DE4310091A1 - Novel 1-(4-bromo-3-pyrazolyl)pyrazoles, their preparation, intermediates for their preparation, and their use as herbicides - Google Patents

Abstract

There are described novel 1-(4-bromo-3-pyrazolyl)pyrazoles of the general formula I <IMAGE> in which R<1>, R<2> and R<3> have the meanings given in the description, processes for their preparation, intermediates for their preparation, and their use as herbicides.

Description

The invention relates to new 1- (4-bromo-3-pyrazolyl) pyrazoles, their preparation and Intermediates for their preparation and their use as herbicidal compositions Effect.

It is already known that 1-phenylpyrazoles have herbicidal properties (EP 154115).

However, the herbicidal activity of the known compounds is frequently inadequate, or selectivity problems occur with a corresponding herbicide effect main agricultural crops.

The object of the present invention is to provide new pyrazolylpyrazoles, which do not have these disadvantages and which in their biological properties are the same as before known connections are superior.

It has now been found that 1- (4-bromo-3-pyrazolyl) pyrazoles of the general formula I

in which R ^{1 is} C ₁ -C ₄ alkyl,
R ² difluoromethoxy or
R ¹ and R ² together form the group - (CH ₂ ) ₄ - and
R ³ nitro or cyano,
mean have better herbicidal properties compared to the known compounds.

The term "alkyl" means that the carbon chain is branched or unbranched can be.

The invention further relates to the intermediates of the general formula II

in which R ¹ and R ^{2 have} the meanings given in the general formula I, the intermediates of the general formula IV

in which R ¹ and R ^{2 have} the meanings given in the general formula I and the intermediates of the general formula V

in which R ¹ , R ² and R ^{3 have} the meanings given in the general formula I.

The intermediates of the general formulas II, IV and V are preferably suitable for Preparation of compounds of general formula I.  

The compounds of the general formula I according to the invention in which R ^{3 represents} cyano can be prepared by:
A) a compound of general formula II

in which R ¹ and R ^{2 have} the meanings given under the general formula I, with compounds of the general formula III

in which Y represents C ₁ -C ₆ alkoxy, hydroxy or halogen, or if R ^{3 represents} nitro
B) a compound of the general formula IV

in which R ¹ and R ^{2 have} the meanings given in the general formula I, nitrided by known methods, or
C) a compound of the general formula V

in which R ¹ , R ² and R ^{3 have} the meanings given in general formula I, are reacted with a brominating agent.

The reaction according to process variant A) is carried out in a suitable solvent, expediently carried out at temperatures between 0 ° and 150 ° C. When Solvents are all organic which are inert under the reaction conditions Solvents such as B. toluene, xylene, dioxane, tetrahydrofuran or ethanol.

The nitration according to process variant B) can expediently be carried out with Perform nitric acid in acetic anhydride according to known methods. The Reaction temperatures range from -10 to 140 ° C.

The reaction according to process variant C) is preferably carried out in one Solvent, at temperatures from -20 ° to the boiling point of the solvent carried out.

All organic solvents which are inert under the reaction conditions are suitable as solvents Solvents such as B. acetonitrile, methylene chloride, chloroform, carbon tetrachloride or acetic acid.

As brominating agent according to process variant C) z. B. N-bromosuccinimide or bromine can be used.

The compounds according to the invention are worked up in the customary manner and Wise. Purification is carried out by crystallization or column chromatography.

The compounds according to the invention are generally colorless or slightly yellow colored crystalline or viscous substances, some of which are readily soluble in chlorinated Hydrocarbons such as methylene chloride or chloroform, ethers such as for example diethyl ether or tetrahydrofuran, alcohols such as methanol  or ethanol, ketones such as acetone or butanone, amides such as Dimethylformamide, or also sulfoxides, such as dimethyl sulfoxide.

The compounds of general formula II required as intermediates

in which R ¹ and R ^{2 have} the meanings given in general formula I, can be prepared analogously to processes known per se (for example: JP 62158260) from the compounds of general formula VI

in which R ¹ and R ^{2 have} the meanings given in the general formula I, produce.

The compounds of general formula VI in which R ¹ and R ^{2 have} the meanings given in general formula I can be prepared by using compounds of general formula VII

in which R ¹ and R ^{2 have} the meanings given in the general formula I, with a brominating agent. The compounds of the general formula VII, in which R ¹ and R ² together denote the group - (CH ₂ ) ₄ -, can be prepared by using a compound of the general formula VIII

in the Q for an amino protecting group Q ₁ , Q ₂ or Q ₃

stands where one
in the case of Q ₁ with hydroxylamine, as described in J. Org. Chem. 49, 1224-27 (1984), and in the case of Q ₂ and Q ₃ with hydrazine, as in Org. Synthesis, Coll. Vol. 3, 148 (1955).

The compounds of the general formulas VI and VII, in which R ^{1 is} C ₁ -C ₄ -alkyl and R ^{2 is} difluoromethoxy, can be prepared by using compounds of the general formula XII or XIII

reacted with a base and bromine according to methods known from the literature. (J. March, Advanced Organic Chemistry, 1985, p. 983).

The compounds of general formula VIII can be prepared by Compounds of the general formula IX

in the Q for the amino protecting group described under the general formula VIII is cyclized according to the Mitsunobu variant (Synthesis, p. 1, 1981).

The compounds of general formula IX can be prepared by Compounds of the general formula X

with hexane-2,5-dione, phthalic anhydride or tetrahydrophthalic anhydride in analogy implemented methods known from the literature. (Bull. Chem. Soc. Jp., 44, 2856-8, 1971, EP 305 826).

The compounds of general formula X can be prepared by Compounds of the general formula XI

reacted with hydrazine.  

The compounds of general formula XII and XIII can be prepared by Compounds of the general formulas XIV and XV

in which R ^{1 is} C ₁ -C ₄ alkyl, R ^{2 is} difluoromethoxy and R ^{4 is} C ₁ -C ₄ , can react with ammonia.

The compounds of general formula XV can be prepared by the Reacts compounds of general formula XIV with a brominating agent.

The compounds of general formula XIV can be prepared by Compounds of the general formula XVI

in which R ^{1 has} the meaning given in the general formula I and R ^{4 is} C ₁ -C ₄ -alkyl, with a compound of the general formula XVII

R ² -U XVII,

in which R ^{2 has} the meaning given under the general formula I and U for an escape group, such as. B. is a bromine or chlorine, can react with the addition of a base.

The compounds of general formula IV can be prepared by Compounds of the general formula XVIII

in which R ¹ and R ^{2 have} the meanings given in the general formula I, decarboxylated.

The compounds of general formula XVIII can be prepared by Compounds of the general formula XIX

in which R ¹ and R ² , which have the meaning given under the general formula I and R ^{4 is} C ₁ -C ₄ -alkyl, are saponified.

The compounds of the general formula XIX can be prepared by compounds of the general formula II in which R ¹ and R ^{2 have} the meanings given in the general formula I with compounds of the general formula XX

in which R ^{4 is} C ₁ -C ₄ alkyl and Y is C ₁ EC ₆ alkoxy, hydroxy or halogen.

The compounds of the general formula V can be analogously described in the above Prepare the process by replacing the compounds of general formulas II and IV the corresponding compounds of the general formulas XXI and XXII

starts.

Let the reactions for the preparation of the intermediates of general formula II perform themselves according to known methods. The hydrazine production will Conveniently carried out so that the amines with sodium nitrite in one Mineral acid, preferably hydrochloric acid, diazotized and then reduced. When The reducing agent is preferably tin chloride. The bromination subsides Carry out process variant C). As a solvent for the preparation of the compounds of the general formulas I, IV and V come the solvents mentioned above Commitment.

As bases z. B. alkali and alkaline earth metal hydroxides, sodium methoxide, Alkali hydrides, alkali and alkaline earth carbonates, tertiary aliphatic and aromatic Amines, such as triethylamine and pyridine, and heterocyclic bases can be used. The Reactions are carried out at a temperature between -30 and 100 ° C.

The compounds according to the invention show a good herbicidal activity broad-leaved weeds and grasses. A selective use of the inventive Active substances are possible in different crops, for example in rapeseed, beets, Soybeans, cotton, rice, corn, barley, wheat and other cereals. Here are individual active substances as selective herbicides in beets, cotton, soybeans, maize and Cereals particularly suitable. Likewise, the compounds for weed control in Permanent crops, such as forest, ornamental wood, fruit, wine, citrus, nut, Banana, coffee, tea, gum, oil palm, cocoa, berry fruit and hop plants be used.

The compounds of the present invention can include, for example, the following Plant genera are used:  

Dicotyledon weeds of the genera

Sinapis, Lepidium, Galium, Stellaria, Matricaria, Anthemis, Galinsoga, Chenopodium, Brassica, Urtica, Senecio, Amaranthus, Portulaca, Xanthium, Convolvulus, Ipomoea, Polygonum, Sesbania, Ambrosia, Cirsium, Sonchus, Solanum, Lamium, Veronica, Abutilon, Datura, Viola, Galeopsis, Papaver, Centaurea and Chrysanthemum.

Monocotyledonous weeds of the genera

Avena, Alopecurus, Echinochloa, Setaria, Panicum, Digitaria, Poa, Eleusine, Brachiaria, Lolium, Bromus, Cyperus, Elymus, Sagittaria, Monochoria, Fimbristylis, Eleocharis, Ischaemum and Apera.

Depending on the type of application, the application rates fluctuate in pre- and post-emergence Limits between 0.001 to 5 kg / ha.

The active compounds according to the invention can also be used as defoliant, desiccant and Herbicides are used.

The compounds of the invention can either be used alone or in a mixture with one another or with other active ingredients. If necessary, others can Plant protection or pesticide depending on the intended purpose be added. If it is intended to broaden the spectrum of activity, other herbicides can also be added. For example, are suitable as herbicides effective mixture partners are those active ingredients that are described in Weed Abstracts, Vol. 1, 1992 under the title "List of common names and abbreviations employed for currently used herbicides and plant growth regulators ".

A promotion of the intensity and speed of action can, for example through additives that increase the effectiveness, such as organic solvents, wetting agents and oils, be achieved. Such additives may therefore reduce the Active ingredient dosage too.

The active compounds according to the invention or mixtures thereof are expedient in the form of preparations such as powders, scattering agents, granules, solutions, emulsions or Suspensions, with the addition of liquid and / or solid carriers respectively Diluents and optionally adhesives, wetting agents, emulsifiers and / or Dispersing aids applied.  

Suitable liquid carriers are, for example, aliphatic and aromatic Hydrocarbons, such as benzene, toluene, xylene, cyclohexanone, isophorone, Dimethyl sulfoxide, dimethylformamide, mineral oil fractions and vegetable oils.

Minerals are suitable as solid carriers, for example bentonite, silica gel, talc, Kaolin, attapulgite, limestone and vegetable products, for example flours.

Examples of surface-active substances include calcium lignin sulfonate, Polyethylene alkylphenyl ether, naphthalenesulfonic acids and their salts, phenolsulfonic acids and their salts, formaldehyde condensates, fatty alcohol sulfates and substituted benzene sulfonic acids and their salts.

The proportion of the active ingredient (s) in the different preparations can vary widely. For example, the agents contain about 10 to 90 Weight percent active ingredient, about 90 to 10 weight percent liquid or solid carriers substances and, if necessary, up to 20 percent by weight of surface-active substances.

The agents can be applied in the customary manner, for example using water as Carrier in spray liquor quantities from about 100 to 1000 liters / ha. An application of funds in the so-called low-volume and ultra-low-volume process is possible as well their application in the form of so-called microgranules.

The preparation of these preparations can be carried out in a manner known per se Example can be carried out by grinding or mixing processes. If desired can preparations of the individual components only shortly before their use be mixed, as is the case, for example, in the so-called tank mix process is carried out.  

For example, the following are used to prepare the various preparations Components used:

A) wettable powder

20 percent by weight of active ingredient
35% by weight of bleaching earth
8 weight percent calcium salt of lignin sulfonic acid
2 percent by weight sodium salt of N-methyl-N-oleyl-taurine
35 weight percent silica

B) paste

45 percent by weight of active ingredient
5% by weight sodium aluminum silicate
15 percent by weight cetyl polyglycol ether with 8 moles of ethylene oxide
2% by weight spindle oil
10% by weight polyethylene glycol
23 weight percent water

C) Emulsion concentrate

20 percent by weight of active ingredient
75 weight percent isophorone
5 percent by weight of a mixture based on the sodium salt of N-methyl-N-oleyl-taurine and the calcium salt of lignin sulfonic acid.

The following examples illustrate the preparation of the compounds according to the invention:

example 1 5-amino-1- (3-bromo-4,5,6,7-tetrahydropyrazolo- [1,5-a] pyridin-2-yl) pyrazole carboxylic acid nitrile

0.5 g (2.2 mmol) of 5-amino-1- (4,5,6,7-tetrahydropyrazolo- [1,5-a] -pyridin-2-yl) -4-pyrazolecarbonitrile are dissolved in 3 ml of glacial acetic acid suspended and 0.35 g (2.2 mmol) of bromine in 1 ml of glacial acetic acid were added dropwise at room temperature. After stirring for 1 hour, the reaction mixture is poured into saturated sodium bicarbonate solution and extracted 3 times with methylene chloride. The organic phase is dried over magnesium sulfate, suction filtered over silica gel and concentrated.
Yield: 0.46 g = 68% of theory
Mp .: 180-182 ° C

Preparation of the starting compounds

5-amino-1- (4,5,6,7-tetrahydropyrazolo- [1,5-a] pyridin-2-yl) -4-pyrazo-carboxylic acid and 2- Hydrazino-4,5,6,7-tetrahydropyrazolo [1,5 -] - pyridine can be prepared according to known Manufacture process:

1. 2-Amino-4,5,6,7-tetrahydropyrazolo- [1,5-a] pyridine

8.19 g (146 mmol) of potassium hydroxide, dissolved in 122 ml of water and 122 ml of ethanol, are added to 19.19 g (292 mmol) of hydroxylamine hypochloride in 200 ml of ethanol. The mixture is stirred for 15 minutes, 12.5 g (58 mmol) of 2- (2,5-dimethyl-1-pyrrolyl) -4,5,6-7-tetrahydropyrazolo [1,5-a] pyridine are added and the mixture is stirred for 30 hours Reflux heated. After the ethanol has been stripped off, acetic acid ester is added, the solid is filtered off, the aqueous phase is saturated with sodium chloride and extracted with ethyl acetate. The organic phase is washed with saturated sodium chloride solution, dried over sodium sulfate and concentrated. The crude product is purified by column chromatography on silica gel (ethyl acetate / methanol).
Yield: 6.12 g = 77% of theory
¹ H NMR (CDCl ₃ , 300 MHz): δ = 1.75-1.85 (m, 2H), 1.95-2.05 (m, 2H) 2.68 (t, 2H, J = 7, 5 Hz), 3.5 (s (broad), 2H), 3.92 (t, 2H4 = 7.5 Hz, 5.33 (s, 1H)

2. 2- (2,5-Dimethyl-1-pyrrolyl) -4,5,6-7-tetrahydropyrazolo (1,5a) pyridine

To 19.7 g (84 mmol) 3 (5) - (4-hydroxybutyl) -5 (3) - (2,5-dimethyl-1-pyrrolyl) pyrazole and 22.1 g (84 mmol) triphenylphosphine in 300 16 g (92 mmol) of diethyl azodicarboxylate are added dropwise with ice cooling to ml of tetrahydrofuran. It is stirred for 4 hours at room temperature. The reaction mixture is then concentrated and purified by column chromatography on silica gel (hexane / ethyl acetate).
Yield: 14.27 g = 79% of theory
n: 1.5630

3. 3 (5) - (4-hydroxybutyl) -5 (3) - (2,5-dimethyl-1-pyrrolyl) pyrazole

A mixture of 18 g (116 mmol) 3 (5) -amino-5 (3) - (hydroxybutyl) pyrazole, 14.6 g (128 mmol) 2,5-hexanedione and 3.2 ml glacial acetic acid in 100 ml toluene is refluxed for 8 hours on the water separator. The resulting precipitate is filtered off, washed with toluene and dried.
Yield: 19.7 g = 72% of theory
Mp .: 147-148 ° C

4. 3 (5) -amino- (3- (hydroxybutyl) pyrazole

4.8 ml of hydrazine monohydrate are added to a solution of 12.3 g (0.1 mol) of tetrahydro-2H-pyran-2-ylidene acetointril in 100 ml of toluene at room temperature and the mixture is heated under reflux for 5 hours. A light yellow oil separates out. The reaction mixture is concentrated and purified by column chromatography on silica gel (ethyl acetate / methanol).
Yield: 11 g = 71% of theory

Example 2 5-amino-4-nitro-1- (4-bromo-5-difluoromethoxy-1-methyl-3-pyrazolyl) pyrazole

8.3 g (0.052 mol) of bromine are added to 13 g (0.047 mol) of 5-amino-4-nitro-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) pyrazole, dissolved in 260 ml of glacial acetic acid Dropped in room temperature and stirred for 30 minutes. The reaction mixture is concentrated and the residue is taken up in ethyl acetate and extracted with 5% sodium hydrocarbonate solution. The phases are separated and the organic phase is dried over magnesium sulfate. The mixture is then concentrated and the residue is purified by column chromatography (SiO ₂ / hexane / ethyl acetate 3: 1).
Yield: 8.3 g = 49.6% of theory
Mp: 148 ° C

Preparation of the starting compounds 1. 5-Amino-4-nitro-1- (5-difiuormethoxy-1-methyl-3-pyrazolyl) pyrazole

15 g (0.065 mol) of 5-amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) pyrazole are dissolved in 60 ml of glacial acetic acid and 7.35 g (0.072 mol) of acetic anhydride are added. After 3 hours of stirring at room temperature, the reaction mixture is cooled to 10 ° C. 4.95 g (0.078 mol) of fuming nitric acid are then added dropwise after the reaction mixture has been mixed with 8.0 g (0.078 mol) of acetic anhydride. After stirring at room temperature for 18 hours, the reaction mixture is poured into 500 ml of ice water. It is extracted 3 times with ethyl acetate, the organic phases are washed with water and concentrated. The residue is mixed with 80 ml of ethanol and 40 ml of concentrated hydrochloric acid. After 8 hours under reflux, the ethanol is drawn off and the residue is extracted with ethyl acetate. The combined ethyl acetate phases are dried with saturated sodium bicarbonate solution and then concentrated. The residue is recrystallized from diisopropyl ether and ethyl acetate.
Yield: 10 g = 56% of theory
Mp: 140 ° C

2. 5-Amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) pyrazole

16.5 (0.06 mol) 5-amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) -4-pyrazolecarboxylic acid are heated to 210 ° C. for 5 minutes and then cooled. The solidified melt is recrystallized from diisopropyl ether.
Yield: 12.6 g = 92% of theory
Mp .: 106-107 ° C

3. 5-Amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) -4-pyrazole-carboxylic acid

18.9 g (0.06 mol) of 5-amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) -4-pyrazolyl carboxylic acid ethyl ester are dissolved in 150 ml of 50% ethanol and with 15 ml of 45% strength Sodium hydroxide solution added. The mixture is heated to 80 ° C. for 2 hours, then the ethanol is distilled off, the residue is mixed with ice water and acidified with concentrated hydrochloric acid. The precipitate is filtered off, washed with water and dried in vacuo at 75 ° C.
Yield: 16.7 g = 97% of theory
Mp .: 173 ° C (dec.)

4. 5-Amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) -4-pyrazole-carboxylic acid, ethyl ester

19 g (0.1 mol) of 5-difluoromethoxy-3-hydrazino-1-methylpyrazole are dissolved in 100 ml of ethanol. Then 18.05 g (0.1 mol) of ethyl ethoxymethylene cyanoacetate are added and the mixture is heated to boiling for 1.5 hours. After cooling, the precipitated product is filtered off, washed with a little ethanol and dried.
Yield: 18.95 g = 59% of theory
Mp: 168-169 ° C

5. 5-difluoromethoxy-3-hydrazino-1-methylpyrazole

39.8 g (0.25 mol) of 3-amino-5-difluoromethoxy-1-methylpyrazole are dissolved in 225 ml of water and 450 ml of concentrated hydrochloric acid. 18.55 g (0.27 mol) of sodium nitrite in 80 ml of water are added dropwise at -10.degree. After stirring for 1 hour at -10 ° C., 137.6 g of tin (II) chloride, dissolved in 180 ml of concentrated hydrochloric acid, are added dropwise at this temperature. After stirring for a further hour at -10 ° C., 805 ml of 32% sodium hydroxide solution are added dropwise at this temperature. The reaction mixture is shaken 8 times with ethyl acetate, the combined organic phases are washed with saturated sodium chloride solution, dried over magnesium sulfate and concentrated.
Yield: 42.24 g = 97.2% of theory

Example 3 5-Amino-1- (4-bromo-5-difluoromethoxy-1-methyl-3-pyrazolyl) -4-pyrazolca-r-boronitrile

5.0 g (20 mmol) of 5-amino-1- (5-difluoromethoxy-1-methyl-3-pyrazolyl) -4-pyrazolecarbonitrile are dissolved in 80 ml of glacial acetic acid. 1.2 ml (23 mmol) of bromine are added dropwise at room temperature. After stirring for 15 minutes, the mixture is concentrated and stirred with diisopropyl ether / propanol. The solid is filtered off and dried.
Yield: 5.7 g = 87% of theory
Mp .: 160 ° C

Example 4 5-Amino-1- (3-bromo-4,5,6,7-tetrahydropyrazolo- [1,5-a] pyridin-2-yl) -4-nitro-pyrazole

3.6 g (12.7 mmol) of 5-amino-1- (3-bromo-4,5,6,7-tetrahydropyrazolo- [1,5-a] -pyridin-2-yl) pyrazole are dissolved in 15 ml Suspend glacial acetic acid and add 1.23 ml (13.0 mmol) of acetic anhydride. The mixture is stirred for 5 hours at room temperature. Thereafter, 1.5 ml (15.9 mmol) of acetic anhydride are added and 0.66 ml (15.5 mmol) of fuming nitric acid are then added dropwise while cooling in an ice bath. After stirring for 12 hours at room temperature, the mixture is concentrated. The residue is dissolved in 30 ml of ethanol and mixed with 11.2 ml of concentrated hydrochloric acid. After heating for 3 hours under reflux, the mixture is concentrated and the residue is taken up in water and ethyl acetate. It is made basic with 2 N sodium hydroxide solution and the organic phase is separated off. The aqueous phase is extracted twice with ethyl acetate. The combined organic phases are washed once with water and once with saturated sodium chloride solution. The organic phase is dried and concentrated. It is recrystallized from ethyl acetate.
Yield: 2.04 g = 49% of theory
Mp .: 190-192 ° C

The following examples explain the possible uses of the invention Links:

Example of use A

The plant species listed were grown in the greenhouse after emergence with the treated compound in an application rate of 0.03 kg of active ingredient / ha. For this purpose the compound was used as an emulsion with 500 liters of water / ha evenly sprayed over the plants. Here shows two weeks after treatment the compound of the invention has an excellent weed action. The Comparative agents did not show the same effectiveness.

In the following table mean:

0 = no damage ALOMY = Alopecurus myosuroides
1 = 1-24% damage SETVI = Setaria viridis
2 = 25-74% damage PANSS = Panicum sp.
3 = 75-89% damage ABUTH = Abutilon theophrasti
4 = 90-100% damage GALAP = Galium aparine
IPOSS = Ipomoea purpurea
MATCH = Matricaria chamomilla
POLSS = Polygonum sp.
SEBEX = Sesbania exaltata
SOLSS = Solanum sp.
VERPE = Veronica persica
VIOSS = Viola sp.

Claims (8)

1. 1- (4-bromo-3-pyrazolyl) pyrazoles of the general formula I in the
R ¹ C ₁ -C ₄ alkyl,
R ² difluoromethoxy or
R ¹ and R ² together form the group - (CH ₂ ) ₄ - and
R ³ nitro or cyano,
mean. 2. Compounds of the general formula II in which R ¹ and R ^{2 have} the meanings given in the general formula I, as intermediates for the preparation of compounds of the general formula I. 3. Compounds of the general formula IV in which R ¹ and R ^{2 have} the meanings given in the general formula I, as intermediates for the preparation of compounds of the general formula I. 4. Compounds of the general formula V in which R ¹ , R ² and R ^{3 have} the meanings given in the general formula I, as intermediates for the preparation of compounds of the general formula I. 5. A process for the preparation of compounds of general formula I, characterized in that

• A) a compound of general formula II in which R ¹ and R ^{2 have} the meanings given under the general formula I, with compounds of the general formula III in which Y represents C ₁ -C ₆ alkoxy, hydroxy or halogen, or if R ^{3 represents} nitro
• B) a compound of the general formula IV in which R ¹ and R ^{2 have} the meanings given in the general formula I, nitrided by known methods, or
• C) a compound of the general formula V in which R ¹ , R ² and R ^{3 have} the meanings given in general formula I, are reacted with a brominating agent.

6. Agents with herbicidal activity, characterized by a content of at least one A compound according to claim 1.   7. Agents with herbicidal activity according to claim 6, in a mixture with carrier and / or Auxiliary materials. 8. Use of compounds according to claim 1 for combating monocotyledons and dicotyledonous weed species in main agricultural crops.