Preparation of .Beta.-Aminopropionamides

1. Field of the Invention

The present invention relates to a catalytic chemical process for making .beta.-aminopropionamides. Such compounds are particularly useful derivatives in further preparing cationic vinyl monomers useful in preparing flocculants, adhesion promoters, oil soluble dispersions, epoxy curing agents and ion exchange resins.

2. Description of the Prior Art

It is well-known that amines will react with acrylic or methacrylic esters to form .beta.-aminopropionamides. Thus, for example, certain .beta.-aminopropionamides compounds can be made by reacting dialkyl amine compounds with an acrylic acid or ester compound, as described in the article by J. G. Erickson, "The Preparation and Stabilities of Some .beta.-dialkylaminopropionamides," J. Am. Chem. Soc. 74, 6281-82 (1952).

Aminolysis of esters is also described by J. F. Bunnett and G. T. Davis, J. Am. Chem. Soc. 82, 665 (1960) and H. T. Openshaw and M. Whittaker, J. Chem. Soc. 89, (1969). Other processes leading to compounds of this type are set out in U.S. Pat. Nos. 2,451,436; 2,529,838; 2,649,438; and 3,652,671.

As set out in U.S. Pat. Nos. 2,719,175 and 2,719,178 the resultant .beta.-aminopropionamides can then be broken down by heat to give monomeric compounds.

However, normally the reaction between an amine and an acrylic or methacrylic ester will proceed only slowly at moderate temperatures. One can elevate the temperature to complete the reaction and form the desired propionamide but then side reactions become significant.

In order to promote the reactions between esters and amines use of certain compounds have been suggested. For example, in the article by H. L. Bassett and C. R. Thomas, J. Chem. Soc. 11, 1188 (1954) the use of stoichiometric quantities of an alkylmagnesium halide has been described. While such compounds have been found to act as an aid in forming amides, it was also found that catalytic quantities were not effective here. In yet another route in producing acrylamides from acrylic esters and amides the use of lithium hydroxide and magnesium methoxide as catalysts were proposed (German Pat. No. 1,164,397).

However to date no simple method has been found to form .beta.-aminopropionamides from acrylic or methacrylic esters and the appropriate amines, which can be run at relatively low reaction temperatures, and which results in few side products compared to the prior art. Some catalysts, for example, in this area may catalyze the desired reaction, and likewise promote undesired side reactions.

It would therefore be an advantage in the art to provide a new catalytic method for preparing .beta.-aminopropionamides, which reaction could be run at relatively low reaction temperature and would produce few quantities of undesired side products.

The present invention is an improved catalytic process for the preparation of .beta.-aminopropionamides of the formula: ##STR4## wherein R.sub.1 is H or methyl, n is an integer of 2 to 6 and R.sub.2 and R.sub.3, taken singly are hydrogen or lower alkyl groups containing 1 to 4 carbon atoms or R.sub.2 and R.sub.3, taken jointly when combined with the nitrogen atom form a heterocyclic group selected from the group consisting of morpholine, pyrollidine and piperidine ring groups; which process comprises reacting in the presence of carbon dioxide acting as a catalyst a tertiaryaminoalkyl amine of the formula. ##STR5## where R.sub.2, R.sub.3 and n are as above with an acrylic or methacrylic compound of the formula: ##STR6## where R.sub.1 is as above and R.sub.4 is lower alkyl and recovering said .beta.-aminopropionamide.

The inventive process can be carried out batch-wise or in a substantially continuous procedure. Usually a molar excess of a tertiary-aminoalkylamine is combined with the acrylic or methacrylic acid ester compound, and the mixture is heated at a temperature within the range of 50.degree.-200.degree. C., most preferably 60.degree.-140.degree. C.

Most often at least two moles of the amine are utilized per mole of ester, and more often to drive the reaction to completion an excess greater than two moles of amine is employed. This insures maximum formation of the corresponding .beta.-aminopropionamide compound. There is no criticality in the maximum amount of amine compound employed other than practical considerations of subsequent excess unreacted amine removal from the reaction mixture. Normally, the reaction product is formed within a time period of about 1/4 to 24 hours, more often 0.5-10 hours. The amount of reaction time depends upon the particular starting materials employed and temperatures employed. The corresponding .beta.-aminopropionamide reaction product can then be separated from the reaction mixture, which usually also contains alcohols and excess unreacted amine compound, if desired, by conventional distillation procedures. However, the inventive process is equally applicable to the continuous running of the entire reaction mixture, for the alcohol of reaction and excess unreacted amine do not adversely effect the process.

Reaction may also be effected at atmospheric, subatmospheric or superatomospheric pressures. Usually the reaction is run at a pressure range slightly greater than 1 atmosphere to retain the carbon dioxide catalyst in the reaction mixture.

Tertiary aminoalkyamines which are especially useful in the practice of the present invention include: 3-dimethylaminopropylamine; 2-dibutylaminoethylamine; 4-(aminopropyl)morpholine; 3-diethylaminopropylamine; 2-dimethylaminoethylamine; 1-(aminopropyl)piperidine; and 4-(aminoethyl)-morpholine. Most preferably, 3-dimethylaminopropylamine is employed.

R.sub.2 and R.sub.3 when lower alkyl are most preferable C.sub.1 -C.sub.4 lower alkyl such as isopropyl and t-butyl and can also contain substituents of the non-interfering type such as halo, aryl, nitro, alkaryl, hindered amines such as tertiary amines and secondary amines, hindered hydroxyl groups, ether linkages, etc. The alkyl group may contain any substituent of this type which is inert to the reaction conditions.

Particular acrylic acid or methacrylic acid ester compounds useful as reactants in the invention include: methyl, acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate. Methyl acrylate and methyl methacrylate are preferred.

The amount of carbon dioxide catalyst utilized may vary over a wide range. Usually based on the total weight of the reactants carbon dioxide is used in an amount ranging from about 0.01 up to about 10% by weight. More often the catalyst is employed in the range of 0.1-5 weight % based on total reactant weight present.

The following examples are for purpose of illustration of the invention and are not intended to be limiting thereof.

To a 500 cc flask were charged

204 g dimethylaminopropylamine (DMAPA)

1.0 g carbon dioxide (as dry ice).

A nitrogen atmosphere was provided and the flask contents were heated to 80.degree. C. with stirring. Then 100 g of methyl methacrylate (MMA) was added dropwise over 30 minutes. The reaction mixture was then held at 80.degree. C. for 3 hours, and then cooled.

Gas liquid chromatography showed that 11.0% of the theoretical amount of methanol was evolved. The product .beta.-(3-dimethylamino)-propylamino)-N-(3-dimethylamino) propyl)-.alpha.-methyl propionamide was formed in 5.4% of the theoretical yield. The low yield was due to some loss of carbon dioxide catalyst due to the fact that the reaction flask was heated open to the atmosphere.

To a one liter steel autoclave were charged

300 g DMAPA

100 g MMA.

Then 9.5 g of dry carbon dioxide gas was pressured into the autoclave. The contents were heated to 100.degree. C. and held at temperature for six hours. Upon cooling, the contents were analyzed by gas liquid chromatography. Essentially, no methyl methacrylate remained. The yield of the propionamide product was 88% of theoretical. The yield of the methyl ester of 3-(3-dimethylamino)propylamino-2-methyl propionic acid was ca. 7%, and the yield of 3-(dimethylamino)propyl methacrylamide (DMAPMA) was ca. 4.5% of theoretical.

An experiment performed in a manner identical to Example I above without any catalyst showed only 0.1% yield of the product propionamide, with only 1.2% yield of methanol.

Obviously, many modifications and variations of the invention as here an before set forth may be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as indicated in the claims.