U.S. patent application number 10/950874 was filed with the patent office on 2006-03-30 for phosphazenium salt phase transfer catalysts.
This patent application is currently assigned to General Electric Company. Invention is credited to Daniel Joseph Brunelle.
Application Number | 20060069291 10/950874 |
Document ID | / |
Family ID | 35655525 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060069291 |
Kind Code |
A1 |
Brunelle; Daniel Joseph |
March 30, 2006 |
Phosphazenium salt phase transfer catalysts
Abstract
A method for carrying out a chemical reaction between at least
two reactants occupying separate phases within a multiphase
reaction mixture has been discovered in which at least one
phosphazenium salt is employed as a phase transfer catalyst. The
remarkable utility of phosphazenium salts as phase transfer
catalysts is illustrated by the preparation of aromatic ethers. The
phosphazenium salt phase transfer catalysts are shown to be
especially useful in the preparation of aromatic polyethers such as
polyether sulfones.
Inventors: |
Brunelle; Daniel Joseph;
(Burnt Hills, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Assignee: |
General Electric Company
|
Family ID: |
35655525 |
Appl. No.: |
10/950874 |
Filed: |
September 24, 2004 |
Current U.S.
Class: |
568/660 |
Current CPC
Class: |
B01J 31/0268 20130101;
B01J 2231/40 20130101; C08G 79/025 20130101; B01J 31/0265 20130101;
C07C 41/16 20130101; C07C 43/29 20130101; C07C 317/22 20130101;
B01J 2231/14 20130101; C07C 315/04 20130101; B01J 2531/98 20130101;
C07C 41/16 20130101; C07C 315/04 20130101; C07F 9/067 20130101;
B01J 31/0239 20130101; C08G 65/4087 20130101 |
Class at
Publication: |
568/660 |
International
Class: |
C07C 43/02 20060101
C07C043/02; C07C 43/20 20060101 C07C043/20 |
Claims
1. A method for carrying out a chemical reaction between at least
two reactants occupying separate phases within a multiphase
reaction mixture, said reaction mixture comprising at least one
phosphazenium salt phase transfer catalyst.
2. The method according to claim 1 wherein said phosphazenium salt
phase transfer catalyst has structure I ##STR18## wherein n is an
integer from zero to about 10, R.sup.1 and R.sup.2 are
independently selected from the group consisting of
C.sub.1-C.sub.20 aliphatic radicals, C.sub.3-C.sub.20
cycloaliphatic radicals, and C.sub.4-C.sub.20 aromatic radicals,
and wherein said R.sup.1 and R.sup.2 may be linked together form a
cyclic structure comprising at least one nitrogen atom, and wherein
X.sup.- is selected from the group consisting of monovalent
inorganic anions, monovalent organic anions, polyvalent inorganic
anions, polyvalent organic anions, and mixtures thereof.
3. A method for making aromatic ethers comprising contacting in a
reaction mixture the salt of at least one aromatic hydroxy compound
with at least one aromatic compound comprising at least one leaving
group, said contacting being carried out in the presence of a
phosphazenium salt.
4. The method according to claim 3 where said phosphazenium salt
has structure ##STR19## wherein n is an integer from zero to about
10, R.sup.1 and R.sup.2 are independently selected from the group
consisting of C.sub.1-C.sub.20 aliphatic radicals, C.sub.3-C.sub.20
cycloaliphatic radicals, and C.sub.4-C.sub.20 aromatic radicals,
and wherein said R.sup.1 and R.sup.2 may be linked together form a
cyclic structure comprising at least one nitrogen atom, and wherein
X.sup.- is selected from the group consisting of monovalent
inorganic anions, monovalent organic anions, polyvalent inorganic
anions, polyvalent organic anions, and mixtures thereof.
5. The method according to claim 4 wherein said contacting further
comprises heating to a temperature in a range between about 50 and
250.degree. C.
6. The method according to claim 4 wherein said contacting further
comprises heating in the presence of an inert solvent to a
temperature in a range between about 50 and about 250.degree.
C.
7. The method according to claim 6 wherein said inert solvent is
selected from the group consisting of ortho-dichlorobenzene,
para-dichlorobenzene, dichlorotoluene, 1,2,4-trichlorobenzene,
diphenyl sulfone, phenetole, anisole, veratrole, toluene, xylene,
mesitylene and mixtures thereof.
8. The method according to claim 4 wherein said phosphazenium salt
is present in an amount corresponding to between about 0.1 and 10
mole percent based on the amount of aromatic hydroxy compound
initially present in the reaction mixture.
9. The method according to claim 4 wherein said salt of at least
one aromatic hydroxy compound is of the formula VI:
R.sup.3(ZM).sub.k (VI) wherein R.sup.3 is a C.sub.5-C.sub.40
aromatic radical; M is a metal selected from the group consisting
of alkali metals, alkaline earth metals, and mixtures thereof; Z is
oxygen, sulfur, or selenium, wherein at least one Z is oxygen; and
k is 1, 2 or 3.
10. The method according to claim 4 wherein said salt of at least
one aromatic hydroxy compound is a salt of a dihydroxy aromatic
compound having formula VII: ##STR20## wherein A.sup.1 is
independently at each occurrence a C.sub.3-C.sub.20 aromatic
radical; E is independently at each occurrence a bond, a
C.sub.1-C.sub.20 aliphatic radical, a C.sub.3-C.sub.20
cycloaliphatic radical, or a C.sub.5-C.sub.20 aromatic radical, a
sulfur atom, a sulfinyl group, a sulfonyl group, a selenium atom,
or an oxygen atom; and t, s and u are independently integers from
0-10 wherein at least one of t, s and u is not zero.
11. The method according to claim 4 wherein said salt of at least
one aromatic hydroxy compound is selected from the group consisting
of salts of bisphenol A, and salts of 4,4'-biphenol.
12. The method according to claim 4 wherein said salt of at least
one aromatic hydroxy compound is a sodium salt.
13. The method according to claim 4 wherein said salt of at least
one aromatic hydroxy compound is the disodium salt of bisphenol
A.
14. The method according to claim 4 wherein said aromatic compound
comprising at least one leaving group has formula XV: ##STR21##
wherein Ar.sup.1 is independently at each occurrence a
C.sub.3-C.sub.20 aromatic radical, L.sup.1 is a leaving group
independently selected from the group consisting of fluoro, chloro,
bromo, iodo, nitro, and organosulfonate groups; B is an activating
group, and g is 1, 2 or 3.
15. The method according to claim 4 wherein said aromatic compound
comprising at least one leaving group has formula XVI ##STR22##
wherein L.sup.1 is a leaving group independently selected from the
group consisting of fluoro, chloro, bromo, iodo, and nitro groups;
and R.sup.6 is selected from the group consisting of divalent
C.sub.1-C.sub.12 aliphatic radicals, divalent C.sub.3-C.sub.12
cycloaliphatic radicals, and divalent C.sub.4-C.sub.30 aromatic
radicals.
16. The method according to claim 15 wherein R.sup.6 is an aromatic
radical having structure XVII ##STR23## wherein Q is a
C.sup.1-C.sub.12 aliphatic radical, a C.sub.3-C.sub.12
cycloaliphatic radical, a C.sub.4-C.sub.18 aromatic radical, an
oxygen, atom, a sulfur atom, a sulfinyl group, a sulfonyl group, a
selenium atom or a bond.
17. The method according to claim 4 wherein said aromatic compound
comprising at least one leaving group is selected from the group
consisting of compounds having formula XVIII ##STR24## wherein G is
a carbonyl group, or a sulfonyl group; L.sup.2 is independently at
each occurrence a fluoro, chloro, bromo, iodo, nitro, or a
trifluormethansulfonate group; and "m" and "p" are independently
integers from 0-5, wherein not both m and p are zero.
18. The method according to claim 4 wherein said salt of the
aromatic hydroxy compound is generated in-situ, from an organic
compound which is not itself an aromatic hydroxy compound.
19. The method according to claim 18 wherein said salt is the salt
of an aromatic hydroxyl compound having formula XIII ##STR25##
wherein R.sup.5 is an organic radical selected from the group
consisting of C.sub.1-C.sub.12 aliphatic radicals, C.sub.3-C.sub.12
cycloaliphatic radicals, and C.sub.4-C.sub.30 aromatic
radicals.
20. The method according to claim 18 wherein said salt is the salt
of an aromatic ydroxyl compound having formula XIV ##STR26##
21. The method according to claim 4 wherein said at least one
aromatic compound comprising at least one leaving group has formula
XIX ##STR27## wherein R.sup.7 is selected from the group consisting
of monovalent C.sub.1-C.sub.12 aliphatic radicals, monovalent
C.sub.3-C.sub.12 cycloaliphatic radicals, and monovalent
C.sub.4-C.sub.30 aromatic radicals; and L.sup.2 is a fluoro,
chloro, bromo, iodo, or nitro group.
22. The method according to claim 4 wherein said aromatic compound
comprising at least one leaving group is selected from the group
consisting of compounds having formula XX ##STR28## wherein L.sup.2
is a fluoro, chloro, bromo, iodo, or nitro group.
23. The method according to claim 4 wherein said aromatic compound
comprising at least one leaving group is selected from the group
consisting of compounds having formula XXI and XXII ##STR29##
wherein in each of structures XXI and XXII D is independently at
each occurrence a carbonyl group or a sulfonyl group, and L.sup.3
is independently at each occurrence a fluoro, chloro, bromo, iodo,
or nitro group.
24. A method for making an aromatic polyether composition, said
method comprising contacting in a reaction mixture the salt of at
least one aromatic dihydroxy compound with at least one aromatic
compound bearing at least two leaving groups, said contacting being
carried out in the presence of a phosphazenium salt having
structure I ##STR30## wherein n is an integer from zero to about
10, R.sup.1 and R.sup.2 are independently selected from the group
consisting of C.sub.1-C.sub.20 aliphatic radicals, C.sub.3-C.sub.20
cycloaliphatic radicals, and C.sub.4-C.sub.20 aromatic radicals,
and wherein said R.sup.1 and R.sup.2 may be linked together form a
cyclic structure comprising at least one nitrogen atom, and wherein
X.sup.- is selected from the group consisting of monovalent
inorganic anions, monovalent organic anions, polyvalent inorganic
anions, polyvalent organic anions, and mixtures thereof.
25. The method according to claim 24 wherein said aromatic
dihydroxy compound is selected from the group consisting of
bisphenol A, and 4,4'-biphenol.
26. The method according to claim 24 wherein said aromatic compound
bearing at least two leaving groups has formula XVIII ##STR31## G
is a carbonyl group, or a sulfonyl group;. L.sup.2 is independently
at each occurrence a fluoro, chloro, bromo, iodo, nitro, or a
trifluormethansulfonate group; and "m" and "p" are independently
integers from 0-5, wherein not both m and p are zero.
27. A method for making an aromatic polyether sulfone, said method
comprising contacting in a reaction mixture the disodium salt of
bisphenol A with bis(4-chlorophenyl)sulfone, said contacting being
carried out in the presence of a phosphazenium salt having
structure I ##STR32## wherein n is an integer from zero to about
10, R.sup.1 and R.sup.2 are independently selected from the group
consisting of C.sub.1-C.sub.20 aliphatic radicals, C.sub.3-C.sub.20
cycloaliphatic radicals, and C.sub.4-C.sub.20 aromatic radicals,
and wherein said R.sup.1 and R.sup.2 may be linked together form a
cyclic structure comprising at least one nitrogen atom, and wherein
X.sup.- is selected from the group consisting of monovalent
inorganic anions, monovalent organic anions, polyvalent inorganic
anions, polyvalent organic anions, and mixtures thereof, said
contacting being carried out at a temperature in a range between
about 200.degree. C. and about 250.degree. C., said contacting
being carried out in the presence of orthodichlorobenzene.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to use of phosphazenium salts as
phase transfer catalysts. In one aspect the invention relates to a
method of making aromatic ethers. More particularly, the method
relates to a method of preparing aromatic ethers using
exceptionally stable phosphazenium salt phase transfer
catalysts.
[0002] Various types of aromatic ethers have gained prominence due
to their utility in diverse fields as agricultural chemistry,
medicinal chemistry and polymer chemistry. One class of aromatic
ethers, aromatic polyethers (e.g. See for example
polyethersulfones, polyetherimides, and polyetherketones), are
important engineering resins due to their exceptional chemical and
physical properties.
[0003] Aromatic ethers are typically prepared by synthetic
methodology involving the reaction of the salt of an aromatic
hydroxy compound with an aromatic compound comprising at least one
suitable leaving group. In one general methodology, aromatic ethers
are prepared in a nucleophilic aromatic substitution reaction
between a nucelophilic aromatic hydroxy compound and an
electrophonic aromatic compound comprising at least one suitable
leaving group, the reaction being mediated by a stoichiometric
amount of a basic reactant such as an alkali metal hydroxide or
alkali metal carbonate. Typically, such nucleophilic aromatic
substitution reactions must be carried out in polar aprotic
solvents such as dimethylformamide, dimethylacetamide,
N-methylpyrrolidinone, dimethyl sulfoxide, or sulfolane in order to
achieve synthetically useful rates of conversion of starting
materials to product aromatic ethers. In such cases, drying,
recovery, and reuse of the solvent is cumbersome and expensive.
[0004] Various phase transfer catalysts (PTC's) are known to
accelerate reaction rates of chemical reactions generally. Phase
transfer catalysts are typically most effective when the chemical
reaction involves reactants which tend to segregate into separate
phases. Among other benefits, the use of phase transfer catalysts
is known to enable the use of solvents in which one or more of the
reactants is insoluble in the absence of the phase transfer
catalyst.
[0005] Known phase transfer catalysts include quaternary ammonium
salts, quaternary phosphonium salts, and hexaalkylguanidinium
salts. Of the known phase transfer catalysts, quaternary ammonium
salts are stable at ambient temperature, but decompose rapidly at
temperatures in excess of about 100.degree. C. Quaternary
phosphonium salts are more stable, but their use typically results
in a lower reaction rate relative to the reaction rate observed in
the corresponding reaction in which a quaternary ammonium salt
phase transfer catalyst is employed. Thus, higher levels of
phosphonium salt phase transfer catalyst must be used in order to
achieve reaction rates comparable to reaction rates attained using
quaternary ammonium salt phase transfer catalysts.
Hexaalkylguanidinium salts are effective phase transfer catalysts
but nonetheless are subject to decomposition at higher
temperatures.
[0006] Much attention has been directed in recent years to organic
reactions in heterogeneous systems, employing a phase transfer
catalyst which facilitates the migration of a reactant into a phase
from which it is normally absent. Many types of phase transfer
catalysts are known to be effective under such conditions,
including quaternary ammonium and phosphonium salts as disclosed in
U.S. Pat. No. 4,273,712. Additionally, various bis-quaternary
ammonium or phosphonium salts have been used as disclosed in U.S.
Pat. No. 4,554,357; and aminopyridinium salts have been used as
disclosed in U.S. Pat. Nos. 4,460,778, 4,513,141 and 4,681,949.
Hexaalkylguanidinium salts, and their bis-salt analogues have been
used as phase transfer catalysts as disclosed in U.S. Pat. Nos.
5,132,423; 5,116,975; and 5,081,298.
[0007] Nucleophilic aromatic substitution reactions, also referred
to as "nucleophilic aromatic displacement reactions" often require
heating a highly insoluble salt of an aromatic hydroxy compound
with a soluble aromatic compound comprising at least one suitable
leaving group in a relatively nonpolar solvent such as
o--dichlorobenzene (o--DCB) in the presence of a phase transfer
catalyst. Frequently, for synthetically useful reaction rates to be
achieved, the reaction mixture must be heated to a temperature at
which the phase transfer catalyst decomposes. While a prodigious
technical effort has been expended in the development of more
thermally stable phase transfer catalysts (See for example the
development of 4-dialkylaminopyridinium salt catalysts and
hexaalkylguanidinium salt catalysts), improved phase transfer
catalyst thermal stability remains an important objective.
[0008] It would be highly desirable, therefore, to discover phase
transfer catalysts having improved stability that could be used
under a wide variety of reaction conditions, including the
formation of aromatic ethers.
BRIEF SUMMARY OF THE INVENTION
[0009] In one aspect the present invention provides phosphazenium
salts and their use as phase transfer catalysts generally.
[0010] In another aspect the present invention provides a method
for making aromatic ethers comprising contacting in a reaction
mixture the salt of at least one aromatic hydroxy compound with at
least one aromatic compound comprising at least one leaving group,
said contacting being carried out in the presence of a
phosphazenium salt having structure I ##STR1## wherein n is an
integer from zero to about 10, R.sup.1 and R.sup.2 are
independently selected from the group consisting of
C.sub.1-C.sub.20 aliphatic radicals, C.sub.3-C.sub.20
cycloaliphatic radicals, and C.sub.4-C.sub.20 aromatic radicals,
and wherein said R.sup.1 and R.sup.2 may be linked together form a
cyclic structure comprising at least one nitrogen atom, and wherein
X.sup.- is selected from the group consisting of monovalent
inorganic anions, monovalent organic anions, polyvalent inorganic
anions, polyvalent organic anions, and mixtures thereof.
[0011] In another aspect the present invention provides a method
for making aromatic polyether compositions, said method comprising
contacting in a reaction mixture the salt of at least one aromatic
dihydroxy compound with at least one aromatic compound bearing at
least two leaving groups, said contacting being carried out in the
presence of a phosphazenium salt having structure I.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 illustrates the reaction kinetics observed in a
series of reactions involving the 4-chlorophenyl phenyl sulfone and
the disodium salt of bisphenol A in the presence of a phosphazenium
salt phase transfer catalyst at various temperatures.
[0013] FIG. 2 compares the reaction kinetics observed in a series
of reactions involving the 4-chlorophenyl phenyl sulfone and the
disodium salt of bisphenol A in the presence of either a
guanidinium salt phase transfer catalyst, or a phosphazenium salt
phase transfer catalyst.
[0014] FIG. 3 illustrates the rate of polymerization observed in a
reaction between bis(4-chlorophenyl) sulfone and the disodium salt
of bisphenol A in the presence of 2 mole percent phosphazenium salt
phase transfer catalyst at 180.degree. C.
[0015] FIG. 4 illustrates the rate of polymerization observed in a
reaction between bis(4-chlorophenyl) sulfone and the disodium salt
of bisphenol A in the presence of 1 mole percent phosphazenium salt
phase transfer catalyst at 200.degree. C.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention may be understood more readily by
reference to the following detailed description of preferred
embodiments of the invention and the examples included therein. In
the following specification and the claims which follow, reference
will be made to a number of terms which shall be defined to have
the following meanings:
[0017] The singular forms "a", "an" and "the" include plural
referents unless the context clearly dictates otherwise.
[0018] "Optional" or "optionally" means that the subsequently
described event or circumstance may or may not occur, and that the
description includes instances where the event occurs and instances
where it does not.
[0019] As used herein the term "BPA" refers to bisphenol A.
[0020] As used herein the term "aliphatic radical" refers to a
radical having a valence of at least one comprising a linear or
branched array of atoms which is not cyclic. The array may include
heteroatoms such as nitrogen, sulfur, silicon, selenium and oxygen
or may be composed exclusively of carbon and hydrogen. Aliphatic
radicals may be "substituted" or "unsubstituted". A substituted
aliphatic radical is defined as an aliphatic radical which
comprises at least one substituent. A substituted aliphatic radical
may comprise as many substituents as there are positions available
on the aliphatic radical for substitution. Substituents which may
be present on an aliphatic radical include but are not limited to
halogen atoms such as fluorine, chlorine, bromine, and iodine.
Substituted aliphatic radicals include trifluoromethyl,
hexafluoroisopropylidene, chloromethyl; difluorovinylidene;
trichloromethyl, bromoethyl, bromotrimethylene (e.g.
--CH.sub.2CHBrCH.sub.2--), and the like. For convenience, the term
"unsubstituted aliphatic radical" is defined herein to encompass,
as part of the "linear or branched array of atoms which is not
cyclic" comprising the unsubstituted aliphatic radical, a wide
range of functional groups. Examples of unsubstituted aliphatic
radicals include allyl, aminocarbonyl (i.e. --CONH.sub.2),
carbonyl, dicyanoisopropylidene (i.e.
--CH.sub.2C(CN).sub.2CH.sub.2--), methyl (i.e. --CH.sub.3),
methylene (i.e. --CH.sub.2--), ethyl, ethylene, formyl, hexyl,
hexamethylene, hydroxymethyl (i.e.--CH.sub.2OH), mercaptomethyl
(i.e. --CH.sub.2SH), methylthio (i.e. --SCH.sub.3),
methylthiomethyl (i.e. --CH.sub.2SCH.sub.3), methoxy,
methoxycarbonyl, nitromethyl (i.e. --CH.sub.2NO.sub.2),
thiocarbonyl, trimethylsilyl, t-butyldimethylsilyl,
trimethyoxysilypropyl, vinyl, vinylidene, and the like. Aliphatic
radicals are defined to comprise at least one carbon atom. A
C.sub.1-C.sub.10 aliphatic radical includes substituted aliphatic
radicals and unsubstituted aliphatic radicals containing at least
one but no more than 10 carbon atoms.
[0021] As used herein, the term "aromatic radical" refers to an
array of atoms having a valence of at least one comprising at least
one aromatic group. The array of atoms having a valence of at least
one comprising at least one aromatic group may include heteroatoms
such as nitrogen, sulfur, selenium, silicon and oxygen, or may be
composed exclusively of carbon and hydrogen. As used herein, the
term "aromatic radical" includes but is not limited to phenyl,
pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl
radicals. As noted, the aromatic radical contains at least one
aromatic group. The aromatic group is invariably a cyclic structure
having 4n+2 "delocalized" electrons where "n" is an integer equal
to 1 or greater, as illustrated by phenyl groups (n=1), thienyl
groups (n=1), furanyl groups (n=1), naphthyl groups (n=2), azulenyl
groups (n=2), anthraceneyl groups (n=3) and the like. The aromatic
radical may also include nonaromatic components. For example, a
benzyl group is an aromatic radical which comprises a phenyl ring
(the aromatic group) and a methylene group (the nonaromatic
component). Similarly a tetrahydronaphthyl radical is an aromatic
radical comprising an aromatic group (C.sub.6H.sub.3) fused to a
nonaromatic component --(CH.sub.2).sub.4--. Aromatic radicals may
be "substituted" or "unsubstituted". A substituted aromatic radical
is defined as an aromatic radical which comprises at least one
substituent. A substituted aromatic radical may comprise as many
substituents as there are positions available on the aromatic
radical for substitution. Substituents which may be present on an
aromatic radical include, but are not limited to halogen atoms such
as fluorine, chlorine, bromine, and iodine. Substituted aromatic
radicals include trifluoromethylphenyl,
hexafluoroisopropylidenebis(4-phenyloxy) (i.e.
--OPhC(CF.sub.3).sub.2PhO--), chloromethylphenyl;
3-trifluorovinyl-2-thienyl; 3-trichloromethylphenyl (i.e.
3-CCl.sub.3Ph--), bromopropylphenyl (i.e.
BrCH.sub.2CH.sub.2CH.sub.2Ph--), and the like. For convenience, the
term "unsubstituted aromatic radical" is defined herein to
encompass, as part of the "array of atoms having a valence of at
least one comprising at least one aromatic group", a wide range of
functional groups. Examples of unsubstituted aromatic radicals
include 4-allyloxyphenoxy, aminophenyl (i.e. H.sub.2NPh--),
aminocarbonylphenyl (i.e. NH.sub.2COPh--), 4-benzoylphenyl,
dicyanoisopropylidenebis(4-phenyloxy) (i.e. --OPhC(CN).sub.2PhO--),
3-methylphenyl, methylenebis(4-phenyloxy) (i.e.
--OPhCH.sub.2PhO--), ethylphenyl, phenylethenyl,
3-formyl-2-thienyl, 2-hexyl-5-furanyl;
hexamethylene-1,6-bis(4-phenyloxy) (i.e.
--Oph(CH.sub.2).sub.6PhO--); 4-hydroxymethylphenyl (i.e.
4-HOCH.sub.2Ph-), 4-mercaptomethylphemyl (i.e. 4-HSCH.sub.2Ph--),
4-methylthiophenyl (i.e. 4-CH.sub.3SPh--), methoxyphenyl,
methoxycarbonylphenyloxy (e.g. methyl salicyl), nitromethylphenyl
(i.e. --PhCH.sub.2NO.sub.2), trimethylsilylphenyl,
t-butyldimethylsilylphenyl, vinylphenyl, vinylidenebis(phenyl), and
the like. The term "a C.sub.3-C.sub.10 aromatic radical" includes
substituted aromatic radicals and unsubstituted aromatic radicals
containing at least three but no more than 10 carbon atoms. The
aromatic radical 1-imidazolyl (C.sub.3H.sub.2N.sub.2--) represents
a C.sub.3 aromatic radical. The benzyl radical (C.sub.7H.sub.8--)
represents a C.sub.7 aromatic radical.
[0022] As used herein the term "cycloaliphatic radical" refers to a
radical having a valence of at least one, and comprising an array
of atoms which is cyclic but which is not aromatic. As defined
herein a "cycloaliphatic radical" does not contain an aromatic
group. A "cycloaliphatic radical" may comprise one or more
noncyclic components. For example, a cyclohexylmethy group
(C.sub.6H.sub.11CH.sub.2--) is an cycloaliphatic radical which
comprises a cyclohexyl ring (the array of atoms which is cyclic but
which is not aromatic) and a methylene group (the noncyclic
component). The cycloaliphatic radical may include heteroatoms such
as nitrogen, sulfur, selenium, silicon and oxygen, or may be
composed exclusively of carbon and hydrogen. Cycloaliphatic
radicals may be "substituted" or "unsubstituted". A substituted
cycloaliphatic radical is defined as a cycloaliphatic radical which
comprises at least one substituent. A substituted cycloaliphatic
radical may comprise as many substituents as there are positions
available on the cycloaliphatic radical for substitution.
Substituents which may be present on a cycloaliphatic radical
include but are not limited to halogen atoms such as fluorine,
chlorine, bromine, and iodine. Substituted cycloaliphatic radicals
include trifluoromethylcyclohexyl,
hexafluoroisopropylidenebis(4-cyclohexyloxy) (i.e.
--OC.sub.6H.sub.11C(CF.sub.3).sub.2C.sub.6H.sub.11O--),
chloromethylcyclohexyl; 3-trifluorovinyl-2-cyclopropyl;
3-trichloromethylcyclohexyl (i.e. 3-CCl.sub.3C.sub.6H.sub.11--),
bromopropylcyclohexyl (i.e.
BrCH.sub.2CH.sub.2CH.sub.2C.sub.6H.sub.11--), and the like. For
convenience, the term "unsubstituted cycloaliphatic radical" is
defined herein to encompass a wide range of functional groups.
Examples of unsubstituted cycloaliphatic radicals include
4-allyloxycyclohexyl, aminocyclohexyl (i.e.
H.sub.2NC.sub.6H.sub.11--), aminocarbonylcyclopenyl (i.e.
NH.sub.2COC.sub.5H.sub.9--), 4-acetyloxycyclohexyl,
dicyanoisopropylidenebis(4-cyclohexyloxy) (i.e.
--OC.sub.6H.sub.11C(CN).sub.2C.sub.6H.sub.11O--),
3-methylcyclohexyl, methylenebis(4-cyclohexyloxy) (i.e.
--OC.sub.6H.sub.11CH.sub.2C.sub.6H.sub.11O--), ethylcyclobutyl,
cyclopropylethenyl, 3-formyl-2-terahydrofuranyl,
2-hexyl-5-tetrahydrofuranyl; hexamethylene-1,6-bis(4-cyclohexyloxy)
(i.e. --OC.sub.6H.sub.11(CH.sub.2).sub.6 C.sub.6H.sub.11O--);
4-hydroxymethylcyclohexyl (i.e. 4-HOCH.sub.2C.sub.6H.sub.11--),
4-mercaptomethylcyclohexyl (i.e. 4-HSCH.sub.2C.sub.6H.sub.11--),
4-methylthiocyclohexyl (i.e. 4-CH.sub.3SC.sub.6H.sub.11--),
4-methoxycyclohexyl, 2-methoxycarbonylcyclohexyloxy (2-CH.sub.3OCO
C.sub.6H.sub.11O--), nitromethylcyclohexyl (i.e.
NO.sub.2CH.sub.2C.sub.6H.sub.10--), trimethylsilylcyclohexyl,
t-butyldimethylsilylcyclopentyl, 4-trimethoxysilyethylcyclohexyl
(e.g. (CH.sub.3O).sub.3SiCH.sub.2CH.sub.2C.sub.6H.sub.10--),
vinylcyclohexenyl, vinylidenebis(cyclohexyl), and the like. The
term "a C.sub.3-C.sub.10 cycloaliphatic radical" includes
substituted cycloaliphatic radicals and unsubstituted
cycloaliphatic radicals containing at least three but no more than
10 carbon atoms. The cycloaliphatic radical 2-tetrahydrofuranyl
(C.sub.4H.sub.7O--) represents a C.sub.4 cycloaliphatic radical.
The cyclohexylmethyl radical (C.sub.6H.sub.11CH.sub.2--) represents
a C.sub.7 cycloaliphatic radical.
[0023] As noted, the present invention provides phosphazenium salts
and their use as phase transfer catalysts generally. Thus, it has
been discovered that phosphazenium salts make outstanding phase
transfer catalysts, in part due to the very high level of thermal
stability phosphazenium salts exhibit. In one embodiment, the
present invention provides a method for carrying out a chemical
reaction between at least two reactants occupying separate phases
within a multiphase reaction mixture comprising at least one
phosphazenium salt phase transfer catalyst. Although, the utility
of phosphazenium salts as phase transfer catalysts is illustrated
experimentally herein in terms of multiphase reactions involving
the formation aryl ethers, the present invention encompasses the
use generally of phosphazenium salts as phase transfer catalysts in
multiphase reactions. Thus, in the description and experimental
details which follow, the use of phosphazenium salts as phase
transfer catalysts is illustrated by chemistry related to the
formation of aromatic ethers but is in no way limited thereto. The
scope of the present invention is not limited methods related to
the formation of aryl ethers. In its broadest sense, the present
invention includes the use of a phosphazenium salt in any and all
multiphase reaction mixtures in which the phosphazenium salt
functions as a phase transfer catalyst.
[0024] As noted, in one aspect the present invention relates to a
method for making aromatic ethers. More particularly, the present
invention relates to preparation of the aromatic ethers by
contacting in a multiphase reaction mixture the salt of at least
one aromatic hydroxy compound with at least one aromatic compound
comprising at least one leaving group, said reaction mixture
comprising a phosphazenium salt phase transfer catalyst.
[0025] In one embodiment, the phosphazenium salt has structure I
##STR2## wherein n is an integer from zero to about 10, R.sup.1 and
R.sup.2 are independently selected from the group consisting of
C.sub.1-C.sub.20 aliphatic radicals, C.sub.3-C.sub.20
cycloaliphatic radicals, and C.sub.4-C.sub.20 aromatic radicals,
and wherein said R.sup.1 and R.sup.2 may be linked together form a
cyclic structure comprising at least one nitrogen atom, and wherein
X.sup.- is selected from the group consisting of monovalent
inorganic anions, monovalent organic anions, polyvalent inorganic
anions, polyvalent organic anions, and mixtures thereof.
[0026] The positive charge in the cation shown in structure I is
represented in a canonical form in which the positive charge is
localized on a phosphorous atom. Those skilled in the art will
understand that numerous canonical forms other than that featured
in structure I are possible, and that the positive charge is
considered to be delocalized over the whole molecule.
[0027] In one embodiment, R.sup.1 and R.sup.2 in the phosphazenium
salt represented by the structure I are the same or different and
each represents a hydrocarbon group having 1 to 10 carbon atoms,
wherein R.sup.1 and R.sup.2 are at any occurrence independently
selected from the group consisting of aliphatic and aromatic
hydrocarbon groups. For example, R.sup.1 and R.sup.2 may be methyl,
ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, tert-butyl,
2-butenyl, 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl,
isopentyl, tert-pentyl, 3-methyl-2-butyl, neopentyl, n-hexyl,
4-methyl-2-pentyl, cyclopentyl, cyclohexyl, 1-heptyl, 3-heptyl,
1-octyl, 2-octyl, 2-ethyl-1-hexyl, 1,1-dimethyl-3,3-dimethylbutyl
(popular name: tert-octyl), nonyl, decyl, phenyl, 4-toluyl, benzyl,
1-phenylethyl, and 2-phenylethyl. In one embodiment, R.sup.1 and
R.sup.2 are aliphatic hydrocarbon groups having from 1 to 8 carbon
atoms, such as methyl, ethyl, n-propyl, isopropyl, tert-butyl,
tert-pentyl and 1,1-dimethyl-3,3-dimethylbutyl.
[0028] In an alternate embodiment R.sup.1 and R.sup.2 together form
a cyclic structure comprising at least one nitrogen atom. In the
case wherein both R.sup.1 and R.sup.2 are bound to the same
nitrogen atom and both R.sup.1 and R.sup.2 represent aliphatic
radicals, R.sup.1 and R.sup.2 may together form a cyclic structure
comprising at least one nitrogen atom. Cyclic structures comprising
one or more nitrogen atoms are exemplified by the pyrrolidin-1-yl
group, the piperidin-1-yl group, the morpholin-4-yl group, and
variants of those groups substituted by alkyl groups, for example
methyl groups and ethyl groups.
[0029] In one embodiment the phosphazenium salt is selected from
the group consisting of phosphazinum salts having structures II,
III, IV, and V ##STR3## wherein R.sup.1, R.sup.2 and X.sup.- are
defined as in structure I.
[0030] The anionic species X.sup.- shown in structures I-V is
selected from the group consisting of monovalent inorganic anions,
monovalent organic anions, polyvalent inorganic anions, polyvalent
organic anions, and mixtures thereof. Monovalent inorganic anions
include chloride, bromide, fluoride, methanesulfonate,
hydrogensulfate, bicarbonate, and the like. Polyvalent inorganic
anions include carbonate, sulfate, sulfite, and the like.
Monovalent organic anions include methanesulfonate, acetate,
alkoxide, acetylacetonate, and the like. Polyvalent organic anions
include malonate, succinate, ethylenedisufonate (i.e.
.sup.-O.sub.3SCH.sub.2CH.sub.2SO.sub.3.sup.-), and the like.
[0031] In one embodiment of the present invention, the salt of at
least one aromatic hydroxy compound is contacted with at least one
aromatic compound comprising at least one leaving group, said
contacting being carried out in the presence of an effective amount
of a phosphazenium salt having structure I. An effective amount of
phosphazenium salt catalyst is defined as that amount of
phosphazenium salt required to affect materially the outcome of the
reaction. Typically, an effective amount of phosphazenium salt
catalyst means an amount of phosphazenium salt needed to produce a
measurable increase in a reaction rate, relative to the rate of
reaction observed in the absence phosphazenium salt. In one
embodiment, the phosphazenium salt is used in an amount
corresponding to between about 0.1 and about 10 mole percent based
upon the amount of the aromatic hydroxyl compound employed. In
another embodiment, the phosphazenium salt is used in an amount
corresponding to between about 0.2 and about 5 mole percent based
upon the amount of the aromatic hydroxyl compound employed. In yet
another embodiment, the phosphazenium salt is used in an amount
corresponding to between about 0.5 and about 2 mole percent based
upon the amount of the aromatic hydroxyl compound employed.
[0032] In one embodiment the salt of at least one aromatic hydroxy
compound has structure VI R.sup.3(ZM).sub.k (VI) wherein R.sup.3 is
a C.sub.5-C.sub.40 aromatic radical; M is a metal selected from the
group consisting of alkali metals, alkaline earth metals, and
mixtures thereof; Z is oxygen, sulfur, or selenium, at least one Z
being oxygen; and k is 1, 2 or 3.
[0033] Typically, the salt of at least one aromatic hydroxy
compound is derived from the corresponding hydroxy compound by
deprotonation. In one embodiment the at least one aromatic hydroxy
compound is a dihydroxy aromatic compound of the formula VII
##STR4## wherein A.sup.1 is independently at each occurrence a
C.sub.3-C.sub.20 aromatic radical; E is independently at each
occurrence a bond, a C.sub.1-C.sub.20 aliphatic radical, a
C.sub.3-C.sub.20 cycloaliphatic radical, or a C.sub.5-C.sub.20
aromatic radical, a sulfur atom, a sulfinyl group, a sulfonyl
group, a selenium atom, or an oxygen atom; and t, s and u are
independently integers from 0-10 wherein at least one of t, s and u
is not zero.
[0034] Suitable aromatic radicals "A.sup.1" include, but are not
limited to, phenylene, biphenylene, naphthylene, and the like.
Suitable groups "E" include but are not limited to alkylene and
alkylidene groups, for example methylene, ethylene, ethylidene,
propylene, propylidene, isopropylidene, butylene, butylidene,
isobutylidene, amylene, amylidene, isoamylidene, and the like. The
group "E" includes C.sub.5-C.sub.20 aromatic radicals for example
the C.sub.12 divalent aromatic radical represented by structure
VIII, the dashed lines (Structure VIII) indicating the points of
attachment of the radical to the A.sup.1 groups shown in structure
VII. ##STR5##
[0035] The group "E" may also be a tertiary nitrogen linkage; an
ether linkage; a carbonyl linkage; a silicon-containing linkage,
silane, siloxy; or a sulfur-containing linkage including, but not
limited to, sulfide, sulfoxide, sulfone, and the like; or a
phosphorus-containing linkage including, but not limited to,
phosphinyl, phosphonyl, and the like. In other embodiments E may be
a cycloaliphatic group including, but not limited to,
1,1-cyclopentylidene; 1,1-cyclohexylidene;
3,3,5-trimethyl-1,1-cyclohexylidene; 3-methyl-1,1-cyclohexylidene;
2-[2.2.1]-bicycloheptylidene, neopentylidene, cyclopentadecylidene,
cyclododecylidene, adamantylidene, and the like.
[0036] In one embodiment the dihydroxy aromatic compound
represented by structure VII, E may be an unsaturated alkylidene
group. Suitable dihydroxy-substituted aromatic hydrocarbons of this
type include those of the formula IX: ##STR6## wherein
independently each R.sup.4 is independently at each occurrence
hydrogen, chlorine, bromine, fluorine, or a C.sub.1-20 monovalent
aliphatic radical (for example a methyl group, a t-butyl group, or
a methoxy group), and each Y is independently at each occurrence
hydrogen, chlorine, bromine, or fluorine.
[0037] Suitable dihydroxy-substituted aromatic hydrocarbons also
include those of the formula X: ##STR7## wherein each R.sup.4 is
independently hydrogen, chlorine, bromine, fluorine, or a
C.sub.1-20 monovalent aliphatic radical (for example a methyl
group, a t-butyl group, or a methoxy group), and R.sup.g and
R.sup.h are independently hydrogen, a C.sub.1-C.sub.20 aliphatic
radical, a C.sub.3-C.sub.20 cycloaliphatic radical, or a
C.sub.4-C.sub.20 aromatic radical. Further R.sup.g and R.sup.h may
together form a C.sub.4-C.sub.20 cycloaliphatic radical.
[0038] In some embodiments of the present invention,
dihydroxy-substituted aromatic hydrocarbons that may be used
comprise those disclosed by name or formula (generic or specific)
in U.S. Pat. Nos. 2,991,273; 2,999,835; 3,028,365; 3,148,172;
3,153,008; 3,271,367; 3,271,368; and 4,217,438. In other
embodiments of the invention, dihydroxy-substituted aromatic
hydrocarbons comprise bis(4-hydroxyphenyl)sulfide;
bis(4-hydroxyphenyl) ether; bis(4-hydroxyphenyl)sulfone;
bis(4-hydroxyphenyl)sulfoxide; 1,4-dihydroxybenzene;
4,4'-oxydiphenol; 2,2-bis(4-hydroxyphenyl)hexafluoropropane;
4,4'-(3,3,5-trimethylcyclohexylidene)diphenol;
4,4'-bis(3,5-dimethyl)diphenol;
1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;
4,4-bis(4-hydroxyphenyl)heptane; 2,4'-dihydroxydiphenylmethane;
bis(2-hydroxyphenyl)methane; bis(4-hydroxyphenyl)methane;
bis(4-hydroxy-5-nitrophenyl)methane;
bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane;
1,1-bis(4-hydroxyphenyl)ethane; 1,2-bis(4-hydroxyphenyl)ethane;
1,1-bis(4-hydroxy-2-chlorophenyl)ethane;
2,2-bis(3-phenyl-4-hydroxyphenyl)propane;
2,2-bis(4-hydroxy-3-methylphenyl)propane;
2,2-bis(4-hydroxy-3-ethylphenyl)propane;
2,2-bis(4-hydroxy-3-isopropylphenyl)propane;
2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane;
3,5,3',5'-tetrachloro-4,4'-dihydroxyphenyl)propane;
bis(4-hydroxyphenyl)cyclohexylmethane;
2,2-bis(4-hydroxyphenyl)-1-phenylpropane; 2,4'-dihydroxyphenyl
sulfone; 2,5-dihydroxy naphthalene; 2,6-dihydroxy naphthalene;
hydroquinone; resorcinol; C.sub.1-3 alkyl-substituted resorcinols;
4-methyl resorcinol; catechol; 1,4-dihydroxy-3-methylbenzene;
2,2-bis(4-hydroxyphenyl)butane;
2,2-bis(4-hydroxyphenyl)-2-methylbutane;
1,1-bis(4-hydroxyphenyl)cyclohexane; 4,4'-dihydroxydiphenyl;
2-(3-methyl-4-hydroxyphenyl)-2-(4-hydroxyphenyl)propane;
2-(3,5-dimethyl-4-hydroxyphenyl)-2-(4-hydroxyphenyl)propane;
2-(3-methyl-4-hydroxyphenyl)-2-(3,5-dimethyl-4-hydroxyphenyl)propane;
bis(3,5-dimethylphenyl-4-hydroxyphenyl)methane;
1,1-bis(3,5-dimethylphenyl-4-hydroxyphenyl)ethane;
2,2-bis(3,5-dimethylphenyl-4-hydroxyphenyl)propane;
2,4-bis(3,5-dimethylphenyl-4-hydroxyphenyl)-2-methylbutane;
3,3-bis(3,5-dimethylphenyl-4-hydroxyphenyl)pentane;
1,1-bis(3,5-dimethylphenyl-4-hydroxyphenyl)cyclopentane;
1,1-bis(3,5-dimethylphenyl-4-hydroxyphenyl)cyclohexane;
bis(3,5-dimethyl-4-hydroxyphenyl) sulfoxide;
bis(3,5-dimethyl-4-hydroxyphenyl) sulfone;
bis(3,5-dimethylphenyl-4-hydroxyphenyl)sulfide; and like
bisphenols. In a particular embodiment the dihydroxy-substituted
aromatic hydrocarbon is bisphenol A.
[0039] In some embodiments the dihydroxy-substituted aromatic
compounds represented by structure VII includes compounds
comprising one or more fused rings represented by component "E",
attached to one or more aromatic groups A.sup.1. Suitable
dihydroxy-substituted aromatic hydrocarbons of this type include
those containing indane structural units such as represented by the
formula (XI), 3-(4-hydroxyphenyl)-1,1,3-trimethylindan-5-ol; and by
the formula (XII), 1-(4-hydroxyphenyl)-1,3,3-trimethylindan-5-ol.
##STR8##
[0040] Also included with the class of dihydroxy aromatic compounds
represented by formula VII are bisphenols comprising spirocyclic
structures as component "E", for example as in
2,2,2',2'-tetrahydro-1,1'-spirobi[1H-indene]diol.
[0041] The term "alkyl" as used in the various embodiments of the
present invention falls within the definition of an "aliphatic
radical" as defined herein and includes both linear alkyl groups
such as methyl groups, and branched alkyl groups such as isobutyl
groups.
[0042] The salt of at least one aromatic hydroxy compound employed
in the present invention is typically a sodium or potassium salt.
Sodium salts are often used in particular embodiments by reason of
their availability and relatively low cost. In one embodiment, the
salt of at least one aromatic hydroxy compound is a disodium salt
of a dihydroxy aromatic compound.
[0043] In one embodiment the salt of the aromatic hydroxy compound
is generated in-situ, from an organic compound which is not itself
an aromatic hydroxy compound. For example, the salt of hydroxyimide
XIII may be formed in-situ from the corresponding chloroimide. For
example, 4-chloro-N-methylphthalimide reacts with sodium hydroxide
in a reaction mixture comprising a phosphazenium salt phase
transfer catalyst to afford 4-hydroxy-N-methylphthalimide which is
then deprotonated by sodium hydroxide, typically at a rate faster
than its formation, to afford the corresponding sodium salt.
Alternately, 4-chloro-N-methylphthalimide reacts with an oxygen
nucleophile such as potassium carbonate or sodium acetate to afford
an intermediate which subsequently converted to the salt of
hydroxyimide XIII. In aromatic hydroxy compounds represented by
##STR9## structure XIII, R.sup.5 is typically an organic radical
selected from the group consisting of C.sub.1C.sub.2 aliphatic
radicals, C.sub.3-C.sub.12 cycloaliphatic radicals, and
C.sub.4-C.sub.30 aromatic radicals. In an alternate embodiment, the
aromatic hydroxy compound has the formula XIV. ##STR10##
[0044] The reaction may be performed in the absence a solvent, or
alternatively in the presence of a solvent. Preferably, the
reaction is carried out in the presence of at least one inert
solvent. Suitable solvents include non-polar solvents and polar
aprotic solvents (also referred to as "dipolar aprotic solvents").
Typically, the reaction is carried out in an aromatic solvent, for
example an aromatic hydrocarbon solvent or chloroaromatic solvent.
In one embodiment the solvent has a boiling point above about
120.degree. C., preferably above about 150.degree. C., and more
preferably above about 180.degree. C. Suitable solvents include,
but are not limited to, toluene, xylene, ortho-dichlorobenzene;
(o-DCB), para-dichlorobenzene, dichlorotoluene;
1,2,4-trichlorobenzene; diphenylether, dimethylsulfone, diphenyl
sulfone, sulfolane, phenetole, anisole, veratrole, and mixtures
thereof. In a preferred embodiment chlorinated aromatic liquids be
employed as solvents, examples of which include, but are not
limited to, ortho-dichlorobenzene (o-DCB); 2,4-dichlorotoluene; and
1,2,4-trichlorobenzene. In some embodiments 2,4-dichlorotoluene is
a preferred solvent. In the case of some solvents, such as
ortho-dichlorobenzene, the proportion of phase transfer catalyst
can be increased and/or the reaction can be run at superatmospheric
pressure to permit higher temperatures and higher reaction
rates.
[0045] Typically, the aromatic compound comprising at least one
leaving group is a compound having formula XV, wherein Ar.sup.1 is
independently at each occurrence a C.sub.3-C.sub.20 aromatic
radical, L.sup.1 is a leaving group independently selected from the
group consisting of fluoro, chloro, bromo, iodo, nitro, and
organosulfonate groups; B is an activating group, and g is 1, 2 or
3. Organosulfonate groups are illustrated by the methanesulfonate
(MeSO.sub.3--), tosylate (C.sub.7H.sub.7SO.sub.3--), and
trifluoromethanesulfonate (CF.sub.3SO.sub.3--) groups.
##STR11##
[0046] In one embodiment the aromatic radical Ar.sup.1 is a
monocyclic aromatic radical, for example a phenylene
(C.sub.4H.sub.4) radical, L.sup.1 is a chlorine atom, B is a
sulfonyl group, and g is 2. The activating group B, is typically an
electron-withdrawing group, which may be monovalent or polyvalent
group. The activating group B is illustrated by halo, nitro, acyl,
cyano, carboxy, carbonyl, alkoxycarbonyl, aldehydo, sulfonyl, and
perfluoroalkyl. In addition B may be a heterocyclic aromatic
activating group such as pyridyl. Examples of divalent groups which
may serve as component "B" in structure XV include the carbonyl
group, carbonylbis(arylene) groups, sulfonyl groups, bis(arylene)
sulfone groups, benzo-1,2-diazine groups, and azoxy groups. When
"g" in structure XV is 2, the moiety "--Ar.sup.1--B--Ar.sup.1--" is
illustrated by a bis(arylene) sulfone moiety, a bis(arylene) ketone
moiety, a bis(arylene)benzo-1,2-diazine moiety, and a
bis(arylene)azoxy moiety.
[0047] Compounds represented by structure XV include compounds
wherein component "B" together with Ar.sup.1, form a fused ring
system such as benzimidazole, benzoxazole, quinoxaline or
benzofuran. In such compounds, L.sup.1 includes leaving groups such
as fluoro, chloro, bromo, iodo, nitro groups. Fluoro and chloro
groups are frequently preferred.
[0048] In one embodiment, the aromatic compound comprising at least
one leaving group is a is a bisimide having structure XVI ##STR12##
wherein L.sup.1 is defined as in structure XV, and R.sup.6 is
selected from the group consisting of divalent C.sub.1-C.sub.12
aliphatic radicals, divalent C.sub.3-C.sub.12 cycloaliphatic
radicals, and divalent C.sub.4-C.sub.30 aromatic radicals.
[0049] In a further embodiment R.sup.6 is a divalent aromatic
radical having structure XVII ##STR13## wherein Q is a
C.sub.1-C.sub.12 aliphatic radical, a C.sub.3-C.sub.12
cycloaliphatic radical, a C.sub.4-C.sub.18 aromatic radical, an
oxygen, atom, a sulfur atom, a sulfinyl group, a sulfonyl group, a
selenium atom or a bond. In a preferred embodiment R.sup.6 is
selected from the group consisting of m-phenylene, p-phenylene,
4,4'-oxybis(phenylene).
[0050] In an alternate embodiment the aromatic compound comprising
at least one leaving group is selected from the group consisting of
compounds having formula XVIII ##STR14## wherein G is a carbonyl
group (--CO--), or a sulfonyl group (--SO.sub.2--); L.sup.2 is
independently at each occurrence a fluoro, chloro, bromo, iodo,
nitro, or a trifluormethansulfonate group; and "m" and "p" are
independently integers from 0-5, wherein not both m and p are
zero.
[0051] In one embodiment the aromatic compound comprising at least
one leaving group is selected from the group consisting of
bis(4-fluorophenyl) sulfone, bis(4-chlorophenyl) sulfone,
bis(4-fluorophenyl) ketone, and bis(4-chlorophenyl) ketone.
[0052] In an alternate embodiment the aromatic compound comprising
at least one leaving group is selected from the group consisting of
1,3- and 1,4-bis[N-(4-fluorophthalimido)]benzene and
4,4'-bis[N-(4-fluorophthalimido)]phenyl ether and the corresponding
chloro, bromo and nitro compounds.
[0053] In yet another embodiment the aromatic compound comprising
at least one leaving group is selected from the group of
substituted aromatic imides having structure XIX ##STR15## wherein
R.sup.7 is selected from the group consisting of monovalent
C.sub.1C.sub.12 aliphatic radicals, monovalent C.sub.3-C.sub.12
cycloaliphatic radicals, and monovalent C.sub.4-C.sub.30 aromatic
radicals; and L.sup.2 is a fluoro, chloro, bromo, iodo, or nitro
group. Suitable substituted aromatic imides include
3-choro-N-methylphthalimide, 4-choro-N-methylphthalimide,
3-fluoro-N-butylphthalimide, 4-fluoro-N-butylphthalimide,
3-choro-N-cyclohexylphthalimide, 4-choro-N-cyclohexylphthalimide,
3-chloro-N-phenylphthalimide, 4-chloro-N-phenylphthalimide, and the
like.
[0054] In yet another embodiment the aromatic compound comprising
at least one leaving group is selected from the group of
substituted phthalic anhydrides XX ##STR16## wherein L.sup.2 is a
fluoro, chloro, bromo, iodo, or nitro group. Suitable substituted
phthalic anhydrides include, 3-chlorophthalic anhydride,
4-chlorophalic anhydride, 3-fluorophthalic anhydride, and the
like.
[0055] In yet still another embodiment, the aromatic compound
comprising at least one leaving group is selected from the group of
compounds represented by structures XXI and XXII ##STR17## wherein
D is independently at each occurrence a carbonyl group or a
sulfonyl group, and L.sup.3 is independently at each occurrence a
fluoro, chioro, bromo, iodo, or nitro group. Compounds XXI are
illustrated by the PEEK monomers
1,1'-(p-phenylenedioxy)bis[4-(4-chlorobenzoyl)]benzene;
1,1'-(p-phenylenedioxy)bis[4-(4-fluorobenzoyl)]benzene, and the
like. Compounds XXII are illustrated by
1,3-bis(4-chlorobenzoyl)benzene; 1,3-bis(4-fluorobenzoyl)benzene;
1,4-bis(4-chlorobenzoyl)benzene;
1,3-bis(4-chlorophenylsulfonyl)benzene; and the like.
[0056] When the reaction between the salt of at least one aromatic
hydroxy compound and at least one aromatic compound comprising at
least one leaving group is complete, the product aromatic ether may
be isolated by conventional techniques. It is often convenient to
filter the product mixture while still hot to remove insoluble
by-products, and subsequently cool the filtrate, whereupon the
desired aromatic ether precipitates and may be collected by
filtration.
[0057] In one embodiment the contacting in a reaction mixture the
salt of at least one aromatic hydroxy compound with at least one
aromatic compound comprising at least one leaving group is carried
out at a temperature in a range from about 50.degree. C. to about
250.degree. C., preferably from about 120.degree. C. to about 25020
C., and still more preferably from about 150.degree. C. to about
250.degree. C. In an alternate embodiment the contacting is carried
out at a temperature range from about 150.degree. C. to about
225.degree. C. Typically, the contacting is carried out at
atmospheric pressure under inert atmosphere, for example under a
nitrogen atmosphere.
EXAMPLES
[0058] The following examples are set forth to provide those of
ordinary skill in the art with a detailed description of how the
methods claimed herein are evaluated, and are not intended to limit
the scope of what the inventors regard as their invention. Unless
indicated otherwise, parts are by weight, and temperature is in
.degree. C.
[0059] Yields in the reactions of 4-chlorophenyl phenyl sulfone
were determined using an internal standard HPLC method. These
reactions are at times referred to as "model" reactions since they
often predict (or model) the behavior of more complex
polymerization reactions. Phenanthrene was used as the internal
standard in all cases, and was added to the reactions along with
the reactants. Aliquots of the reaction mixture were removed
periodically during the reaction, and quenched with 2 drops of
acetic acid. The quenched aliquots were diluted with 2 milliliters
of tetrahydrofuran (hereinafter known as "THF"), filtered, and
analyzed on a Zorbax 150 cm.times.4.6 mm C-8 column, eluting with a
THF-water gradient. Recovered bisphenol A, solvent, phenanthrene,
starting substrate, and product bis-sulfone were separated, and the
amount of starting material and product could be quantified by
comparing to the internal standard. The HPLC was calibrated by
using pure isolated bis-sulfone product relative to phenanthrene.
No mono-substitution product was noted in any case.
[0060] Gel permeation chromatography (hereinafter known as GPC)
characterization was carried out using Turbogel.RTM. Software on a
commercial GPC system using a Polymer Labs Mixed C column, at a
column temperature of 40.degree. C., eluting with 3%
isopropanol/chloroform at 0.7 milliliter per minute, using an
Agilent HPLC pump and UV detection at 255 nm. The system was
calibrated with polystyrene standards daily, using a third order
fit. The correlation coefficient was typically about 0.9996. Sample
size was 5-10 microliters. Two to three drops of polymer solution
were added to 2 drops acetic acid in approximately 0.25 mL
o-dichlorobenzene, to quench the polymerization reaction. The
sample was diluted with 1 milliliter of chloroform, rinsing the
pipette with sufficient chloroform to ensure that all of the
product polymer was dissolved. Water (1 milliliter) was added with
stirring to dissolve the by-product sodium chloride. Ten drops of
the lower (chloroform) phase were added to a sample filter, diluted
with 1 milliliter of chloroform and filtered through a 0.45 micron
polytetrafluoroethylene membrane. The contents were placed directly
into a sampling vial, and analyzed by GPC. Molecular weights are
reported as number average (M.sub.n) or weight average (M.sub.w)
molecular weight.
Preparation of Phosphazenium Salt
[0061] A phosphazene base, P
2-Ethyl[1-ethyl-2,2,4,4,4-pentakis(dimethylamino)-2.lamda.5,4.lamda.5-cat-
enadi(phosphazene)] (CAS No.:165535-45-5, Aldrich Chemical Co., 679
mg; 2.0 millimoles) was dissolved in 5 milliliters of chloroform
and cooled to 0.degree. C. About 2.0 mmol of methyl
methanesulfonate (178.mu.L) was added to the above solution while
maintaining the temperature at 0.degree. C. The proton NMR was
recorded at the end of one hour of reaction, and indicated that all
of the methylsulfonate had reacted. The solvent was removed by
rotary evaporation and o-dichlorobenzene (o-DCB) was added. The
resulting solution was heated and a small amount of o-DCB was
distilled in order to dry the solution of the phosphazenium salt.
The concentration of the phosphazenium salt was determined by
proton NMR.
General Procedure for Model Reactions (Displacement Reactions of
4-Chlorophenyl Phenyl Sulfone)
[0062] Dry bisphenol A disodium salt (BPANa.sub.2) was weighed into
a 50-mL flask, and a 2 mole % excess of 4-chlorophenyl phenyl
sulfone was added. The transfers were carried out in a dry box. The
flask was capped, removed from the dry box, and was fitted with a
condenser and a nitrogen purge. Sufficient solvent was added to
achieve a final product concentration to approximately 20 weight %,
assuming quantitative conversion of starting materials to product.
Phenanthrene was added (typically 100 mg) as an internal standard.
The reaction mixture was stirred magnetically while being heated to
reflux. Once reflux had been achieved, the phase transfer catalyst
(PTC) was added, and the timer was started. Samples were removed
periodically, and were analyzed by HPLC.
[0063] FIGS. 1 and 2 illustrate the behavior of the new phase
transfer catalysts in the formation of
1,1'-(1-methylethylidene)bis[4-[4-(phenylsulfonyl)phenoxy]benzene
(CAS No. 90139-53-0). When the P2-EthylMethyl mesylate was used as
a PTC at 1.0 mole % in the model reaction in refluxing o-DCB at
180.degree. C. (See 4 (FIG. 1)), the reaction exhibited
pseudo-first order kinetics. This indicates that no catalyst
decomposition nor diminution in rate was occurring during the
reaction. In order to further test the stability of the
phosphazenium salt, similar reactions were carried out at higher
temperatures, in 3,4-dichlorotoluene (bp=200.degree. C.) (See 6
(FIG. 1)) and in 1,2,4-trichlorobenzene (bp=214.degree. C.) (See 2
(FIG. 1)). As shown in FIG. 1, even at 200.degree. C., essentially
linear reaction kinetics were observed, indicating no decomposition
of the P2-EthylMethyl mesylate phase transfer catalyst. In
trichlorobenzene, only a small amount of decomposition was
observed, after 60 minutes (See 2 (FIG. 1)). In this instance only
0.5 mole % catalyst was used, since after initial range-finding
experiments it was determined that reaction using 1.0 mole % would
be too fast to follow accurately at 214.degree. C.
[0064] The results shown in FIG. 1 illustrate that because they are
highly stable, the phosphazenium salt phase transfer catalysts are
effective over a broad range of temperatures. Under the reaction
conditions examined (2, 4, 6 FIG. 1) the stability of the
phosphazenium salt catalyst was observed to be superior relative to
a representative guanidinium salt phase transfer catalyst,
hexaethylguanidium chloride (HEGCl). FIG. 2 illustrates the
enhanced stability of the phosphazenium catalysts and compares a
reaction utilizing HEGCl in o-DCB at 180.degree. C. (See 10 FIG. 2)
to the same reaction using a phosphazenium catalyst at either
180.degree. C. (See 20 FIG. 2) or at 200.degree. C. (See 30 FIG.
2). Although HEGCl provides a faster initial rate (See 12 FIG. 2)
than the phosphazenium salt at 180.degree. C. (See 22 FIG. 2), the
reactions incorporating a phosphazenium salt phase transfer
catalyst ultimately give higher yields (Compare 18, 28, and 36 FIG.
2). At 200.degree. C. (30, FIG. 2), the rate increase obtained by
increasing the reaction temperature more than compensates for the
relative effectiveness of the catalysts, and reaction rates faster
than could be achieved with HEGCl were obtained (Compare 12 and 32
FIG. 2).
General Procedure for PTC Mediated Polymerization
[0065] An accurately weighed amount (typical lab-scale amounts were
approximately 10 grams) of bisphenol A disodium salt (abbreviated
here as BPANa.sub.2) was transferred in a dry box into an
oven-dried, 250-mL, 3-necked flask. (An electronic balance, capable
of 0.1 mg accuracy was used in the dry box). The flask was capped
and transferred to an oil bath maintained at 205.degree. C., at
which point it was fitted with a nitrogen sparge tube atop a reflux
condenser, a mechanical stirrer, and a distillation apparatus. The
required amount of solvent to provide a solution of 30 wt % polymer
in solvent, plus an additional 20 mL was added to the flask. The
solvent was distilled at atmospheric pressure, while checking the
distillate by Karl-Fischer titration to ensure dryness. If
Karl-Fischer titration of the distillate indicated the salt was dry
after the 20 mL solvent had distilled, then the required amount of
4,4'-dichlorodiphenylsulfone was added, along with an additional 10
mL of solvent. Again, the excess solvent was distilled, affording a
slurry of reactants in dry solvent. At this stage there was no
evidence that any displacement reaction had occurred. Upon the
addition of the catalyst in dry o-DCB solution, the displacement
reaction initiated, and timing was begun. Samples were removed
periodically and analyzed by GPC analysis. When the desired weight
average molecular weight (M.sub.w) was met, the reaction was
quenched by the addition of approximately 0.5 mL of phosphoric
acid.
[0066] FIGS. 3 and 4 illustrate the effectiveness of the
phosphazenium catalyst in polymerization reactions (See 42 FIG. 3
and 50 FIG. 4). The efficiency of catalysis is readily apparent. In
FIG. 3, the reaction was run in o-DCB at 180.degree. C. using 1
mole percent of the phosphazenium catalyst. After 30 minutes at
180.degree. C. an additional 1 mole percent of the phosphazenium
catalyst was added. The additional catalyst resulted in the
significant rate enhancement observed at 40 (FIG. 3) and the
molecular weight of the growing polymer chain was greater than
40,000 daltons in less than 90 minutes.
[0067] FIG. 4 illustrates the same reaction in a higher boiling
solvent, dichlorotoluene, at 200.degree. C. In the reaction only 1
mole % phosphazenium catalyst was employed. The molecular weight of
the growing polymer chain in the reaction illustrated in FIG. 4 was
greater than 40,000 daltons in less than 60 minutes.
[0068] Further evidence that the phosphazenium salt phase transfer
catalysts of the present invention show enhanced stability and
effectiveness relative to guanidinium catalysts (e.g. HEGCl) is
illustrated by the following examples. Whereas polymerization of an
80/20 biphenol/BPA mixture required 500-700 minutes to reach Mw
approximately 50,000 using 2.0 mole % HEGCl in refluxing o-DCB,
similar reaction using BPANa.sub.2 reached 54,000 in just 120
minutes. Reducing the phosphazenium catalyst level to 1.0% and
increasing the reaction temperature to 200.degree. C. by carrying
out the reaction in refluxing dichlorotoluene also gave excellent
results: The polymer reached Mw=51,650 daltons in just 2 hours.
Similar reaction using 1% HEGCl in o-DCB required more than 40
hours to reach that Mw. Thus, it has been found that because of the
enhanced stability of the phosphazenium catalysts of the present
invention, the rates of chemical reactions employing said catalysts
can be increased merely by increasing the reaction temperature
without destroying the catalyst. Further, the enhanced stability of
the phosphazenium catalysts of the present invention provides for a
reduction in the amount of catalyst need in reactions employing
phase transfer catalysts.
[0069] The invention has been described in detail with particular
reference to preferred embodiments thereof, but it will be
understood by those skilled in the art that variations and
modifications can be effected within the spirit and scope of the
invention.
* * * * *