CA1097678A - Phenoxyphenoxyalkanecarboxylic acid esters - Google Patents

Abstract

Abstract of the Disclosure The present invention relates to novel herbicidally active phenoxyphenoxyalkanecarboxylic acid esters, compositions which contain these compounds as active ingredient, and a method of selectively controlling weeds in crops of cultivated plants or of regulating plant growth which comprises the use of these compounds.

The phenoxyphenoxyalkanecarboxylic acid esters have the formula

Description

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The present invention relates to novel herbicidally acti.ve phenoxy-phenoxyal-kanecarboxylic acid esters, compositions which contain these compounds as active ingredient, and a method of selectively controlling weeds in crops of cultivated plants or of regulating plant growth which comprises the use of these compo~mds.
Tlle act:ive compounds of the present invention have the formula I
lR2 ~Rl ~O-CII-CO-R3 F3C-<~ ~ N2 (I) wherein Rl represents hydrogen, a halogen atom or the cyano group, R2 represents hydrogen or a Cl-C4 alkyl group, R3 represents a radical -OR4 or -SR5, R4 represents a Cl-C12 alkyl radical which is substituted by halogen or cyano or interrupted by one or more oxygen or sulfur atoms, a C3-C12 alkenyl, C3-C12 alkynyl or C3-C12 cycloalkyl radical, a phenyl or benzyl radical ~hich is unsubstituted or mono- or poly-substituted by halogen, Cl-C4 alkyl, Cl-C4 alkoxy, Cl-C4 al.kylthio, nitro, cy,ano or trifluoromethyl, and R5 represents an unsubstituted Cl-C12 alkyl radical or has the same meaning as R4.
In formula (I) above, the alkyl, alkenyl or alkynyl radicals can be straight-chain or branched. The preferred halogen atoms are chlorine or bromine atoms. Examples of 5- to 6-membered heterocyclic radicals are furane, pyrane, pyrrole, pyrrolidine, pyridine, piperidine, pyrazole, pyrazolidine, pyrimidine, oxazolidine, oxazole, morpholine, thiazole, thiazol.idine etc.
These radicals are advantageously bonded through a carbon atom to the oxygen or sulfur atom which links them to the rest of the molecule.
Herbicidally active compounds based on substituted diphenyl ethers ~k ', . .
~. .

- 2 -are known from various patent specifications. Diphenyl ethers having herbicidal activity are described for example in German Offenlcgungsschrift 2,311,63~ and in Si~i55 patent specification 424,3~6. These compounds either have an extraordinarily pronounced herbicidal actlon tGerman Offenlegungsschrift 2,311,638) with less selectivity, or have a one-sided action, for example only against dicotyledonous weeds.
Surprisingly, the active compounds of the formula (I) exhibit not only an excellent action against monocotyledonous and dicotyledonous weeds, but al.so a.marked selectivity in barley, wheat and ri.ce, --especially in post-emergent application.
The present invention provides a novel group of phenoxyphenoxyalkane-carboxylic acid derivatives which, in low rates of application, are able to influence the growth of plants in a manner which is agri-culturally advantageous.
The active compounds of the formula I of the present invention possess a general herbicidal action which is non-specific to grasses, especially in post-emergent application, and they can be used as weed killers in crops of mono- and dicotyledonous plants~ 'rhey also possess an advantagec,us growth-regulating action tgrcwth inhibition) and in:particular, inhibit the growth of dicotyledonous plan-ts.
Exemplary of the;ussful applicatlon oE the compounds of the present inventlon srs~
the:~reduction of the vegetative growth in soya and similar legumlnosae, resultLng ln;an increase in the yield of these plants;
ths inhlbition of; ths~undeslrable growth of suckers in tobacco pIants, the leading~ shoots of which have been cu-t, thus promoting the formation~of l~arger and flner leaves;
the~inhibition of the growth:of grass and dicotyledonous plants, -`
such as~fruit~trees, ornamental trees, bushes and hedgerows, with the object of~savlng~cuttlng work;

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7~78 - the desicca-tion of plants tcotton, potatoes) before harvesting;

- the defoliat:ion of cotton plants before harvestin~.

The compounclc; of the formula I can be subdivided into different ~roups which comprise those compounds w}-ich are most suitable for the respective de~.i.red use~

Each of these groups comprises active compounds of similar chemical constitu:tion and having the following formulae:

& /OCH-CO-P~3 CF3-~\ /~~~ -NO2 (Ia) .=" .=~ .
wherein R3 is as defined in formula I.

/Cl /OCII-COR3 CF3--\ /--O-~ -NO2 (Ib) wherein R3 represents a C3-C12 alkenyloxy or alkenylthio radical, a C3-C12 alkynyloxy or alkynylthio radica]..
c~3 ~._O/~ /OCH-COR3

3 \ / \ i~-NO2 (Ic) = O

wherein R3 represents a C2-C12 alk~xy or alkylthio radical which is interrupted by one or more oxygen or sulfur atoms.

& 1 /OCH-COSR5 CF --~ ~--O-~ -NO (Id) ' " ' ' . ':~ , .
, ~ ~
~: ' 7~7~
. -- 4 --wherei~ R5 is as defined in formula I.

& 1 ~OCII-COR3' r3-~ -O-o\ /~-NO2 (Ie) wherein R3' represents a phenoxy "?henylthio, benzyloxy or benzylthio radica]. which is unsubstituted or mono- or polysubstitutecl by halogen, Cl-C4 alky]., Cl-C4 alkoxy, C~-C4 alkylthio, nitro, cyano or trifluoromethyl.

& 1 OCH-COR""
CF ~ -O-o~ ~-NO2 (If) wherein R3" represents a Cl-C12 alkoxy or alkylthio radical which is substituted by halogen or cyano.

I

CN /OC~-COOR4 -~ ~~\ /--NO2 (I~) = O
:
:wherein R4 is as clefined in formula I.

CH
~:1 3 3-b\ /--O-~ NO2 (Ih) ~' ~
wherein R is as defined in formula I.
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~767~3 /OCH-COOR~
CF -o~ ~--0~ NO (Ii) wherein Rl is as deEined in formula I.

CF3--\ /-~~\ /-_N02 tI~) wherein R5 is as defined in formula I.
The phenoxyphenoxyalkanecarboxylic acid derivatives of the present invention have a low toxicity to waxm-blooded animals and their appli-cation unlikely to cause problems. The suggested ~ates of appli-cation are between 0~1 and 5 kg per hectare.
The compounds of the formula I are obtained by reactions of chemical synthesis which are in themselves known.
A first process consists in nitrating m- (4-trifluoromethylphenoxy)-phenoxycarboxylic acid esters of the formula II

~ 1 /OCH-CO-R3 CF3-o\ /-~ \ / ~ (II) wherein Rl, R2 and R3 are as defined in formula I. The nitration is carried out with nitric acid and sulfuric acid at low temperature (-20 to -~20C) in an inert organic soLvent, for example a chlorinated hydrocarbon. only a little more than the equimolar amount of nitric acid is used. In this way it is possible to bring the nitro group almost exclusively into the desired ortho-position to the oxy-, .

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Provided they are not already known, for example from German Offen-legungsschrift 2,639,796 or 2,732,442 or from Canadian patent application Serial No. 283,018, the starting materials of the formula II can be obtained by condensation of a p-halogenotrifluoromethylbenzene (III) with resorcinol ~IV) and subsequent condensation of the resulting m-(trifluoromethylphenoxy)-phenol (V) with an ~-halogenocarboxylic acid ester according to the reaction scheme: Rl OH Rl OH

CF3 ~ CL + OH ~ ~ CF3 ~ _ III RIV V

Rl OCHCOR ~R2 3 ~ ~ base + Hal-cll-coR3 II

In the formulae II, III, IV and V above, Rl, R2, and R3 are as defined in formula I and Hal represents a halogen atom, preferably a chlorine or bromine atom.
In a second process, the compounds of the formula I are obtained by providing the free hydroxyl group in the m-~4-trifluoromethylphenoxy)-phenol of the formula V with a protective group, for example by esterification with an~ acyl halide ~acetyl chloride) in the presence of a base, and then nitrating the acetylated~diphenyl ether (VI) at low temperature in an inert organic solvent with the equimolar amount of nitric acid in the presence of sulfuric acid. The nitrated and acylated diphenyl ether (VII) is then saponified in a basic medium to the m-hydroxydiphenyl ether (VIII), which in turn can be condensed with an ~-halogenocarboxylic acid ester (IX) to provide a m-~4-tri-fluoromethylphenoxy)-o-nitro-oxycarboxylic acid ester of the formula I.

~ 6 -, The sequence of this process can be illustrated by the following reaction scheine:

/Rl O_ /H /Rl /OCOR
CF -~ O~ . acyl chloride C,F -- ~O-o-O~ ~O
3 \ / \ / Hal COR 3 . . _ ~
_.___ ,;.
base V VI

inert organic solvent /R] ~OH /Rl /OCOR
CF3--\ /-~~~ -NO2 OH ~CF -.\ /-~ \ ~-N2 saponification VIII VII

2 /Rl /OCHCOR3 I base Hal Cll-COR3 ~CF3-.\ /~~~~\ / 2 IX

In the above fc,rmulae, Rl, R2 and R3 are as defined ln formula I, Hal represents a halogen atom, preferably a chlorine or bromine atom, and R represents a Cl-C4 alkyl radical. The reactants are used in these process steps as far as possible in stolchiometric amounts.
The reactions are advantageously carried out in the presence of organic solvents which are inert to the reactants. In the nitratlon steps, the temperature should be kept as low as possible. In the saponifaction and condensations steps, a temperature range from room temperature to the boiling point of the solvent is indicated.
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In certain condensatiorl steps in which a haloc~en atom is removed or hydrocJen halide is formed, the corresponding arnount of an acid acceptor should be en)ployed in ~he reaction.
l1hen the rc~action is complete, the fina] product is isolated, for example by dic;tilliny off the sol~Tent and pouring the residue into ice-water.
Suitable solvents for these reactions are in particular organic aprotic solvents or solvent mixtures which dissolve the reactants but do not react wi-th them, for example acetic acid, ethyl acetate, ketones, ha]ogenated hydrocarbons, dimethyl formamide, dimethyl sulfoxide, and also ethers of higher boiling point.
Some of the starting materials are known. Starting materials of these formulae which are not known can be prepared by conventional methods and techniques. Phenoxypheno]s can be obtained from resorcinol monoalkyl ether and p-halogenotrifluoromet:hylbenzene, for example by the methods described in J.Am. Chem. Soc. 61, 2702 ~1939) or in Chem. ~bst. 54, 922 (1960).
The phenoxyphenoxyalkanecarboxylie acid esters of the Eormula I are also obtained by reacting a phenoxyphenoxyalkanecarboxylic acid halide of the formula X

I

/Rl OCH-CO-Hal CF3~ ~~ \ / 2 (X) wherein Rl and R2 are as defined in~formula I and Hal represents a halocJen atom, preferably a ehlorine or bromine atom, with an alcohol of the formula R40H or with a thiol of the formula , wherein R~ and R5 are as defined in formula I, in an organic solvent .

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and in the presence of an acid acceptor.
Suitable solvents are almost all orgarlic solvents which dissolve the reactants but do not react with thein, for example ethers, ketones, certain stahl.e esters, ]..i.qui.d hyclrocarbons~ al.iphatic, aromatic, and chlorinated llydrocarbonc;. Pre~erab].y tri.alkylamines are preferc~bly used as acicl acceptors, and, prov:Lclecl the solutility enables it, also alkali meta]. hydroxi.des, carbonates or ammon:ia solutions.
The starting materials are best prepared by scaponification of an already existing ester of the formula I to the Eree phenoxyphenoxy-alkanecarboxyl.ic acid, which is then reaeted with a halogenati.ng agent, such as thionyl chloride, thionyl bromide, phosphoroxy chloride or bromide, phosphorus pentachloride or pentabromide, sulfonyl ehl.oride or bromicle, to provide the eorresponding acid ehloride.
The following Example illustrates the produetion of a phenoxyphenoxyalkaneearboxylic acid ester of the formula I. Further eompounds which are prepared in eorresponding manner are iisted in the sabsequent table. Parts or peree~ta~es are by weight.

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Example 2-[Nitro-5-(2'-chloro-4'-triE]uoromethylphenoxy)-phenox~]
propionic acid allyl ester CiI3 /Cl /0-CII-C00-CM2-CEI=CH2 CF3~ -0--\ ~--N02 20 g of trimethylamine are added dropwise at 5 - 15C to a solution of 42.5 g of tc7-[2-nitro-3-t2'-chloro-4'-triIluoromethylphenoxy)-phenoxy] propionyl chloride and 12 g of allyl alcohol in 150 ml of toluene. The reaction mixture is stirred overnight at room temperature.
l`hen 50 ml of water are added anA the organic phase is separated, dried over sodium sulfate and the solvent is distilled off. Distillation in a high vacuum affords 20.8 g oE a viscous oil with a boiling point of 200-210C at 0.04 torr.

The following compounds of the formu]a I are prepared in analogous manner:

/Rl 0-CH-COR

CF3~~ ~~-\ /--N02 -~

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-'' ' ~9767~3 . _ . .. .. . ._ No . Rl ~O-CH-COR phys ical 3 . constarl~ ("C) --- Cl-l, .
1 ~ Cl ~ -OCEI- OOCI77-CE7=C 2 b.p. 00 10/

2 Cl -O~H-COOC2EI40CM3 }~.p. 192-204/

3 Cl -OCEI- COOCH2 -C- CEI m . p . 7 4 - 7 6

4 Cl OCH-COO-\ /o m.p. 119-121 Cl -O~H-COSCH --~ ~7 ' vi3cous oil 6 Cl -OCH-COSCEI2COOC2H5 viscous oil 7 Cl -OCHCOSCH2-CH=CH2 viscous oil . CH3 8 Cl -CElcc2H4c2H4c2 5 viscous oil 9 H -OCH-COO-CH2-C-CH ~ viscous oil CH3 ~3.~ ~
H. -OCH--COO~ . . -~ . . . .
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_ _ _ R2 physical .
No. Rl -O-CH-COR c~nstant (~C) CE~3 1]. H -ocH-cooc2El~OCEl3 12 El -OCH-COOEI

: . 14 H -OCE~-COSCH2-CH=CH2 ~ CN 013 ooCll2-cll2~ Il=C32 16 ~ CN ~ -CCH- OOC32 ; : ~ 17 CN -OCH-COOC2H~OCH3 CH3 C\3 13 CN : -OCH-COO-~ -N02 ~

19 : CN -0~3-COSCH3 ~ :

: : CEI .
~20 CN -Ol}l-COSC2H5 . ~ .

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0~ -COR3 ~ ~C) _ _ _ __ CM3 2l CN -OCM-COSCH2-CII=CH2 22 Cl \ / b.p. 2300.001 23 Cl -OCII-COOH viscous oil 24 Cl -O~'H-COO-\ /- m.p. 64-67 C~13 Cl -OCH-COOC2H45C 3 viscous oil C1~3 ._.~
26 Cl -OCII-COOCH2-~ viscous oil ; CH3 27 H -OCH-COOCH2C_CH ~ ~ .

~: : 1 3 :
: 28 H -CII~CC2H~C2Hs ~

~ ~ CH3 ~ .
: : 2~ CN ~OCH-COOCH2CH--CH2 . .

CH3 .
. 30 CN -OCH-CoOc2H40c2~l4 2 5 . ` . ' : . -- , ' ~g7678 No A~ C01~3 c~n~t.lnt ~C) 31 Cl -OCH-COOC2H~C1 viscous oil L~ ocl~-ooc2ll~c V15C0~50il The invention also relates to herbicidal and plant growth-regulatin~
compositions which ccntaiil a novel active compound of the Eormula I, as well as to a method of controlling weeds by pre- and post-emergent application and of inhibiting the growth of Mono- and dicotyledonous plants, especially grasses, cereals, soya and tobacco shoots.
The compositions of the present invention can be in the conventional formulations.
The compositions of the present invention are obtalned in known manner by homogeneously mixing and grlndlng actlve substances(compounds)of the formula I with suitable carriersl with or without the addition of dispersants or solvents which are inert to the active substances.
The active substances can be processed to the following formulations:
solid forrnulations:
dusts, tracking powders, granules (coated granules, impregnated granules and homogensous grsnules), active substance concentrates which are dispersible in water:
wettable powders, pastes, emulsions;
lio~uid formulations: solutions.
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~976~3 The concentratioll of active substance in the above described compositions is between 0.1 and 95 ~, preferab]y between 1 and 80 %.
Formulatlons can be dilu-tecl to concentrations as low as 0.00] ~. The rates of application are ordinari.].y from 0.1 to 10 kg, preferably from 0.25 to 5 ]~g, of ac-~lve substance per llectare. The act;.ve substances of tlle formu.la I can ~e formu:Lated :Eor example as fol].ows (parts are by weigl-lt):
Emulsifiable Concentrate The following ingredients are mi.xed to manufacture a 25 % emulsi.fiabl.e concentrate:
.25 parts of 2-[2-nitro-5~(2'-chloro~4'-trifluoro-methylphenoxy)-phenoxy] propioni.c acid allyl ester,

5 parts of a mixture of nonylphenol.polyoxy-ethoxy-ethylene and cal.cium dodecylenesul-fonate, 15 parts of cyclohexanolle, 55 parts of xylene.
Thi.s concentrate can be diluted with water to give emulsions of suitable concentrations.
Vusts: The following substances are used to prepare a) a 5 ~ dust and b) a 2 % dust: :
a) 5 parts of 2-[2-nitro~5-(2'-chloro-4'-trifluoro-methylphenoxy)-phenoxy] propionic acid allyl : ester, .
~ 95 par-ts of talc;
.

~ ~b) 2 parts of the above active s~stance ; 1 part of highly dispersed silicic acid 97 parts of talc.
The active substances are mixed with the carriers and ground.

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7~3 Granulace: The fo].lowirlg substances are used to prepare a 5 %
granulate:
par-ts of the above active substance 0.25 palt o:E epichlorohydrin 0.25 part: o:E cetyl po.ly-J:Lycol ethel^ W.it]
~ mol.es of ethylene oxide, 3~25 par-ts of polyethy1.el)e glycol 91 parts of kaolin (particle slæe o.3-0.~3 mm).
The active substarlce i.s m.ixed with epichlorohydrin and the mi.xture is dissolved in 6 parts of acetone. Then polyethylene glycol ar.d cetyl polyglycol ether are added. The resulting solution is sprayed on kaolin and subsequently evaporated in vacuo.
Wettable Powders .. .. _ _ The ollowing constituents are used to prepare a) a 50 %, b) a 25 % and c) a 10 ~ wettabl.e powder:
~) 50 parts of 2-[2-nitro-5-(4'-trifluoromethylphenoxy)-phenoxy] propionic acid all.yl ester, parts of sodium dibutylnaphthylsulfonate, 3 parts of naphthalenesulfonic acid/phenolsul-phonic acid/formaldehyde condensate (3:2:1), .20 parts of kaolin, 22 parts of Champagne chalk;
b) 25 parts of the above active substance, 5 .~ parts of sodium oleylmethyltauride, .2~5 parts of naphthalenesulfonic acid/formaldehyde condensate, 0.5 part of carboxymethyl cellulose, parts of neutral potassium aluminium silica-te, 62 parts of kao]in;
. c) 10 parts of the above active substance, 3 parts of a mixture of the sodium salts of ~:

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satura-ted fatty alcohol sulfates, par-ts of naphthalenesulfonic acid/formalde-hyde condensate, 82 parts o:E kaolin.
The indicated active substcmce is appl:ied to the corresponding carri.e.rs (kaoli.n and chalk) and then these are m.ixed and ground, -to y.i.eld wettable powders of excellent wettabi].ity and suspension power. By di].uti.ng these wettable powders w;.th water it is possible to obtaln suspension having the ~esire~ concentration of active sub-stance.
Pas-te The following substances are used to prepare a 45 ~ paste: -parts of 2-[2-nitro-5--(4'-trifluoromethyl-phenoxy)- phenoxy] propionic acid allyl ester, parts of sod:ium aluminium sili.cate,.
14 parts oE cetyl polyglycol ether with 8 moles of ethylene oxide, 1 part of oleyl polyglycol ether with 5 moles of ethylene oxide, .2 parts of spindle oil, Io parts of polyethylene glycol, .23 parts of water.
The active substance is homogeneously mixed with the adjuvan-ts in appropriate devices and ground,~yielding a paste from which, by dilution with water, it is possible to obtain suspensions of the desired concentration of active substance. Instead of using the respective active substance indicated in the foregoing formulation examples, it is also~possihle to use another of the compounds compris~ed by the formula I.
The active substances contained in the compositions of the present invention influence the plant glowth in differen-t ways. Thus they ' ,.
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inhibit, delay or prevent primarily the growth and germination. Their action is consequently both a pre- and post-emergent herbicidal and growth-inhibiting acti.on.
The novel active substarlces of the formul.a I have a good action ac3ainst monocdtyledollous and dicotyledono~ls weeds as well as a pronoullced se.l.ectivity i.n barley, wheat and rice, especially in post e~nergent app].ication.
The fol.lowin~ test methods were employed to establish the usefulness oE the compounds of the formula I as pre- and post-emergent herbicides.
PreemercJent herbicidal action (germinati.on inhibition) In a greenhouse, immediately af-ter sowing the test plants in seed dishes the surface of the soil is treated with an aqueous suspension of the active substances obtained from a 25 % wettable powder.
Different concentration series were used, corresponding to.4 and 2 kg of active substance per hectare respectively. The seed dishes are kept in the greenhouse at 22-25C and 50 to 70 % relative humidity.
The test is evaluated 3 weeks later according to the following rating:
1 = plants have not germinated or are totally withered 2-8 = intermedia-te stages oE damage ; 9 = plants undamaged (as untreated control)~

: Post-emergent her.bicidaI action (Contract herbicide) -v _ A large number (at least 7~ of weeds and cultivated plants, both mono- and dicotyledonous, were sprayea after emergence in the 4-to 6-lea~ stage with an a~ueous active substance emulsion in rates oi 0.5 and 1 kg of active substance per hectare and kept at 24~-26C
and 45-60 % relative humidity. The test was evaluated, as in the preemergent test, 15 days after treatment in accordance with the same rating.

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Pre-emergent _ . .. . . _ . _ _ Compouncl No. 1 2 l~
rate oE apE)l~ca-tioll ln kcJ/hcl 4 2 4 2 4 2 ~ _ _ __ Plant barley 5 7 6 8 1 wheat 9 9 9 9 1 maize 6 8 2 4 2 2 avena fatua 2 3 6 8 1 lolium perenne 5 5 6 9 1 1 alopecurus myos. 1 1 3 6 1 cyperus esc. 2 4 2 3 4 9 rottboellia exalt. 2 5 3 7 1 digitaxia sang. 1 1 1 1 1 setaria italica 1 1 1 ~ 1 1 echinochloa c.g. 1 1 1 2 1 1 sida spinosa 1 1 1 1 1 1 sesbania exaltata 1 1 1 4 1 1 amaranthus retrof. 1 1 1 1 1 1 sinapis alba 1 1 1 1 1 3 ipomoea puxp. 1 1 1 1 1 galium aparine 1 1 1 1 1 1 pastinaca sativa 1 1 1 1 1 1 rumex sp. 1 1 1 1 1 chrysanthemum 1. 1 1 1 1 1 1 abutilon sp. 1 1 1 1 1 1 solanum nigrum 1 1 1 1 1 1 A = 2-chloro-4-tri~luoromethyl-3'-ethoxy-4'-nitro-diphenyl ether, known from German Offenlegungsschrift 2 311 638 - (Compound 3 æ.

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~7~i~8 Post-~mergent ___ Compound No. _ _ 2 ~3~ 1 0.5 1 0.5 1 0.5 . _~ _ _______ Plant barley 6 7 4 7 wheat 7 8 6 8 2 2 rice 6 8 3 8 avena fatua 6 7 3 7 lolium perenne 2 2 3 6 1 1 alopecurus myos. 2 4 2 2 cyperus esc. 5 9 3 3 3 3 rottboellia exalt. 3 4 2 4 1 2 digitaria sang. 1 2 1 2 setaria italica 1 2 1 1 1 1 echinochloa c.c3. 1 1 1 ~2 sida spinosa 1 1 :L 2 2 2 sesbania exalt. 1 1 1 1 1 1 amaranthus retro. 1 1 1 1 1 1 sinapis alba 1 1 1 1 1 1 ipomoea purp. 1 1 1 1 galium aparine 2 2 1 1 1 1 pastinaca sati~Ta 1 1 1 1 chrysanthemum leuc. 1 1 1 1 4 4 abutilon sp. 1 1 1 1 1 1 solanum nigrum 1 1 1 1 1 1 matricaria cham. ~ 1 1 1 1 2 2 __ .

' ' ~767i~

The cornpounds of the Eorrmula I also possess advantageous growth-regulating effects~ They are suitable for the defoliation and desicca-tion of non-ligniEied parts of plants above the soil, in particulc~r for the dcfoliation arld desicccltion of cotton plants~ lecJurn:inosae~
sorgllum, potatoes and VilleS before harvesting. This action was testet as follows:

Defoliation and desiccatlon Cotton plants of the varie-ty "Del-ta Pine" are rearecl in a greenhouse.
After blossoming, they are sprayed wi-th an active substance suspension in amounts corresponding to a field rate of application of 1.2, 0.6 and 0.3 kg per hectare. The plants are then left in the greenhouse and the test is eva]uated 15 days after treatment.

Defoliation: The leaves are counted before treatment and when evalu-ating the test. The loss is noted and expressed in accordance with the rating ~elow.

Desiccation: The leaves remaining on the plant are examined Eor .
their degree of desiccation and the result is likewise rated as indicated below:

9 = 0-11 ~ defo]iation or desiccation 8 = 11-22 % defoliation or desicca-tion 7 = 23-33 ~ defoliation or desiccation 2 = 78-88 % defoliation or desiccation 1 = 89-100 ~ defoliation or desiccation ,~
:' ' ' .
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Compound Defoliation (Desiccaticn) _.~_ __ ~
rate of application in kg~ha 1.. 2 0.6 0.3 _____ _ --No. 1 1(1) 1(1) 1(1) NoO 2.2(1) 2(1) 3(1) B 4(1) 7(2) 7(3) B - methyl 2-[2-nitro-5-(2'-chloro-4'-trifluoromethylphenoxy)-penoxypropionate, kno~qn from German Offenlegungsschrift 2,311,638 (Compound 32 Z).

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Claims (24)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A phenoxyphenoxyalkanecarboxylic acid ester of the formula I

wherein R1 represents hydrogen, a halogen atom or the cyano group, R2 represents hydrogen or a C1-C4 alkyl group, R3 represents a radical -OR4 or -SR5, R4 represents a C1-C12 alkyl radical which is substituted by halogen or cyano or interrupted by one or more oxygen or sulfur atoms, a C2-C12 alkoxyalkyl, C3-C12 alkenyl, C3-C12 alkynyl or C3-C12 cycloalkyl radical, a phenyl or benzyl radical which is unsubstituted or mono- or polysubstituted by halogen, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkylthio, nitro, cyano or tri-fluoromethyl, and R5 represents a unsubstituted Cl-C12 alkyl radical or has the same meaning as R4.

2. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ia (Ia) wherein R3 is as defined in formula I of claim 1.

3. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ib (Ib) wherein R3 represents a C3-C12 alkenyloxy or alkenylthio radical or a C3-C12 alkynyloxy or alkynylthio radical.

4. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ic (Ic) wherein R3 represents a C2-C12 alkoxy or alkylthio radical which is interrupted by oxygetl or sulfur.

5. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Id (Id) wherein R5 is as defined in formula I of claim 1.

6. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ie (Ie) wherein R3"' represents a phenoxy or phenylthio radical, or a benzyloxy or benzylthio radical which is unsubstituted or mono- or polysubs-tituted by halogen, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkyl thio, nitro, cyano or trifluoronmethyl.

7. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula If (If) wherein R3"" represents a C1-C12 alkoxy or alkylthio radical which is substituted by halogen or cyano.

8. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ig (Ig) wherein R4 is as defined in formula I of claim 1.

9. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ih (Ih) wherein R5 is as defined on formula I of claim 1.

10. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ii (Ii) wherein R4 is as defined in formula I of claim 1.

11. A phenoxyphenoxyalkanecarboxylic acid ester according to claim 1 of the formula Ij (Ij) wherein R5 is as defined in formula I of claim 1.

12. 2-[2-Nitro-5(2'-chloro-4'-trifluoromethylphenoxy)-phenoxy]
propionic acid allyl ester according to claim 1.

13. 2-[2-Nitro-5-2'-chloro-4'-trifluoromethylphenoxy)-phenoxy]
propionic acid methoxyethyl ester according to claim 1.

14. 2-[2-Nitro-5-2'-chloro-4'trifluoromethylphenoxy)-phenoxythiopro-pionic acid ethoxyacetyl ester according to claim 1

15. 2-[2-Nitro-5-(2'-chloro-4'-trifluoromethylphenoxy)-phenoxy] thiopropionic acid allyl ester according to claim 1.

16. 2-[2-Nitro-5-(2'-chLoro-4'-trifluoromethylphenoxy)-phenoxy] propionic acid 2"-chloroethyl ester according to claim 1.

17. 2-[2-Nitro-5-(2'-chloro-4'-trifluoromethylphenoxy)-phenoxy] propionic acid cyclohexyl ester according to claim 1.

18. 2-[2-Nitro-5'(2'-cyano-4'-trifluoromethylphenoxy)-phenoxy] propionic acid allyl ester according to claim 1.

19. 2-[2-Nitro-5-(2'-cyano-4'-trifluoromethylphenoxy)-phenoxy] propionic acid 2"-methoxyethyl ester according to claim 1.

20. 2-[2-Nitro-5-(4'-trifluoromethylphenoxy)-phenoxy]
propionic acid allyl ester according to claim 1.

21. 2-[2-Nitro-5-(4'-trifluoromethylphenoxy)-phenoxy]
propionic acid 2"-methoxyethyl ester according to claim 1.

22. A method of selectively controlling weeds in crops of cultivated plants, especially in cereals and rice, which com-prises the use of a herbicidal phenoxyphenoxyalkanecarboxylic acid ester of the formula I of claim 1 or of a composition containing such a compound.

23. A method of regulating plant growth which comprises the use of a phenoxyphenoxyalkanecarboxylic acid ester of the formula I of claim 1 or of a composition containing such a compound.

24. A method of desiccating and defoliating cotton and potatoes shortly before harvesting, which comprises the use of a phenoxyphenoxyalkanecarboxylic acid ester of the formula I of claim 1 or of a composition containing such a compound.