GB2589919A

GB2589919A - Novel crystalline forms of flufenacet, methods for their preparation and use of the same

Info

Publication number: GB2589919A
Application number: GB1918391.2A
Authority: GB
Inventors: Timothy Bristow James
Original assignee: Rotam Agrochem International Co Ltd
Current assignee: Rotam Agrochem International Co Ltd
Priority date: 2019-12-13
Filing date: 2019-12-13
Publication date: 2021-06-16
Also published as: WO2021115493A2; GB201918391D0; EP4073050A2; EP4073050A4; WO2021115493A3

Abstract

A crystalline modification I of flufenacet (N-(4-fluorophenyl)-N-(1-methylethyl)-2-{[5-(trifluoromethyl)-1,3,4-thiadiazol-2-yl]oxy}acetamide characterised by an X-ray powder diffractogram (XRD) exhibiting at least three of the reflexes 8.0, 15.4, 16.1, 18.6, 19.5, 23.0, 24.1, 26.0, 26.7, and 29.4 as 2θ±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu—Kα radiation at 25 °C. The polymorphic form may also be characterised by an infrared (IR) spectrum with characteristic functional group vibration peaks at wavenumbers (cm-1, ±0.2%) of one or more of 1651.72, 1506.90, 1419.58, 1326.96, 1151.12, 954.10, 941.28, 622.15, and 611.46 cm-1, a melting point of from 79.3-80.8 °C, and and/or a differential scanning calorimetry (DSC) profile having an endothermic melting peak with onset at 79.3 °C and peak maximum at 80.3 °C. There is also provided a method for preparing the crystalline modification of flufenacet comprising: i) providing a solution of flufenacet in a solvent system comprising a one or more solvents; ii) precipitating the crystalline modification I of flufenacet from the solution; and iii) isolating the precipitated crystalline modification I of flufenacet. A preferred solvent is ethanol. Compositions comprising the crystalline modification I of flufenacet and its use in the control of unwanted plant growth are also provided.

Description

NOVEL CRYSTALLINE FORMS OF FLUFENACET, METHODS FOR THEIR PREPARATION AND USE OF THE SAME The present invention relates to novel crystalline forms of N-(4-FluorophenyI)-N-isopropyl-2-1[5-(trifluoromethyl)-1,3, 4-thiadiazol-2-yl]oxylacetamide (flufenacet).

Further, the present invention relates to methods for the preparation of the novel crystalline forms of flufenacet. Still further, the present invention relates to the use of the crystalline forms of flufenacet in agrochemical preparations and for the control of unwanted plant growth.

N-(4-Fluoropheny1)-N-isopropyl-2-{[5-(trifluoromethyl)-1,3, 4-thiadiazol-2-yl]oxy}acetamide, having the common name flufenacet, is an oxyacetamide herbicide, highly effective against a wide range of broadleaf and grassy weeds. Flufenacet has the molecular formula C14F113F4N302S and its chemical structure can be represented as follows: CH.

Flufenacet and formulations containing flufenacet are available commercially. However, it has been found that the commercially available flufenacet exhibits a significant lack of stability. In particular, known forms of flufenacet are susceptible to hydrolysis and N-isomerization, reducing the effectiveness and suitability of the compound as an active component in herbicide compositions and formulations. Hydrolysis and N-isomerization of flufenacet can occur during storage, particularly when the compound is exposed to moisture and heat. As a result, the herbicidal activity of the compound decreases. This in turn requires that larger amounts of lo flufenacet have to be applied in shorter intervals in order to achieve a required level of herbicidal activity, leading to the production of potentially toxic degradation products.

Therefore, there is a need to improve the stability of flufenacet, in particular to decrease the susceptibility of flufenacet to hydrolysis and N-isomerization.

It is known that some organic compounds exist in only one crystalline form, while other compounds can exist in two or more crystalline forms. It is not possible to predict the number of different crystalline forms a given compound will have, nor the physical, chemical and biological properties of the different crystalline forms, which may be markedly different.

It has now been discovered that flufenacet can exist in a crystalline form, herein termed "crystalline modification I", which has been found to exhibit a high resistance to hydrolysis and N-isomerization. This provides significant advantages when using flufenacet in the crystalline modification I when preparing agrochemical formulations and the use thereof in the control of unwanted plant growth.

Accordingly, in a first aspect, the present invention provides a crystalline modification I of flufenacet, the crystalline modification exhibiting at least three of the following reflexes, in any combination, as 28±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu-Ka radiation at 25 °C: = 8.0 ± 0.2 (1) 28 = 14.8 ± 0.2 (2) 2e. 15.4 ± 0.2 (3) 28 = 16.1 ±0.2 (4) 28 = 18.6 ± 0.2 (5) = 19.5 ± 0.2 (6) 20 = 23.0 ± 0.2 (7) 28 = 24.1 ±0.2 (8) = 26.0 ± 0.2 (9) 28 = 26.7 ± 0.2 (10) 28 = 29.4 ± 0.2 (11).

In a second aspect, the present invention provides a crystalline modification I of flufenacet, the crystalline modification exhibiting an infrared (IR) spectrum with characteristic functional group vibration peaks at wavenumbers (cm-1, ± 0.2%) of one or more of 1651.72, 1506.90, 1419.58, 1326.96, 1151.12, 954.10, 941.28, 622.15, and 611.46 cm-1.

In a third aspect, the present invention provides a crystalline modification I of flufenacet, the crystalline modification exhibiting a melting point of from 79.3 to 80.8°C.

In a fourth aspect, the present invention provides a crystalline modification I of flufenacet, the crystalline modification exhibiting a differential scanning calorimetry (DSC) profile having an endothermic melting peak with onset at 79.3°C and peak maximum at 80.4°C.

The crystalline modification I of flufenacet is useful in controlling plant growth. Accordingly, the present invention also provides compositions for controlling plant growth, such as weeds, comprising the crystalline modification I of flufenacet. In the compositions, flufenacet may be employed on its own, as a mixture with auxiliaries and carriers and/or as a mixture with other active compounds.

In a further aspect, the present invention provides the use of the crystalline modification I of flufenacet in the control of undesirable plant growth.

Still further, the present invention provide a method for controlling plant growth at a locus, the method comprising applying to the locus the crystalline modification I of flufenacet.

The aspects of the present invention relating to the crystalline modification I of flufenacet will be described in more detail hereinbelow, having reference where appropriate, to the accompanying figures, in which: Figure 1 is an X-ray powder diffraction (XRD) spectrum of the crystalline modification I of flufenacet; Figure 2 is an infrared (IR) spectrum of the crystalline modification I of flufenacet; and

S

Figure 3 is a Differential Scanning Calorimetry (DSC) spectrum of the crystalline modification I of flufenacet.

As noted above, it has been found that the crystalline modification I of flufenacet exhibits a significant improvement in its stability, which avoids or significantly reduces the hydrolysis and N-isomerization problems encountered with flufenacet as used in the current commercially available formulations. In addition, it has been found that the crystalline modification I of flufenacet is easier to comminute and/or grind than known forms of flufenacet. This facilitates the preparation of a wide range of agrochemical formulations, such as suspension concentrates (SC), oil-based suspension concentrates (OD), water-dispersible granules (WO) and water-soluble granules (SG).

As noted above, in one embodiment, the crystalline modification I of flufenacet may be characterized as exhibiting at least three of the following reflexes, in any combination, as 28±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu Ka is radiation at 25 °C: 28 = 8.0 ± 0.2 (1) 28 = 14.8 ± 0.2 (2) 28 = 15.4 ± 0.2 (3) 28 = 16.1 ±0.2 (4) 28 = 18.6 ± 0.2 (5) 28 = 19.5 ± 0.2 (6) 28 = 23.0 ± 0.2 (7) 2e= 24.1 ±0.2 (8) = 26.0 ± 0.2 (9) = 26.7 ± 0.2 (10) 28 = 29.4 ± 0.2 (11).

The crystalline modification I of flufenacet of the present invention is characterized by an X-ray powder diffractogram having at least three of the reflexes indicated above. Preferably, the crystalline modification I of flufenacet is one having at least four of the aforementioned reflexes, more preferably at least five of the aforementioned reflexes, still more preferably six, more preferably still seven, especially eight of the aforementioned reflexes, again in any combination thereof.

An X-ray powder diffractogram of the crystalline modification I of flufenacet is shown in Figure 1, which will be described in detail hereinafter.

In one preferred embodiment, the crystalline modification I of flufenacet exhibits at least three, more preferably four, still more preferably five, more preferably still six, especially seven, of the following reflexes, in any combination, as 20±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu-Ka radiation at 25°C: = 8.0 ± 0.2 (1) 28 = 14.8 ± 0.2 (2) 28= 15.4 ± 0.2 (3) 28= 16.1 ±0.2 (4) 28 = 19.5 ± 0.2 (6) 28 = 23.0 ± 0.2 (7) 2e= 24.1 ±0.2 (8) = 26.7 ± 0.2 (10).

In a preferred embodiment, the crystalline modification I of flufenacet exhibits all of the following reflexes, in any combination, as 29±0.2 degree in an X-ray powder diffractogram recorded using Cu-Ka radiation at 25°C: 2e = 8.0 ± 0.2 (1) = 14.8 ± 0.2 (2) = 15.4 ± 0.2 (3) 20 = 16.1 ± 0.2 (4) = 19.5 ± 0.2 (6) = 23.0 ± 0.2 (7).

A preferred crystalline modification I of flufenacet exhibits all of the reflexes (1) to (10) listed above.

The X-ray powder diffractogram of the crystalline modification I of flufenacet shown in Figure 1 was taken using a diffractometer with a reflection geometry in the range from 30 to 60° with increments of 0.03° using Cu-Ka radiation at 25°C.

As noted above, in a second aspect, the present invention provides a crystalline modification I of flufenacet exhibiting an infrared (IR) spectrum with characteristic functional group vibration peaks at wavenumbers (cm-1, ± 0.2%) of one or more of the following: 1651.72, 1506.90, 1419.58, 1326.96, 1151.12, 954.10, 941.28, 622.15, and 611.46 cm-1.

An infrared (IR) spectrum of the crystalline modification I of flufenacet is shown in Figure 2.

All IR spectra data were obtained using the following acquisition parameters: FT-IR Bruker Tensor37 spectrometer Diamond ATR unit from Specac Wavelength range 550 -4000 cm-1 Resolution 4 cm-1 Number of scans 16 A preferred crystalline modification I of flufenacet exhibits an infrared (IR) spectrum with characteristic functional group vibration peaks at wavenumbers (cm-1, ± 0.2%) of two or more, preferably three or more, more preferably four or more, still more preferably five or more of the following: 1651.72, 1506.90, 1419.58, 1326.96, 1151.12, 954.10, 941.28, 622.15, and 611.46 cm* A preferred crystalline modification II of flufenacet exhibits an infrared (IR) spectrum with characteristic functional group vibration peaks at wavenumbers (cm-1, ± 0.2%) having all of the aforementioned vibration peaks.

In one embodiment, the crystalline modification I of flufenacet exhibits an X-ray powder diffractogram as described above for the first aspect of the invention and an infrared (IR) spectrum as described above for the second aspect of the present invention.

As discussed above, a third aspect of the present invention provides a crystalline modification I of flufenacet, exhibiting a melting point of from 79.3 to 80.8°C, preferably a melting point of about 80.4°C.

In one embodiment, the crystalline modification I of flufenacet exhibits a melting point of from 79.3 to 80.8°C according to this third aspect of the invention, together with an X-ray powder diffractogram as described above for the first aspect of the invention and/or an infrared (IR) spectrum as described above for the second aspect of the present invention.

As also discussed above, a fourth aspect of the present invention provides a crystalline modification I of flufenacet exhibiting a differential scanning calorimetry (DSC) profile having an endothermic melting peak with onset at 79.3°C and peak maximum at 80.4°C, more preferably with a melting enthalpy of 75.13 J/g.

In one embodiment, the crystalline modification I of flufenacet exhibits a differential scanning calorimetry (DSC) profile having an endothermic melting peak with onset at 79.3°C and peak maximum at 80.4°C according to this fourth aspect of the invention, together with an X-ray powder diffractogram as described above for the first aspect of the invention and/or an infrared (IR) spectrum as described above for the second aspect of the present invention and/or a melting point as described above for the third aspect of the present invention.

In one preferred embodiment, the crystalline modification I of flufenacet is characterized by an X-ray powder diffraction pattern substantially as shown in Figure 1, and/or characterized by an IR spectrum substantially as shown in Figure 2, and/or characterized by a DSC thermogram substantially as shown in Figure 3, and/or by a melting point of about 80.4°C.

Flufenacet is available commercially. Methods for preparing flufenacet are well known in the art. One particularly suitable method for preparing flufenacet is described in US 4,968,342.

In a fifth aspect, the present invention provides a method for preparing a crystalline modification I of flufenacet, the method comprising the steps of: i) providing a solution of flufenacet in a solvent system comprising a one or more solvents; ii) precipitating the crystalline modification I of flufenacet from the solution; iii) isolating the precipitated crystalline modification I of flufenacet.

The solution of flufenacet may be provided in step i) by dissolving flufenacet in the solvent system. The form of flufenacet used in this step may be any form of flufenacet and other than the crystalline modification I. In one embodiment flufenacet dissolved in the solvent system in step i) is amorphous flufenacet.

The solvent system employed in the method is one in which flufenacet is readily soluble and is one from which the crystalline modification I of flufenacet is crystallised.

In this respect, it has been found that appropriate selection of the solvent system is required in order to yield flufenacet in the crystalline modification I. The solvent system yielding the crystalline modification I of flufenacet comprises one or more solvents selected from acetonitrile; ethers, 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, methyl-tetrahydrofuran, dioxane, dichlorodiethyl ether, methyltetrahydrofuran, polyethers of ethylene oxide and/or propylene oxide; esters, 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; and aliphatic alcohols, for example Cl to C8, preferably Cl to C6 alcohols, more preferably Cl to C5 alcohols, in particular methanol, ethanol, n-propanol, isopropanol, n-butanol and tert-amyl alcohol.

Preferably the solvent system comprises one or more solvents selected from acetonitrile, methyl tert-butyl ether, methyl-tetrahydrofuran, malonates, n-butyl acetate, isobutyl acetate, diethyl carbonate, methanol, ethanol, isopropanol, n-butanol. Particularly preferred solvents are methanol, ethanol and acetonitrile.

As noted above, it has been found that the crystalline form of flufenacet obtained by crystallization from a solution in a solvent system comprising one or more of the aforementioned solvents exhibits a significant and surprisingly increased stability and resistance to N-isomerization.

Accordingly, in a further aspect, the present invention provides the use of a solvent system to prepare crystalline flufenacet having an improved stability and resistance to N-isomerisation, wherein the solvent system comprises one or more solvents selected from acetonitrile, ethers, esters and aliphatic alcohols.

The solvent system may consist essentially of a single solvent selected from the aforementioned solvents. Alternatively, the solvent system may comprise a mixture of two or more of the aforementioned solvents, for example a mixture of three or four solvents.

In step i) of the method, a solution of flufenacet in the solvent system is provided.

As noted above, this may be achieved by dissolving flufenacet in the solvent system. To form the solution, flufenacet may be dissolved in the solvent system at any suitable temperature. It is preferred to heat the solvent system to a temperature from ambient temperature to the reflux temperature of the solvent system. In one embodiment, flufenacet is dissolved in the solvent system at the ref lux temperature of the solvent system. In one embodiment, the solvent system is heated to a temperature from 20 to 70°C, more preferably from 30 to 60°C. The temperature will depend upon such factors as the solubility of flufenacet in the solvent system and the boiling point of the solvent system.

In step ii) of the method, flufenacet is caused to precipitate from the solution to yield the crystalline modification I of flufenacet. Any suitable technique for precipitating flufenacet from the solution provided in step i) may be used. In one embodiment, the solution is cooled. The solution may be cooled to any suitable temperature below room or ambient temperature to promote precipitation of crystalline flufenacet. For example, the solution may be cooled to a temperature of from -20 to 10°C, preferably to a temperature of from -15 to 5°C.

Alternatively, or in addition to cooling, precipitation may be facilitated by removing solvent from the solution, for example by applying a vacuum to the solution.

In one embodiment seed crystals are added to the solution. The addition of seed crystals facilitates precipitation of the solute from the solution, as is known in the art. Preferably, the seed crystals are crystals of flufenacet, more preferably crystals of the crystalline modification I of flufenacet.

The amount of seed crystals added to the solution is typically in the range of from 0.001 to 10% by weight, preferably from 0.001% to 2.5% by weight, more preferably from 0.005 to 0.5% by weight, based on the weight of flufenacet present in the solution provided in step i). The seed crystals are preferably added to the solution at a temperature below the boiling point of the solvent system.

In step iii) of the method, the precipitated crystalline modification I of flufenacet is isolated or recovered from the solvent system. Any suitable technique may be used to recover the crystalline modification I of flufenacet, for example filtration, centrifugation and/or decantation.

The isolated solid flufenacet is preferably washed one or more times with a solvent system comprising one or more solvents. Preferably, the solvent system employed in the washing stage comprises one or more components of the solvent system of the solution provided in step (i), as described hereinbefore. Washing is preferably carried out using the solvent system at a temperature from 0°C to room temperature, depending on the solubility of the crystalline form of flufenacet in the solvent, in order to minimize or avoid the loss of crystalline material in the corresponding washing solvent.

The use of flufenacet as an herbicide is known in the art and is used on a commercial scale. It has been found that the crystalline modification I of flufenacet is also active in controlling undesirable plant growth, such as weeds. Techniques of formulating and applying amorphous flufenacet are known in the art, for example as disclosed in the prior art documents described hereinbefore. These techniques can also be applied in an analogous manner to the crystalline modification I of flufenacet.

Accordingly, the present invention further provides a herbicidal composition comprising the crystalline modification I of flufenacet as defined hereinbefore.

The herbicidal composition generally comprises one or more auxiliary components, as described in more detail hereinafter.

The herbicidal composition may comprise the crystalline modification I of flufenacet in any suitable amount, which may depend upon such factors as the type of formulation being employed. Preferably, the comprises the crystalline modification I of flufenacet in to an amount of up 90% by weight of the composition, preferably up to 75% by weight of the composition, more preferably up to 60% by weight of the composition. Preferably, the composition comprises the crystalline modification I of flufenacet in an amount of from 5% by weight of the composition, preferably from 10% by weight of the composition, more preferably from 20% by weight of the composition. In one preferred embodiment, the composition comprises the crystalline modification I of flufenacet in an amount of about 50% by weight of the composition.

The composition may be formulated in any suitable form. Preferably, 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 (OR), microgranules (MG), a suspoemulsion (SE) or water-dispersible granules (WO). The components and techniques required to form the aforementioned formulations are known in the art.

In one preferred embodiment, the composition is in the form of a suspension concentrate (SC). In a further preferred embodiment, the composition is in the form of water-dispersible granules (WG).

The compositions are prepared by combining the crystalline modification I of flufenacet with one or more agriculturally acceptable auxiliaries. The auxiliaries employed in the composition and their amounts will depend upon the type of formulation and/or the manner in which the formulation is to be applied by the end user. Suitable auxiliaries are customary formulation adjuvant or components, such as dispersants, wetting agents, emulsifiers, extenders, carriers, solvents, surfactants, stabilizers, anti-foam agents, anti-freeze agents, preservatives, antioxidants, colourants, thickeners, solid adherents and inert fillers. Such auxiliaries are known in the art and are commercially available. Their use in the formulation of the compositions of the present invention will be apparent to the person skilled in the art.

Surfactants can be an emulsifier, dispersant or wetting agent of ionic or nonionic type.

Examples which may be used include, but are not limited to, salts of polyacrylic acids, salts of lignosulphonic acid, salts of phenylsulphonic or naphthalenesulphonic acids, polycondensates of ethylene oxide with fatty alcohols or with fatty acids or with fatty amines, substituted phenols, especially alkylphenols, sulphosuccinic ester salts, taurine derivatives, especially alkyltaurates, or phosphoric esters of polyethoxylated phenols or alcohols.

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

The composition may further comprise one or more polymeric stabilizers. Suitable polymeric stabilizers that may be used in the present invention include, but are not limited to, polypropylene, polyisobutylene, polyisoprene, copolymers of monoolef ins and diolefins, polyacrylates, polystyrene, polyvinyl acetate, polyurethanes or polyamides.

Suitable stabilizers are known in the art and are commercially available.

The composition may further comprise one or more anti-foam agents. Suitable anti-foam agents include those substances which can normally be used for this purpose in agrochemical compositions and will be readily apparent to the person skilled in the art. Suitable anti-foam agents are known in the art and are commercially available.

lo Particularly preferred anti-foam agents are mixtures of polydimethylsiloxanes and perfluroalkylphosphonic acids, such as the silicone anti-foam agents (for example commercially available from GE or Compton). Other examples of anti-foam agents are fatty acids, tallow, and sodium salts.

The composition may further comprise one or more preservatives. Suitable preservatives include those substances which can normally be used for this purpose in agrochemical compositions of this type and again are well known in the art. Suitable examples that may be mentioned include Preventolg (commercially available from Bayer AG) and Proxelg (commercially available from Bayer AG).

The composition may further comprise one or more antioxidants. Suitable antioxidants are substances which can normally be used for this purpose in agrochemical compositions, as is known in the art. Preference is given, for example, to butylated hydroxytoluene.

The composition may further comprise one or more solid adherents. Such adherents are known in the art and available commercially. Suitable solid adherents include organic adhesives, including tackifiers, such as celluloses of substituted celluloses, natural and synthetic polymers in the form of powders, granules, or lattices, and inorganic adhesives such as gypsum, silica, or cement.

The composition may further comprise one or more inert fillers. Such inert fillers are known in the art and available commercially. Suitable fillers include, for example, natural ground minerals, such as kaolins, aluminas, talc, chalk, quartz, attapulgite, montmorillonite, and diatomaceous earth, or synthetic ground minerals, such as highly dispersed silicic acid, aluminum oxide, silicates, and calcium phosphates and calcium hydrogen phosphates. Suitable inert fillers for granules include, for example, crushed and fractionated natural minerals, such as calcite, marble, pumice, sepiolite, and dolomite, or synthetic granules of inorganic and organic ground materials, as well as granules of organic material, such as sawdust, coconut husks, corn cobs, and tobacco stalks. Examples of inert fillers also include sodium tripolyphosphate and sucrose.

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, and mixtures thereof.

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 naphthalene sulfonates, condensates of naphthalene sulfonates and alkyl-substituted naphthalene sulfonates with formaldehyde, and alcohol ethoxylates, and mixtures thereof. 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. 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.

Thickening agents include, but are not limited to, guar gum, pectin, casein, carrageenan, xanthan gum, alginates, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose, and mixtures thereof. Synthetic thickening agents include derivatives of the former categories, and also polyvinyl alcohols, polyacrylamides, polyvinylpyrrolidones, various polyethers, their copolymers, as well as polyacrylic acids and their salts, and mixtures thereof.

Alkylpolyvinylpyrrolidones are particularly useful for the composition of the invention.

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

The composition of the present invention may comprise the crystalline modification I of flufenacet as the sole active ingredient. Alternatively, other active components may be present, such as attractants, sterilizing agents, bactericides, acaricides, nematicides, fungicides, growth-regulating substances, herbicides, safeners, fertilizers, semiochemicals, insecticides or agents for improving plant properties.

The present invention also provides a method for controlling unwanted plant growth, comprising applying to the plant, plant part, or surroundings of the plant, a herbicidally effective amount of the crystalline modification I of flufenacet as hereinbefore described.

The crystalline modification I of flufenacet is preferably applied in the form of a composition as hereinbefore described.

Methods and techniques for applying the compositions of the present invention are known in the art and will be understood by the person skilled in the art. Techniques include diluting or dispersing the composition in a suitable diluent or carrier liquid, in particular water, and applying the composition by spraying.

All plants, plant parts, and their surroundings can be treated with the crystalline modification I of flufenacet 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 may or may not 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 shoots, leaves, needles, stalks, stems, flowers, fruit bodies, fruits, seeds, roots, tubers and rhizomes. Harvested materials, and vegetative and generative propagation materials, for example, cuttings, tubers, meristem tissue, rhizomes, offsets, seeds, single and multiple plant cells and any other plant tissues, are also included.

Treatment of the plants, plant parts, and/or their surroundings, with the compositions or formulations of the invention can be carried out directly or by allowing the compositions or formulations to act on their surroundings, habitat or storage space by the customary treatment methods known in the art. 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 seeds.

The benefits of the present invention are particularly advantageous when the crystalline modification I of flufenacet or its herbicidal composition are applied to kill weeds in crops of useful plants, such as cereals, for example wheat, barley, rye, oats, maize, rice, sorghum, triticale and related crops; fruit, such as pomes, stone fruit and soft fruit, such as apples, grapes, pears, plums, peaches, almonds, pistachio, cherries, and berries, for example strawberries, raspberries and blackberries, bell pepper, red pepper; leguminous plants, for example beans, lentils, peas and soybeans; oil plants, such as rape, mustard and sunflowers; cucurbitaceae, such as marrows, cucumbers and melons; fiber plants, for example cotton, flax, hemp and jute; citrus, such as calamondin, citrus citron, citrus hybrids, including chironja, tangelo and tangor, grapefruit, kumquat, lemon, lime, mandarin (tangerine), sour orange, sweet orange, pummelo, and satsuma mandarin; vegetables, such as spinach, lettuce, asparagus, cabbages, carrots, onions, tomatoes, potatoes and paprika; coffee; and sugarcane; as well as ornamentals, including flowers, such as rose, shrubs, broad-leaved trees and evergreens, such as conifers. The crop plants are preferably cereals, in particular maize and rice, soybeans, cotton and potatoes.

The invention may be used to control a wide range of undesired plants, including broadleaf plants and grassy weeds. The broadleaf weeds include such plants as shepherds purse (Capse/la bursapastories), fat hen (Chenopodium album), double thorn (Oxygonum sinuatum), black bind weed (Polygonum convolvulus), Mexican marigold (Tagetes minuta), gallant soldier (Galinsogo parviflora), and white charlock (Raphanus raphanastrium). The grassy weeds include such plants as foxtail (Setaria spp.), wild finder millet (Eleusine spp.), couch grass (Digitaria spp.) and rye grass (Lolium spp.).

Throughout the description and claims of this specification, the words "comprise" and variations of the words, for example 'comprising" and "comprises", mean 'including but not limited to", and do not exclude other moieties, additives, components, integers or steps. Moreover the singular encompasses the plural unless the context otherwise requires: in particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

In this specification, references to properties are -unless stated otherwise -to properties measured under ambient conditions, i.e. at atmospheric pressure and at a 10 temperature of about 20°C.

As used herein, the term "about" or "around" when used in connection with a numerical amount or range, means somewhat more or somewhat less than the stated numerical amount or range, and for example 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.

"Precipitation" as used herein, refers to the sedimentation of a solid material (a precipitate), including the sedimentation of a crystalline material, from a liquid solution in which the solid material is present in amounts greater than its solubility in the amount of liquid solution.

The term "herbicidally effective amount" as used herein, refers to the quantity of such a compound or combination of such compounds that is capable of producing a controlling effect on the growth of plants. The controlling effects include all deviation from the natural development of the target plants, for example killing, retardation of one or more aspects of the development and growth of the plant, leaf burn, albinism, dwarfing and the like.

Embodiments of the present invention will now be described by way of the following examples, which are provided for illustrative purposes only.

All percentages are given in weight percent, unless otherwise indicated.

EXAMPLES

Example 1

Preparation of Flufenacet Flufenacet was prepared generally in accordance with the method of Example 1 of US 4,968,342, as follows: 11.8 g (0.05 mol) of 2-methylsulphony1-5-trifluoromethy1-1,3,4-thiadiazole were dissolved in 100 mL of acetone together with 11.4 g (0.05 mol) of 4'-Fluoro-Nisopropylhydroxyacetanilide. A solution of 2.4 g of sodium hydroxide powder and 9 mL of water was slowly added dropwise at -20° C with stirring. Stirring was then continued at -20° C for 3 hours, after which the reaction mixture was poured into water.

The solid flufenacet product was isolated by filtering with suction. Flufenacet obtained was amorphous.

The reaction scheme can be represented as follow:

Example 2

Preparation of crystalline modification I of flufenacet (crystallization from ethanol) Flufenacet prepared in Example 1 (10 g) was placed in a 3 neck round bottom flask, together with ethanol (60 mL) and stirred. The resulting slurry was heated to 90°C to achieve a homogeneous solution. The insoluble particles, if any, were removed by filtration. The remaining solution was slowly cooled to room temperature. Upon cooling, fine crystals formed. The slurry of crystals and solution was stirred at room temperature for 2 hours. Thereafter, the slurry was filtered and washed with ethanol (3 mL). The filtered crystals were dried under vacuum at room temperature in order to remove the ethanol traces from the crystalline product.

The crystalline product thus obtained had a purity of >98% and the product recovered as crystals was found to be not less than 80% yield.

The crystal product was analyzed by IR spectrometry, XRD and DSC and found out to be crystalline modification I of flufenacet as shown in Figures 1, 2 and 3, respectively.

The X-ray diffractogram of the crystal exhibited the reflexes as shown in Figure 1 and the values are summarized in Table 1 below.

Table 1

Crystalline modification I of flufenacet 2 0 (°) d (A) 8.041 ±0.2 10.10 ±0.05 14.806 ± 0.2 5.98 ± 0.05 15.422 ± 0.2 5.75 ± 0.05 16.097 ± 0.2 5.51 ± 0.05 19.490 ± 0.2 4.55 ± 0.05 22.994 ± 0.2 3.87 ± 0.05 24.105 ± 0.2 3.69 ± 0.05 26.705 ± 0.2 3.34 ± 0.05 The IR spectrum of the crystalline flufenacet exhibited the functional group characteristic vibrations peaks at wavenumbers of one or more at about 1651.72, 1506.90, 1419.58, 1326.96, 1151.12, 954.10, 941.28, 622.15, and 611.46 cm-1, as shown in Figure 2.

The Differential scanning calorimetry (DSC) of the crystalline flufenacet exhibited an endothermic melting peak with onset at 79.3°C and peak maximum at 80.4°C, with a melting enthalpy of 75.13 J/g, as shown in Figure 3.

Example 3

Preparation of Suspension Concentrate (SC) Formulation A suspension concentrate (SC) formulation was prepared as follows: All the components list in Table 2 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.

Table 2

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

Example 4

Preparation of Water Dispersible Granules (WG) Water dispersible granules (WO) were prepared as follows: All the components listed in Table 4 below were mixed, blended and milled in a highspeed 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 Weights % Function Flufenacet, crystalline modification I, 98% (prepared in Example 2) 61.22 Active compound Alkyl naphthalene 2 Wetting agent sulphonate, sodium salt (Akzo Nobel) Lignosulfonic acid, 6 Dispersing agent sodium salt, REAX® 88B) Naphthalenesulfonic acid, polymer with formaldehyde, sodium salt (TAMOL® NN8906) 6 Dispersing agent Sucrose 8 Filler Non-ionic aqueous 1 Antifoaming agent emulsion of Polydimethylsiloxanes Mannitol Balance to 100% Carrier Example 5 Stability test The hydrolysis and N-isomerization of the amorphous flufenacet prepared in Example 1, the crystalline modification I prepared in Example 2 and the SC composition prepared in Example 3 was determined by aging samples in heated ovens and comparing the flufenacet content before and after aging to determine the the relative percentage of hydrolysis (RPH) of flufenacet and the relative percentage of Nisomerization (RPN).

The RPH was calculated using the following equation: RPH = [(Final weight °A of flufenacet -Initial weight % of flufenacet)1 x 100% Initial weight % of flufenacet The RPN was calculated by the following equation: RPN = [(Final weight °A) of N-isomer -Initial weight °A) of N-isomer)1 x 100% Initial weight °A) of N-isomer Flufenacet and its N-isomer content was determined by assaying the compositions 20 with high-pressure liquid chromatography (HPLC) using reverse phase columns and eluants.

Samples prepared in Example 1, Example 2 and Example 3 were stored at 110 °C for 16 hours, following the procedures of CIPAC MT 46.3. The concentration of flufenacet was measured initially and at the end of each storage time by HPLC. The results are listed in Table 5 below.

Table 5

Sample Compound Initial Weight Initial Weight RPH RPN of Flufenacet of N-isomer (%) (0k) (%) (%) Example 1 Flufenacet 50 4 -70 40 (amorphous) Example 2 Flufenacet 50 1.5 -6 5 (crystalline modification I) Example 3 Flufenacet 50 1 -2 4

SC

(crystalline modification I) As can be seen from the results set out in Table 5 above, the crystalline modification I of flufenacet exhibits a significantly higher stability, in particular resistance to hydrolysis and resistance to N-isomerization, than amorphous flufenacet.

Claims

CLAIMS1. A crystalline modification I of flufenacet, the crystalline modification exhibiting at least three of the following reflexes, in any combination, as 28±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu-Ka radiation at 25 °C: = 8.0 ±0.2 (1) 2e. 14.8 ± 0.2 (2) 28 = 15.4 ± 0.2 (3) 28= 16.1 ±0.2 (4) 28= 18.6 ± 0.2 (5) 2e. 19.5 ± 0.2 (6) 28 = 23.0 ± 0.2 (7) = 24.1 ±0.2 (8) = 26.0 ± 0.2 (9) 28 = 26.7 ± 0.2 (10) 28 = 29.4 ± 0.2 (11).
2. The crystalline modification I of flufenacet according to claim 1, wherein the crystalline modification exhibits at least three, more preferably four, still more preferably five, more preferably still six, especially seven, of the following reflexes, in any combination, as 20±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu-Ka radiation at 25°C: 28 = 8.0 ±0.2 (1) = 14.8 ± 0.2 (2) 20 = 15.4 ± 0.2 (3) 28= 16.1 ±0.2 (4) 28 = 19.5 ± 0.2 (6) 28 = 23.0 ± 0.2 (7) = 24.1 ±0.2 (8) 20 = 26.7 ± 0.2 (10).
3. The crystalline modification I of flufenacet according to claim 2, wherein the crystalline modification exhibits all of the following reflexes, in any combination, as 20±0.2 degree in an X-ray powder diffractogram (XRD) recorded using Cu-Ka radiation at 25°C: = 8.0 ± 0.2 (1) = 14.8 ± 0.2 (2) = 15.4 ± 0.2 (3) 28= 16.1 ±0.2 (4) 28= 19.5 ± a2 (6) = 23.0 ± 0.2 (7).
4. A crystalline modification I of flufenacet, the crystalline modification exhibiting an infrared (IR) spectrum with characteristic functional group vibration peaks at wavenumbers (cm-1, ± 0.2%) of one or more of 1651.72, 1506.90, 1419.58, 1326.96, 1151.12, 954.10, 941.28, 622.15, and 611.46 cm-1.
5. A crystalline modification I of flufenacet, the crystalline modification exhibiting a melting point of from 79.3 to 80.8°C.
6. A crystalline modification I of flufenacet, the crystalline modification exhibiting a differential scanning calorimetry (DSC) profile having an endothermic melting peak with onset at 79.3°C and peak maximum at 80.4°C.
7. A composition for controlling plant growth, the composition comprising the crystalline modification I of flufenacet according to any preceding claim.
8. The composition according to claim 7, 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 (OR), microgranules (MG), a suspoemulsion (SE) or water-dispersible granules (WG).
9. The composition according to either of claims 7 or 8, wherein the crystalline modification I of flufenacet is present in an amount of from 10 to 90% by weight.
10. The composition according to any of claims 7 to 9, wherein the composition further comprises one or more auxiliaries selected from dispersants, wetting agents, emulsifiers, extenders, carriers, solvents, surfactants, stabilizers, anti-foam agents, anti-freeze agents, preservatives, antioxidants, colourants, thickeners, solid adherents and inert fillers.
11. Use of the crystalline modification I of flufenacet according to any of claim 1 to 6 in the control of undesirable plant growth.
12. A method for controlling plant growth at a locus, the method comprising applying to the locus the crystalline modification I of flufenacet according to any of claims 1 to 6 or a composition according to any of claims 7 to 10.
13. The use of claim 11 or the method of claim 12, wherein the plant growth being controlled is in a crop of plants selected from cereals, for example wheat, barley, rye, oats, maize, rice, sorghum, triticale and related crops; fruit, such as pomes, stone fruit and soft fruit, such as apples, grapes, pears, plums, peaches, almonds, pistachio, cherries, and berries, for example strawberries, raspberries and blackberries, bell pepper, red pepper; leguminous plants, for example beans, lentils, peas and soybeans; oil plants, such as rape, mustard and sunflowers; cucurbitaceae, such as marrows, cucumbers and melons; fiber plants, for example cotton, flax, hemp and jute; citrus, such as calamondin, citrus citron, citrus hybrids, including chironja, tangelo and tangor, grapefruit, kumquat, lemon, lime, mandarin (tangerine), sour orange, sweet orange, pummelo, and satsuma mandarin; vegetables, such as spinach, lettuce, asparagus, cabbages, carrots, onions, tomatoes, potatoes and paprika; coffee; and sugarcane; as well as ornamentals, including flowers, such as rose, shrubs, broad-leaved trees and evergreens, such as conifers.
14. The use of claim 11 or 13 or the method of claim 12 or 13, wherein the plant growth being controlled is that of a plant selected from shepherds purse (Capsella bursapastories), fat hen (Chenopodium album), double thorn (Oxygonum sinuatum), black bind weed (Polygonum convolvulus), Mexican marigold (Tagetes minuta), gallant soldier (Galinsogo parviflora), and white charlock (Raphanus raphanastrium); grassy weeds such as foxtail (Setaria spp.), wild finder millet (Eleusine spp.), couch grass (Digitaria spp.) and rye grass (Lolium spp.).
15. A method for preparing a crystalline modification I of flufenacet, the method comprising the steps of: i) providing a solution of flufenacet in a solvent system comprising a one or more solvents; ii) precipitating the crystalline modification I of flufenacet from the solution; and iii) isolating the precipitated crystalline modification I of flufenacet.
16. The method according to claim 15, wherein amorphous flufenacet is used to prepare the solution of flufenacet in step i).
17. The method according to either of claims 15 or 16, wherein the solvent system comprises one or more solvents selected from acetonitrile; ethers, 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, methyl-tetrahydrofuran, dioxane, dichlorodiethyl ether, methyl-tetrahydrofuran, polyethers of ethylene oxide and/or propylene oxide; esters, 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; and aliphatic alcohols, for example C1 to C8, preferably Ci to C6 alcohols, more preferably Ci to C5 alcohols, in particular methanol, ethanol, n-propanol, isopropanol, n-butanol and tert-amyl alcohol.
18. The method according to claim 17, wherein the solvent system comprises one or more solvents selected from acetonitrile, methyl tert-butyl ether, methyl-tetrahydrofuran, malonates, n-butyl acetate, isobutyl acetate, diethyl carbonate, methanol, ethanol, isopropanol, n-butanol.
19. The method according to any of claims 15 to 18, wherein in step H), the solution is cooled to a temperature of from -20 to 10°C.
20. The method according to any of claims 15 to 19, wherein in step H) a vacuum is applied to the solution.
21. The method according to any of claims 15 to 20, wherein in step H) seed crystals are added to the solution.
22. The method according to claim 21, wherein the seed crystals are crystals of flufenacet, preferably the crystalline modification I of flufenacet.
23. Use of a solvent system to prepare crystalline flufenacet having an improved stability and resistance to N-isomerisation, wherein the solvent system comprises one or more solvents selected from acetonitrile, ethers, esters and aliphatic alcohols.
24. The use according to claim 23, wherein the solvent system comprises one or more solvents selected from acetonitrile, methyl tert-butyl ether, methyl-tetrahydrofuran, malonates, n-butyl acetate, isobutyl acetate, diethyl carbonate, methanol, ethanol, isopropanol, n-butanol.