Stable preparation of arylsulfonyl acrylonitrile

Abstract

The present invention relates to a stable formulation comprising at least one organic solvent selected from aliphatic esters and cyclic esters and a compound of formula (I).

Description

[0001] The present invention relates to a stable formulation comprising a compound of formula (I) and the use of an organic solvent according to the preamble of the attached independent claim. The present invention particularly relates to a formulation comprising arylsulfonylacrylonitrile which is stable on storage. The formulation enables the compound to be transported and stored for a long time at ambient temperature.

[0002] Compounds containing vinylarenesulfonyl moieties have been found to be biologically interesting as a means of combating Staphylococcus aureus by inhibiting the sortase SrtA isoform, to name just a few. Synthetic vinylarenesulfonyls are of interest due to their ability to act as Michael acceptors and because they can be used in a variety of cycloaddition reactions.

[0003] In order to further explore the usefulness of arylsulfonyl acrylonitrile in many application areas, a simple and cost-effective but environmentally friendly formulation is needed to enable the compound to be stored for long periods of time. Typically, when arylsulfonyl acrylonitrile compounds are stored as solids, the instability of the compounds requires prolonged storage at temperatures below room temperature, in many cases below freezing.

[0004] The applicant has recently filed several applications disclosing several uses of arylsulfonylacrylonitriles as biocides, further increasing the interest in stable and transportable formulations of these compounds.

[0005] In addition to the solubility of the compound in the solvent, many other factors influence the choice of solvent when producing a compound formulation. In order to adhere to the principles of sustainable chemistry and manufacturing, factors such as volatility, toxicity and carbon footprint of both the solvent and the formulation must be considered. Depending on the application, factors such as legislative and regulatory restrictions may impose further limitations. In practice, this means that different applications may require formulations with different compositions.

[0006] An object of the present invention is to minimize or even possibly eliminate the disadvantages existing in the prior art.

[0007] Another object of the present invention is to provide a stable formulation comprising a compound of formula (I), which formulation is suitable for long-term storage, preferably at ambient temperature.

[0008] An object of the present invention is to provide a stable formulation suitable for various industrial processes.

[0009] These objects are achieved by the invention having the features presented in the characterizing parts of the following independent claims. Some preferred embodiments of the invention are given in the dependent claims.

[0010] The embodiments listed herein relate, where applicable, to all aspects of the invention, even if this is not always listed individually.

[0011] Typical formulations of the present invention comprise at least one organic solvent selected from aliphatic esters and cyclic esters, and

[0012] Compounds of formula (I)

[0013]

[0014] Wherein R1, R2 and R3 independently represent hydrogen atom; halogen atom; hydroxyl; amino; alkylamino; alkyl; hydroxyalkyl; haloalkyl or alkoxy with 1 to 4 carbon atoms; or acylamido with 1 to 10 carbon atoms, and solvent. The groups R1, R2 and R3 of the compound can vary according to the desired use of the preparation.

[0015] According to the present invention, the typical use of aliphatic esters or cyclic esters is to improve the stability of the compound as an organic solvent in a formulation containing a compound of formula (I), wherein R1, R2 and R3 independently represent a hydrogen atom; a halogen atom; a hydroxyl group; an amino group; an alkylamino group; an alkyl group; a hydroxyalkyl group; a haloalkyl group or an alkoxy group having 1 to 4 carbon atoms; or an acylamino group having 1 to 10 carbon atoms.

[0016] According to the present invention, it is surprisingly found that the storage stability of the compound of formula (I), i.e., the arylsulfonyl acrylonitrile compound, can be significantly increased by preparing a formulation comprising the compound and at least one organic solvent selected from aliphatic esters and cyclic esters. In the formulation, the arylsulfonyl acrylonitrile compound can be stored for a long time without changing the concentration of the arylsulfonyl acrylonitrile in the formulation. The formulation comprising the arylsulfonyl acrylonitrile has improved stability compared to dry storage of the arylsulfonyl acrylonitrile. For example, after the formulation is stored at 25° C. for 6 months, at least 90% of the original amount of the arylsulfonyl acrylonitrile compound in the formulation remains in the formulation.

[0017] As used herein, the term "stability" refers to the stability of the arylsulfonyl acrylonitrile compound, i.e., the compound of formula (I). A reduction in stability in the context of the present application may refer to the degradation of the arylsulfonyl acrylonitrile and the reaction of the arylsulfonyl acrylonitrile with another substance to form a new part. A non-limiting example of a reaction in which the arylsulfonyl acrylonitrile compound forms a new part is the homopolymerization of arylsulfonyl acrylonitrile.

[0018] In the present context, the expressions "compound of formula (I)", "arylsulfonylacrylonitrile compound" and "arylsulfonylacrylonitrile" are used as synonyms. These expressions are fully interchangeable in this context.

[0019] As used herein, the term "formulation" is used to describe a mixture comprising an active ingredient, i.e., a compound of formula (I), and at least one organic solvent selected from aliphatic esters and cyclic esters. Depending on the intended use of the arylsulfonylacrylonitrile, the formulation may be in one of several different physical forms, such as a solution, emulsion, gel, suspension, dispersion or aerosol. Preferably, the formulation is in the form of a solution.

[0020] According to a preferred embodiment, the compound of formula (I) is dissolved in an organic solvent. Preferably, the compound is completely soluble in the organic solvent, which means that the preparation does not contain solid particles of the compound of formula (I). In addition, the compound is preferably fully dispersed in the preparation, which means that the concentration of the compound is uniform throughout the preparation.

[0021] In one embodiment of the invention, the formulation comprises an arylsulfonylacrylonitrile according to formula (I) and a solvent.

[0022]

[0023] In one embodiment of the present invention, R1, R2 and R3 in formula (I) independently represent a hydrogen atom; a halogen atom; a hydroxyl group; an amino group; an alkylamino group having 1 to 4 carbon atoms; an alkyl group having 1 to 4 carbon atoms; a hydroxyalkyl group having 1 to 4 carbon atoms; a haloalkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms; or an acylamino group having 1 to 10 carbon atoms.

[0024] In another embodiment of the present invention, R1 represents methyl; ethyl; propyl; butyl; methoxy; ethoxy; propoxy; isopropoxy; n-butoxy; or tert-butoxy; and R2 and R3 independently represent a hydrogen atom; methyl; ethyl; propyl; butyl; methoxy; ethoxy; propoxy; isopropoxy; n-butoxy; or tert-butoxy.

[0025] In one embodiment of the invention, the formulation comprises a compound of formula (I) wherein R1 represents a methyl group in the 4-position and R2 and R3 both represent hydrogen. The compound is thus of formula (II).

[0026]

[0027] According to one embodiment of the present invention, the compound of formula (I) is (E)-3-tosyl acrylonitrile.

[0028] According to one embodiment of the invention, the formulation may contain a compound of formula (I) in the range of 0.2-20 wt-%, preferably 0.5-15 wt-%, more preferably 0.8-10 wt-%, even more preferably 1-7 wt-%, sometimes even 1-5 wt-%, 1.2-5 wt-%, 1.4-4 wt-% or 1.5-3 wt-% or 2-4 wt-%, calculated by the total weight of the compound and the organic solvent. According to one embodiment, the formulation may contain at least 0.2 wt-% or more, preferably greater than 0.5 wt-%, more preferably greater than 0.8 wt-%, even more preferably greater than 1 wt-%, sometimes even greater than 1.2 wt-%, greater than 1.4 wt-%, or greater than 1.5 wt-% of a compound of formula (I), calculated by the total weight of the compound and the organic solvent. The formulation may contain less than 20 wt-%, preferably less than 15 wt-%, more preferably less than 10 wt-%, even more preferably less than 7 wt-%, sometimes even less than 5 wt-%, less than 4 wt-%, or less than 3 wt-% of the compound of formula (I), calculated on the total weight of the compound and the organic solvent.

[0029] In a specific embodiment of the invention, the formulation comprises 2 weight-% or at least 2 weight-% of arylsulfonyl acrylonitrile dissolved in an organic solvent, calculated from the total weight of the compound and the organic solvent. In an embodiment of the invention, the formulation comprises 2 weight-% or at least 2 weight-% of (E)-3-toluenesulfonyl acrylonitrile dissolved in an organic solvent, calculated from the total weight of the compound and the organic solvent.

[0030] The formulation of the present invention comprises at least one organic solvent selected from aliphatic esters and cyclic esters. The formulation may comprise at least 80 wt-%, preferably at least 90 wt-%, more preferably at least 95 wt-% of an organic solvent selected from aliphatic esters and cyclic esters, calculated from the total weight of the compound of formula (I) and the organic solvent.

[0031] According to one embodiment, the formulation comprises at least one organic solvent selected from aliphatic esters and cyclic esters in the range of 80-99.9 wt-%, more preferably 90-99.9 wt-%, even more preferably 95-99.5 wt-%, calculated by the total weight of the compound of formula (I) and the organic solvent. It is possible that the formulation may comprise at least one organic solvent selected from aliphatic esters and cyclic esters in the range of 80-99.8 wt-%, or 85-99.5 wt-%, or 90-99.2 wt-%, or 93-99 wt-%, or 95-98.8 wt-%, 96-98.6 wt-%, or 97-98.5 wt-%, or even 96-98 wt-%, calculated by the total weight of the compound of formula (I) and the organic solvent.

[0032] The organic solvent can be an aliphatic ester, which is a linear or branched monoester, diester or triester. The aliphatic ester can be selected from, for example, acetate, propionate, butyrate, formates or mixtures thereof. In one embodiment, the ester is an alkyl ester. In a specific embodiment of the present invention, the ester is a methyl ester, an ethyl ester, a propyl ester, a butyl ester or a mixture thereof. According to one embodiment, the aliphatic ester is a monoester, a diester or a triester of glycerol and a C1-C5 acid. According to another embodiment, the aliphatic ester is a monoester, a diester or a triester of citric acid and a C1-C5 alcohol.

[0033] According to a preferred embodiment, the organic solvent may be a cyclic ester selected from propylene carbonate, ethylene carbonate and trimethylene carbonate, preferably trimethylene carbonate.

[0034] In one embodiment of the present invention, the formulation comprises 2 weight-% or at least 2 weight-% of arylsulfonylacrylonitrile dissolved in 1,2-propylene carbonate, calculated on the total weight of arylsulfonylacrylonitrile and organic solvent.

[0035] In one embodiment of the present invention, the formulation comprises 2 wt-% or at least 2 wt-% (E)-3-toluenesulfonyl acrylonitrile dissolved in 1,2-propylene carbonate, calculated from the total weight of (E)-3-toluenesulfonyl acrylonitrile and the organic solvent.

[0036] In one embodiment of the present invention, the formulation may comprise a mixture of two or more organic solvents selected from aliphatic esters and cyclic esters.

[0037] In one embodiment of the invention, the formulation comprises an organic solvent selected from aliphatic esters and cyclic esters, which is a water-miscible solvent.

[0038] In addition to the composition of formula (I) and at least one organic solvent selected from aliphatic esters and cyclic esters, the formulation may contain water. The formulation may contain water in a range of 0.1-90 wt-%, preferably 0.5-50 wt-%, more preferably 1-20 wt-%, even more preferably 2-10 wt-%, calculated by the total weight of the compound of formula (I), the organic solvent and water.

[0039] In one embodiment of the invention, the formulation comprises water in an amount of 0.1% (V / V) to 90% (V / V).

[0040] In another embodiment of the present invention, the amount of water contained in the formulation is less than 90% (V / V), less than 80% (V / V), less than 70% (V / V), less than 60% (V / V), less than 50% (V / V), less than 20% (V / V), less than 15% (V / V), less than 10% (V / V), less than 5% (V / V), less than 2% (V / V), less than 1% (V / V), less than 0.5% (V / V), less than 0.2% (V / V), less than 0.1% (V / V) or 0% (V / V).

[0041] In still another embodiment of the present invention, the amount of water contained in the formulation is higher than 90% (V / V), higher than 80% (V / V), higher than 70% (V / V), higher than 60% (V / V), higher than 50% (V / V), higher than 20% (V / V), higher than 15% (V / V), higher than 10% (V / V), higher than 5% (V / V), higher than 2% (V / V), higher than 1% (V / V), higher than 0.5% (V / V), higher than 0.2% (V / V) or higher than 0.1% (V / V).

[0042] According to one embodiment of the present invention, the preparation may also include additional organic solvents, preferably alcohols. If the preparation includes one or more additional solvents, the total amount of organic solvent in the preparation may be in the range of 80-99.9 wt-%, more preferably 90-99.9 wt-%, even more preferably 95-99.5 wt-% or 90-96 wt-%, calculated by the total weight of the compound of formula (I) and the organic solvent. Possible situations are that the total amount of organic solvent in the preparation may be in the range of 80-99.8 wt-%, or 85-99.5 wt-%, or 90-99.2 wt-%, or 93-99 wt-%, or 95-98.8 wt-%, 96-98.6 wt-%, or 97-98.5 wt-%, or even 96-98 wt-%, of the compound of formula (I) and the organic solvent. The total amount of organic solvent includes all organic solvents present in the preparation, including aliphatic esters and / or cyclic esters and all additional solvents.

[0043] In one embodiment of the present invention, the formulation comprises an additional organic solvent selected from the group consisting of nitriles, alcohols, ketones, deep eutectic solvents, ionic liquids and mixtures thereof. In a specific embodiment of the present invention, the formulation comprises as an additional organic solvent a nitrile selected from the group consisting of acetonitrile and propionitrile, an alcohol selected from the group consisting of methanol, ethanol, n-butanol, sec-butanol, tert-butanol, n-propanol, isopropanol and 2-ethylhexanol, a glycol selected from the group consisting of ethylene glycol and propylene glycol, a ketone selected from the group consisting of acetone and methyl ethyl ketone, or any mixture thereof.

[0044] As a non-limiting example, acetylcholine may be used as an organic solvent in the formulations of the present invention.

[0045] In one embodiment of the present invention, the additional organic solvent is selected from ethers. In one embodiment, the ether is selected from linear ethers, cyclic ethers or mixtures thereof. In one embodiment of the present invention, the ether is selected from diethyl ether dimethyl ether, tetrahydrofuran, dioxane, tert-amyl methyl ether, methyl tert-butyl ether (MTBE) and mixtures thereof.

[0046] In one embodiment of the invention, the formulation comprises an additional organic solvent selected from N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0047] In one embodiment of the present invention, the additional organic solvent is an alcohol selected from the group consisting of sec-butyl alcohol, tert-butyl alcohol, isopropyl alcohol and mixtures thereof.

[0048] In one embodiment of the invention, the formulation comprises an alcohol as an additional organic solvent and a cyclic ester as an organic solvent. In one embodiment of the invention, the formulation comprises a secondary or tertiary alcohol selected from sec-butyl alcohol, tert-butyl alcohol, isopropyl alcohol and mixtures thereof, and a carbonate selected from 1,2-propylene carbonate, ethylene carbonate, 1,3-propylene carbonate and mixtures thereof.

[0049] In one embodiment of the invention, the formulation comprises an additional organic solvent and an organic solvent selected from aliphatic esters and cyclic esters, and the ratio of alcohol to ester is 20:1 to 1:20, 15:1 to 1:15, 10:1 to 1:10, 5:1 to 1:5, 3:1 to 1:3, 2:1 to 1:3 or 1: 1. Preferably, the ester is 1,2-propylene carbonate.

[0050] According to one embodiment of the invention, the formulation does not contain any additional solvent and it consists only of an organic solvent selected from aliphatic esters and cyclic esters.

[0051] In one embodiment of the invention, the formulation may also include one or more additives or adjuvants in an amount of up to 5 weight-%, calculated from the total weight of the formulation, to modify the properties of the formulation. In a specific embodiment of the invention, the formulation may include an additive which is an emulsifier, a gelling agent, a thickening agent, a solubilizing agent or a mixture thereof.

[0052] In one embodiment of the invention, the formulation may further comprise an additive or adjuvant which is a surfactant. The surfactant may function, for example, as an emulsifier or, if the formulation comprises water, as a phase transfer agent to facilitate the transfer of arylsulfonyl acrylonitrile from the organic phase to the aqueous phase. In a specific embodiment of the invention, the surfactant is selected from polysorbates such as TweenTM , dodecylguanidine, dodecylbiguanide, sodium dodecyl sulfate, lauryl sulfate, poly(ethylene glycol) derivatives such as Triton TM X, sodium stearate, ammonium lauryl sulfate, ammonium stearate or a mixture thereof.

[0053] In one embodiment of the invention, the formulation comprises an additive which is a solubilizing agent selected from alkali and alkaline earth metal salts comprising carboxylic acids. Non-limiting examples of compounds suitable as solubilizing agents include sodium formate, sodium acetate, sodium propionate, potassium formate, potassium acetate, potassium propionate or mixtures thereof.

[0054] In one embodiment of the present invention, the formulation comprises one or more stabilizers, which further improve the stability of the arylsulfonyl acrylonitrile compound during storage. In a specific embodiment of the present invention, the formulation comprises an antioxidant to prevent oxidation of the arylsulfonyl acrylonitrile compound during long-term storage of the formulation.

[0055] According to one embodiment, the formulation may contain residual amounts of divalent metal ions, such as Cu 2+ , typically in an amount of 10-100 ppm or 15-80 ppm. The divalent metal typically originates from the polymerization catalyst used. It has been observed that the present formulations are surprisingly stable even though residual amounts of divalent ions may be present.

[0056] As used herein, unless otherwise indicated, all percentages are expressed as mass percentages of the total mass of the formulation.

[0057] In one embodiment of the invention, the preparation can be initially prepared as an arylsulfonyl acrylonitrile with a higher concentration, which is diluted to the desired concentration before use. As will be appreciated by those skilled in the art, the upper concentration limit of the arylsulfonyl acrylonitrile in the preparation will be limited by, for example, the solubility of the arylsulfonyl acrylonitrile in the solvent or medium used. Depending on the desired formulation form, the concentrate can be diluted with a suitable solvent and / or re-formulated by adding a suitable additive material. As a non-limiting example, the concentrated liquid preparation can be re-formulated as a gel by adding a suitable gelling agent.

[0058] In one embodiment of the invention, the stability of the formulation may be further improved by refrigerating the formulation to a temperature below ambient temperature. Preferably, the formulation is stable at an ambient temperature of 25°C.

[0059] In one embodiment of the present invention, an inert gas may be added to a container containing a formulation comprising arylsulfonyl acrylonitrile to further improve the stability of the arylsulfonyl acrylonitrile during storage.

[0060] Another aspect of the present invention is a method for preparing a formulation comprising an arylsulfonyl acrylonitrile and a solvent selected from aliphatic esters and cyclic esters. In one embodiment of the present invention, the formulation can be prepared by dissolving the arylsulfonyl acrylonitrile in an amount to produce a desired concentration in a suitable organic solvent selected from aliphatic esters and cyclic esters. In another embodiment of the present invention, a concentrated liquid formulation is prepared by first dissolving the arylsulfonyl acrylonitrile in a suitable organic solvent selected from aliphatic esters and cyclic esters, then diluting to the desired concentration and / or adding additives.

[0061] Another aspect of the invention is the use of the formulation of the invention comprising arylsulfonyl acrylonitrile and a solvent as a biocide. The formulation of the invention comprising arylsulfonyl acrylonitrile can be used as a biocide in many applications, such as in pulp and paper and petroleum applications. As will be readily observed by those skilled in the art, the exact composition of the formulation may need to be adjusted depending on the limitations imposed by practical considerations of compatibility with the intended application or, for example, by differences in limitations imposed by regulatory agencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The short-term stability of arylsulfonyl acrylonitrile in various solvents is shown.

[0064] Figure 2 The long term stability of a 10 mg / ml solution of arylsulfonylacrylonitrile in 1,2-propylene carbonate is shown.

[0065] Figure 3 The long term stability of a 50 mg / ml solution of arylsulfonylacrylonitrile in 1,2-propylene carbonate is shown.

[0066] Experimental Section

[0067] Some embodiments are described below with the aid of examples. The examples are given for illustrative purposes only and they do not limit the scope of the invention.

[0068] Example 1: Preparation of formulation

[0069] (E)-3-Tosyl acrylonitrile was dissolved by adding the solid material (20 g) all at once to a solvent (1 liter, 1,2-propylene carbonate) and stirring until all the solids were dissolved.

[0070] Example 2: Stability using different solvents

[0071] The stability of (E)-3-tosyl acrylonitrile in different solvents, concentrations and temperatures was studied. Initial testing was conducted at room temperature and the solvents tested were i) 1,2-propylene carbonate; ii) ethanol; iii) dimethyl sulfoxide (DMSO); iv) a combination of 35% ethanol-65% propylene glycol; v) water at pH 4; and water at pH 8.

[0072] The amount of (E)-3-toluenesulfonyl acrylonitrile was analyzed by HPLC-DAD. For sample pretreatment, a solution of about 1.45 mg / ml (E)-3-toluenesulfonyl acrylonitrile was prepared in acetonitrile and analyzed by HPLC. External (ESTD) calibration was used for quantification with authentic standards.

[0073] Figure 1 Initial test results with propylene carbonate, ethanol, dimethyl sulfoxide, 35% ethanol-65% propylene glycol, and water are shown.

[0074] From the results it can be seen that in most cases (E)-3-tosyl acrylonitrile was not completely dissolved or remained dissolved for several days in the tested solvents. Propylene carbonate was the only tested solvent in which (E)-3-tosyl acrylonitrile dissolved immediately and was stable for at least one month.

[0075] After the initial testing, a second round of testing was performed with propylene carbonate. The stability of (E)-3-tosyl acrylonitrile in propylene carbonate was tested at 10 mg / ml and 50 mg / ml concentrations and at different temperatures. The effect of light on the stability was also examined ( Figure 2 and 3 ).

[0076] The degradation of (E)-3-TOS in 1,2-propylene carbonate was slow, and after 6 months, the final concentration of (E)-3-TOS was well above 90% in all conditions tested. As expected, light and temperature accelerated the degradation of (E)-3-TOS, but in general, the stability of (E)-3-TOS in 1,2-propylene carbonate was good even under harsh conditions.

Claims

1. A stable preparation comprising: - at least one organic solvent selected from cyclic esters, and - Compound of formula (I) wherein R1 represents methyl; ethyl; propyl; butyl; methoxy; ethoxy; propoxy; isopropoxy; n-butoxy; or tert-butoxy; and wherein R2 and R3 independently represent a hydrogen atom; a methyl group; an ethyl group; a propyl group; a butyl group; a methoxy group; an ethoxy group; a propoxy group; an isopropoxy group; an n-butoxy group; or a tert-butoxy group; wherein the formulation is stable such that after storage of the formulation at 25° C. for 6 months, at least 90% of the original amount of the compound of formula (I) in the formulation remains in the formulation; wherein the formulation comprises at least 80 weight-% of an organic solvent selected from cyclic esters; and The cyclic ester is selected from 1,2-propylene carbonate, ethylene carbonate and 1,3-propylene carbonate.

2. The formulation of claim 1, wherein the formulation comprises at least 0.2 weight-% of the compound of formula (I).

3. The formulation of claim 2, wherein the formulation comprises 0.2-20 wt-% of the compound of formula (I).

4. The formulation of claim 3, wherein the formulation comprises 1-7 wt-% of the compound of formula (I).

5. The preparation according to claim 1, characterized in that The formulation comprises 80-99.9 wt-% of an organic solvent selected from cyclic esters.

6. The formulation of claim 3, wherein the formulation comprises 90-99.9 wt-% of an organic solvent selected from cyclic esters.

7. The formulation of claim 5, wherein the formulation comprises 90-99.9 wt-% of an organic solvent selected from cyclic esters.

8. The preparation according to claim 1, characterized in that The formulation comprises water.

9. The preparation according to claim 8, characterized in that The preparations contain 0.1 to 90 wt-% water.

10. The formulation of claim 9, wherein the formulation comprises 2-10 wt-% water.

11. The preparation according to claim 1, characterized in that The formulation also comprises an additional organic solvent.

12. The formulation of claim 6, wherein the formulation further comprises an additional organic solvent.

13. The formulation of claim 11, wherein the additional organic solvent is an alcohol.

14. The formulation of claim 12, wherein the additional organic solvent is an alcohol.

15. The formulation of claim 11, wherein the total amount of organic solvent in the formulation is in the range of 80-99.9 wt-%.

16. The formulation of claim 12, wherein the total amount of organic solvent in the formulation is in the range of 80-99.9 wt-%.

17. The formulation of claim 13, wherein the total amount of organic solvent in the formulation is in the range of 80-99.9 wt-%.

18. The formulation of claim 14, wherein the total amount of organic solvent in the formulation is in the range of 80-99.9 wt-%.

19. The formulation of claim 15, wherein the total amount of organic solvent in the formulation is in the range of 90-99.9 weight-%.

20. The preparation according to claim 1, characterized in that The compound of formula (I) is dissolved in an organic solvent.

21. The preparation according to any one of the preceding claims 1 to 20, characterized in that The formulation contains residual amounts of divalent metal ions.

22. The formulation of claim 21, wherein the divalent metal ion is Cu 2+ ion.

23. The formulation of claim 21, wherein the formulation comprises a residual amount of divalent metal ions in an amount of 10-100 ppm.

24. The formulation of claim 22, wherein the formulation comprises a residual amount of divalent metal ions in an amount of 10-100 ppm.

25. Use of a cyclic ester as an organic solvent in a formulation comprising a compound of formula (I) to improve the stability of said compound, wherein R1 represents methyl; ethyl; propyl; butyl; methoxy; ethoxy; propoxy; isopropoxy; n-butoxy; or tert-butoxy; and wherein R2 and R3 independently represent a hydrogen atom; a methyl group; an ethyl group; a propyl group; a butyl group; a methoxy group; an ethoxy group; a propoxy group; an isopropoxy group; an n-butoxy group; or a tert-butoxy group; wherein the formulation is stable such that after storage of the formulation at 25° C. for 6 months, at least 90% of the original amount of the compound of formula (I) in the formulation remains in the formulation; wherein the formulation comprises at least 80 weight-% of an organic solvent selected from cyclic esters; and The cyclic ester is selected from 1,2-propylene carbonate, ethylene carbonate and 1,3-propylene carbonate.

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