CS225516B1 - Preparation of basic esters of the metacrylic acid - Google Patents

Description

The invention relates to a process for the preparation of basic methacrylic esters of the general formula ^IfH 3

C

AND

C00CH ₂ CH ₂ N

(1) in which R represents alkyls having 1 to 3 carbon atoms, which together may form a five-membered methylene chain; the esters of formula (1) are important basic compounds for the preparation of cationic polymers used in the manufacture of flocculating and antistatic agents and lacquers for the coating of tablets in the pharmaceutical industry.

The basic esters of formula (1) are usually prepared by re-esterification of an alkyl ester of methacrylic acid, in particular a methyl or ethyl ester, with a basic alcohol of formula (11),

HOC ^ CHgN ^ (11),

R 'in which R denotes the same as in formula I under the catalytic action of alkali metal alcoholates, in particular sodium methylate. While this is simple to perform, they are obtained

225 516, but the resulting basic esters of formula (I) are contaminated by the products of the addition of an alkoxide ion to the double bond of the acrylate fragment to form compounds which no longer have a double bond and thus cannot react to form the desired polymers. These by-products are formed in an amount of 3 to 10 wt. Their removal by traction distillation is virtually impossible due to slight differences in boiling points and is not cost-effective on a technical scale. The removal of said by-products can only be achieved by crystallizing the quaternary salts of the basic esters of formula I, which are further intermediate polymerizations, but, on a technical scale, this presents additional preparative complications and increases costs.

The aforementioned drawbacks are eliminated by a process for the preparation of basic methacrylic esters of the formula I by re-esterification of the methyl or ethyl methacrylic ester with a basic alcohol of the invention according to the invention in the presence of a catalyst consisting in the presence of a quaternary ammonium base III.

OH '(111), wherein R1 denotes alkyl of 1 to 4 carbon atoms and Rg denotes alkyl of 1 to 4 carbon atoms or benzyl, in an amount of 0.005 to 0.1 mol, based on 1 mol of the methacrylic acid starting ester catalyst.

Suitably, the quaternary ammonium base of the formula III is used in the form of a solution in water, in a C 1 -C 4 alkanol or in an aromatic hydrocarbon, preferably toluene, with a concentration of 5 to 40% by weight.

The process according to the invention makes it possible to obtain the highly pure basic esters of the formula I in good yields.

225 516 farewell use of sodium metal for the preparation of alcoholates ·

All the commercially available and affordable quaternary ammonium bases of formula (111) can be used as re-esterification catalysts, tetramethylammonium hydroxide, tetraethylammonium hydroxide and trimethylbenzylammonium hydroxide have proven to be the most suitable.

Carrying out the re-esterification reaction according to the invention does not depart from the standards of the usual methodology and gives the basic esters of the formula I in yields of 60 to 75% of theory with a content of 96 to 100% by weight.

Further details of the process according to the invention will be apparent from the following examples which illustrate but not limit the process.

Example 1

Roethacrylic acid 2-dimethylaminoethyl ester

In a 3-neck, 6-liter sulfonation flask equipped with a reflux head column, dropping funnel, and thermometer with stirrer, was placed 1000 g (1 mol) of methacrylic acid methyl ester, 890 g (1 mol) of 2-dimethylaminoethanol, 6 g of phenothiazine. 45.5 g of tetramethylammonium hydroxide (0.01 mol) as a 20% methanolic solution are added dropwise over 15 minutes. Stir for an additional 15 minutes at room temperature, then slowly stir the reaction mixture to gentle boiling (bath temperature 100-140 ° C) with stirring and collect the distillate containing methanol, methacrylic acid methyl ester and at higher temperatures up to 2 ° C. After 5 h, all unreacted methacrylic acid ester and methanol are distilled off. The reaction mixture was cooled, the precipitated solids were filtered off and the filtrate was distilled. Unreacted 2-dimethylaminoethanol is recovered in the fractions and the desired ester is collected at a boiling point of 70-74 ° C / 400 Pa. 70 to 75% of a light oil product content of 98 to 100% by weight is obtained.

Example 2

Methacrylic acid 2-diethylaminoethyl ester

The reaction is performed as in Example 1 with the following feedstock:

100 g of methacrylic acid swab (1 mol),

58.5 g of 2-diethylaminoethanol (0.5 mol),

0,6 g phenothiazine,

7.35 g of tetraethylammonium hydroxide (0.01 mol) in the form

20% butanolic solution.

Yield 60-65% of theory, content 96-99% by weight, boiling point 80-85 ° C / 400 Pa.

Note: equivalent amounts of tetrabutylammonium hydroxide can be used with the same result.

Example 3

2-Piperidinoethyl methacrylic ester

The reaction is carried out as in Example 1 with the following batch:

100 g methacrylic acid methyl ester (1 mol),

97.5 g of 2-piperidinoethanol (0.75 mol),

0,6 g phenothiazine,

4.17 g of trimethylbenzylammonium hydroxide (0.1 mol) as a 40% toluene solution.

Yield 57-60% of theory, content 98-99.5% by weight, boiling point 110-115 ° C / 140 Pa.

Example 4

Methacrylic acid 2-dimethylaminoethyl ester

Carrying out the reaction is the same as in Example 1 using the feedstock:

114 g 89

0.6

4.55 ethyl methacrylic ester g 2-dimethylaminoethanol (1 mol), g phenothiazine, g tetramethylammonium hydroxide (0.01) as a 40% aqueous solution.

225 518 with this / 1 mol /,

Yield 75 to boiling 70 to 78% of theory, ° C / 400 Pa.

content 96 to 99 wt.

mol / ve temperature

Claims (2)

- 6 SCOPE OF THE INVENTION 225 516 1. A process for the preparation of basic methacrylic esters of the general formula (I): CH _r (1). C00CH ₂ CH ₂ N: R. ' in which R represents an alkyl with 1-3 carbon atoms, or together form a five-membered methylene chain, transesterification of methyl or ethyl ester of methacrylic basic alcohol of formula IIy hoch ₂ CH ₂ N / 11 /. R 'in which R has the same meaning as in formula I, in the presence of a catalyst, characterized in that during the transesterification catalyst is a quaternary ammonium base of the formula III wherein R₄ is alkyl having from 1 to 4 carbon atoms and R ₂ alkyl 1-4 carbon atoms or benzyl, in an amount of 0.005 to 0.1 mol, based on 1 mol of the methacrylic acid starting ester. - 7 225 518 2. A process according to claim 1, wherein the quaternary ammonium base of formula (111) is used in the form of a solution in water, in a C1-C4 alkanol or in an aromatic hydrocarbon, preferably toluene, at a concentration of 5 to 40% by weight. · Printed by Moravian Printing Works, plant 12, Leninova 21, Olomouc Price: 2.40 K 5