CA2512305C - A process for the production of 2,5-diamino-4,6-dichloropyrmidine - Google Patents

Abstract

A process for the production of 2,5-diamino-4,6--dichloropyrimidine of the formula: (see formula I) wherein, in a first step, an aminomalonic ester of the general formula: (see formula II) in which R1 denotes a C1-C6 alkyl group, or a salt thereof is cyclised with guanidine or a salt thereof in the presence of a base to yield a 2,5-diamino-4,6-dihydroxypyrimidine of the formula: (see formula III) or a salt thereof, chlorinating the latter in a second step with a chlorinating agent in the presence of an amide of the general formula: (see formula (IV) in which R2 is a 5- or 6-membered N-heterocycloalkyl residue, which is optionally substituted on the nitrogen atom, or -NR3R4, in which R3 and R4 are identical or different and represent a C1-C6 alkyl group or a benzyl group, to yield a 4,6--dichloropyrimidine of the general formula: (see formula V) in which R2 is defined as above and R5 denotes -NH21-NH-CH=O or -N=CH-R2, in which R2 is defined as above, and reacting the compound V in a third step with a carboxylic acid of the general formula: (see formula VI) in which R6 denotes a C1-C6 alkyl group, branched or unbranched, or a C3-C6 cycloalkyl group, in an aqueous alcoholic solution to yield the final product of formula (I).

Description

A PROCESS FOR THE PRODUCTION OF 2,5-DIAMINO-4,6-DICHLOROPYRIMIDINE
This application is a division of Canadian Application Serial No. 2,145,928, filed March 30, 1995. The claims of the present application are directed to a process to prepare 2,5-diamino-4,6-dichloropyrimidine. However, for the purpose of understanding the invention, including all objects and features which are inextricably bound-up in one and the same inventive concept, the teachings of those features claimed in the parent Canadian Application Serial No. 2,145,928 are retained herein.
Accordingly, the retention of any such objects or features which may be more particularly related to the parent application or a separate divisional thereof should not be regarded as rendering the teachings and claiming ambiguous or inconsistent with the subject matter defined in the claims of the divisional application presented herein when seeking to interpret the scope thereof and the basis in this disclosure for the claims recited herein.

This invention relates to N-(2-amino-4,6-dichloropyrimidin-5-yl)formamide, and to a process for its preparation. This compound is a valuable intermediate in the preparation of antiviral nucleotide derivatives (PCT Application WO 91/01 310).

N-5-protected-2,5-diamino-4,6-dichloropyrimidines which serve as intermediates in the preparation of antiviral nucleotide derivatives have previously been disclosed (EP-A 0 552 758) . However, these compounds suffer from the disadvantage that they are difficult to convert into the corresponding nucleotide derivatives.

An object of the invention is, therefore, to provide a pyrimidine derivative which can be used as an intermediate to obtain the corresponding nucleotide derivatives in good yield, and also to make available an economic process for preparing this pyrimidine derivative.

According to the invention there is provided an N- (2-amino-4,6-dichloropyrimidin-5-yl)formamide of the formula:

O
HN)~ H
CI CI ( I ) TI-Y Ny N

The invention also provides a process for preparing N-(2-amino-4,6-dichloropyrimidin-5-yl)formamide of the formula:

O
HN H
CI CI
(I) Ny N

NH

which comprises, in a first step, cyclizing an aminomalonic ester of the general formula:

NH
~O O, R (II) 1 ~
O O

in which R1 denotes a C1-C6-alkyl group, or a salt thereof, with guanidine or a salt thereof in the presence of a base to give 2,5-diamino-4,6-dihydroxypyrimidine of the formula:

NH

HO OH

NTN (III) NH

or a salt thereof, chlorinating the latter, in a second step, with a chlorinating agent in the presence of an amide of the general formula:

(1 H C -R (IV) in which R2 denotes a 5- or 6-membered heterocycloalkyl radical, which is optionally substituted on the hetero atom, or denotes -NR3R4, in which R3 and R4 are identical or different and are each a C1-C6-alkyl group or a benzyl group, to give a 4,6-dichloropyrimidine of the general formula:

R

N)", (V) CI CI

NTN
R

in which R2 has the specified meaning and R5 denotes -NH2, and reacting the compound (V), in a third step, with an aqueous solution of a carboxylic acid of the general formula:

R COOH
6 (VI) in which R6 denotes a C1-C6-alkyl group, branched or unbranched, or a C3-C6-cycloalkyl group, to give an end product of formula (I) .

The N-(2-amino-4,6-dichloropyrimidin-5-yl)-formamide of the invention is a novel compound which has not previously been described in the literature.

As indicated above, in the first step of the process of the invention, an aminomalonic ester of the general formula:
NH

pO RI (II) O O

in which Rl denotes a Cl-C6-alkyl group, or a salt thereof, is cyclized with guanidine or a salt thereof in the presence of a base to give 2,5-diamino-4,6-dihydroxypyrimidine of the formula:
NH

HO OH

NTN (III) NH

or a salt thereof.

The aminomalonic esters of general formula (II) which are employed as starting compounds may be obtained in known manner by amidating the corresponding malonic ester derivatives.

An alkali metal alcoholate, such as, for example, sodium or potassium methoxide, or sodium or potassium ethoxide, is expediently used as the base, in conformity with EP-A 0 552 758. In-situ-formed sodium methoxide in methanol or sodium ethoxide in ethanol is preferably employed.

The salts of the aminomalonic ester and of guanidine which are expediently used are their hydrochloride or hydrobromide salts.

The cyclization is expediently carried out at a temperature between room temperature and the reflux temperature of the relevant solvent, preferably at the reflux temperature.

After a customary reaction time of between 2 and 6 hours, the intermediate of formula (III) can then, where appropriate, be isolated using customary methods. The synthesis of the end product of formula (I) is preferably carried out without isolating the intermediate of formula (III).

The second step of the process is carried out by chlorinating the intermediate of formula (III), or salt thereof, with a chlorinating agent in the presence of an amide of the general formula:

H C R2 (IV) to form a 4,6-dichloropyrimidine of the general formula:

R

N)"' ci CI
yl--r (V) NTN

R

The substituent R. denotes -NH2. The substituent R2 denotes either a 5- or 6-membered heterocycloalkyl radical, which is optionally substituted on the heteroatom, such as, for example, piperidinyl, morpholinyl, thiomorpholinyl, pyrrolidinyl or N-methylpiperazinyl, preferably piperidinyl or pyrrolidinyl; or NR3R4, in which R3 and R4 are identical or different and are each a Cl-C6-alkyl group, such a, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl or hexyl, preferably methyl, or a benzyl group.

Consequently, N,N-dimethylformamide, N,N-diethyl-formamide, N,N-diisopropylformamide, N-formylpiperidine, N-formylmorpholine, N-formylthiomorpholine, N,N-methylformyl-piperazine or N,N-dibenzylformamide, preferably N,N-dimethylformamide, N-formylpiperidine or N,N-dibenzyl-formamide may be employed, for instance, as amides of formula (IV).

The salts of the intermediate of formula (III) which are expediently used include the hydrochloride and hydrobromide salts, as well as alkali metal salts, such as, for example, the sodium or potassium salt.

The chlorinating agents which may be employed are those which are familiar to the person skilled in the art, such as, for example, phosphorus oxychioride, thionyl chloride, suiphuryl chloride, phosphorus trichloride, phosphorus pentachloride, phosgene or diphosgene. Phosphorus oxychloride is preferably used as the chlorinating agent.

The chlorinating agent and the amide(IV) are expediently employed in a molar ratio of from 1 to 0.55 up to 1 to 10, preferably in a molar ratio of from 1 to 0.55 up to 1 to 1.

The chlorination is expediently carried out at a temperature of from 50 C up to the reflux temperature of the relevant solvent.

The previously described amide(IV) can also be employed as the solvent for the chlorination. However, the chlorination can additionally be carried out in an inert solvent. Examples of inert solvents which can be employed are toluene, xylene, chloroform, dichloromethane, dichloro-ethane and chlorobenzene, preferably toluene or dichloro-ethane.
Following a customary reaction time of from 3 to 24 hours, the corresponding 4,6-dichloropyrimidine of general formula V(R5 =-NHz) can be isolated in a manner familiar to the person skilled in the art. These 4,6-dichloropyrimidines have not been described in the literature, and are, therefore, novel intermediates in the preparation of N-(2-amino-4,6-dichloropyrimidin-5-yl)-formamide, and an integral part of the invention. 4,6-Dichloro-N'-(dimethyl-aminomethylene)pyrimidine-2,5-diamine and 4,6-dichloro-N'-(piperidin-l-ylmethylene)pyrimidine-2,5-diamine are preferred representative of the 4,6-dichloropyrimidines (V, RS = -NHZ).

Precursors of these 4,6-dichloropyrimidines (V) may also be isolated in dependence on the reaction conditions or working-up conditions which are selected. These precursors are likewise defined by the general formula V. RS then denotes -NH-CH=O or -N=CH-R2, in which R2 has the specified meaning. These precursors are likewise not known from the literature, and are, therefore, novel intermediates in the preparation of N- (2-amino-4,6-dichloropyrimidin-5-yl)formamide, and an integral part of t h e i n v e n t i o n. 4, 6- D i c h l o r o- N, N'-bis(dimethylaminomethylene)pyrimidine-2,5-diamine, 4,6-dichloro-N,N'-bis(piperidin-1-ylmethylene-pyrimidine-2,5-diamine or N-[4,6-dichloro-5-(dimethylamino-methyleneamino)pyrimidin-2-yl]formamide are preferred representatives.

In the third step of the process of the invention, the 4,6-dichloropyrimidines of general formula (V) are reacted with an aqueous solution of a carboxylic acid of the general formula:
R COOH
6 (VI) in which R6 denotes a C1-C6-alkyl group, branched or unbranched, or a C3-C6-cycloalkyl group, to give the end product of formula (I).
Acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, isobutyric acid, pivalic acid, cyclopropanecarboxylic acid, cyclopentanecarobxylic acid, or cyclohexanecarboxylic acid may be employed as the carboxylic acid. Acetic acid, propionic acid or pivalic acid is expediently employed.
The carboxylic acid is expediently employed in a concentration of from 20 to 70 vol.%, preferably from 25 to 50 vol.o %
.
It has also been ascertained that, if the carboxylic acid in the last step (the third step) is employed in an aqueous, alcoholic solution, this results in the direct formation of 2,5-diamino-4,6-dichloropyrimidine of formula (VII), which can also be converted into the corresponding nucleotide derivative.

Accordingly, the present invention also provides a process for the production of 2,5-diamino-4,6-dichloropyrimidine of the formula:
NH

CI CI
N
TN (VII) wherein, in a first step, an aminomalonic ester of the general formula:

NH
O O~R~ (II) O O

in which R1 denotes a C1-C6 alkyl group, or a salt thereof is cyclised with guanidine or a salt thereof in the presence of a base to yield a 2,5-diamino-4,6-dihydroxypyrimidine of the formula:

NH

HO OH ( I I I) NyN

i NH

or a salt thereof, chlorinating the latter in a second step with a chlorinating agent in the presence of an amide of the general formula:

H 1 R ( I V ) in which R2 is a 5- or 6-membered N-heterocycloalkyl residue, which is optionally substituted on the nitrogen atom, or -NR3R4, in which R3 and R4 are identical or different and represent a C1-C6 alkyl group or a benzyl group, to yield a 4,6-dichloropyrimidine of the general formula:

R

N j CI (V) CI

N N
R

in which R2 is defined as above and R5 denotes -NHz, -NH-CH=O or -N=CH-R2, in which R 2 is defined as above, and reacting the compound V in a third step with a carboxylic acid of the general formula:

R COOH ( VI ) -10a-in which R6 denotes a C1-C6 alkyl group, branched or unbranched, or a C3-C6 cycloalkyl group, in an aqueous alcoholic solution to yield the final product of formula (VII).

An aqueous solution of methanol, ethanol, propenol, butanol, pentanol or hexanol may be employed as the aqueous, alcoholic solution.

The reaction in the third step is expediently carried out at a temperature of from 50 to 100 C, preferably at a temperature of from 70 to 90 C.

Following a customary reaction time of from 1 to 10 hours, the end product of formula (I) or (VII) can be isolated using working-up methods which are customary for the person skilled in the art. By contrast with the known N-5-protected-2,5-diamino-4,6-dichloropyrimidines (EP-A 0 552 758), the novel end product of formula (I), and also the known end product of formula (VII), can be converted without difficulty and in good yield into the corresponding nucleotide derivative.

The following Examples illustrate the invention.
Example 1 Preparation of N- (2-amino-4, 6-dichloropyrimidin-5-yl) formamide -lOb-1.1 Preparation of 4,6-dichloro-N'-(dimethylaanino-methylene)tpyrimidine-2,5-diamine One-pot process:

A suspension of 25 g (117 mmol) of aminomalonic ester hydrochloride in 50 ml of methanol was cooled down to 10 C, and 21.07 g of sodium methoxide (30% in methanol) were added. This suspension was added dropwise to a mixture of 63.2 g (351 mmol) of sodium methoxide (30% solution in methanol) and 12.55 g (128.7 mmol) of guanidine hydrochloride in 50 ml of methanol.
The reaction mixture was heated to reflux and then stirred at this temperature for 16 hours. Subsequently, 13.5 g (370 mmol) of HC1 gas were passed into the warm suspension. The methanol was then distilled off. During the distillation, a total of 200 ml of toluene was slowly added dropwise. After all the methanol had been distilled off, 71.6 g (468 mmol) of POC13 were added dropwise, followed by 34.2 g (468 mmol) of dimethylformamide, which was added dropwise at 80 C. The mixture was stirred at 80 C for 17.5 hours and then cooled down to room temperature;
64.7 g of K2C03, dissolved in 150 ml of water, were then added slowly. The mixture was heated once again at 50 C for 5 hours.
After that, it was adjusted to a pH of 7 using a 30% solution of NaOH, cooled, and the product was filtered off. After washing with water and drying in vacuo, 23.2 g (85%) of pure product were obtained as a pale brown solid.

'H-NMR (DMSO, 400 MHz)b: 2.9-3.0 (2s, 6H);
6.9 (s, 2H);

7.6 (s, 1H).

13C-NMR (DMSO, 100 MHz): 33.5;

39.3;
130.3;
153.5;

157.0;
157.1.
m.p.: 195 C (decomp.).

1.2 Preparation of N-(2-amino-4,6-dichloropyrimidin-5-yl)formamide a) A solution of 2.35 g (10 mmol) of the product from procedure 1.1 in 15 g of a 50% aqueous solution of propionic acid was stirred at 70 C for 7 hours. The mixture was then cooled down and the product filtered off. After washing with water and drying in vacuo, 1.66 g of a white solid were obtained. This solid was suspended in 50 ml of a 2M solution of K2CO3, and the suspension was stirred at room temperature for 2 hours. Filtration then took place and the product was washed with water and dried in vacuo. 1.33 g (64%) of pure product were obtained as an almost white solid.

'H-NMR (DMSO, 300 MHz)b: 9.6-10.1 (b, 1H);

8.3 and 8.0 (2s, 1H);
7.7 and 7.6 (2s, 2H).

b) Proceeding analogously with a), pivalic acid was employed as the carboxylic acid in place of propionic acid, and the product was worked up in a corresponding manner. The yield was 70%.

Example 2 Preparation of 4,6-dichloro-N'-(dimethylamino-methylene)pyrimidine-2,5-diamine 2.1 Preparation of 4,6-dichloro-N,N'-bis(dimethvl-aminomethylene)pyrimidine-2,5-diamine A suspension of 4.46 g (25 mmol) of diaminodihy-droxypyrimidine hydrochloride in 45 ml of toluene and 15.33 g (100 mmol) of phosphorus oxychloride was heated to 90 C. 7.31 g (100 mmol) of dimethylformamide were added dropwise over a period of 45 minutes. The mixture was then stirred at 90 C for hours. The reaction mixture was allowed to cool down, and 100 g of a 10% solution of K2C03 were slowly added to it. 19.5 g of solid K2C03 were then added so that the pH rose to 7. The 20 product was extracted three times with ethyl acetate. The combined organic phases were dried over MgSO4 and concentrated on a rotary evaporator. 6.44 g of a pale brown solid were obtained. Yield: 89%.

'H-NMR (DMSO, 400 MHz)b: 2.9-3.1 (4s, 12H);
7.6 (s, 1H);

8.5 (s, 1H).

13C-NMR (DMSO, 100 MHz): 33.5;

39.4;
40.4;
134.2;

153.0;
156.7;
158.0;
159.1.
m.p.: 121.5 - 123 C.

CHN: calculated for C10H14C12N6: C 41.54, H 4.88, N 29.06;
found: C 41.4, H 4.58, N 28.6.

2.2 Preparation of N-[4,6-dichloro-5-(dimethvl-aminomethyleneamino)pyrimidin-2-yl]formamide A suspension of 3 g (10 mmol) of the product from step 2.1 in 10 ml of a 50% aqueous solution of acetic acid was stirred at room temperature for 4.5 hours. The product was then filtered off and washed twice with 10 ml of water on each occasion. After drying in vacuo, 2.18 g (83%) of pure product were obtained as a white solid.

1H-NMR (DMSO, 400 MHz)b: 2.9-3.1 (2s, 6H);
7.7 (s, 1H) ;

9.2 (d, 1H);
11.2 (d, 1H).

13C-NMR (DMSO, 100 MHz): 33.6;

39.6;
136.9;
149.6;

153.4;
156.9;
162.5.
m.p.: 172.5 - 174 C.

CHN: calculated for C8H9C12N5: C 36.66, H 3.46, N 26.72;
found: C 36.7, H 3.07, N 25.9.

2.3 Preparation of 4,6-dichloro-N'-(dimethvlamino-methylene)pvrimidine-2,5-diamine A solution of 1.85 g (7.1 mmol) of the product from procedure 2.2 in 25 ml of 10% hydrochloric acid was heated to 40 C and stirred at this temperature for 1.5 hours. The reaction mixture was cooled down and the pH was adjusted to 8.7 with 2M K2C03. The product, which had precipitated out, was filtered off and washed with water. After drying in vacuo, 1.52 g (91%) of pure product was obtained as a white solid.

The spectroscopic data were analogous to those given above.

2.4 Preparation of 4,6-dichloro-N'-(dimethylamino-methvlene)pyrimidine-2,5-diamine One-pot process:

A suspension of 4.46 g (25 mmol) of diaminodihydroxypyrimidine hydrochloride in 90 ml of toluene and 15.33 g (100 mmol) of phosphorus oxychloride was heated to 80 C.

7.31 g (100 mmol) of dimethylformamide were added dropwise over a period of 60 minutes. The reaction mixture was then stirred at 80 C for 16 hours. It was allowed to cool down and 100 ml of water were then added. The pH was adjusted to 1 using a total of 8.4 g of Na2CO3 . The reaction mixture was heated to 40 C and stirred at this temperature for 4 hours. It was then cooled down to room temperature and neutralized with a 30% solution of NaOH, and the product was filtered off. After washing with water and drying in vacuo, 5.5 g (95%) of product were obtained as a beige solid. This corresponds to a yield of 89%.

The spectroscopic data were analogous to those given above.

Example 3 Preparation of 4,6-dichloro-N'-(piperidin-1-yl-methylene)pyrimidine-2,5-diamine 3.1 Preparation of 4,6-dichloro-N,N'-bis(pineridin-l-ylmethylene)pyrimidine-2,5-diamine A suspension of 3.57 g (20 mmol) of diaminodihy-droxypyrimidine hydrochloride in 70 ml of toluene and 12.27 g (80 mmol) of phosphorus oxychloride was heated to 80 C. 9.05 g (80 mmol) of 1-formylpiperidine were added dropwise over a period of 60 minutes. The reaction mixture was then stirred at 80 C for 22 hours. It was allowed to cool down, and 100 ml of a 1M solution of K2C03 were then added to it and the pH was adjusted to 7 with NaOH. The product was extracted with three portions of ethyl acetate. The combined organic phases were dried over MgSO4 and concentrated on a rotary evaporator. 10.87 g of an oil were obtained which still contained a large quantity of N-formylpiperidine. The product was purified by suspending in hexane and then filtering. Yield: >90%.

1H-NMR (DMSO, 300 MHz)b: 8.5 (s, 1H);
7.7 (s, 1H) ;
3.4-3.8 (m, 8H);
1.5-1.9 (m, 12H).

3.2 Preparation of 4,6-dichloro-N'-(piperidin-1-yl-methylene)gvrimidine-2,5-diamine A solution of 9.9 g (18.2 mmol) of the product from procedure 3.1 in 73 g of 10% HC1 was first stirred at room temperature for 4.5 hours and then s t i rred at 470C for 2 hours.
It was cooled down and the pH was adjusted to 7 using 30% NaOH.
The product was filtered off, washed with water and dried in vacuo. 4.68 g (88%) of product were obtained as a pale brown solid.

'H-NMR (DMSO, 300 MHz)b: 7.55 (s, 1H);
7.4 (s, 2H);
3.2-3.7 (m, 4H);

1.5-1.8 (m, 6H).

Example 4 Subsequent conversion of N-(2-amino-4,6-dichloro-pyrimidin-5-yl)formamide into 2-amino-9-butyl-6-chloropurine 4.1 Preparation of N-(2-amino-4-butylamino-6-chloro-pyrimidin-5-yl)formamide A solution of 0.43 g (2 mmol) of N-(2-amino-4,6-dichloropyrimidin-5-yl)formamide and 0.31 g (4.2 mmol) of n-butylamine in 10 ml of tetrahydrofuran was stirred at room temperature for 17 hours. Water was then added to the reaction mixture and the product was extracted with ethyl acetate. After drying the organic phase over MgSO4, and concentrating it on a rotary evaporator, 0.49 g of a white solid was obtained which was purified by recrystallizing in toluene. 0.46 g of pure product was obtained, corresponding to a quantitative yield.

'H-NMR (DMSO, 300 MHz)b: 9.0 and 8.6 (s and d, 1H);
8.1 and 7.8 (s and d, 1H);
7.0 and 6.75 (2t, 1H);

6.5 and 6.4 (2s, 2H);
3.3-3.4 (m, 2H);

1.4-1.6 (m, 2H);
1.2-1.4 (m, 2H);
0.9 (t, 3H).

4.2 Preparation of 2-amino-9-butyl-6-chloropurine A suspension of 0.51 g (2 mmol) of the product from procedure 4.1 in 10 ml of diethoxymethyl acetate was heated under reflux for 3.5 hours. It was then completely evaporated, and 30 ml of a 0.5M solution of HC1 was added to the residue.
After 3 hours at room temperature, the yellow solution was adjusted to a pH of 8 using NaOH, and the resulting suspension was extracted 3 times with ethyl acetate. The combined organic phases were dried and concentrated on a rotary evaporator. 0.46 g (97%) of the desired product was obtained, which was 95% pure (according to 1H-NMR) .

'H-NMR (DMSO, 300 MHz)b: 8.2 (s, 1H);
6.9 (s, 2H) ;
4.05 (t, 2H);
1.6-1.9 (m, 2H);

1.1-1.4 (m, 2H);
0.9 (t, 3H).

Comparative Example 4.3 Conversion of 5-(N-ethoxvcarbonyl)-2-amino-4,6-dichloroAVrimidine into 2-amino-9-butvl-6-chloro-7,9-dihydroyurin-8-one As a Comparative Example, 5-(N-ethoxycarbonyl)-2-amino-4,6-dichloropyrimidine, as a derivative of an N-5-protected-2,5-diamino-4,6-dichloropyrimidine (EP-A 0 552 758), was reacted under conditions which were analogous to those in Example 4.

However, under these conditions, 2-amino-9-butyl-6-chloro-7,9-dihydropurin-8-one was obtained rather than 2-amino-9-butyl-6-chloropurine.

Example 5 Preparation of 2,5-diamino-4,6-dichlorogvrimidine A mixture of 2.35 g (10 mmol) of the product from Example 1.1 in 5 g of pivalic acid, 10 ml of methanol and 15 ml of water was stirred at 80 C for 4.5 hours. The precipitated solid was subsequently filtered off and the filtrate was neutralized with a concentrated solution of NaOH. It was then extracted with ethyl acetate and the combined organic phases were dried over MgSO4. Following concentration on a rotary evaporator, 1.40 g of a product mixture remained, 65% of which (determined by 'H-NMR) consisted of the desired product (yield 51%). The product was not subjected to further purification.
Example 6 Subsequent conversion of 2,5-diamino-4,6-dichloro-pyrimidine into 2-amino-9-butyl-6-chloropurine 6.1 2,5-Diamino-4-butylamino-6-chlorovyrimidine A suspension of 2.5 g (14 mmol) of 2,5-diamino-4,6-dichloropyrimidine, 1.37 g (18.7 mmol) of n-butylamine and 6 ml of triethylamine in 60 ml of butanol was stirred at 100 C for 9 hours. The reaction mixture was then cooled down and concentrated to dryness on a rotary evaporator. Water was added to the residue and the product was extracted with ethyl acetate.
After the organic phase had been dried over Na2SO4 and concentrated on a rotary evaporator, the residue was suspended in 10 ml of isopropyl ether, and the product was filtered off and dried. 2.24 g(75%) of an orange-red solid were obtained.
1H-NMR (CDC13, 300 MHz)5: 5.4 (broad s, 1H) ;

4.6 (s, 2H);
3.4 (t, 2H) ;
2.7 (s, 2H);

1.6 (m, 2H);
1.4 (m, 2H) ;
0.95 (t, 3H).

6.2 Preparation of 2-amino-9-butvl-6-chloropurine A solution of 1.0 g (4.63 mmol) of the product from procedure 6.1 in 10 ml of dimethylformamide and 10 ml of ethyl orthoformate was cooled down to 0 C, and 0.5 ml of concentrated HC1 was added. As a result, the temperature rose to 10 C. The mixture was then stirred at room temperature for 22 hours. It was then completely evaporated, and 40 ml of an 0.5M solution of HC1 were added to the residue. After 2 hours at room temperature, the yellow solution was adjusted to a pH of 8 with NaOH, and the resulting suspension was extracted 3 times with ethyl acetate. The combined organic phases were dried and concentrated on a rotary evaporator. 1.1 g (quantitative) of the desired product was obtained, which was 95% pure (by 1H-NMR ) .

The spectroscopic data were analogous to those in Example 4.2.

Claims (8)

1. A process for the production of 2,5-diamino-4,6-dichloropyrimidine of the formula:

wherein, in a first step, an aminomalonic ester of the general formula:

in which R1 denotes a C1-C6 alkyl group, or a salt thereof is cyclised with guanidine or a salt thereof in the presence of a base to yield a 2,5-diamino-4,6-dihydroxypyrimidine of the formula:

or a salt thereof, chlorinating the latter in a second step with a chlorinating agent in the presence of an amide of the general formula:

in which R2 is a 5- or 6-membered N-heterocycloalkyl residue, which is optionally substituted on the nitrogen atom, or -NR3R4, in which R3 and R4 are identical or different and represent a C1-C6 alkyl group or a benzyl group, to yield a 4,6-dichloropyrimidine of the general formula:

in which R2 is defined as above and R5 denotes -NH2,-NH-CH=O or -N=CH-R2, in which R2 is defined as above, and reacting the compound V in a third step with a carboxylic acid of the general formula:

in which R6 denotes a C1-C6 alkyl group, branched or unbranched, or a C3-C6 cycloalkyl group, in an aqueous alcoholic solution to yield the final product of formula (VII).

2. A process according to claim 1, wherein the reaction is performed in the absence of isolating the intermediates of the formula (III).

3. A process according to claim 1 or 2, wherein an alkali metal alkoxide is provided as the base in the first step.

4. A process according to any one of claims 1 to 3, wherein phosphorus oxychloride is provided as the chlorinating agent in the second step.

5. A process according to any one of claims 1 to 4, wherein dimethylformamide, N-formylpiperidine or N, N-dibenzylformamide is provided as the amide in the second step.

6. A process according to any one of claims 1 to 5, wherein the chlorination in the second step is performed at a temperature of 50°C to reflux temperature.

7. A process according to any one of claims 1 to 6, wherein acetic acid, propionic acid or pivalic acid is provided as the aliphatic carboxylic acid in the third step.

8. A process according to any one of claims 1 to 7, wherein the reaction in the third step is performed at a temperature of 50 to 100°C.