GB2028821A - New imidazole derivatives - Google Patents

Abstract

The invention provides new imidazole derivatives of the general formula:- <IMAGE> wherein R<1> represents a methyl or ethyl group, R<2>, R<3> and R<4>, which may be the same or different, each represent a hydrogen or halogen atom or an alkyl or alkoxy group which may optionally be substituted by one or more fluorine atoms, and R<2>, R<3> and R<4> do not all represent hydrogen atoms, which possess useful herbicidal properties.

Description

SPECIFICATION New imidazole derivatives This invention relates to new imidazole derivatives, processes for their preparation, herbicidal compositions which contain them, and their use as herbicides.

As a result of research and experimentation, it has been found that the new imidazole derivatives of the general formula:

wherein R1 represents an ethyl or, preferably, a methyl group and R2, R3 and R4, which may be the same or different, each represent a hydrogen or halogen (i.e. fluorine, chlorine, bromine or iodine, preferably chlorine or bromine) atom or an alkyl or alkoxy group which may optionally be substituted by one or more fluorine atoms, for example a trifluoromethoxy, 1, 1, 2, 2 - tetrafluoroethoxy or, preferably, a trifluoromethyl group, and R2, R3 and R4 do not all represent hydrogen atoms, possess useful herbicidal activity.

Compounds of general formula I wherein one of the symbols R2, R3 and R4 represents a hydrogen atom and the other two symbols and R1 are as hereinbefore defined are preferred.

Especially preferred compounds of general formula I are those wherein R1 is as hereinbefore defined, R2 and R3, which may be the same or different, each represent a hydrogen or halogen atom or an alkyl group which may optionally be substituted by one or more fluorine atoms and R2 and R3 do not both represent hydrogen atoms, and R4 represents a hydrogen or halogen atom.

Compounds of general formula I wherein R' is as hereinbefore defined, R2 and R3 each represent a halogen atom or R2 represents a hydrogen atom and R3 represents a halogen atom or an alkyl group which may optionally be substituted by one or more fluorine atoms, and R4 represents a hydrogen atom are more especially preferred.

Alkyl groups and the alkyl moieties of alkoxy groups represented by the symbols R2, R3 and R4 may be straight- or branched-chain and contain from 1 to 6 carbon atoms.

As will be apparent to those skilled in the art, compounds of general formula I may exist in optically isomeric, i.e. stereoisomeric forms. The present invention comprises all isomeric forms of general formula I and mixtures, including racemic mixtures, thereof.

Accordingly, a feature of the present invention is 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 imidazole derivative of general formula I. For this purpose, the imidazole derivatives are normally used in the form of herbicidal compositions (i.e. in association with compatible diluents or carriers suitable for use in herbicidal compositions), for example as hereinafter described.

The compounds of general formula I show herbicidal activity against dicotyledonous (i.e. broadleafed) weeds by pre- and/or, more especially, postemergence 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 general formula I may be used to control, more especially by postemergence application, the growth of annual broadleafed weeds, for example,Abutilon theophrasti, Amsinckia intermedia, Anthemis arvensis, pigweeds (Amaranth us spp., e.g. Amaranthus retroflexus), Anoda cristata, Acanthospermum spp., e.g.Acanthos- permum hispidum, Bidens pllosa, fat hen (Chenopodium spp., e.g.Chenopodium album), Chrysanthemum segetum, Datura stramonium, Descurainea sophia, Emex australis, Galeopsis tetrahit, lpomoea spp., e.g. Ipomoea purpurea, Lamium spp., e.g. Lamium purpureum, Merremia aegyptea, Papaverrhoeas, Physalis spp., e.g. Physalis lanceifolia, Sida spinosa, Sida rhombifolia, Sinapis spp., e.g. Sinapis arvensis, Stellaria media, Solanum spp., e.g. Solanum nigrum, Urtica urens, Veronica spp, e.g. Veronica persica and Xanthium strumarium.

The amounts of compounds of general 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 0.25 kg and 20 kg 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 general formula I may be used to control selectively the growth of weeds, for exam ple to control the growth of those species hereinbefore mentioned, by pre- or, preferably, postemergence application in a directional or nondirectional fashion, e.g. by directional or nondirectional spraying, to a locus of weed infestation which is an area used, or to be used, for growing crops, for example graminaceous crops, e.g. wheat, barley, oats, rye, maize, rice and sorghum, soya, beans, field and dwarf beans, peas, sugar beet, fodder beet and red beet, cotton, peanuts, potatoes, flax, onions, carrots, herbage seed crops, oilseed rape and pasture, 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 infesta tion which is an area used, orto be used, for the growing of crops, e.g. the crops hereinbefore men tioned, application rates between 0.25 kg and 8.0 kg of active material per hectare are particularly suit able.

More particularly, the compounds of general for mula I, especially 1 - (4 - chloro - a - methoxybenzyl) N, N' - dimethylimidazole-4, 5- dicarboxamide, 1 (3 - chloro - a - methoxybenzyl) - N, N' dimethylimidazole - 4, 5 - dicarboxamide, N, N' dimethyl - 1 - ( - methoxy - 3 - trifluoromethylbenzyl) imidazole - 4, 5 - dicarboxamide and 1 - (3, 5 - dich loro- a - methoxybenzyl) - N, N'- dimethylimidazole - 4,5 - dicarboxamide, and more especially N, N' dimethyl - 1 - (3,4 - dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide, N, N' - dimethyl - 1 (3, 4 - dichloro - a - ethoxybenzyl) imidazole - 4,5 dicarboxamide, N, N' - dimethyl - 1 - (a - methoxy - 4 - trifluoromethylbenzyl) imidazole - 4, 5 - dicarboxamide and 1 - (3, 4- dibromo - a - methoxybenzyl) N, N' - dimethylimidazole - 4, 5 - dicarboxamide, (Compounds A to D respectively in the following Tests) may be used to control selectively the growth of annual broad leaf weeds, for example to control the growth of those annual broad leaf weed species herein before mentioned, by post-emergence application in a non-directional fashion, e.g. by nondirectional spraying, to an area used for growing crops of cereals, cotton or soya bean after emergence of both the crop and weeds.

For this purpose, i.e. the selective control of annual broad leaf weeds by post-emergence application to an area used for growing crops of cereals, cotton or soya bean, application rates between 0.25 kg and 8.0 kg of active material per hectare are particularly suitable. More especially (+) - N, N' dimethyl - 1 - (3, 4- dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide at rates of 0.5 to 4 kglha gives excellent control of broad leaf weeds by post-emergence application in cotton.

When used to control the growth of weeds by Weed species (i) Broad leafed weeds Sinapis arvenis Polygonum lapathffolium Stellaria media (iii) Grass weeds Avena fatua Alopecurus m yosuroides Echinochloa crus-galli The test compounds were applied to the uncovered seeds as described in (1)(a) above at dose rates of 0.125 to 8 kg/ha in the case of test compounds A two D and the seeds were covered with 25 ml of sharp sand after spraying. A single pot of each weed species was allocated to each treatment, with unsprayed controls and controls sprayed with solvent alone. After treatment, the pots were kept in the green house and were watered overhead. Visual assess ment of weed control activity was made 21 days after spraying.The results were expressed as the pre-emergence application, the compounds of general 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 general 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 general formula I will also normally come into contact with the soil and may also then exercise a pre-emergence control on latergerminating weeds in the soil.

Where especially prolonged weed control is required, the application of the compounds of general formula I may be repeated if required.

In experiments on herbicidal activity carried out on representative compounds of general formula I, the following results have been obtained: TEST METHODS (1) Weed Control Test (a) General The test compounds Ato D (as hereinbefore identified) were dissolved in acetone. Application was from a standard laboratory herbicide sprayer delivering the equivalent of 530 litres of spray fluid per hectare, the spray pressure being 2.81 kg/cm2 (40 poundslinch2). The solutions of test compounds A to D were prepared by dissolving 0.513 g of test compound in acetone and making up with more acetone to 34 ml (1.5% w/v), equivalentto an application rate of 8 kg of test compound per hectare.Solutions equivalent to 8,4,2, 1, 0.5, 0.25 and 0.125 kilogrammes per hectare (kg/ha) were prepared from these solutions by serial dilution with acetone in the case of test compounds A two D.

(b) Weed Control: Pre-emergence application Weed seeds were sown on the surface of John Innes No. 1 potting compost (7 parts by volume of sterilised loam, 3 parts by volume of peat and 2 parts by volume of fine grit) in 9 cm diameter bitumenised paper pots. The quantities of seeds per pot were as follows:- Approximate Volume of number seedipot seedsipot 0.14 ml 30 0.3 ml 30 0.01 ml 60 15seeds 15 1.7 ml 150 0.3 ml 30 minimum effective dose (MED) in kg/ha which gave 90 /O reduction in growth or kill of the weeds in comparison with plants in the control pots. The results obtained are presented below in Table (c) Weed Control: Post-emergence application Weed species were grown and then transplanted at the seedling stage into John Innes No. 1 potting compost in 9 cm diameter bitumenised paper pots.

The plants were then grown in the greenhouse until ready for spraying with the test compounds. The number of plants per pot and the growth stage of the plant at spraying were as follows:- Number of Growth stages Weed species plantsipot at spraying (i) Broad lea fed weeds Polygonum lapathifolium 5 2-3 leaves Stellaria media 5 4-5 pairs of leaves Abutilon theophrasti 3 2-3 pairs of leaves (ii) Grass weeds * Avena fatua 10 1-2 leaves Alopecurus myosuroides 5 1-3 leaves Echinochloa crus-galli 5 3 leaves Cyperus rotundus 5 3 leaves * Avena fatua was sown directly in the test pot and not transplanted.

The test compounds were applied to the plants as described in (1) (a) above at dose ratesoffrom 0.125 to 8 kg/ha in the case of test compounds A to D. A single pot of each weed species was allocated to each treatment with unsprayed controls and controls sprayed with acetone alone. After spraying, the pots were watered overhead, commencing 24 hours after spraying. Assessment of the control of the growth of the weeds was made 21 days after spraying by recording the number of plants which had been killed and the reduction in growth. The results were expressed as the minimum effective dose (MED) in kg/ha which gave 90% reduction in growth or kill of the weeds in comparison with the plants in the control pots. The results obtained are presented below in Table II.

KEY TO WEED SPECIES (a) GRASS WEEDS: Am = Alopecurus myosuroides Af = Avena fatua Ec = Echinochloa crus-galli Cr = Cyperus rotundus (b) BROAD-LEAFED WEEDS Sm = Stellaria media PI = Polygonum lapathifolium Sa = Sinapis arvensis At = Abutilon theophrasti TABLE I

Test Pre-emergence MED (kg/ha) Compound Sm PI Sa Af Am ( A -8 NR 2 Mt 8 Mt D #8 NR NR Mt NR NR B 8 NR a Mt > B C 4-8 NR 4 > e > 8 NR TABLE II

Test Post-emergence MED (kg,"ha) Compound Sm P1 At Af Am Sc Cr A 0.25 NR 025 ) > e > 8 8 Mt D 1 Mt 0.5 NR Mt B 2 Mt 1 #8 NR NR NR C 1 NR 0.25 #8 NR NR NR (2) Selective Herbicidal Test (t) - N, N' - dimethyl - 1 - (3,4 - dichloro - a- methoxybenzyl) imidazole - 4, 5 - dicarboxamide (Compound A) was formulated as an emulsifiable concentrate by dissolving 20 g of the compound with 10 g of Duoterics MB1/MB2 (an anionic emulsifier blend containing calcium alkyl sulphonate and alkyl phenol ethylene oxide condensates) in a 1:1 mixture of cyclohexanone and Aromasol "H" (an aromatic solvent consisting predominantly of isomeric trimethylbenzenes) and making upto 100 ml volume by adding more of the 1::1 cyclohexanone/Aromasol "H" mixture. This emulsifiable concentrate formulation was then diluted by pipetting 4.35 ml offormula- tion into a 100 ml measuring cylinder and adding waterto 100 ml by volume. This gave a spray emulsion formulation equivalent to a dose rate of 2 kg of compound of formula I in 230 litres of water for application to an area of 1 hectare. Spray emulsion formulations equivalent to 1, 0.5,0.25 and 1.125 kg of active ingredient in 230 litres of water were then prepared by serial dilution.For comparative purposes a similar series of dose rates of a 50% w/w wettabie powder formulation offluometuron N'- (3 - trifluoromethylphenyl) - N, N - dimethylurea a widely used cotton herbicide, were prepared by weighing out 1.74 g of wettable powder into a cylinder, making up to 100 ml volume by adding water and then shaking vigorously to form a homogeneous suspension (containing the equivalent of 2 kg of N' - (3 - trifluoromethylphenyl) - N, N - dimethylurea in 230 litres water per hectare). The 1, 0.5, 0.25 and 0.125 kg dose rates were prepared by serial dilution.

These emulsions and suspensions were then applied through a flat fan jet, post-emergence, to the foliage of weeds and cotton using a laboratory spraying apparatus at a pressure of 2.1 kg/cm2 and a speed of 2.6 km/hr to deliver a dose rate equivalent to 230 litres/hectare.

Details of plants used were as follows:-

Species Height No. of No. plants No. of (cm) leaves per pot pots per treatment Cotton 6-8 1 3 3 (Gossypium hirsutum) Abutilon theophrasti 2-4 1 3 3 Bidens pilosa 3 2 3 3 Merremia aegyptea 3-5 1-2 3 3 Sida spinosa 1-3 1 3 3 Ipomoea purpurea 3-5 1 3 3 Xanthium strumarium 6 3-4 1 2 Solanum nigrum 2.5 3-4 3 3 Physalis 1.25 lanceifolia l.875 3 3 3 Acanthospermum hispidum 1.25 2 2 3 Amaranthus retroflexus 2.5 3 3 3 All the plants were grown in John Innes Potting Compost No. 1. Weeds were grown in 9 cm diameter bitumenised paper pots; cotton was grown in 12.5 cm diameter plastic pots.

After spraying, the plants were placed in a greenhouse and watered daily, commencing 24 hours after spraying. The day temperature in the greenhouse was 25"C and the night temperature 15"C.

Natural light was supplemented by the use of artificial Solacolour iights (high pressure sodium lamps) for 14 hours a day. One month after spraying a visual assessment of the dose rate, expressed in kg of active ingredient per hectare (kgai/ha), giving 90 /O destruction of the weeds and 20% destruction of the crop in comparison with untreated plants was made.

Results were as follows:- Dose giving 20% destruction (cotton) and 900/c destruction (weeds (kgailha)

Compound ()-N,N'-dimethyl-1-(3.4- N'-(3-trifluoromethyl dichloro-&alpha;-methoxybenzyl) phenyl)-N ,N-dimethylurea imidazole-4,5- (Fluometuron) Species dicarboxamide (Compound A) Cotton (Gossypium hirsutum) > ,2.0 2.0 Abutilon theophrasti 1.0 2.0 Bidens pilosa 0.7 1.3 Merremia aegyptea 1.3 2.0 Sida spinosa 0.75 1.3 Ipomoea purpurea 1.3 2.0 Xanthium strumarium 0.5 1.5 Solanum nigrum 1.0 0.5 Physalis lanceifolia 0.5 0.6 Acanthospermum hispidum 0.4 0.5 Amaranthus retroflexus 1.0 1.5 The following symbols which appear in the above Tables have the following meanings:- 'o' means = much greater than ' - ' means = greater than 'NR' means = no reduction at any dose rate means = equal to or greaterthan.

According to a feature of the present invention, the compounds of general formula I wherein R1, R2, R3 and R4 are as hereinbefore defined are prepared by the following processes:- Process 1 The reaction of a compound of the general for mula:

(wherein X represents a halogen, preferably chlorine or bromine, atom, and R8, R2, R3 and R4 are as hereinbefore defined) with an alkali metal, preferably sodium, salt of imidazole - N, N' - dimethyl - 4,5 - dicarboxamide of the formula::

The reaction may be effected in the presence of an inert organic solvent, such as dimethylformamide or t-butanol, at a temperature between ambient temperature and 150"C, and preferably at a temperature between 50"C and 110"C.

Process 2 The reaction of a compound of the general formula:

(wherein R', R2, R3 and R4 are as hereinbefore defined, and R5 represents a straight- or branched chain alkyl group containing from 1 to 6 carbon atoms) with methylamine in the presence of an inert organic solvent, such as toluene or ethanol, at a temperature between 0 and 100 C.

The compounds of general formula II may be pre pared by known methods, for example by the proce dure described in British Patent Specification No.

1,230,347.

The compound of formula Ill may be prepared by the reaction of the compound of the formula:

with methylamine in the presence of an acid-binding agent, which is preferably an excess of methylamine, and an inert organic solvent, e.g.

toluene, at a temperature between 0" and 30"C, and preferably at ambient temperature.

Alternatively, the compounds of formula III may be prepared by the reaction of a compound of the general formula:

(wherein R5 is as hereinbefore defined) with methylamine. The reaction may be effected in a manner similar to that hereinbefore described in Process 2.

The compound of formula V may be prepared by the reaction of imidazole - 4, 5 - dicarboxylic acid of formula:

with thionyl chloride. The reaction may be effected optionally in the presence of an inert organic solvent, optionally in the presence of a catalytic amount of dimethylformamide or pyridine, at the reflux temperature of the reaction mixture.

The compounds of general formula VI may be prepared by the reaction of the compound of formula VII with an alkanol containing from 1 to 6 carbon atoms, e.g. ethanol, in the presence of an acid catalyst, e.g. hydrogen chloride. The reaction may conveniently be effected by bubbling gaseous hydrogen chloride through an alkanolic, e.g. ethanolic, solution of the compound of formula VII at the reflux temperature of the reaction mixture.

The compounds of general formula IV may be prepared by the reaction of a compound of general formula II with an alkali metal, preferably sodium, salt of a compound of general formula VI. The reaction may be effected in a manner similar to that hereinbefore described in Process 1.

The alkali metal salts of compounds of formula Ill and of general formula VI may optionally be prepared in situ, by the application or adaptation of known methods, for example the sodium salts thereof may be prepared by the reaction of compounds of formula III and VI with sodium hydride in the presence of dimethylformamide.

The potassium salts of compounds of general formula VI may be prepared by the reaction of a compound of general formula VI with potassium t-butoxide in the presence of dimethylformamide.

By the term "known methods" as used in the pre sent specification is meant methods heretofore used or described in the chemical literature.

The following Example illustrates the preparation of the compounds of the present invention.

EXAMPLE 1 Sodium hydride (9.0 g) was added to a stirred sus pension of imidazole - N, N' - dimethyl - 4, 5 - dicar boxamide [described by Vinogradova and Khromov-Borisov, Zhur. Obschii. Khim, 31, 1466 (1961)1 in dry dimethylformamide (350 ml). The temperature of the mixture rose to 50"C and was then maintained at 40 - 50"C for 2.5 hours until all the solid material had dissolved. The solution thus obtained was cooled to 15"C and maintained at this temperature during the addition, over 0.5 hours, of 3, 4 - dichloro - a - methoxybenzyl chloride (84.6 g).The mixture was then stirred for 2.5 hours, maintained at laboratory temperature (about 25"C) for a further 16 hours and then heated, with stirring, for a further 2 hours at 50 - 60"C. The solution thus obtained was filtered and the solid residue was washed with dry dimethylformamide. The combined filtrate and washings were added to water (2.5 litres) and the oil which precipitated was extracted with diethyl ether (3 x 1.2 litres). The combined ethereal extracts were washed with water (8 x 50 ml). The combined strongly alkaline aqueous liquors and washings were acidified to pH 3-4 with concentrated hydrochloric acid and the diethyl ether which separated from them was washed with water (4 x 50 ml) and combined with ethereal extract previously obtained.

The combined ethereal solutions were dried over anhydrous sodium sulphate and evaporated to give a crude product (129 g) which was purified by treatmenu with hot hexane (1.4 litres) and diethyl ether (350 ml), treatment with charcoal and filtration, after which the product slowly crystallised and was separated to give (+) - N, N' - dimethyl - 1 - (3,4- dichloro - a - methoxybenzyl) - imidazole - 4, 5 - dicarboxamide (76 g), m.p. 112" - 114 C, as a white microcrystalline solid.

By proceeding in a similar manner, but replacing the 3,4 - dichloro - a - methoxybenzyl chloride by the appropriately substituted a-alkoxybenzyl chlorides, there were prepared: (+) - N, N' - dimethyl - 1 - (3,4- dichloro a- ethoxybenzyl) imidazole - 4,5 - dicarboxamide, m.p.

115 - 117"C (after crystallisation from hexane), from 3,4 - dichloro - a - ethoxybenzyl chloride; (+) - 1 - (4 - chloro - a - methoxybenzyl) - N, N' dimethylimidazole - 4, 5 - dicarboxamide, m.p. 93 - 94"C (after crystallisation from petroleum ether b.p.

60 - 80"C), from 4 - chloro - a - methoxybenzyl chloride; (+) - 1 - (3 - chloro - a - methoxybenzyl) - N, N' dimethylimidazole-4, 5 - dicarboxamide, m.p. 120"C (after crystallisation from a mixture of methanol and petroleum ether b.p. 60" - 80"C), from 3 - chloro - cr methoxybenzyl chloride.

() - N, N' - dimethyl - 1 - (a - methoxy-4-trifluoromethylbenzyl) - imidazole- 4,5 - dicarboxamide, m.p. 78"C (after crystallisation from petroleum ether b.p. 60" - 80"C), from a - methoxy - 4 trifluoromethylbenzyl chloride; (t) - 1 - (3,4- dibromo - a - methoxybenzyl) - N, N' - dimethylimidazole - 4, 5 - dicarboxamide, m.p.

113.5 - 11 4'C (after crystallisation from petroleum ether b.p. 60" - 80"C), from 3,4 - dibromo - a methoxybenzyl chloride; (+) - N, N' - dimethyl - 1 - (a - methoxy - 3 - trif- luoromethylbenzyl) imidazole - 4, 5 - dicarboxamide, m.p. 75" - 77"C (after crystallisation from petroleum ether b.p. 60 - 80"C), from a - methoxy - 3 - trif luoromethylbenzyl chloride;; (+) - 1 - (3,5 - dichloro - a - methoxybenzyl) - N, N' dimethylimidazole-4, 5- dicarboxamide, m.p. 155'- 156"C (after crystallisation from a mixture of toluene and petroleum ether b.p. 60" - 80"C), from 3, 5 - dich loro - .V- methoxybenzyl chloride.

The os-alkoxybenzyl chlorides used as starting materials in the above preparations were prepared according to the procedure described in British Patent Specification No. 1,230,347, by the following method: A mixture of acetyl chloride (77 g) and thionyl chloride (0.8 ml) was added, with stirring, to 3, 4 dichlorobenzaldehyde dimethyl acetal (110 g). The mixture was kept at laboratory temperature (about 27"C) for 22 hours and then evaporated at 30"C under reduced pressure (0.15 mm Hg) forabout4 hours until constant in weight. 3,4 - Dichloro - a - methoxybenzyl chloride (112 g) was thus obtained as an oil, which was used without further purification as a starting material in the above preparations.

By proceeding in a similar manner, but replacing the 3,4 - dichlorobenzaldehyde dimethyl acetal by the appropriately substituted benzaldehyde dialkyl acetals, there were prepared: 3,4 - dichloro - a - ethoxybenzyl chloride, as a clear, mobile oil, from 3,4 - dichlorobenzaldehyde diethyl acetal; 4 - chloro a- methoxybenzyl chloride, as a clear, mobile oil, from 4 - chlorobenzaldehyde dimethyl acetal; 3 - chloro - a - methoxybenzyl chloride as a clear, mobile oil, from 3 - chlorobenzaldehyde dimethyl acetal; a - methoxy - 4 - trifluoromethylbenzyl chloride, as a clear mobile oil, from 4 - trifluoromethylbenzaldehyde dimethyl acetal; 3,4 - dibromo - a - methoxybenzyl chloride, as a clear, mobile oil from 3,4 - dibromobenzaldehyde dimethyl acetal;; cx - methoxy - 3 - trifluoromethylbenzyl chloride, as a clear, mobile oil, from 3 - trifluoromethylbenzaldehyde dimethyl acetal; 3, 5 - dichloro - a - methoxybenzyl chloride, as a clear, mobile oil, from 3,5 - dichlorobenzaldehyde dimethyl acetal.

The benzaldehyde acetals used as starting materials in the above preparations were prepared according to the procedure described in British Patent Specification No. 1,230,347 by the following method: Concentrated hydrochloric acid (1.0 ml) was added to a stirred suspension of 3,4 - dichlorobenzaldehyde (140 g) in a mixture of trimethyl orthoformate (94 g) and dry methanol (400 ml). After stirring for 24 hours at laboratory temperature (about 25"C), the reaction solution was adjusted to pH 7-8 by the addition of a solution of sodium methoxide in methanol and concentrated on a rotatory evaporator. The residual oil was then dissolved in diethyl ether (600 ml).The ethereal solution was washed with water until the washings were neutral and then dried over anhydrous sodium sulphate, filtered and distilled to give 3,4 - dichlorobenzaldehyde dimethyl acetal (157.5 g).

b.p. 137" - 140"C/25 mm Hg, as a clear mobile oil.

By proceeding in a similar manner, but replacing the 3,4 - dichlorobenzaldehyde by the appropriate substituted benzaldehyde and, where indicated, the trimethyl orthoformate bytriethyl orthoformate and the methanol by ethanol, there were prepared: 3,4- dichlorobenzaldehyde diethyl acetal, b.p. 137" - 138 C/15mm Hg, from 3,4 - dichlorobenzaldehyde, triethyl orthoformate and ethanol; 4 - chlorobenzaldehyde dimethyl acetal, b.p.

112 C/20mm Hg, from 4 - chlorobenzaldehyde; 3 - chlorobenzaldehyde dimethyl acetal, b.p. 98 100"C/20mm Hg, from 3 - chlorobenzaldehyde; 4 - trifluoromethylbenzaldehyde dimethyl acetal, b.p. 80' - 83 C/17mm Hg, from 4 - trifluoromethylbenzaldehyde; 3,4 - dibromobenzaldehyde dimethyl acetal, b.p.

150"C/20mm Hg, from 3,4 - dibromobenzaldehyde; 3 - trifluoromethylbenzaldehyde dimethyl acetal, b.p. 88" - 90'C/1 5mm Hg, from 3 - trifluoromethylbenzaldehyde; 3,5 - dichlorobenzaldehyde dimethyl acetal, b.p.

118'- 123"C/17mm Hg, from 3,5 - dichlorobenzaldehyde.

According to a further feature of the present invention, there are provided compositions suitable for herbicidal use comprising one or more of the imidazole derivatives of general formula I in association with, and preferably homogeneously dispersed in, one or more compatible herbicidally-acceptable diluents or carriers (i.e. diluents or carriers of the type generally accepted in the art as being suitable for use in herbicidal compositions and which are compatible with compounds of general formula 1).

The term "homogeneously dispersed" is used to include compositions in which the compounds of general formula I are dissolved in the 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 general formula I.

The herbicidal compositions may contain both a diluent or carrier and a 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, for example sulphoricinoleates, quaternary ammonium derivatives, products based on condensates of ethylene oxide with nonyl- or octyl-phenols, or carboxylic acid esters of anhyd rosorbitols which have been rendered soluble by etherification of the free hydroxy groups by condensation with ethylene oxide, alkali and alkaline earth metal salts of sulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodium sul phonosuccinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates.

Examples of suitable solid diluents or carriers are aluminium silicate, talc, calcined magnesia, kiesel guhr, tricalcium phosphate, powdered cork, adsor bent carbon black and clays such as kaolin and ben tonite. The solid compositions (which may take the form of dusts, granules or wettable powders) are preferably prepared by grinding the compounds of general formula I with solid diluents or by impregnating the solid diluents or carriers with solutions of the compounds of general formula I in volatile solvents, evaporating the solvents and, if necessary, grinding the products so as to obain powders.

Granular formulations may be prepared by absorbing the compounds of general formula I (dissolved in volatile solvents) onto the solid diluents or carriers in granular form and evaporating the solvents, or by granulating compositions in powder form obtained as described above. Solid herbicidal compositions, particularly wettable powders, 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 aqueousorganic solutions, suspensions and emulsions which may incorporate a surface-active agent. Suitable liquid diluents for incorporation in the liquid compositions include water, acetophenone, cyclohexanone, isophorone, toluene, xylene and mineral, animal and vegetable oils (and mixtures of these diluents). Surface-active agents, which may be present in the liquid compositions, may be ionic or nonionic (for example of the types described above) and may, when liquid, also serve as diluents or carriers.

The addition of an organic base, for example a tertiary amine preferablytriethanolamine (0.1 - 10% w/v), to maintain alkaline conditions in liquid formulations, is beneficial for long term stability. Wettable powders 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 general 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 orwaterto such concentrates producing compositions ready for use.

Herbicidal compositions according to the present invention may also contain, if desired, conventional adjuvants such as adhesives, colouring agents and corrosion inhibitors. These adjuvants may also serve as carriers or diluents.

Herbicidal compositions according to the present invention may also comprise the compounds of general 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, for example, to increase the range of weed species controlled, e.g. bentazone (3 - isop ropyl - 2,1,3 - benzothiadiazin - 4 - one - 2,2 - dioxide), ch loroxuron [N' - 4 - (4 - chlorophenoxy) phenyl - N, N' -dimethylureaj, - dimethylureaj,fluometuron[N' - (3 - trifluoromethylphenyl) - N,N - dimethylurea], diuron [N' - (3,4 - dichlorophenyl) - N, N dimethylureaj, metribuzin [4 - amino - 6 - t- butyl - 3 - methylthio - 1,2,4 - triazin - 5(4H) - one], MSMA (monosodium methylarsonate), alloxydimedon sodium42-[1 - (N - allyloxyamino) butylidenej - 5, 5dimethyl - 4 - methoxycarbonylcyclohexane - 1,3 dine}, mefluidide (5 - trifluoromethylsulphonylamino - 2,4 - acetoxylidide), diclofop - methyl methyl (+) - 2 - [4 - (2,4 - dichlorophenoxy) phenol propionatet and clofop-isobutyl( isobutyl (i) - 2 - [4 - (4 - chlorophenoxy) phenoxy] propion atet and insecticides, e.g. dimethoate (0, 0 dimethyl S - methylcarbamoylmethylphosphorodithioate), monocrotophos [(E)dimethyl 1 methyl - 2 - methylcarbamoylvinylphosphate], organochlorine compounds, e.g. endosulphan(6, 7, 8,9, 10, 10 - hexachloro - 1,5, 5a, 6,9, 9a - hexahydro - 6,9 - methano - 2,4,3 - benzo[e] dioxathiepin - 3 oxide}, and carbamates, e.g. carbaryl (1-naphthyl methylca rbamate). Other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention include fertilizers e.g. containing nitrogen, potassium and phosphorus and trace elements known to be essential to successful plant life, e.g.

iron, magnesium, zinc, manganese, cobalt and copper.

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, for example those hereinbefore mentioned, and which are acids, may, if desired, be utilised in the form of conventional derivatives, for example alkali metal and amine salts and esters.

According to a further feature of the present invention there is provided an article of manufacture comprising at least one of the imidazole derivatives of general formula I or, as is preferred, a herbicidal composition as hereinbefore described, and preferably a herbicidal concentrate which must be diluted before use, comprising at least one of the imidazole derivatives of general formula I within a container for the aforesaid derivative or derivatives of general formula I, or a said herbicidal composition, and instructions physically associated with the aforesaid container setting out the manner in which the aforesaid derivative or derivatives of general formula I or herbicidal composition contained therein is to be used to control the growth of weeds. The containers will normally be of the types conventionally used for the storage of chemical substances which are solids at normal ambient temperatures and herbicidal compositions particularly in the form of concentrates, for example cans and drums of metal, which may be internally-lacquered, and plastics materials, bottles of glass and plastics materials and, when the contents of the container is a solid, for example granular herbicidal compositions, boxes, for example of cardboard, plastics materials and metal, or sacks. The containers will normally be of sufficient capacity to contain amounts of the imidazole derivatives or herbicidal compositions sufficient to treat at least one acre of ground to control the growth of weeds therein but will not exceed a size which is convenient for conventional methods of handling.The instructions will be physically associated with the container, for example by being printed directly thereon or on a label or tag affixed thereto. The directions will normally indicate that the contents of the container, after dilution if necessary, are to be applied to control the growth of weeds at rates of application between 0.25keg and 20 kg of active material per hectare in the manner and for the purposes hereinbefore described.

The following Examples illustrate herbicidal compositions according to the present invention.

EXAMPLE2 An aqueous suspension concentrate is formed from: (-t)-N, N' -dimethyl-l-(3, 4- dichloro - a - methoxybenzyl) - imidazole - 4, 5 - dicarboxamide 40 /O w/v Ethylan BCP (a nonylphenol ethylene oxide condensation product containing 9 moles of ethylene oxide per mole of phenol) 5% w/v distilled water 100% by volume by intimately mixing the ingredients and grinding in a ball mill for 24 hours. The concentrate thus obtained may be dispersed in water and applied at a rate of 2.0 kg of imidazole derivative in 200 litres of spray fluid per hectare to a crop growing area planted with soya bean to control the growth of broad-leaf weeds, for exampleAbutilon theophrasti, Xanthium strumarium and Ipomoea purpurea by post-emergence application after emergence of crop and weeds.

The (t) - N, N' - dimethyl - 1 - (3,4 - dichloro - amethoxybenzyl) imidazole - 4,5 - dicarboxamide may, if desired, be replaced in the above aqueous suspension concentrate by any other compound of general formula I.

EXAMPLE 3 A wettable powder concentrate is formed from: (t) - N, N' - dimethyl - 1 - (3, 4 dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide 50% w/w Ethylan BCP 2.5% w/w Clarcelflo SAS 132 (synthetic magnesium silicate carrier) 47.5% w/w by dissolving the imidazole and Ethylan BCP in the minimum volume of acetone and adding the solution to the Clarcelflo in a blender. After the acetone has evaporated, the product is ground in a hammer mill to give a wettable powder which may be dispersed in water and applied at a rate of 3 kg of imidazole derivative in 400 litres of spray fluid per hectare to a crop growing area sown with cotton to control the growth of broad-leaf weeds e.g. Sida spinosa, Abutilon theophrasti, Anoda cristata and Amaranthus retroflexus by post-emergence application after emergence of the crop and weeds.

The (+) - N, N' - dimethyl - 1 - (3,4 - dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide may, if desired, be replaced in the above wettable powder by any other compound of general formula EXAMPLE4 An emulsifiable concentrate is formed from: (t) - N, N' - dimethyl - 1 - (3, 4 dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide 20% w/v Duoterics MB1/MB2 (an anionic emulsifier blend containing calcium alkyl sulphonate and alkyl phenol ethylene oxide condensates) 10% w/v triethanolamine 1% w/v a 1::1 by volume mixture of cyclohexanone and Aromasol "H" (an aromatic solvent consisting predominantly of isomeric trimethylbenzenes)to 100% by volume by dissolving the imidazole derivative and the Duoterics MB1/MB2 and triethanolamine in a portion of the 1:1 cyclohexanone and Aromasol "H" mixture, and adding, with stirring, the remainder of the cyclohexanone-Aromasol "H" mixture. The emulsifiable concentrate thus obtained may be diluted with water and applied at a rate of 1.0 kg of imidazole derivative in 200 litres of spray fluid per hectare to a crop area planted with cotton to control the growth ofAmaranthus retroflexus, Acanthospermum hispidum. Abutilon theophrasti, Bidens pllosa, Sida spinosa, Xan thium strumarium, lpomoea purpurea and Physalis sp. by post-emergence application after the emergence of both crop and weeds.

The (+) - N, N' - dimethyl - 1 - (3,4 - dichloro - a- methoxybenzyl) imidazole - 4, 5 - dicarboxamide may, if desired, be replaced in the above emulsifiable concentrate by any other compound of general formula I.

Claims (49)

1. Imidazole derivatives of the general formula:

wherein R' represents a methyl or ethyl group, R2, R3 and R4, which may be the same or different, each represent a hydrogen or halogen atom or an alkyl or alkoxy group which may optionally be substituted by one or more fluorine atoms, and R2, R3 and R4 do not all represent hydrogen atoms.

2. Imidazole derivatives according to claim 1 wherein one of the symbols R2, R3 and R4 represents a hydrogen atom and the other two symbols and R1 are as defined in claim 1.

3. Imidazole derivatives according to claim 1 wherein R1 is as defined in claim 1, R2 and R3, which may be the same or different, each represent a hydrogen or halogen atom or an alkyl group which may optionally be substituted by one or more fluorine atoms and R2 and R3 do not both represent hydrogen atoms, and R4 represents a hydrogen or halogen atom.

4. Imidazole derivatives according to claim 1 wherein R' is as defined in claim 1, R2 and R3 each represent a halogen atom or R2 represents a hydrogen atom and R3 represents a halogen atom or an alkyl group which may optionally be substituted by one or more fluorine atoms, and R4 represents a hydrogen atom.

5. Imidazole derivatives according to any one of the preceding claims wherein R1 represents a methyl group.

6. Imidazole derivatives according to any one of the preceding claims wherein, within the definition of R2, R3 and R4, the or each halogen atom is chlorine or bromine and the or each alkyl or alkoxy group which may optionally be substituted by one or more fluorine atoms is a trifluoromethyl, trifluoromethoxy or 1,1,2, 2 - tetrafluoroethoxy group.

7. Imidazole derivatives according to claim 6 wherein the or each alkyl or alkoxy group which may optionally be substituted by one or more fluorine atoms is a trifluoromethyl group.

8. N, N' - Dimethyl - 1 - (3,4 - dichloro - a - methoxybenzyl) imidazole - 4,5 - dicarboxamide.

9. N, N' - Dimethyl -1 - (3,4 - dichloro - a - ethox- ybenzyl) imidazole - 4, 5 - dicarboxamide.

10. N, N' - Dimethyl - 1 -(a-methoxy-4-trif- luoromethylbenzyi) imidazole - 4, 5 - dicarboxamide.

11. 1 - (3,4- Dibromo - a - methoxybenzyl) - N, N' - dimethylimidazole - 4, 5 - dicarboxamide.

12. 1 - (4 - Chloro- a - methoxybenzyl) - N, N' dimethylimidazole - 4, 5 - dicarboxamide.

13. 1 - (3 - Chloro - a- methoxybenzyl) - N, N' dimethylimidazole - 4, 5 - dicarboxamide.

14. N, N' - Dimethyl - 1 - (a - methoxy - 3 - trifluoromethylbenzyl) imidazole - 4,5 - dicarboxamide.

15. 1 - (3, 5- Dichloro a- methoxybenzyl) - N, N' - dimethylimidazole - 4, 5 - dicarboxamide.

16. A process for the preparation of imidazole derivatives as claimed in claim 1 which comprises the reaction of a compound of the general for mula:--

(wherein X represents a halogen atom and R', R2, R3 and R4 are as defined in claim 1) with an alkali metal salt of imidazole - N, N' - dimethyl - 4, 5 - dicarboxamide of the formula:

17. A process according to claim 16 in which the reaction is effected in the presence of an inert organic solvent at a temperature between ambient temperature and 150"C.

18. A process for the preparation of imidazole derivatives as claimed in claim 1 which comprises the reaction of a compound of the general formula:

(wherein R1, R2, R3 and R4 are as defined in claim 1 and R5 represents a straight- or branched-chain alkyl group containing from 1 to 6 carbon atoms) with methylamine in the presence of an inert organic solvent at a temperature between 0" and 100"C.

19. A process for the preparation of imidazole derivatives of the general formula specified in claim 1 substantially as hereinbefore described with especial reference to Example 1.

20. A process according to claim 16 or 18 substantially as hereinbefore described.

21. Imidazole derivatives of the general formula specified in claim 1 when prepared by the process claimed in any one of claims 16 to 20.

22. A herbicidal composition which comprises, as active ingredient, at least one imidazole derivative as claimed in any one of claims 1 to 15 and 21 in association with one or more compatible herbicidally acceptable diluents or carriers.

23. A herbicidal composition according to claim 22 which contains a surface-active agent.

24. A herbicidal composition according to claim 22 or 23 in the form of a dust, granules or wettable powder.

25. A herbicidal composition according to claim 22 or 23 in the form of aqueous, organic or aqueous-organic solutions, suspensions or emulsions.

26. A herbicidal composition according to claim 22, 23 or 25 in which the diluent is water.

27. A herbicidal composition according to any one of claims 22 to 26 which contains from 0.05 to 90 /O by weight of imidazole derivative.

28. A herbicidal composition according to any one of claims 25 to 27 which contains an organic base to maintain alkaline conditions in a liquid composition.

29. A herbicidal composition according to any one of claims 25 to 28 which contains from 0.1 to 10% w/v of triethanolamine.

30. A herbicidal composition according to any one of claims 22 to 29 which contains one or more other pesticidally active compounds.

31. A herbicidal composition according to any one of claims 22 to 30 which contains in addition one or more herbicides, insecticides or fertilizers.

32. A herbicidal composition according to any one of claims 22 to 31 in which the imidazole derivative incorporated in the composition is a compound claimed in any one of claims 8 to 11.

33. A herbicidal composition according to any one of claims 22 to 31 in which the imidazole derivative incorporated in the composition is a compound claimed in any one of claims 12 to 15.

34. A herbicidal composition according to any one of claims 22 to 31 in which the imidazole derivative incorporated in the composition is (t) - N, N' dimethyl - 1 - (3, 4- dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide.

35. A herbicidal composition according to claim 22 substantially as hereinbefore described with especial reference to Example 2,3 or 4.

36. A method of controlling the growth of weeds at a locus which comprises applying to the locus a herbicidally effective amount of an imidazole derivative in a herbicidal composition as claimed in any one of claims 22 to 35.

37. A method according to claim 36 in which the weeds are annual broad-leafed weeds and the herbicidal composition is applied post-emergence.

38. A method according to claim 36 or 37 in which weeds controlled by application of the herbicidal composition are one or more ofAbutilon theophrasti, Amsinckia intermedia, Anthemis arvensis, Amaranth us spp., Anoda cristata, Acanthospermum spp., Bidens pllosa, Chenopodium spp., Chrysanthemum segetum, Datura stramonium, Descurainea sophia, Emex australis, Galeopsis tetrahit, lpomoea spp., Lamium spp., Merremia aegyptea, Palaver rhoeas, Physalis spp., Sida spinosa, Sida rhombifolia, Sinapis, spp., Stellaria media, Solanum spp., Urtica urens, Veronica spp., and Xanthium strumarium.

39. A method according to claim 36,37 or 38 in which the herbicidal composition is applied to a crop-growing area at a rate sufficient to control the growth of weeds without causing substantial permanent damage to the crop.

40. A method according to any one of claims 36 to 39 in which the imidazole derivative is applied at a rate between 0.25 kg and 20 kg per hectare.

41. A method according to any one of claims 36 to 39 for the selective control of the growth of weeds in an area used, orto be used, for growing crops.

42. A method according to claim 41 in which the imidazole derivative is applied at a rate between 0.25 kg and 8.0 kg per hectare.

43. A method according to claim 41 or 42 in which the crop is a graminaceous crop, soya beans, field or dwarf beans, peas, sugar beet, fodder beet or red beet, cotton, peanuts, potatoes, flax, onions, carrots, herbage seed crops, oilseed rape or pasture.

44. A method according to claim 43 in which the graminaceous crop is wheat, barley, oats, rye, maize, rice or sorghum.

45. A method according to any one of claims 36 to 39 in which the herbicidal composition contains as active material 1 - (4 - chloro - a - methoxybenzyl) - N, N' - dimethylimidazole - 4, 5 - dicarboxamide, 1 - (3 - chloro - a- methoxybenzyl) - N, N' dimethylimidazole - 4, 5 - dicarboxamide, N, N' dimethyl - 1 - (a - methoxy - 3 - trifluoromethylbenzyl) imidazole - 4, 5 - dicarboxamide and 1 - (3, 5 dichloro - a - methoxybenzyl) - N, N' dimethylimidazole - 4, 5 - dicarboxamide, N, N' dimethyl - 1 - (3,4 - dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide, N, N' - dimethyl - 1 (3,4 - dichloro - a - ethoxybenzyl) imidazole - 4, 5 dicarboxamide, N, N' - dimethyl - 1 - (a - methoxy - 4 - trifluoromethylbenzyl) imidazole - 4, 5 - dicarbox- amide or 1 - (3,4 - - dibromo - a - methoxybenzyl) - N, N' - dimethylimidazole - 4, 5 - dicarboxamide.

46. A method according to claim 45 in which the weeds are controlled by post-emergence application of the herbicidal composition in a non-directional fashion to an area used for growing crops of cereals, cotton or soya bean after emergence of the crop and weeds.

47. A method according to claim 45 or46 in which the imidazole derivative is applied at a rate between 0.25 kg and 8.0 kg per hectare.

48. A method according to claim 46 in which (+) N, N' - dimethyl - 1 - (3,4- dichloro - a - methoxybenzyl) imidazole - 4, 5 - dicarboxamide is applied at a rate of 0.5 to 4 kg/ha to control broad-leaf weeds in a crop of cotton.

49. A method of controlling the growth of weeds according to claim 36 substantially as herein before described.