Production method of alkylated cyanoacetylurea

A method for producing alkylated cyanoacetylurea from an easily obtainable starting material. An industrially available cyanoacetylurea and a carbonyl compound are reacted in a polar solvent under reducing conditions to alkylate cyanoacetylurea In addition, a reaction of cyanoacetylurea and acetone under reducing conditions affords isopropylation of cyanoacetylurea.

TECHNICAL FIELD OF THE INVENTION 
The present invention relates to a production method of an alkylated 
cyanoacetylamino compound, and to a production method of alkylated 
cyanoacetylurea which is a useful starting material of a 5-alkyl 
substituted uracil that is an important intermediate for the production of 
a pharmaceutical product such as an anti-HIV drug and the like. More 
particularly, the present invention relates to a production method 
comprising reacting cyanoacetylurea and a carbonyl compound in a polar 
solvent under reducing conditions to alkylate cyanoacetylurea. More 
particularly, the present invention relates to a production method 
comprising reacting cyanoacetylurea with acetone under reducing conditions 
to isopropylate the acetyl moiety of cyanoacetylurea. 
BACKGROUND OF THE INVENTION 
The product of the present invention, alkylated cyanoacetylurea, is a 
useful starting material of a 5-alkyl substituted uracil which is an 
important intermediate for producing a pharmaceutical agent (e.g., 
anti-HIV drug, antiviral agent and the like), agents for photographs 
(e.g., stabilizer of silver halide and the like), and the like. 
As a prior art method for producing alkylated cyanoacetylurea, a method 
comprising condensing cyanoalkylacetic acid, urea and acetic anhydride by 
heating is known [Journal of the American Pharmaceutical Association, 44, 
545 (1955)]. Cyanoalkylacetic acids (starting material) can be obtained by 
reacting an ester compound of cyanoacetic acid and alkyl halide. However, 
the reaction requires use of a dangerous reagent (e.g., sodium hydride and 
the like) in an anhydrous solvent, as well as hydrolysis of ester and 
subsequent neutralization with an acid for isolation of the product. The 
inorganic salt (e.g., sodium sulfate and the like) produced at this stage 
contaminates tools and the like used for the reaction and this method is 
disadvantageous for the production at a plant scale. 
What is more, alkylated cyanoacetylurea cannot be obtained at a high yield 
by a production method comprising direct alkylation of cyanoacetylurea. 
There is therefore a demand for an easy, convenient and 
industrially-utilizable method for producing alkylated cyanoacetylurea 
from a starting material that is easily obtainable. 
It is therefore an object of the present invention to provide a method for 
an easy, convenient and industrially-utilizable method for producing 
alkylated cyanoacetylurea useful as a synthetic starting material of 
5-alkyl substituted uracils from a starting material that is easily 
obtainable. Another object of the present invention is to provide a method 
for an easy, convenient and industrially-utilizable method for producing 
an alkylated cyanoacetylamino compound. 
SUMMARY OF THE INVENTION 
Such object can be achieved by the following method of the present 
invention, comprising reacting an industrially available cyanoacetylamino 
compound and a carbonyl compound in a polar solvent under reducing 
conditions to alkylate the cyanoacetylamino compound, and a method 
comprising reacting cyanoacetylurea and a carbonyl compound in a polar 
solvent under reducing conditions, whereby cyanoacetylurea can be 
alkylated. It has been also found that by reacting cyanoacetylurea with 
acetone as a solvent and reagent under reducing conditions, the acetyl 
moiety of cyanoacetylurea can be converted to isopropyl. 
Accordingly, the present invention provides the following. 
(1) A method for producing a cyanoacetylamino compound having a group of 
the formula 
##STR1## 
an acetyl moiety thereof is alkylated with an optionally substituted 
alkyl, comprising reacting a cyanoacetylamino compound having a group of 
the formula 
##STR2## 
a carbonyl compound in a polar solvent under reducing conditions. (2) The 
production method of (1) above, wherein the reaction proceeds in the 
presence of a reduction catalyst. 
(3) The production method of (1) above, wherein the cyanoacetylamino 
compound is cyanoacetylurea. 
(4) The production method of (2) above, wherein the cyanoacetylamino 
compound is cyanoacetylurea. 
(5) A method for producing an alkylated cyanoacetylurea of the formula (c) 
##STR3## 
wherein R.sup.1 and R.sup.2 may be the same or different and each is a 
hydrogen atom, an alkyl having 1 to 12 carbon atoms, a cyclic alkyl having 
3 to 8 carbon atoms, an aromatic ring or an aralkyl, comprising reacting 
cyanoacetylurea of the formula (a) 
##STR4## 
and a carbonyl compound of the formula (b) 
##STR5## 
wherein R.sup.1 and R.sup.2 are as defined above, in a polar solvent 
under reducing conditions. 
(6) A method for producing N-(2-cyano-3-methylbutanoyl)urea, comprising 
reacting cyanoacetylurea of the formula (a) 
##STR6## 
with acetone under reducing conditions. (7) The production method of (6) 
above, wherein the reaction is carried out in the presence of a reduction 
catalyst. 
DETAILED DESCRIPTION OF THE INVENTION 
Each symbol used in the present specification is explained in the 
following. 
The alkyl having 1 to 12 carbon atoms at R.sup.1 and R.sup.2 may be linear 
or branched and is exemplified by methyl, ethyl, propyl, isopropyl, butyl, 
isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, 
dodecyl and the like. Preferred is alkyl having 1 to 6 carbon atoms, such 
as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, 
hexyl and the like. 
The cyclic alkyl having 3 to 8 carbon atoms at R.sup.1 and R.sup.2 may be, 
for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, 
cycloheptyl, cyclooctyl and the like, with preference given to cyclohexyl. 
The aromatic ring at R.sup.1 and R.sup.2 may be, for example, phenyl, 
pyridyl and the like, with preference given to phenyl. 
The aralkyl at R.sup.1 and R.sup.2 may be, for example, that wherein the 
alkyl moiety has 1 or 2 carbon atoms, such as benzyl, phenylethyl and the 
like. 
In the present invention, the optionally substituted alkyl is an alkyl 
having 1 to 25, preferably 1 to 3, carbon atoms, which is optionally 
substituted by 1 to 3 substituent(s) selected from C.sub.3 -C.sub.8 cyclic 
alkyl, aromatic ring and aralkyl. As used herein, C.sub.3 -C.sub.8 cyclic 
alkyl, aromatic ring and aralkyl are as defined for the above-mentioned 
R.sup.1 and R.sup.2. 
Examples of the carbonyl compound include formaldehyde, acetone, methyl 
ethyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopropyl methyl 
ketone, acetophenone, acetaldehyde, propionaldehyde, 
cyclohexanecarbaldehyde, benzaldehyde, 3-pyridinecarbaldehyde, 
phenylacetaldehyde and the like. 
The carbonyl compound (starting material) may be commercially available or 
one synthesized by the method disclosed in, for example, Organic 
Reactions, Vol. VI, 207 and Journal Organic Chemistry, 52, 2559 (1987). 
The production method of the present invention using a polar solvent is 
explained in the following by referring to the alkylation of 
cyanoacetylurea as an example. Other compounds can be also produced in a 
similar manner. 
##STR7## 
wherein R.sup.1 and R.sup.2 are as defined above. 
The cyanoacetylurea of the formula (a) is suspended or dissolved in a polar 
solvent, and a carbonyl compound of the formula (b), acetic acid and 
ammonium acetate are added to allow reaction under reducing conditions to 
give cyanoacetylurea of the formula (c), that has been alkylated with an 
optionally substituted alkyl. Preferably, the reaction is carried out in 
the presence of a reduction catalyst. The termination of the reaction is 
confirmed by the disappearance or decrease of the starting material, which 
is known by way of high performance liquid chromatography. After reaction, 
the objective product is isolated by any method which is free of any 
limitation. For example, the catalyst is filtered off and water is added 
to the filtrate or the filtrate is cooled to precipitate and isolate the 
objective product. 
In the same manner as above, a compound having cyanoacetylamino group is 
reacted with a carbonyl compound to give a compound having a 
cyanoacetylamino group, wherein the acetyl moiety is alkylated with an 
optionally substituted alkyl. 
While the reaction time varies depending on the amount of catalyst, it is 
generally 3 to 12 hours and the reaction temperature is from 0.degree. C. 
to 50.degree. C., preferably from 20.degree. C. to 30.degree. C. The 
hydrogen pressure is from under normal pressure to 30 kg/cm.sup.2, 
preferably from under normal pressure to 15 kg/cm.sup.2. 
The carbonyl compound, which is the starting material, is added in a 
1.0-fold to 2.0-fold amount, preferably 1.1-fold to 1.5-fold amount, per 
mole of cyanoacetylurea. 
Acetic acid is added in a 0.1-fold to 1.0-fold amount, preferably 0.2-fold 
to 0.4-fold amount, per mole of cyanoacetylurea. 
Ammonium acetate is added in a 0.05-fold to 0.5-fold amount, preferably 
0.1-fold to 0.2-fold amount, per mole of cyanoacetylurea. 
The reduction catalyst may be one typically used for reductive alkylation, 
which is preferably palladium carbon, platinum carbon and the like. 
The reduction catalyst is used in a proportion of 0.5-30 wt %, preferably 
1-10 wt %, relative to cyanoacetylurea, when, for example, 10% palladium 
carbon (50% wet product) is used. 
The polar solvent to be used for the reaction has a relative dielectric 
constant of not less than 10. 
Examples of the reaction solvent include linear or branched lower alcohols 
having 1 to 4 carbon atoms (e.g., methanol, ethanol, propanol, 
isopropanol, butanol and tert-butanol), polar organic solvent (e.g., 
N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and the 
like), glycols [e.g., ethylene glycol, ethylene glycol monomethyl ether 
(trademark: methyl cellosolve) and the like], water and mixed solvents 
thereof. Preferred are isopropanol and N,N-dimethylformamide. When the 
carbonyl compound to be used as a reaction reagent can be used as a polar 
solvent, this carbonyl compound may be used as a reaction solvent. 
The reaction solvent is used in a 1-fold to 10-fold weight amount relative 
to cyanoacetylurea. 
The acetyl moiety of cyanoacetylurea can be converted to isopropyl 
according to the above-mentioned production method. Acetone (formula (b) 
wherein R.sup.1 and R.sup.2 are methyl) to be used as a reaction reagent 
can be also used as a reaction solvent for the reaction. 
When acetone is used as a reaction solvent, the production method is almost 
the same as the one mentioned above, wherein cyanoacetylurea is suspended 
or dissolved in acetone, and acetic acid and ammonium acetate are added to 
allow reaction under reducing conditions to give 
N-(2-cyano-3-methylbutanoyl)urea. Preferably, the reaction is carried out 
in the presence of a reduction catalyst. The termination of the reaction 
can be confirmed and the objective product can be isolated after the 
reaction, according to the above-mentioned methods. 
While the reaction time varies depending on the amount of catalyst, it is 
preferably 3 to 12 hours and the reaction temperature is from 0.degree. C. 
to 50.degree. C., preferably from 30.degree. C. to 40.degree. C. The 
hydrogen pressure is from normal pressure to 30 kg/cm.sup.2, preferably 
from normal pressure to 10 kg/cm.sup.2. 
In the method using acetone as a reaction solvent, acetone is used as a 
solvent and reaction reagent. The amount of acetone as a reaction reagent 
is 1.0-fold to 2.0-fold molar amount, preferably 1.1-fold to 1.5-fold 
molar amount, per mole of cyanoacetylurea, and the amount of acetone as a 
solvent is 1-fold to 20-fold weight amount, preferably 5-fold to 10-fold 
weight amount, relative to cyanoacetylurea. 
In the method using acetone as a reaction solvent, the amount of acetic 
acid to be used is 0.1-fold to 1.0-fold molar amount, preferably 0.2-fold 
to 0.4-fold molar amount, per mole of cyanoacetylurea. 
In the method using acetone as a reaction solvent, the amount of ammonium 
acetate to be used is 0.05-fold to 0.5-fold molar amount, preferably 
0.1-fold to 0.2-fold molar amount, per mole of cyanoacetylurea. 
The reduction catalyst is generally one used for reductive alkylation, 
which is preferably palladium carbon, platinum carbon and the like. 
The reduction catalyst is used in a proportion of 0.5-30 wt %, preferably 
1-10 wt %, relative to cyanoacetylurea, when, for example, 5% palladium 
carbon (50% wet product) is used. 
The present invention is explained in detail by illustrative examples, to 
which the present invention is not limited in any way.

EXAMPLE 1 
Cyanoacetylurea (38.7 g) was suspended in N,N-dimethylformamide (77.4 ml), 
and acetone (24.6 ml), acetic acid (3.43 ml) and ammonium acetate (2.31 g) 
were added. This suspension was subjected to catalytic hydrogenation in 
the presence of 10% palladium carbon (0.78 g, 50% wet product) under 
normal pressure at 30.degree. C. for 9 hours. The reaction mixture was 
heated to 70.degree. C., and the catalyst was filtered off. Water (150 ml) 
was added to the filtrate to allow precipitation of crystals. The crystals 
were collected by filtration to give N-(2-cyano-3-methylbutanoyl)urea 
(yield 40.1 g). 
Melting point: 173-174.degree. C. IR(Nujol):3336,2256,1690,1106 cm.sup.-1 
.sup.1 H-NMR(270 MHz, DMSO-d.sub.6).delta. 0.97(3H,d), 1.00(3H,d), 
2.15-2.35(1H,m), 3.85(1H,d), 7.44(2H,br), 10.49(1H,br) 
EXAMPLE 2 
Cyanoacetylurea (116.1 g) was suspended in N,N-dimethylformamide (219.3 
ml), and acetone (73.1 ml), acetic acid (10.8 ml) and ammonium acetate 
(6.93 g) were added. This suspension was subjected to catalytic 
hydrogenation in the presence of 10% palladium carbon (2.33 g, 50% wet 
product) under hydrogen pressure at 10 kg/cm.sup.2 and at 25.degree. C. 
for 4 hours. The reaction mixture was heated to 70.degree. C., and the 
catalyst was filtered off. Water (745 ml) was added to the filtrate to 
allow precipitation of crystals. The crystals were collected by filtration 
to give crystals of N-(2-cyano-3-methylbutanoyl)urea (yield 134.5 g). 
The data of the obtained compound were as those obtained in Example 1. 
EXAMPLE 3 
Cyanoacetylurea (38.7 g) was suspended in isopropanol (77.4 ml), and 
acetone (24.6 ml), acetic acid (3.43 ml) and ammonium acetate (2.31 g) 
were added. This suspension was subjected to catalytic hydrogenation in 
the presence of 10% palladium carbon (0.78 g, 50% wet product) under 
normal pressure at 30.degree. C. for 8 hours. The reaction mixture was 
heated to 80.degree. C. for 1 hour, and the catalyst was filtered off. 
Water (150 ml) was added to the filtrate to allow precipitation of 
crystals. The crystals were collected by filtration to give crystals of 
N-(2-cyano-3-methylbutanoyl)urea (yield 21.7 g). 
The data of the obtained compound were as those obtained in Example 1. 
EXAMPLE 4 
Cyanoacetylurea (38.7 g) was suspended in N,N-dimethylformamide (77.4 ml), 
and acetaldehyde (18.8 ml), acetic acid (3.43 ml) and ammonium acetate 
(2.31 g) were added. This suspension was subjected to catalytic 
hydrogenation in the presence of 10% palladium carbon (0.78 g, 50% wet 
product) under normal pressure at 30.degree. C. for 5 hours. The catalyst 
was filtered off. Water (350 ml) was added to the filtrate to allow 
precipitation of crystals. The crystals were collected by filtration to 
give crystals of N-(2-cyanobutanoyl)urea (yield 24.2 g). .sup.1 H-NMR(270 
MHz, DMSO-d.sub.6).delta. 0.99(3H,t), 1.75-1.95(2H,m), 3.86(1H,t), 
7.42(2H,br), 10.50(1H,br) 
EXAMPLE 5 
Cyanoacetylurea (78.6 g) was suspended in N,N-dimethylformamide (154.9 ml), 
and acetone (48.8 g), acetic acid (7.2 g) and ammonium acetate (4.6 g) 
were added. This suspension was subjected to catalytic hydrogenation in 
the presence of 10% palladium carbon (3.1 g, 50% wet product) under 
hydrogen pressure at 10 kg/cm.sup.2 and at 25.degree. C. for 4 hours. The 
reaction mixture was heated to 70.degree. C. to dissolve an insoluble 
matter, and the catalyst was filtered off. Water (390 ml) was added to the 
obtained filtrate to allow precipitation of crystals. The crystals were 
collected by filtration to give crystals of 
N-(2-cyano-3-methylbutanoyl)urea (yield 89.7 g). 
The data of the obtained compound were as those obtained in Example 1. 
EXAMPLE 6 
Cyanoacetylurea (51.6 g) was suspended in acetone (516 ml), and acetic acid 
(4.8 g) and ammonium acetate (3.2 g) were added. This suspension was 
subjected to catalytic hydrogenation in the presence of 5% palladium 
carbon (4.1 g, 50% wet product) under normal pressure at 40.degree. C. for 
5 hours. The reaction mixture was refluxed under heating to dissolve an 
insoluble matter, and the catalyst was filtered off. The obtained filtrate 
was concentrated to a half, and water (258 ml) was added to the filtrate 
to allow precipitation of crystals. The crystals were collected by 
filtration to give crystals of N-(2-cyano-3-methylbutanoyl)urea (yield 
62.5 g). 
Melting point: 173-174.degree. C. IR(Nujol):3336,2256,1690,1106 cm.sup.-1 
.sup.1 H-NMR(270 MHz, DMSO-d.sub.6) 0.96(3H,d), 1.00(3H,d), 
2.15-2.35(1H,m), 3.85(1H,d), 7.44(2H,br), 10.49(1H,br) 
EXAMPLE 7 
Cyanoacetylurea (25.8 g) was suspended in acetone (258 ml), and acetic acid 
(2.4 g) and ammonium acetate (1.5 g) were added. This suspension was 
subjected to catalytic hydrogenation in the presence of 5% palladium 
carbon (2.1 g, 50% wet product) under hydrogen pressure at 10 kg/cm.sup.2 
and at 40.degree. C. for 1 hour. The reaction mixture was refluxed under 
heating to dissolve an insoluble matter, and the catalyst was filtered 
off. The obtained filtrate was concentrated to a half. Water (130 ml) was 
added to the filtrate to allow precipitation of crystals. The crystals 
were collected by filtration to give crystals of 
N-(2-cyano-3-methylbutanoyl)urea (yield 30.7 g). 
The data of the obtained compound were as those obtained in Example 6. 
According to the present invention, industrially available cyanoacetylurea 
can be alkylated by an easy, convenient and industrially-utilizable 
method, whereby a useful starting material of a 5-alkyl substituted uracil 
which is an important intermediate for producing pharmaceutical agents 
(e.g., anti-HIV drug, antiviral drug and the like), agents for photographs 
(e.g., stabilizer of silver halide and the like), and the like can be 
provided. Further, the present invention enables alkylation of acetyl 
moiety of the compound having cyanoacetylamino group, according to the 
easy, convenient and industrially-utilizable method. 
This application is based on patent application Nos. 172483/1998 and 
261949/1998 filed in Japan, the contents of which are hereby incorporated 
by reference.