Process for the preparation of pyrimidine compounds

Abstract

A process for preparing agrochemical intermediates of formula (I), wherein W is (CH.sub.3 O).sub.2 CH.CHCO.sub.2 CH.sub.3 or CH.sub.3 O.CH.dbd.CCO.sub.2 CH.sub.3 ; Z.sup.1 is a halogen atom; and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently hydrogen, halogen, C.sub.1-4 alky, C alkoxy, acetoxy or acyl; the process comprising the steps of: (a) reacting a compound of formula (II), wherein X, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as defined above, with a compound of formula ROCH.sub.3, wherein R is a metal; and, (b) reacting the product of (a) with a compound of formula (III), wherein Z.sup.1 and Z.sup.2 are halogen atoms. A process for the preparation of compounds of formula (II) and compounds of formula (II) themselves. A process for obtaining, in substantially pure form, a compound of formula (11) and compounds of formula (II) themselves. A process for obtaining, in substantially pure form, a compound of formula (11) wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are all hydrogen.

Description

The present invention relates to a process for preparing (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate, an intermediate in the agrochemical industry.

Methods for preparing (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate are described in WO 92/0870.

The present invention provides a process for preparing a compound of formula (I), comprising treating a compound of formula (II) with an acid catalyst in the presence of an acid anhydride, an acid chloride or 2-acetoxybenzonitrile at a temperature in the range 70-110.degree. C.

Acid catalysts include acids (such as sulphonic acid or a derivative thereof (for example chlorosulphonic acid, methane sulphonic acid or p-toluene sulphonic acid), hydrochloric acid or an acetic acid derivative (for example trifluoroacetic acid or di- or trichloroacetic acid)), a suitable phenol derivative (such as 2-cyanophenol) or potassium bisulfate.

Acid anhydrides are preferably C.sub.2-5 alkyl anhydrides, for example acetic anhydride.

Acid chlorides are preferably C.sub.2-5 alkyl chlorides, for example acetyl chloride or propionyl chloride.

The process of the invention can be carried out in the presence of a solvent. Such a solvent is preferably inert under the process conditions. Suitable solvents include saturated or unsaturated hydrocarbons (such as toluene, o-xylene, m-xylene, p-xylene, cyclohexane or methylcyclohexane), an ether (such as glyme or diglyme) or a ketone (such as methylisobutylketone). It is preferred that the solvent has a boiling point in the range 70-140.degree. C., especially in the range 85-120.degree. C.

In one aspect the present invention provides a process for preparing a compound of formula (I), comprising treating a compound of formula (II) with an acid catalyst in the presence of an acid anhydride.

In another aspect the present invention provides a process for preparing a compound of formula (I), comprising treating a compound of formula (II) with methane sulphonic acid, chlorosulphonic acid or 2-cyanophenol in the presence of an acid anhydride, an acid chloride or 2-acetoxybenzonitrile, the process being conducted in the presence of a solvent.

In a further aspect the present invention provides a process for preparing a compound of formula (I), comprising treating a compound of formula (II) with methane sulphonic acid or chlorosulphonic acid in the presence of an acid anhydride, the process being conducted in the presence of a solvent.

The process of the present invention can be carried out by treating a compound of formula (II) with an acid catalyst (preferably methane sulphonic acid) in the presence of an acid anhydride (especially acetic anhydride), an acid chloride (especially acetyl chloride) or 2-acetoxybenzontrile at a temperature in the range 70-110.degree. C. (especially 85-100.degree. C.) at ambient pressure.

Alternatively, the process of the present invention can be carried out by treating a compound of formula (II) with an acid catalyst (preferably methane sulphonic acid) in solvent (especially toluene or methylcyclohexane) in presence of a suitable acid anhydride (especially acetic anhydride) at a temperature in range 70-110.degree. C. (especially 85-100.degree. C.) at ambient pressure.

In a further aspect the present invention provides a process for preparing a compound of formula (I) comprising treating a compound of formula (II) (1 equivalent) with methane sulphonic acid (about 0.05 equivalents) in the presence of acetic anhydride (about 1 equivalent, preferably 1 to 1.1 equivalents) at a temperature in the range 85-105.degree. C. (especially 90-95.degree. C.), the process being carried out in the absence of a solvent.

It is preferred that, when the process is carried out in the absence of a solvent, the compound of formula (I) is isolated by: (i) distilling off by-products (preferably at a temperature in the range 50-150.degree. C. and under atmospheric pressure), (ii) partitioning the resulting residue between an organic solvent (such as toluene or a xylene) and water, and (iii) evaporating the organic phase to leave a compound of formula (I).

The following Examples illustrate the invention. Throughout the Examples the following abbreviations are used:

gc=gas chromatography NMR=nuclear magnetic resonance

EXAMPLE 1

Methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (44.8 g) was heated to 95.degree. C. 2-Cyanophenol (14.3g) was added and acetic anhydride (11.7 g) was added via a syringe pump running at 6.35 ml h.sup.-1. The reaction was monitored by gc and .sup.1 H NMR, which showed that demethanolysis was complete in 4 hours.

EXAMPLE 2

Methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (44.6 g) was heated to 90-95.degree. C. 2-Acetoxybenzonitrile (19.3 g) was added and then methane sulphonic acid (0.61 g) was added via a syringe. The reaction was monitored by gc and .sup.1 H NMR, which showed that demethanolysis was complete in 5 hours.

EXAMPLE 3

A mixture of methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (17.98 g), acetic anhydride (5.16 g) and toluene (73 ml) was stirred at 90.degree. C. for 20 minutes. Methane sulphonic acid (0.49 g) was added to the mixture and the mixture was heated at 90.degree. C. for 1 hour. The mixture was cooled to room temperature, washed with cold water (25 ml) and with hot (50.degree. C.) water (2.times.25 ml). The organic layer was evaporated at 75.degree. C. (initially on a rotary evaporator, then at circa 15 mm Hg) to leave (E)-methyl 2-[-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate as a solid (16.1 g).

EXAMPLE 4

Preparation of Starting Material

To a stirred mixture of 3-(.alpha.-methoxy)methylenebenzofuran-2(3H)-one (193.4 g of 91% pure material) and 4,6-dichloropyrimidine (165.5 g) in methyl formate (400 g) at 20-25.degree. C. under nitrogen was added sodium methoxide (207 g of a 30% w/w solution in methanol) portionwise, over 10 hours while maintaining the temperature at 20-25.degree. C. Once all the sodium methoxide solution had been added the reaction mixture was stirred for 2 hours after which water (9 g) was added. The methanol and methyl formate were distilled from the reaction mixture (internal temperature 90-95.degree. C.) to leave a residue.

Water (700 g) was added to the residue and the mixture stirred at 80.degree. C. for 30 minutes.

Methylcyclohexane (400 g) was added at 65.degree. C., the temperature adjusted to 70.degree. C. and the mixture stirred for a further 30 minutes before being allowed to settle for 30 minutes. The aqueous layer was separated and the organic phase washed at 70.degree. C. with aqueous potassium hydroxide (400 g of a 3% solution) and aqueous hydrochloric acid (80 g of a 1% solution). Each wash was stirred for 30 minutes and allowed to settle for 30 minutes prior to separation. The methylcyclohexane solution was cooled to 25.degree. C., stirred for 30 minutes and allowed to settle for 1 hour. A two phase system was obtained, a lower layer comprising:

(E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate 7.28% methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate 63.5% methylcyclohexane 15-20% and an upper layer comprising: (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate 1.4% methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate 11.4% methylcyclohexane 80-85%

The upper layer was retained for use in future reactions.

Solvent was removed from the lower layer by distillation at 50 mm Hg at a gradually increasing temperature until 90.degree. C. was achieved. The mixture was held at 90.degree. C. for 30 minutes. After this time the pressure was reduced to 5-10 mm Hg and the temperature increased to 120.degree. C. during which time chloromethoxypyrimidine distilled. [The condenser coolant was at 35-40.degree. C.] The mixture is held at 120.degree. C. until analysis showed that the level of chloromethoxypyrimidine was acceptable.

A sample comprising methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (230.7 g) and (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate (21 g) prepared by a method analogous to the above was heated to 90-95.degree. C. Acetic anhydride (74.2 g) and methane sulphonic acid (1.75 g) were added sequentially with stirring. The resulting mixture was heated at 90-95.degree. C. for 2 hours to leave (E)-methyl [2-(6-chloropyrimidin-4-yloxy)-phenyl]-3-methoxypropenoate (216.9 g).

Chemical Structures

(in description) ##STR1##

Claims

1. A process for preparing a compound of formula (I): comprising treating a compound if formula (II) ##STR2## with an acid catalyst in the presence of an acid anhydride, an acid chloride or 2-acetoxybenzonitrile at a temperature in the range of 70-110.degree. C.; provided that when the acid catalyst is p-toluene sulphonic acid or potassium bisulphate then the process is conducted in the presence of an acid anhydride.

2. A process as claimed in claim 1 wherein the acid catalyst is methane sulphonic acid, chlorosulphonic acid or 2-cyanophenol.

3. A process as claimed in claim 2 which is conducted in the presence of a solvent.

4. A process as claimed in claim 1 wherein a compound of formula (II) is treated with methane sulphonic acid or chlorosulphonic acid in the presence of an acid anhydride, the process being conducted in the presence of a solvent.

5. A process as claimed in claim 1 wherein a compound of formula (II) is treated with methane sulphonic acid in the presence of acetic anhydride at a temperature in the range 85-105.degree. C., the process being conducted in the absence of a solvent.

6. A process as claimed in claim 5 wherein the ratio of compound of formula (II):

methane sulphonic acid: acetic anhydride is about 1:0.05:1 equivalents.