JPH11302214A - Production of acetal compounds - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject compound useful as a perfume, etc., in high selectivity by performing a reaction in the presence of a specific acid catalyst. SOLUTION: This method for producing an acetal compound comprises reacting (B) an α,β-unsaturated linear alkenyl ether (for example, ethylvinyl ether) with (C) an alcohol (for example, cis-3-hexen-1-ol) in the presence of (A) an acid having a pKa of 0-4, such as maleic acid. The components A and B and used is amounts of, for example, 0.001-1 mole and 0.1-10 moles, respectively, per mole of the component C in the reaction, and the reaction is carried out at a reaction temperature of -10 to 100 deg.C at a reaction pressure of 0.5-1 atm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an acetal. More specifically, the present invention relates to a method for producing an objective 1: 1 adduct, acetal, with a high selectivity from an α, β-unsaturated linear alkenyl ether and an alcohol by suppressing an acetal exchange reaction which is a side reaction.

[0002]

2. Description of the Related Art Acetaldehyde ethyl cis-3-hexenyl acetal is a fragrance having a fresh green scent, and can be used in a floral blended fragrance to give a natural green tinge. It is known that this acetaldehyde ethyl cis-3-hexenyl acetal is produced from acetaldehyde diethyl acetal and cis-3-hexen-1-ol by an acetal exchange reaction (synthetic fragrance, p299 to p30).
0). However, what is obtained by the acetal exchange reaction is a mixture of three types of acetaldehyde ethyl acetaldehyde ethyl cis-3-hexenyl acetal, acetaldehyde dicis-3-hexenyl acetal, and acetaldehyde diethyl acetal. -Low yield of hexenyl acetal. There is also a problem that it is necessary to remove ethanol generated by the acetal exchange reaction.

[0003] By the way, in the presence of an inorganic acid catalyst,
A method of producing an acetal by adding an alcohol to a cyclic alkenyl ether is known. For example,
Journal of American Chemical Society (Journal of American Che
medical Society), Vol. 69, p. 224
6 (1947) describes a method of reacting 2,3-dihydropyran which is a cyclic alkenyl ether with an alcohol such as methanol in the presence of concentrated hydrochloric acid to synthesize an acetal. Also, the Journal of
Chemical Society (Journal of Ch)
Chemical Society, p. 3646 (19)
(1975) discloses a method of reacting 2,3-dihydropyran with an alcohol in the presence of phosphoryl chloride.

Therefore, the present inventors have proposed these methods as follows.
An attempt was made to apply it to the reaction between ethyl vinyl ether, which is an α, β-unsaturated chain alkenyl ether, and cis-3-hexen-1-ol. However, the reaction product is a mixture of three acetals including the acetaldehyde ethyl cis-3-hexenyl acetal, which is the target product, and the acetaldehyde diethyl acetal and the acetaldehyde dicis-3-hexenyl acetal, which are the acetal exchange reaction products. However, the desired 1: 1 adduct, ie, acetaldehyde ethyl cis-3-hexenyl acetal, could not be selectively obtained.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide α,
It is an object of the present invention to provide a method for obtaining an intended acetal as a 1: 1 adduct at a high selectivity from a β-unsaturated linear alkenyl ether and an alcohol.

The present inventors have conducted intensive studies to achieve this object, and as a result, ethyl vinyl ether and cis-3-
It has been found that the desired acetaldehyde ethyl cis-3-hexenyl acetal can be obtained with high selectivity by reacting hexen-1-ol in the presence of a specific acid catalyst, and the present invention has been completed based on this finding. Reached.

[0007]

Thus, according to the present invention, an acid having a pKa value of 0 or more and 4 or less is used as a catalyst.
There is provided a process for producing an acetal, which comprises reacting an α, β-unsaturated linear alkenyl ether with an alcohol.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the acetal production method of the present invention, an α, β-unsaturated linear alkenyl ether is reacted with an alcohol using an acid having a pKa value of 0 to 4 as a catalyst.

The α, β-unsaturated chain alkenyl ether to which the production method of the present invention can be applied is an ether having a structure in which an α, β-unsaturated chain alkenyl group and a hydrocarbon group are bonded via an oxygen atom. is there.

The α, β-unsaturated alkenyl group usually has 2 to 8 carbon atoms. The α, β-unsaturated alkenyl group may be branched. Specific examples include a vinyl group, a 1-propenyl group, a 1-butenyl group, a 1-pentenyl group, a 1-hexenyl group, a 1-heptenyl group, a 1-octenyl group, and the like.

The hydrocarbon group which forms an ether by bonding to an α, β-unsaturated alkenyl group via an oxygen atom is
It has 1 to 8 carbon atoms. This hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
The aliphatic hydrocarbon group may be a saturated group or an unsaturated group, may be linear or branched, and may have various substituents. Examples of the aliphatic hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group and an octyl group; for example, a vinyl group, a propenyl group, and a butenyl group Alkenyl groups such as pentenyl group, hexenyl group, heptenyl group, octenyl group; for example, acetylene group,
Alkynyl groups such as propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group and octynyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; aralkyl groups such as benzyl group and phenethyl group; Examples of the hydrogen group include a phenyl group and a tolyl group.

Specific examples of the α, β-unsaturated alkenyl alkyl ether include, for example, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether,
Examples thereof include butyl vinyl ether, pentyl vinyl ether, hexyl vinyl ether, heptyl vinyl ether, octyl vinyl ether, and methyl propenyl ether.

The alcohol to which the production method of the present invention can be applied is not particularly limited. The carbon number of alcohol is usually
1 to 12. The alcohol may be a straight-chain alcohol or a branched alcohol, may have a substituent, and may be a saturated alcohol or an unsaturated alcohol. Furthermore, a monohydric alcohol or a polyhydric alcohol may be used. Further, the alcohol in the present invention includes an aryl alcohol (phenol). Specific examples of the saturated aliphatic alcohol include methanol, ethanol, propanol,
Butanol, pentanol, hexanol, heptinol, octanol, nonanol, decanol, undecanol, dodecanol, isopropanol, isobutanol and the like.

Specific examples of the unsaturated aliphatic alcohol include cis-3-hexen-1-ol, linalool, citronellol, geraniol and the like. Specific examples of aralkyl alcohol include benzyl alcohol,
Phenethyl alcohol and the like can be mentioned. Also,
Specific examples of aryl alcohol (phenol) include:
For example, phenol, eugenol, isoeugenol and the like can be mentioned.

The acid used as a catalyst in the production method of the present invention has a pKa value of 0 or more and 4 or less. The pKa value is preferably 1 or more and 3 or less. For polyvalent acids, the pKa value is a value for the first stage dissociation. The pKa values of these acids can be determined, for example, from “Chemical Handbook Basic Edition 2, p993-p1000”.

The acid used as a catalyst in the production method of the present invention is not particularly limited as long as its pKa value is within the above range, and may be an inorganic acid or an organic acid. Examples of the inorganic acid include sulfurous acid (pKa = 1.76) and phosphoric acid (pKa = 2.15). Examples of the organic acid include carboxylic acids, sulfonic acids, sulfinic acids, phenols, and enols, and among them, carboxylic acids are preferred.

The carboxylic acids may be aliphatic carboxylic acids or aromatic carboxylic acids, and may be monocarboxylic acids or polycarboxylic acids. Further, it may have a substituent such as a hydroxyl group or a carbonyl group.

Specific examples of the aliphatic carboxylic acid include, for example, trichloroacetic acid (pKa: 0.1), dichloroacetic acid (pKa: 1.29), and pyruvic acid (pKa: 2.4).
9), formic acid (pKa: 3.76), glycolic acid (pK
a: 3.83); monocarboxylic acids such as oxalic acid (pKa: 1.27), maleic acid (pKa: 1.9)
2), oxaloacetic acid (pKa: 2.56), malonic acid (pKa: 2.86), fumaric acid (pKa: 3.0)
2), tartaric acid (pKa: 3.06), citric acid (pK
a: 3.16). Among these, polycarboxylic acids are preferred, and oxalic acid,
Maleic acid, malonic acid and the like are particularly preferred.

The amount of the acid catalyst to be used is generally 0.001-1 mol, preferably 0.0025-0.2 mol, per 1 mol of alcohol.

In the method of the present invention, the amount of the α, β-unsaturated linear alkenyl ether to be used per 1 mol of the alcohol is usually 0.1 to 10 mol, preferably 0.5 to 2 mol.

In the method for producing acetal of the present invention, a solvent may or may not be used, but it is preferable not to use it in order to reduce the number of steps.

In the production method of the present invention, the reaction temperature is
Usually, it is -10 to + 100 ° C, preferably 0 to +5
0 ° C. The reaction can be carried out under reduced pressure or under increased pressure, and the reaction pressure is usually -0.5 to +1 atm, preferably -0.2 to +0.2 atm.

After reacting an α, β-unsaturated linear alkenyl ether with an alcohol in the presence of an acid catalyst,
An alkaline aqueous solution is added to the reaction solution to neutralize the acid catalyst. The organic layer is separated from the aqueous layer and washed with an aqueous alkaline solution. Thereafter, the desired product is isolated and purified according to a conventional method such as distillation or chromatography. As the alkaline aqueous solution, for example, carbonates, bicarbonates, and the like of alkali metals such as sodium and potassium can be used.

Embodiments of the present invention will be summarized below. (1) A method for producing an acetal, comprising reacting an α, β-unsaturated linear alkenyl ether with an alcohol using an acid having a pKa value of 0 to 4 as a catalyst. (2) The pKa value of the acid catalyst is 1 or more and 3 or less. (3) The acid catalyst is a carboxylic acid. (4) The acid catalyst is maleic acid or oxalic acid.

(5) The α, β-unsaturated linear alkenyl ether is ethyl vinyl ether. (6) The alcohol is cis-3-hexen-1-ol. (7) Solventless reaction. (8) The amount of the organic acid catalyst used is from 0.001 to 1 mol, preferably from 0.0025 to 1 mol, per mol of the alcohol.
2 moles. (9) The amount of the α, β-unsaturated alkenyl ether is 0.1 to 10 mol, preferably 0.5 to 2 mol, per 1 mol of the alcohol.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A mechanical stirrer was placed in a two-liter four-necked flask.
A dropping funnel, a thermometer and a reflux tube were attached, and cis-3-hexen-1-ol 500 was added to the reaction vessel as alcohol.
g (5 mol), maleic acid 58.0 g as acid catalyst
(0.5 mol) was added in this order, and the mixture was stirred at 25 ° C. to dissolve maleic acid in cis-3-hexen-1-ol. Next, the reaction vessel was cooled on ice to raise the temperature of the reaction solution to 5 to 5.
Heated to 15 ° C. While maintaining the temperature of the reaction solution not to exceed 15 ° C., the ethyl vinyl ether 360.
6 g (5 mol) were added dropwise. Cis-3-hexene-1-
The reaction rate of all was monitored by gas chromatography, and after this exceeded 50%, the temperature of the reaction solution was reduced to 15 to 15%.
While maintaining the temperature at 25 ° C., stirring was continued for another 24 hours to complete the reaction.

According to gas chromatography analysis of the reaction mixture, cis-3-hexene-1-
All and the reaction products acetaldehyde ethyl cis-3-hexenyl acetal, acetaldehyde diethyl acetal and acetaldehyde dicis-3-hexenyl acetal were 4.6: 91.4: 1.3:
2.7 in a ratio of cis-3-hexene-1-
The conversion of all was 95.5%, and the selectivity for the target substance, acetaldehyde ethyl cis-3-hexenyl acetal, was 95.8%.

The reaction solution was added with a 20% aqueous potassium carbonate solution 332.
g, neutralize the maleic acid, separate the organic layer,
Washed with 0.1% potassium carbonate aqueous solution. Then, vacuum distillation was performed to obtain 570 g of crude acetaldehyde ethyl cis-3-hexenyl acetal having a purity of 95% in a fraction at 70 to 75 ° C./10 Torr. Further, the crude acetaldehyde ethyl cis-3-hexenyl acetal was continuously distilled, and at 10 Torr, the ratio of the bottom extraction amount and the top distillation amount was 1:15, and the target acetaldehyde ethyl cis-3-hexenyl acetal (510 g, purity 98%). The yield of acetaldehyde ethyl cis-3-hexenyl acetal based on cis-3-hexen-1-ol was 59%. As by-products, acetaldehyde diethyl acetal (6 g, yield based on cis-3-hexen-1-ol) in a cooling trap and acetaldehyde dihexenyl acetal (40 g, cis-3-hexen- 4% yield based on 1-ol).

1H-NMR of acetaldehyde ethyl cis-3-hexenyl acetal (500 MHz, internal standard (CDCl ₃ )) δ (ppm): 0.97 (t, 3
H), 1.20 (t, 3H), 1.31 (d, 3H),
1.91 (m, 2H), 2.17 (m, 2H), 3.3
8 to 3.69 (m, 4H), 4.70 (q, 1H),
5.35 (m, 1H), 5.46 (m, 1H) ¹³ C-NMR of acetaldehyde ethyl cis-3-hexenyl acetal (126 MHz, internal standard (CDCl
₃ )) δ (ppm): 14.3, 15.4, 19.9,
20.6, 28.1, 60.8, 64.9, 99.5,
125.1, 133.8 IR (neat, cm ^-1 ) of acetaldehyde ethyl cis-3-hexenyl acetal: 1660, 1060
1140 GC-MS of acetaldehyde ethyl cis-3-hexenyl acetal: 171 (M-1)

Example 2 A reaction was carried out in the same manner as in Example 1 except that oxalic acid was used instead of maleic acid. According to gas chromatography analysis of the reaction solution, the ratio of cis-3-hexen-1-ol, acetaldehyde ethyl cis-3-hexenyl acetal, acetaldehyde diethyl acetal, and acetaldehyde dicis-3-hexenyl acetal was 28.8: 65. 1: 4.2: 1.8 and cis-3
The reaction rate of -hexen-1-ol was 70.5%, and the selectivity for the target substance, acetaldehyde ethyl cis-3-hexenyl acetal, was 91.5%.

Example 3 Example 1 was repeated except that pyruvic acid was used instead of maleic acid.
The reaction was carried out in the same manner as described above. According to gas chromatography analysis of the reaction solution, the ratio of cis-3-hexen-1-ol, acetaldehyde ethyl cis-3-hexenyl acetal, acetaldehyde diethyl acetal, and acetaldehyde dicis-3-hexenyl acetal was 23.7: 73. 1.6: 1.9: 0.9, and cis-3
The reaction rate of -hexen-1-ol was 76.1%, and the selectivity for the target substance, acetaldehyde ethyl cis-3-hexenyl acetal, was 96.4%.

Example 4 A reaction was carried out in the same manner as in Example 1 except that trichloroacetic acid was used instead of maleic acid. According to gas chromatography analysis of the reaction solution, cis-3-hour after 3 hours of the reaction.
Hexen-1-ol, acetaldehyde ethyl cis-
The ratio of 3-hexenyl acetal, acetaldehyde diethyl acetal and acetaldehyde dicis-3-hexenyl acetal is 5.3: 91.7: 1.1: 1.9.
And the conversion of cis-3-hexen-1-ol is 9
4.8%, the target substance, acetaldehyde ethyl cis-
The selectivity for 3-hexenyl acetal was 96.8%.

Example 5 A reaction was carried out in the same manner as in Example 1 except that phosphoric acid was used instead of maleic acid. According to gas chromatography analysis of the reaction solution, the ratio of cis-3-hexen-1-ol, acetaldehyde ethyl cis-3-hexenyl acetal, acetaldehyde diethyl acetal, and acetaldehyde dicis-3-hexenyl acetal after 1 hour of the reaction was as follows: 13.4: 78.1: 3.7: 4.8, and the conversion of cis-3-hexen-1-ol was 86.
7%, the target substance, acetaldehyde ethyl cis-3-
The selectivity for hexenyl acetal was 90.2%.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that concentrated hydrochloric acid was used instead of maleic acid. According to gas chromatography analysis of the reaction solution, the ratio of cis-3-hexen-1-ol, acetaldehyde ethyl cis-3-hexenyl acetal, acetaldehyde diethyl acetal, and acetaldehyde dicis-3-hexenyl acetal after 1 hour of the reaction was as follows: 16.4: 42.5: 9.5: 31.6, and the conversion of cis-3-hexen-1-ol was 86.
6%, the target substance, acetaldehyde ethyl cis-3-
The selectivity for hexenyl acetal was 50.8%.

[0036]

According to the production method of the present invention, acetal compounds can be synthesized with high yield and high selectivity.

Claims (1)

[Claims] 1. A process for producing an acetal, comprising reacting an α, β-unsaturated linear alkenyl ether with an alcohol using an acid having a pKa value of 0 or more and 4 or less as a catalyst.