PL153722B1 - Method for manufacturing 3-fluoro-4-aminephenol - Google Patents

Description

RZECZPOSPOLITA PATENT DESCRIPTION 153 722

POLAND

OFFICE

PATENT

RP

Additional patent to patent no. Applied for: 88 02 04 (P. 278058)

Priority: 87 08 27 Japan

Application announced: 89 07 24

Patent description published: 1992 03 31

Int. A. 'CI7C215 / 76

Invention Creators: Noriyasu Sakamoto, Tatsuya Mori, Tadashi Ohsumi, Toshibiko Yano, Izumi Fujimoto, Yoji Takada

Patent holder: Sumitomo Chemical Company Limited,

Osaka (Japan)

Method for the production of 3-fluoro-4-aminophenol

The subject of the invention is a process for the preparation of 3-fluoro-4-aminophenol, used e.g. for the preparation of a new 2-fluoro-4 / 1,2,2-tetrafluoroethoxyaniline, from which the new N-2,6-difluorobenzoyl Insecticidal N '- [2-fluoro-4- (1,1,2,2, -tetrafluoroethoxy / phenyl] urea.

According to the hitherto known method described in J. Chem. Soc., 1964, 471-479,3-fluoro-4-aminophenol is prepared by reacting a diazonium salt of sulfanilic acid with m-fluorophenol and subjecting the resulting diazotium compound to reductive cleavage with sodium bisulfite. The disadvantage of this process, however, is that the m-nitrophenol reactant is expensive, the process produces a dangerous diazo intermediate, and the yield is only 16%, so it is not always considered satisfactory.

Due to the fact that usually p-aminophenol can be easily obtained by reducing p-nitrophenol, it was also possible to prepare 3-fluoro-4-aminophenol by reduction of the nitro group in 3-fluoro-4-nitrophenol. However, from 3-fluoro-4-nitrophenol which has a fluorine atom ortho to the nitro group, 3-fluoro-4-aminophenol cannot be obtained even by catalytic reduction with hydrogen or reduction with iron.

The aim of the invention was to develop a new process for the production of 3-fluoro-4-aminophenol, advantageous on an industrial scale.

As a result of intensive research to develop a better method for the preparation of this compound, it has surprisingly been found that 3-fluoro-4-aminophenol can be easily prepared from fluoronitrobenzene with high yield and high stereospecificity.

The process of the invention for the preparation of the 3-fluoro-4-aminophenol of the formula I consists in reacting the o-fluoronitrobenzene of the formula II with aluminum metal in dilute sulfuric acid.

The metallic aluminum used in this process may be in the form of a powder or chips, but is preferably a powder. The concentration of sulfuric acid is 1-50%, preferably about 10%, and the reaction temperature is 50-100 ° C, preferably 90-95 ° C. Sulfuric acid is used in an amount of 1-5 moles, especially about 3.0 moles, per 1 mole of o-fluoronitrobenzene, and metal aluminum in an amount of 1-3 moles, preferably about 1.7 moles, per 1 mole of o-fluoronitrobenzene.

By the process of the invention, using cheap and readily available o-fluoronitrobenzene, 3-fluoro-4-aminophenol can be cheaply produced in high yield, which is confirmed by the example below, in which an 86% yield was achieved.

The following example illustrates the invention.

Example: 2.03 g of o-fluoronitrobenzene, 0.70 g of powdered aluminum, 43 ml of rod and 4.4 g of concentrated sulfuric acid are placed in a reactor and stirred at 90-95 ° C for 40 minutes and then cooled. and 5% aqueous sodium bicarbonate solution is added so as to obtain a slightly alkaline solution. This solution is then extracted with 3 portions of 100 ml of diethyl ether, the ether layers are combined, dried and evaporated to give the crude product. The product was chromatographed on silica gel, yielding 1.58 g (86% of theory)

3-fluoro-4-aminophenol, m.p. 137-138 ° C.

Claims (1)

Patent claim A method for the preparation of 3-fluoro-4-aminophenol based on the reaction of o-fluoronitrobenzene with aluminum metal in dilute sulfuric acid. Formula 1 Pattern Department of Publishing of the UP RP. Circulation 100 copies Price: PLN 3,000