Process for preparing N,N'-difluorodiazoniabicycloalkane salt, i

Details Process for preparing N,N'-difluorodiazoniabicycloalkane salt, i Process for preparing N,N'-difluorodiazoniabicycloalkane salt, i

1997-05-15

1999-04-06

Berch, Mark L.

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

Organic compounds

Nitrogen attached directly or indirectly to the purine ring...

540472, 540556, C07D48708, C07B 3900

Patent

active

058920358

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/JP96/02183, filed Aug. 2, 1996.


FIELD OF THE INVENTION

The present invention relates to a process for preparing a N,N'-difluorodiazoniabicycloalkane salt, an intermediate useful for synthesizing such the salt, a product and use of the product.
The N,N'-difluorodiazoniabicycloalkane salts are useful as an electrophilic fluorinating agent for organic compounds (see U.S. Pat. No. 5,367,071, EP-A-0 657 457 and JP-A-7-233167).


PRIOR ART

The following processes have been developed for the preparation of the N,N'-difluorodiazoniabicycloalkane salts: (F.sub.2) in the presence of an alkali metal salt (LiOSO.sub.2 CF.sub.3) (see U.S. Pat. No. 5,367,071); Lewis acid (BF.sub.3, PF.sub.5 or SO.sub.3), and then fluorinated with F.sub.2 (see EP-A-0 657 457, Examples 3, 4 and 5); acid (BF.sub.3), followed by fluorination with F.sub.2 in the presence of an alkali metal salt (NaBF.sub.4) and a monofluorinated intermediate is obtained. Then, this intermediate is treated with 100% F.sub.2 in a sealed reactor under reduced pressure (20 mmHg) (see EP-A-0 657 457, Examples 1 and 2). SiOSO.sub.2 CF.sub.3), followed by fluorination with F.sub.2 (see EP-A-0 657 457, Example 6). perfluorobutyl chloride in the presence of NaBF.sub.4 and 1-perfluorobutyl-1,4-diazoniabicycloalkane-trifluoroborane tetrafluoroborate is obtained. Then, this tetrafluoroborate is fluorinated with F.sub.2 in the presence of NaBF.sub.4 (see EP-A-0 657 457, Example 7).
However, these recently developed processes are not industrially advantageous processes since they have the following material drawbacks:
In the process (1), the product is obtained as a mixture with the unreacted raw materials, and a metal fluoride which is another product of the reaction induces the decomposition of the desired product. Therefore, it is difficult to isolate the desired product in the pure form. Furthermore, it is difficult to remove the insoluble metal salt from the product having the low solubility.
In the process (2), a large amount of the solvent is necessary, for example, 25 ml of CH.sub.3 CN per 1 mmol of the diazabicycloalkane, in particular when a N,N'-difluorodiazoniabicycloalkane bis(tetrafluoroborate) which is a useful fluorinating agent is prepared. The yield of the product is low. Furthermore, the product is obtained as a mixture of the raw material, its monofluoride and the desired product and the obtained mixture is a hygroscopic solid and decomposes through moisture absorption. Therefore, the purification of the product is impossible.
The process (3) is highly dangerous since fluorination is carried out in a sealed reactor under reduced pressure (F.sub.2 pressure of 20 mmHg) with contacting extremely dangerous 100% F.sub.2 gas, which may ignite and explode when it comes in contact with the organic solvent around atmospheric pressure to increase the yield, to the reaction solution in the organic solvent.
The process (4) uses the expensive trialkylsilyl ester, and is also dangerous since a large amount of volatile trialkylsilyl fluoride which is generated as a by-product reacts with F.sub.2 vigorously and may explode.
The process (5) must use the expensive perfluoroalkanoyl fluoride, and requires a large amount of the solvent like the process (2). The yield is low. Furthermore, the product after post-treatment is a mixture of the monofluoride and the desired product in a ratio of 7:10, and therefore, the purification of the product is difficult.


SUMMARY OF THE INVENTION

As the result of diligent studies for solving the above problems, a novel process has been found which can prepare a desired product of high purity by fluorinating a diazabicycloalkane in the presence of a Br.o slashed.nsted acid, and if necessary treating the product with an acid and the like, and the present invention has been completed.
That is, the objects of the present invention are to solve the above described problems, and to provide a process for easily preparing a N,N'-difluorodiazoniabicycloalkane salt of high purity, which is a useful fluorinati

REFERENCES:
patent: 5367071 (1994-11-01), Syvret
patent: 5459267 (1995-10-01), Ross
Banks, JCS Chem Comm 1992, 595.
Stavber, Tet. Letters 35, 1105 (1994).
Umemoto, B. C. S. J. 64, 1081 (1991).

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