GB1602046A - Herbicidal a-fluorophenylacetic acid derivatives and their use - Google Patents

Description

(54) HERBICIDAL sz -FLUOROPHENYLACETIC ACID DERIVATIVES AND THEIR USE (71) We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., a company organised under the laws of The Netherlands, of 30 Carel van Bylandtlaan, The Hague, The Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of eradicating and controlling weeds using an a-fluorophenylacetic acid derivative, to compositions containing such derivatives, to novel e:-fluorophenylacetic acid derivatives and to a novel process for the preparation of such derivatives.

The invention provides a method of eradicating and controlling weeds which comprises applying to the weeds or their habitat a herbicidally effective amount of an afluorophenylacetic acid derivative of formula:

wherein each X independently represents a halogen atom or an alkyl group; n=O, 1, 2 or 3; and R represents a hydroxyl or an alkoxy group or a group of formula -NR1R2 in which each of R1 and R2 independently represents a hydrogen atom or an alkyl or aralkyl group, or an aryl group optionally substituted by one or more halogen atoms and/or alkyl groups.

The preferred la-fluorophenylacetic acid derivatives for use in the method according to the present invention are compounds of formula I wherein each X represents a halogen atom, preferably a chlorine atom, or an alkyl group of up to 4 carbon atoms; n=O, 1 or 2; and R represents a hydroxyl group, an alkoxy group containing 1 to 4 carbon atoms, for example a methoxy or ethoxy group, or a group of formula -NR1R2 in which each of R1 and R2 independently represents a hydrogen atom or an alkyl group of 1 to 4 carbon atoms, for example a methyl group, or an aralkyl group of up to 10 carbon atoms, for example a benzyl group, or an aryl group, for example a phenyl group, optionally substituted by up to 2 halogen atoms, preferably fluorine or chlorine atoms, or up to 2 alkyl groups.

Particularly preferred in the method according to the invention are those afluorophenylacetic acid derivatives of formula I in which n=O or, when n=2, each X represents a chlorine atom, in particular a 2,4-dichloro-substituent; and R represents a hydroxyl or a methoxy or ethoxy group or an amino or a phenylamino group or a 4-fluorophenylamino, a 3,4-dichlorophenylamino or a 3-chloro-4-fluorophenylamino group.

The invention also provides herbicidal compositions comprising a carrier or a surface active agent, or a carrier and a surface active agent and as active ingredient at least one a-fluorophenylaceflc acid derivative of formula I as defined above, provided that R in formula I may represent an ethoxy group only when X is halogen and n is 1, 2 or 3, and that, when R represents -NR'R2, any aralkyl group represented by R1 and/or R2 is an arylmethyl group.

Apart from a few compounds of formula I above which have been fortuitously disclosed previously, the Applicants believe that these a-fluorophenoxyacetic acid derivatives are novel. Accordingly the invention further provides novel cr-fludro- phenoxyacetic acid derivatives of formula I, as defined above in relation to the herbicidal compositions, provided that, when X is alkyl or 3,4-dichloro, R is not an ethoxy or hydroxyl group, and when n=O, R is not a hydroxyl, an ethoxy, an amino or a dimethylamino group.

The er-fluorophenylacetic acid derivatives of formula I may be prepared by processes known in the art. For example compounds of formula I wherein R represents a hydroxyl or an alkoxy group and X and n are as defined above may be prepared by a process which comprises reacting a compound of formula II:

wherein X, and n are as defined above and R represents an alkoxy group, with a suitable fluoride, for example potassium fluoride, according to the method described in J.C.S. (C) (1967) 528. The reaction takes place under anhydrous or substantially anhydrous conditions.

The n-fluorophenylacetic acid acid ester may subsequently be converted into the corresponding acid by alkaline hydrolysis and acidification.

An advantageous method believed to be novel, has been found to effect replacement of an -bromo atom by an a-fluoro atom which comprises reacting a compound of formula II with an alkali metal or alkaline earth metal fluoride in a solvent in the presence of a crown ether under substantially anhydrous conditions. Crown ethers are as defined in Synthesis, (168-184) (1976). Preferred crown ethers are those selected from the class of macrocyclic polyethers of the type (-CH2-CH2-O) wherein n is preferably from 4 to 8. A preferred process involves refluxing a compound of formula II with potassium fluoride in acetonitrile containing 18-crown-6.

Those compounds of formula I wherein R represents a group of formula -NR1R2 and X, n, R1 and R2 have the meanings defined above can be prepared by reacting a compound of formula III:-

with an appropriate amino compound of formula

wherein X, n, Rt and R2 have the meanings defined above. The reaction is carried out in a preferably dry hydrocarbon solvent for example dry benzene or toluene and takes place at room temperature.

The term carrier' as used herein means a material, which may be inorganic or organic and of synthetic or natural origin, with which the active compound is mixed or formulated to facilitate its application to the plant, seed, soil or other object to be treated, or its storage, transport or handling. The carrier may be a solid or a liquid.

Any of the materials usually applied in formulating pesticides, herbicides or fungicides may be used as carrier.

Suitable solid carriers are natural and synthetic clays and silicates for example natural silicas such as diatomacious earths; magnesium silicates, for example, talcs; magnesium aluminium silicates, for example, attapulgites and vermiculites; aluminium silicates, for example, kaolinites, montmorillonites and micas; calcium carbonates; calcium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example, carbon and sulphur; natural and synthetic resins, for example, coumarone resins, polyvinyl chloride and styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes, for example, beeswax, paraffin wax, and chlorinated mineral waxes; and solid fertilisers, for example, superphosphates.

Suitable liquid carriers are water, alcohols, for example, isopropanol and glycols; ketones, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers, aromatic hydrocarbons, for example, benzene, toluene and xylene; petroleum fractions, for example, kerosine and light mineral oils; chlorinated hydrocarbons, for example, carbon tetrachloride, including liquefied, normally vaporous, gaseous compounds. Mixtures of different liquids are often suitable.

The surface-active agent may be an emulsifying agent or a dispersing agent or a wetting agent; it may be nonionic or ionic. Any of the surface-active agents usually applied in formulating pesticides, herbicides or fungicides may be used. Examples of suitable surface-active agents are the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation products of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; partial esters of the above fatty acids with glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of alkyl phenols for example p-octylphenol or p-octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates of these condensation products; alkali or alkaline earth metal salts, preferably sodium salts, of sulphuric or sulphonic acid esters containing at least 10 carbon atoms in the mole- cule, for example, sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as sodium dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders are usually compounded to contain 25, 50 or 75% w of toxicant and usually contain, in addition, to solid carrier, 310% w of a dispersing agent and, where necessary, 010% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usually containing 10% w of toxicant. Granules are usually prepared to have a size between 10 and 100 BS mesh (1.67v0.152 mm), and may be manufactured by agglomeration or impregnation techniques. Generally, granules will contain -25% w toxicant and 0-25% w of additives such as stabilisers, slow release modifiers and binding agents.

Emulsifiable concentrates usually contain, in addition to the solvent, and when necessary, co-solvent, 10-50% w/v toxicant, 2-20% w/v emulsifiers and 0-20% w/v of appropriate additives such as stabilisers, penetrants and corrosion inhibitors.

Suspension concentrates are compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 10-75% w toxicant, 0.515% w of dispersing agents, 0.110% w of suspending agents such as protective colloids and thixotropic agents, S10% w of appropriate additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and as carrier, water or an organic liquid in which the toxicant is substantially insoluble; certain organic solids or inorganic salts may be dissolved in the carrier to assist in preventing sedimentation or as an antifreeze agents for water.

Aqueous dispersions and emulsions, for example, compositions obtained by diluting a wettable powder or a concentrate according to the invention with water, also lie within the scope of the present invention. The said emulsions may be of the waterin-oil or of the oil-in-water type, and may have a thick 'mayonnaise'-like consistency.

The compositions of the invention may also contain other ingredients, for example, other compounds possessing pesticidal, herbicidal or fungicidal properties.

The invention is further illustrated by the following examples.

Example 1.

Preparation of Ethyl α-fluoro-2,4-dichlorophenylacetate.

Dried potassium fluoride (1.0 g, .017M) was added to 18-crown-6 (0.5 g, .02M) dissolved in dry acetonitrile (20 ml) and the mixture stirred vigorously at room temperature for 30 minutes. A solution of ethyl α-bromo-2,4-dichlorophenylacetate (5.3 g, .017M) in dry acetonitrile (10 ml) was added and the mixture refluxed with stirring for 16 hours. The reaction mixture was poured into water, extracted with diethyl ether and the combined ether extracts washed with water and dried over magnesium sulphate. Removal of ether gave a pale yellow oil which was distilled to give the desired product as a colourless oil b.p. 113-1150C at 1 mm. Yield 65%.

Analysis Calculated for CloH9FCl202: C 47.8; H 3.6% Found : C 47.7; H 3.6% Example 2.

Preparation of a-Fluoro-2,4-dichlorophenylacetic acid.

Ethyl a-fluoro-2,4-dichlorophenylacetate (5.0 g, .02M), prepared as described in Example 1, and 2N sodium hydroxide (150 ml) were refluxed for 30 minutes. The reaction mixture was cooled and extracted with diethyl ether. The aqueous layer was acidified with concentrated hydrochloric acid, followed by ether extraction. The combined ether extracts were washed with water and dried over magnesium sulphate. The solvent was evaporated to give the desired product as a colourless solid m.p.

143-145 C. Yield 90%.

Analysis Calculated for C8H5FCl2O2: C 43.0; H 2.2% Found : C 42.6; H 2.4% Example 3.

Preparation of N-phenyl-a-fluorophenylacetamide. a-Fluorophenylacetic acid (6.2 g, .04M) and thionyl chloride (14 ml) were refluxed for 1 hour and excess thionyl chloride then removed. The product, a-fluorophenylacetyl chloride was not isolated, but dissolved in dry benzene (30 ml). 8 ml of this solution (containing 1.6 g, .lM of acid chloride) was then added slowly to a cooled solution of aniline (1.0 g, .OlM) in benzene (8 ml) and the mixture stirred at room temperature for 30 minutes. The solvent was evaporated and the residue crystallised from aqueous isopropanol to give the desired product as a colourless solid. m.p. 98-1000C. Yield 66%.

Analysis Calculated for Cl4Hl2NOF: C 73.4; H 5.2; N 6.1% Found : C 73.1; H 5.3; N 6.1% Example 4.

Preparation of N-(3,4-dichlorophenyl) - a - fluorophenylacetamide.

A solution of a-fluorophenylacetyl chloride, prepared as in the previous example (1.0 g,.006M) in dry benzene (5 ml) was added slowly to an ice-cooled stirred solution of 3,4-dichloroaniline (1.1 g, .007M) in benzene (5 ml). The mixture was stirred for 30 minutes at room temperature. The reaction mixture was filtered and the solid collected and crystallised from aqueous ethanol to give the desired product as a white solid m.p. 10e-1020C. Yield 70%.

Analysis Calculated for CD14HloNOCl2F: C 56.4; H 3.4; N 4.7% Found : C 56.0; H 3.4; N 4.7% Examples 5-13.

Following procedures similar to those given in Examples 1-4 further compounds were prepared which are described and characterised in Table I.

TABLE I

ZcNm OOpz PI\D sa;a;odod v;v; M.p. or Ex.No. X B.P. m m yield Analysis -NH 5H 1n r 2 Calculated for ) O u, m 9.2 Found 62.5 5.3 \D t t vD \0 (S CS 00 or 6 XD aD Calculated for CaH1cN0F: 64.7 6.0 8.4 Found 65.0 6.0 8.3 7 Q -NHCH2 Calculated for C1aH14NOF: 74.1 5.8 5.8 L c a a p a a a $ 8 S S d cd Ld (d d aag "1 aad-a a 8 ? 8 8 o* "Y. Q O Lr, b u a e, > E m t ai u U gUd E o U aa I AX X 1 C) CC c: Z : : N l l I Z Z l Z X m t-~ OD CX O 23 H TABLE I (contd)

Z qO oovi 6e ma 4 1; C?r? mm mvi Nc U rlOFic? Orl 8 m m or Ex.No. X R B.p.0C %yield Analysis Lr, Ej f zero 45 Calculated 3:0 ;^ r o o ~-ct3 for : o U U 5.4 a 13 2,4-diCi Ct 92-940C 78 Calculated for C14H aNOCl4F 45.8 2.2 3.8 e t o Found 45.7 2.2 3.5 L tS xle Wt I Z l x :C = t Z x H cs Example 14.

Demonstration of Herbicidal Activity.

To evaluate their herbicidal activity, the compounds of the invention were tested using as a representative range of plants:-- maize, Zea mays (MZ); rice, Oryza sativa (R); barnyard grass, Echinchloa crus-galli (BG); oat, Avena sativa (0); linseed, linum usitatissimum (L); mustard, Sinapsis alba (M); sugar beet, Beta vulgaris (SB); and soya bean, Glycine max (S).

The tests fall into two categories, pre-emergence and post-emergence. The preemergence tests involved spraying a liquid formulation of the compound to be tested onto the soil in which seeds of the plant species mentioned above had recently been sown. The post-emergence tests involved two types of test, viz. soil drench and foliar spray tests. In the soil drench tests the soil in which seedling plants of the above species were growing, was drenched with a liquid formulation containing a compound of the invention, and in the foliar spray tests the seedling plants were sprayed with such a formulation.

The soil used in the tests was a steam sterilised, modified John Innes Compost mixture in which half the peat, by loose bulk, had been replaced by vermiculite.

The formulation used in the tests were prepared by diluting with water solution of the compounds in acetone containing 0.4% by weight of an alkylphenyl/ethylene oxide condensate available under the trade name Triton X-155 ("TRITON" is a Registered Trade Mark). In the soil spray and foliar spray tests the acetone solution were diluted with an equal volume of water and the resulting formulation applied at two dosage levels corresponding to 5 and 1 kilogram of active material per hectare respectively in a volume equivalent to 400 litres per hectare. In the soil drench tests one volume of the acetone solution was diluted to 155 volumes with water and the resulting formulation applied at one dosage level equivalent to 10 kilograms of active material per hectare in a volume equivalent to approximately 3,000 litres per hectare.

The herbicidal effects of the compounds were assessed visually seven days after spraying the foliage and drenching the soil and eleven days after spraying the soil, and were recorded on a > 9 scale. A rating 0 indicates no effect on the treated plants, a rating 2 indicates a reduction in fresh weight of stem and leaf of the plants of approximately 25%, a rating 5 indicates a reduction of approximately 55%, a rating 9 indicates a reduction of 95%.

The results of the tests are set out in Table II.

TABLE II

Phytotoxicity Rating (0-9) Post-Emergence (Plants) Seeds Soil drench Foliar spray Pre-Emergence Example Dose Dose No.

Kg/ha MZ R BG O L M SB S Kg/ha MZ R BG O L M SB S MZ R BG O L M SB S 1 10 0 6 6 6 7 8 9 9 5 6 7 9 5 9 9 9 9 6 8 7 7 8 9 9 9 1 0 0 2 0 7 9 9 8 0 8 4 3 7 9 9 8 2 10 0 7 6 5 6 8 9 9 5 6 7 9 7 9 9 9 9 6 8 7 7 8 9 9 9 1 3 4 5 4 5 8 9 8 1 7 4 2 6 8 9 7 3 10 1 0 3 1 5 8 6 5 5 3 0 8 8 9 9 9 7 0 5 7 0 3 8 8 5 1 2 0 6 2 5 9 6 5 0 4 5 0 1 6 5 0 4 10 0 0 0 0 3 4 7 5 5 5 5 6 4 7 9 9 8 0 0 3 0 3 9 7 3 1 0 3 2 3 3 9 8 6 0 0 0 0 0 6 2 0 5 10 0 0 0 0 6 5 7 5 5 0 0 2 2 6 7 7 7 5 8 6 4 7 7 8 8 1 0 0 0 0 4 3 5 5 2 6 2 0 3 5 5 5 9 10 0 2 6 6 5 8 8 8 5 - - - - - - - - - - - - - - - 1 0 0 0 3 5 6 6 6 0 0 0 0 5 3 0 4 10 10 0 0 0 0 3 8 5 4 5 - - - - - - - - - - - - - - - 1 0 0 0 0 0 6 4 4 0 0 0 0 0 6 6 5 11 10 0 2 0 2 3 6 4 6 5 - - - - - - - - - - - - - - - 1 0 2 5 2 4 9 7 7 0 0 6 0 0 7 1 0 12 10 0 4 6 4 6 7 8 7 5 0 0 5 4 8 6 6 2 2 7 7 6 7 7 8 8 1 0 0 0 0 3 2 1 4 0 5 3 1 0 0 0 5 - Not tested.

Claims (14)

WHAT WE CLAIM IS:

1. A method of eradicating and controlling weeds which comprises applying to the weeds or their habitat a herbicidally effective amount of an a-fluorophenylacetic acid derivative of formula:

wherein each X independently represents a halogen atom or an alkyl group; n 1, 2 or 3; and R represents a hydroxyl or an alkoxy group or a group of formula -NR1R2 in which each of R1 and R2 independently represents a hydrogen atom, or an alkyl or aralkyl group, or an aryl group optionally substituted by one or more halogen atoms and/or alkyl groups.

2. A method as claimed in claim 1 wherein the wr-fluorophenylacetic acid derivative is a compound of formula I in which each X independently represents a halogen atom or an alkyl group of up to 4 carbon atoms; n=O, 1 or 2; and R represents a hydroxyl group, an alkoxy group containing 1 to 4 carbon atoms, or a group of formula --NR1R2 in which each of R1 and R2 independently represents a hydrogen atom or an alkyl group of 1 to 4 carbon atoms or an aralkyl group of up to 10 carbon atoms, or an aryl group optionally substituted by up to 2 halogen atoms or up to 2 alkyl groups.

3. A method as claimed in claim 1 or 2 wherein the a-fluorophenylacetic acid derivative is a compound of formula I in which each X represents a chlorine atom or an alkyl group.

4. A method as claimed in claim 1, 2 or 3 wherein the a-fluorophenylacetic acid derivative is a compound of formula I in which R represents a hydroxyl, methoxy or ethoxy group or a group of formula -NR1R2 in which each of R1 and R2 independently represents a hydrogen atom, a methyl or benzyl group, or a phenyl group optionally substituted by up to 2 fluorine and/or chlorine atoms or by up to two alkyl groups.

5. A method as claimed in claim 2, 3 or 4 wherein n=0 or, when n=2, each X represents a chlorine atom; and R represents a hydroxyl or a methoxy or ethoxy group or an amino or a phenylamino group or a 4-fluorophenylamino, a 3,4-dichlorophenylamino or a 3-chloro-4-fluorophenylamino group.

6. A method as claimed in any of the preceding claims wherein X represents a 2,4-dichloro substituent

7. A method as claimed in claim 1 and as described hereinbefore, with specific reference to Example 14.

8. A herbicidal composition comprising a carrier or a surface active agent, or a carrier and a surface active agent and as active ingredient at least one a-fluorophenylacetic acid derivative of formula I in claim 1 and as defined in any of the preceding claims, provided that R in formula I may represent an ethoxy group only when X is halogen and n is 1, 2 or 3 and that when R represents ,NR1R2 any aralkyl group represented by R1 and/or R2 is an arylmethyl group.

9. A composition as claimed in claim 8 and as described herein with specific reference to Example 14.

10. An a-fluorophenylacetic acid derivative of formula I in claim 1 as defined in claim 8, provided that, when X is an alkyl group or a 3,4-dichloro substituent, R is not an ethoxy or hydroxyl group, and when n=0, R is not a hydroxyl, an amino, or a dimethylamino group.

11. An ,xz-fluorophenylacetic acid derivative as claimed in claim 10, and described herein with specific reference to any one of the Examples except Examples 3, 5, 8 and 9 and 14.

12. A process for the preparation of compounds having the formula I wherein n, X and R have the meanings as defined in claim 1, which comprises the step of reacting a compound of formula II

wherein X, and n are as defined above and R represents an alkoxy group, with an alkali metal or alkaline earth metal fluoride, in a solvent, in the presence of a crown ether, under substantially anhydrous conditions.

13. A process as claimed in claim 12 which comprises refluxing a compound of formula II with potassium fluoride in acetonitrile containing 18-crown-6.

14. Compounds having the general formula I, wherein n, X and R are as defined in claim 1, whenever prepared according to a process as claimed in claim 12 or 13.