Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~.~.3.~
- 1 - ~
The present invention relates to certain new 4,5- -
dichloroimidazole derivatives, to a process for their
preparation and to their use as herbicides.
It has already been disclosed that certain 4,5-dichloro-
imidazole-2-carboxylic acid derivatives have herbicidal
properties (see DE-OS (German Published Specification)
2,610,527). Thus, for example, 4,5-dichloroimidazole-2-
carboxylic acid ethylamide can be employed for combating
weeds, However, this substance is not always sufficiently
active and its selectivity is not always completely
satisfactory.
The present invention now provides, as new compounds,
the 4,5-dichloroimidazole derivatives of the general formula
Cl ~N ~ C - C ~ X5 (I)
' x2 X4
in which
xl represents hydrogen, chlorine, bromine or iodine,
X2, X3 and X4 independently represent hydrogen,
chlorine or bromine and
X5 represents hydrogen or chlorine, and
Xl and X3 together can represent a C-C bond, and
x2 and X4 together can represent a C-C bond, or
xl and x2 together can represent oxygen or the grouping
=N-Y,
in which
y represents hydroxyl or a radical -NH-C~NHR,
z
-NH-Rl or ~ ~ ~ f-~l '
Le A 19 ~92
~ 3~ 3~5t~3
in which
R represents hydrgen or alkyl with 1 to 4 carbon
atoms,
Rl represents aryl which optionally carries one or more
substituents selected from halogen, alkyl, alkoxy,
halogenoalkyl and nitro~
Z represents oxygen or sulphur and
R2, R3 and R4 independently of one another repre-
sent hydrogen or chlorine,
provided that Xl, X2, X3, X4 and X5 do not simultaneously
represent hydrogen.
It has been found that the 4,5-dichloroimidazole
derivatives of the formula (I) have powerful herbicidal
properties and, in p~rticular~ selective herbicidal
properties
Preferred compounds of the formula (I) are those in which
xl represents hydrogen, chlorine, bromine or iodine,
x2 represents hydrogen, chlorine or bromine,
X3 represents hydrogen, chlorine or bromine,
X4 represents hydrogen, chlorine or bromine, and
X5 represents hydrogen or chlorine, provided that : -
Xl, X2, X3, X4 and X5 never simultaneously all represent --
hydrogen,
xl and X3 together may alternatively represent a C-C
bond,
x2 and X4 together may alternatively represent ~ C-C
bond, or
xl and x2 together may represent oxygen or the grouping
=N-Y,
Y represents hydroxyl or a radical -NH-C-NH-R,-NHRl or
~Cl
-N=C-~ Y~C1
Le A 19 392
~L~3S7~3
R represents hydrogen or alkyl with 1 to 2 carbon atoms
(especially hydrogen),
Z represents sulphur,
Rl represents phenyl or naphthyl, either of which
may optionally carry one or more substituents selected
from fluorine, chlorine, bromine, alkyl with 1 or 2
carbon atoms, alkoxy with 1 or 2 carbon akoms, trichloro-
methyl, tri~luoromethyl and nitro, and
R2, R3 and R4 each represent hydrogen.
The invention also provides a process for the preparation
of a 4,5-dichloroimidazole derivative of the formula (I),
in which
(a) 2-ethylimidazole, of the formula
N
~ N ~ 2H5 (II),
or its hydrochloride i9 reacted with up to 7 moles of
chlorine per mole of 2-ethylimidazole in a solvent which
is inert under the reaction conditions, or
(b) a 4,5-dichloroimidazole derivative of the general
formula
Cl
20 ~ ~ x6 X3 (III),
H x7 x4
in which
x6 represents chlorine or bromine,
X7 represents chlorine or bromine and
X3, X4 and X5 have the meanings indicated.above,
provided that X , X and X do not simultaneously
represent hydrogen,
() is hydrolysed with water, or
(e) is reacted with at least the stoichiometrically required
A
Le A 19 392
~3.~ 3
-- 4 --
amount of a dehalogenating agent, if appropriate in the
presence of a diluent, or
(y) is reacted with at least the stoichiometrically required
amount of a metal hydride customary for hydrogenation
reactions, in the presence of a diluent, or
(c) a 4,5-dichloroimidazole derivative of the general
formula
Cl- --N x6
~ N ~ CH2-C-X5 (IV),
cl ' X7
in which
X5, x6 and X7 have the meanings indicated above,
i8 reacted with an agent which splits off hydrogen
chloride, in ~he presence of a diluent, or
(d) 2,4,5-trichloro-2-(1,1-dichloroethyl)-2 H-imidazole~ of
the formula
Cl\~N~Cl
Cl ~ N CC12-CH3 (V),
(~) is reacted with a reducing agent, in the presence of a
diluent, or
(B) is reacted with an excess of at least 3 moles of an
alkali metal iodide or with an excess of at least 1.5
moles of an alkaline earth metal iodide, in the presence
of a lower aliphatic ketone as the diluent, or
(y) is reacted with an at least equimolar amount of an
alkali metal bromide or with an at least equivalent amount
of an alkaline earth metal bromide, in the presence of a
lower aliphatic nitrile or of a lower aliphatic ketone as
the diluent, or
(e) a 4,5-dichloroimidazole derivative of the general
formula
Le A 19 392
.: ~
,
' :
.
.
_ 5 _
Cl ~ C-CH2 (VI),
in which
Hal represents chlorine or iodine,
(u) is reacted with an agent which splits off hydrogen
halide, if appropriate in the presence of a diluent, or
(~) is hydrolysed with water, in the presenoe of a base or
of a basic salt, or
(f) a 4,5-dichloroimidazole derivative of the general formula
~ ~ C- ~- X4 (VII),
Cl H \ X5
in which
X3, X4 and X5 have the meanings indicated above,
is reacted with a compound of the general formula
H2N-Y t (VIII),
in which
Y' represents amino, hydroxyl or a radical
-NH-C-NHR or -NHRl
~t
in which
Z represents oxygen or sulphur,
R represents hydrogen or alkyl with 1 to 4 carbon
atoms and
Rl represents aryl which optionally carries one or more
substituents ~elected from halogen, alkyl, alkoxy,
halogenoalkyl and nitro,
in the presence of a diluent, or
(g) 4,5-dichloro-2-ethynyl-imidazole, of the formula
Cl
~ (IX),
Cl N C-CH
H
v, ~ ,
Le A 19 392
~3~ 3
-- 6 --
is reacted with a chlorinatin~ or brominating agent, in the
presence of a solvent which is inert under the reaction
conditions, or
(h) a 4,5-dichloroimidazole derivative of the general
formula
Cl~3`c-c\ (x)
in which
Xl, X3 and X4 have the meanin~s indicated above,
is reacted with a chlorinating or brominating agent, in
the presence of a solvent which is inert under the reaction
conditions, or
(i) a 4,5-dichloroimidazole derivative of the general
formula
Cl_
~ ~ Hal
Cl - , ~ C-CH2-X (XI),
in which
x6 and X7 have the meanin~ indicated above and
Hal' represents chlorine, bromine or iodine,
is dehydrohalogenated under the influence of heat, in the
presence of a lower aliphatic nitrile.
Surprisingly, whilst having a very good herbicidal
action, the 4,5-dichloroimidazole derivatives of the
formula (I) according to the invention have, in particular,
better possibilities for use as agents for selectively
combating weeds in important crops than ~,5-dichloro-
imidazole-2-carboxylic acid ethylamide, which is known from
the state of the art and is an active compound of high
activity and the same type o~ action The substances
Le A 19 392
~35~
according to the invention thus represent a valuable enrich-
ment of herbicidal agents for selectively combating weeds.
If, in process variant (a),7 moles of chlorine are used
per moleo~ 2-ethyl-imidazole, the course of the reaction
can be represented by the following equation:
H C ~,~
If 4,5-dichloro-2-pentachloroethyl-imidazole is
used as the starting material and water is used as the
hydrolysing agent, the course of process variant (b)(~),
10 can be represented by the following equation:
Cl Cl
Cl ~N ~ C2C15 + H20 ~ Cl ~ ~ C-CC13 + 2 HCl
H H O
If 4~5-dichloro-2-pentachloroethyl-imidazole is used
as the starting material and sodium iodide in acetone -
is used as the dechlorinating agent, the course of process
15 variant (b)(~) can be represented by the following equation:
C ~ ~ 2 NaI Cl ~ N
H ~ .
If 4,5-dichloro-2-pentachloroethyI-imidazole is used
as the starting material and sodium boranate is used as
the hydrogenating agent, the course o~ process variant (b)(y)
20 can be represented by the following equation:
'-:,'
Le A 19 392
~3S~3
-- 8 -- -
4 ' ~ ~ 2 HCl
H H
If 4,5-dichloro-2-(2,2,2-trichloroethyl)-imidazole
is used as the starting material and triethylamine is used
as the agent which splits off hydrogen chloride, the course
of process variant (c) can be represented by the following
equation:
~ N 3 ~ ~ CH=CC12 + HCl
Cl N H2-ccl3 - i Cl N
H H
If 2,4~5-trichloro-2-(1,1-dichloroethyl)-2H-imidazole
is used as the starting material and catalytically activated
hydrogen is used as the reducing agent, the course of process
variant (d)(~) can be represented by the following equation:
Cl ~ 1 ~2 ~ N ~ C-CH2 + 2 HCl
2 3 toluene
H
If 2,4,5-trichloro-2-(1,1-dichloroethyl)-2H-imidazole
and sodium iodide are used as starting materials, the
course of process variant (d)(~) can be represented by the
following equation:
Cl
~ ~ Cl -CH3 + 3 NaI > Cl 1 2
Cl 2 - 3 NaCl H
Le A 19 392
~ ~.3.5~
_ 9 _
If 2,4,5~trichloro-2-(1,1-dichloroethyl)-2H-imidazole
and potassium bromide are used 2S starting substances,
the course of process variant (d)(~) can be represented
by the following equation:
Cl ~N ~ Cl2-CH3 ~ C ~ N l C-CH-Br
- H Br
If 4,5-dichloro-2-(l-iodo-ethenyl)-imidazole is
used as the starting material and triethylamine is used as
the agent which splits off hydrogen halide, the course of
process variant (e)(a) can be represented by the following
lO equation: ;.
Cl ~N 1 C=CH2 _ 3l ~ ~N l C--CN
If 4,5-dichloro-2-(l-iodo-vinyl)-imidazole is used
as the starting material and water and sodium formate are
used as the hydrolysing agent, the course of process
variant (e)(~) can be represented by the following
equation:
Cl~---N Cl N
NaOOCH ~
Cl/ N, C=CH2 + H20 ~ Cl/ N C-CH3 + ~I
H H 0
If 4,5-dichloro-2-acetyl-imidazole and phenylhydra-
zine are used as starting materialS the course of process
variant (f) can be represented by following equation:
C ~, ~ C-C~33 + N2N-NN ~ ____ ~ C ~ C-N-N3
Le A 19 392
5~
- 10
If 4,5-dichloro-2-ethynyl-imidazolé is used as th0
starting material and sulphuryl chloride is used as the
chlorinating agent, the course of process variant (g)
can be represented by the following equation:
Cl ~ ;lC~:H ~ 3 C ~ ~ -CHCl
If 4,5-dichloro-2-(1-chlorovinyl)-imidazole is used
as the starting material and sulphuryl chloride is used as
the chlorinating agent, the course of process variant (h)
can be represented by the ~ollowing equation:
Cl
~ ~ Cl S02C12 ~ IN
H 2 CHC13 ~ Cl/~N CC12-CH2C
If 4,5-dichloro-2-(1,1,2-trichloro-ethyl)-imidazole
is used as the starting substance, the course of process
variant (i) can be represented by the following equation:
~ ~ CCl2-CH2Cl ~ Cl/ ~NJl--C--CHC1
Cl H ~0C H
-HCl
The 2-ethylimidazole, or its hydrochloride, required
as the starting material in process variant (a) is known.
Chlorine gas is used as the chlorinating agent in
process variant (a).
Possible solvents in carrying out process variant (a)
are any of the customary solvents which are inert under
the reaction conditions. Preferred solvents include
phosphorus oxychloride, 1,1,2,2-tetrachloroethane,
tetrachlorethylene and thionyl chloride.
Le A 19 392
.
. . . ~
.
.
~ ~3S~
The reaction temperatures can be varied within a
certain range in process variant (a)depending on the
desired end product. If 4,5-dichloro-2-pentachloroethyl-
imidazole is to be synthesised, the reaction is in
general carried out at temperatures of from 90C to
150C, preferably from 100C to 130C. To prepare com-
pounds chlorinated to a lesser extent, the reaction is in
general carrled out at temperatures of from 60C to 100C,
preferably from 70C to 90C.
In carrying out process variant (a), 2-ethylimidazole
or its hydrochloride is reacted with various amounts
of chlorine, depending on the desired end product. If
4,5-dichloro-2-pentachloroethyl-imidazole is to be
prepared, 3 to 7 moles of chlorine are in general employed
per mole of 2-ethylimidazole To moderate the strongly
exothermic chlorination reaction, the formation of the
hydrochloride from 2-ethylimidazole and hydrogen chloride,
which is likewise exothermic, can be eliminated by using
not 2-ethylimidazole itself but its hydrochloride as the
starting material. The reaction product is isolated by
customary methods. In general, a procedure is followed
in which the solvent is distilled off and the residue is
stirred with formic acid at room temperature. The re~
action product which is thereby obtained as crystals is
filtered off. However, it is also possible to sublime the
reaction product out of the residue, which has been freed
from solvent, in vacuo, for example at 125C/0.01 mm Hg.
If a 4,5-dichloroimidazole derivative of the formula
(I) in which the side chain contains fewer than 5 chlorine
atoms is to be prepared in process variant (a), up to 6
moles of chlorine are employed per mole of 2-ethylimidazole
or its hydrochloride, but in this case the reaction
temperature is kept below that for the perchlorination of
the ethyl group. In some cases, the reaction product
is formed not in the pure form but as a mixture with
varyin~ amounts of 4,5-dichloro-2-pentachloro-ethyl-
Le A 19 392
~3~V~
imidazole. However, the desired reaction product canthen be obtained in the pure form by customary methods
of separation, such as (fractional) crystallisation, for
example from chlorobenzene or from acetone, or by
chromatography.
The formula (III) provides a definition of the
4,5-dichloroimidazole derivatives required as starting
materials in carrying out process variant (b). In this
formula, X3, X4 and X5 preferably have those meanings
which have already been mentioned as preferred for X3, X4
and X5 in connection with the description of the compounds
according to the invention. However, X3, X4 and X5 do not
simultaneously represent hydrogen. x6 and X7 preferably
represent chlorine or bromine.
The compounds of the formula (III) were hitherto
unknown. However, they can be prepared by process variant
(a) or by other process variants according to the ~-
invention.
In carrying out process variant (b)(~), a 4,5-
dichloroimidazole derivative of the formula (III) ishydrolysed with water. In this reaction, the water
simultaneously functions as the reaction medium and is
thus employed in a large excess.
The reaction temperature can be varied within a
certain range in carrying out process variant (b) (a) . In
general, the reaction is carried out at temperatures of
~rom 70C to 120C, preferably at the boiling point of the
reaction mixture.
The reaction products are isolated by customary
methods in the case of process variant (b)(a3. In
general, the reaction products are obtained as crystals;
thus they can be filtered off.
Possible dehalogenating agents for carrying out process
~ariant (b)(~) are any of the reagents which can usually
be employed for such purposes. The dehalogenating agents
Le A 19 392
,
' -'
., ~ - ,, ' .
5~
which are preferably used in this variant are sodium
iodide in acetone, copper(I~ chloride, zinc dust, iron
powder, sulphur and phosphorus.
Possible diluents for process variant (b)(~) are
any of the solvents customary for such dehalogenatlon
reactions. Acetone, toluene, chlorobenzene, 1,2-
dichlorobenzene and 1,2,4-trichlorobenzene are preferably
used.
The particularly preferred dehalogenating agent is
the sodium iodide/acetone system.
The reaction temperatures can be varied within a
substantial range in process variant (b)(~). The re-
action is in general carried out at temperatures of from
0 to 200C, preferably from 50C to 150C. If the sodium
iodide/acetone system is used, the reaction is in general
carried out at temperatures of from 0C to 50C, pre-
ferably from 20C to 30C.
In carrying out process variant (b)(~), the 4,5-
dichloroimidazole derivative of the formula (III) is
reacted with at least the stoichiometric amount of de-
halogenating agent. If sodium iodide is used~ this canbe employed in a several-fold excess without further de-
chlorination taking place. The reaction products are
isolated by customary methods. In general, if sodium
iodide is used as the dechlorinating agent, a procedure
is followed in which the reaction mixture is poured into
water, the free iodine is removed by adding a reducing
agent, for example aqueous sodium bisulphite solution, and
the product, which is obtained as crystals, is then filtered
of~.
Possible hydrogenating agents for carrying out process
variant (b)(y) are any of the (complex) metal hydrides
customary for such reactions. Sodium boranate may be
mentioned in particularl
Possible diluents for process variant (b)(y) according
5 ~3
- 14 -
to the invention are any of the solvents which can
usually be used for such reactions. Water may be men-
tioned in particular.
The sodium boranate/water system is particularly
preferred.
The reaction temperatures can be varied within a
substantial range in process variant (b) (r) . In general,
the reaction is carried out at temperatures of from 0C
to 50C, preferably Erom 10C to 40C. If the sodium
boranate/water system is used, the reaction is preferably
carried out at room temperature or slightly below room
temperature.
In carrying out process variant (b)(y), the 4,5-
dichloroimidazole derivative of the formula (III) is~
in general, reacted with at least the stoichiometrically
required amount of metal hydride. If sodium boranate is
used, this can be employed in a several-fold, for example
up to a ten-fold, excess without further undesired hydro-
genation reactions taking place. The reaction products
are isolated by customary methods. In general, if sodium
boranate is used as the hydrogenating agent, a procedure
is followed in which any excess sodium boranate present is
first destroyed by carefully adding acid and any boric
acid obtained is dissolved out of the reaction mixture with
~'ot water.
The formula (IV) provides a definition of the 4,5-
dichloroimidazole derivatives required as starting materials
in carrying out process variant (c). In this formula, X5
preferably represents hydrogen or chlorine. x6 and X7
preferably represent chlorine or bromine.
The compounds of the formula (IV) were hitherto
unknown; however, they can be prepared by process variant
(b)(y).
Possible agents which splik off hydrogen halide
for carrying out process variant (c) are any of the reagents
Le A 19 392
,, , . , , ~
: , ,
;
' , . ~ .
.: ~
.
..
. , ~ .
. .
5~ r~
customary for such reactions. These include inorganic
and organic bases, such as alkali metal hydroxides, carbon-
ates and bicarbonates, alkaline earth metal hydroxides,
carbonates and bicarbonates, aluminium oxides and organic
amines, especially tertiary amines, for example triethyl-
amine.
Possible diluents for process variant (c) are any of
the solvents customary for such dehydrohalogenation re-
actions.
Water, an amine (which simultaneously serves as an
agent which splits off hydrogen halide) or dioxan can
preferably be used.
The reaction temperatures can be varied within a
substantial range in process variant (c). The reaction
is in general carried out at temperatures of from 0C
to 150C~ preferably from 20C to 120C.
In carrying out process variant (c), 1-1.2 moles of
dehydrohalogenating agent are in general employed per
mole of 4,5-dichloroimidazole derivative of the formula
(IV). The reaction products are isolated by customary
methods. In general, a procedure is followed in which
the reaction mixture is acidified, water is added, if
appropriate, and the reaction product, which is obtained
as crystals, is then filtered off.
The 2,4,5-trichloro-2-(1,1-dichloroethyl)-2H-imidazole
of the formula (V) required as the starting material in
process variant (d) is known (see DE-OS (German Published
Specification) 2,550,157).
Possible reducing agents for process variant (d)(a) are
preferably hydrogen, activated by noble metals, for
example platinum or palladium, or reducing agents such as
hydrogen iodide or hydrogen bromide J if appropriate in
the presence of sulphur dioxide.
Various solvents can be used as diluents in process
variant (d)()~ depending on the reducing agent employed.
Le ~ 19 392
' ~ ' . '~ ' '
'
- 16 --
Thus, in the case of catalytic hydrogenation, aromatic
hydrocarbons, such as benzene, toluene and xylene, and
cyclic ethers, such as dioxan and tetrahydrofuran, are
generally employed as diluents. If the reaction is
carried out with a chemical compound, such as hydrogen
bromide or hydrogen iodide, preferred solvents are inert,
water-immiscible organic solvents, such as methylene
chloride, chloroform or toluene.
The reaction temperatures can be varied within a
certain range in process variant (d)(a). The reaction is
in general carried out at temperatures of from 0C to
50C, preferably from 10C to 30C.
In carrying out process variant (d)(), either an
excess of catalytically activated hydrogen or at least
2 moles of a chemical reducing agent, such as hydrogen
bromide or hydrogen iodide, are employed per mole of
2,4,5-trichloro-2-(1,1-dichloroethyl)-2H-imidazole of the
formula (V). Hydrogen bromide and hydrogen iodide can
preferably be employed in the form of their commercially
available concentrated aqueous solutions (azeotropes).
In this case, saturation of the reaction mixtures with
sulphur dioxide gas has a favourable effect on the yield
of end product.
The end product is isolated by customary methods.
In general, a procedure is followed in which the solvent
is first stripped o~f, the residue is suspended in water,
the suspension is then neutralised and the solid is
filtered off. The product can be purified by recry-
stallisation, for example from acetonitrile, or by
sublimation in vacuo.
Possible reactants in process variant (d)(~) are alkali
metal iodides and alkaline earth metal iodides. These
include) as preferences, sodium iodide, potassium iodide
and calcium iodide.
Diluents which can be used in process variant (d)(~)
Le A 19 392
'' ,:. . . ' " -
3-~
-- 17 -
are any of the customary lower aliphatic ketones. Pcetone
is particularly preferred.
The reaction temperatures can be varied within a
substantial range in process variant (d)(~). The reaction
is in general carried out at temperatures of from -20 to
+100C, preferably from 0C to 60C.
In carrying out process variant (d)(~), at least 3
moles of alkall metal iodide or at least 1.5 moles of
alkaline earth metal iodide are generally employed per
10 mole of 2,4,5-trichloro-2-(1,1-dichloroethyl)-2H-imidazole
of the formula (V). The sodium iodide/acetone system is
particularly preferred. In this case, sodium iodide can
be employed in a large excess without troublesome side
reactions proceeding. The reaction product is isolated
by customary methods. In general, a procedure is followed
in which the reaction mixture is poured into water, the
free iodine present is removed by adding a reducing agent,
such as aqueous sodium bisulphite solution, and the mixture
is then filtered.
Possible reactants in process variant (d)(~) are
alkali metal bromides and alkaline earth metal bromides.
These include, as preferences sodium bromide, potassium
bromide and calcium bromide. Potassium bromide is
particularly preferred.
Diluents which can be used for process variant (d)(y)
are any of the customary lower aliphatic nitriles and
lower aliphatic ketones. Acetonitrile and acetone are
particularly preferred.
The reaction temperatures can be varied within a
3 substantial range in process variant (d)(y). The reaction
is in general carried out at temperatures of from 50C to
150C, preferably from 70C to 120C.
In carrying out process variant (d) (r), at least 1 mole
of alkali metal bromide or at least 0.5 mole of alkaline
earth metal bromide is generally employed per mole of
Le A 19 ~2
,
.
3~
- 18 -
2,4,5-trichloro-2-(l,l-dichloroethyl)-2H-imidazole
of the formula (V). The potassium bromide/acetonitrile
and sodium bromide/acetone systems are particularly
preferred. In these cases, the alkali metal bromide is
preferably used in a 5-fold to lO-fold molar excess. The
reaction products are isolated by customary methods. In
general, a procedure is followed in which, after cooling,
the mixture is poured into water (5 to 10 times the amount),
the aqueous suspension is filtered and the residue is
washed with water and dried.
The formula (VI) provides a definition of the 4,5-
dichloroimidazole derivatives required as starting materials
in process variant (e). In this formula, Hal preferably
represents chlorine or iodine.
The compounds of ~he formula (VI) were hitherto
unknown. However, they can be prepared by process
variants (d)() and (d)(~).
Possible dehydrohalogenating agents for process variant
(e)() are any of the reagents that are customary for
such reactions. These include inorganic and organic bases,
such as alkal metal hydroxides, carbonates and bicarbonates,
alkaline earth metal hydroxides, carbonates and bicarbonates,
and organic amines, such as tertiary aliphatic amines, for
example triethylamine. Non-quaternisable aliphatic amines,
such as ethyl diisopropylamine ("H~nig base") are
particularly preferred.
Possible diluents for process variant (e)(~) are any
of the inert organic solvents. Ethers, such as diethyl
ether, dioxan or tetrahydrofuran, can preferably be
used. It is furthermore possible for an amine used for
splitting off a hydrogen halide to be simultaneously
utilised as the solvent. In addition, water can also
function as the diluent.
The reaction temperatures can be varied within a
substantial range in process variant (e) (a) . The reaction
~ .
Le A 19 392
, .,
r~
- 19 --
is in general carried out at temperatures of from 0C
to 100G, preferably from 10C and 50C.
In carrying out process variant (e)(~), 2 moles or a
larger excess of almost any desired size of dehydrohalo-
genating agent are in general employed per mole of a 4,5-
dichloroimidazole derivative Or the formula (VI). The
reaction product is isolated by customary methods. In
general, a procedure is followed in which the reaction
mixture is poured into water and acidified and the re-
action product, which is obtained as crystals, isfiltered off.
In carrying out process variant (e)(~), a 4,5-
dichloroimidazole derivative of the formula (VI) is hydro-
lysed with water. In this variant, the water simultaneously
functions as the reaction medium and is thus employed in
a large excess.
Acid-binding agents which can be used f`or process
variant (e)(~) are any of the customary bases or basic
salts. Alkali metal salts of lower aliphatic carboxylic
acids are preferred, sodium formate being mentioned in
particular.
The reaction temperatures can be varied within a
substantial range in process variant (e)(~). The reaction
is in general carried out at temperatures of from 0C to
25 150C, preferably from 10C to 120C.
In carrying out process variant (e)(~)~ a large excess
of water is employed per mole of 4,5-dichloroimidazole
derivative of the formula (VI), it being necessary to
remove the hydrogen halide acid, formed during the
hydrolysis, continuously from the reaction mixture in
order to achieve complete conversion. This can in principle
be effected by bringing the pH value from the strongly
acid range (pH 1-2) to the weakly acid to neutral range
(pH 5-7) by controlled addition of a total of one mol of
any desired customary base, with the proviso that pH 7 must
Le A 19 392
~3~5~S~
- 20 -
not be exceeded in any case, in order to avoid side
reactions In a preferred embodiment of process variant
(e)(~), the hydrolysis is carried out in the presence of
at least one mol of an alkali metal salt of a lower ali-
phatic carboxylic acid. Sodium formate, which can beemployed in any desired excess, can preferably be used in
this embodiment. The reaction product is isolated by
customary methods. In general, a procedure is followed
in which the aqueous phase is separated off under the
influence of heat and is allowed to cool and the reaction
product, which thereby separates out as crystals~ is
filtered off.
The formula (VII) provides a definition of the
4,5-dichloroimidazole derivatives required as starting
materials in process variant (f). In this formula, X3,
X4 and X5 preferably have those meanings which have
already been mentioned as preferred in connection with
the description of the compounds of the formula (I).
The compounds of the formula (VII) were hitherto
unknown. However, they can be prepared by process
variant (b)() or by process variant (e)(~). -
The formula (VIII) provides a general definition of
compounds also required as starting materials in process
variant (f). In this formula~ Y' preferably has those ~ -
meanings which have already been mentioned as preferred
for Y in connection with the description of the compounds
of the formula (I)~ but does not represent the radical of
the formula
N ~ Cl
-N = C ~ ~ 1
R Y ~ R4 H
R
Y' furthermore preferably represents amino.
~:'
Le A 19 392
7~r~3
- 21 -
The compounds of the formula (VIII) are known, or
they can be prepared by processes which are known in prin-
ciple.
Diluents which can be used in process variant (f) are
any of the customary inert organic solvents, as well as
water.
The reaction temperatures can be varied within a
substantial range in process variant (f). The reaction is
in general carried out at temperatures of from 20C to
120C, preferably from 80C to 110C.
In carrying out process variant (f), at least 1 mole
of a compound of the formula (VIII) is in general employed
per mole of 4,5-dichloroimidazole derivative of the
formula (VII). The reaction products are isolated by
customary methods. In general, a procedure is followed in
which, if water is used as the diluent, the precipitate
obtained, if necessary after prior acidification, is
filtered off. If an organic solvent is used, when the
reaction has ended, the mixture is concentrated, water is
added to the residue, the mixture is heated and the pro
cedure followed is then as described above.
The formula (IX) provides a definition of the 4,5-
dichloro-2-ethynylimidazole required as the starting
material in process variant (g). The substance was
hitherto unknown; however3 it can be prepared by process
variant (e).
Chlorinating and brominating agents which can be
employed in process variant (g) are any of the customary
reagents which can be used for such purposes. Chlorine,
sulphuryl chloride and bromine are preferably used.
Diluents which can be employed in process variant (g)
are any of the customary inert organic solvents. Chloro-
form, methylene chloride and carbon tetrachloride are
preferably used.
The reaction temperatures can be varied within a
~ . . ,
..
Le A 19 392
57~
- 22 -
certain range in process variant (g). The reaction is in
general carried out at temperatures of from 0C to 50C,
preferably from 10C to 30C.
In carrying out process variant tg), 4,5-dichloro-2-
ethynylimidazole of the formula (IX) is reacted withvarious amounts of chlorinating or brominating agent,
depending on the desired end product. If an end product
in which the side chain is saturated is to be prepared, at
least 2 moles of chlorinating or brominating agent are
employed per mole of 4~5-dichloro-2-ethynylimidazole of
the formula (IX). If only 1 mole of chlorinating or
brominating agent is used, compounds with an unsaturated
side chain are formed. ~he reaction products are isolated
by customary methods. In some cases~ the reaction product
i3 obtained directly in the crystalline form, so that it
can be filtered off.
The formula (X) provldes a definition of the 4,5-
dichloroimidazole derivatives required as starting materials
in process variant (h). In this formula, X1 preferably
represents hydrogen, chlorine, bromine or iodine. X3 and
X4 preferably have those meanings which have already been
mentioned as preferred for X3 and X4 in connection with
the description of the compounds of the formula (I).
The 4,5-dichloroimidazole derivatives of the formula
(X) were hitherto unknown. However, they can be prepared
by process variants according to the invention.
Chlorinating and brominatlng agents which can be
employed in process variant (h) are any of the customary
reagents which can be used for such purposes. Chlorine,
sulphuryl chloride and bromine are preferably used.
Diluents which can be employed in process variant (h)
are any of the customary inert organic solvents. Chloroform,
methylene chloride and carbon tetrachloride can preferably
be used.
The reaction temperatures can be varied within a
~
Le A 19 392
,
rj~Q r,~
- 23 -
certain ran~e in process variant (h). The reaction is
in general carried out at temperatures of from 0C to
50 C, preferably between 10C and 30C.
In carrying out process variant (h), 1 mole or even
an excess Or chlorinating or brominating agent is employed
per mole of 4,5-dichloroimidazole derivative of the formula
(X). Working up is effected by customary methods. In
general, a procedure is followed in which, if appropriate
after prior concentration, the reaction product obtained in
the crystalline form is filtered off.
The formula (XI) provides a definition of the 4,5-
dichloroimidazole derivatives required as starting
materials in process variant (i). In this formula, Hal'
preferably represents chlorine, bromine and iodine. x6
and X7 preferably represent chlorine or bromine.
The compounds of the formula (XI) were hitherto --
unknown. However, they can be prepared by process variants
according to the invention.
Possible solvents in process variant (i) are any of
the customary lower aliphatic nitriles. Acetonitrile is
preferably used.
The reaction temperatures can be varied within a
substantial range in process variant (i). The reaction is
in general carried out at temperatures of from 50C to
150 C, preferably from 60C to 100C.
In carrying out process variant (i), a compound of
the formula (XI) is heated in a lower aliphatic nitrile
~or some time. Thereafter, the mixture is worked up
by customary methods. In general, a procedure is followed
in which, after cooling, the reaction mixture is filtered,
water is then added to the product phase and the product,
which is obtained as crystals, is filtered off.
The active compounds according to the invention
influence plant growth and can therefore be used as
defoliants, desiccants, agents for destroying broad-
Le A 19 392
' ~
,:
. .
, ' ' ~' , .
,
~3~
- 24 -
leaved plants, germination inhibitors and, especially,
as weed-killers. By ~'weeds" in the broadest sense
there are meant plants growing in places where they
are not desired.
Whether the compounds according to the invention
act as total herbicides or selective herbicides depends
essentially on the amount used.
The ac~ive compounds according to the present
invention may be used, f~or example, to combat the
following plants:
dicotyledon weeds of the genera Sinapis, Lepidium,
Galium~ -Stellaria,' Matricaria,' Anthemi:, Ga'li'ns'o~_ ,
, IJrtica, Se'necio, Amaranthus, Portu'l'aca,
Xanthium, Convolvulus, Ipomoea, ~ , Sesbania,
Ambrosia, Cirsium, Carduus, Sonchus, Rorippa,-Rotala,
Lindernia, Lamium, Veronica, Abut lon, Emex,' Datura,
Viola, Galeo~sis, ~ , Centaurea and Solanum; and
monocotyledon weeds of the genera Echinochloa,
Setaria, Panicum, Digitaria, Phleum, Poa, Festuca,
' Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus,
Sorghum, Agropyron, Cynodon, MonochOria3 Fimbristylis,
Sagittaria, Eleocharis, Scirpus, Paspalum,- Is-chae~um,
Sphenoclea, Dactyloctenium, Agrostis, Alopecurus and
-- . .
Apera.
-
The active compounds according to the present
invention may be used, for example, as selective herbicides
in the following cultures:
dicotyledon cultures of the genera Gossypium,
Glycine, Beta, Daucus, Phaseolus, Pisum, Solanum, Linum,
3o Ipomoea, Vicia, ~icotiana,' ~ , Arachis,
~as~sica, La'ctuca, Cucu~is and Cucurbita; and
monocotyledon cultures of the genera 0ryza, Zea,
Triticum, Hordeum, Avena, Se-cale, Sorghum, Panicum,
Saccharum,'An'anas,' ~ and Allium.
However, the use of the active compounds according
to the invention is in no way restricted to these genera
, .
Le A 19 392
` .
,
'
- 25 -
but also embraces other plants, in the same way.
Depending on the concentrations, the compounds can
be used for the total combating of weeds, for example
on industrial terrain and railway tracks and on paths
and squares with or without trees. Equally, the compounds
can be employed for combating weeds in perennial cultures,
for example afforestations, decorative tree plantings,
orchards, vineyards, citrus groves, nut orchards, banana
plantations, coffee plantations, tea plantations, rubber
plantations, oil palm plantations, cacao plantations,
soft fruit plantings and hopfields, and for the selective
combating of weeds in annual cultures.
In addition to a powerful herbicidal action, the
substances according to the invention also exhibit a very
good selective herbicidal activity in various crops. The
active compounds according to the invention are thus
suitable, for example, for selectively combating weeds in
maize, cotton and cereals.
The active compounds can be converted into the cus-
tomary formulations, such as solutions, emulsions, suspen-
sions, powders, dusting agents, pastes, soluble powders,
granules, suspension-emulsion concentrates, natural and
synthetic materials impregnated with active compound, and
very fine capsules in polymeric substances.
These formulations may be produced in known manner, for
example by mixing the active compounds with extenders~
that is to say liquid or solid diluents or carriers, option-
ally with the use of surface-active agents,that is to
say emulsifying agents and/or dispersing agents and/or
foam-forming agents. In the case of the use of water
as an extender, organic solvents can, for example,
also be used as auxiliary solvents.
As liquid diluents or carriers, especially sulvents,
there are suitable in the main, aromatic hydrocarbons,
such as xylene, toluene or alkyl naphthalenes, chlorinated
,
Le A 19 392
,:
,
~ ~ 3~Ul~
- 26 -
aromatic or chlorinated aliphatic hydrocarbons, such
as chlorobenzenes, chloroethylenes or methylene chloride,
aliphatic or alicyclic hydrocarbons, such as cyclohexane
or paraffins, for example mineral oil fractions, alcohols,
such as butanol or glycol as well as their ethers and
esters, ketones, such as acetone, methyl ethyl ketone,
methyl isobutyl ketone or cyclohexanone, or strongly
polar solvents, such as dimethylformamide and dimethyl-
sulphoxide, as well as water.
As solid carriers there may be used ground natural
minerals, such as kaolins, clays, talc, chalk, quartz,
attapulgite, montmorillonite or diatomaceous earth, and
ground synthetic minerals, such as highly-dispersed
silicic acid, alumina and silicates. As solid carriers
for granules there may be used crushed and fractionated
natural rocks such as calcite, marble, pumice, sepiolite
and dolomite, as well as synthetic granules of inorganic
and organic meals, and granules of organic material
such as sawdust, coconut shells, maize cobs and tobacco
stalks.
As emulsifying and/or foam-forming agents there
may be used non-ionic and anionic emulsifiers, such
as polyoxyethylene-fatty acid esters, polyoxyethylene-
fatty alcohol ethers, for example alkylaryl polyglycol
ethers, alkyl sulphonates, alkyl sulphates, aryl sul-
phonates as well as albumin hydrolysis products. Dis-
persing agents include, for example, lignin sulphite
waste liquors and methylcellulose.
Adhesives such as carboxymethylcellulose and natural
and synthetic polymers in the form of powders, granules
or latices, such as gum arabic, polyvinyl alcohol and
polyvinyl acetate, can be used in the formulations.
It is possible to use colorants such as inorganic
pigments, for example iron oxide, titanium oxide and
Prussian Blue, and organic dyestuffs, such as alizarin
"~,'
Le A 19 392
,
7~3
,
- ~7 -
dyestuffs, azo dyestuf~s or metal phthalocyanine dyestuffs,
and trace nutrients, such as salts of iron, manganese,
boron, copper, cobalt, molybdenum and zinc.
The formulations in general contain from 0.1 to
95 per cent by weight of active compound, preferably
from 0.5 to 90 per cent by weight.
The active compounds according to the invention, as
such or in the form of thelr formulations, can also be used
for combating weeds as mixtures with othcr herbicides,
finished formulations or tank mixing being possible. Mix-
tures with other active compoundsJ such as fungicides,
insecticides, acaricides, nematicides, bird repellants,
growth factors 3 plant nutrients and agents which improve
soil structure, are also possible.
The active compounds can be used as such, in the
form of their formulations or in the use forms prepared
therefrom by ~urther dilution, such as ready-to-use solu-
tions, suspensions, emulsions~ powders, pastes and granules.
They may be used in the customary manner, for example by
watering, spraying, atomising or scattering.
The active compounds according to the invention can
be applied either before or after emergence of the plants.
They are preferably applied before emergence of the plants,
that is to say by the pre-emergence method. They can
also be incorporated into the soil before sowing.
The amount Or active compound used can vary within
a substantial range. It depends essentially on the nature
of the desired effect. In general~ the amounts used are
from 0.1 to lO kg of active compound per hectare, preferably
from 0.1 to 5 kg/ha.
The present invention also provides a herbicidal
composition containing as active ingredient a compound
of the present invention in admixture with a solid
diluent or carrier or in admixture with a liquid diluent
or carrier containing a surface-active agent.
Le A l9 392
~3~
- 28 -
The present invention also provides a method of
combating weeds which comprises applying to the weeds,
or to a habitat thereof, a compound of the present in
vention alone or in the form of a composition containing
as active ingredient a compound of the present invention
in admixture with a diluent or carrier.
The present invention further provides crops protected
from damage by weeds by being grown in areas in which
immediately prior to and/or during the time of the growing
a compound of the present invention was applied alone
or in admixture with a diluent or carrier.
It will be seen that the usual methods of providing
a harvested crop may be improved by the present invention.
The herbicidal activity of the compounds of this
invention is illustrated by the following biotest Examples.
In these Examples, the compounds according to the
present invention are each identified by the number (given
in brackets) of the corresponding preparative Example,
which will be found later in this specification.
The known comparison compound is identified as
follows:
C~N
(A)= ~ ~ 0
Cl N C-NH-C2H5
H
.
(4,5 Dichloroimidazole-2-carboxylic acid ethylamide)
Pre-emergence test
Solvent: 5 parts by weight of acetone
Emulsifier: 1 part by weight of alkylaryl polyglycol
ether
To produce a suitable preparation of active compound,
1 part by weight of active compound was mixed with the
Le A 19 392
: ~ .
Q~
- 29 -
stated amount of solvent) the stated amount of emulsifier
was added and the concentrate was diluted with water
to the desired concentration.
Seeds of the test plants were sown in normal soil
and, after 24 hours, watered with the preparation of
the active compound. It was expedient to keep constant
the amount of water per unit area. The concentration
of the active compound in the preparation was of no
importance, only the amount of active compound applied
per unit area being decisive. After three weeks, the
degree of damage to the plants was determined in % damage
in comparison to the development of the untreated control.
The figures denoted:
0% - no action (like untreated control)
100% - total destruction
In this test, active compounds (6), (9), (14), (18)
and (19) exhibited a better activity than comparison
substance (A).
Example B
Post-emergence Test
Solvent: 5 parts by weight of acetone
Emulsifier: 1 part by weight of alkylaryl polyglycol
ether
To produce a suitable preparation of active compound
1 part by weight of active compound was mixed with the
stated amount of solvent, the stated amount of emulsifier
was added and the concentrate was then diluted with
water to the desired concentration.
Test plants which had a height of 5-15 cm were
sprayed with the preparation of the active compound in
such a way as to apply the amounts of active compound
per unit area which were prescribed. The concentration
of the spray liquor was so chosen that the amounts of
active compound prescribed were applied in 2,000 1 of
water/ha. After three weeks, the degree of damage
Le A 19 392
3j 3r3
~ 30 ~
to the plants was rated in % damage in comparison to
the development of the untreated control. The figures
denoted: -
0% - no action (like untreated control)
100% - total destruction.
In this test, compounds (6), (9), (14) and (19)
exhibited a better activity than comparison substance (A).
Preparative Examples
Example 1
C~NlC2Cl5 (1~ .
(a) 480 g (5 mol) of 2-ethylimidazole were introduced,
whilst stirring and cooling, into 2 litres of phosphorus
oxychloride, which had been pre-cooled to 5C, and HCl gas
was then passed in between 20 and 40C until the exothermic
reaction had ended. The mixture was then heated to the
reflux temperature (about 107C) and 2,490 g (35 mol) of
chlorine gas were then passed in at this temperature in the
course of about 5 hours. After distilling off the phos-
phorus oxychloride under a water pump vacuum up to a
20 bath temperature of 100C, 1.75 litres of formic acid were
gradually stirred into the residue at room temperature.
The colourless, crystalline powder thereby formed was fil-
tered off and rinsed first with formic acid and then
thoroughly with water. After dryîng, 520 g (30.8% of
theory) of 4,5-dichloro-2-pentachloroethyl-imidazole of
melting point 232C (long thin needles when crystallised
from wash benzine or a little anhydrous acetonitrile) were
thus obtained.
IR (KBr): 1540, 1450, 1410, 1358, 1250, 1205, 1040, 780,
30 665 and 555 cm 1.
Le A 19 392
~31.3S ;7~r3
~ 31 -
(b) 125 g (1.3 mol) of 2-ethylimidazole were introduced,
whilst stirring and cooling, into 500 ml of POC13, which
had been pre-cooled to about 5C. The mixture was then
heated to the reflux temperature (about 107C) and 300 g
(4.22 mol) of chlorine were passed in at this temperature
in the course of 3 hours. The solvent was stripped off in
vacuo and the residue was stirred with 400 ml Or formic
acid at about 20C. The crystalline precipitate thereby
formed was isolated as under (a) and was likewise 415-
dichloro-2-pentachloroethyl-imidazole. Yield: 63 g,
corresponding to 38% of theory, relative to the chlorine
employed in less than the equivalent amount.
(c) 480 g (6.75 mol) of chlorine were passed into a
solution of 96 g (1.0 mol) of 2-ethylimidazole in 400 ml of
1,1,2,2-tetrachloroethane between 110 and 115C in the
course of 4.5 hours. The tetrachloroethane was then
stripped off under a water pump vacuum up to a bath
temperature of 100C. The cooled residue was stirred with
200 ml of pure formic acidg whereupon a colourless powder
precipitated, which, after filtering off~ washing with formic
acid and drying, gave 103 g (31.6% of theory) of 4,5-
dichloro-2-pentachloroethyl-imidazole9 which was identical
to the compound obtained under (a). In a repeat batch,
the pure compound was also obtained by being sublimed out
of the crude product at about 125C/O.Ol mm Hg.
Exam~e 2
Cl__~__ N
~ N ~ C12-CHC12 (2)
(a) 34 g (0.25 mol) of sulphuryl chloride were added
dropwise to a stirred mixture of 16.1 g (0.1 mol) of 4,5-
dichloro-2-ethynyl-imidazole (for the preparation, see
Example 13) and 100 ml of chloroform in the course of one
Le A 19 392
' . .
,t~r~
- 32 -
hour, whilst cooling at 15-20C. After subsequently
stirring the mixture for two hours, the solid was filtered
off and washed with a little chloroform. 4,5-Dichloro-
2--(1,1,2,2-tetrachloroethyl)-imidazole of melting point
180C was thus obtained.
IR (K3r): 1547, 1465, 1427, 1360, 1260, 1248, 1208, 1055,
1015, 830, 770, 740, 682, 596 and 555 cm 1
(b) 120 g (1.25 mol) of 2-ethylimidazole were introduced
into 500 ml of thionyl chloride, whilst stirring and
cooling. The mixture was then heated to the reflux
temperature (76C) and 530 g (7.5 mol) of chlorine were
passed in at this temperature in the course of 5 hours.
After distilling off the thionyl chloride under a water
pump vacuum up to a bath temperature of 100C, the residue
was stirred with about 300 ml of formic acid at room
temperature. The crystalline powder thereby formed was
filtered off, washed with formic acid and dried. 72 g
(19% of theory) of 4,5-dichloro-2-(1,1,2,2-tetrachloro-
ethyl)-imidazole, which was identical to the compound
obtained under (a), were thus obtained.
Example 3
Cl ~ ~
Cl/ N' ~C-CC13 (3)
H 0
A suspension of 68 g (0.2 mol) of 4,5-dichloro-2-
pentachloroethyl-imidazole in 1.2 litres of water was
heated to the boil and about 700 ml of water were boiled
off in the course of 2 hours. The solid was then fil-
tered off and dried. Yield: 46 g (81~ of theory) of
4,5-dichloro-2-trichloroacetyl-imidazole of melting point
lg9o~ ~
IR(K~r): 1700, 1525, 1410, 1270, 1200, 1090, 1050, 977,
845, 810, 754, 700, 660, 621, 609 and 527 cm 1.
Le A 19 392
- 33 -
~xample 4
Cl
N C-C~Cl (4)
H O 2
4,5-Dichloro-2-dichloro-acetyl-imidazole of melting
point 150C was obtained from 4,5-dichloro-2-(1,1,2,2-
tetrachloroethyl)-imidazole in a manner analogous to that
described in Example 3.
IR (KBr): 1692, 1535, 1423, 1412, 1190, 1075, 965, 808,
785, 758 and 608 cm 1.
Example 5
Cl N
Cl , ~ -C~2Cl (5)
4,5-Dichloro-2-chloroacetyl~imidazole of melting
point 182C (when recrystallised from a little acetonitrile)
was obtained ~rom 4,5-dlchloro-2-(1,1,2,2-tetrachloroethyl)-
imidazole (for the preparation, seeExample 21) in a manner
analogous to that described in Example 3.
IR(KBr): 1683, 1414, 1329, 1185, 1062, 1045, 945, 781 and
740 cm 1.
Example 6
C ~N ~C-C \ (6)
50 g (0.148 mol) of 4~5-dichloro-2-pentachloroethyl-
imidazole were introduced into a solution of 150 g (1 mol)
of sodium iodide in 900 ml of acetone at room temperature~
whilst stirring. After further stirring the mixture for
Le A 19 392
~. ' ., ,
, '
.
'
r~
~ 34 ~
one hour, about 500 ml of acetone were stripped off, and
2 litres of ~ater and an amount of 40% strength aqueous
NaHS03 solution such that the brown iodine colour disap-
peared completely were added to the resi~ue. The solid
was then filtered off, washed with water and dried.
Yield: 37 g (93.5% Or theory) of 4,5-dichloro-2-trichloro-
vinyl-imidazole of melting point 168C.
IR (KBr): 1590, 1542, 1458, 1405, 1265, 1061, 1042, 965,
958, 869, 770, 700 and 556 cm 1.
Example 7
Cl N
Cl ~N ~ CH2-CC13 (7)
506 g (1.5 mol) of 4,5-dichloro-2-pentachloroethyl-
imidazole were introduced into a solution of 285 g (7.5
mol) of sodium boranate in 1.3 litres of water in the course
15 f about 5 hours whilst stirring and cooling at 15-250C.
After subsequently stirring the mixture for three hours, it
was acidified to a pH of about 1 with hydrochloric acid,
whilst cooling. The precipitate was filtered off and then
boiled up with about 4 litres of water, whilst stirring,
filtered off at the boiling point and rinsed several times
with hot water (removal of boric acid). After drying, 377 g
(g3.5% of theory) of 4,5-dichloro-2 (2,2,2-trichloroethyl)-
imidazole of melting point 224C (decomposition) were thus
obtained.
25 I~ (KBr): 1557, 1425, 1370, 1248, 1222, 1194, 1045, 1035,
1011, 946, 840, 730, 709 and 558 cm 1.
Example 8
Cl FN, CH2-CHC12 (8)
Le A 19 392
:, .
,
,
.
.
3~ -
4,5-Dichloro-2-t2,2-dichloroethyl)-imidazole of
melting point 143C, (when recrystallised from cyclo-
hexane) was isolated from 4,5-dichloro-2-(1,1,2,2-tetra-
chloroethyl)-imidazole in a manner analogous to that
described in Example 7.
IR (KBr): 1577, 1560, 1435, 1410, 1215, 1038, 1015, 925,
810, 720, 688 and 648 cm 1.
Exam~le 9
Cl
CH=CCl 2 ( 9 )
10 (a) 4,5-Dichloro-2-(2,2,2-trichloroethyl)-imidazole
was introduced into excess saturated, aqueous sodium
bicarbonate solution and the mixture was heated to the
boil, whereupon a clear solution was formed. After cooling
the solution, it was acidified with dilute hydrochloric
acid and the precipitate which had separated out was filtered
ofr, washed with water and dried. 4,5-Dichloro-2-(2,2-
dichlorovinyl)-imidazole of melting point 134C was thus
obtained. The compound could be sublimed at 110C/0.01 mm
Hg.
20 IR (KBr): 1625, 1550, 1465, 1414, 1235, 1035, 920, 835, 675
and 539 cm 1.
(b) A mixture of 67 g (0.25 mol) of 4,5-dichloro-2-
(2,2,2-trichloroethyl)-imidazole, 200 ml of dioxan and
28 g (0.277 mol) of triethylamine was stirred under reflux
for one hour. After cooling, it was poured into 1 litre of
water, the mixture was acidified with hydrochloric acid and
the precipitate was filtered off, washed with water and
dried. Subsequent sublimation at 110C/0.01 mm Hg gave
47.5 g (82%) of 4,5-dichloro-2-(2,2-dichlorovinyl)-imida-
zole, which was identical to the compound obtained under(a)-
Le A 19 392
-- , . ~ , ..
- , : ' - : :
.. - ' ,
s~
- 36 -
Example 10
Cl`~r--N
~ Cl (10)
C ~ N C=CH
H 2
(a) 5 g of catalyst (5% strength palladium-on-charcoal)
were added to a solution of 50 g (0.186 mol) Or 2,4,5-tri-
chloro-2-(1,1-dichloroethyl)-2H-imidazole in 450 ml of
toluene in a glass autoclave and ~ydrogenation was carried
out at about 20C in the course of 5 hours. The reaction
mixture was concentrated to dryness on a rotary evaporator
in vacuo, the residue was suspended in water and the suspen-
sion was neutralised wi~h aqueous sodium bicarbonate solu-
tion. The solid was then filtered off, washed with
water and dried. Subsequent extraction with hot aceto-
nitrile gave, after cooling and, as appropriate, concen-
trating the filtered acetonitrile solution, 4J5-dichloro-2-
(l-chlorovinyl)-imidazole as co~lpact, colourless crystals
of melting point 210C (decomposition). The compound could
be sublimed at 100C/0.1 mm Hg.
(b) A mixture of 67 g (0.25 mol) of 2,4,5-trichloro-2-
(l,l-dichloroethyl)-2H-imidazole, 28.3 g (0.275 mol) of
sodium bromide and 350 ml of acetone was stirred under reflux
(58C) for 1 hour. After cooling, it was poured into 2
litres of water and the precipitate was filtered off,
washed with water and dried. 41 g (83% of theory) of 4,5-
dichloro-2-(1-chlorovinyl)-imidazole, which was identical to
the compound obtained under (a), were obtained.
IR (KBr): 1622, 1550, 1477, 1430, 1355, 1265, 1120, 1050,
1009J 883J 795 and 734 cm 1
Example 11
C1
r, ( 11 )
Cl - N C=CH2
H
Le A 19 392
A solution of 806 g (3 mol) of 2,4,5-trichloro-2-
(l,l-dichloroethyl)-2H-imidazole (for the preparation, see
DE-OS (German Published Specification) 2,550,157) in
1.5 litres of acetone was added dropwise to a stirred mix-
ture of 1,600 g (10.6 mol) of sodium iodide in 2 litres of
acetone at a maximum temperature of 50C in the course of
2 hours, whilst coolingn The mixture was then introduced
into a mixture of 12 litres of water and 1,600 g of 40%
strength aqueous NaHS03 solution and the solid was filtered
Off, washed with water and dried. Yield: 770 g (89% of
theory) of 4,5-dichloro~-3-(1-iodovinyl)-imidazole.
Decomposition point: about 215C.
Example 12
Cl~ N
~ ~ Cl (12)
Cl H
(a) A mixture of 400 g (3.36 mol) of potassium bromide,
135 g (0.5 mol) of 2,4,5-trichloro-2-(1,1-dichloroethyl)-2H-
imidazole and 1.5 litres of acetonitrile was stirred under
reflux (81C) for 10 hours. After cooling, it was added
to 7.5 litres of water and the precipitate was filtered
off, washed with water and dried. 121 g (87% of theory) of
4,5-dichloro-2-(1-chloro-2-bromovinyl)-imidazole were
obtained. Melting point: 190C (from toluene).
IR (KBr): 1585, 1540, 1465, 1402, 1370, 1260, 1205, 1050,
895, 870, 775, 740, 690, 622 and 540 cm 1.
(b) 3.58 g (0.01 mol) of the compound of the formula
Cl~ N
Cl ~ C-c~2Br (22)
Br
(for the preparation, see Example 22) were boiled in 30 ml
of acetonitrile for 5~inutes. After cooling, the mixture
Le A 19 392
,
-
.
- 3~ -
was added to 200 ml of water and the precipitate was
filtered off, washed with water and dried. 2.60 g (94%
of theory) of 4,5-dichloro-2-(1-chloro-2-bromovinyl)-
imidazole, which was identical to the compound obtained
5 under (a), were obtained.
Example 13
Cl
~ N ~ (13)
Cl/~`H C'C~
(a) 25 g (0.25 mol) of triethylamine were added to a
suspension of 28.9 g (0~1 mol) of 4,5-dichloro-2-(1-iodo-
vinyl)-imidazole in 50 ml of dioxan at room temperature,
a solution being formed on warming. After subsequently
stirring the solution for half an hour, it was poured into
1 litre of water, the mixture was rendered weakly acid with
dilute hydrochloric acid and the solid was filtered off,
washed with water and dried. Yield: 11.1 g (69% of
theory) of 4,5-dichloro-2-ethynylimidazole. Decomposition
point: about 185C. The compound could be sublimed at
100C/0.01 mm Hg.
(b) 32.3 g (0.25 mol) of ethyl-diisopropyl-amine
("H~ni~ base") were added to a solution of 28.9 g (0.1 mol)
of 4,5-dichloro-2-(1-iodovinyl)-imidazole in 150 ml of
dioxan at 20C. After subsequently stirring the mixture
for one hour, it was poured into 750 ml of water and rendered
weakly acid with dilute hydrochloric acid and the solid was
filtered off, washed with water and dried. Yield: 11.7 g
of 4,5-dichloro-2-ethynylimidazole. The filtrate was
concentrated to about one third în vacuo, after which a
further 4.3 g of 4,5-dichloro-2-ethynylimidazole could be
isolated. Total yield: 16.0 g (99% of theory).
3 IR (KBr): 3295, 2125, 1563, 1545, 1470, 1390, 1050, 1020,
875, 702,688 and 610 cm 1
Le A 19 392
,
,
- ~ ~3~7~3
- 39 -
Example 14
~ . .. _, ~
Cl
N
N~ - C-CH (14)
o
(a) 289 g (1 mol) of 4,5-dichloro-2-(1-iodovinyl)-
imidazole were added in portions to a stirred solution,
boiling under re~lux, of 136 g (2 mol) of sodium formate in
4 litres of water and the mixture was further heated under
reflux until the imidazole dissolved. The small amount of
dark oil at the bottom of the reaction flask was then
separated off whilst still at the boiling point and the
clear aqueous solution was allowed to cool. Light yellow
needles one centimetre in length separated out and were
filtered off cold, washed with a little cold water and
dried. Yield: 125 g (70% of theory) of 2-acetyl-4,5-
dichloroimidazole of melting point 162C.
(b) A repeat batch in which the mother liquor of the
batch described above was used instead of pure water gave an
approximately 80% yield of 2-acetyl-4,5-dichloroimidazole.
(c) When the procedure was analogous to (a), with the -
difference that instead of 4,5-dichloro-2-(1-iodovinyl)-
imidazole the appropriate molar amount of 4,5-dichloro-2-
(l-chlorovinyl)-imidazole was employed, 2-acetyl-4,5-
dichloroimidazole was likewise obtained in comparable
yields. -
IR (KBr): 1666, 1432, 1408, 1212, 1050, 993, 950, 785, 693,
619, 580, 552, 512 and 592 cm 1.
Exam~le 15
C~
~ N (15)
C ~ H ~ C~CH3
NOH
~i¢l
Le A 19 392
- . . .
- 40 -
4.60 g (0.055 mol) of sodium bicaroonate were added
in portions, initially at room temperature, to a mi%ture of
8.95 g (0.05 mol) of 2-acetyl-4,5-dichloroimidazole, 200 ml
of water and 6.95 g (0.1 mol) of hydroxylamine hydrochloride
and the mixture was then heated to the boil, whereupon a
clear solution was formed. The precipitate which ~ystal-
lised out on cooling was filtered off, washed with water and
dried. Yield: 8.7 g (97% of theory) of the oxime with
the above structural formula, of melting point 213 C
(decomposition).
Example 16
Cl\ Cl
cl r~ ~ ==N - N = C ~
8.95 g (0.1 mol) of 2-acetyl-4,5-dichloroimidazole
were dissolved in a mixture of 20 g of hydrazine hydrate and
200 ml of water and the solution was briefly heated to the
boil. After cooling, it was acidified with hydrochloric
acid~ whereupon a precipitate separated out. After
filtering off, washing with water and drying, the azine with
the above structural formula was obtained in virtually
quantitative yield. The decomposition point was above
290C
Example 17 Cl
Cl H C _ N-NH-c-NH2 (17)
S
17.9 g (0.1 mol) of 2-acetyl-4,5-dichloroimidazole
were dissolved in800 ml of water under the influence of
heat and a hot solution of 15 g (0.165 mol) of thiosemicar- -
bazide in 200 ml of water was added. After about half a
Le A 19 392
3~3~
- 41 -
minute, a colourless precipitate formed, which, after
cooling, was filtered off, washed with water and dried.
The thiosemicarbazine with the above structural formula and
with a melting point above 290C was thus obtained.
Example 18
C ~N ~ C _ N-NH ~ (18)
17.9 g (0.1 mol) of 2-acetyl-4,5-dichloroimidazole
were dissolved in 800 ml of water under the influence of heat,
14 g (0.13 mol) of phenylhydrazine were added and the mix-
ture was briefly heated to the boil. After cooling;j thesolid was filtered off, washed with water and dried. The
phenylhydrazone with the above structural formula, of
melting point 175C, was obtained in virtually quantitative
yield.
Example l9
4-Chlorophenylhydrazone with the structural formula
Cl ~ ~ C -N-NN ~ Cl (19)
was obtained in a manner analogous to that of Example 18.
Melting point: 240C (decomposition).
Example 20
~ ~ C-CUCl (20)
(a) 13.4 g (0.05 mol) of the compound of the formula
Le A 19 392
~ ~3~ 7.~
- 42 -
Cl ~
Cl ~ N ~ ,-CH2Cl (21)
Cl
(for the preparation, see Example 21) were boiled in 50 ml
of acetonitrile for 10 minutes. The precipitate which
crystallised out after cooling was filtered off, washed
with some cold acetonitrile and dried. It was then
stirred with water at about 20C, filtered off, washed
with water and dried. 4,5-Dichloro-2-(1,2 dichlorovinyl)-
imidazole of melting point 198C (when recrystallised from
a little toluene) was thus obtained.
10 IR (KBr): 1591, 1545, 1468, 1407, 1375, 1257, 1055, 916,
694, 632 and 548 cm 1
(b) 26.8 g (0.0772 mol) of the compound of the formula
C~
~ I Cl Br
C ~ N ~ _ CH (23)
Cl Cl
(for the preparation see Example 23) were added to a solu- -
15 tion of 50 g (0.33 mol) of sodium iodide in 150 ml of
acetone and the mixture was then subsequently stirred at
room temperature for 2 hours. Thereafter it was poured
into about 1.5 litres of water and the free iodine was
removed by adding 40% strength aqueous NaHS0~ solution
20 until decoloration took place. 17.1 g (95.5% of theory) of
435-dichloro-2-(1,2-dichlorovinyl)-imidazole, which was
identical to the compound obtained under (a), were obtained
by subsequent filtration3 washing with water and drying.
(c) A mixture of 6.75 g (0.05 mol) of sulphuryl chloride
and 50 ml of chloroform was added dropwise to a solution of
8.05 g (0.05 mol) of the compound of the formula
Le A 19 392
, ~ ,
` ~ ~ 3
- 43 -
~ (13)
(for the preparation, see Example 13) in 50 ml of chloro-
form at 10-15C in the course of one hour. The mixture was
then subsequently stirrecl for 2 hours. Thereafter, the
chloroform was stirpped off in vacuo and the residue was
stirred with about 100 ml of water at 20C, ~iltered off,
rinsed with water and dried. The crude product was then
sublimed at 100C/0.01 mm Hg ~or the purpose of puri-
fication. Colourless crystals of 4,5-dichloro-2-(1,2-
dichlorovinyl)-imidazole~ which was identical to the
compound obtained under ~a), were obtained.
Example 21 C
l~l
Cl -CH2Cl (21)
H
15.0 g (0.11 mol) of` sulphuryl chloride in about
40 ml of pure chloroform were added dropwise to a stirred
mixture of` 19.75 g (0.1 mol) of 475-dichloro-2-(l-chloro-
vinyl)-imidazole and 100 ml of pure chloroform in the course
of 2 hours, whilst cooling at about 10C. The mixture
was then subsequently stirred at room temperature for about
3 hours. Thereafter, the solid was filtered off, washed
with chloroform and dried. 19.5 g (72.5% of theory) of
colourless, crystalline 4,5-dichloro-2~ 1,2-trichloro-
ethyl)-imidazole of melting point 140C (decomposition) were
obtained. Further amounts of the product could be obtained
by concentrating the mother liquor.
IR (KBr): 1545J 1465, 1420, 1360, 1254, 1215, 1185, 1075,
1040, 1010, 950, 812, 760, 7353 688 and 590 cm 1
Exam~le 22 C
~ ~ Cl
Clf~N C-CH2Br
~r (22)
~, .
Le A 19 392
7~3
- 4~ -
18.0 g (0.112 mol) of bromine in 50 ml of pure
chloroform were added dropwise to a stirred mixture of
19.75 g (0.1 mol) of 4,5-dichloro-2-(1-chlorovinyl)-
imidazole and 100 ml of pure chloroform in the course of
one hour, whilst cooling at about 10C. After subsequently
stirring the mixture at room temperature for four hours,
it was filtered off, washed with chloroform and dried. 32.0 g
(89.5% of theory) of crystalline 4,5-dichloro-2-(1-chloro-
1,2-dibromoethyl)-imidazole of melting point 160C (decom-
position) were obtained.IR (KBr): 1542, 1462, 1417, 13573 1253, 1219, 1168, 1072,
1040, 1004, 918, 795, 760, 6803 647, 618 and 575 cm 1.
Example 23
Cl
~ ~ Cl Br
C~ N C -CH (23)
~1 Cl
4,5-Dichloro-2-(1,1,2-trichloro-2-bromoethyl)-imidazole
of melting point 180C ~decomposition) (when recrystallised ~ -
from toluene) were obtained from 4,5-dichloro-2-(1-chloro-
2-bromovinyl)-imidazole in a manner similar to that of
Example 21.
IR (KBr): 1545, 1462, 1425, 1357, 1257, 1208, 1170, 1050,
1011, 825, 809, 767, 680 and 655 cm 1
Example 24
Cjl
~ ~ C1 Br
Cr~~H C - CH (24)
Br sx
4,5-Dichloro-2-(1-chloro-1,2,2-tribromoethyl)-imidazole
was obtained from 4,5-dichloro-2-(1-chloro-2-bromovinyl)-
imidazole in 91.5% yield in a manner similar to that of
Example 22.
IR (KBr)i 1540, 1455, 1415~ 1350, 1253, 1204, 1034 and
1005 cm
Le A 19 392
' . ' ' .
~3 .~ 3 3
.
- 45 -
Example 25
C~
~1¦ Cl Cl
Cl ~ H ~ C - CH (25)
sr Br
4,5-Dichloro-2-(1,2-dichloro-1,2-dibromoethyl)-
imidazole of melting point 150C (decomposition) was
obtained from 4,5-dichloro-2-(1,2-dichlorovinyl)-imidazole -
in a manner similar to that of Example 22.
IR (KBr): 1540, 1454, 1415, 1350, 1252, 1230, 1203, 1165,
1135, 1043 and 1005 cm 1
Example 26
C ~ C'H-CCl3 (26)
6 g (0.044 mol) of sulphuryl chloride in 30 ml of
chloroform were added dropwise to a stirred mixture of 5.9 g
(0.0255 mol) of 4,5-dichloro-2-(2,2-dichlorovinyl)-lmidazole
and 50 ml of pure chloroform in the course of half an hour,
whilst cooling at about 10C. After subsequently stirring
the mixture for two hours, the clear solution was concen-
trated to dryness on a rotary evaporator in vacuo. The
residue was recrystallised from acetonitrile. Colourless
crystals of 495-dichloro-2~ 2,2,2-tetrachloroethyl)-
imidazole of melting point 230C (decomposition) wereobtained.
IR (KBr): 1540, 1463, 1449~ 1420, 1391, 1305, 1260, 1237,
1037, 782, 759, 699, 684 and 625 cm 1
Example 27
C ~ ~ -CH2-Hr (27)
H 0
Le A 19 392
,
~.~3~
.
- 46 -
1.79 g (0.005 mol) of 4,5-dichloro-2-(1-chloro-1,2-
dlbromoethyl)-imidazole (for the preparation, see Example
22) were stirred in a solution of 3.4 g (0.05 mol) of sodium
formate in 50 ml of water at room temperature for 10 minutes.
5 The solid was then filtered off, washed with water and
dried. 1.20 g (93% of thery) of 4,5-dichloro-2-~romo-
acetylimidazole were thus obtained. After recrystallising
from cyclohexane, the compound melted at 177C.
IR (KBr): 1676, 1421, 1408, 1372, 1177, 1063, 1049, 949,
10 767 and 669 cm 1.
The following compounds were prepared according to
processes, which are desc:ribed in the preceding Examples:
Le A 19 392
,, : : ,. . . .
.
' ~
-
'
.
S70~
- 47 -
Starting
Melting point(C) material Preparation
Example (recrystallized disclosed according
No. Conç~ d _from) in Example to Example
28 C ~ N ~ C-C~rCl (cyclohexane) 25 27
H 0
C ~ N ~ CBr2-CHBr (decomposition) 13 22
C ~ ~ -Ch3r2 (cyclohexene) 29 27
5 31 C ~ ~ Br-CHBr (cyclohexane) 29 6
H
C ~ 220
C ~ N ~ r-cBrcl~ (decomposition) 9~ 22
H (CC14)
33 C ~ N ~ -CHCl (tolu~ne) a 9
.,, i
Le A 19 392
