GB2199577A - Herbicidal diphenyl ether compounds - Google Patents

Abstract

The invention relates to herbicidal compounds of the general formula I, <IMAGE> in which A<1> represents a hydrogen or halogen atom or an alkyl or haloalkyl group, and each of A<2> and A<3> independently represents a hydrogen or halogen atom or an alkyl, haloalkyl, nitro or cyano group; each of R<1> and R<2> independently represents a hydrogen atom or an alkyl group which is unsubstituted or substituted by one or more moieties selected from halogen atoms and cyano groups, and groups of formula SR<3>, S(O)R<3>, S(O)2R<3>, OR<3>, COR<3> and COOR<3> in which R<3> represents a hydrogen atom or an optionally substituted alkyl or phenyl group; and n represents 1 or 2; and their use and preparation.

Description

DIPHENYL ETHER COMPOUNDS The invention relates to certain diphenyl ether compounds, the preparation of such compounds, herbicidal compositions containing. them, and to their use in combating undesired plant growth.

Various diphenyl ethers are known to be effective herbicides, for example bifenox and diclofop as described respectively in UK Patents Nos. 1232368 and 1423006. It has now been found that useful herbicidal activity is present in certain diphenyl ethers carrying a substituted thiazine ring.

Accordingly, the present invention provides diphenyl ether compounds of the general formula I

in which A1 represents a hydrogen or halogen atom or an alkyl or haloalkyl group, and each of A2 and A3 independently represents a hydrogen or halogen atan or an alkyl, haloalkyl, nitro or cyano group; each of R1 and R2 independently represents a hydrogen atom or an alkyl group which is unsubstituted or substituted by one or more moieties selected from halogen atoms and cyano groups, and groups of formula SR , S(O)R , S(O)2R , -OR , COR and COOR in which R represents a hydrogen atom or an optionally substituted alkyl or phenyl group; and n represents 1 or 2.

Generally, when any of the above mentioned moieties represents an (optionally substituted) alkyl group this alkyl group may be linear or branched and may suitably 1 to 6, preferably 1 to 4 carbon atoms, especially methyl.

When any groups are designated as being optionally substituted, the substituent groups which are optionally present may be any of those customarily employed in the development of pesticidal compounds, and/or the modification of such compounds to influence their structure/activity, persistence, penetration or other property. In relation to alkyl groups, specific examples of such substituents include halogen atoms and nitro, cyano, hydroxyl, C14 alkyl, C14 haloalkyl, C14 alkoxy, C14 haloalkoxy and (C1 4 alkoxy)carbonyl groups. It is preferred, however, that any alkyl moieties in compounds of formula I are unsubstituted.In relation to a phenyl moiety, optional substituents include halogen atoms, and nitro, cyano, amino, hydroxyl, C1-4 alkyl, C1-4 haloalkyl (especially CF3) and C1-4 alkoxy groups. 1 to 3 substituents may suitably be employed.

Halogen atoms are preferably fluorine, chlorine or bromine.

Preferably A1 is a haloalkyl, especially trifluoranethyl, group, A2 is a halogen, especially chlorine, atom or a nitro or cyano group and A3, is a halogen, especially chlorine atom or, more preferably, a hydrogne atom.

Preferably, each of R and R independently represents a hydrogen atom or a C14 alkyl group, most preferably a hydrogen atom or a methyl group. Preferably, R1 and R2 are identical.

Preferably, n represents 1.

It will be appreciated that compounds of formula I may exist in isomeric form; isomers fall within the scope of this invention. As is well knawn, it is frequently the case that one isamer will have greater biological activity than another isaner.

The invention also provides a process for the preparation of a compound of formula I. The process according to the invention comprises reacting a compound of formula II with a compound of formula III

where Q represents a halogen atom or a nitro group or a group of formula -QM where M represents a hydrogen or alkali metal atom or a group of formula

and R1 and R2 are as defined above; and, when the product is a compound in which Q does not represent a group of formula

reacting that product with a compound of formula IV

in which compound W represents a halogen atom or a nitro group when Q represents a group -CM and W represents such a group -a4 when Q represents a halogen atom or a nitro group; and optionally converting the product of the preceding step(s) into a further compound of formula I.

Preferably the reaction of compounds of formulae II and III takes place at an elevated temperature, for example 40 to 125 C, suitably at the reflux temperature. An inert organic solvent is not required but may optionally be added. Benzene is preferred.

The reaction preferably takes place in an inert atmosphere, suitably nitrogen.

The compound of formula II is suitably generated by reaction of a compound of formula V

with thionyl chloride, at an elevated temperature, for example 40-1250C, suitably at the reflux temperature. An inert organic solvent, for example benzene, is preferably present.

When the above reactions are effected to make compounds in which Q is other than a group

that is to say, compounds in which one of W and Q represents a halogen, suitably chlorine, atom or nitro group and the other represents a group of formula -QM where M represents a hydrogen atom or alkali metal atom, it is preferably the moiety Q which represents the halogen atom or nitro group.The reaction is conveniently carried out by reacting a compound of formula II wherein Q represents a halogen, suitably chlorine, atom or a nitro group with an alkali metal alkoxide compound produced by reacting the product of the above defined reaction in which product W represents hydroxy, with an alkali metal hydroxide. The reaction of the alkoxide with the compound III is preferably carried out in a suitable solvent, for example, dimethyl sulphoxide, sulpholane, dimethyl formamide, or dimethyl acetamide at elevated temperature, conveniently under reflux, and also under an inert atmosphere such as nitrogen.

It is Preferred, however, to effect the above reactions with starting materials in which Q represents a group

so that a further step to produce compounds of formula I is not required.

Compounds of formula V are known, for example from GE-A-2157679. Compounds of formula III are known or readily derivable by standard/analogous techniques. Compounds of formula III wherein R2 and h are both alkyl groups may, in order to produce compounds in which R2 and R3 are substituted alkyl groups, be halogenated. Standard reaction conditions for halogenation reactions may be employed, for example using reagents such as N-bromosuccinimide (NBS), N-chlorosuccinimide or bromine. Preferred conditions employ NBS in a halogenated hydrocarbon, for example carbon tetrachloride, at an elevated temperature, for example 500C to the reflux temperature, and preferably at the reflux temperature.

The thus-halogenated diene precursor may then be reacted with a nucleophile so that a halogen atom is replaced by a cyano group or a group of formula -SR3, -OR3, as defined above. Where there is more than one halogen atom, one or more halogen atoms is so replaced, (depending on the quantity of the nucleophile employed). Any halogen atoms which remain after the reaction with the nucleophile may be retained, and so be present in the final compound of formula I, or may be replaced in further nucleophilic reaction(s).

Standard reaction conditions may be employed for reaction with a nucleophile. Thus, the reaction preferably takes place in polar aprotic solvent, for example tetrahydrofuran, acetonitrile or dimethylformamide, at an elevated temperature, suitably 500C to the reflux temperature, preferably the latter.

Alternatively such techniques may be carried out not on the compound of formula III but on compounds of formula I.

A compound of formula I wherein a group Q contains a group 9 of formula -SOR9 or -SO2R9 is preferably prepared by oxidation of the diester precursor, containing a group -SR9. Various oxidising agents can be used, for example hydrogen peroxide and peracids, suitably peroxycarboxylic acids such as metachloroperbenzoic acid. The reaction preferably takes place in the range 10 to 300C, conveniently at ambient temperature. A low boiling-point solvent, suitably a halogenated lower alkane such as dichlorsmethane, is preferably present. These conditions may also be employed to prepare a compound of formula I wherein n is 2, from a compound of formula I in which n is 1.

A cyano group may be readily converted to a group of formula COOR3 by hydrolysis optionally followed by esterification, or to an acyl group -COR3 by a Grignard reaction.

The compounds of general formula I have been found to show interesting activity as herbicides. Accordingly, the invention further provides a herbicidal composition comprising a compound of formula I as defined above in association with at least one carrier, and a method of making such a composition which comprises bringing a compound of formula I into association with at least one carrier.

The invention also provides the use of such a compound or composition according to the invention as a herbicide. Further, in accordance with the invention there is provided a method of combating undesired plant growth at a locus by treating the locus with a compound or composition according to the invention.

Application to the locus may be pre-emergence or post-emergence.

The dosage of active ingredient used may, for example, be from 0.01 to 10 kg/ha, suitably 0.05 to 4kg/ha. A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated which may for example be a plant, seed or soil, or to facilitate storage, transport or handling. A carrier may be a solid or a liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in formulating herbicidal compositions may be used. Preferably compositions according to the invention contain 0.5 to 958 by weight of active ingredient.

Suitable solid carriers include natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for example talcs; magnesium aluminium silicates, for example attapulgites and vermiculites; aluminium silicates, for example kaolinites, montomorillonites and micas; calcium carbonate, calcium sulphate; ammonium 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; and solid fertilisers, for example superphosphates.

Suitable liquid carriers include water; alcohols, for example isopropanol and glycols; ketones, for example acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic or araliphatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosine and light mineral oils; chlorinated hydrocarbons, for example carbon tetrachloride, perchloroethylene and trichloroethane. Mixtures of different liquids are often suitable.

Agricultural compositions are often formulated and transported in a concentrated form which is subsequently diluted by the user before application. The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution. Thus preferably at least one carrier in a composition according to the invention is a surface-active agent. For example the composition may contain at least two carriers, at least one of which is a surface-active agent.

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surface-active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example E octylphenol or E poctylcresol, 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 molecule, for example sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders usually contain 25, 50 or 75% w of active ingredient and usually contain in addition to solid inert carrier, 3-10% w of a dispersing agent and, where necessary, 0-10% 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 -10g w of active ingredient.Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676 0.152 mum), and may be manufactured by agglomeration or impregnation techniques. Generally, granules will contain -75% w active ingredient and 0-10% w of additives such as stabilisers, surfactants, slow release modifiers and binding agents. The so-called "dry flowable powders" consist of relatively small granules having a relatively high concentration of active ingredient. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 10-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 10-75% w active ingredient, 0.5-158 w of dispersing agents, 0.1-108 w of suspending agents such as protective colloids and thixotropic agents, 0-108 w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as anti-freeze 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 invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, and may have a thick 'mayonnaise'-like consistency.

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

The invention is illustrated in the following Examples.

Example 1 Preparation of (2-chloro-4-trifluoromethylphenoxy)-3-(4,5-dimethyl-1,2- thiazine-S-oxide)-4-nitrobenzene (A1 -CF3; A2=C1; A3=H; n=1; R=R=CH3) (a) 3-(2-Chloro-4-(trifluoromethylphenoxy)-6-nitro aniline (3g) was dissolved in benzene (40ml), and thionyl chloride (l.lg) in benzene (10ml) was added dropwise at roam temperature. The reaction mixture was refluxed for 4 hours. The solvent was removed by evaporation. Petroleum ether (40-60, 100ml) was added to the residue and filtered, and the solvent was evaporated from the filtrate leaving 5- (2-chloro- 4-tri fluoromethylphenoxy) -2-nitro-N-sulphinyl aniline as an orange oil (2.6g) which was used directly in the next step.

(b) The product of preceding step (a) was added to excess 2,3-dimethyl-1,3-butadiene (25ml) and the reaction mixture refluxed overnight. Evaporation of solvent gave an orange oil which solidified. Recrystallisation from hexane/ethylacetate gave the title compound as yellow crystals (1.7g, mp 128-1310C) Analysis Calculated: 49.5%C 3.5%H 6.1%N Found: 49.7%C 3.4%H 6.4%N Examples 2 to 5 Following procedures similar to those described above, the further compounds presented in Table I below were prepared. In the Table, the compounds are identified by reference to the substituents in the general formula I:

TABLE I Ex. No.A R R MP CHN Analayis ( C) (Calculated) (Found) 2 Cl H CH3 85-87 48.4%C 3.1%H 6.3%N 48.3%C 3.7%H 5.9%N 3 CN CH3 CH3 182-183 53.2%C 3.5%H 9.3%N 53.2%C 3.6%H 9.6%N 4 NO2 CH3 CH3 161-162 48.4%C 3.4%H 8.9%N 48.4%C 3.7%H 9.2%N 5 Cl H H 169-170 47.2%C 2.8%H 6.5%N 47.4%C 2.8%H 6.8%N Example 6 Herbicidal Activity To evaluate their herbicidal activity, compounds according to the invention were tested using as representative range of plants: maize, Zea mays (Mz); rice, Oryza sativa (R); barnyard grass, Echinochloa crusgalli (BG); oat, Avena sativa (0); linseed, Linum usitatissisum (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 pre-emergence tests involved spraying a liquid formulation of the compound onto the soil in which the seeds of the plant species mentioned above had recently been sawn. 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 the 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 prepared horticultural loam.

The formulations used in the tests were prepared from solutions of the test compounds in acetone containing 0.4% by weight of an alkylphenol/ethylene oxide condensate available under the trade mark TRITON X-155. These acetone solutions were diluted with water and the resulting formulations applied at dosage levels corresponding to 5 kg or 1 kg of active material per hectare in a volume equivalent to 900 litres per hectare in the soil spray and foliar spray test, and at a dosage of level equivalent to 10 kilograms of active material per hectare in a volume equivalent to approximately 3,000 litres per hectare in the soil drench tests.

In the pre-errergence tests untreated sown soil and in the post-emergence tests untreated soil bearing seedling plants were used as controls.

The herbicidal effects of the test compounds were assessed visually twelve days after spraying the foliage and the soil, and thirteen days after drenching the soil and were recorded on a 0-9 scale. A rating 0 indicates growth as untreated control, a rating 9 indicates death. An increase of 1 unit on the linear scale approximates to a 10% increase in the level of effect.

The symbol '-' indicates that testing was not effected.

The results of the tests are set out in Table I below. TABLE 2 Compound of Soil drench 10/kg/ha Dosage Foliar spray Pre-emergence Ex. No. 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 4 0 0 3 7 6 6 0 5 7 6 8 8 9 9 9 7 4 2 7 7 8 8 9 0 1 7 6 6 6 9 9 9 7 2 2 5 5 6 7 9 0 2 0 0 0 5 4 7 6 4 5 6 4 8 7 9 9 9 8 3 0 6 4 9 7 8 0 1 3 2 3 5 8 9 7 6 0 0 2 1 6 5 6 0 3 0 0 0 0 2 2 3 0 5 3 2 6 4 6 6 4 3 0 0 2 2 4 3 4 3 1 0 0 4 1 4 5 3 2 0 0 1 1 3 2 2 2 4 0 0 0 0 0 0 0 0 5 3 2 6 2 6 6 5 3 0 0 2 0 2 5 7 2 1 1 1 4 2 6 5 4 3 0 0 0 0 2 3 7 0 5 0 2 6 4 7 7 6 3 5 6 6 3 8 9 9 9 8 3 4 9 7 8 9 9 7 1 4 4 7 6 9 8 8 6 1 1 7 4 8 9 9 0

Claims (11)

1. CLAIMS 1. A compound of the general formula I

   in which A represents a hydrogen or halogen atom or an alkyl or haloalkyl group, and each of A2 and A3 independently represents a hydrogen or halogen atom or an alkyl, haloalkyl, nitro or cyano group, each of R and R independently represents a hydrogen atom or an alkyl group which is unsubstituted or substituted by one or more moieties selected from halogen atoms and cyano groups, and groups of formula SR , S(O)R , S(O)2R , OR , COR and COOR in which R represents a hydrogen atom or an optionally substituted alkyl or phenyl group; and n represents 1 or 2.
2. 2. A compound according to claim 1 wherein A represents a haloalkyl group, A represents a halogen atom or a nitro or cyano group and A3 represents a hydrogen or halogen atom.
3. 3. A compound according to claim 2 wherein A represents trifluoromethyl group, A2 represents a chlorine atom and A3 represents a hydrogen atom.
4. 4. A compound according to any preceding claim wherein each of R1 and R2 independently represents a hydrogen atom or a C14alkyl group.
5. 5. A compound of formula I, as named herein or substantially as herein described with reference to the Examples.
6. 6. A process for the preparation of a compound of formula I, as claimed in any preceding claim, which comprises reacting a compound of formula II with a compound of formula III

   where Q represents a halogen atom or a nitro group or a group of formula -OM where M represents a hydrogen or alkali metal atom or a group of formula

   and R and R are as defined above, and, when the product is a compound in which Q does not represent a group of formula

   reacting said compound with a compound of formula IV

   in which compound W represents a halogen atom or a nitro group when Q represents a group -CM and W represents such a group -QM when Q represents a halogen atom or a nitro group; and optionally converting the product of the preceding step(s) into a further compound of formula I.
7. 7. A process substantially as hereinbefore described with reference to the Examples.
8. 8. A compound of formula I produced by a process as claimed in 6 or 7.
9. 9. A herbicidal composition comprising a compound of formula I as defined in any one of claims 1 to 5, or in claim 8, with at least one carrier.
10. 10. The use of a compound according to claim 1 to 5, or 8, or of a composition according to claim 9, as a herbicide.
11. 11. A method of combating undesired plant growth at a locus by treating the locus with a compound of formula I as defined in any of claims 1 to 5, or 8, or a composition according to claim 9.