4-phenoxy-pyridines having herbicidal activity

Abstract

Compounds of the formula ##STR1## wherein W and X, which may be identical to or different from each other, are each hydrogen, fluorine, chlorine, bromine, iodine, nitro, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms or chloro-substituted alkyl of 1 to 4 carbon atoms;Y is hydrogen, fluorine, chlorine, bromine, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms or chloro-substituted alkyl of 1 to 4 carbon atoms;Z is fluorine, chlorine, bromine, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms, chloro-substituted alkyl of 1 to 4 carbon atoms, --COOH or --COO-(alkyl of 1 to 4 carbon atoms); andn is 0 or 1;and, when Z is COOH, salts thereof, especially their alkali metal salts. The compunds as well as the salts are useful as selective herbicides.

Description

This invention relates to novel 4-phenoxy-substituted pyridines, to a method of preparing these compounds, to herbicidal compositions containing them as active ingredients, and to a method of using them as selective herbicides.

THE PRIOR ART

German Offenlegungsschrift No. 1,542,736 discloses herbicidal aryloxy-substituted pyridines of the formula ##STR2## and particularly the compound of the formula ##STR3## However, these compounds, which lack additional substituents on the pyridine ring, do not exhibit satisfactory herbicidal properties.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide novel phenoxy-substituted pyridines having one or more additional substituents attached to the pyridine ring, which are more effective herbicides than the prior art compounds.

Other objects and advantages of the invention will become apparent as the description thereof proceeds.

DESCRIPTION OF THE INVENTION

More particularly, the present invention relates to a novel class of compounds represented by the formula ##STR4## wherein

W and X, which may be identical to or different from each other, are each hydrogen, fluorine, chlorine, bromine, iodine, nitro, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms or chloro-substituted alkyl of 1 to 4 carbon atoms;

Y is hydrogen, fluorine, chlorine, bromine, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms or chloro-substituted alkyl of 1 to 4 carbon atoms;

Z is fluorine, chlorine, bromine, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms, chloro-substituted alkyl of 1 to 4 carbon atoms, --COOH or --COO--(alkyl of 1 to 4 carbon atoms); and

n is 0 or 1;

and, when Z is COOH, salts thereof, especially their alkali metal salts.

Those alkyl radicals in formula I which contain 3 or 4 carbon atoms may be straight-chain or branched-chain alkyls. Preferred fluoro-alkyls and chloro-alkyls are trifluoromethyl or trichloromethyl.

Preferred embodiments of variables W, X, Y, Z and n are the following:

W: Hydrogen, chlorine, fluorine, methyl, trifluoromethyl and nitro;

X: Hydrogen, fluorine, chlorine, methyl, trifluoromethyl and nitro;

Y: Hydrogen, fluorine, chlorine, trifluoromethyl, trichloromethyl and methyl;

Z: Fluorine, chlorine, trifluoromethyl, methyl, carboxyl, methoxycarbonyl and ethoxycarbonyl;

n: 0.

The compounds embraced by formula I may be prepared by a method involving known chemical synthesis principles, namely by reacting a pyridine derivative of the formula ##STR5## wherein

Y and X have the same meanings as in formula I, and

A is halogen, especially chlorine or fluorine, or nitro,

with a phenol of the formula ##STR6## or with a phenolate of the formula ##STR7## wherein

W, X and n have the same meanings as in formula I, and

M is one equivalent of a cation, preferably Na.sup.+, K.sup.+ or 1/2Ca.sup.++.

The reaction is carried out at temperatures between ambient temperature and about 160.degree. C., preferably in a polar solvent, such as acetone, butan-2-one, acetonitrile, dimethylformamide or dimethylsulfoxide, at room temperature or moderately elevated temperature. If the reaction is performed with a phenol of the formula IIIa, an acid-binding agent, for example an alkali metal carbonate, such as sodium carbonate or potassium carbonate, or an alkali metal or alkaline earth metal hydroxide such as sodium hydroxide, potassium hydroxide or calcium hydroxide, is added to the reaction mixture. In order to achieve a favorable yield, it can be of advantage to provide the phenol or phenolate and/or the acid-binding agent in excess.

The starting compounds of the formulas II, IIIa and IIIb are either known compounds or may be prepared by the same method as the known compounds.

The following examples illustrate the present invention and will enable others skilled in the art to understand it more completely. It should be understood, however, that the invention is not limited solely to the particular examples given below.

EXAMPLE 1

2,6-Dichloro-4-(2-chloro-4-trifluoromethyl-phenoxy)-pyridine

16.5 gm (0.12 mol) of potassium carbonate were added in portions to an ice-cooled and stirred suspension of 19.65 gm (0.1 mol) of 2-chloro-4-trifluoromethyl-phenol and 19.29 gm (0.1 mol) of 2,6-dichloro-4-nitro-pyridine. The resulting mixture was stirred for 2 hours at room temperature, and was then stirred into 250 ml of ice water. An oil separated out, which crystallized after some time. The crystalline product was collected by suction filtration, washed with water and dissolved in chloroform. The resulting solution was shaken with water, and the organic phase was separated, dried with sodium sulfate and evaporated to dryness. 25.3 gm (75% of theory) of the title compound were obtained as a colorless substance having a melting point of 66.degree. C.

EXAMPLE 2

2-Chloro-6-methyl-4-(2-chloro-4-trifluoromethyl-phenoxy)-pyridine

16.5 gm (0.12 mol) of potassium carbonate were added in portions to a stirred solution of 19.65 gm (0.1 mol) of 2-chloro-4-trifluoromethyl-phenyl and 17.25 gm (0.1 mol) of 2-chloro-6-methyl-4-nitro-pyridine in 40 ml of dimethylformamide, and the mixture was heated to 80.degree. C. and maintained at that temperature for 3 hours. Thereafter, the reaction mixture was allowed to cool and was then poured into 200 ml of ice water, and the aqueous mixture was extracted with chloroform. The organic phase was separated, washed with water, dried with sodium sulfate and evaporated. The residue was purified by column chromatography on silicagel, yielding a viscous oil which crystallized after some time. 20.9 gm (65% of theory) of the title compound, m.p. 75.degree. C., were obtained.

Analysis: C.sub.13 H.sub.8 Cl.sub.2 F.sub.3 NO (mol. wt. 322.11); Calc.: C-48.5%; H-2.5%; N-4.35%; Found: C-47.92%; H-2.27%; N-4.75%.

EXAMPLE 3

2-Chloro-4-(2-chloro-4-trifluoromethyl-phenoxy)-pyridine

2.48 gm (0.018 mol) of potassium carbonate were added in portions to a stirred solution of 2.95 gm (0.015 mol) of 2-chloro-4-trifluoromethyl-phenol and 2.2 gm (0.015 mol) of 2-chloro-4-nitro-pyridine in 10 ml of dimethylformamide, and the mixture was stirred first for 1 hour at room temperature and then for 11/2 hours at 80.degree. C. Thereafter, the reaction mixture was poured into ice water and the aqueous mixture was extracted with chloroform. The organic phase was separated, washed with 2N sodium hydroxide and with water, dried with sodium sulfate and evaporated, yielding the title compound as a colorless oil.

Analysis: C.sub.16 H.sub.6 Cl.sub.2 F.sub.3 NO; Calc.: C-46.7%; H-1.96%; Cl-23.01%; Found: C-46.03%; H-1.61%; Cl-22.67%.

1H-NMR (CDCl.sub.3, ppm):

Protons in the pyridine moiety: 1 proton at 8.22 ppm, 2 protons at 6.71 ppm.

Protons in the phenyl moiety: 1 proton each at 7.76, 7.56 and 7.22 ppm.

EXAMPLE 4

2-Chloro-6-methoxycarbonyl-4-(2-chloro-4-trifluoromethylphenoxy)-pyridine

A mixture consisting of 2.06 gm (0.01 mol) of methyl 4,6-dichloro-picolinate, 2.15 gm (0.011 mol) of 2-chloro-4-trifluoromethyl-phenol, 1.5 gm of pulverized potassium carbonate and 5 ml of dimethylformamide was heated at 120.degree. C. for one hour, while stirring. The mixture solidified. The solid mass was stirred and decanted several times with ice water, then acidified with acetic acid, and finally extracted with ethyl acetate. The organic phase was separated, washed with water and dried with sodium sulfate. The solvent was distilled off, and the residual oil was purified by chromatography on 40 gm of silicagel (eluant: Diisopropyl ether). 1.4 gm (38% of theory) of the title compound were obtained as a virtually colorless oil. R.sub.f -value: 0.48 (prepared thin-layer chromatography plates manufactured by E. Merck, Darmstadt, Germany, with silicagel 60-F-254. Eluant: Acetone/diisopropyl ether 1:2; the spots are visible in ultraviolet light at 254 .mu.m).

The prepared thin-layer chromatography plates of the type used in this example and the ultra-violet light of the indicated wavelength were also used for the determination of the R.sub.f -values in the subsequent examples.

The following tables I-VI show compounds of the formula I which were prepared in analogy to Examples 1-4.

TABLE I______________________________________ ##STR8##Example Y Z Remarks______________________________________ 5 H CH.sub.3 6 CH.sub.3 CH.sub.3 7 H CF.sub.3 8 H F 9 F F Kp. 112-114.degree. C./0.05 mbar10 Cl CF.sub.311 F CH.sub.312 Cl CCl.sub.313 F CCl.sub.314 H Br15 Br Br16 CH.sub.3 Br17 CCl.sub.3 Br18 Br CF.sub.319 H OCH.sub.320 Cl OCH.sub.321 H On-C.sub.4 H.sub.922 H COOH23 H COOC.sub.2 H.sub.524 Cl COONa______________________________________ TABLE II______________________________________ ##STR9##Example Y Z Remarks______________________________________25 H CH.sub.326 CH.sub.3 CH.sub.327 H CF.sub.328 H F29 F F30 Cl CF.sub.331 F CH.sub.332 Cl CCl.sub.333 F CCl.sub.334 H Br35 Br Br36 CH.sub.3 Br37 CCl.sub.3 Br38 Br CF.sub.339 H OCH.sub.340 Cl OCH.sub.341 H On-C.sub.4 H.sub.942 H CH(CH.sub.3).sub.243 H COOK44 Cl Cl oil, R.sub.f -value 0.58.sup.(1)45 Cl COOCH.sub.3______________________________________ .sup.(1) Eluant: diisopropyl ether/gasoline 1:1 TABLE III______________________________________ ##STR10##Example Y Z Remarks______________________________________46 H CH.sub.347 CH.sub.3 CH.sub.348 H CF.sub.349 H F50 F F51 Cl CF.sub.352 F CH.sub.353 Cl Cl oil, R.sub.f -value 0.64.sup.(1)54 F CCl.sub.355 H Br56 Br Br57 CH.sub.3 Br58 CCl.sub.3 Br59 Br CF.sub.360 H OCH.sub.361 Cl OCH.sub.362 H On-C.sub.4 H.sub.963 C.sub.2 H.sub.5 C.sub.2 H.sub.564 H C(CH.sub.3).sub.365 H COOH66 Cl CH.sub.3 oil, R.sub.f -value 0.52.sup.(2)67 H Cl oil, R.sub.f -value 0.54.sup.(1)______________________________________ .sup.(1) Eluant: Diisopropyl ether/acetone 5:1 .sup.(2) Eluant: Diisopropyl ether TABLE IV______________________________________ ##STR11##Example Y Z Remarks______________________________________68 H CH.sub.369 CH.sub.3 CH.sub.370 H CF.sub.371 H F72 F F73 Cl CF.sub.374 F CH.sub.375 Cl CCl.sub.376 F CCl.sub.377 H Br78 Br Br79 CH.sub.3 Cl m.p. 90.degree. C.80 CCl.sub.3 Br81 Br CF.sub.382 H OCH.sub.383 Cl OCH.sub.384 H On-C.sub.4 H.sub.985 H CH(CH.sub.3).sub.286 H COOH87 H COOC.sub.2 H.sub.588 Cl Cl m.p. 92.degree. C.______________________________________ TABLE V______________________________________ ##STR12##ExampleNo. Y Z Remarks______________________________________89 H CH.sub.390 CH.sub.3 CH.sub.391 H CF.sub.392 H F93 F F94 Cl CF.sub.395 F CH.sub.396 Cl CCl.sub.397 F CCl.sub.398 H Br99 Br Br100 CH.sub.3 Br101 CCl.sub.3 Br102 Br CF.sub.3103 H OCH.sub.3104 Cl OCH.sub.3105 H On-C.sub.4 H.sub.9106 Cl Cl m.p. 113-115.degree. C.107 CH.sub.3 Cl108 H COOH109 Cl COOCH.sub.3______________________________________ TABLE VI______________________________________ ##STR13##ExampleNo. Y Z______________________________________110 H CH.sub.3111 CH.sub.3 CH.sub.3112 H CF.sub.3113 H F114 F F115 Cl CF.sub.3116 F CH.sub.3117 Cl CCl.sub.3118 F CCl.sub.3119 H Br120 Br Br121 CH.sub.3 Br122 CCl.sub.3 Br123 Br CF.sub.3124 H OCH.sub.3125 Cl OCH.sub.3126 H On-C.sub.4 H.sub.9127 H n-C.sub.3 H.sub.7128 H n-C.sub.4 H.sub.9129 F C.sub.2 H.sub.5130 H COOH______________________________________

The compounds of the present invention, that is, those embraced by formula I above and, when Z is --COOH, their salts, especially their alkali metal salts, have useful properties. More particularly, they exhibit biocidal, especially herbicidal activity.

Unlike the prior art compounds above referred to, the compounds of the present invention are very effective herbicides, against numerous monocotyl and dicotyl weeds, including such difficultly combatable weeds as Galium aparine and Veronica hederifolia.

An especially valuable pointes is that various important gaps in the range of activities of a number of otherwise very useful products can be filled by using these products in conjunction with the novel compounds of this invention. Examples of partners for combined use in this way include chlortoluron and related urea derivatives, terbutryn and related triazine derivatives, trifluralin and related derivatives, alachlor, dimethachlor and related compounds.

The herbicidal activity of the novel compounds was tested in a greenhouse test using a quantity of 2 kg/ha (pre-emergence values). The comparison substance used was A=4-(2,4-dichloro-phenoxy)-pyridine according to German Offenlegungsschrift No. 15 42 736. The results were evaluated on the nine-point evaluation scale, where 1=100% activity and 9=no activity.

______________________________________Compound SIN* LYC* ECH*______________________________________A (prior art) 9 9 9According to the inventionExample 1 1 1 1Example 2 1 1 1______________________________________ *SIN = Sinapis alba- LYC = Lycopersicum esculentum- ECH = Echinocloa crus galli-

The novel compounds not only have a good weed killing activity, but are also well tolerated by numerous useful crops such as oats, wheat, barley, potatoes, soybeans, cotton and peas, thus permitting selective use.

The compounds may be applied both pre- and post-emergence. If the new active substances are used by themselves, they are preferably applied pre-emergence. If they are to be used in combination, especially for post-emergence treatment, the following are particularly suitable partners:

1. Growth-active herbicides, such as 2,4-DP, MCPA, CMPP;

2. Contact herbicides such as ioxynil, bromoxynil, bentazone, bromophenoxime, dinoterb;

3. Grass herbicides such as isoproturon and diclofopmethyl.

For herbicidal purposes the compounds of the present invention are incorporated as active ingredients into conventional herbicidal compositions, such as solutions, dusting powders, wettable powders, emulsion concentrates and the like, consisting essentially of inert ingredients, such as carriers, dispersants, emulsifiers, wetting agents and the like, and an effective herbicidal amount of a compound of the present invention.

For weed control the compounds of the present invention are applied to the weed-infested area at the rate of about 0.05 to 2 kg, preferably 0.1 to 1 kg, per hectare, depending on the particular compound which is used and the weed to be controlled. When they are used in conjunction with other herbicides, even smaller quantities (down to about 0.03 kg/ha) of the compounds according to the invention are generally used.

The following examples illustrate a few herbicidal compositions comprising a compound of the present invention as an active ingredient and represent the best modes contemplated of using the invention. The percentages in these examples are percent by weight.

EXAMPLE 131

Wettable powder 1 25% active ingredient of the formula I 55% kaolin 9% lignin sulfonate as dispersant 1% sodium tetrapropylenebenzene sulfonate as wetting agent.

EXAMPLE 132

Wettable powder 2 80% active ingredient of the formula I 8% calcium lignin sulfonate 5% colloidal silicic acid 5% sodium sulfate 2% sodium diisobutyl naphthalene sulfonate.

EXAMPLE 133

Emulsion concentrate 40% active ingredient of the formula I 25% Shellsol A (liquid mixture of aromatic hydrocarbon) 25% N-methyl-pyrrolidone 10% Emulsogen I 40 (anionic emulsifier)

Prior to use, the compositions of Examples 131 to 133 are diluted with water to an active ingredient content of 0.5 to 5% by weight.

While the present invention has been illustrated with the aid of certain specific embodiments thereof, it will readily be apparent to others skilled in the art that the invention is not limited to these particular embodiments, and that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

Claims

1. A compound of the formula ##STR14## wherein W is hydrogen, chlorine, nitro or trifluoromethyl;

X is hydrogen or chlorine;

Y is hydrogen, fluorine, chlorine, bromine, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms or chloro-substituted alkyl of 1 to 4 carbon atoms; and

Z is fluorine, chlorine, bromine, alkyl of 1 to 4 carbon atoms, fluoro-substituted alkyl of 1 to 4 carbon atoms, chloro-substituted alkyl of 1 to 4 carbon atoms, --COOH or --COO--(alkyl of 1 to 4 carbon atoms);

or, when Z is --COOH, an alkali metal or alkaline earth metal salt thereof.

2. A compound of claim 1, where

W is hydrogen, chlorine, nitro or trifluoromethyl;

X is hydrogen or chlorine;

Y is hydrogen, fluorine, chlorine, methyl, trifluoromethyl or trichloromethyl; and

Z is fluorine, chlorine, methyl, trifluoromethyl or carboxyl;

or, when Z is carboxyl, an alkali metal or alkaline earth metal salt thereof.

3. A compound of claim 1, where said salt is an alkali metal salt.

4. A herbicidal composition consisting essentially of an effective herbicidal amount of a compound of claim 1 in combination with an inert carrier.

5. The method of killing weeds, which comprises contacting said weeds with an effective herbicidal amount of a composition of claim 4.

6. The method of killing weeds, which comprises contacting said weeds with an effective herbicidal amount of a compound of claim 1.