JPH0873434A - Production of n-fluoropentachloropyridinium salt - Google Patents

Abstract

PURPOSE: To safely obtain the subject compound useful as a fluorinating agent in high yield by reacting pentachloropyridine, fluorine and a Brϕnsted acid or a Lewis acid in a secondary fluoroalcohol. CONSTITUTION: This compound is expressed by the formula (X<-> is a conjugate salt of a Brϕnsted acid) and obtained by reacting pentachloropyridine, fluorine and a Brϕnsted acid (e.g. trifluoromethane sulfonic acid) or a Lewis acid (e.g. BF3 ) in a fluoroalcohol expressed by the formula: RfRf'CHOH (Rf and Rf' are each a 1-4C fluoroalkyl) (e.g. hexafluoroisopropanol) preferably in an atmosphere of inert gas such as nitrogen. The reaction has no uneasiness of corrosion of the reacting vessel, no by-product having any risk of inducing voluminal dilation with decomposition by using a neutral secondary fluoroalcohol as the solvent and further the solvent is easily recovered and easily recyclable by distillation because of a low boiling point.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an N-fluoropentachloropyridinium salt.

[0002]

PRIOR ART General formula:

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The N-fluoropentachloropyridinium salt represented by the formula (wherein X ⁻ represents a conjugated base of Bronsted acid) is a reagent for introducing a fluorine atom into an unsaturated compound such as an aromatic compound or an alkene, It is a compound useful as a so-called fluorinating agent (J. Am. Chem. So.
c., 112 (1990) 8563 and JP-A-2-231.
474))).

Heretofore, as a useful method for producing an N-fluoropentachloropyridinium salt, pentachloropyridine, fluorine (F ₂ ), Bronsted acid or Lewis acid in a lower perfluoro fatty acid such as trifluoroacetic acid or pentafluoropropionic acid has been used. A method of reacting with an acid is known (see JP-A-2-231474). However, since the lower perfluoro fatty acid used as a solvent is a strong acid, it is highly toxic and corrodes the metal reactor. Furthermore, perfluoroacyl hypofluorite (RCOOF: R represents a perfluoroalkyl group) produced by a side reaction of fluorine with a lower perfluorofatty acid easily decomposes into a gaseous perfluoroalkane and carbon dioxide according to the reaction of the following formula. (Journal of the American Chemical Society, 77 (1955) 6110): RCOOF → R-F + CO ₂

This means that an uncontrollable rapid volume expansion occurs during the reaction, and there is a risk of causing an explosion state. Therefore, it cannot be said that the conventional method using a lower perfluoro fatty acid as a solvent has a fatal defect in safety in addition to the problem of corrosion of the reaction device when it is industrially attempted.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies to solve the problems of these conventional methods for producing N-fluoropentachloropyridinium salts, and as a result, have found that the strongly acidic perfluorofatty acid is used. On the other hand, an almost neutral secondary fluoroalcohol such as hexafluoroisopropanol is an excellent solvent as it has very low corrosiveness and does not produce a by-product which may cause volume expansion due to decomposition. The present invention has been discovered and the present invention has been completed.

[0007]

In order to solve the above problems, the present invention provides a compound represented by the general formula: RfRf'CHOH (I) (wherein Rf and Rf 'are the same or different and have 1 to 1 carbon atoms).
4 represents a fluoroalkyl group. ), Pentachloropyridine and fluorine (F ₂ ) in the fluoroalcohol
And a Bronsted acid or a Lewis acid are reacted with the general formula:

[0008]

[Chemical 3]

A method for producing an N-fluoropentachloropyridinium salt represented by the formula (wherein X ⁻ represents a conjugate base of Bronsted acid) is provided.

The pentachloropyridine used in the present invention is
It is a known compound and easily available industrially.

Rf and R in fluoroalcohol (I)
f ′ is CF ₃ , C ₂ F ₅ , C ₃ F ₇ , C ₄ F ₉ , CF ₂
H, C ₂ F ₄ H and the like can be exemplified, and typical examples of the fluoroalcohol (I) are hexafluoroisopropanol,
Octafluoro-2-butanol, decafluoro-3-
Pentanol and the like, which can be easily obtained or synthesized.

Examples of Bronsted acids include trifluoromethanesulfonic acid, difluoromethanesulfonic acid, trichloromethanesulfonic acid, nonafluoromethanesulfonic acid, heptafluorooctanesulfonic acid, fluorosulfonic acid, chlorosulfonic acid, sulfuric acid, monomethyl sulfuric acid, and permethyl sulfuric acid. Bronsted acid such as chloric acid, or HBF ₄ , HBCl
₃ F, HBCl ₄ , HAlF ₄ , HAlCl ₃ F, HPF ₄ , H
PF ₆ , HPCl ₅ F, HAsF ₄ , HAsCl ₃ F, HAs
F ₆ , HAsCl ₆ , HAsCl ₅ F, HSbF ₄ , HSbF ₆ ,
A Bronsted acid of a compound of a Lewis acid such as HSbCl ₂ F ₄ , HSbCl ₅ F and HSbCl ₆ and hydrogen halide can be exemplified.

The reaction temperature in the case of using Bronsted acid can be selected from the temperature range in which the reaction mixture can maintain the liquid state, but it is -20 ° C to + 60 ° C, and further,
Temperatures in the range of -10 ° C to + 40 ° C are preferable in terms of economic efficiency and good reaction yield. In order to carry out the reaction in good yield, the amount of Bronsted acid used is 0.8 to 3 mol per 1 mol of pentachloropyridine, but it is 0.9 to 1.5 in consideration of economic efficiency. Molar is preferred.

Although the fluorine used in the present invention may be used as it is, an inert gas is used to control the vigorous reaction of the fluorine, and the volume of the inert gas is 99% to 25%.
It is preferred to use diluted fluorine gas which is Examples of the inert gas include nitrogen, helium, argon and the like. The amount of fluorine used varies depending on the method of introducing fluorine, the reaction temperature, the reaction apparatus, etc., and thus may be appropriately selected with the amount of fluorine necessary for pentachloropyridine to react with fluorine and disappear.

The Lewis acids include BF ₃ , BC
l ₃ , AlF ₃ , AlCl ₃ , PF ₃ , PF ₅ , PCl ₅ , As
_{F 3, AsCl 3, AsF 5} , AsCl 5, SbF 3, SbF 5, Sb
Examples include Cl ₂ F ₃ , SbCl ₅ , SO _{3 and the} like.
Further, these Lewis acids may be used as a complex with various ethers or nitrile compounds. In order to carry out the reaction in good yield, the amount of Lewis acid used is 0.8 to 3 mol per 1 mol of pentachloropyridine, but in consideration of economical efficiency and yield, it is 0.9 to 1 mol. 0.5 mol is preferred. In addition, fluoroalcohol (I) and fluorine used in this reaction
The usage form of (F ₂ ) is the same as in the case of the above method. The reaction temperature is the same as in the above method.

[0016]

INDUSTRIAL APPLICABILITY As described above, when an almost neutral secondary fluoroalcohol, particularly hexafluoroisopropanol, is used as a solvent, an N-fluoropentachloropyridinium salt useful as a fluorinating agent can be safely and efficiently reacted. Good, it can be manufactured, and the durability of the reactor is dramatically improved. Furthermore, since fluoroalcohols have a low boiling point, they can be easily recovered by distillation. Therefore,
Easy to reuse.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLES Example 1 20 ml of 1,1,1,3,3,3-hexafluoroisopropanol, 2.51 g (10 mmol) of pentachloropyridine and 1.50 g (10 mmol) of trifluoromethanesulfonic acid.
Fluorine in a container containing a mixture of
30 ml of a mixed gas of (F ₂ ) and nitrogen (N ₂ ) (volume ratio 1: 9)
Introduced at a flow rate of / min. The number of moles of fluorine used is 2
It was 8.5 mmol). Then, nitrogen was passed to remove the residual fluorine, the solvent was distilled off, and ethyl acetate was added. Precipitated crystals were filtered off and 3.10 g of N-fluoropentachloropyridinium trifluoromethanesulfonate
Was obtained (yield 74%). The physical properties were in agreement with those of the standard sample as shown below. Melting point: 122-123 ° C. ¹⁴ FNMR (CFCl ₃ internal standard in deuterated acetonitrile);-
48.0ppm (s, N-F) , 78.2ppm (s, CF 3) Mass spectrum (m / z); 274,272,270,268
In the practice of the (M ⁺ -OSO ₂ CF ₃₎ This reaction, abnormal reaction or explosion does not occur at all, safe, yet it was possible to obtain a good yield desired product. Since the solvent used is almost neutral, the durability of the metallic reactor part has been dramatically improved.

Example 2 20 ml of 1,1,1,3,3,3-hexafluoroisopropanol, 2.51 g (10 mmol) of pentachloropyridine and 1.08 g (10 mm) of boron trifluoride acetonitrile complex.
ol) in a container containing a mixture of fluorine (F ₂ ) and nitrogen (N ₂ ) (volume ratio 1: 9) while stirring at room temperature.
It was introduced at a flow rate of 0 ml / min. The number of moles of fluorine used was 33 mmol. Then, nitrogen was flowed to remove residual fluorine, the solvent was distilled off, ethyl acetate was added, and the precipitated crystals were filtered off to obtain 3.10 g of N-fluoropentachloropyridinium tetrafluoroborate ( Yield 9
2%). Material values were in agreement with standard samples as shown below. Melting point; 198-200 ° C. (in sealed tube) ¹⁹ FNMR (CFCl ₃ internal standard in deuterated acetonitrile); -4
7.6ppm (s, N-F) 152.6ppm (s, BF 4) Mass spectrum (m / z); 293,291,289,287
(M ⁺ -BF ₃ ) In carrying out this reaction, no abnormal reaction or explosion occurred, and the desired product could be obtained safely and in good yield. Since the solvent used is almost neutral, the durability of the metallic reactor part has been dramatically improved.

Claims (2)

[Claims] 1. A general formula: RfRf'CHOH
(I) (In the formula, Rf and Rf ′ are the same or different and have 1 to
4 represents a fluoroalkyl group. ) In the fluoroalcohol represented by the formula (1), pentachloropyridine, fluorine and Bronsted acid or Lewis acid are reacted with each other. (In the formula, X ⁻ represents a conjugate base of Bronsted acid.)
The manufacturing method of the N-fluoro pentachloro pyridinium salt shown by these. 2. The method according to claim 1, wherein the fluoroalcohol is hexafluoroisopropanol.