DESCRIPTION
PROCESS FOR PRODUCING AN INTERMEDIATE FOR A CYCLIC
CARBODIIMIDE COMPOUND
TECHNICAL FIELD
The present invention relates to a process for
producing an amine compound or a thiourea compound which is
useful as an intermediate for a cyclic carbodiimide compound.
10
BACKGROUND ART
Since the hydrolysis of a compound having an ester bond
such as a polyester is promoted by a polar group such as a
carboxyl group, it is proposed to reduce the concentration
15 of the carboxyl group by using a sealing agent for a carboxyl
group (Paten Document 1, Patent Document 2). A carbodiimide
compound is used as the sealing agent for a carboxyl group.
However, since this carbodiimide compound is a linear
compound, a volatile isocyanate compound is by-produced
20 during use and generates a bad odor, thereby deteriorating
work environment.
Then, the inventors of the present invention found as.
the sealing agent a cyclic carbodiimide compound which does'
not by-produce an isocyanate compound when it reacts with
25 a carboxyl group and filed an international application
(Patent Document 3). However, industrial processes for
producing this useful cyclic carbodiimide compound and an
intermediate therefor have not been established.
(Patent Document 1) JP`-A 2004-332166
30 (Patent Document 2)y JP-A 2005-350829
(Patent Document 3) PCT/JP2009/071190
DISCLOSURE OF THE INVENTION
2
It is an object of the present invention to improve
the reaction yield of an amine compound represented by the
following formula (B) when it is synthesized by reducing a
nitro compound represented by the following formula (A) in
5 the presence of a metal catalyst.
The inventors of the present invention investigated
means of improving the reaction yield of the amine compound
represented by the following formula (B) when it is
synthesized by reducing the nitro compound represented by
10 the following formula (A) in the presence of a metal catalyst.
As a result, they found that the nitro compound
represented by the following formula (A) which is a raw
material for the production of the amine compound contains
a compound having a haloarene skeleton as an impurity derived
15 from its production process and that the yield of the amine
compound is reduced by this compound having a haloarene
skeleton. They also found that the yield is remarkably
improved when a basic compound capable of capturing a
dehalogenating component such as hydrogen halide is existent
20 during a reaction. The present invention was accomplished
based on these findings.
When the dehalogenating component is existent in the
reaction system as it is, the decomposition of the nitro'
compound and the amine compound is promoted with the result
25 that the yield of the amine compound drops. However, when
the basic compound is existent, the dehalogenating component
is captured and there exists no free dehalogenating component
in the reaction system, thereby making it possible to greatly
suppress the decomposition of the nitro compound and the
30 amine compound.
It is another object of the present invention to provide
a process for producing a thiourea compound represented by
the following formula (C) from the obtained amine compound
3
represented by the formula (B)
The inventors found that the yield of the thiourea
compound represented by the formula (C) is remarkably
improved by making imidazole existent when it is synthesized
5 by reacting the amine compound represented by the formula
(B) with carbon disulfide. The present invention was
accomplished based on this finding.
That is, the present invention includes the following
inventions.
10 1. A process for producing an amine compound represented
by the following formula (B), comprising the step of reducing
a nitro compound represented by the following formula (A)
and containing a compound having a haloarene skeleton in the
presence of a metal catalyst and a basic compound.
15
(A)
(R is a hydrogen atom or an alkyl group having 1 to 6 carbon
atoms.)
20 (B)
(R is as defined in the above formula (A).)
4
2. The production process in the above paragraph 1,
wherein the metal catalyst is at least one selected from the
group consisting of palladium, ruthenium, platinum, rhodium,
nickel, copper, metal oxides thereof, metal hydroxides
5 thereof and metal-supported catalysts obtained by
precipitating any one of them on a carrier selected from
activated carbon, alumina, titania and silica.
3. The production process in the above paragraph 1,
wherein the basic compound is triethylamine.
10 4. A process for producing a thiourea compound
represented by the following formula (C), comprising the step
of reacting the amine compound represented by the formula
(B) and obtained by the process in the above paragraph 1 with
carbon disulfide in the presence of imidazole.
15 S (C)
20
(R is a hydrogen atom or an alkyl group having 1 to 6 carbon
atoms.)
5. The production process in the above paragraph 4,
wherein methyl ethyl ketone is used as a reaction solvent.
BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is a process for producing an
amine compound represented by the following formula (B),
25 comprising the step of reducing a nitro compound represented
5
by the following formula (A) and containing a compound having
a haloarene skeleton in the presence of a metal catalyst and
a basic compound.
5 (Nitro compound)
The nitro compound is represented by the following
formula (A)
(A)
In the above formula (A), R is a hydrogen atom or an
10 alkyl group having 1 to 6 carbon atoms. Examples of the alkyl
group having 1 to 6 carbon atoms include methyl group, ethyl
group, n-propyl group, sec-propyl group, iso-propyl group,
n-butyl group, tert-butyl group, sec-butyl group, iso-butyl
group, n-pentyl group, sec-pentyl group, iso-pentyl group,,
15 n-hexyl group, sec-hexyl group and iso-hexyl group.
The compound having a haloarene skeleton is a
monocyclic or polycyclic aromatic hydrocarbon compound
having at least one halogen atom. Examples of the monocyclic
aromatic hydrocarbon compound include halogenated benzene
20 and halogenated nitrobenzene. Examples of the polycyclic
aromatic hydrocarbon compound include halogenated
naphthalene and halogenated nitronaphthalene.
Since o-halogenated nitrobenzene such as
o-chloronitrobenzene is used as a raw material to synthesize
25 the nitro compound (A) at low cost, a compound similar to
the nitro compound (A) and containing a halogen component
6
or a halogenated aromatic hydrocarbon compound such as
o-halogenated nitrobenzene is often contained in the nitro
compound.
Although the effect of the present invention is
5 confirmed without limiting the content of the compound having
a haloarene skeleton in the nitro compound (A), from the
viewpoint of the production cost of the amine compound, the
content of the above compound is preferably 0.001 to 0.5
equivalent, more preferably 0.001 to 0.1 equivalent based
10 on 1 equivalent of the nitro compound.
(Amine compound)
The amine compound obtained by the production process
of the present invention is represented by the following
15 formula (B)
(B)
In the °above formula (B), R is as defined in the above formula
(A).
20 (Reaction)
The reaction is a;reduction reaction of the nitro
compound (A) by contacting a hydrogen gas in a solvent in
the presence of "a metal catalyst and a basic compound.
The reaction temperature is selected from a range from
25 25°C to 150°C. When the reaction temperature is lower than
7
25°C, reactivity becomes unsatisfactory and the reaction may
take a long time. When the reaction temperature is higher
than 150°C, a side reaction different from the intended
reaction such as a decomposition reaction may occur. From
5 this point of view, the reaction temperature is preferably
50 to 120°C, more preferably 70 to 100°C.
Although the reaction proceeds at normal pressure, to
promote the reaction, pressure is preferably applied. The
pressure is selected from a range of 0.2 MPa or more. When
10 the pressure is lower than 0.2 MPa, an effect may not be
obtained from the application of pressure. From the
viewpoint of equipment, the pressure is preferably in the
range of 0.5 to 1.0 MPa.
The metal catalyst is preferably at least one selected
15 from the group consisting of palladium, ruthenium, platinum,
rhodium, nickel, copper, metal oxides thereof, metal
hydroxides thereof and metal-supported catalysts obtained
by precipitating any one of them on a carrier selected from
activated carbon, alumina, titania and silica. Specific
20 examples thereof include palladium carbon, palladium.,,
carbon-ethylenediamine complex, palladium-fibroin,
palladium-polyethyleneimine, rhodium carbon, platinum
oxide, nickel and copper. Activated carbon is preferably
used as the carrier from the viewpoint of cost. The amount
25 of the metal catalyst may be suitably set based on the weight
of the nitro compound (A) to ensure that the reaction proceeds.
When the amount of the metal 'catalyst is 0.05 wto or more,
the reaction fully proceeds. There is no upper limit but
it may be 5 wto or less from the viewpoint of balance with
30 cost.
Examples of the basic compound include inorganic bases
such as sodium carbonate, potassium carbonate and sodium
hydrogen carbonate, and organic bases such as triethylamine,
8
pyridine and imidazole. Triethylamine is particularly
preferred from the viewpoints of cost and handling ease. The
amount of the basic compound is 1 equivalent or more based
on halogen equivalent contained in the nitro compound (A)
5 When the amount of the basic compound is smaller than 1
equivalent, satisfactory capturing ability is not obtained
and the purity of the amine compound (B) may lower. Although
there is no upper limit, the amount of the basic compound
is preferably 1 to 5 equivalents, more preferably 1 to 3
10 equivalents from the viewpoint of balance with cost.
Examples of the solvent include methanol, ethanol,
isopropyl alcohol, dioxane, tetrahydrofuran, ethyl acetate,
dichloromethane, chloroform, N,N-dimethylformamide, methyl
ethyl ketone, acetone, toluene, acetonitrile and mixed
15 solvents thereof.
A pressure reactor having stirring and heating
functions is used as equipment.
20
25
30

The present invention includes a process for producing
a thiourea compound represented by the following formula (C),
comprising the step of reacting the amine compound
represented by the formula (B) and obtained by the above
process with carbon disulfide in the presence of imidazole.
(Amine compound)
As described above, the amine compound can be produced
by reducing a nitro compound represented by the formula (A)
in the presence of a metal catalyst and a basic compound.
(Thiourea compound)
The thiourea compound obtained by the production
process of the present invention is represented by the
9
following formula (C)
(C)
In the formula (C), R is a hydrogen atom or an alkyl
group having 1 to 6 carbon atoms.
5
(Reaction)
The reaction is a reaction of the amine compound (B)
in a solvent in the presence of carbon disulfide and imidazole.
The weight ratio of the amine compound (B) and carbon
10 disulfide may be suitably set to ensure that the reaction
proceeds. When 2 equivalents or more of carbon disulfide
is used based on 1 equivalent of the amine compound (A), the
reaction fully proceeds. There is no upper limit but it may
be 10 equivalents or less from the viewpoint of balance with
15 cost. The weight ratio of the amine compound and imidazole
may be also suitably set to ensure that the reaction proceeds,
When 2 equivalents or more of imidazole is used based on 1
equivalent of the amine compound (B), the reaction fully
proceeds. There is no upper limit but it may be 10
20 equivalents or less from1the viewpoint of balance witl_i cost.
The reaction temperature is selected from a range from
25°C to 150°C. When the reaction temperature is lower than
25°C, reactivity becomes low and a satisfactory yield may
not be obtained. When the reaction temperature is higher
10
than 150°C, a side reaction different from the intended
reaction such as a decomposition reaction may occur. From
this point of view, the reaction temperature is preferably
50 to 100°C, more preferably 70 to 90°C. Although the
5 reaction fully proceeds at normal pressure, it may be carried
out under an increased pressure.
Examples of the solvent include methanol, ethanol,
isopropyl alcohol, dioxane, tetrahydrofuran, ethyl acetate,
dichloromethane, chloroform, N,N-dimethylformamide, methyl
10 ethyl ketone, acetone, toluene and acetonitrile. Although
the reaction may be carried out in any one of the above
solvents, methyl ethyl ketone is preferably used from the
viewpoints of the yield and purity of the obtained thiourea
compound.
15 A reactor having stirring and heating functions which
is combined with an apparatus for collecting hydrogen sulfide
produced during the reaction is used as equipment.
Examples
20
1. The following examples are given to further illustrate
the process for producing an amine compound. Physical
properties were measured by the following methods.
(1) Identification of amine compound by NMR:
25 The synthesized amine compound was confirmed by 1H-NMR
and 13C-NMR. JNR-EX270 of JEOL Ltd. was used for NMR. Heavy
chloroform was used as a solvent. The purity of the amine
compound was obtained from,an integral value of 'H-NMR.
(2) Yield of amine compound:
30 The yield of the synthesized amine compound was
obtained from the following equation by measuring the dry
weight of the amine compound identified by NMR.
Yield of amine compound [%] = (dry weight of amine
11
compound/molecular weight of amine compound) /number of moles
of nitro compound) x 100 x purity of amine compound [%]
Example 1 synthesis of amine compound Al
5 Ni . . . compound of the formula (A) in which R=H
Al . . . compound of the formula (B) in which R=H
A nitro compound Ni (0.1 mol) represented by the
following formula and containing o-chloronitrobenzene (0.01
mol), 5 % palladium carbon (Pd/C) (1.24 g), 62 ml of
10 N,N-dimethylformamide and triethylamine (0.025 mol) were
charged into an autoclave reactor having a stirring function,
the inside of the autoclave reactor was substituted by
nitrogen 3 times, and a reaction was carried out under
agitation while 0.8 MPa hydrogen'was always supplied at 90°C
15 and terminated when the amount of hydrogen did not decrease
any more.
The reaction solution from which Pd/C had been separated was
added to 30 % (v/v) methanol water in a weight ratio of 1:3
20 to be crystallized, and then the resulting product was
collected by filtration to obtain a solid product. It was
confirmed by NMR that the solid product was an amine compound
Al represented by the following formula.
12
The yield of the amine compound Al was 95.1. The
amine compound Al was creamy white.
5 Comparative Example 1 synthesis of amine compound Al
A nitro compound Nl (0.1 mol) represented by the
following formula and containing o-chloronitrobenzene (0.01
mol), 5 % palladium carbon (Pd/C) (1.24 g) and 62 ml of
N,N-dimethylformamide were charged into an autoclave reactor
10 having a stirring function, the inside of the autoclave
reactor was substituted by nitrogen 3 times, and a reaction
was carried out under agitation while 0.8 MPa hydrogen was
always supplied at 90°C and terminated when the -mount of
hydrogen did not decrease any more.
NO2 O2N
15
The reaction solution from which Pd/C had been separated was
13
added to 30 % (v/v) methanol water in a weight ratio of 1:3
to be crystallized, and then the resulting product was
collected by filtration to obtain a solid product. It was
confirmed by NMR that the solid product was an amine compound
5 Al represented by the following formula.
The yield of the amine compound Al was 75.9 The
amine compound Al was reddish brown.
10
The following examples are given to further illustrate
the production of a thiourea compound. Physical properties
were measured by the following methods.
15 (1) Identification of thiourea compound by NMR:
The synthesized thiourea compound was confirmed by
1H-NMR and 13C-NMR. JNR-EX270 of JEOL Ltd. was used for NMR.
20
Heavy dimethyl sulfoxide was'used as a solvent.
(2) Yield of thiourea compound:
The yield of the synthesized thiourea compound was
obtained from the following equation by measuring the dry
weight of the thiourea compound identified by NMR.
Yield of thiourea compound [%] = (dry weight of thiourea
compound/molecular weight of thiourea compound)/number of
14
moles of amine compound) x 100 [%]
Example 2 synthesis of thiourea compound Ti
Al . . . compound of formula (A) in which R=H
5 Ti . . . compound of formula (B) in which R=H
An amine compound Al (0.025 mol) represented by the
following formula, imidazole (0.15 mol), carbon disulfide
(0.15 mol) and 60 ml of methyl ethyl ketone were charged into
a reactor having a stirrer,, a heater and a wafter containing
10 alkaline water in an N2 atmosphere.
NH2 H2N
The reaction solution was heated at 80°C to be reacted for
15 hours. A solid precipitated after the reaction was
collected by filtration and washed with acetone to obtain
15 a product. It was confirmed by NMR that the product was a
thiourea compound Ti represented by the following formula.
15
The yield of the thiourea compound Ti was 89.4 %.
Comparative Example 2 synthesis of thiourea compound Ti
5 An amine compound Al (0.025 mol) represented by the
following formula, triethylamine (0.2 mol), carbon disulfide
(0. 2 mol) and 60 ml of methyl ethyl ketone were charged into
a reactor equipped with a stirrer, a heater and a waiter
containing alkaline water in an N2 atmosphere. The reaction
10 solution was heated at 80°C to be reacted for 15 hours. A
solid precipitated after the reaction was collected by
filtration and washed with acetone to obtain a product. It
was confirmed by NMR that the product was a thiourea compound
Ti represented by the following formula.
15
16
The yield of the thiourea compound Ti was 66.1 %.
5 Effect of the Invention
According to the production process of the present
invention, a specific amine compound which is useful as an
intermediate for a cyclic carbodiimide compound can be
produced at a high yield. That is, according; to the
10 production process of the present invention, an amine
compound (B) can be produced from a nitro compound (A),
containing a compound having a haloarene skeleton at a high
yield. Particularly, an amine compound (B) can be produced
from a nitro compound (A) containing a halogenated aromatic`
15 compound having a plurality of halogenated aromatic rings
at a high yield.
According to the production process of the present
invention, a thiourea compound represented by the formula
(C) which is useful as an intermediate for a cyclic
20 carbodiimide compound can be produced at a high yield.
Industrial Applicability
The amine compound and the thiourea compound obtained
by the production processes of the present invention are
17
useful as intermediates for a cyclic carbodiimide compound
which is useful as a sealing agent for polyesters.
18
CLAIMS
1. A process for producing an amine compound represented
by the following formula (B) , comprising the step of reducing
a nitro compound represented by the following formula (A)
5 and containing a compound having a haloarene skeleton in the
presence of a metal catalyst and a basic compound.
(A)
(R is a hydrogen atom or an alkyl group having 1 to 6 carbon
atoms.)
H2N
10 (B)
(R is as defined in the above formula (A).)
2. The production process according to claim 1, wherein
the metal catalyst is at least one selected from the groupy
15 consisting of palladium, ruthenium, platinum, rhodium,
nickel, copper, metal oxides thereof, metal hydroxides
thereof and metal-supported catalysts obtained by
precipitating any one- of them on a carrier selected from
activated carbon, alumina, titania and silica.
20
3. The production process according to 1, wherein the
19
basic compound'is triethylamine.
4. A process for-producing a thiourea compound
represented by the following formula (C) , comprising the step
of reacting the amine compound represented by the formula
(B) and obtained by the process of claim 1 with carbon
disulfide in the presence of imidazole.
(C)
(R is a hydrogen atom or an alkyl group having 1 to 6 carbon
10 atoms.)
5. The production process according to claim 4, whereir`i
methyl ethyl ketone is used as a reaction solverrL.