Benzoylpyrazoles and their use as herbicides

Details Benzoylpyrazoles and their use as herbicides Benzoylpyrazoles and their use as herbicides

2001-03-29

2002-07-16

Ramsuer, Robert W. (Department: 1616)

Plant protecting and regulating compositions

Plant growth regulating compositions

Organic active compound containing

C548S369400

Reexamination Certificate

active

06420317

ABSTRACT:

DESCRIPTION
Benzoylpyrazoles and their use as herbicides
The invention relates to the technical field of the herbicides, in particular of the herbicides for the selective control of broad-leaved weeds and weed grasses in crops of useful plants.
It is already known from various publications that certain benzoylpyrazoles have herbicidal properties. Thus, the German laid-open publication D-A 25 13 750 describes 1-alkyl-4-benzoyl-5-hydroxypyrazoles and 1-alkyl-4-benzoyl-5-thiopyrazoles which are preferably substituted on the phenyl ring by one or two radicals. In addition to hydrogen, radicals mentioned as being preferred for the 2-position are bromine, chlorine, iodine, methyl and nitro, for the 3-position methoxy, for the 4-position chlorine, methoxy, methylsulfonyl and nitro and for the 5-position methyl. The hydroxy or thio group of the compounds described therein is optionally substituted by various radicals, such as acyl radicals. J5 5033-45 mentions further 5-hydroxypyrazoles and 5-thiopyrazoles in which the hydroxy or thio group is in principle substituted by various radicals. U.S. Pat. No. 4,643,757 discloses, as herbicides, 1-methyl4-benzoylpyrazoles which preferably carry halogen, nitro or sulfonylmethyl in the 2-position of the phenyl ring, hydrogen, halogen or methyl in the 3-position and halogen or sulfonylmethyl in the 4-position. EP-A 0 203 428 discloses, as herbicides, 1-alkyl-4-benzoylpyrazoles which preferably carry halogen or methyl in the 2-position of the phenyl ring, hydrogen or methyl in the 3-position and halogen or sulfonylmethyl in the 4-position.
However, the compounds known from these publications frequently have an insufficient herbicidal activity and/or insufficient crop plant compatibility. Accordingly, it is an object of the present invention to provide herbicidally active compounds having improved herbicidal properties and improved crop plant compatibility than the compounds known from the prior art.
It has now been found that certain 4-benzoylpyrazoles which are substituted at specific positions by selected radicals are particularly suitable for use as herbicides. Accordingly, the present invention provides compounds of the formula (I) or salts thereof
in which
R
1
is methyl or ethyl;
R
2
is trifluoromethyl;
R
3
is hydrogen, methyl or ethyl;
R
4
is methyl, ethyl or n-propyl;
R
5
is hydrogen, (C
1
-C
6
)-alkylcarbonylmethyl, (C
1
-C
4
)-alkylsulfonyl, phenylsulfonyl, benzyl, benzoylmethyl, (C
1
-C
3
)-alkylsulfonyl which is mono- or polysubstituted by halogen, phenylsulfonyl which is monosubstituted by methyl or halogen, benzyl which is substituted by halogen, nitro or methoxy or benzoylmethyl which is mono- or polysubstituted by halogen, nitro, methyl or methoxy and
n is 0, 1, or 2.
If R
5
is hydrogen the compounds of the formula (I) according to the invention can, depending on external conditions such as solvent and pH, be present in different tautomeric structures:
Depending on the type of substituents, the compounds of the formula (I) may contain an acidic proton which can be removed by reaction with a base. Suitable bases are, for example, hydrides, hydroxides and carbonates of lithium, sodium, potassium, magnesium and calcium, and also ammonia and organic amines, such as triethylamine and pyridine. Such salts are likewise provided by the invention.
In formula (I) and all other formulae hereinbelow, alkyl radicals having more than two carbon atoms can be straight-chain or branched. Alkyl radicals are, for example, methyl, ethyl, n- or isopropyl, n-, iso, t- or 2-butyl, pentyls, hexyls, such as n-hexyl, isohexyl and 1,3-dimethylbutyl. Halogen is fluorine, chlorine, bromine or iodine. Tosyl is 4-methylphenylsulfonyl.
If a group is polysubstituted by radicals, this is to be understood as meaning that this group is substituted by one or more identical or different of the radicals mentioned.
Depending on the type and the attachment of the substituents, the compounds of the formula (I) can be present as stereoisomers. If, for example, one or more asymmetrically substituted carbon atoms are present, enantiomers and diastereomers may occur. Stereoisomers can be obtained from the mixtures obtained in the preparation by customary separation methods, for example by chromatographic separation processes. It is also possible to prepare stereoisomers by using stereoselective reactions, employing optically active starting materials and/or auxiliaries. The invention also relates to all stereoisomers and mixtures thereof which are embraced by the formula (I) but not defined specifically.
Of particular interest are compounds of the formula (I), in which n is 2.
Preference is given to compounds of the formula (I), in which
R
1
is methyl and
R
3
is hydrogen or methyl.
Preference is also given to compounds of the formula (I), in which
R
4
is methyl or ethyl.
Particular preference is given to compounds of the formula (I), in which
R
5
is methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, phenylsulfonyl, 4-methylphenylsulfonyl, benzyl, benzoylmethyl, nitrobenzoylmethyl or 4-fluorobenzoylmethyl.
Particular preference is likewise given to compounds of the formula (I), in which
R
5
is hydrogen.
Very particular preference is given to compounds of the formula (I), in which
R
3
is methyl.
In all of the formulae mentioned hereinbelow, the substituents and symbols have the same meaning as described under formula (I), unless defined otherwise. Compounds according to the invention in which R
5
is hydrogen can be prepared, for example, by the process shown in Scheme 1 and known from DE-A 25 13 750 by base-catalyzed reaction of a benzoyl halide with a pyrazolone, or according to the process shown in Scheme 2 and known, for example, from EP-A 0 186 117 by base-catalyzed reaction of a benzoyl halide with a pyrazolone and subsequent rearrangement.
Compounds according to the invention in which R
5
is different from hydrogen are, according to Scheme 3, expediently prepared from the compounds obtainable according to Scheme 1 or 2 by base-catalyzed reaction with a suitable acylating agent R
5
—X in which X is a leaving group such as halogen. Such methods are known, for example, from DE-A 25 13 750.
The starting materials used in the schemes above are either commercially available or can be prepared by methods known per se. Thus, the pyrazolones of the formula (II) can be prepared, for example, by the methods described in EP-A 0 240 001 and J. Prakt. Chem. 315, 382, (1973), and the benzoyl chlorides of the formula (III) can be prepared by the process as described in EP-A 0 527 036.
The compounds of the formula (I) according to the invention have an outstanding herbicidal activity against a broad spectrum of economically important monocotyledonous and dicotyledonous harmful plants. The active compounds also act efficiently on perennial weeds which produce shoots from rhizomes, root stocks or other perennial organs and which are difficult to control. In this context, it is generally immaterial whether the substances are applied pre-sowing, pre-emergence or post-emergence. Specifically, examples may be mentioned of some representatives of the monocotyledonous and dicotyledonous weed flora which can be controlled by the compounds according to the invention, without these being a restriction to certain species. Examples of weed species on which the active compounds act efficiently are, from amongst the monocotyledons, Avena, Lolium, Alopecurus, Phalaris, Echinochloa, Digitaria, Setaria and also Cyperus species from the annual sector and from amongst the perennial species Agropyron, Cynodon, Imperata and Sorghum, and also perennial Cyperus species.
In the case of the dicotyledonous weed species, the spectrum of action extends to species such as, for example, Galium, Viola, Veronica, Lamium, Stellaria, Amaranthus, Sinapis, lpomoea, Sida, Matricaria and Abutilon from amongst the annuals, and Convolvulus, Cirsium, Rumex and Artemisia in the case of the perennial weeds. The active compounds according to the invention also effect outstanding control of harmful plants which occur

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