DE1111186B - Process for the production of carboxylic acid esters - Google Patents

Description

The conversion of carboxylic acids with alcohols to carboxylic acid esters is usually done in The presence of strong acids as catalysts, which accelerate the establishment of the ester equilibrium will. Carboxylic acids or alcohols sensitive to strong acids can therefore be used in this way not be esterified or only with poor yield.

It has been found that carboxylic acid esters can be easily prepared without the addition of Acids is required when using the carboxylic acid and the alcohol or the phenol together Carbonyl-diimidazole, carbonyl-ditriazole or carbonyl-dipyrazole implements. The carboxylic acids can be mono- or polyvalent, saturated or unsaturated aliphatic or cycloaliphatic and aromatic carboxylic acids, such as acetic acid, propionic acid, Use fumaric acid, sorbic acid, benzoic acid, or cinnamic acid. The alcohols used can primary, secondary or tertiary, mono- or polyvalent and saturated or unsaturated. You can also functional groups, such as. B. Ethylenimine rings wear. So z. B. ethanol, isopropanol, Use ethylene glycol or 3-hydroxy-4-ethyleneiminobutene-1. Phenol itself, resorein, «-Naphthol or / 3-naphthol are used.

In addition to carbonyl-diimidazole, carbonyl-ditriazole and carbonyl-dipyrazole, their substitution products are also used, for example the alkyl derivatives, such as carbonyl-di-4-methylimidazole or carbonyl-di-3,5-dimethylpyrazole are suitable. On every carboxyl group to be esterified one mole of a heterocyclic carbonyl compound is generally used. In some In some cases, however, an excess of the alcohol or the carboxylic acid can be advantageous.

The reaction, which is preferably carried out with exclusion of water, can be carried out with or without the addition of Diluents are carried out. As such, tetrahydrofuran, benzene, and chloroform can be used other solvents are used, which are indifferent to the reactants. Will the esterification carried out in the presence of diluents, the reaction usually begins at room temperature with strong evolution of carbon dioxide. After they have subsided, one warms up expediently under reflux for some time. From the reaction mixture obtained, in addition to the Ester formed imidazole, triazole or pyrrazole z. B. by washing the reaction product or its essential solution can be easily removed with water.

In contrast to the conventional degree of esterification processes, the process according to the invention permits production
of carboxylic acid esters

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Dr. Heinz August Staab, Heidelberg,
has been named as the inventor

took on sensitive carboxylic acids or alcohols quickly and gently in excellent yields to esterify. In addition, these components can be esterified in one go, without strong mineral acids are split off or must be present. The esterification process according to the invention therefore enriches technology considerably and in a way that was not foreseeable. Also the Work and theoretical considerations published in Chemischenberichte, Vol. 89, p. 1927 on the behavior of acid azolides contain no reference to the esterification process. The parts mentioned in the examples are parts by weight.

example 1

12.2 parts of benzoic acid, 16.2 parts of N, N'-carbonyldiimidazole, 23 parts of ethanol and 50 parts of tetrahydrofuran are combined at room temperature. There is an evolution of carbon dioxide, which ends after about 10 minutes. The reaction mixture is then heated to boiling under reflux for a ^{further 1} J _{2 hours.} By fractional distillation, the ethyl benzoate of boiling point 100 to 105 ⁰ C at 15 mm in a yield of 80 to 90 ° / ₀ of theory.

Example 2

Instead of the benzoic acid used according to Example 1, 14.8 parts of cinnamic acid are used in the form given there Esterified way. Which in a yield of

109 648/421

90% of the theoretical ethyl cinnamate obtained boils at 165 to 170 ^° C. at 15 mm.

Example 3

12.2 parts of benzoic acid, 16.2 parts of N, N'-carbonyldiimidazole and 9.4 parts of phenol are added to 50 parts of tetrahydrofuran at room temperature. The onset of carbon dioxide evolution ends after about 10 minutes. Thereafter, the mixture is heated to boiling under reflux for a _{further 2 hours.} The tetrahydrofuran is then removed by evaporation, the residue is washed with 100 parts of water and finally recrystallized from a mixture of alcohol and ether. The phenyl benzoate is obtained in prisms with a melting point of 70 ° C. in a yield of 85% of theory.

Example 4

To a slurry of 20 parts of N, N'-carbonyl-di-1,2-triazole in 100 parts of tetrahydrofuran 14.2 parts of benzoic acid are stirred for 2 hours at room temperature and this reaction mixture is then treated with a solution of 15.7 parts Cinnamon alcohol in 30 parts of tetrahydrofuran. The mixture is refluxed for 1 hour and then evaporated Tetrahydrofuran from, the residue is treated with water, the reaction product is extracted with ether and purifies the cinnamyl benzoate by distillation. Boiling point: 160 ° C at 2 mm Hg. The yield is 75% of theory.

Claims (1)

PATENT CLAIM: Process for the preparation of esters from carboxylic acids and alcohols or phenols, characterized in that carboxylic acids are reacted with alcohols or phenols in the presence of carbonyl diimidazoles, carbonyl ditriazoles or carbonyl pyrazoles, preferably with exclusion of water and optionally in the presence of an inert organic solvent. Considered publications:
Angewandte Chemie, Vol. 68, 1956, p. 754;
Chemical Reports, Vol. 89, 1956, p. 1934.