JPS62103040A - Production of cinnamic acid - Google Patents

Abstract

PURPOSE:To obtain cinnamic acids of high purity in good yield, by reacting an alkyl cinnamate with an alkali in a heterogeneous two-phase liquid system using water as a solvent and adding the obtained aqueous solution of an alkali salt of cinnamic acids to an acid. CONSTITUTION:A cinnamic acid ester expressed by the formula (R<1> represents H, halogen atom, alkyl, OH, etc.; R<2> and R<3> represent H or alkyl; R<4> represents alkyl or alkenyl) is reacted with an alkali in a heterogeneous two-phase liquid system using water as a solvent at 60-100 deg.C and an alcohol is recovered from thus obtained aqueous solution of an alkali salt of cinnamic acids. The aqueous solution is then added to an acid to obtain cinnamic acids. The amount of the water to be used is adjusted so that the concentration of the alkali salt of cinnamic acids in the aqueous solution comes into 1-30wt% range and the concentration of produced cinnamic acids is maintained at 1-35wt%. The acid is added to make pH in the system <=3. USE:Raw material for perfumes and photosensitive resins.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing cinnamic acids by hydrolysis of cinnamic acid alkyl esters.

Cinnamic acids are industrially important compounds, such as raw materials for perfumes and photosensitive resins.

(Prior Art) Various methods have been known for synthesizing cinnamic acids. For example, using benzaldehyde as a raw material,
Perkin reaction, Knoevenage 1 reaction, C
1aisen condensation, a method using benzene or a benzene derivative and an acrylic ester as raw materials, etc.
7, U.S. Pat. No. 3,783,140, U.S. Pat. No. 3,922,299, etc.). In addition, a method of reacting styrene or its derivatives with carbon monoxide, alcohol, and oxygen in the presence of a catalyst has recently been proposed (for example, Japanese Patent Publication No. 59-5570,
Go-23661 etc.).

Among these methods, the Claisen B combination using benzaldehyde and acetate, the method using benzene or benzene derivative and acrylic ester as raw materials, the method using styrene or its derivatives, carbon oxide, alcohol and oxygen as raw materials, etc. In both cases, cinnamic acid esters are formed once, so it is necessary to hydrolyze the esters in order to obtain free cinnamic acids.

Recently, a method using an acid as a catalyst has been proposed as a method for hydrolyzing cinnamic acid esters (Japanese Unexamined Patent Publication No. 60-12736), but generally it is carried out in a mixed solvent of alcohol, dioxane, acetone, etc. and water. It is carried out homogeneously using an alkali such as sodium hydroxide (for example, JP-A-49-1
02614).

(Problems to be Solved by the Invention) When cinnamic acid esters are hydrolyzed with acid, the reaction time is generally long because the reaction is slow.

In addition, as mentioned above, the method using alkali is carried out in a homogeneous system using an organic solvent, so operations such as extraction and concentration are required to isolate the target product. It is necessary to recover the solvent used.

In addition, in the conventional method to finally obtain cinnamic acids,
An acid is added to an aqueous solution of an alkaline salt of cinnamic acids, but in this method, it is the national policy to increase the concentration of cinnamic acids in the system, and the throughput per unit volume of the reaction vessel is low, making it inefficient.

(Means for resolving the problem) As a result of intensive studies on the hydrolysis of cinnamic acid esters using an alkali, the present inventors have determined that the reaction between cinnamic acid esters and an alkali can be carried out using water as a solvent without using an organic solvent. By starting with a heterogeneous two-phase liquid system and adding an aqueous alkaline salt solution of the cinnamic acids to the acid, it is possible to increase the throughput per unit volume of light and efficiently produce high-quality cinnamic acids. The present invention has been achieved based on the discovery that this can be obtained industrially advantageously and also alleviate problems regarding drainage. That is, the present invention provides a method for producing cinnamic acids by hydrolyzing cinnamic acid alkyl esters using an alkali, in which an aqueous solution of an alkali salt of cinnamic acids obtained by the reaction of cinnamic acid alkyl esters and an alkali is dissolved in an acid. This is a method for producing cinnamic acids, characterized by adding the cinnamic acids to the cinnamic acids.

The cinnamic acid ester of the raw material used in the method of the present invention (in the formula:
R is hydrogen or at least one substituent on the aromatic ring, and represents a halogen, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms; R2 and R3 are the same or It is a heterogeneous group, hydrogen,
cinnamic acid esters (representing an alkyl group having 1 to 6 carbon atoms, where R represents an unsubstituted or substituted alkyl group or alkenyl group), specifically methyl cinnamate, ethyl cinnamate, Propyl cinnamate, butyl cinnamate, ethyl goomethyl-ρ-phenylacrylate, σ
-propyl-ρ -methyl chlorophenylacrylate,
Methyl ρ-3,4-dimethoxyphenylacrylate, p
Examples include methyl -4-methoxyphenylacrylate, benzyl cinnamate, cinnamyl cinnamate, and guaiacol cinnamate.

These cinnamic acid esters can be produced by various methods. For example, as mentioned above, it may be made by C1aisen condensation from benzaldehyde and acetate, it may be made by oxidative carbonylation of styrene, or it may be made by reaction between benzene or a benzene derivative and acrylic ester. It may be a manufactured product, or it may be separated from a natural product such as Soai perfume oil.

As the alkali used in the method of the present invention, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, etc. can be used, but sodium hydroxide or potassium hydroxide is preferably used. These alkalis can also be used as a mixture of two or more.

The reaction medium for the reaction of cinnamic acid esters with an alkali in the method of the present invention is not particularly limited. Since the reaction starts in a liquid system, only water is used as the solvent. If the amount used is too small, the alkaline salt of cinnamic acids will not be completely dissolved in water, and will not form a homogeneous solution, and in extreme cases will solidify, making it virtually impossible to operate. Moreover, if it is too large, the yield of cinnamic acids will decrease. Therefore, in order for the method of the present invention to be carried out industrially and effectively, it is necessary to use the alkaline cinnamic acid salt at a concentration of 1 to 30% by weight in the aqueous solution.

Preferably, amounts ranging from 2-25% by weight are suitable. The reaction temperature is suitably 4O-1200C, preferably 6O-too@c.

The reaction pressure is usually normal pressure, but it may be effective to carry out the reaction under slightly reduced or increased pressure.

The reaction time depends on the reaction temperature and pressure, but ■-120
minutes is suitable, more preferably 3-30 minutes.

Since the method of the present invention starts with a cinnamic acid alkyl ester and an alkali heterogeneous two-phase liquid system, a homogeneous solution is obtained after the reaction, in which vigorous stirring is effective.

In the method of the present invention, the alcohol produced during the reaction can be recovered by distilling it out of the yarn during or after the reaction.

In addition to heating the reaction solution above its boiling point, effective methods for distilling alcohol out of the system include methods such as blowing an inert gas into the reaction solution and distilling the generated alcohol out of the system along with the exhaust gas. be.

As the acid used to obtain cinnamic acids from the alkali salts of cinnamic acids, water-soluble acids commonly used in industry can be used. For example, hydrochloric acid, sulfuric acid, phosphoric acid, etc. can be used.

In order to obtain cinnamic acids in high yield by the method of the present invention, the amount of acid used is such that the pH of the solution after reaction is 3 or less, preferably 2 or less.

In the method of the present invention, in the reaction between an alkali salt of cinnamic acids and an acid, the final concentration of the resulting suspension of cinnamic acids is 1-
The amount of water used is adjusted so that the amount of water is 35% by weight, preferably 2-30% by weight. If the concentration is outside this range, the object of the present invention cannot be fully achieved; if it is less than 1% by weight, the yield of the target product will decrease, and if it exceeds 35% by weight, a highly concentrated slurry will result, and stirring will be insufficient, resulting in a reaction. may become incomplete or the purity of the target product may decrease.

The method of the present invention can be carried out either by a batch method in which the cinnamic acid esters and aqueous alkali solution are charged into a reactor all at once and reacted, or in a semi-batch method in which a part of them is added dropwise little by little, or by a continuous method in which the raw materials and aqueous alkali solution are charged into a reactor and reacted. It can be carried out by any continuous reaction method in which the reaction solution is charged in water and the reaction solution is continuously discharged. Similarly, the reaction between the alkaline salt aqueous solution of cinnamic acids and the acid aqueous solution can be carried out in a batch, semi-batch or continuous manner.

(Effects of the Invention) According to the method of the present invention, the reaction between an alkaline aqueous solution of cinnamic acids obtained by hydrolyzing cinnamic acid esters with an alkali and an acid aqueous solution can be carried out at a high concentration. This is an extremely advantageous method for producing cinnamic acids.

(Example) The present invention will be explained in detail below using Examples and Comparative Examples.

Example 1 Methyl cinnamate IG, 2 g (0.10 mol), 9
4.3 g of 7% sodium hydroxide and 140 g of water
were charged and reacted for 15 minutes with vigorous stirring. The obtained aqueous solution of sodium cinnamate was transferred to a heat-retaining funnel kept at 80°C, and 20% of the aqueous sulfuric acid solution containing 0.053 mol of sulfur was added.
The mixture was added dropwise to a beaker containing ml while stirring. After the resulting suspension was cooled to room temperature, the crystals separated by suction filtration were transferred to a beaker, and 50 ml of water was added thereto, washed with water with stirring, and dried under reduced pressure after being separated. The weight of the crystal is 14.7
As a result of analysis, the content of cinnamic acid was 99.9% by weight or more.

Comparative Example 1 Same as Example 1 except that 64g of water was used in Example 1.
reacted in the same way. As a result, about 5 minutes after the start of the reaction between methyl cinnamate and sodium hydroxide, the reaction solution solidified, making it impossible to continue the reaction.

Comparative Example 2 In Example 1, 2400 g of water and 0.0 g of sulfuric acid
The reaction was carried out in the same manner as in Example 1, except that 40 ml of an aqueous sulfuric acid solution containing 89 mol was used. As a result, the yield of cinnamic acid was 13.8 g, which was low.

Comparative Example 3 To a sodium cinnamate aqueous solution obtained in the same manner as in Example 1, 20 ml of a sulfuric acid aqueous solution containing 0.053 mol of sulfuric acid was slowly added at 80°C. As a result, the reaction solution solidified when a portion of the acid aqueous solution was added, making it impossible to continue the reaction.

Comparative Example 4 A reaction was carried out in the same manner as in Example 1, except that the acid aqueous solution used in Example 1 was changed to 2000 ml of a sulfuric acid aqueous solution containing 0.085 mol of sulfuric acid. The resulting cinnamic acid is 1
The yield decreased at 3.9 g.

Example 2 In a 300 ml separable flask equipped with a stirring device, 24.3 g (0.15 mol) of methyl cinnamate, 9
6.5 g of 7% by weight sodium hydroxide and 260 g of water were charged, and the mixture was reacted at 80°C for 15 minutes with vigorous stirring. A Liebig condenser was attached to the flask and the mixture was further heated to obtain 50 g of distillate. Transfer the remaining aqueous solution of sodium cinnamate to a heat-insulated funnel maintained at 801C, and add sulfuric acid 0.0
The mixture was added dropwise to a beaker containing 30 ml of an aqueous sulfuric acid solution containing 8 mol of sulfuric acid while stirring. After the resulting suspension was cooled to room temperature, the crystals separated by suction filtration were transferred to a beaker, and 50 ml of water was added thereto, stirred, and washed with water; the crystals were separated and dried under reduced pressure. The weight of the crystals was 22.1 g, and analysis revealed that the content of cinnamic acid was 99.9% by weight or more. As a result of analyzing the distillate by gas chromatography, 4.7g
of methanol.

Example 3 The reaction was carried out in the same manner as in Example 1 except that 17.6 g (0.1 mol) of ethyl cinnamate was used instead of methyl cinnamate. The resulting cinnamic acid was 14.6
Example 4 Same as Example 1 except that 6.9 g of 85% potassium hydroxide was used instead of sodium hydroxide in Example 1. Made it react. The resulting amount of cinnamic acid was 14.5g.
The content of cinnamic acid was 99.9% or more. Example 5 In Example 1, 0.053 mol of sulfuric acid was replaced with 0.05 mol of hydrochloric acid.
．． The reaction was carried out in the same manner as in Example 1 except that 102 mol was used. The resulting cinnamic acid was 14.4 g, and the cinnamic acid content was 99.9% or more.

Claims (1)

[Claims] 1) In a method for producing cinnamic acids by hydrolyzing cinnamic acid alkyl esters using an alkali, an aqueous solution of an alkali salt of cinnamic acids obtained by the reaction of the cinnamic acid alkyl esters and an alkali is 2) A method for producing cinnamic acids, characterized in that the aqueous solution of an alkali salt of a cinnamic acid has a concentration of 1 to 30% by weight. 3) A method of producing an aqueous alkali salt of a cinnamic acid. 4) A method according to claim 1 or 2 for recovering alcohol from cinnamic acids 4) Adding an aqueous aqueous solution of an alkaline salt of cinnamic acids to the acid so as to maintain the concentration of the produced cinnamic acids at 1-35% by weight. Method described in Section 1-3