Process for producing 1, 3-dialkyl-2-imidazolidinone

An improved process of producing 1, 3-dialkyl-2-imidazolidinones directly from N, N'-dialkylethylenediamine and urea with a high yield is provided, which process comprises reacting a N, N'-dialkylethylenediamine of the formula ##STR1## wherein R represents --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7 or --C.sub.4 H.sub.9, with urea at 180.degree. C. or higher in the presence of a polar solvent, to obtain a 1, 3-dialkyl-2-imidazolidinone of the formula ##STR2## and preferably comprises carrying out the reaction at two stages, that is, the initial period reaction being carried out at 140.degree. C. or lower to from a 1, 1'-dialkyl-1 1'-dimethylenebisurea and successively the latter reaction being carried out at 180.degree. C. or higher.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for producing a 
1,3-dialkyl-2-imidazolidinone expressed by the formula (2) 
##STR3## 
wherein R represents --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7 or 
--C.sub.4 H.sub.9, by reacting a N,N'-dialkylethylenediamine expressed by 
the formula (1) 
##STR4## 
wherein R is as defined above, with urea. 
1,3-Dialkyl-2-imidazolidinones expressed by the formula (2) such as 
1,3-dimethyl-2-imidazolidinone are very useful substances as a polar, 
non-protonic solvent. In particular, they are an excellent solvent for 
various high molecular substances such as polyamides, polyvinyl chloride, 
polyvinyl alcohol, polystyrene, polyurethane, phenolic resins, etc. 
Further, they are a useful substance which forms a complex with many 
inorganic salts and dissolves, and also is used as a solvent for many 
organic reactions. 
2. Description of the Prior Art 
Among 1,3-dialkyl-2-imidazolidinones, 1,3-dimethyl-2-imidazolidinone 
(hereinafter abbreviated to DMI) is a generally well known compound, and 
as to the process for producing it, various proposals have been made. 
For example, a process wherein ethylenediamine is reacted with urea to 
obtain 2-imidazolidinone (ethylene-urea) which is subjected to addition 
reaction to formalin, followed by reducing the resulting reaction product 
with trichloroacetic acid, formic acid or the like, into the corresponding 
N,N'-dimethyl compound; a process having improved the above reduction 
process wherein hydrogenation is carried out using a noble metal catalyst 
in an acidic state; a process wherein N,N'-dimethylethylenediamine is 
reacted with phosgene or trichloromethyl chloroformate while it is 
decomposed into phosgene, etc. have been known. Further, a report has been 
made that N,N'-dimethylethyleneamine is reacted on heating with urea to 
form 1,1'-dimethyl-1,1'-dimethylenebisurea 
##STR5## 
as an intermediate, which is then heated to above 300.degree. C. to obtain 
DMI with a yield of 35% (Journal of the Chemical Society (Perkin Trans.) 
2, (1981), 317-319). 
As described, the process for producing 2-imidazolidinone by reacting 
ethylenediamine with urea has so far been industrially possible, but it is 
not easy to dialkylate the above 2-imidazolidinone into 
1,3-dialkyl-2-imidazolidinone. Further, in the case of production of DMI 
by reacting N,N'-dimethylethylenediamine with urea, the yield is so low as 
described in the above literature that the process has been commercially 
unsatisfactory at all. 
Thus if the objective compound can be produced directly from 
N,N'-dialkylethyleneamine and urea with a good yield, such a process is a 
very simple one. 
SUMMARY OF THE INVENTION 
A first object of the present invention is to provide a commercial 
production process of 1,3-dialkyl-2-imidazolidinones, particularly DMI. 
A second object of the present invention is to provide an improved process 
of producing 1,3-dialkyl-2-imidazolidinones directly from 
N,N'-dialkylethylenediamine and urea with a high yield. 
The present invention resides in: 
In the production of a 1,3-dialkyl-2-imidazolidinone expressed by the 
formula (2) 
##STR6## 
wherein R represents --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7 or 
--C.sub.4 H.sub.9, by reacting a N,N'-dialkylethylenediamine expressed by 
the formula (1) 
##STR7## 
wherein R is as defined above, with urea, the improvement which comprises 
carrying out the reaction at a temperature of 180.degree. C. or higher in 
the presence of a polar solvent. 
According to a preferred embodiment of the present invention, the reaction 
is carried out at two stages provided with temperature gradient, that is, 
the initial period reaction forming a 1,1'-dialkyl-1,1'-dimethylenebisurea 
##STR8## 
is carried out at 140.degree. C. or lower until its formation is 
completed, followed by successively raising the temperature and carrying 
out the latter period reaction at a temperature of 180.degree. C. or 
higher, and preferably 300.degree. C. or lower. According to a more 
preferred embodiment of the present invention, the ratio by mol of the 
quantity of urea fed relative to that of the N,N'-dialkylethylenediamine 
at the time of the initial period reaction is made preferably 2 or less, 
more preferably 0.6 to 1.2 and the reaction is completed under pressure, 
or urea is used in a ratio by mol of about 2 at the time of the initial 
period reaction and N,N'-dialkylethylenediamine is additionally added at 
the time of heat elevation at the time of the latter stage so that the 
quantities of the N,N'-dialkylethylenediamine and urea used in the whole 
reaction may amount almost to equal mols, whereby it is possible to obtain 
1,3-dialkyl-2-imidazolidinones with a higher yield according to the above 
reaction. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the present invention, as the N,N'-dialkylethylenediamine expressed by 
the formula (1), N,N'-dimethylethylenediamine, 
N,N'-diethylethylenediamine, N,N'-dipropylethylenediamine, 
N,N'-diisopropylethylenediamine, N,N'-dibutylethylenediamine, etc. are 
enumerated. When urea is reacted with these compounds, the corresponding 
1,3-dialkyl-2-imidazolidinones expressed by the formula (2) are obtained. 
In particular, the process of the present invention is the most suitable 
process for commercially producing DMI from N,N'-dimethylethylenediamine. 
The N,N'-dialkylethylenediamines of the formula (1) may be easily prepared 
from the corresponding lower monoamines according to various known 
methods. 
For example, N,N'-dimethylethylenediamine may be obtained by reacting 
ethylene dichloride with an excess quantity of methylamine in water 
solvent. 
The process of the present invention wherein these 
N,N'-dialkylethylenediamines and urea are used, is carried out in the 
presence of a polar solvent at 180.degree. C. or higher, and in the 
initial period reaction of the present invention is a reaction for forming 
a 1,1'-dialkyl-1,1'-dimethylenebisurea as an intermediate. 
Thus, in the initial period reaction, in order to inhibit the reaction of 
urea itself and thereby quantitatively form the 
1,1'-dialkyl-1,1'-dimethylenebisurea as an intermediate, it is preferred 
to carry out the reaction at 180.degree. C. or lower, preferably at 
140.degree. C. or lower. 
When the initial period reaction is carried out at such a temperature or 
lower, reaction proceeds quantitatively between the 
N,N'-dialkylethylenediamine and urea, and at that time the pressure in the 
reactor is gradually raised by NH.sub.3 gas released with the advance of 
the reaction and becomes a constant pressure before long, whereby it is 
possible to confirm the end point of the initial period reaction. 
When the temperature is successively raised up to 180.degree. C. or higher, 
preferably 200.degree. C.-300.degree. C., to subject the intermediate to 
thermal decomposition reaction, the corresponding 
1,3-dialkyl-2-imidazolidinone is obtained with a high yield. If the 
temperature is lower than 180.degree. C., the reaction rate is low, while 
if it exceeds 300.degree. C., a problem is raised with respect of heating 
method. 
As the solvent used in the process of the present invention, hydrocarbons 
and halogenated hydrocarbons are unsuitable and polar solvents are used. 
Examples of preferred solvents are polar, non-protonic solvents such as 
N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, 
dimethylsulfoxide, hexamethylphosphoroamide, sulfolane, methyl isobutyl 
ketone, nitrobenzene, tetrahydrofuran, dioxane, etc. Further, since low 
boiling temperatures require an excessively pressure-resistant apparatus, 
solvents having a boiling point of 180.degree. C. or higher are preferred. 
In particular, with respect of the yield and in order to avoid the 
troublesome solvent separation, it is preferred to use as the solvent, the 
desired 1,3-dialkyl-2-imidazolidinone itself, which has been produced by 
the reaction. 
In the process of the present invention, by using such polar solvents, it 
is possible to carry out a mild reaction at a relatively low temperature 
to obtain the desired objective product with a high yield. 
The ratio of the quantity of urea fed, to that of 
N,N'-dialkylethylenediamine may be usually in the range of 0.5 to 2.5 in 
mol ratio. However, if urea of more than 2 mols relative to 
N,N'-dialkylethylenediamine are fed and used, i.e. if the theoretical 
quantity of more is used, then when the latter period higher temperature 
reaction is carried out at 180.degree. C. or higher, cyanuric acid is 
byproduced in a large quantity to thereby reduce the yield of the 
objective product and result in a troublesome operation of removing it. 
Thus, in order to avoid cyanuric acid formation, it is necessary to use 
urea in a quantity less than its theoretical equivalent, that is, less 
than twice by mol, preferably in the range of 0.6 to 1.2 times by mol 
based on N,N'-dialkylethylenediamine at the time of their feed and cause 
N,N'-dialkylethylenediamine to remain in the latter period reaction 
system, but in such a case, if unreacted N,N'-alkylethylenediamine remains 
in excess, it is impossible to raise the temperature up to a desired one 
under the atmospheric pressure since the boiling point of 
N,N'-alkylethylenediamine is lower than that of the latter period 
decomposition reaction; hence it is necessary to carry out the reaction 
under pressure. 
In order to avoid this matter, when the initial period reaction is carried 
out using urea in a quantity of about 2 mols in the vicinity of equivalent 
based on N,N'-dialkylethylenediamine when it is fed, and successively the 
temperature is raised and the latter period decomposition reaction is 
carried out at 180.degree. C. or higher, then if 
N,N'-dialkylethylenediamine is reacted while it is added, it is also 
possible to carry out the reaction under the atmospheric pressure. At that 
time, the quantity of N,N'-dimethylethylenediamine added freshly is added 
so that the quantity may be nearly equimolar to that of 
1,1'-dimethyl1,1'-dimethylenebisurea. Namely it is preferred that the 
ratio of the quantities of N,N'-dimethylethylenediamine and urea used in 
the whole reaction be chosen so as to be nearly equimolar, and 
N,N'-dimethylethylenediamine be used in nearly two divided portions in the 
initial period reaction and the decomposition reaction step. 
A concrete preferred embodiment wherein the process of the present 
invention is carried out under the atmospheric pressure is as follows: 
Into a reactor equipped with a reflux condenser, a thermometer, a dropping 
funnel and a mechanical stirrer are added N,N'-dialkylethylenediamine, 
urea in an about equivalent quantity thereto, and as solvent a portion of 
the objective product itself obtained by distilling the reaction fluid 
under reduced pressure, each in definite quantities. The temperature is 
raised and reaction is carried out at 140.degree. C. or lower. As the 
reaction proceeds, NH.sub.3 gas is generated, and the end point of the 
reaction can be judged by termination of the gas generation. 
The temperature is successively raised to 180.degree. C. or higher. When 
the temperature reached a temperature in the vicinity of 180.degree. C., 
reaction is carried out while a definite quantity of 
N,N'-dialkylethylenediamine is freshly dropwise added in small portions. 
After completion of the reaction, it is possible to take out the objective 
product from the reaction fluid only by direct distillation. When the 
objective product itself is used as the solvent for the reaction, it is 
unnecessary to separate it from the solvent at the time of distillation to 
afford a very simplified process, and after completion of the reaction, it 
is possible to use the distillate at the time of distillation, as it is, 
without purification, as the solvent for the next time reaction.

The present invention will be described in more detail by way of Examples. 
EXAMPLES 1 
Into a 500 ml stainless autoclave were fed N,N'-dimethylethylenediamine 
(88.1 g, 1.0 mol), urea (60.1 g, 1.0 mol) and DMI (100.0 g). The reaction 
temperature was raised up to 210.degree. C. over about 30 minutes and 
reaction was carried out at the temperature for 3 hours. The pressure 
inside the system reached 14.5 kg/cm.sup.2 G as the highest pressure. 
After completion of the reaction, the reaction fluid was distilled and 
after about 2/3 of the quantity of DMI was distilled off, crystals 
deposited in the still residue were filtered off, followed by successively 
distilling the filtrate to obtain a DMI fraction (192.7 g) having a purity 
of 99.5% according to gas chromatography (yield: 80.8%). The still residue 
consisted of cyanuric acid partly containing DMI. 
In addition, using various kinds of solvents in place of DMI, reaction and 
treatment were carried out in all the same manner as in Example 1, to 
obtain results shown in the following Table: 
TABLE 
______________________________________ 
Use of various kinds of solvents 
No. Solvent DMI yield (%) 
______________________________________ 
2 Toluene 5.0 
3 1,2-Dichloroethane 
25.4 
4 Ethylene glycol 55.5 
5 Isopropyl alcohol 
70.0 
6 Methyl isobutyl ketone 
83.0 
7 N--methyl-2-pyrrolidone 
80.5 
8 N, N'--dimethylacetamide 
82.2 
______________________________________ 
EXAMPLE 2 
Into a 500 ml stainless autoclave were fed N,N'-diethylethylenediamine 
(116.2 g, 1.0 mol), urea (60.1 g, 1.0 mol) and 
1,3-diethyl-2-imidazolidinone (100.0 g). The temperature was raised up to 
a reaction temperature of 210.degree. C. in about 30 minutes and reaction 
was carried out at the temperature for 3 hours. 
The pressure in the system reached 14 kg/cm.sup.2 G as the highest 
pressure. After completion of the reaction, the reaction fluid was 
distilled, and after about 2/3 of the quantity of 
1,3-diethyl-2-imidazolidinone was distilled off (boiling point: 
120.degree.-123.degree. C./20-23 mmHg), crystals deposited in the still 
residue was filtered, followed by successively distilling the filtrate to 
obtain a fraction of 1,3-diethyl-2-imidazolidinone (214.8 g) having a 
purity of 99.5% according to gas chromatography (yield: 80.0%). The still 
residue after the distillation consisted of cyanuricacid partly containing 
1,3-diethyl-2-imidazolidinone. 
EXAMPLE 3 
Reaction and treatment were carried out in the same manner as in Example 2 
except that N,N'-diethylethylenediamine was replaced by 
N,N'-dipropylethylenediamine (144.3 g, 1.0 mol) and reaction was carried 
out in 1,3-dipropyl-2-imidazolidinone (100.0 g), to obtain 
1,3-dipropyl-2-imidazolidinone having a purity of 99.7% according to gas 
chromatography (boiling point: 146.degree.-148.degree. C./20-24 mmHg, 
yield: 81.5%). 
EXAMPLE 4 
Into a 500 ml stainless autoclave were fed N,N'-dimethylethylenediamine 
(88.1 g, 1.0 mol), urea (60.1 g, 1.0 mol) and DMI (100 g). The temperature 
was raised and reaction was carried out at a reaction temperature of 
120.degree. C. for 8 hours. After start of the reaction, the pressure in 
the system rose gradually and became constant at 5.5 kg/cm.sup.2 G; thus 
the temperature was raised up to 210.degree. C. in about 30 minutes, and 
reaction was carried out at the temperature for 3 hours. The pressure in 
the system reached 14.5 kg/cm.sup.2 G at the highest temperature. After 
completion of the reaction, the reaction fluid was distilled under reduced 
pressure to obtain a DMI fraction having a purity of 99.5% according to 
gas chromatography (208.6 g, yield: 94.7%). The still residue after the 
distillation consisted of cyanuric acid partly containing DMI. 
EXAMPLE 5 
Into a 500 ml stainless autoclave were fed N,N'-diethylethylenediamine 
(116.2 g, 1.0 mol), urea (60.1 g, 1.0 mol) and 
1,3-diethyl-2-imidazolidinone (100.0 g). The temperature was raised. 
Reaction was carried out at a reaction temperature of 120.degree. C. for 8 
hours. After start of the reaction, the pressure in the system rose 
gradually and became almost constant in the vicinity of 5.5 kg/cm.sup.2 G; 
thus the temperature was successively raised up to 220.degree. C. in about 
30 minutes and reaction was carried out at the temperature for 3 hours. 
The pressure in the system reached 14.0 kg/cm.sup.2 G as the highest 
pressure. After completion of the reaction, the reaction fluid was 
distilled under reduced pressure to obtain a 1,3-diethyl-2-imidazolidinone 
fraction having a purity of 99.5% according to gas chromatography (237.0 
g, yield: 95.5%). The still residue after the distillation consisted of 
cyanuric acid partly containing 1,3-diethyl-2-imidazolidinone. 
EXAMPLE 6 
Into a 300 ml glass flask equipped with a reflux condenser, a thermometer, 
a dropping funnel and a stirrer were fed N,N'-dimethylethylenediamine 
(44.1 g, 0.5 mol), urea (60.1 g, 1.0 mol) and DMI (100.0 g) as solvent. 
Into the dropping funnel was put N,N'-dimethylethylenediamine (44.1 g). 
The temperature was raised up to 120.degree. C. at which reaction was 
carried out. As the reaction proceeds, NH.sub.3 gas was generated and 
crystals separated during the reaction. After about 12 hours, NH.sub.3 gas 
generation ceased. At that time, the temperature was further raised up to 
210.degree. C. Above a temperature in the vicinity of 200.degree. C., 
N,N'-dimethylethylenediamine was dropwise added through the dropping 
funnel over about 2 hours. Reaction was then carried out at the same 
temperature for one hour. After completion of the reaction, the reaction 
fluid was distilled under reduced pressure to obtain a DMI fraction having 
a purity of 99.5% according to gas chromatography (211.3 g, yield: 97.0%).