JPWO2007063939A1 - Method for producing tetrafluorocyclobutenone - Google Patents

Abstract

As shown below, the present invention includes a process for producing a tetrafluorocyclobutenone represented by the formula (2), which comprises a step of bringing the compound represented by the formula (1) into contact with an acid catalyst. It is. According to the present invention, tetrafluorocyclobutenone can be produced with high yield and good reproducibility. In the following formula, R represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom, and n represents an integer of 1 to 5.

Description

  The present invention relates to a method for producing tetrafluorocyclobutenone useful as a plasma reaction gas, a fluoropolymer production raw material, and a fluoropharmaceutical intermediate used in the field of manufacturing semiconductor devices.

  Tetrafluorocyclobutenone is

It is a fluorine-containing compound shown by these. Since this compound has a low molecular weight and an appropriate boiling point (boiling point: 45 to 46 ° C.), it is easy to handle and is expected to have high utility value in the field of manufacturing semiconductor devices.
However, the manufacturing method of this compound is not well known, and the fact is that detailed studies have not been made.

  As a conventional method for producing tetrafluorocyclobutenone, for example, in Non-Patent Document 1, hexafluorocyclobutene and benzyl alcohol are reacted in the presence of potassium hydroxide to give 1-benzyloxypentafluorocyclobutene. The 1-benzyloxypentafluorocyclobutene obtained is heated to 150 ° C. in the presence of concentrated sulfuric acid to obtain the desired product in a yield of 77.5%.

  However, this method has poor reproducibility of the reaction, and sometimes the target tetrafluorocyclobutenone cannot be obtained at all.

  In Non-Patent Document 2, hexafluorocyclobutene is reacted with sodium methoxide to synthesize 1-methoxypentafluorocyclobutene, and the resulting 1-methoxypentafluorocyclobutene is treated with sulfur trioxide. This indicates that the desired product is obtained in a yield of 27%.

However, since this method uses sulfur trioxide, which has a low yield and is highly toxic and corrosive, it is not preferable as a method for producing tetrafluorocyclobutenone on an industrial production scale.
Therefore, development of an industrial production method of tetrafluorocyclobutenone that can produce tetrafluorocyclobutenone with high yield and high reproducibility has been desired.

Dokl. Akad. Nauk SSSR, 1976, 229 (4), 870 (Chemical Abstract, Vol. 85, 176886n) Journal of American Chemical Society, 1977, 99 (4), 1218

  The present invention has been made in view of the above-described prior art, and provides an industrial process for producing tetrafluorocyclobutenone that can produce tetrafluorocyclobutenone with high yield and good reproducibility. This is the issue.

As a result of diligent research to solve the above-mentioned problems, the present inventors brought the target tetrafluorocyclobutenone into a high yield by bringing the compound represented by the formula (1) described later into contact with an acid catalyst. The present inventors have found that it can be produced with good reproducibility and have completed the present invention.
Thus, according to the present invention, the formula (1)

(Wherein R represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom, and n represents any integer of 1 to 5). , Characterized in that it comprises a step of contacting with an acid catalyst, formula (2)

The manufacturing method of tetrafluorocyclobutenone represented by these is provided.
In the method for producing tetrafluorocyclobutenone according to the present invention, it is preferable to use an acid having an acid dissociation constant (pKa) at 25 ° C. of 13 or less in dimethyl sulfoxide as the acid catalyst. The step of bringing the compound to be brought into contact with the acid catalyst is preferably a step of bringing the compound represented by the formula (1) into contact with the acid catalyst in an aromatic hydrocarbon having a boiling point of 100 ° C. or higher.

  According to the production method of the present invention, tetrafluorocyclobutenone can be produced with good reproducibility and high yield under relatively mild conditions. Therefore, the production method of the present invention is useful as an industrial production method of tetrafluorocyclobutenone.

Hereinafter, the present invention will be described in detail.
The method for producing tetrafluorocyclobutenone of the present invention comprises a step of bringing a compound represented by the formula (1) (hereinafter sometimes referred to as “compound (1)”) into contact with an acid catalyst. And

In the production method of the present invention, compound (1) is used as a starting material.
In the formula (1), R is a methyl group, an ethyl group, an isopropyl group, an n-propyl group having 1 to 3 carbon atoms; a methoxy group, an ethoxy group, an isopropoxy group, or an n-propoxy group. 1 to 3 alkoxy groups or a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

  n represents an integer of 1 to 5, and n is preferably 1 from the viewpoint of obtaining the target product in good yield and the production cost. When n is 2 or more, the plurality of R may be the same or different.

  Specific examples of the compound (1) include 1- (4-methylbenzyloxy) pentafluorocyclobutene, 1- (3-methylbenzyloxy) pentafluorocyclobutene, 1- (2-methylbenzyloxy) pentafluorocyclo Butene, 1- (4-ethylbenzyloxy) pentafluorocyclobutene, 1- (3-ethylbenzyloxy) pentafluorocyclobutene, 1- (2-ethylbenzyloxy) pentafluorocyclobutene, 1- (4-isopropyl Benzyloxy) pentafluorocyclobutene, 1- (3-isopropylbenzyloxy) pentafluorocyclobutene, 1- (2-isopropylbenzyloxy) pentafluorocyclobutene, 1- (4-n-propylbenzyloxy) pentafluorocyclo Butene, 1- (3-n Propylbenzyloxy) pentafluorocyclobutene, 1- (2-n-propylbenzyloxy) pentafluorocyclobutene, 1- (3,5-dimethylbenzyloxy) pentafluorocyclobutene, 1- (3,4-dimethylbenzyl) Oxy) pentafluorocyclobutene, 1- (2,6-dimethylbenzyloxy) pentafluorocyclobutene, 1- (2,4-dimethylbenzyloxy) pentafluorocyclobutene, 1- (2,4,6-trimethylbenzyl) Compounds wherein R is an alkyl group having 1 to 3 carbon atoms, such as oxy) pentafluorocyclobutene;

  1- (4-methoxybenzyloxy) pentafluorocyclobutene, 1- (3-methoxybenzyloxy) pentafluorocyclobutene, 1- (2-methoxybenzyloxy) pentafluorocyclobutene, 1- (4-ethoxybenzyloxy) ) Pentafluorocyclobutene, 1- (3-ethoxybenzyloxy) pentafluorocyclobutene, 1- (2-ethoxybenzyloxy) pentafluorocyclobutene, 1- (4-isopropoxybenzyloxy) pentafluorocyclobutene, 1 -(3-isopropoxybenzyloxy) pentafluorocyclobutene, 1- (2-isopropoxybenzyloxy) pentafluorocyclobutene, 1- (4-n-propoxybenzyloxy) pentafluorocyclobutene, 1- (3- n-propoxy Benzyloxy) pentafluorocyclobutene, 1- (2-n-propoxybenzyloxy) pentafluorocyclobutene, 1- (3,5-dimethoxybenzyloxy) pentafluorocyclobutene, 1- (3,4-dimethoxybenzyloxy) ) Pentafluorocyclobutene, 1- (2,6-dimethoxybenzyloxy) pentafluorocyclobutene, 1- (2,4-dimethoxybenzyloxy) pentafluorocyclobutene, 1- (2,3,5-trimethoxybenzyl) Compounds wherein R is an alkoxy group having 1 to 3 carbon atoms, such as oxy) pentafluorocyclobutene;

1- (4-fluorobenzyloxy) pentafluorocyclobutene, 1- (3-fluorobenzyloxy) pentafluorocyclobutene, 1- (2-fluorobenzyloxy) pentafluorocyclobutene, 1- (4-chlorobenzyloxy) ) Pentafluorocyclobutene, 1- (3-chlorobenzyloxy) pentafluorocyclobutene, 1- (2-chlorobenzyloxy) pentafluorocyclobutene, 1- (4-bromobenzyloxy) pentafluorocyclobutene, 1- (3-bromobenzyloxy) pentafluorocyclobutene, 1- (2-bromobenzyloxy) pentafluorocyclobutene, 1- (4-iodobenzyloxy) pentafluorocyclobutene, 1- (3-iodobenzyloxy) penta Fluorocyclobutene, -(2-iodobenzyloxy) pentafluorocyclobutene, 1- (3,5-dichlorobenzyloxy) pentafluorocyclobutene, 1- (3,4-dichlorobenzyloxy) pentafluorocyclobutene, 1- (2, 6-dichlorobenzyloxy) pentafluorocyclobutene, 1- (2,4-dichlorobenzyloxy) pentafluorocyclobutene, 1- (2,4,6-trichlorobenzyloxy) pentafluorocyclobutene, 1- (2, Compounds in which R is a halogen atom, such as 3,4,5-tetrachlorobenzyloxy) pentafluorocyclobutene, 1- (2,3,4,5,6-pentafluorobenzyloxy) pentafluorocyclobutene;

  1- (2-methyl-4-methoxybenzyloxy) pentafluorocyclobutene, 1- (3-methoxy-4-methylbenzyloxy) pentafluorocyclobutene, 1- (2-methyl-4-chlorobenzyloxy) penta Fluorocyclobutene, 1- (3-chloro-4-methylbenzyloxy) pentafluorocyclobutene, 1- (2-chloro-4-methoxybenzyloxy) pentafluorocyclobutene, 1- (3-chloro-4-methoxy Benzyloxy) pentafluorocyclobutene, 1- (2-methyl-4-methoxy-6-chlorobenzyloxy) pentafluorocyclobutene and the like, wherein R is a different group;

  Among these, 1- (4-methylbenzyloxy) pentafluorocyclobutene, 1- (2-methylbenzyloxy) pentafluorocyclobutene, 1 can be easily obtained and the target product can be obtained with high yield. -(4-ethylbenzyloxy) pentafluorocyclobutene, 1- (2-ethylbenzyloxy) pentafluorocyclobutene, 1- (4-methoxybenzyloxy) pentafluorocyclobutene, 1- (2-methoxybenzyloxy) Pentafluorocyclobutene, 1- (4-ethoxybenzyloxy) pentafluorocyclobutene, and 1- (2-ethoxybenzyloxy) pentafluorocyclobutene are preferable, and 1- (4-methoxybenzyloxy) pentafluorocyclobutene, 1 -(4-Ethoxybenzyloxy) Printer fluoro cyclobutene is more preferred.

  As shown in the following reaction formula, the starting material compound (1) has a hexafluorocyclobutene represented by the formula (3) and a substituent corresponding to the target compound represented by the formula (4). It can be obtained by reacting benzyl alcohol (hereinafter referred to as “compound (4)”) in the presence of a base.

Bases used include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide; metal carbonates such as sodium carbonate, potassium carbonate and calcium carbonate Metal alkoxides such as sodium methoxide, sodium ethoxide, magnesium ethoxide and potassium t-butoxide; metal hydrides such as sodium hydride, potassium hydride and calcium hydride; triethylamine, pyridine, 1,8-diazabicyclo [5 4.0] organic bases such as undec-7-ene (DBU);
The usage-amount of a base is 1-3 equivalent normally with respect to hexafluorocyclobutene.

  The reaction for obtaining the compound (1) is preferably carried out in a solvent. The solvent to be used is not particularly limited as long as it is inert to the reaction. For example, nitriles such as acetonitrile; ethers such as tetrahydrofuran; amides such as dimethylformamide; sulfoxides such as dimethyl sulfoxide; water; These solvents can be used alone or in combination of two or more.

While the reaction temperature depends on the kind of the compound (4) to be used, etc., it is generally −50 ° C. to + 70 ° C., preferably −30 ° C. to + 30 ° C.
Although depending on the reaction scale and the like, the reaction time is usually 30 minutes to 24 hours, preferably 1 hour to 10 hours.

  After completion of the reaction, water and an organic solvent immiscible with water are added to the reaction solution containing the compound (1) obtained by reacting hexafluorocyclobutene with the compound (4) as described above. Is added and separated to separate the organic layer. Next, the compound (1) can be isolated from the collected organic layer. In addition, as the organic solvent immiscible with water, an organic solvent containing a compound (1) obtained by removing a low-boiling substance from an organic layer using an organic solvent used in the subsequent step of contacting with an acid catalyst. The solution can also be used for the next reaction as it is.

The starting material hexafluorocyclobutene is a known compound, and can be obtained, for example, by subjecting commercially available 1,2-dichlorohexafluorocyclobutane, 1,2-dibromohexafluorocyclobutane, etc. to a known dehalogenation reaction. Can do. Examples of the dehalogenating method include a method of reacting 1,2-dichlorohexafluorocyclobutane with zinc.
As the compound (4), 2-methylbenzyl alcohol, 4-methylbenzyl alcohol, 2-methoxybenzyl alcohol, 4-methoxybenzyl alcohol, 2-ethoxybenzyl alcohol, 4-methoxy are easily available industrially. Benzyl alcohol is preferred.

The production method of the present invention includes a step of bringing compound (1) into contact with an acid catalyst (hereinafter, the reaction in this step is referred to as “main reaction”).
The reaction mechanism of this reaction can be considered as follows. That is, first, when the compound (1) comes into contact with the acid catalyst, the substituted benzyl group is released from the compound (1) very efficiently depending on the molecular structure of the compound (1), and 1-hydroxypenta Fluorocyclobutene is produced. Next, since this 1-hydroxypentafluorocyclobutene is unstable, it is considered that hydrogen fluoride is easily eliminated and tetrafluorocyclobutenone which is the target product is generated.

  The acid catalyst used in this reaction is not particularly limited as long as it is an acidic substance, but from the viewpoint of obtaining the desired product in good yield, the acid dissociation constant (pKa) at 25 ° C. in dimethyl sulfoxide (DMSO) is 13 or less. Certain acids are preferred. The lower limit of pKa is usually about 1.

The value of the acid dissociation constant in dimethyl sulfoxide is described in Pure & Applied Chemistry, Vol. 49, pp 963-968, Chemistry Handbook, Rev. 5 Basic Edition, page II354 (Chemical Society of Japan, published by Maruzen Co., Ltd.).
The values of the acid dissociation constant are, for example, hydrochloric acid: 2.1, sulfuric acid: 1.4, acetic acid: 12.6, methanesulfonic acid: 1.6, dichloroacetic acid: 6.4 (according to the above chemical handbook). In the case of an acid that dissociates in multiple stages, such as sulfuric acid, it is preferable to use an acid having a first dissociation constant of 13 or less.

The acid dissociation constant is defined as follows for an n-valent acid (H _n A; n is the number of hydrogen atoms). That is, the first-stage dissociation equilibrium reaction of H _n A in dimethyl sulfoxide (DMSO) is as follows:

The acid dissociation constant pKa is as follows:

Is defined as follows.

  In the present invention, these acids may be appropriately selected and used according to the type of the compound (1). Among these, hydrochloric acid, sulfuric acid, methanesulfonic acid, and dichloroacetic acid are preferable, and hydrochloric acid, sulfuric acid, and methanesulfonic acid are more preferable because they are easy to handle and the target product can be obtained with high yield.

  The usage-amount of an acid is 0.001-5 equivalent normally with respect to a compound (1), Preferably it is 0.01-2 equivalent. By using an acid in such a range, the target product can be obtained with good yield.

This reaction can be carried out without solvent or in a solvent.
The solvent to be used is not particularly limited as long as it is an inert solvent for the reaction. In this reaction, since hydrogen fluoride is by-produced as described above, it is not preferable to use a solvent that reacts with hydrogen fluoride. For example, an ether solvent is not preferable because the ether moiety is cleaved.

  Moreover, when performing reaction at high temperature in order to accelerate | stimulate reaction, use of the solvent whose boiling point is 100 degreeC or more is preferable as a reaction solvent, and since boiling point is 100 degreeC from being stable with respect to an acid and hydrogen fluoride. The use of the above aromatic hydrocarbons is more preferable.

Aromatic hydrocarbons having a boiling point of 100 ° C. or higher include toluene, xylene, trimethylbenzene, ethylbenzene, benzotrifluoride, hexafluorometaxylene, tris (trifluoromethyl) benzene, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene. Chlorobenzene, dichlorobenzene, trichlorobenzene, benzonitrile, tetralin and the like. These solvents can be used alone or in combination of two or more.
Among these, xylene, dichlorobenzene and 1-methylnaphthalene having a relatively high boiling point are preferable, and use of dichlorobenzene and 1-methylnaphthalene is particularly preferable.

  The aromatic hydrocarbon may be used alone as a reaction solvent, but may be used by mixing with an aromatic hydrocarbon having a boiling point of less than 100 ° C. or any other solvent other than aromatic hydrocarbons. .

  In the case of using a solvent, the amount of the solvent used is not particularly limited, but from the viewpoint of production cost and ease of handling, etc., it is usually 0.01 to 100 parts by weight, preferably 0. 1 to 20 parts by weight.

The reaction temperature is usually 15 to 200 ° C, preferably 50 to 150 ° C.
The reaction time is usually 30 minutes to 24 hours, depending on the reaction scale and the like.

  The pressure in the reaction system may be normal pressure, but as described later, it is preferable to reduce the pressure in the reaction system in order to quickly take out the target product from the reaction system. When reducing the pressure inside the reaction system, it is necessary to select the degree of pressure by setting the reaction temperature so that the target product distills out of the reaction system quickly and the solvent used does not distill out of the system. There is.

  The target product, tetrafluorocyclobutenone, is a compound having a relatively low boiling point. Therefore, as a method for completely collecting tetrafluorocyclobutenone distilled from the reaction system, a method for collecting using a cooled trap or the like is desirable.

The method of collecting using a cooled trap or the like is not particularly limited, and a known trap method that is usually used for obtaining a low-boiling target can be employed. For example, the reaction can be carried out while trapping the target substance using a reaction vessel equipped with a simple distillation apparatus connected to a trap tube. More specifically, the inside of the system is depressurized by using a vacuum pump from the out side (extraction port side) of the simple distillation apparatus, and the trap tube is immersed in a refrigerant (for example, a dry ice-ethanol bath) and cooled. Thus, the reaction can be carried out while trapping the low-boiling target product produced.
After completion of the reaction, the collected target product is preferably purified by ordinary rectification in order to further increase the purity.

  In the present invention, the reaction is conducted without taking out the target product out of the reaction system while continuing the reaction. After the reaction is completed, the reaction solution is neutralized with an alkali, and subjected to usual post-treatment operations such as washing with water, drying and distillation. Of course, it is also possible to manufacture the object.

  In this reaction, hydrogen fluoride is by-produced. The by-produced hydrogen fluoride may be left in the reaction system as it is, but it is harmful to the human body and corrodes the metal or the like, so it is preferable to remove it as soon as possible.

Examples of the method for removing hydrogen fluoride include a method in which a substance that can remove hydrogen fluoride and is inactive in this reaction is present in the reaction system.
Examples of such substances include compounds that form complex salts with hydrogen fluoride such as sodium fluoride and potassium fluoride; substances that react with hydrogen fluoride such as alumina, molecular sieves, and synthetic zeolite.

The amount of the substance that removes hydrogen fluoride may be determined in consideration of the removal ability of the substance to be used, the cost, etc., but it is preferably an excess equivalent to the compound (1). Further, the form of the substance for removing hydrogen fluoride is not particularly limited, and may be in the form of powder or pellet.
The substance for removing hydrogen fluoride is disposed in a reaction vessel for performing the reaction and / or a trap provided for collecting a target object.

According to the production method of the present invention, the desired tetrafluorocyclobutenone can be obtained with good reproducibility.
According to the manufacturing method of the present invention, tetrafluorocyclobutenone, which is useful as a plasma reaction gas used in the field of manufacturing semiconductor devices, a raw material for manufacturing a fluorine-containing polymer, and a fluorine-containing pharmaceutical intermediate, is industrially advantageous. Can be manufactured.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited at all by these Examples. “Parts” represents parts by weight.

In the following examples and comparative examples, gas chromatography, gas chromatography-mass spectrometry (GC / MS), ¹⁹ F-NMR, and IR were measured using the following measuring apparatus.

(1) Gas chromatography detector: HP-6850 (manufactured by Hewlett-Packard Company)
Column: NB-1 (manufactured by GL Sciences)
Column temperature: After maintaining at an initial temperature of 40 ° C. for 10 minutes, the temperature was raised to 240 ° C. at 20 ° C./min, and the same temperature was maintained for 10 minutes.
(2) GC / MS
GC part: HP-6890 (manufactured by Hewlett-Packard Company)
MS part: 5773, NETWORK (manufactured by Hewlett-Packard)
(3) ¹⁹ F-NMR
GX-500 (manufactured by JEOL Ltd.)
(4) IR
FT-IR8100 (manufactured by Shimadzu Corporation)

[Production Example 1] Production of hexafluorocyclobutene In a glass reactor equipped with a dropping funnel, a stirrer, and a reflux condenser, 56 parts of zinc dust, 80 parts of triethylene glycol dimethyl ether (triglyme), and 8 parts of acetic acid were added. I put it in. While stirring the whole volume at 15 ° C., 100 parts of 1,2-dichlorohexafluorocyclobutane (manufactured by Synquest) was dropped using a dropping funnel, and after completion of the dropping, the temperature was raised to 70 ° C. and further increased for 3 hours. Stir.
Meanwhile, the gaseous product emerging from the upper part of the reflux condenser was introduced and collected in a glass trap cooled to dry ice-ethanol (−80 ° C.). As a result of analyzing the collected contents by gas chromatography, the target product was hexafluorocyclobutene (yield: 53 parts, yield 76%).

[Production Example 2] Preparation of 1- (4-methoxybenzyloxy) pentafluorocyclobutene solution 140 parts of hexafluorocyclobutene obtained by repeating the reaction of Production Example 1 in a glass reactor equipped with a dropping funnel , And 40 parts of acetonitrile, and cooled to -30 ° C.
On the other hand, a mixture consisting of 127 parts of 4-methoxybenzyl alcohol, 51 parts of potassium hydroxide, 56 parts of acetonitrile, and 40 parts of water was placed in a dropping funnel. Next, the mixture in the dropping funnel was dropped over 2 hours while stirring the contents in the reactor with a polytetrafluoroethylene stirrer. After completion of the dropwise addition, the reaction was further stirred for 6 hours while gradually raising the reaction temperature to room temperature (about 25 ° C.).
After completion of the reaction, a part of the reaction mixture was collected and subjected to gas chromatography-mass spectrometry (GC / MS). As a result, 1- (4-methoxybenzyloxy) pentafluorocyclobutene, which was the target product, was produced. It was confirmed that

Next, 210 parts of water and 51 parts of 1-methylnaphthalene were added to the reaction mixture, and 1- (4-methoxybenzyloxy) pentafluorocyclobutene which was the target product was extracted into the organic layer. The organic layer was reduced under reduced pressure of 1 kPa to remove low-boiling substances (such as acetonitrile) to obtain 220 parts of 1-methylnaphthalene solution containing 1- (4-methoxybenzyloxy) pentafluorocyclobutene.
The yield of 1- (4-methoxybenzyloxy) pentafluorocyclobutene by gas chromatography analysis was 74.6% based on the raw material hexafluorocyclobutene.
The obtained 1-methylnaphthalene solution containing 1- (4-methoxybenzyloxy) pentafluorocyclobutene was directly subjected to the next reaction.
GC / MS (EI-MS): m / z 280 (M +), 157, 121

[Production Example 3] Preparation of 1- (4-methoxybenzyloxy) pentafluorocyclobutene solution 100 parts of hexafluorocyclobutene obtained by repeating the reaction of Production Example 1 in a glass reactor equipped with a dropping funnel , And 20 parts of acetonitrile, and cooled to -30 ° C. On the other hand, a mixture consisting of 63 parts of 4-methoxybenzyl alcohol, 26 parts of potassium hydroxide, 28 parts of acetonitrile, and 20 parts of water was placed in a dropping funnel. Next, the mixture in the dropping funnel was dropped over 1 hour while stirring the contents in the reactor with a polytetrafluoroethylene stirrer. After completion of the dropwise addition, the reaction was further stirred for 4 hours while gradually raising the reaction temperature to room temperature (about 25 ° C.).
After completion of the reaction, a part of the reaction mixture was collected and subjected to gas chromatography-mass spectrometry (GC / MS). As a result, 1- (4-methoxybenzyloxy) pentafluorocyclobutene, which was the target product, was produced. It was confirmed that

Next, 100 parts of water and 26 parts of toluene were added to the resulting reaction mixture, and the target 1- (4-methoxybenzyloxy) pentafluorocyclobutene was extracted into the organic layer. The organic layer was reduced under a reduced pressure of 3 kPa to remove organic low-boiling substances (such as acetonitrile) to obtain 152 parts of a toluene solution containing 1- (4-methoxybenzyloxy) pentafluorocyclobutene.
The yield of 1- (4-methoxybenzyloxy) pentafluorocyclobutene by gas chromatography analysis was 82% based on the raw material hexafluorocyclobutene.
The obtained toluene solution containing 1- (4-methoxybenzyloxy) pentafluorocyclobutene was directly subjected to the next reaction.

[Production Example 4] Synthesis of 1-benzyloxypentafluorocyclobutene In a glass reactor equipped with a dropping funnel, 200 parts of hexafluorocyclobutene obtained by repeating the reaction of Production Example 1 and 120 parts of acetonitrile were added. And cooled to -40 ° C. Meanwhile, 135 parts of benzyl alcohol, 74 parts of potassium hydroxide, 25 parts of acetonitrile, and 50 parts of water were placed in a dropping funnel. The mixture in the dropping funnel was added dropwise over 2.5 hours while stirring the contents in the reactor with a polytetrafluoroethylene stirrer. After completion of the dropwise addition, the reaction was further stirred for 7 hours while gradually raising the reaction temperature to 0 ° C.
After completion of the reaction, acetonitrile was distilled off from the reaction solution with an evaporator, and the solid matter contained in the obtained residue was collected by filtration. The obtained solid was washed twice with water and dried over diphosphorus pentoxide under reduced pressure to obtain 260 parts of 1-benzyloxypentafluorocyclobutene as the target product as white crystals.

[Example 1]
100 parts of 1-methylnaphthalene solution of 1- (4-methoxybenzyloxy) pentafluorocyclobutene obtained in Production Example 2 was placed in a glass flask equipped with a simple distillation apparatus connected with a glass trap, and methane was added thereto. 0.8 part of sulfonic acid was added. The content in the glass flask was stirred at 100 ° C. for 4 hours while reducing the pressure on the out side of the simple distillation apparatus to 10 kPa with a vacuum pump. Meanwhile, the gaseous reaction product obtained from the simple distillation apparatus was collected in a glass trap cooled by a dry ice-ethanol bath (−72 ° C.). The amount of liquid collected in the glass trap was 58 parts. As a result of analyzing this product by gas chromatography, it was tetrafluorocyclobutenone which was the target product. The yield of tetrafluorocyclobutenone based on 1- (4-methoxybenzyloxy) pentafluorocyclobutene was 69%.

When this operation was performed again under the same conditions, tetrafluorocyclobutenone which was the target product was obtained with a yield of 67%, and it was confirmed that it was reproducible.
¹⁹ F-NMR, IR, and GC / MS data of this product are shown below.

¹⁹ F-NMR (CFCl ₃ , CCl ₄ ) δ ppm; -100 (s, 1F), -111.3 (s, 1F), -114.9 (s, 2F)
IR (gas); 1860, 1725, 1400, 1140, 1025 cm ⁻¹
GC / MS (EI-MS): m / z 140 (M +), 112, 93

[Example 2]
In Example 1, the reaction was performed in the same manner as in Example 1 except that the acid catalyst used was changed from 0.8 part of methanesulfonic acid to 10 parts of dichloroacetic acid. As a result, 51 parts of tetrafluorocyclobutenone which was the target product was obtained (yield 60%).

[Example 3]
100 parts of a toluene solution of 1- (4-methoxybenzyloxy) pentafluorocyclobutene obtained in Production Example 3 was placed in a glass flask equipped with a simple distillation apparatus connected with a glass trap, and methanesulfonic acid 1 .5 parts were added. The reaction mixture was stirred at 100 ° C. for 7 hours while the pressure on the out side of the simple distillation apparatus was reduced to 10 kPa with a vacuum pump. During this time, the reaction product obtained as a gaseous product from the simple distillation apparatus was collected in a glass trap cooled by a dry ice-ethanol bath (-72 ° C.). The liquid collected in the glass trap was 24 parts. As a result of analyzing this product by gas chromatography, it was tetrafluorocyclobutenone which was the target product. The yield based on 1- (4-methoxybenzyloxy) pentafluorocyclobutene was 34%.

[Comparative Example 1]
Comparative Example 1 was performed according to the method described in Non-Patent Document 1. In a glass flask equipped with a simple distillation apparatus connected to a glass trap, a toluene solution containing 30 parts of 1-benzyloxypentafluorocyclobutene obtained in Production Example 4, 10 parts of sodium fluoride, and a commercially available 95% concentrated solution. 24 parts of sulfuric acid was added and the contents were stirred at 150 ° C. Stirring was continued for 7 hours, but nothing was collected in the glass trap cooled by a dry ice-ethanol bath (−72 ° C.). Further, the inside of the glass flask was changed to black. The reaction mixture was analyzed by gas chromatography, but formation of the objective tetrafluorocyclobutenone was not observed.

[Comparative Example 2]
In a glass flask equipped with a single distillation apparatus connected with a glass trap, 30 parts of 1-benzyloxypentafluorocyclobutene obtained in Production Example 4, 10 parts of sodium fluoride, 24 parts of commercially available 95% concentrated sulfuric acid, and 20 parts of toluene was added and the contents were stirred at 70 ° C.
Stirring was continued for 9 hours, but nothing was collected in the glass trap cooled by a dry ice-ethanol bath (-72 ° C). Further, the inside of the glass flask was changed to black. When the reaction mixture was analyzed by gas chromatography, the production of the target tetrafluorocyclobutenone was not observed, and decomposition of the starting material 1-benzyloxypentafluorocyclobutene was observed.

  In the experimental results of Comparative Examples 1 and 2, when 1-benzyloxypentafluorocyclobutene was used as a raw material, formation of the desired tetrafluorocyclobutenone could not be confirmed.

Claims (3)

Formula (1)

(Wherein R represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom, and n represents any integer of 1 to 5). , Characterized in that it comprises a step of contacting with an acid catalyst, formula (2)

The manufacturing method of tetrafluorocyclobutenone represented by these.   The production method according to claim 1, wherein an acid having an acid dissociation constant (pKa) at 25 ° C of 13 or less is used as the acid catalyst in dimethyl sulfoxide.   The production method according to claim 1 or 2, wherein the step of bringing the compound represented by the formula (1) into contact with an acid catalyst is performed in an aromatic hydrocarbon having a boiling point of 100 ° C or higher.