Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Patent
1992-02-24
1992-12-15
Ford, John M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
C07D25128
Patent
active
051718561
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an improved process for the preparation of 2,4,6-trifluoro-1,3,5-triazine (cyanuric fluoride) in high purity and high yield by reaction of cyanuric chloride with an alkali metal fluoride in a dipolar aprotic solvent at relatively low temperatures. Cyanuric fluoride is a useful starting compound for agrochemicals, pharmaceuticals, dyes, photochemicals and optical brighteners.
PRIOR ART
It is known that cyanuric fluoride can be prepared by fluorination of cyanuric chloride with sodium fluoride in a dipolar aprotic solvent (Tullock, Coffman, J. org. Chem. 25, 2016 (1960)). In this process, cyanuric chloride is added to a suspension of sodium fluoride in sulfolane and the reaction mixture is heated from 45.degree. C. to 248.degree. C. The cyanuric fluoride formed is distilled off from the reaction mixture. The yield is 74% of theory. According to DE-OS 3,727,973, cyanuric fluoride is obtained by the same method. 75.degree. C. is already mentioned here as the lowest temperature for the reaction. According to Example A and lines 11 to 15, column 2 (description), the reaction mixture must finally be heated to 220.degree. C. in order to obtain cyanuric fluoride approximately quantitatively, i.e. in 87% yield. By-products mentioned are, inter alia, partially fluorinated substances, such as 6-chloro-2,4-difluorotriazine, which superficially indicates an incomplete reaction.
A slightly altered process is described in EP-0,035,704. Cyanuric chloride or mixed chlorinated/fluorinated 1,3,5-triazines, if desired in the form of a melt or dissolved in a dipolar aprotic solvent, are metered into a suspension of sodium fluoride in a dipolar aprotic solvent, in particular sulfolane, which is heated to 120.degree. C. to 220.degree. C., in particular 140.degree. to 160.degree. C. Cyanuric fluoride is obtained from the reaction mixture by distillation, the distillation even having to be carried out in vacuo in the presence of a component of intermediate boiling point in order to be able to remove the cyanuric fluoride formed completely.
In these known processes, the reaction mixture is kept above about 120.degree. C. over a relatively large part of the reaction time (Tullock, Coffman) or at temperatures above 120.degree. C., preferably at 140.degree. C.-160.degree. C., over the entire reaction time (EP-0,035,704). Even with the addition of phase transfer catalysts, such as, for example, 18-crown-6 (CS) 247,969, JP 61,047,465), temperatures of about 140.degree.-400.degree. C. are necessary in order to obtain cyanuric fluoride from cyanuric chloride using alkali metal fluorides in a dipolar aprotic solvent.
These processes thus confirm the prejudice prevailing up to now that the preparation of cyanuric fluoride (2,4,6-trifluoro-1,3,5-triazine) from cyanuric chloride and potassium fluoride requires very high reaction temperatures (HOUBEN-WEYL, volume V/3, 1962).
AIM OF THE INVENTION
An improved process for the preparation of 2,4,6-trifluoro-1,3,5-triazine (cyanuric fluoride) in high purity and high yield at relatively low temperatures.
ESSENCE OF THE INVENTION
According to the invention, it has surprisingly been found that 2,4,6-trifluoro-1,3,5-triazine (cyanuric fluoride) can advantageously be prepared in high purity and virtually quantitative yield at relatively low temperatures by reacting 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) or mixed chlorinated/fluorinated 1,3,5-triazines with at least the equivalent amount of sodium fluoride, potassium fluoride or cesium fluoride or any suitable mixture of these alkali metal fluorides in a dipolar aprotic solvent at a temperature from about 30.degree. C. to about 110.degree. C., preferably about 50.degree. C. to about 105.degree. C., in particular about 70.degree. C. to about 100.degree. C.
In particular, a process can be used in which cyanuric chloride and/or mixed chlorinated/fluorinated 1,3,5-triazines, the alkali metal fluoride or mixtures of the alkali metal fluorides and the dipolar aprotic solvent are mixed and all
REFERENCES:
patent: 4329458 (1982-05-01), Klauke et al.
C. W. Tullock et al., J. Org. Chem. 25, 2016-2019 (1960).
Ford John M.
Hoechst Aktiengesellschaft
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