FIELD OF THE INVENTION

This invention relates to novel nitrone derivatives, compositions containing them, processes and intermediates for their preparation, and their use as herbicides. BACKGROUND ART Tikhonov and Volodatsku, Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk. volume 3, pages 144- 147, (1979) describe the preparation of 3-(N- benzylideneamino)-2-methyl-l-phenyl-l-propanone N-oxide, 3-(N-benzylideneamino)-1-methyl-l- propanone N-oxide, 3-(N-benzylideneamino)-1,2- dimethyl-1-propanone N-oxide, and 2-(N- benzylideneaminomethyl)-3,4-dihydro-l(2H) naphthalenone. Russian patent application number 390073 discloses the preparation of 3-(N- benzylideneamino)-1-phenyl-l-propanone N-oxide as a pharmaceutical intermediate. Tikhonov, Sedova, Volodarskii and amaev, Khim. Get. Soedin volume 4, pages 526-529 (1981) specifically discloses the preparation of 3-(N- benzylideneamino)-l-phenyl-1-butanone N-oxide. Japanese patent application number 6,923,322 discloses the preparation of 3-N-(5-nitro-2- furylideneamino)-l-(2-carboxyphenyl)-1-propanone N-oxide useful as an antibiotic or food preservative. Tikhonov and Volodarskii describe in Izv. Akad. Nauk SSSR, Ser. Khim. (10), 2372, 3-(N-benzylideneamino)-l,3-dimethylbutan-l-one N-oxide. Tikhonov and Volodarskii describe in Zh. Org. Khim. 9(4), 770 (1973), 3-(N- benzylideneamino)-l-methylbutan-1-one N-oxide. None of these publications therefore disclose or suggest using the above-mentioned compounds as pesticides, much less herbicides.

DESCRIPTION OF THE INVENTION

The present invention provides nitrone derivatives of formula (I) :

(I) wherein: R ¹ represents:-

-(CH ) _m -(phenyl optionally substituted by one or more groups R ⁸ which may be the same or different) ; or pyridyl, furyl or thienyl optionally substituted by one or more groups selected from R ⁹ , -S(0) _n R ⁹ and halogen; or a group R ⁹ ;

R ² represents hydrogen;

R ³ is selected from hydrogen, R ⁹ , cycloalkyl containing from three to six carbon atoms, -OR ⁹ , -S(0) _p R ⁹ and -(CH ₂ ) _q C0 ₂ R ⁹ ; or when R ¹ is phenyl optionally substituted by one or more groups R ⁸ , R ¹ and R ³ may be linked together via an ortho-carbon atom of R ¹ to form a five or six membered saturated carbocyclic ring which is fused to the phenyl ring;

R ⁴ and R ⁶ which may be the same or different each represent hydrogen or R ⁹ ; or when R ¹ is phenyl optionally substituted by one or more groups R ⁸ , R ¹ and R ⁴ may be linked together via an ortho-carbon atom of R ¹ to form a five or six membered saturated carbocyclic ring which is fused to the phenyl ring;

R ⁵ represents hydrogen, R ⁹ or phenyl;

R ⁷ represents: phenyl optionally substituted by one or more groups R ⁸ ; or a heterocyclic ring containing from one to four heteroatoms in the ring selected from oxygen, nitrogen and sulphur, and which is optionally substituted by one or more groups R ⁸ ;

R ⁸ represents halogen, R ⁹ , -C0 ₂ H, -C0 R ⁹ , -OH, -OR ⁹ , -S(0) _r R ⁹ , -NR ¹⁰ R ^1:L , nitro and cyano; R ⁹ represents a straight- or branched- chain alkyl group containing from one to six carbon atoms which is optionally substituted by one or more halogens;

R ¹⁰ and R ¹¹ which may be the same or different, each represent hydrogen or R ⁹ ; m is zero or one; n, p and r independently are zero, one or two; and g is one or two; and agriculturally acceptable salts thereof, which possess valuable herbicidal properties, with the proviso that:

(a) when R ¹ and R ⁷ are phenyl; R ³ , R ⁵ and R ⁶ are hydrogen; and one of R ³ and R ⁴ is hydrogen, the other is not methyl or hydrogen;

(b) when R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are hydrogen and R ¹ is 2-carboxyphenyl, R ⁷ is not 5-nitro-2- furyl;

(c) when R ¹ is phenyl, R ¹ and R ³ are linked together via an ortho carbon atom of R ¹ to form a six membered saturated carbocyclic ring which is fused to the phenyl ring; and R ² , R , R ⁵ and R ⁶ are hydrogen; R ⁷ is not phenyl;

(d) when R ¹ is methyl; R , R ⁵ and R ⁶ are hydrogen; and R ⁷ is phenyl; R ³ is not hydrogen or methyl; or

(e) when R ¹ and R ⁴ are methyl; R ³ and R ⁶ are hydrogen; and R ⁷ is phenyl; R ⁵ is not hydrogen or methyl.

Whilst nitrones of general formula (I) generally exist in the cis (Z) form, in certain cases the trans (E) isomer may be obtained in which the R ⁶ and R ⁷ groups are interposed. Nitrones of general formula (I) may in certain cases exist in tautomeric forms, shown in general formula (la) , (lb) or (Ic) below:

(la) (lb) (Ic)

Such tautomerism in nitrones is known and a description of the geometric isomerism and tautomism of nitrones is given in "Nitrones, Nitronates and Nitroxides", by E.Breuer, H.G.Aurich and A.Nielsen (Chapter 2, pages 149 to 154) and also in "Organic Functional Group Preparations", Vol 3 by S.R.Sandier and W.Karo (Chapter 9, p368) . It will be understood that all such isomeric and tautomeric forms are embraced by the present invention.

It will be understood that while compounds in which the compounds of formula (I) listed in the provisos (a) to (e) above are not considered per se part of the invention, compositions containing them and their use as herbicides do form part of the invention.

In certain cases the substituents R ¹ , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ contribute to optical isomerism and/or stereo isomerism. All such forms are embraced by the present invention.

By the term "agriculturally acceptable salts" is meant salts the cations or anions of which are known and accepted in the art for the formation of salts for agricultural or horticultural use. Preferably the salts are water-soluble. Suitable salts with bases include alkali metal (e.g. sodium and potassium) , alkaline earth metal (e.g. calcium and magnesium) , ammonium and amine (e.g. diethanolamine, triethanolamine, octylamine, morpholine and dioctylmethylamine) salts. Suitable acid addition salts, e.g. formed by compounds of formula I containing an amino group, include salts with inorganic acids, for example hydrochlorides, sulphates, phosphates and nitrates and salts with organic acids for example acetic acid.

7

When R represents a heterocyclic ring examples of such rings include the following: thiophene, furan, pyrrole, pyrazine, pyrimidine, pyridazine, thiazole, oxazole, imidazole, pyrazole, isoxazole, isothiazole, oxadiazole, thiadiazole, triazole, pyridine, oxadiazine, thiadiazine, triazine and tetrazole. These compounds, in certain aspects of their properties, for example their control pre- emergence of grass weed species, possess high levels of activity.

Detailed Description of the Invention Compounds of formula (I) above in which R ¹ is a phenyl optionally substituted by from one

Q to five (in particular one or two) groups R are preferred.

Compounds of formula (I) above in which R ³ represents a straight- or branched- chain alkyl group containing from one to six carbon atoms

which is optionally substituted by one or more halogens are preferred (most preferably ethyl) .

Compounds of formula (I) above in which R ⁴ and R ⁵ represent hydrogen are also preferred. Compounds of formula (I) above in which R ⁷ represents phenyl optionally substituted by one to five groups R ⁸ are also preferred.

Compounds of formula (I) above in which R ⁶ represents hydrogen are also preferred. g R is preferably halogen, a methyl or ethyl group optionally substituted by one or more halogens, a methoxy or ethoxy group optionally substituted by one or more halogens;

Another preferred class of compounds of formula (I) are those wherein:

R ¹ represents phenyl which is optionally substituted by one or two R ⁸ groups, wherein R ⁸ represents halogen, a methyl or ethyl group optionally substituted by one or more halogens, a methoxy or ethoxy group optionally substituted by one or more halogens;

R ³ represents a straight- or branched- chain alkyl group containing from one to three carbon atoms; R , R ⁵ and R ⁶ represent hydrogen;

R ⁷ represents phenyl which is optionally substituted by one or two groups R ⁸ , wherein R ⁸ represents halogen, nitro or dimethylamino; or R is pyridyl. The following compounds are particularly preferred:

1. 2-(N-benzylideneaminomethyl) -l-(4- chlorophenyl) -1-butanone N-oxide;

2. 2-(N-benzylideneaminomethyl) -l-(4- methylphenyl) -1-butanone N-oxide;

3. 2-(N-benzylideneaminomethyl) -1-(4- methoxyphenyl) -1-butanone N-oxide;

3. 2-(N-benzylideneaminomethyl)-1-(4- methoxyphenyl)-l-butanone N-oxide; . 2-(N-benzylideneaminomethyl)-l-phenyl- 1-butanone N-oxide; 5. 2-[N-(4-fluorobenzylidene)aminomethyl]-

1-phenyl-l-butanone N-oxide;

6. 2-[N-(3-chlorobenzylidene)aminomethyl]- 1-phenyl-l-butanone N-oxide;

7. 2-[N-(4-chlorobenzylidene)aminomethyl]- 1-phenyl-l-butanone N-oxide;

8. 3-(N-benzylideneamino)-l-(4- fluorophenyl)-2-methyl-l-propanone N-oxide;

9. 3-(N-benzylideneamino)-l-(3- fluorophenyl)-2-methyl-l-propanone N-oxide; 10. 3-(N-benzylideneamino)-l-(2- fluorophenyl)-2-methyl-l-propanone N-oxide;

11. 3-(N-benzylideneamino)-l-(4- chlorophenyl)-2-methyl-l-propanone N-oxide;

12. 3-(N-benzylideneamino)-2-methyl-l- phenyl-1-propanone N-oxide;

13. 2-(N-benzylideneaminomethyl)-1-phenyl- 1-pentanone N-oxide;

14. 2-(N-benzylideneaminomethyl)-1-(2,6- difluorophenyl)-l-butanone N-oxide; 15. 2-[N-(2-fluorobenzylidene)aminomethyl]-

1-phenyl-l-butanone N-oxide;

16. 2-(N-benzylideneaminomethyl)-l-(2- chlorophenyl)-1-butanone N-oxide;

17. 2-(N-benzylideneaminomethyl)-l-(2- methoxyphenyl)-1-butanone N-oxide;

18. 2-(N-benzylideneaminomethyl)-l-(2- methylthiophenyl)-1-butanone N-oxide;

19. 2-(N-benzylideneaminomethyl)-l-(2- fluorophenyl)-l-butanone N-oxide; 20. 2-[N-(2-fluorobenzylidene)aminomethyl]- l-(2-fluorophenyl)-1-butanone N-oxide;

21. 2-(N-benzylideneaminomethyl)-1-(2- methylsulphinylphenyl)-1-butanone N-oxide;

22. 2-(N-benzylideneaminomethyl)-l-(3- trifluoromethylphenyl)-1-butanone N-oxide; 23. 3-(N-benzylideneamino)-l-(4- bromophenyl)-1-propanone N-oxide;

24. 3-[N-(4-chlorobenzylideneamino) ]-2- methyl-l-phenyl-l-propanone N-oxide;

25. 3-[N-(4-dimethylaminobenzylideneamino) ]- 2-methyl-l-phenyl-l-propanone N-oxide;

26. 3-[N-(3-nitrobenzylideneamino) ]-2- methyl-1-phenyl-l-propanone N-oxide; and

27. 3-[N-(2-pyridylmethylideneamino) ]-2- methy1-1-phenyl-l-propanone N-oxide. The numbers 1-27 are assigned to these compounds for reference and identification hereafter.

The following compounds of formula (I) above also form part of the present invention. In the table that follows it will be understood that Me means methyl, Et means ethyl, Pr means n-propyl, nBu means n-butyl and Ph means phenyl. Also, where numbers appear directly after atoms or groups they are understood to be subscript (e.g. N02 means NO ₂ , CF3 means CF ₃ etc. ) .

Compounds of formula (I) above may be prepared by the application or adaptation of known methods (i.e. methods heretofore used or described in the literature) .

It is to be understood that in the descriptions of the following processes the sequences may be performed in different orders, and that suitable protecting groups may be required to achieve the compounds sought.

According to a feature of this present invention compounds of formula (I) may be prepared by the reaction of a compound of general formula (II) :

(II) wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are as defined above, X represents halogen (preferably chlorine, bromine or iodine) and R ¹² , R ¹³ and R ¹⁴ represent alkyl (preferably methyl) , with an oxime of formula (III) or an oxime trimethylsilylether (IV) :

R ⁶

(III) (IV) wherein R ⁶ and R ⁷ are as defined above and TMS represents the trimethylsilyl group. When the reaction is performed using a compound of formula (III) it is preferably carried out in the presence of a base e.g. potassium hydroxide in an inert solvent such as tetrahydrofuran and water at a temperature from 0°C to 60°C. When a compound of formula (IV) is employed the reaction is preferably performed in the absence of base in an inert solvent e.g. tetrahydrofuran and at a temperature from 0°C to 60°C.

Whereas the use of syn-(E)-benzaldoximes in this reaction may give a mixture of the desired nitrone and the analogous oxime ether, the use of anti-(Z)-benzaldoximes give predominantly the nitrone.

The preparation of certain compounds of formula (II) is described in the literature. For example EP-A-0423524 describes certain compounds of formula (II) as pharmaceutical intermediates. GB 1097566 and 1097567 describe compounds of formula (II) as an helmintics. US 3824271 describe compounds of formula (II) as pharmaceutical intermediates. J.R.Dimmock et. al., Pharmazie, vol 39, pages 467-470, (1984); Arm. Khim. Zh. (1969), vol 22(8), pages 693-701 (CA vol 71, No 25, 123786J); Indian J. Chem. (1973), vol 11(3), pages 214-218; and

Tikhonov and Volodatsku, Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk. volume 3, pages 144- 147, (1979) also describe certain compounds of formula (II) .

However, compounds of formula (II) in which R ¹ represents phenyl optionally substituted by one to five groups R ; R ³ represents ethyl; R ⁴ and R ⁵ represent hydrogen; R ⁸ is selected from halogen, optionally halogenated methyl, optionally halogenated methoxy or -S(0) _r CH ₃ - and r represents 0,1 or 2, are novel and as such form a further feature of the present invention. According to a further feature of the present invention compounds of formula (I) may be prepared by the reaction of a compound of general formula (V) :

(V) wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are as defined above and Y represents a leaving group, for example halo preferably chloro or bromo, with an oxime of formula (III),or an oxime trimethylsilyl ether (IV) above. When the reaction is performed using a compound of formula (III) it is preferably carried out in the presence of a base, e.g. potassium hydroxide in an inert solvent such as 1,4-dioxan and at a temperature from 20°C-60°C. When a compound of formula (IV) is employed the reaction is preferably performed in the absence of base in an inert solvent e.g. tetrahydrofuran and at a temperature from 0°C to 60°C.

Whereas the use of syn-(E)-benzaldoximes in this reaction may give a mixture of the desired nitrone and the analogous oxime ether, the use of anti-(Z) -benzaldoximes give predominantly the nitrone.

According to a further feature of the present invention compounds of formula (I) may

be prepared by the reaction of a compound of formula (Va) :

O

R ⁴

R ¹

R ³ R ⁵

(Va) wherein R ¹ , R ³ , R ⁴ and R ⁵ are as defined above, with an oxime of formula (III) above,or an oxime trimethylsilyl ether (IV) above. When the reaction is performed using a compound of formula (III) it is preferably carried out in the presence of a base, e.g. potassium hydroxide in an inert solvent such as 1,4-dioxan and at a temperature from 20°C-60°C. When a compound of formula (IV) is employed the reaction is preferably performed in the absence of base in an inert solvent e.g. tetrahydrofuran and at a temperature from 0°C to 60°C.

Whereas the use of syn-(E)-benzaldoximes in this reaction may give a mixture of the desired nitrone and the analogous oxime ether, the use of anti-(Z)-benzaldoximes give predominantly the nitrone.

According to a further feature of the present invention compounds of formula (I) may be prepared by the oxidation of a compound of general formula (VI) :

(VI) wherein R ¹ , R2 , R , R , R , R . ⁶ and R ⁷ are as defined above, using a peracid (for example m-chloroperbenzoic) and in an inert solvent, for example dichloromethane, at a temperature from

0°C to the reflux temperature of the solvent. It will be understood that compounds (VI) may be in the form of their carbonyl protected derivative for example the ethylene ketal. Certain compounds of formula (VI) and their carbonyl protected derivatives are novel and as such form a further feature of the present invention.

Frequently this process provides an intermediate oxaziridine of general formula

(VII) wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are defined above.

In this instance the intermediates (VII) may be converted into the desired (I) either by thermolysis optionally in the presence of a solvent (for example xylene) at a temperature from 100°C-250°C, or alternatively in the presence of an acid (preferably in the form of silica gel) , conveniently performed by column chromatography.

According to a further feature of the present invention compounds of formula (I) may be prepared by the oxidation of a compound of formula (VIII):

(VIII)

wherein R ¹ , R ² , R ³ , R , R ⁵ , R ⁶ and R ⁷ are as defined above, using for example pyridinium chlorochromate in dichloromethane at 0°C to the reflux temperature. Compounds of formula (VIII) are novel and as such form a further feature of the present invention.

According to a further feature of the present invention compounds of formula (I) may be prepared by the oxidation of N,N-dialkylated hydroxylamines of general formula (IX) :

(IX) wherein R ¹ ,R ² , R ³ , R , R ⁵ , R ⁶ and R ⁷ are defined above, for example by utilising palladium black at a temperature from 80°C-110°C, or a mixture of potassium permanganate and sodium hydroxide in an inert solvent preferably acetone at 20°C-80°C.

Compounds of formula (IX) are novel and as such form a further feature of the present invention.

According to a further feature of the present invention compounds of formula (I) in which R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are defined above may be prepared by the reaction of an N- alkyl hydroxylamine of formula (X) :

wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ as defined above, with a compound of formula R ⁶ R ⁷ C=0 wherein R ⁶ and R ⁷ are as defined above. The

reaction may be performed in an inert solvent for example an alcohol preferably methanol and at a temperature from 0°C to the reflux temperature of the solvent, generally at ambient temperature.

Intermediates of formula (X) are novel and as such form a further feature of the present invention.

Intermediates of formula (II) may be prepared by alkylation of an a ine of formula

(XI):

(Xi) wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ¹² and R ¹³ are as defined above. The reaction is performed in the presence of an alkyl halide R ¹⁴ X, wherein R ¹⁴ represents an alkyl group preferably methyl, and X represents a halogen atom preferably iodo or bromo, and in an inert solvent for example ether, at 0°C to the reflux temperature of the solvent.

Intermediates of formula (X) may be prepared by the reaction of a compound of formula (V) with hydroxylamine. The reaction is preferably performed in an inert solvent for example ethanol and optionally in the presence of a base for example potassium hydroxide and at a temperature from 0°C to 60°C.

It is understood that compounds of formula (X) may exist in tautomeric equilibrium with the isoxazolidine of formula (Xa) , which when the R ² and R ³ , and/or R ⁴ and R ⁵ values differ may exist in diastereomeric forms:

H

(X) (Xa)

Intermediates of formula ( X) wherein R ⁵ represents hydrogen may be prepared by the reduction of an oxime of formula (XII) :

( XII ) with borane-pyridine complex or sodium cyanoborohydride in an inert solvent for example ethanol in the presence of an acid preferably hydrochloric acid at a temperature from 0°C to 60°C. The carbonyl group in (XII) may be in a protected form, for example as the ethylene ketal.

Intermediates of formula (X) may also be prepared by the reaction of a compound of formula (I) with hydroxylamine in an inert solvent generally an alcohol for example methanol at a temperature from 0°C to 60°C preferably at ambient temperature.

Intermediates of formula (VI) may be prepared by the reaction of an amine of formula

(XIII) with an aldehyde or ketone of formula R ⁶ R ⁷ CO. The reaction is conducted in an inert solvent e.g. toluene in the presence of an acid

catalyst preferably 4-toluenesulphonic acid at a temperature from 60°C to the reflux temperature, preferably with removal of the water formed by azeotropic distillation. The carbonyl group in (XIII) may be in a protected form, for example as the ethylene ketal.

Intermediates of formula (IX) may be prepared by the reaction of an N- alkylhydroxylamine R ⁶ R CH-NH-OH, with a compound of formula (V) as defined above, or with a compound of formula (II) as defined above. The reaction is performed in an inert solvent for example ethanol and optionally in the presence of a base for example potassium hydroxide and at a temperature from 0°C to 60°C.

Intermediates of formula (VIII) may be prepared by the oxidation of a compound of formula (XIV) :

(XIV) using a peracid for example m- chloroperbenzoic acid in dichloromethane at 0°C to the reflux temperature.

Intermediates of formula (XIV) may be prepared by the reaction of an aminoalcohol of formula (XV) :

(XV) with a ketone of formula R ⁶ R ⁷ C=0. The reaction is conducted for example in toluene in

the presence of an acid catalyst for example 4- toluenesulphonic acid at a temperature from 60°C to the reflux temperature, preferably with removal of the water formed by azeotropic distillation.

Compounds of formula (III) , (IV) , (V) , (Va) , (XI) , (XII) , (XIII) and (XV) may be prepared using well known methods.

The following Examples illustrate the preparation of compounds of formula (I) and the Reference Examples illustrate the preparation of intermediates in their synthesis.

Example 1 Anti-benzaldoxime (0.63g) was added to a stirred solution of [2-(4-chlorobenzoyl)-but-1- yljtrimethylammonium iodide (2.0g) in a mixture of water and tetrahydrofuran and the resultant mixture treated with potassium hydroxide (0.43g). The mixture was stirred for 4 hours, diluted with water and then hydrochloric acid (2N) and extracted with ether. The organic phase was washed with brine, dried (magnesium sulphate) and evaporated to give a residue which was purified by dry column chromatography eluting with ethyl acetate/hexane, to give 2-(N- benzylideneaminomethyl)-1-(4-chlorophenyl)-1- butanone N-oxide (Compound 1, 0.99g) as a colourless oil, !H NMR d (CDC1 ₃ ): 0.95(t,3H), 1.6-1.75(m,lH) , 1.75-1.9(m,1H) , 4.05(m,lH),

4.4(m,2H), 7.4(m,6H), 7.95(d,2H), 8.2(m,2H).

By proceeding in a similar manner the following compounds were prepared:

2-(N-benzylideneaminomethyl)-1-(4- ethylphenyl)-1-butanone N-oxide (Compound 2), as a colourless oil, ¹ H NMR d (CDCI ₃ ) : 0.9(t,3H), 1.7(m,lH), 1.85(m,lH), 2.4(m,3H),

4.0(m,lH), 4.45(ιrt,2H) , 7.25(m,2H) , 7.4(m,3H) ,

7.45(s,lH) , 7.9(d,2H), 8.15 (m, 2H) ;

2-(N-benzylideneaminomethyl) -l-(4- methoxyphenyl) -1-butanone N-oxide (Compound 3) , as an oil, ^X H NMR d (CDC1 ₃ ): 0.95(t,3H) ,

1.7(m,lH), 1.85(m,lH), 3.85(s,3H), 4.0(m,lH),

4.45(m,2H), 6.95(d,2H), 7.4(m,3H), 7.45(s,lH),

8.0(d,2H) , 8.15(m,2H) ;

2-(N-benzylideneaminomethyl) -1-phenyl-l- butanone N-oxide (Compound 4) , as a solid, m.p.

51-53°C;

2-[N-(4-fluorobenzylidene)aminomethyl]-l- phenyl-1-butanone N-oxide (Compound 5) , as a yellow oil, !H NMR d (CDC1 ₃ ): 0.95(t,3H), 1.7(m,lH), 1.9(m,lH), 4.05(m,lH), 4.5(m,2H),

7.05(t,2H), 7.45(m,3H), 7.55(m,lH), 8.0(m,2H),

8.2(m,2H) ;

2-[N-(3-chlorobenzylidene) aminomethyl]-1- phenyl-1-butanone N-oxide (Compound 6) , as a yellow oil, !H NMR d (CDC1 ₃ ): 1.0(t,3H),

1.7(m,lH), 1.9(m,lH), 4.05(m,lH), 4.4-

4.55(m,2H), 7.3(m,2H), 7.45(m,3H), 7.55(m,lH) ,

7.9(d,lH), 8.0(d,2H), 8.35(S,1H) ;

2-[N-(4-chlorobenzylidene)aminomethyl]-1- phenyl-1-butanone N-oxide (Compound 7) , as a yellow oil, ^λ H NMR d (CDC1 ₃ ) : 1.0(t,3H),

1.7(m,lH), 1.85(m,lH), 4.05(m,lH), 4.4-

4.55(m,2H), 7.35(m,2H), 7.45(m,3H), 7.55(m,lH),

8.0(d,2H), 8.1(d,2H); 3-(N-benzylideneamino)-l-(4-fluorophenyl) -2- ethyl-1-propanone N-oxide (Compound 8) , m.p.

75-76°C.

3-(N-benzylideneamino) -l-(3-fluorophenyl) -2- methyl-1-propanone N-oxide (Compound 9) , as a yellow oil, ^-H NMR d (CDC1 ₃ ) : 1.3(d,3H),

4.0(m,lH), 4.5(m,2H) ,.7.25(m,lH) , 7.35-

7.5(m,5H), 7.7(m,lH), 7.8(d,lH), 8.2(m,2H);

3-(N-benzylideneamino) -1-(2-fluorophenyl) -2- methyl-1-propanone N-oxide (Compound 10) , as a yellow oil, ^-H NMR d (CDC1 ₃ ) : 1.3(d,3H) , 4.0(m,lH), 4.35(m,lH), 4.5(m,lH), 7.1- 7.25(m,2H), 7.4(m,3H), 7.5(m,2H), 7.85(t,lH),

8.2(m,2H) ;

3-(N-benzylideneamino) -l-(4-chlorophenyl) -2- methyl-1-propanone N-oxide (Compound 11) , m.p. 77-79.5°C; 3-(N-benzylideneamino) -2-methyl-l-phenyl-l- propanone N-oxide (Compound 12) , m.p. 63-65°C;

2-(N-benzylideneaminomethyl) -1-phenyl-l- pentanone N-oxide (Compound 13) , as a colourless oil, ,NMR d (CDCI3): 0.9(t,3H), 1.35(m,2H) , 1.6(m,lH), 1.8(m,lH), 4.0(m,lH), 4.5(m,2H) , 7.4(m,3H), 7.5(m,3H), 7.55(m,lH), 8.0(d,2H), 8.2(m,2H) ;

2-(N-benzylideneaminomethyl) -l-(2, 6- difluorophenyl) -1-butanone N-oxide (Compound 14), as a yellow oil, H NMR d (CDCI3)

1.0(t,3H), 1.6-1.8(m,lH) , 1.85-2.0(m,1H) , 3.95- 4.1((m,2H) , 4.5(m,lH), 6.9(t,2H), 7.3-7.5(m, 5H) , 8.2(m,2H) ;

2-[N-(2-fluorobenzy1idene)aminomethyl]-1- phenyl-1-butanone N-oxide (Compound 15) , as a yellow oil, !H NMR d (CDCI3) 0.95(t,3H), 1.65- 1.8(m,lH) , 1.8-1.95(m,lH) , 4.0-4.15 (m, 1H) , 4.4- 4.6(m,2H), 7.0-7.1(m,lH) , 7.1-7.2 (t,1H) , 7.3- 7.4(m,lH), 7.45-7.5(t,2H) , 7.55-7.6 (m, 1H) , 7.75(s,lH) , 8.0(d,2H), 9.1(m,lH).

2-(N-benzylideneaminomethyl) -l-(2- chlorophenyl) -1-butanone N-oxide (Compound 16) , m.p. 87-89°C;

2-(N-benzy1ideneaminomethy1)-1-(2- methoxyphenyl) -1-butanone N-oxide (Compound 17) , NMR 0.91 (t,3H) , 1.6(m,lH) , 1.8(m,lH),

3.85(s,3H), 3.94(m,lH), 4.4(m,lH), 4.5(m,lH), 6.93(m,2H), 7.3-7.5(m,5H) , 8.22(m,2H) ; 2-(N-benzylideneaminomethyl) -1-(2- methylthiophenyl)-1-butanone N-oxide (Compound 18), NMR 0.92(t,3H), 1.7(m,lH) , 1.85(m,lH),

2.4(s,3H), 4.02(m,lH), 4.4-4.5 (m,2H) , 7.15- 7.45(m,7H), 7.98(m,lH), 8.18(m,2H);

2-[N-(2-fluorobenzylidene) aminomethyl]-1-(2- fluorophenyl)-1-butanone N-oxide (Compound 20), NMR 0.98 (t,3H) , 1.69(m,lH), 1.9(m,lH), 4.1(m,lH), 4.26(m,lH), 4.56(m,lH), 7.0- 7.27(m,4H), 7.35(m,lH), 7.5(m,lH), 7.78(s,lH), 7.87(m,lH), 9.16(m,lH);

2-(N-benzylideneaminomethyl) -1-(2- methylsulphinylphenyl)-1-butanone N-oxide (Compound 21), NMR 0.84(t,3H), 1.6(m,lH), 1.7(m,lH) , 2.76(s,3H), 4.05(m,lH), 4.35(m,lH), 4.48(m,lH), 7.3(m,3H), 7.39(s,lH), 7.55(m,lH), 7.76(m,lH), 8.1(m,3H), 8.31(m,lH); 2-(N-benzylideneaminomethyl) -l-(3- trifluoromethylphenyl) -1-butanone N-oxide (Compound 22) , NMR 0.91(t,3H), 1.7(m,lH), 1.82(m,lH), 4.07(m,lH), 4.4-4.52 (m,2H) , 7.3- 7.4(m,3H) , 7.4(s,lH), 7.59(m,lH), 8.1- 8.25(m,4H);

3-(N-benzylideneamino)-1-(4-bromophenyl) -1- propanone N-oxide (Compound 23) , m.p. 120-123°C.

Example 2 Water (2.2ml) was added to a mixture of 2- ethyl-1-(2-fluorophenyl)prop-2-en-l-one (2. lg) and anti-(Z) -benzaldoxime (1.5g) in tetrahydrofuran. Potassium hydroxide (0.37g) was added, the mixture stirred at room temperature for 3 hours, then added to water and extracted (ether) . The extract was dried (magnesium sulphate) , evaporated and the residue

purified by dry column chromatography eluting with hexane/ethyl acetate to give 2-(N- benzylideneaminomethyl) -1-(2-fluorophenyl)-1- butanone N-oxide (Compound 19) , m.p. 57-59°C.

Example 3

A solution of 4-chlorobenzaldehyde (0.88 g) in methanol was added dropwise to a stirred solution of 3-hydroxyamino-2-methyl-l- phenylpropan-1-one (1.12 g) in methanol. After 20 hours the mixture was evaporated and triturated with ether to give 3-[N-(4- chlorobenzylideneamino) ]-2-methyl-1-pheny1-1- propanone N-oxide (Compound 24, 1.24 g), m.p. 99-101°C.

By proceeding in a similar manner the following compounds were prepared:

3-[N-(4-dimethylaminobenzylideneamino) ]-2- methyl-1-phenyl-l-propanone N-oxide (Compound 25) , m.p. 132-134°C;

3-[N-(3-nitrobenzylideneamino) ]-2-methyl-l- phenyl-1-propanone N-oxide (Compound 26) , m.p. 107-108°C;

3-[N-(2-pyridyImethy1ideneamino) ]-2-methyl- 1-phenyl-1-propanone N-oxide (Compound 27) , m.p. 107-109°C.

Reference Example 1

Methyl iodide (4.5g) was added to a stirred solution of l-(4-chlorophenyl)-2- dimethylaminomethyl-l-butanone (5.98g) in ether under an inert atmosphere. After 5 days the precipitated solid was filtered off, washed with ether and dried in a desiccator to give [2-(4- chlorobenzoy1)but-l-yl]trimethylammonium iodide (3.35g) as a white solid, m.p. 206-208°C.

By proceeding in a similar manner the following compounds were prepared:

[2-(4-methoxybenzoyl)but-l- yl]trimethylammonium iodide, m.p. 165-167°C; [2-(3-fluorobenzoyl)prop-l- yl]trimethylammonium iodide, m.p. 155-156°C;

[2-(2-fluorobenzoyl)prop-1- yl]trimethylammonium iodide, m.p. 152-153°C;

[2-(benzoyl)pent-1-yl]trimethylammonium iodide, m.p.192-196°C;

[2-(2,6-difluorobenzoyl)but-1- yl]trimethylammonium iodide, m.p. 135°(dec) ;

[2-(2-chlorobenzoyl)but-1- yl]trimethylammonium iodide, m.p. 159-162°C; [2-(2-methoxybenzoyl)but-l- yl]trimethylammonium iodide, m.p. 130-140°C;

[2-(2- ethylthiobenzoy1)but-1- yl]trimethylammonium iodide m.p. 100-104°C;

[2-(2-fluorobenzoyl)but-1- yl]trimethylammonium iodide, m.p. 120-125°C;

[2-(2-methylsulphinylbenzoyl)but-l- yl]trimethylammonium iodide as a hygroscopic solid used directly in the following stage;

[2-(3-trifluoromethylbenzoyl)but-l- yl]trimethylammonium iodide m.p. 150°C (dec);

[2-(4-bromobenzoyl)eth-l yl]trimethylammonium iodide m.p. 195-198°C (dec. ) .

Reference Example 2

Dimethylamine hydrochloride (2.65g) was added to a stirred solution of l-(2- fluorophenyl) -1-propanone (3.8g) in ethanol at ambient temperature. Paraformaldehyde (l.Og) and concentrated hydrochloric acid (0.31 ml) were then added and the mixture stirred at reflux overnight. The cooled mixture was

diluted with water, extracted (ether) and the organic phase itself extracted with hydrochloric acid (2M) . The combined aqueous solutions were brought to pH 9 with sodium carbonate solution (1M) and extracted (ether) . The organic phase was dried (magnesium sulphate) and the resulting solution of 1-(2-fluorophenyl)-2- dimethylaminomethyl-1-propanone was used directly in the next stage. By proceeding in a similar manner the following compounds were prepared and used directly in the next stage: l-(3-fluorophenyl)-2-dimethylaminomethyl-l- propanone; l-(4-methoxyphenyl)-2-dimethylaminomethyl-l- butanone; l-(4-chlorophenyl)-2-dimethylaminomethyl-l- butanone;

1-(2,6-difluorophenyl)-2- dimethylaminomethy1-1-butanone. l-(2-chlorophenyl)-2-dimethylaminomethyl-l- butanone;

1-(2-methoxyphenyl)-2-dimethylaminomethyl-l- butanone; 2-dimethylaminomethyl-l-(2- methylthiophenyl)-1-butanone;

2-dimethylaminomethyl-l-(2- methylsulphinylphenyl)-1-butanone; and

2-dimethylaminomethyl-l-(3- trifluoromethylphenyl)-1-butanone.

Reference Example 3

Hydrogen chloride gas was passed over the surface of a solution of syn 2-fluoro- benzaldoxime (5.9g) in toluene stirred initially at 80°C under an inert atmosphere. When the temperature of the mixture had fallen to 60°C,

the addition of hydrogen chloride was discontinued. The mixture was cooled and the solid filtered off and washed (hexane) . To a suspension of the solid in cold ether was added a cold (0°C) solution of sodium hydroxide (3M) , followed by a cold solution of ammonium chloride. The organic phase was dried (magnesium sulphate) and evaporated to give anti 2-fluorobenzaldoxime (3.56g), m.p. 55°C-60°C. This was shown by NMR to contain 25% of the syn- isomer and was used directly in the next stage.

Reference Example 4

A solution of 1-(2-chlorophenyl)-1-butanone (4.7g) in dry tetrahydrofuran was added to sodium thio ethoxide (2.0g) and the resulting suspension heated at reflux for 20 hours. The mixture was diluted with water, sodium hydroxide solution (2M) added, and extracted (ether) . The extract was dried (magnesium sulphate) and evaporated to give l-(2-methylthiophenyl)-l- butanone (4.8g), NMR 1.01(t,3H) , 1.75(m,2H), 2.42(S,3H), 2.95(m,2H), 7.15-7.5(m,4H) .

Reference Example 5

A mixture of dimethylamine hydrochloride (4.24g), l-(2-fluorophenyl)-1-butanone (6.6g) and paraformaldehyde (1.6g) in ethanol was treated with concentrated hydrochloric acid (0.5ml) . The mixture was heated at reflux for 18 hours, cooled, added to water and extracted (ether) . The extract was dried (magnesium sulphate) and evaporated to give 2-ethyl-l-(2- fluorophenyl) rop-2-en-l-one (3.36 g) , NMR l.l(t,3H), 1.68(q,2H), 5.6(S,1H), 5.88(s,lH),

7.0-7.5(m,4H) contaminated with unchanged l-(2-

fluorophenyl)-1-butanone in a 2:1 ratio and was used as such in the following stage.

The aqueous phase (from above) was basified (1 M sodium carbonate solution) , extracted (ether) and the extract dried (magnesium sulphate) to give l-(2-fluorophenyl)-2- dimethylaminomethyl-l-butanone, used directly in the following stage.

Reference Example 6

A solution of 2-fluorobenzonitrile (4.48ml) in ether was added dropwise to a stirred solution of propylmagnesiu chloride (25ml of a 2M solution in ether) . When the addition was complete the mixture was heated at reflux for 18 hours, cooled and added to a stirred mixture of ice and concentrated hydrochloric acid. The aqueous phase was washed (ether) and heated at reflux for 3 hours, cooled and extracted (ether) . The organic phase was dried (magnesium sulphate) and evaporated to give l-(2- fluorophenyl)-1-butanone (6.6 g) as a green oil, NMR 0.98(t,3H) , 1.72(m,2H), 2.96(m,2H), 7.1- 7.25(m,2H), 7.48(m,lH), 7.86(m,lH).

Reference Example 7 m-Chloroperbenzoic acid (4.07g of 70% pure reagent) was added portionwise to a stirred solution of l-(2-methylthiophenyl)-1-butanone (4.6g) in dichloromethane maintained at 0 C to - 10°C. The mixture was allowed to warm to 9°C during 1 hour, and stirred with a 5% solution of sodium metabisulphite for 0.25 hour. The mixture was extracted (dichloromethane) and the extract washed (saturated sodium bicarbonate solution) , dried (magnesium sulphate) and evaporated. The residue was purified by dry

column chromatography eluting with hexane/ethyl acetate to give l-(2-methylsulphinyl)-1-butanone (3.0g), NMR 1.0(t,3H), 1.75(m,2H), 2.84(s,3H), 2.99(m,2H), 7.61(m,lH), 7.82(m,lH), 7.96(m,lH), 8.4(m,lH).

Reference Example 8

The solution obtained by mixing hydroxylamine hydrochloride (0.86g) and potassium hydroxide (0.66g) in methanol was added to a stirred solution of 3-(N- benzylideneamino)-2-methyl-1-phenyl-1-propanone N-oxide (3.0g) in methanol. After 20 hours the mixture was evaporated and ether and water added. The organic phase was extracted with (3% hydrochloric acid) and the extract brought to pH 7-8 by addition of sodium carbonate solution. The mixture was extracted (dichloromethane) , the extract dried (magnesium sulphate) and evaporated to give 3-hydroxyamino-2-methyl-l- phenyl-1-propanone as an oil (1.25g), which exists in an equilibrium with diastereomeric 5- hydroxy-4-methyl-5-phenylisoxazolidine. Treatment of the above oil with oxalic acid gave the oxalate, m.p. 133-135 °C.

According to a feature of the present invention, there is provided a method for controlling the growth of weeds (i.e. undesired vegetation) at a locus which comprises applying to the locus a herbicidally effective amount of at least one nitrone derivative of formula I or an agriculturally acceptable salt thereof. For this purpose, the nitrone derivatives are normally used in the form of herbicidal compositions (i.e. in association with compatible diluents or carriers and/or surface

active agents suitable for use in herbicidal compositions) , for example as hereinafter described.

The compounds of formula I show herbicidal activity against dicotyledonous (i.e. broad- leafed) and monocotyledonous (e.g. grass) weeds by pre- and/or post-emergence application.

By the term "pre-emergence application" is meant application to the soil in which the weed seeds or seedlings are present before emergence of the weeds above the surface of the soil. By the term "post-emergence application" is meant application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil. For example, the compounds of formula I may be used to control the growth of: broad-leafed weeds, for example, Abutilon theophrasti, Amaranthus retroflexus. Bidens pilosa. Chenopodium album. Galiu aparine. Ipomoea spp. e.g. Ipomoea purpurea. Sesbania exaltata. Sinapis arvensis. Solanum nigrum and Xanthium strumarium. and grass weeds, for example Alopecurus mvosuroides. Avena fatua. Diσitaria sanσuinalis. Echinochloa crus-σalli, Eleusine indica and Setaria spp. e.g. Setaria faberii or Setaria viridis. and sedges, for example, Cvperus esculentus. The amounts of compounds of formula I applied vary with the nature of the weeds, the compositions used, the time of application, the climatic and edaphic conditions and (when used to control the growth of weeds in crop-growing areas) the nature of the crops. When applied to a crop-growing area, the rate of application should be sufficient to control the growth of weeds without causing substantial permanent

damage to the crop. In general, taking these factors into account, application rates between 1 g and 1000 g of active material per hectare give good results. However, it is to be understood that higher or lower application rates may be used, depending upon the particular problem of weed control encountered.

The compounds of formula I may be used to control selectively the growth of weeds, for example to control the growth of those species hereinbefore mentioned, by pre- or post- emergence application in a directional or non- directional fashion, e.g. by directional or non- directional spraying, to a locus of weed infestation which is an area used, or to be used, for growing crops, for example cereals, e.g. wheat, barley, oats, maize and rice, soya beans, field and dwarf beans, peas, lucerne, cotton, peanuts, flax, onions, carrots, cabbage, oilseed rape, sunflower, sugar beet, and permanent or sown grassland before or after sowing of the crop or before or after emergence of the crop. For the selective control of weeds at a locus of weed infestation which is an area used, or to be used, for growing of crops, e.g. the crops hereinbefore mentioned, application rates between 10 g and 500 g, and preferably between 25 g and 250 g, of active material per hectare are particularly suitable. The compounds of the invention are especially useful for controlling grass weed species.

The compounds of formula I may also be used to control the growth of weeds, especially those indicated above, by pre- or post-emergence application in established orchards and other tree-growing areas, for example forests, woods

and parks, and plantations, e.g. sugar cane, oil palm and rubber plantations. For this purpose they may be applied in a directional or non- directional fashion (e.g. by directional or non- directional spraying) to the weeds or to the soil in which they are expected to appear, before or after planting of the trees or plantations at application rates between 50 g and 5000 g, and preferably between 50 g and 2000 g, most preferably between 100 g and 1000 g of active material per hectare.

The compounds of formula I may also be used to control the growth of weeds, especially those indicated above, at loci which are not crop- growing areas but in which the control of weeds is nevertheless desirable.

Examples of such non-crop-growing areas include airfields, industrial sites, railways, roadside verges, the verges of rivers, irrigation and other waterways, scrublands and fallow or uncultivated land, in particular where it is desired to control the growth of weeds in order to reduce fire risks. When used for such purposes in which a total herbicidal effect is frequently desired, the active compounds are normally applied at dosage rates higher than those used in crop-growing areas as hereinbefore described. The precise dosage will depend upon the nature of the vegetation treated and the effect sought.

Pre- or post-emergence application, and preferably pre-emergence application, in a directional or non-directional fashion (e.g. by directional or non-directional spraying) at application rates between 50 g and 5000 g, and preferably between 50 g and 2000 g, most preferably between 100 g and 1000 g of active

material per hectare are particularly suitable for this purpose.

When used to control the growth of weeds by pre-emergence application, the compounds of formula I may be incorporated into the soil in which the weeds are expected to emerge. It will be appreciated that when the compounds of formula I are used to control the growth of weeds by post-emergence application, i.e. by application to the aerial or exposed portions of emerged weeds, the compounds of formula I will also normally come into contact with the soil and may also then exercise a pre-emergence control on later-germinating weeds in the soil. Where especially prolonged weed control is required, the application of the compounds of formula I may be repeated if required.

According to a further feature of the present invention, there are provided compositions suitable for herbicidal use comprising one or more of the nitrone derivatives of formula I or an agriculturally acceptable salt thereof, in association with, and preferably homogeneously dispersed in, one or more compatible agriculturally- acceptable diluents or carriers and/or surface active agents [i.e. diluents or carriers and/or surface active agents of the type generally accepted in the art as being suitable for use in herbicidal compositions and which are compatible with compounds of formula I]. The term "homogeneously dispersed" is used to include compositions in which the compounds of formula I are dissolved in other components. The term "herbicidal compositions" is used in a broad sense to include not only compositions which are ready for use as herbicides but also concentrates which must be diluted before use.

Preferably, the compositions contain from 0.05 to 90% by weight of one or more compounds of formula I.

The herbicidal compositions may contain both a diluent or carrier and surface-active (e.g. wetting, dispersing, or emulsifying) agent. Surface-active agents which may be present in herbicidal compositions of the present invention may be of the ionic or non-ionic types. Suitably, the herbicidal compositions according to the present invention may comprise up to 10% by weight, e.g. from 0.05% to 10% by weight, of surface-active agent but, if desired, herbicidal compositions according to the present invention may comprise higher proportions of surface-active agent, for example up to 15% by weight in liquid emulsifiable suspension concentrates and up to 25% by weight in liquid water soluble concentrates. Examples of suitable solid diluents or carriers are aluminium silicate, microfine silicon dioxide, talc, chalk, calcined magnesia, kieselguhr, tricalcium phosphate, powdered cork, adsorbent carbon black and clays such as kaolin and bentonite. The solid compositions (which may take the form of dusts, granules or wettable powders) are preferably prepared by grinding the compounds of formula I with solid diluents or by impregnating the solid diluents or carriers with solutions of the compounds of formula I in volatile solvents, evaporating the solvents and, if necessary, grinding the products so as to obtain powders. Granular formulations may be prepared by absorbing the compounds of formula I (dissolved in suitable solvents, which may, if desired, be volatile) onto the solid diluents or carriers in granular form and, if desired,

evaporating the solvents, or by granulating compositions in powder form obtained as described above. Solid herbicidal compositions, particularly wettable powders and granules, may contain wetting or dispersing agents (for example of the types described above) , which may also, when solid, serve as diluents or carriers. Liquid compositions according to the invention may take the form of aqueous, organic or aqueous-organic solutions, suspensions and emulsions which may incorporate a surface-active agent. Surface-active agents, which may be present in the liquid compositions, may be ionic or non-ionic and may, when liquid, also serve as diluents or carriers.

Powders, dispersible granules and liquid compositions in the form of concentrates may be diluted with water or other suitable diluents, for example mineral or vegetable oils, particularly in the case of liquid concentrates in which the diluent or carrier is an oil, to give compositions ready for use.

When desired, liquid compositions of the compound of formula I may be used in the form of self-emulsifying concentrates containing the active substances dissolved in the emulsifying agents or in solvents containing emulsifying agents compatible with the active substances, the simple addition of such concentrates to water producing compositions ready for use.

Liquid concentrates in which the diluent or carrier is an oil may be used without further dilution using the electrostatic spray technique. Herbicidal compositions according to the present invention may also contain, if desired, conventional adjuvants such as adhesives,

protective colloids, thickeners, penetrating agents, spreading agents, stabilisers, sequestering agents, anti-caking agents, colouring agents and corrosion inhibitors. These adjuvants may also serve as carriers or diluents.

Preferred herbicidal compositions according to the present invention are aqueous suspension concentrates, wettable powders, water soluble or water dispersible powders, liquid water soluble concentrates, liquid emulsifiable suspension concentrates, water dispersible granules and emulsifiable concentrates.

Herbicidal compositions according to the present invention may also comprise the compounds of formula I in association with, and preferably homogeneously dispersed in, one or more other pesticidally active compounds and, if desired, one or more compatible pesticidally acceptable diluents or carriers, surface-active agents and conventional adjuvants as hereinbefore described.

Examples of other pesticidally active compounds which may be included in, or used in conjunction with, the herbicidal compositions of the present invention include herbicides (which are preferred partners) , insecticides and fungicides. Pesticidally active compounds and other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention and which are acids, may, if desired, be utilized in the form of conventional derivatives, for example alkali metal and amine salts and esters.

The following non-limiting examples illustrate herbicidal compositions according to the present invention. The following trade marks appear in the description: Ethylan, Soprophor, Sopropo, Rhodorsil, Atagel,

Synperonic, Solvesso, Arkopon, Tixosil. Example Cl;

A suspension concentrate is formed from: Nitrone derivative (Compound 1) 20% Ethylan BCP (surfactant) 0.5%

Soprophor FL 0.5%

Sopropon T36 (Dispersant) 0.2%

Rhodorsil 426R (Antifoaming agent) 0.01% Propylene glycol (antifreeze) 5.0% Atagel 50 (anti-settling agent) 2.0

Water to 100%

Similar suspension concentrates may be prepared by replacing Compound 1 with other nitrone derivatives of formula I. Example C2

An emulsion concentrate is formed from the following:

Nitrone derivative (Compound l) 10% Synperonic NPE1800 (surfactant) 4.9% Arylan CA (surfactant) 5.0%

Cyclohexanone (solvent) 9.8%

NMP (solvent) 9.8%

Solvesso 150 (blending agent) 5.0% Water to 100% Note: NMP means N-methylpyrrolidine

Similar emulsion concentrates may be prepared by replacing Compound 1 with other nitrone derivatives of formula I. Example C3 A wettable powder is formed from the following:

Nitrone derivative (Compound 1) 20.0%

Arylan SX flake (surfactant) 3.0% Arkopon T (surfactant) 5.0%

Sodium polycarboxylate (dispersant) 1.0% Tixosil 38 (flow aid) 3.0% China Clay 68.0%

Similar wettable powders may be prepared by replacing Compound 1 with other nitrone derivatives of formula I.

METHOD OF USE OF HERBICIDAL COMPOUNDS:

TEST METHOD A a) General

Appropriate quantities of the compounds used to treat the plants were dissolved in acetone to give solutions equivalent to application rates of up to 4000g test compound per hectare (g/ha) . These solutions were applied from a standard laboratory herbicide sprayer delivering the equivalent of 290 litres of spray fluid per hectare.

b) Weed control : Pre-emergence

The seeds were sown in 70 mm square, 75 mm deep plastic pots in non-sterile soil . The quantities of seed per pot were as follows:-

Weed species Approx number of seeds/pot

1) Broad-leafed weeds

Abutilon theophrasti 10

Amaranthus retroflexus 20 Galium aparine 10

Ipomoea purpurea 10

Sinapis arvensis 15

Xanthium strumarium 2.

2 ) Grass weeds Alopecurus myosuroides 15

Avena fatua 10

Echinochloa crus-galli 15

Setaria viridis 20.

3) Sedges

Cyperus esculentus 3.

Crop

1) Broad-leafed

Cotton 3

Soya 3.

2) Grass

Maize 2

Rice 6

Wheat 6.

The compounds of the invention were applied to the soil surface, containing the seeds, as described in (a) . A single pot of each crop and each weed was allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.

After treatment the pots were placed on capillary matting kept in a glass house, and watered overhead. Visual assessment of crop damage was made 20-24 days after spraying. The results were expressed as the percentage reduction in growth or damage to the crop or weeds, in comparison with the plants in the control pots.

c) Weed control : Post-emergence

The weeds and crops were sown directly into John Innes potting compost in 75 mm deep, 70 mm square pots except for Amaranthus which was pricked out at the seedling stage and transferred to the pots one week before spraying. The plants were then grown in the greenhouse until ready for spraying with the

compounds used to treat the plants. The number of plants per pot were as follows :-

1) Broad leafed weeds

Weed species Number of plants per pot Growth stage

Abutilon theophrasti 3 1-2 leaves

Amaranthus retroflexus 4 1-2 leaves

Galium aparine 3 1 ^st whorl

Ipomoea purpurea 3 1-2 leaves

Sinapis arvensis 4 2 leaves

Xanthium strumarium 1 2-3 leaves.

2) Grass weeds

Weed species Number of plants per pot Growth stage Alopecurus myosuroides 8-12 1-2 leaves

Avena fatua 12-18 1-2 leaves

Echinochloa crus-galli 4 2-3 leaves

Setaria viridis 15-25 1-2 leaves.

3) Sedges

Weed species No. of plants per pot Growth stage Cyperus esculentus 3 3 leaves.

1) Broad leafed Crops

Crops Number of plants per pot Growth stage

Cotton 2 1 leaf

Soya 2 2 leaves.

2) Grass Crops Crops Number of plants per pot Growth stage Maize 2 2-3 leaves Rice 4 2-3 leaves Wheat 5 2-3 leaves.

The compounds used to treat the plants were applied to the plants as described in (a) . A single pot of each crop and weed species was

allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.

After treatment the pots were placed on capillary matting in a glass house, and watered overhead once after 24 hours and then by controlled sub-irrigation. Visual assessment of crop damage and weed control was made 20-24 days after spraying. The results were expressed as the percentage reduction in growth or damage to the crop or weeds, in comparison with the plants in the control pots. TEST METHOD B a) General As in Test Method A above but the solutions were applied from an automated sprayer delivering the equivalent of 720 litres of spray fluid per hectare.

b) Weed control : Pre-emergence

The seeds were sown in 70 mm square, 75 mm deep plastic pots in non-sterile soil, 3 species per pot . The quantities of seed per pot were as follows:- Weed species Approx no. of seeds/species

1) Broad-leafed weeds

Abutilon theophrasti 7-8

Amaranthus retroflexus 20 (pinch)

Galium aparine 4-5 Ipomoea purpurea 5

Sinapis arvensis 7-8

Matricaria inodora 20 (pinch)

Stellaria media 20 (pinch)

2 ) Grass weeds Alopecurus myosuroides 15-20

Avena fatua 10

Echinochloa crus-galli 15

Setaria viridis 15

Setaria faberii 15

Apera spica-venti 20 (pinch)

Crop 1) Broad-leafed

Cotton 3

Soya 2

2) Grass

Maize 2 Rice 5

Wheat 5

The compounds of the invention were applied to the soil surface, containing the seeds, as described in (a) . Pots containing the species represented were allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.

After treatment the pots were placed on capillary matting kept in a glass house, and watered overhead. Visual assessment of crop damage was made 17 days after spraying. The results were expressed as the percentage reduction in growth or damage to the crop or weeds, in comparison with the plants in the control pots.

When applied at 4000 g/hectare or less pre- emergence in Test Method A, compounds 1-22 gave at least 90% reduction in growth of one or more of the weed species listed above; at levels of applications toxic to the weeds these compounds were selective in at least one crop species.

When applied at 4000 g/hectare or less pre- emergence in Test Method B, compounds 23 - 27 gave at least 90% reduction in growth of one or more of the weed species listed above.