Process for preparing bis(fluoroaryl)boron derivatives

Details Process for preparing bis(fluoroaryl)boron derivatives Process for preparing bis(fluoroaryl)boron derivatives

2002-09-09

2004-11-02

Davis, Brian (Department: 1621)

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

Organic compounds

Heavy metal containing

C568S001000, C568S006000

Reexamination Certificate

active

06812360

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method for producing a bis(fluoroaryl)borane derivative such as a bis(pentafluorophenyl)borinic acid, which is useful as a polymerization catalyst, a polymerization co-catalyst, a catalyst for photopolymerization of silicone, an intermediate thereof, and an intermediate of a medicine or an agricultural chemical, for example.
BACKGROUND ART
Bis(fluoroaryl)borane derivatives such as bis(pentafluorophenyl)borinic acid, are compounds useful as polymerization catalysts, polymerization co-catalysts, catalysts for photopolymerization of silicone, intermediates thereof, and intermediates of medicines or agricultural chemicals, for example.
For instance, as a manufacturing method of bis(pentafluorophenyl)borinic acid, J. Chem. Soc (1965) 3933-3939 discloses a method in which water is added to bis (pentafluorophenyl) chloro borane in acetone at a temperature of −20° C., then the acetone solution is concentrated, so that the bis(pentafluorophenyl)borinic acid is sublimated for purification, so as to be isolated. Furthermore, bis(pentafluorophenyl) chloro borane, which is a precursor of bis(pentafluorophenyl)borinic acid, is synthesized by reacting bis(pentafluorophenyl) dimethyl tin with boron trichloride. However, it is difficult to purify bis (pentafluorophenyl) chloro borane, because dimethyltin dichloride, which is a byproduct of the reaction, is sublimated when bis (pentafluorophenyl) chloro borane is isolated by distillation.
Moreover, J. Molecular Catalysis A: Chemical 144 (1999) 137-150 and WO 0037376 (2000) disclose that bis(pentafluorophenyl)borinic acid is prepared by heating tris (pentafluorophenyl)borane hydrate.
However, the method disclosed in the above-mentioned J. Molecular Catalysis A: Chemical 144 (1999) 137-150 discloses only how to manufacture bis(pentafluorophenyl)borinic acid, and fails to recite how to isolate bis(pentafluorophenyl)borinic acid from a reaction mixture, even though easy isolation and purification of the bis(fluoroaryl)borane derivative are necessary for industrial application of the bis(fluoroaryl)borane derivative as a catalyst or the like.
J. Molecular Catalysis A: Chemical 144 (1999) 137-150 recites only that it was confirmed by
19
F-NMR that bis(pentafluorophenyl)borinic acid was prepared by adding water to a toluene-d8 solution of tris(pentafluorophenyl)borane so as to prepare tris(pentafluorophenyl)borane hydrate, then heating the solution of tris(pentafluorophenyl)borane hydrate.
Moreover, WO 0037476 (2000) discloses preparation of bis(pentafluorophenyl)borinic acid by heating tris (pentafluorophenyl)borane hydrate, and an isolation method of bis(pentafluorophenyl)borinic acid. Specifically, a toluene solution of tris(pentafluorophenyl)borane is heated up to 100° C. Then, to the solution, a toluene solution containing water of 2.5 molar equivalent is dropped so that reaction is carried out at 100° C. After the reaction, the solvent is concentrated in vacuo to dryness so as to isolate bis(pentafluorophenyl)borinic acid. However, it is recited that the bis(pentafluorophenyl)borinic acid obtained by this method contained boroxine by 5% as impurities. In short, this method has such a problem that the isolated bis(pentafluorophenyl)borinic acid has a low purity.
Moreover, that patent also discloses a method in which aluminum sulfate 18 hydrate is used instead of water. Specifically, aluminum sulfate 18 hydrate containing water of 1.77 molar equivalent vs. tris(pentafluorophenyl)borane is added to a toluene solution of tris(pentafluorophenyl)borane. After the solution is refluxed, insoluble aluminum sulfate is separated from the reaction mixture. A solvent of the filtrate is removed in vacuo. Toluene is added to the thus obtained residues. After stirring, the insoluble material is filtered through a G4 sintered-glass so as to be separated. The solvent of the filtrate is again removed in vacuo. Heptane is added to the residues. The solution is stirred and filtered so that a cake is obtained. Finally, the thus obtained cake is washed with heptane, and dried in vacuo so as to isolate bis(pentafluorophenyl)borinic acid. However, this method has such a problem that it is necessary to remove the byproduct aluminum sulfate and its process is so complicated.
Therefore, for industrial application of a bis(fluoroaryl) borane derivative, such as bis(pentafluorophenyl)borinic acid, as a catalyst or the like, there is a desire for a method by which the bis (fluoroaryl)borane derivative is easily isolated from a reaction mixture, and purified. Thus, the present invention, which is contrived in view of the foregoing problems, has an object of providing a method by which a bis(fluoroaryl)borane derivative can be produced, isolated, and purified with ease and at a low cost.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.
DISCLOSURE OF INVENTION
The inventor of the present invention, in order to attain the above-mentioned object, carried out an intensive study on a method for producing a bis(fluoroaryl)borane derivative such as bis(pentafluorophenyl)borinic acid. As a result, a molar ratio between tris(fluoroaryl)borane and a compound was studied, the tris(fluoroaryl)borane being represented by General Formula (1):
(where each of R
1
, R
2
, R
3
, R
4
, and R
5
independently represents one of a hydrogen atom, a fluorine atom, a hydrocarbon group, and an alkoxy group, at least one of R
1
, R
2
, R
3
, R
4
, and R
5
representing the fluorine atom), the compound being represented by General Formula (2):
R
0
—MR
6
(R
7
)
n
  (2)
(where each of R
0
, R
6
, and R
7
independently represents one of a hydrogen atom and a hydrocarbon group, M represents an atom belonging to Group 15 or Group 16, and n represents 0 or 1). As a result, it was found that reaction rate was extremely decreased as the molar ratio was increased. Further, it was found that selectivity coefficient of the bis(fluoroaryl)borane derivative, which is a target compound, is decreased as the molar ratio is increased, the bis(fluoroaryl)borane derivative being represented by General Formula (3):
(where each of R
1
, R
2
, R
3
, R
4
, and R
5
independently represents one of a hydrogen atom, a fluorine atom, a hydrocarbon group, and an alkoxy group, at least one of R
1
, R
2
, R3, R
4
, and R
5
representing the fluorine atom, and each of R
6
and R
7
independently represents one of a hydrogen atom and a hydrocarbon group, M represents an atom belonging to Group 15 or Group 16, and n represents 0 or 1), so that an optimal molar ratio between General Formulas (1) and (2) was found. Specifically, it was found that a bis (fluoroaryl)borane derivative having a high purity can be easily produced by having a molar ratio of 1:0.9 to 1:1.1 between the General Formulas (1) and (2). It was found that a hydrocarbon solvent is preferable as a reaction solvent, and that the bis(fluoroaryl) borane derivative can be isolated by concentrating a reaction mixture obtained by the reaction, more preferably by filtering the thus concentrated reaction mixture.
Specifically, in order to attain the above-mentioned object, a method of the present invention for producing a bis(fluoroaryl)borane derivative represented by General Formula (3):
(where each of R
1
, R
2
, R
3
, R
4
, and R
5
independently represents one of a hydrogen atom, a fluorine atom, a hydrocarbon group, and an alkoxy group, at least one of R
1
, R
2
, R
3
, R
4
, and R
5
representing the fluorine atom, and each of R
6
and R
7
independently represents one of a hydrogen atom and a hydrocarbon group, M represents an atom belonging to Group 15 or Group 16, and n represents 0 or 1), includes the step of reacting tris (fluoroaryl)borane and a compound in a hydrocarbon solvent, in a molar ratio ranging from 1:0.9 to 1:1.1, the tris(fluoroaryl)borane being represented by General Formula (1):
(where each of R
1
, R
2
, R
3
, R
4
, and R
5
independently repr

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