JP2018193340A - Method for producing sulfone compound - Google Patents

Abstract

A method for producing a sulfone compound from a sulfide compound in an efficient and high yield is provided. SOLUTION: The sulfide compound represented by the general formula (1) is subjected to photo-oxygen oxidation at 40 ° C. or higher in the presence of a secondary alcohol, a gas containing 25% by volume or more of oxygen, anthracene or a derivative thereof. The sulfone compound represented by (2) is produced. (In the formula, R 1 and R 2 are each independently an organic group having 1 to 6 carbon atoms, and S, R 1 and R 2 may form a ring.)

Description

  The present invention relates to a method for producing a sulfone compound from a sulfide compound.

  Dimethyl sulfone is used in a wide range of applications such as electrolytes, extraction solvents for petroleum products, high-temperature reaction solvents, and supplements. A general method for synthesizing dimethylsulfone is to oxidize dimethylsulfoxide with aqueous hydrogen peroxide (see, for example, Patent Document 1). However, hydrogen peroxide water is explosive and is designated as a hazardous material class 6 (oxidizing liquid) under the Fire Service Act. High-concentration aqueous solution is a deleterious substance designated by the Poisonous and Deleterious Substances Control Law and is transported. , Subject to laws and regulations in handling, storage and transfer. Moreover, since the reaction product dimethyl sulfone has a high solubility in water, it is necessary to distill off a large amount of water from the reaction solution when it is isolated and purified, which entails a significant energy cost.

  In addition, a method for synthesizing sulfone using sulfide as a raw material instead of using hydrogen peroxide as an oxidizing agent and sulfoxide as a raw material has also been reported (see Non-Patent Document 1). However, there is a problem that hydrogen peroxide is used in a large amount of 4 equivalents or more.

  Therefore, as a safer oxidant, Patent Document 2 supplies oxygen-containing gas in the form of nanobubbles and generates singlet oxygen by light irradiation in the presence of a dye sensitizer to photooxygenate sulfides. Suggest a method. Although this method can produce a sulfoxide from a sulfide in a high yield, it cannot produce a sulfone compound efficiently.

JP 54-44611 A Japanese Patent Laying-Open No. 2015-168667

Organic Letters, Vol.7, No.4, p.625, (2005)

  In view of such problems, an object of the present invention is to provide a method for efficiently producing a sulfone compound from a sulfide compound in a high yield.

（式（１）中、Ｒ¹，Ｒ²は互いに独立して炭素数１〜６の有機基であり、Ｓ，Ｒ¹およびＲ²が環を形成してもよい。）

（式（２）中、Ｒ¹，Ｒ²は互いに独立して炭素数１〜６の有機基であり、Ｓ，Ｒ¹およびＲ²が環を形成してもよい。） In the present invention, the sulfide compound represented by the following general formula (1) is subjected to photo-oxygen oxidation at 40 ° C. or higher in the presence of a secondary alcohol, a gas containing 25% by volume or more of oxygen, anthracene, or a derivative thereof. This is a method for producing a sulfone compound represented by the general formula (2).

(In formula (1), R ¹ and R ² are each independently an organic group having 1 to 6 carbon atoms, and S, R ¹ and R ² may form a ring.)

(In formula (2), R ¹ and R ² are each independently an organic group having 1 to 6 carbon atoms, and S, R ¹ and R ² may form a ring.)

  The production method of the present invention is a one-pot synthesis in which hydrogen peroxide is produced from oxygen and secondary alcohol in a reaction system, and this hydrogen peroxide oxidizes a sulfide compound to produce a sulfone compound. The sulfone compound can be obtained in a high yield in a short time.

  By supplying the gas containing oxygen in the form of fine bubbles, the reaction can be made faster and the yield can be increased. The secondary alcohol may have 3 to 6 carbon atoms. The sulfone compound represented by the general formula (2) is preferably dimethyl sulfone, dibutyl sulfone, sulfolane, methylphenyl sulfone or diphenyl sulfone.

  Furthermore, the production method of the present invention can achieve higher speed and higher yield by the presence of an organic acid having 1 to 3 carbon atoms. At this time, the photooxygen oxidation is preferably performed at 40 to 80 ° C., and the volume ratio of the secondary alcohol and the organic acid (secondary alcohol / organic acid) is preferably 5/95 to 98/2. In addition, after bringing the organic acid into contact with the solid acid catalyst, photo-oxygen oxidation is preferably performed.

It is explanatory drawing which shows typically the reactor used for the manufacturing method of the Example and comparative example of this specification. It is explanatory drawing which shows typically the other reactor used for the manufacturing method of the Example of this specification.

  The present invention relates to a method for producing a sulfone compound from a sulfide compound, wherein the sulfide compound is supplied with a gas containing 25% by volume or more of oxygen at a temperature of 40 ° C. or higher in the presence of a secondary alcohol, anthracene or a derivative thereof. This is a method for producing a sulfone compound by photo-oxygen oxidation.

（式（１）中、Ｒ¹、Ｒ²は互いに独立して炭素数１〜６の有機基であり、Ｓ，Ｒ¹およびＲ²が環を形成しても良い。） The sulfide compound is represented by the following general formula (1).

(In the formula (1), R ^1, R ² are mutually independently an organic group having 1 to 6 carbon atoms, S, R ¹ and R ² may form a ring.)

In the general formula (1), R ¹ and R ² are organic groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, which may be the same or different. Moreover, the organic group which has a substituent may be sufficient. Preferred examples of the organic group include aliphatic hydrocarbons and aromatic hydrocarbons, and alkyl groups and phenyl groups are more preferable. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable. S, R ¹ and R ² may form a ring, and examples thereof include a ring structure such as tetrahydrothiophene.

  Preferred examples of the sulfide compound represented by the general formula (1) include dimethyl sulfide, dibutyl sulfide, tetrahydrothiophene, thioanisole, and diphenyl sulfide.

（式（２）中、Ｒ¹，Ｒ²は互いに独立して炭素数１〜６の有機基であり、Ｓ，Ｒ¹およびＲ²が環を形成してもよい。） In the present invention, the sulfone compound is represented by the following general formula (2).

(In formula (2), R ¹ and R ² are each independently an organic group having 1 to 6 carbon atoms, and S, R ¹ and R ² may form a ring.)

In the general formula (2), S, R ¹ and R ^2, the general formula (1) S, is the same as R ¹ and R ^2.
Preferred examples of the sulfone compound represented by the general formula (2) include dimethyl sulfone, dibutyl sulfone, sulfolane, methylphenyl sulfone, and diphenyl sulfone.

  In the production method of the present invention, a secondary alcohol is used as a reaction solvent. Secondary alcohols produce ketones and hydrogen peroxide by photooxygen oxidation, and hydrogen peroxide oxidizes sulfide compounds to produce sulfone compounds. The secondary alcohol has 3 or more carbon atoms, preferably 3 to 6 carbon atoms. Moreover, you may mix individually or 2 or more types of secondary alcohol. Preferred examples of the secondary alcohol include 2-propanol, 2-butanol, and cyclohexanol, and 2-propanol is more preferable.

  Moreover, you may mix the other solvent which does not inhibit reaction with secondary alcohol as a reaction solvent. Other solvents that do not inhibit the reaction include alcohols such as methanol, ethanol and t-butanol, ketones such as acetone, 2-butanone and methyl isobutyl ketone, nitriles such as acetonitrile, ethers such as tetrahydrofuran and dimethoxyethane Is mentioned. The mixing ratio with the secondary alcohol and other solvent is not particularly limited as long as it does not inhibit the reaction.

  In the production method of the present invention, a gas containing 25% by volume or more of oxygen is used. The gas containing 25% by volume or more of oxygen represents a gas having an oxygen concentration of 25% by volume or more, preferably 40 to 100% by volume, and is inert, for example, oxygen, a mixture of oxygen and air, or oxygen and nitrogen. Examples thereof include a mixture with gas and a gas whose oxygen concentration is increased from air by an oxygen generator. If a gas having an oxygen concentration of less than 25% by volume is used, photooxygen oxidation does not proceed sufficiently and the yield of the sulfone compound decreases.

  A gas containing 25% by volume or more of oxygen is preferably supplied into the reaction solution, and more preferably supplied into the reaction solution in the form of fine bubbles. The fine bubbles are fine bubbles having a diameter of 100 μm or less, and preferably have a diameter of 50 μm or less. Generally, microbubbles are classified into millimeter bubbles (diameter 1 mm or more), sub-millibubbles (diameter 0.1 mm or more and less than 1 mm), and fine bubbles (diameter less than 0.1 mm, that is, less than 100 μm). It is classified into bubbles (diameter 1 μm or more and less than 100 μm) and ultra fine bubbles (diameter 1 less than 1 μm). In the present invention, a gas containing 25% by volume or more of oxygen is preferably supplied into the reaction liquid in the form of fine bubbles, and more preferably supplied in the form of ultra fine bubbles. Fine bubbles can be provided by a usual method.

  The supply amount of the gas containing 25% by volume or more of oxygen is not particularly limited, and can be determined in consideration of the size of the reaction vessel, the light transmittance, the capability of the bubble generator, and the like. For example, when the reaction solution is 80 mL, the supply amount of oxygen is preferably 0.1 to 100 mL / min, and more preferably 1 to 10 mL / min. If the supply amount of oxygen is less than 0.1 mL / min, photooxygen oxidation does not proceed sufficiently and the yield of the sulfone compound may be reduced. Moreover, when the supply amount of oxygen exceeds 100 mL / min, a large amount of unreacted oxygen that is not used in the reaction may remain and become inefficient.

  In the present invention, anthracene or a derivative thereof is used as a photosensitizer. Anthracene and its derivatives are colorless to light gray, have no coloring and are fat-soluble, and therefore have an advantage that they can be easily separated from a water-soluble sulfone compound in a purification process.

  Preferred anthracene derivatives include anthracene, anthraquinone or anthraquinone derivatives having one or more substituents. The anthraquinone or anthraquinone derivative may further have one or more substituents. As the substituent, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, a formyl group, or a cyano group is preferable. Preferred anthracene derivatives include anthracene-9-carboxylic acid, anthracene-1-carboxylic acid, anthracene-2-carboxylic acid, 9-cyanoanthracene, anthraquinone, anthraquinone-2-carboxylic acid, 2-amylanthraquinone, and the like. it can. Anthracene is particularly preferable as the photosensitizer of the present invention.

  The amount of anthracene or anthracene derivative added is preferably 0.01 to 0.5, more preferably 0.1 to 0.3, in terms of a molar ratio to the sulfide compound. If the amount of anthracene or anthracene derivative added is small, the yield of the sulfone compound will be low. In addition, if the amount of anthracene or anthracene derivative added is large, removal in the purification step becomes difficult and the cost increases.

  In the production method of the present invention, the concentration of the sulfide compound in the reaction solution containing the sulfide compound, secondary alcohol, and anthracene or a derivative thereof is preferably 0.01 to 10 mol / L, and preferably 0.02 to 1 mol / L. .

  The light source for photo-oxygen oxidation is not particularly limited, and for example, a high-pressure, medium-pressure or low-pressure mercury lamp, a halogen lamp such as a xenon lamp, an LED lamp, an excimer lamp, a fluorescent lamp, an incandescent lamp, etc. can be used. .

  The reaction temperature of photooxygen oxidation is 40 ° C. or higher, and is preferably lower than the boiling point of the reaction solvent. The reaction temperature is preferably 40 to 85 ° C, more preferably 50 to 82 ° C, still more preferably 60 to 80 ° C. If the reaction temperature is less than 40 ° C., the yield of the sulfone compound will be low.

  The reaction time is not particularly limited, and is preferably, for example, preferably 1 hour or more, more preferably 3 hours or more, and further preferably 5 hours or more. The reaction time is preferably 15 hours or less, more preferably 13 hours or less, and even more preferably 10 hours or less.

  The production method of the present invention can be carried out at normal pressure, but may be pressurized to increase the reaction rate. The pressure for pressurization is not particularly limited.

  In the present invention, an organic acid can be present in the photooxygen oxidation reaction. Since the reaction is accelerated by adding the organic acid, the sulfone compound can be obtained under milder conditions, and the yield can be further increased. As the organic acid, a carboxylic acid having 1 to 3 carbon atoms is preferable, and formic acid, acetic acid and propionic acid are exemplified, formic acid and acetic acid are preferable, and acetic acid is more preferable. In the presence of a carboxylic acid, percarboxylic acid is generated by hydrogen peroxide and acts as an oxidant, accelerating the reaction.

  The addition amount of the organic acid can be determined as a mixing ratio of the organic acid to the secondary alcohol. The volume ratio of the secondary alcohol and the organic acid (secondary alcohol / organic acid) is preferably 5/95 to 98/2, more preferably 10/90 to 90/10, still more preferably 20/80 to 80/20. It is good to be. When the volume ratio of the secondary alcohol and the organic acid (secondary alcohol / organic acid) is less than 5/95 or more than 98/2, the yield of the sulfone compound is lowered.

  When adding an organic acid, in order to further increase the reaction rate, it is preferable that the organic acid is brought into contact with a solid acid catalyst and subjected to photo-oxygen oxidation. The solid acid catalyst may be added to the reaction system, or a solid acid catalyst may be disposed in the middle of the reaction liquid circulation path for generating fine bubbles so as to come into contact with the organic acid in the reaction liquid. . Examples of the solid acid catalyst include silica gel, alumina, zeolite, heteropoly acid, weakly acidic ion exchange resin, and strongly acidic ion exchange resin, and strong acid ion exchange resin is particularly preferable. Examples of strongly acidic ion exchange resins include benzenesulfonic acid type ion exchange resins. As specific examples of such strongly acidic ion exchange resins, “Diaion” SK series, “Diaion” PK series, manufactured by Mitsubishi Chemical Corporation, “Amberlite” IR-120B, manufactured by Organo Corporation, “Amberlist” 15 and “Dowex” 50W series manufactured by Dow Chemical Co., but are not limited thereto. Among these, “Amberlyst” 15 manufactured by Organo Corporation is more preferable. Moreover, a plurality of these strongly acidic ion exchange resins can be mixed and used. The addition amount of the solid acid catalyst is preferably 0.01 to 1 times by weight of the weight of the organic acid, and more preferably 0.1 to 0.5 times by weight. By making the addition amount of a solid acid catalyst into such a range, the yield of a sulfone compound can be made higher.

  The reaction temperature can be further lowered by bringing the organic acid into contact with the solid acid catalyst in the reaction system. For example, even when the reaction temperature is preferably 40 to 80 ° C., more preferably 55 to 75 ° C., the yield of the sulfone compound can be increased without increasing the reaction time.

  The sulfone compound obtained by this reaction can be purified by a usual method. As a pretreatment for purification, it is preferable to remove anthracene or a derivative thereof from the reaction solution. As a method for removing these, extraction with an organic solvent such as hexane, heptane, cyclohexane, adsorption separation with an adsorbent such as ion exchange resin, silica gel, activated carbon, and alumina is preferable. As a purification method for isolating the sulfone compound from the pretreated reaction solution, it can be purified by methods such as distillation, sublimation, crystallization, and column chromatography purification. The separated reaction solvent and catalyst may be discarded, or recovered and reused.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely with reference to an Example, this invention is not limited to those Examples.
The sulfone compound was measured by gas chromatography under the following conditions.
-Equipment used: Shimadzu Corporation GC-2010 (FID)
Column TC-17 manufactured by GL Sciences Inc. 0.25 mm × 30 m, film thickness 0.50 μm
Carrier gas N ₂ 129.2kPa
Column heating conditions 80 ° C x 5 minutes → 5 ° C / min → 150 ° C → 20 ° C / min → 250 ° C
・ Inlet temperature 250 ℃
・ Detector temperature 250 ℃
· FID Air 400ml / min, H ₂ 40ml / minute
Makeup 30ml / min, split ratio 39
・ Injection volume 1.0μl

Example 1
FIG. 1 is a conceptual diagram of a reactor used in Example 1, and has the following configuration.
Fine bubble generator: MA3FS (manufactured by Asp Corporation)
Gas flow control device: Digital mass flow controller MQV9005 (manufactured by Azbil Corporation)
Internal irradiation type photochemical reactor (100W high-pressure mercury lamp): UVL-100HA (manufactured by Riko Kagaku Sangyo Co., Ltd.)

  In FIG. 1, an internal irradiation type photochemical reaction device 4 contains a light source 5 and a reaction solution, and the reaction solution circulates between the fine bubble generator 3 through a pipe. The oxygen source 1 is an oxygen cylinder, and the gas flow rate control device 2 controls the flow rate of oxygen gas and supplies it to the fine bubble generator 3 at a predetermined flow rate. The fine bubble generator 3 generates oxygen gas in the form of fine bubbles in the circulating reaction solution and sends it to the reaction solution of the internal irradiation type photochemical reaction device 4 together with the reaction solution. The fine bubble generator 3 is an ultra fine bubble in which the number of bubbles having a diameter of 5 nm or more and less than 1 μm is 90% or more with respect to the total number of bubbles. The reaction liquid in the internal irradiation type photochemical reaction device 4 contains a sulfide compound, secondary alcohol, anthracene or a derivative thereof, and oxygen gas, and receives light irradiation from the light source 5 to oxidize the sulfide compound into a sulfone compound.

In the production method of Example 1, 0.30 g (4.8 mmol) of dimethyl sulfide and 0.17 g of anthracene (0.96 mmol, 20 mol% of dimethyl sulfide) were added to 80 mL of 2-propanol in the internal irradiation type photochemical reaction apparatus 4. Dissolved and stored. At 55 ° C., while supplying oxygen as ultrafine bubbles at 5 mL / min, the light source was immersed in the reaction solution and irradiated with light. The reaction solution was circulated for 5 hours while supplying oxygen in the form of ultrafine bubbles. The yield of dimethyl sulfone (DMSO ₂ ) was analyzed by gas chromatography and calculated by the following formula.
Yield (%) = [(DMSO ₂ concentration in the reaction solution) / (DMSO ₂ concentration when 100% yield)] × 100
The (DMSO ₂ concentration in the reaction solution) was calculated by absolute calibration from the area count number of DMSO _{2 in} gas chromatography.
The results are shown in Table 1.

Example 2
FIG. 2 is a conceptual diagram of the reaction apparatus used in Example 2, in which a solid acid catalyst layer 6 is arranged in the circulation path returning from the fine bubble generation apparatus 3 to the internal irradiation type photochemical reaction apparatus 4, and in the reaction solution. 1 except that the organic acid is in contact with the solid acid catalyst.

In the production method of Example 2, dimethyl sulfide 0.37 g (6 mmol), anthracene 0.21 g (1.2 mmol, 20 mol% of dimethyl sulfide) were added to 75 mL of 2-propanol and 25 mL of acetic acid. And dissolved. While supplying oxygen as ultrafine bubbles at 5 mL / min at 75 ° C., the light source was immersed in the reaction solution and irradiated with light. Amberlyst 15 (manufactured by Organo Co., Ltd.) was filled in 5 g of the solid acid catalyst layer 6 and installed in the circulation path before entering the reaction vessel so that the organic acid in the reaction solution was in contact with the solid acid catalyst. When the reaction liquid was circulated for 2 hours while supplying oxygen in the form of ultrafine bubbles, dimethyl sulfide as a raw material disappeared. The yield of dimethyl sulfone (DMSO ₂ ) was analyzed by gas chromatography. The results are shown in Table 1.

Example 3
Dimethylsulfone was produced by photooxidation of dimethyl sulfide in the same manner as in Example 2 except that the reaction temperature was changed to 55 ° C. and the reaction time was changed to 4 hours. The results are shown in Table 1.

Example 4
Dibutylsulfone was produced by photooxidation of dibutylsulfide in the same manner as in Example 2 except that the sulfide compound was changed to 0.88 g (6 mmol) of dibutylsulfide. The yield of dibutyl sulfone was analyzed by gas chromatography and calculated by the following formula.
Yield (%) = [(dibutylsulfone concentration in the reaction solution) / (dibutylsulfone concentration at 100% yield)] × 100
The (dibutyl sulfone concentration in the reaction solution) was calculated by absolute calibration from the area count of dibutyl sulfone in gas chromatography. The results are shown in Table 1.

Example 5
A sulfolane was produced by photooxidation of tetrahydrothiophene in the same manner as in Example 2 except that the sulfide compound was changed to 0.53 g (6 mmol) of tetrahydrothiophene and the reaction time was changed to 3 hours. The yield of sulfolane was analyzed by gas chromatography and calculated by the following formula.
Yield (%) = [(sulfolane concentration in the reaction solution) / (sulfolane concentration at 100% yield)] × 100
The (sulfolane concentration in the reaction solution) was calculated by absolute calibration from the area count of sulfolane in gas chromatography. The results are shown in Table 1.

Example 6
Methylphenylsulfone was produced by photo-oxidizing thioanisole in the same manner as in Example 2 except that the sulfide compound was changed to 0.75 g (6 mmol) of thioanisole and the reaction time was changed to 3 hours. The yield of methylphenylsulfone was analyzed by gas chromatography and calculated by the following formula.
Yield (%) = [(Methylphenylsulfone concentration in reaction solution) / (Methylphenylsulfone concentration at 100% yield)] × 100
The (methylphenylsulfone concentration in the reaction solution) was calculated by absolute calibration from the area count number of methylphenylsulfone by gas chromatography. The results are shown in Table 1.

Comparative Example 1
As Comparative Example 1, an example of a photooxygen oxidation reaction that does not generate hydrogen peroxide without adding a secondary alcohol is shown. In Comparative Example 1, the reaction apparatus represented by the conceptual diagram of FIG. 1 is used.
In the production method of Comparative Example 1, 1.2 g (10 mmol) of thioanisole was dissolved in 100 mL of methanol and stored in the internal irradiation type photochemical reaction device 4. The oxygen source 1 was an air cylinder, and light was irradiated by immersing the light source in the reaction solution while supplying air at 30 ° C. as ultrafine bubbles at 3 mL / min. When the reaction liquid was circulated for 6 hours and air in the form of ultrafine bubbles was continuously supplied, thioanisole as a raw material almost disappeared. As a result of analysis by gas chromatography, methylphenylsulfone was not produced, and methylphenylsulfoxide was produced only in a yield of 70%.
As described above, in the photo-oxygen oxidation reaction that does not generate hydrogen peroxide, sulfone cannot be efficiently produced from sulfide.

  The method for producing a sulfone compound by oxidation of the sulfide compound of the present invention does not use hydrogen peroxide as a raw material, and therefore is safe without danger of explosion and the like, and the sulfone compound can be obtained in a short time and in a high yield. . The sulfone compound obtained by this production method can be used as an electrolyte, a supplement, an extraction solvent for petroleum products, and a high-temperature reaction solvent.

DESCRIPTION OF SYMBOLS 1 Oxygen source 2 Gas flow control apparatus 3 Fine bubble generator 4 Internal irradiation type photochemical reaction apparatus 5 Light source 6 Solid acid catalyst layer

Claims (8)

The sulfide compound represented by the following general formula (1) is photooxygenated at 40 ° C. or higher in the presence of a secondary alcohol, a gas containing 25% by volume or more of oxygen, anthracene, or a derivative thereof. The manufacturing method of the sulfone compound represented by these.

(In formula (1), R ¹ and R ² are each independently an organic group having 1 to 6 carbon atoms, and S, R ¹ and R ² may form a ring.)

(In formula (2), R ¹ and R ² are each independently an organic group having 1 to 6 carbon atoms, and S, R ¹ and R ² may form a ring.)   The method for producing a sulfone compound according to claim 1, wherein the gas containing oxygen is supplied in the form of fine bubbles.   Furthermore, the manufacturing method of the sulfone compound of Claim 1 or 2 in which C1-C3 organic acid exists.   The method for producing a sulfone compound according to claim 3, wherein the photooxygen oxidation is performed at 40 to 80 ° C.   The method for producing a sulfone compound according to claim 3 or 4, wherein the volume ratio of the secondary alcohol and the organic acid (secondary alcohol / organic acid) is 5/95 to 98/2.   The method for producing a sulfone compound according to any one of claims 3 to 5, wherein the photo-oxygen oxidation is performed after contacting the organic acid with a solid acid catalyst.   The method for producing a sulfone compound according to any one of claims 1 to 6, wherein the secondary alcohol has 3 to 6 carbon atoms.   The method for producing a sulfone compound according to any one of claims 1 to 7, wherein the sulfone compound represented by the general formula (2) is dimethyl sulfone, dibutyl sulfone, sulfolane, methylphenyl sulfone, or diphenyl sulfone.

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