DE2330453A1 - Thidiazolyl ureidoacetaldehyde acetals - as herbicies - Google Patents

Abstract

Cpds (I), their ammonium substd ammonium Na, K, Li, Ca, Mg, Mn, Cr, Fe, Ni, Cu, Zn or Al salts sol in water (where R1 and R2 are 1-3C alkyl and X is isoPr, t-bu or CF3) are pref. prepd by reacting 2-isocyanato-5-X-thiadiazole dimer with (R1O)(R2O)CH-CH2NHMe.

Description

VELSICOL CHEMICAL CORPORATION

341 East Ohio Street
Chicago, 111. 60611 / V.St.A.

Our reference: V 688

Dialkyl acetals from heterocyclic! Ureidoacetaldehyde and their water-soluble salts

The invention relates to new substances and in particular to new chemical compounds of the formula

H
r'-OCOR ² NN

t If Il

H ~~ 0 ~~ N ~~ C ~~ N C C X

«I Il I \ /

H CH ₃ 0 HS (I)

1 2
wherein R and R each represent an alkyl group with up to 3 carbon atoms and X is isopropyl, tert-butyl or trifluoromethyl; the invention also relates to the water-soluble salts of these compounds.

The compounds according to the invention have a surprising one Effective as herbicide and act against a wide variety of weeds without valuable plants, e.g. wheat or rice.

Dr Ha / Mk

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The compounds according to the invention can easily be prepared from a dimeric isocyanate of the formula

Nile

= Ν · -C

N If

c-

(II)

wherein X has the meaning described above, by reaction with a dialkyl acetal of the formula

HI

IH ₂ C-

O-R ²

N-H

CH ₃

(III)

1 2

wherein R and R are each alkyl groups mean with up to 3 carbon atoms. This reaction can be achieved by heating a mixture of one molar Proportion of the dimeric isocyanate of the formula II with about two molar proportions of the acetal of formula III in an inert organic reaction medium, e.g. benzene Reflux temperature of the mixture are effected. Heating to reflux can take about 2 to about 30 minutes persist so that the reaction is certain to have ended. After this time, the desired product can be made obtained after evaporation of the reaction medium and used as such or standard methods, e.g. recrystallization and the like, are further purified.

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The compounds of the formula II can be prepared by reacting an aminothiadiazole of the formula

N N

Il H

H ₂ NC CX

^ S ' (IV)

wherein X has the meaning described above, can be obtained with phosgene. This reaction can turn into one inert organic reaction medium, e.g. ethyl acetate, by adding a solution of phosgene in ethyl acetate carried out a slurry or solution of the aminothiadiazole of the formula IV with stirring at room temperature will. Stirring can be continued for up to about 24 hours to ensure complete reaction is. After this time, the reaction mixture can not be used to remove nitrogen gas converted phosgene are flushed through. The desired product can then, if it forms a precipitate, can be filtered off or if it remains in solution it can be obtained after evaporation of the organic solvent. The product can then be used as such or further cleaned if necessary.

It has surprisingly been found that the compounds according to the invention can form water-soluble salts. Such salts have the following structural formula

H
I.
_R i__ ₀ - _c - ₀ - _R2 ji

I 11 II

H ₃ 0 ^N S ^X

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1 2

wherein R and R each represent alkyl groups of up to 3 carbon atoms; X consists of isopropyl, tert-butyl or trifluoromethyl; M is ammonia, a primary amine, a secondary amine, a tertiary amine, sodium, potassium, lithium, calcium, magnesium, chromium, manganese, iron, nickel, Copper, zinc or aluminum; and η is an integer from 1 to 3 corresponding to the valence of M. Thus, η is an integer equal to the valence of M if M is a metal or it corresponds to the acid equivalent of M when M is an unsubstituted or substituted ammonium radical.

The water solubility of these salts makes them particularly suitable for incorporation into agricultural compositions.

In a preferred embodiment of the invention, M consists of ammonia, methylamine, dimethylamine, trimethylamine, Aethylamine, Diaethylamine, Triaethylamine, Sodium, Potassium, Lithium and Zinc.

The water-soluble salts according to the invention can easily be obtained from the compounds of formula I by reaction with ammonia, a suitable amine, or a water-soluble salt or hydroxide of the type defined in M above metals are produced. This reaction can be effected by placing the reactants in a suitable container in an inert Reaction medium, e.g. water, methanol or ether, and the reactants at one temperature stirred between room temperature and the reflux temperature of the mixture for about 1/2 to about 12 hours. To this time the desired product can after evaporation

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^u "T330453

of the reaction medium used and recovered in the usual way, e.g. by washing, recrystallization and like cleaned.

The preparation of the compounds according to the invention and their water-soluble salts are illustrated in more detail by the following examples.

example 1

Preparation of dimeric 2-trifluoromethyl-1,3,4-thiadiazol-5-yl isocyanate

A saturated solution of phosgene in ethyl acetate (100 ecm) was placed in a glass reaction flask equipped with a mechanical stirrer. A slurry of 2-trifluoromethyl-5-amino-1,3,4-thiadiazole (45 g) in Ethyl acetate (300 ecm) was added to the reaction vessel and the resulting mixture was taken for about 16 hours Formation of a precipitate stirred. The reaction mixture was then used to remove unreacted phosgene flushed with nitrogen. The rinsed mixture was filtered to give 48 g of a white solid. This solid was made from dimethylformamide to give the desired product, namely the dimeric 2-trifluoromethyl-1,3,4-thiadiazol-5-yl isocyanate recrystallized .

Example 2

Preparation of the dimethyl acetal of 2- £ i-methyl-3- (2-trifluoro> methyl-1,3,4-thiadiazol-5-yl) ureidq] acetaldehyde.

A mixture of 2-trifluoromethyl-1,3,4-thiadiazol-5-yl-isocyanate dicers (9.5 g) the dimethyl acetal of 2-methylaminoacetaldehyde (5.8 g) and benzene (60 ecm) was in a

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equipped with a mechanical stirrer and reflux condenser Given glass reaction vessel. The reaction mixture was refluxed for about 5 minutes. Thereafter the benzene was distilled off from the mixture under reduced pressure to give a residue Solid received. This product was recrystallized from heptane and the desired product was obtained, namely the dimethyl acetal of 2- £ i-methyl-3 - (- trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido / acetaldehyde with a melting point of 101 to 1O2 ° C.

Example 3

Preparation of the potassium salt of dimethyl acetal of 2- £ i -methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido ^ acetaldehyde

The dimethylacetal of 2- (j-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl-) ureido7r-acetaldehyde (15.6g) and methanol (100 ecm) were poured into one equipped with a stirrer Given glass reaction vessel. A methanolic solution of potassium hydroxy (6 g) was then added with stirring. Stirring was continued for about 1 hour at room temperature. The reaction mixture was then freed from solvent and the desired product was obtained as a solid residue.

Example 4

Preparation of the dimeric 2-tert-butyl-1,3,4-thiadiazol-5-yl isocyanate

A saturated solution of phosgene in ethyl acetate (100 ecm) was placed in a glass reaction vessel equipped with a mechanical stirrer. A slurry was given

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of 2-tert-butyl-5-amino-1,3,4-thiadiazole (10 g) in Add ethyl acetate (300 ecm) to the reaction vessel and stir the resulting mixture for about 16 hours to form of a precipitate. The reaction mixture was then filled with nitrogen gas to remove none flushed converted phosgene. The rinsed mixture was obtained to give the desired product, viz "2-tert-butyl-1,3,4-thiadiazol-5-yl-isocyanate dimer, which was obtained as a solid with a melting point of 261 to 263 ° C, filtered.

Example 5

Preparation of the dimethyl acetal of 2-f 1-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidq] acetaldehyde

A mixture of 2-tert-butyl-1,3 »4-thiadiazol-5-yl-isocyanate dimer (6g) the dimethyl acetal of 2-methylaminoacetaldehyde (3.9g) and benzene (50ccm) was poured into a with a mechanical stirrer glass flask equipped with a reflux condenser. The reaction mixture was refluxed with stirring for about 5 minutes. The benzene was then distilled off and an oil was obtained which solidified on standing. The solid obtained was then recrystallized from pentane and the desired product was obtained, namely the dimethyl acetal of 2- [i-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureido } -acetaldehyde with a melting point of 80 to 82 ⁰ C.

Example 6

Preparation of the sodium salt of the dimethyl acetal of 2- £ i-methyl-3- ( 2-tert-butyl-1,3,4-thiadiazol-5-yl) ureido "} - acetaldehyde

The dimethyl acetal of 2- {j1-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureido-7-acetaldehyde (15g) and methanol

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(100 ecm) was placed in one equipped with a mechanical stirrer Glass flask given. The reaction mixture was stirred with a methanolic solution of sodium hydroxide (5g) offset. The mixture was stirred for about another hour. Thereafter, the reaction mixture was freed from methanol and one received the desired product as a solid residue.

Example 7

Preparation of the diaethyl acetal of 2 - {/ 1-methyl-3- (2-tert, -butyl-1,3,4-thiadiazol-5-yl) ureido ^ -acetaldehyde

A mixture of the dimeric 2-tert-butyl-1,3,4-thiadiazol-5-yl isocyanate (6g), the di-ethyl acetal of 2-methylaminoacetaldehyde (4g) and benzene (50 ecm) are poured into one with a mechanical stirrer and reflux condenser Gals reaction vessel equipped. The reaction mixture is stirred for about 10 minutes to Heated to reflux. The benzene is then separated off from the reaction mixture and a solid product is obtained. This is the di-ethyl acetal of 2- £ i-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidol -acetaldehyde.

Example 8

Preparation of the ammonium salt of the diethyl acetal of 2-Li-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidol-acetaldehyde

The di-ethyl acetal of 2- [i-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureido / acetaldehyde (17g) and methanol (lOOccm) are in one with a mechanical stirrer and one Gas inlet tube equipped glass reaction flask. The reaction mixture is left with vigorous stirring slowly bead ammonia (3g). After the addition of ammonia has ended, the mixture is stirred for a further 1 hour. Then you rinse them

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The reaction mixture is passed through with air and the methanol is removed, the desired product being obtained as a solid residue.

Example 9

Preparation of the diisopropyl acetal of 2- £ i-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido} acetaldehyde

A mixture of the dimeric 2-trifluoromethyl-1,3,4-thiadiazol-5-yl isocyanate (6 g), the isopropyl acetal of 2-methylaminoacetaldehyde (4.2 g) and benzene (50 ecm) is placed in a glass reaction flask equipped with a mechanical stirrer and reflux condenser. The reaction mixture is refluxed with stirring for about 10 minutes. Then the benzene is taking Distilled to obtain a solid product from the reaction mixture. This product is recrystallized from pentane and the desired product is obtained, namely the desired diisopropyl acetal of 2-Γ1-methyl-3- (2-trifluoromethyl-1,3,4-thiädiazol-5-yl) ureidoj-acetaldehyde.

Example 10

Preparation of the trimethylamine salt of the diisopropyl acetal of 2-C1-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureidcrj -acetaldehyde

The diisopropyl acetal of 2- / Ϊ-methyl-3- (2-trifluoromethyl-1,3, 4-thiadiazol-5-yl) ureidcT] acetaldehyde (21g) and trimethylamine (6g) are stirred in water (50 ecm) for about 15 minutes to obtain a solution of the desired product. The aqueous solution can be used as such without isolating the reaction product.

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Further, for example, compounds that fall within the scope of the invention and are obtainable by the methods described in the preceding examples are the dimethylacetal of 2 - [_ 1-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazole- 5-yl) ureido] acetaldehyde, the di-ethyl acetal of 2-Jj-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureidq] acetaldehyde, the dipropyl acetal of 2-1 -Methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido]] acetaldehyde, the dimethyl acetal of 2- [i -methyl-3- (2-isopropyl-i, 3,4 -thiadiazol-5-yl) ureidq] -acetaldehyde, the diaethylacetal of 2- £ i-methyl-3- (2-isopropyl-1,3 »4-thiadiazol-5-yl) ureidoj-acetaldehyde, the dimethylacetal of 2- B-methyl-3- (2-tert.-butyl-1,3,4-thiadiazol-5-yl) ureidol-acetaldehyde, the di-ethyl acetal of 2 - (, 1-methyl-3- (2-tert.-butyl -1,3 »4-thiadiazol-5-yl) ureidq3-acetaldehyde, the dipropyl acetal of 2 - [_ 1-methyl-3- (2-tert-butyl-1,3,4-thiadlazol-5-yl) ureidq } -acetaldehyde, the ethylamine salt of the methylpropylacetal of 2 - [/ I-methyl- 3- (2-isopropyl-1,3,4-thiadiazol-5-yl) ureidoJ-acetaldehyde, the di-n-butylamine salt of dipropyl acetal of 2- [1-methyl-3- (2-trifluoromethyl-1,3, 4-thiadiazol-5-yl) ureidp_
Dimethylacetals of 2-thiadiazol-5-yl) ureido

-acetaldehyde, the lithium salt of .1-methyl-3- (2-trifluoromethyl-1,3,4- -acetaldehyde, the calcium salt of

Dimethylacetal of 2 - [_ 1-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidoJ-acetaldehyde, the magnesium salt of the diaethylacetal of 2- [i-methyl-3- ( 2-isopropyl-1,3,4-thiadiazol-5-yl) ureidoJ-acetaldehyde, the chromium salt of the dimethylacetal of 2- [1-methyl-3- (2-tert-butyl-1,3,4-thiadiazole- 5-yl) ureidoj-acetaldehyde, the manganese salt of the diaethylacetal of 2- [i -methyl- 3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido] -acetaldehyde, the iron salt of the dimethylacetal of 2 - £ i-Methyl-3- (2-isopropyl-1,3,4-thiadiazol-5-yl) ureidoy-acetaldehyde, the nickel salt of the dimethylacetal of 2- {j-methyl-3- (2-tert.-butyl -1,3,4-thiadiazol-5-yl) ureido / acetaldehyde, the zinc salt of the dimethylacetal of 2- £ ~ 1-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl ) ureidoJ-acetaldehyde, the aluminum salt of the dimethylacetals of 2- £ i-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureidoJ-acetaldehyde, the cyclohexylamine salt of the dimethylacetal of 2- [i- Methyl-3- (2-trifluoromethyl-1,3,4-

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thiadiazol-5-yl) ureidq / acetaldehyde, the dimethylamine salt of the dimethyl acetal of 2- £ i-methyl ~ 3- (2-trlfluoromethyl-1 »3,4-thiadiazol-5-yl) ureido7-acetaldehyde and the same.

The water-soluble salts of the compounds according to the invention can be used for practical use as herbicides dissolved in water and the aqueous solutions can then be applied to the weed infestation site in the usual way will. Thus, one method of preventing weeds from growing is to stand on the spot this weed growth applies a herbicidal composition that uses water as an inert carrier and as an essential active ingredient contains a compound of the invention in an amount suitable for these weeds herbicidally toxic.

All compounds according to the invention can be brought into the customary form of herbicidal compositions e.g. in the form of powders, granules, wettable powders, aerosols or emulsifiable concentrates.

For example, a powdery powder can be produced by grinding and mixing the active compound with a solid inert carrier, e.g., talc, clays, silica, pyrophylite and the like. Granules can be obtained by dissolving the compound, usually is impregnated in a suitable solvent on and in granular carriers, e.g. in attapulgite or vermiculite, usually with particle sizes of about 0.3 to 1.5 mm. Wettable powder, which is in oil in any concentration the active compound can be dispersed

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by incorporating wetting agents in concentrated powder compositions can be obtained.

The concentration of the compounds according to the invention in the herbicidal compositions can vary widely depending on the nature of the composition and the intended use; but generally the herbicidal compositions will contain about 0.05 to 95 wt -.% to the active compounds of this invention. In a preferred embodiment of the invention, the herbicidal compositions contain from about 5 to about 75% by weight of the active compound. The compositions can also contain additional substances, for example other pesticides such as insecticides, nematocides, fungicides and the like; Stabilizers containing spreading agents, deactivators, adhesives, tackifying agents, fertilizers, activators, synergistic agents, and the like.

Weeds are unwanted plants that grow in unwanted places, have no economic value, disturb the harvest of grain, the growth of ornamental plants or the welfare of livestock. Many types of Weeds are known, including annuals, e.g. Chenopodium, Chenopodium album, Alopecurus, Digitaria sanguinalis, Brassica, field pennycress, Lolium temulentum, Eleusine indica, Stellaria media, Avenua sativa, Cissampelos pareira, Portulaca oleracea, Echinochloa crus-galli, Polygonum, Xanthium, Fagopyrum, kochia, Medicago, Agrostemma pallida, Ambrosia, Sonchus oleraceus, Coffea, Croton, cuphea, Cuscuta, Fumaria officinalis, Senecio, Galeopsis tetrahit, knowel, Daphne laureola, Spergula, emex, Oryza (sativa), Potamogeton, Anthemis cotula, Axonopus compressus, Ipomoea purpurea, Galium, Lemna,

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Naias, Daucus carota, matricaria, Hordeum vulgar, campion, Anthemis nobilis, Arctium lappa, Verbascum thapsus, Malva rotundi-folia, Cirsium lanceolatum, Cynoglossum officinale, Verbascum Blattaria, Cirsium, or perennials such as Agrostemma, Agropyron repens, Sorghum halepense, Cirsium canadense, Convolvulus, Cynodon dactylon, Rumex acetosella, Rumes crispus, Cyperus rotundus, Stellaria, Taraxacum officinale, Campanula, Convolvulus, Polygonum, Prosopis juliflora, Linaria vulgaris, Achillea, Aster, Lithospermum officinale, Equisetum, Vernonia, sesbania, Scirpus lacustris, Typha, Cressa.

Such weeds can also be called broad-leaved or grass-like get ranked. It is for economic reasons desirable to stop the growth of such weeds without affecting valuable plants or Cattle suffer.

The compounds according to the invention are particularly valuable for weed control, as they are poisonous to many genera and groups of weeds, while äie are relatively non-toxic for many valuable plants. The exact amount of compound required depends on several factors including the tenacity of the specific weed species, the weather, the type of soil, the Type of application, the type of desired plants growing on the same area and the like. While thus applying up to only about 1 or 2 ounces of active compound per acre (about 4,000 square feet) for good Control of only light weed infestations under poor growing conditions may be sufficient, the Apply 10 pounds or more of active compound per approximately 4,000 square feet for good tackling of a leak Infestation of stubborn perennial weeds that under

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grow CONDITIONS cheap ^B may be required.

The herbicidal toxicity of the compounds according to the invention can be determined by many test methods known in this field, carried out, for example, before or after the seeds have sprouted.

The herbicidal activity of the compounds according to the invention has been shown by tests which are used as controls the emergence of the seeds on various weeds. In these attempts were small Plastic greenhouse pots filled with dry earth and sown with the weed seeds. 24 hours or less after sowing the pots, they were sprayed with water until the soil was soaked and the in Test compounds in the form of aqueous emulsions of acetone solutions containing emulsifiers were used sprayed onto the surface of the earth in the specified concentrations.

After spraying, the pots were moved to the greenhouse and given additional heat as needed and watered daily or more frequently. The plants were kept under these conditions for 15 to 21 days, at what time the condition of the plants and the degree of their impairment on one of ο to 10 was determined with the following meaning: 0 = no impairment, 1.2 = slight impairment, 3,4 = moderate impairment, 5.6 = fairly severe impairment, 7,8,9 = severe impairment Impairment and 10 = death. The effectiveness of these compounds is determined by the values in the Tables I and III shown.

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The herbicidal activity of the compounds according to the invention was also shown by experiments carried out on various weeds after the seeds had come up became. In these experiments, the compounds to be tested were in the form of aqueous emulsions in the specified Spray amount on the foliage of the weed after it has reached a prescribed size. After spraying, the plants were placed in a greenhouse and watered daily or more frequently. No water was applied to the foliage of the treated plants. The severity of the impairment the plants were observed 10 to 15 days after treatment and according to that described by vonstohond Rated on a scale from ο to 10, the effectiveness of these compounds is determined by the data in the Tables II and IV illustrated.

Table I.

Herbicidal activity of the product of Example 2 before the seeds emerge

Weed extent of impairment

in pounds / acre

8 4 2

Echinochloa crus-galli 10 10 10 Digitaria sanguinalis 9 9 6th Bromis 10 10 7th Alopecurus 10 10 9 Sorghum halepense 9 9 8th Avena sativa 10 10 8th Coffea 10 10 10 Rumex crispus 10 10 8th Cissampelos pareira 9 9 9 Brassica 10 10 10

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Table II

Herbicidal activity of the product of Example 2 after the seed has emerged

weed Extent of impairment
in pounds / acre
8 4 2 9 8th Echinochloa crus-galli 10 10 9 Digitaria sanguinalis 10 10 9 Bromis 10 9 8th Alopecurus 10 10 10 Sorghum halepense 10 10 8th Avena sativa 10 10 10 Coffea 10 10 7th Rumex crispus 10 9 5 Convolvulus sepium 9 10 10 Matricaria 10 10 7th Chenopodium 10 10 9 Cissampelos pareira 10 10 10 Brassica 10

Table III

Herbicidal activity of the product of Example 5. the emergence of the seeds

Weed extent of impairment

in pounds / acre

10 4 2 1

Avena sativa 10 10 10 10 Datura stramonium 10 10 "9 10 Cissanpelos pareira 10 10 10 10 Sorghum halepense 10 9 9 '8th Chenopodium 9 9 9 9 Brassica 10 10 10 9 Setaria lutescens • 9 9 9 9

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- ■ ι / - Table IV 10 10 2330453 10 Echinochloa crus-galli 10 10 10 10. Digitaria sanguinalis 9 9 10 θ Bromis 10 10 9 10 Ipomoea purpurea 9

Herbicidal activity of the product of Example 5 after seed emergence

Extent of weed impairment in pounds / acre

10 .4. 2 1

Avena sativa 10 9 8th 9 Datura stramonium 10 10 10 10 Chenopodium 10 10 9 9 Sorghum haiepense 10 9 3 2 Convolvolus 9 9 10 10 Brassica 10 10 10 10 Setaria lutescens 10 10 10 10 Echinochloa crus-galli 10 10 10 10 Digitaria sanguinalis 10 9 7th 5 Ipomoea purpurea 10 10 10 10

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Claims (14)

7330453 - 18 - Claims Compound of formula H
I. R ^ O - C - O -R ² NN I Il II H- C-N-C-N-C C- I I I I \ / H CH ₃ OHS 1 2
wherein R and R each represent an alkyl group having up to 3 carbon atoms; X is isopropyl, tert-butyl or trifluoromethyl / and their water-soluble ammonium, primary amine, secondary amine, tertiary amine, potassium, sodium, lithium, calcium, magnesium, chromium, manganese, Iron, nickel, copper, zinc and aluminum salts. 2. Compound according to claim 1, namely the dimethyl acetal of 2- £ i -methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido]] acetaldehyde. 3. A compound according to claim 1, namely the diethyl acetal of 2-ti-methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) tireidoU-acetaldehyde. 4. Compound according to claim 1, namely the dipropyl acetal of 2- £ i-methyl-3- (2 - trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido ~ 7-acetaldehyde. 5. Compound according to claim 1, namely the dimethyl acetal of 2-Jj-methyl-3- (2-tert-butyl-1,3-, 4-thiadiazol-5-yl) ureidoj-acetaldehyde. 409882/1104 6. Compound according to claim 1, namely the di-ethyl acetal of 2- £ i-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidoj-acetaldehyde. 7. Compound according to claim 1, namely the dipropyl acetal of 2 *. // l-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidq ^ -acetaldehyde. 8. The compound of claim 1 which is the potassium salt of the dimethyl acetal of 2- £ i-methyl-3 -. (2-trifluoromethyl-1,3, A-thiadiazol-5-yl) ureido7 ~ acetaldehyde. 9. The compound of claim 1 which is the sodium salt of the dimethyl acetal of 2- £ / i-methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureido ^ -acetaldehyde. 10. A compound according to claim 1, namely the ammonium salt of the diethyl acetal of 2-f / ^1- methyl-3- (2-tert-butyl-1,3,4-thiadiazol-5-yl) ureidqI-acetaldehyde. 11. The compound of claim 1 which is the dimethylamine salt of the dimethyl acetal of 2- | n -methyl-3- (2-trifluoromethyl-1,3,4-thiadiazol-5-yl) ureido ^ -acetaldehyde. 12. The compound of claim 1 which is the cyclohexylamine salt of the dimethyl acetal of 2- £ i-methyl-3- (2-trifluoromethyl-1,3 »4-thiadiazol-5-yl) ureido7-acetaldehyde. 13. A weed-toxic amount of a compound according to claim 1 and an inert carrier herbicidal composition. 409882/1104 14. Method for controlling weed growth, characterized in that that weeds with an amount of a compound according to claim 1 which is toxic for the weeds and contacting an inert carrier herbicidal composition. 409882/1104