U.S. patent number RE46,151 [Application Number 14/321,865] was granted by the patent office on 2016-09-20 for method for the production of 4,4'-[1-(trifluoromethyl)alkylidene]-bis-(2,6-diphenylphenols).
This patent grant is currently assigned to BASF SE. The grantee listed for this patent is BASF SE. Invention is credited to Klaus Ebel, Gabriele Gralla, Gunnar Heydrich, Wolfgang Krause.
United States Patent |
RE46,151 |
Gralla , et al. |
September 20, 2016 |
Method for the production of
4,4'-[1-(trifluoromethyl)alkylidene]-bis-(2,6-diphenylphenols)
Abstract
The present invention relates to a process for preparing
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols), in
particular for preparing
4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol), which
comprises the self-condensation of cyclohexanone in the presence of
a basic catalyst to form tricyclic condensation products,
dehydrogenation of the resulting tricyclic condensation products in
the presence of a supported transition metal catalyst in the
condensed phase to form 2,6-diphenylphenol and reaction of the
2,6-diphenylphenol with a trifluoromethyl ketone. The invention
further provides an improved process for preparing
2,6-diphenylphenol by aldol self-condensation of cyclohexanone.
Inventors: |
Gralla; Gabriele (Mannheim,
DE), Heydrich; Gunnar (Limburgerhof, DE),
Ebel; Klaus (Lampertheim, DE), Krause; Wolfgang
(Bruehl-Rohrhof, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
BASF SE |
Ludwigshafen OT |
N/A |
DE |
|
|
Assignee: |
BASF SE (Ludwigshafen,
DE)
|
Family
ID: |
1000001779405 |
Appl.
No.: |
14/321,865 |
Filed: |
July 2, 2014 |
PCT
Filed: |
December 17, 2008 |
PCT No.: |
PCT/EP2008/067686 |
371(c)(1),(2),(4) Date: |
June 17, 2010 |
PCT
Pub. No.: |
WO2009/077549 |
PCT
Pub. Date: |
June 25, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
12808865 |
Dec 17, 2008 |
8212084 |
Jul 3, 2012 |
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Foreign Application Priority Data
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Dec 17, 2007 [EP] |
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07123368 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C
37/62 (20130101); C07C 37/07 (20130101); C07C
37/62 (20130101); C07C 45/74 (20130101); C07C
37/20 (20130101); C07C 37/07 (20130101); C07C
37/20 (20130101); C07C 45/74 (20130101); C07C
45/74 (20130101); C07C 45/74 (20130101); C07C
49/613 (20130101); C07C 49/613 (20130101); C07C
45/74 (20130101); C07C 45/74 (20130101); C07C
49/653 (20130101); C07C 49/653 (20130101); C07C
37/07 (20130101); C07C 37/07 (20130101); C07C
39/15 (20130101); C07C 39/15 (20130101); C07C
37/62 (20130101); C07C 37/62 (20130101); C07C
39/367 (20130101); C07C 39/367 (20130101); C07C
37/20 (20130101); C07C 37/20 (20130101); C07C
39/367 (20130101); C07C 39/367 (20130101) |
Current International
Class: |
C07C
39/16 (20060101); C07C 45/74 (20060101); C07C
39/12 (20060101); C07C 37/07 (20060101); C07C
37/62 (20060101); C07C 37/20 (20060101) |
Field of
Search: |
;568/718,747 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1643402 |
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May 1970 |
|
DE |
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1643403 |
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Apr 1971 |
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DE |
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2211721 |
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Sep 1972 |
|
DE |
|
1207524 |
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Oct 1970 |
|
GB |
|
S52-3041 |
|
Jan 1977 |
|
JP |
|
S52-17450 |
|
Feb 1977 |
|
JP |
|
S52-27156 |
|
Jul 1977 |
|
JP |
|
WO-2006/092433 |
|
Sep 2006 |
|
WO |
|
Other References
Bibo et al., "Analysis of 2,6-Substituted Cyclohexanones and
Phenols by Gas-Chromatography Combined with Thin-Layer
Chromatography," Z, Anal Chem.. vol. 236, pp. 208-215 (1967). cited
by applicant .
Database CAPLUS on STN, Acc. No. 1982:405891, Dana et al.,
Synthesis (1982), 2, p. 164-165 (abstract). cited by
applicant.
|
Primary Examiner: Huang; Evelyn
Attorney, Agent or Firm: Drinker Biddle & Reath LLP
Claims
The invention claimed is:
1. A process for preparing
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) of the
formula (I) ##STR00017## where the radical R is unbranched or
branched C.sub.1-C.sub.6-alkyl or C.sub.1-C.sub.6-perfluoroalkyl,
which comprises the process steps a) reaction of cyclohexanone in
the presence of a basic catalyst to form a reaction mixture
comprising the tricyclic condensation products of the formula
(IIa), (IIb) and/or (IIc) ##STR00018## and water, b) separation of
a mixture of the tricyclic condensation products comprising the
compounds of the formulae (IIa), (IIb) and/or (IIc) from the
reaction mixture formed in step a), c) dehydrogenation of the
tricyclic condensation products comprising the compounds of the
formulae (IIa), (IIb) and/or (IIc) obtained in step b) in the
presence of a .Iadd.Al.sub.2O.sub.3 .Iaddend.supported
.[.transition metal.]. .Iadd.Pd .Iaddend.catalyst.Iadd., and
carbonates of alkali metals or alkaline earth metals, .Iaddend.in
the condensed phase to form a reaction mixture comprising
2,6-diphenylphenol of the formula (III), ##STR00019## d) separation
of 2,6-diphenylphenol of the formula (III) from the reaction
mixture formed in step c) and e) reaction of the 2,6-diphenylphenol
of the formula (III) obtained in step d) with a trifluoromethyl
ketone of the formula (IV) ##STR00020## where the radical R is as
defined for formula (I), in the presence of a strong organic acid
to form the
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenol) of the
formula (I).
2. The process of claim 1, wherein an aqueous solution of an alkali
metal hydroxide or alkaline earth metal hydroxide is used as basic
catalyst in step a).
3. The process of claim 1, wherein an aqueous solution of sodium
hydroxide is used as basic catalyst in step a).
4. The process of claim 1, wherein the reaction according to step
a) is carried out at a temperature in the range from 90 to
180.degree. C.
5. The process of claim 1, wherein the reaction according to
process step a) is carried out in the presence of a solvent or
solvent mixture which forms an azeotrope with water.
6. The process of claim 5, wherein the water formed in step a) is
separated from the reaction mixture by distillation in the form of
an azeotrope with the solvent or solvent mixture used during the
reaction.
7. The process of claim 5, wherein xylene, toluene or ethylbenzene
or a mixture thereof is used as solvent.
8. The process of claim 1, wherein the separation according to
process step b) is carried out in the form of a distillation.
.[.9. The process of claim 1, wherein the dehydrogenation according
to process step c) is carried out in the presence of a catalyst
comprising palladium and/or platinum on a support..].
.[.10. The process of claim 1, wherein the dehydrogenation
according to process step c) is carried out in the presence of a Pd
catalyst supported on Al.sub.2O.sub.3 or a carbon support..].
.[.11. The process of claim 1, wherein the dehydrogenation
according to process step c) is carried out in the presence of
hydroxides or carbonates of alkali metals or alkaline earth
metals..].
12. The process of claim 1, wherein the isolation of
2,6-diphenylphenol according to process step d) is carried out in
the form of a crystallization.
13. The process of claim 1, wherein the reaction according to
process step e) is carried out at a temperature in the range from
10 to 60.degree. C.
14. The process of claim 1, wherein the reaction according to
process step e) is carried out in the presence of an organic acid
having a pKa of up to 2.
15. The process of claim 1, wherein the reaction according to
process step e) is carried out in the presence of methanesulfonic
acid.
16. The process of claim 1, wherein 2,6-diphenylphenol and the
trifluoromethyl ketone of the formula (IV) are used in a molar
ratio of from 1:1 to 2:1 in process step e).
17. The process of claim 1, wherein the radical R is methyl or
trifluoromethyl.
18. The process of claim 1, wherein the radical R is methyl.
19. The process of claim 1, wherein the
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenol) of the
formula (I) formed in process step e) is separated off from the
resulting reaction mixture by extraction.
20. A process for preparing 2,6-diphenylphenol of the formula (III)
##STR00021## which comprises the steps i) reaction of cyclohexanone
in the presence of a basic catalyst to form a reaction mixture
comprising the tricyclic condensation products of the formula
(IIa), (IIb) and/or (IIc) ##STR00022## and water in the presence of
a solvent or solvent mixture other than cyclohexanone which forms
an azeotrope with water, with the water formed being separated off
from the reaction mixture by distillation in the form of an
azeotrope with the solvent or solvent mixture used during the
reaction, ii) separation of a mixture of the tricyclic condensation
products of the formulae (IIa), (IIb) and/or (IIc) from the
reaction mixture formed in step i) and iii) dehydrogenation of the
tricyclic condensation products comprising the compounds of the
formulae (IIa), (IIb) and/or (IIc) obtained in step ii) in the
presence of a .Iadd.Al.sub.2O.sub.3 .Iaddend.supported
.[.transition metal.]. .Iadd.Pd .Iaddend.catalyst.Iadd., and
carbonates of alkali metals or alkaline earth metals, .Iaddend.in
the condensed phase to form a reaction mixture comprising
2,6-diphenylphenol of the formula (III) ##STR00023##
.Iadd.21. A process for dehydrogenating compounds of formula (IIa),
(IIb), and/or (IIc) ##STR00024## in the presence of an
Al.sub.2O.sub.3 supported Pd catalyst, and carbonates of alkali
metals, in the condensed phase to form a reaction mixture
comprising 2,6-diphenylphenol of formula (III), ##STR00025##
.Iaddend.
.Iadd.22. The process of claim 21, further comprising separating
the supported Pd catalyst from the reaction mixture and reuse the
catalyst for at least four times in subsequent dehydrogenation
processes of compounds of formula (IIa), (IIb), and/or (IIc)
without appreciable decreases in activity or
selectivity..Iaddend.
.Iadd.23. The process of claim 1, further comprising separating the
supported Pd catalyst from the reaction mixture and reuse the
catalyst for at least four times in subsequent dehydrogenation
processes of compounds of formula (IIa), (IIb), and/or (IIc)
without appreciable decreases in activity or
selectivity..Iaddend.
.Iadd.24. The process of claim 20, further comprising separating
the supported Pd catalyst from the reaction mixture and reuse the
catalyst for at least four times in subsequent dehydrogenation
processes of compounds of formula (IIa), (IIb), and/or (IIc)
without appreciable decreases in activity or selectivity..Iaddend.
Description
RELATED APPLICATIONS
This application is a national stage application (under 35 U.S.C.
.sctn.371) of PCT/EP2008/067686, filed Dec. 17, 2008, which claims
benefit of European Application No. 07123368.8, filed Dec. 17,
2007.
The present invention relates to a process for preparing
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols), in
particular for preparing
4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol), which
comprises the self-condensation of cyclohexanone in the presence of
a basic catalyst to form tricyclic condensation products,
dehydrogenation of the resulting tricyclic condensation products in
the presence of a supported transition metal catalyst in the
condensed phase to form 2,6-diphenylphenol and reaction of the
2,6-diphenylphenol with a trifluoromethyl ketone. The invention
further provides an improved process for preparing
2,6-diphenylphenol by aldol self-condensation of cyclohexanone and
subsequent dehydrogenation.
4,4'-[1-(Trifluoromethyl)ethylidene]bis(2,6-diphenylphenol) and
4,4'-[1,1-bis(trifluoromethyl)methylidene]bis(2,6-diphenylphenol)
are known from U.S. Pat. No. 3,739,035 and are described as
valuable starting materials for preparing polycarbonates or
polyesters. They are prepared by reacting 2,6-diphenylphenol with
in each case large excesses of gaseous hexafluoroacetone or
1,1,1-trifluoroacetone in methanesulfonic acid.
The compounds mentioned are also important starting materials for
preparing bis(diarylphenoxy)aluminum compounds as are described in
WO 2006/092433.
DE 1 643 402 relates to a process for preparing 2,6-diphenylphenol
by self-condensation of cyclohexanone to form tricyclic
condensation products and subsequent dehydrogenation of these.
Here, the self-condensation of cyclohexanone is carried out under
solvent-free conditions at temperatures of up to 200.degree. C. in
the presence of a strong base, preferably aqueous solutions of
sodium hydroxide or potassium hydroxide, as catalyst. The
dehydrogenation of the tricyclic condensation products obtained in
admixture with bicyclic condensation products which is to be
carried out in the second step is carried out in the presence of a
dehydrogenation catalyst at a temperature of up to 350.degree. C.,
preferably from 300 to 350.degree. C. Suitable dehydrogenation
catalysts described are supported platinum, palladium, nickel,
ruthenium and rhodium catalysts.
DE 1 643 403 discloses a process for crystallizing
2,6-diphenylphenol from a mixture comprising 2,6-diphenylphenol
together with at least one further phenol which has an aliphatic
6-membered ring instead of a phenyl ring in the 2 or 6 position.
For this purpose, the mixtures are dissolved in a mixture of from
75 to 99% by weight of an aliphatic solvent with from 1 to 25% by
weight of an aromatic solvent and the temperature of the solution
is reduced to a point below the crystallization temperature of
2,6-diphenylphenol.
DE 2 211 721 relates to a process for preparing orthophenylphenol,
wherein the product of the bimolecular dehydration condensation of
cyclohexanone is introduced into a bed of a catalyst supported on
an inactive support and the condensate is subjected to
dehydrogenation at from 230 to 520.degree. C. in the presence of an
inert gas. The document also discloses catalysts which are suitable
for carrying out the process and comprise one or more of the
elements palladium, platinum, iridium and rhodium and may further
comprise an alkali.
Proceeding from this prior art, it was an object of the present
invention to provide a process which makes it possible to prepare
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) and
2,6-diphenylphenol in a particularly economical manner, i.e. with a
very high yield of the desired compounds and with very little
formation of undesirable by-products which may, if appropriate,
have to be separated off in a complicated fashion and be disposed
of or recirculated, and in a manner which is very advantageous from
a process engineering point of view.
The object was achieved according to the invention by provision of
a process for preparing
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) of the
formula (I)
##STR00001## where the radical
R is unbranched or branched C.sub.1-C.sub.6-alkyl or
C.sub.1-C.sub.6-perfluoroalkyl,
which comprises the process steps
a) reaction of cyclohexanone in the presence of a basic catalyst to
form a reaction mixture comprising the tricyclic condensation
products of the formula (IIa), (IIb) and/or (IIc)
##STR00002## and water, b) separation of a mixture of the tricyclic
condensation products comprising the compounds of the formulae
(IIa), (IIb) and/or (IIc) from the reaction mixture formed in step
a), c) dehydrogenation of the tricyclic condensation products
comprising the compounds of the formulae (IIa), (IIb) and/or (IIc)
obtained in step b) in the presence of a supported transition metal
catalyst in the condensed phase to form a reaction mixture
comprising 2,6-diphenylphenol of the formula (III),
##STR00003## d) separation of 2,6-diphenylphenol of the formula
(III) from the reaction mixture formed in step c) and e) reaction
of the 2,6-diphenylphenol of the formula (III) obtained in step d)
with a trifluoromethyl ketone of the formula (IV)
##STR00004## where the radical R is as defined for formula (I), in
the presence of a strong organic acid to form the
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenol) of the
formula (I).
The process of the invention is suitable for preparing
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) of the
formula (I)
##STR00005## where the radical R is unbranched or branched
C.sub.1-C.sub.6-alkyl or C.sub.1-C.sub.6-perfluoroalkyl. Here, the
term branched or unbranched C.sub.1-C.sub.6-alkyl refers to
branched or unbranched alkyl radicals having from 1 to 6 carbon
atoms, for example methyl, ethyl, propyl, isopropyl, butyl,
sec-butyl, tert-butyl, pentyl or hexyl. Preferred
C.sub.1-C.sub.6-alkyl radicals are methyl, ethyl, isopropyl,
particularly preferably methyl. The term branched or unbranched
C.sub.1-C.sub.6-perfluoroalkyl refers to branched or unbranched
perfluoroalkyl radicals, i.e. alkyl radicals in which all hydrogen
atoms have been replaced by fluorine atoms, having from 1 to 6
carbon atoms, for example trifluoromethyl, pentafluoroethyl,
heptafluoropropyl, heptafluoroisopropyl, nonafluorobutyl. Preferred
C.sub.1-C.sub.6-perfluoroalkyl radicals are trifluoromethyl,
pentafluoroethyl, heptafluoroisopropyl, particularly preferably
trifluoromethyl. Possible particularly preferred process products
are accordingly
4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol) of the
formula (Ia)
##STR00006## and
4,4'-[1,1-(bistrifluoromethyl)methylidene]bis(2,6-diphenylphenol)
of the formula (Ib)
##STR00007##
A process product which is very particularly preferred according to
the invention is
4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol) of the
formula (Ia).
The process of the invention comprises the process steps a) to e).
In process step a) of the process of the invention, a reaction of
cyclohexanone in the presence of a basic catalyst is carried out to
form a reaction mixture comprising the tricyclic condensation
products of the formula (IIa), (IIb) and/or (IIc)
##STR00008## and water. Accordingly, cyclohexanone serves as
starting material for carrying out the process of the invention.
This can be used in commercial purity, i.e. without particular
purity requirements, production process or nature, usually in a
purity of about 95% by weight or above, preferably 99% by weight or
above.
The reaction of cyclohexanone according to step a) of the process
of the invention is an intermolecular self-condensation of 3
molecules of cyclohexanone in an aldol condensation (aldol addition
with subsequent elimination of water), as is known per se to those
skilled in the art. This forms product mixtures of tricyclic
cyclohexanones which comprise the compounds of the formulae (IIa),
(IIb) and/or (IIc) depicted above. The mixtures mentioned can
comprise one, two or all three of the compounds (IIa), (IIb) and
(IIc) mentioned and may additionally comprise further isomers of
the compounds mentioned, for example those in which an ethylenic
double bond is localized in the cyclohexanone ring of the molecule.
It is usual for all three tricyclic ketones of the formulae (IIa),
(IIb) and (IIc) to be present in the product mixtures
mentioned.
Bicyclic cyclohexanones, especially those of the formulae (Va)
and/or (Vb)
##STR00009## are generally also formed as undesirable by-products
of the self-condensation of cyclohexanone to be carried out in step
a) of the process of the invention. However, these can, as
described below under step b) of the process of the invention, be
separated off from the tricyclic reaction products of the formulae
(IIa), (IIb) and/or (IIc), preferably by distillation, and, if
desired, be recirculated to the reaction in process step a).
The reaction in process step a) is carried out in the presence of a
basic catalyst, preferably in the presence of an inorganic,
especially strongly basic, catalyst. As basic or strongly basic, in
particular inorganic, catalysts or bases, mention may be made of
those which are able to convert cyclohexanone at least partly into
the corresponding enolate anion by deprotonation. The reaction in
process step a) is preferably carried out in the presence of a
strong base, particularly preferably a base which has a pKb of less
than 4. As preferred strong bases for this purpose, mention may be
made of the hydroxides, alkoxides, hydrides, amides or carbonates
of alkali metals or alkaline earth metals, for example lithium,
sodium, potassium, calcium and barium hydroxide, sodium ethoxide,
sodium methoxide, potassium tert-butoxide, sodium and potassium
hydride, lithium diisopropylamide and also lithium, sodium,
potassium, calcium and barium carbonate. Particularly preferred
strong bases are the hydroxides and carbonates of the alkali metals
or alkaline earth metals, very particularly preferably the
hydroxides of the alkali metals. The compounds mentioned can be
used in pure form or in the form of mixtures with one another or in
the form of mixtures with other bases. They can be used in solid or
dissolved form, preferably in the form of aqueous solutions.
The amount of basic catalyst to be used in process step a) is not
critical and can be varied within a wide range. However, taking
into account the economic aspect, it is advantageous to use the
catalyst in the smallest possible amount, preferably in an amount
of up to 20 mol %, particularly preferably up to 10 mol % and very
particularly preferably up to 5 mol %, in each case based on the
base equivalents and the amount of cyclohexanone used.
In process step a) of the process of the invention, preference is
given to using an aqueous solution of an alkali metal hydroxide or
alkaline earth metal hydroxide, particularly preferably an aqueous
solution of sodium hydroxide, as basic catalyst. If the base
selected is used in the form of a solution, preferably in the form
of an aqueous solution, the preferred concentration range of these
solutions is from about 5 to about 50% by weight (based on the
finished solution), particularly preferably from about 25 to about
50% by weight.
The self-condensation of cyclohexanone to be carried out in process
step a) can be carried out in a wide temperature range, usually at
temperatures of from about 70.degree. C. to about 200.degree. C. A
preferred temperature range for carrying out process step a) of the
process of the invention is the range from 90 to 180.degree. C.
During the course of the self-condensation of the cyclohexanone
used, i.e. as conversion progresses, the dimeric, bicyclic
condensation products of the formulae (Va) and (Vb) are firstly
formed as primary condensation products from the reaction of two
molecules of cyclohexanone. These have a boiling point higher than
that of cyclohexanone itself and have to react with a further
molecule of cyclohexanone to form the desired tricyclic
condensation products of the formulae (IIa), (IIb) and/or
(IIc).
In an embodiment of the process of the invention which is
particularly preferred according to the invention, the reaction
according to process step a) is carried out in the presence of a
solvent (other than cyclohexanone) or solvent mixture which forms
an azeotrope with water. Preferred "solvents which form an
azeotrope with water" are solvents, preferably organic solvents,
which are inert under the reaction conditions and have a boiling
point at atmospheric pressure of from about 100.degree. C. to about
200.degree. C., preferably in the range from 100.degree. C. to
150.degree. C., particularly preferably in the range from
110.degree. C. to 140.degree. C. and very particularly preferably
in the range from 130.degree. C. to 140.degree. C., and are
different from cyclohexanone. Particular preference is given to
those organic solvents which form an azeotrope with water which has
a boiling point lower than that of cyclohexanone, i.e. less than
155.degree. C., and a boiling point lower than that of the
respective solvent itself (low-boiling azeotrope). Very particular
preference is given to those solvents or solvent mixtures whose
azeotropic boiling point is below the azeotropic boiling point of
cyclohexanone of 95.degree. C. To ensure a satisfactory reaction
rate, it is advantageous for the azeotropic boiling point of the
solvent or solvent mixture selected to be as high as possible,
preferably 70.degree. C. or above, particularly preferably
80.degree. C. or above. In process step a) of the process of the
invention, solvents which can particularly preferably be used
according to the invention accordingly have an azeotropic boiling
point in the range from 70.degree. C. to 95.degree. C., preferably
from 80.degree. C. to 95.degree. C., particularly preferably up to
<95.degree. C., for example toluene, xylene and ethylbenzene or
mixtures thereof, preferably xylene. The abovementioned "solvent
which forms an azeotrope with water" can therefore also be referred
to as an entrainer.
The solvents mentioned can be used as such or in the form of
mixtures of two or more different solvents. Preference is given to
using only one solvent, preferably a solvent which forms an
azeotrope as described above with water, in process step a) of the
process of the invention.
In another preferred embodiment, the process of the invention is
carried out so that the water formed in process step a) by aldol
self-condensation of cyclohexanone is separated from the reaction
mixture by distillation in the form of an azeotrope with the
solvent used during the reaction. The removal of the water of
reaction formed in the aldol self-condensation of cyclohexanone and
any water added in the form of an aqueous solution of the basic
catalyst can be carried out by azeotropic distillation methods
known per se to those skilled in the art using apparatuses which
are likewise known for the separation or removal of water from a
reaction mixture, for example a water separator. The water can be
separated off completely or largely completely or only partly.
However, preference is given to separating off the
stoichiometrically expected amount of water to be formed (and also
any amount of water added with the catalyst) as completely as
possible in order to aid the desired formation of the
above-mentioned tricyclic reaction products.
The amount of solvent which forms an azeotrope with water to be
used in this preferred embodiment can be selected within a wide
range and can be dependent on various factors, in particular on the
choice of the specific solvent or solvent mixture used and on the
process or apparatus used for separating off or removing the water.
The selected solvent is usually, taking account of economic
factors, used in an amount of from 5 to 100% by weight, preferably
from 10 to 60% by weight and particularly preferably from 15 to 40%
by weight, of the amount of cyclohexanone used.
This gives a reaction mixture which comprises, apart from the basic
catalyst used, essentially the desired tricyclic ketones of the
formulae (IIa), (IIb) and/or (IIc) together with bicyclic
condensation products of the formula (Va) and/or (Vb) and unreacted
cyclohexanone. The reaction mixture obtained in this way can be
processed further in this form or firstly be worked up, for example
by extractive processes with which those skilled in the art will be
familiar. It is advantageous firstly to carry out a neutralization
of the basic catalyst by treatment with an acid.
In process step b) of the process of the invention, the tricyclic
condensation products comprising the compounds of the formulae
(IIa), (IIb) and/or (IIc) are separated off from the optionally
worked-up and largely neutralized reaction mixture formed in this
way in process step a). The separation can be effected by methods
which appear suitable to those skilled in the art, for example by
chromatography or distillation. The separation of the tricyclic
reaction products of the formulae IIa, IIb and/or IIc from the
reaction mixture obtained in process step a), if appropriate after
neutralization and work-up by extraction, in process step b) is
preferably carried out in the form of a distillation.
The isolation of the tricyclic condensation products by
distillation can be carried out batchwise, semicontinuously or
fully continuously. Preference is given to carrying out a batch or
semicontinuous distillation, particularly preferably a batch
distillation. The design of the distillation column to be used does
not have to meet any particular requirements. It can be
advantageous to use packed columns, e.g. columns packed with
suitable mesh packing, sheetmetal packing or disordered beds of
packing elements. The distillation is advantageously carried out
under reduced pressure, preferably at a pressure at the bottom of
from about 1 to about 100 mbar, particularly preferably from about
5 to about 30 mbar abs., and a pressure at the top of from about 1
to about 100 mbar abs., particularly preferably from about 5 to
about 20 mbar abs. Accordingly, the temperature at the bottom is
advantageously from about 200 to about 250.degree. C., preferably
from about 210 to about 230.degree. C., and the temperature at the
top is from about 190 to about 220.degree. C., preferably from
about 200 to about 210.degree. C. The tricyclic ketones of the
formulae (IIa), (IIb) and/or (IIc) are obtained as high-boiling
bottom product from which the lower-boiling components, in
particular the bicyclic condensation products of the formulae (Va)
and/or (Vb), are distilled off as overhead product. These can, if
desired, be recirculated as starting material to the aldol
self-condensation of cyclohexanone in process step a) of the
process of the invention.
In process step c) of the process of the invention, a
dehydrogenation of the tricyclic condensation products comprising
the compounds of the formula (IIa), (IIb) and/or (IIc) obtained
according to process step b) is carried out in the presence of a
supported transition metal catalyst in the condensed phase to form
a reaction mixture comprising 2,6-diphenylphenol of the formula
(III)
##STR00010##
The dehydrogenation step in process step c) of the process of the
invention is carried out in the condensed, i.e. liquid, phase.
Here, the mixture comprising the tricyclic ketones of the formulae
(IIa), (IIb) and/or (IIc) to be reacted and the 2,6-diphenylphenol
of the formula (III) obtained as dehydrogenation product and also
any partially dehydrogenated compounds obtained, for example
2-cyclohexyl-6-phenylphenol, are present largely, i.e.
predominantly, in liquid form. The dehydrogenation is usually
carried out at elevated temperature, preferably at temperatures in
the range from about 200.degree. C. to about 300.degree. C., i.e.
at temperatures below the boiling point of the tricyclic starting
materials mentioned or products of the dehydrogenation. The
dehydrogenation is preferably carried out at a temperature in the
range from 240 to 300.degree. C., particularly preferably in the
range from 250 to 300.degree. C.
Furthermore, the dehydrogenation in process step c) is carried out
in the presence of a supported transition metal catalyst. Suitable
supported transition metal catalysts are in principle all those
which are known to those skilled in the art as catalysts for such
dehydrogenation reactions to form aromatic systems, for example
those comprising one or more of the transition metals palladium,
platinum, nickel, ruthenium, rhodium on a suitable support. The
dehydrogenation in process step c) is preferably carried out in the
presence of a catalyst comprising palladium (Pd) and/or platinum
(Pt) on a support. The catalysts which are preferably to be used in
process step c) can comprise the transition metals palladium and
platinum either individually or in the form of a mixture with one
another, if appropriate together with further metals. Preference is
given to using catalysts which comprise palladium as catalytically
active metal. The metals mentioned are used in supported form, i.e.
in a form in which they have been applied to materials which are
known per se to those skilled in the art as support materials. As
suitable support materials, mention may be made by way of example
of: silica gel (SiO.sub.2), aluminum oxide (Al.sub.2O.sub.3),
carbon, activated carbon, zirconium oxide (ZrO.sub.2), titanium
dioxide (TiO.sub.2). In a preferred embodiment, the dehydrogenation
in process step c) of the process of the invention is carried out
in the presence of a Pd catalyst supported on Al.sub.2O.sub.3 or on
a carbon support such as activated carbon. Here, the
Al.sub.2O.sub.3 can be used in the form of .gamma.-Al.sub.2O.sub.3
(gamma-Al.sub.2O.sub.3) or in the form of .delta.-Al.sub.2O.sub.3
(delta-Al.sub.2O.sub.3) or in the form of .theta.-Al.sub.2O.sub.3
(theta-Al.sub.2O.sub.3) or in the form of
.delta./.theta.-Al.sub.2O.sub.3 (delta/theta-Al.sub.2O.sub.3) or in
the form of .alpha.-Al.sub.2O.sub.3 (alpha -Al.sub.2O.sub.3), as
described, for example, in Hollemann Wiberg, Lehrbuch der
Anorganischen Chemie, 102nd edition, de Gruyter, 2007, page 1161.
Preference is given to using .gamma.-Al.sub.2O.sub.3
(gamma-Al.sub.2O.sub.3) as support. A supported catalyst which is
particularly preferred for the purposes of the present invention is
therefore Pd on .gamma.-Al.sub.2O.sub.3
(gamma-Al.sub.2O.sub.3).
The catalytically active metals, preferably palladium and/or
platinum, are usually present in the supported catalyst in a
proportion by weight of from about 0.1 to about 20% by weight,
preferably from about 0.1 to 10% by weight (in each case based on
the finished catalyst). They are usually, depending on the type of
catalyst used, used in an amount of from 1 to 40% by weight,
preferably from 1 to 35% by weight, based on the weight of the
mixture of tricyclic ketones to be dehydrogenated.
The supported transition metal catalyst to be used according to the
invention can be used in a wide variety of forms known to those
skilled in the art, for example in the form of spheres, extrudates
or as powder.
In a further preferred embodiment, the dehydrogenation in process
step c) can be carried out in the presence of hydroxides or
carbonates of alkali metals or alkaline earth metals, for example
in the presence of lithium, sodium, potassium, calcium or barium
hydroxide and/or lithium, sodium, potassium, calcium or barium
carbonate, in addition to the supported transition metal catalyst
used. The basic compounds mentioned can, depending on the type of
compound or compounds used, be used in an amount of usually from 3
to 20% by weight based on the supported catalyst used. As an
alternative, it is also possible to use supports or supported
catalysts which have been treated with the abovementioned alkali
metal or alkaline earth metal hydroxides or carbonates.
The dehydrogenation in process step c) generally proceeds quickly
and at the reaction temperatures mentioned is usually substantially
complete after about 24 h, often after about 12 h or less. The
dehydrogenation gives a reaction mixture which comprises the fully
dehydrogenated compound 2,6-diphenylphenol of the formula (III),
generally together with tricyclic ketones which have not been
dehydrogenated or been only partially dehydrogenated.
The heterogeneous dehydrogenation catalysts described above can be
separated off by methods with which those skilled in the art are
familiar, for example by filtration or centrifugation, preferably
by filtration. When the above-described supported transition metal
catalysts are used, in particular when the abovementioned catalyst
comprising palladium (Pd) and/or platinum (Pt) on a support is
used, it has been found that the catalysts separated off after the
reaction in process step c) generally still have a high activity.
They can therefore advantageously be reused, preferably in further
reactions as per process step c). In a preferred embodiment of the
process of the invention, the catalyst used in process step c) is
therefore separated off from the reaction mixture after the
reaction has been carried out and is reused in one or more further
reactions as per process step c).
The catalyst which has been recovered in each case can in principle
be used for as long and as often as it still retains the desired
activity. This generally depends on the catalyst selected in each
case, on the starting materials selected and on the reaction
conditions. When a catalyst comprising palladium (Pd) and/or
platinum (Pt), especially palladium (Pd) on a support is used, this
can usually be recirculated, i.e. reused, up to ten or more times,
but at least up to five times or up to four times, without
appreciable decreases in activity or selectivity in the
dehydrogenation reaction occurring.
The above-described addition of hydroxides or carbonates of alkali
metals or alkaline earth metals in process step c), which is
preferred according to the invention, can also have an advantageous
effect on the activity, operating life or reusability of the
supported transition metal catalyst used in each case. The addition
of alkali metal or alkaline earth metal carbonates, preferably
sodium and/or potassium carbonate and very particularly preferably
potassium carbonate (K.sub.2CO.sub.3), in particular, can lead to
an increase in activity and thus to improved reusability of the
particular supported catalyst used. This effect is particularly
pronounced in reactions using supported palladium catalysts,
especially in reactions using the particularly preferred Pd on
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) as catalyst. In a
particularly preferred embodiment, step c) of the process of the
invention is accordingly carried out in the presence of Pd on
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) as supported
transition metal catalyst and in the presence of an alkali metal
carbonate, preferably in the presence of potassium carbonate.
In process step d) of the process of the invention, a separation of
2,6-diphenylphenol of the formula (III) from the reaction mixture
formed in process step c) is carried out. The separation according
to process step d) can in principle be carried out by means of
customary methods for effecting separation of materials, for
example distillation, chromatography or crystallization. It has
been found to be advantageous to separate 2,6-diphenylphenol from
the undesirable undehydrogenated or only partially dehydrogenated
tricyclic ketones by crystallization. Solvents which have been
found to be suitable for this purpose are lower hydrocarbons having
up to 8 carbon atoms, for example pentane, hexane, cyclohexane,
heptane, octane, toluene, xylene, if appropriate in admixture with
lower aliphatic alcohols having from 1 to 4 carbon atoms, e.g.
methanol, ethanol, propanol, isopropanol or butanol, or with
ketones, ethers or esters having up to 5 carbon atoms, for example
acetone, tert-butyl methyl ether or ethyl acetate. It has been
found to be particularly advantageous to carry out the isolation of
2,6-diphenylphenol according to process step d) in the form of a
crystallization from heptane or a heptane-comprising solvent
mixture. Pure heptane or a mixture of heptane and isopropanol in a
volume ratio of from about 20:1 to about 30:1 has been found to be
very particularly useful as solvent or solvent combination. The
term heptane encompasses both n-heptane and also isomers thereof,
for example 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane,
2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane,
3-ethylpentane, 2,2,3-trimethylbutane or mixtures thereof.
The 2,6 diphenylphenol of the formula (III) obtained by the
above-described crystallization can subsequently be separated off
from the mother liquor in the customary manner, preferably by
filtration or centrifugation.
In this way, 2,6-diphenylphenol of the formula (III) can be
obtained in pure form, i.e. in a purity of at least 98% by weight,
often at least 99% by weight. This material is low in undesirable
undehydrogenated or only partially dehydrogenated tricyclic ketones
which would be separated off only with difficulty in further
process steps or reactions and would lead to undesirable product
mixtures and secondary reactions.
In process step e) of the process of the invention, the
2,6-diphenylphenol of the formula (III) obtained in process step d)
is reacted with a trifluoromethyl ketone of the formula (IV)
##STR00011## where the radical R is as defined for formula (I), in
the presence of a strong organic acid to form the
4,4-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenol) of the
formula (I).
Depending on the desired target compound, the 2,6-diphenylphenol
prepared according to process steps a) to d) is reacted in process
step e) with a trifluoromethyl ketone of the formula (IV), where
the radical R can be C.sub.1-C.sub.6-alkyl or
C.sub.1-C.sub.6-perfluoroalkyl as described above for the compounds
of the formula (I). To prepare the process products of the formulae
(Ia) and (Ib) which are particularly preferred according to the
invention, the 2,6-diphenylphenol obtained in process step d) is
accordingly reacted either with 1,1,1-trifluoroacetone of the
formula (IVa)
##STR00012## or with hexafluoroacetone of the formula (IVb)
##STR00013##
Both reagents can be used in commercial form without any particular
requirements in terms of purity or production process.
Hexafluoroacetone of the formula (IVb) is preferably passed in
gaseous form into the reaction mixture.
The chosen trifluoromethyl ketone is advantageously used according
to the stoichiometry of the reaction, preferably in a slight
excess. The compounds 2,6-diphenylphenol and the trifluoromethyl
ketone of the formula (IV) selected are usually used in a molar
ratio of from about 1:1 to about 2:1, preferably from about 2.0:1.2
to about 2.0:1.1.
The reaction in process step e) is carried out in the presence of a
strong organic acid, preferably an organic acid having a pKa of up
to 2, particularly preferably a pKa in the range from -1 to 2, very
particularly preferably a pKa in the range from 1 to 2. As
preferred organic acids which can be used in process step e),
mention may be made of sulfonic acids, especially alkylsulfonic or
phenylsulfonic acids. Preferred sulfonic acids are, for example:
methanesulfonic acid, trifluoromethanesulfonic acid,
benzenesulfonic acid, para-toluene-sulfonic acid, particularly
preferably methanesulfonic acid or trifluoromethanesulfonic acid
and very particularly preferably methanesulfonic acid.
The strong organic acid selected, preferably methanesulfonic acid
or trifluoromethanesulfonic acid, particularly preferably
methanesulfonic acid, is used in undiluted form (100% strength) in
a preferred embodiment. The acid is usually used in a significant
excess over the amount of 2,6-diphenylphenol to be reacted. In
general, with a view to economic aspects, a weight ratio of the
acid selected to 2,6-diphenylphenol of from about 10:1 to about
30:1, preferably from about 10:1 to about 20:1, is selected.
To carry out the reaction according to process step e), the
selected reagents can be brought into contact with one another in
any order, usually at temperatures in the range from 0 to
100.degree. C. The reaction according to process step e) is
preferably carried out at a temperature in the range from 10 to
60.degree. C., particularly preferably in the range from 20 to
50.degree. C. The reaction is then usually largely complete after
reaction times of from 10 to 24 hours.
The target compound of the formula (I), which is generally obtained
in solid form, can be isolated from the resulting reaction mixture
by conventional separation methods, preferably by filtration or
preferably by extraction, preferably by extraction with toluene,
xylene or ethylbenzene or mixtures thereof. In a preferred
embodiment, the process of the invention is carried out with the
4,4'-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) of the
formula (I) formed in process step e) being separated off from the
resulting reaction mixture by extraction. An extractant which is
particularly preferred in this embodiment is toluene. In this way,
the organic acid used, preferably the methanesulfonic acid or
trifluoromethanesulfonic acid used, can be recovered and reused if
desired, preferably in a further reaction according to process step
e) of the process of the invention. The extractant used, preferably
toluene, which is dissolved in the recovered methanesulfonic acid
after the extraction to be carried out in this preferred embodiment
can be separated off by distillation in order to avoid secondary
reactions with 1,1,1-trifluoroacetone and toluene.
The process of the invention therefore comprises, in a further
optional process step f), the separation of the target compound of
the formula (I) from the reaction mixture obtained in process step
e). The desired target compound is usually obtained in a purity of
95% by weight or above, preferably in a purity of 97% by weight or
above.
The process of the invention therefore offers an effective route to
the desired target compounds of the formula (I), in particular the
compounds of the formulae (Ia) and (Ib), which are preferred target
compounds for the purposes of the present invention. The process of
the invention makes it possible to prepare the abovementioned
compounds in a high total yield and high purity.
In a further aspect, the present invention provides a process for
preparing 2,6-diphenylphenol of the formula (III)
##STR00014## which comprises the steps i) reaction of cyclohexanone
in the presence of a basic catalyst to form a reaction mixture
comprising the tricyclic condensation products of the formula
(IIa), (IIb) and/or (IIc)
##STR00015## and water in the presence of a solvent or solvent
mixture other than cyclohexanone which forms an azeotrope with
water, with the water formed being separated off from the reaction
mixture by distillation in the form of an azeotrope with the
solvent used during the reaction, ii) separation of a mixture of
the tricyclic condensation products comprising the compounds of the
formulae (IIa), (IIb) and/or (IIc) from the reaction mixture formed
in step i) and iii) dehydrogenation of the tricyclic condensation
products comprising the compounds of the formulae (IIa), (IIb)
and/or (IIc) obtained in step ii) in the presence of a supported
transition metal catalyst in the condensed phase to form a reaction
mixture comprising 2,6-diphenylphenol of the formula (III)
##STR00016##
This aspect of the present invention accordingly concerns a process
for preparing 2,6-diphenylphenol which corresponds to process steps
a) to c) of the above-described process, with the self-condensation
of cyclohexanone being carried out in the presence of a basic
catalyst according to process step i) in the presence of a solvent
or solvent mixture which forms an azeotrope with water (and is
different from cyclohexanone) and the water formed being separated
off from the reaction mixture by distillation in the form of an
azeotrope with the solvent used during the reaction.
The term "solvent which forms an azeotrope with water" can have the
same general and preferred meanings as described above under
process step a). Accordingly, the term "solvents which form an
azeotrope with water" as used for the purposes of this aspect of
the present invention, too, refers to preferably organic solvents
which are inert under the reaction conditions and have a boiling
point at atmospheric pressure of from about 100.degree. C. to about
200.degree. C., preferably in the range from 100 to 150.degree. C.,
particularly preferably in the range from 110 to 140.degree. C. and
very particularly preferably in the range from 130 to 140.degree.
C., and are different from cyclohexanone. Particular preference is
given to those organic solvents which together with water form an
azeotrope which has a boiling point lower than that of
cyclohexanone, i.e. lower than 155.degree. C., and a boiling point
lower than the respective solvent itself (low-boiling azeotrope).
Among these, very particular preference is given to solvents or
solvent mixtures whose azeotropic boiling point is below the
azeotropic boiling point of cyclohexanone of 95.degree. C. To
ensure a satisfactory reaction rate, it is advantageous for the
azeotropic boiling point of the solvent or solvent mixture selected
to be as high as possible, preferably 70.degree. C. or above,
particularly preferably 80.degree. C. or above. Solvents which are
particularly preferably used according to the invention in process
step a) of the process of the invention accordingly have an
azeotropic boiling point in the range from 70.degree. C. to
95.degree. C., preferably from 80.degree. C. to 95.degree. C.,
particularly preferably up to <95.degree. C., for example
toluene, xylene and ethylbenzene or mixtures thereof, preferably
xylene. The "solvent which forms an azeotrope with water" mentioned
can therefore also be referred to as an entrainer.
The solvents mentioned can be used as such or in the form of
mixtures of two or more different solvents. Preference is given to
using only one solvent, preferably one which together with water
forms an azeotrope as described above, in process step i) of the
process of the invention.
According to this aspect of the present invention, process step i)
of the process of the invention is carried out so that the water
formed by aldol self-condensation of cyclohexanone is separated off
from the reaction mixture by distillation in the form of an
azeotrope with the solvent used during the reaction. The removal of
the water of reaction formed in the aldol self-condensation of
cyclohexanone and, if appropriate, the water added in the form of
an aqueous solution of the basic catalyst can be effected by the
azeotropic distillation methods known per se to those skilled in
the art using likewise known apparatuses for separating off or
removing water from a reaction mixture, for example a water
separator. The water can be removed completely or largely
completely or only partly. However, preference is given to
separating off the stoichiometrically expected amount of water to
be formed (and any amount of water added with the catalyst) to a
very substantial extent in order to aid the desired formation of
the tricyclic reaction products mentioned.
The amount of the solvent which forms an azeotrope with water to be
used according to this aspect of the present invention can be
selected within a wide range and can depend on various factors, in
particular on the choice of the particular solvent or solvent
mixture used and on the process or the apparatus used for
separating off or removing the water. The solvent selected is
usually, taking into account economic factors, used in an amount,
based on the amount of cyclohexanone used, of from 5 to 100% by
weight, preferably from 10 to 60% by weight and particularly
preferably from 15 to 40% by weight.
As regards the basic catalysts to be used in process step i) and
further features of this process step, reference is made to the
entirety of the above description of process step a) including all
preferred embodiments and their combinations.
Accordingly, the reaction in process step i) is generally carried
out in the presence of a basic catalyst, preferably in the presence
of an inorganic, in particular strongly basic catalyst. As basic or
strongly basic, in particular inorganic catalysts or bases, mention
may be made of those which are able to convert cyclohexanone at
least partly into the corresponding enolate anion by deprotonation.
The reaction in process step i) is preferably carried out in the
presence of a strong base, particularly preferably a base which has
a pKb of less than 4. As preferred strong bases for this purpose,
mention may be made of the hydroxides, alkoxides, hydrides, amides
or carbonates of alkali metals or alkaline earth metals, for
example lithium, sodium, potassium, calcium and barium hydroxide,
sodium ethoxide, sodium methoxide, potassium tert-butoxide, sodium
and potassium hydride, lithium diisopropylamide and also lithium,
sodium, potassium, calcium and barium carbonate. Particularly
preferred strong bases are the hydroxides and carbonates of the
alkali metals or alkaline earth metals, very particularly
preferably the hydroxides of the alkali metals. The compounds
mentioned can be used in pure form or in the form of mixtures with
one another or in the form of mixtures with other bases. They can
be used in solid or dissolved form, preferably in the form of
aqueous solutions.
In process step i) of the process of the invention, too, preference
is given to using an aqueous solution of an alkali metal or
alkaline earth metal hydroxide, particularly preferably an aqueous
solution of sodium hydroxide, as basic catalyst. If the base
selected is used in the form of a solution, preferably in the form
of an aqueous solution, the preferred concentration range of the
solutions is from about 5 to about 50% by weight (based on the
finished solution), particularly preferably from about 25 to about
50% by weight.
Process steps ii) and iii) of the process for preparing
2,6-diphenylphenol described under this aspect of the present
invention also correspond to process steps b) and c) of the
above-described process for preparing
4,4'-[(1-trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) of the
formula (I). The separation to be carried out according to step ii)
of a mixture of the tricyclic condensation products comprising the
compounds of the formulae (IIa), (IIb) and/or (IIc) from the
reaction mixture formed in step i) and the dehydrogenation to be
carried out according to step iii) of the tricyclic condensation
products comprising the compounds of the formulae (IIa), (IIb)
and/or (IIc) obtained in step ii) in the presence of a supported
transition metal catalyst in the condensed phase to form a
2,6-diphenylphenol of the formula (III) can accordingly be carried
out as described above for process steps b) and c), including all
preferred embodiments and their combinations. Accordingly, process
step iii) can also be carried out as described above in the
presence of a supported transition metal catalyst. Here, suitable
supported transition metal catalysts are in principle all those
which are known to those skilled in the art as catalysts for such
dehydrogenation reactions to form aromatic systems, for example
those comprising one or more of the transition metals palladium,
platinum, nickel, ruthenium, rhodium on a suitable support. The
dehydrogenation in process step iii) is preferably carried out in
the presence of a catalyst comprising palladium (Pd) and/or
platinum (Pt) on a support. The catalysts which are preferably to
be used in process step c) can comprise the transition metals
palladium and platinum, in each case either individually or in the
form of a mixture with one another, optionally together with
further metals. Preference is given to using catalysts which
comprise palladium as catalytically active metal. The metals
mentioned are used in supported form, i.e. in a form in which they
have been applied to materials which are known per se to those
skilled in the art as support materials. As suitable support
materials, mention may be made by way of example of: silica gel
(SiO.sub.2), aluminum oxide (Al.sub.2O.sub.3), carbon, activated
carbon, zirconium oxide (ZrO.sub.2), titanium dioxide (TiO.sub.2).
In a preferred embodiment, the dehydrogenation in process step iii)
of the process of the invention is carried out in the presence of a
Pd catalyst supported on Al.sub.2O.sub.3 or on a carbon support
such as activated carbon. Here, the Al.sub.2O.sub.3 can be used in
the form of .gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) or in
the form of .delta.-Al.sub.2O.sub.3 (delta-Al.sub.2O.sub.3) or in
the form of .theta.-Al.sub.2O.sub.3 (theta-Al.sub.2O.sub.3) or in
the form of .delta./.theta.-Al.sub.2O.sub.3
(delta/theta-Al.sub.2O.sub.3) or in the form of
.alpha.-Al.sub.2O.sub.3 (alpha-Al.sub.2O.sub.3). Preference is
given to using .gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) as
support. A supported catalyst which is particularly preferred for
the purposes of the present invention is therefore Pd on
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3).
The catalytically active metals, preferably palladium and/or
platinum, are usually present in the supported catalyst in a
proportion by weight of from about 0.1 to about 20% by weight,
preferably from about 0.1 to 10% by weight (in each case based on
the finished catalyst). They are usually used, depending on the
type of catalyst used, in an amount of from 1 to 40% by weight,
preferably from 1 to 35% by weight, based on the weight of the
mixture of tricyclic ketones to be dehydrogenated.
In a further preferred embodiment, the dehydrogenation in process
step iii) can, in addition to the supported transition metal
catalyst used, be carried out in the presence of hydroxides or
carbonates of alkali metals or alkaline earth metals, for example
in the presence of lithium, sodium, potassium, calcium or barium
hydroxide and/or lithium, sodium, potassium, calcium or barium
carbonate. The basic compounds mentioned can, depending on the type
of compound or compounds used, be used in an amount of usually from
3 to 20% by weight, based on the supported catalyst used. As an
alternative, supports or supported catalysts pretreated with alkali
metal or alkaline earth metal hydroxides or carbonates as mentioned
above can also be used.
Here, the catalyst recovered in each case can in principle be used
for so long and as often as it still has the desired activity. This
generally depends on the catalyst selected in each case, on the
starting materials selected and on the reaction conditions. When a
catalyst comprising palladium (Pd) and/or platinum (Pt), especially
palladium (Pd), on a support is used, this can usually be
recirculated, i.e. reused, up to about ten or more times, but at
least up to five times or up to four times, without appreciable
decreases in activity or selectivity occurring in the
dehydrogenation reaction.
The above-described addition of hydroxides or carbonates of alkali
metals or alkaline earth metals in process step iii), which is
preferred according to the invention, can also have an advantageous
effect on the activity, operating life or reusability of the
supported transition metal catalyst used in each case. The addition
of alkali metal or alkaline earth metal carbonates, preferably
sodium and/or potassium carbonate and very particularly preferably
potassium carbonate (K.sub.2CO.sub.3), in particular, can lead to
an increase in activity and thus to improved reusability of the
supported catalyst used in each case. This effect is particularly
pronounced in reactions using supported palladium catalysts,
especially in reactions using the particularly preferred Pd on
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) as catalyst. In a
particularly preferred embodiment, step iii) of the process of the
invention is accordingly carried out in the presence of Pd on
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) as supported
transition metal catalyst and in the presence of an alkali metal
carbonate, preferably in the presence of potassium carbonate.
If desired, an additional process step iv) involving the separation
of 2,6-diphenylphenol of the formula (III) from the reaction
mixture formed in step iii) can be carried out after process step
iii). This additional process step iv) corresponds to process step
d) of the above-described process for preparing the compounds of
the formula (I) and can accordingly be carried out as described
above for process step d), including all preferred embodiments and
their combinations.
The following examples illustrate the invention without restricting
it in any way:
Gas-chromatographic analyses were carried out by the following
method:
30 m RTX 200, ID. 0.25 mm, FD: 0.50 .mu.m; 200.degree. C.,
3.degree. C./min-290.degree. C.; t.sub.R (min) t.sub.R (bicyclic
ketones of the formulae (Va, Vb)): 8.4, 8.8; t.sub.R (tricyclic
ketones of the formulae (IIa, IIb, IIc)): 17.1, 18.2, 18.5; t.sub.R
(2-cyclohexyl-6-phenylphenol): 15.2; t.sub.R (2,6-diphenylphenol):
18.7; t.sub.R (.alpha.-phenyldibenzofuran): 21.6. Concentrations of
the crude products obtained (% by weight) were determined by GC
analysis using an internal standard.
HPLC analyses were carried out by the following method: CC250/4
Nucleodur C18 Gravity, 5 .mu.m; C: water-0.05% H.sub.3PO.sub.4; D:
acetonitrile 20:80; outlet: 93 bar, 25.degree. C.; t.sub.R (min)
t.sub.R (2,6-diphenylphenol): 4.8; t.sub.R
(4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol)):
14.5.
EXAMPLE 1
Self-Condensation of Cyclohexanone
900 g (9.1 mol) of cyclohexanone together with 190 g of xylene were
placed in a flask at room temperature. 33 g (0.21 mol) of NaOH
solution (25%) were subsequently added. The reaction solution was
stirred under reflux. Over a period of 7 hours, the temperature of
the reaction mixture rose from 120 to 180.degree. C., with 126 ml
of water being removed by means of a water separator. The reaction
solution was subsequently cooled to room temperature.
To work up the reaction solution, 500 g of water were added to this
solution and the solution was neutralized with 11 g of
H.sub.3PO.sub.4 (85%). The phases were separated at 90.degree. C.
The organic phase was subsequently washed at 90.degree. C. with 500
g of NaHCO.sub.3 solution (2%). Phase separation was likewise
carried out at 90.degree. C.
This gave 965 g of a crude product having the following
composition: tricyclic ketones (formulae (IIa, IIb, IIc)): 48.3%;
bicyclic ketones (formulae (Va, Vb)): 24.6% (in each case in GC-%
by weight).
The crude product (965 g) was distilled batchwise in a laboratory
glass column provided with 1 m of Sulzer DX packing (number of
theoretical plates: about 20) and having an internal diameter of 50
mm and provided with a still pot and a thin film evaporator with
pumped circulation (0.1 m.sup.2). The bicyclic ketones (formulae
(Va, Vb)) were distilled off at 20 mbar and a temperature at the
top of 144.degree. C. from the tricyclic ketones (formulae (IIa,
IIb, IIc)) (temperature at the top: 212.degree. C.; 20 mbar). The
yield of bicyclic ketones of the formulae (Va, Vb) was 223 g (27%)
and that of tricyclic ketones of the formulae (IIa, IIb, IIc) was
410 g (50% of theory; 96 GC-% by weight).
EXAMPLE 2
Recirculation of Bicyclic Ketones of the Formulae (Va, Vb)
360 g (3.0 mol) of cyclohexanone and 300 g (1.67 mol) of bicyclic
ketones of the formulae (Va, Vb) together with 140 g of xylene were
placed in a flask at room temperature. 22.4 g (0.14 mol) of NaOH
solution (25%) were subsequently added. The reaction solution was
stirred under reflux. Over a period of 5 hours, the temperature
rose from 120 to 180.degree. C., with 62 ml of water being removed
by means of a water separator. The red reaction solution was cooled
to room temperature and a work-up as described in example 1 was
carried out.
This gave 728 g of a crude product having the following
composition: tricyclic ketones (formulae (IIa, IIb, IIc): 45.7%;
bicyclic ketones (formulae (Va, Vb)): 27.0%; xylene: 14.5%;
cyclohexanone: 3% (in each case in GC-% by weight).
EXAMPLES 3 to 5
Dehydrogenation of the Tricyclic Ketones of the Formulae (IIa, IIb,
IIc) to Form 2,6-diphenylphenol of the Formula (III)
EXAMPLE 3
10 g of Pd/Al.sub.2O.sub.3 catalyst (0.5% by weight of palladium on
a .theta.-Al.sub.2O.sub.3 (theta-Al.sub.2O.sub.3) support in the
form of spheres having a diameter of 3 mm) together with 30 g (0.11
mol) of the tricyclic ketones of the formulae (IIa, IIb, IIc) (97%)
and 0.3 g of NaOH were placed in a flask at room temperature. The
suspension was stirred at 290-300.degree. C. for 4 hours. After the
reaction mixture had cooled to room temperature, the reaction
mixture was admixed with 200 ml of heptane. The reaction solution
was heated to 90.degree. C. and the catalyst was subsequently
filtered off and washed with 100 ml of heptane. The crude product
was evaporated on a rotary evaporator.
This gave a crude product having the following composition:
2,6-diphenylphenol: 71.3%, tricyclic ketones of the formulae (IIa,
IIb, IIc): 8.2% (in each case in GC-% by weight) and
2-cyclohexyl-6-phenylphenol: 5.0 GC-% by area. The
2,6-diphenylphenol product was isolated by crystallization from
heptane (120 ml) in a yield of 62% (17.8 g, 97 GC-% by weight).
EXAMPLE 4
10 g of Pd/Al.sub.2O.sub.3 (0.72% by weight of palladium on a
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) support in the form
of extrudates having a length of 4 mm) together with 30 g (0.11
mol) of the tricyclic ketones of the formulae (IIa, IIb, IIc) (97%)
and 0.3 g of NaOH were placed in a flask at room temperature. The
suspension was stirred at 290-300.degree. C. for 8 hours. The
reaction mixture was cooled to 95.degree. C., admixed with 200 ml
of heptane and a work-up as described in example 3 was carried
out.
This gave a crude product having the following composition:
2,6-diphenylphenol: 44.8%, tricyclic ketones of the formulae (IIa,
IIb, IIc): 4.9% (in each case in GC-% by weight) and
2-cyclohexyl-6-phenylphenol: 12.3 GC-% by area.
The 2,6-diphenylphenol product was isolated by crystallization from
heptane in a yield of 34% (9.5 g, 99 GC-% by area).
EXAMPLE 5
10 g of Pd/Al.sub.2O.sub.3 (0.72% by weight of palladium on a
.gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) support in the form
of extrudates having a length of 4 mm) together with 30 g (0.11
mol) of the tricyclic ketones of the formulae (IIa, IIb, IIc) (97%)
and 1.5 g of K.sub.2CO.sub.3 were placed in a flask at room
temperature. The suspension was stirred at 290-300.degree. C. for 8
hours. The reaction mixture was cooled to 90.degree. C., admixed
with 200 ml of heptane and a work-up as described in example 3 was
carried out.
This gave a crude product having the following composition:
2,6-diphenylphenol: 47.3%, tricyclic ketones of the formulae (IIa,
IIb, IIc): 5.8% (in each case in GC-% by weight) and
.alpha.-phenyldibenzofuran: 13.6 GC-% by area. The
2,6-diphenylphenol product was isolated by crystallization from
heptane in a yield of 44% (12.5 g, 99 GC-% by area).
EXAMPLE 6
10 g of Pd/Al.sub.2O.sub.3 catalyst (0.72% by weight of palladium
on a .gamma.-Al.sub.2O.sub.3 (gamma-Al.sub.2O.sub.3) support in the
form of extrudates having a length of 4 mm) together with 30 g
(0.12 mol) of the tricyclic ketones of the formulae (IIa, IIb, IIc)
(97%) were placed in a flask at room temperature. The suspension
was stirred at 290-300.degree. C. for 8 hours. This gave a crude
product having the following composition: 2,6-diphenylphenol:
25.7%, tricyclic ketones of the formulae (IIa, IIb, IIc): 10.3% (in
each case in GC-% by weight) and 2-cyclohexyl-6-phenylphenol: 34.6
GC-% by area.
EXAMPLE 7
0.24 g of 5% Pd/C catalyst and 15 g (0.06 mol) of the tricyclic
ketones of the formulae (IIa, IIb, IIc) (97%) were placed in a
flask at room temperature. The suspension was stirred at
290-300.degree. C. for 2 hours. The suspension was cooled and, at
25.degree. C., diluted with 50 ml of acetone. The catalyst was
filtered off and the crude product was evaporated on a rotary
evaporator. The 2,6-diphenylphenol product was subsequently
isolated by two-stage crystallization of the crude product (13 g)
from heptane/isopropanoll (25:1) in a yield of 50% (7 g, 99 GC-% by
area).
EXAMPLE 8
13.3 g of Pd/Al.sub.2O.sub.3 (from example 5) together with 30 g
(0.11 mol) of the tricyclic ketones of the formulae (IIa, IIb, IIc)
(97%) were placed in a flask at room temperature. The suspension
was stirred at 295.degree. C. for 8 hours. The reaction mixture was
cooled to 60.degree. C. and then admixed with 200 ml of heptane and
a work-up as described in example 3 was carried out. The catalyst
which had been separated off was reused for the next
dehydrogenation reaction.
This gave a crude product (24.5 g) having the following
composition: 2,6-diphenylphenol: 54.3%, tricyclic ketones of the
formulae (IIa, IIb, IIc): 8.2% (in each case in GC-% by weight) and
2-cyclohexyl-6-phenylphenol: 6.9 GC-% by area and
.alpha.-phenyldibenzofuran: 6.3 GC-% by area.
EXAMPLE 9
Synthesis of 4,4'-[1-(trifluoromethyl)ethylidene]bis
(2,6-diphenylphenol)
61.5 g (0.25 mol) of 2,6-diphenylphenol and 875 g of
methanesulfonic acid (100%) were placed in a flask. 15.4 g (0.14
mol) of 1,1,1-trifluoroacetone were subsequently added at
20.degree. C. To complete the reaction, the suspension was stirred
at 45.degree. C. for 10 hours. The suspension was subsequently
cooled to 20.degree. C. and filtered. The filtercake was washed
with distilled water (730 g each time) until neutral and dried.
This gave 71 g (97% of theory) of
4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol) in the
form of a white powder (HPLC-% by weight: 98%).
EXAMPLE 10
325 g (1.31 mol) of 2,6-diphenylphenol (99%) and 2400 g of
methanesulfonic acid (100%) were placed in a double-walled reactor
at 20.degree. C. The suspension was admixed with 81.3 g (0.73 mol)
of 1,1,1-trifluoroacetone and stirred at 50.degree. C. for 10
hours. After the reaction was complete, the suspension was admixed
with 4200 g of toluene and the reaction mixture was stirred at
50.degree. C. for 30 minutes. The phases were separated at
50.degree. C. and the toluene phase was washed with 1680 g of
water, 1680 g of 2% strength sodium carbonate solution and 1680 g
of water. The solvent toluene was distilled off. This gave 376 g
(95% of theory) of
4,4'-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol) in the
form of a white powder (HPLC-% by weight: 97%).
* * * * *