DE1288094B - Process for the production of carboxylic acid esters - Google Patents

Description

According to a known process (cf. German Patent 1115 252), aryl carboxylates are obtained by mixing mixtures of preferably approximately equivalent amounts of carboxylic acids and diaryl carbonates, expediently with the addition of alkali and / or alkaline earth oxides or hydroxides, alcoholates, salts, or tertiary organic amines or tri- or tetraalkylammonium hydroxides, with one molecule of an aromatic hydroxy compound and one molecule of carbon dioxide being split off for each carboxyl group to be esterified. However, this known process still requires comparatively high reaction temperatures, preferably in the range between about 150 and about 300 ^° C., in particular if a conversion rate which is useful for industrial purposes is to be achieved. When esterifying such carboxylic acids which also contain other reactive groups, there is also the risk of undesirable side reactions.

It has now been found that aryl carboxylates are preferably obtained by heating mixtures approximately equivalent amounts of carboxylic acids and diaryl carbonates or sulfites in the presence of less Quantities of nitrogen-containing, heterocyclic compounds as catalysts much faster and / or or at lower reaction temperatures than in the known process with practically no disruptive effects Side reactions obtained by using nitrogen-containing 5-membered heterocyclic compounds as Catalysts used.

There is a particular advantage of the new method in that aryl esters of such carboxylic acids can now also be produced, the reactive ones Contain groups which under the previously necessary reaction conditions with formation of undesirable By-products would react. So it is z. B. now possible when using, for example Imidazole as a catalyst, phenyl salicylate and phenyl p-hydroxybenzoate in almost quantitative terms To produce yield. In contrast, without a catalyst or with the addition of the known Catalysts obtained either little or no ester, since at the required reaction temperatures large amounts of resinous reaction products are formed.

Carboxylic acids which can be converted to aryl carboxylates according to the invention are for example aliphatic and aromatic mono- and polycarboxylic acids, such as acetic acid, chloroacetic acid, Propionic acid, lactic acid, butyric acid, n-valeric acid, caprylic acid, lauric acid, palmitic acid, Stearic acid, phenylacetic acid, oleic acid, linoleic acid, ricinoleic acid, glutaric acid, adipic acid, pimelic acid, α-methyladipic acid, suberic acid, azelaic acid, sebacic acid, Ascorbic acid, p-toluic acid, a-naphthoic acid, Terephthalic acid, isophthalic acid, phthalic acid, o-, m- and p-hydroxybenzoic acid, 3,5-dichloro-4-hydroxy-benzoic acid, Naphthalenedicarboxylic acid (1.5), benzophenonedicarboxylic acid, Ν, Ν-diethylaminobenzoic acid and isonicotinic acid.

Suitable diaryl carbonates and -suhlte are, for. E.g .: diphenyl carbonate, dicresyl carbonate, di - /? - naphthyl carbonate and bis (2-chlorophenyl) carbonate and the corresponding diaryl sulfites.

Examples of nitrogen-containing compounds to be used according to the invention 5-membered heterocyclic compounds are: imidazole, pyrazole, indazole, 1,2,3-triazole, 1,2,4-triazole, petrol midazole, benzotriazole, 3-amino-1,2,4-triazole, 3-Amino-1,2,4-triazole-corboxylic acid- (5), tetrazole and 5-aminotetrazole.

The catalysts are expediently added to the reaction mixtures in amounts of 0.1 to 10.0 mol percent, preferably 1.0 to 5.0 mol percent, based on the amount of carboxylic acid equivalents used, added.

The crude esters can be easily purified by distillation or recrystallization.

ίο The implementation according to the invention between the Carboxylic acids and diaryl esters can generally be used at lower temperatures than when using the known catalysts or if the same reaction temperatures are used in a shorter time. So is z. B. the implementation of salicylic acid with diphenyl carbonate to salicylic acid phenyl ester at 160 ° C below Addition of imidazole as a catalyst ended completely after just 3 hours, while for example using potassium hydroxide as a catalyst

ao sator after 15 hours under otherwise identical conditions only about 75% conversion takes place.

example 1

a) 151.9 g (1.1 mol) of salicylic acid, 214.2 g (1.0 mol) of diphenyl carbonate and 0.03 mol of imidazole are mixed in a 1-1 three-necked flask and, with stirring and reflux, to a sump temperature of 160 ° C., a gentle stream of nitrogen being passed over the reaction mixture. After a few minutes, a violent evolution of carbon dioxide sets in. After heating for 1 hour, the weight loss of the reaction mixture is 42 g (95% of the theoretical amount of carbon dioxide). After further 2 hours of heating at 160 ⁰ C, no more evolution of carbon dioxide takes place virtually. The weight loss is 44.1 g, corresponding to a quantitative conversion, based on the amount of diphenyl carbonate used.
The reaction mixture is then cooled to 8O ⁰ C. Then 102 g of phenol are distilled off at a vacuum of about 12 Torr with a bath temperature rising slowly to about 120 ° C. Thereafter, the remaining phenyl salicylate is distilled off under a vacuum of 0.1 to 0.4 torr. After a slight first run, 198 g of phenyl salicylate are obtained with a boiling point of bp. _{0> 2} = 110 ^° C., corresponding to a yield of 92.5% of theory, based on diphenyl carbonate. By seeding is obtained a crystalline product of melting point 39.5 to 40.5 ⁰ C. saponification value: 261 to 264 (calculated 262) percent carbon dioxide after saponification: less than 0.01.

About 7 g of a yellow-brown resin remain as residue.

b) For comparison, the reaction is given under the same conditions as in Example 1, a), but with the addition of 0.03 mol each of the catalysts indicated in the table below or carried out without the addition of a catalyst.

The slowly proceeding reactions are interrupted after 15 hours. The split off The amount of carbon dioxide is used as a measure of the conversion achieved.

catalyst sales
duration
(Hours) Abgespal
tenes coals
dioxide
(G) 0 /
Sales*) Lithium hydroxide 15th 0.6 1.4 Potassium hydroxide 15th 4.7 10.7 Magnesia 15th 33.2 75.5 Benzimidazole ... 15th 5.4 12.3 3-amino-1,2,4- 8th 44.0 100 triazole carbon acidic (5) 14th 44.1 100

*) Based on diphenyl carbonate.

Example 2

a) 151.9 g (1.1) mol of p-hydroxybenzoic acid, 214.2 g (1.0MoI) diphenyl carbonate and 3.00 g (0.044MoI) Imidazole are, as described in Example 1, a), but at a bottom temperature of 140 ° C, implemented. After one hour, 38.0 g of carbon dioxide have been evolved. After a total of 5 hours, the evolution of carbon dioxide ceases completed. The total weight loss is 48.5 g.

The reaction product is then slurried in 500 ml of xylene, the phenol formed and the catalyst going into solution. The remaining insoluble ester is filtered with suction, first with 50 ml of xylene and then with 300 ml of petroleum ether (bp. = 60 to 70 ⁰ C) and finally dried. This gives 176.4 g (82.0 ° / ₀ of theory based on diphenyl carbonate) p-Hydroxybenzoesäurephenylester.

Melting point: 175 ° C, saponification number: 263 to 265 (calculated 262), percent carbon dioxide after saponification: less than 0.01.

b) Comparison: If one proceeds as stated under a) above, but using 1.05 g (0.044 mol) of lithium hydroxide as a catalyst, so are after a 2.8 g of carbon dioxide are split off after 15 hours, only 14.2 g after 15 hours. The conversion after 15 hours is measured by the carbon dioxide development, therefore only 32.3% of theory.

Example3

A mixture of 41.4 g (0.2 mol) of 3,5-dichloro-4-hydroxybenzoic acid, 42.8 g (0.2 mol) of diphenyl carbonate and 0.50 g (0.007 mol) of imidazole is stirred in a stream of nitrogen heated a bottom temperature of 160 ° C. The evolution of carbon dioxide ceased after 3 hours and the weight loss was 8.8 g. 18.4 g of phenol are then distilled off under a water jet vacuum. After recrystallization of the residue (57.1 g) in 120 ml of toluene, 49.6 g are obtained (87.5 ° / o of theory based on diphenyl carbonate) of pure SjS-dichloro ^ -hydroxy-benzoic acid phenyl ester with a melting point of 138 ⁰ C.

C ... Found 55.22 to 55.88%;

calculated 55.1 ° / _0;
Cl ... Found 24.7 to 24.9% / ₀ ,

calculated 25.1%.

Example 4

a) 122.1 g (1.0 mol) of benzoic acid, 214.2 g (1.0 mol) of diphenyl carbonate and 3.00 g (0.044 mol) of imidazole are, as indicated in Example 1, a), at a bottom temperature of 16O ⁰ C implemented. After just one hour, the weight loss is 44.0 g, and the evolution of carbon dioxide has practically ended. After stirring for a further ¹ hour at 160 ° C., 92.5 g of phenol are distilled off from the reaction mixture under a water jet vacuum. The phenyl benzoate that remains is then _{distilled off with a boiling point of boiling point> 2} = 103 to 105 ^° C. with practically no residue. Man

ίο receives 187.0 g, corresponding to a yield of 94.4% of theory, based on diphenyl carbonate, pure phenyl benzoate with a melting point of 70 ° C. Saponification number: 280 to 282 (calculated 282), percent carbon dioxide after saponification: less than 0.01.

b) Comparison: Proceed as indicated under a) above, but using 1.76 g (0.044 Mol) magnesium oxide as a catalyst, 29.5 g of carbon dioxide are split off after 2 hours; sales is therefore only 67.1% The carbon dioxide

Ao development is ended after a total of ⁶ hours of heating at 160 ° C. The work-up carried out as under a) gives 93.0 g of phenol, 12.0 g of first runnings, which contain phenyl benzoate in addition to phenol, and 186.1 g (94.0 _{% of theory) phenyl benzoate with a boiling point of 0p2} = 102 to 104 ⁰ C.

Melting point: 71 ⁰ C. saponification ungszahl: 281 (calculated 282) to 282 percent carbon dioxide after saponification: less than 0.01.
c) comparison: 122,1g (1 mol) of benzoic acid, 214 g (lmole) of diphenyl carbonate and 3.95 g (0.05 mol) of pyridine are brought out at a bottom temperature of 160-185 ⁰ C for reaction. The reaction is only complete after 5 hours. The weight loss due to CO ₂ elimination is 41 to 42 g. 86 g of phenol are distilled off from the reaction mixture. Further, 181.5 g benzoic acid phenyl ester are distilled off with a melting point of 69 to 7O ⁰ C. The saponification number is 280 to 281. (yield 91.5 ° / ₀ of theory.) A resinous residue of about 20 g There remains.

Example 5

, 83,1g (0,5MoI) isophthalic acid, 214.2 g (1,0MoI) of diphenyl carbonate and 3.00 g (0,044MoI) imidazole as described in Example 1 a), heated to 16O ⁰ C bottom temperature. After one hour the weight loss in carbon dioxide is 40.0 g. The evolution of carbon dioxide has ended after a total of 3 ^{1 1} ₂ hours, the weight loss is 44.5 g.

93.0 g of phenol are distilled off from the reaction mixture under a water jet vacuum. Are (theory 89.4 ° / ₀₎ obtained 134 ⁰ C in pure Isophthalsäurediphenylester a melting point of 142.3 g by recrystallization from 300 ml of xylene from the residue (161.5 g).

Saponification number: 352 to 352 (calculated 352), percent carbon dioxide after saponification: less than 0.01.

Example 6

102.1 g (1.0 mol) of n-valeric acid, 214.2 g (1.0 mol) of diphenyl carbonate and 3.00 g (0.044 mol) of imidazole, as described in Example 1 a), at 16O ⁰ C Heated sump temperature. After about an hour the weight loss in carbon dioxide is already 41.0 g, after a total of 27 g hours the evolution of carbon dioxide has ended, the total weight loss is 45.0 g.

Claims (1)

5 6 The reaction mixture is obtained under a water jet (boiling point = 195 ^° C.) in addition to 93 g of phenol. The vacuum is fractionally distilled. After a forerun yield is thus 99 ° / _0th The saponification number of 108.5 g, the phenol and some n-valeric acid product is 410-412. includes phenyl, distill 164.0 g (92.0% of c) By proceeding as indicated above under a), except that theory) n-Valeriansäurephenylester (Kp. = ₉ 115-5 instead of pyrrole, 3.4 g imidazole (0 .05 mol) as catalyst 8 ⁰ C) practically residue-free over, lyser, then the elimination of sulfur dioxide begins Saponification value: 310-311 (calculated 315) percent at 7O ⁰ C. It is at 100 ⁰ C after 4 hours with a Carbon dioxide after saponification: 0.02. Elimination of 64 g of SO ₂ ended. Be as forerun ... obtained 93 g of phenol. Furthermore, 135 g of acetic acid B e ι s ρ ι e 1 7 ₁₀ ph _eny i _ester (bp = 195 ⁰ C) with a saponification number 36.3 g (0.25 mol + 5%) salicylic acid, 58.6 g (0.25 from 410 to 412. The yield is thus obtained Mole) diphenyl sulfite and 0.25 g (0.0037 mole) imidazole 99%. are as described in Example 1 a), at 100 ⁰ C d) comparison: The procedure as described above under a) Toggle Heated sump temperature, which immediately gave a violent, but instead of pyrrole 3.95 g of pyridine Development of sulfur dioxide sets in. After one hour 15 (0.05 mol) as a catalyst, the reaction takes place the weight loss is 14.9 g, after 5 hours it is only above 140 ° C. The elimination of sulfur the evolution of sulfur dioxide ends, the weight dioxide is only 60 g. She is loaded after 4 hours loss is then 16.2 g. ends. The yield of phenyl acetate is 115 g of the reaction mixture obtained are added, which corresponds to a yield of 85%. As a closing under a water jet vacuum 23.0 g of phenol ao forerunner, 80 g of phenol are obtained with a back distillation. The residue is in 250 ml of ligroin stood from 35 g.
(Kp. = 90 to 100 ⁰ C) added. The ligroin example 9
solution and then washed twice with 2 ° / ₀ sodium hydroxide solution three times with water. After a) 60.5 g of acetic acid (1 mol), 214 g of diphenylcarbo evaporation of the ligroin under a water jet vacuum 25 nat (1 mol) and 3.4 g of imidazole (0.05 mol), the residue is finally distilled off in vacuo - 80 to 100 ⁰ C implemented. The cleavage of 63 g liert. After a first run of 6.4 g, 48.2 g of carbon dioxide are distilled after 2 ¹ l ₂ hours. 93 g Phe-salicylate (89.6% of theory, based nol be distilled off. The distilled Essigsäureauf diphenyl) from the boiling point Kp. _0, i = 103 phenyl ester (Kp. = 195 ⁰ C) is 132 g, which corresponds to a to 104 ° C with practically no residue. The distillate yield of 97 30 ° / ₀ of the theoretical equivalent (Vererstarrt during seeding to give a crystalline product saponification index 410-412).
a melting point of 40.0 to 40.5 ⁰ C. b) Comparison: The procedure as described above under a) Toggle Saponification number: 262 to 263 (calculated 262). given, but used 3.9 g of pyridine instead of imidazole (0.05 moles). The reaction takes place only at about 130 ⁰ C ^{ß e J s} P ^{l e [8} 35 takes place and the carbon dioxide elimination (42 g to 43) a) 60.5 g (1 mol) of acetic acid, 234.3 g (1 mol) of di- is not complete until after 7 hours. 88 g of phenol and 3.3 g of pyrrole phenylsulfit are distilled off at 100 to 105 ⁰ C. The distilled phenyl acetate be brought to reaction. The splitting off of sulfur carries only 127 g, which corresponds to a yield of 93.5% of the dioxide (63 g) is complete after 7 hours. Corresponds by theory (saponification number 408 to 410).
Phenol and vinegar are then distilled acid phenyl ester separated. There are 92 g of phenol and claim 129.5 g of phenyl acetate of a boiling point obtained from 195 ° C, which corresponds to a yield of 95%. is equivalent to. The saponification number of the ester is 409 esters by heating mixtures of preferred to 411 (calculated 412). There remains a residue 45 wise approximately equivalent amounts of carbon from 8 g. acids and diaryl carbonates or sulfites in b) By proceeding as indicated above under a), sets the presence of small amounts of nitrogen, but instead of 3.4 g of pyrrole pyrazole as a catalyst, of heterocyclic compounds as catalysts, the reaction takes place at 90 to 100 ⁰ C. It is characterized in that it ends after 8 hours, with 64 g of SO ₂ split off in this way, nitrogen-containing, 5-membered heterocyclic Vererden. 135 g of phenyl acetate are used as catalysts.