WO1997030037A1

WO1997030037A1 - New intermediates to pesticides

Info

Publication number: WO1997030037A1
Application number: PCT/EP1997/000491
Authority: WO
Inventors: Virginie Pevere
Original assignee: Rhone Poulenc Agro
Priority date: 1996-02-16
Filing date: 1997-02-04
Publication date: 1997-08-21
Also published as: PT882028E; DE69709626D1; TW422831B; EP0882028A1; ATE212017T1; CN1211241A; KR19990082598A; KR100449062B1; KR20040036720A; ES2171255T3; AU722612B2; AR005839A1; JP2000505436A; ZA971137B; DK0882028T3; DE69709626T2; EA199800730A1; HUP9900972A3; EA002126B1; BR9707525A

Abstract

The invention relates to a process for preparing a compound of formula (I), wherein R, R1 and Ar are as defined in the description, by the reaction of a compound of formula (II), wherein R, R1 and Ar are as defined in the description, with hydroxylamine or a salt thereof.

Description

New Intermediates to Pesticides

This invention relates to novel 2-(aminomethylidene)propane-l ,3-dione derivatives, processes for their preparation, and their use as intermediates in the manufacture of herbicidally active compounds.

European patent Publication numbers 0487357, 0560482, 0580439, 0609797, 0609798, 0636622, 0682659 and International Patent Publication Number WO 95/16678 describe, inter alia, 3-ester-

4-benzoylisoxazole herbicides. In particular, EP-A-0560482 describes the synthesis of ethyl 5-cyclopropyl-4-[3,4-dichloro-2- (methylsulphenyl)-benzoyl]isoxazole-3-carboxylate. Herbicidal 3-ester- 4-heteroaroylisoxazoles are also known in the literature, for example in EP-A-0588357, EP-A-0636622 and O96/25413. Each of these publications describe various processes for the preparation of such 3- ester-4-arylisoxazoles. such as the reaction of a l-cyclopropyl- 3-aryl-propane-l,3,-dione with a chloro-oxime. It is however desirable to provide alternative routes for preparing such compounds Certain 2-(aminomethylidene)-propane- 1 ,3 -dione derivatives are described in the literature. A. Veronese et al, J. Molecular Catalysis, Vol. 54 (1989) pp 73-80 describes the preparation of 2-(l ' -amino- 1'- ethoxycarbonyl-methylidine)-l-phenylbutane-l,3-dione and Italian Patent No. 1200768 describes compounds of formula:

in which R_a and Rι_a, which may be the same or different, each represent C1-C4 alkyl, aryl or C1-C4 alkoxy, and R2_a is C1-C4 alkyl or benzyl. These compounds are said to be useful as intermediates in the synthesis of, for example, pharmaceuticals. It is an object of the present invention to provide a novel process for preparing herbicidally active compounds.

It is a further object of the invention to provide novel intermediates in the manufacture of herbicidally active compounds.

It is a still further object of the invention to provide processes for preparing such intermediates and herbicides in high yield. These and other objects of the invention will become apparent from the following description, and are achieved in whole or in part by the present invention.

The present invention provides a process for preparing a compound of formula (I):

(I) wherein:

R .S -CO2R³; R S lower alkyl or cycloalkyl having from three to seven ring carbon atoms, optionally substituted by lower alkyl or halogen; Ar is: phenyl optionally substituted by one to five groups R^ which may be the same or different; or is phenyl optionally substituted by from one to three groups R^ which may be the same or different and wherein two additional substituents on adjacent positions of the phenyl ring, together with the two atoms to which they are attached, form a 5- to 7- membered ring which is optionally substituted by one or groups R 1 which may be the same or different; or is a group Het which is optionally substituted by one or more groups R , wherein Het represents a first heterocyclic ring containing from one to four heteroatoms in the ring selected from oxygen, nitrogen and sulphur, which is optionally fused with a benzene, or carbocyclic or second heterocyclic ring (which is optionally saturated or partially saturated) to form a bicyclic system, wherein the first heterocyclic ring of the group Het is attached to the carbonyl group in the 4-position of the isoxazole ring;

R2 is halogen, lower alkyl, lower alkoxy, lower haloalkyl, lower haloalkoxy, -S(O)_mR⁴, -(CR⁵R⁶)_qS(O)_mR⁴, nitro, cyano,

-N(R⁵)SO2R⁸, -OSO2R8, cycloalkyl having from three to seven ring carbon atoms, straight- or branched- chain alkenyl or alkynyl having up to six carbon atoms, -CO₂R⁷, -S(O)_mR⁹, -O(CH2)_r R⁸, -NR5R6, -CONR5R6, -N(R⁵)C(=O)Rl0, -(CR5R6)_qN(R5)_SO₂R⁸, -(CR5R6)_qN(R⁵)C(=O)RlO, -(CR5R⁶)_qP(=O)R¹²R¹³, -(CR5R )_qR14_? -(CR5R6)_qRl _{5 or a} straight- or branched-chain alkyl containing up to six carbon atoms substituted by -OR^; where R² is present on a heterocyclic or carbocyclic ring of the group Het, R² may also represent =O, =S, cyclic ketal or cyclic thioketal;

R³ is lower alkyl, lower haloalkyl, aryl or benzyl;

R⁴ is lower alkyl, or phenyl optionally substituted by from one to five groups selected from lower alkyl, lower haloalkyl, halogen and -S- alkyl; R^ and R^ independently are hydrogen, lower alkyl or lower haloalkyl;

R? is hydrogen or lower alkyl;

R⁸ is lower alkyl or lower haloalkyl;

R9 is lower haloalkyl, lower alkenyl or lower haloalkenyl; Rl 0 is R⁸, lower alkoxy or lower alkylthio;

Rl 1 is R² or =O, =S, lower alkylimino, cyclic ketal or cyclic thioketal;

R^² and R ³ are lower alkyl, hydroxy, lower alkoxy or lower haloalkoxy; Rl ⁴ is a 5-membered heteroaromatic ring of formula

— N L

in which D, E, G and J independently represent -CR^- or a nitrogen atom, with at least one of D, E, G and J representing -CR^.; two adjacent groups D, E, G and J may together form a second phenyl or 5- to 7- membered heteroaromatic ring optionally substituted by one or more groups selected from halogen or lower alkyl, in which the 5- to 7- membered heterocyclic ring contains from one to four heteroatoms in the ring which may be the same or different selected from nitrogen, oxygen and sulphur; Rl 5 is hydrogen, halogen, lower alkyl, lower haloalkyl, nitro, cyano, -CO2R⁷, -SfO^R , lower alkoxy, lower haloalkoxy or cyclopropyl;

R*6 is phenyl optionally substituted by halogen, nitro, cyano, lower alkyl, lower alkoxy, lower haloalkyl, lower haloalkoxy, -S(O)_mR⁸, -(CR5R6)S(O)_mR⁸; m is zero, one or two; q is one or two; and r is one, two or three; characterised by the reaction of a compound of formula (II):

(ID wherein R, R , and Ar are as defined above, with hydroxylamine or a salt thereof.

Hydroxylamine may be used in this reaction in the form of a salt, for example hydroxylamine sulfate or, hydroxylamine hydrochloride. Where the reaction is performed using a salt of hydroxylamine it is preferable, for reasons of speed of reaction, to include a base in the reaction mixture to liberate hydroxylamine and initiate the reaction. Examples of suitable bases include metal bases such as sodium acetate, carbonate or hydrogen carbonate; or organic bases, for example amines such as diisopropylamine and triethylamine. Where base is present, the ratio of base: hydroxylamine is generally from 0.01 :1 1.5:1, preferably from 0.1 :1 to 1.1:1.

The reaction is preferably performed in a solvent. Examples of suitable include: aromatic, aliphatic and cycloaliphatic hydrocarbons and halogenated or non-halogenated hydrocarbons, for example dichloromethane, toluene, dichloroethane or chlorobenzene; ether solvents such as tert butyl methyl ether (MTBE) and tetrahydrofuran. an alcohol solvent such as ethanol and methanol; or water.

It will be understood that the reaction may be performed in a mixture of two or more different solvents.

The reaction is preferably performed at a temperature of from 20°C to the boiling point of the solvent, preferably from 30 to 80°C The molar ratio of the compound of formula (II): hydroxylamine is generally from 1:1 to 1:2, preferably from 1:1.01 to 1 :1.2.

By the terms 'lower alkyl', 'lower alkenyl', 'lower alkoxy' or' lower alkylthio' is meant a straight- or branched- chain alkyl, alkenyl, alkoxy or alkylthio radical respectively, having from one to six carbon atoms. By the term 'lower haloalkyl', 'lower haloalkenyl' or 'lower haloalkoxy' is meant a straight- or branched- chain alkyl, alkenyl or alkoxy radical respectively, having from one to six carbon atoms substituted by one or more halogens. When a 5- to 7- membered ring forming part of the group Ar is present it may be carbocyclic or heterocyclic containing one or more heteroatoms, preferably selected from oxygen, sulphur and nitrogen (preferably from one to four), it being understood that a sulphur atom, where present, may be in the form of a group -SO- or -SO2-, and may be aromatic, saturated or partially saturated.

Where R* represents cyclic ketal or cyclic thioketal preferably the ketal or thioketal ring contains 5 or 6 ring members.

Examples of the group Ar when it represents phenyl fused to a 5- to 7- membered ring include the following optionally substituted ring systems and corresponding dihydro compounds (where applicable): benzo-l,2,3-thiadiazole, benzo[b]thiophene, benzo[b]furan, benzo[c]thiophene, benzo[c]furan, benzthiazole, 1 ,2-benzisothiazole, 2,1-benzisothiazole, 1 ,2-benzthiazin, 2,1-benzthiazin, 1,3-benzothiazine, 1 ,4-benzothiazine, benzimidazole, indazole, thiochroman, chroman, 2H- thiochromene, 2H-chromene, 4H-thiochromene, 4H-chromene, isothiochroman, isochroman, isothiochromene, isochromene, benzofurazan, 1 ,3-benzodithiole, 1,3-benzodioxole, 1,3-benzoxathiole, 1 ,4-benzodithiin, 1 ,4-benzoxathiin, 1,3-benzoxathiin, 3,1-benzoxathiin, 1,3-benzodithiin, thiochroman-4-one and saccharin. Compounds of formula (I) above of this type are decribed in

EP-A-0636622.

When a group Het is present preferably the first heterocyclic ring contains from 4 to 7 ring atoms, and the carbocyclic or second heterocyclic ring contains from 4 to 7 ring atoms. Het may be aromatic or non-aromatic. Examples of the ring system Het include: thienyl, furyl, pyrrolyl and their benzo-fused analogues; oxazinyl, thiazinyl, pyrazinyl, pyrimidinyl, pyridazinyl and their benzo-fused analogues; thiazolyl, oxazolyl, imidazolyl and their benzo-fused analogues; pyrazolyl, isoxazolyl, isothiazolyl and their benzo-fused analogues; oxadiazolyl, thiadiazolyl, triazolyl and, where appropriate, their benzo-fused analogues; pyridyl, pyranyl, thiinyl and their benzo-fused analogues; oxadiazinyl, thiadiazinyl, triazinyl and, where appropriate, their benzo-fused analogues; tetrazolyl, piperidinyl, morpholinyl and piperazinyl. Compound of formula (I) in which Ar is Het are described in EP-A-0588357.

Preferably the compound of formula (I) is a compound of formula

(la):

(Ia) wherein R and Rl are as defined above;

R² is halogen, lower alkyl, lower alkoxy, lower haloalkyl, lower haloalkoxy, -S(O)_mR⁴, -(CR⁵R⁶)_qS(O)_mR⁴, nitro, cyano, -N(R7)Sθ2R⁸, -OSO2R⁸, cycloalkyl having from three to seven ring carbon atoms; or straight- or branched- chain alkenyl or alkynyl having up to six carbon atoms;

R³ is lower alkyl, lower haloalkyl, aryl or benzyl; n is an integer from one to five;

R⁴ is lower alkyl, or phenyl optionally substituted by from one to five groups selected from lower alkyl, lower haloalkyl, halogen and -S- alkyl;

R5 and R independently are hydrogen, lower alkyl or lower haloalkyl;

R is hydrogen or lower alkyl;

R⁸ is lower alkyl or lower haloalkyl; m is zero, one or two; and q is one or two; which is prepared by the reaction of a compound of formula (Ila):

(Ha) wherein R, R , R² and n are as defined above, with hydroxylamine or a salt thereof.

Compounds of formula (II) and (Ila) above are novel and therefore constitute a further feature of the present invention.

Compounds of formula (II) and (Ila) above in which R is cycloalkyl having from three to seven ring carbon atoms, optionally substituted by lower alkyl or halogen are preferred. More preferably, Rl is 1 -methylcyclopropyl or, most preferably, cyclopropyl.

In formula (Ila) above, preferably one group R² is in the ortho- position of the phenyl ring.

R² is preferably selected from lower alkyl, lower haloalkyl, halogen and -S(O)_mR⁴. More preferably R² is selected from -CF3, halogen and -S(O)_mR⁴.

In formula (Ila) above preferred groups (R²)_n include 2-SCH3- 3-C1-4-C1, 2-SOCH3-3-CI-4-CI, 2-SCH3-4-CF3, 2-SO2CH3-4-CF3 and 2-SO2CH3-4-halogen (preferably Cl or Br). Compounds of formula (Ila) in which (R²)_n is 2-SCH -3-Cl-4-Cl or 2-SCH₃-4-CF₃ are particularly preferred.

Preferably R³ is lower alkyl, especially ethyl. In formula (Iia) above preferably n is two or three. According to a further feature of the present invention compounds of formula (II) may be prepared by the reaction of a compound of formula (ffl):

(III) wherein R^ and Ar are as defined above, with a cyanoacetate of formula (IV): R3θC(=O)-CN (IV) wherein R³ is as defined above, in the presence of a catalyst. This reaction is described in the literature, for example see Iimori et al, Tetrahedron letters, 1979, Vol. 27, pp 2525-2528, A. Veronese et al, J. Molecular Catalysis, Vol. 54 (1989) pp 73-80; and Italian Patent No. 1200768.

The reaction is preferably performed in a solvent. Examples of solvents which may be suitable include: aromatic, aliphatic and cycloaliphatic hydrocarbons and halogenated or non-halogenated hydrocarbons, for example, chlorobenzenes, dichloromethane, dichloroethane or preferably toluene; and ether solvents, for example methyl t-butyl ether (MTBE). Suitable catalysts include the following: a transition metal catalyst, preferably a zinc or nickel catalyst such as zinc acetate, zinc acetoacetate, nickel acetoacetate or zinc chloride; or an organic acid catalyst such as acetic acid or trifluoroacetic acid.

Various mixtures of the above catalysts may also be used. Base catalysts generally give poor results and lead to the formation of by-products.

The metal catalyst is generally present in a small quantity, for example about 2 mole percent of the compound of formula (III).

The reaction is preferably performed at a temperature of from 20°C to the boiling point of the solvent, preferably from 40 to 90°C (for example from 50 to 90°C).

The molar ratio of the compounds of formula (III): (IV) is generally from 1 :1 to 1 :2, preferably from 1 : 1.05 to 1 :1.2.

Compounds of formula (III) are known in the literature from the European and International Patent Publications listed above, or can be prepared by known methods. Compounds of formula (IV) above are also known in the literature, or can be prepared by known methods. According to a further feature of the present invention compounds of formula (I) above wherein R, R , R² and n are as defined above may be prepared by reacting a compound of formula (III) above with a compound of formula (IV) above and directly reacting the compound of formula (II) thus obtained with hydroxylamine or a salt thereof. The following non-limiting examples illustrate the invention. In the description that follows "mM" means millimoles, and "m.p." means melting point.

Exa le 1 Preparation of ethyl 5-cyclopropyl-4-(3,4-dichloro-2- methylsulpheny.benzoyl)isoxazole-3-carboxylate. l-Cyclopropyl-3-(3,4-dichloro-2-methylsulphenyl- phenyl)propane- 1,3, -dione (9.087 g, 30mM) is charged to a 100ml reactor, followed by toluene (10 ml), ethyl cyanoformate (3.11 ml, 31.5mM) and zinc acetate dihydrate (132.5 mg, 0.6mM). The mixture is stirred at 80°C for 2.3 hours to give ethyl 2-amino-3- cyclopropylcarbonyl-4-oxo-4-(3,4-dichloro-2-methylsulphenyl- phenyl)but-2-enoate. The reaction temperature is allowed to fall to 50°C. Hydroxylamine hydrochloride (2.296 g, 33mM)and sodium acetate (0.494 g, 6mM) in ethanol (40 ml) are added and the mixture stirred at 50°C for 2.8 hours, by which time the reaction is complete. The reaction mixture is diluted by addition of toluene (15 ml) and the ethanol is eliminated by evaporation under reduced pressure at 45°C. Further toluene is added and the mixture again partially evaporated. The reaction is extracted at 50°C with water and the aqueous phases re- extracted with toluene. The toluene phases are evaporated to dryness under reduced pressure. The crude product (light orange solid) is dried to constant weight to give the title compound, (m.p. 79.5°C) in a yield of 11.84 g (theoretical 12g; a yield of 98.7%).

The preparation of l-cyclopropyl-3-(3,4-dichloro-2- methylsulphenyl-phenyl)-propane- 1,3, -dione is described in EP-A-0560482, which also describes the synthesis of ethyl 5- cyclopropyl-4-(3,4-dichloro-2-methylsulphenylbenzoyl)isoxazole-3- carboxylate by treating the magnesium salt of l-cyclopropyl-3- (3,4-dichloro-2-methylsulphenyl-phenyl)propane-l,3,-dione with ethyl chloro-oximidoacetate in dichloromethane (see Example 2 of EP-A-0560482). The reaction is reported as giving 2.19g of the title compound (5.47mM) from 2.0g of dione (6.60mM), i.e. a yield of 82.9% (cf. 98.7% in the present invention), which further illustrates the advantages of the present invention.

Example 2

Preparation of ethyl 2-amino-3-cyclopropylcarbonyl-4-oxo-4- (3,4-dichloro-2-methylsulphenyl-phenyl)but-2-enoate.

1 -Cyclopropyl-3-(3 ,4-dichloro-2-methylsulphenyl- phenyl)propane-l,3-dione (1.82g, 6mM), ethyl cyanoacetate (0.66ml, 6.6mM) were stirred in 1,2-dichloroethane (5ml) for 1.5 hours at 50°C, then for 3 hours at 80°C. After cooling to ambient temperature, the solution was washed with water. The organic phase was evaporated under reduced pressure to give 2.5g of crude product, which was purified by column chromatography using a mixture of heptane and ethyl acetate to give a solid product which was crystallized in pentane to give 1.5g of the title product, m.p. 78°C.

Example 3 Preparation of ethyl 5-cyclopropyl-4-(3,4-dichloro-2- methylsulphenyI-benzoyl)isoxazole-3-carboxylate.

Ethyl 2-amino-3-cyclopropylcarbonyl-4-oxo-4-(2,4-dichloro-2- methylsulphenyl-phenyl)but-2-enoate (l .Og, 2.58mM) was dissolved in ethanol (7ml). Hydroxylamine hydrochloride (0.198g, 2.85mM) and sodium acetate (0.233 g, 2.84mM) were added and the reaction stirred for one hour at 50 C. The reaction was cooled to room temperature and water added, followed by removal of the ethanol present under reduced pressure. The reaction mixture was extracted with MTBE and the organic phase washed with water and evaporated under reduced pressure to give 0.82g of the title compound as a white solid.

Example 4

Preparation of ethyl 2-amino-3-cyclopropylcarbonyl-4-oxo-4- (2-methylsulphenyl-4-trifluoromethyl-phenyl)but-2-enoate. l-Cyclopropyl-3-(2-methylsulphenyl-4-trifluoromethyl- phenyl)propane- 1,3 -dione (2.4 lg, 8mM)was charged to a 25 ml reactor followed by toluene (6 ml), zinc acetate dihydrate (35mg, 0.16 mM)and ethyl cyanoformate (860 microl, 8.7 mM). The mixture was stirred at 78°C for 4 hours. After cooling to ambient temperature , toluene (20 ml) was added to the mixture and the solution was wasched with brine. The organic phase is evaporated under reduced pressure to give 3.34 g of crude product as a viscous oil which was triturated with diethyl ether and pentane. After filtration of the insoluble material obtained, the solution was evaporated under reduced pressure to give 2.95 g of a dark viscous oil (Yield : 87.5% Assay : 95%).

Example 5

Preparation of ethyl 5-cyclopropyl-4-(2-methylsulphenyl-4- trifluoromethylbenzoyl)-isoxazole-3-carboxylate.

Zinc acetate dihydrate (151 mg, 0.69 mM)was charged to a 50 ml reactor, followed by dichloromethane (14 ml),l-cyclopropyl-3-(2- methylsulphenyl-4-trifluoromethyl-phenyl)propane-l,3-dione (10 g, 33mM) and ethyl cyanoformate (3.7ml, 37.5mM). The mixture was stirred at 45°C for 6 hours to give ethyl 2-amino-3-cyclopropylcarbonyl-

4-oxo-4-(2-methylsulphenyl-4-trifluoromethylphenyl)but-2-enoate.

Dichloromethane was distilled before adding ethanol (20ml).Hydroxylamine hydrochloride (2.53g, 36.38mM )in ethanol (5 ml)then sodium acetate (0.546g, 6.66mM) were added and the mixture stirred at 50°C for 4 hours. After cooling to ambient temperature, ethanol (10 ml) was added and the resulting yellow suspension was pourred onto water. The solid was filtered then dried to constant weight to give the title compound as a yellow solid (13g, m.p = 93 - 95°C) giving an overall yield of 93.4% (Assay : 95%).

Claims

1. A process for preparing a compound of formula (I)

(I) wherein R is -CO2R³;

Rl is lower alkyl or cycloalkyl having from three to seven ring carbon atoms, optionally substituted by lower alkyl or halogen; Ar is: phenyl optionally substituted by one to five groups R² which may be the same or different; or is phenyl optionally substituted by from one to three groups R² which may be the same or different and wherein two additional substituents on adjacent positions of the phenyl ring, together with the two atoms to which they are attached, form a 5- to 7- membered ring which is optionally substituted by one or groups Rl which may be the same or different; or is a group Het which is optionally substituted by one or more groups R², wherein Het represents a first heterocyclic ring containing from one to four heteroatoms in the ring selected from oxygen, nitrogen and sulphur, which is optionally fused with a benzene, or carbocyclic or second heterocyclic ring (which is optionally saturated or partially saturated) to form a bicyclic system, wherein the first heterocyclic ring of the group Het is attached to the carbonyl group in the 4-position of the isoxazole ring;

R² is halogen, lower alkyl, lower alkoxy, lower haloalkyl, lower haloalkoxy, -S(O)_mR⁴, -(CR⁵R⁶)_qS(O)_mR⁴, nitro, cyano, -N(R5)Sθ2R⁸, -OSO2R⁸, cycloalkyl having from three to seven ring carbon atoms, straight- or branched- chain alkenyl or alkynyl having up to six carbon atoms, -CO₂R⁷, -S(O)_mR9, -O(CH₂)_rOR⁸, -NR5R6, -CONR5R6, -N(R5)C(=O)R10, -(CR⁵R⁶)_qN(R⁵)SO₂R⁸, -(CR5R6)_qN(R5)C(=O)RlO, -(CR⁵R<>)_qP(=O)R¹²R¹³, -(CR5R6)_qR14₎ -(CR⁵R6)_£.RI6_{J or a} straight- or branched-chain alkyl containing up to six carbon atoms substituted by -OR^; where R² is present on a heterocyclic or carbocyclic ring of the group Het, R² may also represent =0, =S, cyclic ketal or cyclic thioketal;

R3 is lower alkyl, lower haloalkyl, aryl or benzyl; R⁴ is lower alkyl, or phenyl optionally substituted by from one to five groups selected from lower alkyl, lower haloalkyl, halogen and -S- alkyl;

R5 and R^ independently are hydrogen, lower alkyl or lower haloalkyl; R⁷ is hydrogen or lower alkyl;

R⁸ is lower alkyl or lower haloalkyl;

R9 is lower haloalkyl, lower alkenyl or lower haloalkenyl;

RIO is R⁸, lower alkoxy or lower alkylthio;

Rl 1 is R² or =O, =S, lower alkylimino, cyclic ketal or cyclic thioketal;

R ² and R^ are lower alkyl, hydroxy, lower alkoxy or lower haloalkoxy;

Rl⁴ is a 5-membered heteroaromatic ring of formula

in which D, E, G and J independently represent -CR* *. or a nitrogen atom, with at least one of D, E, G and J representing -CR15-; two adjacent groups D, E, G and J may together form a second phenyl or 5- to 7- membered heteroaromatic ring optionally substituted by one or more groups selected from halogen or lower alkyl, in which the 5- to 7- membered heterocyclic ring contains from one to four heteroatoms in the ring which may be the same or different selected from nitrogen, oxygen and sulphur;

R!5 is hydrogen, halogen, lower alkyl, lower haloalkyl, nitro, cyano, -CO2R⁷, -S(O)_mR⁸, lower alkoxy, lower haloalkoxy or cyclopropyl;

Rl6 is phenyl optionally substituted by halogen, nitro, cyano, lower alkyl, lower alkoxy, lower haloalkyl, lower haloalkoxy, -S(O)_mR⁸, -(CR5R6)S(O)_mR⁸; m is zero, one or two; q is one or two; and r is one, two or three, characterised by the reaction of a compound of formula (IT):

(II) wherein R, Rl and Ar are as defined above, with hydroxylamine or a salt thereof.

2. A process for preparing a compound of formula (Ia):

(Ia)

R is -CO2R³;

Rl is lower alkyl or cycloalkyl having from three to seven ring carbon atoms, optionally substituted by lower alkyl or halogen;

R² is halogen, lower alkyl, lower alkoxy, lower haloalkyl, lower haloalkoxy, -S(O)_mR⁴, -(CR⁵R⁶)_qS(O)_mR⁴, nitro, cyano, -N(R )SO2R , -OSO2R⁸, cycloalkyl having from three to seven ring carbon atoms; or straight- or branched- chain alkenyl or alkynyl having up to six carbon atoms;

R5 and R independently are hydrogen, lower alkyl or lower haloalkyl;

R? is hydrogen or lower alkyl;

R⁸ is lower alkyl or lower haloalkyl; m is zero, one or two; and q is one or two; characetized by the reaction of a compound of formula (Ila):

(Ha) wherein R, Rl , R² and n are as defined above, with hydroxylamine or a salt thereof.

3. A process according to claim 1 or 2, characterised in that the reaction is performed at a temperature of from 20 C to the boiling point of the solvent, preferably from 30 to 80 C.

4. A process according to claim 1 , 2 or 3, characterised in that the molar ratio of the compound of formula (II): hydroxylamine is generally from 1 :1 to 1 :2, preferably from 1 : 1.01 to 1 : 1.2.

5. A process according to any one of claims 1 to 4, characterised in that the reaction is performed in the presence of a base.

6. A compound of formula (II) :

(II) wherein R, and Ar are as defined in claim 1.

7. A compound of formula (Ila):

(Oa) wherein R, R , R² and n are as defined in claim 2.

8. A compound according to claim 6 or 7 in which Rl is cycloalkyl having from three to seven ring carbon atoms, optionally substituted by lower alkyl or halogen.

9. A compound according to claim 9 in which R^ is 1- methylcyclopropyl or cyclopropyl.

10. The use of a compound of formula (II) as defined in claim

6 as an intermediate in the synthesis of a herbicide of formula (I) as defined in claim 1.

1 1. A process for the preparation of a compound of formula (II) as defined in claim 1 , characterised by the reaction of a compound of formula (III):

(III) wherein R and Ar are as defined in claim 1, with a cyanoacetate of formula (TV):

R³OC(=O)-CN (IV) wherein R³ is as defined in claim 1 , in the presence of a catalyst.

12. A process according to claim 11, characterised in that the catalyst is a transition metal catalyst, preferably a zinc or nickel catalyst; or an organic acid catalyst such as acetic acid or trifluoroacetic acid.

13. A process according to claim 11 or 12, characterised in that the reaction is performed at a temperature of from 20°C to the boiling point of the solvent, preferably from 50 to 90°C.

14. A process according to claim 10, 11 or 12, characterised in that the molar ratio of the compounds of formula (III): (TV) is from 1 :1 to 1 :2, preferably from 1 : 1.05 to 1 : 1.2.