MXPA97006048A - 2.4-disustitute pyrimidines and 2,6-disused pirimidines herbici - Google Patents

Abstract

The new pyrimidine and pyridine derivatives of the general formula (I), (See Formula) wherein A represents an optionally substituted aryl group, or a 5- to 6-membered nitrogen-containing heteroaromatic group, optionally substituted, or a difluorobenzodioxolyl group m represents an integer from 0 to 5, n represents an integer from 0 to 2, R1 (or each R1) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, alkynyl, alkoxy, alkoxyalkyl, dialkoxyalkyl, alkoxyalkoxy group alkyl, alkyl, amino, alkylamino, dialkylamino, alkoxyamino, or optionally substituted formamidino; R2 (or each R2) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, alkynyl, alkyloxy, alkylthio, alkylsulfonyl, or optionally substituted alkylsulfinyl group or a nitro, cyano, haloalkyl, haloalkoxy, or haloalkylthio group, X represents an oxygen or sulfur atom, and Z represents a nitrogen atom or n CH group, with the provisos that if A represents a 1-methyl-3-trifluluoromethyl-pyrazol-5-yl group, n is 0, X represents an oxygen atom, and Z represents a group Ch, then R2m does not represent hydrogen -trifluoromethylo-2,4-dichloro-2,4-dimethyl can be prepared by conventional methods and are particularly useful as a herbicide

Description

"PYRIMIDINES 2, 4-DISUSTITOIDS AND 2, 6-DISUSTITUTE HERBICIDES PYRIMIDINS" The present invention relates to certain 2,6-disubstituted pyridines and 2,4-disubstituted pyrimidines, their preparation and use as herbicides. Pyridines, pyrimidines, and their derivatives have many uses in the pharmaceutical area as well as in reagents, intermediates, and agricultural chemicals (herbicides, fungicides, acaricides, anthelmintics, bird repellents), for the textile industry and polymer. 2-Arylpyrimidines and 2-pyrimidyl-pyrimidines for example have been described as fungicides (DE 40 29 654 and JO 2131-480, respectively). EP 263,958 relates to herbicidal 2,6-diphenylpyridines, and .. have discovered structurally related 2,4-diphenylpyrimidines in EP 354,766 and 425,247. respectively, which is also said to be herbicides. Another example is the 2,6-diphenoxypyridines, which have been published in EP 572 093 as herbicides. 4-Phenoxy-2-pyrazol-1-yl-pyrimidines are disclosed in DE 29 35 578 as possessing fungicidal activity. Huelsen (Dipiomarbeit, Konstanz 1993) describes four distinct 2- (1-methyl-3-trifluorometH-pyrazol-5-ylioxy) -6-phenylpyridines, although no biological activity is discovered. Surprisingly, it has now been found that a good herbicidal activity is present in new related pyridine and pyrimidine derivatives, which have both an aryl group and an aryloxy or a heteroaryloxy group. These compounds unexpectedly show excellent activity and good crop selectivity in pre and post-emergence applications, both as broadleaf and grass weed species. Accordingly, the present invention provides 2,6-substituted pyridines and 2,4-substituted pyrimidines of the general formula I REF: 25410 O) wherein A represents an optionally substituted aryl group, or a 5- or 6-membered nitrogen-containing heteroaromatic group, optionally substituted, or a difluorobenzodioxolyl group; m represents an integer from 0 to 5; n represents an integer from 0 to 2; R1 (or each R1) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, alipyl, alkoxy group. alkoxyalkyl, dialkoxycyclic, akoxyalkoxy, alkylthio, amino, alkylamino, dialkylamino, alkoxyamino, or optionally substituted formamidino; R 2 (or each R 2) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, aikinyl, haloalkyl, haloalkoxy, alkoxy, alkoxyalkyl, akoxyalkoxy, aikylthio, optionally substituted haloaxykylthio group, or a nitro, cyano, SF5 group , or an aminosulfonyl or alkylsulfinyl; X represents an oxygen or sulfur atom; and Z represents a nitrogen atom or a CH group; with the provisos that (a) A represents a pyridyl group being substituted by at least one haloalkyl, haloalkoxy, or haloacylthio group, in the case where Z represents N: or (b) myn are 1. R1 denotes an alkyl group, alkoxy, or alkylamino adhered at the 4-position, and R ** represents a trifluoromethyl, in the case where Z represents CH.

An aryl group as a substitute or part of other substituents, or in the definition of A is suitably an optionally substituted phenyl or naphthyl group. Within the definition of A, the 5- or 6-membered heteroaryl group comprises optionally substituted 5 or 6-membered heterocycles containing one or more nitrogen and / or oxygen and / or sulfur atoms, with 1 to 3 nitrogen atoms being preferred. Examples of such groups are pyrazolyl, imidazolyl, triazolyl, tetrazolite, pyridyl, pyrazinyl groups. pyrimidyl, pyridazinyl. isoxazolyl, isothiazolinium, and triazinyl. As far as A is concerned, the definition "aryl" does not include bicyclic systems consisting of a benzene ring condensed with a 5- or 6-membered heterocyclic ring as defined above, and in turn, 5- or 6-membered heterocycles may be condensed with a benzene ring. Another preferred embodiment of A is a difluorobenzodioxolyl group of the formula In general, if one of the aforementioned portions comprises an alkyl, aannyl, or alkynyl group, said groups, unless otherwise specified, may be linear or branched, and may contain 1 to 12, preferably 1 to 4 carbon atoms. Examples of such groups are methyl, ethyl, propyl, vinyl, allyl, isopropyl, butyl, isobutyl, and tertiary butyl groups. The alkyl portion of a haloalkyl, haloalkoxy, alkylthio, haloacylthio, or alkoxy group suitably has from 1 to 4 carbon atoms, preferably 1 or 2 carbon atoms. The number of carbon atoms in the alkoxyalkyl, alkoxykoxy groups. or dialkoxyicyl is up to 6, preferably up to 4, for example methoxymethio, methoxymethoxy, methoxyethyl, ethoxymethyl, ethoxyethoxy, dimethoxymethyl. "Halogen" means fluoro, chloro, bromo, or iodo atoms, with preferred fluorine, chlorine, or bromine, Haloatquilo, haloatquiltio, and halohaoxy are preferably mono, di, or trifluoroalkyl, -alkylthio, and -alkoxy, in special trifluororpethyl, difluoromethoxy, trifluoromethylthio, and triforomethoxy When any group is designated as optionally substituted, the substituent groups that are optionally present may be any of those usually employed in the modification and / or development of pesticide compounds, and especially are substituents which maintain or improve the herbicidal activity associated with the compounds of the present invention, or influence the persistence of the action, penetration of plant or soil, or any other desirable property of said herbicidal compounds.There may be one or more of the same or different substituent present in each part of the molecules, in relation to the portions defined above as An optionally substituted alkyl group, including alkyl portions of haloalkyl, akoxy, aikylthio, haloalkoxy, alkylamino, and dialkylamino groups, specific examples of such substituents include phenyl groups, halogen atoms, nitro, cyano, hydroxyl, C- alkoxy, haloalkoxy d. *, and alkoxycarbonyl d, *. In relation to the previously defined portions as comprising an optionally substituted aryl or heteroaryl group, optional substituents include halogen, especially fluoro, chloro, and bromine atoms, and nitro, cyclo, amino groups. hydroxyl, Ciu alkyl. alkoxy d. " haloalkyl and halosuifanil, as SFS. Approximately 1 to 5 substituents may be employed, with 1 to 2 substituents being preferred. Typically the haloaicyl, haloalkoxy, and haloacylthio groups are trifluoromethyl, trifluoromethoxy, difluoromethoxy, and trifluoromethylthio groups. The index m preferably means an integer from 1 to 3, n is preferably 1 (then R 'is not hydrogen). The compounds according to the general formula i are oils, gums, or predominantly crystalline solid materials. They can be used in agriculture or related fields, for the control of unwanted plants such as Alopecurus myosuroides, Echinochloa crus-ga / li, Setaria viriúis, Galium aparíne, SteUaria media, Verónica persica, Lamium purpureu Viola arvensis, Abutilón theophrasti, Ipomoea purpurea, and Amaranthus retrofíexus, through pre and post emergency application. The compounds of the general formula I according to the invention possess an herbicidal activity within a wide range of concentration, and can be used in agriculture. Preferred compounds are those wherein A represents a phenyl, pyridyl, or pyrazolyl group, being replaced by one or more identical or different substituents selected from halogen atoms, alkyl, alkoxy, haloalkyl, haloalkoxy, and pentahalosulfanyl groups. Especially preferred are the compounds having a substituent in group A in me / a-position relative to the point of adhesion of this group.

Good results are obtained in terms of controlling the growth of unwanted plants, when A is mefa-substituted by a chlorine atom or a trifluoromethyl group, especially A being a 2-chloropyrid-4-ylo, 1-methyl-3-trifluoromethyl-pyrazol-5-yl group. or 3-trifluoromethylfenyl. Particularly good results are achieved in the control of weeds with the compounds wherein X represents an oxygen atom. Especially good results are obtained with the compounds wherein Z represents a nitrogen atom. The following formulas IA, IB, and IC represent preferred embodiments of the invention: (I A) (I C) In formula IA, A represents a 2-trifluoromethylpyrid-4-yl group. or 2-difluoromethoxy-pyrid-4-yl, R1 has the meaning given above; R2, R ** ", and Rr independently represent a hydrogen atom, a fluorine, chlorine, or bromine atom, one or two of them also a trifluoromethyl group, trif] uoromethoxy, or a cyano group, R ~~" also it can be an alkyl group, in particular a tere-butyl. In the formula IB X represents haloalkyl, haloalkoxy, or haloacylthio, preferably difloromethoxy, and R 1 denotes a halogen atom or an alkyl or alkoxy group. In the formula IC R1 denotes alkyl, alkoxy, or alkylamino, and A has the meaning given above. The invention is exemplified by the following compounds: 6-ethyl-2- (4'-trifluoromethylphenii) -4- (2", - trifluoromethyl-pyrid-4 *, - iloxy) pyrimidipa 6-et.}. | -2- (4'-trifluoromethylphenyl) ^ - [2 -'- (2t2,2-trifluoroethyl) -pyrid-4 -, - yloxy] pyrimidine 6-methyl-2- (4, -trifluoromethylphenyl) -4- (2"- difluoromethoxy-pyrid-4"-yloxy) pyrimidine 6-ethyl-2- (4, -trifluoromethylphenyl) -4- (2 ', - difluoromethoxy-pyrid-4" -yloxy) pyrimidine 6-rri-oxymethyl-2- ( 4'-trifluoromethylphenyl - (2 * '- difluoromethoxy-pyrid-4', - yloxy) pyrimidine 6-M-toxymethyl-2- (4'-trifluoromethyl-phenyl) -4- [2"- (2,2,2-tr Fluoroethyl) -pyrid-, - loxíjpirimidina 6-met'l-2- (4, -trifluorom? Tilfenil) -4- [2 * '- (1) 1, 2,2-t? Trafluoroe * ül) -pyridyl "-iiloxy] pyrimidine 5-methyl-2- (4, -trifluoromethylphenyl) -4 - [2" "- (1,1,1,2-tetrafluoroethyl) -pyrid-4" -yloxy] pyrimidine 6-methyl-2- (4'-trifluoromethylphenyl) -4- (2"-difluoromethylthio-pyrid ^ 4" -ilox!) pyrimidine 5-methyl-2-. {4'-trifluoromethyl-phepyl) -4- (2 '' - difluoromethylthio-pyrid-4"-yloxy) pyrimidine 6-methoxy-2- (4'-trifiuorome) tilfepiI) -4- (2"-difluoromethylthio-pyrid-4" -yloxy) pyrimidine 4-ethyl-2- (4'-trifluoromethyl-pyl) -6- (1"-rnethyl-3-tpfluorornethylpyrol-5-) ilox?) pyridine 4-methyl-2- (4'-trifluoromethyl-phenyl) -6- (2 * '- difluorornetoxipyrid-4', - iioxy) pyridine 4-methyl-2- (4, -trifluoromethyl) Nil) -6- (2"-trifluoromethylpyrid-4" -yloxy) pyridine 4-rnethyl-2- (4, -trifluoromethylphenol!) - 6- (3, '- trifluoromethylphenyloxy) pyridine The compounds according to the invention are They can prepare by conventional methods. A process suitable for the preparation of the compounds of the general formula I comprises the reaction of a compound of the general formula III (III) with a compound of the general formula IV A- XM (v) where Z. A, R1, R2, m, n. and X are as defined in Fa present above; Hai represents a halogen atom; and M represents a metal atom. The halogen atom Hal can be any halogen atom, suitably a fluorine, chlorine, or bromine atom is used. The metal atom can be any metal atom, suitably alkali metal atoms are used, sodium and potassium being preferred. Alternatively, a compound of the general formula XV (XV) wherein A, R ** and m are as defined hereinbefore, they can react with R1-H, preferably in the presence of a base, if R1 is alkoxy, akoxyalkoxy, aicytthio, amino, alkylamino, diacylamino, or alkoxyamino optionally substituted, to give compound of the general formula I. The compounds I, wherein R 1 is alkynyl or alkenyl, for example of the aiyl or propargyl type, can be prepared from the compounds I, wherein R 1 is a halogen atom , preferably chlorine or bromine, by the reaction of R'-H or organometallic denudates thereof, preferably in the presence of a transition metal catalyst or a base. Compounds XV can be prepared from III, wherein R1 is Hal, Z is nitrogen, Hal, R * and m are defined as above, by reaction with (V as described above, X means oxygen, applying about 2. IV equivalents In practice, the reaction can be carried out in the absence or presence of a solvent that promotes the reaction, or at least does not interfere with it., aprotic or protic, suitably N, N-dimethiiformamide or dimethisulfoxide or sulfolane, or an ether, such as t-tetrahydrofuran or dioxane, or alcohols, or water, or mixtures thereof. The reaction is carried out at a temperature between room temperature and the reflux temperature of the reaction mixture, preferably at elevated temperature, especially reflux temperature. The compounds of formula III in which Z represents a group C-H, and n is 0, can be obtained by reacting a compound of the general formula V (V) wherein R2 and m are as defined hereinbefore, with an aldehyde, suitably formaldehyde, and a dialkylamine, suitably dimethylamine, according to Org. Synthesis Col. Vol. MI, 305f, in a solvent, conveniently an alcohol, preferably ethanol, to give a compound of the general formula VI, (SAW) which is subsequently reacted according to DBP 21 47 288 (1971) with an ammonium salt, suitably ammonium acetate, and a compound of the general formula VII, p (Vile) wherein Y is an alkoxy group or an NH2 group, preferably an ethoxy group, in a solvent, suitably an alcohol, preferably ethanol, to give a compound of the general formula Vlll, which is further converted by reacting Vlll with phosphoryl halides (üller, E., Chem. Bβr 42, 423 (1909); Katritzky et al., J. Chem. Soc., Perkin Trans. Part 1, 1980, 2743-2754) , preferably phosphoryl bromide or phosphoryl chloride, at elevated temperatures, ideally reflux temperature, to give a compound of the general formula III. An alternative and preferred process for the preparation of compounds of the general formula III. wherein Z represents a C-H group, comprises reacting a 2,6-dihalopyridine of the general formula IX (IX) wherein R 'and n are as defined hereinbefore, and each Hal, and Hab independently represent a halogen atom, with an organometallic benzene derivative of the general formula (X), in an approximately equimolar ratio, (X) wherein R2 and m are defined above, and represents an alkali metal atom, or boron, or tin, or magnesium, or zinc or copper optionally in the presence of a transition metal catalyst. The alkali metal can be any alkali metal, preferably lithium, and the reaction can be carried out in a polar, aprotic solvent, preferably ethers, to give a compound of the general formula III, essentially as found in Cook and Wakefield , J Chem. Soc. 1969, 2376, or in non-polar solvents or water, for example as described in Ali, NM et al., Tetrahedron, 1992, 81 17. Compounds of formula III, wherein Z means CH, Hal is fluoro, R1 is hydrogen, R2 and m are as defined above, can further be converted to compounds of formula III, wherein = 1, Z means CH, Hal is fluoro, R2, m are as defined above, and R1 is in position 3 and means methylthio (or other group of the game described above, which can be introduced in the form of an electrophilic reagent), analogous to the method described by Gungor, T, Marsais, F, and Queguiner, G, J. Organometaüic Chem., 1981, 139-150. A process for the preparation of compounds of formula III, in which Z represents a nitrogen atom , comprises the reaction of b-zaminidine hydrochlorides of the general formula XI (XI) wherein R2 and m are as defined above, with a compound of formula XII or a salt thereof, (XII) wherein each R \ and R12 independently are as defined above; and the O-alkyl group is suitably methoxy or ethoxy, to give a pyrimidinone of the general formula XIII, in which R1 may also be hydroxyl. pon) Compounds of the general formula XI are known or can be prepared according to methods disclosed in the art, for example, in Tetrahedron, 33, 167f (1979), and J Org Chem, 26, 412f (1960). The reaction of the compounds of the formulas XI and XII can be carried out according to Liebigs Ann. 1980, 139f, in an organic solvent, suitably an alcohol, and preferably ethanol, and in the presence of a base, suitably metal alkoxides, preferably sodium ethoxide. The compounds of formula XIII can be subsequently converted to compounds of formula III, essentially as described in Davies and Pigott, J. Chem Soc., 1945, 347, by reaction with a phosphoryl halide or thionyl halide, or phosgene, with preferably phosphoryl chloride, phosphoryl bromide, ideally in the absence of a solvent, at elevated temperatures, to obtain compounds of the formula III. The compounds of formula III which have the meaning above with R1 = F, can be obtained from compound III when R1 is chloro or amino. according to procedures known in the art, as described in Tu I lock C.

W et al., J Am Chem. Soc. 1960, 5197, or Kibups J Klister J J Chem. Soc.

Chem Com 1969, 381 The compounds of the general formula IV are known or can be prepared by known methods. They can be prepared and isolated separately, or they can be prepared in situ. In general, a compound of the general formula XIV A-H (XIV) wherein A and X are as defined herein above, is reacted with a suitable metallic base, for example a metal hydride or carbonate. Preferably the metal salt is a potassium or sodium salt.

The compounds of the general formula I, if desired, can be isolated and purified using conventional techniques. The present invention further provides the use of a compound of the general formula I as a herbicide. Furthermore, according to the invention there is provided a method for combating the unwanted growth of plants in one place, by treating the site with a composition according to the invention, or a compound of formula I. As a useful action it is by application of foliar spray, the place is more adequately the plants in a growing area, being the typical crops, cereals, corn, soya bean, sunflower or cotton. However, the application may also be to the soil for those compounds that have pre-emergence herbicidal action. The dosage of active ingredient used can be, for example, in the range from 0.01 to 10 kg ha, preferably 0.05 to 1 kg / ha. The present invention further extends to a method for making a herbicidal composition of the invention, which comprises combining a compound of formula I with at least one carrier. Preferably there are two carriers in a composition of the present invention, at least one of which is a surface active agent. A carrier in a composition according to the invention is any material with which the active ingredient is formulated, to facilitate application to the site to be treated, which may be, as appropriate, a plant, seeds or soil, or to facilitate the storage, transport or handling. A carrier can be a solid or a liquid, including a material that is normally gaseous but that has been compressed to form a liquid, and any of the carriers normally used in the formulation of herbicidal compositions can be used. Preferably the compositions according to the invention contain 0.5 to 95% by weight of active ingredient.

Suitable solid carriers include natural and synthetic silicates and clays, for example natural silicates such as diatomaceous earth; magnesium silicates, for example talcs; magnesium aluminum silicates, for example attapulguites and vermiculites; aluminum silicates, for example kaolinites, montmorillonites, and micas; calcium carbonate; calcium sulfate; ammonium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminum silicates; elements, for example carbon and sulfur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and copolymers and styrene polymers; solid polychlorophenols; bitumen; waxes; solid fertilizers, for example superphosphates. Suitable liquid carriers include water, alcohols, for example isopropane and glycols; ketones, for example acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers; aromatic or araliphatic hydrocarbons, for example benzene, toluene, and xylene; petroleum fractions, for example kerosene and light mineral oils: chlorinated hydrocarbons, for example carbon tetrachloride, perchlorethylene, and trichloroethane. Mixtures of different liquids are often useful. Agricultural compositions are often formulated and transported in concentrated form, which is subsequently diluted by the user before application. The presence of small amounts of a carrier that is an active surface agent facilitates this dilution process. Accordingly, preferably at least one carrier in a composition according to the invention is a surface active agent. For example, the composition may contain at least two carriers, at least one of which is a surface active agent. A surface active agent can be an emulsifying agent, a dispersing agent, or a wetting agent; it can be non-ionic or ionic.

Examples of suitable surface active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation products of fatty acids or amides or aliphatic amines containing at least 12 carbon atoms in the molecule, with ethylene oxide and / or propylene oxide; fatty acid esters of glycerol, sorbitol, sucrose, or pentaerythrol; condensed thereof with ethylene oxide and / or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example, -octylphenol or f-octylcresol, with oxide of ethylene and / or propylene oxide; sulfates or sulfonates of these condensation products; alkali metal or alkaline earth metal salts, preferably sodium salts, or sulphonic or sulfuric acid esters containing at least 10 carbon atoms in the molecule, for example sodium lauryl sulfate, secondary sodium alkyl sulfates, sodium salts of suffixed castor oil, and sodium alkylaryl sulphonates, such as dedecybenzene suifonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide. The herbicidal composition of the invention may also contain other active ingredients, for example, compounds possessing fungicidal or insecticidal properties, or other herbicides. A formulation containing a compound according to the invention may consist of 100 g of active ingredient (compound of formula I), 30 g of dispersing agent, 3 g of antifoaming agent, 2 g of structure agent, 50 g of anti-inflammatory agent. -freezer, 0.5 g of a biocidal agent, and water ad 1000 ml. Before use it is diluted with water to give the desired concentration of active ingredient. The following examples illustrate the invention. The structures of the compounds prepared in the following examples were further confirmed by NMR and mass spectrometry.

Examples Example 1: β-Oimethylamino propiohenone hydrochloride Acetophenone (29.1 ml, 0.25 mol), para-formaldehyde (12.0 g, 0.40 mol) and dimethyl amine hydrochloride (28.5 g, 0.35 mol) ) are suspended in ethanol (50 ml). Concentrated hydrochloric acid (0.5 ml) is added and the mixture is heated to reflux for 4 hours. Then acetone (200 ml) is added and the resulting clear solution is allowed to cool to room temperature. The precipitate is collected by filtration and crystallized from etapoi, yielding the title compound (40.7 g, 76.0% theoretical μr? Dut-? Iun) as colorless crystals with mp. 158 ° C Examples 2-4: Additional examples of the general formula VI are prepared as exemplified by Example 1. Details are given in Table I.

Table I (VI) S: 6-Fepil-2-pyridone Etii 2-chloroacetate (10.6 ml, 0.1 mol) is slowly added to hot pyridipate (105 ° C) (8.9 ml, 0.11 mol) , whereby the temperature is maintained in the range of 100 ° C to 110 ° C. The resulting brown oil is dissolved in ethanol (60 ml), β-dimethylamino propiohenone hydrochloride (17.7 g, 0.1 mol, prepared according to Example 1) and ammonium acetate (60 g) are added, and the mixture is made boil under reflux for 4 h. After cooling, the mixture is filtered and the solvent is evaporated in a vacuum. The residue is crystallized from water, collected by filtration and purified by re-crystallization from toluene. The compound of the statement is obtained as colorless crystals (4.7 g, 28% of t.), With mp. 200 ° C.

Example »6-ß: Additional examples are prepared analogously to Example 5. Details are given in Table II.

Table II (Vlll) Example 9: 2-Bromo-β-phenyl pyridine A mixture of 6-phenyl pyridone (3 g, 17.5 mmol, prepared according to Example 6) and phosphoryl bromide (7.2 g, 25.0 mmol) is heated up to 100 ° C for 5 h. The cooled mixture is poured into water (40 ml) and the pH is adjusted to 9 by the addition of saturated aqueous sodium carbonate. Then the layers are separated and the aqueous layer is extracted with ethyl acetate (50 ml). The combined organic layers are dried with anhydrous magnesium sulfate, and the solvent is evaporated in a vacuum. The crude product is crystallized from aqueous etapol. Subsequent purification by flash chromatography (silica gel, hexane / ethyl acetate 9/1 vv) gives 2-bromo-6-phenyl pyridine (3.1 g, 76% t) as light brown crystals with mp 50 ° C.

Examples 10-12: Additional compounds of the general formula III are prepared by analogous procedures to that of Example 9. Details are given in Table III.

Table (111) Eiemolo 13: 2- (1 '-Methyl-3'-trifluoromethylpyrazol-5'-yloxy) -6-phenyl-pyridine A mixture of 2-bromo-6-phenol pyridine (0.5 g, 2.1 mmol, prepared according to Example 9), 1-methyl-3-fluoromethyl-5-hydroxypyrazole (0.65 g, 3.9 mmol). Potassium carbonate (0.6 g, 4.3 mmol), and N, N-dimethyl formamide (2 mL) is heated at reflux for 12 hours. Then the reaction mixture is directly applied on a flash chromatography column (silica gel). Elution with hexane / ethyl acetate (9/1 v / v) gives the title compound (0.35 g, 52.0% of t) as light yellow oil.

Examples 14-16: The compounds specified in Table IV are obtained by procedures analogous to that of Example 13.

Table IV Example 17: 2-Fiuoro-6-f4'-fluorophenyl) -pyridine Butyl lithium (105.0 rnl, 0.26 mol, 2.5 M solution in hexane) is added to a solution of 1-bromo-4-fluoro Benzene (34.3 ml, 0.31 mol) in anhydrous diethyl ether (200 ml) at -20 ° C. The pellet is stirred for 60 min and then cooled to -40 ° C. 2,6-Difluoropyridine (22, 7 ml, 0.25 mol) is added, and the reaction mixture is allowed to warm to room temperature, then the mixture is washed with saturated aqueous ammonium chloride (300 ml), the layers are separated and the aqueous layer is washed. with diethyl ether 3 times (100 ml each) After drying the combined organic layers with anhydrous magnesium sulfate, the solvent is removed in vacuo The crude product is purified by flash column chromatography (silica gel, hexane / AcOEt 8 2), yielding colorless crystals of 2-fluoro-6- (4'-fluorophenyl) -pyridine (19.8 g, 41.0% of t.) with mp 34 ° C).

Example 18: 2-Fluoro-6-rL4'-fluorophenyl) -4-methylpyridine A mixture of 2-bromo-6-fluoro-4-methylpyridipa (9.5 g, 50 mmol), 4-fluorobenzeneboronic acid (7 8 g, 56 mmol). sodium bicarbonate (12.6 g, 150 mmol). Water (200 ml), and catalytic amounts of tetrakis (triphenylphosphine) palladium (0) in DME under nitrogen is heated at reflux overnight. After filtration of the reaction mixture the solvents are removed under reduced pressure. The residue is fractionated between water -. atil acetate. The layers are separated and the aqueous layer is washed with ethyl acetate. After drying the combined organic layers with anhydrous magnesium sulfate, the solvent is removed in a vacuum. The crude product is purified by flash column chromatography (silica gel, pentane / ethyl acetate 9/1). producing colorless crystals of 2-fluoro-6- (4'-fluoro * phenyl) -4-methylpyridine (3.7 g, 36.1% of t.) with mp 49 ° C.

Example 19: 2-Ffuoro-β- (4'-trifluorofentl) -3-methylthio-pyridine To a solution of 2-phtoro-6 ~ (4, -trifiuorophenyl) pyridine (2.4 g, 10 mmol, prepared in accordance to Example 17), in dry THF (35 ml) a solution of 2 M LDA in THF (7.5 ml, 5 mmol) is added dropwise at -70 ° C. After 2 h at -70 ° C, dimethyl disulfide (1.41 g, 15 mmoi) is added and the reaction mixture is allowed to warm to -20 ° C. The mixture is hydrolyzed and extracted with diethyl ether. After separation, the organic layer is dried with anhydrous magnesium sulfate. The solvents are removed and the crude product is purified by flash column chromatography (silica gel). Elution with hexane / ethyl acetate (20/1 v v) gives the title compound (1.2 g, 42%) with mp 70-73 ° C.

Examples 20-23: In a manner analogous to Example 17, the examples of general formula III are prepared as specified in Table V.

Table V 2- (3'-Chlorpyrid-5'-yloxy) -6- (4"-fluorophenyloxy) -pyridine A mixture of 2-fluoro-6- (4'-fluorophenyl) -pyridine (1.9 g. mmol, prepared according to Example 17), 3-chloro-5-hydroxypyridine (1.4 g, 1.0 mmol), and potassium carbonate (1.5 g, 11.0 mmol) in sulfolane (10 ml) it is heated to reflux for 8 hrs. The mixture is allowed to cool to room temperature, and then it is filtered through a silica gel bed which is then washed with ethyl acetate. The organic solutions are combined and the solvent is evaporated in a vacuum. The remaining material is applied to the top of a flash chromatography column (silica gel) and eluted with hexane / ethyl acetate. Elution with hexane / ethyl acetate (8 2 vv) gives 2- (3 * -clofyrid-5'-yloxy) -6- (4"-fluorophenyloxy) -pyridine (1.4 g, 46% of t) as light brown crystals with mp 139 ° C.

Examples 26-43: Additional compounds are prepared analogously to Example 24. The details are found in Table VI.

Table VI (OR Eiemolo 40: 4-Fluorobenzamidine hydrochloride 4-Fluorobenzonitrile (10 g, 83 mmol) is dissolved in a mixture of anhydrous ethanol (5 ml) and diethyl ether (70 ml). The reaction mixture was cooled to an ice bath temperature and saturated with gaseous hydrogen chloride for 90 minutes. The mixture is allowed to warm to room temperature and is stirred overnight. The colorless precipitates are separated by filtration, washed with diethyl ether and dissolved in anhydrous ethanol (20 ml). Diethyl ether (100 ml) saturated with gaseous ammonia is added and the solution is stirred for 3 hours. The resulting suspension is filtered and the filtrate solvent is removed in a vacuum. The residue is washed with diisopropyl ether. After drying, colorless crystals (5.15 g, 35.5%) of melting point 210 ° C are obtained.

Examples 41 to 60: By methods analogous to that of Example 40, other compounds of the general formula XI are prepared. The details are given in Table VII.

Table VII (XI) Example 51: 2- (4'-Fluorophenyl) -5-methyl-4-pyrimidinone Sodium hydride (0.52 g, 13 mmol) is added to 20 ml of anhydrous ethanol and is stirred for 30 minutes at room temperature. To this, 4-fluorobenzamidine hydrochloride (1.47 g, 8.5 mmol) (from Example 40) is added and the mixture is stirred for an additional 30 minutes. Methyl 2-formylpropionate (1 g, 1.6 mmol) is added dropwise and the reaction mixture is left for 4 days under stirring at room temperature. After cooling, the solvent is removed in vacuo, and the residue is dissolved in aqueous sodium hydroxide (10 ml, 1). Then the mixture is brought to pH with 2 molar hydrochloric acid. The precipitate is separated by filtration and washed with diisopropyl ether. After drying, colorless crystals are obtained (0.44 g, 10.3%) melting point > 250 ° C.

Example 62: 6-Hydroxy-2- (4'-trifluoromethylphepin-4-pyrim? Dinone 4-trifluoromethylbenzamidipa hydrochloride (22.4 g, 0.1 mol, from Example 41) is added to a solution of potassium methylate ( , 22 mol) in anhydrous methyl alcohol (65 ml) and stirred for 15 minutes at room temperature, dimethyl malonate (12.6 ml, 0.11 mol) is added and the mixture is heated to reflux for 4 hours. The resulting suspension is diluted with methyl alcohol (50 ml).

The solvent is removed in vacuo, and the residue is dissolved in water (50 ml). Then the mixture is brought to pH 1 with concentrated hydrochloric acid. The precipitate is separated by filtration and washed with water. After drying, pale yellow crystals (15.1 g, 59%) of melting point > 200 ° C.

Example 63: 5-Methoxy-2- (4'-trifluoromethylphenyl) -4-pyrimidinone To a suspension of sodium hydride (60%, 6 g, 0.15 mol) in dry THF (225 ml), a solution is added of ethyl methoxyacetate (14.9 ml, 0.15 mol) in methyl formate (11.1 ml, 0.18 mol) over a period of 30 min. The mixture is stirred for 2 hours at room temperature. After the addition of diethyl ether (300 ml), the resulting sodium salt of methyl methoximalonate monoaldehyde can be isolated by suction. Now the sodium salt (0.075 mol) is added to 4-trifluoromethylbenzamide dicarbohydrate (16.8 g, 0.075 mol, of Example 41) in dry ethyl alcohol (150 ml), and the mixture is stirred for 48 hours at room temperature. ambient. After heating to reflux for 1 hour, water (100 ml) is added to the mixture and the solution is filtered. The filtrate is brought to? H5 with acetic acid and the ethyl alcohol is removed in a vacuum. The precipitate is separated by filtration and washed with ethyl alcohol. After drying, crystals (13.7 g, 68%) of melting point > 200.

Examples, 64 i 79 By the method exemplified in Example 53, other compounds of the general formula III are prepared. The details are given in Table Vlll.

Table Vlll flll) Example 79: 2- (4'-Fluorotenyl) -4-chloro-5-methylPyrimidine A mixture of 2- (4, -fluorophenyl) -5-methyl-4-pyrimidinone (0.79 g, 3.9 mmol) (from Example 55) and phosphorus oxychloride (3 ml) is heated to reflux for 1 hour. The main excess of phosphorus oxychloride is removed in a vacuum, and the residue is cooled with water (10 ml) to hydrolyze the remaining reagent. The mixture is neutralized and then extracted with ethyl acetate (50 ml). After drying the organic layer with anhydrous magnesium sulfate, the solvent is removed in a vacuum. The title compound (0.63 g, 72.6%) is obtained as colorless crystals of melting point 133 ° C.

Example 80: 2-f4'-Chlorophenyl) -4,5-dichloro-6-methoxyPyrimidine To a solution of 2- (4'-chlorophenyl) -4,5,6-trichloropyrimidine (1.85 g, 6.3 mmol) in Methyl alcohol (30 ml) and THF (60 ml) is added a solution of sodium (0.145 g, 6.3 mmol) in methyl alcohol (10 ml), and the mixture is stirred at room temperature overnight. After removal of the solvents in a vacuum, dichloromethane is added to the residue, and the resulting mixture is washed with water. After drying the organic layer with anhydrous magnesium sulfate, the solvent is removed. The treatment of the residue with pentane achieves the title compound (1.75 g, 96%) as colorless crystals of melting point 157-150 ° C.

Examples 81-108: The compounds of general formula (XIII) which are listed in Table IX are prepared analogously to the method of Example 83.

Table IX (IM) Example 10g: 2- (4'-Fluorophenyl-4-f3 '* - trifluoromethyl phenoxy) -6-methylpyrimidine A mixture of 2- (4'-fluorophenyl) -4-chloro-6-methylpyridine (0.6 g, 2 g) , 7 mmol) (from Example 85), a, a, a-3-hydroxybenzotrifluoride (0.49 g, 3 mmol) and potassium carbonate (0.41 g, 3 mmol) in NN-dimethylformamide (3 mL) is heated to reflux for 2 hours. After cooling, ethyl acetate (10 ml) is tureated and the suspension is filtered through a pad of silica gel using ethyl acetate. The solvent in the filtrate is removed in a vacuum, and the residue is purified by silica gel column flash chromatography, using hexane / ethyl acetate 7/2. Removal of the solvent achieves colorless crystals (0.53 g, 56.4%) of melting point 58 ° C.

Examples 110 • 183: Other compounds of the general formula I are prepared by the procedure of Example 109. Details are given in Table X.

Table X (•) Example 184: 4,6-Bis (2 *, - chloropyrid-4"-yloxy) -2- (4'-trifluoromethylphenyl) pyrimidine A mixture of 4,6-dichloro-2- (4, -trifluoromethylphenyl) pyrimidine (2) , 93 g, 10 mmol) (from Example 11), 2-chloro-4-hydroxypyridine (2.85 g, 22 mmol), and potassium carbonate (3.04 g, 22 mmol) in anhydrous N-dimethylformamide. (20 ml) is heated at 80 ° C for 1 hour, after cooling, the solvent is removed in a vacuum, ethyl acetate / hexane 1/1 (10 ml) is added and the suspension is filtered through a bed of silica gel The resulting solution is washed 3 times with water After drying the organic layer with anhydrous magnesium sulfate, the solvent is removed and the residue is purified by silica gel flash chromatography using hexane / ethyl acetate. / 2 Removal of the solvent produces colorless crystals (4.1 g, 86%) of melting point 141 ° C.

Eiemolos 186-187 The compounds of the general formula (XV a) listed in Table XI are prepared analogously to the method of Example 184.

Table XI (XV a) EXAMPLE 188 6-Methoxy-4-f2"-chloropyrid-4 * '-yloxy) -2- (4'-trifluoroethyl) / pyrimidine 4,6-Bis (2" -chloropyrid-4 *, - ilox!) -2- (4'-trifluoromethylphenyl) pyrimidine (2.0 g, 4.2 mmol) (from Example 184) is dissolved in anhydrous methyl alcohol (5 ml), a solution of potassium methylate (4.2 mmol) is added dropwise. in methyl alcohol (1.2 mL) to this solution, and the mixture is heated to reflux for 30 minutes.The solvent is removed in vacuo and the residue is purified by flash chromatography on silica gel using hexane / ethyl acetate. / 1. The elimination of the solvents achieves colorless (1, 0, 62%) cnstaies of melting point 128 ° C.

Example 189 4.6-Dibromo-2-f4'-trifluoromethyl-phenyl) pyrimidine A mixture of 4.6-dihydroxy-2- (4'-trifluoromethyl-phenyl) pyrimidine (5.12 g, 20 mmol) and phosphorus oxybromide (10 ml) is heated for 3 hours at 100 ° C. The resulting hot suspension is added to ice, and the product can be isolated by suction. After drying, almost colorless crystals (6.5 g, 86%) of melting point 87 ° C are obtained.

Examples 190-203 The compounds of the general formula I are prepared by the procedures of Examples 188 or 109. Details are given in Table XII. Table XII (») EXAMPLE 204 6-Vtnil-4-p "-rnethyl-3" -trifluoromethyl-pyrazol-5"-yl) -2- (4'-trifluoromethylphenyl) pyrimtdine A mixture of 6-bromo-4- (1" -methyl) -3"-trifluoromethylpyrazol-5 '* - il) -2- (4'-trifluoromethyl-phenyl) pyrimidine (2 g, 4.3 mmol, from Example 201), vinyltributi-intannate (1.4 ml, 4.7 mmol), tetrakis (triphenylphosphine) palladium (0) (0.1 g, 0.09 mmol), toluene (20 ml), and 3 crystals of 2,6-diferbutyl-4-methylphenol, is heated at reflux for 90 minutes. After cooling, a solution of 1.2 N of pyridinium fluoride in THF / pyridine (4 ml) and pyridine (2 ml) is added. The solution is stirred for 17 hours at room temperature. To the resulting mixture ethyl acetate (100 ml) is added and the solution is washed twice with water and a saturated solution of sodium bicarbonate. After drying the organic layer with anhydrous magnesium sulfate, the solvent is removed and the residue is purified by flash chromatography on silica gel, using hexane / ethyl acetate 7/3. Removal of the solvent achieves almost colorless crystals (1.45 g, 82%) of melting point 1 12 ° C.

Examples 206-214: Additional compounds are prepared analogously to Example 24. The details are found in Table XIII.

Table XIII (i) Examples 215-221: Additional compounds are prepared in analogous manner to Example 188, starting with 2,4-bisaryloxy-6-aryl? Iridines. The details are found in Table XIV.

Table XIII (0 The required 2,4-bisaryloxy-6-aryipyridines are obtained analogously to the one explicitly described below for: 2.4-Bis-f 1"-n-til-3 rifluoromethylorazole-5" -iyl-i) - 6- (4'-trifluoromethylphenidine) A mixture of 4-nitro-2,6-dichloropyridine (3.9 g, 20 mmol), 1-methyl-3-trifluoromethyl-5-hydroxy-irazole (7.3 g, 44 mmol) and potassium carbonate (6.7 g, 48 mmol) in anhydrous sulfolane, is heated to 10 ° C overnight The reaction mixture is cooled to room temperature, diluted with swamp / ethyl acetate (volume ratio 1 / 1) and filtered through a pad of silica gel The filtrate is washed 10 times with water, dried over anhydrous magnesium sulfate, and the solvents are removed in vacuo.The residue is purified by flash gel chromatography. silica, using pentane / ethyl acetate, 2,4-bi3- (1'-methyl-3'-trifluoromethylpyrazol-5'-yloxy) -6-chloropyridine (4.3 g, mp: 105"C) is obtained.

A mixture of bis (benzonitrile) palladium (II) chloride (0.19 g, 0.5 mmot) and 1,4-bis (diphenylphosphino) butane (0.2 g, 0.5 mmol) in anhydrous toluene (10 ml) ) is heated to reflux under a nitrogen atmosphere. After 2 hours, 4-trifluoromethylbenzeneboronic acid (1.2 g, 6.5 mmol), 2,4-bis- (1"-rnethyl-3" -trrfluoromethylpyrazal-5"* -lyloxy) -6-chloropyridine ( 2.2 g, 5 mmol), ethanol (2.5 ml), and a 1 M hydrated solution of sodium carbonate (5 ml), and the mixture is heated at reflux for an additional 2 hours under a nitrogen atmosphere. The reaction mixture is diluted with ethyl acetate and filtered through a silica padded bed.The filtrate is washed with water, dried over anhydrous magnesium sulfate, and the solvents are removed in vacuo.The residue is purified by silica gel flash using pentane / ethyl acetate (volume ratio 8/2). Colorless crystals of the title compound (2 g, 73%) are obtained with melting point 133 ° C Examples 222-300: Other compounds of General formula I are prepared by the procedure of Example 1 13. The details are given in Table XIV.

Table XIV H) Example 301: Herbicidal Activity To evaluate its herbicidal activity, the compounds according to the invention are evaluated using a representative range of plants: TRICKS Triticum aestivum HORVW Hordeum vuigare GOSHI Gossypium hirsutum HELAN Helianthus annuus ORYSA Oryza sativa GLXMA Glycine max BEAVA Beta vulgaris ZEAMX Zea mays ALOMY Alopecurus myosuroides AVEFA Avena fatua ECHCG Echinocioa crus-galli SETVl Setaria viridis GALAP Galium aparine STEME Stellaria media CHEAL Chenopodium album VERPE Veronica persica AMPU Lamium purpureum VIOAR Viola arvensis SIDSP AIDS spinosa AMBER Ambrosia artemisifolia ABUTH Abutilon theophrasti IPOPU Ipomoea purpurea SINAL Sinapis alba AMARE Amaranthus retroflexus The tests are grouped into two categories, pre-emergency and post-emergency. Pre-emergence tests involve spraying a liquid formulation of the compound onto the soil in which the seeds of the plant species mentioned above have been recently sown. The post-emergency tests involve spraying seed plants of the previous species, with said formulation. The soil used in the tests is a prepared horticultural slime. The formulations used in the test are prepared from solutions of the test compounds in acetone containing 0.4% by weight of an ethylene / alkylphenyl oxide capped surfactant, which can be obtained under the trademark TRITON X 155. The acetone solutions are diluted with water, and the resulting formulations at dosage levels corresponding to 1000 g or 300 g of active material per hectare in a volume equivalent to 400 liters per hectare. They are used like controls, in the tests of pre-emergency ground sown not treated, and in the tests of post-emergence untreated soil that has seed plants not treated. The herbicidal effects of the evaluation compounds are assessed visually twenty days after spraying the foliage and the soil (in the case of Examples 13-16, thirteen days after the treatment), and recorded on a scale of O - 9. A classification of O indicates growth as untreated control, a classification of 9 indicates death. An increment of 1 unit on the linear scale is approaching? 10% increase in the level of effect. An asterisk indicates that the specified plant species was not treated in the test. The results of the test are established in the tables shown below, in which the compounds are identified by reference to the preceding examples. An asterisk indicates that the specified plant species was not treated in the test.

Table XV Efficacy of the compounds of the invention in the application of pre-emergence and post-emergence Table XVI Ethics a of the compounds of the invention in the pre-emergence application.

X evaluation not possible. Table XVII Efficacy of the compounds of the invention in the post-emergency application.

Claims (10)

1. CLAIMS Having thus specially described and determined the nature of the present invention and the manner in which it is to be put into practice, it is claimed to claim as property and exclusive right: 1. a compound of the general formula (I) < J > characterized in that A represents an optionally substituted aryl group, or a 5- or 6-membered nitrogen-containing heteroaromatic group, optionally substituted, or a difluorobenzodioxolyl group; m represents an integer from 0 to 5; n represents an integer from 0 to 2; R1 (or each R1) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, alkynyl, alkoxy, alkoxyalkoxy group. alkoxyalkyl, dialkoxyalkyl, alkylthio, amino, alkylamino, dialkylamino, aikoxyamipo, or optionally substituted formandrid; R2 (or each R2) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, alkynyl, alkoxy, alkoxyalkyl, alkoxyalkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, optionally substituted group, or a nitro, cyano, haloalkyl group, haloalkoxy, haloacylthio, or SF5. X represents an oxygen or sulfur atom; and Z represents a nitrogen atom or a CH group; with the provisos that (a) A represents a pyridyl group being replaced by at least one haloaicyl, haloalkoxy, or hafoalki- thio group, in the case where Z represents N; or (b) m and n are 1, R1 denotes an alkyl, alkoxy, or alkylamino group attached at the 4-position, and R3 represents a trifluoromethyl, in the case where Z represents CH. 2. A compound as set forth in claim 1, characterized in that A represents a phenyl, pyridyl, or pyramyloyl group, being replaced by one or more of the same or different substituents selected from halogen atoms, alkyl group, alkoxy groups, haloalkyl groups , haloalkoxy groups, haloacylthio groups, and SF5 groups. 3. A compound of formula IA ( the )
2. Catheterized PARC-ue A is neither 2-tritluoromethylpyrid-4-yl or 2-d-fluoro-methoxypyrid-4-yl group, R1 bepe the meaning given above, R2, Rz, and Rr independently represent a hydrogen atom, a fluoro atom , chlorine, or bromine, one or two of them also a trifluoromethyl, trifluoromethoxy, or a cyano group, Rr can also be a C1-C4 alkyl group, in particular tere-butyl. 4. A compound of formula IB
3. (I B) wherein X represents haloalkyl, haloalkoxy, or haloacylthio, and R1 denotes a halogen atom or an alkyl or alkoxy group. 5. A compound of formula IB selected from the group consisting of 6-methyl-2-. { 4-trifluoromethyl-tenyl) -4 ~ (2"-difluoromethoxy-pyrid-4" -yloxy) pyrimidine 6-ethyl-2- (4'-trifluorometp- phenyl) -4- (2"-t? ^ 6 ^ til- 2- (4, -trifluoromethylphenyl) -4- (2 * '- (2I2,2-tr1fluoroethyl) -pyrid-4 *, - iloxy] pyrimidine 6 ^ til-2- (4, -trifluoromethyl-renyl) -4- (2", - difluoromethoxy-pyrid-4 * '- loxi) pyrimidine 6-m? Toxirrtethyl-2- (4'-trifluoromethylphenyl) -4- ^ 6-methoxymethyl-2- (4'-trichloromethylphenyl) -4- [2"- < 2,2,2-trifluoroethyl) -? Irid-4"-yloxy] pyrimidine 6-rn-til-2- (4, -trifluoromethylphenyl) -4- {2 *" - (1.1, 2 , 2-tetrafluoroethyl) -pyrid-4"-yl? I] pyrimidine 5-methyl-2- (4 * -trifluoromethylphenyl) -
4. 4- [2"- (1,1,1,2-tetrafluofoethyl) -pyrid-4" -yloxy] pyrimidine 6-methyl-2- (4'-trifluoromethylphenyl) ) ^ -. { 2"-difluoromethylthio-pyrld ^ -, - loxi) pyrimidine
5. 5-methyl-2- (4'-tri-puoromethyl-phenyl) -4- (2"lifluoromethylthio-pyrid-4 * '- yloxy) pyrimidine 6 ~ methoxy-2- (4 * -trifluoromethyl * phenyl) -4- (2"thifluoror ^ 6. A compound of formula IC (I C) in giving R1 da-uta alkyl, alxxscL, or alkyl annin, and A tiare the sif rifrado that is given in any of the preceding claims. 7. A compound of formula IC selected from the group consisting of 4-tyl-2- (4, -trifluororethylethyl) -
6. 6- (1 * '- methyl-3-trrfluoromethylpyrazol-5-yloxy) pyridine 4-m? - 2- (4-trl * puorornetylphenyl) -6- (2"-difluoromethoxy-pyrid-4" -yloxy) pyridipa 4L-methyl-2- (4'-tn-uoromethyl-phenyl) -6- (2") -trifluoromethylpyrid-4"-iloxl) pyridine 4-methyl-2-. { 4, -tri * nuoromethylphenyl) -6- (3 *, - trifluoromethylphenyloxy) pyridine 8. A herbicidal composition comprising at least one compound as set forth in claims 1 to 14 and a carrier and / or active surface agent . 9. A method for combating the growth of unwanted plants in one place, characterized by the fact that the treatment of the place effectively involves a compound as set forth in claims 1 to 14. 10. The use of an effective amount of a compound of claim 1 to 14 to combat the growth of unwanted plants. p. AMERICAN CYANAMID COMPANY SUMMARY The new pyrimidine and pyridine derivatives of the general formula (I), (i) wherein A represents an optionally substituted aryl group, or a 5- or 6-membered nitrogen-containing heteroaromatic group, optionally substituted, or a difluorobenzodioxolyl group; m represents an integer from 0 to 5; n represents an integer from 0 to 2; R1 (or each R1) independently represents a hydrogen atom, a halogen atom, an alkyl, ayanyl, alkynyl, alkoxy, alkoxyalkyl, dialkoxycyclic, alkoxyalkoxy, aicytthio, amino, alkylamino, dialkylamino, alkoxyamino, or optionally substituted formamidino; R2 (or each R2) independently represents a hydrogen atom, a halogen atom, an alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulfonyl, or optionally substituted alkylsulphniphenyl group, or a nitro, cyano, haloalkyl, haloalkoxy, or haloacylthio group; X represents an oxygen or sulfur atom; and Z represents a nitrogen atom or a CH group; with the provisos that if A represents a 1-methyl-3-trifluoromethyl-pyrazol-5-yl group, n is 0, X represents an oxygen atom, and Z represents a CH group, then R2m does not represent hydrogen or 3- trifluoromethyl or 2,4-dichloro or 2,4-dimethyl, can be prepared by conventional methods and are particularly useful as herbicides.