IE45522B1 - Novel herbicidally active phenoxy-alkanecarboxylic-acid derivatives and use thereof for controlling grass-like weeds - Google Patents

Abstract

The invention is concerned with new herbicidal active 4-(cyanophenoxy)-.alpha.-phenoxy-alkanecarboxylic acid derivatives of the type wherein R1 is hydrogen, halogen, CF3 or CN, preferably chlorine, R2 is preferably hydrogen, R3 and R4 is hydrogen or lower alkyl, preferably R4 is hydrogen and R3 is methyl, and R5 is an acid derivative, especially an ester group. The invention is further concerned with herbicidal compositions containing such new derivatives and with methods for the selective control of grass-like weeds in crops of dicotyledonous and also monocotyledonous plants such as cereals.

Description

The present invention provides novel herbicidally active, nuclear-substituted phenoxy-phenoxy- alkanecarboxylic acid derivatives, processes for their preparation, herbicidal compositions which contain these novel compounds as active ingredients, and methods of selectively controlling grass-like weeks in crops of cultivated plants which comprise the use of the novel active substances including compositions which contain them.

According to the present invention, there are provided compounds of the formula I CN *2 wherein Rj. represents a hydrogen or halogen atom or a trifluoro-methyl or cyano group.

R2 represents a hydrogen or halogen atom, each of Rg and R^ independently represents a hydrogen atom or a lower alkyl group, and Rg represents an OH, -0-cation, -0-alkyl, -O-alkoxy-alkyl, -S-alkyl, -S-alkenyl, S-CHg-COO-alkyl, -0-alkenyl, -0-alkynyl, -0-cvcloalkyl, or -0-alky1-N(dialkyl)group, a chloroalkenylossy group, an unsubstituted or substituted benzyloxy, phenoxy or phenylthio radical, or an NHg, NH-alkyl. alkyl -N(dialkyl)or-N group, 0-alkyl ϊ ΰ 5 2 2 Lower alkyl groups represented by R^ and R^ are to be understood as meaning herein straight-chain or branched radicals containing 1 to 4 carbon atoms. The alkyl-containing groups represented by can contain a higher number of carbon atoms and have longer alkyl chains (up to 10 carbon atoms), preferably also in this case 1 to 6 or 1 to 4 carbon atoms. Corresponding alkenyloxy, alkenylthio and alkynyloxy groups contain up to 4 carbon atoms. Cycloalkoxy groups contain 3 to 12, preferably 5 or 6, carbon atoms.

Particularly preferred active compounds are those in which is hydrogen and R^ represents hydrogen, ethyl and, in particular, methyl.

Possible substituents of phenoxy, phenylthio and benzyloxy groups R^ are one or more selected from the group consisting of halogen, alkyl and nitro.

By cations of the -O-cation group (represented by R$) are meant mono- and polyvalent cations of inorganic or organic bases, including quaternary ammonio bases, in particular the cations of alkali metal and alkaline earth metal hydroxides. The preferred halogen atom represented by R^ and R2 is chlorine.

Herbicidal compositions containing 4-phenoxy-phenoxyalkanecarboxylic acid derivatives of similar structure and having a special action on grass for the selective control of grass-like weeds in mono- and dicotyledonous cultivated plants are known from German Offenlegungsschrift 2,223,894. Derivatives of these 4S522 v alkanecarboxylic acids which axe trifluoromethylated in the para-position of the terminal phenyloxy radical have also been described (Belgian patents 831,218 and 831,469).

The surprising discovery has now been made that, on 5 account of the presence of the cyano substituent, the novel active compounds of the formula I of the present invention are clearly superior in their action on grass to the above mentioned active substances as a consequence either of their better action against grass-like weeds and/or their better selectivity, for example in soya and cotton.

Accordingly,the active compounds of the invention are suitable for the preemergent and especially postemergent selective control of grass-like weeds (for example panicgrasses) of the genera Digitaria. Setaria, Echinochloa.

Rottboellia, and also Alopecurus, Apera, Lolium etc. and especially also Avena fatua (wild oats), not only in crops of dicotyledonous cultivated plants (such as cotton, soya, sugar beet etc)., but in particular in crops of monocotylede nous plants as well, such as cereals (wheat, barley, rye, 2o oats), rice etc. Xn this respect, and especially for solving the problem of controlling wild oats in wheat, the novel active compounds and the compositions which contain them constitute a notable enrichment of the stock of technical knowledge.

Some of the active compounds of the invention also - 4 SI) 9 possess advantageous growth-regulating effects (growth inhibition).

Particularly preferred active compounds of the formula I are those wherein Rj represents hydrogen and which contain a further substituent R^ in addition to the cyano group, such as in particular chlorine or a CF^ group. Moreover, it has been established that compounds in which the cyano group and (if present) are in the ortho- or para-position have a particularly good action and selectivity. If R^ is chlorine, then compounds with ortho-cyano—para-chloro and ortho-chloropara-cyano configuration have the best action. If R^ is hydrogen, the cyano group is preferably in the para-position.

Further important compounds are those in which represents hydrogen and different from hydrogen, for example lower alkyl, in particular methyl. The simplest ester form (R^ = OCHj) has outstandingly good activity.

The novel compounds of the formula I are obtained by the methods which are known per se for the synthesis of phenoxy-phenoxy-alkanecarboxylic acids and derivatives thereof.

In a first such process, according to the invention a substituted nalogenonitrilobenzene of the formula II - 5 43523 is reacted with a p-hydroxy-phenoxy-alkanoic acid derivative of the formula III (III) in the presence of a base.

In a second process, according to the invention a substituted p-hydroxy-diphenyl ether of the formula IV (IV) is reacted with an α-halogenoalkanoic acid derivative of the formula V Hal t C ι R„ CO - R, (V) in the presence of a base.

In a third process, the cyano group is introduced in the final process step. Accordingly, in this process a 4-(halogenophenoxy)-a-phenoxy-alkanecarboxylic acid derivative -ϊ 5 5 2 2 of the formula VI wherein Hal represents a halogen atom, such as a chlorine, bromine or iodine atom, is reacted with potassium or sodium cyanide in a polar solvent in the presence of a catalyst which activates the halogen atom, such as tetrakis-(triphenylphosphine) -nickel (pO64), preferably in a protective gas atmosphere (nitrogen, argon etc.) at temperatures between 20° and 120°C, preferably between 50° and 70°υ, i.e. in analogy to the reactions described in Adv. Chem. Ser. 132, 252 (1974) and Journ. Organomet. Chem. 54, C 57 (1973).

If Rj represents halogen in the starting material of the formula VI, it is also possible to replace this further halogen atom by a cyano group.

If a carboxylic acid (R^ ” OH) is used in these processes as starting material of the formulae III, V or VI, then this group can subsequently be converted into another derivative of the formula I as defined herein, for example by esterification etc. Conversely, when using an ester of the formula III, 20 V or VI, the ester group can subsequently be converted into the free carboxylic acid or a salt thereof by saponification - 7 or into another ester by transesterification.

In the formulae II to VI of the starting materials, the symbols R^ to R^ are as defined in formula I and Hal represents a halogen atom, such as a chlorine or bromine atom.

The above reactions can be carried out in the presence or absence of solvents or diluents which are inert to the reactants. Polar organic solvents, such as methyl ethyl ketone, dimethyl formamide, dimethyl sulphoxide, alcohols, ketones etc., are preferred. Generally the reaction tenperatures.are between 0° and 200°C, and the reaction time is from 1 hour to several days, depending on the starting material, choice of reaction temperature, and solvent. The process is usually carried out at normal pressure. Suitable bases (condensation agents) for the reaction are those normally employed, for example KOH, NaOCHg, NaHCOj, Kg COg, potassium tert, butylate etc., and also organic bases, such as triethylamine etc.

The starting materials of the formulae II to VI are partly known. Starting materials of these formulae which have not yet been described can be easily prepared by conventional processes and techniques. Phenoxyphenols of the formula IV can be prepared from hydroquinonemonoalkyl ethers and monochloroor dichlorobenzonitriles for example in accordance with the methods described in Journ. Am. Chem. Soc. 61, 2702 (1939) or in Chem. Abstracts 54, 922^1 (1960). te X *> K> Μ *5 The following Examples illustrate the process of the present invention. Further active compounds which are prepared in corresponding manner are.listed in the subsequent table.

Example 1 a) Preparation of the starting material: A three-necked flask is charged at room temperature with 7 g of pulverised potassium hydroxide and 12.4 g of hydroquinone5 monomethyl ether in 300 ml of dimethyl sulphoxide. With stirring and at a temperature between 15° and 20°C, 17.2 g of dichlorobenzonitrile are added in small amounts and stirring is continued initially for one hour at room temperature. The reaction mixture is then heated for 12 hours at 70°C. For working up, the reaction mixture is poured into an ice-water mixture and the precipitated substance becomes solid after a time. The solid is collected with suction and recrystallised from methanol, affording 20 g of 2-cyano-4-chloro-(4'-methoxyphenoxy)-benzene with a melting point of 101°-102°C.

A three-necked flask is charged, while introducing a flow of nitrogen, with 60 ml of glacial acetic acid and 25 ml of acetic anhydride. Thereafter 24 ml of 677. hydriodic acid are added dropwise while cooling with ice. The ambient temperature rises to 30°C. The mixture is then heated to a bath temperature of 90°C and 26 g of 2-cyano-4-chloro-(4'-methoxyphenoxy)benzene are added in small amounts at this temperature. The bath temperature is raised to 12o°C and the reaction mixture is further stirred for 3 hours. After cooling, the reaction mixture is poured into ice-water with vigorous stirring. The precipitate is collected with suction, washed with water and - 10 dried. Recrystallisation from benzene/petroleum ether yields 20 g of 2-cyano-4“chloro-(4'-oxy-phenoxy)~benzene of the formula CN with a melting point of 1O5°-1O7°C. b) A mixture of 20 g of this 2-cyano-4-chloro-(4'-oxy-phenoxy)benzene, 18 g of methyl 2-bromo-propionate, 12 g of anhydrous potassium carbonate and 250 ml of methyl ethyl ketone is heated, with stirring, for 12 hours to reflux temperature.

After cooling, the reaction mixture is filtered and washed with methyl ethyl ketone. The filtrate is then concentrated in vacuo. The residual viscous oil is subjected to high vacuum distillation, affording 16 g of methyl 4-(2'-cyano-4'-chlorophenoxy)-a-phenoxy-propionate with a boiling point of 199°2O3°C/O.Ol Torr.

Example 2 A two-necked flask is charged, in an atmosphere of argon, with 1.7 g of tetrakis-(triphenylphosphine)-nickel(0) and a degassed solution of 8.5 g of ethyl 4-(4'-chlorophenoxy)-apher.oxy-propionate in 25 ml of absolute ethanol is added. The mixture is heated with stirring to 60°C for 30 minutes. Then 1 g of sodium cyanide is added and stirring is continued for 2 hours at 70°C. Then a further 0.25 g of sodium cyanide is added and stirring is continued for a further 2 hours at 70°G, in the process of which a transesterification also takes place After the reaction mixture has cooled, it is filtered through ’'Hyflo*' and the Solvent is removed by rotary evaporation. The residual viscous oil is chromatographed over 200 g of silica gel with benzene/methylene chloride, yielding 2.5 g of ethyl 4-(4'-cyanophenoxy)-a-phenoxy-propionate as the very last fraction; b.p. 171°-174°C/O.O1.

The compounds of the above Examples as well as further active compounds of the formula I which are prepared in corresponding manner according to the invention are listed in the following table. j5 The listed compounds are those.in which R2 and R^ represent hydrogen and which therefore have the narrower formula CN l i *> O 'i J >2 TABLE Conpound Position of the CN groupR! with positionR3 *5 Physical constants n.pOC/b,p°C/torr 1 2-CN 4-C!CH3 -och3 b.p. 199-203°/0.01 n.p. 72 torr 2 4-CN HCH3 -0¾ b.p. 171-i?4°/0.0! torr 3 2-CN 4-C1 H -och3 B.p. 119-120° ί 4-CN 2-CIffl3 -och3 b.p. 2(0°/0.002 5 4-CN H CH -och3 n.p. 64-65° 6 2-CN 4-CI ”, -OH B.p. 154-155° 7 2-CN 4-Br Cll3 -0CH3 8 2-CN 4-CN ch3 -OCH, rt 2-CN 4-C! ch3 -oc2h5 b.p. 194°/0.05 10 2-CN IICll3 -cch3 oil 11 2-CN 4-C1 H -oc2h5 m.p. 102-104° 12 2-CN 1-C1 1! -GC (I (ii) oil 13 2-CN 4-C! % -Λ oil 14 2-CN VC* CH -nh2 B.p. 197° 15 2-CN 4-CI ”, -Nic2H5)2 oil 16 2-CN 4-C1 ”, -0-bcnzyl B.p. 113-115° 17 2-CN 4-CICH3 -0-Cfl-CH-CH oil 18 2-CN 4-CI CH -O-CH C=CH oil 19 2-CN 4-CI ”, -O-CH-C-CH , · Cl oil 20 2-CN 4-C! CH3 -0-CH2-C«CH2 % CH oil 21 2-CN 4-CICH3 ./ 3 W’ oil 22 2-CN 4-C! CH, J -0C3H.,(n) oil 23 2-CN 4-CIC,!3 -0¾ (iso) oil 24 2-CN 4-CIW3 -OC.i! (nJ 4 9 b.p. 203°/0.08 torr 25 2-CH 4-CI ch3 -OC.fi. (iso) 4 9 b.p. 1S6.°/O.O2 ton- Compound Position of the CH groupR. with positionR3R5 Physical constants o.p. /b.p. C/torr 26 2-CN 4-C1CH3 -0C,H*(sec) oil 27 2-CH 4-CICH3 -0-cyci ohexyl oil 28 2-CH 4-C1CH3 -0-phenyl B.p. 155° 29 2-CH 4-C1 -o-(cii?)?-o-ch3 oil 30 2-CH 4-CI CH3 -OC.H (tert) 49 Cl oil 31 2-CH 4-CICH3 -0-CH2-CH«C-CH3 oil 32 2-CH 4-C1 CH -O-CH2-CH=CII-CH3 oil 33 2-CH 4-CI ”5 -S-phenyl oil 34 4-CH H «5 -0C3H?(n) b.p. 190°/0.01 torr 35 4-CH HC,!3 -0C4Hg(n) b.p. 177-183°/0.015 torr 36 4-CH HCH3 -0C4Hg(iso) b.p. 203°/0.05 tori· 37 4-CH 2-CICH3 oil 38 4-CH 2-C1 ch3 -0C4Hg(n) oil 39 2-CH 4-CI ch3 -0-CH2-^-CI Cl oil 40 2-CH 3-CICH3 -0CH3 Π.Ρ. 84-85° 41 4-CH 11 »3 -O-(CH2),-OCH3 b.p. 188°/0.04 42 2-CH 4-CICH3 -S(CK3)2 oil 43 2-CH 4-CICfl3 -S-CHj-COOCjH,. oil 44 2-CH 4-Ci »3 -NHCH o.p. 140° 45 2-CH 4-CI % -O-CnJ^ Cl resinous 46 2-CH 4-CICll3 -0-CH-h» resinous 47 2-CH 4-CIC,l3 Cl -O-(CH ) -CH viscous oil 48 2-CH 4-CI ch3 /»3 -o-ch2-ch-c2h5 oil 49 2-CH 4-CI ch3 -O-fCHyJj-CHtCHP;, oil 50 2-CH 4-CI ch3 -o-ch2-c(ch3)3 oil 5 2 2 Compound Position of the CN group positionR3R5 Physical constants m.p. C/b.p. C/torr 51 4-CN H ch3 -O-CH,-CII-C,Hr 2 , 2 5 oil 52 2-CN 4-CiCH3CR3 -O-CH7-CH-(CH7)7CH^ oil 53 4-CN H ch3CK3 -O-CH^-CH-CCHj,)^ oil 54 2-CN 4-CiCH3 CH3 -O-CH^CHiCyH^ oil 55 4-CN H »3 -O-CHy-CHfC^),, oil 5ΰ 57 56 2-CN 4-CN 2-CN 4-CI H 4-CF3CH3 CH3 CH -sch3 -SCH -3 B.p. ,05-106° 59 2-CN 4-CF “3 -OH B.p. 158-162° 60 2-CN «3RR3 -oc2h5 B.p. !60°/0.65 61 2-CN 4-CF3C,l3 -OCH -CH-CH b.p. 173°/0.018 62 2-CK 4-CF3 ”, -0-(01.^-0011^ b.p. 195°/0.02 63 2-CN 4-CF, CH3 -S-CII2-CH.CH2 b.p. 200°/0.07 64 2-CN 4-CF3CK3 -ock-CsCH oi! 65 2-CN “3 -0CII7-CH(CH3)7 B.p. 69-70° 65 2-CN 4-CF3 CH. 0 -OC^tiso) oil 67 2-CN 4-CF3Cil3 -OCH-C.CH oil 63 2-CN 4-CF3 ch3 CHj -n(c2h5)2 B.p. 115-119° 69 2-CN 4-CF, ch3 -O-phenyl B.p. 97-99° 70 2-CN 4-CF3 ch3 -OC H (n) oil 71 2-CN «3 ch3 -,¾ b.p. 2OO-21O°/O.4 72 73 4-CN 4-CN 2-CF3 il CH3 Cli3 -OCH3 -OC3H (iso) oil 74 4-CN K , ~0C H (sec.) A 9 oil 75 4-CN il ch3 -sch3 oil 76 4-CN 2-C1 CH -0-C H (n) oil 77 4-CN 2-C1 “3 -0C3H?(iso) oil Conpound Position of the CN group A posit: ionr3R5 Physical constants B.p,°C/b.p.°C/torr 78 4-CN 2-Cl ™3 -OC^Hgtiso) oil 79 4-CH 2-Cl ICH3 -OC H (sec.) oil . 4-Cll 2-Cl ch3 >H3 -OCH -CH< oil 81 4-CII 2-Cl ICH3 /C(l3 -O-CH -CHS oil The compound methyl 4-(2,-cyano-4'-chlorophenoxy)-a-3-chlorophenoxy-propionate of the formula CH, ι 3 is prepared as an example of active compounds in which R2 10 represents halogen, and is obtained in the form of an oil.

The novel active substances (compounds) of the formula I are stable compounds which are soluble in conventional organic solvents, such as alcohols, ethers, ketones, dimethyl formamide, dimethyl sulphoxide etc.

The compositions of the present invention are obtained in known manner by homogeneously mixing and grinding active substances of the general formula I with suitable carriers and/or additives, with or without the addition of antifoam agents, wetting agents, dispersants and/or solvents which are inert to the active substances. The active substances can be formulated as follows: - 16 A 5 5 2 ίϊ solid formulations: dusts, tracking agents, granules (coated granules, impregnated granules and homogeneous granules); active substance concentrates which are dispersible in water: ' wettable powders, pastes, emulsions, emulsifiable concentrates ; liquid formulations: solutions.

The concentration of active substance in the compositions of this invention is between 1 and 80 percent by weight. As jq circumstances may require, the active substances 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 biocidally active substances or compositions. Thus in addition to containing the cited compounds of the formula I, the compositions of the present invention can also contain, for example, insecticides, fungicides, bactericides, fungistatic agents, bacteriostatic agents, nematocides or further pesticides, in order to broaden the activity spectrum. 2q In the following illustrative oonpositions parts and percentages are by weight, erapuleg The following substances are used to prepare 5% granules: parts of one of the active substances of the formula I, 0.25 parts of epichlorohydrin, 0.25 parts of cetyl polyglycol ether, 3.50 parts of polyethylene glycol, parts of kaolin (particle size 0.3 - 0.8 nan).

The active substance is mixed with epichlorohydrin and dissolved with 6 parts of acetone, and the polyethylene 5 glycol and cetyl polyglycol ether are then added. The resultant solution is sprayed on kaolin and subsequently evaporated in vacuo.

Wettable Powder The following constituents are used to prepare 10 a) a 70% and b) a 10% wettable powder: a) 70 parts of methyl 4-(2'-cyano-4'-chlorophenoxy)α-phenoxypropionafce, parts of sodium dibutyInaphtha1ene sulphate, parts of naphthalenesulphonic acid/phenolsulphonic acid/formaldehyde condensate (3:2:1), parts of kaolin, parts of Champagne chalk; b) 10 parts of methyl 4-(2'-cyano-4'-trifluoromethylphenoxy)-α-phenoxypropionate, parts of a mixture of the sodium salts of saturated fatty alcohol sulphates, parts of naphthalenesulphonic acid/formaldehyde condensate. parts of kaolin.

The respective active substance is applied to the <553 2 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 5 containing 0.1 to 8% of active substance. These suspensions aye suitable for controlling weeds in cultivations of plants.

Paste The following substances are used to prepare a 45% paste: parts of ethyl 4-(4'-cyano-phenoxy)-a-phenoxypropionate or one of the other cited active compounds of the formula I, parts of sodium aluminium silicate, parts of cetyl polyglycol ether with 8 moles of ethylene oxide, 1 part of oleyl polyglycol ether with 5 moles of ethylene oxide, parts of spindle oil, parts of polyethylene glycole, parts of water.

The active substance is intimately mixed with the additives in appropriate devices and ground. A paste is obtained from which, by dilution with water, it is possible to manufacture suspensions of the desired concentration of active substance.

Emulsifiable Concentrate The following ingredients are mixed to prepare a 25% emulsi fiable concentrate: 4 5 5112 parts of isobutyl 4-(21-cyano-4'-chlorophenoxy)α-phenoxy-propionate or one of the other cited active compounds of the formula I, parts of a mixture of nonylphenolpolyoxyethylene and calcium dodecylbenzenesulphonate, parts of 3,5,5-trimethyl-2-cyclohexen-l-one, parts of dimethyl formamide.

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 cultivations of plants.

The novel 4-phenoxy-a-phenoxyalkanecarboxylic acids which contain at least one cyano group in one phenyl nucleus and their derivatives of the formula I, and the compositions which contain them, have an excellent selective herbicidal action against grass-like weeds in a wide variety of crops of cultivated plants.

Since the novel active compounds destroy virtually only grass-like weeds and attack broad-leafed (dicotyledonous) plants only to an insignificant extent, they are accordingly suitable for controlling grass-like weeds in crops of all dicotyledonous cultivated plants, such as cotton, soya, sugar beet, leguminosae, celery, clover, lucernes, melons, cucumbers, tobacco etc. In addition, they exhibit a markedly better selectivity, for example in soya, cotton and sugar beet, than do the closely related chlorinated and trifluoromethylated >4S 5 2 2 active substances of German Offenlegungschrift 2,223,894 and of Belgian patents 831,218 and 831,469 which do not contain a cyano group. A control of maize in soya cultures is also possible.

However, it is particularly surprising that the novel active compounds of the formula I also possess an outstanding selectivity in the control of grass-like weeds, especially of Panicum-like weeds, in cultures of monocotyledonous plants, such as cereals (wheat, barley etc.) and rice.

Accordingly, panic-grasses e.g. of the genera Setaria, Echinochloa, Digitaria, Rottboellia can also be controlled exceptionally well selectively in cultures of monocotyledonous plants, such as wheat and barley etc. , aside from in soya.

The novel compounds also have an excellent action against other grass-like weeds, such as Alopecurus, Lolium, Apera, Agrostis etc.

An especially preferred field of use is the selective control of the problem weed Avena fatua (wild oats) and its related species in wheat, barley and sugar beet.

Although the novel active compounds of the formula I are effective in pre- and post-emergent application, the postemergent application in the form of contact herbicides is preferred. But the pre-emergence use is also of interest.

In particular 4-(cyano-ehlorophenoxy)-a~phenoxy-propionic acid esters of the formula I may be used for the post-emergent control of Avena fatua and Panicum-like weeds in what, soya, cotton or sugar beet. Similarly 4-(trifluoromethyl- cyanophenoxy)a-phenoxy-propionic acid esters may be used for the post-emergent control of Avena fatua and Panicum-like weeds in cereals, soya, cotton or sugar beet.

S Β 2 2 The novel active compounds are preferably formulated for example as' 25% wettable powders or for example 20% emulsifiable concentrates and diluted with water, and applied to the plant cultures in the post-emergence stage.

Herbicidal action on applying the active compounds after emergence of the plants (post-emergent application) Different cultivated plants and grass-like weeds are reared from seeds in pots in a greenhouse until they have reached the 4- to 6-leaf stage. Then the plants are sprayed with aqueous active substance emulsions (obtained from a 20% 'emulsifiable concentrate) in different rates of application corresponding to 8, 4, 2, 1 and 0.5 kg/hectare. The treated plants are then kept at optimum light, watering, temperature (22°-25°C) and humidity (50-70% relative humidity) conditions.

Evaluation of the test was made 15 days after treatment using the following rating: - plants undamaged (as untreated control plants) *= plants completely withered 8-2 = intermediate stages of damage.

Cultivated plants: Hordeum (barley) Triticum (wheat) Oryza (rice) Glycine (soya) Gossypium (cotton) Beta (sugar beet) Grass-like weeds and undesirable plants: Avena fatua Lolium perenne 05522 Alopeeurus myos.

Zea (maize) Rottboellia exaltata Digitaria sang.

Setaria italica Echinochloa g£HS galli.

The result of the test showed that the tested active compounds of the invention of the formula I containing a cyano substituent exhibit a markedly better selectivity towards wheat, soya, cotton, sugar beet and rice in that they damage these cultivated plants very much less that the constitutionally closest known compounds which do not contain a cyano group. - 23 A compound of the formula I

Claims (15)

1. O-C-CO-R. wherein R, represents a hydrogen or halogen atom or a trif luoromethyl , s . t 5 or cyano group, : R 2 represents a hydrogen or halogen atom, each of and R^ independently represents a hydrogen atom or a lower alkyl group, and Rg represents an OH, -O-cation, -0-alkyl, -0- alkoxy-alkyl, -S-alkyl, -S-alkenyl, S-CH^-COO-alkyl, -O-alkenyl, -0-alkynyl, -O-cycloalkyl, or -0-alky1-N(dialkyl)group, a chloroalkenyloxy group, an unsubstituted or substituted benzyloxy, phenoxy or phenylthio radical, or an NHj-NH-alkyl, alkyl z -N(dialkyl)or -N group. O-alkyl

2. A compound according to claim 1 wherein R^ represents a halogen atom or a trifluoromethyl or cyano group.

3. A compound according to claim 1 or claim 2, wherein Rj represents a chlorine atom or a trifluoromethyl group. * S3 2 2

4. A coinpound according to any one of claims 1 to 3, wherein and the illustrated CN group are in the orthoand para-position on the phenocy radical.

5. A compound according to claim 4 wherein the CN group is in the para-position.

6. A compound according to any one of claims 1 to 5 wherein R 2 represents a hydrogen atom.

7. A compound according to claim 6, wherein R 2 and represent hydrogen atoms and R^ represents a methyl radical.

8. A compound according to any one of the preceding claims wherein Rg represents an OH, -0-cation, -O-alkyl, -0alkoxy-alkyl, -S-alkyl, -S-alkenyl, -S-CH 2 - COO-alkyl, 0-alkenyl, -0-alkynyl, -O-cycloalkyl, or -O-alky1-N(dialkyl) group, an unsubstituted or substituted benzyloxy, phenoxy or phenylthio radical, or an NII 2 NH-alkyl. alkyl -N(dialkyl)or -N group O-alkyl,

9. Methyl 4-(2’-cyano-4’-chlorophenoxy)-a-phenoxy-propionate,

10. Isobutyl 4-(2'-cyano-4'-chlorophenoxy)-a-phenoxy-propionate

11. Methyl or ethyl 4-(4'-cyanophenoxy)-a-phenoxy-propionate.

12. Methyl 4-(4 1 -trifluoromethyl-2 1 -cyanophenoxy)-aphenoxy-propionate.

13. A process for the manufacture of a compound of the formula I as claimed in claim 1, wherein a compound of the formula II (wherein Hal represents a halogen atom and R^ is as defined in claim 1) is reacted with a compound of the formula III - 25 (III) (wherein Rg, R 3' Rj a nd Rg are as defined in claim 1), in a manner known per se in the presence of a base and, if desired, replacing the Rg group of the compound of the formula I obtained by another Rg group according to the formula I.

14. A process for the manufacture of a compound of the formula I as claimed in claim 1, wherein a compound of the formula IV (IV) (wherein R^ and Rg are as defined in claim 1) is reacted with a compound of the formula V. Hal - C - CO - R(V) (wherein Rg, R^ and Rg are as defined in claim 1 and Hal represents a halogen atom) in a manner known per se in the ig presence of a base and, if desired, replacing the Rg group of the formula I obtained by another Rg group according to the formula I 15. A process for the manufacture of a compound of the formula I as claimed in claim 1, wherein a compound of the formula VI V-Q0 - C - CO - Rg (VI) R, - 26 >4G522 (wherein Hal represents a halogen atom and to R~ are as defined in claim 1) is reacted with potassium or sodium cyanide and, if desired, replacing the Rg group of the compound of the formula I obtained by another Rg group according to the formula I. 16. A process according to claim 15 wherein the compound of the formula VI is reacted with the cyanide in a polar solvent and in the presence of a catalyst which activates the halogen atom. 17. A process according to claim 16 wherein the said catalyst is Ni JJ (CgHg) 3]4. 18. A process according to any one of claims 15 to 17 wherein the compound of the formula VI is reacted with the cyanide with the exclusion of air and under an atmosphere of a protective gas. 19. A process for preparing a compound of the formula I as claimed in claim 1 substantially as described with reference to Example 1 or 2. 20. A compound of the formula I as claimed in claim 1 prepared by the process claimed in any one of claims 13 to 19. 21. A herbicidal composition which contains, as active ingredient, a compound of the formula I as claimed in any one of claims 1 to 7 and 10 together with a solid extender and, optionally, a surface active agent or together with a liquid diluent and a surface active agent. 22. A herbicidal composition which contains, as active ingredient, a compound of the formula I as claimed in any one of claims 1 to 7 and 10 in the form of granulate, wettable powder, paste or emulsifiable concentrate. 27 23. A method for the selective control of grass-like weeds in a crop of dicotyledonous or monocotyledonous cultivated plants, which comprises applying to sown cultivated areas before emergence, or to crops of cultivated plants after emergence a compound as claimed in any one of claims 1 to 7 and 10. 24. A method according to claim 23 wherein the cultivated plants are soya, cotton, sugar beet or cerals. 25. A method according to claim 23 or 24 which comprises the post-emergent application of a compound as claimed in claim 5. 26. A method according to claim 23 for the post-emergent control of Avena fatua and Panicum-like weeds in wheat, soya, cotton or sugar beet using a 4-(cyano-chlorophenoxy)-a- phenoxypropionic acid ester. 27. A method according to claim 23 for the post-emergent control of Avena fatua and Panicum-like weeds in cereals, soya, cotton or sugar beet using a 4-(trifluoromethylcyanophenOxy)-a- phenoxy-propionic acid ester. 28. A method according to claim 26 wherein there is used methyl or isobutyl 4-(2 1 -cyano-4'-chlorophenoxy)-a-phenoxy propionate. 29. A method according to any one of claims 23 to 28 wherein the said compound is applied in the form of a composition as claimed in claim 21 or 22. 30. A herbicidal composition which contains, as active ingredient, a compound of the formula I as claimed in any one of Claims 8, 9, 11 and 12 together with a solid extender and, optionally, a surface active agent or together with a liquid diluent and a surface active agent. - 28 i S 5 3 2 31. A herbical composition which contains, as active ingredient, a compound of the formula 1 as claimed in any one of claims 8, 9, 11 and 12 in the form of a granulate, wettable powder, paste or emulsifiable concentrate. 5 32. A method for the selective control of grass-like weeds in a crop of dicotyledonous or monocotyledonous cultivated plants, which comprises applying to sown cultivated areas before emergence, or to crops of cultivated plants after emergence a compound as claimed in any one of claims 8, 9, 10 11 and 12. 33. A method according to claim 32 wherein the cultivated plants are soya, cotton, sugar beet or cereals. 34. A method according to claim 32 or 33 wherein the said compound is applied in the form of a composition as

15. Claimed in claim 30 or 31.