KR100609033B1 - Processes for fluorinating aromatic ring compounds - Google Patents

Abstract

A method of increasing the fluorine content of a benzene ring or a pyridine ring optionally substituted by one to three inert substituents is provided. The process comprises (a) contacting a metal fluoride composition comprising cupric fluoride (CuF ₂ ) with an aromatic ring at a temperature of at least 250 ° C. sufficient to transfer F from cupric fluoride to the aromatic ring. Chemically reduced; (b) oxidizing the reduced metal fluoride composition of (a) in the presence of HF to regenerate a metal fluoride composition comprising cupric fluoride; (c) using the recycled metal fluoride composition of (b) in (a).

Aromatic ring compounds, fluorinated, cupric fluoride

Description

Fluorination of aromatic ring compounds {PROCESSES FOR FLUORINATING AROMATIC RING COMPOUNDS}

The present invention relates to a method for increasing the content of benzene or pyridine using copper fluoride.

Fluorobenzene, a pesticide intermediate, is typically prepared by the reaction of aniline with sodium nitrite in the presence of hydrofluoric acid. Diazonium salt intermediates are formed during the process, which increases manufacturing costs because of their instability. US Pat. No. 4,394,527 discloses a method for monofluorinating a benzene nucleus comprising reacting a benzene compound in a liquid phase with silver difluoride which is reduced to argentous fluoride during the reaction.

There is still a need for an efficient commercial production process using lower cost materials using fluorobenzene or, more generally, fluorinated compounds with benzene nuclei.

A method of increasing the fluorine content of an aromatic ring selected from the group consisting of a benzene ring, a pyridine ring, a benzene ring substituted by one to three inert substituents and a pyridine ring substituted by one to three inert substituents is provided. The method comprises the steps of (a) contacting a metal fluoride composition comprising cupric fluoride (CuF ₂ ) with an aromatic ring at a temperature of at least 250 ° C. sufficient to transfer F from cupric fluoride to the aromatic ring, thereby providing a metal fluoride composition Chemically reducing; (b) oxidizing the reduced metal fluoride composition of (a) in the presence of HF to regenerate the metal fluoride composition comprising cupric fluoride; (c) using the recycled metal fluoride composition of (b) in (a).

In one embodiment of the invention, the regenerating reagent, cupric fluoride (CuF ₂ ), is reacted with unsubstituted benzene to produce fluorobenzene. Benzene may be excessive relative to cupric fluoride under reaction conditions until an economically insufficient amount of fluorobenzene is regenerated. This reaction is schematically shown in the following scheme.

C ₆ H ₆ + CuF ₂ → C ₆ H ₅ F + HF + Cu ⁰ (metal)

As shown in Scheme 2 below, fluoric acid can be used to regenerate cupric fluoride from the copper metal.

Cu ^O (metal) + 2HF + 1/20 ₂ → CuF ₂ + H ₂ 0

The copper metal typically reacts with HF and oxygen at temperatures between about 250 ° C. and about 700 ° C., preferably between about 375 ° C. and about 425 ° C.                 

Pure oxygen, air or oxygen diluted with an inert gas such as nitrogen or argon can be used with HF. Normally, the regeneration reaction is carried out for about 1 hour to about 24 hours at atmospheric pressure or slightly above atmospheric pressure. One of the reaction variables such as time, temperature and oxygen flow rate can be stabilized relative to the other to optimize the copper reaction to copper fluoride. For example, as the air flow rate and temperature increase, the reaction time decreases. The regenerated metal fluoride composition can then be regenerated for contact with the added benzene.

In another embodiment of the invention, a mixture of benzene, HF and oxygen is contacted with a metal fluoride composition comprising cupric fluoride at reaction conditions. The overall reaction is schematically shown in Scheme 3 below.

C ₆ H ₆ + HF + _1/2 0 ₂ → C ₆ H ₅ F + H ₂ 0

This embodiment may be considered at least in part to regenerate the metal fluoride composition itself.

Contact of cupric fluoride (CuF 2), HF and oxygen with benzene in the vapor phase is carried out at a temperature of about 250 ° C. or higher. The reaction pressure may be subatmospheric, atmospheric or superatmospheric; Generally near atmospheric pressure is preferred.

The contact time is typically about 1 to about 120 seconds (eg about 5 to 60 seconds).

The reaction can also be carried out in the presence of an inert gas such as nitrogen and argon which are stable under the reaction conditions.

Unreacted benzene can be recycled to the reactor for the production of further fluorobenzene. Fluorobenzene can be regenerated from the reaction product and unreacted benzene by conventional procedures such as distillation.

Unsupported cupric fluoride can be used as the metal fluoride composition. Supported cupric fluoride may also be used. Suitable carriers include carriers selected from the group consisting of fluorinated alumina, fluorinated magnesia, fluorinated calcia and oxidatively stable carbon.

Fluorinated alumina means a composition comprising alumina, oxygen and fluorine. The fluorine content of the fluorinated alumina can vary in various ranges from about 0.001% to about 67.9% by weight. Fluorinated magnesia means a composition comprising magnesium, oxygen and fluorine. The fluorine content of the fluorinated magnesia can vary in various ranges from about 0.001% to about 61.0% by weight. Fluorinated calcia means a composition comprising calcium, oxygen and fluorine. The fluorine content of the fluorinated calcia can vary in various ranges from about 0.001% to about 48.7% by weight.

Oxidatively stable carbon is described in WO 97/30932. Particularly preferred carbons include three-dimensional matrix porous carbonaceous materials. Examples are described in US Pat. No. 4,978,649, which is incorporated herein by reference in its entirety. Introducing a gaseous or vapor phase carbon-containing compound (eg hydrocarbon) into a large amount of carbonaceous material (eg carbon black); The carbon-containing compound is decomposed and deposited on the surface of the granules; Of note is the three-dimensional metric yarn carbonaceous material obtained by treating the obtained material with an active gas comprising steam to provide a porous carbonaceous material. Thus, a carbon-carbon composite material is formed.

Although described above for the fluorination of benzene, the procedure may also be used to fluorine benzene or pyridine partially substituted by pyridine or an inert substituent (eg a substituent that is inert under fluorination conditions). U.S. Patent 5,756,834 refers to representative substituents (except chlorine) that are considered inert under fluorination conditions.

Examples of substituents include F, CF ₃ , COOH, COOR, CONH ₂ , CONR ¹ R ² , CN, CHO, N0 ₂ , NH ₂ , OCH ₃ , OCF ₃ , OCCl ₃ , OH and CC1 ₃ , wherein R, R ¹ and R ² are independently selected from C ₁ to C ₆ linear or branched alkyl groups. Examples of substituted benzenes suitable for fluorination are fluorobenzene and trifluoromethylbenzene. Examples of substituted pyridines suitable for fluorination are fluoropyridine and trifluoromethylpyridine.

The reaction zones and their associated feed lines, outlet lines and associated units shall be made of materials which are resistant to hydrofluoric acid.                 

Typical materials well known in the fluorination art are stainless steels, in particular austenitic type, well-known high nickel alloys such as Monel ^R nickel-copper alloys, Hastelloy ^R nickel-based alloys, and Inconel ^R nickel- Chromium alloys, and copper-plated steels. Silicon carbide is also suitable as reactor material.

Those skilled in the art can, of course, utilize the present invention to the widest scope in accordance with the present disclosure. The following embodiments are construed for illustrative purposes and are in no way to be construed as limiting the present disclosure.

Example 1

Preparation of Fluorobenzene

Inconel ^R nickel alloy tube reactor was charged with cupric fluoride (CuF ₂ , 5 g). The catalyst was heated to reaction temperature under nitrogen flow. The nitrogen flow rate was adjusted to 20 cc / min, then benzene was passed through the evaporator on the catalyst at a flow rate of 2 mL / hour. The reaction product was analyzed using Hewlett Packard 6890 Gas Chromatograph / 5973 Mass Spectrometer. All analyzes are reported in area% and are shown in Table 1 below.

The conversion decreased with time by the production of copper metal. Microscopic examination of the partially required CuF ₂ showed that a copper metal was formed on the particle surface.

T (℃)% C ₆ H ₅ F     450 6.3 475 9.4 550 15

Example 2

In this example, CuF ₂ was reacted with benzene under the same conditions as in Example 1 to form fluorobenzene. At the end of the reaction, all CuF ₂ was converted to copper metal. The copper metal thus formed was left in the reactor and treated with anhydrous HF and O ₂ at 400 ° C. for 6 hours. X-ray analysis of the product showed that CuF ₂ was formed. Regenerated CuF ₂ was again reacted with benzene to form fluorobenzene. For the same flow of N ₂ / benzene through the reactor, it can be seen that the conversion of fluorobenzene at 550 ° C. for a single-pass is about 30%, which is almost twice as much as before. .

Claims (1)

(a) chemically reducing the metal fluoride composition by contacting the metal fluoride composition comprising cupric fluoride (CuF ₂ ) with an aromatic ring at a temperature of at least 250 ° C. sufficient to transfer F from the cupric fluoride to the aromatic ring. To; (b) oxidizing the reduced metal fluoride composition of (a) in the presence of HF to regenerate a metal fluoride composition comprising cupric fluoride; (c) a benzene ring, a pyridine ring, a benzene ring substituted by one to three inert substituents and one to three inert substituents, comprising using the recycled metal fluoride composition of (b) in (a) A method of increasing the fluorine content of an aromatic ring selected from the group consisting of substituted pyridine rings.