienic acid are dissolved in 50 ml of di-methylsulfoxide and 3.2 g of 25% aqueous sodium hydroxide solution are added. The mixture was stirred at room temperature for 1 hour, then isopropyl bromide (10 g) was added and the reaction mixture was stirred at room temperature for 3 days. 50 ml of water are added under cooling and the mixture is extracted twice with 50 ml of cyclohexane each. The pH of the organic layer was adjusted to 9 by addition of 8% aqueous sodium hydroxide solution, and the organic layer was then washed first with 10 ml of sodium chloride solution, then with 10 ml of water. The solvent was removed by evaporation to give 5.8 g of the title compound (94% yield) with a purity of 99-100% (as determined by gas chromatography).

and

Example 6

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

The procedure is as in Example 5, but using 10 g of a 13.5% methanolic sodium methoxide solution instead of 3.2 g of a 25% aqueous sodium hydroxide solution. This gave 5.5 g of the title compound (yield 90%) with a purity of 98% (determined by gas chromatography).

CS 266 596 B2

Example 7

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

The procedure was as in Example 1 except that potassium 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate was used as the starting compound. 5.8 g of the title compound are obtained (yield 94%) with a purity of 99% (determined by gas chromatography).

Example 8

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

The procedure was as in Example 1 except that 6.15 g of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate calcium was used as the starting compound. 5.7 g of the title compound are obtained (yield 93.5%) with a purity of 99% (determined by gas chromatography).

Example 9

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

The procedure was as in Example 1 except that 5.9 g of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienoate aluminum was used as the starting compound. 5.5 g of the title compound are obtained with a purity of 99% (yield 90%) (determined by gas chromatography).

Example 10

Preparation of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienic acid siopropyl ester

To 6.25 g of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienic acid ethylammonium salt was added 50 ml of dimethylsulfoxide and 3.2 g of 25% aqueous sodium hydroxide solution. The reaction mixture is stirred for one hour at room temperature, then 10 g of isopropyl bromide is added and the reaction mixture is stirred at room temperature for 3 days. Thereafter, the reaction mixture is extracted twice with 50 ml of cyclohexane each and 8% sodium hydroxide solution is added to the cyclohexane phase until the pH reaches 9. Then the cyclohexane phase is washed with water to remove the alkali. The solvent was removed by evaporation. 5.7 g of the title compound are obtained with a purity of 99% (determined by gas chromatography). Yield 93.5%.

Example 11

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

The procedure is as in Example 10 except that the starting material is used

9.3 g of dibenzylammonium salt of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienic acid.

This gives 5.5 g of the title compound with a purity of 99% (determined by gas chromatography). Yield 90%.

Example 12

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

The procedure was as in Example 10 except that the starting compound was used

7.4 g of triethylammonium salt of 11-methoxy-3,7,11-trimethyl-2E, 4E-dodecadienic acid. 5.6 g of the title compound are obtained with a purity of 99% (determined by gas chromatography) in a yield of 92%.

Claims (4)

What is claimed is: 1. A process for the preparation of an unsaturated carboxylic acid ester of the general formula I of the stereoconfiguration 2E, 2Z, which is characterized in that: OBJECT V Y N COOR is hydrogen or alkoxy alkyl having 1 to a salt of Formula LIX 1-4 carbon atoms and (LIX) atoms means a single alkyl and / or aralkyl metal ion, an ammonium ion or an ammonium ion substituted with at least a radical as defined above, and is 1, 2 or 3, at a temperature in the range of 10 to 100 ° C, preferably in the range of 20 to 40 ° C, is reacted with an alkyl halide of formula LXIII R-Y (LXIII), wherein halogen is as defined above, in a polar solvent, particularly a dipolar aprotic solvent, preferably dimethylformamide, dimethylsulfoxide, hexamethylphosphoric triamide, methanol, butanol or acetone. 2. A process according to claim 1, wherein the starting compound is a compound of formula LIX wherein X and n are as defined above and M is an alkali metal, alkaline earth metal, aluminum or iron ion. 3. A process according to claim 2, wherein the starting compound is a compound of formula LIX wherein X and n are as defined above and M is a sodium, potassium or calcium ion. 4. A process according to claim 1, wherein XIX is as defined above and M is ammonium, methylammonium, ethylammonium, benzylammonium, dimethylammonium, diethylammonium, dibenzylammonium, trimethylammonium, triethylammonium. , tribenzylammonium, benzyldimethylammonium, benzyldiethylammonium, tetraethylammonium or tetramethylammonium.