JP2006104085A - Method for suppressing decomposition of ketal or acetal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for suppressing decomposition of a ketal or an acetal and a method for manufacturing the ketal or the acetal while suppressing decomposition thereof. <P>SOLUTION: The decomposition of the ketal or the acetal derived from an α-hydroxyketone compound or an α-hydroxyaldehyde compound is suppressed by causing a base to be present. In the manufacture of the ketal or the acetal derived from the α-hydroxyketone compound or the α-hydroxyaldehyde compound, a post-treatment step after the reaction is carried out in the presence of the base. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for suppressing the decomposition of a ketal or an acetal, and a method for producing a ketal or an acetal while suppressing the decomposition of the ketal or an acetal, and more specifically derived from α-hydroxyketones or α-hydroxyaldehydes. The present invention relates to a method for inhibiting the decomposition of ketal or acetal, or a method for producing it while inhibiting decomposition. Ketals or acetals are useful compounds as organic compounds such as pharmaceuticals, agricultural chemicals and functional materials, and synthetic intermediates thereof.

There are few production examples of ketals or acetals of α-hydroxy ketones or α-hydroxy aldehydes (for example, Non-Patent Documents 1 to 3), and in addition, little knowledge about their stability is known. Here, ketals or acetals derived from α-hydroxy ketones or α-hydroxy aldehydes, when decomposed, become raw α-hydroxy ketones or α-hydroxy aldehydes. Since it becomes an acidic substance, when a trace amount of acetal or ketal is decomposed, the decomposition is accelerated in a vicious manner. In addition, α-hydroxy ketones or α-hydroxy aldehydes as raw materials are produced by partial oxidation of (1,2-) diol, for example, α-hydroxyacetone is produced by gas phase oxidation of propylene glycol. In this process, by-products such as carboxylic acid are produced and remain unseparated in the ketal or acetal production process, so that there is a problem of promoting the decomposition of the ketal or acetal. Furthermore, there is a problem that α-hydroxy ketones or α-hydroxy aldehydes further react with the target ketal or acetal to form a high-boiling product.
Tetrahedron Lett. , Vol 37.3881 (1996) Bull. Chem. Soc. Jpn. , Vol. 70.561 (1997) J. et al. Fluorine. Chem. , Vol. 112.109 (2001)

  Accordingly, an object of the present invention is to provide a method for suppressing the decomposition of ketals or acetals derived from α-hydroxyketones or α-hydroxyacetones.

  Still another object of the present invention is to provide a method for producing a ketal or acetal derived from α-hydroxy ketones or α-hydroxy aldehydes while suppressing the decomposition of the ketal or acetal. .

As a result of intensive studies to achieve the above object, the present inventors have suppressed the decomposition of a ketal or acetal having a specific structure by adding a base, and the decomposition of the ketal or acetal. The present invention has been completed by finding that the production can be carried out while suppressing the above.
That is, the present invention provides a method for inhibiting degradation of a ketal or acetal derived from α-hydroxy ketones or α-hydroxy aldehydes in the presence of a base.
Furthermore, the present invention relates to a method for producing a ketal or acetal in which a post-treatment step after ketalization or acetalization is carried out in the presence of a base in the production of a ketal or acetal derived from an α-hydroxyketone or α-hydroxyaldehyde. I will provide a.

  ADVANTAGE OF THE INVENTION According to this invention, decomposition | disassembly of the ketal or acetal derived from (alpha) -hydroxy ketones or (alpha) -hydroxy aldehydes which are ketals or acetals which have an unstable structure can be suppressed. Furthermore, in this invention, it can manufacture, suppressing decomposition | disassembly of this ketal or acetal.

[Ketal or Acetal]
The ketal or acetal derived from α-hydroxy ketones or α-hydroxy aldehydes that are the subject of the present invention is represented by the following formula (1):

で表される骨格を１つまたは複数個有するものであればよい。式（１）で表される骨格を１つ有するアセタール又はケタールとしては、例えば下記式（２）又は（３）

Any one having one or more skeletons represented by As an acetal or ketal having one skeleton represented by the formula (1), for example, the following formula (2) or (3)

（式中R、Rは同一又は異なって有機基を示し、R〜Rは同一又は異なって水素原子、有機基を示す）で表される。

(Wherein R and R are the same or different and each represents an organic group, and R to R are the same or different and each represents a hydrogen atom or an organic group).

Examples of the organic group represented by R ¹ or R ² in Formula (2) include a hydrocarbon group and a heterocyclic group.
Examples of the organic group represented by R ^{3 to} R ⁹ in the formula (2) or (3) include a halogen atom (fluorine, chlorine, bromine, iodine atom), a hydrocarbon group, a heterocyclic group, and a substituted oxycarbonyl. Groups (alkoxycarbonyl groups, aryloxycarbonyl groups, aralkyloxycarbonyl groups, cycloalkyloxycarbonyl groups, etc.), substituted or unsubstituted carbamoyl groups, cyano groups, nitro groups, sulfonyl groups (including halosulfonyl groups and trihalomethanesulfonyl groups) , Sulfur acid ester groups, acyl groups (aliphatic acyl groups such as acetyl groups; aromatic acyl groups such as benzoyl groups), substituted oxy groups (alkoxy groups such as C _1-6 alkoxy groups such as methoxy groups and ethoxy groups) ; vinyloxy group, alkenyloxy groups such as C _2-6 alkenyloxy groups such as allyloxy group; cyclohexyl Cycloalkyloxy groups such as xy groups; aryloxy groups such as phenoxy groups; aralkyloxy groups such as benzyloxy groups; acyloxy groups such as acetoxy groups), hydroxyl groups, substituted or unsubstituted amino groups (amino groups; N- Mono- or di-C _1-6 alkyl-substituted amino groups such as methylamino group and N, N-dimethylamino group; cyclic amino groups such as 1-pyrrolidinyl group, piperidino group and morpholino group), etc. Groups and the like. The hydroxyl group, amino group and the like may be protected with a protective group known or commonly used in the field of organic synthesis, and may be substituted with a metal.

  The hydrocarbon group includes an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group in which these are bonded. Examples of the aliphatic hydrocarbon group include 1 to 20 carbon atoms (preferably 1 to 1) such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, decyl, and dodecyl groups. 10, more preferably an alkyl group of about 1 to 3); an alkenyl group of about 2 to 20 carbon atoms (preferably 2 to 10, more preferably 2 to 3) such as vinyl, allyl, 1-butenyl group; Examples thereof include alkynyl groups having about 2 to 20 carbon atoms (preferably 2 to 10, more preferably 2 to 3) such as propynyl groups.

As the alicyclic hydrocarbon group, a cycloalkyl group having about 3 to 20 members (preferably 3 to 15 members, more preferably 5 to 8 members) such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cyclooctyl groups; Cycloalkenyl groups of about 3 to 20 members (preferably 3 to 15 members, more preferably 5 to 8 members) such as pentenyl and cyclohexenyl groups; perhydronaphthalen-1-yl group, norbornyl, adamantyl, tetracyclo [4 4.0.1, ^2,5 . 1 ^7,10 ] bridged cyclic hydrocarbon groups such as dodecan-3-yl groups. Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having about 6 to 14 (preferably 6 to 10) carbon atoms such as phenyl and naphthyl groups.

The hydrocarbon group in which an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are bonded includes a cycloalkyl-alkyl group such as cyclopentylmethyl, cyclohexylmethyl, 2-cyclohexylethyl group (for example, C _3-20 cycloalkyl- C _1-4 alkyl group and the like). The hydrocarbon group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded to each other includes an aralkyl group (for example, a C _7-18 aralkyl group) and an alkyl-substituted aryl group (for example, about 1 to about 4). A phenyl group substituted with a C _1-4 alkyl group or a naphthyl group).

Preferred hydrocarbon groups include C _1-10 alkyl groups, C _2-10 alkenyl groups, C _2-10 alkynyl groups, C _3-15 cycloalkyl groups, C _6-10 aromatic hydrocarbon groups, C _3-15 A cycloalkyl-C _1-4 alkyl group, a C _7-14 aralkyl group and the like are included.

  When the organic group represented by R1 to R9 is a hydrocarbon group, the hydrocarbon group may have various substituents. Examples of the substituent include a halogen atom, a haloalkyl group, an oxo group, a hydroxyl group. Group, substituted oxy group (eg, alkoxy group, aryloxy group, aralkyloxy group, acyloxy group), substituted oxycarbonyl group (alkoxycarbonyl group, aryloxycarbonyl group, aralkyloxycarbonyl group, etc.), substituted or unsubstituted carbamoyl Group, cyano group, nitro group, substituted or unsubstituted amino group, sulfonyl group (including halosulfonyl group and trihaloalkylsulfonyl group), heterocyclic group and the like. The hydroxyl group may be protected with a protecting group conventionally used in the field of organic synthesis. In addition, an aromatic or non-aromatic heterocycle may be condensed with the ring of the alicyclic hydrocarbon group or aromatic hydrocarbon group.

The heterocyclic ring constituting the heterocyclic group in R ^{1 and the} like includes an aromatic heterocyclic ring and a non-aromatic heterocyclic ring. Examples of such a heterocyclic ring include a heterocyclic ring containing an oxygen atom as a hetero atom (for example, 5-membered ring such as furan, tetrahydrofuran, oxazole, isoxazole, and γ-butyrolactone ring, 4-oxo-4H-pyran, tetrahydro 6-membered ring such as pyran, morpholine ring, condensed ring such as benzofuran, isobenzofuran, 4-oxo-4H-chromene, chroman, isochroman ring, 3-oxatricyclo [4.3.1.1 ^4,8 ] undecane 2-one ring, a bridged ring such as 3-oxatricyclo [4.2.1.0 ^4,8 ] nonan-2-one ring), a heterocycle containing a sulfur atom as a hetero atom (for example, thiophene, 5-membered ring such as thiazole, isothiazole, thiadiazole ring, 6-membered ring such as 4-oxo-4H-thiopyran ring, benzothiophene ring Any condensed ring), heterocycles containing nitrogen atoms as heteroatoms (eg, 5-membered rings such as pyrrole, pyrrolidine, pyrazole, imidazole, and triazole rings, 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, piperidine, and piperazine rings) Ring, indole, indoline, quinoline, acridine, naphthyridine, quinazoline, a condensed ring such as a purine ring, etc.). In addition to the substituents that the hydrocarbon group may have, the heterocyclic group includes an alkyl group (eg, a C _1-4 alkyl group such as a methyl or ethyl group), a cycloalkyl group, an aryl group It may have a substituent such as (for example, phenyl, naphthyl group).

In the formula (2) or (3), R ¹ and R ² , R ³ to R ⁵ , or R ⁶ to R ⁹ may form a bond with each other to form a ring. Examples of such a ring include a hydrocarbon ring and a heterocyclic ring. Examples of the hydrocarbon ring include cyclopropane rings, cyclobutane rings, cyclopentane rings, cyclohexane rings, cycloheptane rings, cyclooctane rings, cyclodecane rings, cyclododecane rings and the like, and cyclopentene rings. And a cycloalkene ring having about 3 to 20 members such as a cyclohexene ring; a bridged hydrocarbon ring such as an adamantane ring, a norbornane ring and a norbornene ring. Examples of the heterocycle include a perhydroazole ring, a perhydroazine ring, a perhydroazepine ring, an oxolane ring, an oxane ring, an oxepane ring, a thiolane ring, a thiane ring, and a thiepan ring. Heterocycles containing at least one heteroatom selected from atoms and sulfur atoms).

  Specific examples to which the present invention is applied include the following formulas (4) to (16).

本発明に用いられるケタール又はアセタールは、骨格内に水酸基を有するために、水との親和性の高い物質が多く、水との親和性の高いこともケタール又はアセタールの分解（すなわち加水分解）を促進する１つの要因となる場合がある。とりわけ、Ｆｒｄｒｏｓの方法による溶解度パラメーター（以下、ＳＰ値として表示する）が２１．８以上のケタール又はアセタールは加水分解されやすい場合が多く、本発明の方法の使用に適している。ＳＰ値が２１．８以上の化合物としては、例えば、上記例示の化合物のうち（４）、（５）、（６）、（７）、（８）、（１２）、（１３）、（１５）、（１６）などが挙げられる。なお、ＳＰ値の算出は、塗装技術１９８７年３月号および、ポリマーハンドブック第４版ＶＩＩ/６７５記載の方法に従った。

Since the ketal or acetal used in the present invention has a hydroxyl group in the skeleton, there are many substances having a high affinity for water, and the high affinity for water also indicates the decomposition (ie, hydrolysis) of the ketal or acetal. It may be one factor that promotes. In particular, a ketal or acetal having a solubility parameter (hereinafter referred to as SP value) of 21.8 or more by the Frdros method is often easily hydrolyzed and is suitable for use in the method of the present invention. Examples of the compound having an SP value of 21.8 or more include (4), (5), (6), (7), (8), (12), (13), (15) among the compounds exemplified above. ), (16) and the like. The SP value was calculated according to the method described in the March 1987 issue of the coating technology and the polymer handbook 4th edition VII / 675.

  The ketal or acetal used in the present invention can be synthesized by reacting a corresponding alcohol with a corresponding hydroxyketone or hydroxyaldehyde in the presence of an acid catalyst. For example, the compound (5) can be synthesized as follows: It can be synthesized by a synthetic route.

〔塩基〕
本発明で用いられる塩基は、ケタール又はアセタールの分解抑制効果が得られる限り特に限定されないが、炭酸ナトリウム、炭酸カリウム、炭酸カルシウム、炭酸マグネシウムカルシウム、炭酸アンモニウム等の炭酸塩、炭酸水素ナトリウム、炭酸水素カリウム、炭酸水素カルシウム、炭酸水素マグネシウムカリウム、炭酸水素アンモニウム等の炭酸水素塩、水酸化ナトリウム、水酸化カリウム、水酸化カルシウム、水酸化バリウム、水酸化アンモニウム等の水酸化物、水素化ナトリウム、水素化リチウム、水素化カリウム等のアルカリ金属若しくはアルカリ土類金属の水素化物等の無機塩基、塩基性イオン交換樹脂等の担体に塩基を担持したもの、酸吸着剤（例えばハイドロタルサイト系の酸吸着剤など）、又はメチルアミン、エチルアミン、イソプロピルアミン、ブチルアミン、ジメチルアミン、ジエチルアミン、ジイソプロピルアミン、トリメチルアミン、トリエチルアミン、トリブチルアミン、Ｎ−メチルピペリジン、Ｎ−メチルピロリジン、ピリジン、メチルピリジン、ジメチルピリジン、トリメチルピリジン等の有機アミンなどが例示される。これら塩基は単独で又は２種以上を組み合わせて用いてもよい。無機塩基を使用する場合、固体のまま用いても水溶液として用いてもよい。ケタール又はアセタール骨格中に塩基により加水分解される置換基（例えばハロゲン基、エステル基、ハロスルホニル基など）を有する場合には、上記塩基のうち、一般に弱塩基とされるものが好ましく、特に炭酸塩や炭酸水素塩などが好ましく、また、酸吸着剤のうちアニオンとカチオンを同時に除去できるもの［例えば商品名「キョーワード２０００」、協和化学工業株式会社製など］を用いるのも好適である。

〔base〕
The base used in the present invention is not particularly limited as long as the effect of inhibiting the decomposition of ketal or acetal is obtained, but carbonates such as sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, ammonium carbonate, sodium bicarbonate, hydrogen carbonate Hydrogen carbonate such as potassium, calcium hydrogen carbonate, magnesium potassium hydrogen carbonate, ammonium hydrogen carbonate, hydroxide such as sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonium hydroxide, sodium hydride, hydrogen Inorganic bases such as alkali metal or alkaline earth metal hydrides such as lithium hydride and potassium hydride, bases supported on basic ion exchange resins, acid adsorbents (eg hydrotalcite-based acid adsorption) Agent), or methylamine, ethylamino And organic amines such as isopropylamine, butylamine, dimethylamine, diethylamine, diisopropylamine, trimethylamine, triethylamine, tributylamine, N-methylpiperidine, N-methylpyrrolidine, pyridine, methylpyridine, dimethylpyridine, trimethylpyridine, etc. . These bases may be used alone or in combination of two or more. When an inorganic base is used, it may be used as a solid or as an aqueous solution. When the ketal or acetal skeleton has a substituent that is hydrolyzed by a base (for example, a halogen group, an ester group, a halosulfonyl group, etc.), among the above bases, those generally regarded as weak bases are preferred. Salts and hydrogen carbonates are preferred, and it is also suitable to use acid adsorbents that can remove anions and cations at the same time (for example, trade name “KYOWARD 2000”, manufactured by Kyowa Chemical Industry Co., Ltd.).

Although the usage-amount of a base is not specifically limited, It is effective in 0.01-50 weight part with respect to 100 weight part of ketal or acetal. Preferably it is 0.1-10 weight part, More preferably, it is 0.5-5 weight part. When the amount of the base is less than 0.01 parts by weight, the base is consumed by neutralization when a trace amount of impure acid component remains, which is not preferable because the stabilizing effect is not sustained. On the other hand, when the amount is more than 50 parts by weight, the handling becomes complicated, and the ketal and acetal are lost when the base as a stabilizer is removed, which is not preferable.
[Post-treatment process]
In the present invention, in the production of ketals or acetals derived from α-hydroxyketones or α-hydroxyaldehydes, the decomposition is suppressed by performing the post-treatment step after ketalization or acetalization in the presence of a base. The ketal or acetal can be produced, and the post-treatment step here refers to the step of stopping the reaction by neutralization after ketalization or acetalization, and extracting the ketal or acetal from the reaction crude liquid with a general-purpose solvent. The concentration process, the purification process, and the like.

  Neutralization can be performed using the bases exemplified above. In particular, when the ketal or acetal skeleton has a substituent that is hydrolyzed by a base (for example, a halogen group, an ester group, a halosulfonyl group, etc.), a weak base is generally preferred. When neutralization is controlled by the pH value, it may be in a range where the reaction can be stopped and the target product is not decomposed, but it is, for example, about pH 5 to pH 11, preferably about pH 6 to pH 9.

  Extraction can be performed using a general-purpose solvent. For example, alcohols (methanol, ethanol, normal or isopropanol, tertiary butanol, amyl alcohol, cyclohexanol, etc.), polyhydric alcohols (ethylene glycol, propylene glycol) , Glycerin, etc.), esters (ethyl acetate, butyl acetate, etc.), ketones (acetone, methyl ethyl ketone, etc.), chain or cyclic ethers (ethyl ether, isopropyl ether, dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons ( Hexane, octane, etc.), alicyclic hydrocarbons (cyclopentane, cyclohexane, methylcyclohexane, etc.), nitro compounds such as nitromethane, nitroethane, phosphorus compounds (phosphate esters, etc.), halogenated hydrocarbons (chloroform) Dichloromethane, ethylene dichloride and the like), aromatic hydrocarbons (benzene, toluene, xylene and the like) are exemplified. The extraction solvent may be selected in consideration of the affinity with the target product.

The base may be simultaneously distributed to the solvent layer to which the target product has been distributed in the extraction step after neutralization. At this time, if the amount of the simultaneously distributed base is sufficient to suppress the distribution of ketal or acetal. If the amount of the base is insufficient, the concentration step or purification step may be carried out as it is, and then the base may be further added to carry out the concentration step or purification step.
[Preservation process]
The ketal or acetal obtained in the post-treatment process may be decomposed even in the storage process, and can be stably stored for a long time when stored in the presence of a base. In addition, if the base of the post-treatment step remains and the addition of the base is unnecessary, it can be stored as it is, and if the base is insufficient, it is preferably stored by the addition of a further base.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The compound was quantified by an internal standard method using gas chromatography (GC).

Example 1
A slurry of 2.5 g of sodium carbonate as a base in a solution of 50.7 g of 2,4-dimethyl-1,3-dioxolane-2-methanol, 0.5 g of propylene glycol and 1.0 g of hydroxyacetone in 300 ml of methylene chloride And methylene chloride was distilled off over 1 hour using a rotary evaporator under the conditions of a temperature of 40 ° C. and 200 torr. As a result of analyzing the concentrated residue by gas chromatography, it was confirmed that no decomposition occurred in any of 2,4-dimethyl-1,3-dioxolane-2-methanol, propylene glycol, and hydroxyacetone.
Example 2
The same operation as in Example 1 was performed except that the base was replaced with sodium bicarbonate. As a result, it was confirmed that no decomposition occurred.
Example 3
The same operation as in Example 1 was carried out except that the base was changed to triethylamine. As a result, it was confirmed that no decomposition occurred.

Comparative Example 1
To a solution of 48.0 g of 2,4-dimethyl-1,3-dioxolane-2-methanol, 0.9 g of propylene glycol, and 1.5 g of hydroxyacetone in 300 ml of methylene chloride, the temperature was measured with a rotary evaporator without adding a base. Methylene chloride was distilled off over 1 hour under the conditions of 40 ° C. and 200 torr. As a result of analyzing the concentrated residue by gas chromatography, 44.3 g of 2,4-dimethyl-1,3-dioxolane-2-methanol, 2.3 g of propylene glycol, and 2.0 g of hydroxyacetone were quantified. Multiple peaks were confirmed on the boiling side. These high-boiling substances were acetalized 2,4-dimethyl-1,3-dioxolane-2-methanol and hydroxyacetone.

Example 4
2,4-Dimethyl-1,3-dioxolane-2-methanol 97.1 wt%, propylene glycol 0.7 wt%, and hydroxyacetone 0.2 wt% were mixed with sodium carbonate as a base. 5 parts by weight was added to -1,3-dioxolane-2-methanol, and the mixture was stored at 25 ° C. in a nitrogen atmosphere for 3 months. As a result of analyzing the mixture after storage by gas chromatography, it was confirmed that no decomposition occurred in any of 2,4-dimethyl-1,3-dioxolane-2-methanol, propylene glycol, and hydroxyacetone.

Example 5
The same operation as in Example 4 was performed except that the base was replaced with sodium bicarbonate. As a result, it was confirmed that no decomposition occurred.

Example 6
The same operation as in Example 4 was carried out except that the base was changed to triethylamine. As a result, it was confirmed that no decomposition occurred.

Comparative Example 2
To a mixture containing 97.1 wt% 2,4-dimethyl-1,3-dioxolane-2-methanol, 0.7 wt% propylene glycol, and 0.2 wt% hydroxyacetone, at 25 ° C. without adding a base, It was stored for 3 months under a nitrogen atmosphere. As a result of analyzing the mixture after storage by gas chromatography, 84.1 wt% of 2,4-dimethyl-1,3-dioxolane-2-methanol, 4.5 wt% of propylene glycol, and 0.9 wt% of hydroxyacetone were quantified. Furthermore, a plurality of peaks were confirmed on the higher boiling point side. These high-boiling substances were acetalized 2,4-dimethyl-1,3-dioxolane-2-methanol and hydroxyacetone.

Examples 7-12, Comparative Examples 3-7
Table 1 shows the results of experiments conducted on several compounds according to the procedure of Example 1. In addition, the retention rate in Table 1 shows the ratio of the acetal after concentration when the acetal before concentration is 100%. Moreover, the weight part of a base shows the numerical value with respect to 100 weight part of acetal.

Claims (5)

  A method for inhibiting the decomposition of a ketal or acetal derived from α-hydroxy ketones or α-hydroxy aldehydes in the presence of a base. In the production of ketals or acetals derived from α-hydroxyketones or α-hydroxyaldehydes, a method for producing ketals or acetals in which a post-treatment step after ketalization or acetalization is carried out in the presence of a base. Ketal or acetal is represented by the following formula (1)

The method according to claim 1, which is a ketal or acetal having one or more skeletons represented by the formula: Ketal or acetal is represented by the following formula (2) or (3)

The method according to claim 3, wherein R ¹ and R ² are the same or different and each represents an organic group, and R ^{3 to} R ⁹ are the same or different and each represents a hydrogen atom or an organic group.   The method according to claim 3 or 4, wherein the ketal or acetal has a solubility parameter of 21.8 or more according to the method of Fedoros.