GB2573115A - Process for the preparation of oxamyl - Google Patents
Process for the preparation of oxamyl Download PDFInfo
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- GB2573115A GB2573115A GB1806612.6A GB201806612A GB2573115A GB 2573115 A GB2573115 A GB 2573115A GB 201806612 A GB201806612 A GB 201806612A GB 2573115 A GB2573115 A GB 2573115A
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- United Kingdom
- Prior art keywords
- oxamyl
- process according
- solvent system
- solution
- lower alcohol
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
- C07C319/26—Separation; Purification; Stabilisation; Use of additives
- C07C319/28—Separation; Purification
-
- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
- A01N47/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid
- A01N47/08—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid the carbon atom having one or more single bonds to nitrogen atoms
- A01N47/10—Carbamic acid derivatives, i.e. containing the group —O—CO—N<; Thio analogues thereof
- A01N47/24—Carbamic acid derivatives, i.e. containing the group —O—CO—N<; Thio analogues thereof containing the groups, or; Thio analogues thereof
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C323/00—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups
- C07C323/23—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and nitrogen atoms, not being part of nitro or nitroso groups, bound to the same carbon skeleton
- C07C323/39—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and nitrogen atoms, not being part of nitro or nitroso groups, bound to the same carbon skeleton at least one of the nitrogen atoms being part of any of the groups, X being a hetero atom, Y being any atom
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C323/00—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups
- C07C323/23—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and nitrogen atoms, not being part of nitro or nitroso groups, bound to the same carbon skeleton
- C07C323/46—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and nitrogen atoms, not being part of nitro or nitroso groups, bound to the same carbon skeleton having at least one of the nitrogen atoms, not being part of nitro or nitroso groups, further bound to other hetero atoms
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C327/00—Thiocarboxylic acids
- C07C327/58—Derivatives of thiocarboxylic acids, the doubly-bound oxygen atoms being replaced by nitrogen atoms, e.g. imino-thio ethers
Abstract
Disclosed is a process for preparing oxamyl (Methyl 2-(dimethylamino)-N-[(methylcarbamoyl)oxy]-2-oxoethanimidothioate, also known as Vydate (RTM)), the process comprising: a) providing a solution of oxamyl in a solvent system comprising a lower alcohol (i.e. C1-C6 alcohol) or a mixture of a lower alcohol and water, and b) precipitating oxamyl from the solution. Preferably, the oxamyl material employed in step a) comprises at least 80 wt.% oxamyl. Most preferably, the alcohol is monohydric and, more preferably, is one of methanol, ethanol, propanol (propan-1-ol) and isopropanol (IPA, propan-2-ol). Preferably, the solvent system is heated in step a), most preferably, heated to the boiling point of the solvent system. Preferably, the solution provided in step a) is filtered to remove undissolved material; more preferably, this is a hot filtration. Preferably, the solution of oxamyl in the solvent system is cooled in step b).
Description
PROCESS FOR THE PREPARATION OF OXAMYL
The present invention relates to a process for the preparation of oxamyl, in particular to the preparation of oxamyl by crystallization.
Oxime carbamates are a known class of pesticidally active compounds. They are known to exhibit activity as insecticides, acaricides and miticides. Their use in the control of pest infestations in plants, in particular crop plants, is known in the art. Pesticidal formulations comprising oxime carbamates are commercially available.
Methyl 2-(dimethylamino)-N-[[(methylamino)carbonyl]oxy]-2-oxoethanimidothioate is an oxime carbamate compound having the common name oxamyl and having the following structure:
Oxamyl is known to be active as an acaricide, an insecticide and a nematicide. Formulations comprising oxamyl as the active ingredient are known in the art and are available commercially. For example, Vydate® 10G is a commercial granule formulation available from E.l. DuPont de Nemours containing 10% by weight oxamyl. Vydate® L is a liquid concentrate formulation comprising 24% by weight oxamyl.
Oxamyl finds particular use in the treatment or prevention of insect infestations in a range of plants, in particular thrips, aphids, potato beetle and mites. Oxamyl may be formulated for application as a foliar treatment or a soil treatment. Foliar application of
oxamyl allows the compound to be transported to the roots of the plants, in turn controlling infestations of nematodes.
Oxamyl may be synthesised using techniques disclosed in US 3,576,834, US 3,639,633 and US 3,530,220. US 3,658,870 discloses a range of oxime carbamate compounds active as insecticides and their preparation. This document discloses the preparation of oxamyl in two isomeric forms. A first form, having a melting point of from 109 to 110°C is prepared by crystallization from benzene. A second form of oxamyl, having a melting point of from 101 to 103°C is prepared by crystallization from water. A similar teaching is provided in US 3,557,190, US 3,584,032 and US 3,560,555. EP 0 200 506 discloses a process for the preparation of methyl carbamates in which a methyl isocyanate is reacted with an oxime or a phenol in the presence of a solvent. The solvents contemplated in EP 0 200 506 are those in which the oxime or phenol are soluble and include one or a mixture of toluene, dimethylformamide, xylene, cyclohexanone, methylisobutylketone or a chlorinated hydrocarbon, such as methylene chloride, chloroform, or a chlorobenzene. EP 0 200 506 indicates that the product can be isolated from the solvent employed in the reaction by crystallization or fractionation. EP 0 200 429 discloses a process for the preparation of methyl carbamate insecticides, in which an oxime or a phenol is reacted with a methyl isocyanate formed by reacting an alkali metal cyanate salt with dimethyl sulfate in acetonitrile solvent. Suitable solvents for the reaction of the oxime or phenol with the methyl isocyanate are methylene chloride, water, cyclohexanone or a mixture of methylene chloride with acetone. EP 0 200 429 indicates that the product can be isolated by extraction with a suitable organic solvent or evaporation of the reaction solvent. EP 0 192 421 discloses a process for the preparation of N-methyl carbamates, such as oxamyl, by reacting the corresponding oxime or phenol in aqueous suspension with phosgene and methylamine in the presence of an alkaline base. The reaction is conducted in an aqueous medium. EP 0 192 421 indicates that the reaction product can be recovered by filtration or by extraction in an organic solvent, such as methylene chloride, followed by evaporation of the solvent. US 4,096,166 discloses a process for the preparation of carbamates of N-hydroxythioimidates. The process involves reaction an N-hydroxythioimidate with methylcarbamoyl chloride at a pH above 10 in a two-phase reaction medium comprising water and a water-immiscible organic solvent. Suitable organic solvents are indicated as being chlorinated alkanes having one or two carbon atoms and chlorinated ethylene, and aromatic compounds, such as benzene, toluene and xylene. The product is isolated by phase separation of the reaction mixture and evaporation of the organic solvent. US 5,284,962 discloses a multistage process for preparing methyl carbamates, in which an oxime or phenol is reacted with methyl isocyanate. The reaction is conducted in water in the substantial absence of an organic solvent.
More recently, in 2006, two methods for the preparation of oxamyl were disclosed by Xiao hui Zhu, Journal of Taishan Medical College, Vol. 27 No.1, 2006. In a first method, oxamyl is synthesised by reacting an oxime and methyl isocyanate in acetone as the solvent. Oxamyl was obtained directly from the reaction mixture by removing the solvent. However, this method is shown to yield oxamyl with a high concentration of impurities, with the result that further purification is necessary. A second, so-called ‘solvent-free’ method is disclosed, which replaces acetone with water in the reaction medium. Unfortunately, this solvent-free method, based on the use of water, for producing oxamyl is not satisfactory, due to the low product yield. More seriously, oxamyl derived from the solvent-free method has a low solubility during subsequent formulation procedures, which adversely affected the quality of the formulated product.
While the prior art discloses a number of different processes for preparing oxamyl, there is a continuing need for an improved process for producing an oxamyl product. It would be advantageous if the process could produce an oxamyl product having a high purity with minimal impurities present. It would also be advantageous if the process could be more environmentally friendly and avoid the need to use many of the solvents, such as aromatic solvents, for example benzene, described in the prior art documents discussed above.
According to the present invention there is provided a process for preparing oxamyl, the process comprising: a) providing a solution of oxamyl in a solvent system comprising a lower alcohol or a mixture of a lower alcohol and water; and b) precipitating oxamyl from the solution.
The process of the present invention provides oxamyl in a high level of purity. The process employs components, in particular solvents, that are obtainable from renewable sources and have reduced impact on the environment. The process is particularly suitable for use on a commercial scale, especially to produce oxamyl in a high level of purity for formulation in a wide range of pesticidal formulations.
In one particular aspect, the process of the present invention may be employed to purify an oxamyl starting material, for example an oxamyl material produced by the current commercial processes or the processes of the prior art.
In the first step of the process, a solution of oxamyl in a solvent system is provided. The oxamyl starting material may be any suitable oxamyl material. It is a feature of the process of the present invention that the oxamyl material may contain impurities.
In one preferred embodiment, the oxamyl starting material comprises oxamyl in an amount of at least 80% by weight, more preferably at least 85% by weight, still more preferably at least 90% by weight. A starting material comprising oxamyl in an amount less than 100% may be employed, for example up to 99% by weight, or less, such as up to 98% by weight or up to 96% by weight. In one preferred embodiment, the oxamyl starting material comprises from 90 to 96% by weight of oxamyl. The oxamyl starting material may be commercial grade oxamyl, that is a product comprising about 95% by weight of oxamyl.
In the first step of the process, a solution of oxamyl in the solvent system is formed. The solvent system comprises a lower alcohol or a mixture of a lower alcohol and water. In one embodiment, the solvent system consists essentially of a lower alcohol or a mixture of a lower alcohol and water.
The term ‘lower alcohol’ as used herein is a reference to an alcohol, that is an alkanol, comprising from 1 to 6 carbon atoms.
The solvent system may comprise a single lower alcohol or a mixture of two or more lower alcohols.
The alcohol used in the solvent system may be a monohydric alcohol or a polyhydric alcohol. Monohydric alcohols are preferred.
When the solvent system does not contain water, preferred alcohols are those having from 1 to 5 carbon atoms, more preferably from 1 to 4 carbon atoms. Alcohols having from 1 to 3 carbon atoms are especially preferred. Particularly preferred alcohols are methanol, ethanol, propanol and isopropanol.
The solvent system may comprise water in combination with a lower alcohol.
When the solvent system contains water, it is preferred that the alcohol has from 1 to 4 carbon atoms, more preferably from 1 to 3 carbon atoms, with mixtures of water and methanol, and water and ethanol being particularly preferred.
In embodiments in which the solvent system comprises a lower alcohol and water, the alcohol is preferably present in a weight excess to the water. The weight ratio of the lower alcohol to water may be up to 20:1, preferably up to 15:1, more preferably up to 12:1, still more preferably up to 10:1, more preferably still up to 8:1.
In embodiments in which the solvent system comprising a lower alcohol and water and in which water is present in a weight excess to the alcohol, the weight ratio of the lower alcohol to water may be up to 1:8, more preferably up to 1:6, still more preferably up to 1:5, more preferably still up to 1:4, for example up to 1:3, up to 1:2. A weight ratio of lower alcohol to water of 1:1 may also be employed.
In step a) of the process, the weight ratio of oxamyl to the solvent system may be any suitable ratio to achieve the desired yield of oxamyl. The amount of oxamyl that can be dissolved on the solvent system will depend upon such factors as the components of the solvent system and the operating conditions of step a) of the process. The weight ratio of the solvent system to oxamyl may be up to 15:1, preferably up to 10:1, with a preferred weight ratio being from 1.5:1 to 6:1, more preferably from 2:1 to 4:1.
In one embodiment, the solution of oxamyl in the solvent system in step a) is obtained by dissolving oxamyl in the solvent system. This is most preferably achieved by heating the solvent system. The solution may be obtained by heating to a temperature from 0°C up to the boiling point of the solvent system. Preferably, the solvent system is heated to a temperature higher than 15°C below the boiling point of the solvent system, more preferably higher than 10°C, still more preferably higher than 5°C below the boiling point of the solvent system. In one preferred embodiment, oxamyl is dissolved in the solvent system at the temperature at which the solvent system boils, more preferably under reflux.
As noted above, the oxamyl starting material may contain significant amounts of impurities. It is an advantage of the present process that many of the impurities typically present in commercial or technical grade oxamyl are not soluble in the solvent system used in the present invention. Such impurities remain as a solid in the solution provided in step a). Therefore, in one embodiment, the process of the present invention comprises a further step of: a1) subjecting the solution provided in step a) to a filtration step to remove undissolved solid material.
The filtration is preferably conducted at an elevated temperature, in order to maintain the oxamyl component in solution in the solvent system. Preferably, the filtration step is conducted at a temperature that is not less than 20°C below the temperature used in step a) to dissolve oxamyl in the solvent system, more preferably not less than 15°C, still more preferably not less than 10°C below the temperature used in step a).
If the solution provided in step a) is subjected to filtration, a reduction in temperature may cause oxamyl present in solution to come out of solution. This may become apparent by the filtrate being cloudy. Therefore, in embodiments in which step a1) is employed to filter the solution provided in step a), the process may further comprises the step of: a2) heating the filtrate obtained in step a1).
The filtrate is preferably heated to a temperature at which all the oxamyl is dissolved in the solvent system. This is apparent when the solution is clear. Preferably, the filtrate is heated to a temperature higher than 20°C below the temperature employed in step a) to form the oxamyl solution, more preferably higher than 15°C, still more preferably higher than 10°C, more preferably still higher than 5°C below the temperature used in step a).
In the process of the present invention, the solution of oxamyl in the solvent system is processed to precipitate oxamyl from the solution. This is most preferably achieved by cooling the solution. The solution may be cooled to any suitable temperature to recover a precipitate of oxamyl. Preferably, the solution is cooled to a temperature below 20°C, more preferably to a temperature below 15°C, still more preferably to a temperature below 10°C, more preferably still to a temperature of 5°C or below.
Oxamyl is recovered from the solution as a precipitate. The precipitate may then be processed in a conventional manner, for example collected by filtration and dried. Techniques for recovering and drying the precipitate are known in the art.
Embodiments of the process of the present invention will now be described, for illustration purposes only, by way of the following working examples.
EXAMPLES
Example 1
Oxamyl (commercial grade having a purity of 95% by weight; 110g) and methanol (250g) were added to a 500ml four arms round bottle flask equipped with a mechanical stirrer, a thermometer and a reflux condenser. The flask was heated and the contents held under reflux until the oxamyl had dissolved to form a solution.
Undissolved impurities were removed from the solution by hot filtration.
The filtrate was collected and was heated to 60°C until a clear solution was observed. The solution was held at this temperature for 30 minutes with stirring.
Thereafter, the solution was cooled to room temperature (about 25°C), after which the solution was further cooled in an ice water bath to a temperature of 5°C. The solution was held at this temperature and stirred until all the solid had precipitated.
The precipitate was recovered by filtration. The filter cake was then dried under vacuum. 104g of solid, white oxamyl was obtained having a purity of 97.5%wt in a yield of 97% by weight.
Example 2
Oxamyl (commercial grade having a purity of 95% by weight; 110g) and solvent system made up of methanol (230g) and water (30g) were added to a 500ml four arms round bottle flask equipped with a mechanical stirrer, a thermometer and a reflux condenser. The flask was heated and the contents held under reflux until the oxamyl had dissolved to form a solution.
Undissolved impurities were removed from the solution by hot filtration.
Thereafter, the solution was cooled to room temperature (about 25°C), after which the solution was further cooled in an ice water bath to a temperature of 3°C. The solution was held at this temperature and stirred until all the solid had precipitated.
The precipitate was recovered by filtration. The filter cake was then dried under vacuum. 104.5g of solid, white oxamyl was obtained having a purity of 97.0%wt in a yield of 97% by weight.
Claims (25)
1. A process for preparing oxamyl, the process comprising: a) providing a solution of oxamyl in a solvent system comprising a lower alcohol or a mixture of a lower alcohol and water; and b) precipitating oxamyl from the solution.
2. The process according to claim 1, wherein the oxamyl material employed in step a) comprises at least 80% by weight oxamyl.
3. The process according to either of claims 1 or 2, wherein the solvent system comprises a single lower alcohol.
4. The process according to any preceding claim, wherein the lower alcohol is monohydric.
5. The process according to any preceding claim, wherein the lower alcohol has from 1 to 4 carbon atoms.
6. The process according to claim 5, wherein the lower alcohol is selected from methanol, ethanol, propanol and isopropanol.
7. The process according to any preceding claim, wherein the solvent system consists essentially of a lower alcohol.
8. The process according to any of claims 1 to 6, wherein the solvent system comprises mixture of a lower alcohol and water.
9. The process according to claim 8, wherein the solvent system consists essentially of a mixture of a lower alcohol and water.
10. The process according to either of claims 8 or 9, wherein the lower alcohol is selected from methanol and ethanol.
11. The process according to any of claims 8 to 10, wherein the lower alcohol is present in the solvent system in a weight excess up to a weight ratio of 20:1.
12. The process according to any of claims 8 to 10, wherein water is present in the solvent system in a weight excess up to weight ratio of 1:8.
13. The process according to any preceding claim, wherein the weight ratio of oxamyl to the solvent system in step a) is up to 15:1.
14. The process according to any preceding claim, wherein the solvent system is heated in step a).
15. The process according to claim 14, wherein the solvent system is heated to a temperature higher than 15°C below the boiling point of the solvent system.
16. The process according to claim 15, wherein the solvent system is heated to the boiling point of the solvent system.
17. The process according to any preceding claim, further comprising the step of: a1) subjecting the solution provided in step a) to a filtration step to remove undissolved sold material.
18. The process according to claim 16, wherein the filtration is conducted at an elevated temperature.
19. The process according to claim 18, wherein the filtration is conducted at a temperature of not less than 20°C below the temperature of the solvent system in step a).
20. The process according to any of claims 17 to 19, further comprising the step of: a2) heating the filtrate obtained in step a1).
21. The process according to claim 20, wherein the filtrate is heated to a temperature higher than 20°C below the temperature employed in step a).
22. The process according to any preceding claim, wherein the solution of oxamyl in the solvent system is cooled in step b).
23. The process according to claim 22, wherein the solution is cooled to a temperature below 20°C.
24. The process according to any preceding claim, further comprising the step of recovering the oxmyl precipitate from the solution.
25. The process according to claim 24, wherein oxamyl is recovered by filtration.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1806612.6A GB2573115B (en) | 2018-04-24 | 2018-04-24 | Process for the preparation of oxamyl |
| PCT/CN2018/123767 WO2019205693A1 (en) | 2018-04-24 | 2018-12-26 | Process for the preparation of oxamyl |
| TW108113541A TW201945334A (en) | 2018-04-24 | 2019-04-18 | Process for the preparation of oxamyl |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1806612.6A GB2573115B (en) | 2018-04-24 | 2018-04-24 | Process for the preparation of oxamyl |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB201806612D0 GB201806612D0 (en) | 2018-06-06 |
| GB2573115A true GB2573115A (en) | 2019-10-30 |
| GB2573115B GB2573115B (en) | 2022-04-27 |
Family
ID=62236238
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1806612.6A Active GB2573115B (en) | 2018-04-24 | 2018-04-24 | Process for the preparation of oxamyl |
Country Status (3)
| Country | Link |
|---|---|
| GB (1) | GB2573115B (en) |
| TW (1) | TW201945334A (en) |
| WO (1) | WO2019205693A1 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4032654A (en) * | 1974-06-28 | 1977-06-28 | E. I. Du Pont De Nemours And Company | Water-soluble, liquid concentrates of S-methyl-[(methyl-carbamoyl)oxy]-thioacetimidate and methyl N', N'-dimethyl-N-[(methyl-carbamoyl)oxy]-1-thiooxamimidate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3584032A (en) * | 1968-11-01 | 1971-06-08 | Du Pont | Preparation of alkyl 1-(carbamoyl)-n-(carbamoyloxy) thioformimidates |
| US3557190A (en) * | 1968-12-27 | 1971-01-19 | Du Pont | Preparation of 1-(carbamoyl)-n-(carbamoyloxy)thio-formimidates from alkyl acetoacetates |
-
2018
- 2018-04-24 GB GB1806612.6A patent/GB2573115B/en active Active
- 2018-12-26 WO PCT/CN2018/123767 patent/WO2019205693A1/en active Application Filing
-
2019
- 2019-04-18 TW TW108113541A patent/TW201945334A/en unknown
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4032654A (en) * | 1974-06-28 | 1977-06-28 | E. I. Du Pont De Nemours And Company | Water-soluble, liquid concentrates of S-methyl-[(methyl-carbamoyl)oxy]-thioacetimidate and methyl N', N'-dimethyl-N-[(methyl-carbamoyl)oxy]-1-thiooxamimidate |
Also Published As
| Publication number | Publication date |
|---|---|
| GB201806612D0 (en) | 2018-06-06 |
| WO2019205693A1 (en) | 2019-10-31 |
| TW201945334A (en) | 2019-12-01 |
| GB2573115B (en) | 2022-04-27 |
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