PT104664A - STABLE CRYSTALLINE POLYMER OF 2- (2-CHLORO-4-MESYL-BENZOYL) CYCLOHEXANE-1,3-DIONA AND PROCESS FOR PREPARING THE SAME - Google Patents

Abstract

The present invention relates to a novel stable crystalline polymorph of 2- (2-chloro-4-methyl-benzoyl) -cyclohexane-1,3-dioxide and a process for the preparation thereof. More particularly, it relates to compositions having the above-mentioned polymorph to control unwanted plants. COMPOSING THE PROCESS FOR PREPARING THE CRYSTAL POLYMER OF 2- (2-CHLORO-4-MESYL-BENZOYL) -CYCLOHEXANE-1,3-DIONA THE FOLLOWING STEPS OF: 1) PREPARATION OF 4-SULFOMETHYL-2-CHLORO CHLORIDE BENZOÍLO; 2) PREPARATION OF ENERGY ESTER DERIVATIVES; 3) ENERGETIC ESTER DERIVATIVE REARRANGE 2- (2-CHLORO-4-MESYL-BENZOYL) -CYCLOHEXANE-1,3-DIONA; And 4) PURIFICATION OF 2- (2-CHLORO-4-MESYL-BENZOYL) -CYCLOHEXANE-1,3-DIONA. POLYMORPHATE STRUCTURE IS ASSESSED USING INFRARED AND RAMAN SPECTROS AND X-RAY CRYSTALLOGRAPHY DATA. The polymorph has a spectrum of X-ray diffraction of post-axes with characteristic peaks at 2θ = 17,2º, 17,6º, 19,1º, 21,0º, 26,0º and 28,7º. A stable formulation of the above-mentioned polymorph is used as herbicide.

Description

STABLE CRYSTALLINE POLYMER OF 2- (2-CHLORO-4-MESYL-BENZOYL) -CYCLOHEXANE-1,3-DIONA AND PROCESS FOR PREPARING THE SAME "

FIELD OF THE INVENTION The present invention relates to a novel stable crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione and to a process for preparing the same. More particularly, it relates to compositions containing said polymorph to control unwanted plants.

BACKGROUND OF THE INVENTION The manufacture of biologically active compounds, such as pharmaceuticals, agrochemicals and other fine chemicals involves the synthesis, purification, isolation and recovery by recrystallization. Many of these biologically active compounds exhibit polymorphism: the ability of a substance to exist in two or more solid forms with different arrangements of atoms or molecules. Polymorphs other than a biologically active compound may have different physical properties, which may advantageously be used to select a polymorph specific for a specific application. There has been a growing need in the development of biologically active compounds with specific crystalline polymorphism. 1

In the field of agrochemicals, 1,3-cyclohexanedione-based molecules have gained importance because of their good efficacy as herbicides in maize, particularly against a wide range of monocotyledonous and dicotyledonous weeds.

These compounds were first described by Stauffer Chemical, U.S. Patent No. 4,775,411 (1988). The process disclosed therein involves the rearrangement of an enol ester derivative using triethylamine as the base and acetone cyanohydrins as the catalyst.

One of the derivatives thus produced, namely 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione was of commercial importance.

Although the product may exist in two or more different polymorphs, no study or report was available to define specific polymorphic polymorphs.

Subsequent patent documents, in particular US 4775411; (1988) and EP 249150; (1991) disclose process improvements. The resulting product was characterized by the melting point. Crystalline polymorphism studies of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione were first described in 2003, describing the existence of 2- (2-chloro-4-mesyl-benzoyl ) -cyclohexane-1,3-dione in two forms, a metastable form I and a thermodynamically stable form II.

A process for recrystallizing Form II from 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione using isopropanol 2 as solvent was also described in EP 1517731 (2003).

SUMMARY OF THE INVENTION The present invention relates to a novel stable crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione (referred to as Form III in the following description) and to a process for preparing the same. The resulting products of this Form III are effective when applied as weed control agents. The novel stable crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione has an X-ray powder diffraction spectrum with characteristic peaks at 2θ = 17.2ø , 17.6 °, 19.1 °, 21.0 °, 26.0 ° and 28.7 ° (± 0.10 ° in each case).

In one aspect, the crystalline polymorph of the invention has the following reticular parameters: a = 10,326 (6);; b 11.875 (5) Â; c = 12.130 (5) Â; β = 95.00 (3) °; V = 1481.7 (18) Â3.

In another aspect, the crystalline polymorph of the invention has a density of about 1.474 g / cm 3.

In another aspect, the crystalline polymorph of the invention has a molecular weight of about 328.78 and a volume per atom of about 17.6 ± 3. The present invention also relates to a composition comprising a crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione as defined above.

In one aspect, the composition of the invention comprises at least one form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione which differs from the polymorph of 2- (2-chloro- 4-mesyl-benzoyl) -cyclohexane-1,3-dione of the invention.

In another aspect, said composition comprises less than about 20% by weight of the at least one form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione which differs from 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione polymorph of the invention.

The composition preferably comprises less than about 5% by weight of the at least one form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione which differs of the 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione polymorph of the invention.

In another aspect, said composition further comprising other herbicides.

Preferably, said herbicides are selected from the group comprising sulfonylureas, chloroacetamides, dinitroanilines, triazines, isoxazoles, oxyacetamides and combinations thereof. The invention further relates to the use of the above composition for controlling undesired plants, in particular for controlling weeds selected from the group comprising Cyperus 4 Esculentus, Cyperus rotundus, Chenopodium spp., Amaranthus spp., Datura stramonium, Polygonum aviculare and Solanum nigrum. The present invention also relates to a process for preparing a crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione as defined in claim 1, comprising the steps of: ) preparation of 4-sulfomethyl-2-chloro benzoyl chloride; 2) preparation of the enol ester derivative; 3) rearrangement of the enol ester derivative to 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione; and 4) purification of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione; wherein in step 1, a reaction of benzoic acid derivative with thionyl chloride, in the presence of a catalyst, is carried out to produce the benzoyl chloride derivative; in step 2, the benzoyl chloride derivative produced in step 1 is condensed with 1,3-cyclohexane-dione in the presence of a catalyst and a solvent to obtain an enol ester derivative; in step 3, the enol ester derivative of step 2, dissolved in a solvent, undergoes rearrangement using catalytic amount of CN2; and in step 4, 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione is purified by dissolving it under mild alkaline conditions using an alkaline solution; extraction using an organochlorine solvent; and acidifying the resulting aqueous layer using an acidic solution.

In one aspect, the catalyst of step 1 is DMF, the catalyst of step 2 is piperidine, the solvent of step 2 is acetonitrile and the solvent of step 3 is acetonitrile.

In another aspect, the concentration of the alkaline solution is in the range of about 5% -20%. 5

In addition, in another aspect, the alkaline solution is selected from the group comprising sodium, potassium, alkaline earth metal salts and combinations thereof.

In another aspect of the invention, said concentration of the acid solution is in the range of about 10-20%.

In yet another aspect of the invention, in step 4 of the above process, the alkaline solution is sodium hydroxide, the organochlorine solvent is dichloroethane and the acidic solution is hydrochloric acid.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows the X-ray diffraction pattern of Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione. The strongest reflections are marked with arrows. Fig. 2 shows the IR spectrum of Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione in the range of 4000-700 cm -1.

Fig. 3, 4 and 5 show the Raman spectrum of Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione at Raman shifts of 3150-2800 cm -1, 1750- 1000 crrf1 and 950-200 cm -1. 6

DETAILED DESCRIPTION OF THE INVENTION

In order to prepare a pure form of the novel crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione, it is necessary to produce and control the purity of the raw materials and intermediates. The key raw materials are 1,3-cyclohexane-dione and 4-sulfomethylbenzoic acid, which are commercially available in the pure form. The process for the preparation of Polymorph Form III 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione of the invention comprises the following steps:

Step 1: Preparation of 4-sulfomethyl-2-chloro benzoyl chloride The reaction of the benzoic acid derivative with thionyl chloride in the presence of a catalyst such as DMF is carried out to produce the respective benzoyl chloride derivative.

Step 2: Preparation of enolic ester derivative The benzoyl chloride derivative produced in Step 1 is condensed with 1,3-cyclohexane-dione in the presence of piperidine as the catalyst and acetonitrile as the solvent. The reaction is carefully monitored to verify the absence of starting materials and the product thus obtained is an enol ester derivative. 7

Step 3: Rearrangement of the enol ester derivative to 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione.

Enol ester, dissolved in acetonitrile solvent, undergoes rearrangement using a catalytic amount of CN ". CN "may be provided by the use of KCN or acetone cyanohydrin.

Step 4: Purification of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione to produce the specific Form III Polymorph of the invention. The thus-produced 2- (2-chloro-4-mesylbenzoyl) -cyclohexane-1,3-dione is further purified by dissolving it under mild alkaline conditions using a low concentration aqueous alkaline solution (5% -20% ). The alkaline solution can be any suitable solution. Preferably, the alkaline solution is selected from the group comprising sodium, potassium and alkaline earth metal salts and combinations thereof, the salts of which are, for example, hydroxides and carbonates. The side products causing instability are extracted using an organochlorine solvent, for example dichloroethane. The resulting aqueous layer is acidified using a dilute acidic solution, for example hydrochloric acid, at a concentration in the range of about 10-20%, to afford 2- (2-chloro-4-mesyl-benzoyl) hexane-1,3-dione in the pure crystalline polymorph Form III form. The process of the invention provides a stable stable Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione having an X-ray diffraction spectrum shown in Fig. 1, with the relative intensities of the reflections versus 2Θ

represented in the following Table 1. Accordingly, Form III has characteristic peaks at 2θ = 17.2ø, 17.6ø, 19.1ø, 21.0ø, 26.0ø and 28.7ø, (± 0 , 10 ° in each case).

Table 1 2Θ Int. (%) 8.58 8 10.44 13 11.37 3 13.12 20 13, 93 3 14, 65 14 14, 91 15 16.34 34 16.62 8 17, 23 100 17, 65 55 17, 97 7 18, 44 4 18, 81 9 19, 00 32 19.14 48 19, 61 16 20, 96 40 21, 68 23 22.17 32 22, 94 7 23.18 26 23, 65 21 24, 07 31 9 2Θ Int. (%) 24.47 4 25.41 33 25.54 23 25.96 42 26.72 20 26.88 19 27, 44 4 27, 89 12 28.08 9 28.43 17 28.74 44 29.00 7 29.55 7 29.77 8 OD OO CO 8 30.28 8 30.51 8 31.01 9 32.02 5 32.47 8 33.03 5 33.72 7 34 , 42 7 of 2 Table 2 shows the crystallographic data of Form III (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione. 10

(B) Structural parameters (determined at RT) a = 10.326 (6) Ã b = 11.875 (5) The structure of the structure is determined by the following equation: A c = 12.130 (5) Á β = 95.00 (3) 0 V = 1.481.7 (18) Á3 Molecules per cell Z = 4 Molecular Weight: 328.78 Calculated Density: 1.474 g / cm3 Coef. The X-ray diffraction analysis of powders was performed using a STOE Θ / Θ- Difractometer, Cu-Kα (λ) radiation, = 1.5418 Ã); U = 40 kV, I = 40 mA; secondary beam monochromator: " plane Graphite "(002); scintillation counter; slits: 0.75 mm, 0.35 mm, 2x8 mm; angular region, incremental width, time / increment: 2Θ = 4.0 ° - 35.0 °, Δ 2Θ = 0.04 °, 5s. The analysis was performed by filling the sample holder and the sample surface carefully smoothed and adjusted against a knife edge. Specific stable Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione according to the invention can further be characterized by IR and Raman spectroscopy. 11

Accordingly, the invention further provides a stable stable Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione having an IR spectrum with the bands shown in Table 3 and signals shown in Fig. 2.

Table 3 [cm " 1] 1667.0 1554.1 1405.0 1317.0 1159.7 1147.8 1092.7 966.1 934.3 890.4 790.3 777, 4 756.5

FT-IV spectra were obtained using a B-Optics Spectrophotometer, model ALPHA-P, from Bruker. The analysis was performed by placing the sample on the sample holder and carrying out the measurement. Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione has a Raman spectrum with the bands shown in Table 4 and the signals shown in Fig. 3 to Fig. 5. 12

Table 4

Form III 3062 993 3009 937 2962 920 2926 752 2883 720 1672 670 1595 613 1460 596 1410 550 1351 502 1337 438 1323 426 1276 401 1251 337 1224 299 1160 265 1050 247

Raman spectra were acquired on a FT-Raman 960 (Thermo Nicolet) spectrometer equipped with an arsenide gallium and indium (inGaAs) detector. Wavelength verification was performed using sulfur and cyclohexane. Each sample for analysis was prepared by placing the sample in a glass tube and positioning the tube in a gold-coated tube holder. Approximately 0.5 W of Nd: YV04 laser power (excitation wavelength of 1064 nm) was used to irradiate the sample. Each spectrum represents 256 co-added scans collected at a spectral resolution of 4 cm -1. The stable crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione of the invention has such physico-chemical properties as to permit easy handling in formulations. The stable crystalline 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione Form III polymorph of the present invention is particularly suitable for preparing solid and liquid formulations. Examples of such formulations are: granules, encapsulated granules, lozenges, water dispersible granules, water dispersible tablets, water dispersible powders, powder formulations, concentrated suspensions, concentrated oil-based suspensions, suspoemulsions or concentrated plant protection suspensions . Because of its stability, the stable crystalline Form III polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione is highly suitable for preparing compositions for controlling unwanted plants, alone or in together with auxiliaries, vehicles, and other active compounds. The invention also relates to compositions comprising the stable Form III polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione and at least one form of 2- (2 chloro-4-mesylbenzoyl) -cyclohexane-1,3-dione which differs from the Form III polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3- dione. Preferred are compositions comprising less than about 20% by weight of at least one form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione which differs from the polymorph of Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione. Preferably, compositions comprising less than about 15%, more preferably less than about 10%, and most preferably less than about 5%, by weight of at least , a form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione which differs from stable crystalline Form III of the 2- (2-chloro-4-mesyl-benzoyl ) -cyclohexane-1,3-dione. The stable crystalline 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione Form III polymorph of the invention may preferably be employed as a plant protection agent, by controlling a wide variety of Dicotyledon and Monocotyledon weeds selected from the group comprising Cyperus esculentus, Cyperus rotundus, Chenopodium spp., Amaranthus spp., Datura stramonium, Polygonum aviculare and Solanum nigrum.

The above compositions may comprise other herbicides in order to broaden the range of weeds to be controlled, particularly some weeds. The herbicides are selected from the group comprising sulfonylureas, chloroacetamides, dinitroanilines, triazines, isoxazoles, oxyacetamides and combinations thereof. The active compound may be formulated into granules, encapsulated granules, lozenges, water dispersible granules, water dispersible tablets, water dispersible powders, powder formulations, concentrated suspensions, concentrated oil-based suspensions, suspoemulsions, concentrated suspensions or any other formulations appropriate. Such formulations are produced in a manner known, for example, by mixing the active compounds, liquid solvents and / or solid carriers, optionally with the use of surfactants. 15

The following examples further illustrate some aspects of the invention but are not intended to limit its scope. EXAMPLES Example 1:

Production of stable crystalline structure of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione a) Conversion of acid to acid chloride.

In a reactor equipped with a stirrer, condenser, a neutralizer with 10% sodium hydroxide solution, was charged with toluene (500 mL) followed by 2-chloro-4-sulfomethylbenzoic acid (100 g) and catalytic amount of DMF ( 2 mL). The reaction mixture was cooled to 0 ° C and thionyl chloride (50 g) was added slowly over a period of 3 hours keeping the temperature below 5 ° C. The reaction mixture was slowly warmed to 50øC allowing the formed HCl and SO 2 to escape into the neutralizer. The end of the reaction was determined by the absence of acid. The solvent was distilled off with the excess thionyl chloride used for the reactor. The residue thus obtained (105 g) was used directly in the next step. B) Condensation for acid chloride with cyclohexanedione.

In a reactor equipped with a stirrer, cyclohexanedione (6 g), acid chloride (12 g), acetonitrile (35 ml) and piperidine (1 ml) were stirred at room temperature and the stirring was continued for 5 hours. The end of the reaction was verified by the absence of cyclohexanedione and the enol ester thus formed was obtained by recovering the acetonitrile followed by filtration of the solid mass thus obtained. The purity of the enol ester thus obtained was 97%. The enol ester was further purified by the use of isopropanol. c) Rearrangement of enol ester to 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione. 5 g of enol ester was taken in acetonitrile solvent along with acetone cyanohydrin (0.15 g) and triethylamine (2.0 g) and the reaction mixture was stirred at room temperature for 10 hours. The solvent was removed by distillation. Ethylenedichloride (25 mL) was added and the organic layer was washed with sodium bicarbonate solution (5%) to remove the hydrolyzed acid. The crude 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione was obtained by distillation of EDC and recrystallized from methylene dichloride. The purity of the crude 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione was 96% and 3.85 g of 2- (2-chloro-4- benzoyl) -cyclohexane-1,3-dione. D) Purification to obtain Form III of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione. (2 g) obtained above was dissolved in 5% sodium hydroxide (50 ml) and dichloroethane (30 ml) was added added to remove by-products. After stirring the reaction mixture for 30 minutes, stirring was stopped and two layers were allowed to separate. The lower organic layer was removed and the aqueous layer was acidified using 15% HCl solution to pH = 3.5. The product thus obtained was filtered and dried to obtain 1.6 g of pure 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione and their characteristics were determined using XPRD.

Example 2:

Formulation 2- (2-Chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione (Form III)

A premix of water (45.3 g), MPG (9.0 g), Atlox 4913 (3.4 g), Atlox 4894 (2.3 g), Brij-96 (9.9 g) and AF9030 (0.1 g). 30.5 g of Form III polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione, obtained in Example 1, was added and mixed until homogeneous. The formulation was milled twice in a Dyno-mill, maintaining the product temperature below 20 ° C. Then AF9030 (0.1 g) and thickening agent (9.9 g) was added with gentle stirring. 18

Example 3:

Storage Properties The storage life of the liquid formulation of Example 2 was determined using the method described in CIPAC Handbook, Volume J, MT46.3, p. 128; Publishers W Dobrat and A Martijn; Collaborative International Pesticides Analytical Council Limited, 2000). The samples obtained in Example 2 were stored at 54øC for 14 days. After storage, the samples were allowed to return to room temperature and compared to those freshly prepared.

A slight phase separation was observed but was rapidly dispersed. The formulation properties of the formulation did not change after storage.

Lisbon, 3 September 2010 19

Claims (18)

A crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione characterized by having a powder X-ray diffraction spectrum of characteristic peaks at 2θ = 17, 2, 17.6 °, 19.1 °, 21.0 °, 26.0 ° and 28.7 ° (± 0.10 ° in each case). The crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione according to claim 1, characterized in that it has the following reticular parameters: a = 10,326 (6) THE; b = 11.875 (5) Â; c = 12.130 (5) Â; β = 95.00 (3) 0; V = 1481.7 (18) Ã-3. A crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione according to claim 1 or 2, having a density of about 1.474 g / cm 3 . A crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione, according to any of the preceding claims, having a molecular weight of about 328, a volume per atom of about 17.6 Å. Composition comprising a crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione as defined in any of the preceding claims. Composition according to Claim 5, characterized in that it further comprises at least one form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione which differs from the polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione of any of claims 1-4. Composition according to the preceding claim, characterized in that it comprises less than about 20% by weight of the at least one form of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane- 3-dione which differs from the 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione polymorph of any of claims 1-4. Composition according to the preceding claim, characterized in that it comprises less than about 5% by weight of the at least one form of 2- (C-chloro-1-mesyl-benzoyl) -cyclohexane- 3-dione which differs from the 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione polymorph of any of claims 1-4. Composition according to any of claims 5 to 8, characterized in that it further comprises other herbicides. Composition according to the preceding claim, characterized in that the other herbicides are selected from the group comprising sulfonylureas, chloroacetamides, dinitroanilines, triazines, isoxazoles, oxyacetamides and combinations thereof. 2 Use of the composition according to any of claims 5 to 10, characterized in that the composition is applied in the control of unwanted plants. Use according to the preceding claim, characterized in that the composition is applied in the control of weeds selected from the group comprising Cyperus esculentus, Cyperus rotundus, Chenopodium spp., Amaranthus spp., Datura stramonium, Polygonum aviculare and Solanum nigrum. A process for preparing crystalline polymorph of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione as defined in claim 1, characterized in that it comprises the steps of: 4-sulfomethyl-2-chloro benzoyl; 2- preparation of enol ester derivative; 3- rearrangement of enol ester derivative to 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione; and 4-purification of 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione; wherein in step 1, a reaction of benzoic acid derivative with thionyl chloride in the presence of a catalyst is carried out to produce the benzoyl chloride derivative; 3 in step 2, the benzoyl chloride derivative produced in step 1 is condensed with 1,3-cyclohexane-dione in the presence of a catalyst and a solvent to obtain an enol ester derivative; in step 3, the enol ester derivative of step 2 dissolved in a solvent undergoes rearrangement using catalytic amount of CPT; and in step 4, 2- (2-chloro-4-mesyl-benzoyl) -cyclohexane-1,3-dione is purified by: - dissolution thereof under mild alkaline conditions using an alkaline solution; extraction using an organochlorine solvent; and acidification of the resulting aqueous layer using an acidic solution. The process of claim 13, wherein the catalyst of step 1 is DMF; the catalyst of step 2 is piperidine; the solvent from step 2 and 3 is acetonitrile. The process of claim 13, wherein the concentration of the alkaline solution is in the range of about 5% -20%. The process of the preceding claim, wherein the alkaline solution is selected from the group comprising sodium, potassium, alkaline earth metal salts and combinations thereof. 4 The process of claim 13, wherein the concentration of the acid solution is in the range of about 10-20%. The process of claim 13, wherein the alkaline solution of step 4 is sodium hydroxide, the organochlorine solvent is dichloroethane and the acidic solution is hydrochloric acid. Lisbon, September 3, 2010 5