JP5853771B2 - Method for producing α, α-difluoroaromatic compound - Google Patents

Description

  The present invention relates to a method for producing an α, α-difluoroaromatic compound.

  An α, α-difluoroaromatic compound is important as an intermediate for medical and agricultural chemicals (for example, Patent Document 1). A typical method for producing the compound includes deoxodifluorination reaction of an aromatic carbonyl compound using DAST or Deoxo-Fluor (Non-patent Documents 1 and 2).

  On the other hand, as a technique related to the present invention, a method for producing α, α-difluoroethylbenzene in which a vinyl chloride moiety of α-chlorostyrene is reacted (added or substituted) with hydrogen fluoride (Non-patent Document 3) is disclosed. .

International publication 2011/154298

J. et al. Org. Chem. (USA), 1975, 40, p. 574 J. et al. Org. Chem. (USA), 1999, Vol. 64, p. 7048 J. et al. Org. Chem. (USA), 1962, 27, p. 4015

  The production methods described in Non-Patent Documents 1 and 2 are not suitable for industrial production because they use expensive fluorinating agents.

  In the production method described in Non-Patent Document 3, the yield was low in both the liquid phase method and the gas phase method (28% and 11%, respectively). In addition, the gas phase method requires a catalyst in which highly toxic mercury oxide is supported on activated carbon, and the reaction apparatus is complicated and the operation is complicated.

In general, in the production of geminal difluoro compounds, it is known that the yield is greatly influenced by whether or not the difluoromethylene (CF ₂ ) group in the target product is directly bonded to the aromatic ring. For example, a method for producing a geminal difluoro compound in which two molecules of hydrogen fluoride are added to the triple bond of an acetylene compound has been reported [J. Org. Chem. (USA), 1979, vol. 44, p. 3872, Non-Patent Document 3], 2,2-difluorohexane and 3,3-difluorohexane can be obtained in high yields (70% and 75%, respectively), whereas α, α-difluoroethylbenzene can only be obtained in low yields. Not obtained [liquid phase method 18%. Comparative Example 1; 1-bromo-4- (1,1-difluoroethyl) benzene is also less than 5%]. In addition, a deoxodifluorination reaction of a carbonyl compound via an acyl having two trifluoromethylcarbonyloxy (CF ₃ CO ₂ ) groups has been reported [J. Fluorine Chem. (Netherlands), 2010, vol. 131, p. 29, JP-A-1-199922], 1,1-difluorocyclohexane can reproduce the described high yield (91%), but α, α-difluoroethylbenzene cannot be reproduced at all [described yield 90%, Comparative Example 2 Less than 10%, 1-bromo-4- (1,1-difluoroethyl) benzene is also about 15%]. Furthermore, the present inventors have applied for a patent for a method for producing a geminal difluoro compound comprising a step of reacting a fluorine-containing sulfuric acid enol ester with a fluorinating agent (Japanese Patent Application No. 2011-166797 / Geminal Difluoro Compound). Production method), also in this production method, when the CF ₂ group in the target compound was directly bonded to the aromatic ring, the yield was significantly reduced (Comparative Example 3 vs. 4).

As described above, in the production of α, α-difluoroaromatic compounds (CF ₂ group is directly bonded to the aromatic ring) which is difficult to expect a high yield, a highly toxic catalyst is not required, the reaction apparatus is simple and the operation is easy. There has been a strong demand for a method that is simple, inexpensive, and can be industrially produced in good yield.

  As a result of intensive studies, the present inventors have replaced the hydrogen fluoride used as the fluorinating agent in Non-Patent Document 3 with “a salt or complex composed of an organic base and hydrogen fluoride” to obtain a desired reaction. Has been found to proceed very well and the present invention has been reached. Hydrolyzate (acetophenone when the raw material substrate is α-chlorostyrene) and tar by-product, which was a problem when hydrogen fluoride was used as the fluorinating agent, were significantly suppressed, and the target product was It was clarified that it can be obtained in high yield.

  Specifically, the present inventors have made α, α-difluoroaromatic compounds by reacting 1-chloro-1-aromatic ring-substituted ethenes with “a salt or complex comprising an organic base and hydrogen fluoride”. Was found to be able to be produced with good yield. 1-Chloro-1-aromatic ring-substituted ethene is one in which the aromatic ring part at the 1-position is an aromatic hydrocarbon group or a substituted aromatic hydrocarbon group, and the two substituents at the 2-position are both hydrogen atoms Are preferred, and the resulting products are particularly important as pharmaceutical and agrochemical intermediates. The “salt or complex comprising an organic base and hydrogen fluoride” is preferably “a salt or complex comprising pyridine and hydrogen fluoride” or “a salt or complex comprising triethylamine and hydrogen fluoride”. “Salts or complexes comprising hydrogen fluoride” are particularly preferred, and can be obtained inexpensively on a large scale at low cost.

  That is, the present invention includes [Invention 1] to [Invention 4] and provides a method for producing an α, α-difluoroaromatic compound. The production method disclosed in the present invention has never been reported before and is novel.

[Invention 1]
General formula [1]:

[In the formula, Ar ¹ represents an aromatic ring group or substituted aromatic ring group, R ¹ and R ² are independently a hydrogen atom, an alkyl group, a substituted alkyl group, an aromatic ring group or substituted aromatic ring group, Ar ¹ And R ¹ , Ar ¹ and R ² , or R ¹ and R ² can form a cyclic structure by a covalent bond. ]
The method includes a step of reacting 1-chloro-1-aromatic ring-substituted ethene represented by general formula [2] with a salt or complex comprising an organic base and hydrogen fluoride:

[Wherein Ar ¹ , R ¹ and R ² are the same as those in the general formula [1]. ]
The manufacturing method of the (alpha), (alpha)-difluoro aromatic compound shown by these.

[Invention 2]
The 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1] is represented by the general formula [3]:

[Wherein Ar ² represents an aromatic hydrocarbon group or a substituted aromatic hydrocarbon group. ]
The α, α-difluoroaromatic compound represented by the general formula [2] is a 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [4]:

[Wherein Ar ² is the same as in general formula [3]. ]
The method of the invention 1, which is an α, α-difluoroaromatic compound represented by the formula:

[Invention 3]
The salt or complex composed of an organic base and hydrogen fluoride is a salt or complex composed of pyridine and hydrogen fluoride, or a salt or complex composed of triethylamine and hydrogen fluoride. Method.

[Invention 4]
The method according to Invention 1 or Invention 2, wherein the salt or complex comprising an organic base and hydrogen fluoride is a salt or complex comprising pyridine and hydrogen fluoride.

  The 1-chloro-1-aromatic ring-substituted ethene and “salt or complex comprising an organic base and hydrogen fluoride” used in the present invention can be obtained relatively inexpensively on a large scale. Moreover, since the reaction conditions employed are relaxed, the selectivity is high and the yield is also good. Furthermore, a highly toxic catalyst is not required, the reaction apparatus is simple and the operation is simple. Thus, the present invention is very useful as an industrial production method for α, α-difluoroaromatic compounds.

  Further, the present invention is clearly superior to Non-Patent Document 3 [Comparative Example 5; 1-bromo-4- (1,1-difluoroethyl) benzene is similarly used with reference to Non-Patent Document 3. Even if manufactured, the yield is low.

  The production method of the α, α-difluoroaromatic compound of the present invention will be described in detail.

  The scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be appropriately changed and implemented without departing from the spirit of the present invention. It should be noted that all publications cited in the present specification, for example, prior art documents, patent documents such as publications and patent applications, other non-patent documents, and books shall be incorporated herein by reference. .

R ¹ and R ² of the ¹ -chloro-1-aromatic ring-substituted ethene represented by the general formula [1] each independently represent a hydrogen atom, an alkyl group, a substituted alkyl group, an aromatic ring group, or a substituted aromatic ring group. . Among them, both R ¹ and R ² are preferably hydrogen atoms. The alkyl group is a linear or branched chain or cyclic group having 1 to 18 carbon atoms (in the case of 3 or more carbon atoms). The aromatic ring group is an aromatic hydrocarbon group having 1 to 18 carbon atoms such as a phenyl group, a naphthyl group and an anthryl group, or a pyrrolyl group (including a nitrogen protector), a pyridyl group, a furyl group, a thienyl group, an indolyl group. An aromatic heterocyclic group containing a hetero atom such as a nitrogen atom, oxygen atom or sulfur atom such as a group (including a nitrogen-protected form), a quinolyl group, a benzofuryl group and a benzothienyl group. The substituted alkyl group and the substituted aromatic ring group have a substituent in any number and in any combination on any carbon atom or nitrogen atom of the alkyl group and aromatic ring group, respectively. Such substituents include fluorine, chlorine, bromine and iodine halogen atoms, lower alkyl groups such as nitro, methyl, ethyl and propyl, lower haloalkyl groups such as fluoromethyl, chloromethyl and bromomethyl, methoxy Group, lower alkoxy group such as ethoxy group and propoxy group, lower haloalkoxy group such as fluoromethoxy group, chloromethoxy group and bromomethoxy group, lower acyloxy group such as formyloxy group, acetyloxy group, propionyloxy group and butyryloxy group , Lower alkoxycarbonyl groups such as cyano group, methoxycarbonyl group, ethoxycarbonyl group and propoxycarbonyl group, phenyl group, naphthyl group, anthryl group, pyrrolyl group (including nitrogen-protected products), pyridyl group, furyl group, thienyl group, B Aromatic group such as drill group (including nitrogen protector), quinolyl group, benzofuryl group and benzothienyl group, carboxyl group, protector of carboxyl group, amino group, protector of amino group, hydroxyl group, and hydroxyl group It is a protector. Further, in the substituted alkyl group, any carbon-carbon single bond of the above alkyl group can be replaced with a carbon-carbon double bond or a carbon-carbon triple bond in any number and in any combination (of course, The alkyl group partially substituted for these unsaturated bonds may have the above-mentioned substituents as well, and hydrogen fluoride may be added to these unsaturated bonds. By adopting the preferred reaction conditions, it is possible to selectively carry out only the desired reaction). In the present specification, “lower” means a linear or branched chain or cyclic group (in the case of 3 or more carbon atoms) having 1 to 6 carbon atoms. The “aromatic ring group” of the “substituent” is a halogen atom, nitro group, lower alkyl group, lower haloalkyl group, lower alkoxy group, lower haloalkoxy group, formyloxy group, lower acyloxy group, A cyano group, a lower alkoxycarbonyl group, a carboxyl group, a protected body of a carboxyl group, an amino group, a protected body of an amino group, a hydroxyl group, a protected body of a hydroxyl group, and the like can be substituted. Furthermore, pyrrolyl, indolyl, carboxyl, amino and hydroxyl protecting groups are described in Protective Groups in Organic Synthesis, Third Edition, 1999, John Wiley & Sons, Inc. And the like.

Ar ¹ of the ¹ -chloro-1-aromatic ring-substituted ethene represented by the general formula [1] represents an aromatic ring group or a substituted aromatic ring group. The aromatic ring group and the substituted aromatic ring group are the same as the aromatic ring group and the substituted aromatic ring group described in R ¹ and R ² of the ¹ -chloro-1-aromatic ring-substituted ethene represented by the general formula [1]. is there. Among these, an aromatic hydrocarbon group or a substituted aromatic hydrocarbon group is preferable.

Ar ¹ and R ¹ , Ar ¹ and R ² , or R ¹ and R ² of the 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1] form a cyclic structure by a covalent bond. You can also. Specifically, between Ar ¹ and R ¹ , Ar ¹ and R ² , or R ¹ and R ² , between any carbon atoms (via a hetero atom such as a nitrogen atom, an oxygen atom or a sulfur atom) And in any number and in any combination, a cyclic structure (for example, monocyclic, condensed polycyclic, bridged, spiro ring, ring assembly, etc.) can be formed by a covalent bond [however, Substituents (hydrogen atoms) that cannot participate in covalent bonds are excluded.

As the 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1], Ar ¹ is an aromatic hydrocarbon group or a substituted aromatic hydrocarbon group, and both R ¹ and R ² are hydrogen atoms. Are preferred (corresponding to 1-chloro-1-aromatic ring-substituted ethenes represented by the general formula [3]).

The 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1] is synthesized by the Chemical Society of Japan, 4th edition, Experimental Chemistry Course 19 Organic Synthesis I Hydrocarbon / Halogen Compound Maruzen Co. 416-460, Chemical Society of Japan, 5th edition, Experimental Chemistry Course 13 Synthesis of Organic Compounds I Hydrocarbons / halides Maruzen Co., Ltd. p. It can manufacture similarly with reference to 374-443 etc. (reference examples 1 and 2). Depending on the raw material substrate preparation method, the general formula [5]:

[In the formula, Ar ¹ represents an aromatic ring group or substituted aromatic ring group, R ¹ and R ² are independently a hydrogen atom, an alkyl group, a substituted alkyl group, an aromatic ring group or substituted aromatic ring group, Ar ¹ And R ¹ , Ar ¹ and R ² , or R ¹ and R ² can form a cyclic structure by a covalent bond. ]
In some cases, an α, α-dichloro aromatic compound represented by the formula (1) is contained as a by-product. The α, α-difluoroaromatic compound that is the object of the present invention may also be obtained from the by-product in a relatively high yield. Accordingly, the 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1] contains the α, α-dichloroaromatic compound represented by the general formula [5] as a minor component (1-chloro-1-aromatic The case where it is included as a ring-substituted ethene> (relation of α, α-dichloroaromatic compound) is also handled as the raw material substrate described in the claims of the present invention.

  The organic base in the “salt or complex comprising an organic base and hydrogen fluoride” is trimethylamine, triethylamine, diisopropylethylamine, tri-n-propylamine, tri-n-butylamine, N-methylpiperidine, 4-methylmorpholine, N, N -Dimethylcyclohexylamine, N, N-dimethylbenzylamine, pyridine, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-lutidine, 3,5-lutidine 2,3,4-collidine, 2,4,5-collidine, 2,5,6-collidine, 2,4,6-collidine, 3,4,5-collidine, 3,5,6-collidine, 4, -Dimethylaminopyridine, 4-pyrrolidinopyridine, 1,4-diazabicyclo [2.2.2] octane, 1,5-diazabicyclo [4. .0] non-5-ene, 1,8-diazabicyclo [5.4.0] undec-7-ene or the like. However, it is not limited to these, The organic base generally used in organic synthesis can also be employ | adopted. Of these, triethylamine and pyridine are preferable, and pyridine is particularly preferable. These organic bases can be used alone or in combination. Further, “a salt or complex comprising an organic base and hydrogen fluoride” prepared in the reaction system is also handled as being included in the claims of the present invention. For example, when hydrogen fluoride is gradually added to a mixture containing a raw material substrate and an organic base (including a reaction solvent as necessary).

  The molar ratio of the organic base and hydrogen fluoride in the “salt or complex comprising an organic base and hydrogen fluoride” may be used in the range of 100: 1 to 1: 100, preferably 50: 1 to 1:50. Particularly preferred is 25: 1 to 1:25. "Complex consisting of 1 mol of triethylamine and 3 mol of hydrogen fluoride" or "pyridine ~ 30% (-10 mol%) and hydrogen fluoride ~ 70% (~ 90 mol%) commercially available from Aldrich (Aldrich, 2009-2010 catalog) It is convenient to use a complex consisting of

  The “salt or complex composed of an organic base and hydrogen fluoride” is preferably “a salt or complex composed of pyridine and hydrogen fluoride” or “a salt or complex composed of triethylamine and hydrogen fluoride”. Particularly preferred is a salt or complex comprising hydrogen fluoride.

  The amount of the “salt or complex comprising an organic base and hydrogen fluoride” is used as hydrogen fluoride (HF) with respect to 1 mol of 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1]. What is necessary is just to use 1.4 mol or more, 1.6-2000 mol is preferable and 1.8-1000 mol is especially preferable.

  The present invention comprises reacting a 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1] with a “salt or complex comprising an organic base and hydrogen fluoride” in the presence of an acid catalyst. In some cases, the α, α-difluoroaromatic compound represented by the general formula [2] can be obtained with a significantly higher yield. However, by employing the preferred reaction conditions of the present invention, the desired reaction can be carried out smoothly even in the absence of an acid catalyst (an acid catalyst is not essential for the present invention). Such acid catalysts include hydrogen chloride, hydrogen bromide, sulfuric acid, nitric acid, perchloric acid, fluorosulfuric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluoroantimonic acid, boron trifluoride, antimony trifluoride, five Inorganic acids such as antimony fluoride, antimony trichloride, antimony pentachloride, antimony trifluoride dichloride, iodine pentafluoride and iodine heptafluoride, and 2,2,2-trifluoroethanol, 1,1,1, Organic acids such as 3,3,3-hexafluoro-2-propanol, formic acid, acetic acid, trifluoroacetic acid, trichloroacetic acid, propionic acid, oxalic acid, methanesulfonic acid, paratoluenesulfonic acid and trifluoromethanesulfonic acid . These acid catalysts can be used alone or in combination.

  Reaction solvents include aliphatic hydrocarbons such as n-hexane and n-heptane, aromatic hydrocarbons such as toluene and xylene, methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane and α, α, α -Halogens such as trifluorotoluene, diethyl ether, diisopropyl ether, tert-butyl methyl ether, ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, esters such as ethyl acetate and n-butyl acetate, N, N-dimethylformamide And amides such as 1,3-dimethyl-2-imidazolidinone, nitriles such as acetonitrile and propionitrile, and dimethyl sulfoxide. Of these, halogen-based, ether-based, amide-based and nitrile-based are preferable, and halogen-based and ether-based are particularly preferable. These reaction solvents can be used alone or in combination.

  The amount of the reaction solvent used may be 0.0001 L (liter) or more with respect to 1 mol of 1-chloro-1-aromatic ring-substituted ethene represented by the general formula [1], preferably 0.0005 to 30 L, 0.001 to 15 L is particularly preferable. This reaction can also be carried out neat without using a reaction solvent.

  The reaction temperature may be in the range of −50 to + 150 ° C., preferably −40 to + 125 ° C., particularly preferably −30 to + 100 ° C.

  The reaction time may be within a range of 48 hours, and varies depending on the raw material substrate, the reactants, and the reaction conditions. Therefore, the progress of the reaction is traced by analytical means such as gas chromatography, liquid chromatography, and nuclear magnetic resonance. It is preferable to set the end point when the decrease in the raw material substrate is hardly recognized.

  In the post-treatment, an α, α-difluoroaromatic compound represented by the general formula [2] can be obtained by employing a general operation in organic synthesis. The crude product can be purified to a high purity by activated carbon treatment, fractional distillation, recrystallization, column chromatography or the like, if necessary.

[Example]
Hereinafter, the embodiments of the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

In the fluororesin lining reaction vessel, the following formula:

1.60 g of 1-chloro-1-aromatic ring substituted ethene represented by the formula (gas chromatography purity 64.1%, α, α-dichloroaromatic compound 17.9%, total 20.5 mmol, 1.00 eq) Add 26.0 mL (1.27 L / mol) of methylene chloride, cool to 5 ° C., and 3.54 g of “complex consisting of pyridine and hydrogen fluoride” (hydrogen fluoride content 65.0%, as hydrogen fluoride) 115 mmol, 5.61 eq) was added (two-phase system), and the mixture was vigorously stirred at the same temperature for 40 minutes and at room temperature overnight. The reaction-terminated liquid was diluted with 50 mL of chloroform, washed with 20 mL of water, washed with 30 mL of water, washed with 30 mL of 5% aqueous potassium carbonate solution, washed with 10% brine, and the recovered organic layer was internalized by ¹⁹ F-NMR. When determined by a standard method (internal standard substance: α, α, α-trifluorotoluene), the following formula:

The α, α-difluoroaromatic compound represented by the formula (1) was contained in an amount of 15.1 mmol. The yield according to the internal standard method was 74%. The conversion rate and purity were 97% and 78.7% (4-bromoacetophenone was 4.1%), respectively, from gas chromatography analysis of the recovered organic layer. ¹ H and ¹⁹ F-NMR of the recovered organic layer are shown below.

¹ H-NMR (reference material; Me ₄ Si, deuterated solvent; CDCl ₃ ), δ ppm; 1.89 (t, 3H), 7.46 (Ar—H, 4H).

¹⁹ F-NMR (reference material; C ₆ F ₆ , heavy solvent; CDCl ₃ ), δ ppm; 73.93 (q, 2F).

In the fluororesin lining reaction vessel, the following formula:

1-chloro-1-aromatic ring-substituted ethene represented by the formula (gas chromatography purity 99.5%, 35.9 mmol, 1.00 eq) and methylene chloride 36.0 mL (1.00 L / mol) were added. Cool to 5 ° C. and add 5.55 g of “complex composed of pyridine and hydrogen fluoride” (hydrogen fluoride content 65.0%, 180 mmol as hydrogen fluoride, 5.01 eq) (two-phase system), The mixture was vigorously stirred at 20 ° C. for 3 hours and 10 minutes. The reaction solution is diluted with 30 mL of chloroform, washed with 10 mL of water, washed twice with 20 mL of water, washed with 30 mL of 5% aqueous potassium carbonate solution, washed with 10 mL of 10% brine, dried over anhydrous sodium sulfate, The recovered organic layer was quantified by an internal standard method by ¹⁹ F-NMR (internal standard material: α, α, α-trifluorotoluene), and the following formula:

19.7 mmol of an α, α-difluoroaromatic compound represented by the formula: The yield by the internal standard method was 55%. From the gas chromatography analysis of the recovered organic layer, the conversion rate and purity were 98% and 75.6% (acetophenone was 0.6%), respectively. ¹ H and ¹⁹ F-NMR of the recovered organic layer are shown below.

¹ H-NMR (reference material; Me ₄ Si, heavy solvent; CDCl ₃ ), δ ppm; 1.92 (t, 3 H), 7.47 (Ar—H, 5 H).

¹⁹ F-NMR (reference material; C ₆ F ₆ , heavy solvent; CDCl ₃ ), δ ppm; 74.02 (q, 2F).

[Reference Example 1]
To 289 mL (0.576 L / mol) of toluene, 131 g (629 mmol, 1.25 eq) of phosphorus pentachloride and the following formula:

4-bromoacetophenone 100 g (502 mmol, 1.00 eq) was added, the oil bath temperature was set to 73 ° C., and the mixture was stirred for 3 hours (hydrogen chloride was generated). 116 mL of toluene is added to the reaction end solution, poured into 300 mL of ice water, and the recovered organic layer is washed with 200 mL of water, washed with 200 mL of 10% brine, and concentrated under reduced pressure to obtain the following formula:

154 g of a crude product of 1-chloro-1-aromatic ring-substituted ethene represented by the formula:

By subjecting the whole crude 1-chloro-1-aromatic ring-substituted ethene obtained above to fractional distillation (boiling point 92 to 104 ° C., reduced pressure 0.3 kPa), 77.4 g of a purified product was obtained. The purified product has a gas chromatographic purity of 74.6%.

The α, α-dichloro aromatic compound and 4-bromoacetophenone represented by 21.2% and 1.7% were contained, respectively. The yield in terms of purity (including α, α-dichloroaromatic compound) was 66%. The ¹ H-NMR of the purified product is shown below.

¹ H-NMR (reference material; Me ₄ Si, deuterated solvent; CDCl ₃ ), δ ppm; 5.54 (d, 1H), 5.77 (d, 1H), 7.52 (Ar—H, 2H) 7.62 (Ar-H, 2H).

[Reference Example 2]
Following formula:

1.84 g (11.2 mmol, 0.00560 eq) of 2,2′-azobisisobutyronitrile was added to 212 g (2.00 mol, 1.00 eq) of ethylbenzene represented by the formula, and the mixture was stirred at an internal temperature of 20 to 50 ° C. Then, chlorine (Cl ₂ ) gas was blown in at 1.00 mol / hour for 4 hours and 30 minutes (total 4.50 mol, 2.25 eq; α, α-dichloroation), and stirred at an internal temperature of 113 to 134 ° C. for 2 hours and 30 minutes. (Dehydrochlorination). The same reaction is repeated, and the reaction-terminated liquids are combined and subjected to fractional distillation (boiling point: 86 ° C., degree of vacuum: 3.5 kPa).

288 g of a purified product of 1-chloro-1-aromatic ring-substituted ethene represented by the following formula: The purified product had a gas chromatography purity of 99.5% (no α, α-dichloroaromatic compound was contained). The yield in terms of purity was 52%. The ¹ H-NMR of the purified product is shown below.

¹ H-NMR (reference material; Me ₄ Si, deuterated solvent; CDCl ₃ ), δ ppm; 5.52 (m, 1H), 5.76 (m, 1H), 7.36 (Ar—H, 3H) , 7.63 (Ar-H, 2H).

[Comparative Example 1]
In a fluororesin-lined reaction vessel, 220 mg (11.0 mmol, 19.9 eq) of hydrogen fluoride and 0.300 mL (0.543 L / mol) of methylene chloride were added, cooled to 5 ° C., and the following formula:

100 mg (0.552 mmol, 1.00 eq) of 1-bromo-4-ethynylbenzene represented by the formula (2 phase system) was added, and the mixture was vigorously stirred at the same temperature for 2 hours. The reaction-terminated liquid is diluted with 5 mL of chloroform, washed with 5 mL of water, washed with 5 mL of 5% aqueous potassium carbonate solution, and the recovered organic layer is subjected to internal standard method (internal standard substance; α, α, α-trimethyl) by ¹⁹ F-NMR. Fluorotoluene), the following formula:

The amount of 1-bromo-4- (1,1-difluoroethyl) benzene represented by the formula was less than 27.6 μmol. The yield by the internal standard method was less than 5%. The conversion rate and purity were 100% and 0.6% (4-bromoacetophenone was 87.5%) from gas chromatography analysis of the recovered organic layer, respectively.

[Comparative Example 2]
Following formula:

Was added to 1.00 g (8.32 mmol, 1.00 eq) of acetophenone, and 4.37 g (20.8 mmol, 2.50 eq) of trifluoroacetic anhydride was added and stirred at 35 ° C. for 4 days. From the gas chromatographic analysis of the reaction finished liquid, the conversion rate and the following formula:

An acyl having _two CF ₃ CO ₂ groups represented by the formula:

The purity of the trifluoroacetic acid enol ester represented by the formula was 52%, 15.2%, and 16.4%, respectively. A post-treatment operation similar to that in Example 1 of JP-A-1-199922 was performed on the reaction end solution, and a similar fluorination step was performed.

The α, α-difluoroethylbenzene represented by the formula was contained less than 0.832 mmol. The yield by the internal standard method was less than 10%.

  Separately, the same asylation step and fluorination step were performed using 4-bromoacetophenone as a raw material substrate, and the yield of the corresponding 1-bromo-4- (1,1-difluoroethyl) benzene was about 15%. there were.

  On the other hand, cyclohexanone gave 1,1-difluorocyclohexane in a yield of 87%.

[Comparative Example 3]
A fluororesin-lined reaction vessel is immersed in a −5 ° C. refrigerant bath, and 3.45 g (172 mmol, 20.0 eq) of hydrogen fluoride, the following formula:

2.00 g (8.61 mmol, 1.00 eq) of a fluorine-containing sulfuric acid enol ester represented by the following, 0.200 mL (0.0232 L / mol) of chloroform and 196 mg (1.72 mmol, 0.200 eq) of trifluoroacetic acid were added, The mixture was stirred at -5 ° C for 3 hours and 15 minutes. The reaction-terminated liquid was diluted with 10 mL of chloroform, washed twice with 10 mL and 5 mL of water, washed with 10 mL of 10% aqueous potassium carbonate solution, washed with 5 mL of 10% brine, and the recovered organic layer was an internal standard by ¹⁹ F-NMR. When quantified by the method (internal standard substance: hexafluorobenzene), the following formula:

6.59 mmol of the geminal difluoro compound represented by The yield according to the internal standard method was 77%. ¹⁹ F-NMR is shown below.

¹⁹ F-NMR (reference material; C ₆ F ₆ , heavy solvent; CDCl ₃ ), δ ppm; 71.45 (m, 2F).

[Comparative Example 4]
The reaction vessel of the fluororesin lining is immersed in a −5 ° C. refrigerant bath, 1.56 g (78.0 mmol, 19.7 eq) of hydrogen fluoride, the following formula:

1.00 g (3.96 mmol, 1.00 eq) of fluorine-containing sulfuric acid enol ester represented by the following formula: 0.100 mL (0.0253 L / mol) of chloroform and 90.3 mg (0.792 mmol, 0.200 eq) of trifluoroacetic acid. In addition, the mixture was stirred at −5 ° C. for 3 hours. The reaction-terminated liquid was diluted with 5 mL of chloroform, washed twice with 5 mL and 2.5 mL of water, washed with 5 mL of 10% aqueous potassium carbonate solution, and washed with 2.5 mL of 10% brine, and the recovered organic layer was replaced with ¹⁹ F- When quantified by the internal standard method by NMR (internal standard substance; hexafluorobenzene), the following formula:

The geminal difluoro compound represented by was contained less than 0.396 mmol. The yield by the internal standard method was less than 10%.
[Comparative Example 5]

1.84 g (92.0 mmol, 20.4 eq) of hydrogen fluoride was added to a fluororesin-lined reaction vessel, cooled to −5 ° C., and the following formula:

1.06 g of 1-chloro-1-aromatic ring-substituted ethene represented by the formula (gas chromatography purity 74.6%, α, α-dichloroaromatic compound 21.2%, total 4.52 mmol, 1.00 eq) In addition (two-phase system), the mixture was stirred at the same temperature for 30 minutes and at 5 ° C for 1 hour. A post-treatment operation similar to that in Example 1 was performed, and the conversion rate and the following formula were determined by gas chromatography analysis of the recovered organic layer:

The purity of the α, α-difluoroaromatic compound represented by the formulas was 100% and less than 10.0%, respectively (6-bromoacetophenone was 63.5%).

  The α, α-difluoroaromatic compound targeted in the present invention is important as a pharmaceutical and agrochemical intermediate.

Claims (4)

General formula [ 3 ]:

Wherein, Ar ² is to display the aromatic hydrocarbon group or substituted aromatic hydrocarbon group. ]
And a step of reacting a 1-chloro-1-aromatic ring-substituted ethene represented by general formula (I) with a salt or complex composed of pyridine and hydrogen fluoride, or a salt or complex composed of triethylamine and hydrogen fluoride. [ 4 ]:

[Wherein Ar ² is the same as the general formula [ 3 ]. ]
The manufacturing method of the (alpha), (alpha)-difluoro aromatic compound shown by these. The method according to claim 1, wherein the salt or complex composed of an organic base and hydrogen fluoride is a salt or complex composed of pyridine and hydrogen fluoride. Ar of general formula [3] ² The method according to claim 1 or 2, wherein the substituted aromatic hydrocarbon group in has a halogen atom in any number and in any combination on any carbon atom of the substituted aromatic hydrocarbon group. The method according to any one of claims 1 to 3, wherein a halogen-based or ether-based reaction solvent is used.