PROCESS FOR THE PREPARATION OF PYRIMIDINE COMPOUNDS

Abstract: A process for preparing a compound of formula (I) comprising treating a compound of formula (II) with either (a) an acid catalyst optionally in the presence of a means for removing methanol, or (b) an acid chloride; provided that when the acid catalyst is <u>p</u>-toluene sulphonic acid or potassium bisulphite then the process is conducted in the presence of an acid anhydride.

Description: PROCESS FOR THE PREPARATION OF PYRΪMIDTNE COMPOUNDS The present invention relates to a process for preparing (E)-methyl 2-[2-(6-chloro- pyrimidin-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 92/08703. The present invention provides a process for preparing a compound of formula (I), comprising treating a compound of formula (II) with either (a) an acid catalyst optionally in the presence of a means for removing methanol, or (b) an acid chloride; provided that when the acid catalyst is p-toluene sulphonic acid or potassium bisulphite then the process is conducted in the presence of an acid anhydride. 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 bisulphite. The means for removing methanol can be physical or chemical means. Physical means includes distillation (such as distillation at elevated temperature preferably under reduced pressure, or co-distillation with a suitable solvent (for example toluene)). Chemical means includes using in the process a compound (such as an acid derivative [for example an acid anhydride, an acid chloride or a suitable ester (especially 2-acetoxybenzonitrile)]) that will react with methanol under the process conditions. Acid anhydrides are preferably C 2 . 5 alkyl anhydrides, for example acetic anhydride. Acid chlorides are preferably C 2 . 5 alkyl chlorides, for example acetyl chloride or propionyl chloride. 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, Q-xylene, m-xylene, p-xylene, cyclohexane or methylcyclohexane), an ether (such as glyme or diglyme) or a ketone (such as methyl/.røbutylketone). It is preferred that the solvent has a boiling point in the range 70- 140°C, especially in the range 85-120°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 optionally in the presence of a means for removing methanol; provided that when the acid catalyst is p- toluene sulphonic acid or potassium bisulphite then the process is conducted in the presence of an acid anhydride. 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 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) fth methane sulphonic acid, chlorosulphonic acid or 2-cyanophenol. In yet 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 a means for removing methanol, 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, chlorosulphonic acid or 2-cyanophenol) at a temperature in range 70-110°C (especially 85-100 °C) under reduced pressure (such as a pressure in the range 5-70mm Hg). 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 the presence of a suitable acid derivative (such as an acid anhydride (especially acetic anhydride), an acid chloride (especially acetyl chloride) or 2-acetoxybenzonitrile) at a temperature in range 70- 1 10°C (especially 85- 100 °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 suitable acid anhydride (especially acetic anhydride) at a temperature in range 70-1 10°C (especially 85-100 °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°C (especially 90-95°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°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). 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) under reflux conditions, whereby methanol is distilled from the reaction mass (for example as an azeotrope). The following Examples illustrate the invention. Throughout the Examples the following abbreviations are used: gc = gas chromatography lc = liquid chromatography NMR = nuclear magnetic resonance DMF = N.,N.-dimethylformamide EXAMPLE 1 A mixture of methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3- dimethoxypropanoate (78.75g) and 2-cyanophenol (26.5g) was heated to 90-95°C under a vacuum (50mm Hg) in a flask equipped with a condenser. Some solid (2-cyanophenol) was observed in the condenser and so heat from a hot gun was used to return this material to the flask. The reaction was followed by gc, lc and H NMR and conversion to (E)-methyl 2-[2- (6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate was judged to be complete after 3 hours. The mixture was allowed to cool to 50°C and the condenser removed. DMF (1 15g) was added and the resulting mixture was allowed to cool and left overnight. Potassium carbonate (43.2g) was added and the mixture was heated at 120-125°C. The reaction was followed by gc and was judged to be complete after 2 hours. The reaction mixture was cooled to 50°C and the DMF was distilled off under vacuum (circa 15mm Hg) until the flask temperature reached 80°C (circa). After releasing the vacuum and cooling to 50°C, toluene (63.5g) and water (190g) were added. The two phase mixture was stirred at 80°C for 30 minutes, the organic layer seperated, and evaporated under vacuum (circa: 15 mmHg, 80°C) to leave crude (E)-methyl 2-[2-(6-(2- cyanophenoxy)pyrimidin-4-yloxy)phenyl]-3-methoxypropenoate which was purified by crystalisation from methanol (57.4g, yield 70%). EXAMPLE 2 Methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (40.7g) was heated to 90-95°C and chlorosulfonic acid (CSA) in dichloromethane (0.25g CSA in 3.7g dichloromethane) was added using a syringe. The temperature dropped a few degrees as the dichloromethane distilled off. A vacuum (50mm Hg) was applied to the reaction mixture and the temperature returned to 90-95°C. The reaction was followed by gc. (NB Samples for gc were washed with water before analysis.) The crude (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3- methoxypropenoate formed was allowed to cool to 50°C after which DMF (59g), potassium carbonate (22.3g) and 2-cyanophenol (13.6g) were added and the reaction mixture heated to between 118-122°C. The reaction was followed by gc and judged to be complete after 2 hours. The reaction mixture was cooled to 50°C and the DMF was distilled off under vacuum (circa 20 mmHg) until the flask temperature reached 80°C (circa). After releasing the vacuum and cooling to 50°C, toluene (33.4g) and water (lOOg) were added. The two phase mixture was stirred at 80°C for 30 minutes, the organic layer seperated, and evaporated under vacuum (circa: 15 mmHg, 80°C) to leave crude (E)-methyl 2-[2-(6-(2- cyanophenoxy)pyrimidin-4-yloxy)phenyl]-3-methoxypropenoate which was purified by crystalisation from methanol (27. lg, yield 60%). EXAMPLE 3 Methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (45.5g) was heated to 95°C. 2-Cyanophenol (14.72g) was added and vacuum was applied (50mm Hg). The reaction was monitored by gc and Η NMR, which showed that demethanolysis was complete in 5 hours. EXAMPLE 4 Methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (44.8g) was heated to 95°C. 2-Cyanophenol (14.3g) was added and acetic anhydride (11.7g) was added via a syringe pump running at 6.35 ml h " . The reaction was monitored by gc and l H NMR, which showed that demethanolysis was complete in 4 hours. EXAMPLE 5 Methyl 2-[2-(6-chloropyrimidin-?-yloxy)phenyl]-3,3-dimethoxypropanoate (44.6g) was heated to 90-95°C. 2-Acetoxybenzonitrile (19.3g) was added and then methane sulphonic acid (0.6 lg) was added via a syringe. The reaction was monitored by gc and Η NMR, which showed that demethanolysis was complete in 5 hours. EXAMPLE 6 Stage 1 To a stirred mixture of 3-(α-methoxy)methylenebenzofuran-2(3H)-one (176g) and 4,6-dichloropyrimidine (165.5g) in methyl formate (400g) at 20-25°C under nitrogen was added sodium methoxide (240g of a 27% w/w solution in methanol) portionwise, over 10 hours while maintaining the temperature at 20-25°C. Once all the sodium methoxide solution had been added the reaction mixture was stirred for 2 hours. The methanol and methyl formate were then distilled from the reaction mixture (70-75°C) to leave a residue. Aqueous potassium hydroxide (700g of a 1.5% w/w solution) was added to the residue and the resulting mixture stirred at 90-95°C for 30 minutes. After cooling to 80°C, toluene (700g) was added and the mixture stirred at 50°C for 15 minutes, allowed to settle at 50°C for 15 minutes and the organic and aqueous phases separated. Water (440g) was added to the organic phase, the mixture was stirred at 50°C for 30 minutes, allowed to settle for 15 minutes and the organic and aqueous phases separated. The organic phase comprised methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (237.5g) and (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate (40.38g). Stage 2 Using a method analogous to the foregoing provided a toluene solution (lOOOg) comprising methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (250g) and (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate (29.2g). The toluene was removed from this solution (90 °C, 10mm Hg) and a residue remained. Methane sulphonic acid (5.8g) was added to the residue and the resulting mixture was stirred at 90-95°C and 10mm Hg for 1 hour. Analysis showed the reaction mixture to contain (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate (217.9g). EXAMPLE 7 A mixture of methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxy- propanoate (17.98g), acetic anhydride (5.16g) and toluene (73ml) was stirred at 90°C for 20 minutes. Methane sulphoϋfic acid (0.49g) was added to the mixture and the mixture was heated at 90°C for 1 hour. The mixture was cooled to room temperature, washed with cold water (25ml) and with hot (50°C) water (2 x 25ml). The organic layer was evaporated at 75°C (initially on a rotary evaporator, then at circa 15mm Hg) to leave (E)-methyl 2-[2-(6- chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate as a solid (16. lg). EXAMPLE 8 Using a method analogous to Stage 1 of Example 7 provided a toluene solution (200g) comprising (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3- methoxypropenoate (5.2g) and methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3- dimethoxypropanoate (34.6g). The toluene solution was placed in a flask equipped with a binary distillation head and the solution refluxed to remove any moisture. The volume of toluene that had distilled was replaced with dry toluene and methane sulphonic acid (0.83g) added. The reaction mixture was refluxed for 2 hours after which time gc analysis showed that the ratio of (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3-methoxypropenoate : methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate was 90.0:0.3. EXAMPLE 9 Step l To a stirred mixture of 3-(α-methoxy)methylenebenzofuran-2(3H)-one (193.4g of 91% pure material) and 4,6-dichloropyrimidine (165.5g) in methyl formate (400g) at 20- 25°C under nitrogen was added sodium methoxide (207g of a 30% w/w solution in methanol) portionwise, over 10 hours while maintaining the temperature at 20-25°C. Once all the sodium methoxide solution had been added the reaction mixture was stirred for 2 hours after which water (9g) was added. The methanol and methyl formate were distilled from the reaction mixture (internal temperature 90-95°C) to leave a residue. Water (700g) was added to the residue and the mixture stirred at 80°C for 30 minutes. Methylcyclohexane (4 0g) was added at 65°C, the temperature adjusted to 70°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°C with aqueous potassium hydroxide (400g of a 3% solution) and aqueous hydrochloric acid (80g 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°C, stirred for 30 minutes and allowed to settle for 1 hour. A two phase system wsδ 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 50mm Hg at a gradually increasing temperature until 90°C was achieved. The mixture was held at 90°C for 30 minutes. After this time the pressure was reduced to 5- 10mm Hg and the temperature increased to 120°C during which time chloromethoxypyrimidine distilled. [The condenser coolant was at 35-40°C] The mixture is held at 120°C until analysis showed that the level of chloromethoxypyrimidine was acceptable. Step 2 The residue remaining at the end of the distillations was heated to 90-95°C at 50mm Hg. Methane sulphonic acid (5.2g) was added over 1 hour with stirring, and the resulting mixture was stirred for a further hour to provide (E)-methyl 2-[2-(6-chloropyrimidin-4- yloxy)phenyl]-3-methoxypropenoate. EXAMPL 10 A sample [comprising methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3- dimethoxypropanoate (230.7g) and (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3- methoxypropenoate (21 g)] prepared by a method analogous to Step 1 of Example 9 was heated to 90-95°C. Acetic anhydride (74.2g) and methane sulphonic acid (1.75g) were added sequentially with stirring. The resulting mixture was heated at 90-95°C for 2 hours to leave (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)-phenyl]-3-methoxypropenoate (216.9g). EXAMPLE 1 1 Methylcyclohexane (lOOg) was added to a sample [comprising methyl 2-[2-(6- chloropyrimidin-4-yloxy)phenyl]-3,3-dimethoxypropanoate (98.3g) and (E)-methyl 2-[2-(6- chloropyrimidin-4-yloxy)-phenyl]-3-methoxypropenoate (9.2 lg)] prepared by a method analogous Step 1 of Example 9. The resulting mixture was heatec?to 95°C with stirring and methane sulphuric acid (2.30g) added over 1 hour. Vacuum was then gradually applied, while keeping the temperature at 95°C, until a pressure of 50mm Hg was obtained. Analysis showed the ratio of methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3,3- dimethoxypropanoate : (E)-methyl 2-[2-(6-chloropyrimidin-4-yloxy)phenyl]-3- methoxypropenoate to be 4.3:76.3. CHEMICAL STRUCTURES (in description)

Claims: CLAIMS A process for preparing a compound of formula (I): comprising treating a compound of formula (II): with either (a) an acid catalyst optionally in the presence of a means for removing methanol, or (b) an acid chloride; provided that when the acid catalyst is p-toluene sulphonic acid or potassium bisulphite then the process is conducted in the presence of an acid anhydride. 2. A process as claimed in claim 1 wherein the means for removing methanol is an acid derivative. 3. A process as claimed in claim 1 wherein the acid derivative is an acid anhydride or an acid chloride. 4. A process as claimed in claim 1 wherein the acid catalyst is methane sulphonic acid, chlorosulphonic acid or 2-cyanophenol. 5. A process for preparing a compound of formula (I) as claimed in claim I 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 °C, the process being conducted in the absence of a solvent. 6. A process for preparing a compound of formula (I) 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. 7. A process for preparing a compound of formula (I) as claimed in claim 1 comprising treating a compound of formula (II) with an acid catalyst at a temperature in the range 70-1 10°C under reduced pressure.

Inventors: BERRY IAN GORDON, COX BRIAN JEFFREY, DE BOOS GARETH ANDREW, FLEMING IAN GEORGE, JONES RAYMOND VINCENT HEAVON, WHITTON ALAN JOHN, BERRY, IAN, GORDON, COX, BRIAN, JEFFREY, DE BOOS, GARETH, ANDREW, FLEMING, IAN, GEORGE, JONES, RAYMOND, VINCENT, HEAVON, WHITTON, ALAN, JOHN
Applicants: BERRY IAN GORDON, BOOS GARETH ANDREW DE, COX BRIAN JEFFREY, FLEMING IAN GEORGE, JONES RAYMOND VINCENT HEAVON, WHITTON ALAN JOHN, ZENECA LTD, BERRY, IAN, GORDON, COX, BRIAN, JEFFREY, DE BOOS, GARETH, ANDREW, FLEMING, IAN, GEORGE, JONES, RAYMOND, VINCENT, HEAVON, WHITTON, ALAN, JOHN, ZENECA LIMITED
Application year: 1997
Main classification: C07D239
IPC codes: C07D239