JPH0623127B2 - Method for producing cinnamic acids - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing cinnamic acids by hydrolyzing cinnamic acid alkyl esters.

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

(Prior Art) As a method for synthesizing cinnamic acids, various methods have been known so far. For example, using benzaldehyde as a raw material,
Perkin reaction, Knoevenagel reaction, Claisen condensation, a method of using benzene or a benzene derivative and an acrylic ester as a raw material are known (for example, Japanese Patent Publication No. 47-50611, Japanese Patent Publication No. 58-59927, U.S. Pat. No. 3,783,140, 3922299). Such).
Also, a method of reacting styrene or a derivative thereof with carbon monoxide, alcohol and oxygen in the presence of a catalyst has recently been proposed (for example, Japanese Examined Patent Publication Nos. 59-5570 and 60-23661).
Such).

Among these methods, Claisen condensation using benzaldehyde and acetic acid ester, a method using benzene or a benzene derivative and an acrylic ester as a raw material, a method using styrene or a derivative thereof and carbon monoxide, alcohol and oxygen as a raw material, In each case, cinnamic acid esters are once formed, and therefore it is necessary to hydrolyze the esters to obtain free cinnamic acids.

Recently, a method using an acid as a catalyst has been proposed as a hydrolysis method of cinnamic acid esters (JP-A-60-112736), but generally, in a mixed solvent of alcohol, dioxane, acetone, etc. and water, It is carried out in a homogeneous system using an alkali such as sodium hydroxide (see, for example, JP-A-49-10261).
Four).

(Problems to be Solved by the Invention) When the cinnamic acid ester is hydrolyzed with an acid, the reaction time is generally long because the reaction is slow. Further, in the method using an alkali, as described above, since it is carried out in a homogeneous system using an organic solvent, an operation such as extraction or concentration is required to isolate the target product, and further industrially, the extraction is performed. It is necessary to recover the solvent used.

(Means for Solving the Problem) As a result of earnest studies on the hydrolysis of cinnamic acid esters with alkali, the present inventors have found that the reaction is a heterogeneous two-phase liquid using water as a solvent without using an organic solvent. The inventors have found that high-quality cinnamic acids can be industrially advantageously obtained by initiating the reaction in a system and carrying out the reaction under specific conditions, and arrived at the present invention.

That is, the present invention is a method for hydrolyzing cinnamic acid esters with an alkali to produce cinnamic acids, in which the reaction of alkyl cinnamic acid alkyls with an alkali is heterogeneous using water as a solvent without using an organic solvent. Start the reaction in a two-phase liquid system,
The concentration of the obtained aqueous solution of an alkali salt of cinnamic acids is 1-20.
To an aqueous alkali salt solution of cinnamic acid so that the pH of the system becomes 3 or less and the concentration of cinnamic acids formed is kept at 1 to 7% by weight. Is a method for producing cinnamic acids.

The raw material cinnamic acid ester used in the method of the present invention has the general formula (In the formula, R ¹ is hydrogen or at least one substituent on an aromatic ring, and represents halogen, a hydroxyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. R ² and R ³ is the same or different group and represents hydrogen or an alkyl group having 1 to 6 carbon atoms, and R ⁴ represents an unsubstituted or substituted alkyl group or alkenyl group) Kind,
Specifically, methyl cinnamate, ethyl cinnamate, propyl cinnamate, butyl cinnamate, ethyl α-methyl-β-phenyl acrylate, methyl α-propyl-β-chlorophenyl acrylate, β-3,4-dimethoxyphenyl Methyl acrylate, β-4-methoxyphenyl methyl acrylate,
Examples include benzyl cinnamate, cinnamyl cinnamate, and guaiacol cinnamate.

These cinnamic acid esters can be produced by various methods. For example, as described above, it may be prepared by Claisen condensation from benzaldehyde and acetic acid ester, by oxidative carbonylation reaction of styrene, or by reaction of benzene or benzene derivative with acrylic ester. It may be made. In addition, it may be separated from natural products such as Sugo perfume oil.

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

Since the reaction of the cinnamic acid ester and the alkali in the method of the present invention is initiated in a heterogeneous two-phase liquid system, only water is used as the solvent. If the amount used is too small, the alkali salt of cinnamic acid will not be completely dissolved in water to form a uniform solution, and in an extreme case, it will solidify, making it virtually impossible to operate. On the other hand, if the amount is too large, the yield of cinnamic acids decreases. Therefore, in order for the method of the present invention to be effectively carried out industrially, the concentration of the cinnamic acid alkali salt in the aqueous solution is 1 to 20% by weight.
Need to be used. Amounts preferably in the range of 2-15% by weight are suitable.

The reaction temperature is suitably 40 to 120 ° C, more preferably 60 to 100 ° C.

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

The reaction time depends on the reaction temperature and pressure, but is appropriately 1 to 120 minutes, more preferably 3 to 30 minutes.

Since the method of the present invention initiates the reaction between the cinnamic acid alkyl ester and the alkali in a heterogeneous two-phase liquid system, vigorous stirring is effective. After the reaction, it becomes a homogeneous solution.

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

As means for distilling alcohol out of the system, other than the method of heating the reaction solution to the boiling point or higher, a method of distilling out the alcohol produced while blowing an inert gas into the reaction solution together with the exhaust gas is effective. is there.

As the acid used to obtain the cinnamic acids from the alkali salt of the cinnamic acids, water-soluble acids usually 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 a high yield by the method of the present invention, the amount of acid used in the solution after the reaction is 3 or less, preferably 2 or less.

In the method of the present invention, in the reaction of an alkali salt of cinnamic acids with an acid, the concentration of cinnamic acids formed in the suspension is finally 1-
The amount of water used is adjusted to 7% by weight, more preferably 2-5% by weight, and the reaction is carried out. Outside the range of this concentration, the object of the present invention cannot be sufficiently achieved. That is, 1% by weight
If the amount is less than the above, the yield of the target substance decreases, and if it exceeds 7% by weight, a slurry having a high concentration is formed, and the reaction is incomplete due to insufficient stirring, or the purity of the target substance decreases.

The method of the present invention may be a batch system in which cinnamic acid esters and an aqueous alkali solution are charged in a reactor at a time for reaction, or a semi-batch system in which a part of them is gradually added dropwise, or the raw material and the aqueous alkali solution are continuously fed. It can be carried out by any method of continuous reaction in which the reaction liquid charged in the above is continuously discharged. Similarly, the reaction between the aqueous solution of an alkali salt of cinnamic acid and the acid solution can be carried out in a batch system, a semi-batch system or a continuous system.

(Effect of the Invention) According to the method of the present invention, hydrolysis of cinnamic acid esters with alkali proceeds in a heterogeneous two-phase liquid system using water as a solvent without using an organic solvent, and recovery of the organic solvent is unnecessary, Moreover, since the cinnamic acids can be easily separated, the method of the present invention is an industrially extremely advantageous method for producing cinnamic acids.

(Examples) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

Example 1 In a separable flask equipped with a stirrer, 16.2 g (0.10 mol) of methyl cinnamate and 97% by weight of sodium hydroxide 4.3
g and 200 g of water were charged and reacted for 15 minutes with vigorous stirring. 0.05% sulfuric acid was added to the obtained aqueous solution of sodium cinnamate.
200 ml of a sulfuric acid aqueous solution containing 6 mol was slowly added with stirring. After cooling the resulting suspension to room temperature, the pH was measured to be about 1.5. Transfer the crystals separated by suction to a beaker, add 50 ml of water, wash with stirring,
After separation, it was dried under reduced pressure. The weight of the crystal was 14.6 g, and as a result of the analysis, the cinnamic acid content was 99.9% or more.

Comparative Example 1 A reaction was performed in the same manner as in Example 1 except that 64 g of water was used. As a result, after about 5 minutes from the start of the reaction between methyl cinnamate and sodium hydroxide, the reaction solution solidified and the reaction could not be continued.

Comparative Example 2 A reaction was performed in the same manner as in Example 1 except that 2100 g of water and 200 g of a sulfuric acid aqueous solution containing 0.086 mol of sulfuric acid were used. As a result, the yield of cinnamic acid obtained was 13.8 g, which was a decrease in yield.

Comparative Example 3 The reaction was performed in the same manner as in Example 1 except that the amount of water used was changed to 140 g and the aqueous acid solution was changed to 20 ml of an aqueous solution containing 0.053 mol of sulfuric acid. As a result, when a part of the acid aqueous solution was added to the sodium cinnamate aqueous solution, the reaction solution solidified and the reaction could not be continued.

Comparative Example 4 The reaction was performed in the same manner as in Example 1 except that the acid aqueous solution used in Example 1 was replaced with 2000 ml of a sulfuric acid aqueous solution containing 0.085 mol of sulfuric acid. As a result, the yield of cinnamic acid obtained was 13.9 g, which was a decrease in yield.

Example 2 The same reaction as in Example 1 was carried out except that 230 g of water was used. After heating and stirring for 15 minutes, a Liebig condenser was attached to the flask and further heated to obtain 30 g of distillate. As a result of gas chromatographic analysis of the distillate, it contained 3.1 g of methanol.

Example 3 The reaction was performed in the same manner as in Example 1 except that 17.6 g (0.1 mol) of ethyl cinnamate was used instead of the methyl cinnamate used in Example 1. The resulting cinnamic acid was 14.5 g, and the cinnamic acid content was 99.9% or more.

Example 4 A reaction was performed in the same manner as in Example 1 except that 6.9 g of 85% potassium hydroxide was used instead of sodium hydroxide in Example 1. The resulting cinnamic acid was 14.5 g, and the cinnamic acid content was 99.9% or more. Example 5 A reaction was conducted in the same manner as in Example 1 except that 0.112 mol of hydrochloric acid was used instead of 0.056 mol of sulfuric acid in Example 1. The resulting cinnamic acid was 14.4 g, and the cinnamic acid content was 99.9% or more.

Claims (2)

[Claims] 1. A method for producing a cinnamic acid by hydrolyzing a cinnamic acid ester with an alkali, wherein the reaction of an alkyl cinnamic acid alkyl ester with an alkali is started in a heterogeneous two-phase liquid system using water as a solvent. The concentration of the obtained aqueous solution of cinnamic acid alkali salt is adjusted to 1 to 20% by weight, and the cinnamic acid solution is added to the aqueous solution of alkali salt of cinnamic acid until the pH of the system becomes 3 or less. Method for producing cinnamic acids, characterized in that an acid is added so as to maintain the concentration of 1-7% by weight 2. The method according to claim 1, wherein alcohol is recovered from an aqueous solution of an alkali salt of cinnamic acid.