U.S. patent application number 09/758607 was filed with the patent office on 2001-05-31 for process for production of 1,4-bis (difluoroalkyl) benzene derivative.
This patent application is currently assigned to Nippon Shokubai Co., Ltd., a Japan Corporation. Invention is credited to Asako, Yoshinobu, Teshima, Seiichi.
Application Number | 20010002425 09/758607 |
Document ID | / |
Family ID | 11712195 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002425 |
Kind Code |
A1 |
Teshima, Seiichi ; et
al. |
May 31, 2001 |
Process for production of 1,4-bis (difluoroalkyl) benzene
derivative
Abstract
A process is provided which allows a
1,4-bis(difluoroalkyl)benzene derivative to be produced
inexpensively by a simple procedure without requiring any special
facility. This process comprises causing a compound (A) of the
following formula (1): 1 wherein X.sub.1, X.sub.2, X.sub.3, and
X.sub.4 independently stand for an oxygen or sulfur atom, Y.sub.1
and Y.sub.2 independently stand for a group of the formula:
--C.sub.nH.sub.2n--, in which n is 2 or 3, k is an integer in the
range of 0 to 4, G stands for a halogen group, an alkyl group, a
perfluoroalkyl group, or an alkoxy group, and m is an integer in
the range of 0 to 4, to react with a fluorine-containing species,
the molar ratio of the fluorine-containing species to compound (A)
being in the range of 20-40. The process is carried out in the
presence of a bromine-containing compound, which is in an amount of
2 to 3 equivalences to the amount of compound (A), in an organic
solvent at -80.degree. C. to 30.degree. C., the final concentration
of compound (A) being in the range of 3 to 30% by weight.
Inventors: |
Teshima, Seiichi; (Ibaraki,
JP) ; Asako, Yoshinobu; (Ibaraki, JP) |
Correspondence
Address: |
Y. Rocky Tsao
Fish & Richardson P.C.
225 Franklin Street
Boston
MA
02110-2804
US
|
Assignee: |
Nippon Shokubai Co., Ltd., a Japan
Corporation
|
Family ID: |
11712195 |
Appl. No.: |
09/758607 |
Filed: |
January 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09758607 |
Jan 11, 2001 |
|
|
|
09233557 |
Jan 20, 1999 |
|
|
|
Current U.S.
Class: |
568/426 ;
570/161 |
Current CPC
Class: |
C07D 339/00 20130101;
C07C 45/56 20130101; C07C 17/093 20130101; C07D 321/00 20130101;
C07D 327/02 20130101; C07C 45/567 20130101; C07C 45/60 20130101;
C07C 45/59 20130101; C07C 17/093 20130101; C07C 22/04 20130101;
C07C 45/56 20130101; C07C 47/55 20130101; C07C 45/567 20130101;
C07C 47/55 20130101; C07C 45/59 20130101; C07C 47/55 20130101; C07C
45/60 20130101; C07C 47/55 20130101 |
Class at
Publication: |
568/426 ;
570/161 |
International
Class: |
C07C 045/00; C07C
045/90 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 1998 |
JP |
10-009135 |
Claims
1. A process for the production of a 1,4-bis(difluoroalkyl)benzene
derivative of the formula: 8wherein k is an integer in the range of
0 to 4, G stands for a halogen group, an alkyl group, a
perfluoroalkyl group, or an alkoxy group, and m is an integer in
the range of 0 to 4, which process comprises reacting compound (A)
of the formula: 9wherein k, G, and m are as defined above, X1, X2,
X3, and X4 independently stand for an oxygen or sulfur atom, and Y1
and Y2 independently stand for --C.sub.nH.sub.2n--, in which n is 2
or 3, with a fluorine-containing species, the molar ratio of the
fluorine-containing species to compound (A) being in the range of
20-40, in the presence of a bromine-containing compound, which is
in an amount of 2 to 3 equivalences to the amount of compound (A),
in an organic solvent at -80.degree. C. to 30.degree. C., the final
concentration of compound (A) being in the range of 3 to 30% by
weight.
2. The process of claim 1, wherein the reaction temperature is
-20.degree. C. to 25.degree. C.
3. The process of claim 2, wherein the reaction temperature is
0.degree. C. to 5.degree. C.
4. The process of claim 1, wherein m is 0, 3, or 4.
5. The process of claim 4, wherein m is 0 or 4.
6. The process of claim 5, wherein m is 0.
7. The process of claim 3, wherein m is 0, 3, or 4.
8. The process of claim 7, wherein m is 0 or 4.
9. The process of claim 8, wherein m is 0.
10. The process of claim 1, wherein compound (A) is selected from
the group consisting of 10
11. The process of claim 7, wherein compound (A) is 11
12. The process of claim 7, wherein compound (A) is 12
13. The process of claim 10, wherein the reaction temperature is
0.degree. C. to 5.degree. C.
14. The process of claim 11, wherein the reaction temperature is
0.degree. C. to 5.degree. C.
15. The process of claim 12, wherein the reaction temperature is
0.degree. C. to 5.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] Pursuant to 35 U.S.C. .sctn.120, this application is a
continuation of, and claims priority from U.S. application No.
09/233,557, filed Jan. 20, 1999.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a process for the production of a
novel 1,4-bis(difluoroalkyl)benzene derivative. More particularly,
this invention relates to a process which, through a simple and
inexpensive procedure relying on the reaction of a compound (A) of
the formula (1) with fluorine at a low temperature under a normal
pressure, accomplishes the production of a
1,4-bis(difluoroalkyl)benzene derivative which is of the formula
(2) and is useful as a raw material for a resin excellent in
heat-resistance, chemical-resistance, water-repellency, low
dielectric property, and low refractivity.
[0004] 2. Description of the Related Art
[0005] 1,4-Bis(difluoromethyl)benzene is used as a raw material for
the synthesis of 1,4-bis(bromodifluoromethyl)benzene, which is
further used for derivation of
per-.alpha.-fluoro[2,2]paracyclophane therefrom. This product of
derivation allows synthesis of fluorine-substituted Parylene resin
(PA-F) which excels in heat-resistance, chemical-resistance, and
water-repellency. As methods for producing
1,4-bis(difluoromethyl)benzene- , a method which relies on the
reaction of terephthal aldehyde with sulfur tetrafluoride
(SF.sub.4) [J. Am. Chem. Soc., 82, pp. 543-551 (1960)], a method
which resorts to the reaction of .alpha.,.alpha.,.alpha.',.alpha.'-
-tetrabromo-p-xylene with antimony trifluoride [RU 2032654, Zn,
Org. Khim., 29, pp. 1999-2001 (1993)], and etc. have been known to
the art to date.
[0006] Of these methods, the former method which uses sulfur
tetrafluoride is at a disadvantage in needing such facilities as
special reaction vessels made of Hastelloy, a (Ni-Mo type)
stainless alloy excellent in corrosion-resistance and, as a
consequence, incurring an increase in the cost of production
because the sulfur tetrafluoride shows strong toxicity and
corrosiveness, costs dearly, and entails such harsh reaction
conditions as 150.degree. C. and 8 MPa.
[0007] Then, the latter method which uses antimony trifluoride is
likewise at a disadvantage in needing special facilities and, as a
result, incurring an increase in the cost of production because the
reaction involved therein proceeds at such elevated reaction
temperatures as 100.degree. to 150.degree. C.
[0008] Therefore, a demand for a method which permits
1,4-bis(difluoromethyl)benzene and the derivatives thereof to be
produced inexpensively by a simple procedure without requiring any
special facility has been still strong.
SUMMARY OF THE INVENTION
[0009] This invention, originated in the light of the present
situation of prior art mentioned above, has an object to provide a
process for the production of a novel 1,4-bis(difluoroalkyl)benzene
derivative.
[0010] Another object of this invention is to provide a process for
producing a 1,4-bis(difluoroalkyl)benzene derivative inexpensively
by a simple procedure without requiring any special facility.
[0011] The objects mentioned above can be accomplished by a process
for the production of a 1,4-bis(difluoroalkyl)benzene derivative of
the formula (2): 2
[0012] wherein k is an integer in the range of 0 to 4, G stands for
a halogen group, an alkyl group, a perfluoroalkyl group, or an
alkoxy group, and m is an integer in the range of 0 to 4, which
process comprises causing a compound (A) of the formula (1): 3
[0013] wherein k, G, and m are as defined above, X.sub.1, X.sub.2,
X.sub.3, and X.sub.4 independently stand for an oxygen or sulfur
atom, and Y.sub.1 and Y.sub.2 independently stand for a group of
the formula: --C.sub.nH.sub.2n--, in which n is 2 or 3 (hereinafter
occasionally referred to simply as "compound (A)"), to react with a
fluorine-containing species, the molar ratio of the
fluorine-containing species to compound (A) being in the range of
20-40. The process is carried out in the presence of a
bromine-containing compound, which is in an amount of 2 to 3
equivalences to the amount of compound (A), in an organic solvent
at -80.degree. C. to 30.degree. C., the final concentration of
compound (A) being in the range of 3 to 30% by weight.
[0014] The above and other objects, features and advantages of the
present invention will become clear from the following description
of the preferred embodiments.
[0015] The process of the present invention permits the omission of
such special facilities as have been heretofore needed and also
allows 1,4-bis(difluoroalkyl)benzene derivative of the formula (2)
to be produced inexpensively as aimed at because the reaction of
the compound (A) of the formula (1) with fluorine can be carried
out at a low temperature under a normal pressure and also because
the fluorine source can be supplied at a relatively low cost.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0016] Now, this invention will be described specifically
below.
[0017] This invention is characterized in producing a
1,4-bis-(difluoroalkyl)benzene derivative of the following formula
(2) by causing the compound (A) of the following formula (1) to
react with fluorine. 4
[0018] In the formula (1), X.sub.1, X.sub.2, X.sub.3, and X.sub.4
independently stand for an oxygen atom or a sulfur atom, preferably
a sulfur atom. In the formula (1), Y.sub.1 and Y.sub.2
independently stand for a group denoted by the formula:
--C.sub.nH.sub.2n--, in which n is 2 or 3. Though the numerical
value of n is suitably selected depending on the reactivity of the
compound (A) with fluorine, it is preferably 2. Further, the symbol
G in the formulas (1) and (2) represents a halogen group such as a
fluoro group, a bromo group, and a chloro group; an alkyl group of
one to four carbon atoms such as, for example, a methyl group, an
ethyl group, and a propyl group; a perfluoroalkyl group of one to
four carbon atoms such as, for example, a trifluoromethyl group and
a pentafluoroethyl group; or an alkoxy group of one to four carbon
atoms such as, for example, a methoxy group, an ethoxy group, a
perfluoromethoxy group, and a perfluoroethoxy group, etc. Among
other groups mentioned above, G particularly advantageously
represents a halogen group such as a fluoro group, a bromo group,
and a chloro group, more preferably a fluoro group or a chloro
group, and most preferably a fluoro group. When a plurality of G's
are present (namely when m is from 2 to 4), the individual G's may
be either the same or different to each other. The symbol m in the
formulas (1) and (2) is an integer in the range of 0 to 4,
preferably 0, 3 or 4, and more preferably 0 or 4. In this case, the
position of linkage of G to a benzene ring is properly selected
depending on the reactivity of the compound (A) with fluorine. When
m is 2, for example, the linkage is preferred to occur at the (2,
5) position. The numbering used in specifying the position
mentioned above is based on the numbers which are assigned to the
positions shown in the formula (1) just mentioned above.
Furthermore, the symbol k in the formulas (1) and (2) is an integer
in the range of 0 to 4, preferably 0 or 1, more preferably 0.
[0019] The compound (A) which may be particularly advantageously
used in this invention is a compound which is represented by the
following formula. 5
[0020] The compound (A) to be used in this invention has no
particular restriction, so far as it should be a compound of the
formula (1). When k and m in the formula (1) are both 0, for
example, it is obtained by causing terephthal aldehyde to react
with the compound (B.sub.1) of the following formula (3) and the
compound (B.sub.2) of the following formula (4) in accordance with
a well-known method. To be more specific, the compound (A) can be
prepared efficiently by dissolving terephthal aldehyde in an
organic solvent including toluene, adding the compound (B.sub.1)
and the compound (B).sub.2 to the resultant solution, heating the
mixture, and effecting the reaction aimed at meanwhile expelling
the water. For the purpose of improving the yield, the reaction is
preferably carried out in the presence of an acid catalyst. As
typical examples of the acid catalyst to be used herein, inorganic
acids such as hydrochloric acid, sulfuric acid, and nitric acid and
organic acids such as oxalic acid, acetic acid, paratoluene
sulfonic acid, benzene sulfonic acid, and trifluoroboron ether
complex may be cited. Among other acid catalysts cited above,
paratoluene sulfonic acid and trifluoroboron ether complex prove
particularly advantageous on account of excellent solubility.
H--X.sub.1--Y.sub.1--X.sub.2--H (3)
H--X.sub.3--Y.sub.2--X.sub.4--H (4)
[0021] In the formulas (3) and (4) mentioned above, the symbols,
X.sub.1-X.sub.4 and Y.sub.1and Y.sub.2, have the same meanings as
defined in the formula (1) above.
[0022] The compound (B.sub.1) and the compound (B.sub.2) to be used
in this invention may be either equal or different to each other so
long as they should be compounds represented respectively by the
formula (3) and the formula (4). As typical examples of the
compounds of the formula (3) and the formula (4), 1,2-ethane
dithiol, 1,3-propane dithiol, ethylene glycol, 1,3-propane diol,
and 2-mercapto ethanol may be cited. Among other compounds
mentioned above, 1,2-ethane dithiol and 1,3-propane dithiol may be
used particularly advantageously.
[0023] The typical examples of the compound (A) wherein in the
formula (1), both k and m are 0 according to this invention are as
following: 6
[0024] Among these compounds, 7
[0025] may be preferably used as the compound (A) in this
invention.
[0026] The term "fluorine", as used herein, includes fluorine
molecules (F.sub.2), fluorine compounds, and fluorine ions. Of
these specific examples of the "fluorine", the fluorine compounds
and the fluorine ions may be preferably used as the fluorine
according to this invention.
[0027] When this invention elects to use a fluorine compound as the
"fluorine", it does not need to impose any specific restriction on
this fluorine compound. As typical examples of the fluorine
compound which may be advantageously usable in this invention,
pyridine hydrogen fluoride, ammonium hydrogen fluoride, potassium
hydrogen fluoride, hydrofluoric acid, sodium hydrogen fluoride,
ammonium fluoride, antimony III fluoride, antimony V fluoride, and
cesium fluoride may be cited. Among other fluorine compounds
mentioned above, pyridine fluoride, cesium fluoride, and
hydrofluoric acid are usable particularly advantageously.
[0028] When this invention elects to use a fluorine ion as the
"fluorine", it does not need to discriminate particularly the
fluorine ions on account of the specific source of fluorine ions to
be adopted. They nevertheless may be preferably supplied from the
fluorine compound as mentioned above.
[0029] This invention does not need to impose any particular
restriction on the amount of fluorine but properly selects this
amount with consideration for the yield of reaction and the cost of
manufacture. For the purpose of enabling the incorporation of
fluorine atoms into the compound (A) to proceed efficiently and
improving the yield of the product aimed at, the fluorine is
preferably present in an excess concentration relative to the
compound (A). Specifically, the amount of the fluorine is
preferably not less than 4 mols, more preferably in the range of 4
to 100 mols, furthermore preferably in the range of 4 to 40 mols,
and most preferably in the range of 4 to 20 mols, per mol of the
compound (A). If the amount of fluorine is less than 4 mols, the
shortage will be at a disadvantage in preventing the fluorine from
being completely incorporated into the compound (A) and
consequently lowering the yield of the product aimed at.
Conversely, if the amount of fluorine exceeds 100 mols, the excess
will be at a disadvantage in bringing no proportionate addition to
the yield, only impairing the economy of the reaction, and
incurring extra cost in the disposal of the residual fluorine.
[0030] Though this invention is allowed to introduce the compound
(A) and the fluorine either simultaneously or sequentially, the
compound (A) is preferably introduced last of all the reactants in
consideration of the yield of the reaction.
[0031] The temperature during the reaction of the compound (A) with
the fluorine according to the present invention is properly in the
range of -100.degree. to 80.degree. C., more preferably in the
range of -80.degree. to 30.degree. C., and most preferably in the
range of -20.degree. to 25.degree. C., with a view to obviating the
necessity for providing a special facility capable of withstanding
a high-temperature reaction and preventing the yield from being
lowered by the decomposition of reaction reagents. The control of
the reaction temperature may be attained by any of various known
methods such as, for example, by immersing the reaction solution in
a coolant retained at a desired temperature, by flowing into a
reaction vessel an inert gas (such as, for example, nitrogen,
argon, or helium) cooled in advance with liquid nitrogen, or by
bubbling the cooled inert gas through the reaction solution. The
reaction time, though variable with the particular kinds of
compound (A) and fluorine and the reaction conditions, generally
falls within the range of 1 to 24 hours, preferably in the range of
2 to 12 hours.
[0032] Though in this invention, the reaction of the compound (A)
with the fluorine may be carried out in the absence of a solvent,
in the presence of an inorganic solvent, or in the presence of an
organic solvent, the reaction may be preferably performed in the
presence of an organic solvent because the organic solvent, by
dissolving the compound (A) and the fluorine therein, improves the
efficiency of the reaction and facilitates the release of heat.
[0033] In the above-mentioned embodiment, the reaction of the
compound (A) with the fluorine in the presence of an organic
solvent may be implemented by adding the compound (A) to an organic
solvent containing the fluorine therein, preferably gradually. As
used herein, the expression "organic solvent containing the
fluorine" means a state in which the fluorine is uniformly
dissolved or dispersed in the organic solvent. Specifically, the
organic solvent containing the fluorine may be obtained by any of
known techniques such as, for example, by adding the fluorine
compound mentioned above to the organic solvent which will be
specifically described below. In this case, the final concentration
of the compound (A) in the organic solvent is required to fall
within the range of 1 to 40% by weight, preferably 3 to 30% by
weight, in consideration of the yield of the reaction and the cost
of production.
[0034] Further, in the above-mentioned embodiment, the reaction of
the compound (A) with the fluorine in the presence of the organic
solvent may be attained by blowing the fluorine such as the
hydrogen fluoride gas into the organic solvent containing the
compound (A) therein. In this case, the concentration of the
compound (A) in the organic solvent is properly in the range of 1
to 40% by weight, preferably 3 to 30% by weight, in consideration
of the yield of the reaction and the cost of production. The flow
rate of the fluorine gas, though only required to permit the
introduction of the fluorine in such an amount as is mentioned
above, generally falls within the range of 5 to 200 ml/min.,
preferably in the range of 10 to 100 ml/min.
[0035] The organic solvent which may be used in this invention has
no particular restriction, excepting that it be a solvent incapable
of being fluorinated. As typcical examples of such an organic
solvent, aliphatic or aromatic hydrocarbons such as pentane,
hexane, cyclohexane, octane, and xylene, halogen-containing
aliphatic or aromatic hydrocarbons such as dichloromethane,
1,2-dichloroethane, chloroform, 1,1,2,2-tetrachloroethan- e, carbon
tetrachloride, trichloro fluoromethane, and chlorotoluene, and
diglyme, and tetrahydrofuran may be cited. Among other organic
solvents cited above, dichloromethane, chloroform, and
1,2-dichloroethane may be used particularly favorably with a view
to enabling the reaction to proceed with high efficiency and thus
improving the yield. The organic solvent to be used in this
invention may be preferably used in such a dry state as dried with
any of such known desiccators as LiAlH.sub.4, CaH.sub.2, and
molecular sieve.
[0036] The reaction of the compound (A) with the fluorine according
to this invention may be properly carried out in an atmosphere such
that the gaseous phase of the reaction system may have a moisture
content of not more than 100 volppm, more preferably not more than
50 volppm, and most preferably not more than 10 volppm. If the
moisture content exceeds 100 volppm, the excess will be at a
disadvantage in degrading the efficiency of the introduction of the
fluorine atoms and inducing corrosion of the reaction vessel. With
a view to preventing the moisture content from exceeding 100
volppm, therefore, the interior of the reaction vessel, prior to
being charged with the solvent containing the fluorine, is
preferred to be displaced with an inert gas such as, for example,
argon, helium, or nitrogen which has been dried by being passed
through liquid nitrogen.
[0037] The present invention, for the purpose of further improving
the efficiency of the reaction, prefers the reaction of the
compound (A) with the fluorine to proceed in the presence of a
bromine-containing compound.
[0038] In the above-mentioned embodiment, the bromine-containing
compound imposes no particular restriction but requires only to
contain a bromine atom. It nevertheless is preferred to be a
compound possessing as many bromine atoms per molecule as
permissible. More preferably, this compound is capable of
generating Br.sup.+. As typical examples of the compound answering
this description, N-bromosuccinimide and 1,3-dibromo-5,5-dimethyl
hydantoin may be cited. In this case, the amount of the
bromine-containing compound to be present, though it is not
particularly limited, is generally in the range of one to three
equivalences, preferably in the range of one to two equivalences,
based on the amount of the compound (A). The term "equivalent
weight" as used herein means the numerical value to be calculated
by the following formula.
[0039] (Equivalence)
=(Number of mols of the bromine-containing compound).times.(Number
of bromine atoms per molecule of the bromine-containing
compound)/[4 (mols)]
[0040] The reaction vessel to be used in this invention imposes no
particular restriction and requires only to be incapable of being
fluorinated. As typical examples of such a reaction vessel, vessels
which are made of or coated with glass, polyethylene, polypropylene
or a fluorine resin may be cited. Among other coating materials
mentioned above, polyethylene, polypropylene, and a fluorine resin
may be used particularly advantageously for the purpose of
precluding the reaction vessels from the pollution due to the
otherwise possible elution of an alkali metal ion and a heavy metal
ion.
[0041] Then, after the reaction of the compound (A) with the
fluorine has been completed, the product aimed at can be isolated
from the resultant reaction solution by subjecting the solution to
separation or purification by such a known technique as, for
example, silica column chromatography, distillation, or
recrystallization.
[0042] In this case, the yield of the product in the resultant
reaction solution is determined by subjecting the reaction solution
to gas chromatography furnished with a hydrogen flame ionizing
detector. For a fixed content, this method produces a peak strength
which is proportionate to the number of carbon atoms of a given
sample. For a fixed number of carbon atoms, this method is enabled
to accomplish quantitative analysis because the peak strength is
proportionate to the amount of the product.
[0043] Now, this invention will be described more specifically
below with reference to working examples. In the working examples,
the yields of the products by relevant reactions were calculated in
the same manner as in the embodiment mentioned above. Note that
Referential Examples 1-4 and Examples 1-11 and 14-19 are not within
the scope of the current invention. Examples 12 and 13, on the
other hand, are within the scope of this invention. Examples 1-11
and 14-19 therefore should be deemed as comparative examples.
[0044] Referential Example 1
[0045] In a three-neck flask, 100 ml in inner volume, made of glass
and provided with a stirrer, 6.65 g (50 mmols) of terephthal
aldehyde and 50 g of dichloromethane were placed. The reactants,
after having added 10 ml (120 mmols) of 1,2-ethane dithiol, were
stirred continuously at 25.degree. C. for 20 minutes and, after
having subsequently added 10 ml (80 mmols) of a boron trifluoride
diethyl ether complex, further stirred continuously at 25.degree.
C. for two hours, to form a white precipitate. By filtrating this
white precipitate, 10.8 g (75% in yield) of 2,2'-(1,4-phenylene)
bis-1,3-dithioran (hereinafter referred to as "Intermediate
(1)").
[0046] Referential Example 2
[0047] In a three-neck flask, 100 ml in inner volume, made of glass
and provided with a stirrer and a Dean-Stark trap, 6.65 g (50
mmols) of terephthal aldehyde and 50 g of toluene 50 g were placed.
The reactants, after having added 3.4 g (55 mmols) of ethylene
glycol and 0.21 g (1 mmol reduced as paratoluene sulfonic acid) of
paratoluenesulfonic monohydride, were continuously stirred as
refluxed at 110.degree. C. for two hours. The resultant product was
separated and refined by silica gel column chromatography, to
obtain 8.3 g (75% in yield) of 2,2'-(1,4-phenylene)bis-
-1,3-dioxoran (hereinafter referred to as "Intermediate (2)").
[0048] Referential Example 3
[0049] In a three-neck flask, 100 ml in inner volume, made of glass
and provided with a stirrer, 4.0 g (30 mmols) of terephthal
aldehyde and 30 g of dichloromethane were placed. The reactants,
after having added 8.1 g (75 mmols) of 1,3-propane dithiol, were
stirred continuously at 25.degree. C. for 20 minutes and, after
having subsequently added 6.3 ml (50 mmols) of a boron trifluoride
diethyl ether complex, further stirred continuously at 25.degree.
C. for two hours, to form a white precipitate. The resultant white
precipitate was filtered, to obtain 6.6 g (70% in yield) of
2,2'-(1,4-phenylene) bis-1,3-dithian (hereinafter referred to as
"Intermediate (3)").
[0050] Referential Example 4
[0051] In a three-neck flask, 300 ml in inner volume, made of glass
and provided with a stirrer and a Dean-Stark trap, 51.6 g (385
mmols) of terephthal aldehyde, 64.4 g (767 mmols) of ethane
dithiol, and 150 ml of toluene were placed. The reactants, after
having added 0.037 g (0.19 mmol) of paratoluene sulfonic
monohydride, were continuously stirred as refluxed at 110.degree.
C. for three hours, with the water generated in consequence of the
reaction kept expelled by distillation. The white solid
precipitated consequently was separated by filtration and dried, to
obtain 100 g (91% in yield) of 2,2'-(1,4-phenylene)
bis-1,3-dithioran (hereinafter referred to as "Intermediate
(4)")
EXAMPLE 1
[0052] In a three-neck flask, 2 liters in inner volume, made of
glass and provided with a stirrer, 14.9 g (52 mmols) of
1,3-dibromo-5,5-dimethyl hydantoin (hereinafter abbreviated as
"DMH") and 660 g of dichloromethane were placed and thoroughly
dissolved by stirring. The three-neck flask, with argon gas (having
a moisture content of not more than 1 volppm) continuously flowing
through the interior thereof, was immersed in ice water. Then, in
the solution in the flask, 25 ml (1060 mmols) of pyridine hydrogen
fluoride (HF-Pyridine: produced by Aldrich Corp.; the weight ratio
of HF to pyridine: 7 to 3; density 1.2) was added through the
medium of a syringe. Further, 7.7 g (27 mmols) of the intermediate
(1) prepared in Referential Example 1 was introduced as split into
several portions while stirred at 0.degree. C., and continuously
stirred at 0.degree. C. for two hours and then made to add 660 g of
dichloromethane. The molar amount of HF-Pyridine is about 40 times
that of the intermediate (1).
[0053] The resultant mixture was distilled to expel the reaction
solvent by evaporation and the residue of the distillation was
passed through a basic alumina column. When the effluent from the
column was analyzed by the GC-MS, it was confirmed to contain
therein 4-difluoromethyl benzaldehyde (product 1) and
1,4-bis-(difluoromethyl)benzene (product 2). In the GC analysis
which was separately performed, the area ratio of product 1/product
2 was found to be 10/90.
[0054] When the reaction mixture obtained in consequence of the
preceding operation was distilled under a reduced pressure (50
mmHg, 93.degree. C. to 99.degree. C.), it separated 3.8 g of
1,4-bis(difluoromethyl)benzene (80% in yield).
EXAMPLES 2 to 4
[0055] Reactions were performed by following the procedure of
Example 1 while changing the temperature of adding the intermediate
(1) and the temperature of reaction to the levels shown in Table 1
below and the 1,4-bis(difluoromethyl)benzenes consequently produced
were measured for yield. The results of Examples 1 to 4 are
summarized in Table 1 below.
1TABLE 1 Temperature Yield Example (.degree. C.) (%) 1 0 80 2 -80
35 3 23 60 4 40 8
[0056] From Table 1 given above, it is clearly noted that the
1,4-bis(difluoromethyl)benzene aimed at can be obtained in a high
yield by adjusting both the temperature of adding the intermediate
(1) and the reaction temperature within the range of -20.degree. to
25.degree. C.
EXAMPLE 5
[0057] In a three-neck flask, 200 ml in inner volume, made of glass
and provided with a stirrer, 1.49 g (5.2 mmols) of DMH and 66 g of
dichloromethane were placed and thoroughly dissolved by stirring.
The three-neck flask, with argon gas (having a moisture content of
not more than 1 volppm) continuously flowing through the interior
thereof, was immersed in ice water. To the solution in the flask,
2.5 ml (106 mmols) of pyridine hydrogen fluoride (HF-Pyridine:
produced by Aldrich Corp.; the weight ratio of HF to pyridine: 7 to
3; d 1.2) was added through the medium of a syringe. Then, 0.6 g
(2.7 mmols) of the intermediate (2) prepared in Referential Example
2 was introduced as split into several portions while stirred at
0.degree. C. and continuously stirred at 0.degree. C. for two hours
and then made to add 66 g of dichloromethane.
[0058] The resultant mixture was distilled to expel the reaction
solvent by evaporation and the residue of the distillation was
passed through a basic alumina column. When the effluent from the
column was analyzed by the GC-MS, it was confirmed to contain
therein 4-difluoromethyl benzaldehyde (product 1) and
1,4-bis-(difluoromethyl)benzene (product 2). In the GC analysis
which was separately performed, the area ratio of product 1/product
2 was found to be 30/70.
EXAMPLE 6
[0059] A reaction was performed by following the procedure of
Example 5 while using 0.85 g (2.7 mmols) of the intermediate (3)
synthesized in Referential Example 3 in place of the intermediate
(2).
[0060] When the effluent from the column was analyzed by the GC-MS,
it was confirmed to contain therein 4-difluoromethyl benzaldehyde
(product 1) and 1,4-bis(difluoromethyl)benzene (product 2). In the
GC analysis which was separately performed, the area ratio of the
product 1/product 2 was found to be 15/85.
EXAMPLE 7
[0061] In a three-neck flask, 200 ml in inner volume, made of glass
and provided with a stirrer, 1.49 g (5.2 mmols) of DMH and 66 g of
dichloromethane were placed and thoroughly dissolved by stirring.
The three-neck flask, with argon gas continuously flowing through
the interior thereof, was immersed in ice water. To the solution in
the flask, 0.77 g (2.7 mmols) of the intermediate (1) prepared in
Referential Example 1 was introduced as split into several
portions. Then, 2.5 ml (106 mmols) of pyridine hydrogen fluoride
(produced by Aldrich Corp.; the weight ratio of HF to pyridine is 7
to 3) was further added as split into several portions through the
medium of a syringe, and stirred continuously at 0.degree. C. for
two hours and then made to add 66 g of dichloromethane.
[0062] The resultant mixture was distilled to expel the reaction
solvent by evaporation and the residue of the distillation was
passed through a basic alumina column. When the effluent from the
column was analyzed by the GC-MS, it was confirmed to contain
therein 4-difluoromethyl benzaldehyde (product 1) and
1,4-bis-(difluoromethyl)benzene (product 2). In the GC analysis
which was separately performed, the area ratio of product 1/product
2 was found to be 60/40.
EXAMPLE 8
[0063] In a three-neck flask, 200 ml in inner volume, made of glass
and provided with a stirrer, 1.49 g (5.2 mmols) of DMH and 66 g of
dichloromethane were placed and thoroughly dissolved by stirring.
The three-neck flask, with argon gas continuously flowing through
the interior thereof, was immersed in ice water. To the solution in
the flask, 0.6 g (2.1 mmols) of the intermediate (1) prepared in
Referential Example 1 was added. Further, 4.89 dm.sup.3 (volume at
25.degree. C., 0.2 mol reduced as HF) of hydrofluoric acid was
introduced as gradually blown in the resultant solution,
continuously stirred at 0.degree. C. for two hours and then made to
add 66 g of dichloromethane.
[0064] The resultant mixture was distilled to expel the reaction
solvent by evaporation and the residue of the distillation was
passed through a basic alumina column. When the effluent from the
column was analyzed by the GC-MS, it was confirmed to contain
therein 4-difluoromethyl benzaldehyde (product 1) and
1,4-bis-(difluoromethyl)benzene (product 2). In the GC analysis
which was separately performed, the area ratio of product 1/product
2 was found to be 30/70.
EXAMPLE 9
[0065] A three-neck flask, 200 ml in inner volume, made of glass
and provided with a stirrer was charged with 50 mL dichloromethane
(DCM) and 36 g N-bromosuccinimide (NBS) and, after having the
interior thereof displaced with argon gas (moisture content of not
more than 1 volppm), further charged with 2.4 mL pyridine hydrogen
fluoride (produced by Aldrich Corp.; the weight ratio of HF to
pyridine: 7 to 3; density 1.2; abbreviated as "HF-Pyr" in Table 2
below). The mixture in the three-neck flask, with the flask placed
in ice water, was made to add 7.4 g (25.9 mmols) of the
intermediate (4) synthesized in Referential Example 4 as kept
continuously stirred at an inner temperature of 0.degree. to
5.degree. C. The amount of NBS was about two equivalences to the
amount of intermediate (4). It was further stirred continuously at
the temperature of ice for two hours.
[0066] To the resultant reaction mixture, an aqueous 20% sodium
hydroxide solution was added until the pH value of the water phase
rose above 10. The precipitate which was generated during the
course of the neutralization was separated by filtration. The
organic layer of the filtrate was washed with dilute hydrochloric
acid and then distilled under a reduced pressure (50 mmHg,
93.degree. to 99.degree. C.), to isolate
1,4-bis(difluoromethyl)benzene.
EXAMPLES 10 TO 19
[0067] Isolation of 1, 4-bis (difluoromethyl)benzene was performed
by following the procedure of Example 9 while changing the amounts
of relevant reactants as shown in the following table. In Examples
16 and 17, 1,3-dibromo-5,5-dimethyl hydantoin (DMH) was used as a
bromine-containing compound in place of N-bromosuccinimide (NBS).
In Examples 16 and 17, a three-neck flask having an inner volume of
1 liter was used in place of the three-neck flack having the inner
volume of 200 ml. In Example 19, the use of a bromine-containing
compound was omitted.
[0068] The compositions of Examples 9 to 19 and the results
obtained therefor are shown in Table 2 below. Unexpectedly, the
yields in Examples 12 and 13 were 100%, i.e., no by-products were
formed in these examples.
2 TABLE 2 DCM NBS HF-Pyr Intermediate (ml) (g) (ml) (4) Yield
Example 9 50 36 2.4 7.4 6 Example 10 50 36 6.1 7.4 18.8 Example 11
50 36 9.7 7.4 39.0 Example 12 50 36 12.1 7.4 100 Example 13 50 36
24.2 7.4 100 Example 14 50 18 24.2 7.4 40.8 Example 15 50 9 24.2
7.4 21.0 Example 16 300 DMH; 17.4 14.5 4.44 30 Example 17 300 DMH;
174 145 44.4 30 Example 18 50 3.6 2.4 0.74 32 Example 19 50 --*
12.0 7.4 20 *No bromine-containing compound used.
[0069] The entire disclosure of Japanese Patent Application No.
10-9135 filed on Jan. 20, 1998 including specification, claims,
drawings and summary are incorporated herein by reference in its
entirety.
* * * * *