WO2007068352A1

WO2007068352A1 - A use of barbituric acid derivatives as herbicidal efficacy-enhancing agents or herbicidal agents and process for their preparation

Info

Publication number: WO2007068352A1
Application number: PCT/EP2006/011445
Authority: WO
Inventors: Akihiko Yanagi; Shinichi Narabu; Keiji Endo; Shinichi Shirakura; Teruyuki Ichihara; Shin Nakamura
Original assignee: Bayer Cropscience Ag
Priority date: 2005-12-15
Filing date: 2006-11-29
Publication date: 2007-06-21
Also published as: JP2007161658A

Abstract

Barbituric acid derivatives of the formula (I): or salts thereof, wherein, R1 represents C4-I2 alkyl which is unsubstituted or substituted with C1-4 alkoxy; C5-9 alkenyl or C5-9 alkynyl; R2 represents methyl or ethyl; R3 represents methyl or ethyl; and X represents O or S can be used as herbicidal efficacy-enhancing agents, and some of which can be used as herbicides. Some compounds being embraced by the formula (I) are also claimed. The herbicidally effective compounds show very quick effective action.

Description

A use of barbituric acid derivatives as herbicidal efficacy-enhancing agents or herbicidal agents and process for their preparation

The present invention relates to a use of the barbituric acid derivatives and salts thereof as herbicidal efficacy-enhancing agents and herbicides having very quickly effective action, to novel barbituric acid derivatives and to a process for their preparation.

It has been known that certain barbituric acid derivatives have the insecticidal or fungicidal action although they are harmful to crops (see, for example, US Patent No. 3,828,043). It has also been known that certain barbituric acid derivatives have the prophylactic or therapeutic action against bone- or cartilage-related diseases (see, for example, WO99/50252).

Further, various barbituric acid derivatives have been synthesized and reported in the field of organic chemistry (for example, see WO99/15510; Tetrahedron Letters, Vol. 44(10), pp. 2203-2210 (2003); and Magnetic Resonance in Chemistry, Vol. 36 (Spec. Issue), pp. 104-110 (1998)).

There have now been found that barbituric acid derivatives of the formula (I) and salts thereof show herbicidal efficacy-enhancing activities:

wherein,

R¹ represents C₄-₁₂ alkyl which is unsubstituted or substituted with Ci_-4 alkoxy; C_5-9 alkenyl or C_5-g alkynyl;

R² represents methyl or ethyl;

R³ represents methyl or ethyl; and

X represents O or S.

There have now been also found that barbituric acid derivatives of the formula (IB) show excellent herbicidal activities having very quickly effective action:

or a salt thereof, wherein, R^1B represents n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl or 5-hexenyl; R^2B represents methyl or ethyl; R^3B represents methyl or ethyl; and X^B represents O or S; provided that: (i) where X^B represents O, and both R^2B and R^3B represent methyl, then R ,1B

represents n-pentyl, n-hexyl, n-heptyl, n-octyl or 5-hexenyl; (ii) where X^B represents O, R^2B represents methyl and R^3B represents ethyl, then R^1B represents n-pentyl, n-heptyl, n-octyl or 5-hexenyl;

(iii) where X^B represents O, and both R^2B and R^3B represent ethyl, then R^1B represents n-pentyl, n-hexyl, n-heptyl or 5-hexenyl; and (iv) where X^B represents S, then both R^2B and R^3B represent methyl and R i1 B

represents n-butyl, n-pentyl or 5-hexenyl.

Furthermore, the barbituric acid derivatives of the following formula (IA) and salts thereof, being embraced by the above formula (I) of the present invention are novel. The formula (IA):

wherein R^1A represents C_5-12 alkyl which is unsubstituted or substituted with Ci_-4 alkoxy;

C_5-9 alkenyl or C_5-9 alkynyl; R^2A represents methyl or ethyl; R^3A represents methyl or ethyl; and X^A represents O or S; provided that the following (i) and (ii) are excluded: (i) X^A represents O, both R^2A and R^3A represent methyl and R^1A represents n-hexyl or n-nonyl; or (ii) X^A represents S, both R^2A and R^3A represent methyl and R^1A represents n-pentyl, n-nonyl or 3-methyl-1-butenyl.

The compounds of the formula (IA) can be obtained by a process in which

(a) compounds of the formula (II):

wherein

R^2A, R^3A and X^A have the same definition as aforementioned, are reacted with compounds of the formula (III):

wherein

R^1A has the same definition as aforementioned, and Z represents halogen or hydroxyl, preferably chlorine, bromine or hydroxyl, in the presence of inert solvents, and if appropriate, in the presence of an acid binding agent, (b) compounds of the formula (II) as defined above in step (a), are reacted with compounds of the formula (IV):

wherein

R^1A has the same definition as aforementioned, in the presence of inert solvents, and if appropriate, in the presence of an acid binding agent, and if appropriate in the presence of an acid catalyst.

The compounds of the formula (I) and the compounds of the formula (IB) can also be obtained by the process (a) or (b).

According to the present invention, surprisingly, the barbituric acid derivatives of the formula (I) or salt thereof show a strong herbicidal efficacy-enhancing action when it is mixed with other herbicide. In particular, a part of the barbituric acid derivatives of the formula (I) and salts thereof, according to the present invention, exhibit a strong herbicidal efficacy-enhancing action without showing any herbicidal action.

The barbituric acid derivatives of the formula (I) also show, as specifically mentioned after, stronger herbicidal action as a mixed herbicide compositions by mixing with other herbicidal active compounds.

Also the barbituric acid derivatives of the formula (IB) exhibit an excellent herbicidal activities having very quickly effective action. Though the compounds of the formulae (I) and (IB) are generically in part embraced by US Patent No. 3,828,043, and also include known compounds disclosed in US Patent No. 3,828,043, WO99/15510 and the afore-cited Tetrahedron Letters, such surprisingly unexpected biological effects, according to the invention, have not been described in the known literature.

The term "alkyl" in the specification may be either in straight or branched chain, such as C_4-I2 straight-chain alkyl or C_4-I2 branched chain alkyl, examples thereof include n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, 1-methylheptyl, n-nonyl, 7-methyloctyl, 3-methyloctyl, 2-methylheptyl, 1-propylbutyl, 1-ethylpentyl, 1-propylpentyl, 1-ethylhexyl, 1-butylpentyl, n-decyl, n-undecyl and n-dodecyl.

Examples of "C_5-9 alkenyl" include 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl and 6-nonenyl.

Examples of "C₅-₉ alkynyl" include 4-pentynyl, 5-hexynyl, 6-heptynyl and 7-octynyl.

Examples of "Ci_-4 alkoxy" include methoxy and ethoxy.

"Herbicidal efficacy-enhancing agent" means a compound which enhances the effect of herbicidal compounds, in mixing each other, on a condition that the compound has no herbicidal activities. "Herbicides having very quickly effective action" mean compounds which demonstrate herbicidal efficacies within several hours at latest after an application thereof.

A group of compounds suitable for exhibiting the herbicidal efficacy-enhancing action of the invention include the salts of the barbituric acid derivatives of the formula (I), and specific examples thereof include organic and inorganic salts such as tertiary amine salts, alkali metal salts and alkaline earth metal salts. Specific examples thereof include salts of triethylamine, diisopropylethylamine, triethanolamine, sodium and potassium. Among the compounds of the formula (IA) the followings are preferable:

R^1A represents C₅-₉ alkyl which is unsubstituted or substituted with methoxy or ethoxy, or C_5-g alkenyl; R^2A represents methyl or ethyl; R^3A represents methyl or ethyl; and X^A represents O or S, provided that

(i) where X^A represents S, then R^1A represents C_5-9 alkyl or C_5-9 alkenyl, R^2A represents methyl and R^3A represents methyl, and provided that the following (ii) and (iii) are excluded: (ii) X^A represents O, both R^2A and R^3A represent methyl and R^1A represents n-hexyl or n-nonyl; or

(iii) X^A represents S, both R^2A and R^3A represent methyl and R^1A represents n-pentyl, n-nonyl or 3-methyl-1-butenyl.

Among the compounds of the formula (IA) the followings are more preferable:

R^1A represents n-pentyl, n-hexyl, n-heptyl, n-octyl, 7-methyloctyl, 3-methyloctyl, 2-methylheptyl, 1-propylbutyl, 1-ethylpentyl, 1-ethylhexyl, 1-butylpentyl, 4-methoxyoctyl, 3-methoxyoctyl, 3-ethoxyoctyl, 4-methoxynolyl, 4-ethoxynonyl, 3-methoxynonyl 4-pentenyl, 5-hexenyl, 6-heptenyl or 7-octenyl;

R^2A represents methyl or ethyl; R^3A represents methyl or ethyl; and X^A represents O or S, provided that:

(i) where R^2A represents methyl, R^3A represents methyl and X^A represents O, then R^1A represents n-pentyl, n-heptyl, n-octyl, 7-methyloctyl, 3-methyloctyl, 2-methylheptyl, 1-propylbutyl, 1-ethylpentyl, 1-ethylhexyl, 1-butylpentyl, 4-methoxyoctyl, 3-methoxyoctyl, 3-ethoxyoctyl, 4-methoxynonyl, 4-ethoxynonyl, 3-methoxynonyl, 4-pentenyl, 5-hexenyl, 6-hepteny or

7-octenyl;

(ii) where R^2A represents methyl, R^3A represents ethyl and X^A represents O, or where R^2A represents ethyl, R^3A represents ethyl and X^A represents O, then R^1A represents n-pentyl, n-hexyl, n-heptyl, n-octyl or 5-hexenyl; and (iii) where X^A represents S, then R^1A represents n-hexyl, n-heptyl, n-octyl or 5-hexenyl, R^2A represents methyl and R^3A represents methyl.

The aforementioned preparation process (a) can be illustrated by the following reaction scheme when, e.g., 1 ,3-dimethylbarbituric acid and octanoyl chloride are used together with, e.g., triethylamine, as a base:

The aforementioned preparation process (b) can be illustrated by the following reaction scheme when, e.g.,

1 ,3-dimethylbarbituric acid and octanoic acid anhydride are used together with cone, sulfuric acid, as an acid catalyst:

The compounds of the formula (I) may take the form of a tautomer of the formulae (Ia), (Ib), (Ic), or (Id) below. While the compounds are illustrated by the structure of the formula (Ia) as a representative example in this specification, the compounds of the formula (I) also include the tautomers of formulae (Ib), (Ic), and (Id).

The compounds of the formula (II), used as the starting materials in the preparation process (a) and (b), are known compounds per se. And the compounds can be prepared according to the process described in any one of Chemische Berichte, Vol. 49, p. 652 (1916); Journal of the American Chemical Society, Vol.73, pp. 5326-5332 (1951); US Patent No. 5,674,870; Journal of Heterocyclic Chemistry, Vol. 18, pp. 1095-1100; and Japanese Patent Application Laid-Open (KOKAI) No. 63-121828.

A part of the compounds of the formula (III), in which Z represents a hydroxyl, used as the starting materials in the preparation process (a), are novel, and can be prepared according to the process described, e.g., in Journal of Organic Chemistry, Vol. 59, pp. 2253-2256 (1994). The compounds of the formula (III) wherein Z represents halogen are known, and can be prepared according to the method described in either Organic Synthesis, Collective Vol. I, p. 147, (1941 ) or Organic Synthesis, Collective Vol. IV, p. 554 (1963).

As specific examples of the compounds of the formula (II), used as the starting materials in the preparation process (a) and (b), there can be mentioned as follows:

1 ,3-dimethylbarbituric acid, 1-ethyl-3-methylbarbituric acid, 1 ,3-diethylbarbituric acid and so on.

As specific examples of the compounds of the formula (III), used as the starting materials in the preparation process (a), there can be mentioned as follows: octanoic acid, nonanoic acid, decanoic acid, 5-methoxynonanoic acid, 4-methoxydecanoic acid, octanoyl chloride, nonanoyl chloride, decanoyl chloride, 5-methoxynonanoyl chloride, 4-methoxydecanoyl chloride and so on.

The compounds of the formula (IV), used as the starting materials in the preparation method (b), are known and can be prepared according to the method described in Journal of the American Chemical Society, Vol.63, pp. 699-700 (1941).

As specific examples of the compounds of the formula (IV) used as the starting materials in the preparation method (b), there can be mentioned as follows: octanoic acid anhydride, nonanoic acid anhydride, decanoic acid anhydride and so on. The reaction of the preparation process (a) can be carried out in an appropriate diluent, and examples thereof to be used in the reaction include: aliphatic, alicyclic and aromatic hydrocarbons, optionally which may be chlorinated, such as pentane, hexane, cyclohexane, petroleum ether, ligroin, benzene, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, 1 ,2-dichloroethane, chlorobenzene and dichlorobenzene; ethers such as ethylether, methylethylether, isopropylether, butylether, dioxane, dimethoxyethane (DME), tetrahydrofuran (THF) and diethyleneglycoldimethylether (DGM); ketones such as acetone, methyl ethyl ketone (MEK), methyl isopropyl ketone and methyl isobutyl ketone (MIBK); nitriles such as acetonitrile and propionitrile; esters such as ethyl acetate; amides such as dimethylformamide (DMF)₁ dimethylacetamide (DMA), N-methylpyrrolidone, 1 ,3-dimethyi-2-imidazolidinone and hexamethylphosphoric triamide(HMPA); sulfone and sulfoxides such as dimethylsulfoxide (DMSO) and sulfolane; and bases such as pyridine. The preparation process (a) can be carried out in the presence of an acid binding agent. Examples thereof include inorganic bases such as hydrides, carbonate salts and hydrogen carbonate salts of alkali metals and alkali earth metals, such as sodium hydride, lithium hydride, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate and potassium carbonate; carbodiimides such as N,N'-dicyclohexyl carbodiimide and N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide hydrochloride; and organic bases including tertiary amines, dialkylaminoanilines and pyridines, such as triethylamine, 1 ,1 ,4,4-tetramethylethylenediamine (TMEDA), N,N-dimethylaniline and N.N-diethylaniline, pyridine, 4-dimethylaminopyridine (DMAP), 1 ,4-diazabicyclo[2,2,2]octane (DABCO) and 1 ,8-diazabicyclo[5,4,0]undeca-7-ene (DBU).

The preparation process (a) can be carried out in a substantially wide temperature range. The temperature is generally in the range of about -20 to about 100°C, preferably about 0 to about 50⁰C. While the reaction is desirably carried out under normal pressure, the reaction may also be carried out under high or reduced pressure.

In carrying out the preparation process (a), for example, the compounds of the formula (II) in an amount of 0.5 moles to 1.5 moles may be reacted with 1 mole of the compounds of the formula (III) in a diluent such as tetrahydrofuran in the presence of triethylamine thereby to obtain aimed compounds of the formula (IA).

The preparation process (b) can be carried out in an appropriate diluent. Examples thereof to be used for the reaction include: aliphatic, alicyclic and aromatic hydrocarbons, optionally which may be chlorinated, such as pentane, hexane, cyclohexane, petroleum ether, ligroin, benzene, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, 1 ,2-dichloroethane, chlorobenzene and dichlorobenzene; sulfones and sulfoxides such as dimethylsulfoxide (DMSO) and sulfolane; and bases such as pyridine.

The preparation process (b) can be carried out in the presence of an acid binding agent. Examples thereof include inorganic bases such as carbonate salts and bicarbonate salts of alkali metals and alkali earth metals such as sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate and potassium carbonate; and organic bases including tertiary amines, dialkylaminoanilines and pyridines, such as triethylamine, 1 ,1 ,4,4-tetramethylethylenediamine (TMEDA), N,N-dimethylaniline and N,N-diethylaniline, pyridine, 4-dimethylaminopyridine (DMAP), 1 ,4-diazabicyclo[2,2,2]octane (DABCO) and 1 ,8-diazabicyclo[5,4,0]undeca-7-ene (DBU).

The preparation process (b) can be carried out in the presence of an acid catalyst. Examples thereof include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid and sodium hydrogen sulfite; and organic acids such as formic acid, acetic acid, trifluoroacetic acid, propionic acid, methane sulfonic acid, benzene sulfonic acid and p-toluene sulfonic acid. The preparation process (b) can be carried out in a substantially wide temperature range. The reaction temperature is generally about -20 to 150⁰C, preferably about 1O⁰C to about 120°C. While the reaction is desirably carried out under normal pressure, the reaction may also be carried out under high or reduced pressure.

In carrying out the preparation process (b), for example, the compounds of the formula (II) in an amount of 0.01 mole to 1 mole may be reacted with 1 mole of the compounds of the formula (IV) in the presence of a catalytic amount of cone, sulfuric acid without using any solvent thereby to obtain aimed compounds of the formla (IA).

The compounds of the formula (I), according to the present invention, can be used as a herbicidal efficacy-enhancing agent by adding it to a known herbicide (common names) as listed below to enhance their herbicidal efficacy. Examples of the known herbicide include: sulfonylurea herbicides such as chlorsulfuron, sulfometuron-methyl, chlorimuron ethyl, triasulfuron, amidosulfuron, oxasulfuron, tribenuron-ethyl, prosulfuron, ethametsulfuron methyl, triflusulfuron methyl, thifensulfuron-methyl, flazasulfuron, rimsulfuron, nicosulfuron, flupyrsulfuron, bensulfuron-methyl, pyrazosulfuron-ethyl, foramsulfuron, sulfosulfuron, cinosulfuron, azimsulfuron, metsulfuron-methyl, halosulfuron methyl, ethoxysulfuron, cyclosulfamuron and iodosulfuron, iodosulfuron-methyl, and salts of said sulfonylurea herbicides; carbamate herbicides such as phenmedipham, chloropropham, asulam, bentiocarb, molinate, esprocarb, pyributicarb, dimepiperate and swep; chloroacetanilide herbicides such as propachlor, metazachlor, alachlor, acetochlor, metolachlor, butachlor, pretilachlor and thenylchlor; diphenylether herbicides such as acifluorfen, oxyfluorfen, lactofen, fomesafen, aclonifen, chlomethoxynyl, bifenox and CNP; triazine herbicides such as simazine, atrazine, propazine, cyanazine, ametryn, simetryn, dimethametryn and prometrin; phenoxy acid or benzoic acid herbicides such as 2,3,6-TBA, dicamba, quinclorac, quinmerac, clopyralid, picloram, triclopyr, fluroxypyr, fenoxaprop-ethyl, fenoxaprop-P-ethyl, diclofop-methyl, fluazifop-butyl, haloxyfop-methyl, quizalofop-ethyl, cyhalofop-butyl, 2,4-PA, MCP, MCPB and phenothiol and salts of the acidic herbicides mentioned; acid amide or urea herbicides such as isoxaben, diflufenican, daiuron, linuron, fluometuron, difenoxuron, methyldymron, isoproturon, isouron, tebuthiuron, methabenzothiazuron, propanil, mefenacet, chlomeprop, naproanilide, bromobutide, daimuron, cumyluron, etobenzanid, oxadichlomefon and oxaziclomefone; organic phosphorous herbicides such as glyphosate, bialaphos, glufosinate, L-glufosinate, amiprophos methyl, anilophos, bensulide, piperophos and butamiphos and salts of the herbicides mentioned; dinitroaniline herbicides such as trifluralin and prodiamine and salts of the herbicides mentioned; phenol herbicides such as bromoxinyl, ioxynil and dinoseb and salts of the herbicides mentioned, cyclohexanedione herbicides such as alloxydim, sethoxydim, cloproxydim, clethodim, cycloxidim and tralkoxydim; imidazolinone herbicides such as imazametabenz, imazapyr, imazamethapyr, imazethapyr, imazamox and imazaquin and salts of the herbicides mentioned; bipyridium herbicides such as paraquat and diquat and salts of the herbicides mentioned; carbamoyl tetrazolinone herbicides such as fentrazamide; and other herbicides or safeners such as bentazone, tridiphane, indanofan, amitrol, carfentrazon-ethyl, sulfentrazon, fenchlorazol-ethyl, isoxaflutole, clomazone, maleic acid hydrazide, pyridate, chloridazon, norflurazon, pyrithiobac, bromacil, terbacil, metribuzin, oxaziclomefone, cinmethylin, flumiclorac pentyl, flumioxadin, fluthiacet-methyl, azafenidin, benfuresate, oxadiazon, oxadiargyl, pentoxazone, cafenstrole, pyriminobac, bispyribac (or bispyribac sodium), pyribenzoxim, pyriftalid, pyraflufen-ethyl, benzobicyclon, dithiopyr, dalapon, chlorthiamid and dichlofenil and salts of the herbicides mentioned.

Among the herbicides listed above, preferable herbicides include sulfometuron methyl, phenmedipham, asulam, oxyfluorfen, simazine, atrazine, ametryn, prometrin, triclopyr, fenoxaprop, fluazifop butyl, 2,4-PA, MCP, isoxaben, daiuron, linuron, isouron, tebuthiuron, propanil, glyphosate, bialaphos, glufosinate, amiprophos methyl, bromoxinyl, ioxynil, trifluralin, sethoxydim, imazapyr, paraquat, diquat, fentrazamide, bentazone, amitrol, carfentrazon ethyl, pyridate, bromacil, terbacil, metribuzin, flumioxadin, oxadiazon, oxadiargyl, bispiribac sodium and pyraflufen ethyl and salts of the herbicides mentioned.

The active compounds listed above are known herbicides described in "Pesticide Manual," 2000, published from British Crop Protect Council.

The common name when used generally here, also comprises the active ingredients or their agriculturally acceptable esters or salts, preferably the salts or esters commercially used, if they are existing.

The mixing ratio of the compound of the formula (I), according to the present invention, as a herbicidal efficacy-enhancing agent, with a known herbicide may vary in a wide range depending, for example, on the object of use thereof. For example, the following herbicides in the following ranges may be used per part by weight of the compound of the formula (I), according to the present invention (the amount of herbicide is preferably calculated on the basic compound if a salt or ester is used): a sulfonylurea herbicide: 0.0001 to 10 parts by weight, preferably 0.001 to 1 parts by weight; a carbamate herbicide: 0.01 to 100 parts by weight, preferably 0.1 to 10 parts by weight; a chloroacetanilide herbicide: 0.01 to 100 parts by weight, preferably 0.1 to 10 parts by weight; a diphenylether herbicide: 0.001 to 100 parts by weight, preferably 0.01 to 10 parts by weight; a triazine herbicide: 0.05 to 500 parts by weight, preferably 0.5 to 50 parts by weight; a phenoxy acid or benzoic acid herbicide: 0.01 to 100 parts by weight, preferably 0.1 to 10 parts by weight; an acid amide or urea herbicide: 0.01 to 200 parts by weight, preferably 0.1 to 20 parts by weight; an organic phosphorous herbicide: 0.05 to 500 parts by weight, preferably 0.5 to 50 parts by weight; a dinitroaniline herbicide: 0.05 to 500 parts by weight, preferably 0.5 to 50 parts by weight; a phenol herbicide: 0.05 to100 parts by weight, preferably 0.5 to 10 parts by weight; a cyclohexanedione herbicide: 0.005 to 5 parts by weight, preferably 0.05 to 5 parts by weight; an imidazolinone herbicide: 0.001 to 50 parts by weight, preferably 0.01 to 5 parts by weight; a bipyridium herbicide: 0.05 to 300 parts by weight, preferably 0.5 to 30 parts by weight; and a carbamoyl tetrazolinone herbicide: 0.01 to 30 parts by weight, preferably 0.1 to 3 parts by weight.

The following other herbicides, for example, in the following ranges may be used per part by weight of the compound of the formula (I) of the invention: bentazone: 0.05 to 100 parts by weight, preferably 0.5 to 10 parts by weight; amitrol: 0.001 to 10 parts by weight, preferably 0.01 to 1 parts by weight; carfentrazon ethyl: 0.001 to 10 parts by weight, preferably 0.01 to 0.1 parts by weight; pyridate: 0.05 to 200 parts by weight, preferably 0.5 to 20 parts by weight; bromacil: 0.01 to 100 parts by weight, preferably 0.1 to 10 parts by weight; terbacil: 0.02 to 200 parts by weight, preferably 0.2 to 20 parts by weight; metribuzin: 0.005 to 200 parts by weight, preferably 0.05 to 20 parts by weight; flumioxadin: 0.005 to 10 parts by weight, preferably 0.05 to 1 parts by weight; oxadiazon: 0.05 to 200 parts by weight, preferably 0.5 to 20 parts by weight; oxadiargyl: 0.005 to 10 parts by weight, preferably 0.05 to 1 parts by weight; bispiribac sodium: 0.001 to 10 parts by weight, preferably 0.01 to 1 parts by weight; and pyraflufen ethyl: 0.0005 to 5 parts by weight, preferably 0.005 to 0.5 parts by weight.

As shown in the biological test examples below, the compounds of the formula (I), according to the present invention, when they are mixed with a known herbicide, unexpectedly enhances the herbicidal efficacy of the mixture thereby showing excellent herbicidal activity against various weeds. Hence, the compounds of the formula (I) can be used as a herbicidal efficacy-enhancing agent.

The active compounds of the formula (IB), as herbicides having very quickly effective action, are capable of expressing a stronger synergic herbicidal action, as a mixed herbicide composition, by mixing them with other herbicides, for example, the herbicides listed above (common names).

The mixing ratio of the active compounds of the formula (IB), according to the present invention, as herbicides having very quickly effective action, with a known herbicides may vary in a wide range depending on the object of use thereof. For example, the following herbicides in the following ranges may be used per part by weight of the compounds of the formula (IB), according to the present invention: a sulfonyl urea herbicide: 0.00001 to 1 parts by weight, preferably 0.0001 to 0.1 parts by weight; a carbamate herbicide: 0.001 to 10 parts by weight, preferably 0.01 to 1 parts by weight; a chloroacetanilide herbicide: 0.001 to 10 parts by weight, preferably 0.01 to 1 parts by weight; a diphenylether herbicide: 0.0001 to 10 parts by weight, preferably 0.001 to 1 parts by weight; a triazine herbicide: 0.005 to 50 parts by weight, preferably 0.05 to 5 parts by weight; a phenoxy acid or benzoic acid herbicide: 0.001 to 10 parts by weight, preferably 0.01 to 1 parts by weight; an acid amide or urea herbicide: 0.001 to 20 parts by weight, preferably

0.01 to 2 parts by weight; an organic phosphorous herbicide: 0.005 to 50 parts by weight, preferably 0.05 to 5 parts by weight; a dinitroaniline herbicide: 0.005 to 50 parts by weight, preferably 0.05 to 5 parts by weight; a phenol herbicide: 0.005 to 10 partts by weight, preferably 0.05 to 1 parts by weight; a cyclohexanedione herbicide: 0.0005 to 0.5 parts by weight, preferably 0.05 to 0.5 parts by weight; an imidazolinone herbicide: 0.0001 to 5 parts by weight, preferably 0.001 to 0.5 parts by weight; a bipyridium herbicide: 0.005 to 30 parts by weight, preferably 0.05 to 3 parts by weight; and a carbamoyl tetrazolinone herbicide: 0.001 to 3 parts by weight, preferably 0.01 to 0.3 parts by weight.

The following other herbicides, for example, in the following ranges may be used per part by weight of the compound of the formula (IB) of the invention: bentazone: 0.005 to 10 parts by weight, preferably 0.05 to 1 parts by weight; amitrol: 0.01 to 1 parts by weight, preferably 0.1 to 1 parts by weight; carfentrazon ethyl: 0.001 to 1 parts by weight, preferably 0.005 to 0.1 parts by weight; pyridate: 0.005 to 20 parts by weight, preferably 0.05 to 2 parts by weight; bromacil: 0.001 to 10 parts by weight, preferably 0.01 to 1 parts by weight; terbacil: 0.02 to 20 parts by weight, preferably 0.02 to 2 parts by weight; metribuzin: 0.0005 to 20 parts by weight, preferably 0.005 to 2 parts by weight; flumioxadin: 0.0005 to 1 parts by weight, preferably 0.005 to 0.1 parts by weight; oxadiazon: 0.0005 to 20 parts by weight, preferably 0.05 to 2 parts by weight; oxadiargyl: 0.0005 to 1 parts by weight, preferably 0.005 to 0.1 parts by weight; bispiribac sodium: 0.0001 to 1 parts by weight, preferably 0.001 to 0.1 parts by weight; and pyraflufen ethyl: 0.00005 to 0.5 parts by weight, preferably 0.0001 to 0.05 parts by weight.

The compounds (I), (IA) and (IB) according to the invention show good herbicidal or herbicidally enhancing effects, respectively, on monocotyledonous or dicotyledonous harmful plants.

Specifically, the following examples may be mentioned of some representatives of the monocotyledonous and dicotyledonous weed flora where such effects can be found and which can be controlled by applying the compounds according to the invention.

Amongst the monocotyledonous weed species are, for example, Agrostis, Alopecurus, Apera, Avena, Brachicaria, Bromus, Dactyloctenium, Digitaria, Echinochloa, Eleocharis, Eleusine, Festuca, Fimbristylis, Ischaemum, Lolium, Monochoria, Panicum, Paspalum, Phalaris, Phleum, Poa, Sagittaria, Scirpus, Setaria, Sphenoclea and Cyperus species from the annual group and, amongst the perennial species, Agropyron, Cynodon, lmperata and Sorghum and also perennial Cyperus species.

In the case of dicotyledonous weed species, the spectrum of action extends to species such as, for example, Galium, Viola, Veronica, Lamium, Stellaria, Amaranthus, Sinapis, Ipomoea, Matricaria, Abutilon and Sida amongst the annuals and Convolvulus, Cirsium, Rumex and Artemisia in the case of the perennial weeds. Herbicidal action or herbicidally-enhancing action is also achieved in the case of dicotyledonous harmful plants such as Ambrosia, Anthemis, Carduus, Centraurea, Chenopodium, Cirsium, Convolvulus, Datura, Emex, Galeopsis, Galinsoga, Kochia, Lepidium, Lindernia, Papaver, Portlaca, Polygonum, Ranuculus, Rorippa, Rotala, Seneceio, Sesbania, Solanum, Sonchus, Taraxacum, Trifolium, Urtica and Xanthium.

Examples of harmful plants occurring under the specific cultivation conditions of rice are for example, Sagittaria, Alisma, Eleocharis, Scirpus and Cyperus.

The compounds, according to the invention, show also controlling activities against unwanted cyanobacteria, algae, moss and other algae and bryophytes in lawns, gardens, trees, shrubs, golf courses, rooftops, decks, concrete structures and the water area such as sea, river, lake, marsh, rice paddy and so on.

Preferred species of moss include for example, Antitrichia, Bryum, Barbulavinealis, Dendroalsia, Dicranoweisia, Didymodon, Homalothecium, Hoalothecium, Metaneckera, Neckerca, Peterogonium, Scleropodium, Tortula and Zygodon.

Preferred species of bryophytes include for example, Marchaentia, Conocephalum, Proellaroellii, Porella, Oscillatoria, Euglena, Chlamydomonas, Chlorella, Ulothrix, Monomastix, Tabellaria and Melosira.

The herbicidal or herbicidally-enhancing properties of the compounds (I)₁ (IA) or (IB), respectively, thus comprising in a broad sense actions against organisms capable of phytosynthesis, particularly organisms of low and high order within the plant kingdom.

The active compounds of the formula (IB), according to the present invention, and the mixed composition may be respectively formulated into a conventional preparation. Such preparations (formulations) comprise the compounds of formula (I), (IA) or (IB) respectively, and one or more formulation auxiliaries. Examples of the form of the preparation include solutions, wettable powders, emulsions, suspensions, dusts, water-dispersible granules, tablets, granules, suspended emulsion concentrates, microcapsules in a polymer substance, and jumbo formulation-package.

These preparations may be prepared by conventionally known methods per se, for example, by mixing an active compound with formulation auxiliaries such as extenders, i.e., a liquid or solid diluent or carrier, and if necessary, together with a surfactant, i.e., an emulsifier and/or a dispersant.

Examples of the liquid diluent or carrier include aromatic hydrocarbons (e.g., xylene, toluene, and alkylnaphthalene), chlorinated aromatic or chlorinated aliphatic hydrocarbons (e.g., chlorobenzenes, ethylene chlorides, and methylene chloride), aliphatic hydrocarbons (e.g., cyclohexane and etc., paraffins (e.g., mineral oil fractions)), alcohols (e.g., butanol and glycol), ethers, esters, and ketones thereof (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone), strongly polar solvents (e.g., dimethylformamide and dimethyl sulfoxide) and water. In the case where water is used as a developer, an organic solvent may be used as an auxiliary solvent.

Examples of the solid diluent or carrier include pulverized natural minerals (e.g., kaolin, clay, talc, chalk, quartz, attapulgite, montmorillonite, and kieselguhr), pulverized synthetic minerals (e.g., highly dispersed silicic acid, alumina, and silicates). Examples of the solid carrier for granules include pulverized and classified rocks (e.g., calcite, marble, pumice, meerschaum, and muscovite), synthesized inorganic and organic particles, fine particles of organic substances (e.g., sawdust, husks of coconuts, stems of Sorghum, and stalks of tobacco).

Examples of the emulsifying agent include nonionic and anionic emulsifying agents (e.g., polyoxyethylene fatty acid ester, polyoxyethylene fatty acid alcohol ether (e.g., alkyl aryl polyglycol ethers, alkylsulfonates, alkylsulfate, and arylsulfonates)), and hydrolysis products of albumin. Examples of the dispersant include lignin sulfite waste solution and methyl cellulose.

A fixing agent may be used for the preparation (dusts, granules, and emulsions) and examples thereof include carboxymethyl cellulose, natural and synthetic polymers (e.g., gum arabic, polyvinyl alcohol, and polyvinyl acetate). A coloring agent may also be used and examples thereof include inorganic pigments (e.g., iron oxide, titanium oxide, and Prussian blue); organic dyes such as alizarine dyes, azo dyes and metal phthalocyanine dyes; and a trace element such as metal salts of iron, manganese, boron, copper, cobalt, molybdenum and zinc.

The preparation may contain the compounds of the formula (I) generally in the range of 0.1 to 95% by weight, and preferably in the range of 1 to 50% by weight. Further, the preparation may contain the active compounds of the formula (IB) generally in the range of 1 to 95% by weight, and preferably in the range of 5 to 90% by weight.

The active compounds of the formula (IB) and the mixed compositions may be used directly as they are, or in the form of the preparation mentioned above, or in the form of a further diluted preparation thereof for use. When the active compounds are used in the mixed compositions they may be used in a previously formulated form as mentioned above, or may also be used by tank-mixing the respective ingredients thereof at the time of application thereof. The application method includes, for example, watering, spraying, atomizing and spraying granules.

The active compounds of the formula (IB), according to the present invention and mixed compositions may be used in any stage before or after sprouting of plants.

The amount of addition (amount of application) of the compounds of the formula (I), according to the present invention, as a herbicidal efficacy-enhancing agent, added to known herbicides, and the amount of application of the active compounds of the formula (IB), according to the present invention, as herbicides having very quickly effective action, may vary in practically available ranges. The amount of addition differs basically depending on desired properties of the efficacy. For example, the amount of application per hectare is: about 0.05 to about 1 kg, preferably about 0.05 to about 0.5 kg, as a free compound of the formula (I); about 0.02 to about 2 kg, preferably about 0.05 to about 1 kg, as a salt of the compound of the formula (I); about 0.5 to about 20 kg, preferably about 1 to about

5 kg, as a free active compound of the active compound of the formula (IB); and about 0.5 to about 50 kg, preferably about 1.5 to about 20 kg, as a salt of the active compound of the formula (IB). While the preparation process and use of the compounds, according to the present invention, are described in detail below, the present invention is by no means restricted to these examples.

Synthesis Example 1

A THF solution (20 ml) of n-octanoyl chloride (4.07 g) was added drop-wise to a THF solution (80 ml) of 1 ,3-dimethylbarbituric acid (4.10 g) and triethylamine (5.57 g) at 5°C, and the reaction mixture was stirred at room temperature for 12 hours. The reaction solution was diluted by adding cool water (100 ml), acidified using dilute hydrochloric acid, and extracted with ether (200 ml). The organic layer was washed with saline, and dried over anhydrous magnesium sulfate. The residue after removing ether by distillation was purified by silica gel column chromatography (elution solvent, ether : hexane = 1 :5) to obtain the desired 5-octanoyl-1 ,3-dimethylbarbituric acid (6.60 g). n_D ²⁰: 1.5107 Table 1 below shows examples of the barbituric acid derivatives of the formula (I) which comprise the compounds of the formula (IA) that are obtained by the same way as Synthesis Example 1 or are readily obtained in accordance with the general preparation method (a) or (b), and which comprise known compounds, as well as the compound of Synthetic Example 1. In Table 1 , "Me" denotes methyl, "Et" denotes ethyl, "Pr-n" denotes n-propyl, and "Bu-n" denotes n-butyl. Table 1

Notes

1 : Compound No. 43 is a sodium salt of Compound No. 4. 2: Compound No. 44 is a potassium salt of Compound No. 4. 3: Compound No. 45 is a sodium salt of Compound No. 7. Tested compounds

An aqueous glufosinate solution (18.5%) (active ingredient: glufosinate ammonium)

An aqueous glyphosate ammonium salt solution (41%) (active ingredient: glyphosate isopropylammonium)

The above tested compounds are commercially available.

Biological Test Example 1 : herbicidal efficacy-enhancing test Preparation of formulation of active compound Carrier: Dimethylformamide (DMF) 5 parts by weight

Emulsifier: benzyloxypolyglycol ether 1 part by weight The formulations of active compounds were obtained as emulsions by mixing 1 part by weight of the active compound with the carrier and emulsifier in the prescribed amounts. The formulations were diluted with water so as to adjust a prescribed dosage. Test method:

In a greenhouse, respective seeds of Digitaria ciliaris, Echinochloa crus-galli, Amaranthus lividus, Abutilon theophrasti and Polygonum lapathifolium were inoculated on the surface layer of pots filled with 45 cm² of field soil and covered with the soil. Ten days after the inoculation (the weeds were grown to second-leaf stages in an average), the prescribed diluted solutions of the formulations of the respective active compounds and of the mixed formulations containing the respective active compounds were uniformly sprayed over the stalk and leave portions of the plants in each test pot. The degrees of the herbicidal effect were investigated after 1 day from the spray. Evaluations of the herbicidal effect were rated as 100% in the case of complete withering and 0% in the case of no herbicidal effect.

The results of the cases in which Compound Nos. 4, 7, 43, 44 and 45 of the present invention were used, and the cases in which glufosinate or glyphosate of known herbicide was used, are set forth in Table 2, as representative examples.

Table 2: herbicidal efficacy-enhancing test (%)

Tested compound Herbicidal efficacy (%)

Dose (g a.i./ha) Dig. Echi. Ama. Abu. Poly.

Glufosinate (1000) 30 20 20 10 0

Glufosinate (500) 20 20 10 0 0

Glyphosate (2500) 10 10 0 0 0

Glyphosate (500) 0 10 0 0 0

Compound No. 4 (250) 60 45 0 0 40

Compound No. 4 (250) + Glufosinate (500) 80 65 65 50 90 Compound No. 4 (250)

+ Glyphosate (500) 80 70 50 60 90 Compound No. 4 (100) 40 35 0 0 0 Compound No. 4 (100)

+ Glufosinate (500) 65 60 30 50 60

Compound No. 4 (100)

+ Glyphosate (500) 60 50 10 40 40

Compound No.7 (250) 0 5 0 10 0

Compound No.7 (250)

+ Glufosinate (500) 65 60 65 60 70 Compound No.7 (250)

+ Glyphosate (500) 60 50 65 50 40

Compound No.43 (250) 0 0 0 0 0

Compound No.43 (250)

+ Glufosinate (500) 80 65 60 70 90

Compound No.43 (250)

+ Glyphosate (500) 70 65 45 60 70

Compound No.44 (250) 0 0 0 0 0 Compound No.44 (250)

+ Glufosinate (500) 75 65 65 65 90

Compound No.44 (250)

+ Glyphosate (500) 75 65 60 65 90

Compound No.45 (250) 0 0 0 0 0 Compound No.45 (250)

+ Glufosinate (500) 65 60 65 50 50

Compound No.45 (250)

+ Glyphosate (500) 65 50 60 60 50

a.i. = Active compound Dig. = Digitaria ciliaris Echi. = Echinochloa crus-galli Ama. = Amaranthus lividus Abu. = Abutilon theophrasti Poly. = Polygonum lapathifolium

Biological Test Example 2: herbicidal efficacy test Test method: In a greenhouse, respective seeds of Echinochloa crus-galli, Setaria viridis, Amaranthus lividus and Polygonum lapathifolium were inoculated on the surface layer of pots filled with 120 cm² of field soil and covered with the soil. Ten days after the inoculation (the weeds were grown to second-leaf stages in an average), the respective active compounds prepared in the same manner as in Test Example 1 were uniformly sprayed over the stalk and leave portions of the plants in each test pot. The degrees of the herbicidal effect were investigated after 5 days from the spray. Evaluations of the herbicidal effect were ratted as 100% in the case of complete withering and 0% in the case of no herbicidal effect. The results for Compound Nos. 1 , 3, 4, 12, 30, 34, 36 and 43 of the present invention are set forth in Table 3, as representative examples. Table 3: Herbicidal efficacy test (%)

Compound No. Herbicidal efficacy (%)

(g a.i. / ha) Echi. Seta. Ama. Poly.

1 (5000) 90 90 90 90

3 (5000) 90 90 90 90

4 (5000) 70 80 90 90 12 (5000) 80 90 90 90

30 (5000) 70 100 90 90

34 (5000) 90 90 90 90

36 (5000) 70 90 90 90

43 (5000) 70 70 90 90 a.i. = Active compound

Echi. = Echinochloa crus-galli

Seta. = Setaria viridis

Ama. = Amaranthus lividus

Poly. = Polygonum lapathifolium

Formulation Example 1 (granules)

To a mixture of the compound No. 4 of the invention (10 parts), bentonite (montmorillonite) (30 parts), talc (58 parts), and lignosulfonate (2 parts) was added water (25 parts) and the mixture was kneaded well and granulated into 10-40 mesh size by an extrusion type granulator and dried at 40 to 5O⁰C to obtain granules.

Formulation Example 2 (granules) Clay mineral particles (95 parts) having a particle size distribution in a range of 0.2 to 2 mm were put in a rotary mixer and under rotating condition, the compound No. 1 (5 parts) was sprayed together with a liquid diluent to wet the particles homogeneously and then the resulting mixture was dried at 40 to 5O⁰C and granulated to obtain granules.

Formulation Example 3 (emulsifiable concentrate )

The compound No. 4 (30 parts) of the invention, fenoxaprop-ethyl (5 parts), xylene (55 parts), polyoxyethylene alkyl phenyl ether (8 parts), and calcium alkylbenzenesulfonate (7 part) were mixed and stirred to obtain emulsions.

Formulation Example 4 (wettable powders)

The compound No. 30 (15 parts) of the invention, a mixture of white carbon (hydrated amorphous silicon oxide fine powder) and powdered clay (1 : 5) (80 parts), sodium alkylbenzenesulfonate (2 part), and sodium alkylnaphthalenesulfonate-formalin condensate (3 parts) were mixed in pulverized form to obtain wettable powders. Formulation Example 5 (water-dispersible granules)

The compound No. 43 (20 parts) of the invention, sodium ligninsulfonate (30 parts), bentonite (15 parts), and calcined diatomaceous earth powder (35 parts) were well mixed, water was added, extruded and dried using a 0.3 mm screen to obtain water-dispersible granules.

Formulation Example 6 (soluble concentrate)

The compound No. 45 (10 parts) of the invention, glufosinate (10 parts), polyoxyethylene alkyl ether (5 parts), propyleneglycol (5 parts) and water (79 parts) were mixed to prepare solutions.

Claims

1. Use of barbituric acid derivatives of the formula (I):

or salts thereof, wherein,

R¹ represents C_4--_I2 alkyl which is unsubstituted or substituted with C_1-4 alkoxy; Cs-g alkenyl or Cs-g alkynyl;

R² represents methyl or ethyl; R³ represents methyl or ethyl; and

X represents O or S as herbicidal efficacy-enhancing agents.

2. The use according to claim 1 , wherein the effective ingredient is the salt of the barbituric acid derivatives.

3. Novel barbituric acid derivatives of the formula (IA):

or a salt thereof, wherein

R^1A represents C5-12 alkyl which may be substituted with C_1-4 alkoxy; C5-9 alkenyl or C_5-9 alkynyl;

R^2A represents methyl or ethyl; R^3A represents methyl or ethyl; and

X^A represents O or S, provided that the following (i) and (ii) are excluded:

(i) X^A represents O, both R^2A and R^3A represent methyl and R^1A represents n-hexyl or n-nonyl; or (ii) X^A represents S, both R^2A and R^3A represent methyl and R^1A represents n-pentyl, n-nonyl or 3-methyl-1 -butenyl.

4. The compounds according to claim 3, wherein

R^1A represents C₅-₉ alkyl which may be substituted with methoxy or ethoxy, or C_5-9 alkenyl;

R^2A represents methyl or ethyl;

R^3A represents methyl or ethyl; and

X^A represents O or S, provided that (i) where X^A represents S, then R^1A represents C₅.₉ alkyl or C_5-9 alkenyl,

R^2A represents methyl and R^3A represents methyl; and provided that the following (ii) and (iii) are excluded:

(ii) X^A represents O, both R^2A and R^3A represent methyl and R i¹iA

represents n-hexyl or n-nonyl; or (iii) X^A represents S, both R^2A and R^3A represent methyl and R^1A represents n-pentyl, n-nonyl or 3-methyl-1-butenyl.

5. The compounds according to claim 3, wherein R^1A represents n-pentyl, n-hexyl, n-heptyl, n-octyl, 7-methyloctyl, 3-methyloctyl, 2-methylheptyl, 1-propylbutyl, 1-ethylpentyl, 1-ethylhexyl, 1-butylpentyl, 4-methoxyoctyl, 3-methoxyoctyl, 3-ethoxyoctyl, 4-methoxynonyl, 4-ethoxynonyl, 3-methoxynonyl, 4-pentenyl, 5-hexhenyl, 6-heptenyl or 7-octenyl;

R^2A represents methyl or ethyl; R^3A represents methyl or ethyl; and

X^A represents O or S, provided that:

(i) where R^2A represents methyl, R^3A represents methyl and X^A represents O, then R^1A represents n-pentyl, n-heptyl, n-octyl, 7-methyloctyl, 3-methyloctyl, 2-methylheptyl, 1-propylbutyl, 1-ethylpentyl, 1-ethylhexyl,

1 -butylpentyl, 4-methoxyoctyl, 3-methoxyoctyl, 3-ethoxyoctyl, 4-methoxynonyl, 4-ethoxynonyl, 3-methoxynonyl, 4-pentenyl, 5-hexhenyl, 6-heptenyl or 7-octenyl;

(ii) where R^2A represents methyl, R^3A represents ethyl and X^A represents O, or where R^2A represents ethyl, R^3A represents ethyl and X^A represents O, then R^1A represents n-pentyl, n-hexyl, n-heptyl, n-octyl or 5-hexenyl; and

(iii) where X^A represents S, then R^1A represents n-hexyl, n-heptyl, n-octyl or 5-hexenyl, R^2A represents methyl and R^3A represents methyl.

6. A process for the preparation of the compounds of the formula(IA)

or a salt thereof, wherein

R^1A represents C_5-12 alkyl which may be substituted with Ci_-4 alkoxy; C_5-9 alkenyl or C_5-g alkynyl;

R^2A represents methyl or ethyl; R^3A represents methyl or ethyl; and X^A represents O or S, provided that the following (i) and (ii) are excluded:

(i) X^A represents O, both R^2A and R^3A represent methyl and R^1A represents n-hexyl or n-nonyl; or

(ii) X^A represents S, both R^2A and R^3A represent methyl and R^1A represents n-pentyl, n-nonyl or 3-methyl-1 -butenyl, characterized in that

a) compounds of the formula (II):

wherein R^2A, R^3A and X^A have the same definition as aforementioned, are reacted with compounds of the formula (III):

wherein

R^1Ahas the same definition as aforementioned, and Z represents halogen or hydroxyl, preferably chlorine, bromine or hydroxyl, in the presence of inert solvents, and if appropriate, in the presence of an acid binding agent,

(b): compounds of the formula (II) are reacted with compounds of the formula (IV):

wherein R^1A has the same definition as aforementioned, in the presence of inert solvents, and if appropriate, in the presence of an acid binding agent, and if appropriate in the presence of an acid catalyst.

7. Process for enhancing herbicidal efficacy, characterized in that one or more barbituric acid derivatives of the formula(l) or their salts according to claim 1 are applied simultaneously, before or after the application of one or more herbicides onto plants part of the plants or plant seeds or to the soil where the plants grow.

8. Herbicidal efficacy-enhancing compositions comprising barbituric acid derivatives of the formula (I) as defined in claim 1 or their salts and one or more formulation auxiliaries.

9. Use of barbituric acid derivatives of the formula (IB):

or a salt thereof, wherein,

R^{1 B} represents n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl or 5-hexenyl; R^2B represents methyl or ethyl; R^3B represents methyl or ethyl; and

X^B represents O or S₁ provided that: (i) where X^B represents O, and both R^2B and R^3B represent methyl, then R^{1 B} represents n-pentyl, n-hexyl, n-heptyl, n-octyl or 5-hexenyl; (ii) where X^B represents O, R^2B represents methyl, and R^3B represents ethyl, then R^1B represents n-pentyl, n-heptyl, n-octyl or 5-hexenyl; (iii) where X^B represents O, and both R^2B and R^3B represent ethyl, then R^1B represents n-pentyl, n-hexyl, n-heptyl or 5-hexenyl; and (iv) where X^B represents S, then both R^2B and R^3B represent methyl, and R^1B represents n-butyl, n-pentyl or 5-hexenyl, as herbicides.

10. Process for combating weeds, characterized in that one or more barbituric acid derivatives of the formula (IB) according to claim 9 or their salts are allowed to act on weeds or their habitat or on weeds and their habitat.

11. Herbicidal compositions comprising one or more herbicidal barbituric acid derivatives of the formula (IB) according to claim 9 or their salts and one or more formulation auxiliaries.

12. Process for the preparation of a herbicidal composition as defined in claim 11 , characterized in that one or more barbituric acid derivatives of the formula (IB) or their salts are mixed with one or more formulation auxiliaries.