GB2058048A - Process for the manufacture of carbamoyloxypyrimidines - Google Patents

Abstract

A process for the manufacture of a pyrimidine compound having the formula: <IMAGE> wherein R1, R2, R5 and R6 represent hydrogen, substituted or unsubstituted hydrocarbon groups, or together with the adjacent nitrogen atoms, R1 and R2 together, or R5 or R6 together, form a substituted or unsubstituted heterocyclic ring, and R3 and R4 represent hydrogen or halogen, substituted or unsubstituted hydrocarbon groups joined directly or through an O, N or S atom to the pyrimidine ring, or an alkylene group, comprises reacting a hydroxy- pyrimidine having the formula: <IMAGE> with phosgene in the presence of aqueous alkali and subjecting the resulting product to reaction with an amine of the formula: <IMAGE>

Description

SPECIFICATION Chemical process This invention relates to a new chemical process for the manufacture of carbamoyloxypyrimidines.

UK Specification No. 1,181,657 describes compounds of the formula:

in which X and Y are atoms of oxygen or sulphur; R1, R2, R5 and Re represent hydrogen, substituted or unsubstituted hydrocarbon groups, ortogetherwith the adjacent nitrogen atoms, R1 and R2together, or R5 and R6together, form a substituted or unsubstituted heterocyclic ring; and R3 and R4 represent hydrogen or halogen, substituted or unsubstituted hydrocarbon groups joined directly or through an O-, S- or N-atom, to the pyrimidine ring, or an alkylene group.The specification also describes a number of methods of manufacture of those compounds including, where X and Y are both oxygen, the reaction of a hydroxypyrimidine of the formula:

with phosgene, if necessary in the presence of a base, and also if necessary in the presence of a solvent, and reacting the reaction product -h an amine of the formula:

The above reaction is preferably carried out at a temperature below 1 0 C with the phosgene dissolved in an inert solvent, for example, benzene, and the hydroxypyrimidine is added to this solution. The hydroxypyrimidine is preferably admixed beforehand, for example to form a slurry with the base, a suitable base being, for example, triethylamine.The amine, for example, dimethylamine, is then added to the reaction mixture as a solution, for example an aqueous solution.

The latter process is believed to be represented by the following reaction sequence:

It has now been found that the reaction between the hydroxypyrimidine and phosgene can be carried out in the presence of aqueous alkali as base.

According to the present invention there is provided a process for the manufacture of a pyrimidine compound having the formula:

wherein R1, R2, R3, R4, R5 and R6 have the previously defined meanings, which comprises reacting hydroxypyrimidine having the formula:

with phosgene in the presence of aqueous alkali and subjecting the resulting product to reaction with an amine of the formula:

The aqueous alkali used in t he first stage of the process, i.e. reaction of the hydroxpyrimidine of formula (II) with phosgene, may be for example aqueous potassium hydroxide but is preferably aqueous sodium hydroxide. It is also preferred that this stage of the process is carried out in the presence of an inert solvent, for example toluene.

The aqueous alkali is used in an excess over the theoretical amount necessary to absorb the hydrogen chloride generated in the reaction between (II) and phosgene to give (IV). Conveniently from 1.5 to 2.0 mols of aqueous alkali are used per mol of compound (II).

A slight excess of phosgene, i.e. up to 1.1 mols per mol of compound (II) is also used.

When reaction with phosgene is complete, the reaction mixture is added to an excess of amine of formula (III), preferably in the form of an aqueous solution. The compound of formula (V) so obtained is then isolated from the resulting mixture by conventional means.

Both stages of the process are conveniently carried out at normal room temperature, i.e. from 15 to 25 C.

Although phosgene is known to have a high rate of reaction with aqueous alkali and the chloroformate intermediate of formula (IV) would also be expected to be unstable in the presence of aqueous alkali, it is found, surprisingly, that satisfactory yields of high quality products of formula (V) can be obtained by the present process.

The invention is illustrated by the following Examples in which parts and percentages are by weight.

Example 1 2-Dimethylamino-4-hydroxy-5, 6-dimethylpyrimidine (83.5 parts at 100% strength) is slurried in toluene (400 parts) at room temperature and aqueous sodium hydroxide solution (70 parts; 47%) is added. Gaseous phosgene (53.5 parts) is added during 23 minutes via a gas inlet tube dripping below the surface of the stirred reaction mixture, maintaining the reaction temperature at 20-25C. When addition of phosgene is complete, the mixture is stirred for 20 minutes and then added to 60% aqueous dimethylamine solution (75 parts), again maintaining the reaction temperature at 20-25 C. The reaction mass is then extracted twice with aqueous sodium hydroxide solution (33 parts of 47% solution in 100 parts of water) and water (35 parts) is added to the resulting toluene solution of product, followed by sufficient 20% sulphuric acid to adjust the pH to 7. The toluene is then removed by azeotropic distillation with water and the resulting mixture of molten product and water is cooled to 70 c and then crash cooled to granulate the produce by addition of cold water (100 parts). The solid product is collected and dried to give 2-dimethylamino-5, 6-dimethyl-4dimethylcarbamoyloxypyrimidine (71.1 parts) having a strength of 99.7%, equivalent to a 59.6% yield based on the hydroxypyrimidine starting material.

Example 2 The procedure of Example 1 was followed except that a slurry of sodium carbonate (87.2 parts) in water (35 parts) is used in place of the aqueous sodium hydroxide solution as acid binder.

52 Parts of 2-dimethylamino-5, 6-dimethyl-4-dimethylcarbamoyloxypyrimidine are obtained having a strength of 99.1 % equivalent to a 43.3% yield based on the hydroxypyrimidine starting material.

Example 3 The procedure of Example 1 is followed except that aqueous potassium hydroxide solution (98.5 parts at 47% strength) is used in place of the aqueous sodium hydroxide solution as acid binder.

70.3 Parts of 2-dimethylamino-5,6-dimethyl-4-dimethylcarbamoyloxypyrimidine are obtained having a strength of 99.9% equivalent to a 59% yield based on the hydroxypyrimidine starting material.

Example 4 The procedure of Example 1 is followed except that aqueous sodium hydroxide solution (42.6 parts at 47% strength) saturated with sodium chloride (50 parts) is used in place of the aqueous sodium hydroxide solution as acid binder and the phosgene is added over 7 minutes, maintaining the temperature of the reaction mixture at 0-10C. 83.5 Parts of 2-dimethylamino-5,6-dimethyl-4-dimethylcarbamoyloxypyrimidine are obtained having a strength of 99.5% equivalent to a yield of 69.8% based on the hydroxypyridimine starting material.

Example 5 2-Dimethylamino-4-hydroxy-5, 6-dimethylpyrimidine (167 parts at 1000/c strength) is slurried in toluene (690 parts) at room temperature and an aqueous sodium hydroxide solution (140 parts, 4740) is added at a steady rate over a period of 88 minutes. 5 Minutes after the addition of the sodium hydroxide solution has started, the addition of phosgene (106.4 parts) as a liquid is started and continues at an even rate over 85 minutes with the temperature of the reaction mixture maintained at 0-1 0-C. On completion of the phosgene and sodium hydroxide addition, 60% aqueous dimethylamine solution (150 parts) is added to the mixture over a period of 75 minutes, again maintaining the reaction temperature at 0-10'C. The product is isolated as described in Example 1 and 2-dimethylamino-5,6-dimethyl-4-dimethylcarbamoylOxypyrimidine (138.2 parts) having a strength of 99.3% is obtained, being equivalent to a 57.70o yield based on the hydroxypyrimidine starting material.

Claims (8)

1. A process for the manufacture of a pyrimidine compound having the formula:

wherein R1, R2, R5 and Re represent hydrogen, substituted or unsubstituted hydrocarbon groups, or together with the adjacent nitrogen atoms, R1, and R2 together, or R5 or Re together, form a substituted or unsubstituted heterocyclic ring, and R3 and Ra represent hydrogen or halogen, substituted or unsubstituted hydrocarbon groups joined directly or thorough an O, N or S atom to the pyrimidine ring, or an alkylene group, which comprises reacting a hydroxypyrimidine having the formula:

with phosgene in the presence of aqueous alkali and subjecting the resulting product to reaction with an amine of the formula:

2.A process as claimed in claim 1 wherein the aqueous alkali is aqueous sodium hydroxide.

3. A process as claimed in claim 1 or claim 2 wherein the reaction between the hydroxypyrimidine compound of formula (II) and phosgene in the presence of aqueous alkali is carried out in the presence of an inert solvent.

4. A process as claimed in any one of claims 1 to 3 wherein from 1.5 to 2.0 mols of alkali are used per mol of the hydroxypyrimidine compound of formula (II).

5. A process as claimed in any one of claims 1 to 4 wherein there are used up to 1.1 mols of phosgene per mole of the hydroxypyridimine compound of formula (II).

6. A process as claimed in any one of claims 1 to 5 wherein the amine of formula (ill) is used in the form of an aqueous solution.

7. A process as claimed in claim 1 and substantially as hereinbefore described in any one of the foregoing Examples.

8. A pyrimidine compound of formula (V) whenever obtained by a process as claimed in any one of the preceding claims.