Note: Descriptions are shown in the official language in which they were submitted.
~5 ~ ~'7
The present invention relates to substituted phenyl-
ureas) to processes for their preparation~ also to
plant-regulating agents containing these new compounds
as active substances, as well as to methods for the
selective control of weeds in cultivated crops entailing
the use of the new active substances or of agents
containing them.
Herbicidally active phenylureas have become known
from the literature in exceedingly large numbers. From
the abundance of literature available to one skilled in the
art, reference is made here to the following patent
specifications as relevant prior art: German Patent
Specification No. 935,165; US Patent Specifications Nos.
2,705,195, 2,764,478 and 2,876,088; as well as the
published German Patent Application P 19 66 298.7-41.
In the US Patent Specification No. 2,876,088, reference
is made, for example, to various classes of soil-sterilising
substituted phenylureas known from US Patents 2,655,444 - 447
corresponding to the German Patent Specification No.
935,165. Phenylureas given as being particularly suitable
total herbicidal cornpounds for the subject of this US-
patent specification are those which can be alkyl- and also
halogen-substituted in the phenyl radical in any position,
and which carry, for example, methyl groups on the nitrogen
atom not linked with the phenyl nucleus. Herbicidal phenylureas
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of this type are described also in the US Patent
Specification No. 2,705,195. Furthermore, there are
known from the US Patent Specification No. 2,764,478
herbicidal phenylureas which are obligatorily substituted
in the 3~position of the phenyl radical by a methyl
group, and additionally, in any chosen remaining positions
of the phenyl radical, by halogen. A representative
of this group of compounds, l,l-dimethyl-3-(3-methyl~4-
chlorophenyl)-urea, is given in the mentioned US patent
specification as being, in the pre-emergence application
method, selective-herbicidally effective in cotton and in
maize crops. On the other hand, the unsuitability of
this compound for use as a selective weed-control agent
in cereal crops is taught, for example, by the known
German Patent Application No. P 19 66 298.7-41. Equally
unsuitable for selective-herbicidal application in grain
crops, as well as in a number of other useful plant crops,
such as, for example, maize and soya bean crops, are
the known halogenated phenylureas, l,l-dimethyl-3-(4-chloro-
phenyl)-urea and 1,1-dimethyl-3-(3,4-dichlorophenyl~-urea.
The use of these two compounds in cotton crops results in
the destruction or serious damaging of the crops.
On the basis of the teaching of the prior art, one skilled
in the art had to accept firstly that, for the attainment
of selective-herbicidal action, phenylureas methyl-substituted
in the 3-position of the phenyl radical were to be
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preferentially used, this application moreover being
limited to speciflc useful plant crops, and secondly
that phenylureas with higher alkyl substitution in
the 3-position of the phenyl radical were not suitable
as selective herbicides for practical purposes on
account of a phytotoxic action too intense and too
unspecific.
It has now been found that, surprisingly, the new
active substances according to the present invention,
which do not have the constitution alleged in the literature
to be essential for selective-herbicidal action,
have, contrary to the teaching of the US Patent Specification
No. 29876,088, excellent selective-herbicidal properties
in a number of useful-plant crops, and are also vastly
superior in effectiveness against weeds and in crop
compatibility to the constitutionally homologous phenyl~
ureas disclosed in the US Patent Specification No.
2,764,478.
The new phenylureas according to the invention
correspond to for~ula I
~ \\ CH3
R~ H C0 - N j (I3
/ : C~13
R2
wherein
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R1 represents hydrogen or chloxine, and
R2 represents ethyl, or tert.butyl.
A particularly pronounced selectivity between weeds
and useful-plant crops is exhibited, even with small applied
amounts, by the following compounds according to the invention
which correspond to formula I wherein
Rl represents hydrogen:
1,1-dimethyl-3-(3'-ethyl-phenyl)-urea,
1,1-dimethyl-3-(3'-tert.butyl-phenyl)-urea,
as well as the compound according to the invention l,l-dimethyl-
3-(3-ethyl-4-chlorophenyl)-urea.
The new phenylureas of formula I are prepared accord-
ing to known methods, with, in principle, all processes usually
employed for the preparation of urea derivatives, including
processes commonly used for manufacture on a commercial scale,
being applicable. A very advantageous process comprises,
reacting an isocyanate of formula II
f~
1 ~ ~ N = C = O
~ (II),
R2
wherein R1 and R2 have the meanings given under formula I,
with dimethylamine in a solvent or diluent inert to the
D
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reactants, for example, benzene, toluene, dioxane and other
similar ones. The reaction is performed preferably in a
temperature range of between room temperature and about
80C. After completion of the reaction, the phenylureas
according to the invention precipitate, on cooling, from
the reaction mix~ure, or are caused to precipitate by the
addition of ice water to the reaction mixture. After
filtration of the precipitate thus obtained, the phenyl-
ureas are crystallised from suitable solvents or
solvent mixtures, such as, for example, benzene/hexane.
The isocyanates used in this reaction as starting
material, or the amines used for the preparation thereof,
are known compounds, or are prepared by methods analogous
to those known from prior art for the preparation of
such compounds.
Another process for preparation of the new phenylureas
of formula I consists in the reaction of compo-mds of
formula III
NH - C0 - N ~ 3
~2 ~ CH3 (III),
wherein
R2 has the meaning given under formula I, wi~h chlorine
or with a ~hlorine-releasing agent.
The urea derivatives serving as starting materials
~5~
are advantageously chlorinated or brominated in the
presence of a solvent or diluent in which they are
dissolved or suspended, as well as, optionally, in the
presence of an acid-binding agentj e.g. sodium acetate.
Suitable solvents or dispersing agents for the starting
materials of formula III to be chlorinated or brominated
are, for example, glacial acetic acid, halogenated
hydrocarbons such as carbon tetrachloride, chlorobenzene, etc..
Chlorine-releasing agents used for chlorination of the
compounds of formula III are, in particular, sulphuryl
chloride, or organic chlorine-releasing compounds.
Chlorination of the compounds of formula III is advantageously
performed in the presence of halogen-carriers, such as,
for example, iron, antimony or salts thereof, or sulphur.
As for the rest, the techniques applied are those commonly
used for the nucleus-halogenation of aromatic compounds.
The preferred temperature range suitable for the above-
described chlorination is one between 0 and 100C; the
reaction time is between half an hour and 100 hours. The
processing of the reaction mixture is performed analogously
to that for the previously described first preparation
process.
The starting materials of formula III correspond to the
final products of formula I for the case where Rl is
hydrogen, and are obtained by a process corresponding to the
above-described first preparation process for the phenylureas
of formula I. _ 7 _
S~ .t~
The following examples illustrate the processes
according to the invention, including the preparation
of starting materials. Further active substances of
formula I, which are prepared by one of the described
processes, are shown in the following table. The
temperatures are given in degrees Centigrade.
Example 1
a) 3-Isopropyl-phenylisocyanate
167 g of 3-isopropyl-aniline is reacted with phosgene
by the method described in HOUBEN-WEYL, Methoden der
organischen Chemie,Vol. VIII, page 122 (1952). There
is obtained in practically quantitative yield 3-
isopropyl phenylisocyanate, B.P. 90/11 mm Hg.
b) 1,1-dimethyl-3-(3-isopropyl-phenyl~-urea
; 64,5 g of 3-isopropyl~phenylisocyanate is added dropwise
- 15 to a solution of 55 ml of 40% aqueous dimethylamine
and 200 ml of dioxane. Ice water is addedg and the
precipitate is collected and dried to thus obtain
72 g of 1,1-dimethyl-3-(3-isopropyl-phenyl)-urea,
M.P. 102-103 (from benzene/hexane).
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Example 2
1,1-Dimethyl-3-(3-ethyl-4-chlorophenyl)-urea
37 g of 1,1-dimethyl-3-(3-ethyl-phenyl)-urea is dissolved
in 250 ml of glacial acetic acid, and 18.5 ml of sulphuryl
chloride is added at 15 within one hour. Stirring is
maintained overnight at room temperature, and 1 litre of
ice water is then added to the reaction mixture. The
resulting precipitate is separated, and crystallised from
~enzene/hexane: yield 22 g of 1,1-dimethyl-3-(3-ethyl-4-
chlorophenyl)-urea; M.P. 138-140.
_ g _
., ,, . , . , . , . . ... . , . , . , .. , .. , , .. ,, . . . , . , .. , .... ,,,, .. , .,, . , . , ., .. , . ,
., , . ,, . , . , .. , ",,, ., ., ", , .. . . .. . ~ .. ,, ., .,, . ~ . , .
Teb 1 e
Constitution Melting poi-nt
:
C l~ Nil- CO~N ~ c~l 102 - 103
C31-17 (iso)
- Cl~ ,C1-13 163 - 16~
C41-lg(tert )
..
~ CoN~C}l3 123 - 124
C ~/ C113
2 5
~N ~ . 8l~
C~13
C4~!9 ~tel .. )
.
.
: ' .
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The compounds according to the invention possess
very good herbicidal properties against Gramineae such
as millet-like plants of the genera Setaria, Digitaria,
Echinochloa, etc., against grasses such as Lolium species,
Alopecurus, Avena fatua, etc., and also against many
dicotyledonous weeds such as Amaranthus, Sesbania,
Chrysanthemum, Sinapis, Ipomoea, Pastinaca, etc., without
the useful crops on which the active substance is applied
being damaged, even where large amounts are employed.
Useful crops that may be mentioned are, in particular,
cotton and also maize, soya bean, lucerne, sorghum,
and cereals such as wheat, barley and rye.
The active substances are applied either before or
after emergence of the cultivated plants and of the weeds
and wild grasses. The applied amounts per hectare are
between 0.2 and 16.0 kg of active substance, preferably
between 0.5 and 4.0 kg.
Example 3
Herbicidal action with application of the active substances
before emergence (pre-emergence) of the plantsO
__
Immediately after the sowing of the test plants, the
active substances are applied, as an aqueous suspension
obtained from 25% wettable powders, to the surface of the
soil. The seed trays are then kept in a greenhouse at
22-23C with 50-70% relative humidity.
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Each active substance is applied in amounts equivalent
to 4 kg, 2 kg, l kg and 0.5 kg of actlve substance
per hectare.
The test results are evaluated after 5, 15 and 25
S days; evaluation is on the basis of a scale of values
from l to ~:
l = plants dead,
2 - 4 = in~ermediate stages of destruction (over 50%
irreversible damage),
5 - 8 = intermediate stages of destruction (under 50%
reversible damage),
9 = plants undamaged (control).
In this test,
19 l-dimethyl-3-(3-ethyl-4-chlorophenyl)-urea,
l,l-dimethyl-3-(3-ethyl-phenyl)-urea and
l,l-dimethyl-3-(3-isopropyl-phenyl)-urea
prove to be very effective against grasses/millet and
dicotyledonous weeds, with very good compatibility in
cotton, maize, sorghum, soya bean, wheat and barley.
Example 4
Herbicidal action with application of the active substances
after emergence (post-emergence) of the plants.
, _ _
The test plants are treated in the 2-4-leaf stage
with aqueous suspensions of active substances obtained
from ~5% wettable powders. The amounts applied correspond
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..... . . . . . .. ... .. . . . .. . .
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to 4 kg, 2 kg, 1 kg and 0.5 kg of active substance
per hectare.
After the treatment, the plants are kept in a green-
house at 22-25C with 50-70% relative humidity.
S The test results are evaluated after 14 days and
21 days. Evaluation is on the basis of a scale of values
rom 1 to 9:
1 = plants dead,
2 - 4 = intermediate stages of destruction (over 50%
irreversible damage),
5 - 8 = intermediate stages of destruction (below 50%
reversible damage),
9 = plants undamaged (control).
The compounds according to the invention have a good
uniform action against undesirable grasses, and, furthermore,
are effective against broad-leaved weeds, and have very good
compatibility with useful crops. The compo~mds specially
mentioned in Example 3 prove also in this test to be
particularly effec~ive against weeds and compatible with
cultivated crops.
The compounds of formula I according to the invention
are used in varying ways for the selective control of weeds
in useful-plant crops. Thus, they may be formulated together
with suitable carriers and/or distributing agents to give
agents which can be applied as dusts, wettable powders,
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emulsions, granu]ates, etc., for the regulating of
plant growth. The processing of the active substances
to obtain the most favourable preparation for application
is covered by prior art, i.e. it is part of the
S general knowledge of the experts concerned. The preparation
of some such agents is further described below: the
given examples are intended to illustrate but in no
way to limit the invention. Parts are expressed as parts
by weight.
A) Dusts
Equal parts of active substance according to formula I
and precipitated silicic acid are finely ground. The mixture
is combined with kaolin and ~alcum to obtain dusts having
preferably an active-substance content of 1 to 6%.
B) Wettable ~owders
The following constituents, for example, are mixed
together and finely ground to obtain a wettable powder:
50 parts of active substance according to formula I,
~ 20 par~s of Hisil1(highly adsorptive silicic acid)~
-~ 20 25 parts of bolus alba (kaolin),
3.5 parts of reaction product from p-tert.-octyl-
phenol and ethylene oxide,
1.5 parts of sodium salt of 1-benzyl-2-stearyl-
benzimidazole-6,3'-disulphonic acid.
~ a~ n~rk
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~s~
C) Emulsion concentrate
The active substance can also be formulated as an
emulsion concentrate in the following manner:
20 parts of active substance according to formula I,
70 parts of xylene, and
parts of a mixture of a reaction product of an
alkylphenol with ethylene oxide and
calcium-dodecylbenzenesulphonate
are mixed together. On dilution with water to the desired
concentration, there is obtained a sprayable emulsion.
Other biocidal active substances or agents can be
added to the described agents according to the invention.
Thus, the new agents may contain, in addition to the
mentioned compounds of formula I, e.g. insecticides,
fungicides, bactericides, fungistatics, bacteriostatics,
nematocides or further herbicides for the broadening of
the range of action, and also, if desired, fertilisers,
trace elements, etc..
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