U.S. patent application number 09/781961 was filed with the patent office on 2001-11-22 for process for producing octafluoro[2,2]paracyclophane.
Invention is credited to Amii, Hideki, Uneyama, Kenji.
Application Number | 20010044561 09/781961 |
Document ID | / |
Family ID | 18559731 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010044561 |
Kind Code |
A1 |
Uneyama, Kenji ; et
al. |
November 22, 2001 |
Process for producing octafluoro[2,2]paracyclophane
Abstract
A process for producing an octafluoro[2,2]paracyclophane
includes the steps of (a) reacting 1,4-bis(trifluoromethyl)benzene
with a halogenated silane represented by the general formula (1),
in the presence of a low valence metal, thereby obtaining a novel
compound (precursor) represented by the general formula (2); and
(b) conducting in the presence of a fluoride ion a dimerization of
the compound into the octafluoro[2,2]paracyclophane, R.sub.3SiX (1)
where each R is independently an alkyl group or aryl group, and X
is a halogen atom, 1 where R is defined as above. It is possible to
produce octafluoro[2,2]paracyclophane with a high yield from
1,4-bis(trifluoromethyl)benzene, which is easily available, via the
above compound.
Inventors: |
Uneyama, Kenji; (Okayama,
JP) ; Amii, Hideki; (Okayama, JP) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Family ID: |
18559731 |
Appl. No.: |
09/781961 |
Filed: |
February 14, 2001 |
Current U.S.
Class: |
570/144 ;
556/478 |
Current CPC
Class: |
C07C 17/281 20130101;
C07C 17/263 20130101; C07F 7/0827 20130101; C07C 17/281 20130101;
C07C 22/08 20130101 |
Class at
Publication: |
570/144 ;
556/478 |
International
Class: |
C07C 025/22; C07F
007/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2000 |
JP |
2000-035548 |
Claims
What is claimed is:
1. A process for producing octafluoro[2,2]paracyclophane,
comprising: reacting 1,4-bis(trifluoromethyl)benzene with a
halogenated silane represented by the general formula (1), in the
presence of a low valence metal, thereby obtaining a compound
represented by the general formula (2); and conducting in the
presence of a fluoride ion a dimerization of said compound into
said octafluoro[2, 2]paracyclophane, R.sub.3SiX (1) where each R is
independently an alkyl group or aryl group, and X is a halogen
atom, 7where R is defined as above.
2. A process for producing a compound represented by the general
formula (2), comprising: reacting 1,4-bis(trifluoromethyl)benzene
with a halogenated silane represented by the general formula (1),
in the presence of catalyst comprising a low valence metal, thereby
obtaining said compound, 8where each R is independently an alkyl
group or aryl group, R.sub.3SiX (1) where R is defined as above,
and X is a halogen atom.
3. A process for producing octafluoro[2,2]paracyclophane,
comprising: conducting in the presence of a fluoride ion a
dimerization of a compound, which is represented by the general
formula (2) into said octafluoro[2,2]paracyclophane, 9where each R
is independently an alkyl group or aryl group.
4. A process according to claim 1, wherein said halogenated silane
is selected from the group consisting of chlorotrimethylsilane,
chlorotriethylsilane, chlorophenyldimethylsilane, chlorodiphe
nylmethylsilane, and bromotriethylsilane.
5. A process according to claim 4, wherein said halogenated silane
is chlorotrimethylsilane.
6. A process according to claim 1, wherein said halogenated silane
is in an amount of 1 mole or greater per mole of said
1,4-bis(trifluoromethyl)b- enzene.
7. A process according to claim 1, wherein said reacting is
conducted in a solvent.
8. A process according to claim 7, wherein said solvent is in an
amount of 1-100 parts by weight per one part by weight of said
1,4-bis(trifluoromethyl)benzene.
9. A process according to claim 1, wherein said low valence metal
comprises a metal element selected from the group consisting of
magnesium, zinc, copper, iron, cadmium, tin, titanium, and
sodium.
10. A process according to claim 9, wherein said low valence metal
is magnesium.
11. A process according to claim 1, wherein said low valence metal
is in the form of a metal alloy.
12. A process according to claim 1, wherein said low valence metal
is in the form of a metal compound.
13. A process according to claim 1, wherein said low valence metal
is in the form of a metal complex.
14. A process according to claim 1, wherein said low valence metal
is in an amount of 1-50 moles per mole of said
1,4-bis(trifluoromethyl)benzene.
15. A process according to claim 1, wherein said reacting is
conducted at a temperature of from -78 to 120.degree. C.
16. A process according to claim 1, wherein said dimerization is
conducted in the presence of an alkali metal fluoride comprising
said fluoride ion.
17. A process according to claim 16, wherein said alkali metal
fluoride is cesium fluoride.
18. A process according to claim 1, wherein said dimerization is
conducted in a solvent selected from aromatic hydrocarbons,
condensed-ring aromatic compounds, polycyclic aromatic compounds,
and aliphatic hydrocarbons.
19. A process according to claim 18, wherein said solvent is an
aromatic hydrocarbon.
20. A process according to claim 18, wherein said solvent has a
boiling point of 120-300.degree. C.
21. A process according to claim 19, wherein said solvent has a
boiling point of 120-300.degree. C.
22. A process according to claim 19, wherein said solvent is
selected from the group consisting of mesitylene, o-xylene,
m-xylene and p-xylene.
23. A process according to claim 1, wherein said dimerization is
conducted at a temperature of from 100 to 300.degree. C.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a process for producing
octafluoro[2,2]paracyclophane, which is useful as an intermediate
for functional materials. This compound is particularly useful as a
raw material for a heat-resistant parylene polymer film.
[0002] There are several processes for producing
octafluoro[2,2]paracyclop- hane. J. Org. Chem. 1970, 35, 20-22
discloses a process for producing this target compound with a yield
of 9-28% by a pyrolytic dimerization of a compound represented by
the general formula (1) at a temperature of 600-800.degree. C.,
2
[0003] where X is chlorine, bromine or SO.sub.2R' where R' is an
alkyl group. U.S. Pat. No. 5,210,341 discloses a process for
producing the target compound with a yield of 32% by a reductive
dimerization of the compound represented by the general formula (1)
where X is bromine, by TiCl.sub.4--LiAlH.sub.4 at 70.degree. C.
There is another process for producing the target compound by a
reductive dimerization of the compound represented by the general
formula (1) wherein X is bromine, by a combination of
BU.sub.3SnSiMe.sub.3 and CsF (see J. Org. Chem., 1997, 62,
1827-1830 and J. Org. Chem., 1999, 64, 9137-9143).
[0004] WO 98/24743 discloses a process for producing
1,4-bis(difluoromethyl)benzene by the steps of (a) chlorinating
paraxylene to obtain 1,4-bis(dichloromethyl)benzene and (b)
fluorinating this compound by a metal fluoride into the target
product. In this publication, it is proposed that
1,4-bis(dichloromethyl)benzene is fluorinated with CsF or KF under
a slurry condition at a temperature of 180.degree. C. or
higher.
[0005] Chemical Abstract, Vol. 124, 116848 discloses a process for
producing 1,4-bis(trifluoromethyl)benzene by fluorinating
1,4-bis(dibromomethyl)benzene by antimony trifluoride in the
absence of solvent under a condition of 100-150.degree. C. and
20-100 mmHg.
[0006] J. Am. Chem. Soc., 82, 543 (1960) discloses a fluorination
of terephthalaldehyde by sulfur tetrafluoride at 150.degree. C.
French Patent 2109416 discloses a fluorination of
terephthalaldehyde by molybdenum fluoride and boron
trifluoride.
[0007] It is disclosed in J. Chem. Soc., Chem. Commun., 1993, 678
that 1-trifluoromethyl -4-difluorotrimethylsilylmethylbenzene can
be synthesized by a silylmethylation of bis(trifluoromethyl)benzene
through a photo-inducing reaction using tetramethyldisilane.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide a
process for producing octafluoro[2,2]paracyclophane with a high
yield, using a raw material that is easily available.
[0009] According to the present invention, there is provided a
process for producing octafluoro[2,2]paracyclophane. This process
comprises:
[0010] reacting 1,4-bis(trifluoromethyl)benzene with a halogenated
silane represented by the general formula (1), in the presence of a
low valence metal, thereby obtaining a compound represented by the
general formula (2); and
[0011] conducting in the presence of a fluoride ion a dimerization
of said compound into said octafluoro[2, 2]paracyclophane,
R.sub.3SiX (1)
[0012] where each R is independently an alkyl group or aryl group,
and X is a halogen atom, 3
[0013] where R is defined as above.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The inventors have eager examined a dimerization of
1,4-bis(trifluoromethyl)benzene by removing fluorine atom from this
compound. In this examination, we unexpectedly found that it is
possible to easily break C--F bond, which is generally difficult to
be broken due to its large bonding energy, of
1,4-bis(trifluoromethyl)benzene by setting a special intermediate
(as a precursor of octafluoro[2,2]paracycl- ophane), that is, the
compound represented by the general formula (2), and that it is
possible to produce octafluoro[2,2]paracyclophane by a dimerization
of this compound.
[0015] Hereinafter, the reaction of 1,4-bis(trifluoromethyl)benzene
with the halogenated silane may be referred to as the first step,
and the dimerization may be referred to as the second step.
[0016] The halogenated silane used in the first step is not
particularly limited. In the general formula (1) representing the
halogenated silane, the alkyl group (R) may be a lower alkyl group
(e.g., methyl group, ethyl group, propyl group, or isopropyl
group), and the aryl group (R) may be phenyl group or tolyl group.
Furthermore, X may be chlorine, bromine or iodine. Preferable
examples of the halogenated silane are chlorotrimethylsilane,
chlorotriethylsilane, chlorophenyldimethylsilane,
chlorodiphenylmethylsilane, and bromotriethylsilane. Of these,
chlorotrimethylsilane is the most preferable, since it is easily
available.
[0017] The amount of the halogenated silane to be used in the first
step may be 1 mole or greater (from the viewpoint of
stoichiometry), preferably about 1-50 moles, more preferably about
1-10 moles, per mole of 1,4-bis(trifluoromethyl)benzene.
[0018] It is optional to use a solvent in the first step, as long
as the solvent is inert under reaction conditions of the first
step. Examples of such solvent are aliphatic hydrocarbons (e.g.,
pentane, hexane and heptane), aromatic hydrocarbons (e.g., benzene,
toluene and xylene), nitriles (e.g., acetonitrile, propionitrile,
phenylacetonitrile, isobutyronitrile, and benzonitrile), acid
amides (e.g., N,N-dimethylformamide, N,N-dimethylacetoamide,
methylformamide, formamide, hexamethylphosphoric acid, and
hexamethyl phosphoric acid triamide), and lower ethers (e.g.,
tetrahydrofuran, 1,2-dimethoxyethane, diglyme, triglyme, diethyl
ether, 1,2-epoxyethane, 1,4-dioxane, dibutyl ether, t-butyl methyl
ether, and substituted tetrahydrofuran). Of these,
N,N-dimethylformamide and tetrahydrofuran are preferable. It is
optional to use a mixture of at least two of these solvents. The
solvent may be in an amount of about 1-100 parts by weight,
preferably 1-20 parts by weight, per one part by weight of the
1,4-bis(trifluoromethyl)benzene.
[0019] It is preferable to remove water as much as possible from
the solvent to be used in the first and second steps. It is,
however, not necessary to remove water completely. The amount of
water generally contained in a commercially available solvent is
acceptable in the first and second steps. Therefore, it is possible
to directly use a commercially available solvent in the invention,
without removing water.
[0020] The low valence metal used in the first step is not
particularly limited. In this specification, the low valence metal
can be defined as being an element that belongs to typical elements
and as being a metal that does not have an oxidation number of 5 or
greater under a normal condition. It may be a metal element, for
example, selected from magnesium, zinc, copper, iron, cadmium, tin,
titanium, and sodium. Furthermore, the low valence metal may be in
the form of a metal alloy containing at least one of these metal
elements as a major component. Examples of such metal alloy are an
alloy of zinc and copper, Raney nickel, an alloy of silver and
zinc, and an alloy of copper and magnesium. Furthermore, metal ion
in a low oxidation state may also be applicable, such as titanium
trichloride, samarium diiodide, and chromium dichloride.
Furthermore, such metal ion in a low oxidation state may be in the
form of a metal complex such as sodium naphthalenide, sodium
benzophenon ketyl complex, or
tetrakis(triphenylphosphine)palladium. Still furthermore, the low
valence metal may be in the form of a mixture of the metal element
or the metal alloy and the metal compound or the metal complex.
Examples of such mixture are a mixture of titanium tetrachloride
and metallic zinc, a mixture of titanocene dichloride and zinc, a
mixture of samarium diiodide and samarium, and a mixture of
samarium diiodide and magnesium. Of these, it is preferable to use
magnesium or a mixture containing magnesium.
[0021] When the low valence metal is used in the form of a metal
element (metallic form), its shape is not particularly limited. In
fact, it may be in the form of powder, granules, aggregates, porous
solid, chips or rod. For example, it is possible to directly use a
magnesium having a known shape generally used for Grignard
reaction. The amount of the low valence metal may be about 1-50
moles, preferably about 1-10 moles, per mole of the
1,4-bis(trifluoromethyl)benzene.
[0022] The reaction temperature of the first step may be a
temperature of -78 to 120.degree. C. The reaction time may be
varied depending on the reagents, and may be adjusted to about 10
minutes to about 20 hours. The reaction pressure of the first step
may be in the vicinity of normal pressure. The other reaction
conditions of the first step may be the same as those of a reaction
using a conventional organic magnesium compound.
[0023] In the first step, it is optional to use various reaction
accelerations generally used in Grignard reaction, in order to
accelerate the reaction. For example, it is optional to add to the
reaction system a halogen (e.g., bromine or iodine), Grignard's
reagent, an organic halide (e.g., ethyl bromide, methyl iodide,
methylene diiodide, ethyl iodide, or .beta.-bromoethyl ether), or
ethyl orthosilicate. Furthermore, it is optional to conduct
stirring or ultrasonic agitation as the reaction acceleration.
[0024] Each reaction of the first and second steps does not depend
on pressure. Thus, when the reaction is conducted under a
pressurized condition, the pressure may be 1.0 MPa or lower. The
reaction may be conducted under an atmosphere of air. It is,
however, preferable to conduct the reaction under an atmosphere of
inert gas (e.g., nitrogen, argon or helium).
[0025] It is preferable to subject a crude product of the first
step, which contains the target compound represented by the general
formula (2), to purification, depending on the use of this target
compound. This purification is not particularly limited, and may be
conducted by a conventional extraction or column
chromatography.
[0026] As stated above, the second step is conducted by a
dimerization of the compound (represented by the general formula
(2)) into octafluoro[2,2]paracyclophane, in the presence of a
fluoride ion. This presence of a fluoride ion can be achieved by
adding a fluoride. This addition of fluoride may be replaced with
the addition of a compound that accelerates the release of fluorine
atom from the compound represented by the general formula (2).
Examples of the fluoride are alkali metal fluorides (e.g., sodium
fluoride, potassium fluoride, and cesium fluoride), alkali earth
metal fluorides (e.g., barium fluoride and magnesium fluoride),
fluorides of other metals (e.g., copper fluoride and chromium
fluoride), and ammonium fluoride. Examples of the
fluorine-release-accelerating compound are quaternary ammonium
salts in which an alkyl or aryl group is bonded to N, such as
triethylbenzylammonium chloride, tetramethylammonium chloride,
triethylbenzylammonium bromide, trioctylmethylammonium chloride,
tributylbenzylammonium chloride, trimethylbenzylammonium chloride,
N-laurylpyridinium chloride, n-butylammonium hydroxide,
tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide,
trimethylphenylammonium bromide, tetramethylammonium bromide,
tetraethylammonium bromide, tetra -n-butylammonium bromide,
tetrabutylammonium hydrosulfate, N-benzylpicolinium chloride,
tetramethylammonium iodide, and tetra-n-butylammonium iodide. The
anion of the fluorine-release-accelerating compound is not
particularly limited. The amount of the fluoride or the
fluorine-release-accelerating compound may be a catalytic amount.
In fact, it may be 0.0001 to 1 mole, preferably 0.001 to 0.5 moles,
per mole of the 1,4-bis(triiEluoromethyl)b- enzene. Furthermore, it
is optional to use a crown ether in order to accelerate the second
step. The amount of this crown ether may be about 0.001 to 10
moles, preferably 0.01 to 1 mole, per mole of the fluoride.
[0027] It is preferable to use a solvent in the second step. This
solvent is preferably a nonpolar solvent or a solvent that is low
in polarity. In fact, Examples of the solvent are aromatic
hydrocarbons, condensed-ring aromatic compounds, polycyclic
aromatic compounds, and aliphatic hydrocarbons. Of these solvents,
aromatic hydrocarbons are preferable. Concrete examples of the
aromatic hydrocarbons are toluene, xylene, ethylbenzene, cumene,
mesitylene, durene, and tetralin). Of these, mesitylene, o-xylene,
m-xylene, and p-xylene are particularly preferable. It is optional
to use a mixture of aromatic hydrocarbons (e.g., SOLVESSO (trade
name)). Examples of the condensed-ring aromatic compounds and
polycyclic aromatic compounds are mono-, di- and
tri-methylnaphthalenes, mono-, di- and tri-isopropylnaphthalene,
ethyl diphenyl, and dibenzyltoluene. Examples of the aliphatic
hydrocarbons are heptane and octane. It is optional to use a
mixture of at least two of the above-mentioned solvents. When the
second step is conducted under a normal pressure, it is preferable
to use a solvent having a high boiling point. So that, these
exemplary solvents are preferably those having a boiling point of
higher than 100.degree. C., more preferably 120-300.degree. C. It
is, however, possible to use a lower-boiling-point solvent in the
reaction under a pressurized condition.
[0028] The reaction temperature of the second step may be about
100-300.degree. C., preferably about 130-250.degree. C. If it is
lower than about 100.degree. C., desilylated compounds, for
example, a compound represented by the following formula may be
produced. With this, the yield of octafluoro[2,2]paracyclophane may
be lowered. 4
[0029] The second step can be conducted by charging a reaction
vessel with
1-trifluoromethyl-4-difluorotrimethylsilylmethylbenzene, a solvent,
a fluoride and the like and then by maintaining the reaction vessel
at a predetermined temperature for a predetermined time. During the
reaction, it is optional to conduct stirring and reflux of the
contents of the reaction vessel. After the reaction, a solid matter
can be collected by removing the catalyst and then by distilling
the solvent off or by filtration. This solid matter can be purified
by a conventional method. For example, it may be recrystallization,
sublimation or column chromatography.
[0030] The following nonlimitative examples are illustrative of the
present invention.
EXAMPLE 1
[0031] At first, 288 mg (12 mmol) of magnesium powder and 2.6 g (24
mmol) of chlorotrimethylsilane were added to 20 ml of
N,N-dimethylformamide (DMF). Then, 1.28 g (6 mmol) of
1,4-bis(trifluoromethyl)benzene were dropped to the resulting
mixture, followed by stirring for 30 minutes under an argon
atmosphere at room temperature. Then, ammonium chloride was added,
thereby terminating the reaction. Then, the reaction liquid was
extracted with hexane, and the resulting extract (hexane solution)
was dried with magnesium sulfate. Then, it was found by 19FNMR for
analyzing fluorine that the dried extract contained 64% of
1-trifluoromethyl4-difluorotrimethylsilylmethylbenzene and 5% of
1-trifluoromethyl-4-fluorotrimethylsilylmethylbenzene. The dried
extract was subjected to a Kugelrohr distillation, thereby
obtaining 961 mg of 1
trifluoromethyl-4-difluorotrimethylsilylmethylbenzene (yield: 56%)
in the form of a colorless oil-like substance.
[0032] The analytical data of this product are as follows.
[0033] Boiling point: 95.degree. C. (30 mmHg)
[0034] .sup.1HNMR (200 MHz, CDCl.sub.3)): .delta.=0.15 (s, 9H),
7.46 (d, J=8.6 Hz, 2H), 7.68 (d, J=8.6 Hz, 2H)
[0035] .sup.19FNMR (188 MHz, CDCl.sub.3, internal standard:
C.sub.6F.sub.6): .delta.=48.7(s, 2F), 99.0 (s, 3F)
[0036] Elemental analysis (C.sub.10H.sub.13F.sub.3Si): calculated
value (C, 79.27; H, 9.15); measured value (C, 79.53; H, 9.14).
EXAMPLES 2 AND 3
[0037] In each of these examples, Example 1 was repeated except
that the reaction conditions were modified as shown in Table 1.
1 TABLE 1 Reaction Reaction a* Mg Temp. Time Product Yield (%)
(mmol) (mmol) (.degree. C.) (hr) b* c* Ex. 1 6.0 12.0 Room Temp.
0.5 64 5 Ex. 2 0.6 0.66 Room Temp. 3 35 7 Ex. 3 0.6 1.20 Room Temp.
1 58 15 *a: 1,4-bis(trifluoromethyl)benzene; b:
1-trifluoromethyl-4-difluo- rotrimethylsilylmethylbenzene; and c:
1-trifluoromethyl-4-fluorotrimethyls- ilylmethylbenzene, as shown
by the following formulas.
[0038] 5
EXAMPLE 4
[0039] At first, 107 mg (0.4 mmol) of 20
1-trifluoromethyl-4-difluorotrime- thylsilylmethylbenzene and 6.1
mg (0.04 mmol) of cesium fluoride were added to 1.0 ml of
mesitylene. Then, the reaction was conducted for 24 hr for
160.degree. C. After the reaction, the reaction liquid was analyzed
by
[0040] 19FNMR for fluorine. With this, the yield of
octafluoro[2,2]paracyclophane was found to be 53%. The reaction
liquid was filtered, followed by recrystallization from chloroform
at room temperature, thereby obtaining 30 mg of a colorless
octafluoro[2,2]paracyclophane (yield: 48%).
[0041] The analytical data of this target product were as
follows.
[0042] Melting point: 261.degree. C.
[0043] .sup.1HNMR (200 MHz, CDCl.sub.3)): .delta.=7.16 (s, 8H)
[0044] .sup.19FNMR (188 MHz, CDCl.sub.3, internal standard:
C.sub.6F.sub.6): .delta.=43.5(s, 8F)
EXAMPLE 5 AND REFERENTIAL EXAMPLE
[0045] In each of Example 5 and Referential Example, Example 4 was
repeated except that the reaction conditions were modified as shown
in Table 2. In Referential Example,
1-trifluoromethyl-4-difluoromethylbenzen- e was formed.
2 TABLE 2 b* Reaction Reaction Product Yield (mmol) Solvent Temp.
(.degree. C.) Time (hr) (%) d* Ex. 4 0.4 mesitylene 160 24 53 Ex. 5
0.4 o-xylene 140 24 21 Ref. Ex. 0.4 toluene 100 24 a trace amount
*b: 1-trifluoromethyl-4-difluorotrimethylsilylmethylbenzene; and d:
octafluoro[2,2]paracyclophane, as shown in the following
formulas.
[0046] 6
[0047] The entire disclosure of Japanese Patent Application No.
2000-35548 filed on Feb. 14, 2000, including specification, claims
and summary, is incorporated herein by reference in its
entirety.
* * * * *