TITLE OF INVENTION:
METHOD FOR PRODUCING CYCLOBUTANE TETRACARBOXYLIC ACID
DERIVATIVE
5
TECHNICAL FIELD
The present invention relates to a novel method for producing a cyclobutane
tetracarboxylic acid derivative useful as a raw material for e.g. a polyimide.
BACKGROUND AR10 T
A cyclobutane tetracarboxylic acid derivative is a compound useful as a raw
material for e.g. a polyimide. As a method for producing the compound, a
photodimerization reaction of a maleic anhydride derivative is known (Patent
Documents 1 to 5).
15 However, the method for producing a cyclobutane tetracarboxylic acid derivative
by a photodimerization reaction of maleic anhydride, disclosed in each of Patent
Documents 1 to 5, is not necessarily sufficient in photoreaction efficiency even when a
sensitizer is used.
For example, Patent Document 1 discloses, as a method for producing 1,2,3,4-
20 cyclobutane tetracarboxylic acid-1,2:3,4-dianhydride (CBDA), a photodimerization
reaction of maleic anhydride in a solvent having a carbonyl group, such as a ketone.
However, Patent Document 1 discloses that the use of e.g. acetophenone,
benzophenone or anthraquinone as a sensitizer is not effective for this reaction, and the
absence of such a sensitizer is rather preferred for this reaction (the last line in the
25 lower right column on page (2) to the fourth line in the upper left column on page (3) of
Patent Document 1).
As mentioned above, a conventional method for producing a 1,2,3,4-cyclobutane
tetracarboxylic acid-1,2:3,4-dianhydride (CBDA) by a photodimerization reaction of
maleic anhydride, is useful in that maleic anhydride as a raw material is available at a
30 relatively low cost and that this production method is simple, but such a method is
insufficient in photoreaction efficiency and thus has a problem in yield of a desired
product.
2
Patent Document 2 discloses that it is possible to obtain a mixture of 1,3-
dimethylcyclobutane-1,2,3,4-tetracarboxylic acid-1,2:3,4-dianhydride (1,3-DMCBDA)
and 1,2-dimethylcyclobutane-1,2,3,4-tetracarboxylic acid-1,2:3,4-dianhydride (1,2-
DMCBDA) by photodimerization reaction of citraconic anhydride (abbreviated as MMA),
as represented by the following scheme5 .
Meanwhile, when 1,3-DMCBDA and 1,2-DMCBDA are compared, it is known that
the former 1,3-DMCBDA having a highly symmetric structure, is more useful since it is
possible to produce a polyimide having a higher molecular weight than the latter 1,2-
10 DMCBDA.
Although Patent Document 2 discloses that it is possible to obtain a mixture of 1,3-
DMCBDA and 1,2-DMCBDA, it fails to disclose that the former 1,3-DMCBDA having a
higher utility, is selectively produced in a high yield.
15 PRIOR ART DOCUMENTS
PATENT DOCUMENTS
Patent Document 1: JP-A-59-212495
Patent Document 2: JP-A-4-106127
Patent Document 3: JP-A-2003-192685
20 Patent Document 4: JP-A-2006-347931
Patent Document 5: JP-A-2008-69081
DISCLOSURE OF INVENTION
TECHNICAL PROBLEM
25 The object of the present invention is to provide a method for producing a 1,3-
dialkyl-1,2,3,4-cyclobutane tetracarboxylic acid-1,2:3,4-dianhydride (hereinafter, also
referred to as 1,3-DACBDA), at a high photoreaction efficiency and in a high yield, by
subjecting the maleic anhydride compound of the formula (1) to a photodimerization
3
reaction.
SOLUTION TO PROBLEM
The present inventors have conducted extensive studies to solve the above
problems and as a result, have found that, when a specific solvent is used, it is possibl5 e
to improve a photoreaction efficiency of a maleic anhydride compound and further
produce a 1,3-DACBDA derivative, which is an isomer having a higher symmetric
structure, in an improved selectivity and in a high yield, by subjecting a maleic
anhydride compound in the presence of a sensitizer, as is different from a conventional
10 disclosure of e.g. Patent Document 1.
The present invention has been made based on the above novel discovery and
provides the following.
1. A method for producing a 1,3-dialkyl 1,2,3,4-cyclobutane tetracarboxylic acid-
1,2:3,4-dianhydride derivative represented by the formula (2), which comprises
15 subjecting a maleic anhydride compound represented by the following formula (1) to a
photodimerization reaction, in a solvent containing a C1-4 fatty acid ester, in the
presence of a sensitizer.
wherein R is a C1-20 alkyl group.
2. The method according to the above 1, wherein R is a C1-6 alkyl group.
20 3. The method according to the above 1 or 2, wherein the amount of the solvent to
be used is from 3 to 300 times by mass to the maleic anhydride compound.
4. The method according to any one of the above 1 to 3, wherein the C1-4 fatty acid
ester is a fatty acid alkyl ester represented by the formula: R1COOR2 (wherein R1 is
hydrogen, or preferably a C1-4 alkyl group, and R2 is a C1-4 alkyl group).
25 5. The method according to any one of the above 1 to 4, wherein the solvent
contains a sub solvent of a carbonic acid diester.
4
6. The method according to any one of the above 1 to 5, wherein the sensitizer is
benzophenone, acetophenone or benzaldehyde.
7. The method according to any one of the above 1 to 6, wherein the sensitizer is
benzophenone substituted with an electron-withdrawing group, acetophenone
substituted with an electron-withdrawing group, or benzaldehyde substituted with 5 an
electron-withdrawing group.
8. The method according to the above 7, wherein the electron-withdrawing group is
at least one member selected from the group consisting of a fluoro group, a chloro
group, a bromo group, an iodo group, a nitro group, a cyano group and a trifluoromethyl
10 group.
9. The method according to the above 7 or 8, wherein the number of electronwithdrawing
groups is from 1 to 5.
10. The method according to any one of the above 1 to 9, wherein the sensitizer is
used in a proportion of from 0.1 to 20 mol% to the maleic anhydride compound.
15 11. The method according to any one of the above 1 to 10, wherein the reaction
temperature is from 0 to 20 C.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, an inexpensive maleic anhydride compound as
20 a raw material is subjected to a photodimerization reaction at a photoreaction efficiency,
whereby it is possible to improve a photoreaction efficiency of a maleic anhydride
compound, and further produce a 1,3-DACBDA derivative, which is an isomer having a
higher symmetric structure, in an improved selectivity and in a high yield, by subjecting
the maleic anhydride compound in the presence of a sensitizer, as is different from a
25 conventional disclosure of e.g. Patent Document 1.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a graph illustrating the correlation of an irradiation time and a remaining
amount of citraconic anhydride in Example 1 of the present invention and Comparative
30 Examples 1 and 2.
DESCRIPTION OF EMBODIMENTS
The method for producing a 1,3-dialkyl-1,2,3,4-cyclobutanetetracarboxylic acid5
1,2:3,4-dianhydride derivative represented by the formula (2), by subjecting a maleic
anhydride compound represented by the formula (1) to a photodimerization reaction, is
represented by the following reaction scheme.
wherein R is a C1-20, preferably a C1-12, more preferably a C1-6 alkyl group, particularl5 y
preferably methyl.
The C1-20 alkyl group may be a linear or branched saturated alkyl group, or a linear
or branched unsaturated alkyl group.
As a specific example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t10
butyl, n-pentyl, 1-methyl-n-butyl, 2-methyl-n-butyl, 3-methyl-n-butyl, 1,1-dimethyl-npropyl,
n-hexyl, 1-methyl-n-pentyl, 2-methyl-n-pentyl, 1,1,-dimethyl-n-butyl, 1-ethyl-nbutyl,
1,1,2-trimethyl-n-propyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-dodecyl or n-eicosyl,
1-methylvinyl, 2-allyl, 1-ethylvinyl, 2-methylallyl, 2-butenyl, 2-methyl-2-butenyl, 3-methyl-
2-butenyl, 3-methyl-3-butenyl, 2-hexenyl, 4-methyl-3-pentenyl, 4-methyl-4-pentenyl, 2,3-
15 dimethyl-2-butenyl, 1-ethyl-2-pentenyl, 3-dodecenyl, propargyl, 3-butynyl, 3-methyl-2-
propynyl or 9-decynyl may be mentioned.
Here, n represents normal, i represents iso, s represents secondary, and t
represents tertiary, respectively.
The maleic anhydride compound represented by the formula (1) may, for example,
20 be citraconic anhydride, 2-ethyl maleic anhydride, 2-isopropyl maleic anhydride, 2-nbutyl
maleic anhydride, 2-t-butyl maleic anhydride, 2-n-pentyl maleic anhydride, 2-nhexyl
maleic anhydride, 2-n-heptyl maleic anhydride, 2-n-octyl maleic anhydride, 2-nnonyl
maleic anhydride, 2-n-decyl maleic anhydride, 2-n-dodecyl maleic anhydride, 2-neicosyl
maleic anhydride, 2-(1-methyl vinyl) maleic anhydride, 2-(2-allyl) maleic
25 anhydride, 2-(1-ethyl vinyl) maleic anhydride, 2-(2-methyl allyl) maleic anhydride, 2-(2-
butenyl) maleic anhydride, 2-(2-hexenyl) maleic anhydride, 2-(1-ethyl-2-pentenyl) maleic
anhydride, 2-(3-dodecenyl) maleic anhydride, 2-propargyl maleic anhydride, 2-(3-
6
butynyl) maleic anhydride, 2-(3-methyl-2-propynyl) maleic anhydride or 2-(9-decynyl)
maleic anhydride. Among them, e.g. citraconic anhydride, 2-ethyl maleic anhydride, 2-
isopropyl maleic anhydride, 2-n-butyl maleic anhydride, 2-t-butyl maleic anhydride, 2-npentyl
maleic anhydride, 2-n-hexyl maleic anhydride, 2-n-heptyl maleic anhydride, 2-noctyl
maleic anhydride, 2-n-nonyl maleic anhydride, 2-n-decyl maleic anhydride or 2-5 ndodecyl
maleic anhydride is preferred, and citraconic anhydride, 2-ethyl maleic
anhydride, 2-isopropyl maleic anhydride, 2-n-butyl maleic anhydride, 2-t-butyl maleic
anhydride, 2-n-pentyl maleic anhydride or 2-n-hexyl maleic anhydride is more preferred,
in view of high photoreaction efficiency.
10 The photoreaction of the present invention is carried out by adding a
(photo)sensitizer to a reaction system, in the presence of the sensitizer. The sensitizer
is not limited so long as it functions as a photosensitizer, and benzophenone,
benzaldehyde or anthraquinone may, for example, be mentioned.
Among them, it is particularly preferred to use, as a sensitizer, benzophenone
15 substituted with an electron-withdrawing group, acetophenone substituted with an
electron-withdrawing group or benzaldehyde substituted with an electron-withdrawing
group. In such a case, the electron-withdrawing group may be at least one member
selected from the group consisting of a fluoro group, a chloro group, a bromo group, an
iodo group, a nitro group, a cyano group and a trifluoromethyl group, preferably a fluoro
20 group, a chloro group, a bromo group, a cyano group or a trifluoromethyl group. A
particularly preferred electron-withdrawing group is a fluoro group or a chloro group.
The number of the electron-withdrawing group is from 1 to 10, preferably from 1 to 5,
particularly preferably from 1 to 3.
The substitution position of the electron-withdrawing group in benzophenone,
25 benzaldehyde or anthraquinone as a sensitizer, may be ortho position, meta position or
para position, preferably ortho position or para position, to the carbonyl group. When
the number of the electron-withdrawing group is two or more, the electron-withdrawing
groups may be the same or different. Further, it may be a case (anthraquinone) in
which carbonyl groups having an electron-withdrawing effect are crosslinked at each
30 ortho position.
As a specific example of benzophenone or benzophenone substituted with an
electron-withdrawing group, benzophenone, 2-fluorobenzophenone, 3-
7
fluorobenzophenone, 4-fluorobenzophenone, 2-chlorobenzophenone, 3-
chlorobenzophenone, 4-chlorobenzophenone, 2-cyanobenzophenone, 3-
cyanobenzophenone, 4-cyanobenzophenone, 2-nitrobenzophenone, 3-
nitrobenzophenone, 4-nitrobenzophenone, 2,4’-dichlorobenzophenone, 4,4’-
difluorobenzophenone, 4,4’-dichlorobenzophenone, 4,4’-dibromobenzophenone, 3,35 ’-
bis(trifluoromethyl)benzophenone, 3,4’-dinitrobenzophenone, 3,3’-dinitrobenzophenone,
4,4’-dinitrobenzophenone, 2-chloro-5-nitrobenzophenone, 1,3-bis(4-
fluorobenzoyl)benzene, 1,3-bis(4-chlorobenzoyl)benzene, 2,6-dibenzoylbenzonitrile,
1,3-dibenzoyl-4,6-dinitrobenzene or anthraquinone may be mentioned. Among them,
10 4,4’-difluorobenzophenone or 4,4’-dichlorobenzophenone is preferred.
As a specific example of acetophenone or acetophenone substituted with an
electron-withdrawing group, acetophenone, 2’-fluoroacetophenone, 3’-
fluoroacetophenone, 4’-fluoroacetophenone, 2’-chloroacetophenone, 3’-
chloroacetophenone, 4’-chloroacetophenone, 2’-cyanoacetophenone, 3’-
15 cyanoacetophenone, 4’-cyanoacetophenone, 2’-nitroacetophenone, 3’-
nitroacetophenone, 4’-nitroacetophenone, 2’,4’-difluoroacetophenone, 3’,4’-
difluoroacetophenone, 2’,4’-dichloroacetophenone, 3’,4’-dichloroacetophenone, 4’-
chloro-3’-nitroacetophenone, 4’-bromo-3’-nitroacetophenone or 4’-fluoro-3’-
nitroacetophenone may, for example, be mentioned. Among them, 4’-
20 fluoroacetophenone, 4’-chloroacetophenone, 2’,4’-difluoroacetophenone, 3’,4’-
difluoroacetophenone, 2’,4’-dichloroacetophenone or 3’,4’-dichloroacetophenone is
preferred.
Benzaldehyde or benzaldehyde substituted with an electron-withdrawing group
may, for example, be benzaldehyde, 2-fluorobenzaldehyde, 3-fluorobenzaldehyde, 4-
25 fluorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-
chlorobenzaldehyde, 2-cyanobenzaldehyde, 3-cyanobenzaldehyde, 4-
cyanobenzaldehyde, 2-nitrobenzaldehyde, 3-nitrobenzaldehyde, 4-nitrobenzaldehyde,
2,4-difluorobenzaldehyde, 3,4-difluorobenzaldehyde, 2,4-dichlorobenzaldehyde, 3,4-
dichlorobenzaldehyde, 2-chloro-5-nitrobenzaldehyde, 4-chloro-2-nitrobenzaldehyde, 4-
30 chloro-3-nitrobenzaldehyde, 5-chloro-2-nitrobenzaldehyde, 2-fluoro-5-
nitrobenzaldehyde, 4-fluoro-3-nitrobenzaldehyde or 5-fluoro-2-nitrobenzaldehyde.
Among them, 4-fluorobenzaldehyde, 4-chlorobenzaldehyde, 2,4-difluorobenzaldehyde,
8
3,4-difluorobenzaldehyde, 2,4-dichlorobenzaldehyde or 3,4-dichlorobenzaldehyde is
preferred.
The amount of the sensitizer to be used is not particularly limited so long as it is
possible to accelerate a photoreaction rate, but it is preferably from 0.1 to 20 mol%,
more preferably from 0.1 to 5 mol% to the maleic anhydride compound. The sensitize5 r
may be used alone or two or more of them may be used in combination. the sensitizer
is preferably used alone in view of easiness of treatment after the reaction.
In the photoreaction of the present invention, it is essential to use a C1-4 fatty acid
ester as a reaction solvent with a view to accelerating a photoreaction rate. The C1-4
10 fatty acid ester, preferably a C1-2 fatty acid ester is suitably a fatty acid alkyl ester
represented by the formula: R1COOR2 (wherein R1 is hydrogen, or preferably a C1-4
alkyl group, more preferably a C1-2 alkyl group, and R2 is a C1-4 alkyl group, more
preferably a C1-3 alkyl group). As a preferred specific example, methyl formate, ethyl
formate, n-propyl formate, i-propyl formate, n-butyl formate, i-butyl formate, methyl
15 acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate,
methyl propionate, ethyl propionate, n-propyl propionate, i-propyl propionate, n-butyl
propionate or i-butyl propionate may be mentioned. Particularly preferred is methyl
acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, methyl propionate, ethyl
propionate, n-propyl propionate or i-propyl propionate. One or at least two of them
20 may be used.
Further, as a reaction solvent, a C1-4 fatty acid ester may be used alone, but other
sub solvent other than the reaction solvent may be used. It is preferred that the sub
solvent to be used in such a case meets requirements (1) to be a carbonyl compound
having a high photosensitization effect, (2) to have a high solubility of the maleic
25 anhydride compound as a raw material, and to have a low solubility of the CBDA
derivative compound produced so as to suppress a decomposition reaction of the CBDA
derivative compound, (3) to have a high solubility of a by-product so that a CBDA
derivative compound can be purified only by washing with the same solvent, (4) to be a
compound having no low-boiling point as to increase the risk of flammability and further
30 having a boiling point of around 100°C so as not to leave the compound in a CBDA
derivative compound product, (5) to be environmentally safe, (6) to be stable during
photoreaction, (7) to be available at a low cost, and the like.
9
In order to meet these requirements, as a specific example of the sub solvent,
carbonic acid diester is preferred, and in particular, a carbonic acid dialkyl ester having
preferably a C1-3 alkyl, more preferably a C1-2 alkyl, is suitable. As a preferred
example, dimethyl carbonate or diethyl carbonate may be mentioned, and diethyl
carbonate or dimethyl carbonate is particularly preferred. As the sub solvent, a glyco5 l
diester such as ethylene glycol diformate, ethylene glycol diacetate, ethylene glycol
dipropionate, propylene glycol diformate, propylene glycol diacetate, propylene glycol
dipropionate or butylene glycol diacetate may be used.
As one of excellent features of the production method where a C1-4 fatty acid ester
10 is used as a reaction solvent in the present invention, a desired compound is readily
precipitated as a crystal during a reaction since the solubility of a CBDA compound
produced is low despite that the solubility of the maleic anhydride compound as a raw
material is high, and therefore it is possible to suppress a reverse reaction from the
CBDA derivative compound to the maleic anhydride compound or a side reaction such
15 as production of oligomer.
The amount of the reaction solvent to be used is from 3 to 300 times by mass,
more preferably from 4 to 250 times by mass to the maleic anhydride compound. The
above solvent may be used alone or in combination of two or more, but the solvent is
preferably used alone in view of easiness of treatment after the reaction. In the case of
20 using a sub solvent, the amount of the sub solvent is preferably from 0.1 to 100 times by
mass, more preferably from 0.1 to 10 times by mass to the C1-4 fatty acid ester. If the
amount of the sub solvent to be used is too large, the desired compound is dissolved in
a reaction fluid, and the recovery rate decreases, such being undesirable.
Further, the amount of the reaction solvent to be used is preferably low, and in
25 such a case, for example, the concentration of a maleic anhydride compound becomes
high, the reaction rate becomes high, and the yield of the product per hour becomes
large. Accordingly, in order to increase the reaction rate and the yield of the product,
the amount of the solvent to be used is preferably from 3 to 10 times by mass to the
maleic anhydride compound.
30 In this photoreaction, a wavelength of light is from 200 to 400 nm, more preferably
from 250 to 350 nm, particularly preferably from 280 to 330 nm. As a light source, a
low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury
10
lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, an electrodeless lamp or a
light-emitting diode, etc. is used. Among them, a high-pressure mercury lamp, an
ultrahigh-pressure mercury lamp or a light-emitting diode is preferred since it is possible
to obtain a CBDA derivative compound in a high yield.
Further, with respect to a photochemical reaction apparatus, if a light source5 -
cooling pipe is changed from lime glass to Pyrex (registered trademark) glass, a colored
polymer is less attached to the light source-cooling pipe and impurities are less
produced, and therefore it is possible to improve the yield of a CBDA derivative
compound.
10 If the reaction temperature becomes high, a polymer tends to be produced as a
by-product, and if the reaction temperature becomes low, the solubility of the maleic
anhydride compound tends to be low, whereby the production efficiency will be
deteriorated. Therefore, the reaction temperature is preferably from -20 to 80°C, more
preferably from -10 to 50°C. In particular, when the reaction temperature is from 0 to
15 20°C, the production of a by-product is significantly suppressed, and therefore it is
possible to obtain a CBDA derivative compound in a high selectivity and a high yield.
The reaction time may vary depending upon e.g. the type of a light source or the
irradiation dose, but it is possible to carry out the reaction until the proportion of an
unreacted maleic anhydride compound reaches preferably a range of from 0 to 40%,
20 more preferably a range of from 0 to 10%. The reaction time is usually from 1 to 200
hours, but it can be from 1 to 60 hours as the case requires.
As the reaction time becomes long, the conversion rate of a maleic anhydride
compound increases and the precipitation amount of a CBDA derivative compound
thereby increases, and as a result, the CBDA derivative compound produced tends to
25 attach to an exterior wall (a reaction fluid side) of a light source-cooling pipe, whereby
crystal coloration or a decrease of light efficiency (unit power × yield per hour)
accompanied by decomposition reaction tends to be observed. Therefore, it is
practically undesirable to take a long time in one batch for increasing the conversion
rate of the maleic anhydride compound since the production efficiency decreases.
30 The reaction may be carried out by either a batch-type or a flow-type, but a batchtype
is preferably used. Further, the reaction pressure may be either atmospheric
pressure or elevated pressure, but is preferably atmospheric pressure.
11
The CBDA derivative compound as the desired compound may be obtainable by
carrying out photoreaction, filtrating a precipitate in a reaction fluid, washing a collected
product with an organic solvent, folowed by drying under reduced pressure.
The amount of the organic solvent to be used for washing the collected product, is
not limited so long as it is possible to transfer a precipitate remained in a reactor to 5 a
filter, but if the amount of the organic solvent is large, the desired compound tends to be
transferred to a filtrate, whereby the recovery rate decreases. Therefore, the amount
of the organic solvent to be used for washing the collected product, is preferably from
0.5 to 10 times by mass, more preferably from 1 to 2 times by mass, to the maleic
10 anhydride compound used in the reaction.
The organic solvent to be used for washing the collected product is not particularly
limited, but it is undesirable to use a solvent having high solubility of the product, since
the desired compound tends to be transferred to a filtrate and the recovery rate thereby
decreases. Therefore, the organic solvent to be used for washing the collected
15 product may, for example, be methyl formate, ethyl formate, n-propyl formate, i-propyl
formate, n-butyl formate, i-butyl formate, methyl acetate, ethyl acetate, n-propyl acetate,
i-propyl acetate, n-butyl acetate, i-butyl acetate, methyl propionate, ethyl propionate, npropyl
propionate, i-propyl propionate, n-butyl propionate, i-butyl propionate, ethylene
glycol diformate, ethylene glycol diacetate, ethylene glycol dipropionate, dimethyl
20 carbonate or diethyl carbonate, or a solvent which does not solve a product and is not
reactive with the product, such as toluene, hexane, heptane, acetonitrile, acetone,
chloroform or acetic anhydride, or a mixed solvent thereof, as a reaction solvent to be
used for photodimerization reaction. Among them, ethyl acetate, dimethyl carbonate or
acetic anhydride is preferred, and ethyl acetate or dimethyl carbonate is more preferred.
25
EXAMPLES
Now, the present invention will be described in further detail with reference to
Examples, but it should be understood that the present invention is by no means
restricted thereto.
30 Further, analytical methods employed in Examples are as follows.

A small amount of a reaction fluid was sampled, and subjected to GC analysis in a
12
case where a solid is not precipitated. In a case where a solid is precipitated, the solid
is removed off by filtration, and then a filtrate is subjected to GC analysis.

According to quantitative analysis by means of gas chromatography, an area ratio
(an area value of citraconic anhydride/an area value of butyl lactate) is calculated fro5 m
the respective area values of citraconic anhydride and butyl lactate. An area ratio
obtained from a reaction fluid before photoirradiation is regarded as 100%, and the
remaining ratio (an area ratio in each irradiation time/an area ratio before
photoirradiation × 100) of citraconic anhydride is calculated on a reaction ratio of a
10 reaction fluid in each irradiation time.

Apparatus: GC-2010 Plus (manufactured by SHIMADZU Corporation),
Column: DB-1 (manufactured by AgilentTechnologies) 0.25 mm ×30 m, film
thickness 0.25 um,
15 Carrier gas: He, detector: FID, sample injection amount: 1 um, inlet port
temperature: 160°C, detector temperature: 220°C, column temperature: 70°C (20 min)-
40°C/min-220°C (15 min), split ratio: 1:50, internal standard substance: butyl lactate.
<1H NMR sampling method>
A crystal taken out after the photoirradiation is measured after drying under
20 reduced pressure. Further, from the filtrate and washing fluid, a solvent is removed by
drying under reduced pressure to measure a residue.
<1H NMR analysis method>
An integral value at 3.89 ppm of 1,3-DM-CBDA, as a standard basis, is compared
with an integral value at 3.72 ppm of 1,2-DM-CBDA, whereby the selectivity is
25 calculated. Specifically, the sum of the integral values of 1,3-DM-CBDA and 1,2-DMCBDA
is regarded as 100%, and each proportion of ([1,3-DM-CBDA integral value] or
[1,2-DM-CBDA integral value]/[sum of integral values of 1,3-DM-CBDA and 1,2-DMCBDA]
×100) is calculated.
<1H NMR analytical conditions>
30 Apparatus: Fourier transform superconducting NMR spectrometer (FT-NMR)
INOVA-400 (manufactured by Varian) 400 MHz,
Solvent: DMSO-d6, internal standard substance: tetramethylsilane (TMS).
13
COMPARATIVE EXAMPLE 1
In a nitrogen atmosphere, into a 300 mL Pyrex (registered trademark) glass fivenecked
flask, 35.0 g (312 mmol) of a citraconic anhydride (CA), 152 g (1720 mmol, 4.33
times by weight to citraconic anhydride (CA)) of ethyl acetate were charged, an5 d
dissolved with stirring by a magnetic stirrer. Then, the resultant was irradiated with a
100 W high-pressure mercury lamp with stirring at a temperature of from 5 to 10°C.
According to the above analytical method, the remaining ratio of citraconic
anhydride in a reaction fluid in each irradiation time was calculated.
10 EXAMPLE 1
In a nitrogen atmosphere, into a 300 mL Pyrex (registered trademark) glass fivenecked
flask, 35.0 g (312 mmol) of a citraconic anhydride (CA), 0.290 g (1.59 mmol, 0.5
mol% to the citraconic anhydride (CA)) of benzophenone (BP) and 152 g (1720 mmol,
4.33 times by weight to citraconic anhydride (CA)) of ethyl acetate were charged, and
15 dissolved with stirring by a magnetic stirrer. Then, the resultant was irradiated with a
100 W high-pressure mercury lamp with stirring at a temperature of from 5 to 10°C.
According to the above analytical method, the remaining ratio of citraconic
anhydride in a reaction fluid in each irradiation time was calculated.
EXAMPLE 2
20 In a nitrogen atmosphere, into a 300 mL Pyrex (registered trademark) glass five-
O
O
O
h
1,3-DM-CBDA
O O
O O
O O
CA 1,2-DM-CBDA
O O
O O
O O
AcOEt
O
O
O h
BP
1,3-DM-CBDA
O O
O O
O O
CA 1,2-DM-CBDA
O O
O O
O O
AcOEt
O
O
O h
DClBP
1,3-DM-CBDA
O O
O O
O O
CA 1,2-DM-CBDA
O O
O O
O O
AcOEt
14
necked flask, 35.0 g (312 mmol) of a citraconic anhydride (CA), 0.392 g (1.56 mmol, 0.5
mol% to the citraconic anhydride (CA)) of 4,4’-dichlorobenzophenone (DCIBP) and 152
g (1720 mmol, 4.33 times by weight to citraconic anhydride (CA)) of ethyl acetate were
charged, and dissolved with stirring by a magnetic stirrer. Then, the resultant was
irradiated with a 100 W high-pressure mercury lamp with stirring at a temperature o5 f
from 5 to 10°C.
According to the above analytical method, the remaining ratio of citraconic
anhydride in a reaction fluid in each irradiation time was calculated. The results
obtained in Comparative Example 1 and Examples 1 to 2 are shown in Table 1 and the
10 graph of Fig.1.
[Table 1]
Comparative
Example 1 Example 1 Example 2
Solvent Ethyl acetate Ethyl acetate Ethyl acetate
Sensitizer - Benzophenone 4,4’-Dichlorobenzophenone
Photoirradiation
time [hr]
Remaining ratio of
citraconic
anhydride [%]
Remaining ratio of
citraconic
anhydride [%]
Remaining ratio of
citraconic anhydride [%]
0 100 100 100
2 89.7 82.7
6 70.2 59.1
15 76.0
16 32.8 4.3
24 8.7
28
30 40.9 2.8
34
40 18.7
48
50 6.7
55 3.0
COMPARATIVE EXAMPLE 2
A photodimerization reaction was carried out in the same manner as in
15 Comparative Example 1. A white crystal precipitated was obtained by filtration at a
temperature of from 5 to 10°C. This crystal was washed twice with 43.8 g (497 mmol,
1.25 times by weight to the citraconic anhydride (CA)) of ethyl acetate. Then, this
crystal was dried under reduced pressure to obtain 5.8 g (yield: 16.6%) of a white
crystal. This crystal was analyzed by 1H NMR and confirmed to be a mixture (1,3-DM15
CBDA:1,2-DM-CBDA = 92.4:7.6) containing 1,3-DM-CBDA and 1,2-DM-CBDA.
Further, a crystal, a filtrate and a washing liquid obtained were quantitatively analyzed
respectively by 1H NMR analysis and gas chromatography, and as a result, mass
balance to the charged amount was found to be 93.1%.
1H NMR (DMSO-d6, ppm) (1,3-DM-CBDA): 1.38 (s, 6H), 3.89 (s, 2H)5 .
1H NMR (DMSO-d6, ppm) (1,2-DM-CBDA): 1.37 (s, 6H), 3.72 (s, 2H).
EXAMPLE 3
A photodimerization reaction was carried out in the same manner as in Example
1. A white crystal precipitated was obtained by filtration at a temperature of from 5 to
10 10°C. This crystal was washed twice with 43.8 g (497 mmol, 1.25 times by weight to
the citraconic anhydride (CA)) of ethyl acetate. Then, this crystal was dried under
reduced pressure to obtain 8.8 g (yield: 25.2%) of a white crystal. This crystal was
analyzed by 1H NMR and confirmed to be a mixture (1,3-DM-CBDA:1,2-DM-CBDA =
85.0:15.0) containing 1,3-DM-CBDA and 1,2-DM-CBDA. Further, a crystal, a filtrate
15 and a washing liquid obtained were quantitatively analyzed respectively by 1 H NMR
analysis and gas chromatography, and as a result, mass balance to the charged
amount was found to be 88.0%.
1H NMR (DMSO-d6, ppm) (1,3-DM-CBDA): 1.38 (s, 6H), 3.89 (s, 2H).
1H NMR (DMSO-d6, ppm) (1,2-DM-CBDA): 1.37 (s, 6H), 3.72 (s, 2H).
20 EXAMPLE 4
A photodimerization reaction was carried out in the same manner as in Example
2. A white crystal precipitated was obtained by filtration at a temperature of from 5 to
10°C. This crystal was washed twice with 43.8 g (497 mmol, 1.25 times by weight to
the citraconic anhydride (CA)) of ethyl acetate. Then, this crystal was dried under
25 reduced pressure to obtain 8.0 g (yield: 22.8%) of a white crystal. This crystal was
analyzed by 1H NMR and confirmed to be a mixture (1,3-DM-CBDA:1,2-DM-CBDA =
86.5:13.5) containing 1,3-DM-CBDA and 1,2-DM-CBDA. Further, a crystal, a filtrate
and a washing liquid obtained were quantitatively analyzed respectively by 1 H NMR
analysis and gas chromatography, and as a result, mass balance to the charged
30 amount was 95.7%.
1H NMR (DMSO-d6, ppm) (1,3-DM-CBDA): 1.38 (s, 6H), 3.89 (s, 2H).
1H NMR (DMSO-d6, ppm) (1,2-DM-CBDA): 1.37 (s, 6H), 3.72 (s, 2H).
16
INDUSTRIAL APPLICABILITY
The cyclobutane carboxylic acid derivative obtained in the present invention is a
compound useful as a raw material for e.g. a polyamic acid or a polyimide, and such a
polyimide is industrially applicable as a resin composition used in a field of a display
such as a television using a liquid crystal panel or a semiconductor field5 .
The entire disclosure of Japanese Patent Application No. 2014-007187 filed on
January 17, 2014 including specification, claims, drawings and summary is incorporated
herein by reference in its entirety.
17

CLAIMS
1. A method for producing a 1,3-dialkyl 1,2,3,4-cyclobutane tetracarboxylic acid-
1,2:3,4-dianhydride derivative represented by the formula (2), which comprises
subjecting a maleic anhydride compound represented by the following formula (1) to a
photodimerization reaction, in a solvent containing a C1-4 fatty acid ester, in th5 e
presence of a sensitizer.
wherein R is a C1-20 alkyl group.
2. The method according to Claim 1, wherein R is a C1-6 alkyl group.
3. The method according to Claim 1 or 2, wherein the amount of the solvent to be
10 used is from 3 to 300 times by mass to the maleic anhydride compound.
4. The method according to any one of Claims 1 to 3, wherein the C1-4 fatty acid
ester is a fatty acid alkyl ester represented by the formula: R1COOR2 (wherein R1 is
hydrogen, or preferably a C1-4 alkyl group, and R2 is a C1-4 alkyl group).
5. The method according to any one of Claims 1 to 4, wherein the solvent contains a
15 sub solvent of a carbonic acid diester.
6. The method according to any one of Claims 1 to 5, wherein the sensitizer is
benzophenone, acetophenone or benzaldehyde.
7. The method according to any one of Claims 1 to 6, wherein the sensitizer is
benzophenone substituted with an electron-withdrawing group, acetophenone
20 substituted with an electron-withdrawing group, or benzaldehyde substituted with an
electron-withdrawing group.
8. The method according to Claim 7, wherein the electron-withdrawing group is at
least one member selected from the group consisting of a fluoro group, a chloro group,
a bromo group, an iodo group, a nitro group, a cyano group and a trifluoromethyl group.
25 9. The method according to Claim 7 or 8, wherein the number of electronwithdrawing
groups is from 1 to 5.10. The method according to any one of Claims 1 to 9, wherein the sensitizer is used
in a proportion of from 0.1 to 20 mol% to the maieic anhydride compound.
11. The method according to any one of Claims 1 to 10, wherein the reaction
temperature is from 0 to 20QC.