WO1994021589A1 - Citraconic anhydride preparation process - Google Patents

Citraconic anhydride preparation process Download PDF

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Publication number
WO1994021589A1
WO1994021589A1 PCT/EP1994/000897 EP9400897W WO9421589A1 WO 1994021589 A1 WO1994021589 A1 WO 1994021589A1 EP 9400897 W EP9400897 W EP 9400897W WO 9421589 A1 WO9421589 A1 WO 9421589A1
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Prior art keywords
itaconic acid
citraconic anhydride
citric acid
groups
acid
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PCT/EP1994/000897
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French (fr)
Inventor
Auke Gerardus Talma
Anna Gerdine Bovenkamp Van De-Bouwman
Hendrika Petronella Maria Verlaan-Hooft
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Akzo Nobel N.V.
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Publication of WO1994021589A1 publication Critical patent/WO1994021589A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/54—Preparation of carboxylic acid anhydrides
    • C07C51/56—Preparation of carboxylic acid anhydrides from organic acids, their salts, their esters or their halides, e.g. by carboxylation

Definitions

  • the invention relates to a process for the preparation of citraconic anhydride from itaconic acid or citric acid.
  • Citraconic anhydride may be prepared from melted itaconic acid.
  • British patent 827,638 describes this process at pressures between 20 and 500 ⁇ imHg and temperatures between 155° and 185°C. Apart from the extreme conditions required, the process results in a very irregular heating and melting of the itaconic acid which is not beneficial for the conversion to citraconic anhydride and the final yield.
  • US patent 2,966,498 reveals that it is also possible to melt itaconic acid in the presence of an alkali metal salt at temperatures between 165° and 190°C at atmospheric pressure to produce citraconic anhydride. Although the process conditions are ameliorated, the second disadvantage as described above is still present.
  • European patent application 0495 544 describes two additional processes for the preparation of citraconic anhydride from itaconic acid.
  • the first process converts itaconic acid into citraconic anhydride by melting itaconic acid in a solvent in the presence of an alkali metal salt at 180°C. Because of the high temperature involved an oil bath is needed, which renders the process unremunerative.
  • the second process is a two-step reaction.
  • the first step comprises the reaction in xylene of itaconic acid with acetic anhydride to form itaconic anhydride.
  • the formed itaconic anhydride is converted into citraconic anhydride in the presence of a tertiary amine at reflux temperatures.
  • German patent application 3321 703 describes the conversion of citraconic acid and itaconic acid in solution into citraconic anhydride and itaconic anhydride, respectively, in the presence of a tertiary amine at reflux temperatures. No mention is made of the possibility of converting itaconic acid into citraconic anhydride, nor is the possibility of using a tertiary amide compound mentioned. Finally, Galanti A.V. et al., J. Pol. Sci : Pol. Chem. Ed., Vol. 19, 1981, pp. 451-475, describes the preparation of biscitraconimide compounds by reacting itaconic anhydride in the presence of an aliphatic amine in dimethyl formamide as a solvent at reflux temperatures.
  • the itaconic anhydride used in this process is prepared by dehydrating itaconic acid with acetyl chloride at reflux temperatures. No mention is made of another manner to prepare itaconic anhydride, nor is it disclosed how to prepare citraconic anhydride. Accordingly, there is a need in the art for a process for the synthesis of citraconic anhydride that allows for a simple and economically viable preparation.
  • the present invention relates to an improved process for the conversion of a compound selected from itaconic acid and citric acid to citraconic anhydride, said process comprising the step of contacting itaconic acid or citric acid at a temperature between 90° and 400°C with 10 to 500 wt%, based on itaconic acid or citric acid, of a liquid medium having a boiling temperature above 100°C at atmospheric pressure and which comprises at least 0.01 to 200 wt%, based on itaconic acid or citric acid, of a tertiary amide compound for a period of time sufficient to convert at least some itaconic acid or citric acid to citraconic anhydride.
  • the process of the present invention has the advantage that it is carried out in a liquid medium, so a regular heat transfer takes place. Furthermore, high conversions are obtained.
  • the temperature of the process ranges from 90° to 400°C. It is possible to carry out the process at subatmospheric pressure or under pressure. However, it is preferred that the reaction is carried out in a temperature range between 90° and 180°C at atmospheric pressure. These temperature and pressure conditions result in the use of normal equipment with steam heating which renders the process economically attractive in addition to the above-mentioned advantages.
  • the tertiary amide compound has the following formula
  • R 1 is selected from hydrogen, C 1 -C 20 alkyl group, C 2 -C 20 alkenyl group, C 2 -C 20 alkynyl group, C 6 -C 18 aryl group, C 7 -C 22 aralkyl group, and C 7 -C 30 alkaryl group, all groups may be linear or branched;
  • R 2 and R 3 are independently selected from linear or branched C 1 -C 20 alkyl groups, C 2 -C 20 alkenyl groups, C 2 -C 20 alkynyl groups, C 6 -C 18 aryl groups, C 7 -C 22 aralkyl groups, and C 7 -C 30 alkaryl groups;
  • R 1 and R 2 , R 1 and R 3 , or R 2 and R 3 may combine to form a C 2 to C 10 ring; all of groups R 1 , R 2 , and R 3 may be linear or branched and may be optionally substituted with one or more groups selected from hydroxy, alkoxy
  • R 1 is a hydrogen group or a C 1 -C 20 alkyl group
  • R 2 and R 3 are independently selected from C 1 -C 20 alkyl groups
  • R 1 and R 2 , R 1 and R 3 , or R 2 and R 3 may combine to form a C 2 to C 10 ring
  • all of groups R 1 , R 2 , and R 3 may be linear or branched and may be optionally substituted with one or more groups selected from hydroxy, alkoxy, epoxy, halogen, acid, ester, nitrile, ketone, and amido.
  • tertiary amide compounds which can be used in the present invention include dimethyl formamide, di ethyl formamide, dimethyl acetamide, diethyl acetamide, dimethyl acetoacetamide, and diethylacetoacetamide, and mixtures thereof.
  • the amount in which the tertiary amide compound may be used is between 0.1 and 100 wt%, based on itaconic acid or citric acid. More particularly, in case of the conversion of itaconic acid to citraconic anhydride an amount of 0.1 to 20 wt% of the tertiary amide compound is preferably used. In case of the conversion of citric acid to citraconic anhydride an amount of 5 to 100 wt% is preferably used.
  • the liquid medium comprises at least one component, i.e. a tertiary amide compound.
  • other components may also be present in the liquid medium as long as the boiling temperature of the liquid medium is above 100°C.
  • the liquid medium is formed by a combination of tertiary amide compound and at least one other liquid up to at least 10 wt%, based on itaconic acid or citric acid.
  • the presence of more than 10 wt% of the tertiary amide compound does not exclude the presence of other liquids to form the liquid medium.
  • the liquid medium is able to solubilize at least some of the itaconic acid or citric acid.
  • the first goal of the use of a liquid medium is the regular heat transfer to the itaconic acid or citric acid, so that at least some itaconic acid or citric acid reacts to citraconic anhydride.
  • this reaction proceeds faster when at least some of the itaconic acid or citric acid is solubilized in the liquid medium.
  • the process temperature is above the melting temperature at atmospheric pressure of itaconic acid or citric acid, upon heating of the liquid medium itaconic acid or citric acid not only dissolves, but also melts and dissolves.
  • components which are able to solubilize at least some itaconic acid or citric acid include toluene, xylene, cumene, cymene, decaline, o-dichlorobenzene, petroleum ethers boiling above 100°C, and Shell Ondina oil ® .
  • the liquid medium may also comprise a second component in addition to the components mentioned above. This second component should be polar and aprotic and may not influence the reaction, i.e. it has to be inert. Examples of these second components include dimethyl sulfoxide and propionic acid.
  • the process of the present invention is carried out under reflux conditions.
  • Some liquid media may codi still with the water produced during the conversion, i.e. form an azeotrope with water and, accordingly, the reflux conditions enables the removal of water from the reaction.
  • tertiary amide compound which does not codistil at reflux conditions with the produced water and the other components optionally present in the liquid medium. More particularly, when the tertiary amide compound does not form an azeotrope with water and the other components optionally present in the liquid medium, catalytic amounts of tertiary amide compound may be used.
  • tertiary amide When catalytic amounts of tertiary amide are used, at least one other component will be present in the liquid medium to form at least 10 wt%, based on itaconic acid or citric acid, of a liquid medium in which the process of the present invention is carried out, as explained above. Then it is preferred that the tertiary amide compound has a boiling temperature at atmospheric pressure above that of the other components present in the liquid medium. Accordingly, the tertiary amide will not be removed from the reaction system at reflux conditions.
  • An example of such a tertiary amide compound is diethyl acetoacetamide.
  • the formed citraconic anhydride is removed and purified in conventional ways.
  • the product may be removed by distillation under reduced pressure or by chromatographic procedures.
  • Citraconic anhydride may be used as a precursor for, among others, citraconimide compounds.
  • the following examples are presented to further illustrate the present invention. Except for examples 9 and 21, all the examples are carried out at reflux conditions at atmospheric pressure. In view of the fact that the liquid media form an azeotrope with water a precise temperature at which the examples are carried out cannot be given. The temperature will range from 90°C (lowest azeotropic temperature of water/liquid medium) to 180°C (highest boiling temperature of the liquid medium) .
  • a clear solution is formed.
  • the tertiary amide compound used forms a clear one phase system with the other component (s) present in the liquid medium. Itaconic acid or citric acid being suspended in the liquid medium dissolves upon heating in the tertiary amide compound.
  • the solution of tertiary amide and itaconic acid or citric acid separates from the component(s) present. Accordingly, a two phase system of clear liquids are formed.
  • the citraconic anhydride formed dissolves in the component(s) and so at the end of the reaction again a one phase system is present, comprising citraconic anhydride, tertiary amide and component(s).
  • example 28 wherein the amount of tertiary amide is so small that it is not possible to dissolve all itaconic acid in the tertiary amide. Accordingly, at least part of the itaconic acid remains suspended in a one phase liquid medium until all itaconic acid is converted.
  • DMAA dimethylacetoacetamide
  • Citraconic anhydride was prepared starting from itaconic acid and citric acid as described in examples 1 and 2, respectively, except that AA, a primary amide, was substituted for DEAA and DMF, respectively.
  • the crude yield of citraconic anhydride was 60% starting from itaconic acid and 40% starting from citric acid. Comparing these results with those of examples 1 and 2 clearly shows that the use of a tertiary amide in the process of the present invention yields citraconic anhydride in a higher yield in comparison to the use of a primary amide.

Abstract

A process is disclosed for the conversion of a compound selected from itaconic acid and citric acid to citraconic anhydride, said process comprising the step of contacting itaconic acid or citric acid at a temperature between 90° and 400 °C with 10 to 500 wt%, based on itaconic acid or citric acid, of a liquid medium having a boiling temperature above 100 °C at atmospheric pressure and which comprises at least 0.01 to 200 wt%, based on itaconic acid or citric acid, of a tertiary amide compound for a period of time sufficient to convert at least some itaconic acid or citric acid to citraconic anhydride. The process according to the present invention has the advantage that it is carried out in a liquid medium, so a regular heat transfer takes place. Furthermore, high conversions are obtained.

Description

Citraconic anhydride preparation process
The invention relates to a process for the preparation of citraconic anhydride from itaconic acid or citric acid.
Methods for the conversion of itaconic acid and citric acid into citraconic anhydride are known in the art. Citraconic anhydride may be prepared from melted itaconic acid. British patent 827,638 describes this process at pressures between 20 and 500 πimHg and temperatures between 155° and 185°C. Apart from the extreme conditions required, the process results in a very irregular heating and melting of the itaconic acid which is not beneficial for the conversion to citraconic anhydride and the final yield. US patent 2,966,498 reveals that it is also possible to melt itaconic acid in the presence of an alkali metal salt at temperatures between 165° and 190°C at atmospheric pressure to produce citraconic anhydride. Although the process conditions are ameliorated, the second disadvantage as described above is still present.
European patent application 0495 544 describes two additional processes for the preparation of citraconic anhydride from itaconic acid. The first process converts itaconic acid into citraconic anhydride by melting itaconic acid in a solvent in the presence of an alkali metal salt at 180°C. Because of the high temperature involved an oil bath is needed, which renders the process unremunerative. The second process is a two-step reaction. The first step comprises the reaction in xylene of itaconic acid with acetic anhydride to form itaconic anhydride. In the second step the formed itaconic anhydride is converted into citraconic anhydride in the presence of a tertiary amine at reflux temperatures. Due to the two steps involved and the formation of acetic acid as a by-product which has to be removed, this second process is very elaborate and, therefore, economically unattractive. A comparable process is described by Galanti M.C. et al., J . Org. Chem., 47, 1982, pp. 1572-1574. Here itaconic acid is reacted with acetyl chloride to form itaconic anhydride, which is subsequently converted into citraconic anhydride in the presence of a tertiary amine. Again, the two steps involved and the by-products formed, acetic acid and hydrogen chloride, render the process economically unattractive.
A method for the conversion of citric acid into citraconic anhydride is described in British patent 452,460. A concentrated aqueous solution is heated to 230°C under vacuum. Depending on the temperature, either itaconic anhydride or citraconic anhydride is formed. Apart from the extreme conditions that are required, the process is very difficult to control.
German patent application 3321 703 describes the conversion of citraconic acid and itaconic acid in solution into citraconic anhydride and itaconic anhydride, respectively, in the presence of a tertiary amine at reflux temperatures. No mention is made of the possibility of converting itaconic acid into citraconic anhydride, nor is the possibility of using a tertiary amide compound mentioned. Finally, Galanti A.V. et al., J. Pol. Sci : Pol. Chem. Ed., Vol. 19, 1981, pp. 451-475, describes the preparation of biscitraconimide compounds by reacting itaconic anhydride in the presence of an aliphatic amine in dimethyl formamide as a solvent at reflux temperatures. The itaconic anhydride used in this process is prepared by dehydrating itaconic acid with acetyl chloride at reflux temperatures. No mention is made of another manner to prepare itaconic anhydride, nor is it disclosed how to prepare citraconic anhydride. Accordingly, there is a need in the art for a process for the synthesis of citraconic anhydride that allows for a simple and economically viable preparation.
The present invention relates to an improved process for the conversion of a compound selected from itaconic acid and citric acid to citraconic anhydride, said process comprising the step of contacting itaconic acid or citric acid at a temperature between 90° and 400°C with 10 to 500 wt%, based on itaconic acid or citric acid, of a liquid medium having a boiling temperature above 100°C at atmospheric pressure and which comprises at least 0.01 to 200 wt%, based on itaconic acid or citric acid, of a tertiary amide compound for a period of time sufficient to convert at least some itaconic acid or citric acid to citraconic anhydride.
The process of the present invention has the advantage that it is carried out in a liquid medium, so a regular heat transfer takes place. Furthermore, high conversions are obtained.
The temperature of the process ranges from 90° to 400°C. It is possible to carry out the process at subatmospheric pressure or under pressure. However, it is preferred that the reaction is carried out in a temperature range between 90° and 180°C at atmospheric pressure. These temperature and pressure conditions result in the use of normal equipment with steam heating which renders the process economically attractive in addition to the above-mentioned advantages.
Preferably, the tertiary amide compound has the following formula
Figure imgf000006_0001
wherein R1 is selected from hydrogen, C1-C20 alkyl group, C2-C20 alkenyl group, C2-C20 alkynyl group, C6-C18 aryl group, C7-C22 aralkyl group, and C7-C30 alkaryl group, all groups may be linear or branched; R2 and R3 are independently selected from linear or branched C1-C20 alkyl groups, C2-C20 alkenyl groups, C2-C20 alkynyl groups, C6-C18 aryl groups, C7-C22 aralkyl groups, and C7-C30 alkaryl groups; R1 and R2, R1 and R3, or R2 and R3 may combine to form a C2 to C10 ring; all of groups R1, R2, and R3 may be linear or branched and may be optionally substituted with one or more groups selected from hydroxy, alkoxy, epoxy, halogen, acid, ester, nitrile, ketone, and amido.
More preferably, R1 is a hydrogen group or a C1-C20 alkyl group; R2 and R3 are independently selected from C1-C20 alkyl groups; R1 and R2, R1 and R3, or R2 and R3 may combine to form a C2 to C10 ring; all of groups R1, R2, and R3 may be linear or branched and may be optionally substituted with one or more groups selected from hydroxy, alkoxy, epoxy, halogen, acid, ester, nitrile, ketone, and amido. Examples of tertiary amide compounds which can be used in the present invention include dimethyl formamide, di ethyl formamide, dimethyl acetamide, diethyl acetamide, dimethyl acetoacetamide, and diethylacetoacetamide, and mixtures thereof.
Preferably, the amount in which the tertiary amide compound may be used is between 0.1 and 100 wt%, based on itaconic acid or citric acid. More particularly, in case of the conversion of itaconic acid to citraconic anhydride an amount of 0.1 to 20 wt% of the tertiary amide compound is preferably used. In case of the conversion of citric acid to citraconic anhydride an amount of 5 to 100 wt% is preferably used.
The liquid medium comprises at least one component, i.e. a tertiary amide compound. However, other components may also be present in the liquid medium as long as the boiling temperature of the liquid medium is above 100°C. For example, in view of the fact that the process is carried out in 10 to 500 wt%, based on itaconic acid or citric acid, of a liquid medium, it is clear that when less than 10 wt%, based on itaconic acid or citric acid, of the tertiary amide compound is present, the liquid medium is formed by a combination of tertiary amide compound and at least one other liquid up to at least 10 wt%, based on itaconic acid or citric acid. However, the presence of more than 10 wt% of the tertiary amide compound does not exclude the presence of other liquids to form the liquid medium.
Although not necessary, it is preferred that the liquid medium is able to solubilize at least some of the itaconic acid or citric acid. More particularly, the first goal of the use of a liquid medium is the regular heat transfer to the itaconic acid or citric acid, so that at least some itaconic acid or citric acid reacts to citraconic anhydride. However, this reaction proceeds faster when at least some of the itaconic acid or citric acid is solubilized in the liquid medium. Furthermore, when the process temperature is above the melting temperature at atmospheric pressure of itaconic acid or citric acid, upon heating of the liquid medium itaconic acid or citric acid not only dissolves, but also melts and dissolves.
Examples of components which are able to solubilize at least some itaconic acid or citric acid include toluene, xylene, cumene, cymene, decaline, o-dichlorobenzene, petroleum ethers boiling above 100°C, and Shell Ondina oil®. The liquid medium may also comprise a second component in addition to the components mentioned above. This second component should be polar and aprotic and may not influence the reaction, i.e. it has to be inert. Examples of these second components include dimethyl sulfoxide and propionic acid.
Although it is possible to carry out the process of the present invention with a liquid medium having a boiling temperature above 100°C at atmospheric pressure, it is preferred to use a liquid medium with a boiling temperature between 130° and 170°C at atmospheric pressure. The conversion to citraconic anhydride can then be completed in a shorter time period in comparison with the time period when using a liquid medium having a boiling temperature below 130°C.
Preferably, the process of the present invention is carried out under reflux conditions. Some liquid media may codi still with the water produced during the conversion, i.e. form an azeotrope with water and, accordingly, the reflux conditions enables the removal of water from the reaction.
It is also preferred to use a tertiary amide compound which does not codistil at reflux conditions with the produced water and the other components optionally present in the liquid medium. More particularly, when the tertiary amide compound does not form an azeotrope with water and the other components optionally present in the liquid medium, catalytic amounts of tertiary amide compound may be used.
When catalytic amounts of tertiary amide are used, at least one other component will be present in the liquid medium to form at least 10 wt%, based on itaconic acid or citric acid, of a liquid medium in which the process of the present invention is carried out, as explained above. Then it is preferred that the tertiary amide compound has a boiling temperature at atmospheric pressure above that of the other components present in the liquid medium. Accordingly, the tertiary amide will not be removed from the reaction system at reflux conditions. An example of such a tertiary amide compound is diethyl acetoacetamide.
The formed citraconic anhydride is removed and purified in conventional ways. For example, the product may be removed by distillation under reduced pressure or by chromatographic procedures.
Citraconic anhydride may be used as a precursor for, among others, citraconimide compounds. The following examples are presented to further illustrate the present invention. Except for examples 9 and 21, all the examples are carried out at reflux conditions at atmospheric pressure. In view of the fact that the liquid media form an azeotrope with water a precise temperature at which the examples are carried out cannot be given. The temperature will range from 90°C (lowest azeotropic temperature of water/liquid medium) to 180°C (highest boiling temperature of the liquid medium) .
Furthermore, in all examples it is mentioned that a clear solution is formed. This means the following. The tertiary amide compound used forms a clear one phase system with the other component (s) present in the liquid medium. Itaconic acid or citric acid being suspended in the liquid medium dissolves upon heating in the tertiary amide compound. The solution of tertiary amide and itaconic acid or citric acid separates from the component(s) present. Accordingly, a two phase system of clear liquids are formed. During the reaction the citraconic anhydride formed dissolves in the component(s) and so at the end of the reaction again a one phase system is present, comprising citraconic anhydride, tertiary amide and component(s). The only exception is example 28, wherein the amount of tertiary amide is so small that it is not possible to dissolve all itaconic acid in the tertiary amide. Accordingly, at least part of the itaconic acid remains suspended in a one phase liquid medium until all itaconic acid is converted.
Materials
DMF = dimethylformamide
DEF = diethylformamide
DMAA = dimethylacetoacetamide
DEAA = diethylacetoacetamide
DMA = dimethylacetamide
DEA = diethylacetamide
AA = acetamide
DMSO = dimethylsulfoxide
Example 1
Synthesis of citraconic anhydride starting from itaconic acid
In a one litre reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 232.1 g (1.79 moles) of itaconic acid and 5 ml DEAA (2.3 wt%, based on itaconic acid) were suspended in 500 ml xylene at 100°C. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved and a clear solution was formed from which the water is removed. After 4 hours' reflux, the xylene was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The citraconic anhydride was obtained as a colourless liquid in a yield of 74%. Example 2
Synthesis of citraconic anhydride starting from citric acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 30 g (143 mmoles) of citric acid and 10 ml DMF (9.5 wt% based on citric acid) were suspended in 90 ml xylene at 100°C. The suspension was heated to reflux temperature. Upon heating the citric acid dissolved and a clear solution was formed from which water and CO2 is removed. After 2.5 hours' reflux, the xylene was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The citraconic anhydride was obtained as a colourless liquid in a yield of 52.5i?%.
Comparative Example A
Synthesis of citraconic anhydride in the presence of acetamide
Citraconic anhydride was prepared starting from itaconic acid and citric acid as described in examples 1 and 2, respectively, except that AA, a primary amide, was substituted for DEAA and DMF, respectively. The crude yield of citraconic anhydride was 60% starting from itaconic acid and 40% starting from citric acid. Comparing these results with those of examples 1 and 2 clearly shows that the use of a tertiary amide in the process of the present invention yields citraconic anhydride in a higher yield in comparison to the use of a primary amide.
Comparative Example B
Synthesis of citraconic anhydride starting from itaconic acid in the presence of benzene
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g of itaconic acid and 10 ml DMF (12.5 wt%) were suspended in 90 ml of benzene at 80°C. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved and a clear solution was formed. After 24 hours' reflux, the solvent was distilled off. No citraconic anhydride was formed during this reaction. The absence of any citraconic anhydride formed is relating to the fact that benzene and DMF form a solvent system with a boiling temperature below 100°C at atmospheric pressure. Comparative Example C
Synthesis of citraconic anhydride starting from citric acid in the presence of benzene
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 30 g of citric acid and 10 ml DMF (9.5 wt%) were suspended in 90 ml benzene at 80°C. The suspension was heated to reflux temperature. Upon heating the citric acid dissolved and a clear solution was formed. No citraconic anhydride was formed after 24 hours.
Examples 3-8
Synthesis of citraconic anhydride starting from itaconic acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g of itaconic acid and 10 ml DMF (12.5 wt%) were suspended in 90 ml of solvent at 100°C. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved and a clear solution was formed from which the water is removed. After several hours' reflux, the solvent was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The solvents used and the results obtained are given in Table 1. Table 1
Figure imgf000013_0001
As is shown in Table 1, the use of solvent systems having a boiling temperature above 100°C at atmospheric pressure results in a very high conversion. Furthermore, it is shown that the use of solvent systems such as toluene/DMF, having a boiling temperature below 130°C at atmospheric pressure, results in a slower process.
Example 9
Synthesis of citraconic anhydride starting from itaconic acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g of itaconic acid and 10 ml DMF (12.5 wt%) were suspended in 90 ml Shell Ondina Oil® at 100°C. The suspension was heated to 170°C. Upon heating the itaconic acid dissolved/melted and a clear solution was formed from which the water is separated. After 3.5 hours, the Shell Ondina Oil® layer was separated from the anhydride layer and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The conversion was 80%. As is shown the process of the present invention can also be carried out without reflux conditions. Examples 10-11 and Comparative Example D
Synthesis of citraconic anhydride starting from itaconic acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g of itaconic acid and a certain amount of DEAA, DMSO or both (see Table 2) were suspended in 90 ml of xylene at 100°C. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved and a clear solution was formed from which the water is removed. After several hours' reflux, the xylene was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The results obtained are given in Table 2. It is shown that it is also possible to use a solvent system comprising three compounds, i.e. xylene, DMSO, and DEAA. The use of DMSO solely in the presence of xylene (comparative example D) results in a very slow process.
Table 2
Figure imgf000014_0001
Examples 12-15
Synthesis of citraconic anhydride starting from itaconic acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g of itaconic acid and 10 ml of a tertiary amide compound were suspended in 90 ml of solvent at 100°C. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved/melted and a clear solution was formed from which the water is removed. After several hours' reflux, the solvent was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The tertiary amide compounds used and the results obtained are given in Table 3.
Table 3
Figure imgf000015_0001
As the results in Table 3 show, the process of the present invention results in a high conversion in a short time period.
Examples 16-20
Synthesis of citraconic anhydride from citric acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 30 g of citric acid and 10 ml DMF (9.5 wt%) were suspended in 90 ml of a solvent at 100°C. The suspension was heated to reflux temperature. Upon heating the citric acid dissolved and a clear solution was formed from which water and CO2 is removed. After several hours' reflux, the solvent was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The solvents used and the results obtained are listed in Table 4. Table 4
Figure imgf000016_0001
As is shown in Table 4, the use of solvent systems having a boiling temperature above 100°C at atmospheric pressure results in a very high conversion. Furthermore, it is shown that the use of solvent systems such as toluene/DMF, having a boiling temperature below 130°C at atmospheric pressure, results in a slower process.
Example 21
Synthesis of citraconic anhydride starting from citric acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 30 g of citric acid and 10 ml DMF (9.5 wt%) were suspended in 90 ml Shell Ondina Oil® at 100°C. The suspension was heated to 170°C. Upon heating the citric acid dissolved/melted and a clear solution was formed from which water and CO2 is separated. After 3.5 hours, the Shell Ondina Oil® layer was separated from the citraconic anhydride layer and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The conversion was 50%. As is shown the process of the present invention can also be carried out without reflux conditions. Examples 22-25
Synthesis of citraconic anhydride starting from citric acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 30 g of citric acid and 10 ml of a tertiary amide compound were suspended in 90 ml xylene at 100°C. The suspension was heated to reflux temperature. Upon heating the citric acid dissolved and a clear solution was formed from which water and CO2 is removed. After several hours' reflux, the xylene was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The tertiary amide compounds used and the results obtained are given in Table 5.
Table 5
Figure imgf000017_0001
As the results in Table 5 show, the process of the present invention results in a high conversion in a short time period.
Examples 26-27 and Comparative Example E
Synthesis of citraconic anhydride starting from citric acid
In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 30 g of citric acid and a certain amount of DEAA, DMSO or both (see Table 6) were suspended in 90 ml of xylene at 100°C. The suspension was heated to reflux temperature. Upon heating the citric acid dissolved and a clear solution was formed from which water and CO2 is removed. After several hours' reflux, xylene was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The results obtained are given in Table 6. It is shown that it is also possible to use a solvent system comprising three compounds, i.e. xylene, DMSO, and DEAA. The use of DMSO solely in the presence of xylene (comparative example E) results in a very slow process.
Table 6
Figure imgf000018_0001
Example 28
Synthesis of citraconic anhydride starting from itaconic acid
In a one litre reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 232 g of itaconic acid and 0.4 wt% DEAA suspended in 500 ml xylene at 100°C. The suspension was heated to reflux temperature. During the reaction the itaconic acid dissolved gradually, when at the same time water was removed. After 5 hours' reflux, the xylene was distilled off and subsequently the citraconic anhydride was distilled off at 90°C and 15 mbar. The citraconic anhydride was obtained as a colourless liquid in a yield of 74%.
The foregoing examples have been presented for the purpose of illustration and description only and are not to be construed as limiting the scope of the invention in any way. The scope of the invention is to be determined by the claims appended hereto.

Claims

Claims
1. A process for the conversion of a compound selected from itaconic acid and citric acid to citraconic anhydride, said process comprising the step of contacting itaconic acid or citric acid at a temperature between 90° to 400°C with 10 to 500 wt%, based on itaconic acid or citric acid, of a liquid medium having a boiling temperature above 100°C at atmospheric pressure and which comprises at least 0.01 to 200 wt%, based on itaconic acid or citric acid, of a tertiary amide compound for a period of time sufficient to convert at least some itaconic acid or citric acid to citraconic anhydride.
2. Process according to claim 1, characterized in that the process is carried out at a temperature between 90° to 180°C at atmospheric pressure.
3. Process according to any one of the preceding claims, characterized in that the tertiary amide compound has the following formula
Figure imgf000019_0001
wherein R1 is selected from hydrogen, C1-C20 alkyl group, C2-C20 alkenyl group, C2-C20 alkynyl group, C6-C18 aryl group, C7-C22 aralkyl group, and C7-C30 alkaryl group, all groups may be linear or branched; R2 and R3 are independently selected from linear or branched C1-C20 alkyl groups, C2-C20 alkenyl groups, C2-C20 alkynyl groups, C6-C18 aryl groups, C7-C22 aralkyl groups, and C7-C30 alkaryl groups; R1 and R2, R1 and R3, or R2 and R3 may combine to form a C2 to C10 ring; all of groups R1, R2, and R3 may be linear or branched and may be optionally substituted with one or more groups selected from hydroxy, alkoxy, epoxy, halogen, acid, ester, nitrile, ketone, and amido.
4. Process according to claim 3, characterized in that R1 is a hydrogen group or a C1-C20 alkyl group; R2 and R3 are independently selected from C1-C20 alkyl groups; R1 and R2, R1 and R3, or R2 and R3 may combine to form a C2 to C10 ring; all of groups R1, R2, and R3 may be linear or branched and may be optionally substituted with one or more groups selected from hydroxy, alkoxy, epoxy, halogen, acid, ester, nitrile, ketone, and amido.
5. Process according to claim 4, characterized in that the tertiary amide compound is selected from dimethyl acetoacetamide, diethylacetoacetamide, dimethyl formamide, diethyl formamide, dimethyl acetamide, di ethyl acetamide, and mixtures thereof.
6. Process according to any one of the preceding claims, characterized in that the boiling temperature of the liquid medium is between 130° and 170°C at atmospheric pressure.
7. Process according to any one of the preceding claims, characterized in that the process is carried out under reflux conditions.
8. Process according to any one of the preceding claims, characterized in that itaconic acid is converted to citraconic anhydride in the presence of 0.1 to 20 wt% of a tertiary amide compound.
9. Process according to claims 1 to 7, characterized in that citric acid is converted to citraconic anhydride in the presence of 5 to 100 wt% of a tertiary amide compound.
PCT/EP1994/000897 1993-03-24 1994-03-21 Citraconic anhydride preparation process WO1994021589A1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0749952A1 (en) * 1995-06-21 1996-12-27 Rhone-Poulenc Chimie Process for the preparation of citraconic anhydride
US8273903B2 (en) 2009-12-30 2012-09-25 Industrial Technology Research Institute Method for preparing the citraconic anhydride and method for isomerizing/dehydrating itaconic acid
CN103739539A (en) * 2013-12-24 2014-04-23 武汉径河化工有限公司 Method for preparing anti-vulcanization reversion agent 1,3-bis(citraconimidomethyl)benzene
JP2017008010A (en) * 2015-06-25 2017-01-12 キヤノン株式会社 Method for producing carboxylic acid anhydride, method for producing carboxylic imide, and method for manufacturing electrophotographic photosensitive member

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2966498A (en) * 1958-04-23 1960-12-27 Pfizer & Co C Preparation of citraconic anhydride
GB1246349A (en) * 1968-05-20 1971-09-15 Balm Paints Ltd Isomerisation of unsaturated carboxylic acids and their derivatives

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2966498A (en) * 1958-04-23 1960-12-27 Pfizer & Co C Preparation of citraconic anhydride
GB1246349A (en) * 1968-05-20 1971-09-15 Balm Paints Ltd Isomerisation of unsaturated carboxylic acids and their derivatives

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0749952A1 (en) * 1995-06-21 1996-12-27 Rhone-Poulenc Chimie Process for the preparation of citraconic anhydride
FR2735775A1 (en) * 1995-06-21 1996-12-27 Rhone Poulenc Chimie PROCESS FOR THE PREPARATION OF CITRACONIC ANHYDRIDE
US5824820A (en) * 1995-06-21 1998-10-20 Rhone-Poulenc Chimie Process for the preparation of citraconic anhydride
US8273903B2 (en) 2009-12-30 2012-09-25 Industrial Technology Research Institute Method for preparing the citraconic anhydride and method for isomerizing/dehydrating itaconic acid
CN103739539A (en) * 2013-12-24 2014-04-23 武汉径河化工有限公司 Method for preparing anti-vulcanization reversion agent 1,3-bis(citraconimidomethyl)benzene
CN103739539B (en) * 2013-12-24 2016-08-17 武汉径河化工有限公司 Anti-recovery agent 1, the preparation method of double (the lemon acid imide methyl) benzene of 3-
JP2017008010A (en) * 2015-06-25 2017-01-12 キヤノン株式会社 Method for producing carboxylic acid anhydride, method for producing carboxylic imide, and method for manufacturing electrophotographic photosensitive member

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