U.S. patent application number 09/966954 was filed with the patent office on 2003-05-22 for process for preparing pentacene derivatives.
Invention is credited to Vogel, Dennis E., Vogel, Kim M..
Application Number | 20030097010 09/966954 |
Document ID | / |
Family ID | 25512110 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030097010 |
Kind Code |
A1 |
Vogel, Dennis E. ; et
al. |
May 22, 2003 |
Process for preparing pentacene derivatives
Abstract
A process for preparing substituted pentacene compounds
comprises the step of cyclizing substituted bis(benzyl)phthalic
acids using an acid composition comprising trifluoromethanesulfonic
acid, the substituted bis(benzyl)phthalic acids being represented
by the following general formulas: 1 wherein each R (that is, each
of the groups R.sup.1 through R.sup.8) is independently an
electron-donating group, a halogen atom, a hydrogen atom, or a
combination thereof.
Inventors: |
Vogel, Dennis E.; (Lake
Elmo, MN) ; Vogel, Kim M.; (Lake Elmo, MN) |
Correspondence
Address: |
Attention: Lucy C. Weiss
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Family ID: |
25512110 |
Appl. No.: |
09/966954 |
Filed: |
September 27, 2001 |
Current U.S.
Class: |
552/208 |
Current CPC
Class: |
C07C 65/36 20130101;
H01L 51/0003 20130101; C07C 2603/52 20170501; C07C 17/35 20130101;
C07D 219/06 20130101; C07C 63/72 20130101; C07C 49/697 20130101;
C07C 65/34 20130101; C07C 49/675 20130101; C07C 65/40 20130101;
C07D 337/12 20130101; H01L 51/0055 20130101; C07C 50/22 20130101;
C07C 25/22 20130101; C07C 51/377 20130101; H01L 51/0071 20130101;
C07C 1/2078 20130101; C07C 45/46 20130101; C07C 49/665 20130101;
C07C 2527/03 20130101; C07D 337/14 20130101; C07C 15/20 20130101;
C07C 63/331 20130101; C07C 49/753 20130101; C07C 50/24 20130101;
C07C 17/35 20130101; C07C 25/22 20130101; C07C 45/46 20130101; C07C
49/76 20130101; C07C 51/377 20130101; C07C 63/331 20130101; C07C
51/377 20130101; C07C 65/34 20130101; C07C 1/2078 20130101; C07C
15/38 20130101 |
Class at
Publication: |
552/208 |
International
Class: |
C07C 045/27; C07C
050/18 |
Claims
We claim:
1. A process for preparing pentacene derivatives comprising the
step of cyclizing at least one substituted bis(benzyl)phthalic acid
to form the corresponding substituted pentacenedione by using an
acid composition comprising trifluoromethanesulfonic acid, said
substituted bis(benzyl)phthalic acid being selected from those
represented by the following general formulas: 14wherein each R
group is independently selected from the group consisting of
electron-donating groups, halogen atoms, hydrogen atoms, and
combinations thereof.
2. The process of claim 1 wherein each said R group is
independently selected from the group consisting of alkyl groups,
alkoxy groups, thioalkoxy groups, halogen atoms, hydrogen atoms,
and combinations thereof.
3. The process of claim 2 wherein each said R group is
independently selected from the group consisting of alkyl groups,
alkoxy groups, hydrogen atoms, and combinations thereof.
4. The process of claim 3 wherein each said R group is
independently selected from the group consisting of alkyl groups
and hydrogen atoms.
5. The process of claim 4 wherein each said R group is
independently selected from the group consisting of methyl,
n-hexyl, n-nonyl, n-dodecyl, sec-butyl, 3,5,5-trimethylhexyl,
2-ethylhexyl, and hydrogen.
6. The process of claim 1 wherein said R.sup.2 and said R.sup.6 of
said Formula 1(a) are independently selected from the group
consisting of electron-donating groups, halogen atoms, and
combinations thereof; and said R.sup.1, R.sup.3, R.sup.4, R.sup.5,
R.sup.7, and R.sup.8 are hydrogen atoms.
7. The process of claim 1 wherein said R.sup.2 and said R.sup.7 of
said Formula 1(b) are independently selected from the group
consisting of electron-donating groups, halogen atoms, and
combinations thereof; and said R.sup.1, R.sup.3, R.sup.4, R.sup.5,
R.sup.6, and R.sup.8 are hydrogen atoms.
8. The process of claim 6 wherein said electron-donating group is
selected from the group consisting of alkyl groups, alkoxy groups,
and thioalkoxy groups.
9. The process of claim 7 wherein said electron-donating group is
selected from the group consisting of alkyl groups, alkoxy groups,
and thioalkoxy groups.
10. The process of claim 8 wherein said R.sup.2 and said R.sup.6
are independently selected from the group consisting of alkyl
groups, alkoxy groups, and combinations thereof.
11. The process of claim 9 wherein said R.sup.2 and said R.sup.7
are independently selected from the group consisting of alkyl
groups, alkoxy groups, and combinations thereof.
12. The process of claim 10 wherein said R.sup.2 and said R.sup.6
are independently alkyl.
13. The process of claim 11 wherein said R.sup.2 and said R.sup.7
are independently alkyl.
14. The process of claim 12 wherein said R.sup.2 and said R.sup.6
are independently selected from the group consisting of methyl,
n-hexyl, n-nonyl, n-dodecyl, sec-butyl, 3,5,5-trimethylhexyl,
2-ethylhexyl, and hydrogen.
15. The process of claim 13 wherein said R.sup.2 and said R.sup.7
are independently selected from the group consisting of methyl,
n-hexyl, n-nonyl, n-dodecyl, sec-butyl, 3,5,5-trimethylhexyl,
2-ethylhexyl, and hydrogen.
16. The process of claim 1 further comprising the step of reducing
said substituted pentacenedione to the corresponding substituted
pentacenediol.
17. The process of claim 16 further comprising the step of
dehydrating said substituted pentacenediol to the corresponding
substituted pentacene.
18. The process of claim 1 further comprising the step of preparing
said substituted bis(benzyl)phthalic acid by (a) reacting (1) at
least one substituted benzene selected from those represented by
the following general formulas: 15wherein each of the groups
R.sup.1 through R.sup.8 is defined as in claim 1; with (2)
pyromellitic dianhydride (or a derivative of pyromellitic
dianhydride) to form a substituted bis(benzoyl)phthalic acid; and
(b) reducing said substituted bis(benzoyl)phthalic acid to the
corresponding substituted bis(benzyl)phthalic acid.
19. The process of claim 17 further comprising the step of
preparing said substituted bis(benzyl)phthalic acid by (a) reacting
(1) at least one substituted benzene selected from those
represented by the following general formulas: 16wherein each of
the groups R.sup.1 through R.sup.8 is defined as in claim 1; with
(2) pyromellitic dianhydride (or a derivative of pyromellitic
dianhydride) to form a substituted bis(benzoyl)phthalic acid; and
(b) reducing said substituted bis(benzoyl)phthalic acid to the
corresponding substituted bis(benzyl)phthalic acid.
20. A process for preparing pentacene derivatives comprising the
steps of (a) reacting (1) at least one substituted benzene selected
from those represented by the following general formulas: 17wherein
each of the groups R.sup.1 through R.sup.8 is independently
selected from the group consisting of alkyl groups and hydrogen
atoms; with (2) pyromellitic dianhydride (or a derivative of
pyromellitic dianhydride) to form a substituted
bis(benzoyl)phthalic acid; (b) reducing said substituted
bis(benzoyl)phthalic acid to the corresponding substituted
bis(benzyl)phthalic acid; (c) cyclizing said substituted
bis(benzyl)phthalic acid to form the corresponding substituted
pentacenedione by using an acid composition comprising
trifluoromethanesulfonic acid; (d) reducing said substituted
pentacenedione to the corresponding substituted pentacenediol; and
(e) dehydrating said substituted pentacenediol to the corresponding
substituted pentacene.
21. A process for preparing a diaryl cyclic ketone comprising the
step of cyclizing a diaryl carboxylic acid comprising at least two
aromatic rings, one said ring having at least one aromatic ring
carbon atom that is directly bonded to a carboxylic acid moiety,
and another said ring having at least one aromatic ring carbon atom
that is capable of undergoing aromatic electrophilic substitution
with said carboxylic acid moiety; said cyclizing being effected by
using an acid composition comprising trifluoromethanesulfonic
acid.
22. The process of claim 21 wherein said diaryl carboxylic acid is
2,5-dibenzylterephthalic acid or 4,6-dibenzylisophthalic acid.
23. The process of claim 21 wherein said diaryl carboxylic acid is
substituted.
24. Substituted pentacenedione compounds represented by the
following general formulas: 18wherein each R group is independently
selected from the group consisting of electron-donating groups,
halogen atoms, hydrogen atoms, and combinations thereof.
25. The compounds of claim 24 wherein each said R group is
independently selected from the group consisting of alkyl groups
and hydrogen atoms.
26. Substituted bis(benzyl)phthalic acid compounds represented by
the following general formulas: 19wherein each R group is
independently selected from the group consisting of
electron-donating groups, halogen atoms, hydrogen atoms, and
monovalent combinations thereof.
27. The compounds of claim 25 wherein each said R group is
independently selected from the group consisting of alkyl groups
and hydrogen atoms.
28. Substituted bis(benzoyl)phthalic acid compounds represented by
the following general formulas: 20wherein each R group is
independently selected from the group consisting of hydrogen atoms
and alkyl groups having at least two carbon atoms.
Description
FIELD
[0001] This invention relates to a process for preparing aromatic
organic compounds that are useful as semiconductors. In another
aspect, this invention relates to novel compounds that are useful
in the preparation of aromatic organic semiconductor compounds.
BACKGROUND
[0002] Traditionally, inorganic silicon and gallium arsenide
semiconductors, silicon dioxide insulators, and metals such as
aluminum and copper have dominated the semiconductor industry. In
recent years, however, there has been an increasing research effort
in using organic thin-film transistors (OTFTs) as an alternative to
the traditional thin-film transistors based on inorganic
materials.
[0003] Pentacene, thiophene oligomers, and regioregular
polythiophenes have been the most widely researched organic
semiconductors. Of these classes of semiconducting organic
materials, the highest charge-carrier mobility values have been
observed for pentacene. Charge-carrier mobility values greater than
1.5 cm.sup.2 V.sup.-1 s.sup.-1, on/off current ratios greater than
10.sup.8, and sub-threshold voltages of less than 1.6 V have been
reported for pentacene-based transistors. These values are
comparable or superior to those of amorphous silicon-based
devices.
[0004] However, the performance of pentacene-based devices can be
difficult to reproduce. This lack of reproducibility is due to the
polymorphic nature of pentacene. The alignment or structural order
of the pentacene molecules differs for each polymorph or
crystallographic phase, and this structural order determines the
electronic properties of the device. The crystallographic phase
adopted by pentacene depends on the process and conditions under
which the crystals are formed. For example, when pentacene is
vapor-deposited onto a substrate, a thin film phase is formed. This
thin film phase is more effective at transporting charge than
pentacene's bulk or single crystal phase, but it is meta-stable.
For example, the thin film form of pentacene can be converted to
the bulk phase by exposure to solvents such as isopropanol, acetone
or ethanol. (See, for example, Gundlach et al., Applied Physics
Letters, 74(22) 3302 (2000).)
[0005] In order to achieve maximum performance, pentacene must
generally be deposited from the vapor phase by vacuum sublimation.
The vacuum sublimation process, however, requires expensive
equipment and lengthy pump-down cycles. Solution processing has the
potential to greatly reduce the manufacturing costs associated with
the use of organic semiconductors. Pentacene, however, is insoluble
in common solvents and is therefore not a good candidate for
solution processing.
SUMMARY
[0006] In view of the foregoing, we recognize that there is a need
for organic semiconductors that can provide stable, reproducible
electronic performance characteristics, that exhibit charge-carrier
mobilities comparable to or better than those of pentacene, and
that are preferably at least somewhat more soluble than pentacene
in common organic solvents. Furthermore, in order for such
compounds to be commercially attractive, we recognize that there is
a need for a scaleable and economical process for preparing the
compounds.
[0007] Briefly, in one aspect, the present invention provides a
process for preparing substituted pentacene compounds that are
useful as organic semiconductors. The process comprises the step of
carrying out intramolecular Friedel-Crafts cyclization of
substituted bis(benzyl)phthalic acids using an acid composition
comprising trifluoromethanesulfonic acid, the substituted
bis(benzyl)phthalic acids being represented by the following
general formulas: 2
[0008] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is independently selected from the group consisting of
electron-donating substituents (for example, alkyl, alkoxy, or
thioalkoxy), halogen atoms, hydrogen atoms, and combinations
thereof. As used herein, the term "phthalic acid" refers to
terephthalic acid (1,4-benzenedicarboxylic acid) and isophthalic
acid (1,3-benzenedicarboxylic acid) collectively.
[0009] Intramolecular Friedel-Crafts cyclization reactions of
carboxylic acids can generally be accomplished using a strong acid
such as concentrated sulfuric acid, fuming sulfuric acid,
polyphosphoric acid or anhydrous hydrofluoric acid. However, both
the above-described substituted bis(benzyl)phthalic acids and the
corresponding substituted is(benzoyl)phthalic acids are usually
unreactive under these conditions. It appears that the
intramolecular Friedel-Crafts cyclization of these substituted
compounds usually cannot be accomplished with the strong acids that
are typically used for this type of reaction.
[0010] It has been discovered, however, that Friedel-Crafts
cyclization of substituted bis(benzyl)phthalic acids to form the
corresponding substituted pentacenediones can be accomplished using
an acid composition comprising trifluoromethanesulfonic acid.
Surprisingly, the cyclization can be carried out at room
temperature in many cases. The resulting substituted pentacenedione
compounds can then be reduced and dehydrated to the corresponding
substituted pentacene compounds. The substituted pentacene
compounds provide charge-carrier mobilities comparable to those of
pentacene, while also exhibiting improved electronic stability and
reproducibility of performance characteristics in a semiconductor
device.
[0011] The process of the invention meets the need for a scaleable
and economical route to the substituted pentacenediones and
substituted pentacenes. The process can also be more generally
applied to the preparation of diaryl cyclic ketones other than the
substituted pentacenediones, if desired.
[0012] In other aspects, this invention also provides novel
intermediates in the form of the substituted pentacenediones
resulting from the intramolecular Friedel-Crafts cyclization
reaction, as well as certain substituted bis(benzyl)phthalic acid
starting compounds and certain substituted bis(benzoyl)phthalic
acid starting compound precursors.
DETAILED DESCRIPTION
[0013] The process of the invention for preparing substituted
pentacene compounds comprises the step of cyclizing the
above-described substituted bis(benzyl)phthalic acids to form the
corresponding substituted pentacenediones (that is, substituted
7,14-dihydropentacene-5,12-diones and substituted
pentacene-5,7(12H,14H)-diones).
[0014] Preparation of Substituted Bis(benzyl)phthalic Acid Starting
Compounds
[0015] The above-described substituted bis(benzyl)phthalic acid
starting compounds can be prepared by first preparing the
corresponding substituted bis(benzoyl)phthalic acids and then
reducing them. The substituted bis(benzoyl)phthalic acids can be
prepared by combining at least one substituted benzene with
pyromellitic dianhydride (benzene-1,2,4,5-tetracarboxylic acid
dianhydride) or a derivative thereof (for example, dimethyl
2,5-bis(chlorocarbonyl)terephthalate) in the presence of a Lewis
acid (for example, AlCl.sub.3), as can be represented by the
following general scheme: 3
[0016] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is independently selected from the group consisting of
electron-donating groups, halogen atoms, hydrogen atoms, and
combinations thereof. As used herein, the term "combinations" of
substituents includes, monovalent combinations (for example, a
bromomethyl substituent)as well as substituents formed by the
bonding together of the substituents on two adjacent carbon atoms
to form a ring structure (for example, two alkyl substituents on
adjacent carbon atoms can be bonded together to form a divalent
alkylene group that bridges or links the carbon atoms).
[0017] Preferably, each R is independently selected from the group
consisting of alkyl groups, alkoxy groups, thioalkoxy groups,
halogen atoms, hydrogen atoms, and combinations thereof. More
preferably, each R is independently selected from the group
consisting of alkyl groups, alkoxy groups, hydrogen atoms, and
combinations thereof. Even more preferably, each R is independently
selected from the group consisting of alkyl groups and hydrogen
atoms. Most preferably, each R is independently selected from the
group consisting of methyl, n-hexyl, n-nonyl, n-dodecyl, sec-butyl,
3,5,5-trimethylhexyl, 2-ethylhexyl, and hydrogen.
[0018] Preferably, only R.sup.2 and R.sup.6 of the substituted
bis(benzoyl)terephthalic acids (or R.sup.2 and R.sup.7 of the
substituted bis(benzoyl)isophthalic acids) are moieties other than
hydrogen. That is, preferably, R.sup.2 and R.sup.6 of the
substituted bis(benzoyl)terephthalic acids (or R.sup.2 and R.sup.7
of the substituted bis(benzoyl)isophthalic acids) are independently
selected from the group consisting of electron-donating groups,
halogen atoms, and combinations thereof, and R.sup.1, R.sup.3,
R.sup.4, R.sup.5, R.sup.7, and R.sup.8 of the substituted
bis(benzoyl)terephthalic acids (or R.sup.1, R.sup.3, R.sup.4,
R.sup.5, R.sup.6, and R.sup.8 of the substituted
bis(benzoyl)isophthalic acids) are hydrogen.
[0019] More preferably, said R.sup.2 and R.sup.6 (or said R.sup.2
and R.sup.7) are independently selected from the group consisting
of alkyl groups, alkoxy groups, thioalkoxy groups, halogen atoms,
and combinations thereof, and said R.sup.1, R.sup.3, R.sup.4,
R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1, R.sup.3, R.sup.4,
R.sup.5, R.sup.6, and R.sup.8) are hydrogen.
[0020] Still more preferably, said R.sup.2 and R.sup.6 (or said
R.sup.2 and R.sup.7) are independently selected from the group
consisting of alkyl groups, alkoxy groups, and combinations
thereof, and said R.sup.1, R.sup.3, R.sup.4, R.sup.5, R.sup.7, and
R.sup.8 (or said R.sup.1, R.sup.3, R.sup.4, R.sup.5, R.sup.6, and
R.sup.8) are hydrogen.
[0021] Even more preferably, said R.sup.2 and R.sup.6 (or said
R.sup.2 and R.sup.7) are independently alkyl, and said R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.6, and R.sup.8) are hydrogen.
[0022] Most preferably, said R.sup.2 and R.sup.6 (or said R.sup.2
and R.sup.7) are independently selected from the group consisting
of methyl n-hexyl n-nonyl n-dodecyl sec-butyl,
3,5,5-trimethylhexyl, and 2-ethylhexyl, and said R.sup.1, R.sup.3,
R.sup.4 , R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1, R.sup.3,
R.sup.4, R.sup.5, R.sup.6, and R.sup.8) are hydrogen.
[0023] Reactions of this type (electrophilic aromatic substitution
reactions) are well known in organic chemistry and have been
described, for example, by Henri de Diesbach and Victor Schmidt in
Helv. Chim. Acta 7, 648 (1924); by William Hobson Mills and Mildred
Mills in J. Chem. Soc. 101, 2200 (1912); by Ernst Philippi in
Monatshefte fur Chemie 32, 634 (1911); by Ernst Philippi and
Reinhard Seka in Monatshefte fur Chemie 43, 615 (1922); by Ernst
Philippi and Fedora Auslaender in Monatshefte fur Chemie 42, 1
(1921); and by Guido Machek in Monatshefte fur Chemie 56, 130
(1930).
[0024] Preferably, the reaction is carried out in the presence of
an inert solvent and an amine base in order to keep the reaction
mixture fluid and to decrease the amount of rearrangement of the
substituents on the aromatic ring during the reaction. Examples of
useful inert solvents include 1,2-dichloroethane, dichlorobenzene,
dichloromethane, carbon disulfide, nitrobenzene, and nitromethane.
Examples of useful amine bases include tertiary amines such as
triethylamine, diisopropylethylamine, and
1,4-diazabicyclo[2.2.2]octane (DABCO). If desired, the reaction
mixture can be agitated and/or heated.
[0025] Suitable substituted benzenes can be represented by the
following formula: 4
[0026] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is independently selected from the group consisting of
electron-donating groups, halogen atoms, hydrogen atoms, and
combinations thereof.
[0027] Preferably, each R is independently selected from the group
consisting of alkyl groups, alkoxy groups, thioalkoxy groups,
halogen atoms, hydrogen atoms, and combinations thereof. More
preferably, each R is independently selected from the group
consisting of alkyl groups, alkoxy groups, hydrogen atoms, and
combinations thereof. Even more preferably, each R is independently
selected from the group consisting of alkyl groups and hydrogen
atoms. Most preferably, each R is independently selected from the
group consisting of methyl, n-hexyl, n-nonyl, n-dodecyl, sec-butyl,
3,5,5-trimethylhexyl, 2-ethylhexyl, and hydrogen.
[0028] Representative examples of substituted benzenes that can be
used to prepare the substituted bis(benzoyl)phthalic acids include
mono- and dialkoxybenzenes; mono- and dithioalkoxybenzenes; mono-
and dihalobenzenes; and mono-, di-, tri-, and tetraalkylbenzenes
(for example, toluene, hexylbenzene, nonylbenzene, dodecylbenzene,
sec-butylbenzene, p-xylene, 1,2,3,4-tetrahydronaphthalene, and
1,2,3,4-tetramethylbenzene, 3,5,5-trimethylhexylbenzene, and
2-ethylhexylbenzene).
[0029] Examples of substituted bis(benzoyl)phthalic acids that can
be prepared by the Friedel-Crafts reaction of the above-described
substituted benzenes with pyromellitic dianhydride (or a derivative
thereof) include: 5
[0030] A novel class of the substituted bis(benzoyl)phthalic acid
compounds can be represented by the following general formulas:
6
[0031] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is independently selected from the group consisting of
hydrogen atoms and alkyl groups having at least two carbon atoms.
Preferably, each R is independently selected from the group
consisting of n-hexyl, n-nonyl groups, n-dodecyl groups, sec-butyl,
3,5,5-trimethylhexyl, 2-ethylhexyl, and hydrogen.
[0032] Preferably, only R.sup.2 and R.sup.6 of the substituted
bis(benzoyl)terephthalic acids (or R.sup.2 and R.sup.7 of the
substituted bis(benzoyl)isophthalic acids) are moieties other than
hydrogen. That is, preferably, R.sup.2 and R.sup.6 of the
substituted bis(benzoyl)terephthalic acids (or R.sup.2 and R.sup.7
of the substituted bis(benzoyl)isophthalic acids) are independently
alkyl groups having at least two carbon atoms, and R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.7, and R.sup.8 of the substituted
bis(benzoyl)terephthalic acids (or R.sup.1, R.sup.3, R.sup.4 ,
R.sup.5, R.sup.6 , and R.sup.8 of the substituted
bis(benzoyl)isophthalic acids) are hydrogen. More preferably, said
R.sup.2 and R.sup.6 (or said R.sup.2 and R.sup.7) are independently
selected from the group consisting of n-hexyl groups, n-nonyl
groups, n-dodecyl groups, and sec-butyl groups,
3,5,5-trimethylhexyl groups, 2-ethylhexyl groups, and said R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1,
R.sup.3 , R.sup.4 , R.sup.5, R.sup.6, and R.sup.8) are
hydrogen.
[0033] Alternatively, the substituted bis(benzoyl)phthalic acids
can be prepared by reaction of pyromellitic dianhydride (or a
derivative thereof with) a substituted aromatic organometallic
reagent (for example, an aryl magnesium halide or an aryl lithium
compound).
[0034] The resulting substituted bis(benzoyl)phthalic acids can be
reduced to the corresponding substituted bis(benzyl)phthalic acids
via reduction methods known in the art. For example, the reduction
can be accomplished by using either zinc and aqueous ammonium
hydroxide (preferably, with agitation) or catalytic hydrogenation
with, for example, palladium or platinum on carbon at, for example,
about 2 to 3 atmospheres (preferably, by catalytic hydrogenation;
more preferably, by catalytic hydrogenation with palladium on
carbon) as shown, for example, below: 7
[0035] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is as defined above for Reaction Scheme A (where the
preferences stated for the substituted bis(benzoyl)terephthalic
acids also correspond to preferences for the substituted
bis(benzyl)terephthalic acids (and the preferences stated for the
substituted bis(benzoyl)isophthalic acids also correspond to
preferences for the substituted bis(benzyl)isophthalic acids)).
[0036] If desired, the substituted bis(benzoyl)terephthalic acids
can be separated from the substituted is(benzoyl)isophthalic acids
by methods commonly used in the art (for example, by
recrystallization, trituration, or chromatography) before the
reduction reaction is carried out (or, alternatively, the resulting
substituted bis(benzyl)phthalic acid isomers can be separated
therafter).
[0037] Examples of substituted bis(benzyl)phthalic acids that can
be prepared by reduction of substituted bis(benzoyl)phthalic acids
include: 8
[0038] A novel class of the substituted bis(benzyl)phthalic acid
compounds can be represented by the following general formulas:
9
[0039] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is independently selected from the group consisting of
electron-donating groups, halogen atoms, hydrogen atoms, and
monovalent combinations thereof. Preferably, each R is
independently selected from the group consisting of alkyl groups,
alkoxy groups, thioalkoxy groups, halogen atoms, hydrogen atoms,
and monovalent combinations thereof. More preferably, each R is
independently selected from the group consisting of alkyl groups,
alkoxy groups, hydrogen atoms, and monovalent combinations thereof.
Even more preferably, each R is independently selected from the
group consisting of alkyl groups and hydrogen atoms. Most
preferably, each R is independently selected from the group
consisting of methyl, n-hexyl, n-nonyl, n-dodecyl, sec-butyl,
3,5,5-trimethylhexyl, 2-ethylhexyl, and hydrogen.
[0040] Preferably, only R.sup.2 and R.sup.6 of the substituted
bis(benzyl)terephthalic acids (or R.sup.2 and R.sup.7 of the
substituted bis(benzyl)isophthalic acids) are moieties other than
hydrogen. That is, preferably, R.sup.2 and R.sup.6 of the
substituted bis(benzyl)terephthalic acids (or R.sup.2 and R.sup.7
of the substituted bis(benzyl)isophthalic acids) are independently
selected from the group consisting of electron-donating groups,
halogen atoms, and monovalent combinations thereof, and R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.7, and R.sup.8 of the substituted
bis(benzyl)terephthalic acids (or R.sup.1, R.sup.3, R.sup.4,
R.sup.5, R.sup.6, and R.sup.8 of the substituted
bis(benzyl)isophthalic acids) are hydrogen.
[0041] More preferably, said R.sup.2 and R.sup.6 (or said R.sup.2
and R.sup.7) are independently selected from the group consisting
of alkyl groups, alkoxy groups, thioalkoxy groups, halogen atoms,
and monovalent combinations thereof, and said R.sup.1, R.sup.3,
R.sup.4, R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1, R.sup.3 ,
R.sup.4, R.sup.5, R.sup.6, and R.sup.8) are hydrogen. Still more
preferably, said R.sup.2 and R.sup.6 (or said R.sup.2 and R.sup.7)
are independently selected from the group consisting of alkyl
groups, alkoxy groups, and monovalent combinations thereof, and
said R.sup.1, R.sup.3 , R.sup.4, R.sup.5, R.sup.7, and R.sup.8 (or
said R.sup.1, R.sup.3 , R.sup.4, R.sup.5, R.sup.6, and R.sup.8) are
hydrogen.
[0042] Even more preferably, said R.sup.2 and R.sup.6 (or said
R.sup.2 and R.sup.7) are independently alkyl, and said R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1,
R.sup.3, R.sup.4, R.sup.5, R.sup.6 and R ) are hydrogen.
[0043] Most preferably, said R.sup.2 and R.sup.6 (or said R.sup.2
and R.sup.7) are independently selected from the group consisting
of methyl, n-hexyl, n-nonyl, n-dodecyl, sec-butyl,
3,5,5-trimethylhexyl, and 2-ethylhexyl, and said R.sup.1, R.sup.3,
R.sup.4, R.sup.5, R.sup.7, and R.sup.8 (or said R.sup.1, R.sup.3,
R.sup.4, R.sup.5, R.sup.6, and R.sup.8) are hydrogen.
[0044] Preparation of Substituted Pentacene Compounds
[0045] The cyclization step of the process of the invention can be
accomplished via intramolecular Friedel-Crafts cyclization of the
substituted bis(benzyl)phthalic acids to form the corresponding
substituted pentacenediones (the substituted
7,14-dihydropentacene-5,12-d- iones and the substituted
pentacene-5,7(12H,14H)-diones; hereinafter, the "5,12-diones" and
the "5,7-diones"), a novel class of compounds that can be
represented by the following general formulas: 10
[0046] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is as defined above for Reaction Scheme A (where the
preferences stated for the substituted bis(benzoyl)terephthalic
acids correspond to preferences for the 5,12-diones (and the
preferences stated for the substituted bis(benzoyl)isophthalic
acids correspond to preferences for the 5,7-diones)).
[0047] The use of acid catalyzed Friedel-Crafts cyclization to form
cyclic ketones is well known in literature and has been described,
for example, by Premasagar et al. in J. Org. Chem., 46(14), 2974
(1981); by Allen et al. in Tetrahedron, 33(16), 2083 (1977); and by
Hulin et al. in J. Org. Chem., 49, 207 (1984). These reactions can
generally be carried out at about 0.degree. C. to 100.degree. C. in
the presence of a strong acid such as concentrated sulfuric acid,
fuming sulfuric acid, polyphosphoric acid or anhydrous hydrofluoric
acid. For example, unsubstituted bis(benzoyl)phthalic acid
(2,5-dibenzoylterephthalic acid or 4,6-dibenzoylisophthalic acid)
will form the corresponding tetrone when heated to 100.degree. C.
with concentrated sulfuric acid for several hours.
[0048] However, both the above-described substituted
bis(benzyl)phthalic acids and the corresponding substituted
bis(benzoyl)phthalic acids are usually unreactive under these
conditions. It appears that, in general, the intramolecular
Friedel-Crafts cyclization of these substituted compounds cannot be
readily accomplished with the strong acids that are typically used
for this type of reaction. It has been discovered, however, that
Friedel-Crafts cyclization of substituted bis(benzyl)phthalic acids
to form the corresponding substituted pentacenediones can be
accomplished using an acid composition comprising
trifluoromethanesulfonic acid at room temperature or, optionally,
at elevated temperatures (for example, a temperature in the range
of about 20.degree. C. to 60.degree. C.) and, preferably, with
agitation of the reaction mixture.
[0049] This cyclization method can be extended to other substituted
diaryl carboxylic acids, as well as to unsubstituted diaryl
carboxylic acids (for example, 2,5-dibenzyl terephthalic acid and
4,6-dibenzylisophthalic acid which can be cyclized to the
corresponding pentacenediones and then reduced and dehydrated to
form pentacene). Surprisingly, the method enables the cyclization
of such carboxylic acids at lower temperatures than those generally
required when using conventional acids such as sulfuric acid. The
use of trifluoromethanesulfonic acid also avoids the formation of
sulfonated by-products that can occur when sulfuric acid is
utilized.
[0050] Thus, the method enables the preparation of a broad class of
diaryl cyclic ketones by cyclizing a compound comprising at least
two aromatic rings, one of the rings having at least one aromatic
ring carbon atom that is directly bonded to a carboxylic acid
moiety, and the other of the rings having at least one aromatic
ring carbon atom that is capable of undergoing aromatic
electrophilic substitution with the carboxylic acid moiety using an
acid composition comprising trifluoromethanesulfonic acid. For
example, 2- biphenylcarboxylic acid can be cyclized to
9H-fluoren-9-one. Preferably, the diaryl carboxylic acid is
substituted.
[0051] In carrying out the cyclization, trifluoromethanesulfonic
acid can be used alone or in combination with, for example,
trifluoroacetic acid, or a perfluoroalkanesulfonic acid of higher
molecular weight than trifluoromethanesulfonic acid, or a neutral
solvent that will not react with trifluoromethanesulfonic acid (for
example, a hydrocarbon solvent, a chlorinated solvent such as
methylene chloride or a fluorinated solvent)or a Lewis acid (for
example, antimony pentafluoride).
[0052] Representative examples of substituted pentacenediones that
can be prepared by this process include the following: 11
[0053] The resulting substituted pentacenediones can be Reduced and
dehydrated to give the corresponding substituted Pentacenes. Good
yields can usually be obtained by, for example, a sodium
borohydride reduction procedure, as shown, for example, below:
12
[0054] wherein each R (that is, each of the groups R.sup.1 through
R.sup.8) is as defined above for Reaction Scheme A (where the
preferences stated above for the substituted bis(benzoyl)phthalic
acids correspondingly apply to the substituted pentacenediones, the
substituted pentacenediols, and the substituted pentacenes).
[0055] Treatment of the diones with sodium borohydride in solvent,
such as alcohol(s) or ether(s) (preferably, diglyme) or a
combination thereof, preferably followed by addition of methanol
and then treatment with additional sodium borohydride gives the
corresponding substituted diols. The diols can then be dehydrated
to substituted pentacenes by treatment with an acid (for example,
hydrochloric acid), preferably with application of heat (for
example, heating to about 50.degree. C. to 60.degree. C.) and
agitation. Suitable acids include, for example, acetic acid,
phosphoric acid, hydrochloric acid, sulfuric acid, hydroiodic acid,
hydrobromic acid, trifluoroacetic acid, and
trifluoromethanesulfonic acid. Optionally, the diols can be first
treated with a weak acid such as acetic acid, followed by treatment
with a stronger acid such as hydrochloric acid.
[0056] Representative examples of substituted pentacenes that can
be prepared by this process include: 13
[0057] It is possible to over reduce the substituted
pentacenediones to substituted dihydropentacenes and then oxidize
to obtain the corresponding substituted pentacenes. It has been
discovered, however, that treatment of the diones with sodium
borohydride in diglyme followed by addition of methanol and then
treatment with additional sodium borohydride minimizes
over-reduction.
[0058] If desired, the resulting substituted pentacenes can be
purified by standard methods such as recrystallization,
sublimation, or a combination thereof. Purification can be
accomplished by sublimation, for example, using a 3-zone furnace
(for example, a Thermolyne 79500 tube furnace, available from
Barnstead Thermolyne, Dubuque, Iowa) at reduced pressure under a
constant flow of nitrogen gas.
[0059] The substituted pentacenes prepared by the process of the
invention can be used as the semiconductor layer in semiconductor
devices, for example, organic thin film transistors.
EXAMPLES
[0060] Objects and advantages of this invention are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this invention.
[0061] Unless otherwise specified, all starting materials were
obtained from Aldrich, Milwaukee, Wis.
2,5-Bis(4-methylbenzoyl)terephthalic and
4,6-bis(4-ethylbenzoyl)isophthalic acids were prepared essentially
as described in H. de Diesbach, V. Schmidt, Helv. Chim. Acta, 7,
648 (1924). 2,5-Dibenzoylterephthalic acid and
4,6-dibenzoylisophthalic acid were prepared essentially as
described in W. Hobbson, M. Mills, J. Chem. Soc. 101, 2200
(1912).
Example 1
Preparation of 2,9-Dimethylpentacene
[0062] Preparation of 2,5-Bis(4-methylbenzyl)terephthalic Acid
[0063] A mixture of 30.0 grams of
2,5-bis(4-methylbenzoyl)terephthalic acid, 500 mL of acetic acid,
and 3 grams of 5% palladium on activated carbon (as a catalyst) was
heated to 64.degree. C. for 17 hours in an atmosphere of hydrogen
at 270 kPa. The mixture was filtered to remove the catalyst and the
product. The catalyst and the product were slurried in 500 mL of
tetrahhydrofuran and filtered through Celite.TM. diatomaceous earth
filter agent. The resulting filtrate was concentrated in vacuo. The
resulting wet solid was slurried in ethyl acetate and collected by
filtration and dried to give 2,5-bis(4-methylbenzyl)terephthalic
acid.
[0064] Preparation of
7,14-Dihydro-3,10-dimethylpentacene-5,12-dione
[0065] To a mixture of 12.7 grams of
2,5-bis(4-methylbenzyl)terephthalic acid and 90 mL of
trifluoroacetic acid was added 81.6 grams of
trifluoromethanesulfonic acid. The reaction was stirred 22 hours at
room temperature. The mixture was poured over 500 grams of ice. The
resulting solid precipitate was collected by filtration, washed
with 750 mL of saturated aqueous sodium bicarbonate and 1 L of
water until the filtrate was neutral to pH paper. The solid was
washed with heptane and dried to give
7,14-dihydro-3,10-dimethylpentacene-5,12-dione.
[0066] Preparation of 2,9-Dimethylpentacene
[0067] A mixture of 24.6 grams of
7,14-dihydro-3,10-dimethylpentacene-5,12- -dione in 250 mL of
2-methoxyethyl ether was stirred and flushed with nitrogen for 10
minutes. To this was added in small portions 16.5 grams of sodium
borohydride and stirring was continued at room temperature
overnight. To the resulting reaction mixture was added slowly over
30 minutes 155 mL of methanol with the temperature maintained below
0.degree. C. The mixture was stirred for 1.5 hours at room
temperature. To the mixture was added slowly 360 mL of glacial
acetic acid over 10 minutes. The resulting mixture was heated to
60.degree. C. for 1.5 hours. To the mixture was added 100 mL of
concentrated hydrochloric acid. The resulting mixture was heated
for one hour and cooled to room temperature. To the mixture was
added 250 mL of water and stirring was continued for five minutes.
The resulting solid was collected by filtration and washed
sequentially with 3 L of water, and 1 L of acetone, 1 L of
tetrahydrofuran, and 1 L of acetone and dried to give
2,9-dimethylpentacene.
Example 2
Preparation of 2,10-Dimethylpentacene
[0068] Preparation of 4,6-Bis(4-methylbenzyl)isophthalic Acid
[0069] A mixture of 21.1 grams of 4,6-bis(4
ethylbenzoyl)isophthalic acid, 350 mL of acetic acid, and 2.10
grams of 5% palladium on carbon (as a catalyst) was heated to
65.degree. C. for 17 hours in an atmosphere of hydrogen at 270 kPa.
The mixture was filtered through Celite.TM. diatomaceous earth
filter agent to remove the catalyst. The resulting filtrate was
concentrated in vacuo to give 4,6-bis(4-methylbenzyl)isophth- alic
acid.
[0070] Preparation of 3,9-Dimethylpentacene-5,7(12H,14H)-dione
[0071] To 14.1 grams of 4,6-bis(4-methylbenzyl)isophthalic acid was
added 75 mL of trifluoroacetic acid followed by 48 grams of
trifluoromethanesulfonic acid. After stirring for 3 days at room
temperature, the mixture was poured over 200 g of ice, and the
resulting solid was collected by filtration. The solid was washed
with 400 mL of saturated aqueous sodium bicarbonate solution,
followed by 1100 mL of water until the filtrate was neutral to pH
paper. The solid was washed with heptane and dried to give
3,9-dimethylpentacene-5,7(12H,14H)-dione.
[0072] Preparation of 2,10-Dimethylpentacene
[0073] A mixture of 1 gram of
3,9-dimethylpentacene-5,7(12H,14H)-dione and 10 mL of
2-methoxyethyl ether was stirred and flushed with nitrogen for 15
minutes. To this was added 0.948 grams of sodium borohydride and
stirring was continued at room temperature overnight. To the
mixture was added 6.3 mL of methanol and stirring was continued for
1.5 hours at room temperature. To the mixture was added 15 mL of
acetic acid and 10 mL of concentrated hydrochloric acid. The
mixture was stirred for one hour at room temperature followed by
heating for one hour at 60.degree. C. To the mixture was added 50
mL of water and the resulting solid was isolated by filtration and
washed with water. The solid was washed with tetrahydrofuran until
a pale filtrate resulted. The solid was washed with heptane and
dried under an atmosphere of nitrogen to give
2,10-dimethylpentacene.
Example 3
Preparation of 2,9-Dihexylpentacene
[0074] Preparation of 2,5-Bis(4-hexylbenzoyl)terephthalic Acid
[0075] To a mixture of 25.7 grams of aluminum chloride, 51.3 mL of
1,2-dichloroethane, and 10 grams of benzene-1,2,4,5-tetracarboxylic
acid dianhydride (pyromellitic dianhydride) was added with cooling,
a solution of 14.9 grams of hexylbenzene and 6.40 grams of
diisopropylethylamine in 25 mL of 1,2-dichloroethane over a period
of 3.5 hours, keeping the temperature between 15.degree. C. and
20.degree. C. The resulting mixture was stirred for an additional
15 minutes after the addition was complete, and it was then heated
to 40.degree. C. for one hour. The warm mixture was poured into a
beaker with 200 grams of ice and 75 mL of concentrated hydrochloric
acid and stirred overnight at room temperature. The aqueous phase
was poured off, and the resulting oily solid was stirred with 500
mL of water, and the water was poured off. This water wash was
repeated, and the resulting residue was dissolved in 250 mL of
acetone and concentrated in vacuo. This residue was stirred with 55
mL of ethyl acetate, and the resulting solid was collected by
filtration, washed with 100 mL of ethyl acetate, and dried to give
2,5-bis(4-hexylbenzoyl)terepht- halic acid.
[0076] Preparation of 2,5-Bis(4-hexylbenzyl)terephthalic Acid
[0077] A mixture of 5.26 grams of
2,5-bis(4-hexylbenzoyl)terephthalic acid, 100 mL of
tetrahydrofuran, and 0.53 grams of 5% palladium on carbon (as a
catalyst) was heated at 65.degree. C. for 17 hours in an atmosphere
of hydrogen at 270 kPa. The resulting mixture was filtered through
Celite.TM. diatomaceous earth filter agent to remove the catalyst.
The filtrate was concentrated in vacuo to give
2,5-bis(4-hexylbenzyl)terephth- alic acid.
[0078] Preparation of
3,10-Dihexyl-7,14-dihydropentacene-5,12-dione
[0079] A mixture of 2.56 grams of
2,5-bis(4-hexylbenzyl)terephthalic acid, 25.6 grams of
trifluoroacetic acid, and 12.8 gram of trifluoromethanesulfonic
acid was stirred overnight at room temperature. The resulting
mixture was poured over 200 grams of ice. The solid was collected
by filtration and washed with saturated aqueous sodium bicarbonate
solution and then with 400 mL of water until the filtrate was
neutral to pH paper. The solid was dried to give
3,10-dihexyl-7,14-dihydr- opentacene-5,12-dione.
[0080] Preparation of 2,9-Dihexylpentacene
[0081] A mixture of 20 grams of
3,10-dihexyl-7,14-dihydropentacene-5,12-di- one and 200 mL of
2-methoxyethyl ether was stirred and flushed with nitrogen for 15
minutes. To this was added 13.4 grams of sodium borohydride, and
stirring was continued at room temperature overnight. To the
resulting mixture was added 126 mL of methanol over 1.25 hours. The
temperature increased to 40.degree. C. and was maintained at
40.degree. C. during the addition by intermittent application of a
cold water bath. When addition was complete stirring was continued
at room temperature. After stirring for 2 hours at room temperature
an additional 50 mL of 2-methoxyethyl ether was added. After
stirring with methanol for a total of 3.5 hours, 300 mL of acetic
acid was added, and the resulting mixture was heated to 60.degree.
C. for 1.5 hours. To the mixture was added 100 mL of concentrated
hydrochloric acid and heating at 60.degree. C. was continued for
one hour. The mixture was cooled to room temperature and the
resulting solid was collected by filtration and washed with 500 mL
of water. The solid was washed with 500 mL of acetone and then 60
mL of tetrahydrofuran. The solid was washed with an additional one
liter of acetone and dried to give 2,9-dihexylpentacene.
Example 4
Preparation of 2,9-Dinonylpentacene
[0082] Preparation of 2,5-Bis(4-nonylbenzoyl)terephthalic Acid
[0083] To a mixture of 1370 grams of aluminum chloride, 533.7 grams
of benzene-1,2,4,5-tetracarboxylic acid dianhydride and 2750 mL of
1,2-dichloroethane stirred at 15.degree. C. was added a solution of
341.5 grams of N,N-diisopropylethylamine in 1334 mL of
1,2-dichloroethane over a period of 3.5 hr, keeping the reaction
temperature between 15.degree. C. and 20.degree. C. The resulting
reaction mixture was stirred overnight at room temperature. The
reaction mixture was added to a mixture of 2500 grams of ice and
2500 mL of concentrated hydrochloric acid with efficient stirring.
The mixture was divided into 800 mL portions and each portion was
worked up as follows. To 800 mL of the mixture was added 800 mL of
tetrahydrofuran, 800 mL of ethyl acetate and 800 mL of water. The
mixture was stirred and phase split. The organic phase was filtered
and the filtrate was concentrated in vacuo. The resulting residues
were combined. To 711 grams of the combined residue was added 4 L
of acetone and the mixture was stirred until a suspension of a fine
solid resulted. The solid was collected by filtration and washed
with 1 L of acetone. The solid was dried to give
2,5-bis(4-nonylbenzoyl)terephthalic acid.
[0084] Preparation of 2,5-Bis(4-nonylbenzyl)terephthalic Acid
[0085] A mixture of 109 grams of
2,5-bis(4-nonylbenzoyl)terephthalic acid, 1500 mL of
tetrahydrofuran, and 7.43 grams of 10% palladium on carbon (as a
catalyst) was heated at 65.degree. C. for 17 hours in an atmosphere
of hydrogen at 270 kPa. The reaction mixture was filtered through
Celite.TM. diatomaceous earth filter agent to remove the catalyst.
The filtrate was concentrated in vacuo to give
2,5-bis(4-nonylbenzyl)terephthalic acid.
[0086] Preparation of
7,14-Dihydro-3,10-dinonylpentacene-5,12-dione
[0087] A mixture of 26.3 grams of
2,5-bis(4-nonylbenzyl)terephthalic acid and 100 mL of
trifluoromethanesulfonic acid was heated to 60.degree. C. and
maintained for one hour. The mixture was cooled to room temperature
and poured over 500 grams of ice. The resulting solid was collected
by filtration and washed sequentially with one liter of water, two
liters of saturated aqueous sodium bicarbonate solution, and four
liters of water until the filtrate was neutral to pH paper. The
solid was washed with two liters of acetone and dried to give
7,14-dihydro-3,10-dinonylpentacene-5,- 12-dione.
[0088] Preparation of 2,9-Dinonylpentacene
[0089] A mixture of 20 grams of
7,14-dihydro-3,10-dinonylpentacene-5,12-di- one and 400 mL of
2-methoxyethyl ether was stirred and flushed with nitrogen for 15
minutes. To this was added 11.4 grams of sodium borohydride and
stirring was continued at 60.degree. C. for 18 hours. The resulting
mixture was cooled to room temperature, 3.0 grams of sodium
borohydride was added, and stirring was continued for 16 hours at
room temperature. To the resulting mixture was added 170 mL of
acetic acid, and the mixture was heated at 60.degree. C. for one
hour. To this mixture was added 120 mL of concentrated hydrochloric
acid and heating was continued at 60.degree. C. for one hour. The
resulting mixture was cooled to room temperature and the resulting
solid was collected by filtration and dried to give
2,9-dinonylpentacene.
Example 5
Preparation of 2,9-Didodecylpentacene
[0090] Preparation of 2,5-Bis(4-dodecylbenzoyl)terephthalic
Acid
[0091] To a mixture of 492 grams of aluminum chloride and 988 mL of
1,2-dichloroethane was added 192 grams of
benzene-1,2,4,5-tetracarboxylic acid dianhydride (pyromellitic
dianhydride). The resulting mixture was cooled to 16.degree. C. and
a solution of 434 grams of 1-dodecylbenzene, 123 grams of
diisopropylethylamine and 480 mL of 1,2-dichloroethane was added
over a period of 3.5 hours, keeping the temperature between
15.degree. C. and 20.degree. C. during the addition. The mixture
was stirred overnight at room temperature and poured into a beaker
of 1000 grams of ice and 1000 grams concentrated hydrochloric acid.
The mixture was stirred for one hour and the liquid was poured from
the coagulate. The mixture was divided into 800 mL portions and
each portion was worked up as follows. To 800 mL of the mixture was
added 800 mL of tetrahydrofuran, 800 mL of ethyl acetate and 800 mL
of water. The mixture was stirred and phase split. The organic
phase was filtered and the filtrate was concentrated in vacuo. The
resulting residues were combined. To 127 grams of the combined
residue was added 800 mL of ethyl acetate and the resulting mixture
was stirred until a suspension of a fine solid resulted. The solid
was collected by filtration and washed with 50 mL of ethyl acetate.
The solid was dried to give 2,5-bis(4-dodecylbenzoyl)terep- hthalic
acid.
[0092] Preparation of 2,5-Bis(4-dodecylbenzyl)terephthalic Acid
[0093] A solution of 133 grams of
2,5-bis(4-dodecylbenzoyl)terephthalic acid and 1 L of
tetrahydrofuran was treated with 8 grams of 10% palladium on carbon
(as a catalyst) and heated to 65.degree. C. for 17 hours in an
atmosphere of hydrogen at 270 kPa. The mixture was filtered through
Celite.TM. diatomaceous earth filter agent to remove the catalyst.
The filtrate was concentrated in vacuo to give a solid. The solid
was triturated with ethyl acetate, and the residue was dried to
give 2,5-bis(4-dodecylbenzyl)terephthalic acid.
[0094] Preparation of
3,10-Didodecyl-7,14-dihydropentacene-5,12-dione
[0095] A mixture of 22.7 grams of
2,5-bis(4-dodecylbenzyl)terephthalic acid and 80 mL of
trifluoromethanesulfonic acid was heated to 60.degree. C. for one
hour. The mixture was cooled to room temperature and poured over
500 grams of ice. The resulting precipitate was collected by
filtration and washed sequentially with one liter of water, two
liters of saturated aqueous sodium bicarbonate solution, and four
liters of water until the filtrate was neutral to pH paper. The
resulting solid was washed with two liters of acetone and dried to
give 3,10-didodecyl-7,14-dihydropentacene-5,12-dione.
[0096] Preparation of 2,9-Didodecylpentacene
[0097] A mixture of 8.5 grams of
3,10-didodecyl-7,14-dihydropentacene-5,12- -dione and 250 mL of
2-methoxyethyl ether was stirred and flushed with nitrogen for 15
minutes. To this was added 4.46 grams of sodium borohydride. The
resulting mixture was heated to 60.degree. C. for 18 hours. The
mixture was cooled to room temperature, and 42 mL of methanol was
added slowly. The resulting mixture was stirred at room temperature
for 30 minutes. To this was added 1.2 grams of sodium borohydride,
and stirring was continued at room temperature for 16 hours. To the
resulting mixture was added 60 mL of acetic acid, and the mixture
was heated at 60.degree. C. for one hour. To this mixture was added
43 mL of concentrated hydrochloric acid, and heating was continued
at 60.degree. C. for one hour. To the resulting mixture was added
100 mL of water and the mixture cooled to room temperature and the
solid was collected by filtration and dried to give
2,9-didodecylpentacene.
Example 6
Preparation of 1,2,3,4,10,11,12,13-Octahydroheptacene
[0098] Preparation of 2,5-Bis
(5,6,7,8-tetrahydronaphthalene-2-carbonyl)te- rephthalic Acid and
4,6-Bis(5,6,7,8-tetrahydronaphthalene-2-carbonyl)isoph- thalic
Acid
[0099] A mixture of 250 grams of aluminum chloride, 500 mL of
1,2-dichloroethane, and 97.4 grams of
benzene-1,2,4,5-tetracarboxylic acid dianhydride (pyromellitic
dianhydride) was cooled to 15.degree. C., and a solution of 124.1
grams of 1,2,3,4-tetrahydronaphthalene, 48.79 grams of
triethylamine, and 243 mL of 1,2-dichloroethane was added slowly
dropwise over a period of 1.5 hours keeping the temperature between
15-20.degree. C., followed by stirring overnight at room
temperature. The resulting mixture was poured into 1600 grams of
ice and 400 grams of concentrated hydrochloric acid and stirred for
20 minutes at room temperature. The top aqueous layer was poured
off, and the remaining mixture was diluted with 2 L of ethyl
acetate and stirred until a homogeneous solution resulted. The
resulting mixture was phase split, and the organic phase was
filtered. The organic phase was washed with 600 mL of brine, dried
over magnesium sulfate, filtered, and concentrated in vacuo. To the
resulting residue was added 500 mL of isopropyl acetate, and the
resulting mixture was stirred at room temperature. The residue was
treated with additional isopropyl acetate and heptane to
crystallize the product. The resulting solid product was isolated,
washed with heptane, and dried to give a mixture of
2,5-bis(5,6,7,8-tetrahydronaphtha- lene-2-carbonyl)terephthalic
acid and 4,6-bis(5,6,7,8-tetrahydronaphthalen-
e-2-carbonyl)isophthalic acid.
[0100] Preparation of
2,5-Bis(5,6,7,8-tetrahydronaphthalen-2-ylmethyl)tere- phthalic Acid
and 4,6-Bis(5,6,7,8-tetrahydronaphthalen-2-ylmethyl)isophtha- lic
Acid
[0101] A mixture of 94.7 grams of
2,5-bis(5,6,7,8-tetrahydronaphthalene-2-- carbonyl)terephthalic
acid and 4,6-bis(5,6,7,8-tetrahydronaphthalene-2-car-
bonyl)isophthalic acid, 1 L of tetrahydrofuran, and 6 grams of 10%
palladium on carbon (as a catalyst) was heated at 65.degree. C. for
17 hours in an atmosphere of hydrogen at 270 kPa. The reaction
mixture was filtered through Celite.TM. diatomaceous earth filter
agent to remove the catalyst. The filtrate was concentrated in
vacuo to give a solid. The solid was triturated with ethyl acetate,
collected by filtration, and dried to give a mixture of
2,5-bis(5,6,7,8-tetrahydronaphthalen-2-ylmethy- l)terephthalic acid
and 4,6-bis(5,6,7,8-tetrahydronaphthalen-2-ylmethyl)is- ophthalic
acid.
[0102] Preparation of
1,2,3,4,8,10,11,12,13,17-Decahydroheptacen-6,15-dion- e and
1,2,3,4,10,11,12,13-Octahydroheptacen-6,8(15H,17H)-dione
[0103] To a mixture of 35.3 grams of
2,5-bis(5,6,7,8-tetrahydronaphthalen-- 2-ylmethyl)terephthalic acid
and 4,6-bis(5,6,7,8-tetrahydronaphthalen-2-yl- methyl)isophthalic
acid was added 120 grams of trifluoromethanesulfonic acid. The
mixture was stirred at room temperature for one hour followed by
heating to 60.degree. C. for six hours. The mixture was poured over
500 grams of ice. The resulting solid was isolated by filtration
and washed sequentially with 500 mL of saturated aqueous sodium
bicarbonate solution and 4 L of water until the filtrate was
neutral to pH paper. The solid was dried to give a mixture of
1,2,3,4,8,10,11,12,13,17-decahydrohe- ptacen-6,15-dione and
1,2,3,4,10,11,12,13-octahydroheptacen-6,8(15H,17H)-d- ione.
[0104] Preparation of 1,2,3,4,10,11,12,13-Octahydroheptacene
[0105] A mixture of 1.0 gram of
1,2,3,4,8,10,11,12,13,17-decahydroheptacen- -6,15-dione and
1,2,3,4,10,11,12,13-octahydroheptacen-6,8(15H,17H)-dione and 20 mL
of 2-methoxyethyl ether was stirred and flushed with nitrogen for
15 minutes. To this was added 0.766 grams of sodium borohydride.
The resulting mixture was stirred overnight at room temperature. To
the mixture was added 7.2 mL of methanol and stirring was continued
for 30 minutes. To the resulting mixture was added 0.2 grams of
sodium borohydride, and stirring was continued at room temperature
for 5 hours. The resulting mixture was heated to 60.degree. C. for
one hour. To the mixture was added 11.4 mL of glacial acetic acid
and 7.3 mL of concentrated hydrochloric acid. The resulting mixture
was heated at 60.degree. C. for one hour. To this mixture was added
20 mL of water and the resulting solid was collected by filtration.
The solid was washed with water followed by acetone followed by
tetrahydrofuran and dried to give
1,2,3,4,10,11,12,13-octahydroheptacene.
Example 7
Preparation of 2,9-Di-sec-butylpentacene
[0106] Preparation of 2,5-Bis(4-sec-butylbenzoyl)terephthalic
Acid
[0107] A mixture of 417 grams of aluminum chloride, 837 mL of
1,2-dichloroethane, and 162 grams of
benzene-1,2,4,5-tetracarboxylic acid dianhydride (pyromellitic
dianhydride) was stirred and cooled to 16.degree. C. To the mixture
was added a solution of 200 grams of sec-butylbenzene, 104 grams of
diisopropylethylamine and 140 mL of 1,2-dichloroethane over a 3.5
hour period maintaining the reaction temperature between 15.degree.
C. and 20.degree. C. The resulting mixture was stirred overnight at
room temperature and added slowly to 500 grams of ice and 500 mL of
concentrated hydrochloric acid. The mixture was stirred for one
hour and the liquid poured from the coagulate. The coagulate was
worked up in 500 mL portions as follows. To 500 mL of the coagulate
was added 500 mL of water, 500 mL of ethyl acetate and 500 mL of
tetrahydrofuran. The mixture was stirred until the solid dissolved
and then phase split. The organic phase was filtered and
concentrated in vacuo. To 178 grams of the residue was added 178 mL
of ethyl acetate and 1600 mL of heptane and the mixture was stirred
until a suspension of a fine solid formed. The solid was collected
by filtration and washed with a mixture of 60 mL of ethyl acetate
and 540 mL of heptane. The solid was treated with 982 mL of ethyl
acetate and 392 mL of heptane and stirred. The solid was collected
by filtration and washed with a mixture of 120 mL of ethyl acetate
and 480 mL of heptane. The solid was dried to give
2,5-bis(4-sec-butylbenzoyl)terephthalic acid
[0108] Preparation of 2,5-bis(4-sec-butylbenzyl)terephthalic
Acid
[0109] A mixture of 120 grams of
2,5-bis(4-sec-butylbenzoyl)terephthalic acid, 1.5 L of
tetrahydrofuran, and 9.65 grams of 10% palladium on carbon (as a
catalyst) was heated at 65.degree. C. for 17 hours in an atmosphere
of hydrogen at 270 kPa. The reaction mixture was filtered through
Celite.TM. diatomaceous earth filter agent to remove the catalyst.
The filtrate was concentrated in vacuo to give a solid. The solid
was triturated with 10% ethyl acetate in heptane, collected and
dried to give 2,5-bis(4-sec-butylbenzyl)terephthalic acid.
[0110] Preparation of
3,10-Di-sec-butyl-7,14-dihydropentacene-5,12-dione
[0111] To five mL of trifluoromethanesulfonic acid was added two
grams of 2,5-bis(4-sec-butylbenzyl)terephthalic acid. The
temperature was maintained between 16.degree. C. and 25.degree. C.
during the addition. The mixture was stirred for five days at room
temperature. The mixture was poured over ice and the solid was
collected by filtration, washed with saturated aqueous sodium
bicarbonate and water until the pH of the filtrate was neutral to
pH paper. The solid was dried to give
3,10-di-sec-butyl-7,14-dihydropentacene-5,12-dione.
[0112] Preparation of 2,9-Di-sec-butylpentacene
[0113] A mixture of 2 grams of
3,10-di-sec-butyl-7,14-dihydropentacene-5,1- 2-dione and 45.3 mL of
2-methoxyethyl ether was stirred and flushed with nitrogen for 15
minutes. To this was added 1.52 grams of sodium borohydride and the
mixture was heated to 60.degree. C. overnight. The mixture was
cooled to room temperature. To the mixture was added 0.4 grams of
sodium borohydride and stirring was continued for 30 minutes. To
the mixture was added 15 mL of isopropyl alcohol and stirring was
continued at room temperature for 5 hours. To the mixture was added
15 mL of methanol. To the mixture was added one gram of sodium
borohydride and stirring was continued at room temperature. To the
mixture was added 16 mL of acetic acid and the mixture was heated
to 60.degree. C. for one hour. To the mixture was added 16 mL of
concentrated hydrochloric acid and heating was continued at
60.degree. C. The solid was collected by filtration and washed with
water followed by ethyl acetate and then acetone. The solid was
dried to give 2,9-di-sec-butylpentacene.
Example 8
Preparation of 1,4,8,11-Tetramethylpentacene
[0114] Preparation of 2,5-Bis(2,5-dimethybenzoyl)terephthalic
Acid
[0115] A mixture of 144 grams of benzene-1,2,4,5-tetracarboxylic
acid dianhydride (pyromellitic dianhydride), 439 grams of aluminum
chloride, and 915 grams of 1,2-dichloroethane was cooled to
15.degree. C. To this was added a mixture of 140 grams of p-xylene,
109 grams of N,N-diisopropylethylamine, and 426 mL of
1,2-dichloroethane over a period of 3.5 hours keeping the
temperature between 15.degree. C. and 20.degree. C. The resulting
mixture was stirred overnight at room temperature, poured into 2876
grams of ice and 1078 mL concentrated hydrochloric acid and stirred
for one hour. The organic layer was washed with 7 L of water. Three
liters of water was poured off and the mixture allowed to stand for
4 days, after which the remaining 3 L of water was poured off. To
the resulting residue was added 7 L of ethyl acetate and 3 L of
tetrahydrofuran. The organic phase was separated and concentrated
in vacuo. To 92 grams of the residue was added 1910 mL of ethyl
acetate and the mixture was heated to 77.degree. C. for one hour.
The mixture was cooled to room temperature and the solid was
collected by filtration and dried to give
2,5-bis(2,5-dimethybenzoyl)terephthalic acid.
[0116] Preparation of 2,5-Bis(2,5-dimethybenzyl)terephthalic
Acid
[0117] A mixture of 92 grams of
2,5-bis(2,5-dimethybenzoyl)terephthalic acid in 1.5 L of
tetrahydrofuran was treated with 9.2 grams of 10% palladium on
carbon (as a catalyst) in an atmosphere of hydrogen at 270 kPa and
65.degree. C. for 17 hours. The reaction mixture was filtered
through Celite.TM. diatomaceous earth filter agent to remove the
catalyst. The filtrate was concentrated in vacuo to give a solid.
The solid was triturated with ethyl acetate, collected by
filtration, and dried. To 75 grams of the solid was added 1250
grams of acetic acid, and the resulting mixture was heated to
117.degree. C. for 30 minutes and cooled to room temperature. The
resulting solid was collected by filtration and washed with acetic
acid followed by heptane. The resulting residue was dried to give
2,5-bis(2,5-dimethybenzyl)terephthalic acid.
[0118] Preparation of
7,14-Dihydro-1,4,8,11-tetramethylpentacene-5,12-dion- e
[0119] To 200 mL of trifluoromethanesulfonic acid cooled to
18.degree. C. was added slowly 53 grams of
2,5-bis(2,5-dimethylbenzyl)terephthalic acid in small portions as a
solid at a rate such that the temperature remained below 25.degree.
C. The mixture was allowed to stir for 10 minutes and the cooling
bath was removed. The mixture was stirred overnight at room
temperature. The mixture was poured over 600 grams of ice and the
resulting solid was collected by filtration. The solid was washed
with 1 L of water followed by 500 mL of saturated aqueous sodium
bicarbonate solution. The solid was washed with water until the pH
of the filtrate was neutral to pH paper. The solid was stirred for
one hour with 500 mL of tetrahydrofuran and collected by
filtration. The solid was washed with tetrahydrofuran and dried to
give 7,14-dihydro-1,4,8,11-tetramethylpentac- ene-5,12-dione.
[0120] Preparation of 1,4,8,11-Tetramethylpentacene
[0121] A mixture of 1.0 grams of
7,14-dihydro-1,4,8,11-tetramethylpentacen- e-5,12-dione and 10 mL
of 2-methoxyethyl ether was stirred and flushed with nitrogen for
15 minutes. To this was added 0.875 grams of sodium borohydride and
stirring was continued at room temperature overnight. To the
mixture was added 20 mL of 2-methoxyethyl ether and 0.75 grams of
sodium borohydride and heating was continued overnight at
60.degree. C. To the mixture was added 6.3 mL of methanol and 0.75
grams of sodium borohydride and stirring was continued for 6 hours
at room temperature. To the mixture was added 15 mL of acetic acid
and the mixture was stirred for one hour at room temperature. To
the mixture was added 10 mL of concentrated hydrochloric acid and
the mixture was heated to 60.degree. C. for 1.5 hours. The solid
was isolated by filtration, washed with water and dried to give
1,4,8,11-tetramethylpentacene.
Example 9
Preparation of
1,2,3,4,8,9,10,11-Octamethylpentacene-5,7(12H,14H)-dione
[0122] Preparation of
4,6-Bis(1,2,3,4,5-tetramethylbenzoyl)isophthalic Acid
[0123] A mixture of 73 grams of benzene-1,2,4,5-tetracarboxylic
acid dianhydride (pyromellitic anhydride), 188 grams of aluminum
chloride, and 465 grams of 1,2-dichloroethane was cooled to
15.degree. C. To this was added a mixture of 90 grams of
1,2,3,4-tetramethylbenzene, 46.8 gram of N,N-diisopropylethylamine,
and 183 mL of 1,2-dichloroethane over a period of 3.5 hours keeping
the temperature between 15.degree. C. and 20.degree. C. The mixture
was stirred overnight at room temperature, poured into a mixture of
225 grams of ice and 225 mL of concentrated hydrochloric acid and
stirred for one hour. As much solution as possible was poured from
the coagulate. The coagulate was worked up in 100 mL portions as
follows. To 100 mL of the coagulate was added 600 mL of
tetrahydrofuran and 300 mL of brine. The mixture was stirred and
phase split. The organic phase was filtered and concentrated in
vacuo. The combined residues were treated with 2500 grams of acetic
acid and heated to 117.degree. C. for 30 minutes. The mixture was
cooled to room temperature and the solid was collected by
filtration and washed with acetic acid and then heptane. The solid
was dried to give 4,6-bis(1,2,3,4,5 tetramethylbenzoyl)isophthalic
acid.
[0124] Preparation of
4,6-Bis(1,2,3,4,5-tetramethylbenzyl)isophthalic Acid
[0125] A mixture of 78.3 grams of
4,6-bis(1,2,3,4,5-tetramethylbenzoyl)iso- phthalic acid, 1.5 L of
tetrahydrofuran, and 6.3 grams of 10% palladium on carbon (as a
catalyst) was heated to 65.degree. C. for 17 hours in an atmosphere
of hydrogen at 270 kPa. The mixture was filtered through Celite.TM.
diatomaceous earth filter agent to remove the catalyst. The
filtrate was concentrated in vacuo to give
4,6-bis(1,2,3,4,5-tetramethylb- enzyl)isophthalic acid.
[0126] Preparation of
1,2,3,4,8,9,10,11-Octamethylpentacene-5,7(12H,14H)-d- ione
[0127] To 339 grams of trifluoromethanesulfonic acid was added 48
grams of 4,6-bis(1,2,3,4,5-tetramethylbenzyl)isophthalic acid with
cooling. The mixture was stirred at room temperature overnight and
then poured over 600 grams of ice. The resulting solid was isolated
by filtration and washed sequentially with water, saturated aqueous
sodium bicarbonate, and water until the filtrate was neutral to pH
paper. The solid was dried to give
1,2,3,4,8,9,10,11-octamethylpentacene-5,7(12H,14H)-dione.
Example 10
Preparation Process for Pentacene Including Step of Using
Trifluoromethanesulfonic Acid
[0128] Preparation of 2,5-Dibenzylterephthalic acid and
4,6-Dibenzylisophthalic Acid
[0129] To a mixture of 100 grams of 2,5-bis-benzoylterephthalic
acid and 4,6-dibenzoylisophthalic acid was added 1.5 L of
tetrahydrofuran and 10.4 grams of 10% palladium on carbon (as a
catalyst). This mixture was heated to 65.degree. C. for 17 hours in
an atmosphere of hydrogen at 270 kPa. The resulting mixture was
filtered through Celite.TM. diatomaceous earth filter agent to
remove the catalyst. The filtrate was concentrated in vacuo to give
a mixture of 2,5-dibenzylterephthalic acid and
4,6-dibenzylisophthalic acid.
[0130] Preparation of 7,14-Dihydropentacene-5,12-dione and
Pentacene-5,7(12H,14H)-dione
[0131] To 20 mL of trifluoromethanesulfonic acid cooled to
7.degree. C. was added 3.0 grams of a mixture of
2,5-dibenzylterephthalic acid and 4,6-dibenzylisophthalic acid. The
mixture was stirred at room temperature for three hours and poured
over 50 grams of ice. The resulting solid was isolated by
filtration and washed sequentially with water, saturated aqueous
sodium bicarbonate, and water until the filtrate was neutral to pH
paper. The solid was dried to give a mixture of
7,14-dihydropentacene-5,12-dione and
pentacene-5,7(12H,14H)-dione.
[0132] Preparation of Pentacene
[0133] A mixture of 1.0 gram of 7,14-dihydropentacene-5,12-dione
and pentacene-5,7(12H,14H)-dione, and 10 mL of 2-methoxyethyl ether
was stirred and flushed with nitrogen for 15 minutes. To this was
added 1.03 grams of sodium borohydride and stirring was continued
at room temperature overnight. To the mixture was added 10 mL of
2-methoxyethyl ether and 6.3 mL of methanol and stirring was
continued for 1.5 hours at room temperature. To the mixture was
added 15 mL of acetic acid and 10 mL of concentrated hydrochloric
acid. The mixture was stirred for one hour at room temperature and
heated to 60.degree. C. for one hour. To the mixture was added 50
mL of water, and the resulting solid was isolated by filtration and
washed with-water. The solid was washed with tetrahydrofuran until
a pale filtrate resulted. The solid was washed with heptane and
dried to give pentacene.
Example 11
Preparation Process for Fluorenone (9H-Fluoren-9-one) Using
Trifluoromethanesulfonic Acid
[0134] Preparation of Fluorenone (9H-Fluoren-9-one).
[0135] To 1.0 grams of 2-biphenylcarboxylic acid was added 3 mL of
trifluoromethanesulfonic acid. The sample was maintained at room
temperature for 2.5 hours The mixture was poured over ice-water and
extracted with ethyl acetate. The organic phase was washed with a
saturated aqueous sodium bicarbonate solution until the aqueous
phase was basic. The aqueous phase was separated. The organic phase
was washed with water, dried over magnesium sulfate, and
concentrated in vacuo to give 9H-fluoren-9-one.
Comparative Example C1
Combining 2,5-Dibenzylterephthalic Acid, 4,6-Dibenzylisophthalic
Acid, and Sulfuric Acid
[0136] To an 80 mg mixture of 2,5-dibenzylterephthalic acid and
4,6-dibenzylisophthalic acid was added 3 grams of concentrated
sulfuric acid. The resulting mixture was stirred at room
temperature. After three hours the mixture contained an impurity
that was not present in the reaction mixture containing
trifluoromethanesulfonic acid and dibenzylphthalic acids.
Comparative Example C2
Combining 2,5-Bis(4-methylbenzyl)terephthalic Acid and
Polyphosphoric Acid
[0137] A mixture of 0.2 grams of
2,5-bis(4-methylbenzyl)terephthalic acid and 4 mL of polyphosphoric
acid was heated to 80.degree. C. The solid did not dissolve
completely, and the mixture remained colorless. The viscous mixture
was heated for 2 hours at 80.degree. C. The mixture was cooled to
room temperature and added to water. The solid was collected by
filtration, washed with hexane and dried to give recovered starting
material.
Comparative Example C3
Combining 2,5-Bis(4-methylbenzyl)terephthalic Acid and Sulfuric
Acid with Short Reaction Time
[0138] A mixture of 0.1 grams of
2,5-bis(4-methylbenzyl)terephthalic acid and 2 mL concentrated
sulfuric acid was stirred at room temperature for 34 minutes. The
mixture was poured over ice and the solid was collected by
filtration to give recovered starting material.
Comparative Example C4
Combining 2,5-Bis(4-methylbenzyl)terephthalic Acid and Sulfuric
Acid with Long Reaction Time
[0139] To an 80 mg sample of 2,5-bis(4-methylbenzyl)terephthalic
acid was added 3 grams of concentrated sulfuric acid. The mixture
was stirred at room temperature. After remaining at room
temperature for 24 hours the reaction mixture contained
approximately 20% of 7,14-dihydro-3,10-dimethy-
lpentacene-5,12-dione, 40% of
6-methyl-3-(4-methylbenzyl)-10-oxo-9,10-dihy-
droanthracene-2-carboxylic acid (the mono-cyclized intermediate)
and 40% of 2,5-bis(4-methylbenzyl)terephthalic acid (starting
material).
Comparative Example C5
Combining 2,5-Bis(4-nonylbenzyl)terephthalic Acid and Sulfuric
Acid
[0140] A mixture of 0.5 grams of 2,5-bis(4-nonylbenzyl)terephthalic
acid in 10 mL of concentrated sulfuric acid was heated to
65.degree. C. After one hour at 65.degree. C. an aliquot of the
mixture was quenched and only starting material was recovered. No
7,14-dihydro-3,10-dinonylpentacene-5,- 12-dione was formed after 24
hours at 65.degree. C.
[0141] The complete disclosures of the publications cited herein
are incorporated by reference in their entirety as if each were
individually incorporated. Various modifications and alterations to
this invention will become apparent to those skilled in the art
without departing from the scope and spirit of this invention. It
should be understood that this invention is not intended to be
unduly limited by the illustrative embodiments and examples set
forth herein and that such examples and embodiments are presented
by way of example only with the scope of the invention intended to
be limited only by the claims set forth herein as follows.
* * * * *