CS204022B2 - Herbicide means and method of makinf the active substance - Google Patents

Description

The present invention relates to a herbicidal composition comprising as active ingredient novel substituted 3-phenoxy-α-phenoxypropionic acid derivatives having a substituent in the α-femoxy group in the para position to the 3-phenoxy group. The invention further relates to a process for the production of these novel herbicidally active compounds, as well as to the use of these active compounds or of compositions containing them for the selective control of weeds in crops.

The new active substances correspond to the general formula I

B is acetoxime —O — N - = C (CH3) 2 or OR, SR1 or NR2R3,

Hal is a halogen atom, n is 0 or 1,

Y is hydrogen, chlorine, or cyano,

Z represents a halogen atom or a cyano group,

R1 represents hydrogen, an alkali metal or alkaline earth metal cation or an alkylammonium group whose alkyl radicals contain 1 to 4 carbon atoms and may be substituted by a methoxy or hydroxyl group, - an alkyl group having 1 to 8 carbon atoms which is unsubstituted or substituted halogen, cyano, bis-alkylamino in which the alkyl contains 1 to 4 carbon atoms, cycloalkenyl of 3 to 8 carbon atoms or morpholino or is interrupted by an oxygen or sulfur atom or a carbonyl group, - an alkenyl or alkynyl group having 2 to 8 atoms - phenyl or benzyl, unsubstituted or substituted by halogen, nitro, cyano, (C1-C4) -alkyl or (C1-C4) -alkoxy,

R 2 is hydrogen, C 1 -C 6 alkyl optionally substituted with C 1 -C 4 alkoxy; an alkenyl group having from 3 to 6 ato204022

2040 my carbon, a (C 3 -C 6) alkynyl group, a (C 3 -C 6) cycloalkyl group; phenyl or benzyl, these groups being optionally substituted by halogen, nitro, cyano, (C 1 -C 4) alkyl or (C 1 -C 4) alkoxy;

R 3 has the same meaning as R 2 and is furthermore alkoxy having 1 to 4 carbon atoms or together and R 2 and the nitrogen atom to which this residue is attached also include pyrrolidino, piperidino or morpholino, with the meaning of B and R @ 1 are not hydrogen, a metal cation or an alkyl group having from 1 to 8 carbon atoms which is optionally substituted by C1 to 4 alkoxy group when Z is halogen and CF3 is in the para position and Y or / and (Hal) _n , as halogen atoms, are located in ortho-polysilane to the oxygen atom forming the bridge between the phenyl rings.

From DOS Nos. 2 136 828, 2 223 894, 2 433 067 and 2 531 643 similar phenoxyphenoxyalkanecarboxylic acid derivatives are known which, however, contain an alkanecarboxylic acid residue in para-p-olose.

These known compounds have a special action against grasses and are suitable for the selective control of long-standing weeds in monocotyledonous and dicotyledonous crop plants. However, these compounds are not effective at all or only in very high application rates against dicotyledonous weeds.

Surprisingly, it has now been found that the novel phenoxy-.alpha.-alkanecarboxylic acid derivatives of formula (I) having a meta-position of the alkamic carboxylic acid are surprisingly suitable for controlling dicotyledonous weeds in predominantly monocotyledonous crops, such as o- herbaceous plants (wheat, barley, sorghum), maize, as well as rosehip (Sagittaria) and cobweed (Cyperus) in rice, and also to selectively control weeds in dicotyledonous crops such as sugar beet, soybean, cotton.

The compounds of formula I have proved to be most effective against the following dicotyledonous weeds:

arrowhead (Sagittaria pygmea), white mustard (Simapis alba),

Sida spinosa,

Sesbania exalt-ata, Ipoim-oea purpure-a, Galium aparine, Chrysanthemum leucum, Abutilon, Solanum nigrum,

Amm-ania indica

Rotal-indica, chess-or (Cyperus difformis),

Elatine-e triandra.

Linder-nia pr-ocumbems etc.

Although the novel compounds are also effective in pre-emergence application, post-emergence application has proved to be particularly effective and expedient.

Some of the new active ingredients are also suitable for the desiccation and defoliation of cotton or potatoes shortly before harvesting.

The amount of herbicide used according to the invention per hectare depends on the effectiveness of the active compound used, the soil properties, the climatic and weather conditions, the method of application and the time of application and the type of crop plant and the weeds to be controlled. 0 kg and preferably 0.5 to 4.0 kg.

The preparation of the novel compounds of the formula (I) is carried out by methods known per se for t-aceto-synthesis.

The last step of the synthesis always consists of the following step and represents the process according to the invention:

fWaíJ ΠΗ

+ HaI-CH-COB (II)

The process according to the invention starts from the 3-hydroxydifeinyl ether of the formula II, which is reacted with an α-halopropionic acid derivative of the formula III in the presence of a base.

If carboxylic acids (B-OH) are used as starting materials of formula III in this process, this group can additionally be converted to another derivative of formula I according to the invention, either directly or via the corresponding acid chloride.

When an ester of formula (III) is used, this compound can be converted by saponification of the ester group into the free carboxylic acid, its salt and then to the amide.

In the formulas II and III, n-and B and Z have the meanings given in formula I and Hal represents a halogen atom, such as chlorine or bromine, etc.

Said reaction may be carried out in the presence or absence of inert solvents or diluents which are inert

S towards reactants. Preferred solvents are polar organic solvents such as methyl ethyl ketone, dimethylformamide, dimethylsulfoxide, etc. The reaction temperatures are between 0 and 200 ° C, preferably between 20 and 100 ° C, and the reaction time depends on the starting material used, the reaction and temperature chosen. between 1 hour and several days.

The process is generally carried out at atmospheric pressure. Suitable bases (condensing agents) for the reaction are customary bases, such as potassium hydroxide, sodium methoxide, sodium bicarbonate, potassium carbonate, potassium tert-butoxide, etc., but also organic bases such as triethylamine, etc.

The starting materials of the formula III are known or can be easily prepared by conventional methods. The starting phenols of the formula II are also known.

The hitherto not described phenoxyphenols of the formula II can be readily prepared according to the usual methods as described, for example, in DOS 2,433,066 and 2,433,067.

Thus, for example, can be reacted with 2-methoxy-4-chloronitrobenzene of formula OCH ₃ C / ^NO 7 and a phenol of formula IV

in which

Hal, η, Y are as defined above, in an alkaline medium to form the nitro compounds of formula (V)

for example according to the data contained in DOS 2 304 006.

The same nitro compound of formula V is also obtained by reacting 2 moles of phenol IV with 2,4-dichloronitrobenzene to give the compound of formula β as an intermediate.

which is then 're-etherified' by heating with methanol and potassium hydroxide in dioxane to the methoxy derivative of formula V (the method is described in DOS 2,533,172).

The thus obtained nitrated substituted compound of formula V (intermediate) is converted to the corresponding amine by conventional reduction of the initro group, which is then converted to the diazonium salt (e.g. diazoinium chloride). Finally, the diazonium of the diazonium salt is replaced by cyano or halogen.

The reduction of the nitro group in the compound of formula V is carried out either with hydrogen catalytically (e.g., Rainey nickel) in an inert solvent solution or by slowly adding a mixture of iron powder and dilute hydrochloric acid to the compound of formula V at elevated temperature.

The diazotization of the amine obtained is carried out in a customary manner in a solution of dilute hydrochloric acid by dropwise addition of an aqueous solution of sodium nitrite at a temperature below 5 degrees Celsius.

The exchange of the diazo group with a cyano group is carried out by dropwise addition of the diazonium salt to an aqueous solution of K 3 [Cu (CN) 4] or by the addition of powdered copper and cuprous cyanide to the diazonium salt solution. These reactions leading to p-cyanediphenyl ethers, using substituted p-nitrodephenyl ethers as starting materials, have already been described in DOS 1,912,600.

The exchange of the diazo group with chlorine is accomplished by the addition of cuprous chloride and finely dispersed brown powder to the diazonium chloride solution.

The replacement of the diazo group with bromine is best accomplished by the addition of potassium bromide and cuprous bromide to the solution of the diazonium salt, while the iodine replacement can already be carried out by the action of potassium iodide on the diazonium salt.

A halogen atom in the meaning of the symbol Z can also be introduced by halogenation of a diphenyl ether unsubstituted in the 4 poloze position.

Finally, in order to obtain the corresponding starting phenol of formula (II) from the compounds thus prepared, the meta-position (-O-CH3J) ether-protecting group is cleaved, for example with hydrogen bromide in glacial acetic acid.

The following examples describe the preparation of some phenoxy-α-phenoxypropionic acid derivatives of formula I. Other active ingredients which have been prepared in a corresponding manner are shown in the following table. Temperatures are given in degrees Celsius.

Example 1

3- (2 ^'J cyano-4'-trifluoromethylphenoxy © phenoxy) -a- (6-chlorophenoxy) propionic acid

15.9 g (0.05 mol) of 3- (2'-cyano-4'-trifluoromethylphenoxy) -6-chlorophenol and 50 ml of methyl 2-bromopropionate are stirred in 100 ml of ethyl methyl ketone with 19.5 g of potassium carbonate and 1 g of potassium iodide overnight at a bath temperature of 100 ° C. After filtration, the filtrate was evaporated to dryness and the residue distilled under high vacuum. Boiling point is 189 ° C / 1 Pa. Yield 15 g.

Example 2

3- (2'-Cyano-4'-trifluoromethylphenoxy) -α- (6-chlorophenoxy) propionic acid g (0.15 mol) of the methyl ester obtained in Example 1 is dissolved in 400 ml of methanol and 100 ml of 2 ml are added. The mixture was stirred at room temperature for 3 hours, the solvent was distilled off and the residue was dissolved in water, acidified with concentrated hydrochloric acid to give the product as an oil, followed by extraction with ethyl acetate-toluene (1: 1). 61.5 g of the title compound as a viscous oil.

Example 3

3- (2'-Cyano-4'-difluoromethyl-phenoxy) -ce- (6-chloro-phenoxy) -propionic acid allyl ester

55.5 g of the acid obtained in Example 2 are dissolved in 120 ml of toluene and, after addition of 2 ml of pyridine with 40 ml of thiomyl chloride, the reaction mixture is stirred for 3 hours at a bath temperature of 80 ° C, then concentrated on a rotary evaporator. 56 g) is dissolved in 200 ml of toluene. After addition of 12.5 g of allyl alcohol, 28 g of triethylamine are added dropwise at 5 to 15 ° C and the reaction mixture is stirred overnight at room temperature. 50 ml of water are then added, the organic phase is separated and dried over sodium sulphate. After distilling off the solvent, 57.8 g of a dark oil are obtained. For purification, the oil is dissolved in toluene and the toluene solution is chromatographed over an aluminum hydroxide column. 31 g of the reaction product are obtained in the form of a viscous oil.

Analysis:

calculated:

% C, 56.42;% H, 3.55%;

56.7% C, 3.8% H, 3.1% N.

Other compounds were prepared in an analogous manner to these examples:

2- (3‘-Trifluoromethylphenoxy) -is- (6-phenoxy) propionic acid methyl ester, boiling point 183 ° C / 1 Pa, as well as those listed in the following table:

Compound Y n.

physical constants (Hal) _m

1 H - Cl OCH3 mp 165 ° C / 1 Pa 2 CN - Cl 0CH3 mp 103-107 ° C 3 H - Cl OH 1.1. Mp 110-120 ° C 4 CN 6-C1 Cl OCH 2 - CH-CH 2 mp 165 ° C / 1 Pa 5 H - Cl 0CH ₂ - £) mp 193 ° C / 3 Pa 6 H _ Cl OC-tHasek. mp 173 ° C / 15 Pa 7 H 5-C1 Cl OCH3 mp 167 ° C / 7 Pa 8 H - J OCH3 mp 171 ° C / 35 Pa 9 H - CN OCH3 mp 170 ° C / 2 Pa 10 Cl - CN OCH3 oil 11 Cl - Cl ON®C _[CH3) 2 n _D ²⁴ = 1.5293 12 Cl - Cl N (CH 3) OCH 3 n _D ²⁴ = 1.5275

compound Y (Hal), "Z B nina no.

physical constants

13 Cl - Cl ° \ H / Mp: 61-65 ° C 14 Cl. - CN OCiHan oil 15 Dec Cl - CN OC4H9sec. oil 16 Cl - CN oil 17 II - CN ON = C (CH 3) 2 oil 18 H - CN N (C 2 H 5) 2 oil 19 Dec H - CN OC 2 H 4 N (C 2 H 5) 2 oil ' 20 May Cl - Cl mp> 200 ° C / 1 Pa 21 Cl - Cl OC ₂ H ₄ N (O ₂ H 5) 2 mp 126-128 ° C 22nd Cl - Cl oil 23 _: Cl - Cl oil 24 Cl - Cl OC2H4C1 mp 61-62 ° C 25 Cl - Cl OCH (CH 3) CN n _D ²⁴ = 1.5215 26 Cl - Cl OCH2CN n _D ²⁴ = 1.5340 27 Mar: Cl - Cl OC2H4CN in _D ²⁴ = 1.5295 28 Cl - Cl OCH2COCH3 n _D ²⁴ = 1.5260 29 Cl - Cl OO2H4SCH3 n _D ²⁴ = 1.5375 30 Cl - Cl ° wO oil 31 Cl - Cl OCH _Z - ^ oil 32 Cl - Cl NHC2H4OCH3 n _D ²⁴ = 1.5330 33 Cl - Cl Ό oil 34 Cl - Cl OCH2CF3 n _D ²⁴ = 1.5015 35 H - Bl ’ 0CH3 oil 36 CN - ] 0CH3 oil 37 CN - CN OCH3 oil C / I3 0¾ OCH-COB ^Y VL / ⁰

compound no. Y (Hal) _m OF (B) physical constants 38 H 5-C1 Cl OCH3 mp 167 ° C / 7 Pa 39 CN - Cl OCH3 mp> 200 ° C / 1 Pa 40 Cl - Cl OCH3 mp> 200 ° C / 1 Pa 41 Cl - CN OCH3 tv> 200 ^Q C / 1 Pa 42 H 3-C1 Cl OCH3 mp 174 ° C / 2 Pa

The novel active compounds of the formula I are stable compounds which are soluble in conventional organic solvents such as alcohols, ethers, ketones, dimethylformamide, diethylsulfoxide, etc.

The compositions according to the invention are prepared in a manner known per se by thoroughly mixing and grinding the active compounds of the formula I with suitable carriers and / or diluents, optionally with the addition of antifoams, wetting agents, dispersants and / or solvents inert to the active compounds. The active substances can be present in the following processing forms and can be applied in the same forms:

solid processing forms: dusting, spreading, granulate, coated granulate, impregnated granulate and homogeneous granulate;

water-dispersible active ingredient concentrates: wettable powder, pastes, emulsions, emulsion concentrates;

liquid forms of processing: solutions.

The concentration of active ingredient in the compositions of the invention is from 1 to 80% by weight, and these concentrations may optionally be between about 0.05 to 1% when applied at low concentrations.

Other biocidal active ingredients or compositions may be admixed with the compositions of the present invention. Thus, the novel compositions may contain, for example, insecticides, fungicides, bactericides, fungistatics, bacteriostats, nematicides or other herbicides in addition to the compounds of the formula I in order to broaden the spectrum of action.

Granulate:

The following ingredients are used to prepare the 5% granulate:

parts of the active compound of the formula I,

0.25 parts of epichlorohydrin,

0.25 parts of cetyl polyglycol ether,

3.50 parts of polyethylene glycol, part of kaolin (particle size 0.3 to 0.8 mm)

The active ingredient is mixed with epichlorohydrin and the mixture is dissolved in 6 parts of acetone, after which polyethylene glycol and acetyl polyglycol ether are added. The solution thus obtained is sprayed onto kaolin and then the solvent is evaporated off under vacuum.

Wettable powder:

The following ingredients are used to prepare a) 70% and b) 10% wettable powder:

(a) 70 parts of methyl 3- (4'-trifluoromethyl-2'-cyanophenoxy) - (6-chlorophenoxy) propionic acid methyl ester, parts of sodium dibutylsulfonate, parts of the naphthalenesulfonic acid condensation product, phenolsulfonic acids and formaldehyde (3: 2: 1); parts of kaolin, parts of chalk (prov. Champagne);

10 parts of the active ingredient, parts of a mixture of sodium salts of saturated sulfated alcohols, parts of the condensation product of naphthalenesulfonic acids and formaldehyde, parts of kaolin.

The active ingredient is applied to the appropriate carriers (kaolin and chalk) and then the other ingredients are admixed and the mixture is ground. A wettable powder of excellent wettability and suspensibility is obtained. From such wettable powders, suspensions containing from 0.1 to 80% of the active ingredient which are suitable for controlling weeds in crop plants can be obtained by dilution with water.

Paste:

The following substances are used to prepare 45% paste:

parts of 3- (4'-trifluoromethyl-2'-cyanophenoxy) -α- (6-chlorophenoxy) -propionic acid methyl ester, parts of sodium silicate, parts of cetyl glycol ether with 8 moles of ethylene oxide, parts of oleyl polyglycol ether with 5 moles of ethylene oxide, polyethylene glycol, parts of water.

The active ingredient is intimately mixed with the ingredients in equipment suitable for this purpose and the mixture is ground. A paste is obtained which, by dilution with water, can be used to prepare suspensions of the desired concentrations.

Emulsion concentrate:

In order to prepare 25% of the emulsion concentrate, parts of the active ingredient, parts of a mixture of nonylphenol polyoxyethylene and dodecylbenzenesulfuric acid calcium salt, parts of cyclohexanone and 55 parts of xylene are mixed together.

This concentrate may be diluted with water to emulsions of suitable concentrations, for example from 0.1 to 10%. Such emulsions are suitable for controlling weeds in crop plants.

The novel 3-phenoxy-.alpha.-phenoxyalkanecarboxylic acid derivatives of the formula I, as well as the compositions containing them, have an excellent herbicidal activity against weeds in various crops of crops, furthermore they have the ability to control plant growth.

A particularly preferred field of application is the selective control of, in particular, dicotyledonous weeds in cereal crops and, moreover, of rosehip (Sagittaria) and broadflower (Cyperus) in rice.

Although the new active compounds of formula I are effective in pre-emergence and post-emergence application, post-emergence application to my contact herbicides seems to be advantageous, although pre-emergence application is also of importance.

Advantageously, the novel active compounds are processed, for example, into 25% wettable powders or, for example, into 25% emulsion concentrates, which are then diluted with water and applied to the crop stands in a diluted state (post-emergence).

Herbicidal effect after application of active substances after emergence of plants (postemergence)

Various crops and weeds are grown from potted seeds in a greenhouse until they reach the 4-6 leaf stage. Thereafter, the plants are sprayed with aqueous emulsions of the active ingredient (which were obtained from 20% emulsifiable concentrate) at various dosages. The treated plants are then maintained under optimal conditions of light, irrigation, heat ( ^22-25 ° C) and air humidity (50-70% relative air humidity). Evaluation of the experiment is performed 15 days after treatment.

The condition of the plants shall be assessed and expressed on the following scale:

= normal state 1 = dead plants to 2 = intermediate stages

The herbicidal activity of a number of active substances according to the invention was compared with the known active substances described in British Patent Specification No. 1,423,006. The application rate of active substance was always 4 kg per ha. The numbering of the active compounds according to the invention corresponds to the numbering given in the tables. The following 6 active substances served as comparative substances:

And CLX ^ O - ^ - O-CH-COOC ^ _CH3

Β € ΐ - (θ ^ -0 - ^ Ο ^ -0 <-<0-ΝΗ0Η ₃

CH 2 Cl 2 O 2 O - O 2 O-CH-cooch 3

Cl

D _and ^^. _O - (d 6 O-CH-COOH

CH $

Cho, ^F \ 2 / ~ ^{for 'ch' COOCH}

Br

Results:

Compound No. Evaluation of Effect for Chickweed Tomato, Mustard Cracker Compound Known From British Patent.

Document 1 423 006:

A 7

B 8

C 7

D 5

E 7

F8 compounds of the invention:

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

8 9

1.

Each of the active compounds tested according to the invention has a very good score for at least one plant 1.

Selective herbicidal action against sowing and cotton in pre-emergence application

The seeds of the test plants are sown in pots filled with sterilized garden soil in a greenhouse. The active ingredient is processed to a 25% emulsion concentrate and applied as an aqueous dispersion directly after sowing to the soil surface of the pots. The pots were sprayed with 100 ml of spray suspension per m ² and then placed in the air-conditioned section of the greenhouse at 22-25% C and 60-70% relative humidity and watered daily. Control and assessment of growth is carried out after 3 weeks and the condition of plants is evaluated according to the above scale.

The test compounds of the invention exhibit a good herbicidal effect in this test, which is expressively selective (rating 7, 8 or 9) against cotton and soy. Desiccation and defoliation effect

Cotton plants of the Deltapine species are grown in pots in the greenhouse. At the end of the capsule formation, spraying with the active ingredient aqueous preparations is carried out, the application rates of active substances corresponding to 1.2, 0.6 and 0.3 kg / ha, respectively. Untreated plants were left as a control. Evaluation of the experiment was performed 3, 7 and 14 days after. administration of the test substance by determining the degree of defoliation (% of fallen leaves) and the degree of desiccation (% of dried leaves remaining on the plant).

The active compounds tested according to the invention caused that after 14 days only a few dried leaves remained on the plant.

Claims (11)

A herbicidal composition, characterized in that it contains at least one 3-phenoxy-.alpha.-phenoxypropioic acid derivative of the formula I as active ingredient in which: B represents an acetoxime group -O-N - = C (CH 3) 2 or an group OR, SR 1 or NR 2 R 3, Hal is a halogen atom, n is 0 or 1, Y is hydrogen, chloro or cyano, Z represents a halogen atom or a cyano group, R 1 is hydrogen, an alkali metal or alkaline earth metal cation, or an alkylammonium group whose alkyl radicals contain 1 to 4 carbon atoms and can be substituted by a methoxy or hydroxyl group. - a (C 1 -C 8) alkyl group which is unsubstituted or substituted by halogen, cyano, (C 1 -C 4) -alkylamino, (C 3 -C 8) C 3 -C 8 alkenyl or morpholino or is interrupted by an oxygen atom, or sulfur or carbonyl, - alkenyl or alkynyl of 2 to 8 carbon atoms, - cycloalkyl of 3 to 8 carbon atoms, - phenyl or benzyl, unsubstituted or substituted by halogen, nitro, cyano, (C 1 -C 4) -alkyl carbon or (C 1 -C 4) alkoxy, R '2 is hydrogen, C 1 -C 6 alkyl optionally substituted with C 1 -C 4 alkoxy, C 3 -C 6 alkenyl, C 3 -C 6 alkynyl, C 3 -C 6 cycloalkyl (C 6 -C 6), phenyl or benzyl, optionally substituted by halogen, nitro, cyano, (C 1 -C 4) alkyl or (C 1 -C 4) alkoxy, R3 has the same meaning as R2 and is furthermore alkoxy having 1 to 4 carbon atoms or together with R2 and the nitrogen atom to which this residue is attached also means pyrrolidino, piperidino or morpholino, with the meaning of B and R1 is not hydrogen, a metal cation or an alkyl group having 1 to 8 carbon atoms which is optionally substituted by an alkoxy group having 1 to 4 carbon atoms when Z is halogen and the CF 3 group is in para-position and Y or / and (Hal) is as halogen atoms, they are located ortho-to the oxygen atom forming the bridge between the phenyl rings. 2. A composition according to claim 1, wherein the active ingredient is 3- (2'-cyano-4'-trifluoromethylphenoxy) (6-chlorophenoxy) propionic acid methyl ester. 3. A composition according to claim 1, characterized in that it contains as active ingredient acetoximester 3- (2 ^{<-chloro-4'-trlfluormethylfenoxy)} -a- (6-j chlorophenoxy propionate. 4. A composition according to claim 1, wherein the active ingredient is 3- (2'-chloro-4'-trifluoromethylphenoxy) -α- (6-chlorophenoxy) propionic acid methoxymethylamide. 5. A composition according to claim 1, wherein the active ingredient is 3- (2 &apos; -chloro-4 &apos; -trifluoromethylphenoxy) -α- (6-chloro-phenoxy) -propionic acid beinzylester. 6. A composition according to claim 1, wherein the active ingredient is 3- (2'-chloro-4'-trifluoromethylphenoxy) -α- (6-chlorophenoxy) propionic acid benzylthioester. 7. A composition according to claim 1, wherein the active ingredient is (2 &apos; -chloroethyl) 3- (2 &apos; -chloro-4 &apos; -fluoromethylpheroxy) -α- (6-chlorophenoxy) propionic acid ester. 8. A composition according to claim 1, wherein the active ingredient is (2 &apos; -cyanethyl) 3- (2 &apos; -chloro-4 &apos; -trifluoromethylphenoxy) - [alpha] - (6-chlorophenoxy) propionic acid ester. 9. A composition according to claim 1, wherein the active ingredient is 3- (2'-chloro-4'-trifluoromethylphenoxy) -as- (6-chlorophenoxy) propionic acid cyclohexyl ester. 10. The composition of claim 1 wherein the active ingredient is 3- (2 &apos; -cyano-4 &apos; -trifluoromethylphenoxy) -as- (6-chlorophenoxy) propionic acid allyl ester. 11. A process for the preparation of an active compound as claimed in claim 1, which comprises reacting the 3-hydroxydiphenyl ether of formula II in which: Hal, n and Z have the meaning given in formula (I) (1), act in the presence of a base with a N-halo-propionic acid derivative of the general formula (III) CH3 Hal-CH — COB (III) wherein B and Hal are as defined in formula I in point 1.