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

A novel bis-urea compound, preparation process of the compound, and preparation process of 1,3-dialkyl-2-imidazolidinone are disclosed and the disclosure provides a novel preparation process of 1,3-dialkyl-2-imidazolidinone and simultaneously enables effective utilization of N,N',N"-trialkyldiethylentriamine which lacks a large amount use and is desired to develop new application.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a novel bis-urea compound, a process for 
producing the compounds and a novel process for producing an aprotic polar 
compound 1,3-dialkyl-2-imidazolidinone represented by the formula (2): 
##STR1## 
wherein R is an alkyl group, by using the bis-urea compounds. 
The compounds represented by the formula (2) are a useful substance as an 
aprotic polar solvent and an intermediate for medicines and agricultural 
chemicals. The compounds are particularly excellent solvent for high 
polymers such as polyamides, polyvinyl chloride, polyvinyl alcohol, 
polystyrene, polyurethane and phenolic resins. Further, the compounds 
dissolve many inorganic compounds with ease and can be used as a solvent 
for various characteristic organic reactions. 
2. Prior Art of the Invention 
Various processes have been proposed on the preparation of 
1,3-dialkyl-2-imidazolidinones represented by the formula (2): 
##STR2## 
wherein R is an alkyl group. For example, on 
1,3-dimethyl-2-imidazolidinone, a process wherein ethylenediamine is 
reacted with urea to obtain 2-imidazolidinone which is subjected to 
addition reaction to formaldehyde, followed by reducing the resulting 
reaction product with trichloroacetic acid, formic acid or the like, into 
the corresponding N,N'-dimethylated compound; a process having improved 
the above reducing process wherein hydrogenation decomposition is carried 
out using a noble metal catalyst in an acidic state; a process wherein 
N,N'-dialkylethylenediamine is reacted with phosgene or trichloroformate 
while it is decomposed into phosgene, etc. have been known. 
The present inventors previously proposed a commercial process for 
producing 1,3-dialkyl-2-imidazolidinones in good yield by reaction of 
N,N'-dialkylethylenediamines with urea (U.S. Pat. No. 4,731,453). However, 
preparation of the raw material N,N'-dialkylethylenediamines from 
dichloroethane and alkylamines leads to formation of a by-product 
N,N',N"-trialkyldiethylenetriamines. Consequently, the yield of 
1,3-dialkyl-2-imidazolidinones on the basis of dichloroethane is 
unsatisfactory in industry. For example, the yield is 68% in 
1,3-dimethyl-2-imidazolidinone, 70% in 1,3-diethyl-2-imidazolidinone, 82% 
in 1,3-dipropyl-2-imidazolidinone and 85% in 
1,3-dibutyl-2-imidazolidinone. Further, application of the by-product 
N,N',N"-trialkyldiethylenetriamines in a large amount has not yet been 
found and development of uses has been strongly desired. 
SUMMARY OF THE INVENTION 
A first object of the present invention is to provide a novel process for 
producing 1,3-dialkyl-2-imidazolidinones. 
A second object of the present invention is to provide a preparation 
process which can be effectively utilized a by-product 
N,N',N"-trialkyldiethylenetriamines formed in preparing 
1,3-dialkyl-2-imidazolidinones. 
A third object of the present invention is to provide an useful 
intermediate, i.e. bis-urea compound, for producing the 
1,3-dialkyl-2-imidazolidinones and a process for producing the 
intermediate. 
As result of an intensive investigation for preparing the 
1,3-dialkyl-2-imidazolidinones in order to achieve the above objects, the 
present inventors have found a novel process for producing the compounds 
through a novel substance which is obtainable by using 
N,N',N"-trialkyldiethylenetriamines as raw materials. 
That is, the aspect of the present invention is; 
1. a bis-urea compound represented by the formula (3); 
##STR3## 
wherein R is an alkyl group, 2. a process for producing the bis-urea 
compound represented by the formula (3) comprising reacting 
N,N',N"-trialkyldiethylenetriamines represented by the formula (1): 
##STR4## 
wherein R is an alkyl group, with urea. 3. a process for producing 
1,3-dialkyl-2-imidazolidinones represented by the formula (2): 
##STR5## 
wherein R is an alkyl group, comprising heat-decomposing the bis-urea 
compounds represented by the formula (3). 
4. a process for producing 1,3-dialkyl-2-imidazolidinones represented by 
the formula (2) comprising reacting N,N',N"-trialkyldiethylenetriamines 
represented by the formula (1) with urea, and successively 
heat-decomposing the resultant bis-urea compound without isolation. 
The present invention enables to effectively utilize 
N,N',N"-trialkyldiethylenetriamine which lacks a large amount use and is 
desired to develop new application. Thus, the invention has great 
significance. 
DETAILED DESCRIPTION OF THE INVENTION 
N,N'N"-trialkyldiethylenetriamines used in the present invention represent 
by the above formula (1). Additionally, the bis-urea compounds represented 
by the formula (3) can be obtained by using the 
N,N'N"-trialkyldiethylenetriamines as raw materials. Further, the 
1,3-dialkyl-2-imidazolidinones can be obtained by using the bis-urea 
compound as raw materials. 
R in the formulas (1), (2) and (3) is alkyl groups, preferably an alkyl 
group having 1.about.8 carbon atoms, more preferably an alkyl group having 
1.about.4 carbon atoms. Exemplary alkyl groups include a methyl group, 
ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, 
s-butyl group, t-butyl group, n-pentyl group, i-pentyl group, t-pentyl 
group, n-hexyl group, i-hexyl group, n-octyl group and 2-ethylhexyl group. 
N,N',N"-trialkyldiethylenetriamines used in the process of the invention 
can be preferably prepared by the reaction as shown in the reaction 
formula (A): 
##STR6## 
The compounds can also be prepared, when required, by reacting 
N,N'-dialkylethylenediamines with dichloroethane in the coexistence of an 
alkylamine. 
In the preferred preparation of the raw material 
N,N',N"-trialkyldiethylenetriamines, the molar ratio of alkylamine to 
1,2-dichloroethane is preferably from 4 to 6. A high molar ratio of 
alkylamine is liable to increase the formation of 
N,N'-dialkylethylenediamines. 
No particular limitation is imposed upon the temperature of the amination 
reaction as long as the temperature is in the range giving a suitable 
reaction velocity. The reaction temperature is preferably in the range of 
80.degree..about.150.degree. C. 
The amination reaction is required to carry out under the application of 
pressure depending upon the reaction temperature. 
The reaction mass of amination is neutralized with a suitable base such as 
sodium hydroxide and successively distilled to recover unreacted 
alkylamine. N,N',N"-Trialkyldiethylenetriamines formed is purified by 
distillation of the residual mass. 
N,N',N"-Trialkyldiethylenetriamines thus obtained can be used in the 
preparation process of the present invention. 
The bis-urea compounds represented by the formula (3) can be prepared by 
reacting the compound represented by the formula (1) with urea. 
The reaction temperature is in the range of preferably 
100.degree..about.155.degree. C., more preferably 
120.degree..about.145.degree. C. The reaction temperature higher than 
155.degree. C. leads to decomposition of urea. On the other hand, when the 
reaction temperature is lower than 100.degree. C., the reaction velocity 
becomes too slow. 
Amounts of urea and N,N',N"-trialkyldiethylenetriamines used in the process 
of the present invention is urea of 1.0.about.3.0 moles, preferably 
1.5.about.2.5 moles for a mole of N,N',N"-trialkyldiethylenetria mines. 
When urea is used in excess, solid impurities such as cyanuric acid which 
is a heat decomposition product of urea unfavorably remain in the reaction 
system. On the other hand, use of less than 1.0 mole ratio is unsuitable 
because an increased amount of by-product is formed. 
The reaction progresses quantitatively and the end point of the reaction 
can be checked by determining ammonia gas which is liberated with the 
progress of the reaction. 
The compounds of the formula (2) can be prepared by carrying out heat 
decomposition of the compounds of the formula (3). 
The heat-decomposition is carried out at a temperature of preferably 
180.degree. C. or more, more preferably 200.degree..about.260.degree. C., 
most preferably 210.degree..about.240.degree. C. When the reaction 
temperature is lower than 180.degree. C., the reaction velocity becomes 
slow. On the other hand, the reaction temperature around 300.degree. C. 
unfavorably leads to problems on the heating means. 
The compounds of the formula (2) also can be obtained by reacting the 
compounds of the formula (1) with urea, and successively by 
heat-decomposing the resultant compounds represented by the formula (3) 
without isolation. 
A series of reaction for preparing the compounds of the formula (2) through 
the compounds of the formula (3) from the compounds of the formula (1) is 
illustrated in the reaction formula (B): 
##STR7## 
In this reaction, the reactions are carried out stepwise under the reaction 
conditions and the reaction temperature for preparing the compounds of the 
formula (3) and the compounds of the formula (2). 
Reaction solvents can be used in all processes for preparing the compound 
of the formula (3) from the compounds of the formula (1), the compounds of 
the formula (2) from the compounds of the formula (3) and the compounds of 
the formula (2) from the compounds of the formula (1) without isolating 
the compounds of the formula (3), as exemplary solvent can be used in 
these processes include ethanol, methyl isobutyl ketone, 
N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, diethyleneglycol 
dimethyl ether, triethyleneglycol dimethyl ether and the like. However, it 
is desired for the process of the invention to carry out the reaction 
without solvent also in view of avoiding complex steps such as removal of 
the solvent by distillation. 
1,3-Dialkyl-2-imidazolidinones formed are purified by distillation.

The present invention will hereinafter be illustrated further in detail by 
way of examples. 
Synthesis Example 1 
To a 5.0 liter pressure reactor equipped with a thermometer and stirrer, 
1286.5 g (13 moles) of 1,2-dichloroethane and 2018.9 g (65 moles) of 
methylamine were charged and heated to 100.degree. C. with stirring. 
Thereafter the amination reaction was carried out for 2 hours while 
maintaining the same temperature. 
The reaction mixture was successively cooled to the room temperature and 
analyzed by gas chromatography. Conversion ratio of 1,2-dichloroethane was 
100.0%. 
Next, 1072.2 g of sodium hydroxide flake was charged to neutralize the 
reaction mixture and residual methylamine was recovered by distillation. 
The recovered methylamine was reused for the reaction. After distillation, 
sodium chloride which was separated in the reaction mass was filtered. The 
liltrate was distilled to obtain 229.4 g of 
N,N',N"-trimethyldiethylenetriamine. 
Example 1 
(Synthesis of the compound (3)) 
To a 0.5 liter flask equipped with a reflux condenser, thermometer and 
stirrer, 171.3 g (1.0 mole) of N,N',N"-trimethyldiethylenetriamine 
obtained in synthesis example 1 and 120.1 g (2.0 moles) of urea were 
charged and reacted for 3 hours with stirring while maintaining the 
temperature at 125.degree.-140.degree. C. After finishing the reaction, 
the reaction mass solidified at around 90.degree. C. upon cooling. The 
solidified mass was ground and was dissolved in methanol at 60.degree. C. 
Hexane was added to the solution and then the product crystallized out of 
the solution, the crystalline was filtered and dried. Thus 186.1 g of 
bi-surea compound was obtained in 80.2% yield. Melting point of the 
compound was 145.degree..about.147.degree. C. 
Chemical structure of the compound was identified with 1H NMR, 13C NMR, IR 
and FAB-MS(NH.sup.+ /Z=232). Results of 1H NMR, 13C NMR and IR are as 
follows. 
1H NMR; DMSO-d6 .delta.=2.2(s,3H), 2.4(t,4H), 2.8(s,6H), 3.2(t,4H). 
5.8(s,br,4H) 
13C NMR; DMSO-d6 .delta.=34(q), 42(q), 46(t), 55(t), 159(s). 
IR; 1657 cm.sup.-1 (C=0) 
Example 2 
(Synthesis of the compound (2) from the compound (3)) 
To 0.5 liter flask equipped with a reflux condenser, thermometer and 
stirrer, 115.7 g (0.5 mole) of the bis-urea compound obtained in Example 1 
were charged and heated with stirring. The bis-urea compound began to melt 
at temperature of around 145.degree. C. and leads to a complete fluid at 
temperature of 160.degree. C. The temperature was raised up to 
215.degree..about.225.degree. C. and the reaction was carried out at the 
same temperature for 4 hours. After finishing the reaction the reaction 
fluid was cooled to obtain 1,3-dimethyl-2-imidazolidinone in 87.5% yield 
of formation according to gas chromatography. 
Example 3 
To 0.5 liter flask equipped with a reflux condenser, thermometer and 
stirrer, 217.9 g (1.5 moles) of N,N',N"-trimethyldiethylenetriamine and 
180.2 g (3.0 moles) of urea were charged and reacted for 4 hours with 
stirring while maintaining the temperature 125.degree..about.140.degree. 
C. The temperature was raised up to 215.degree..about.225.degree. C. and 
heat-decomposition was carried out at the same temperature for 4 hours. 
After finishing the decomposition, yield of formation of 
1,3-dimethyl-2-imidazolidinone according to gas chromatography was 88.0% 
on the basis of N,N',N"-trimethyldiethylenetriamine. 
The reaction mixture was successively distilled to obtain 137.0 g of 
1,3-dimethyl-2-imidazolidinone. The product had purity of 99.3% and a 
boiling point of 105.degree. C. under reduced pressure of 15 mmHg. 
Example 4 
The reaction and analysis were carried out by the same procedures as 
described in Example 3 except that N,N',N"-trimethyldiethylenetriamine was 
replaced by N,N',N"-triethyldiethylenetriamine. As a result, 
1,3-diethyl-2-imidazolidinone obtained had 85.4% yield of formation on the 
basis of N,N',N"-triethyldiethylenetriamine. 
The reaction mixture was successively distilled to obtain 163.5 g of 
1,3-diethyl-2-imidazolidinone. The product had purity of 99.4% and a 
boiling point of 109.degree. C. under reduced pressure of 15 mmHg. 
Example 5 
The reaction and analysis were carried out by the same procedures as 
described in Example 3 except that N,N',N"-trimethyldiethylenetriamine was 
replaced by N,N',N"-tripropyldiethylenetriamine. As a result, 
1,3-dipropyl-2-imidazolidinone obtained had 81.2% yield of formation on 
the basis of N,N',N"-tripropyldiethylenetriamine. 
The reaction mixture was successively distilled to obtain 184.6 g of 
1,3-dipropyl-2-imidazolidinone. The product had purity of 99.6% and a 
boiling point of 110.degree. C. under reduced pressure of 5 mmHg. 
Example 6 
The reaction and analysis were carried out by the same procedures as 
described in Example 3 except that N,N',N"-trimethyldiethylenetriamine was 
replaced by N,N',N"-tributyldiethylenetriamine. As a result, 
1,3-dibutyl-2-imidazolidinone obtained had 80.3% yield of formation on the 
basis of N,N',N"-tributyldiethylenetriamine. 
The reaction mixture was successively distilled to obtain 210.1 g of 
1,3-dibutyl-2-imidazolidinone. The product had purity of 99.6% and a 
boiling point of 127.degree. C. under reduced pressure of 10 mmHg.