HU206494B - Process for producing 3-fluoro-4-amino-phenol - Google Patents

Abstract

In a novel process according to the invention, 3-fluoro-4-aminophenol of formula (1) is prepared by reacting o-fluoronitrobenzene with a metal metal in a dilute sulfuric acid solution. F Al dilute H2SO4 r (i) CQ EN 206 494 Scope of the description: 4 pages (including 1 sheet)

Description

The novel process of the present invention provides 3-fluoro-4-aminophenol. 3-Fluoro-4-aminophenol is an important intermediate in the production of insecticides.

J. Chem. Soc., 1964, 471-479, the 3-fluoro-4-aminophenol is prepared by reacting the diazonium salt of sulfanyl acid with m-fluorophenol and reducing the resulting diazo compound with sodium bisulfite. cleaves.

A disadvantage of the known process is that m-fluorophenol is an expensive reagent and the reaction is carried out via a difficult to treat diazo compound and that the yield of the desired compound is only 16%.

It is known that p-aminophenol can be readily prepared by reduction of p-nitrophenol. Nevertheless, the

Reduction of 3-fluoro-4-nitrophenol, in which the fluorine atom is ortho to the nitro group, does not produce the desired end product, even in the case of catalytic reduction with hydrogen gas or reduction with iron. A further disadvantage is that the starting material 3-fluoro-4-nitrophenol is difficult to obtain.

It is an object of the present invention to provide - 3-fluoro-4-aminophenol from a readily available material in a simple reaction with high productivity.

It has been our object to develop a process for reacting inexpensive and readily available o-fluoronitrobenzene with metal aluminum in the presence of dilute sulfuric acid.

The reaction is illustrated in Scheme A.

The metal aluminum used in the process according to the invention may be in any powder or particulate form, but is preferably used in powder form: The concentration of sulfuric acid used is from 1 to 50% by volume, preferably about 10% by volume.

The amount of sulfuric acid used in carrying out the reaction is Ιό mol, preferably 3.0 mol, per mole of o-fluoronitrobenzene. The amount of metal aluminum used is based on 1 mol of o-fluoronitrobenzene

1-3 mol, preferably 1.7 mol.

The above reaction for the preparation of p-aminophenol from nitrobenzene is described in Rev. Chim., 12, 649-51 (1961), however, does not disclose any reaction to a substituent on the benzene ring.

As described above, p-aminophenol can readily be prepared by reduction of p-nitrophenol, however, even this reduction of 3-fluoro-4-nitrophenol does not yield the desired amino compound.

Accordingly, it is surprising that the process of the present invention provides 3-fluoro-4-aminophenol with high yield and selectivity from o-fluoronitrobenzene.

A further advantage of the process according to the invention is that, starting from cheap and readily available o-fluoronitrobenzene, the desired end product is obtained in one step.

The 3-fluoro-4-aminophenol produced by the process of the present invention is e.g. can be converted to the benzoyl urea derivative with insecticidal activity by the process outlined in Scheme B.

The process of the present invention and further modifications of the resulting product are illustrated in detail in the following Example and Reference Examples.

Production Example 1

Preparation of 3fluoro-4-aminophenol

A reactor was charged with 2.03 g of o-fluoronitrobenzene, 0.70 g of aluminum powder, 43 ml of water and 4.4 g of concentrated sulfuric acid and stirred at an internal temperature of 90-95 ° C for 40 minutes. The reaction solution was then cooled and a 5% aqueous sodium bicarbonate solution was added until the solution was slightly alkaline. The reaction solution was then extracted with diethyl ether (3 x 100 mL). The ether layers were combined, dried and concentrated to give crude product. This crude product was chromatographed on silica gel to give 1.58 g

3-Fluoro-4-aminophenol was obtained.

M.p. 137-138 ° C.

Yield: 86%.

Reference Example 1 Preparation of p-aminophenol

3.00 g of p-nitrophenol, 0.50 g of platinum dioxide and 40 ml of ethyl acetate are charged into a reactor which is then purged with hydrogen gas with stirring. The contents of the reactor were then stirred for 4 hours at room temperature with continuous introduction of hydrogen gas. The reaction mixture was filtered and the filtrate was evaporated. 2.30 g of p-aminophenol are obtained. Yield: 98%. Melting point: 187-188 ° C.

Reference Example 2

3-Fluoro-4-nitrophenol (2.00 g), platinum dioxide (0.29 g) and ethyl acetate (25 ml) were charged to the reactor and the reactor was purged with hydrogen under constant stirring. The contents of the reactor were stirred for 3 hours at room temperature with continuous introduction of hydrogen gas. The reaction mixture was filtered and the filtrate was evaporated. A tarry material is obtained.

Reference Example 3

Preparation of -fluoro-4-ß 1,1,2,2-tetrafluoroethoxy) aniline

To a reactor was added 0.70 g of 3-fluoro-4-aminophenol, 0.06 g of potassium hydroxide and 10 ml of dimethylformamide, and the resulting solution was stirred for 20 minutes in an oil bath at 60-70 ° C. . This solution was then stirred vigorously at the same temperature for 2 hours with the introduction of a tetrafluoroethylene gas and an excess of the above phenol. The reaction solution was cooled, water added and extracted with diethyl ether (2 x 150 mL). The ether layers were combined, dried and concentrated to give crude product. This crude product was chromatographed on silica gel to give 1.00 g of 2-fluoro-4- (1,1,2,2-tetrafluoroethoxy) aniline.

Yield: 80% nfr ⁵ : 1.446

HU 206 494 B

Reference Example 4

Preparation of N-2,5-Difluoro-benzoyl-N '- [2-fluoro-4- (1,1,2,2-tetrafluoro-ethoxyphenyl) -carbamide

2-Fluoro-4- (1,1,2,2-tetrafluoro) -ethoxyaniline (0.15 g) was dissolved in toluene (5 ml) and 2,6-difluorobenzoyl (0.12 g) dissolved in toluene (3 ml) was added dropwise. -isocyanate under stirring and ice-cooling. After the addition was complete, the reaction mixture was stirred overnight at room temperature and 5 ml of n-hexane was added. The precipitated crystalline material was filtered off and dried to give 0.19 g of white crystalline N-2,6-difluorobenzoyl-N '- [2-fluoro-4- (1,1,2,2-tetrafluoroethoxy). -phenyl] karmabido was obtained.

M.p. 173-174 ° C.

Yield: 70%. 15

Reference Example 5

Effect against Spodoptera litura An emulsifiable concentrate of the compound prepared in Reference Example 3 is prepared and diluted 200,000 times with water. 2 to 2 ml of the 0.5 ppm active ingredient solution and control solution (without active ingredient) thus obtained were mixed with 13 g of artificial food suitable for Spodoptera litura. The food was then placed in 25 cm polyethylene cups. 10 larvae of Spodoptera litura in the fourth stage of development were then placed in the vessel. After six days, the living and dead individuals were examined and the percent mortality was determined.

Two repetitions were performed.

Claims (1)

PATIENT PERSONALITY Process for the preparation of 3-fluoro-4-aminophenol, comprising reacting o-fluoronitrobenzene with metal aluminum in a dilute sulfuric acid solution. o ₂ n EN 206 494 Β Int. CL ⁵ : C 07 C 215/76 Scheme A) al - * hig H ₂ S0 ^ B) Reaction Scheme Published by the National Inventory Office, Budapest Responsible for release: dr. Gabriella Szvoboda Head of Department ARCANUM Bt.-BUDAPEST