GB1578425A

GB1578425A - Production of highl pure n-substituted maleic imides

Info

Publication number: GB1578425A
Application number: GB1722978A
Authority: GB
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1977-05-06
Filing date: 1978-05-02
Publication date: 1980-11-05
Also published as: DE2720311A1; FR2389604A1; JPS53137956A; FR2389604B1

Description

(54) PRODUCTION OF HIGHLY PURE N SUBSTITUTED MALEIC IMIDES (71) We, BAYER AKTIENGESELLSCHAFT, a body corporate organised under the laws of Germany of 509 Leverkusen, Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a process for the production of highly pure Nsubstituted maleic imides.

N-substituted maleic imides, which have long been known, are of interest as comonomers for the production of plastics with improved thermal stability under load (cf. US Patent No. 2,342,295).

In conventional methods for the production of N-substituted maleic imides, maleic acid semiamides are directly converted into the maleic imides by thermal or chemical dehydration (cf. Lester E. Colemann, J. Org. Chem. 24, 136 (1919), US Patent Nos. 2,727,862; 2,306,918, and 3,018,290).

However, where this procedure is adopted, secondary reactions caused by polymerisation and cracking cannot be completely avoided, which, therefore, results in the formation of products of reduced quality which cannot be directly used for the above-mentioned purpose.

The present invention provides a process for the production of highly pure Nsubstituted maleic imides, wherein the corresponding N-substituted monohalosuccinic acid imides are subjected to dehydrohalogenation. In all formulae nitrogen substituents (R) include alkyl radicals, preferably C1-C4-alkyl, particularly methyl, and aryl radicals, preferably phenyl, and cycloalkyl radicals, preferably cyclohexyl. Chlorine is the preferred halogen in the monohalosuccinic acid imides.

The reaction takes place in accordance with the following equation, for example:

The N-substituted maleic imides are obtained in particularly pure form and in high yields and they may be used without further purification as polymerisation components.

The halosuccinic acid imides, for example a - chloro - N - phenylchlorosuccinic acid imide, used as starting materials can be obtained from the corresponding maleic acid semiamides by treating with inorganic acid chlorides, such as thionyl chloride (cf. A. E. Kretove and Kulchitskaya, J. Gen. USSR 26, 221 (1956), or with organic acid chlorides, such as acetyl chloride (cf. "Maleic Anhydride Derivatives" by L. H. Feh and W. H. Gardner to912), page 36, New York, John Wiley & Sons, Inc.), but are in sufficiently pure for direct further processing into maleic imides. Accordingly, halosuccinic acid imides of the type obtained by the dehydrating hydrohalogenation of ethylene dicarboxylic acid semiamides with dry hydrogen halide (cf. Thanun M. Pyriadi, J. Org. Chem., Vol.

37, No. 25, 1972) are preferably used for the process according to the present invention.

In this process, N-substituted maleic acid semiamides are reacted with hydrogen halide, particularly hydrogen chloride, in an organic solvent, Nsubstituted monohalosuccinic acid imides being obtained in a substantially quantitative yield and in particularly pure form. The solvents may be used for example, aliphatic ketones, such as acetone, 2-butanone, or cyclic ethers such as dioxane and tetrahydrofuran, although liquid aliphatic carboxylic acids, such as acetic acid and propionic acid, are particularly suitable.

The reaction takes place in accordance with the following equation for example:

and is carried out at temperatures above -10"C, preferably at temperatures in the range from 200 to 500C and, more particularly, at temperatures in the range from 30"C to 400C.

In the preferred embodiment of the process according to the invention, the halosuccinic acid imide is converted into the corresponding maleic acid imide by treatment with a substantially equivalent quantity of an inorganic or organic base or mixture thereof. Although alkali metal and alkaline earth metal hydroxides and their carbonates and hydrocarbonates and also organic aromatic bases, such as dimethyl aniline or pyridine, are suitable for this purpose, it is particularly preferred to use aliphatic tertiary amines, such as triethylamine and tributylamine.

This reaction may also be carried out under mild conditions, for example at a temperature in the range from 100 to 500C and preferably at a temperature in the range from 20 to 300 C, and with advantage in an inert, water-immiscible solvent, such as a aliphatic, cycloaliphatic and aromatic hydrocarbon or a chlorinated hydrocarbon.

It is also possible, however, to convert the halosuccinic acid imides into the corresponding maleic imides by thermal dehydrohalogenation in the absence of a base. Unfortunately, this process is technically more difficult to handle than the process based on elimination using a base.

The percentages quoted in the following Examples represent percent by weight.

Starting Material 1 A total of 50 g of hydrogen chloride was introduced over a period of 30 minutes at 350C into a suspension of 129 g (1 mole) of maleic acid mono-Nmethylamide in 300 g of acetic acid. A clear solution was formed. The solution was then left standing at 350C until (after about 50 hours) the NMR-spectrum no longer showed a double bond. The acetic acid was distilled off at 500C/10 Torr. The residue of 147 g (=100% of the theoretical yield) was formed by pure white Nmethylchlorosuccinic acid imide melting at 470C which may be directly used for the synthesis of N-methyl maleic imide in accordance with Example 1.

EXAMPLE 1 101 g (1 mole) of triethylamine were added dropwise over a period of 1 hour at 25"C to a solution of 147.5 g (1 mole) of N-methylchlorosuccinic acid imide in 200 g of methylene chloride. After a reaction time of 1 hour at 250C, the amine hydrochloride formed was washed out twice with 200 ml of water. The clear solution obtained was subjected to fractional distillation. The fraction boiling at 110--112"C/18 Torr gave 107 g (960/, of the theoretical yield) of pure white Nmethyl maleic imide melting at 940 C.

EXAMPLE 2 54 g of sodium carbonate were added to a solution of 215.5 g of N-cyclohexyl chlorosuccinic acid imide (produced in the same way as starting material 1) in 400 g of toluene. The mixture was stirred at 400C until (after about 8 hours) the test for chlorine in the organic phase was negative. After washing twice with 200 g of water, the organic solution was fractionated. The fraction boiling at 130--1330C/18 Torr gave 175 g (98van of the theoretical yield) of N-cyclohexyl maleic imide melting at 89"C.

EXAMPLE 3 209.5 g of N-phenyl chlorosuccinic acid imide (produced in the same way as starting material 1) were dissolved in 600 g of chlorobenzene. 125 g of dimethyl aniline were added to this solution over a period of 1 hour at 250C. The amine hydrochloride formed was then washed out twice with 200 g of water and subjected to fractional distillation. The fraction boiling at 125-1270C/8 Torr gave 168 g (97% of the theoretical) of N-phenyl maleic imide melting at 910C.

EXAMPLE 4 200 g of a 20% sodium hydroxide solution were added to a solution of 215.5 g of N-cyclohexyl chlorosuccinic acid imide in 500 g of toluene at such a rate that a pH-value of 8 was not exceeded. The lower phase was separated off and the upper phase was washed twice with 300 g of water and subjected to fractional distillation.

The fraction boiling at 130--1330C/18 Torr gave 155 g (87% of the theoretical yield) of N-cyclohexyl maleic imide melting at 890 C.

EXAMPLE 5 50 g of N-methyl chlorosuccinic acid imide was heated under reflux in a 100 cc flask surmounted by a Vigreux column while nitrogen was gently bubbled through.

The sump product was kept at 2000C to 2100C. Highly pure N-methyl maleic imide distilled off overhead at 184"C and was collected in a cooled receiver, while the hydrogen chloride formed was removed by the stream of nitrogen. The yield comprised 34 g (91% of the theoretical yield) of N-methyl maleic imide melting at 90"C.

WHAT WE CLAIM IS: 1. A process for the production of an N-substituted maleic imide, wherein an N-substituted monohalosuccinic acid imide is subjected to dehydrohalogenation.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

range from 20 to 300 C, and with advantage in an inert, water-immiscible solvent, such as a aliphatic, cycloaliphatic and aromatic hydrocarbon or a chlorinated hydrocarbon.

It is also possible, however, to convert the halosuccinic acid imides into the corresponding maleic imides by thermal dehydrohalogenation in the absence of a base. Unfortunately, this process is technically more difficult to handle than the process based on elimination using a base.

The percentages quoted in the following Examples represent percent by weight.

Starting Material 1 A total of 50 g of hydrogen chloride was introduced over a period of 30 minutes at 350C into a suspension of 129 g (1 mole) of maleic acid mono-Nmethylamide in 300 g of acetic acid. A clear solution was formed. The solution was then left standing at 350C until (after about 50 hours) the NMR-spectrum no longer showed a double bond. The acetic acid was distilled off at 500C/10 Torr. The residue of 147 g (=100% of the theoretical yield) was formed by pure white Nmethylchlorosuccinic acid imide melting at 470C which may be directly used for the synthesis of N-methyl maleic imide in accordance with Example 1.

EXAMPLE 1

101 g (1 mole) of triethylamine were added dropwise over a period of 1 hour at 25"C to a solution of 147.5 g (1 mole) of N-methylchlorosuccinic acid imide in 200 g of methylene chloride. After a reaction time of 1 hour at 250C, the amine hydrochloride formed was washed out twice with 200 ml of water. The clear solution obtained was subjected to fractional distillation. The fraction boiling at 110--112"C/18 Torr gave 107 g (960/, of the theoretical yield) of pure white Nmethyl maleic imide melting at 940 C.

EXAMPLE 2

54 g of sodium carbonate were added to a solution of 215.5 g of N-cyclohexyl chlorosuccinic acid imide (produced in the same way as starting material 1) in 400 g of toluene. The mixture was stirred at 400C until (after about 8 hours) the test for chlorine in the organic phase was negative. After washing twice with 200 g of water, the organic solution was fractionated. The fraction boiling at 130--1330C/18 Torr gave 175 g (98van of the theoretical yield) of N-cyclohexyl maleic imide melting at 89"C.

EXAMPLE 3 209.5 g of N-phenyl chlorosuccinic acid imide (produced in the same way as starting material 1) were dissolved in 600 g of chlorobenzene. 125 g of dimethyl aniline were added to this solution over a period of 1 hour at 250C. The amine hydrochloride formed was then washed out twice with 200 g of water and subjected to fractional distillation. The fraction boiling at 125-1270C/8 Torr gave 168 g (97% of the theoretical) of N-phenyl maleic imide melting at 910C.

EXAMPLE 4

200 g of a 20% sodium hydroxide solution were added to a solution of 215.5 g of N-cyclohexyl chlorosuccinic acid imide in 500 g of toluene at such a rate that a pH-value of 8 was not exceeded. The lower phase was separated off and the upper phase was washed twice with 300 g of water and subjected to fractional distillation.

The fraction boiling at 130--1330C/18 Torr gave 155 g (87% of the theoretical yield) of N-cyclohexyl maleic imide melting at 890 C.

EXAMPLE 5

50 g of N-methyl chlorosuccinic acid imide was heated under reflux in a 100 cc flask surmounted by a Vigreux column while nitrogen was gently bubbled through.

The sump product was kept at 2000C to 2100C. Highly pure N-methyl maleic imide distilled off overhead at 184"C and was collected in a cooled receiver, while the hydrogen chloride formed was removed by the stream of nitrogen. The yield comprised 34 g (91% of the theoretical yield) of N-methyl maleic imide melting at 90"C.

WHAT WE CLAIM IS: 1. A process for the production of an N-substituted maleic imide, wherein an N-substituted monohalosuccinic acid imide is subjected to dehydrohalogenation.
2. A process as claimed in Claim 1, wherein dehydrohalogenation is carried

out with a basic inorganic and/or organic agent.
3. A process as claimed in Claim 1, wherein dehydrohalogenation is obtained by the action of heat.
4. A process as claimed in Claim 2, wherein the basic agent comprises an aliphatic tertiary amine.
5. A process as claimed in any of Claims 1, 2 and 4 wherein the reaction is carried out at a temperature in the range of from 10 C to 500 C.
6. A process as claimed in any of Claims 1, 2, 4 and 5 wherein the reaction is carried out in an inert, water-immiscible solvent.
7. A process as claimed in any of Claims 1 to 6, wherein the N-substituted mono-halosuccinic acid imide is obtained by reaction of an N-substituted maleic acid semiamide with a hydrogen halide in an organic solvent.
8. A process for the production of an N-substituted maleic imide substantially as herein described with reference to any of the specific Examples.
9. An N-substituted maleic imide when prepared by a process as claimed in any of Claims 1 to 8.