GB2224732A - Oxadiazolidine herbicides - Google Patents

Abstract

Oxadiazolidine compounds having the general formula I: <IMAGE> wherein R<1> represents an alkyl group; R<2> represents an alkyl, formyl, alkylcarbonylalkyl or alkoxycarbonylalkyl group, or a group of formula -CH2-R<3> wherein R<3> represents an alkenyl or alkynyl group; and each of Y and Y<1> independently represents a halogen atom, have herbicidal activity.

Description

OXADIAZOLIDINE HERBICIDES This invention relates to certain oxadiazolidine compounds and their preparation, herbicidal compositions containing these compounds, and their use in combating undesired plant growth.

The preparation of 2-alkyl- and 2-cycloalkyl-4 phenyl-3 , 5-dioxo-l, 2, 4-oxadiazolidines is described by Zinner, Archiv der Pharmazie 294, 765, (1961) and 296, 420 (1963). However no use is mentioned therein for these compounds.

From UK Patent No. 1,168,721 it is known that oxadiazolidine compounds having the general formula:

in which X denotes halogen or a nitro, trifluoromethyl, methyl or methoxy group, or a substituted or unsubstituted phenoxy group or a substituted or unsubstituted methylsulfonyl group, n denotes one of the integers 1 to 3 and R denotes an aliphatic radical which may be substituted by halogen or methoxy or a benzyl, acetyl, carboxymethyl or cyclohexyl radical are active as herbicides. In UK Patent No. 1,168,721 there are specifically disclosed compounds wherein n is 1 or 2. When n is 2, examples are given wherein (X) n is m,p-dichloro, m-chloro-p-methyl, p-bromo-m-chloro and m,p-dibromo.

US Patent No. 4,088,472 contains claims which are directed to use in controlling the growth of vegetation of compounds of the above formula wherein Xn corresponds to Cln and Xm where n is O to 3 and m is 0 or 1, X is alkyl of up to carbon atoms, alkoxy of up to 4 carbon atoms or nitro, and R is alkyl of up to 4 carbon atoms, and the corresponding 3-thiono compounds, and to use in destroying undesired vegetation of compounds of the above formula wherein R is lower alkyl, each X is independently selected from the group consisting of lower alkyl, lower alkoxy, nitro and halogen, and n is O to 4, and the corresponding 3-thiono compounds.In the examples, the only 3,5-dioxo-1,2,4-oxadiazolidine wherein n is greater than 1 is 2-methyl-4- (3', 4 '-dichlorophenyl) - 3, 5-dioxo-1, 2, 4-oxadiazolidine, which may alternatively be named 2-methyl-4-(3,4-dichloro phenyl)-1,2,4-oxadiazolidine-3,5-dione.

Belgian Patent No. 703,985 discloses the herbicidal use of compounds of formula

wherein R and R1 are always different from one another and are independently selected from C14 alkyl, C58 cycloalkyl, methyl-C5 8 cycloalkyl, chloro-C5~8 cycloalkyl, methoxy-C5~8 cycloalkyl, C6 g(cycloalkylmethyl), C58 cycloalkenyl or a moiety

wherein X is selected from chlorine, bromine, iodine and C1 4 alkyl moieties, Z is selected from hydrogen, nitro, C1 4 alkoxy, trifluoromethoxy, chlorine, bromine and fluorine moieties, t is an integer from 1 to 4 and N is oxygen or sulfur, provided that R is not an alkyl group when R1 is an alkyl group and R is not an aryl group when R1 is an aryl group.Various methods for preparing these compounds are also disclosed. There are 272 compounds which are specifically named in Belgian Patent No. 703,985, but the following compounds appear to be the most preferred ones, since they are specifically named in the Claims thereof:2-methyl-4- (3 , 4-dichlorophenyl) -1,2, 4-oxadiazolidine- 3, 5-dione, 2-methyl-4-(p-chlorophenyl)-1,2,4-oxadiazolidine-3,5- dione, 2-methyl-4- (o-fluorophenyl) -1,2, 4-oxadiazolidine-3 '5- dione, 2-methyl-4- (2,4, 5-trichlorophenyl) -1,2, 4-oxadiazo- lidine-3,5-dione, 2-methyl-4-(4-methoxyphenyl)-1,2,4-oxadiazolidine-3, 5-dione, 2-methyl-4-(4-bromophenyl)-1,2,4-oxadiazolidine-3,5- dione, 2-methyl-4-(m-trifluoromethylphenyl)-1,2,4-oxadiazolidine-3,5-dione, 2-methyl-4- (p-isopropylphenyi) -1,2, 4-oxadiazolidine- 3 ,5-dione, 2-(3,4-dichlorophenyl) -4-methyl-l,2,4-oxadiazolidine- 3, 5-dione, 2-(p-chlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5- dione, 2-(o-fluorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5dione, 2-(2,4,5-trichlorophenyl)-4-methyl-1,2,4-oxadiazolid- ine-3,5-dione, 2-(4-methoxyphenyl)-4-methyl-1,2,4-oxadiazolidine-3, 5-dione, 2-(4-bromophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5- dione, 2-(m-trifluoromethylphenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione, and 2-(p-isopropylphenyl)-4-methyl-1,2,4-oxadiazolidine3,5-dione.

Example 16 of Belgian Patent No. 703,985 is 2-methyl-4-(2-fluoro-4-chlorophenyl)-1,2,4-oxadiazolidine-3,5-dione.

It has now unexpectedly been found that a novel group of oxadiazolidine compounds exhibit a valuable level of herbicidal activity.

Accordingly, the present invention provides oxadiazolidine compounds having the general formula I:

R1 represents an alkyl group; R2 wherein represents an alkyl, formyl, alkylcarbonylalkyl or alkoxycarbonylalkyl group, or a group of formula -CH2-R wherein R represents an alkenyl or alkynyl group; and each of Y and y independently represents a halogen atom.

Alkyl groups preferably have 1 to 12 carbon atoms, especially 1 to 6 carbon atoms, while alkenyl and alkynyl groups preferably have 2 to 12 carbon atoms, especially 2 to 6 carbon atoms. Alkoxy groups preferably have 1 to 10 carbon atoms, especially 1 to 4 carbon atoms. The terms alkyl, alkenyl and alkynyl refer to both straight chain and branched groups.

R1 in formula I preferably represents a C16 alkyl group, especially methyl.

R2 preferably represents a C 1-6 alkyl or (C1-4 alkoxy)carbonyl(C1 4 alkyl) group, or a group of 3 formula -CH2-R in which R represents a C26 alkenyl or C2-6 alkynyl group. Preferred compounds are those in which R represents a methyl, l-ethoxycarbonylethyl or 2-propynyl group.

The moiety Y is preferably a chlorine atom.

Preferred compounds are those in which yl represents a fluorine atom.

It will be appreciated that compounds in which the group represented by R1 or R2 include asymmetric carbon atoms, the compounds of formula I will exist in different sterioisomeric forms. The scope of the present invention includes all the various isomeric forms of the compounds of formula I and their mixtures and further includes herbicidal compositions containing the active ingredient in such isomeric forms and mixtures.

The present invention also provides a process for the preparation of an oxadiazolidine compound of formula I as defined above which comprises reacting a compound of general formula II:

wherein R , Y and y are as herein before defined, R4 represents an alkyl group, and Z represents a leaving group, with a cyclising agent to give an oxadiazolidine compound of formula I wherein R2 is an alkyl group, optionally followed by converting the resulting product of formula I wherein R2is an alkyl group into a further compound of formula I wherein R2 is a formyl, alkylcarbonylalkyl or alkoxycarbonylalkyl group, or a group of formula -CH2-R wherein R represents an alkenyl or alkynyl group.

The leaving group represented by Z may suitably be, for example, a halogen atom, preferably chlorine, an alkoxy group, such as ethoxy, or a chlorinated alkyl group, for example trichloromethyl.

The cyclising agent may conveniently be a base, preferably sodium hydroxide in aqueous solution.

Other bases that may suitably be used for this reaction include other alkali metal hydroxides, for example potassium hydroxide, alkaline earth metal hydroxides, for example magnesium hydroxide, alkali metal or alkaline earth metal hydrides, such as sodium hydride or calcium hydride, or an alkali metal alkoxide, for example sodium methoxide.

This reaction is conveniently carried out in a suitable solvent. For example, when the cyclising agent is an alkali metal or alkaline earth metal hydroxide, the solvent is preferably water.

Alternative solvents that may be used include alcohols, for example ethanol. The reaction may be performed at a temperature in the range from O'C to 50"C, preferably o.C.

The compounds of formula I in which R2 is R4 may be converted to other compounds of formula I by methods known to persons skilled in the art.

Treatment of the compound of formula I in which R2is an alkyl group with a Lewis acid, for example boron tribromide, in a suitable solvent, for example methylene chloride, yields a compound corresponding to formula I in which R2 is replaced by a hydrogen atom. Alternative solvents that may be used for this reaction include chloroform and carbon tetrachloride.

Suitable Lewis acids also include aluminium trichloride and boron trifluoride etherate. This reaction may conveniently be effected by mixing the reagents together at a temperature in the range from o-C and 40 C, typically at a temperature of lOC.

The compound corresponding to formula I in which R2 is is replaced by a hydrogen atom may also be prepared by treating the compound of formula I in which R2 is an alkyl group with a mineral acid, for example hydrochloric acid or hydrobromic acid, in a suitable solvent, for example acetic acid.

Alternatively, the conversion may be performed under neutral conditions, for example by treating the compound of formula I in which R2 is an alkyl group with iodotrimethylsilane in a solvent such as acetonitrile.

The compounds corresponding to formula I in which R2 is replaced by a hydrogen atom, although exhibiting herbicidal activity themselves as described below, are useful as intermediates and may be used to prepare other compounds of formula I by further reacting them with a compound of formula R2 ~ zl, wherein R2 is as hereinbefore defined, and is zl represents a leaving group, in the presence of a base, for example an alkali metal carbonate. This preparation is conveniently performed in a suitable solvent, for example acetonitrile or acetone.

Preferably, the base is potassium carbonate.

However, alternative bases that may also be employed include lithium carbonate and sodium carbonate.

Suitable leaving groups for the compounds of formula R2 ~ Z include halogen atoms, for example iodine and, especially, bromine, and sulfonic ester groups, for example tosyl and mesyl groups. This reaction may be performed at a temperature in the range from 0 C to the reflux temperature of the reaction mixture, conveniently at reflux temperature.

Compounds of formula II may be prepared by reacting the corresponding compound of general formula III:

wherein R1, R4, Y and yl are as herein before defined, with a compound of formula Z-CO-Z , in which 2 Z is as hereinbefore defined and Z represents a leaving group. Z may suitably be a halogen atom, preferably chlorine, an alkoxy group, for example ethoxy, or a chlorinated alkyl group, for example trichloromethyl. Preferred compounds are phosgene, for which Z and Z1 both represent a chlorine atom, and ethyl chloroformate, for which one of Z or Z is a chlorine atom and the other is an ethoxy group.

The reaction is preferably performed in a suitable solvent, for example water, an alcohol, such as ethanol, or a mixture of water and ethanol.

Compounds of formula III may conveniently be used to prepare corresponding compounds of formula I by treating the compound of formula III with both a 2 compound of formula Z-C0-Z as described above and a cyclising agent, for example a base, preferably sodium hydroxide in aqueous solution, in a single stage. This preparation may be performed at a temperature in the range from 0 C to 50 C, preferably O"C.

Compounds of formula III may be prepared by methods well known to persons skilled in the art by reacting corresponding isocyanates of general formula IV:

wherein R4, Y and yl are as hereinbefore defined, with a N-alkyl hydroxylamine of general formula R1-NH-OH wherein R1is as defined above. The reaction is preferably carried out in a suitable sblvent, for example dioxane, in the presence of a base, for example sodium hydroxide in aqueous solution. This preparation may be performed at a temperature in the range from 0C to 75 C, .donveniently at ambient temperature, for example -about 20"C. Alternative solvents that may be employed for this reaction include tetrahydrofuran, benzene, chloroform and ether.Suitable bases for use in this reaction include other alkali metal hydroxides, for example potassium hydroxide, and alkali metal alkoxides, such as sodium methoxide.

Isocyanate compounds of formula IV may be prepared from a substituted benzene compound of general formula V.

wherein R4, Y and yl are as hereinbefore defined, by methods well known in the art. For example, the compound of formula V may be reacted with trichloromethyl chloroformate in a suitable solvent, for example dioxane, tetrahydrofuran or chloroform.

Alternative reagents for this reaction include phosgene. The reaction may be performed at a temperature in the range from 10'C to the reflux temperature of the reaction mixture. Preferably the reaction mixture is heated under reflux.

Compounds of formula I have been found to have interesting and valuable activity as herbicides.

Accordingly, the present invention also provides a herbicidal composition comprising a compound of formula I as defined above, in association with at least one carrier.

The present invention also provides the use of such a compound or composition according to this invention as a herbicide.

Further, in accordance with the present 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 this invention. Application to the locus may be pre-emergence or post-emergence. The dosage of the active ingredient used may be, for example, in the range 0.01 kg/ha to 10kg/ha, preferably 0.01 kg/ha to 4 kg/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 95% 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, montmorillonites 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 surfaceactive agents include 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; fatty acid esters of glycerol, sorbitol, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or 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 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 -10% w of active ingredient. Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676 - 0.152 mm), 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 nod 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, 2-20t 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, 0.1-10% w of suspending agents such as protective colloids and thixotropic agents, 0-10% 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 present invention will be further understood from the following Examples.

Example 1.

2-Methyl-4- (2-fluoro-4-chloro-5-methoxyphenyl) -1,2,4- oxadiazolidine-3 ,5-dione a) Trichloromethyl chloroformate (5.4 ml, 0.044 mol) was added to 2-fluoro-4-chloro-5-methoxy aniline (3.5g, 0.02 mol) in dry dioxane (50ml) and the resulting mixture was heated under reflux for 4 hours. The mixture, containing the required product 2-fluoro-4-chloro-5-methoxy phenylisocyanate, was allowed to cool and used directly in the next stage of the synthesis.

b) N-methyl hydroxylamine hydrochloride (1.7g, 0.02 mol) was mixed with water (2ml) and dioxane (l0ml). A solution of sodium hydroxide (0.8g, 0.02mol) in water (1 ml) was added dropwise and the resulting mixture was stirred at ambient temperature (200C) for about 1 hour. The product mixture of a) was cooled to O'C and added dropwise and the resulting mixture was then stirred overnight at ambient temperature (20"C). The solvent was removed and the residue was added to a mixture of water and ethyl acetate and the mixture was stirred. The two phases of the mixture were allowed to separate.

The organic phase of this mixture was removed and the aqueous phase was extracted with ethyl acetate (4 x 100ml). The organic phase and the extracts were combined, washed with water (35ml) and dried using sodium sulphate.

Chromatographic purification of the mixture on a silica column eluted with ethyl acetate yielded the product, N-methyl-N hydroxy-N'-(2-fluoro-4 chloro-5-methoxyphenyl) urea, as the second main fraction eluted from the column in a yield of 3.3g, (66.5%) m.pt. 158 to 159 C.

c) The product of b) (0.5g, 0.002 mol) was dissolved in 2M aqueous sodium hydroxide solution (1 ml, 0.002mol). The solution was cooled to 0C. Ethyl chloroformate (0.22g, 0.16ml) was added and the resulting mixture was stirred for 5 hours. The mixture was neutralised by addition of 2M hydrochloric acid and the resulting mixture was extracted with ethyl acetate (3 x 20ml). The extracts were combined, washed with water (2 x 20ml) and dried over sodium sulphate. The remaining mixture was chromatographically purified on a silica column, using methylene chloride as eluent. The product, 2-methyl-4-(2-fluoro-4-chloro-5 methoxyphenyl)- 1,2,4-oxadiazolidine-3,5-dione, was collected as the first fraction eluted from the column.The product was obtained as a white solid in a yield of 0.364 g (66%), m.pt. 140"C.

Example 2 2 MethYl-4-(2-fluoro-4-chloro-5-(l-ethoxYcarbonY ethoxyphenyl) -1,2, 4-oxadiazolidine-3 , 5-dione a) The product of Example 1 (0.7, 0.0026 mol) was dissolved in dry methylene chloride (lOml) and the solution was cooled to 10 C. A 1M solution of boron tribromide in methylene chloride (9ml) was added dropwise with stirring and the resulting mixture was further stirred overnight.

The mixture was carefully quenched with water and the solvent was then removed using a rotary evaporator. The residue was extracted with ethylacetate (4 x 2Oml). The extracts were combined, washed with water (3pml) and dried using sodium sulphate. Finally, the solvent was removed to leave the product, 2-methyl-4-(2 fluoro-4-chloro-5-hydroxyphenyl) -1,2, 4-oxadiazo- lidine-3,5-dione, as a pale orange oil. The oil solidified to give the product as a white solid in a yield of 0.65g (96%), m.p.t. 133 to 135'C.

b) The product of a) (1.0g, 0.0038 mol) and anhydrous potassium carbonate (l.lg, 0.008mol) were dissolved in dry acetonitrile (2Oml).

Ethyl-2-bromopropionate (0.8g, 0.0045mol) was added and the resulting mixture was heated under reflux for 3 hours. The solvent was then evaporated off under reduced pressure. Water was added to the residue and the mixture was extracted with chloroform (3 x 50ml). The extracts were combined, washed with water (3Oml) and dried using sodium sulphate. The product, 2-methyl-4- (2-fluoro-4 -chloro-5- (1-ethoxycarbo- nylethoxyphenyl) -1,2, 4-oxadiazolidine-3 '5- dione, was obtained by chromatographic purification on a silica column as a straw coloured oil in a yield of 1.37g (99%).

N.M.R. spectral data for the product was obtained by QE 300 Spectrometer at 300 MHz using CDC13 as solvent.

NMR results: 7.35 doublet (lH); 6.9 doublet (lH); 4.7 quartet (lH); 4.2 complex multiplet (2H); 3.5 singlet (3H); 1.65 doublet (3H); 1.25 triplet (3H); Example 3 2-MethYl-4-(2-fluoro-4-chloro-5-(2-ProPynoxy)phenyl) 1,2,4-oxadiazolidine-3,5-dione The product of Example 2 a) (l.Og, 0.0038mol) and anhydrous potassium carbonate (1.0g, 0.008 mol) were dissolved in dry acetonitrile (20ml). An 80% w/w solution of l-bromo-2-propyne in toluene (0.75ml) was added to the solution and the resulting mixture was heated under reflux for 3 hours. The solvent was removed and the residue was added to a mixture of water and ether. The resulting mixture was stirred and the two phases were then allowed to separate.

The organic phase was removed and the aqueous phase was extracted with ether (4 x 30ml). The organic phase and the extracts were combined, washed with water (30ml) and dried using sodium sulphate. The solvent was removed and the product, 2-methyl-4-(2 fluoro-4-chloro-5- (2-propynoxy)phenyl) -1,2, 4-oxadia- zolidine-3,5-dione, was obtained by triturating the residue with hexane as a pale brown solid in a yield of 0.8g, (70%) m.pt 136 to l380C.

Example 4 biological data - Pre-Emergence Tests The herbicidal activity of compounds according to the present invention was compared with the compound 2-methyl-4- (2-fluoro-4-chlorophenyl) -1,2,4- oxadiazolidine-3,5-dione specifically named in Example 16 of Belgian Patent No. 703 985 (hereinafter designated compound A), and the compound 2-methyl-4-(2-fluoro-4-chloro-5-hydroxyphenyl)-1,2,4oxadiazolidine-3,5-dione prepared as an intermediate in Example 2 above (hereinafter designated compound B). The tests were conducted using as a representative range of plants: maize, Zea mays (Mz); rice, Oryza sativa (R); barnyard grass, Echinochloa crusqalli (BG); oat, Avena sativa (0); linseed, Linum usitatissimum (L); sugar beet, Beta vulgaris (SB) and soya bean, Glycine max (S).

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 sown. 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-155n. 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 600 litres per hectare. Untreated sown soil was used as a control.

The herbicidal effects of the test compounds were assessed visually twelve days after spraying 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 results of the pre-emergence tests are set out in Table 1 in which the compounds of the present invention are identified by reference to the preceding Examples.

Table 1 Pre-Emergence Tests

Dosage Compound kg/ha MZ R BG O L SB S Ex. 1 5 8 7 8 7 4 9 4 1 5 2 7 4 0 9 2 Ex. 3 5 8 6 9 7 8 9 3 1 7 1 4 3 2 9 0 A 5 6 5 8 5 3 8 0 1 1 0 4 1 0 2 0 B 1 5 0 0 0 1 0 8 0 1 0 0 0 0 0 6 0 Example 5 Biological Data - Post-Emergence Tests The post-emergence herbicidal activity of compounds according to the invention was tested and compared with that of the compounds designated A and B above.

The post-emergence tests involved two types of test, viz., soil drench and foliar spray tests. The soil drench tests were conducted using as a representative range of plants: maize, Zea mays (Mz); rice, Oryza sativa (R); barnyard grass, Echinochloa crusgalli (BG); and sugar beet, Beta vulgaris (SB).

The Foliar spray tests were conducted using as a representative range of plants: linseed, Linum usitatissimum (L); mustard, Sinapsis alba (M); soya bean, Glycine max (S), in addition to the aforementioned species.

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 alkylphenyl/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 5kg or lkg of active material per hectare in a volume equivalent to 600 litres per hectare in the foliar spray tests, 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. Untreated soil bearing seedling plants was used as a control.

The herbicidal effects of the test compounds were assessed visually twelve days after spraying the foliage and thirteen days after drenching the soil.

The results were recorded on the 0-9 scale discussed in Example 4.

The results of the post-emergence tests are set out in Table 2 in which the compounds of the present invention are identified by reference to the preceding Examples.

Table 2 Post-Emergence Tests

Soil drench Foliar spray (10/kg/ha) Dosage Compound Mz R BG SB kg/ha Mz R BGL M SB S Ex. 1 9 9 9 9 5 5 6 9 8 8 9 9 1 3 2 8 3 6 8 8 Ex. 2 8 8 8 5 5 7 6 9 9 9 9 4 1 5 3 6 7 6 7 2 Ex. 3 9 8 9 9 5 5 7 9 9 9 9 9 1 4 4 9 8 7 9 8 A 8 7 8 9 5 3 3 9 7 9 9 8 1 1 2 6 4 7 9 6 B O 0 4 7 5 2 0 2 7 3 9 1 1 1 0 1 2 1 8 0

Claims (13)

1. CLAIMS 1. An oxadiazolidine compound of the general formula I:

   wherein R1 represents an alkyl group; R2 represents an alkyl, formyl, alkylcarbonylalkyl or alkoxycarbonylalkyl group, 3 or a group of formula -CH2-R wherein R3 represents an alkenyl or alkynyl group; and each of Y and yl independently represents a halogen atom.
2. 2. A compound according to claim 1, wherein R1 represents a C16 alkyl group.
3. 3. A compound according to claim 1 or 2, wherein R2 represents a C16 alkyl, or (C1 4alkoxy)carbonyl(C1 4 alkyl) group or a group of formula -CH2-R wherein R represents a C26 alkenyl or C2 6alkynyl group.
4. 4. A compound according to claim 3, wherein R2 represents a methyl,l-ethoxycarbonylethyl or 2-propynyl group.
5. 5. A compound according to any preceeding claim, wherein Y represents a chlorine atom.
6. 6. A compound according to any preceding claim, wherein yl represents a fluorine atom.
7. 7. A compound according to claim 1 as described in any one of Examples 1 to 3.
8. 8. A process for the preparation of a compound of formula I as defined in any of the preceding claims, comprising reacting a compound of general formula II:

   wherein R1, Y and yl are as defined in any of the preceding claims, R4 represents an alkyl group, and Z represents a leaving group, with a cyclising agent, to give an oxadiazolidine compound of formula I wherein R2 is an alkyl group; optionally followed by converting the resulting product of formula I wherein R is an alkyl group into a compound of formula I wherein R2 is a formyl, alkylcarbonylalkyl or alkoxycarbonylalkyl group, or a group of formula -CH2-R wherein R represents an alkenyl or alkynyl group.
9. 9. A process according to claim 8 substantially as hereinbefore described with reference to any one of Examples 1 to 3.
10. 10. A compound of formula I when prepared by a process according to claim 8 or 9.
11. 11. A herbicidal composition comprising a compound of formula I as defined in any one of claims 1 to 7 or claim 10, in association with at least one carrier.
12. 12. Use of a compound according to any one of claims 1 to 7 a claim 10 or of a composition according to claim 11 in combating undesired plant growth.
13. 13. A method of combating undesired plant growth at a locus by treating the locus with a compound of formula I as defined in any one of claims 1 to 7 or claim 10 or a composition as defined in claim 11.