GB2065649A

GB2065649A - Herbicidal phenoxy-phenoxy-propionic acid esters

Info

Publication number: GB2065649A
Application number: GB8039687A
Authority: GB
Original assignee: F Hoffmann La Roche AG
Current assignee: F Hoffmann La Roche AG
Priority date: 1979-12-12
Filing date: 1980-12-11
Publication date: 1981-07-01
Also published as: RO82489A; NO149351C; DD154570A5; RO82489B; ES8203337A1; IL61638A; DK529580A; EP0030702B1; NO803729L; AU6511280A; ES497621A0; NO149351B; EP0030702A1; CS219297B2; DE3064660D1; CA1142540A; GB2065649B; IL61638A0; FI803873L

Description

SPECIFICATION Propionic acid esters The present invention is concerned with propionic acid esters. The propionic acid esters provided by the present invention are compounds of the general formula

wherein R represents a hydrogen atom, an alkyl group containing 1-6 carbon atoms or a phenyl group, R represents an alkyl group containing 1-6 carbon atoms, an alkenyl group containing 2-6 carbon atoms, an alkynyl group containing 2-6 carbon atoms or a phenyl group or R and R together with the carbon atom to which they are attached form a cycloalkane ring containing 4-10 carbon atoms which, if desired, can be mono-, di-or tri-substituted with alkyl containing 1-3 carbon atoms, R represents a halogen atom or a trifluoromethyl or nitro group and R4 and R5 each represent a hydrogen or halogen atom. The invention is also concerned with a processforthe manufacture of the compounds offormula I, (pre-emergence and post-emergence) herbicidal compositions which contain at least one compound of formula I as the active substance and the use of said compounds or said herbicidal compositions.

R R CNOH VII The process provided by the present invention for the manufacture of the compounds offormula I hereinbefore comprises (a) reacting a salt of an acid of the general formula

wherein R , R4 and R5 have the significance given earlier, with a compound of the general formula R1R2CNOCH2X III wherein R and R have the significance given earlier and X represents a leaving group, or (b) reacting a compound of the general formula

wherein Z represents a leaving group and R and R have the significance given earlier, with a compound of the general formula

wherein R , R4 and R5 have the significance given earlier, or with an alkali metal saltthereof, if necessary in the presence of a base, or (c) reacting a compound of the general formula

wherein R6 represents a lower alkyl, an aryl or a heteroaryl group and R ,R4 and R5 have the significance given earlier, with an oxime of the general formula wherein R and R have the significance given earlier, or with an alkali metal salt thereof in the presence of a base. The alkyl groups containing 1-6 or 1-3 carbon atoms include, unless specified otherwise, straight-chain and branched-chain hydrocarbon groups containing 1-6 or 1-3 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert.butyl and the like. The term "lower alkyl" preferably means an alkyl group containing 1-6 carbon atoms. The alkenyl and alkynyl groups containing 2-6 carbon atoms include unsaturated straight-chain and branched-chain hydrocarbon groups containing 2-6 carbon atoms such as allyl, butenyl, isobutenyl, pentenyl, isopentenyl and the like as well as propargyl, butynyl, isobutynyl, pentynyl and the like. Especially preferred alkynyl groups are 1-propynyl, butynyl and isobutynyl. The term "halogen" includes fluorine, chlorine, bromine and iodine, preferably chlorine, bromine and iodine. The cycloalkane ring preferably contains 4-7 carbon atoms, especially 4-6 carbon atoms. The term "aryl" includes, in particular, phenyl, which may be substituted with 1-3 lower alkyl groups, as well as naphthyl. The lower alkyl groups can be the same or different. Preferred heteroaryl groups are the pyridyl, imidazolyl, thiazolyl and thiophenyl groups. Preferred compounds of formula I are those in which R represents a methyl or ethyl group, those in which R represents a methyl, ethyl or phenyl group, those in which R represents a chlorine atom or a trifluoromethyl group, those in which R4 represents a hydrogen atom and those in which R5 represents a hydrogen atom. The compounds of formula I in which R and R together with the carbon atom to which they are attached form a cycloalkane ring which may be substituted with alkyl are also preferred. Especially preferred compounds of formula I are:

2-[p-(p-chlorophenoxy)phenoxy]-propionicacid [[(isopropylideneamino)oxy]methyl]ester. Examples of other compounds of formula I are:

2-[p-(p-bromophenoxy)phenoxy]-propionicacid [[(isopropylideneamino)oxy]methyl]ester, 2-[p-(p-nitrophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl]ester and lower alkylsubstituted derivatives of the aforementioned cyclopentylideneamino, cyclohexylideneamino and cycloheptylideneamino compounds. Especially preferred are the D-isomers of the compounds of formula I and, consequently, the D-isomers of the aforementioned individually named compounds. In embodiment (a) of the foregoing process for the manufacture of the compounds of formula I, a salt of an acid offormula II is reacted with a compound of formula III. The term "salt of an acid" means, for example, an alkali metal salt such as, for example, the sodium, potassium or lithium salt, an alkaline earth metal salt such as, for example, the magnesium, calcium or barium salt, a salt of an organic base such as, for example, a mono-, di- or trialkylammonium salt or a pyridinium salt, orthe ammonium salt. The leaving group denoted by X in the compounds of formula III is, for example, a chlorine, bromine or iodine atom, a tosyloxy or mesyloxy group, a hydroxyl group in free or esterified form or one of the following groups:

wherein R7, R8 and R9, which can be the same or different, each represent an alkyl group, especially an alkyl group containing 1-6 carbon atoms, or two of R7, R8 and R9 together also form a C4-C7-alkylene group and Y represents an anion (e.g. a chlorine, bromine, iodine, hydroxyl or sulphate anion);

wherein R10 and R", which can be the same or different, each represent an alkyl group, especially an alkyl group containing 1-6 carbon atoms, and Y has the significance given earlier;

wherein R represents a lower alkyl, an aryl or a heteroaryl group and n stands for 1 or 2. The reaction of a salt of an acid of formula II with a compound of formula III is preferably carried out in a suitable inert solvent at about -10[deg]C to 220[deg]C, preferably at room temperature or at an elevated temperature. An especially preferred temperature range lies between 20[deg]C and 70[deg]C. The reaction is carried out, for example, in the presence of an inert solvent such as benzene, toluene, petroleum ether, dimethylformamide, tetrahydrofuran, acetonitrile, N-methyl-2-pyrrolidone, tetramethylurea, dimethoxyethane, diglycol dimethyl ether or hexamethylphosphoric acid triamide. In embodiment (b) of the present process for the manufacture of compounds of formula I, a compound of formula IV is reacted with a compound of formula V or with an alkali metal salt thereof in a manner known per se. The leaving group denoted by Z in compounds of formula IV is, for example, one of the leaving groups already given above for X, or a hydroxyl group activated by reaction with triphenylphosphine and azodicarboxylic acid or an ester thereof, especially azodicarboxylic acid diethyl ester [see, e.g. Bull. Chem. Soc. Japan 46, 2833 (1973) or Angew. Chem. 88,111 (1976)]. The reaction according to embodiment (b) is conveniently carried out in an inert organic solvent such as a hydrocarbon (e.g. benzene ortoluene), an ether (e.g. diethyl ether, tetrahydrofuran or dimethoxyethane) or hexamethylphosphoric acid triamide. The temperature and pressure are not critical, the reaction preferably being carried out at a temperature between -20[deg]C and the reflux temperature of the reaction mixture, preferably between -10[deg]C and 30[deg]C. In embodiment (c) of the present process for the manufacture of compounds offormula I, a compound of formula VI is reacted with an oxime offormula VII in.the presence of a base (e.g. an alkali metal carbonate). In this embodiment, a compound of formula VI can be dissolved in an inert organic solvent such as a chlorinated hydrocarbon (e.g. dichloromethane, chloroform, carbon tetrachloride or trichloroethane), an ether or an ether-like compound (e.g. tetrahydrofuran, diethyl ether, diisopropyl ether, dimethoxyethane or dioxan), an aromatic hydrocarbon (e.g. benzene, toluene or xylene), dimethylformamide, dimethylsulphoxide or hexamethyl-phosphoric acid triamide and thereafter the oxime of formula VII (e.g. in the form of an alkali metal salt) is added.The reaction is generally carried out at a temperature between 0[deg]C and the boiling point of the reaction mixture, preferably at a temperature between 0[deg]C and 50[deg]C. The reaction is normally completed after a short time (e.g. a few minutes). The reaction mixture is conveniently poured into water and extracted with an organic solvent (e.g. ethyl acetate). The residue obtained after evaporation is, if necessary, purified by recrystallisation or chromatography. Formula I includes not only racemic compounds but also optical isomers, since an asymmetric carbon atom is present in the a-position to the carbonyl group. The ester moiety can contain further asymmetric carbon atoms. If desired, the racemic compounds can be separated into dextrorotatory and levorotatory compounds according to known processes. Such processes are described, for example, in Industrial and Engineering Chemistry 60 (8) 12-28. The isomers and the racemic mixtures all possess herbicidal activity, but the extent of this activity is different. The D-isomers have the greatest activity, followed by the racemic mixtures and then the L-isomers.In connection with investigations of this type, it has been found that, for example, in certain experimental procedures the D-isomer of 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(isopropylideneamino)oxy]methyl]ester has a greater activity than the racemic mixture. The isomers can also be manufactured by synthesis from corresponding optically active starting materials. The D-isomers of the compounds offormula I are, as mentioned earlier, especially preferred and, consequently, the corresponding starting materials are also especially preferred. As a result of the nitrogen-carbon double bond in the group of the formula

there are in each case obtained two geometric isomers (when R and R have different significances), these isomers being called the syn- and anti-forms. In certain cases it is possible to isolate such isomers. They also form part of the present invention. The present invention is also concerned with herbicidal compositions which contain as the active ingredient one or more compounds of formula I as defined earlier. These herbicidal compositions conveniently contain at least one of the following inert materials: carrier substances, wetting agents, inert diluents and solvents. The compounds of formula I hereinbefore are especially suitable for controlling weeds, especially slender foxtail (Alopecurus myosuroides) and types of millet such as, for example, cock's foot (Echinochloa crus-galli), great foxtail millet (Setaria faberii) and hair-like millet (Panicum capillare) in cereals, especially barley, oats and wheat, as well as in rice, cotton, soya, sugar beet and vegetable plantations. The compounds of formula I are especially suitable for controlling weeds in sugar beet plantations. Thus, for example 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(isopropylideneamino)oxy]methyl]ester in a concentration of 1.25 kg/ha possesses sufficient activity against weeds without, however, damaging the sugar beet plantations.In general, a concentration of 0.1-6 kg/ha, preferably 0.6-2.0 kg/ha and especially preferably 1-1.5 kg/ha, is sufficient to produce the desired herbicidal effect with the cpmpounds offormula I. When R represents a trifluoromethyl group, the compounds of formula I can only find limited use in cereal growing, since they are somewhat phytotoxic. These compounds are, however, especially suitable for controlling weeds in rice, cotton, soya, sugar beet and vegetable plantations. The compounds of formula I are generally insoluble in water and can be formulated according to any of the methods which are useful for insoluble compounds. When desired, the compounds of formula I can be dissolved in a water-immiscible solvent such as, for example, a high-boiling hydrocarbon, which conveniently contains dissolved emulsifiers, so that it acts as a self-emulsifiable oil upon addition to water. The compounds of formula I can also be mixed with a wetting agent, in the presence or absence of an inert diluent, to form a wettable powder which is soluble or dispersible in water, or they can be mixed with the inert diluents to form a solid or pulverous product. Inert diluents with which the compounds of formula I can be formulated are solid inert media, including pulverous orfinely divided solid substances such as, for example, clays, sands, talc, mica, fertilisers and the like, such products being present either in the form of a dust or as materials having a larger particle size. The wetting agents can be anionic wetting agents such as, for example, soaps, fatty sulphate esters such as dodecyl sodium sulphate, octadecyl sodium sulphate and cetyl sodium sulphate, fatty-aromatic sulphonates, such as alkylbenzenesulphonates or butylnaphthalenesulphonates, more complex fatty sulphonates such as the amide condensation products of oleic acid and N-methyltaurine or the sodium sulphonate of dioctyl succinate. The wetting agents can also be non-ionic wetting agents such as, for example, condensation products of fatty acids, fatty alcohols or fatty substituted phenols with ethylene oxide, fatty acid esters and ethers of sugars or polyvalent alcohols, the products which are obtained from the latter by condensation with ethylene oxide, or the products which are known as block copolymers of ethylene oxide and propylene oxide. The wetting agents can also be cationic wetting agents, such as, for example, cetyltrimethylammonium bromide and the like. The herbicidal compositions provided by the present invention can also be formulated as aerosols, a co-solvent and a wetting agent conveniently being used in addition to the propellant gas, which is suitably a polyhalogenated alkane (e.g. dichlorodi-fluoromethane). The herbicidal compositions provided by the present invention can contain, in addition to compounds of formula I, synergists and other active ingredients (e.g. insecticides, acaricides, bactericides, other herbicides, fungicides, plant growth regulators and fertilisers). Such combination preparations are suitable for increasing the activity or for broadening the spectrum of activity. The compounds of formula i can be used in different proportions in their various fields of application. The herbicidal compositions provided by the present invention can be formulated in a form which is suitable for storage and transport. Such forms can contain, e.g., 2-90 weight percent of one or more compounds of formula I. These forms can then be diluted with similar or different carrier materials to provide concentrations which are suitable for practical use. In ready-for-use herbicidal compositions, there can be present active ingredient concentrations of 0.05-80 weight percent. The active ingredient concentration can, however, also be lower or higher. Depending on the intended use, an active ingredient concentration of 2-8 weight percent or 50-80 weight percent is especially preferred. The starting materials of formulae II, III, IV, V and VII belong to known classes of compounds. The starting materials of formula VI can be prepared by oxidising a compound of the general formula

wherein R , R4, R5 and R6 have the significance given earlier. The oxidation can be carried out, for example, using hydrogen peroxide. The compounds of formulae VI and VIII can be prepared in analogy to the details given in DOS 2 617 804. Thus-obtained racemates can be resolved in the customary manner. The compounds of formulae VI and VIII in which R6 represents a heteroaryl group are novel, i.e. irrespective of whether they are present as racemates or in the form of the optical isomers (e.g. the D-isomers). When R6 in the compounds of formulae VI and VIII represents a lower alkyl group (e.g. a methyl group), an aryl group (e.g. the phenyl group or a halophenyl group), then the corresponding D-isomers are also novel. The aforementioned novel compounds of formulae VI and VIII can be prepared, for example, by reacting the racemate or the D-isomer of a compound of formula II with a compound of the general formula

wherein R6 has the significance given earlier in this paragraph. This reaction can be carried out in a manner known per se, advantageously in an inert organic solvent such as chloroform or dimethyl sulphoxide and in the presence of dicyclohexylcarbodiimide. A thus-obtained compound of formula VIII can then be oxidised, for example with hydrogen peroxide, to give a compound of formula VI. Especially preferred compounds of formulae VI and VIII are: D-2-[p-(p-Bromophenoxy)phenoxy]-propionic acid methylthiomethyl ester, D-2-[p-(p-fluorophenyloxy)phenoxy]-propionic acid methylthiomethyl ester, D-2-[p-(p-nitrophenoxy)phenoxy]-propionic acid methylthiomethyl ester and D-2-[p-(p-trifluoromethylphenoxy)phenoxy]-propionic acid methylthiomethyl ester as well as the corresponding sulphonyl compounds. The aforementioned compounds of formulae VI and VIII, especially the D-isomers thereof, are also valuable as herbicides, since they exhibit a similar spectrum of activity as the compound of formula I. They can therefore be used for the manufacture of herbicidal compositions in the same manner as described earlier for the compounds of formula I. The D-isomers have the advantage that, in comparison to the corresponding racemates, they possess, for example, a lower phytotoxicity on cotton and soya beans. The following Examples illustrate the present invention. I. Manufacture of the compounds of formula /: EXAMPLE 1 36 g of 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester are dissolved in 20 ml of tetrahydrofuran. A mixture of 0.35 g of acetone oxime sodium salt, dissolved in 20 ml of dimethylformamide, is added to this solution and the mixture is stirred at room temperature for 2 minutes. The mixture is poured into water, extracted with ethyl acetate and washed neutral with water. The ethyl acetate is evaporated and the residue is then chromatographed on 100 g of silica gel with hexane/ethyl acetate (8:2). The eluate is evaporated and the residue is recrystallised from ether/hexane. The resulting

76.-77[deg]C. In an analogous manner, From D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and acetone oxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(isopropylideneamino)oxy]methyl]ester; melting point 80[deg]-85[deg]C; [alpha ]22D = +11.62[deg] (c = 1.25% in chloroform); from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl]ester acetophenone oxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(a-methyl-benzylideneamino)oxy]-methyl]ester; melting point 63[deg]-64[deg]C; [alpha ]22D = -13.64[deg] (c = 0.75% in chloroform);from D-2-[p-(p-chlorophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl]ester and acetone oxime sodium salt there is obtained D-2-[p-(p-chlorophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]-methyl]ester; n20D = 1.5480; [alpha ]22D = + 13.58[deg] (c = 1.93% in chloroform); from 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl]ester and acetone oxime sodium salt there is obtained 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]-methyl] ester; n22D = 1.5557. from 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl] ester and acetophenone oxime sodium salt there is obtained 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [[(a-methylbenzylideneamino)oxy]methyl] ester; melting point 66[deg]-67[deg]C; from D-2-[p-(p-bromophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl] ester and acetone oxime sodium salt there is obtained D-2-[p-(p-bromophenoxy)-phenoxy]-propionic acid [[(isopropy-

from D-2-[p-(p-iodophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl] ester and acetone oxime sodium salt there is obtained D-2-[p-(p-iodophenoxy)-phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester; melting point 40[deg]-43[deg]C; [alpha ]22D = +8.60[deg] (c = 0.90% in chloroform);from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and cyclopentanone oxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(cyclopentylideneamino)oxy]methyl] ester; melting point 43[deg]-45[deg]C; [alpha ]22D = +7.52[deg] (c = 2.28% in chloroform); from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and cyclohexanone oxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(cyclohexylideneamino)oxy]methyl] ester; melting point 71[deg]-73[deg]C; [alpha ]22D = +5.55[deg] (c = 1.49% in chloroform);from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and cycloheptanone oxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(cycloheptylideneamino)oxy] methyl] ester; melting point ca 30[deg]C; [alpha ]22D = +6.00[deg] (c = 1.96% in chloroform); from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and 3,3,5-trimethylcyclohexanone oxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-ptolyl)oxy]phenoxy]propionic acid [[(3,3,5-trimethylcyclohexylideneamino)oxy]methyl] ester; n20D = 1.5062; [alpha ]22D = +6.86[deg] (c = 2.73% in chloroform);from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and benzaldoxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(benzylideneamino)oxy]methyl] ester; melting point 65[deg]-66[deg]C; [alpha ]22D = -16.34[deg] (c = 1.60% in chloroform); from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and ethyl methyl ketoxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(sec.butylideneamino)oxy]methyl] ester; melting point 38[deg]-40[deg]C; [alpha ]22D = +10.34[deg] (c = 2.36% in chloroform);from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl] ester and dipentyl ketoxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(1-pentyl-hexylideneamino)oxy]methyl] ester; n20D = 1.4913; [alpha ]22D = +11.71[deg] (c = 3.27% in chloroform); from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [(methylsulphonyl)methyl]ester and methyl (2-methyl-1-propenyl) ketoxime sodium salt there is obtained D-2-[p-[(a,a,a-trifluoro-ptolyl)oxy]phenoxy]propionic acid [[(1,3-dimethyl-2-butenylideneamino)oxy]methyl]ester; melting point 52[deg]54.C; [alpha ]22D = -5.75[deg] (c = 0.78% in chloroform). EXAMPLE 2

dimethylformamide is added dropwise while stirring to a suspension of 1.5 g of 55% sodium hydride dispersion (0.0307 mol) in 20 ml of dimethylformamide. After completion of the addition, the mixture is stirred at room temperature until the hydrogen evolution has stopped. The mixture is stirred for a further 15 minutes and there are added thereto 15 g (0.048 mol) of N-[(isopropylideneamino)oxy]-N-methylpiperidinium iodide and 0.5 g of 15-crown-5 (the polyethylene ether-crown compound with a 15-ring containing 5 oxygen atoms). After stirring at 110[deg]C for 2 hours, the mixture is poured into 500 ml of water and extracted three times with 300 ml of ethyl acetate each time. The ethyl acetate extracts are combined, washed twice with 200 ml of water each time and then evaporated, the residue being subsequently recrystallised from diethyl ether/n-hexane.There are obtained 8.0 g of D-2-[p-[(a,a,a-trifluoro-ptolyl)oxy]phenoxy]propionic acid [[(isopropylideneamino)oxy]-methyl] ester which melts at 85[deg]-86[deg]C; [alpha ]22D = +11.3[deg] (c = 1.2% in chloroform). EXAMPLE 3 1.75 g of L (-)-lactic acid [[(isopropylideneamino)oxy]methyl] ester, 2.65 g of triphenylphosphine and 2.54 g of p-[(a,a,a-trifluoro-p-tolyl)oxy]-phenol are dissolved at 0[deg]C in 10 ml of absolute tetrahydrofuran. 1.75 g of azodicarboxylic acid diethyl ether are added dropwise to the solution while cooling. After completion of the addition, the mixture is stirred for 0.5 hour, then poured into 100 ml of water, extracted twice with 50 ml of water each time, dried over anhydrous sodium sulphate and evaporated. The residue is chromatographed on a 20-fold amount of silica gel with n-hexane/ethyl acetate (4:1) and the eluate is evaporated. The residue is crystallised from diethyl ether/n-hexane and there is obtained D-2-[p-[(a,a,a-trifluoro-p-

+10.9[deg] (c = 1.33% in chloroform). II. Preparation of the starting materials: EXAMPLE 4 100 g (0.03 mol) of 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid and 252 g (3.0 mol) of sodium bicarbonate are suspended in 2.5 litres of dimethyl sulphoxide and thereafter treated slowly with 336.5 ml (3.0 mol) oftert.butyl bromide. The mixture is stirred at room temperature overnight. The mixture, including the separated thick precipitate, is subsequently taken up in 5 litres of ethyl acetate. The ethyl acetate solution is washed twice with 1 litre of water, dried over sodium sulphate and evaporated. The residue is chromatographed on a 10-fold amount of silica gel with hexane/ethyl acetate (7:1) and the eluate is evaporated. There is obtained 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]-phenoxy]propionic acid [(methylthio)methyl] ester in the form of an oil. 40 g (0.096 mol) of 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]-phenoxy]propionic acid [(methylthio)-methyl] ester are dissolved in 120 ml of acetone/water (5:1) and treated slowly with 192 ml of a 30% solution of hydrogen peroxide. 96 ml of ammonium molybdate solution (35.2 g of ammonium molybdate in 96 ml of water) are added dropwise to the mixture which is cooled with an ice-bath. The mixture is stirred at room temperature for 2 hours. It is then extracted several times with ether, the ether extract is washed with sodium dithionite solution and the solution is again washed neutral with eight 100 ml portions of saturated sodium chloride solution and subsequently with five 100 ml portions of water. The mixture is treated with active carbon, filtered and evaporated. The residue is recrystallised from methylene chloride/n-hexane.There is obtained 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [(methylsulphonyl)-methyl] ester which melts at 87.-88[deg]C. In a manner analogous to that described in the first paragraph of this Example, from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionic acid there is obtained D-2-[p-[(a,a,a-trifluorop-tolyl)oxy]phenoxy]-propionic acid [(methylthio)methyl] ester; melting point 47[deg]-48[deg]C; [alpha ]22D = +31.24[deg] (c = 1.58% in chloroform); from D-2-[p-(p-chlorophenoxy)phenoxy]-propionic acid there is obtained D-2-[p-(p-chlorophenoxy)phenoxy]-propionic acid [(methylthio) methyl] ester; melting point 75[deg]C; [alpha ]22D = +50.54[deg] (c = 1.34% in chloroform); from 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid there is obtained 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [(methylthio)methyl] ester; melting point 54[deg]C; from D-2-[p-(p-bromophenoxy)phenoxy]-propionic acid there is obtained 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [(methylthio)methyl] ester;melting point 83[deg]-87[deg]C; [off = +45.52[deg] (c = 1.81% in chloroform); from D-2-[p-(p-iodophenoxy)phenoxy]-propionic acid there is obtained D-2-[p-(p-iodophenoxy)phenoxy]propionic acid [(methylthio)methyl] ester; melting point 71[deg]-74[deg]C; [alpha ]22D = +41.39[deg] (c = 1.43% in chloroform);In a manner analogous to that described in the second paragraph of this Example, from D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [(methylthio)methyl] ester there is obtained D-2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionicacid [(methylsulphonyl)methyl] ester; melting point 79[deg]-82[deg]C; [alpha ]20D = +40.77[deg] (c = 1.66% in chloroform); from 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [(phenylthio)methyl ester there is obtained 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [(phenylsulphonyl)methyl] ester; melting point 89.-92[deg]C; from D-2-[p-(p-chlorophenoxy)phenoxy]-propionic acid [(methylthio)methyl] ester there is obtained D-2-[p-(p-chlorophenoxy)phenoxy]-propionicacid [(methylsulphonyl)methyl] ester; melting point 81[deg]-83[deg]C; [a] = +43.42[deg] (c = 1.02% in chloroform);from 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [(methylthio)methyl] ester there is obtained

from D-2-[p-(p-bromophenoxy)phenoxy]-propionic acid [(methylthio)methyl] ester there is obtained D-2-[p-(p-bromophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl] ester; melting point 84[deg]-87[deg]C; [alpha ]22D = +39.20[deg] (c = 1.43% in chloroform); from D-2-[p-(p-iodophenoxy)phenoxy]-propionic acid [(methylthio)methyl] ester there is obtained D-2-[p(p-iodophenoxy)phenoxy]-propionic acid [(methylsulphonyl)methyl] ester; melting point 121[deg]-123[deg]C; [alpha ]22D= +37.91[deg] (c = 2.66% in chloroform). EXAMPLE 5 153 ml (1.1 mol) of tert.butyl bromide are slowly added dropwise to a suspension of 10 g (0.11 mol) of L (+)-lactic acid and 94.2 g (1.1 mol) of sodium bicarbonate in 200 ml of dimethyl sulphoxide.The mixture is stirred for 48 hours, then poured into 1 litre of water and extracted twice with 100 ml of ethyl acetate each time. The organic phase is back-washed three times with 200 ml of water each time and subsequently evaporated. The crude product is chromatographed on a 20-fold amount of silica gel with n-hexane/ethyl acetate (4:1) and the eluate is evaporated. There are obtained 5.7 g of L (-)-lactic acid [(methylthio)methyl] ester; [alpha ]20D = -39.27[deg] (c = 1.3% in chloroform). The foregoing ester can also be obtained by heating 11.2 g of L (+)-sodium lactate, 0.5 g of 15-crown-5, 9.25 g of chlorodimethyl sulphide and a trace of sodium iodide in 100 ml of absolute acetonitrile at the reflux temperature of the mixture. After 6 hours, the mixture is poured into water and worked-up in the manner described in the preceding paragraph. There are obtained 6.1 g of L (-)-lactic acid [(methylthio)methyl] ester; [ago = -38.5[deg] (c = 0.69% in chloroform). 2.55 g (0.01 mol) of p-[(a,a,a-trifluoro-p-tolyl)-oxy]phenol, 1.5 g (0.01 mol) of L-(-)-lactic acid [(methylthio)methyl] ester and 2.63 g (0.01 mol) of triphenylphosphine are placed in 10 ml of abolute tetrahydrofuran and the mixture is cooled to 0[deg]C. While cooling there is added dropwise 0.011 mol of azodicarboxylic acid diethyl ester, the yellow colour of this ester disappearing during the addition. The mixture is then stirred at room temperature for 30 minutes, poured into 100 ml of water, extracted twice with 50 ml of ethyl acetate each time and the organic phase is washed neutral with water. The ethyl acetate solution is then evaporated, the residue is chromatographed on a 20-fold amount of silica gel with n-hexane/ethyl acetate (9:1) and the eluate is evaporated.After crystallisation from diethyl ether/n-hexane, there are obtained 2.1 g of

[alpha ]20D = +46.87[deg] (c = 0.65% in chloroform). EXAMPLE 6 To 100 ml of 36% formalin at 10[deg]C are added dropwise while cooling 100 ml of piperidine and thereupon 73 g of acetone oxime as well as 75 g of potassium carbonate. The mixture is stirred at room temperature overnight, then taken up in ethyl acetate and the aqueous phase is separated. The organic phase is evaporated, the residue is taken up in acetone and treated dropwise while cooling with 65 ml of methyl iodide, whereafter the product slowly crystallises out. After a further 10 hours, the product is filtered off. There are obtained 291 g of N-[(isopropylideneamino)oxy]-N-methyl-piperidinium iodide; melting point 132.-133[deg]C. EXAMPLE 7 1.1 g of sodium lactate, 3.5 g of N-[(isopropylideneamino)oxy]-N-methyl-piperidinium iodide and 0.1 g of 15-crown-5 in 10 ml of diglycol dimethyl ether are heated at 110[deg]C under nitrogen for 4 hours. The mixture is then poured into 50 ml of water and extracted three times with ethyl acetate. The organic phase is washed four times with water and subsequently evaporated. After chromatography of the residue on a 10-fold amount of silica gel with n-hexane/ethyl acetate (1:1) and evaporation of the eluate, there is obtained 0.35 g of L(-)-lactic acid [[(isopropylideneamino)oxy]methyl] ester; [alpha ]20D = -1.2[deg] (c = 1.50% in chloroform). III. Formulation Examples: EXAMPLE 8 An emulsifiable concentrate is produced by mixing the following ingredients with one another:

This mixture is made up to 1 litre with xylene. EXAMPLE 9 The active ingredient of formula I, for example 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester (compound A in the following Table) is dissolved in acetone to give a 2% solution of active ingredient. Shortly before the beginning of the experiment the solution is diluted with water to provide the desired concentration, which in the present experiment is 312 g/ha. (When an insoluble active ingredient is used, spray powders which contain kaolin as the inert diluent are formulated.) The test plants are sprayed in a greenhouse with the formulated active ingredient, a 16 hours day being simulated by means of mercury vapour lamps. 3 weeks after the spraying the plants are examined for the effects which have occurred; i.e. the % necroses are determined, with 100% necrosis corresponding to a complete destruction of the plant.Solvent effects, as far as present, are compensated by means of the "Abbott formula". The results are compiled in the following Table.

TABLE I (% necrosis)

A = 2-[p-[(a,a,a-Trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester.

TABLE II

TABLE III EXAMPLE 10 % Necrosis in cotton var. Stoneville 7A

Compound A see Example 9

EXAMPLE 11 % Necrosis in soya beans var. Hood

Compound A see Example 9. The notations NMP, Tensiofix B 7425, Phenylsulphonate CA, Shellsol AB and Nonoxynol used in Examples 10 and 11 have the following significance: NMP: N-methyl-2-pyrrolidone. Tensiofix B 7425: Emulsifier consisting of 60 parts of a block polymerisate of ethylene oxide and propylene oxide, 20 parts of the calcium salt of a branched-chain dodecylbenzenesulphonic acid and 20 parts of a

Phenylsulphonate CA: Mixture of 70 parts of the calcium salt of a branched-chain dodecylbenzenesulphonic acid and 30 parts of a solvent mixture of isobutanol and C10-alkyl benzenes. Shellsol AB: Solvent consisting of a mixture of C10-alkylbenzenes. Nonoxynol: Condensation product of nonylphenol and ethylene oxide.

Claims

1. Compounds of the general formula

wherein R represents a hydrogen atom, an alkyl group containing 1-6 carbon atoms or a phenyl group, R represents an alkyl group containing 1-6 carbon atoms, an alkenyl group containing 2-6 carbon atoms, an alkynyl group containing 2-6 carbon atoms or a phenyl group or R and R together with the carbon atom to which they are attached form a cycloalkane ring containing 4-10 carbon atoms which, if desired, can be mono- di- or tri-substituted with alkyl containing 1-3 carbon atoms, R represents a halogen atom or a trifluoromethyl or nitro group and R4 and R5 each represent a hydrogen or halogen atom.

2. Compounds according to claim 1, wherein the cycloalkane ring contains 4-6 carbon atoms.

3. Compounds according to claim 2, wherein R represents a methyl or ethyl group.

4. Compounds according to claim 2 or claim 3, wherein R represents a methyl, ethyl or phenyl group.

5. Compounds according to any one of claims 2 to 4, wherein R represents a chlorine atom or a trifluoromethyl group.

6. Compounds according to any one of claims 2 to 5, wherein R4 represents a hydrogen atom.

7. Compounds according to any one of claims 2-6 wherein R5 represents a hydrogen atom.

8. 2-[p-[(a,a,a-Trifluoro-p-tolyl)oxy]phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester.

9. 2-[p-(p-Chlorophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester.

10. A compound according to claim 2 selected from:

ester, D-2-[p-(p-chlorophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester, 2-[p-(o,p-dichlorophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester,

ester.

11. A compound according to claim 1 selected from: D-2-[p-(p-lodophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester,

butenylideneamino)oxy]methyl] ester.

12. The D-isomers ofthe compounds offormula I given in claim 1.

13. The D-isomers of the compounds of formula I according to any one of claims 2 to 7.

14. A compound or compounds according to any one of claims 1,11 and 12 for the control of weeds.

15. A compound or compounds according to any one of claims 2 to 10 and 13 for the control of weeds.

16. A herbicidal composition which contains an effective amount of at least one compound of the general formula

wherein R represents a hydrogen atom, an alkyl group containing 1-6 carbon atoms or a phenyl group, R represents an alkyl group containing 1-6 carbon atoms, an alkenyl group containing 2-6 carbon atoms, an alkynyl group containing 2-6 carbon atoms or a phenyl group or R and R together with the carbon atom to which they are attached form a cycloalkane ring containing 4-10 carbon atoms which, if desired, can be mono-, di- ortri-substituted with alkyl containing 1-3 carbon atoms, R represents a halogen atom or a trifluoromethyl or nitro group and R4 and R5 each represent a hydrogen or halogen atom, and inert carrier material.

17. A herbicidal composition according to claim 16, wherein the cycloalkane ring contains 4-6 carbon atoms.

18. A herbicidal composition according to claim 17 which contains an effective amount of 2-[p-[(a,a,atrifluoro-p-tolyl)oxy]phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester.

19. A herbicidal composition according to claim 17 which contains an effective amount of 2-[p-(pchlorophenoxy)phenoxy]-propionic acid [[(isopropylideneamino)oxy]methyl] ester.

20. A herbicidal composition according to claim 16, wherein the D-isomers are used as the compound or compounds of formula I.

21. A herbicidal composition according to any one of claims 17 to 19, wherein the D-isomers are used as the compound or compounds of formula I.

22. A process for the manufacture of compounds of the general formula

wherein R represents a hydrogen atom, an alkyl group containing 1-6 carbon atoms or a phenyl group, R represents an alkyl group containing 1-6 carbon atoms, an alkenyl group containing 2-6 carbon atoms, an alkynyl group containing 2-6 carbon atoms or a phenyl group or R and R together with the carbon atom to which they are attached form a cycloalkane ring containing 4-10 carbon atoms which, if desired, can be mono-, di- ortri-substituted with alkyl containing 1-3 carbon atoms, R represents a halogen atom or a trifluoromethyl or nitro group and R4 and R5 each represent a hydrogen or halogen atom, which process comprises (a) reacting a salt of an acid of the general formula

wherein R , R4 and R5 have the significance given earlier in this claim, with a compound of the general formula R R CNOCH2X III wherein R and R have the significance given earlier in this claim and X represents a leaving group, or (b) reacting a compound of the general formula

wherein Z represents a leaving group and R and R have the significance given earlier in this claim, with a compound of the general formula

wherein R , R4 and R5 have the significance given earlier in this claim or with an alkali metal saltthereof, or (c) reacting a compound of the general formula

wherein R6 represents a lower alkyl, an aryl or a heteroaryl group and R , R4 and R5 have the significance given earlier in this claim, with a compound of the general formula R R CNOH VII wherein R and R have the significance given earlier in this claim, or with an alkali metal salt thereof in the presence of a base.

23. A process according to claim 22, wherein the cycloalkane ring contains 4-6 carbon atoms and X and Z each represent a chlorine, bromine or iodine atom or a mesyloxy ortosyloxy group.

24. A process according to claim 23 for the manufacture of 2-[p-[(a,a,a-trifluoro-p-tolyl)oxy]phenoxy]propionic acid [[(isopropylideneamino)oxy]methyl] ester, wherein 2-[p-[(a,a,a-trifluoro-ptolyl)oxy]phenoxy]-propionic acid [(methylsulphonyl)methyl] ester is reacted with acetone oxime sodium salt.

25. A process according to claim 22 wherein the D-isomer of the starting material of formula VI is used.

26. A process according to claim 23 or claim 24, wherein the D-isomer of the starting material of formula VI is used.

27. A method for the control of weeds, which method comprises treating the locus to be protected against weeds and/or the weeds with an effective amount of a compound set forth in any one of claims 1, 11 and 12 or of a herbicidal composition set forth in claim 16 or claim 20.

28. A method for the control of weeds, which method comprises treating the locus to be protected against weeds and/or the weeds with an effective amount of a compound set forth in any one of claims 2 to 10 and 13 or of a herbicidal composition set forth in any one of claims 17, 18 and 19.

29. The use of a compound set forth in claim 1, claim 11 or claim 12 or of a herbicidal composition set forth in claim 16 or claim 20 for the control of weeds.

30. The use of a compound set forth in any one of claims 2 to 10 and 13 or of a herbicidal composition set forth in claim 17, claim 18 or claim 19 forthe control of weeds.

31. A compound of formula I according to claim 1, whenever produced by a process according to anyone of claims 22 to 26 or by an obvious chemical equivalent thereof.

32. A herbicidal composition according to claim 16, substantially as described herein with reference to any one of Examples 8 to 11.

33. A process according to claim 22, substantially as described herein with reference to any one of Examples 1 to 3.