GB2610805A - Novel crystalline form of florasulam, preparation and use of the same - Google Patents

Abstract

A crystalline modification I of florasulam, exhibiting at least four of certain reflexes in an X-ray powder diffractogram recorded using Cu—Kα radiation at 25 °C as defined herein. Preferably, the crystalline modification I of florasulam exhibits an IR spectrum with characteristic bands at 3069, 1636, 1531, 1344, 1243, 1170 and 1100 cm−1. In another aspect, a process for the preparation of a crystalline modification I of florasulam comprising: (i) preparing a solution of florasulam in a solvent; (ii) effecting crystallization of florasulam from the solution to obtain a solid precipitate; and (iii) isolating the solid precipitate. Preferably, the solvent comprises methyl ethyl ketone (MEK) xylene or a mixture thereof. In a further aspect, a composition comprising the crystalline modification I of florasulam and at least one auxiliary. Preferred auxiliaries include solvents, diluents, wetting agents, dispersants, thickeners, antifreeze agents and/or biocides. The crystalline modification I of florasulam or a composition thereof is used as an herbicide. In yet another aspect, the use of a solvent to increase the stability of florasulam, in particular its resistance to hydrolysis, is also provided.

Description

NOVEL CRYSTALLINE FORM OF FLORASULAM, PREPARATION AND USE OF THE

SAM E

The present invention relates to a crystalline form of N-(2,6-difluorophenyI)-8-fluoro-5-methoxy-[1,2,4]triazolo[1,5-c] pyrimidine-2-sulfonamide (florasulam). In a further aspect, the present invention relates to a process for the preparation of the aforementioned crystalline form of florasulam. The present invention further relates to its use in agrochemical preparations and in the treatment and control of unwanted plant growth.

Florasulam (N-(2,6-difluoropheny1)-8-fluoro-5-methoxy[1,2,4]triazolo[1,5-c] pyrimidine-2-sulfonamide) is a member of the triazolo pyrimidine sulfonanilide family. Florasulam is used as herbicide. In particular, it is a selective and highly active herbicide that kills a range of broad leaf weeds. The compound acts by internal disruption of the plant growth. Florasulam is generally applied through the field or foliage using a suitable formulated product and is absorbed through the root or foliage of the plants. It is used in the post-emergent control of annual broadleaved weeds including cleavers, wild buckwheat and chickweed in crops of spring wheat, spring barley, rye, triticale and oats.

Florasulam has molecular formula of C HF NO S. Its chemical structure is: 12 8 3 5 3 (I) Commercially available florasulam is usually manufactured by the process described in EP0537611B1. It is present in an amorphous state. It has been found that florasulam in an amorphous state is highly unstable. In particular, it will undergo significant hydrolysis when dissolved and dispersed in water. Furthermore, hydrolysis can occur during storage, particularly where the compound becomes exposed to moisture. As a result, the stability of florasulam is of great concern for the commercially available formulations. Therefore, there is a need to provide a way to increase the stability of florasulam, preferably increasing its stability in formulations.

A novel crystalline form of florasulam, herein termed "crystalline modification I", has now been found, together with a process for its preparation as well as its use in agrochemical compositions. The novel crystalline modification I has been found to have a significantly increased stability. There have now been found a range of compositions for controlling undesirable weeds comprising the crystalline modification I of florasulam on its own, as a mixture with auxiliaries and carriers, and as a mixture with other active compounds.

According to a first aspect of the present invention there is provided a crystalline modification I of florasulam exhibiting at least 4 of the following reflexes as 20 values in an X-ray powder diffractogram recorded using Cu-Ka radiation at 25 °C: 28 = 11.049 ± 0.2 (1) 29= 11.732 ±0.2 (2) 20 = 12.872 ± 0.2 (3) = 17.593 ± 0.2 (4) = 18.088 ± 0.2 (5) = 18.380 ± 0.2 (6) ze = 20.098 ± 0.2 (7) 20 = 22.063 ± 0.2 (8) 28 = 24.104 ± 0.2 (9) = 25.659 ± 0.2 (10) = 25.892 ± 0.2 (11) = 28.225 ± 0.2 (12) = 33.263 ± 0.2 (13) It has been found that the crystalline modification I of florasulam has a significantly increased stability. In particular, the crystalline modification I exhibits a significantly reduced susceptibility to hydrolysis, which in turn avoids or significantly reduces the hydrolysis problems encountered in current commercially available formulations. In addition, it is found that the crystalline modification I of florasulam is easier to be comminuted or ground compared to amorphous florasulam as currently commercially available, for example as prepared in accordance with the disclosure of EP0537611. This in turn allows commercial formulations, such as suspension concentrates (SC), oil-based suspension concentrates (OD), water-dispersible granules (WG) and water-soluble granules (SG), to be prepared more readily.

By virtue of its high stability, the crystalline modification I of florasulam is highly suitable for preparing compositions for controlling undesirable weeds.

The crystalline modification I of florasulam of the present invention is characterized by an X-ray powder diffractogram having at least four of the reflexes indicated above. Preferably, the crystalline modification I is one having at least five of the aforementioned reflexes, more preferably at least six, seven, or eight of the said reflexes, still more preferably at least nine or ten of the said reflexes. An X-ray powder diffractogram of one preferred embodiment of the crystalline modification I of florasulam is shown in Figure 2, which will be described in detail hereinafter.

According to a preferred embodiment, the crystalline modification I exhibits at least four, preferably at least five, more preferably at least six, especially all of the following reflexes: = 11.049 ± 0.2 (1) = 11.732 ± 0.2 (2) = 12.872 ± 0.2 (3) ze = 17.593 ± 0.2 (4) 2e = 18.088 ± 0.2 (5) = 18.380 ± 0.2 (6) = 20.098 ± 0.2 (7) = 25.892 ± 0.2 (11) ze = 28.225 ± 0.2 (12) 20 = 33.263 ± 0.2 (13) The crystalline modification I of florasulam according to the present invention may be characterized by Infrared (IR) spectroscopy. The IR spectrum of the crystalline modification I is showed in Figure 1 with characteristic bands at 3069, 1636, 1531, 1344, 1243, 1170 and 1100 cm-1.

All IR spectra were obtained using the following acquisition parameters: FT-IR spectrometer Bruker Tensor37 Diamond ATR unit from Specac Wavelength range 550 -4000 cm-1 Resolution 4 cm-I Number of scans 16 Thermogravimetric (TGA) and Differential Scanning Calorimetry (DSC) analyses may also be used to characterize the crystallization modification I of florasulam. The Differential Scanning Calorimetry (DSC) spectrum of the crystalline modification I of florasulam exhibits an endothermic peak at 219.0 °C corresponding to its melting with an immediate exothermic peak of 220.7 °C as shown in Figure 3.

Methods for preparing amorphous florasulam are well known in the art.

Amorphous florasulam is manufactured and available on a commercial scale, as noted above. A particularly suitable method for preparing amorphous florasulam is described in EP0537611.

It has been found that the crystalline modification I of florasulam can be prepared from amorphous florasulam by dissolving the amorphous material in a suitable solvent and crystallizing the modification I from solution.

Accordingly, in a further aspect, the present invention provides a process for preparing a crystalline modification I of florasulam comprising steps of i) preparing a solution of an amorphous florasulam in a solvent; ii) effecting crystallization of florasulam from the solution to obtain a solid precipitate; and Hi) isolating the solid precipitate.

Suitable solvents for preparing the crystalline modification I of florasulam include aliphatic, cycloaliphatic and aromatic hydrocarbons, ethers, esters and aliphatic alcohols.

Suitable hydrocarbons include aliphatic, cycloaliphatic or aromatic hydrocarbons. Suitable aliphatic hydrocarbons include, for example, alkanes having from 5 to 10 carbon atoms, such as pentane, hexane, preferably n-hexane, heptane, preferably n-heptane, octane, preferably n-octane, and nonane, preferably n-nonane. Suitable hydrocarbons also include petroleum fractions, for example within a boiling range of from 70 °C to 190 °C, petroleum ether and ligroin. Suitable cycloaliphatic hydrocarbons include cyclohexane and methylcyclohexane. Suitable aromatic hydrocarbons include benzene, toluene, xylene and cymene, The solvent may comprise one or more halogenated hydrocarbons, preferably halogenated aromatic hydrocarbons, more preferably halogenated benzene and toluene. Preferred halogen moieties are chlorine and bromine. The hydrocarbon may contain a single halogen moiety or alternatively contain a plurality of halogen moieties, more preferably two or three halogen moieties. Examples of preferred halogenated hydrocarbons include chlorobenzene, bromobenzene, dichlorobenzene, chlorotoluene and trichlorobenzene.

The solvent may comprise one or more nitrated hydrocarbons, for example, nitrated aliphatic hydrocarbons, preferably nitrated alkanes having from 1 to 6 carbon atoms, such as nitromethane, nitroethane and nitropropane, or nitrated aromatic hydrocarbons, preferably nitrated benzene or toluene compounds, such as nitrobenzene, chloronitrobenzene and o-nitrotoluene.

Suitable ethers for preparing the crystalline modification I of florasulam include, for example, ethyl propyl ether, n-butyl ether, anisole, phenetole, cyclohexyl methyl ether, dimethyl ether, diethyl ether, dimethyl glycol, diphenyl ether, dipropyl ether, diisopropyl ether, di-n-butyl ether, diisobutyl ether, diisoamyl ether, ethylene glycol dimethyl ether, isopropyl ethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dichlorodiethyl ether, methyl-tetrahydrofuran, and polyethers of ethylene oxide and/or propylene oxide Suitable esters include, for example, malonates, acetic acid n-butyl ester (n-butyl acetate), methyl acetate, ethyl acetate, isobutyl acetate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate and ethylene carbonate.

Suitable aliphatic alcohols include alcohols having from 1 to 6 carbon atoms, such as methanol, isopropyl alcohol, ethanol, n-propanol, isopropanol, n-butanol and tert-amyl alcohol.

The solvent may contain one or a mixture of two or more of the aforementioned solvents.

Preferred solvents are nitrobenzene, toluene, xylene, benzene, chlorobenzene, dichlorobenzene, ethyl benzene, trifluoro methyl benzene, mesitylene, ether, methyl ethyl ketone and mixtures thereof.

In the present invention, it is particularly preferred that the solvent comprises methyl ethyl ketone, xylene or mixtures thereof.

Hence, according to a particularly preferred embodiment of the process, in step (i) amorphous florasulam is dissolved in a solvent comprising methyl ethyl ketone and/or xylene. In a preferred embodiment, the solvent consists essentially of methyl ethyl ketone and/or xylene.

The solution of amorphous florasulam in the solvent may be prepared in step (i) in any suitable manner. In one embodiment, the solution is prepared at ambient temperatures, without heating the solvent. Alternatively, the solution may be prepared by heating the solvent to an elevated temperature.

In step (ii) of the process of the present invention, florasulam is crystallized from the solution. Techniques for effecting crystallization of florasulam from the solution are known to those skilled in the art. For example, in an embodiment where the solution in step (i) is formed at elevated temperatures, crystallization may be effected by cooling the solution to room or ambient temperature. In one preferred embodiment, crystallization is effected by concentrating the solution formed in step (i) of the process by removing solvent from the solution, for example by evaporation. Alternatively, or in addition thereto, seed crystals, in particular seed crystals of the aforementioned crystalline modification I of florasulam, may be added to the solution formed in step (i), to facilitate and/or enhance crystallization.

In step (H) of the process, a solid precipitate of the crystalline modification I of florasulam is recovered. Suitable techniques for recovering the solid precipitate are known in the art and include, for example filtration and centrifugation.

It is preferred that the solid precipitate of florasulam recovered in step (ii) is washed with a solvent one or more times. Preferably, the solvent employed in the washing stage consists of one or more components of the solvent employed for forming the solution in step (i), as described hereinbefore. Methyl ethyl ketone and xylene are particularly suitable solvents for washing the recovered solid of florasulam.

As noted above, it has been found that the crystalline modification I of florasulam may be prepared by precipitation from a solution of florasulam in a suitable solvent. As also noted above, it has been found that the crystalline modification I of florasulam exhibits a significantly increased stability, including a significantly increased resistance to hydrolysis, compared with the known forms of florasulam.

Accordingly, in a further aspect, the present invention provides a method for increasing the stability of florasulam, the method comprising preparing a solution of florasulam in a suitable solvent; and precipitating solid florasulam from the solution.

Still further, the present invention provides the use of a suitable solvent to prepare florasulam having increased stability.

Suitable solvents for preparing florasulam with increased stability are described above.

The invention also relates to a composition comprising the crystalline modification I of florasulam.

Accordingly, in a further aspect, the present invention provides a herbicidal composition comprising florasulam in the crystalline modification I as defined hereinbefore defined.

The crystalline modification I of florasulam may be present in the composition in any suitable amount. The amount of the crystalline modification I of florasulam is preferably less than 75% by weight of the composition, more preferably less than 50% by weight of the composition, still more preferably less than 30% by weight of the composition, more preferably still about 25% by weight of the composition or less.

The use of florasulam as a herbicide is well known in the art and is used on a commercial scale. The crystalline modification I of florasulam is also active in controlling unwanted plant growth, such as weeds. Techniques of formulating and applying florasulam are known in the art, for example as disclosed in the prior art documents discussed hereinbefore. Florasulam in the form of the crystalline modification I of the present invention may be formulated and applied in an analogous manner.

Accordingly, the present invention furthermore provides processes for preparing compositions for controlling unwanted plant growth using the crystalline modification I of florasulam.

The present invention further provides a herbicidal composition comprising the crystalline modification I of florasulam in combination with one or more other auxiliaries.

The crystalline modification I of florasulam can be formulated in a known manner to form a range of herbicidal formulations using suitable auxiliaries, carriers and solvents, as will be known to the person skilled in the art. Examples of formulations of the crystalline modification I of florasulam include suspension concentrates (SC), oil-based suspension concentrates (OD), water-soluble granules (SG), dispersible concentrates (DC), emulsifiable concentrates (EC), emulsion seed dressings, suspension seed dressings, granules (GR), microgranules (MG), suspoemulsions (SE) and water-dispersible granules (WG).

The crystalline modification I of florasulam is present in the compositions in an amount to provide the required dosage to the plants and locus being treated consistent with the practices associated with the formulation in questions. In general, in the herbicidal formulations the crystalline modification I of florasulam may be present in an amount of from about 0.1 to about 75% by weight of the total mixture.

Herbicidal formulations may be prepared, for example, by extending the crystalline modification I of florasulam with water, solvents and carriers, using, if appropriate, emulsifiers and/or dispersants, and/or other auxiliaries. These formulations may be prepared in a known manner by mixing the crystalline modification I of florasulam with the other components, optionally with other customary additives, for example, liquid diluents, solid diluents, wetting agents, dispersants, thickening agent, antifreeze agents, biocide and any necessary adjuvants and other formulation ingredients.

Liquid diluents include, but are not limited to, water, N,N-dimethylmamide, dimethyl sulfoxide, N-alkylpyrrolidone, ethylene glycol, polypropylene glycol, propylene carbonate, dibasic esters, paraffines, alkylbenzenes, alkyl naphthalenes, glycerine, triacetine, oils of olive, castor, linseed, sesame, corn, peanut, cotton-seed, soybean, rapeseed and coconut, ketones such as cyclohexanone, 2-heptanone, isophorone and 4-hydroxy-4-methy1-2-pentanone, acetates such as hexyl acetate, heptyl acetate and octyl acetate, and alcohols such methanol, cyclohexanol, decanol, benzyl and tetrahydrofurfuryl alcohol.

Solid diluents can be water-soluble or water-insoluble. Water-soluble solid diluents include, but are not limited to, salts such as alkali metal phosphates, for example sodium dihydrogen phosphate, alkaline earth phosphates, sulfates of sodium, potassium, magnesium and zinc, sodium and potassium chloride, sodium acetate, sodium carbonate and sodium benzoate, and sugars and sugar derivatives such as sorbitol, lactose, sucrose and mannitol. Examples of water-insoluble solid diluents include, but are not limited to clays, synthetic and diatomaceous silicas, calcium and magnesium silicates, titanium dioxide, aluminum, calcium and zinc oxide.

Wetting agents include, but are not limited to, alkyl sulfosuccinates, laureates, alkyl sulfates, phosphate esters, acetylenic diols, ethoxyfluornated alcohols, ethoxylated silicones, alkyl phenol ethyoxylates, benzene sulfonates, alkyl-substituted benzene sulfonates, alkyl a-olefin sulfonates, naphthalene sulfonates, alkyl-substituted napthalene sulfonates, condensates of naphthalene sulfonates and alkyl-substituted naphthalene sulfonates with formaldehyde, and alcohol ethoxylates. Alkyl naphthalene sulphonates, sodium salts are particularly useful for the composition of the invention.

Dispersants include, but are not limited to, sodium, calcium and ammonium salts of ligninsulfonates (optionally polyethoxylated); sodium and ammonium salts of maleic anhydride copolymers; sodium salts of condensed phenolsulfonic acid; and naphthalene sulfonate-formaldehyde condensates. Of note are compositions comprising up to 10% by weight of dispersant. Ligninsulfonates such as sodium ligninsulfonates are particularly useful for the composition of the invention. Naphthalene sulfonate-formaldehyde condensates such as naphthalenesulfonic acid, polymers with formaldehyde, and sodium salts are particularly useful for the composition of the invention.

Thickener agents include, but are not limited to, guar gum, pectin, casein, carrageenan, xanthan gum, alginates, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose. Synthetic thickeners include derivatives of the aforementioned agents, and also include polyvinyl alcohols, polyacrylamides, polyvinylpyrrolidones, various polyethers, their copolymers as well as polyacrylic acids and their salts. Alkylpolyvinylpyrrolidones are particularly useful for the composition of the present invention.

Suitable antifreeze agents include liquid polyols, for example ethylene glycol, propylene glycol or glycerol. The amount of antifreeze agents is generally from about 1% to about 20% by weight, in particular from about 5 to about 10% by weight, based on the total weight of the composition.

Biocides may also be added to the composition according to the invention. Suitable Biocides are those based on isothiazolones, for example Proxel® from ICI or Acticide® RS from Thor Chemie or Kathon® MK from Rohm & Haas. The amount of biocides is typically from 0.05% to 0.5% by weight, based on the total weight of the composition.

Other formulation ingredients can also be used in the present invention such as dyes, defoamers, drying agents, and the like. These ingredients are known to one skilled in the art.

The crystalline modification I of florasulam according to the present invention can be present in formulations and in its use forms, prepared from these formulations, either the sole active component or as a mixture with other active compounds, such as insecticides, attractants, sterilizing agents, bactericides, acaricides, nematicides, fungicides, growth-regulating substances, herbicides, safeners, fertilizers and semiochemicals, or with agents for improving plant properties, such as growth enhancers.

\Mien used as a herbicide, the crystalline modification I of florasulam according to the present invention can furthermore be present in formulations and its use forms, prepared from these formulations, as a mixture with inhibitors which reduce degradation of the active compounds after their use in the environment of the plant, on the surface of plant parts or in plant tissues.

As noted above, the crystalline modification I of florasulam may be used in combination with one or more other active compounds. Preferred partners for the crystalline modification I of florasulam include sulfonylurea (SU) such as metsulfuronmethyl, tribenuron-methyl, thifensulfuron-methyl, flupyrsulfuron-methyl-sodium, mesosulfuron-methyl, iodosulfuron-methyl-sodium, rimsulfuron, nicosulfuron, halosulfuron-methyl, trifloxysulfuron-sodium and chlorsulfuron. Other partners include diflufenican, fluroxypyr, dicamba, mesotrione and flufenacet.

Particular preferred partners for use in combination with the crystalline modification I of florasulam are metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl and diflufenican.

In a further aspect, the present invention provides a method for controlling unwanted plant growth at a locus, the method comprising applying to the locus the crystalline modification I of florasulam as hereinbefore defined.

In a still further aspect, the present invention provides the use of the crystalline modification I of florasulam as hereinbefore defined in the control of unwanted plant growth All plants and plant parts can be treated in accordance with the present invention. In the present context, plants are to be understood as meaning all plants and plant populations such as desired and undesired wild plants or crop plants, including naturally occurring crop plants. Crop plants can be plants which can be obtained by conventional breeding and optimization methods, by biotechnological and genetic engineering methods, or by combinations of these methods, including the transgenic plants and the plant cultivars which can or cannot be protected by plant breeders' rights. Plant parts are to be understood as meaning all parts and organs of plants above and below the ground, such as shoot, leaves, needles, stalks, stems, flowers, fruit bodies, fruits, seeds, roots, tubers and rhizomes. Harvested materials, and vegetative and generative propagation materials, for example, cutting, tubers, meristem tissue, rhizomes, offsets, seeds, single and multiple plant cells and any other plant tissues, are also included.

As used herein, the term "about," when used in connection with a numerical amount or range, means somewhat more or somewhat less than the stated numerical amount or range, to a deviation of ± 10% of the stated numerical amount or endpoint of the range.

"Surrounding", as used herein, refers to the place on which the plants are growing, the place on which the plant propagation materials of the plants are sown or the place on which the plant propagation materials of the plants will be sown.

Treatment of the plants and plant parts with the compositions or formulations of the inventions is carried out directly or by allowing the compositions or formulations to act on their surroundings, habitat or storage space by the customary treatment methods. Examples of these customary treatment methods include dipping, spraying, vaporizing, fogging, broadcasting, painting on in the case of propagation material, and applying one or more coats particularly in the case of seed.

The composition or formulations of the invention may be used to control the growth of a range of broad-leaved plants. Examples of plants that may be controlled are Gal/urn aparine, Stellaria media, Sisymbrium officinale, Aphanes arvensis, Scandix pecten-veneris, Capsella bursa-pastoris, Brass/ca nap us, Raphanus raphanistrum, Polygonum convolvulus, Matricaria spp., and various cruciferae.

The benefits of the present invention are seen most when the herbicidal composition is applied to kill weeds or other unwanted plant growth in growing crops of useful plants, such as cereals including wheat, barley, durum, triticale, oat, rye, maize, amenity, grassland, cotton, rice, potatoes, sugar beets, plantation crops, for example such as bananas, fruit trees, rubber trees, tree nurseries, vines, asparagus, bushberries, for example such as blueberries, caneberries, cranberries, flax, grain sorghum, okra, peppermint, rhubarb, spearmint and sugarcane. The crystalline modification I of florasulam of this invention is particularly effective in the control of unwanted plant growth in crops of wheat, barley, durum, triticale, oat, rye, maize, amenity, and grassland.

Embodiments of the present invention will now be described by the following examples which are provided for illustrative purposes only, and not intended to limit the scope of the disclosure.

All percentages are given in weight % unless otherwise indicated.

S

Reference will be made herein to the accompanying figures, in which: Figure 1 is an infra-red (IR) spectrum of a crystalline modification I of florasulam; Figure 2 is an X-ray powder diffraction spectrum of a crystalline modification I of florasulam; Figure 3 is a Differential Scanning Calorimetry (DSC) spectrum of a crystalline modification I of florasulam; and Figure 4 is an X-ray powder diffraction spectrum of amorphous florasulam.

EXAMPLES

Example 1: Preparation of amorphous florasulam in accordance with the disclosure of EP0537611 with necessary modification 2, 6-difluoroaniline (0.8 g), 2-chlorosulfony1-8-fluoro-5-methoxy-1,2,4-triazolo (1,5-cppyrimidine (0.8 g), and 20 rnL of dry acetonitrile were placed in a 100 mi_ flask equipped with a gas inlet adapter and a magnetic stirring bar. Pyridine (0.50 rrIL: 6.2 rnmol) and dirnethyl sulfoxide (0.06 mL, 0.8 mmol) were added with stirring under nitrogen and the mixture was allowed to react for 3.5 hr. The volatile components were then removed by evaporation under reduced pressure and the residue was dissolved in 150 rni_ of methylene chloride. The solution obtained was extracted 2 times with 100 rrit_ of 1N NCI and once with 100 mi.. of water, dried over MgSO4, filtered, and concentrated by evaporation under reduced pressure to obtain a yellow solid. This solid was stirred with 200 mL of hexane and filtered to give 0.48 g (34 percent yield) of the title compound as a yellow solid melting at 196198°C (d).

The reaction scheme for this example is as follows: 0 N.N, 7 2 I NH 6Me The solid product obtained was analysed using X-ray powder diffraction (XRD).

The pattern obtained is shown in Figure 4.

As shown in Figure 4, the X-ray powder diffraction pattern of the resulting florasulam product has no significant signals, which indicates that the florasulam product prepared in accordance with the disclosure of EP0537611 is amorphous.

Example 2: Preparation of the crystalline modification I of florasulam A crystalline modification of florasulam was prepared in the following manner: Crystallization from methyl ethyl ketone g of amorphous florasulam prepared in Example 1 was placed in a 3 neck round bottom flask along with 50 mL of methyl ethyl ketone and the resulting slurry was heated to 65 °C to obtain a homogeneous solution. The insoluble particles, if any, were filtered and the solution was slowly cooled to ambient temperature. Fine crystals were formed during the cooling and the mixture was stirred at ambient temperature for 2h. The resulting slurry was filtered and washed with 3 mL of methyl ethyl ketone. The filtered crystals were dried under vacuum at 40 °C in order to remove the methyl ethyl ketone traces from the crystals. The crystals thus obtained had a purity of >98% and the yield was found to be not less than 90%.

The crystals were characterized using DSC, IR spectrometry and X-ray powder diffraction respectively. The crystals were identified to be the crystalline modification I of florasulam as follows: The melting point of the product was measured by DSC and exhibits an endothermic peak at 219.0°C corresponding to its melting with an immediate exothermic peak of 220.7 °C as shown in Figure 3.

The IR spectrum of the product is set out in Figure 1. The IR spectrum exhibits characteristic peaks at 3069, 1636, 1531, 1344, 1243, 1170 and 1100 cm* The product had the X-ray powder diffractogram shown in Figure 2 with the reflexes listed in Table 1 below.

Table 1

2 0 (°) d (A) 11.049 ± 0.2 9.29 ± 0.05 11.732 ± 0.2 8.75 ± 0.05 12.161 ± 0.2 8.44 ± 0.05 12.872 ± 0.2 7.98 ± 0.05 16.353 ± 0.2 6.29 ± 0.05 17.593 ± 0.2 5.85 ± 0.05 18.088 ± 0.2 5.69 ± 0.05 18.380 ± 0.2 5.60 ± 0.05 20.098 ± 0.2 5.13 ± 0.05 21.276 ± 0.2 4.85 ± 0.05 22.063 ± 0.2 4.68 ± 0.05 23.578 ± 0.2 4.38 ± 0.05 24.104 ± 0.2 4.28 ± 0.05 25.659 ± 0.2 4.03 ± 0.05 25.892 ± 0.2 3.99 ± 0.05 27.429 ± 0.2 3.77 ± 0.05 28.225 ± 0.2 3.67 ± 0.05 28.963 ± 0.2 3.58 ± 0.05 30.238 ± 0.2 3.43 ± 0.05 30.940 ± 0.2 3.35 ± 0.05 31.557 ± 0.2 3.29 ± 0.05 33.263 ± 0.2 3.13 ± 0.05 35.570 ± 0.2 2.93 ± 0.05 38.799 ± 0.2 2.69 ± 0.05 41.242 ± 0.2 2.54 ± 0.05 44.017 ± 0.2 2.39 ± 0.05 Example 3: Preparation of the crystalline modification I of florasulam A crystalline modification of florasulam was prepared in the following manner: Crystallization from xylene g of the florasulam product prepared in Example 1 was placed in a 3 neck round bottom flask along with 30 mL of xylene and the resulting slurry was heated to 83 °C to obtain a homogeneous solution. The insoluble particles, if any, were filtered and the solution was slowly cooled to ambient temperature. Fine crystals were formed during the cooling and the mixture was stirred at ambient temperature for 2h. The resulting slurry was filtered, washed with 3 mL of xylene and dried under vacuum at 4500 in order to remove the xylene traces from the crystals. The crystals thus obtained had a purity of >98% and the yield was found to be not less than 80%.

The crystals were characterized as being the crystalline modification I of florasulam using IR spectrometry, X-ray powder diffraction and DSC as described in Example 2.

Example 4: Preparation of oil based suspension concentrate (OD) formulation Two oil-based suspension concentrate formulations, Example 4 and Comparative Example A, were prepared as follows: All the components listed in Table 2 below were mixed uniformly and ground with a Dyno-Mill (manufactured by Willy A. Bachofen AG) to obtain an oil based suspension concentrate.

Table 2

Ingredients Weight % Function Example 4 Comparative A Florasulam, crystalline modification I, 98% (prepared in Example 2) 40.8 0 Active compound Amorphous florasulam (prepared in Example 1) 0 40.8 Active compound Sodium lignosulfonate (REAX® 88B) 22 22 Dispersing agent Alkylpolyvinylpyrrolidone 20 20 Thickening agent Corn oil Balance to Balance to Carrier 100% 100% Example 5: Preparation of Suspension Concentrate (SC) Two oil-based suspension concentrate formulations, Example 5 and Comparative Example B, were prepared as follows: All the components listed in Table 3 below were mixed uniformly and the resulting mixture was ground with a Dyno-Mill (manufactured by Willy A. Bachofen AG) to obtain a suspension concentrate (SC).

Table 3

Ingredients Weight % Function Example 5 Comparative B Florasulam, crystalline modification I, 98% (prepared in Example 2) 51.00 0.00 Active compound Amorphous florasulam (prepared in Example 1) 0.00 51.00 Active compound Sodium lignosulfonate (REAX® 88B) 18.00 18.00 Dispersing agent Alkylpolyvinylpyrrolidone 5.00 5.00 Thickening agent Butylated hydroxytoluene (BHT) 1.00 1.00 Antioxidant Propylene glycol 5.00 5.00 Antifreeze 1,2-Benzisothiazol-3(2H)-one (PROXEL® 1.00 1.00 Biocide Water Balance to Balance to Carrier 100% 100%

S

Example 6: Preparation of soluble granules (SG) Two oil-based suspension concentrate formulations, Example 6 and Comparative Example C, were prepared as follows: All the components listed in Table 4 below were mixed, blended and milled in a high-speed rotary mill. Sufficient water was added to obtain an extrudable paste. The paste was extruded through a die or screen to form an extrudate. The wet extrudate was dried at 70 °C in a vacuum oven and then sifted through 0.71 mm to 2 mm screens to obtain the product granules.

Table 4

Ingredients Weight °A. Function Example 6 Comparative C Florasulam, crystalline modification I, 98% (prepared in Example 2) 25.51 0 Active compound Amorphous florasulam (prepared in Example 1) 0 25.51 Active compound Lignosulfonic acid, sodium 15 15 Dispersing agent salt, (REAX® 88B) Naphthalenesulfonic acid, polymer with formaldehyde, sodium salt (TAMOL® NN 8906) 6 6 Dispersing agent Sodium acetate 4 4 Filler Sodium carbonate 4 4 Filler Non-ionic aqueous emulsion of Polydimethylsiloxanes 1 1 Antiform Mannitol Balance to Balance to carrier 100% 100% Example 7: Preparation of water dispersible granules (WG) Two oil-based suspension concentrate formulations, Example 7 and Comparative Example D, were prepared as follows: All the components listed in Table 5 below were mixed, blended and milled in a high-speed rotary mill. Sufficient water was added to obtain an extrudable paste. The paste was extruded through a die or screen to form an extrudate. The wet extrudate was dried at 70°C in a vacuum oven and then sifted through 0.71 mm -2 mm screens to obtain the product granules.

Table 5

Ingredients Weight % Function Example 7 Comparative D Florasulam, crystalline modification I, 98% (prepared in Example 2) 25.51 0 Active compound Amorphous florasulam (prepared in Example 1) 0 25.51 Active compound Alkyl naphthalene sulphonate, sodium salt (Akzo Nobel) 2 2 Wetting agent Lignosulfonic acid, sodium 15 15 Dispersing agent salt, REAV 88B) Naphthalenesulfonic acid, polymer with formaldehyde, sodium salt (TAMOL® NN8906) 6 6 Dispersing agent Sucrose 10 10 Filler Non-ionic aqueous emulsion of Polydimethylsiloxanes 1 1 Antiform Mannitol Balance to Balance to Carrier 100% 100% Example 8: Stability test The stability of the florasulam in the compositions prepared in Examples 4 to 7 was determined by aging samples of each composition in heated ovens having the same atmosphere therein. Samples were stored at 54 °C for 1 week, following the procedures of the Collaborative International Pesticides Analytical Council CIPAC MT 46.3.

The florasulam content of each sample was determined both before and after aging to determine relative percentage of hydrolysis (RPH).

RPH was calculated by the following equation: (The final weight % of florasulam -The initial weight % of florasulam) RPH= x100% The initial weight % of florasulam Florasulam content was determined by assaying the compositions with high-pressure liquid chromatography (HPLC) using reverse phase columns and eluants.

The results are listed in Table 6.

S Table 6

Sample Compound Weight (%) of florasulam RPH% Example 4 Florasulam, crystalline modification I 40 0 Comparative Example A Amorphous florasulam 40 Example 5 Florasulam, crystalline modification I 50 0 Comparative Example B Amorphous florasulam 50 Example 6 Florasulam, crystalline modification I 25 0 Comparative Example C Amorphous florasulam 25 Example 7 Florasulam, crystalline modification I 25 0 Comparative Example D Amorphous florasulam 25 As can be seen from the results set out in Table 6 above, formulations containing the crystalline modification I of florasulam exhibited a very high stability and were resistant to hydrolysis during the accelerated storage procedure. In contrast, all of the comparative formulations containing amorphous florasulam exhibited significant hydrolysis of the florasulam active ingredient, with up to 50% of the active ingredient being lost during the storage period.

Claims (1)

1. CLAIMS1. A crystalline modification I of florasulam, exhibiting at least four of the following reflexes in an X-ray powder diffractogram recorded using Cu-Ka radiation at 25 °C: = 11.049 ± 0.2 (1) 29= 11132 ±0.2 (2) ze = 12.872 ± 0.2 (3) ze = 17.593 ± 0.2 (4) 20 = 18.088 ± 0.2 (8) 29 = 18.380 ± 0.2 (6) 29 = 20.098 ± 0.2 (7) 28 = 22.063 ± 0.2 (8) = 24.104 ± 0.2 (8) ze = 25.659 ± 0.2 (10) ze = 25.892 ± 0.2 (11) = 28.225 ± 0.2 (12) 29 = 33.263 ± 0.2 (13) 2. The crystalline modification I of florasulam according to claim 1, exhibiting at least four of the following reflexes in an X-ray powder diffractogram recorded using Cu-Ka radiation at 25 °C: = 11.049 ± az (1) 20 = 11.732 ± 02 (2) = 12.872 ± 0.2 (3) 29 = 17.593 ± 0.2 (4) = 18.088 ± 0.2 (5) = 18.380 ± 0.2 (6) = 20.098 ± 0.2 (7) 28 = 25.892 ± 0.2 (11) S 26 = 28.225 ± 0.2 (12) 28 = 33.263 ± 0.2 (13) 3. The crystalline modification I of florasulam according to claim 2, exhibiting at least five of the said reflexes.4. The crystalline modification I of florasulam according to claim 3, exhibiting at least six of the said reflexes.5. The crystalline modification I of florasulam according to any preceding claim, exhibiting an IR spectrum with characteristic bands at 3069, 1636, 1531, 1344, 1243, 1170 and 1100 cm-1.6. A process for the preparation of a crystalline modification I of florasulam comprising: i) preparing a solution of florasulam in a solvent; ii) effecting crystallization of florasulam from the solution to obtain a solid precipitate; and Hi) isolating the solid precipitate.7. The process according to claim 6, wherein the solvent comprises methyl ethyl ketone xylene or a mixture thereof.8. A composition comprising the crystalline modification I of florasulam according to any of claims 1 to 5 and at least one auxiliary.9. The composition according to claim 8, wherein the composition is in the form of a suspension concentrate (SC), an oil-based suspension concentrate (OD), water-soluble granules (SG), a dispersible concentrate (DC), an emulsifiable concentrate (EC), an emulsion seed dressing, a suspension seed dressing, granules (GR), microgranules (MG), a suspoemulsion (SE) or water-dispersible granules (WG) 10. The composition according to claim 9, wherein the composition is in the form of an oil-based suspension concentrate (OD) or a suspension concentrate (SC).11. The composition according to any of claims 8 to 10, wherein the auxiliary is one or more solvents, diluents, wetting agents, dispersants, thickeners, antifreeze agents or 15 biocides.12. The composition according to any of claims 8 to 11, which comprises the crystalline modification I of florasulam in an amount of less than 75 % by weight.13. Use of a crystalline modification I of florasulam according to any of claims 1 to 5 or a composition according to any of claims 8 to 12 for the control of plant growth.14. A method for controlling plant growth at a locus comprising applying to the locus a crystalline modification I of florasulam according to any of claims 1 to 5 or a composition according to any of claims 8 to 12.15. The method according to claim 14, wherein the plant growth comprises one or more of Gal/urn aparine, Ste//aria media, Sisymbrium officinale, Aphanes arvensis, Scandix pecten-veneris, Capsella bursa-pastoris, Brass/ca nap us, Raphanus raphanistrum, Polygonum convolvulus, Matficaria spp., and cruciferae.16. The use of a solvent to increase the stability of florasulam.