Process for the preparation of chlorofluronitrobenzenes and difl

Details Process for the preparation of chlorofluronitrobenzenes and difl Process for the preparation of chlorofluronitrobenzenes and difl

1992-12-22

1996-08-13

Gibson, Sharon

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

568937, 570127, 570141, 570142, 570170, 570182, 570206, C07C20512

Patent

active

055457681

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for the preparation of chlorofluoronitrobenzenes and difluoronitrobenzenes in high yields without additional purification operations by reaction of an excess of the appropriate dichloronitrobenzenes with alkali metal fluorides of a certain water content in the presence of catalysts and in the absence of a solvent.
Chlorofluoronitrobenzenes and difluoronitrobenzenes are important intermediates for the preparation of pharmaceuticals and plant protection agents.
U.S. Pat. No. 4,164,517 describes the reaction of 3,4- and 2,4-dichloronitrobenzene to give chlorofluoro- or difluoronitrobenzenes using predried potassium fluoride in sulfolane at temperatures above 200.degree. C. The yield can be increased here by increasing the proportion of sulfolane. The fact that, in the reaction of 2,4-dichloronitrobenzene without sulfolane, only 20% is converted even after a reaction time of 30 h at 240.degree. C. is thus explained.
A process for the preparation of monofluoronitrobenzenes from, in particular, monochloronitrobenzenes using finely powdered potassium fluoride in the melt at preferably 140.degree. to 150.degree. C. with the addition of tetraalkyl- or aralkylammonium salts as catalysts is described in U.S. Pat. No. 4,287,374. The reaction times here according to the examples are 17 to 28 h. The disadvantages of this process, apart from the poor space-time yield, are to be seen in the fact that the potassium fluoride preferably used has a water content of less than 0.2% by weight, which makes pretreatment of the potassium fluoride necessary.
There was therefore a considerable interest in an industrially more favorable process for the preparation of chlorofluoronitrobenzenes and difluoronitrobenzenes.
It has now surprisingly been found that chlorofluoronitrobenzenes and difluoronitrobenzenes can be prepared in high yields by heating dichloronitrobenzene to not more than 200.degree. C. in molar excess with an alkali metal fluoride having a total water content of about 0.2 to about 2.5% by weight in the presence of a quaternary ammonium and/or phosphonium salt, crown ether and/or polyethylene glycol dimethyl ether as catalyst in the absence of a solvent.
In the process according to the invention, it is particularly important that thorough mixing of the reaction suspension is ensured during the entire reaction time.
The reaction temperature can vary within a range from about 125.degree. to about 200.degree. C.; the temperatures, however, between about 140.degree. and about 190.degree. C. are expediently chosen as in this case, on the one hand, the rate of reaction is satisfactory and, on the other hand, the catalyst remains relatively stable.
Catalysts which can be used are quaternary ammonium compounds, in particular tetraalkyl(C.sub.1 to C.sub.22)-ammonium halides, tetraarylammonium halides, it being possible for the aryl radicals to be, for example, phenyl or naphthyl radicals which can be substituted by halogen atoms or branched or unbranched alkyl, nitro, cyano, amino and/or alkoxy groups, and mixed alkylarylammonium halides, such as octadecyltrimethylammonium chloride, distearyldimethylammonium chloride, tetramethylammonium chloride, tetramethylammonium bromide, hexadecyltrimethylammonium chloride; benzyltrimethylammonium bromide; quaternary phosphonium compounds, in particular tetraalkyl(C.sub.1 to C.sub.22)-phosphonium halides, tetraarylphosphonium halides, it being possible for the aryl radicals to be, for example, phenyl or naphthyl radicals which can be substituted by halogen atoms or branched or unbranched alkyl groups, nitro, cyano, amino and/or alkoxy groups, and mixed alkylarylphosphonium halides such as stearyltributylphosphonium bromide or hexadecyltriethylphosphonium bromide; crown ethers, such as 18-crown-6, polyethylene glycol dimethyl ether and combinations of these in catalytic amounts. The catalyst was employed in the process according to the invention in amounts of about 2 to about 10% by weight, preferably of about 3 to about 5% by weight, relative to d

REFERENCES:
patent: 3064058 (1962-11-01), Duesel
patent: 3240824 (1966-03-01), Boudakian et al.
patent: 3992432 (1976-11-01), Napier et al.
patent: 4140719 (1979-02-01), Tull et al.
patent: 4164517 (1979-08-01), Fuller
patent: 4287374 (1981-09-01), North
patent: 4642239 (1987-02-01), Cantrell
patent: 4642399 (1987-02-01), White
patent: 4780559 (1988-10-01), Brown et al.
patent: 4849552 (1989-07-01), Cantrell
patent: 4978769 (1990-12-01), Kysela et al.
patent: 5081288 (1992-01-01), Blank et al.
patent: 5463148 (1995-10-01), Papenfuhs et al.
patent: 5476976 (1995-12-01), Papenfuhs et al.
Chem. Abs. 111:57247a Jan. 17, 1989.
Chen, W., Chem. Abs. 113:15 200g (1990).

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