WO1996022691A1

WO1996022691A1 - Herbicidal method

Info

Publication number: WO1996022691A1
Application number: PCT/GB1996/000147
Authority: WO
Inventors: Jeremy Paul Reynolds; Ian Bennett Bryan
Original assignee: Korean Research Institute Of Chemical Technology
Priority date: 1995-01-27
Filing date: 1996-01-24
Publication date: 1996-08-01
Also published as: GB9501621D0; AU4456196A

Abstract

A method of inhibiting the growth of, severely damaging, or killing Alopecurus myosuroides (blackgrass) growing in a cereal crop, without causing substantial harm to the crop, the method comprising applying to the crop in which the blackgrass is growing a compound of formula (I), wherein: R1 is a -CH¿2?F or -CH3 group; each of R?2 and R3¿ may be a methyl or methoxy group, and R?2 and R3¿ may be the same or different; or a herbicidally acceptable salt thereof.

Description

HERBICIDAL METHOD

The present invention relates to the use of certain sulfonylureas as herbicides, particularly herbicides for use on cereal crops.

Many sulfonylureas are known to have herbicidal activity and in the past few years literally hundreds of these compounds have been prepared and tested. Many of the compounds are particularly potent and selective herbicides and these include products such as bensulfuron-methyl, chlorimuron-ethyl, chlorsulfuron, cinosulfuron, 1-(4,6,-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-pyridylsulfonyl)urea, flazasulfuron, methyl

2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl) carbamoylsulfamoyl] benzoate,

metsulfuron-methyl, pyrazosulfuron, triasulfuron and tribenuron-methyl.

Other sulfonylureas are disclosed in EP-A-0177163, EP-A-0187489, US 4877440, EP-A-0209230, EP-A-0207609, EP-A-0209232, US 4908056, US 4838925, US4844727, US 4881968, WO-A-9104967, EP-A-0152378, EP-A-0139612 and EP-A-0126711 and there are many more publications which also concern the use of sulfonylureas as herbicides.

Sulfonylurea compounds are useful herbicides because they are effective at low rates and they have relatively low toxicity.

However, although the sulfonylureas are widely used and potent herbicides, they tend, as a class, to have certain disadvantages and one of the most important of these is the failure of all previously tested compounds to eliminate particular commercially important weeds. Up to the priority date of the present application, no commercially available sulfonylurea compound has been able to control Alopecurus myosuroides or blackgrass, selectively in cereal crops such as wheat and barley. Since this weed is extremely common, particularly in cereals, more especially in temperate cereals, it presents a significant problem to farmers.

Clearly, it would be an advantage to the farmer to be able to control all of the major weed species for a particular crop with a single herbicide product but, in the past, this has proved to be extremely difficult. Although sulfonylureas are, in general, capable of controlling a broad spectrum of weed species, and can be used to control most of the prevalent weed species in most crops, there has been a singular lack of success in controlling blackgrass, which is a weed of commercial significance to cereal farmers.

The present inventors have now found that the members of a particular group of sulfonylurea compounds are capable of controlling blackgrass as well as broadleaved weeds which occur commonly in cereal crops. In a first aspect of the present invention there is provided a method for inhibiting the growth of, severely damaging, or killing blackgrass in a cereal crop without causing substantial harm to the crop, the method comprising applying to the crop in which the blackgrass is growing a compound of formula (I) :

wherein:

R¹ is a -CH₂F or -CH₃ group; each of R² and R³ may be a methyl or methoxy group, and R² and R³ may be the same or different;

or a herbicidally acceptable salt thereof.

By the term "herbicidally acceptable salt" we mean a salt formed from a cation that is not incompatible with the use of the compound of formula (I) as a herbicide.

Thus, for example, a salt formed from a heavy metal cation would not be herbicidally acceptable since the application of such a salt would leave residues of the heavy metal cation in the soil and possibly in the crop.

Herbicidally acceptable salts include for example salts formed from sodium or potassium.

Within the general formula (I), several positional isomers exist. Using D to represent the dioxolan urea substituent and S to represent the sulphonyl urea substituent, the isomers may be represented by the formulae 1(A) to 1(F).

Particular examples of compounds that may be used in the method of the invention are listed in Table I below.

The ability of compounds of formula (I) to control blackgrass gives them a significant advantage over sulfonylurea herbicides which are presently in use and which are not able to control this weed. This activity of the compounds of formula (I) is particularly surprising because they are structurally extremely similar to the known sulfonylureas, such as thifensulfuron, which are unable to control blackgrass.

Clearly, from a knowledge of the activity of the sulfonylureas as a group, this ability to eliminate blackgrass would not have been expected.

Certain of the compounds of formula (I) have been disclosed in WO- A-9216525. The authors of this document tested these compounds and a variety of other closely related compounds against a variety of weed and crop species. However, most of the weed species tested were weeds which are commonly found in warm-season crops rather than in temperate cereals. The compounds were not tested at all against blackgrass, perhaps because, from the known activity of other sulfonylureas, there was no expectation that the compounds would be active against this weed.

In addition to blackgrass, the compounds of formula (I) are also active against a broad range of other weed species including monocotyledonous species such as wild oats (Avena fatua), green foxtail (Setaria viridis). ryegrass (Lolium species) and loose silky bent (Apera spica-venti) and dicotyledonous species. Examples of dicotyledonous weeds against which the compounds of formula (I) are active include Galium aparine, Matricaria perforata,

Amaranthus retroflexus, Xanthium spinosum, Sinapis arvensis, Raphanus raphanistrum,

Capsella bursa-pastoris, Sisymbrium orientale, Lamium purpureum, Myosotis arvensis,

Sonchus oleraceus, and Polygonum convolvulus, which are found in temperate cereals. One commercially important broadleaved weed which has proved difficult to control with some sulfonylurea herbicides is Galium aparine. also known as cleavers, and this is one of the weeds which the compounds of formula (I) have proved successful in controlling. It is, however, the ability of the compounds of formula (I) to control blackgrass without causing substantial harm to crops which makes them particularly useful as cereal herbicides.

Although the compounds of formula (I) may be used in most cereal crops, they are more selective in small grain cereals such as wheat, barley, oats and rye than in maize or rice.

They are particularly useful in removing weeds from wheat and barley.

The compounds of formula (I) may be prepared according to the method set out in

WO- A-9216525 or by a method adapted from any of the patent publications mentioned above.

A particularly suitable method for the preparation of compounds of formula (I) is by the reaction of a sulphonamide compound II with a carbamate III. The carbamate III is readily available or may be prepared by methods known in the art. The sulphonamide II may be prepared by a three step reaction from the bromothiophene IV. Compound IV is first reacted with sulphur dioxide in the presence of a base such as n-butyl lithium. Following this, the sulphonated product is reacted with a halogenating agent such as N-chlorosuccinimide to give a sulphonyl halide which can then be reacted with ammonia to give the sulphonamide II.

The dioxolane-substituted bromothiophene IV may be prepared from a R¹CO-substituted bromothiophene V by reaction with ethylene glycol. The R'CO-substituted bromothiophene V may be prepared from 2,3-dibromothiophene and ethyl fluoroacetate, or ethyl acetate, all of which compounds are readily available.

The compounds of formula (I) may be applied directly to the plant (post-emergence application) or to the soil before the emergence of the plant (pre-emergence application) but ther are particularly useful when applied post-emergence.

The rate of application of the compounds used in the invention will depend on a number of factors including, for example, the identity of the plants whose growth is to be inhibited, the formulations selected for use and whether the selected compound is to be applied for foliar or root uptake. As a general guide, however, an application rate of from 0.25g to 20 kg per hectare is suitable. An application rate of 0.25g to 10 kilograms per hectare may be preferred but an optimal application rate will usually be in the range of 0.25 to 500g per hectare.

Although compounds of formula (I) may be applied to a crop alone, they will, in general, be applied in the form of a herbicide composition in which they will be an active ingredient.

Therefore, in a second aspect of the invention, there is provided the use of a compound of formula (I) as an active ingredient in a composition for inhibiting the growth of, severely damaging or killing blackgrass.

Compositions containing a compound of formula (I) include both dilute compositions which are ready for immediate use, and concentrated compositions which require dilution before use, usually with water. Preferably the compositions contain from 0.01% to 90% by weight of the active ingredient. Dilute compositions ready for use preferably contain from 0.01% to 2% of active ingredient, while concentrated compositions may contain from 20% to 90% of active ingredient, although from 20% to 70% is usually preferred. The solid compositions may be in the form of granules, or dusting powders wherein the active ingredient is mixed with a finely divided solid diluent, e.g. kaolin, bentonite, kieselguhr, dolomite, calcium carbonate, talc, powdered magnesia, Fuller's earth and gypsum. They may also be in the form of dispersible powders or grains, comprising a wetting agent to facilitate the dispersion of the powder or grains in liquid. Solid compositions in the form of a powder may be applied as foliar dusts.

Liquid compositions may comprise a solution or dispersion of an active ingredient in water optionally containing a surface-active agent, or may comprise a solution or dispersion of an active ingredient in a water-immiscible organic solvent which is dispersed as droplets in water.

Surface-active agents may be of the cationic, anionic, or non-ionic type or mixtures thereof. The cationic agents are, for example, quaternary ammonium compounds (e.g.

cetyltrimethylammonium bromide). Suitable anionic agents are soaps; salts of aliphatic mono ester of sulphuric acid, for example sodium lauryl sulphate; and salts of sulphonated aromatic compounds, for example sodium dodecylbenzenesulphonate, sodium,calcium, and ammonium lignosulphonate, butylnaphthalene sulphonate, and a mixture of the sodium salts of diisopropyl and triisopropylnaphthalenesulphonic acid. Suitable non-ionic agents are the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, or with alkylphenols such as octyl- or nonyl- phenol (e.g. Agral 90) or octyl-cresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitan monolaurate; the condensation products of the partial ester with ethylene oxide; the lecithins; and silicone surface active agents (water soluble surface active agents having a skeleton which comprises a siloxane chain e.g. Silwet L77). A suitable mixture in mineral oil is Atplus 411F.

The aqueous solutions or dispersions may be prepared by dissolving the active ingredient in water or an organic solvent optionally containing wetting or dispersing agent(s) and then, when organic solvents are used, adding the mixture so obtained to water optionally containing wetting or dispersing agent(s). Suitable organic solvents include, for example, ethylene dichloride, isopropyl alcohol, propylene glycol, diacetone alcohol, toluene, kerosene, methylnaphthalene, the xylenes and trichloroethylene.

The compositions for use in the form of aqueous solutions or dispersions are generally supplied in the form of a concentrate containing a high proportion of the active ingredient, and the concentrate is then diluted with water before use. The concentrates are usually required to withstand storage for prolonged periods and after such storage, to be capable of dilution with water to form aqueous preparations which remain homogeneous for a sufficient time to enable them to be applied by conventional spray equipment. Concentrates

conveniently contain 20-90%, preferably 20-70%, by weight of the active ingredient(s). Dilute preparations ready for use may contain varying amounts of the active ingredient(s) depending upon the intended purpose; amounts of 0.01% to 10.0% and preferably 0.1% to 2%, by weight of active ingredients) are normally used.

A preferred form of concentrated composition comprises the active ingredient which has been finely divided and which has been dispersed in water in the presence of a

surface-active agent and a suspending agent. Suitable suspending agents are hydrophilic colloids and include, for example, polyvinylpyrrolidone and sodium carboxymethylcellulose, and the vegetable gums, for example gum acacia and gum tragacanth. Preferred suspending agents are those which impart thixotropic properties to, and increase the viscosity of the concentrate. Examples of preferred suspending agents include hydrated colloidal mineral silicates, such as montmorillonite, beidellite, nontronite, hectorite, saponite, and saucorite. Bentonite is especially preferred. Other suspending agents include cellulose derivatives and polyvinyl alcohol.

The compositions of the invention may comprise, in addition to a compound of formula (I), one or more additional compounds which possess biological activity. The additional compounds may be, for example, other herbicides, fungicides, insecticides (optionally with an insecticide synergist) or plant growth regulators. Other herbicides are, however, particularly preferred ingredients.

The other herbicide present in the composition may be any herbicide not having the formula (I). It will generally be a herbicide having a complementary action in the particular application.

Examples of other herbicides include:

A. benzo-2,1,3-thiadiazin-4-one-2,2-dioxides such as bentazone;

B. hormone herbicides, particularly the phenoxy alkanoic acids such as MCPA,

MCPA-thioethyl, dichlorprop, 2,4,5-T, MCPB, 2,4-D, 2,4-DB, mecoprop, trichlopyr, fluroxypyr, clopyralid, and their derivatives (eg. salts, esters and amides); C. 1,3 dimethylpyrazole derivatives such as pyrazoxyfen, pyrazolate and benzofenap;

D. Dimtrophenols and their derivatives (eg. acetates) such as dinoterb, dinoseb and its ester, dinoseb acetate;

E. dinitroaniline herbicides such as dinitramine, trifluralin, ethalflurolin,

pendimethalin, oryzalin;

F. arylurea herbicides such as diuron, flumeturon, metoxuron, neburon, isoproturon, chlorotoluron, chloroxuron, linuron, monolinuron, chlorbromuron, daimuron, methabenzthiazuron;

G. phenylcarbamoyloxyphenylcarbamates such as phenmedipham and desmedipham; H. 2-phenylpyridazin-3-ones such as chloridazon and norflurazon;

I. uracil herbicides such as lenacil, bromacil and terbacil;

J. triazine herbicides such as atrazine, simazine, aziprotryne, cyanazine, prometryn, dimethametryn, simetryne, and terbutryn;

K. phosphorothioate herbicides such as piperophos, bensulide, and butamifos;

L. thiocarbamate herbicides such as prosulfocarb, cycloate, vernolate, molinate, thiobencarb, butylate^*, EPTC^*, tri-allate, di-allate, esprocarb, tiocarbazil, pyridate, and dimepiperate;

M. 1,2,4-triazin-5-one herbicides such as metamitron and metribuzin;

N. benzoic acid herbicides such as 2,3,6-TBA, dicamba and chloramben;

O. anilide herbicides such as pretilachlor, butachlor, alachlor, propachlor, propanil, metazachlor, metolachlor, acetochlor, and dimethachlor;

P. dihalobenzonitrile herbicides such as dichlobenil, bromoxynil and ioxynil;

Q. haloalkanoic herbicides such as dalapon, TCA and salts thereof;

R. diphenylether herbicides such as lactofen, fluroglycofen or salts or ester thereof, nitrofen, bifenox, aciflurofen and salts and esters thereof, oxyfluorfen, fomesafen, chlornitrofen and chlomethoxyfen;

S. aryloxyphenoxypropionate herbicides such as diclofop and esters thereof such as the methyl ester, fluazifop and esters thereof, haloxyfop and esters thereof, quizalofop and esters thereof, fenoxaprop^* and esters thereof such as the ethyl ester and clodinofop ^* and esters thereof;

T. cyclohexanedione herbicides such as alloxydim and salts thereof, sethoxydim, cycloxy dim, tralkoxydim, and clethodim; U. other sulfonyl urea herbicides such as chlorsulfuron, sulfometuron, metsulfuron and esters thereof; bensulfuron and esters thereof such as DPX-M6313, chlorimuron and esters such as the ethyl ester thereof pirimisulfuron and esters such as the methyl ester thereof,

2-[3-(4-methoxy-6-methyl-1,3,5-triazin-zyl)-3-methylureido-sulphonyl) benzoic acid esters such as the methyl ester thereof (DPX-L5300) and pyrazosulfuron;

V. imidazolidinone herbicides such as imazaqnin, imazamethabenz, imazapyr and isopropylammonium salts thereof, imazethapyr,

W. arylanilide herbicides such as flamprop and esters thereof, benzoylprop-ethyl, diflufenican;

X. amino acid herbicides such as glyphosate and glufosinate and their salts and

esters, such as glyphosate trimesium, and bialaphos;

Y. organoarsenical herbicides such as monosodium methanearsonate (MSMA);

Z. herbicidal amide derivative such as napropamide, propyzamide, carbetamide, tebutam, bromobutide, isoxaben, naproanilide and naptalam;

AA. herbicidal triketones such as sulcotrione;

AB. miscellaneous herbicides including ethofumesate, cinmethylin, difenzoquat and salts thereof such as the methyl sulphate salt, clomazone, oxadiazon, bromofenoxim, barban, tridiphane, flurochloridone, quinclorac, dithiopyr and mefanacet;

AC. Examples of useful contact herbicides include:

bipyridylium herbicides such as those in which the active entity is paraquat and those in which the active entity is diquat;

* These compounds are preferably employed in combination with a safener such as dichlormid, fenchlorazole or cloquintocet.

It will be appreciated that the main advantage of the compounds of formula (I) is that they can effectively be used to control blackgrass, which is a weed of temperate cereal crops. Thus, the composition will often be a cereal herbicide composition and in that case, any other herbicide will, like the compound of formula (I), have to be cereal selective. Examples of cereal selective herbicides which may be included in a composition containing a compound of formula (I) include:

MCPA, MCPA-thioethyl, dichlorprop, MCPB, 2,4-D, 2,4-DB, mecoprop, trichlopyr, fluroxypyr, clopyralid, and their derivatives (eg. salts, esters and amides);

trifluralin and pendimethalin;

isoproturon, chlorotoluron and methabenzthiazuron;

prosulfocarb, tri-allate and di-allate;

dicamba;

bromoxynil and ioxynil;

TCA;

bifenox;

diclofop, fenoxaprop and clodinofop, the second and third of these being preferably used in combination with a safener such as fenchlorazole or cloquintocet, tralkoxydim;

chlorsulfuron, metsulfuron-methyl, tribenuron-methyl, amidosulfuron, and triasulfuron;

DPX - KE 459, which is methyl 2-[4,6-dimethoxy pyrimidin-2-ylcarbamoyl)sulfamoyl]-6- (trifluoro- methyl)nicotinate, monosodium salt;

imazamethabenz

flamaprop and diflufenican; and

difenozquat.

Since one of the most significant features of compounds of the formula (I) is their ability to control blackgrass in cereal crops, there is provided in a third aspect of the

invention, the use of a compound of formula (I) as the active ingredient of a cereal herbicide composition.

Preferred features of this aspect of the invention are as for the first and second aspects of the invention.

The invention will now be further described with reference to the following examples.

EXAMPLE 1

This Example illustrates the activity of compound 1 of Table I against a variety of weeds.

In a glasshouse test, Compound 1 of Table I was applied post-emergence at 5 and 10g ai/ha to winter and spring varieties of wheat and barley, and a range of associated grass and broadleaved weeds. The spray volume was equivalent to 200 litres per hectare, and all treatments included 0.1% v/v Agral 90. Agral 90 comprises a condensate of from 7 to 8 molar proportions of ethylene oxide with p-octyl or or p-nonyl phenol. There were three replicates per treatment.

After spraying the treated plants were maintained in the glasshouse. Assessments were made 28 days after treatment using a visual 0-100% percentage scale where 0 = 0% crop damage or weed control, and 100 = 100% crop damage or weed control. The results are presented in Table 2 below, in which the abbreviation "If stands for leaf, the number of leaves indicating the growth stage of the crop plant or weed, at the time of treatment. The crops and weeds treated were:

This experiment shows that Compound 1 of Table I can successfully control blackgrass and also a variety of other weeds while leaving cereal crops substantially unaffected.

EXAMPLE 2

This Example illustrates the activity of compound 1 of Table I and other sulphonylurea herbicides on blackgrass.

Compound 1 and various commercially available sulfonylurea herbicides were applied post emergence to blackgrass. The spray volume was equivalent to 200 litres per hectare, and all treatments included 0.1% v/v Agral 90. There were three replicates per treatment.

After spraying the treated plants were maintained in the glasshouse. Assessments were made 28 days after treatment using a visual 0-100% percentage scale where 0 = 0% crop damage or weed control, and 100 = 100% crop damage or weed control. The results are presented in Table 3, below. Table 3: Percentage blackgrass control 28 days after post-emergence treatment comparison with other sulphonyl urea herbicides.

This experiment shows that Compound 1 of Table I is significantly more effective in controlling blackgrass than commercially available sulfonylurea herbicides.

EXAMPLE 3

This Example further illustrates the selective herbicidal activity of compounds used in the method of the invention against blackgrass, as compared with their activity on barley and wheat.

A glass-house test was carried out as described in Example 1. The results are given in Table 4 below.

It should be noted that in biological tests of this kind, some degree of variation from test to test must be expected, and even within a particular test, anomalous results may be encountered. For example, in the results for Compound No. 2, there was in this particular test some damage to winter wheat (TRZAW PRINQUAL) at the lowest rate of application, although at the higher rate of application (10g/ha) no damage was observed. Nevertheless, it is clear that at appropriate rates of application, the compounds used in the process of the invention can give substantial control of blackgrass while not causing significant damage to wheat or barley.

Claims

1. A method of inhibiting the growth of, severely damaging, or killing Alopecurus myosuroides (blackgrass) growing in a cereal crop, without causing substantial harm to the crop, the method comprising applying to the crop in which the blackgrass is growing a compound of formula (I):

wherein:

or a herbicidally acceptable salt thereof.

2. A method as claimed in claim 1 wherein the compound of formula (I) is one in which R¹ is a -CH₂F group.

3. A method as claimed in claim 1 or claim 2 wherein one of R² and R³ is a

methyl group and the other is a methoxy group.

4. A method as claimed in any one of claims 1, 2 or 3, wherein the compound of formula (I) is one in which the dioxolanyl substituent is located in the 3- position of the thiophene ring, and the sulphonylurea substituent is located in the 4-position of the thiophene ring.

5. A method as claimed in any one of claims 1,2, or 3, wherein the compound of formula (I) is one in which the dioxolanyl substituent is located in the 2- position of the thiophene ring and the sulphonylurea substituent is located in the 3-position of the thiophene ring.

6. A method as claimed in any one of claims 1, 2 or 3, wherein the compound of formula (I) is one in which the dioxolanyl substituent is located in the 3- position of the thiophene ring and the sulphonylurea substituent is located in the 2-position of the thiophene ring.

7. A method as claimed in claim 4, wherein the compound of formula (I) is the one in which R¹ is a -CH₂F group, R² is a methyl group and R³ is a methoxy group.

8. The use of a compound of formula (I) as defined in any one of claims 1 to 7, or a herbicidally acceptable salt thereof, as an active ingredient in a composition for inhibiting the growth of, severely damaging, or killing blackgrass.

9. The use of a compound of formula (I) as defined in any one of claims 1 to 7, or a herbicidally acceptable salt thereof, as an active ingredient of a cereal herbicide composition.