Process for producing fluorinated silicon compound

Details Process for producing fluorinated silicon compound Process for producing fluorinated silicon compound

2001-05-07

2002-02-05

Shaver, Paul F. (Department: 1621)

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

Organic compounds

Silicon containing

Reexamination Certificate

active

06344579

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a process for producing a fluorine-containing compound by fluorination of a hydroxyl group, an alkoxy group, or an aryloxy group. More particularly, it relates to a novel process for producing a fluorinated silicon compound by reacting a silicon compound in which at least one group selected from the group consisting of a hydroxyl group, an alkoxy group, and an aryloxy group is bonded to silicon atom, with a fluorinating agent, to fluorinate these groups.
BACKGROUND OF THE INVENTION
Many studies have hitherto carried out with regard to fluorination of a hydroxyl group (also called a silanol group), an alkoxy group, or an aryloxy group bonded to silicon atom, but the known processes have problems to be solved in view of safety of the reagents, convenience of the reaction, and the like.
For example, it is described in Anal. Chem. vol. 58, 499-501(1986) that dimethylaminosulfurtrifluoride (DAST) causes substitution of almost 50% of a silanol group (hydroxyl group bonded to silicon) on the surface of silica by fluorine.
DAST, a four-valent sulfur compound not only causes effective substitution of a hydroxyl group of primary, secondary, and tertiary alcohols by fluorine under mild conditions but also is a useful compound as a fluorinating agent for oxygen-containing functional groups such as a carboxyl group and a carbonyl group [U.S. Pat. No. 3,976,691].
However, DAST is produced by reacting highly dangerous sulfur tetrafluoride and diethylaminotrimethylsilane at a low temperature of −78 to −60° C., and specific equipment is required. Also, in view of safety, there is a report that an explosion occurred in the production and use of DAST [J. Fluorine Chem., 42, 137 (1989)].
Moreover, it is described in Z. Chem. vol. 11, 382-384 (1971) that carbonyl fluoride (COF
2
) has an effective reactivity as a fluorinating reagent for a hydroxyl group or an alkoxy group bonded to silicon atom.
However, carbonyl fluoride is a gas at ordinary temperature, has toxicity and danger of an explosion owing to its high reactivity, and thus is a chemical product which is difficult to handle.
Fluorination of silanol groups on silica surface with HF has been also reported [Teor. Eksp. Khim., 15(4), 400-405(1979); EP 221780]. HF is an inexpensive fluorine source, but is difficult to handle owing to its harmfulness, and has a possibility of destroying the Si—Si bonds or Si—O bonds of the bulk.
In addition, there is a report that silanol group has been fluorinated with TeF
6
[J. Chem. Soc., Chem. Commun. (20), 1113(1972)].
However, TeF
6
has a low boiling point and is liable to hydrolysis. Also, Te is a trace element and is fairly expensive even as a simple substance.
Furthermore, a process for producing a fluorosilane by reacting an alkoxysilane with MPF
6
(M represents Li, K, or Na) is described in Journal of Fluorine Chemistry, vol. 86, 189-197 (1996). It is described that the reaction can be carried out in a yield as high as 90% or more according to the process, but the process has problems that MPF
6
, a corrosive reagent, has to be treated at a high temperature of 200° C. and MPF
6
to be used as a fluorinating agent is expensive.
As other examples of the reaction of an alkoxy group with a phosphorus compound, there are known an example of using R
n
PF
5−n
(n=0, 1, 2, or 3) as a fluorinating agent [Journal of Fluorine Chemistry, 1, 252-254 (1971/1972)], and an example of using CH
3
POF
2
as a fluorinating agent [J. Org. Chem., 53, 3364-3365 (1988)]. However, both technologies require the improvement of the product yields and the stability of the fluorinating agents and reaction products.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a process for producing a fluorinated silicon compound conveniently and effectively.
As a result of the extensive studies for accomplishing the above object, the present inventors have been found that a compound represented by the formula (1):
wherein R
1
, R
2
, R
3
and R
4
may be the same or different, and each represents a substituted or unsubstituted, saturated or unsaturated alkyl group, or a substituted or unsubstituted aryl group; and R
1
and R
2
or R
3
and R
4
can bond to form a ring having one or more nitrogen atoms or having one or more nitrogen atoms and other hetero atoms; or R
1
and R
3
can bond to form a ring having two or more nitrogen atoms or having two or more nitrogen atoms and other hetero atoms; serves an excellent effect as a novel fluorinating agent capable of replacing a hydroxyl group, an alkoxy group, or an aryloxy group bonded to silicon atom with fluorine atom, and the operations from the production of the fluorinating agent to its use in fluorination can be carried out extremely safely and easily without requiring any specific equipments. Based on the findings, they have accomplished the invention.
That is, the invention relates to the following.
(1) A process for producing a fluorinated silicon compound which comprises reacting a silicon compound having at least one group selected from the group consisting of a hydroxyl group, an alkoxy group, and an aryloxy group bonded to silicon atom, with a compound represented by the formula (1):
wherein R
1
, R
2
, R
3
and R
4
may be the same or different, and each represents a substituted or unsubstituted, saturated or unsaturated alkyl group, or a substituted or unsubstituted aryl group; and R
1
and R
2
or R
3
and R
4
can bond to form a ring having one or more nitrogen atoms or having one or more nitrogen atoms and other hetero atoms; or R
1
and R
3
can bond to form a ring having two or more nitrogen atoms or having two or more nitrogen atoms and other hetero atoms, to fluorinate the groups.
(2) The process for producing a fluorinated silicon compound as described in the above (1), wherein the compound represented by the formula (1) is a compound represented by the formula (2):
wherein a is an integer of 2 or 3, and R
5
and R
6
may be the same or different and each represents a substituted or unsubstituted, saturated or unsaturated lower alkyl group having 1 to 6 carbon atoms.
(3) The process for producing a fluorinated silicon compound as described in the above (2), wherein the compound represented by the formula (2) is 2,2-difluoro-1,3-dimethylimidazolidine represented by the formula (3):
(4) The process for producing a fluorinated silicon compound as described in the above (1), wherein the silicon compound having at least one group selected from the group consisting of a hydroxyl group, an alkoxy group, and an aryloxy group bonded to silicon atom, is a compound represented by the formula (5):
wherein R
7
, R
8
, R
9
, R
10
, R
11
and R
12
each represents an alkyl group having 1 to 6 carbon atoms, an aryl group, hydrogen atom, hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or an aryloxy group, provided that at least one of R
7
, R
8
, R
9
, R
10
, R
11
, and R
12
is hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or an aryloxy group; n represents an integer of 0 to 100; and m represents 0 or 1.
(5) The process for producing a fluorinated silicon compound as described in the above (1), wherein the silicon compound having at least one group selected from the group consisting of a hydroxyl group, an alkoxy group and an aryloxy group bonded to silicon atom, is a silica having at least one of these groups.
In the invention, starting with the silicon compound having at least one group selected from the group consisting of a hydroxyl group, an alkoxy group and an aryloxy group (hereinafter, simply referred to as the hydroxyl group, alkoxy group and/or aryloxy group”) bonded to silicon atom, a fluorinated silicon compound can be produced by replacing the hydroxyl group, alkoxy group and/or aryloxy group bonded to silicon atom of the silicon compound with fluorine atom using the compound represented by the formula (1).
This process realizes a high selectivity, safety and easiness to handle. M

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