GB2120652A - Furano-pyrano derivatives - Google Patents

Abstract

A compound with herbicidal properties of the general formula:- <IMAGE> in which: R<1> to R<12> are various substituents with the proviso that at least one of R<1>, R<5> and R<8> represents a group A and A represents a group of the general formula -OCR<14>R<15>Y in which each of R<14> and R<15> independently represents a hydrogen atom or an optionally substituted alkyl group, and Y represents an alkenyl or alkynyl group, an optionally substituted phenyl group, or an optionally substituted ring having 5 or 6 atoms in the ring at least one of which is nitrogen, oxygen, or sulphur.

Description

SPECIFICATION Novel heterocyclic compounds having herbicidal properties This invention relates to novel heterocyclic compounds-having herbicidal properties.

The invention provides a compound of the general formula

in which: either R' represents a group ~OR13, a group -O.CO.R13, or a group A and R2 represents a hydrogen atom or an optionally substituted alkyl group, or R1 and R2 together represent an oxygen atom or a group =N OR13 =N.NH.CO.NHR13, =N.NH.CO.R13, =N.NHR13 or =N.O.CO.R13, in which R13 represents a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted phenyl group; R3 represents a hydrogen atom or an optionally substituted alkyl group; either R5 represents a hydrogen atom, an optionally substituted alkyl group, an alkoxy group or a group A and R4 represents a hydrogen atom or an optionally substituted alkyl group, or R4 and R5 together represent a bond;; R6 represents a hydrogen atom or an optionally substituted alkyl group; either R7 represents a hydrogen atom or an optionally substituted alkyl group and RB represents a hydrogen atom, a group A, an alkenyl or alkoxy group, or an optionally substituted alkyl or phenyl group, or R7 and R8 together represent an alkylene group, or R8 and R11 together with the interjacent carbon atoms form a mono- or bi-cyclic hydrocarbyl ring; either R9 represents a hydrogen atom or an optionally substituted alkyl group and R'O represents a hydrogen atom or an optionally substituted alkyl group, or R9 and R'O together represent a bond;; R11 represents a hydrogen atom or an optionally substituted alkyl group, and R12 represents a hydrogen atom or an optionally substituted alkyl group, or, if R8 represents a hydrogen atom or an optionally substituted alkyl group, R11 and R12 together may represent an alkylene group; and A represents a group of the general formula OCRl4RlBY in which each of R14 and R15 independently represents a hydrogen atom or an optionally substituted alkyl group, and Y represents an alkenyl or alkynyl group, an optionally substituted phenyl group, or an optionally substituted ring having 5 or 6 atoms in the ring at least one of which is nitrogen, oxygen or sulphur; with the proviso that at least one of R1, R5 and R8 represents a group A.

Unless otherwise stated throughout this specification and claims, any alkyl, alkoxy or alkenyl moiety preferably has up to 6, especially up to 4, carbon atoms.

An optionally substituted alkyl group may for example be substituted by one or more of the same or different substituents selected from halogen atoms and cycloalkyl, alkoxy, phenyl, phenoxy, cyano, hydroxy and carboxy groups. Preferably however it is unsubstituted.

Preferably each of R14 and RIB represents a methyl group or, especially, a hydrogen atom.

An alkenyl or alkynyl group Y preferably has up to 6, especially up to 4, carbon atoms. For example, Y may represent an ethynyl group.

Suitable substituents which may be present in an optionally substituted phenyl group Y are those generally found in aromatic groups, for example halogen atoms and hydroxy, amino, cyano, alkylsulphonyl, nitro, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylthio, alkoxycarbonyl, phenyl and phenoxy groups.

A phenyl group Y is preferably unsubstituted or substituted by up to 3 of the same or different exemplified substituents given above. Most preferably it is unsubstituted, monosubstituted or disubstituted. Preferred substituents are selected from halogen atoms and nitro, cyano, alkyl, haloalkyl, alkoxy, haloalkoxy and alkylthio groups, especially preferred substituents being halogen atoms and alkyl, especially methyl, groups.

As noted above, Y may represent an optionally substituted ring having 5 or 6 atoms in the ring at least one of which is nitrogen, oxygen or sulphur. Suitable heterocyclic groups in this regard include optionally substituted pyridyl, pyrrolyl, pyrazolyl, imidazolyl, pyrazinyl, pyridazinyl, pyrimidinyl, furyl, thienyl and triazinyl groups, and also the corresponding partially or fully saturated analogues. Pyridyl groups are especially preferred.

A heterocyclic group may be substituted by one or more of the substituents given above for a phenyl group; preferably however it is unsubstituted or substituted by one or more alkyl groups or halogen atoms; most preferably such a group is unsubstituted.

Most preferably, Y represents a phenyl, 2-chlorophenyl, 2-fluorophenyl, 2,6-dichlorophenyl, 2methylphenyl or 2-pyridyl group.

If R13 represents an optionally substituted phenyl group, this group may for example be one of the preferred groups given above for a phenyl group Y.

Preferably R13 represents a hydrogen atom, a methyl or ethyl group, or an optionally substituted, especially unsubstituted, phenyl group.

Preferably either R1 represents a group A and R2 represents a hydrogen atom, or R1 and R2 together represent an oxygen atom.

Preferably R3 represents a methyl group or, especially, a hydrogen atom.

Preferably Re represents a methyl group or a hydrogen atom.

If R7 and R8 together form an alkylene group, this may be linear or branched, and preferably has 3 or 4 carbon atoms in the chain and up to 3 carbon atoms substituting the chain. Most preferably the group is a tri- or tetra-methylene group.

If R8 and R11 together with the interjacent carbon atoms represent a mono- or bicyclic hydrocarbyl ring, this may be saturated or unsaturated. Preferably, such a ring has from 5 to 8 carbon atoms, especially 6 or 7 carbon atoms; for example, it may be a cyclohexane ring or a norbornene ring:

If R8 represents an optionally substituted phenyl group, this group may for example be one of the preferred groups given above for a phenyl group Y.

Preferably either R7 represents a methyl group or a hydrogen atom and R8 represents a hydrogen atom, an alkyl group, especially a methyl group, an alkenyl group, for example a 1 -methylethenyl group, an alkoxy group, especially a methoxy or ethoxy group, an nptionally substituted, especially unsubstituted, phenyl group, or a group A, or R7 and R8 together represent an alkylene group, or R8 and R71 together with the interjacent carbon atoms represent a mono- or bi-cyclic hydrocarbyl ring.

If R1' and R12 together form an alkylene group, this may be linear or branched, and preferably has 3 or 4 carbon atoms in the chain and up to 3 carbon atoms substituting the chain. Most preferably the group is a tri- or tetra-methylene group.

Preferably either R11 represents a methyl group or, especially, a hydrogen atom, and R12 represents a methyl group or a hydrogen atom, or R8 represents a hydrogen atom or an alkyl group and R11 and R12 together form a tri- or tetra-methylene group, or, as stated above, R8 and R11 together with the interjacent carbon atoms form a ring.

It will be appreciated that the compounds of the general formula I exhibit isomerism. The present invention includes all the individual isomers, as well as mixtures thereof.

Typical compounds of the general formula I include the following:

The compounds according to the invention in which R1 represents a group A may be prepared by reacting a compound of the general formula:

with a compound of the general formula Hal-A (III) in which Hal represents a chlorine, bromine or iodine atom. The reaction is preferably carried out in the presence of a base, for example an alkali metal hydride, hydroxide or alkoxide. The reaction temperature may for example be in the range of from 0 to 1 500C, especially 1 5 to 11 OOC. The molar ratio of the compound II to compound Ill is not crucial; it may for example be in the range 1:5 to 5:1 , especially 1 :3 to 3:1.The reaction may if desired be carried out in the presence of an inert solvent, for example an amide such as dimethylformamide, an ether such as diethyl ether or tetrahydrofuran, or a hydrocarbon or chlorinated hydrocarbon such as toluene or xylene. Mixtures of solvents are often suitable.

A compound of the general formula I in which R5 represents a group A may be prepared by react ing a compound of the general formula:

with a compound of the general formula: (V) HO-A The reaction temperature may for example be in the range of from 0 to 1 500 C, especially 1 5 to 11 OOC. Molar ratios of the reactants are not crucial; typical ratios are in the range 1:5 to 5:1, especially 1:3 to 3:1. The reaction is preferably carried out in the presence of a suitable solvent, for example an ether, such as tetrahydrofuran or diethyl ether, or a hydrocarbon or chlorinated hydrocarbon such as toluene or xylene. It may be convenient to carry out the reaction using an excess of the alcohol V as solvent.The reaction is preferably carried out in the presence of an acid catalyst for example a mineral acid such as sulphuric acid, or a strong organic acid such as trifluoroacetic acid or p-toluene sulphonic acid.

To produce a compound of the general formula I in which RB represents a group A, a compound of the opnernl formtila:

where the group -x represents a suitable leaving group, may be reacted with an olefin or an acetylene of the general formula:

This reaction produces a compound of the general formula I in which R4 and R5 together represents a bond, and R1 and R2 together represent an oxygen atom.

Suitable leaving groups include, for example, chlorine and bromine atoms; hydroxy groups; carboxylate groups, especially alkylcarbonyloxy groups, for example the acetyloxy group, and organic sulphonyloxy groups, for example alkylsulphonyloxy groups such as methylsulphonyloxy, arylsulphonyloxy groups such as benzene sulphonyloxy, and alkaryisulphonyloxy groups such es p- toluenesulphonyloxy. The reaction may for example be carried out at a temperature in the range of from -10 to 1 000C. The reaction may be initiated by heating, or by the pressure of a suitable catalyst. When X is a oxygen-containing group, the reaction is preferably carried out in the presence of a base, for example an amine, for example triethylamine, an azocompound, for example diazopropylamine, or an alkali metal hydroxide or alkoxide.When the group X is a chlorine or bromine atom, an acid catalyst, for example a carboxylic acid, may be more appropriate. Suitable solvents include hydrocarbons, chlorinated hydrocarbons, ethers and amides, for example those specific solvents given above.

Preferably a stoichiometric excess of the compound of the formula VII over the compound of formula VI is used.

Any resulting compound of the general formula I can be converted into other compounds of the general formula I, if desired, by methods known in the art. For example, a compound in which R1 and R2 together represents an oxygen atom can be converted into the corresponding compound in which R1 and R2 together represent N-OR13, or =N-NHR13, = N.N H.C OR13, =N.O.COR13, or =N.NH.CO.NHR13, by reaction with a compound NH2-0R13, N H2.N H.C OR13, NH2-NHR13, NH 2O.CO.R13 or =N.NH.CO.NHR13.It can be reduced to the corresponding alcohol (R1=OH, R2=H), which can in turn be reacted with an acylating agent, for example an acyl chloride Cl-CO-R13 to form the corresponding ester. It can be reacted with an appropriate Grignard reagent MgBrR2 to produce the corresponding alcohol in which R2 represents an alkyl group.

A compound in which R4 and R5 together represent a bond can be reduced by conventional hydrogenation methods to produce the corresponding compound in which R4 and R5 represent hydrogen atoms, or an alkanol can be added across the double bond to produce a compound in which R5 represents an alkoxy group, or an alkylating agent such as lithium dimethyl cuprate can be used to introduce an alkyl group R5.

Starting materials of the formula II may be prepared by reduction of the ketone:

by conventional methods. The double bond may be reduced at the same time, or not, depending on the reaction conditions chosen Compounds of the general formula (IVa) may be prepared by reaction of a compound V shown above with an olefin or acetylene of the formula

or if R'2 and R" together represent an alkylene group, by intramolecular cyclisation of a compound of the general formula:

or, if R7 and RB together represent an alkylene group, by intramolecular cyclisation of a compound of the general formula

Preferred reaction conditions for these reactions are similar to those described above for the reaction of the compounds VI and Viol.

Compounds of the general formulae II, IV, Xl and X are novel, and the invention therefore provides these compounds per se.

Typical compounds of the general formula iV include:

Typical compounds of the general formula II include those alcohols corresponding to the ketones of formula IV given above in which the keto group has been reduced, and those alcohols corresponding to the ketones of formula IV given above in which the keto group has been reduced and the double bond in the ring containing the keto group has also been reduced.

Typical compounds of the general formula IX include:

Typical compounds of the general formula X include:

The compounds of the general formula I exhibit herbicidal properties. The invention therefore also provides a herbicidal composition which comprises a compound of the general formula I together with a carrier.

The invention also provides a method of combating undesired plant growth at a locus, which comprises applying to the locus a compound or a composition according to the invention. The locus may for example be a crop area, typical crops including, for example, small grain cereals and soyabeans.

Application may be post-emergence or, preferably, pre-emergence. Application to a plant may be by foliar or, preferably, root application. Application rates are preferably in the range of from 0.1 to 6 kg/ha, especially 0.1 to 4 kg/ha, active material.

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

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

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

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surface-active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation of fatty acids or aliphatic amines or amides containing at least 1 2 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example poctylphenol 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 caster oil, and sodium alkylaryl sulphonates such as sodium dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may 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, 310% w of a dispersing agent and, where necessary, 0-1 0% 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 21 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 225% w active ingredient and 0-10% w of additives such as stabilisers, slow release modifiers and binding agents. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 10-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabillsers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 1075% w active ingredient, 0.5-1 5% w of dispersing agents, 0.110% w of suspending agents such as protective colloids and thixotropic agents, 0-1 0% 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 present 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 following Examples illustrate the invention. NMR values, when given, are data values in ppm relative to tetramethylsilane, in CDCC3 solvent.

EXAMPLE 1 Preparation of:

(a) Preparation of 2(1 -hydroxyhex-5-enyl)furan.

A solution of 5-bromo-pent-1 -ene (25.7 g; 172 mM) in dry ether (120 ml) was added dropwise with stirring, to magnesium turnings (4.2 g; 17.5 mm) in dry ether (150 ml). The reaction was moderated by cooling in an ice-bath. After the addition was complete, the solution was stirred for a further 0.5 hours before adding dropwise at 0 C a solution of furfural (1 5 g; 1 50 mM) in dry ether (200 ml). The solution was stirred for 0.25 hours before quenching with a solution of saturated NH4CI (1 50 ml).

The organic products were extracted into ether (3 x 200 ml) and the combined extracts washed with brine and water before drying (MgSO4). The ether was evaporated and the crude reaction product distilled under reduced pressure (880 C; 2 mmHg) to give the desired product as a colourless oil (23.0 g; 87%).

(b) Preparation of 2,6-dimethoxy-2-(1-hydroxhex-5-enyl)-2,6-dihydrofuran.

To a solution of the product obtained in (a) above, (20 g; 120 mM) in anhydrous ether (125 ml) and absolute methanol (170 ml), was added dropwise, with stirring, a solution of bromine (23 g; 143 mM) in methanol (250 ml), at -450C. The solution was stirred for 0.5 hours at -480C before quenching with anhydrous ammonia to pH-8. The ammonium bromide was filtered off and the solvents removed in vacuo. The resulting residue was taken up into benzene and filtered through a short alumina column (neutral). The solution was concentrated in vacuo to give the desired product as a colourless oil (26.5 g; 96%).

(c) Preparation of

The product obtained in (b) above, (20 g; 87 mM) was dissolved in water/methanol (40 ml/80 ml) and activated Dowex-50 (Trade Mark) ion exchange resin (2.5 g) added. The suspension was stirred for 1.5 hours at room temperature before filtering off the resin and extracting the organic products into ethyl acetate (3 x 250 ml). The combined extracts were dried (MgSO4) and concentrated in vacuo. The resulting residue was chromatographed on silica gel in 7 g portions (500 g; ether/petroleum ether 1:1) to give the desired pyranone as a colourless oil (14 g; 88%), which solidified to give white crystals, melting point 440C.

Elemental Analysis C H Calculated for C,OH,403 65.9 7.69 Found 65.7 7.9 EXAMPLES 2 AND 3 By methods analogous to that of Example 1, the following compounds were prepared.

EXAMPLE 2

NMR. 1.2-2.2 (8H,m); 4.66 (1H, t); 6.00 (2H, m); 5.85 (1H, d), 5.7 (1H, m); 6.15 (1H, d); 6.95 (1H d.d).

EXAMPLE 3

NMR: 1.2-2.3 (6H, m); 4.6 (1 H, m); 5.00 (2H, m); 5.6 (1 H, d); 6.6-5.8 (1 H, m); 6.2 (1 H, d); 6.9 (1 H, d.d).

EXAMPLE 4 Preparation of

(a) n-Butyllithium (75 ml of 1.5 m solution in hexane; 112.3 mmol) was added to a stirred solution of furfuryl alcohol (5 g; 51 mmol) in dry tetrahydrofuran (300 ml) at-250C, under a nitrogen atmosphere.

After the addition the temperature was allowed to rise to-5 C before recooling to-20 C and stirring for 2 hours. 5-Bromo-pen-1-ene (10 g; 67 mmol) dissolved in tetrahydrofuran (70 ml) and hexamethylphosphorustriamide (2 ml) was added dropwise to the reaction mixture at-20 C. The solution was stirred overnight at room temperature and then poured into a saturated solution of NH4CI (100 ml). The organic products were extracted into ether (3 x 150 ml) and the combined ether extracts washed with brine (100 ml) and water (2 x 76 ml) before drying (MgSO4). The solution was concentrated in vacuo and the residue chromatographed on silica gel (200 g; ether/petroleum ether 1:1) to give 2-hydroxymethyl-5-(pent-4-enyl)-furan as a yellow oil (6.5 g; 76%).

(b) m-Chloroperbenzoic acid (5.7 g; 33 mmol) was dissolved in dry dichloromethane (150 ml) and the solution chilled to 0 C. The product obtained in (a) above (5 g; 30 mmol), dissolved in dichloromethane (150 ml) was added in one portion to the stirred solution of m-chloroperbenzoic acid. Benzoic acid percipitated out of solution after 0.1 hour. The reaction mixture was stirred at room temperature for 3 hours and the benzoic acid filtered off. The dichloromethane filtrate was washed several times with 10% NaHCO3 solution (5 x 75 ml) and water (2 x 50 ml) before drying (MgSO4). The solvents were removed in vacuo and the residue chromatographed on silica gel (200 g; ether/CHCI31:1) to give the desired pyranone as a colourless oil (4.4 g; 80%).

ElementalAnalysis C H Calculated for C,OH,403 65.9 7.7 Found 66.0 7.4 EXAMPLE 5 Preparation of the acetate ester of the compound of Example 1.

The compound of Example 1 (7.5 g; 40.5 mM) was dissolved in acetic anhydride (25 ml) and the solution cooled to 0 C. Pyridine (7.5 ml) was added dropwise at 0 C and the reaction mixture stirred for 3 hours. The solvents were removed at room temperature (1 torr) and the residue dissolved in benzene.

The solution was filtered through a short silica gel column before chromatography on silica gel (500 g; ether/petroleum ether 1:1) to give the corresponding acetate as a pale yellow oil (7.95 g; 86%).

EXAMPLES 6 AND 7 By methods analogous to that of Example 5, the acetates of the alcohols of Examples 2 and 3 were prepared.

EXAMPLE 8 Preparation of:

Method A The compound of Example 5 (4 g; 17.8 mM) was dissolved in acetonitrile (10 ml) and the solution sealed under vacuum in a thick walled pyrolysis tube. The tube was heated at 1 460C for 17 hours. The acetonitrile of the resulting solution was evaporated and the residue chromatographed on silica gel (200 g; ether/petroleum ether 1:1) to give the desired intramolecular cycloadduct as a colourless oil (2.2 9; 75%).

The compound was identified by analysis of its 2,4-dinitrophenylhydrazone, which had the following Elemental Analysis: C H N Calculated for C,6H,6N405 55.8 4.65 16.27 Found 55.6 4.7 16.6 Method B The compound of Example 5 (250 mg; 1.1 mol) was dissolved in dry dichloromethane (10 ml).

1 ,5-Diazabicyclo-(4.3.0)-5-non-5-ene (200 mg; 1.78 mmol) in CH2CI2 (3 ml) was added dropwise to the rapidly stirred solution of (4) at OOC. The reaction mixture was allowed to attain room temperature overnight. The CH2CI2 of the resulting solution was evaporated off and the residue chromatographed on silica gel (20 g; ether/petroleum ether 1:1) to give the desired intramolecular cycloadduct as a pale yellow oil (150 mg; 82%).

EXAMPLES 9-11 By cyclisation of the compounds of Examples 4, 6 and 7, by methods analogous to those of Example 8, the following compounds were prepared.

EXAMPLE 9

NMR: 2.8 (9H, m); 4.7 (1 H, m); 6.05 (1 H, d.d); 7.4 (1 H, d).

EXAMPLE 10

This compound was characterized by analysis of its 2,4-dinitrophenylhydrazone, which had the following Elemental Analysis: C H N Calculated for C17H18N4O5 56.98 5.02 15.64 Found 56.9 4.9 15.6 EXAMPLE 11

NMR: 1.5-2.4 (6H, m); 1.8 (3H, s); 5.0 (1 H, d); 5.7 (1 H, d); 7.45 (1 H, d.d).

EXAMPLE 12 Preparation of:

The compound:

(2.2 g: 14.1 mmol) was dissolved in dichloromethane (2 ml) and ethyl vinyl ether (7 g; 97 mmol). The solution was chilled to 0 C and triethylamine (2.1 g; 21 mmol) added dropwise. The reaction mixture was allowed to reach room temperature overnight. The solvents were removed in vacuo, the residue dissolved in chloroform and chromatographed on silica gel (100 g; ether/CHCl3 1:1)to give the desired intermolecular cycloadduct as a colourless oil (1.4 g; 59%).

Elemental Analysis C H Calculated for C9H12O3 64.3 7.14 Found 64.4 7.4 EXAMPLES 13 to 15 By methods analogous to that of Example 12, the following compounds were prepared.

EXAMPLE 13

Elemental Analysis C H Calculated for C12H12O2 76,54 6.38 Found 76.4 6.4 EXAMPLE 14

NMR: 1.5 (3H, s); 1.8 (3H b.s); 2.1(1 H, d.d); 2.7 (1 H, d.d); 4.4(1 H, d); 4.6 (1 H, m); 4.85 (2H, m); 6.0 (1H, d.d); 7.2 (1H, d.d).

EXAMPLE 15

ElementalAnalysis C H Calculcated for C1oHl202 73.17 7.32 Found 72.85 7.75 EXAMPLE 16 Preparation of:

Pure cuprous iodide (4.6 g; 24.1 mmol) was suspended in dry ether (80 ml) and MeLi/LiBr complex (39 ml of a 1.5 M solution in ether) was added dropwise at 20a. The solution was allowed to warm to OOC for 0.25 hours before recooling to --200C. To the cold solution of (Me)2CuLi was added dropwise, in ether (25 ml) a solutIon of the compound of Example 8 (2 g; 12.2 mmol). The reaction mixture was allowed to stir for 0.75 hours at room temperature before quenching with a solution of saturated NH4CI (75 ml).The organic products were extracted into ether (3 x 1 50 ml) and the combined extracts washed with saturated NaCI solution (2 x 50 ml) and water (2 x 50 ml) before drying (MgS04).

The ether was evaporated and the crude reaction product chromatographed on silica gel (200 g; ether/petroleum ether 1:1) to give the desired product as white crystals (1.7 g; 78%; mpt 450C).

EXAMPLE 17 By a method analogous to that of Example 16, the compound of Example 1 2 was converted into:

This compound was identified by mass spectrometry, the molecular ion having a mass of 184.10996 (calculated value 184.109937).

EXAMPLE 18 Preparation of:

The compound of Example 16 (1.71 g; 9.49 mmol) was dissolved in dry tetrahydrofuran (75 ml) under a nitrogen atmosphere. the solution was cooled to OOC and LiAIH4 (541 mg; 14.25 mmol) added in powdered form. The reaction mixture was stirred for 0.5 hours at OOC. Excess LiAIH4 was neutralised with methanol before pouring into ice/water/ether (50 my/120 ml). The aqueous phase was acidified with dilute HCI (50 ml) and the organic products extracted into ether (2 x 100 ml). The combined ether extracts were washed with NaHCO3 solution, brine and water (50 ml) before drying (MgS04). The ether was evaporated under reduced pressure and the crude reaction product chromatographed on silica gel (100 g; ether/petroleum ether 3:1). The first 30% of the eluted material was discarded and the final 70% collected to give approximately 1 g of the desired product.

Elemental Analysis C H Calculated for C11H18O2 72.53 9.89 Found 72.8 10.1 EXAMPLE 19 By a method analogous to that of Example 18, the compound of Example 17 was converted into:

This compound was identified by mass spectrometry, the molecular ion having a mass 186.12589 (calculated value 186.125586).

EXAMPLE 20 Preparation of:

NaH (200 mg; 4 mmol of a suspension in oil 50% w/w) was suspended in dry dimethylformamide (30 ml). The compound of Example 18 (500 mg; 2.74 mmol) dissolved in dimethylformamide (10 ml).

was added dropwise to the NaH suspension. Benzyl bromide (822 mg; 4.81 mmol) dissolved in dimethylformamide (1 5 ml), was added dropwise to the reaction mixture, after bubbling has creased (0.5 hour). The reaction mixture was warmed to 650C for 0.5 hours before leaving to stir at room temperature for 16 hours. The pale yellow solution was poured into water (50 ml) and the reaction products extracted into ether (2 x 75 ml). The combined ether extracts were washed with water (3 x 40 ml) and dried. The ether was evaporated and the crude reaction product chromatographed on silica gel (50 g; ether/petroleum ether 1:4) to afford the desired benzyl ether as a colourless oil (625 mg; 84%).

NMR: 1.05 (3H, d); 1.15-2.2 (11 H, m); 2.55 (1 H, m); 3.65 (1 H, m); 4.05 (1 H, m); 4.52 (2H, ABq); 7.28 (5H, s).

EXAMPLE 21 By a method analogous to that of Example 20, the compound of Example 19 was converted into:

NMR: 1.19 (3H, t); 1.31 (3H, d); 1.41 (1H, m); 1.60 (1H, m); 1.86 (1H, m); 2.14 (1H, m); 2.40 (1H, m); 3.21(1H, m): 3.5 (2H, m); 4.0 (1H, m); 4.14(1H, m); 4.28(1H. m); 4.59 (2H, ABq); 7.34 (5H, s).

EXAMPLE 22 Herbicidal Activity To evaluate their herbicidal activity, compounds according to the invention were tested using as a representative range of plants: maize, Zea mays (MZ); rice, Oryza sativa (R); barnyard grass, Echinochloa crusgalli (BG); oat, Avena sativa (0); linseed, Linum usitatissimum (L); mustard, Sinapsis alba (M); sugar beet Beta vulgaris (SB) and soya bean, Glycine max (S).

The test fall into two categories, pre-emergence and post-emergence. The pre-emergence tests involved spraying a liquid formulation of the compound onto the soil in which the seeds of the plant species mentioned above had recently been sown. The post-emergence tests involved two types of test, viz., soil drench and foliar spray tests. In the soil drench tests the soil in which 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 by diluting with water, solutions of the test compounds in acetone containing 0.2% by weight of an alkylphenol/ethylene oxide condensate available under the trade mark TRITON X-1 55. The acetone solutions were diluted with water and the resulting formulations applied at dosage levels corresponding to 5 kg and 1 kg of active material per hectare in a volume equivalent to 650 litres per hectare in the soil spray and foliar spray tests, and at a dosage level equivalent to 10 kilograms of active material per hectare in a volume equivalent to approximately 3,000 litres per hectare in the soil drench tests.

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

The herbicidal effects of the test compounds were assessed visually twelve days after spraying the soil and the foliage, and thirteen days after drenching the soil, and were recorded on a linear 0--9 scale. A rating 0 indicates growth as untreated control, a rating 9 indicates death.

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

TABLE OF RESULTS

Compound Soil Drench Dosege of 10 kg/ha kg/ha Example No. Mz R BG O L M SB S Foliar Spray Pre-emergence 20 8 7 9 8 4 5 4 6 5 Mz R BG O L M SB S Mz R BG O L M SB S 1 7 2 9 5 6 3 5 5 7 7 9 5 6 5 5 5 21 9 7 8 6 0 0 0 2 6 5 0 8 3 3 0 2 4 7 6 9 3 5 4 2 3 1 5 2 8 0 3 0 0 5 9 9 9 6 0 0 0 0 0 0 3 0 0 0 0 2 3 2 9 0 0 0 0 0

Claims (3)

1. A compound of the general formula:

in which: either R1 represents a group -OR13, a group -O.CO.R13, or a group A and R2 represents a hydrogen atom or an optionally substituted alkyl group or R1 and R2 together represent an oxygen atom or a group =N.OR13, =N.NH.CO.NHR13 =N.NH.CO.R13, =N.N HR13 or = N.O.C O.R13, in which R13 represents a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted phenyl group; R3 represents a hydrogen atom or an optionally substituted alkyl group;; either R5 represents a hydrogen atom, an optionally substituted alkyl group, an alkoxy group or a group A and R4 represents a hydrogen atom or an optionally substituted alkyl group, or R4 and R5 together represent a bond; R6 represents a hydrogen atom or an optionally substituted alkyl group; either R7 represents a hydrogen atom or an optionally substituted alkyl group and RB represents a hydrogen atom, a group A, an alkenyl or alkoxy group, or an optionally substituted alkyl or phenyl group, or R7 and R8 together represents an alkylene group, or RB and R11 together with the interjacent carbon atoms form a mono- or bi-cyclic hydrocarbyl ring;; either R9 represents a hydrogen atom or an optionally substituted alkyl group and R10 represents a hydrogen atom or an optionally substituted alkyl group, or R9 and R10 together represents a bond; R11 represents a hydrogen atom or an optionally substituted alkyl group, and R12 represents a hydrogen atom or an optionally substituted alkyl group, or, if RB represents a hydrogen atom or an optionally substituted alkyl group, R11 and R12 together may represent an alkylene group; ; and A represents a group of the general formula CR14R15Y in which each of R14 and R15 independently represents a hydrogen atom or an optionally substituted alkyl group, and Y represents an alkenyl or alkynyl group, an optionally substituted phenyl group, or an optionally substituted ring having 5 or 6 atoms in the ring at least one of which is nitrogen, oxygen or sulphur; with the proviso that at least one of R1,R5 and RB represents a group A.

2. A compound according to claim 1 substantially as hereinbefore described with reference to the Examples.

3. The use of a compound claimed in claim 1 or 2 as a herbicide.