WO2021144264A1

WO2021144264A1 - Crystalline form of the herbicide methyl 4-amino-3-chloro-5-fluoro-6-(7-fluoro-1h-indol-6-yl)picolinate

Info

Publication number: WO2021144264A1
Application number: PCT/EP2021/050482
Authority: WO
Inventors: Britta Olenik; Birgit Keil; Michael Gerhard Hoffmann; Michael Charles MCLEOD; Sylvia Dworacek
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 2020-01-16
Filing date: 2021-01-12
Publication date: 2021-07-22
Anticipated expiration: 2022-07-16

Abstract

The present invention relates to a novel crystalline form of methyl 4-amino-3-chloro-5-fluoro-6-(7- fluoro-1H-indol-6-yl)picolinate according to formula (1), to a process for its preparation, to agrochemical formulations comprising the novel crystalline form, to its use for the for the production of a formulation with increased stability and to its use in plant protection applications, especially to its use as a herbicide.

Description

CRYSTALLINE FORM OF THE HERBICIDE METHYL 4-AMINO-3-CHLORO-5-FLUORO-6-(7-FLUORO-1H-INDOL-6-YL)PICOLINATE

Summary of the invention

The present invention relates to a novel crystalline form of methyl 4-amino-3-chloro-5-fluoro-6-(7- fluoro- l//-indol-6-yl)picolinatc according to formula (1), to a process for its preparation, to agrochemical formulations comprising the novel crystalline form, to its use for the for the production of a formulation with increased stability and to its use in plant protection applications, especially to its use as a herbicide.

Methyl 4-am i no-3 -chloro-5 -fl uo ro-6-(7-fl uo ro- l//-indol-6-yl )picol mate. which hereinafter is also termed as P4356716 and a process for its production is known from W02014/151005 and EP2970187B1. The process known from the prior art yields P4356716 as amorphous solid.

Background

Polymorphism is the ability of a compound to crystallize in different crystalline phases with different arrangements and/or conformations of the molecules in the crystal lattice. Hence, polymorphs are different crystalline forms of the same pure chemical compound. On account of the different arrangement and/or conformation of molecules, polymorphs exhibit different physical, chemical and biological properties. Properties which may be affected include but are not limited solubility, dissolution rate, stability, optical and mechanical properties, etc. The relative stability of a polymorph depends on its free energy, i.e. a more stable polymorph has a lower free energy. Under a defined set of experimental conditions only one polymorph has the lowest free energy. This polymorph is the thermodynamically stable form and all other polymorph(s) is (are) termed metastable form(s). A metastable form is one that is thermodynamically unstable but can nevertheless be prepared, isolated and analyzed as a result of its relatively slow rate of transformation. The occurrence of active substances in different polymorphic forms (hereinafter also named as polymorphs or crystalline forms) is of decisive importance for the production in industrial scale as well as for the development of formulations containing the active substance, as unwanted phase change can lead to thickening and potentially solidification of the formulation and/or large crystals, which can lead to blockages in application equipment, e.g. in spray nozzles in agricultural application machinery. The knowledge of the existence of crystalline modifications and their properties is thus of high relevance. Each polymorph is characterized by a specific, uniform packing and arrangement of the molecules in the solid state. Nevertheless, it is generally not predictable whether a given chemical compound forms polymorphs at all and if so, which physical and biological properties the different polymorphs may have. In addition pseudopolymophic forms, in particular hydrates or solvates, can occur. A solvate is a crystalline molecular compound in which molecules of the solvent of crystallisation are incorporated into the host lattice, consisting of unsolvated molecules. A hydrate is a special case of a solvate, when the incorporated solvent is water. The presence of solvent molecules in the crystal lattice influences the intermolecular interactions and confers unique physical properties to each solvate. A solvate thus has its own characteristic values of internal energy, enthalpy, entropy, Gibbs free energy, and thermodynamic activity.

Figures

Fig. 1: X-ray powder diffractogram of crystalline form A of P4356716

Fig. 2: DSC- and TGA-thermogram of crystalline form A of P4356716 Fig. 3: DSC- and TGA-thermogram of the precipitate obtained from Example 1.7 containing crystalline form A and the pseudopolymorphic (hydrate) form of P4356716

Detailed description

In a first embodiment, the present invention relates to a novel crystalline form A of methyl 4-amino-3- chloro-5-fluoro-6-(7-fluoro- l//-indol-6-yl)picolinate according to the following formula (1):

(1).

Methyl 4-am i no-3 -chloro-5 -fl uo ro-6-(7-fl uo ro- l//-indol-6-yl )picol mate is also termed as P4356716 in the context of the present invention.

First attempts to convert P4356716 into a crystalline form failed and only resulted in either the undesired amorphous form or in complex mixtures of different crystal forms, exhibiting uncontrolled phase changes.

Object of the present invention is therefore the provision of a crystalline form of P4356716 of formula (1), preferably having superior application properties, beneficial physicochemical (e.g. stability) and/or formulation properties.

It has now surprisingly been found that the crystalline form A, which is obtained by applying specific crystallisation conditions, has such desired and beneficial properties. In particular, crystalline form A in own experiments displayed improved properties concerning mechanical stability, chemical stability, purity and hygroscopicity, in particular when compared with the amorphous form known from the prior art. In particular, crystalline form A displays an increased stability and thereby ensures that an undesired conversion into another polymorphic form of the compound of formula (1) and thereby associated changes in the properties as described above are prevented. The increase in stability enhances the safety and quality of formulations comprising the compound of formula (1).

It particular, it was found that the crystalline form A of the compound of the formula (1) has improved handling and formulation properties, in particular in view of the observed mechanical stability of said crystalline form A, and the fact that said crystalline form A is not hygroscopic and does for example not convert into the pseudopolymorphic (hydrate) form described hereinbelow during storage in a water containing formulation or a humid environment.

The crystalline form A of methyl 4-am i no-3 -chloro-5 -fl uo ro-6-(7-fl uo ro- l//-indol-6-yl )picol mate can be characterized by X-ray powder diffractometry on the basis of the respective diffraction diagrams, which are recorded at 25°C and with Cu-Ka 1 radiation (1.5406 A). The crystalline form A according to the present invention displays at least 3, preferably at least 5, more preferably at least 7, and especially all of the reflections quoted in the following as values:

Table 1: X-ray reflections of crystalline form A of P4356716

The crystalline form A according to the present invention is further characterized by the X-ray powder diffractogram depicted in Fig. 1.

The order of the most characteristic and intensive reflections of crystalline form A is as follows:

At least the following reflections are present: 19.1; 15.0 and 9.9, preferably at least the following reflections: 19.1; 15.0; 9.9; 13.6 and 19.6, more preferably at least the following reflections: 19.1; 15.0; 9.9; 13.6; 19.6; 15.6 and 20.6, most preferably at least the following reflections: 19.1; 15.0; 9.9; 13.6;

19.6; 15.6; 20.6; 26.3; 25.2 and 17.4, each quoted as 2Q ± 0.2° values.

Table la: X-ray reflections of crystalline form A of P4356716

Crystallographic studies on single crystals of form A revealed that the crystal structure is monoclinic. The unit cell has the space group P2i/c. Single crystal measurement was performed at -163°C.

Table 2: Crystallographic characteristics of crystalline form A of P4356716

a, b, c = Length of the edges of the unit cell, each in [A] a, p, g = Angles of the unit cell Z = Number of the molecules in the unit cell

The crystalline form A of P4356716 according to the present invention is further characterized by the Differential Scanning Calorimetry (DSC) thermogram and Thermogravimetric analysis (TGA) thermogram depicted in Fig. 2. In addition to the crystalline form A, a pseudopolymorphic (hydrate) form has been identified, which is further described in the following.

The pseudopolymorphic (hydrate) form of methyl 4-amino-3-chloro-5-fluoro-6-(7-fluoro- l//-indol-6- yl)picolinate obtained can be characterized by X-ray powder diffractometry on the basis of the respective diffraction diagrams, which are recorded at 25°C and with Cu-Ka 1 radiation (1.5406 A). Since the material obtained and analysed was an intermixture of crystalline form A of P4356716 and the pseudopolymorphic (hydrate) form of P4356716, no X-ray powder diffractogram of the pure pseudopolymorphic (hydrate) form could be obtained.

The reflections listed in Table 3 however can be attributed to said pseudopolymorphic (hydrate) form since these reflections are not present in the crystalline form A of P4356716 and therefore can be considered to characteristic for the XRPD pattern of the pseudopolymorphic (hydrate) form.

Table 3: Characteristic X-ray reflections attributed to pseudopolymorphic (hydrate) form of P4356716

The following reflections attributed to pseudopolymorphic (hydrate) form of P4356716 can be considered as being characteristic: 4.2 and 7.3, both as 2Q ± 0.2° values, the reflection at 4.2 typically being the most intense reflection.

The Differential Scanning Calorimetry (DSC) thermogram and Thermogravimetric analysis (TGA) thermogram of the intermixture of crystalline form A of P4356716 and the pseudopolymorphic (hydrate) form of P4356716 is depicted in Fig. 3. In a second embodiment, the present invention is directed to a process for the production of the crystalline form A, comprising the following steps: a) diluting and/or suspending the compound of formula (1) in a suitable solvent or solvent mixture; b) heating the mixture of step a) to a temperature in the range of from about 20°C below the boiling temperature of the solvent or solvent mixture to the boiling temperature of the solvent or solvent mixture used in step a); c) cooling the solution or slurry obtained in step b) to a temperature of less than about 30°C; d) optionally isolating the precipitate obtained in step c) comprising or consisting of crystalline form A from the solution or slurry, optionally followed by subsequent drying the precipitate comprising or consisting of crystalline form A.

The chemical preparation of P4356716 according to formula (1) is known from W02014/151005 and EP2970187B1. The compound of formula (1) as used in step a) can thus be prepared according to W02014/151005 and EP2970187B1, to which full reference is made hereby.

The compound of formula (1) in step a) can essentially be any known form of P4356716. This means that P4356716 can be used in amorphous form or in a mixture of different polymorphic forms or in a mixture containing an amorphous and one or more different (pseudo)polymorphic forms.

Suitable solvents or solvent mixtures which can be used to dilute and/or suspend the compound of formula (1) in step a) and from which the compound of formula (1) is obtained in crystalline form A, are aliphatic ketones with 3 to 6 carbon atoms, wherein preferably the aliphatic ketones are selected from the group consisting of acetone, butanone, 2-pentanone or 3-pentanone, and most preferably the solvent is acetone.

Other suitable solvents or solvent mixtures which can be used to dilute and/or suspend the compound of formula (1) in step a) and from which the compound of formula (1) can be obtained in crystalline form A, are acetonitrile, ethanol and methanol.

In step b) the solution or slurry is preferably heated to a temperature in the range of from about 10°C below the boiling temperature of the solvent or solvent mixture to the boiling temperature of the solvent or solvent mixture used in step a). In a preferred embodiment the solvent or solvent mixture is heated to its boiling temperature of the solvent or solvent mixture of step a). A solution of P4356716 can also be prepared by transferring a reaction mixture obtained by chemical reaction, containing P4356716, ifnecessary after removal of reagents and/or side products into a solvent or solvent mixture according to the present invention.

In step c) the solution or slurry is typically cooled to a temperature in the range of about -30°C to less than about 30°C, preferably to a temperature in the range of about -20°C to less than about 25°C.

The crystallization of crystalline form A can be promoted or accelerated by seeding with seed crystals of form A.

The isolation of the crystalline form A from the mother liquid is effected by common techniques known in the art, for example by filtration, centrifugation or by decanting.

Alternatively, the crystalline form A is isolated from the solvent or solvent mixture by allowing the solution or slurry to stand at the crystallization conditions of step c) until a substantial amount of the solvent, oftentimes about 90 wt.-% of the solvent or solvent mixture has evaporated.

The isolated crystalline form A can optionally be washed with any solvent, preferably with the solvent or solvent mixture used for crystallization, with water or with a mixture of the solvent or solvent mixture and water. The washing step can optionally be repeated, whereby washing with water often is the last washing step. The washing is typically performed at temperatures below 30°C, often below 25°C and in particular below 20°C, optionally at 0°C. In a further, optionally step, the crystals of crystalline form A can be dried and then supplied for further processing.

By means of the crystallization according to the present invention, crystalline form A of P4356716 is obtained with at least 85 %, in particular with at least 90 %, and most preferably with at least 95 %.

Thus, a particular embodiment of the present invention relates to methyl 4-amino-3-chloro-5-fluoro-6-(7- fluoro-l//-indol-6-yl)picolinatc. which consists of at least 85%, preferably of at least 90 % and particularly preferably of 95 % or more of the crystalline form A.

In a third embodiment, the present invention is directed to a plant protection agent in the form of customary formulations containing the crystalline form A of methyl 4-am i no -3 -eh 1 o ro -5 -fl uo ro -6 -( 7-fl uo ro - 1 //- i ndol - 6-yl)picolinate.

The plant protection agent may additionally comprise one or more further active substance(s) selected from the group consisting of herbicides, insecticides, acaricides, fungicides, safeners and/or plant growth regulators.

Such suitable and preferred further active substance(s) are selected from the group of herbicides and safeners, more specifically the herbicides and the herbicide safeners mentioned in the following. In some embodiments, the compounds, compositions, and methods provided herein are used in conjunction with one or more other herbicides to control a wider variety of undesirable vegetation. When used in conjunction with other herbicides, the crystalline form A of methyl 4-amino-3-chloro-5-fluoro-6-(7-fluoro- l//-indol-6-yl)picolinate of the present invention can be formulated with the other herbicide or herbicides, tank-mixed with the other herbicide or herbicides or applied sequentially with the other herbicide or herbicides. Some of the herbicides that can be employed in conjunction with the compounds of the present disclosure include: 4-CPA, 4-CPB, 4-CPP, 2,4-D, 2,4-D choline salt, 2,4-D esters and amines, 2,4-DB, 3,4- DA, 3,4-DB, 2,4-DEB, 2,4-DEP, 3,4-DP, 2,3,6-TBA, 2,4,5-T, 2,4,5-TB, acetochlor, acifluorfen, aclonifen, acrolein, alachlor, allidochlor, alloxydim, allyl alcohol, alorac, ametridione, ametryn, amibuzin, amicarbazone, amidosulfuron, aminocyclopyrachlor, aminopyralid, amiprofos-methyl, amitrole, ammonium sulfamate, anilofos, anisuron, asulam, atraton, atrazine, azafenidin, azimsulfuron, aziprotryne, barban, BCPC, beflubutamid, benazolin, bencarbazone, benfluralin, benfuresate, bensulfuron-methyl, bensulide, benthiocarb, bentazon-sodium, benzadox, benzfendizone, benzipram, benzobicyclon, benzofenap, benzofluor, benzoylprop, benzthiazuron, bicyclopyrone, bifenox, bilanafos, bispyribac- sodium, borax, bromacil, bromobonil, bromobutide, bromofenoxim, bromoxynil, brompyrazon, butachlor, butafenacil, butamifos, butenachlor, buthidazole, buthiuron, butralin, butroxydim, buturon, butylate, cacodylic acid, cafenstrole, calcium chlorate, calcium cyanamide, cambendichlor, carbasulam, carbetamide, carboxazole, chlorprocarb, carfentrazone-ethyl, CDEA, CEPC, chlomethoxyfen, chloramben, chloranocryl, chlorazifop, chlorazine, chlorbromuron, chlorbufam, chloreturon, chlorfenac, chlorfenprop, chlorflurazole, chlorflurenol, chloridazon, chlorimuron, chlomitrofen, chloropon, chlorotoluron, chloroxuron, chloroxynil, chlorpropham, chlorsulfuron, chlorthal, chlorthiamid, cinidon-ethyl, cinmethylin, cinosulfuron, cisanilide, clethodim, cliodinate, clodinafop-propargyl, clofop, clomazone, clomeprop, cloprop, cloproxydim, clopyralid, cloransulam-methyl, CMA, copper sulfate, CPMF, CPPC, credazine, cresol, cumyluron, cyanatryn, cyanazine, cycloate, cyclosulfamuron, cycloxydim, cycluron, cyhalofop-butyl, cyperquat, cyprazine, cyprazole, cypromid, daimuron, dalapon, dazomet, delachlor, desmedipham, desmetryn, di- allate, dicamba, dichlobenil, dichloralurea, dichlormate, dichlorprop, dichlorprop-P, diclofop, diclosulam, diethamquat, diethatyl, difenopenten, difenoxuron, difenzoquat, diflufenican, diflufenzopyr, dimefuron, dimepiperate, dimethachlor, dimethametryn, dimethenamid, dimethenamid-P, dimexano, dimidazon, dinitramine, dinofenate, dinoprop, dinosam, dinoseb, dinoterb, diphenamid, dipropetryn, diquat, disul, dithiopyr, diuron, DMPA, DNOC, DSMA, EBEP, eglinazine, endothal, epronaz, EPTC, erbon, esprocarb, ethalfluralin, ethbenzamide, ethametsulfuron, ethidimuron, ethiolate, ethobenzamid, etobenzamid, ethofumesate, ethoxyfen, ethoxysulfuron, etinofen, etnipromid, etobenzanid, EXD, fenasulam, fenoprop, fenoxaprop, fenoxaprop-P-ethyl, fenoxaprop-P-ethyl + isoxadifen-ethyl, fenoxasulfone, fenteracol, fenthiaprop, fentrazamide, fenuron, ferrous sulfate, flamprop, flamprop-M, flazasulfuron, florasulam, fluazifop, fluazifop-P -butyl, fluazolate, flucarbazone, flucetosulfuron, fluchloralin, flufenacet, flufenican, flufenpyr-ethyl, flumetsulam, flumezin, flumiclorac-pentyl, flumioxazin, flumipropyn, fluometuron, fluorodifen, fluoroglycofen, fluoromidine, fluoronitrofen, fluothiuron, flupoxam, flupropacil, flupropanate, flupyrsulfuron, fluridone, flurochloridone, fluroxypyr, flurtamone, fluthiacet, fomesafen, foramsulfuron, fosamine, furyloxyfen, glufosinate, glufosinate-ammonium, glyphosate, halosafen, halosulfuron-methyl, haloxydine, haloxyfop-methyl, haloxyfop-P-methyl, halauxifen-methyl, hexachloroacetone, hexaflurate, hexazinone, imazamethabenz, imazamox, imazapic, imazapyr, imazaquin, imazethapyr, imazosulfuron, indanofan, indaziflam, iodobonil, iodomethane, iodosulfuron, iofensulfuron, ioxynil, ipazine, ipfencarbazone, iprymidam, isocarbamid, isocil, isomethiozin, isonoruron, isopolinate, isopropalin, isoproturon, isouron, isoxaben, isoxachlortole, isoxaflutole, isoxapyrifop, karbutilate, ketospiradox, lactofen, lenacil, linuron, MAA, MAMA, MCPA esters and amines, MCPA-thioethyl, MCPB, mecoprop, mecoprop-P, medinoterb, mefenacet, mefluidide, mesoprazine, mesosulfuron, mesotrione, metam, metamifop, metamitron, metazachlor, metazosulfuron, metflurazon, methabenzthiazuron, methalpropalin, methazole, methiobencarb, methiozolin, methiuron, methometon, methoprotryne, methyl bromide, methyl isothiocyanate, methyldymron, metobenzuron, metobromuron, metolachlor, metosulam, metoxuron, metribuzin, metsulfuron, molinate, monalide, monisouron, monochloroacetic acid, monolinuron, monuron, morfamquat, MSMA, naproanilide, napropamide, napropamide-M, naptalam, neburon, nicosulfiiron, nipyraclofen, nitralin, nitrofen, nitrofluorfen, norflurazon, noruron, OCH, orbencarb, ortho dichlorobenzene, orthosulfamuron, oryzalin, oxadiargyl, oxadiazon, oxapyrazon, oxasulfuron, oxaziclomefone, oxyfluorfen, paraflufen-ethyl, parafluron, paraquat, pebulate, pelargonic acid, pendimethalin, penoxsulam, pentachlorophenol, pentanochlor, pentoxazone, perfluidone, pethoxamid, phenisopham, phenmedipham, phenmedipham-ethyl, phenobenzuron, phenylmercury acetate, picloram, picolinafen, pinoxaden, piperophos, potassium arsenite, potassium azide, potassium cyanate, pretilachlor, primisulfuron-methyl, procyazine, prodiamine, profluazol, profluralin, profoxydim, proglinazine, prohexadione-calcium, prometon, prometryn, propachlor, propanil, propaquizafop, propazine, propham, propisochlor, propoxycarbazone, propyrisulfuron, propyzamide, prosulfalin, prosulfocarb, prosulfuron, proxan, prynachlor, pydanon, pyraclonil, pyraflufen, pyrasulfotole, pyrazogyl, pyrazolynate, pyrazosulfuron-ethyl, pyrazoxyfen, pyribenzoxim, pyributicarb, pyriclor, pyridafol, pyridate, pyriftalid, pyriminobac, pyrimisulfan, pyrithiobac-methyl, pyroxasulfone, pyroxsulam, quinclorac, quinmerac, quinoclamine, quinonamid, quizalofop, quizalofop-P-ethyl, rhodethanil, rimsulfuron, saflufenacil, S- metolachlor, sebuthylazine, secbumeton, sethoxydim, siduron, simazine, simeton, simetryn, SMA, sodium arsenite, sodium azide, sodium chlorate, sulcotrione, sulfallate, sulfentrazone, sulfometuron, sulfosate, sulfosulfuron, sulfuric acid, sulglycapin, swep, TCA, tebutam, tebuthiuron, tefuryltrione, tembotrione, tepraloxydim, terbacil, terbucarb, terbuchlor, terbumeton, terbuthylazine, terbutryn, tetrafluron, thenylchlor, thiazafluron, thiazopyr, thidiazimin, thidiazuron, thiencarbazone-methyl, thifensulfuron, thiobencarb, tiocarbazil, tioclorim, topramezone, tralkoxydim, triafamone, triallate, triasulfuron, triaziflam, tribenuron, tricamba, triclopyr esters and amines, tridiphane, trietazine, trifloxysulfuron, trifluralin, triflusulfiiron, trifop, trifopsime, trihydroxytriazine, trimeturon, tripropindan, tritac, tritosulfuron, vemolate and xylachlor.

The crystalline form A of methyl 4-ami no-3 -chloro-5-fluoro-6-(7-fluoro-l//-indol-6-yl)picolinate of the present invention can generally be employed in combination with known herbicide safeners, such as benoxacor, benthiocarb, brassinolide, cloquintocet (e.g., mexyl), cyometrinil, daimuron, dichlormid, dicyclonon, dimepiperate, disulfoton, fenchlorazole-ethyl, fenclorim, flurazole, fluxofenim, furilazole, harpin proteins, isoxadifen-ethyl, mefenpyr-diethyl, cyprosulfamide, MG 191, MON 4660, naphthalic anhydride (NA), oxabetrinil, R29148 and N-phenylsulfonylbenzoic acid amides, to enhance their selectivity.

The plant protection agent may further comprise adjuvants which improve action, such as penetrants, e.g. vegetable oils, for example rapeseed oil, sunflower oil, mineral oils, for example paraffin oils, alkyl esters of vegetable fatty acids, for example rapeseed oil methyl ester or soya oil methyl ester, or alkanol alkoxylates and/or spreaders, for example alkylsiloxanes and/or salts, for example organic or inorganic ammonium or phosphonium salts, for example ammonium sulfate or diammonium hydrogenphosphate and/or retention promoters, for example dioctyl sulfosuccinate or hydroxypropylguar polymers and/or humectants, for example glycerol and/or fertilizers, for example ammonium-, potassium- or phosphorus- containing fertilizers.

Customary formulations are, for example, water-soluble liquids (SL), emulsion concentrates (EC), emulsions in water (EW), suspension concentrates (SC, SE, FS, OD), water-dispersible granules (WG), granules (GR) and capsule concentrates (CS); these and further possible formulation types are described, for example, by Crop Life International and in Pesticide Specifications, Manual on development and use of FAO and WHO specifications for pesticides, FAO Plant Production and Protection Papers - 173, prepared by the FAO/WHO Joint Meeting on Pesticide Specifications, 2004, ISBN: 9251048576.

It was surprisingly found that the crystalline form A of the compound of the formula (1) has improved handling and formulation properties, in particular in view of the observed mechanical stability of said crystalline form A, and the fact that said crystalline form A is not hygroscopic and is for example not converted to the pseudopolymorphic (hydrate) form during storage in a water containing formulation or a humid environment.

In a fourth embodiment, the present invention is therefore directed to (agrochemical) formulations containing the crystalline form A of the present invention and water. Said aqueous (agrochemical) formulations preferably are in the form of suspension concentrates (SC, SE, FS, OD).

Further, the present invention is further directed to the use of the crystalline form A of the compound of formula (1) for the production of a formulation, preferably an agrochemical formulation, wherein said (agrochemical) formulation exhibits improved (i) chemical stability of the compound of formula (1) and/or (ii) physical stability, thus resulting in an improved storage stability of said (agrochemical) formulation.

Preference is given to formulations or use forms comprising auxiliaries, for example extenders, solvents, spontaneity promoters, carriers, emulsifiers, dispersants, frost protection agents, biocides, thickeners and/or further auxiliaries, for example adjuvants. An adjuvant in this context is a component which enhances the biological effect of the formulation, without the component itself having any biological effect. Examples of adjuvants are agents which promote retention, spreading, attachment to the leaf surface or penetration.

These formulations are prepared in a known way, for example by mixing the crystalline form A of the compound of the formula (1) with auxiliaries such as, for example, extenders, solvents and/or solid carriers and/or other auxiliaries such as, for example, surfactants. The formulations are produced either in suitable facilities or else before or during application.

The auxiliaries used may be substances suitable for imparting special properties, such as certain physical, technical and/or biological properties, to the formulation of the crystalline form A of the compound of the formula (1), or to the use forms prepared from these formulations (for example ready- to-use pesticides such as spray liquors or seed dressing products).

Suitable extenders are, for example, water, polar and nonpolar organic chemical liquids, for example from the classes of the aromatic and non-aromatic hydrocarbons (such as paraffins, alkylbenzenes, alkylnaphthalenes, chlorobenzenes), the alcohols and polyols (which, if appropriate, may also be substituted, etherified and/or esterified), the ketones (such as acetone, cyclohexanone), esters (including fats and oils) and (poly)ethers, the unsubstituted and substituted amines, amides, lactams (such as N- alkylpyrrolidones) and lactones, the sulfones and sulfoxides (such as dimethyl sulfoxide).

If the extender utilized is water, it is also possible to use, for example, organic solvents as auxiliary solvents. Useful liquid solvents are essentially: aromatics such as xylene, toluene or alkylnaphthalenes, chlorinated aromatics or chlorinated aliphatic hydrocarbons such as chlorobenzenes, chloroethylenes or methylene chloride, aliphatic hydrocarbons such as cyclohexane or paraffins, for example mineral oil fractions, mineral and vegetable oils, alcohols such as butanol or glycol and their ethers and esters, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, strongly polar solvents such as dimethylformamide and dimethyl sulfoxide, and water.

In principle, it is possible to use all suitable solvents. Examples of suitable solvents are aromatic hydrocarbons, such as xylene, toluene or alkylnaphthalenes, chlorinated aromatic or aliphatic hydrocarbons, such as chlorobenzene, chloroethylene or methylene chloride, aliphatic hydrocarbons, such as cyclohexane, paraffins, mineral oil fractions, mineral and vegetable oils, alcohols, such as methanol, ethanol, isopropanol, butanol or glycol and their ethers and esters, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, strongly polar solvents, such as dimethyl sulfoxide, and also water.

In principle, it is possible to use all suitable carriers. Useful carriers especially include: for example ammonium salts and ground natural minerals such as kaolins, clays, talc, chalk, quartz, attapulgite, montmorillonite or diatomaceous earth, and ground synthetic minerals such as finely divided silica, alumina and natural or synthetic silicates, resins, waxes and/or solid fertilizers. It is likewise possible to use mixtures of such carriers. Useful carriers for granules include: for example crushed and fractionated natural rocks such as calcite, marble, pumice, sepiolite, dolomite, and synthetic granules of inorganic and organic flours, and also granules of organic material such as sawdust, paper, coconut shells, com cobs and tobacco stalks.

It is also possible to use liquefied gaseous extenders or solvents. Especially suitable are those extenders or carriers which are gaseous at standard temperature and under atmospheric pressure, for example aerosol propellants such as halogenated hydrocarbons, and also butane, propane, nitrogen and carbon dioxide.

Examples of emulsifiers and/or foam formers, dispersants or wetting agents having ionic or nonionic properties or mixtures of these surfactants are salts of polyacrylic acid, salts of lignosulfonic acid, salts of phenolsulfonic acid or naphthalenesulfonic acid, polycondensates of ethylene oxide with fatty alcohols or with fatty acids or with fatty amines, with substituted phenols (preferably alkylphenols or arylphenols), salts of sulfosuccinic esters, taurine derivatives (preferably alkyl taurates), phosphoric esters of polyethoxylated alcohols or phenols, fatty acid esters of polyols, and derivatives of the compounds containing sulfates, sulfonates and phosphates, for example alkylaryl polyglycol ethers, alkylsulfonates, alkyl sulfates, arylsulfonates, protein hydrolyzates, lignosulfite waste liquors and methylcellulose. The presence of a surfactant is advantageous if the crystalline form A of the compound of the formula (1) and/or one of the inert carriers is insoluble in water and when the application takes place in water.

Further auxiliaries which may be present in the formulations and the use forms derived therefrom are dyes such as inorganic pigments, for example iron oxide, titanium oxide and Prussian Blue, and organic dyes such as alizarin dyes, azo dyes and metal phthalocyanine dyes, and nutrients and trace nutrients such as salts of iron, manganese, boron, copper, cobalt, molybdenum and zinc.

Additional components which may be present are stabilizers, such as cold stabilizers, preservatives, antioxidants, light stabilizers, or other agents which improve chemical and/or physical stability. Foam generators or antifoams may also be present.

In addition, the formulations and the use forms derived therefrom may also comprise, as additional auxiliaries, stickers such as carboxymethylcellulose and natural and synthetic polymers in the form of powders, granules or latices, such as gum arabic, polyvinyl alcohol and polyvinyl acetate, or else natural phospholipids such as cephalins and lecithins and synthetic phospholipids. Further auxiliaries may be mineral and vegetable oils. It is possible if appropriate for still further auxiliaries to be present in the formulations and the use forms derived therefrom. Examples of such additives are fragrances, protective colloids, binders, adhesives, thickeners, thixotropic agents, penetrants, retention promoters, stabilizers, sequestrants, complexing agents, humectants, spreaders. In general, the crystalline form A of the compound of the formula (1) can be combined with any solid or liquid additive commonly used for formulation purposes.

Useful retention promoters include all those substances which reduce dynamic surface tension, for example dioctyl sulfosuccinate, or increase viscoelasticity, for example hydroxypropylguar polymers.

Suitable penetrants in the present context are all those substances which are usually used for improving the penetration of agrochemical active compounds into plants. Penetrants are defined in this context by their ability to penetrate from the (generally aqueous) application liquor and/or from the spray coating into the cuticle of the plant and hence increase the mobility of the active compounds in the cuticle. The method described in the literature (Baur et al., 1997, Pesticide Science 51, 131-152) can be used for determining this property. Examples include alcohol alkoxylates such as coconut fatty ethoxylate (10) or isotridecyl ethoxylate (12), fatty acid esters, for example rapeseed oil methyl ester or soya oil methyl ester, fatty amine alkoxylates, for example tallowamine ethoxylate (15), or ammonium and/or phosphonium salts, for example ammonium sulfate or diammonium hydrogenphosphate.

In a preferred embodiment of the present invention, the plant protection agent contains more than 90 wt.- %, and preferably more than 95 wt.-%, of the crystalline form A of the compound of the formula (1) based on the total amount of all forms of the compound of the formula (1) present in the composition.

The (agrochemical) formulations of the present invention typically comprise between 0.001% and 90% by weight of the crystalline form A of the compound of the formula (1), more preferably between 0.1% and 80% by weight of the crystalline form A of the the compound of the formula (1), most preferably between 0.5% and 60% by weight of the crystalline form A of the compound of the formula (1), in each case based on the total weight of the (agrochemical) formulation.

The content of the crystalline form A of the compound of the formula (1) in the use forms, i.e. the forms intended for application to e.g. undesired plants, prepared from the (agrochemical) formulations may vary within wide ranges. The concentration of the crystalline form A of the compound of the formula (1) in the use forms may typically be between 0.000001% and 5% by weight of the crystalline form A of the compound of the formula (1), preferably between 0.00001% and l%by weight, based on the total weight of the use form. Application is accomplished in a customary manner appropriate for the use forms.

In a fifth embodiment, the present invention is directed to the use of the crystalline form A of the compound of formula (1) for combatting undesired plant growth. In a particular embodiment, the present invention is directed to combatting undesired plant growth in crops of useful plants. In a particular embodiment of the present invention, the useful plants are transgenic plants. In a sixth embodiment, the present invention is directed to a method for combatting undesired plant growth, wherein the crystalline form A or a plant protection agent as defined above containing the crystalline form A, is applied to plants or the site of the undesired vegetation.

In some embodiments, the compounds and compositions described herein are applied as a post emergence application, pre-emergence application, in-water application to flooded paddy rice or water bodies (e.g., ponds, lakes and streams), or bum-down application.

In some embodiments, the crystalline form A or a plant protection agent as defined above containing the crystalline form A described herein are utilized to control weeds in crops, including but not limited to citrus, apple, rubber, oil, palm, forestry, direct-seeded, water-seeded and transplanted rice, wheat, barley, oats, rye, sorghum, com/maize, pastures, grasslands, rangelands, fallowland, turf, tree and vine orchards, aquatics, or row-crops, as well as non-crop settings, e.g., industrial vegetation management (IVM) or rights-of-way. In some embodiments, the compounds and compositions are used to control woody plants, broadleaf and grass weeds, or sedges.

In some embodiments, the crystalline form A or a plant protection agent as defined above containing the crystalline form A described herein are utilized to control undesirable vegetation in rice. In certain embodiments, the undesirable vegetation is Brachiaria platyphylla (Groseb.) Nash (broadleaf signalgrass, BRAPP), Digitaria sanguinalis (L.) Scop (large crabgrass, DIGSA), Echinochloa crus-galli (L.) P. Beauv. (bamyardgrass, ECHCG), Echinochloa colonum (L.) LINK (junglerice, ECHCO), Echinochloa oryzoides (Ard.) Fritsch (early watergrass, ECHOR), Echinochloa oryzicola (Vasinger) Vasinger (late watergrass, ECHPH), Ischaemum rugosum Salisb. (saramollagrass, ISCRU), Leptochloa chinensis (L.) Nees (Chinese sprangletop, LEFCH), Leptochloa fascicularis (Lam.) Gray (bearded sprangletop, LEFFA), Leptochloa panicoides (Presl.) Hitchc. (Amazon sprangletop, LEFPA), Panicum dichotomiflorum (L.) Michx. (fall panicum, PANDI), Paspalum dilatatum Poir. (dallisgrass, PASDI), Cyperus difformis L. (smallflower flatsedge, CYPDI), Cyperus esculentus L. (yellow nutsedge, CYPES), Cyperus iria L. (rice flatsedge, CYPIR), Cyperus rotundus L. (purple nutsedge, CYPRO), Eleocharis species (ELOSS), Fimbristylis miliacea (L.) Vahl (globe fringerush, FIMMI), Schoenoplectus juncoides Roxb. (Japanese bulrush, SPCJU), Schoenoplectus maritimus L. (sea clubrush, SCPMA), Schoenoplectus mucronatus L. (ricefield bulrush, SCPMU), Aeschynomene species, (jointvetch, AESSS), Altemanthera philoxeroides (Mart.) Griseb. (alligatorweed, ALRPH), Alisma plantago-aquatica L. (common waterplantain, ALSPA), Amaranthus species, (pigweeds and amaranths, AMASS), Ammannia coccinea Rottb. (redstem, AMMCO), Eclipta alba (L.) Hassk. (American false daisy, ECLAL), Heteranthera limosa (SW.) Willd./Vahl (ducksalad, HETLI), Heteranthera reniformis R. & P. (roundleaf mudplantain, HETRE), Ipomoea hederacea (L.) Jacq. (ivyleaf momingglory, IPOHE), Lindemia dubia (L.) Pennell (low false pimpernel, LIDDU), Monochoria korsakowii Regel & Maack (monochoria, MOOKO), Monochoria vaginalis (Burm. F.) C. Presl ex Kuhth, (monochoria, MOOVA), Murdannia nudiflora (L.) Brenan (doveweed, MUDNU), Polygonum pensylvanicum L., (Pennsylvania smartweed, POLPY), Polygonum persicaria L. (ladysthumb, POLPE), Polygonum hydropiperoides Michx. (POLHP, mild smartweed), Rotala indica (Willd.) Koehne (Indian toothcup, ROTIN), Sagittaria species, (arrowhead, SAGSS), Sesbania exaltata (Raf.) Cory/Rydb. Ex Hill (hemp sesbania, SEBEX), or Sphenoclea zeylanica Gaertn. (gooseweed, SPDZE).

In some embodiments, the crystalline form A or a plant protection agent as defined above containing the crystalline form A described herein are utilized to control undesirable vegetation in cereals. In certain embodiments, the undesirable vegetation is Alopecurus myosuroides Huds. (blackgrass, ALOMY), Apera spica-venti (L.) Beauv. (windgrass, APESV), Avena fatua L. (wild oat, AVEFA), Bromus tectorum L. (downy brome, BROTE), Lolium multiflorum Lam. (Italian ryegrass, LOLMU), Phalaris minor Retz. (littleseed canarygrass, PHAMI), Poa annua L. (annual bluegrass, POANN), Setaria pumila (Poir.) Roemer & J.A. Schultes (yellow foxtail, SETPU), Setaria viridis (L.) Beauv. (green foxtail, SETVI), Cirsium arvense (L.) Scop. (Canada thistle, CIRAR), Galium aparine L. (catchweed bedstraw, GALAP), Kochia scoparia (L.) Schrad. (kochia, KCHSC), Lamium purpureum L. (purple deadnettle , LAMPU), Matricaria recutita L. (wild chamomile, MATCH), Matricaria matricarioides (Less.) Porter (pineappleweed, MATMT), Papaver rhoeas L. (common poppy, PAPRH), Polygonum convolvulus L. (wild buckwheat, POLCO), Salsola tragus L. (Russian thistle, SASKR), Stellaria media (L.) Vill. (common chickweed, STEME), Veronica persica Poir. (Persian speedwell, VERPE), Viola arvensis Murr. (field violet, VIOAR), or Viola tricolor L. (wild violet, VIOTR).

In some embodiments, the crystalline form A or a plant protection agent as defined above containing the crystalline form A described herein are utilized to control undesirable vegetation in range and pasture. In certain embodiments, the undesirable vegetation is Ambrosia artemisiifolia L. (common ragweed, AMBEL), Cassia obtusifolia (sickle pod, CASOB), Centaurea maculosa auct. non Lam. (spotted knapweed, CENMA), Cirsium arvense (L.) Scop. (Canada thistle, CIRAR), Convolvulus arvensis L. (field bindweed, CONAR), Euphorbia esula L. (leafy spurge, EPHES), Lactuca serriola L./Tom. (prickly lettuce, LACSE), Plantago lanceolata L. (buckhom plantain, PLALA), Rumex obtusifolius L. (broadleaf dock, RUMOB), Sida spinosa L. (prickly sida, SIDSP), Sinapis arvensis L. (wild mustard, SINAR), Sonchus arvensis L. (perennial sowthistle, SONAR), Solidago species (goldenrod, SOOSS), Taraxacum officinale G.H. Weber ex Wiggers (dandelion, TAROF), Trifolium repens L. (white clover, TRFRE), or Urtica dioica L. (common nettle, URTDI).

In some embodiments, the crystalline form A or a plant protection agent as defined above containing the crystalline form A described herein are utilized to control undesirable vegetation found in row crops. In certain embodiments, the undesirable vegetation is Alopecurus myosuroides Huds. (blackgrass, ALOMY), Avena fatua (L.) (wild oat, AVEFA), Brachiaria platyphylla (Groseb.) Nash (broadleaf signalgrass, BRAPP), Digitaria sanguinalis (L.) Scop (large crabgrass, DIGSA), Echinochloa crus-galli (L.) P. Beauv. (bamyardgrass, ECHCG), Echinochloa colonum (L.) Link (junglerice, ECHCO), Lolium multiflorum Lam. (Italian ryegrass, LOLMU), Panicum dichotomiflorum Michx. (fall panicum, PANDI), Panicum miliaceum L. (wild-proso millet, PANMI), Setaria faberi Herrm. (giant foxtail, SETFA), Setaria viridis (L.) Beauv. (green foxtail, SETVI), Sorghum halepense (L.) Pers. (Johnsongrass, SORHA), Sorghum bicolor (L.) Moench ssp. Arundinaceum (shattercane, SORVU), Cyperus esculentus L. (yellow nutsedge, CYPES), Cyperus rotundus L. (purple nutsedge, CYPRO), Abutilon theophrasti Medik. (velvetleaf, ABUTH), Amaranthus species (pigweeds and amaranths, AMASS), Ambrosia artemisiifolia L. (common ragweed, AMBEL), Ambrosia psilostachya DC. (western ragweed, AMBPS), Ambrosia trifida L. (giant ragweed, AMBTR), Asclepias syriaca L. (common milkweed, ASCSY), Chenopodium album L. (common lambsquarters, CHEAL), Cirsium arvense (L.) Scop. (Canada thistle, CIRAR), Commelina benghalensis L. (tropical spiderwort, COMBE), Datura stramonium L. (jimsonweed, DATST), Daucus carota L. (wild carrot, DAUCA), Euphorbia heterophylla L. (wild poinsettia, EPHHL), Erigeron bonariensis L. (hairy fleabane, ERIBO), Erigeron canadensis L. (Canadian fleabane, ERICA), Helianthus annuus L. (common sunflower, HELAN), Jacquemontia tamnifolia (L.) Griseb. (smallflower momingglory, IAQTA), Ipomoea hederacea (L.) Jacq. (ivyleaf momingglory, IPOHE), Ipomoea lacunosa L. (white momingglory, IPOLA), Lactuca serriola L./Tom. (prickly lettuce, LACSE), Portulaca oleracea L. (common purslane, POROL), Sida spinosa L. (prickly sida, SIDSP), Sinapis arvensis L. (wild mustard, SINAR), Solanum ptychanthum Dunal (eastern black nightshade, SOLPT), or Xanthium strumarium L. (common cocklebur, XANST).

Working examples

Methods

All data which is part of the present application has been prepared according to the methods described below unless otherwise indicated. The samples used for measurement were directly used and did not undergo any further sample preparation.

X-ray powder diffraction (XRPD)

X-ray diffraction patterns were recorded at ambient temperature using XRD-diffractometers X'Pert PRO (PANalytical) and STOE STADI-P (radiation Cu-Ka 1, wavelength 1.5406 A). All X-ray reflections are quoted as °20 (theta) values (peak maxima) with a resolution of ±0.2°.

Thermogravimetric analysis (TGA)

TGA thermograms were recorded using thermobalances (model TGA7) from Perkin-Elmer. The measurements were performed in the temperature range of 35 - 220 °C with a heating rate of 10 Kmin ¹ using open platinum pans. Flow gas was dry nitrogen.

Differential Scanning Calorimetry (DSC)

DSC thermograms were recorded using thermal analysis system DSC 823 from Mettler. The measurements were performed in the temperature range of -60 - 220 °C with a heating rate of 20 Kmin ¹ using perforated aluminium pans. Flow gas was dry nitrogen.

Moisture sorption

Dynamic Vapour Sorption Analyzer; DVS Intrinsic (Surface Measurement Systems SMS); measured at a temperature of25°C.

I Polymorphic form A of methyl 4-amino-3-chloro-5-fluoro-6-(7-fluoro-l//-indol-6- yl)picolinate

1.1 Preparation of crystalline form A

Examples 1.1 to 1.12

400 mg of methyl 4-am i no-3 -chloro-5 -fl uo ro-6-(7-fl uo ro- l//-indol-6-yl )picol mate of formula (1) were dissolved in 60 mL the respective solvent at boiling temperature. The resulting solutions were filtered, an divided in 4 separate portions of about 15 mL each. The first portion was stored at ambient temperature (approximately 25 °C), the second portion was stored in a refrigerator (4°C) and the third portion was stored in a freezer (-20°C). During storage, typically a substantial amount of the respective solvent evaporated.

To the fourth portion water (referred to as “+ Water” in Table 1.1 below) was added at ambient temperature (approximately 25°C) until precipitation occurred. The precipitate of each portion was fdtered off after six days and dried at ambient temperature and ambient humidity.

The obtained crystals of crystalline form A were isolated and analyzed by X-ray powder diffraction (XRPD).

Table 1.1: Solvents used for crystallizing form A

*: The precipitate obtained from Example 1.7 contained crystalline form A and the pseudopolymorphic (hydrate) form described herein

1.2 Preparation of single crystals of crystalline form A and single crystal analysis

400 mg of crystalline form A were dissolved in 60 g of acetone. The resultant solution was filtered and stored in a freezer at -20°C. The resulting precipitate was filtered off after six days and dried at ambient temperature (approximately 25°C) under ambient conditions.

The crystal structure determination was carried out using a Bruker diffractometer equipped with an Apex II-CCD area detector, an IpS-microsource with Cu-Ka radiation, mirrors as monochromator and a Cryostream low temperature device (T =110 K). Fullsphere data collection, omega and phi scans. Programs used: Data collection and reduction Apex II v2014.11.0 (Bruker AXS, 2014), absorption correction / scaling SADABS. Crystal structure solution was achieved using direct methods as implemented in SHELXTL Version 6.14 (Bruker AXS, 2003) and visualized using XP program. Missing atoms were subsequently located from difference Fourier synthesis and added to the atom list. Least-squares refinement on F2 using all measured intensities was carried out using the program SHELXTL Version 6.14 (Bruker AXS, 2003). All non-hydrogen atoms were refined including anisotropic displacement parameters.

1.3 Properties of crystalline form A of P4356716 of formula (1)

The below mentioned properties are beneficial during the manufacturing of a agrochemical composition due to (mechanical) stability and lack of hygroscopicity.

1.3.1 Mechanical stability

The crystalline form A of P4356716 did not change substantially under the influence of mechanical stress (grinding with pestle and mortar and compression with 10 kbar).

1.3.2 Hygroscopicity

The isotherm moisture sorption of crystalline form A was measured: at 25°C a water absorption of 0.2 % was registered up to 95 % relative humidity. Thus, crystalline form A of P4356716 is not hygroscopic.

1.3.3 Slurry / stirring experiments

In each experiment, about 100 mg of the crystalline form A were suspended in the respective solvent and stirred at 25°. The next day an additional volume of the respective solvent was added in case the suspension showed to be too viscous. After one week, each suspension was filtered and the respective residue obtained dried at ambient temperature and ambient humidity. The resulting material was analysed in each case to ascertain whether any change had occurred.

In all three experiments, crystalline form A was unaltered, i.e. no change regarding form or purity of the crystalline form A had occurred. II Pseudopolymorphic (hydrate) form of methyl 4-amino-3-chloro-5-fluoro-6-(7-fluoro-l/Z- indol-6-yl)picolinate

II.1 Preparation of the pseudopolymorphic (hydrate) form

Example 2.1: Process for the production of pseudopolymorphic (hydrate) form

400 mg of methyl 4-am i no-3 -chloro-5 -fl uo ro-6-(7-fl uo ro- l//-indol-6-yl )picol mate were dissolved in 60 ml of non-dried methanol in a refrigerator (approximately 4°C). Crystallization yielded a sample with a mass loss of 1.8 %. TGA in combination with mass spectroscopy identified the volatile component as water. In addition to the melting peak of crystalline form A of P4356716 there was an endothermic event at 70°C followed by an exothermic event at 97°C in the DSC thermogram. This is possibly due to the release of water and recrystallization. According to X-Ray diffraction this sample is a mixture of crystalline form A of P4356716 and a different polymorphic form. Overall, in view of the above observations, the pseudopolymorphic form obtained is presumed to be a hydrate form.

Ill Comparative Data: Amorphous form

The amorphous form was obtained according to prior art. After melting and cooling to -10°C in the DSC calorimeter the drug was amorphous. No recrystallization occurred during heating.

Claims

1. A crystalline form A of the compound of formula (1)

which in a X-ray powder diffractogram at 25 °C and Cu-Ka 1 radiation displays at least 3 of the following reflections, quoted as 2Q value ± 0.2°: 9.9, 15.0 and 19.1.

2. The form A of the compound of claim 1, which in a X-ray powder diffractogram at 25 °C and with Cu-Ka 1 radiation displays at least the following reflections, quoted as 2Q value ± 0.2°: 9.9, 13.6, 15.0, 19.1 and 19.6.

3. The form A of the compound of claim 1, which in a X-ray powder diffractogram at 25 °C and with Cu-Ka 1 radiation displays at least the following reflections, quoted as 2Q value ± 0.2°: 9.9, 13.6, 15.0, 15.6, 19.1, 19.6 and 20.6.

4. The form A of the compound of claim 1, which in a X-ray powder diffractogram at 25 °C and with Cu-Ka 1 radiation displays at least the following reflections, quoted as 2Q value ± 0.2°: 9.9, 13.6, 15.0, 15.6, 17.4, 19.1, 19.6, 20.6, 25.2 and 26.3.

5. A process for the production of crystalline form A according to any of claims 1 to 7, comprising the following steps: a) diluting and/or suspending the compound of formula (1) in a suitable solvent or solvent mixture; b) heating the mixture of step a) to a temperature in the range of from about 20°C below the boiling temperature of the solvent or solvent mixture to the boiling temperature of the solvent or solvent mixture used in step a); c) cooling the solution or slurry obtained in step b) to a temperature of less than about 30°C.

6. The process according to claim 5, wherein the solvent or solvent mixture of step a) is selected from the group consisting of aliphatic ketones with 3 to 6 carbon atoms, acetonitrile, ethanol, and methanol.

7. The process according to claim 5 or 6, wherein the mixture of step a) is heated to a temperature in the range of from about 10°C below the boiling temperature of the solvent or solvent mixture to the boiling temperature of the solvent or solvent mixture used in step a).

8. The process according to any of claims 5 to 7, wherein the solution or slurry of step c) is cooled to a temperature in the range of about -30°C to less than about 30°C, preferably to a temperature in the range of about -20°C to less than about 25 °C.

9. A plant protection agent containing the crystalline form A of formula (1) according to any of claims 1 to 4.

10. The plant protection agent according to claim 9, which further comprises one or more further constituents selected from the group of agriculturally acceptable additive(s) customary for the formulation of plant protection agents, further herbicides, insecticides, acaricides, fungicides, safeners and/or plant growth regulator.

11. The plant protection agent according to any of claims 9 or 10, wherein said plant protection agent contains water.

12. The plant protection agent according to any of claims 9 to 11, wherein said plant protection agent is in the form of a suspension concentrate.

13. Use of the crystalline form A of the compound of formula (1) according to any of claims 1 to 4 or of a plant protection agent according to any of claims 9 to 12 for the production of a formulation in the form of a suspension concentrate.

14. Use of the crystalline form A of the compound of formula (1) according to any of claims 1 to 4 or of a plant protection agent according to any of claims 9 to 12 for combatting undesired plant growth, preferably for combatting undesired plant growth in crops of useful plants.

15. Method for combating undesired plant growth, wherein the crystalline form A according to any of claims 1 to 4 or a plant protection agent according to any of claims 9 to 12 is applied to plants or the site of the undesired vegetation.