Method for producing glycolaldehyde dialkyl acetal

Abstract

To provide means to produce glycolaldehyde dialkyl acetal in high yield.SOLUTION: A production method includes a glycolaldehyde formation step of converting paraformaldehyde to glycolaldehyde in an ether type solvent in the presence of an N-heterocyclic carbene catalyst, and an acetalization step of treating the glycolaldehyde with an alcohol solution of hydrogen chloride to obtain glycolaldehyde dialkyl acetal. The glycolaldehyde formation step and the acetalization step are performed in a single container.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing glycolaldehyde dialkyl acetal.

Background Art

[0002] Glycolaldehyde is a dimerization product of formaldehyde. Glycolaldehyde can be used as a synthetic intermediate for useful compounds such as amino acids, sugars, ethylene glycol, and ethanol. However, glycolaldehyde is highly reactive and easily dimerizes. For this reason, glycolaldehyde is difficult to isolate and store.

[0003] Glycolaldehyde dialkyl acetal is obtained by acetalization of glycolaldehyde. Glycolaldehyde dialkyl acetal is more stable than glycolaldehyde. For this reason, glycolaldehyde dialkyl acetal is useful as a raw material for producing useful compounds.

[0004] For example, Patent Document 1 describes a catalytic production method of a condensation product of formaldehyde, in which formaldehyde or a compound that generates formaldehyde is reacted using a catalyst prepared from a triazolium salt or a tetrazolium salt in the presence of a co-base.

[0005] Patent Document 2 describes a hydroformylation method of aqueous formaldehyde using a rhodium-tricyclophosphine catalyst system, in which formaldehyde, carbon monoxide, and hydrogen are reacted in the presence of a rhodium complex catalyst under hydroformylation conditions to produce glycolaldehyde.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Since glycolaldehyde is highly reactive and easily dimerizes, glycolaldehyde dialkyl acetal with higher stability is expected as a raw material for producing useful compounds. However, a method for producing glycolaldehyde dialkyl acetal in a high yield has not been known.

[0008] Therefore, an object of the present invention is to provide a means for producing glycolaldehyde dialkyl acetal in a high yield.

MEANS FOR SOLVING THE PROBLEMS

[0009] The present inventors have variously studied means for solving the above problems. The present inventors have found that by converting paraformaldehyde to glycolaldehyde using a specific N-heterocyclic carbene catalyst and then carrying out the reaction of acetalizing glycolaldehyde in a single container, the desired glycolaldehyde dialkyl acetal can be obtained in a high yield. Based on the above findings, the present inventors have completed the present invention.

[0010] That is, the present invention includes the following aspects and embodiments. (Embodiment 1) A glycolaldehyde forming step of converting paraformaldehyde to glycolaldehyde in an ether solvent in the presence of an N-heterocyclic carbene catalyst, An acetalization step of treating glycolaldehyde with an alcoholic solution of hydrogen chloride to obtain glycolaldehyde dialkyl acetal including wherein the N-heterocyclic carbene catalyst is of formula (I) or (II):

CHEMICAL FORMULA

[0011] According to the present invention, it becomes possible to provide a means for producing glycolaldehyde dialkyl acetal in a high yield. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0013] One aspect of the present invention relates to a method for producing glycolaldehyde dialkyl acetal. The method of this aspect includes a glycolaldehyde formation step and an acetalization step. Hereinafter, each step will be described in detail.

[0014] [1: Glycolaldehyde formation step] This step includes converting paraformaldehyde into glycolaldehyde in an ether solvent in the presence of an N - heterocyclic carbene catalyst.

[0015] In this step, the N - heterocyclic carbene catalyst is a compound represented by formula (I) or (II): [Chemical formula] In formula (I) and (II), R

[0016] and R 1 and R 4 are, independently of each other, unsubstituted C3 - C6 alkyl or C1 - C6 alkyl substituted with C6 - C 18 aryl, R 2 and R 5 are, independently of each other, unsubstituted C3 - C6 alkyl or C1 - C6 alkyl substituted with C6 - C 18 aryl, R 3 and R 6 are, independently of each other, H, unsubstituted C1 - C6 alkoxy, unsubstituted C3 - C6 alkyl or C1 - C6 alkyl substituted with C6 - C 18 aryl, R 7 and R 8 are both H, or together with the carbon atom to which they are attached, form a C6 - C 18 aryl, A - is a halogen anion or a carbon dioxide radical anion.

[0017] In formula (I) and (II), R 1and R 4 are, independently of one another, unsubstituted C3 to C6 alkyl, R 2 and R 5 are, independently of one another, unsubstituted C3 to C6 alkyl, R 3 and R 6 , and R 7 and R 8 are both H, A - is preferably a halogen anion or a carbon dioxide radical anion, R 1 and R 4 , and R 2 and R 5 are, independently of one another, isopropyl, tert-butyl or sec-butyl, R 3 and R 6 , and R 7 and R 8 are both H, A - is more preferably a chlorine, bromine or iodine anion or a carbon dioxide radical anion, R 1 and R 4 , and R 2 and R 5 are both isopropyl, R 3 and R 6 , and R 7 and R 8 are both H, A - is even more preferably a chlorine anion or a carbon dioxide radical anion.

[0018] In formulas (I) and (II), when R 1 and R 4 , and R 2 and R 5 are the groups exemplified above, side reactions such as dimerization can be suppressed by steric bulk. Thereby, glycolaldehyde can be obtained in high yield and / or high selectivity.

[0019] In this process, the N-heterocyclic carbene catalyst used is 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (i.e., in formula (I), R 1 and R 4 , and R 2 and R 5 are both isopropyl, and R 3 and R 6 , and R 7 and R 8 are both H), 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride (i.e., in formula (II), R 1 and R 4 , and R 2 and R 5 are both isopropyl, and R 3 and R 6 , and R 7 and R 8 are both H, and A - is a chloride anion), or 1,3-bis(2,6-diisopropylphenyl)imidazolium-2-carboxylate (i.e., in formula (II), R 1 and R 4 , and R 2 and R 5 are both isopropyl, and R 3 and R 6 , and R 7 and R 8 are both H, and A - is a carbon dioxide radical anion). It is particularly preferred. By carrying out this process using the N-heterocyclic carbene catalyst exemplified above, glycolaldehyde can be obtained in particularly high yield and / or high selectivity.

[0020] When the N - heterocyclic carbene catalyst used in this process is a compound represented by formula (II), the compound is preferably used together with a base. The base is preferably selected from the group consisting of triethylamine, diisopropylethylamine, 1,8 - diazabicyclo[5.4.0]undec - 7 - ene (DBU), 1,5 - diazabicyclo[4.3.0]-5 - nonene (DBN), 7 - methyl - 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene (MTBD), lithium diisopropylamide (LDA), and phosphazene base, and more preferably DBU, DBN, MTBD, LDA or phosphazene base. Alternatively, the base may be a base in an immobilized form supported on a carrier such as a resin. Examples of the immobilized form of the base include an immobilized form of the base exemplified above bonded to a carrier, and an ion - exchange resin. By carrying out this process using the N - heterocyclic carbene catalyst represented by formula (II) together with the base exemplified above, glycolaldehyde can be obtained in a high yield.

[0021] The amount of the N - heterocyclic carbene catalyst used in this process is preferably in the range of 0.01 to 5 mol% based on the number of moles of paraformaldehyde as the raw material, more preferably in the range of 0.05 to 2 mol%, and even more preferably in the range of 0.1 to 1 mol%. By carrying out this process using the N - heterocyclic carbene catalyst in the amount within the range exemplified above, glycolaldehyde can be obtained in a high yield.

[0022] In this process, the ether solvent is preferably selected from the group consisting of cyclopentyl methyl ether (CPME), tert-butyl methyl ether (TBME), diethyl ether, 1,4-dioxane, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), and anisole, and more preferably cyclopentyl methyl ether (CPME), tert-butyl methyl ether (TBME), diethyl ether, or 1,4-dioxane. By carrying out this process using the ether solvents exemplified above, glycolaldehyde can be obtained in a high yield. Further, the ether solvents exemplified above are known to be inexpensive and industrially safe. Therefore, by carrying out this process using the ether solvents exemplified above, glycolaldehyde can be obtained inexpensively and / or industrially safely.

[0023] The reaction temperature and reaction time of this process may be appropriately set based on the boiling point of the ether solvent used. The reaction time is preferably a temperature of room temperature or higher, more preferably 25°C or higher, and even more preferably 30°C or higher. Further, the reaction temperature is preferably a temperature exceeding the boiling point of the ether solvent used, more preferably 100°C or lower, and even more preferably 90°C or lower. The reaction time is preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 30 minutes or longer. Further, the reaction time is preferably 200 minutes or shorter, more preferably 100 minutes or shorter, and even more preferably 60 minutes or shorter. By carrying out this process under the reaction conditions exemplified above, glycolaldehyde can be obtained in a high yield.

[0024] [2: Acetalization step] This process includes treating glycolaldehyde with an alcoholic solution of hydrogen chloride to obtain glycolaldehyde dialkyl acetal.

[0025] In this process, the alcohol solvent of the alcoholic solution of hydrogen chloride is preferably selected from the group consisting of methanol, ethanol, benzyl alcohol and phenol, and more preferably methanol. By carrying out this process using the alcoholic solution of hydrogen chloride containing the alcohol solvent exemplified above, glycolaldehyde dialkyl acetal can be obtained in a high yield.

[0026] In this process, the concentration of the alcoholic solution of hydrogen chloride used is preferably in the range of 0.01 to 1 M, more preferably in the range of 0.05 to 0.1 M, relative to the number of moles of paraformaldehyde as the raw material. By carrying out this process using the alcoholic solution of hydrogen chloride having a concentration in the range exemplified above, glycolaldehyde dialkyl acetal can be obtained in a high yield.

[0027] In the method of this embodiment, the glycolaldehyde formation step and the acetalization step are carried out in a single container. The glycolaldehyde formation step and the acetalization step are preferably carried out continuously in a single container. For example, after carrying out the glycolaldehyde formation step, it is preferable to carry out the acetalization step as it is in the same reaction vessel without purifying the reaction mixture containing glycolaldehyde. Glycolaldehyde, which is the product of the glycolaldehyde formation step, is highly reactive and easily dimerizes. Therefore, when the glycolaldehyde formation step and the acetalization step are carried out in separate containers (i.e., sequentially), undesirable side reactions such as the dimerization of glycolaldehyde may proceed before carrying out the acetalization step. Therefore, by carrying out the glycolaldehyde formation step and the acetalization step in a single container, undesirable side reactions can be substantially suppressed and glycolaldehyde dialkyl acetal can be obtained in a high yield.

[0028] As described in detail above, by the method of this embodiment, glycolaldehyde dialkyl acetal can be produced in a high yield. The glycolaldehyde dialkyl acetal obtained by the method of this embodiment is expected to be used as a raw material for producing useful compounds such as amino acids, sugars, ethylene glycol, and ethanol. Therefore, by the method of this embodiment, raw materials for these useful compounds can be provided.

Example

[0029] Hereinafter, the present invention will be described more specifically using examples. However, the technical scope of the present invention is not limited to these examples.

[0030] [Experiment 1]

Chemical formula

[0031] [Experiment 2: Optimization of solvent] In the procedure of Experiment 1, glycolaldehyde dialkyl acetal was synthesized in the same procedure as Experiment 1 except that the solvent was changed to the solvents shown below. Table 1 shows the solvents used and the yields (%) of glycolaldehyde dialkyl acetal.

[0032]

Table 1

[0033] As shown in Table 1, by carrying out the glycolaldehyde formation step using an ether solvent, glycolaldehyde dialkyl acetal could be obtained in a high yield.

[0034] [Experiment 3: Optimization of catalyst (1)] In the procedure of Experiment 1, glycolaldehyde dialkyl acetal was synthesized in the same procedure as Experiment 1 except that the catalyst was changed. When using an N - heterocyclic carbene catalyst in which the side chain group bonded to the nitrogen atom of the imidazole ring is an alkyl group, an N - heterocyclic carbene catalyst in which the imidazole ring is an imidazolidine ring, or an N - heterocyclic carbene catalyst in which the phenyl side chain group bonded to the nitrogen atom of the imidazole ring is a methyl group or a diphenylmethyl group, in any case, the reaction hardly proceeded (yield less than 4%). Also, when using a triphenyltriazolylidene catalyst (Japanese Patent Laid - Open No. 06 - 211723), the reaction hardly proceeded (yield less than 1%).

[0035] [Experiment 4: Scale - up of reaction and reduction of catalyst amount]

Chemical formula

[0036]

Table 2

[0037] As shown in Table 2, even when the catalyst amount was reduced to 1 / 10 compared with Experiment 1, glycolaldehyde dialkyl acetal could be obtained in a high yield by increasing the reaction temperature or increasing the reaction time.

[0038] [Experiment 5: Optimization of Catalyst (2)] [Chemical formula] In the procedure of Experiment 4, the catalyst was changed to the combination of the imidazole salt and the base described above, and glycolaldehyde dialkyl acetal was synthesized in the same procedure as Experiment 1 except that the reaction conditions were changed as shown in the above scheme. The bases and solvents used, and the yields (%) of glycolaldehyde dialkyl acetal are shown in Table 3. In the table, DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene, DBN is 1,5-diazabicyclo[4.3.0]-5-nonene, MTBD is 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and LDA is lithium diisopropylamide.

[0039]

Table 3

[0040] As shown in Table 3, by carrying out the glycolaldehyde formation step using a combination of an imidazole salt and a base as the catalyst, glycolaldehyde dialkyl acetal could be obtained in a high yield.

[0041] [Experiment 6: Optimization of Catalyst (3)] [Chemical formula] In the procedure of Experiment 4, glycolaldehyde dialkyl acetal was synthesized in the same procedure as Experiment 1, except that the catalyst was changed to the combination of the above-mentioned imidazole salt and the immobilized base (ion exchange resin), and the reaction conditions were changed as shown in the above scheme. The bases used and the yields (%) of glycolaldehyde dialkyl acetal are shown in Table 4.

[0042] [Table 4]

[0043] As shown in Table 4, even when the glycolaldehyde formation step was carried out using a combination of an imidazole salt and an immobilized base as the catalyst, glycolaldehyde dialkyl acetal could be obtained in a high yield.

[0044] [Experiment 7: Optimization of Catalyst (4)] [Chemical Formula] In the procedure of Experiment 4, glycolaldehyde dialkyl acetal was synthesized in the same procedure as Experiment 1, except that the catalyst was changed to the above-mentioned 1,3-bis(2,6-diisopropylphenyl)imidazolium-2-carboxylate, and the reaction conditions were changed as shown in the above scheme. The glycolaldehyde dialkyl acetal contained in the obtained crude reaction product was analyzed by GC. By this reaction, glycolaldehyde dialkyl acetal was obtained in a yield of 73%.

[0045] Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, it is possible to add, delete, and / or substitute some of the configurations of each embodiment with other configurations.

Claims

1. A glycolaldehyde formation step of converting paraformaldehyde into glycolaldehyde in an ether solvent in the presence of an N - heterocyclic carbene catalyst, An acetalization step of treating glycolaldehyde with an alcoholic solution of hydrogen chloride to obtain glycolaldehyde dialkyl acetal, comprising wherein the N - heterocyclic carbene catalyst is a compound represented by formula (I) or (II): 【Chemical 1】 [wherein, R 1 and R 4 are, independently of each other, unsubstituted C 3 to C 6 alkyl or C 6 to C 18 alkyl substituted with aryl having C 1 to C 6 alkyl, R 2 and R 5 are, independently of one another, unsubstituted C 3 from C 6 alkyl or C 6 from C 18 alkyl substituted with aryl having C 1 from C 6 alkyl, R 3 and R 6 are, independently of one another, H, unsubstituted C 1 from C 6 alkoxy, unsubstituted C 3 from C 6 alkyl or C 6 from C 18 alkyl substituted with C 1 from C 6 alkyl, and R 7 and R 8 are each H, or together with the carbon atoms to which they are attached form a C 6 from C 18 aryl, A - is a halogen anion or a carbon dioxide radical anion. is a compound represented by, A method for producing glycolaldehyde dialkyl acetal, wherein the glycolaldehyde formation step and the acetalization step are carried out in a single container.

2. The method according to claim 1, wherein the ether solvent is selected from the group consisting of cyclopentyl methyl ether (CPME), tert - butyl methyl ether (TBME), diethyl ether, 1,4 - dioxane, tetrahydrofuran (THF), 2 - methyltetrahydrofuran (2 - MeTHF), and anisole.

3. R 1 and R 4 are, independently of one another, unsubstituted C 3 from C 6 alkyl, R 2 and R 5 are, independently of each other, unsubstituted C 3 from C 6 alkyl, R 3 and R 6 as well as R 7 and R 8 both are H, A - The method according to claim 1, which is carried out in the presence of an N-heterocyclic carbene catalyst, wherein - is a halogen anion or a carbon dioxide radical anion.

4. R 1 and R 4 and R 2 and R 5 are both isopropyl, R 3 and R 6 and, and R 7 and R 8 both are H, A - The method according to claim 1, which is carried out in the presence of an N - heterocyclic carbene catalyst, wherein - is a chlorine anion or a carbon dioxide radical anion.

5. The ether solvent is cyclopentyl methyl ether (CPME), tert - butyl methyl ether (TBME), diethyl ether or 1,4 - dioxane, The method according to claim 1, wherein the N - heterocyclic carbene catalyst is 1,3 - bis(2,6 - diisopropylphenyl)imidazol - 2 - ylidene, 1,3 - bis(2,6 - diisopropylphenyl)imidazolium chloride or 1,3 - bis(2,6 - diisopropylphenyl)imidazolium - 2 - carboxylate.

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