# Patent

## Title
Herbicidal

## Abstract

This is a divisional of application Ser. No. 342,879 filed on Jan. 26, 1982, now U.S. Pat. No. 4420328, which is a division of application Ser. No. 174,985 filed on Aug. 4, 1980 now U.S. Pat. No. 4,326,880.

## Background
The present invention relates to novel derivatives of 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid which have herbicidal properties, processes for the production of these novel acid derivatives, compositions containing them as active ingredients, and their use as herbicides, especially as selective herbicides in crops of useful plants.

The derivatives of 5-(pyridyl-2'-oxy)-2-nitro-benzoic acid are novel compounds. Derivatives of 3-(p-trifluoromethylphenoxy)-6-nitrobenzoic acid having herbicidal properties are known from U.S. Pat. No. 3 928 416 and German Offenlegungsschrift No. 2 753 900. Herbicidal 3-(p-trifluoromethylphenoxy)-6-nitrobenzoic acid derivatives are disclosed in U.S. Pat. No. 4 031 131 and, finally, herbicidal 3-(phenoxy)-6-nitrobenzoic acid derivatives are known from U.S. Pat. No. 3 784 635.

The derivatives of 5-(pyridyl-2'-oxy)-nitrobenzoic acid have the formula ##STR2## wherein X is halogen or a halomethyl group, Y is hydrogen, halogen or halomethyl group, A is the cyano group, a radical --COB or a 2-oxazoline radical which is unsubstituted or substituted by one or more methyl groups, B is a radical --OR.sub.1, --SR.sub.2, --NR.sub.3 R.sub.4 or --ON.dbd.C(R.sub.5).sub.2, wherein R.sub.1 is hydrogen or the cation of a base 1/n M.sup.n.sym., wherein M is an alkali metal cation or an alkaline earth metal cation or an iron, copper, zinc or  cation, n as 1, 2 or 3 corresponds to the valency of the cation, whilst each of R.sub.a, R.sub.b, R.sub.c and R.sub.d independently is hydrogen, benzyl, or a C.sub.1 -C.sub.4 alkyl radical which can be substituted by --OH, --NH.sub.2 or C.sub.1 -C.sub.4 alkoxy; R.sub.1 and R.sub.2 are a C.sub.1 -C.sub.18 alkyl radical which is unsubstituted or substituted by halogen, nitro, cyano, C.sub.1 -C.sub.8 alkoxy, C.sub.2 -C.sub.8 alkoxyalkoxy, oxirane, C.sub.3 -C.sub.6 alkenyloxy, C.sub.1 -C.sub.8 alkylthio, C.sub.2 -C.sub.8 alkanoyl, C.sub.2 -C.sub.8 acyloxy, C.sub.2 -C.sub.8 alkoxycarbonyl, carbamoyl, C.sub.1 -C.sub.4 alkylamino, bis(C.sub.1 -C.sub.4 alkyl)amino, C.sub.2 -C.sub.4 alkenylamino, bis(C.sub.2 -C.sub.4 alkenyl)amino, C.sub.2 -C.sub.4 -alkynylamino, bis(C.sub.2 -C.sub.4 alkynyl)amino, tris(C.sub.1 -C.sub.4 alkyl)ammonio, C.sub.3 -C.sub.8 cycloalkyl, C.sub.3 -C.sub.8 cycloalkenyl, or also by a phenyl, phenoxy or 5- or 6-membered heterocyclic radical containing 1 to 3 hetero-atoms, each of which is unsubstituted or is itself mono- or polysubstituted by halogen, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; or is a C.sub.3 -C.sub.10 alkenyl radical which is unsubstituted or mono- to tetrasubstituted by halogen or monosubstituted by phenyl or methoxycarbonyl; a C.sub.3 -C.sub.8 alkynyl radical; a C.sub.3 -C.sub.12 cycloalkyl radical which is unsubstituted or substituted by halogen or C.sub.1 -C.sub.4 alkyl; a C.sub.3 -C.sub.8 cycloalkylene radical, a phenyl radical which is unsubstituted or mono- or polysubstituted by halogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkylthio, NO.sub.2, CF.sub.3, COOH, CN, OH, SO.sub.3 H, NH.sub.2 or --NH(C.sub.1 -C.sub.4 alkyl) or --N(C.sub.1 -C.sub.4 alkyl).sub.2 ; a 5- or 6-membered heterocyclic ring containing 1 to 3 hetero-atoms; and each of R.sub.3 and R.sub.4 is hydrogen, a C.sub.1 -C.sub.4 alkyl radical which is unsubstituted or substituted by C.sub.1 -C.sub.4 alkoxy, hydroxyl, halogen or C.sub.2 -C.sub.8 alkoxycarbonyl, a C.sub.3 -C.sub.5 alkenyl radical, a C.sub.3 -C.sub.5 alkynyl radical, a C.sub.3 -C.sub.7 cycloalkyl radical or an aromatic radical, or one of R.sub.3 and R.sub.4 is also a C.sub.1 -C.sub.4 alkoxy or C.sub.1 -C.sub.4 alkylsulfonyl radical, or R.sub.3 and R.sub.4, together with the nitrogen atom to which they are attached, are also a 5- or 6-membered hetrocyclic ring system which can contain an additional oxygen or sulfur atom or an imino group which is unsubstituted or substituted by C.sub.1 -C.sub.3 alkyl, and each R.sub.5 is C.sub.1 -C.sub.4 alkyl or both together form a C.sub.3 -C.sub.5 alkylene chain.

In formula I, halogen denotes fluorine, chlorine, bromine or iodine.

The term "alkyl" by itself or as moiety of a substituent comprises branched or unbranched alkyl groups, e.g. methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl and the higher homologues amyl, isoamyl, hexyl, heptyl, octyl etc. together with their isomers.

The alkenyl and alkynyl radicals also comprise branched and unbranched radicals which contain the indicated number of carbon atoms and at least one unsaturated position. Preferred alkenyl radicals are the unsubstituted or halogen-substituted allyl, methallyl and n-butenyl radicals. The preferred alkynyl radical is the propynyl or propargyl radical.

Cycloalkyl radicals are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. Cycloalkenyl radicals correspond to these ring systems, but where possible, additionally contain one or more double bonds.

Heterocyclic rings contain 1 to 3 identical or different heteroatoms O, S and N. Examples are in particular 5- or 6-membered heterocyclic ring systems which are saturated, partially saturated or unsaturated and which can be substituted. Without any limitation being implied, examples are: furane, nitrofurane, bromofurane, methylfurane, thiophene, chlorothiophene, pyridine, 2,6-dichloropyridine, pyrimidine, pyridazine, pyrazine, piperidine, methylpiperidine, methylpiperidine, morpholine, thiomorpholine, tetrahydrofurane, oxazole, pyrazole, pyrrole, pyrroline, pyrrolidine, thiazole, 2,3-dihydro-4H-pyrane, pyrane, dioxane, 1,4-oxathi-(2)-ine.

The compounds (active ingredients) of the formula I have in general pronounced selective herbicidal activity and are especially advantageous for controlling weeds in crops of useful plants, particularly in crops of soybeans, cotton, cereals, rice, maize and sugar beet. When employed in sufficiently high rates of application, however, the compounds of the formula I also act as total herbicides. Application can be both pre- and post-emergence. The rates of application can vary within wide limits, e.g. from 0.1 to 10 kg of active ingredient per hectare. However, it is preferred to employ from 0.5 to 5 kg of active ingredient per hectare.

Compounds belonging structurally to the following groups are very effective against weeds in crops of wheat, rice and/or soybeans: ##STR3##

In these compounds, B can have in general any meaning within the definition given for formula I. The most active compounds are those in which B is hydroxyl, C.sub.1 -C.sub.18 alkoxy, C.sub.1 -C.sub.4 cyanoalkoxy, C.sub.3 -C.sub.18 alkoxycarbonylalkyl, di(C.sub.1 -C.sub.4 alkyl)-amino-C.sub.1 -C.sub.4 alkyl, C.sub.3 -C.sub.10 alkenyl, C.sub.3 -C.sub.10 alkynyl, C.sub.1 -C.sub.18 alkylthio, C.sub.3 -C.sub.18 alkoxycarbonylalkylthio, C.sub.3 -C.sub.10 alkenylthio, C.sub.1 -C.sub.4 alkylamino, C.sub.2 -C.sub.8 alkoxyalkylamino, C.sub.3 -C.sub.8 alkoxycarbonylalkylamino or N-C.sub.1 -C.sub.4 alkoxy-N-C.sub.1 -C.sub.4 alkylamino.

In addition to containing the active ingredients of the formula I, the compositions of this invention contain a suitable carrier and/or other adjuvants. Suitable carriers and adjuvants can be solid or liquid and correspond to the substances customarily employed in the art of formulation, e.g. natural or regenerated mineral substances, solvents, diluents, dispersants, emulsifiers, wetting agents, tackifiers, thickeners, binders and/or fertilisers.

For use in herbicidal compositions, the compounds of the formula I can be processed to dusts, emulsifiable concentrates, granules, dispersions or also to solutions or suspensions in conventional formulation.

The compositions of the present invention are obtained in known manner by intimately mixing and grinding active ingredients of the general formula I with suitable carriers and/or adjuvants, with or without the addition of antifoams, wetting agents, dispersants and/or solvents which are inert to the active ingredients. The active ingredients can be processed to the following formulations: impregnated granules and homogeneous granules); powders, pastes, emulsions, emulsifiable concentrates;

The concentrations of active ingredient in the compositions of this invention are between 1 and 80 percent by weight. As circumstances may require, the active ingredients can also be applied in low concentrations of about 0.05 to 1 percent by weight.

The compositions of the present invention can be mixed with other biocidal compounds or compositions. Thus in addition to containing the compounds of the general formula I, the compositions of the invention can also contain e.g. insecticides, fungicides, bactericides, fungistatic agents, bacteriostatic agents, nematocides or further herbicides, in order to broaden the activity spectrum.

The compounds of the formula I are obtained by methods which are known per, for example by one of the following synthesis routes.

One convenient process for obtaining the 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivatives of the formula I comprises reacting a 2-halopyridine of the formula II ##STR4## wherein Hal is halogen and X and Y have the given meanings, in an organic solvent and in the presence of a base, with a 3-hydroxy-6-nitrobenzoic acid derivative of the formula III ##STR5## wherein A is a radical as defined under formula I.

Another synthesis route consists in reacting the 2-halopyridine of the formula II and a 3-hydroxy-benzoic acid derivative of the formula IV ##STR6## wherein A is a radical as defined under formula I, initially in an aprotic solvent and in the presence of a base which acts as acid acceptor, to give the 3-(pyridyl-2'-oxy)-benzoic acid derivative of the formula V ##STR7## wherein A, X and Y have the given meanings.

The second process for obtaining the compounds of formula I comprises nitrating a 3-(pyridyl-2'-oxy)-benzoic acid derivative of the above formula V with a nitrating acid mixture.

Finally, in compounds of the formula I in which A is e.g. the acid nitrile, a carboxyl group or the carboxamide, it is possible to convert these radicals by appropriate reactions such as saponification, esterification, amination, or alkylation, to other carboxylic acid derivatives falling under the definition of A.

These reactions are carried out in the temperature range from 0.degree. to 150.degree. C. Suitable solvents are in particular aprotic solvents such as dimethyl sulfoxide, dimethyl formaldehyde, sulfolane, N-methyl-pyrrolidone etc.

Suitable bases which are added to bind the eliminated halogen atom are both inorganic bases such as alkali metal hydroxides and carbonates and bicarbonates of alkali metals and alkaline earth metals, and organic bases, e.g. alkylamines such as dimethylamine, trimethylamine, diethylamine, triethylamine etc.

Examples of nitrating solutions are mixtures of nitric and sulfuric acid, solutions of nitric acid in glacial acetic acid, or concentrated nitric acid by itself, e.g. in chlorinated hydrocarbons. The nitration reactions are carried out in the temperature range from about 0.degree. C. to room temperature.

The compounds of the formula I are stable compounds which have low mammalian toxicity and no precautionary measures are necessary for handling them. They have relatively good solubility in customary organic solvents and are reluctantly soluble in water.

The following Examples illustrate in more detail the production of the 5-(pyridyl-2'-yl-oxy)-2-nitrobenzoic acids of the formula I. Further compounds obtained in analogous manner are listed in the subsequent table. Parts and percentages are by weight and pressures are indicated in millibars.

5-(3'-Chloro-5'-trifluoromethylpyridyl-2'-oxy)-2-nitrobenzoic acid ##STR8## 8.4 g of 5-(3'-chloro-5'-trifluoromethylpyridyl-2'-oxy)benzoic acid are suspended in 100 ml of ethylene chloride and the suspension is cooled. Then 18 ml of concentrated sulfuric acid and a solution of 1.5 ml of 100% nitric acid in 18 ml of 2.5 ml of sulfuric acid are added dropwise in succession. The reaction mixture is stirred for 2 hours at room temperature and then poured into 100 ml of ice-water. The organic phase is separated and the aqueous phase is extracted with ethylene chloride. The ethylene chloride extract is dried over magnesium sulfate and concentrated. The residue is crystallised by trituration with petroleum ether. The crystals are collected by filtration, affording 5.6 g (60% of theory) of the title compound with a melting point of 114.degree.-117.degree. C.

The starting 5-(3'-chloro-5'-trifluoromethyl-pyridyl-2'-oxy)-benzoic acid is prepared as follows:

A solution of 5.8 g (0.042 mole) of 3-hydroxybenzoic acid in 15 ml of dimethyl sulfoxide is added dropwise to a suspension of 2 g (0.084 mole) of sodium hydride in 15 ml of dimethyl sulfoxide. When all the sodium hydride is dissolved, a solution of 8.3 g of 2-fluoro-2-chloro-5-trifluoromethylpyridine in 10 ml of dimethyl sulfoxide is added dropwise, whereupon the temperature rises to 45.degree. C. The reaction is complete after stirring for 6 hours at 85.degree. C. The dimethyl sulfoxide is evaporated off in vacuo and the residue is poured into ice-water. Acidification with hydrochloric acid results in the formation of a precipitate, which is collected by filtration and washed with water. Recrystallisation from ethanol/water yields 8.4 g (63% of theory) of pure 3-(3'-chloro-5'-trifluoromethylpyridyl-2'-oxy)benzoic acid with a melting point of 141.degree.-145.degree. C.

2-Nitro-5-(3',5'-dichloropyridyl-2'-oxy)-2-benzonitrile ##STR9## A solution of 16.4 g (0.1 mole) of 3-cyano-4-nitrophenol in 50 ml of N-methylpyrrolidone is added dropwise to a suspension of 2.4 g (0.1 mole) of sodium hydride in 30 ml of N-methylpyrrolidone. When the evolution of hydrogen has ceased, 16.6 g (0.1 mole) of 2-fluoro-3,5-dichloropyridine are added. The reaction mixture is stirred for 15 hours at 110.degree.-115.degree. C. and then poured into ice-water. The water is extracted with chloroform and the chloroform extract is dried over sodium sulfate and concentrated. The residue is purified over a column of silica gel with ethyl acetate/hexane as eluant, affording 6.2 g (30% of theory) of the title compound with a melting point of 138.degree.-140.degree. C.

Methyl 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy)benzoate ##STR10## 6.6 g of 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy)benzoic acid (prepared according to Example 1) are mixed with 10 ml of thionyl chloride and the mixture is stirred for 15 hours at 60.degree. C. Excess thionyl chloride is removed by evaporation. The residue is dissolved in 50 ml of toluene and to this solution are added 1 g of methanol and 2.1 g of triethylamine. The salt is collected by filtration after 1 hour and the filtrate is concentrated. The residue is crystallised from ethyl acetate and hexane, affording 4 g (62% of theory) of the title compound with a melting point of 81.degree.-82.degree. C.

The following compounds are obtained by procedures analogous to those described in the foregoing Examples: ##STR11## Physical No.  XY        B                   data (.degree.C.) ______________________________________ 1    ClCl      OH                  m.p. 166-169.degree. 2    ClCl      OCH.sub.3           m.p. 81-82.degree. 3    ClCl      OC.sub.2 H.sub.5 4    ClCl      OC.sub.3 H.sub.7 n 5    ClCl      OC.sub.3 H.sub.7 iso n.sub.D.sup.25 1.5815 6    ClCl      OC.sub.4 H.sub.9 n 7    ClCl      OC.sub.4 H.sub.9 sec n.sub.D.sup.30 1.5840 8    ClCl      OC.sub.4 H.sub.9 iso n.sub.D.sup.25 1.5680 9    ClCl      OC.sub.4 H.sub.9 tert 10   ClCl      OC.sub.5 H.sub.11 iso n.sub.D.sup.27 1.5675 11   ClCl ##STR12##          n.sub.D.sup.27 1.5677 12   ClCl      OCH(C.sub.2 H.sub.5).sub.2 13   ClCl      OCH.sub.2 CH.sub.2 OCH.sub.3 14   ClCl      OCH.sub.2 CH.sub.2 OC.sub.2 H.sub.5 15   ClCl      OCH.sub.2 CH.sub.2 OC.sub.4 H.sub.9 n.sub.D.sup.27 1.5620 16   ClCl ##STR13## 17   ClCl      OCH.sub.2 CH.sub.2 N(CH.sub.3).sub.2 n.sub.D.sup.30 1.5817 18   ClCl ##STR14## 19   ClCl ##STR15##          n.sub.D.sup.27 1.5605 20   ClCl      O(CH.sub.2).sub.3 N(CH.sub.3).sub.2 21   ClCl      OCH.sub.2 CHCH.sub.2 22   ClCl      OCH.sub.2 CHCHCH.sub.3 n.sub.D.sup.25 1.5877 23   Cl Cl     OCH.sub.2 CCH       m.p. 81-82.degree. 24   ClCl      OCH.sub.2 CCCH.sub.3 25   ClCl ##STR16## 26   ClCl ##STR17## 27   ClCl      OCH.sub.2 CN        n.sub.D.sup.27 1.5890 28   ClCl      OCH.sub.2 CH.sub.2 Cl 29   ClCl      OCH.sub.2 CH.sub.2 Br 30   ClCl      NH.sub.2            m.p. 179-180.degree. 31   ClCl      NHCH.sub.3 32   ClCl      NHC.sub.2 H.sub.5   m.p. 119-120.degree. 33   ClCl      NHC.sub.3 H.sub.7 (iso) 34   ClCl      NHCH.sub.2 CHCH.sub.2 35   ClCl      NHCH.sub.2 CCH 36   ClCl      NHC.sub.4 H.sub.9 (sec) 37   ClCl      NHCH(C.sub.2 H.sub.5).sub.2 38   ClCl      NHCH.sub.2 COOCH.sub.3 39   ClCl      N(CH.sub.3).sub.2 40   ClCl      N(C.sub.2 H.sub.5).sub.2 41   ClCl ##STR18## 42   ClCl ##STR19## 43   ClH       OH                  m.p. 166-169.degree. 44   ClH       OCH.sub.3 45   ClH       OC.sub.2 H.sub.5 46   ClH       N(CH.sub.3).sub.2 47   ClH       NHCH.sub.2 COOC.sub.2 H.sub.5 48   ClCl ##STR20## 49   ClH ##STR21## 50   ClCl      SCH.sub.3 51   ClCl      SC.sub.2 H.sub.5    n.sub.D.sup.27 1.6200 52   ClCl      SC.sub.4 H.sub.9 (iso) n.sub.D.sup.27 1.5965 53   ClCl      SCH.sub.2 CHCH.sub.2 54   ClCl      SCH.sub.2 COOCH.sub.3 n.sub.D.sup.27 1.6060 55   ClCl      SCH.sub.2 CCH 56   ClCl      SCH.sub.2 CCHCH.sub.3 57   ClBr      OH 58   ClBr      OCH.sub.3 59   ClBr      OC.sub.2 H.sub.5 60   ClBr      OC.sub.5 H.sub.9 (iso) 61   ClBr      OC.sub.4 H.sub.9 (sec) 62   ClBr      SC.sub.3 H.sub.7 (n) 63   ClBr      SC.sub.4 H.sub.9 (n) 64   ClBr      SCH.sub.2 CHCH.sub.2 65   ClBr      OCH(CH.sub.2).sub.4 66   ClBr      OCH.sub.2 CH(CH.sub.2 ).sub.5 67   ClBr      NHC.sub.2 H.sub.5 68   ClBr      NHC.sub.3 H.sub.7 (iso) 69   ClBr      NHC.sub.8 H.sub.17 70   ClBr      N(CH.sub.2 CHCH.sub.2).sub.2 71   BrCl      OH 72   BrCl      OCH.sub.3 73   BrCl      OC.sub.2 H.sub.5 74   BrCl      OC.sub.3 H.sub.7 (iso) 75   BrCl      OC.sub.4 H.sub.9 (sec) 76   BrCl      OC.sub.4 H.sub.9 (iso) 77   BrCl      OC.sub.4 H.sub.9 (tert) 78   BrCl      OCH(CH.sub.2 CH.sub.3).sub.2 79   BrCl ##STR22## 80   BrCl      SCH.sub.3 81   BrCl      SC.sub.3 H.sub.7 82   CF.sub.3Cl OH                  m.p. 114-117.degree. 83   CF.sub.3Cl OCH.sub.3           n.sub.D.sup.25 1.5357 84   CF.sub.3Cl OC.sub.2 H.sub.5 85   CF.sub.3Cl OC.sub.3 H.sub.7 (n) 86   CF.sub.3 Cl OC.sub.3 H.sub.7 (iso) n.sub.D.sup.30 1.5278 87   CF.sub.3Cl OC.sub.4 H.sub.9 (n) 88   CF.sub.3Cl OC.sub.4 H.sub.9 (iso) n.sub.D.sup.20 1.5225 89   CF.sub.3Cl OC.sub.4 H.sub.9 (sec) n.sub.D.sup.30 1.5265 90   CF.sub.3Cl O(CH.sub.2).sub.4 Cl n.sub.D.sup.30 1.5350 91   CF.sub.3Cl OC.sub.5 H.sub.11 (n) 92   CF.sub.3Cl ##STR23##          n.sub.D.sup.30 1.5174 93   CF.sub.3Cl OCH(C.sub.2 H.sub.5).sub.2 94   CF.sub.3Cl OCH.sub.2 CH.sub.2 CH(CH.sub.3).sub.2 95   CF.sub.3Cl OC.sub.6 H.sub.13 (n) 96   CF.sub.3Cl OC.sub.7 H.sub.15 (n) 97   CF.sub.3Cl ##STR24## 98   CF.sub.3Cl OC.sub.8 H.sub.17 (n) n.sub.D.sup.30 1.5125 99   CF.sub.3Cl OCH.sub.2 CH.sub.2 Cl n.sub.D.sup. 30 1.5485 100  CF.sub.3Cl OCH.sub.2 CH.sub.2 Br 101  CF.sub.3Cl OCH.sub.2 CH.sub.2 F 102  CF.sub.3Cl OCH.sub.2 CH.sub.2 OCH.sub.3 n.sub.D.sup.30 1.5365 103  CF.sub.3Cl OCH.sub.2 CH.sub.2 OC.sub.4 H.sub.9 104  CF.sub.3Cl OCH.sub.2 CH.sub.2 OC.sub.2 H.sub.5 105  CF.sub.3Cl OCH.sub.2 CN        m.p. 100-102.degree. 106  CF.sub.3Cl ##STR25##          n.sub.D.sup.30 1.5213 107  CF.sub.3Cl OCH.sub.2 CHCH.sub.2 n.sub.D.sup.30 1.5411 108  CF.sub.3Cl OCH.sub.2 CHCHCH.sub.3 109  CF.sub.3Cl ##STR26## 110  CF.sub.3Cl OCH.sub.2 CCH       m.p. 94-96.degree. 111  CF.sub.3Cl ##STR27## 112  CF.sub.3Cl O(CH.sub.3).sub.2 CCH 113  CF.sub.3Cl ##STR28## 114  CF.sub.3Cl ##STR29## 115  CF.sub.3Cl ##STR30##          m.p. 89-91.degree. 116  CF.sub.3Cl ##STR31## 117  CF.sub.3Cl ##STR32##          m.p. 92-94.degree. 118  CF.sub.3Cl ##STR33##          m.p.79-81.degree. 119  CF.sub.3Cl OCH.sub.2 CH.sub.2 N(CH.sub.3 ).sub.2 n.sub.D.sup.30 1.5336 120  CF.sub.3Cl ##STR34## 121  CF.sub.3Cl ##STR35## 122  CF.sub.3Cl SCH.sub.3           n.sub.D.sup.30 1.5695 123  CF.sub.3Cl SC.sub.2 H.sub.5 124  CF.sub.3Cl SC.sub.3 H.sub.7 (n) 125  CF.sub.3Cl SC.sub.3 H.sub.7 (iso) n.sub.D.sup.30 1.5590 126  CF.sub.3Cl SC.sub.4 H.sub.9 (n) 127  CF.sub.3Cl SC.sub.4 H.sub.9 (iso) 128  CF.sub.3Cl SC.sub.5 H.sub.11 (n) 129  CF.sub.3Cl SCH.sub.2 COOCH.sub.3 n.sub.D.sup.30 1.5650 130  CF.sub.3Cl SCH.sub.2 CHCH.sub.2 n.sub.D.sup.30 1.5725 131  CF.sub.3Cl SCH.sub.2 C CH 132  CF.sub.3Cl SCH.sub.2 CHCHCH.sub.3 133  CF.sub.3Cl ##STR36## 134  CF.sub.3Cl ##STR37## 135  CF.sub.3Cl ##STR38##          n.sub.D.sup.30 1.5972 136  CF.sub.3Cl NHCH.sub.3          m.p. 139-42.degree. 137  CF.sub.3Cl NHC.sub.2 H.sub.5 138  CF.sub.3Cl NHC.sub.3 H.sub.7 (iso) 139  CF.sub.3Cl NHC.sub.4 H.sub.9 (n) 140  CF.sub.3Cl NHC.sub.4 H.sub.9 (iso) 141  CF.sub.3Cl NHC.sub.5 H.sub.11 (n) 142  CF.sub.3Cl NHCH(C.sub.2 H.sub.5).sub.2 143  CF.sub.3Cl NHC.sub.8 H.sub.17 (n) 144  CF.sub.3Cl NHCH.sub.2 CH.sub.2 Cl 145  CF.sub.3Cl NHCH.sub.2 CH.sub.2 OH 146  CF.sub.3Cl NHCH.sub.2 CH.sub.2 OCH.sub.3 147  CF.sub.3Cl NHCH.sub.2 CH.sub.2 OC.sub.4 H.sub.9 148  CF.sub.3Cl NHCH.sub.2 COOC.sub.2 H.sub.5 149  CF.sub.3Cl NHCH.sub.2 CCH 150  CF.sub.3Cl NHCH.sub.2 CHCH.sub.2 151  CF.sub.3Cl NHC(CH.sub.3).sub.2CH 152  CF.sub.3Cl NHC(CH.sub.3).sub.2 CN 153  CF.sub.3Cl ##STR39## 154  CF.sub.3Cl ##STR40## 155  CF.sub.3Cl N(CH.sub.3).sub.2 156  CF.sub.3Cl N(C.sub.2 H.sub.5).sub.2 n.sub.D.sup.30 1.5352 157  CF.sub.3Cl N(CH.sub.2 CHCH.sub.2).sub.2 158  CF.sub.3Cl ##STR41## 159  CF.sub.3Cl ##STR42## 160  CF.sub.3Cl NH.sub.2 161  CF.sub.3Cl S.sup..crclbar. K.sup..sym. 162  CF.sub.3Cl S.sup..crclbar. Na.sup..sym. 163  CF.sub.3Cl ##STR43## 164  CF.sub.3H OH                  m.p. 139-144.degree. 165  CF.sub.3H OCH.sub.3 166  CF.sub.3H OC.sub.2 H.sub.5 167  CF.sub.3H OC.sub.3 H.sub.7 (n) 168  CF.sub.3H OC.sub.4 H.sub.9 (iso) 169  CF.sub.3H OC.sub.4 H.sub.9 (sec) 170  CF.sub.3H ##STR44## 171  CF.sub.3H SCH.sub.3 172  CF.sub.3H SC.sub.2 H.sub.5 173  CF.sub.3H SC.sub.3 H.sub.7 (iso) 174  CF.sub.3H SC.sub.4 H.sub.9 (iso) 175  CF.sub.3H SC.sub.5 H.sub.11 176  CF.sub.3H NH.sub.2 177  CF.sub.3H NHCH.sub.3 178  CF.sub.3H NHC.sub.2 H.sub.5 179  CF.sub.3H NHC.sub.3 H.sub.7 (iso) 180  CF.sub.3H NHC.sub.4 H.sub.9 (n) 181  CF.sub.3H NHC.sub.6 H.sub.13 182  CF.sub.3H NHCH.sub.2 CH.sub.2 Cl 183  CF.sub.3H NHCH.sub.2 CH.sub.2 OCH.sub.3 184  CF.sub.3H NHCH.sub.2 CCH 185  CF.sub.3H NHCH.sub.2 CCH 186  CF.sub.3H NHCH.sub.2 COOCH.sub.3 187  CF.sub.3H ##STR45## 188  CF.sub.3H N(CH.sub. 3).sub.2 189  CF.sub.3H N(CH.sub.2 CHCH.sub.2).sub.2 190  HCF.sub.3 OH 191  HCF.sub.3 OCH.sub.3 192  HCF.sub.3 OC.sub.2 H.sub.5 193  HCF.sub.3 OC.sub.4 H.sub.9 (iso) 194  HCF.sub.3 SCH.sub.3 195  HCF.sub.3 SCH.sub.2 CHCH.sub.2 196  HCF.sub.3 SC.sub.4 H.sub.9 (n) 197  HCF.sub.3 NHCH.sub.3 198  HCF.sub.3 NHC.sub.2 H.sub.5 199  HCF.sub.3 NHC.sub.4 H.sub.9 (iso) 200  ClCF.sub.3 OH 201  ClCF.sub.3 OCH.sub.3 202  ClCF.sub.3 OC.sub.2 H.sub.5 203  ClCF.sub.3 OC.sub.3 H.sub.7 (iso) 204  ClCF.sub.3 OCH.sub.2 CH.sub.2 OCH.sub.3 205  ClCF.sub.3 SCH.sub.3 206  ClCF.sub.3 NHCH.sub.3 207  ClCF.sub.3 NHC.sub.2 H.sub.5 208  ClCF.sub.3 N(CH.sub.3).sub.2 209  ClCF.sub. 3 N(CH.sub.2 CHCH.sub.2).sub.2 210  CCl.sub.2 F Cl OH 211  CCl.sub.2 F Cl OCH.sub.3 212  CCl.sub.2 F Cl OC.sub.2 H.sub.5 213  CCl.sub.2 F Cl OC.sub.3 H.sub.7 (n) 214  CCl.sub.2 F Cl OC.sub.3 H.sub.7 (iso) 215  CCl.sub.2 F Cl OC.sub.4 H.sub.9 (iso) 216  CCl.sub.2 F Cl OC.sub.4 H.sub.9 (sec) 217  CCl.sub.2 F Cl OCH.sub.2 CH.sub.2 OCH.sub.3 218  CCl.sub.2 F Cl SCH.sub.3 219  CCl.sub.2 F Cl SC.sub.2 H.sub.5 220  CCl.sub.2 F Cl SCH.sub.2 COOCH.sub.3 221  CCl.sub.2 F Cl NHCH.sub.3 222  CCl.sub.2 F Cl N(CH.sub.3).sub.2 223  CClF.sub.2 Cl OH 224  CClF.sub.2 Cl OCH.sub.3 225  CClF.sub.2 Cl OC.sub.2 H.sub.5 226  CClF.sub.2 Cl OC.sub.3 H.sub.7 227  CClF.sub.2 Cl OC.sub.4 H.sub.9 (iso) 228  CClF.sub.2 Cl OC.sub.4 H.sub.9 (sec) 229  CClF.sub.2 Cl SCH.sub.3 230  CClF.sub.2 Cl NHCH.sub.3 231  CF.sub.3Cl ##STR46## 232  CF.sub.3Br OCH.sub.3 234  CF.sub.3Br OC.sub.2 H.sub.5 235  CF.sub.3Br OC.sub.4 H.sub.9 (iso) 236  CF.sub.3Br OC.sub.4 H.sub.9 (sec) 237  CF.sub.3Br SCH.sub.3 238  CF.sub.3Br SC.sub.3 H.sub.7 (iso) 239  CF.sub.3Br NHCH.sub.2 COOCH.sub.3 240  CF.sub.3Br N(CH.sub.3).sub.2 241  CF.sub.3Br OCH.sub.2 CHCH.sub.2 242  ClCl      NHC(CH.sub.3).sub.2 CN m.p. 160-162.degree. 243  ClCl      NHCH.sub.2 CH.sub.2 OCH.sub.3 m.p. 130-135.degree. 244  ClCl ##STR47##          m.p. 96-99.degree. 245  ClCl      OCH(CH.sub.3)C.sub.5 H.sub.11 n.sub.D.sup.27 1.5600 246  ClCl      N(CH.sub.3)OCH.sub.3 n.sub.D.sup.34 1.6055 247  ClCl      OCH(CH.sub.3)COOCH.sub.2 CH.sub.3 248  ClCl      SC.sub. 4 H.sub.9 (sec) n.sub.D.sup.27 1.6000 249  CF.sub.3Cl SCH.sub.2 COOCH.sub.2 CH.sub.3 250  CF.sub.3Cl N(CH.sub.3)OCH.sub.3 n.sub.D.sup.30 1.5438 251  CF.sub.3Cl NHSO.sub.2 CH.sub.3 m.p. 159-162.degree. 252  CF.sub.3Cl O.sup..crclbar. Na.sup..sym. m.p. 200-201.degree. 253  CF.sub.3Cl O.sup..crclbar. K.sup..sym. m.p. 152.degree. deliquesces ______________________________________

Preparation of a number of ready-for-use formulations and active ingrdient concentrates:

The following substances are used to formulate a 45% paste:

The active ingredient is intimately mixed with the additives in appropriate devices and ground. By diluting the resultant paste with water, it is possible to prepare suspensions of the desired concentration.

The following ingredients are mixed to formulate a 25% emulsifiable concentrate: dodecylbenzenesulfonate,

This concentrate can be diluted with water to give emulsions in suitable concentrations of e.g. 0.1 to 10%. Such emulsions are suitable for controlling weeds in crops of cultivated plants.

The following constituents are used to formulate (a) a 70% and (b) a 10% wettable powder: ester, condensate (3:2:1), sulfates,

The indicated active ingredient is applied to the corresponding carriers (kaolin and chalk) and then these are mixed and ground, to yield wettable powders of excellent wettability and suspension power. By diluting these wettable powders with water it is possible to obtain suspensions containing 0.1 to 80% of active ingredient. These suspensions are suitable for controlling weeds in cultivations of plants.

The herbicidal activity of the compounds of the invention was determined by means of the following greenhouse tests:

In a greenhouse, seeds of plants are sown in flower pots having a diameter of about 15 cm, such that 12-30 plants are able to develop in each pot. Directly after sowing the test plants, the surface of the soil is treated with an aqueous dispersion of active ingredient obtained from a 25% emulsifiable concentrate or from a 25% wettable powder with active ingredients which, because of insufficient solubility, cannot be formulated to emulsifiable concentrates. Four different concentration series are used, corresponding to 4, 2, 1 and 0.5 kg of active ingredient per hectare. The pots are kept in the greenhouse at 22.degree.-25.degree. C. and 50 to 70% relative humidity, and the test is evaluated after 3 weeks.

In this test, the compounds of the formula I at rates of application of 1 and 2 kg/ha are effective against the broad-leafed and also most grass-like weeds, whilst cultivated plants such as maize, and also to some extent wheat, millet, rice, soybeans and cotton, are not damaged or suffer only minor damage.

A large number of weeds and cultivated plants (both monocots and dicots) are sprayed post-emergence in the 4- to 6-leaf stage with an aqueous active ingredient dispersion at rates of application of 0.5, 1, 2, and 4 kg/ha, and then kept at 24.degree.-26.degree. C. and 45-60% relative humidity. The test is evaluated after 3 weeks.

In this test too, the compounds of formula I are thoroughly effective against the broad-leafed and most grass-like weeds at a rate of application of 1 kg/ha, whilst maize, barley, millet, rice, as well as cotton and soybeans are not damaged or are damaged only at higher rates of application.

## Claims

1. A 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative of the formula ##STR48## wherein X is halogen or halomethyl selected from amongst --CF.sub.3, CCl.sub.2 F and --CClF.sub.2, --CCl.sub.2 F and CClF.sub.2, and alkoxy-carbonyl.

2. A 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1, wherein X is trifluoromethyl and Y is chloro.

3. A 5-(pridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1, wherein methoxycarbonylmethyl or ethoxycarbonylmethyl.

4. A 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1 wherein X and Y are chloro.

5. A 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1, wherein X is trifluoromethyl and Y is hydrogen.

6. A compound according to claim 1, wherein one of X or Y is chlorine and the other is bromine.

7. A compound according to claim 1, wherein X is chlorine and Y is hydrogen.

8. A compound according to claim 1, wherein X is trifluoromethyl and Y is bromine.

9. 5-(3'-Chloro-5'-trifluoromethylpyridyl-2'-oxy)-2-nitrobenzoic acid (methoxycarbonylmethylthio) ester according to claim 3.

10. 5-(3',5'-Dichloropyridyl-2'-oxy)-2-nitrobenzoic acid methoxycarbonylmethylthio ester according to claim 3.

11. 5-(3'-Chloro-5'-trifluoromethylpyridyl-2'-oxy)-2-nitrobenzoic acid ethoxycarbonylmethylthio ester according to claim 3.

12. A herbicidal composition which comprises, as active ingredient, an effective amount of a 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1, and a herbicidally acceptable carrier.

13. A method of selectively controlling weeds in a crop of useful plants, which comprises applying to said crop a herbicidally effective amount of a 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1.

14. A method according to claim 13, wherein the crop is a soybean crop.

15. A method according to claim 13, wherein the crop is a cereals crop.

16. A method according to claim 13, wherein the crop is a rice crop.