Note: Descriptions are shown in the official language in which they were submitted.
il984fl5
PREPARATION OF AROMATIC ~ALOFORMATE
When carbonic dihalide and aromatic alcohol are reacted to fonm
sromatic haloformate, there is a considerable tendency to form aromatic
carbonate. Such aromatic carbonate formation represents a loss in yield
of the de~ired aromatic haloformate and hence is undesirable.
The present invention provides a proces~ which produces aromatic
haloformate while maintaining the production of aromatic carbonate at low
levels. Accordingly, the present invention contemplates a process for pro-
ducing aromatic haloformate comprising (a) reacting, under substantially
anhydrous conditions and at a temperature in the range of from about 60~C
to the temperature at which carbonate forms in a sub6tantial a~ount, car-
bonic dihalide and aromatic alcohol in the presence of quaternary phospho-
nium ~alt catalyst wherein the anion of the quaternary phosphonium salt is
halide or the anion of the aromatic alcohol, and (b) removing hydrogen
halide from the vicinity of the reaction mixture.
The two reactants are generally ultimately introduced to the
reaction zone in about equiequivalent amounts. Although an exce3s of
either reactant may be used, it i8 ordinarily preferable to employ a slight
excess of carbonic dihalide. Usually the equivalent ratio of carbonic
dihalide tG ~roma~ic alcohol ultimately introduced i8 in the range of from
about 0.9:1 to about 1.5:1. From about 1:1 to about 1.2:1 is preferred.
Examples of carbonic dihalides which may be used include phosgene,
bromophosgene, and bromochlorophosgene. The preferred carbonic dihalide
is phosgene. Only one carbonic dihalide or a mixture of carbonic dihalides
may be u~ed a~ desired.
~'
-- 1 --
84~5
The ~romatic alcohols which may be used in the invention include
both monofunctional and polyfunctional aromatic alcohols. The aromatic alco-
hol may be unsubstituted or it may be substi~uted with any of a wide variety
of substituents which do not ~eriou~ly interfere with the haloformate-
producing reaction. Exa~ples of ~ubstitutents which may be used include
alkyl containing from 1 to about 4 carbon atoms, haloalkyl containing from
1 to about 4 carbon atoms, cycloalkyl of from three eo about 8 carbon atoms,
halo-sub~tituted cycloalkyl Of from 3 to about 8 carbon atoms, slkoxy and
substituted alkoxy having from 1 to about 4 carbon atoms in the alkyl
portion, halo, nitro and cyano. Where two hydroxyl groups are present on
the same aromatic nucleus, they should be located on non-adjacent carbon
atoms. The aromatic alcohol may contain a plurality of aromatic nuclei
joined by carbon-carbon bonds, alkylidene group~, sulfone linksges or other
small linking ~roups which are stsble under the reaction conditions employed
in the haloformate-forming process de~cribed herein.
Examples of aromatic alcohol~ which may be used inc;ude phenol,
4-chlorophenol, 2-chlorophenol, 4-bromophenol, 2,4-dichlorophenol, 2,5-
dichlorophenol, 2,4,6-tribromophenol, 3-nitrophenol, 2-ethylphenol, 2-
isopropoxyphenol, 2-chloro-3-nitrophenol, 2-butylphenol, 2,4-xylenol, 2-
(trichloromethyl)phenol, 4-cyclohexylphenol, 4-(4-chlorocyclohexyl)phenol,
2,4-dinitro-6-sec-butylphenol, l-naphthol, 4-chloro-1-naphthol, 2-naphthol,
6-chloro-2-naphthol, hydroquinone, 2,7-dihydroxynaphthalene, 4,6-di~ethyl-
2,7-dihydroxynaphthalene, 4,6-dinitro-2,7-tihydroxynaphthalene, p,p'-biphenol,
o,o'-biphenol, o,p'-biphenol, m,m'-biphenol, bi~(4-hydroxyphenyl)methane,
2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(2,6-dichloro-4-hydroxyphenyl)propane,
2,2-bis(2,6-dibromo-4-hydroxyphenyl)propsne, bis(4-hydroxyphenyl)sulfone
and bi~2-methyl-4-hydroxyphenyl)sulfone. Only one aromatic alcohol or a
mixture of aromatic alcohols may be used as desired.
-- 2 --
1~8~5
The quaternary phosphonium ~alts which can be used as cataly8t~
in the present invention vary widely. Such catalyst~ may contain only one
pho~phonium salt group or they may contain more than one phosphonium sslt
group.
One subclas~ of quaternary phosphonium salt which is of particular
utility in the invention is that repre~ented by the formula
12
Rl--p ~--R4 Ae (I)
R3
wherein Rl, R2, R3 and R4 are each independently unsubstituted alkyl, ~ub-
stituted alkyl, unsubstituted phenyl, substituted phenyl, unsubstituted phe-
nylalkyl or substituted phenylalkyl. When substituted groups are employed,the substituents should be such that they do not seriou~ly interfere with
the function of the catalyst. The various Rl, R2, R3 and R4 groups may all
be the same, some may be the same, or all may be different. The cation, Ae,
may be halide or it may be the anion of the sromatic alcohol being converted
to aromatic halofo~mate. The latter is derived by removal of the hydrogen
atom from a hydroxyl group of the aromatic alcohol. Ordinarily, the unsub-
stituted alkyl groups and the substituted alkyl groups each contains from l
to about 16 carbon atoms; from 1 to about 4 carbon atoms is preferred. The
especially preferred unsubstituted alkyls are methyl, ethyl, propyl, iso-
propyl and butyl. Of the substituted alkyl groups, halo-substituted alkyl
is preferred. Such halo-substituted alkyl may contain one or more than one
balo sub~tituents. Typically, the halo substituents are chloro or bromo.
The ~ubstituents of the ~ubstituted phenyl groups are usually halo or lower
alkyl. The preferred substituted phenyl groups are monohalophenyl and
dihalophenyl wherein the halo substituents are fluro, chloro or bromo. The
alkyl portion of the unsub~tituted phenylalkyl and the substituted phenyl-
alkyl generally contains from l to about 4 carbon atoms.
1198445
Another subclass of quaternary phosphonium salt which may be
used is that represented by Formula I wherein Rl and R2 are joined
together to form and be a part of a r-ln~ conta~ning up to about 8 nuclear
atoms including the phosphorous atom, and wherein R3, R4 and A~ as
previously described.
Still another subclass of quaternary phosphonium salt which is
useful is that represente~ by the structure
12
Rl - p _ O - Ar A (II)
R3
wherein Ar iB an aromatic group~such as, for example, unsubstituted or
sub~tituted phenyl or an aromatic group derived by removal of a hydroxyl
group from the aromatic alcohol being converted to aromatic haloformate,
and wherein Rl, R2, R3 and A are a~ previously described with respect to
Formuls I.
Yet another subclass of useful quaternary phosphonium salt is
that represented by either Formula I or Formula II wherein one or more of
Rl, R2, R3 and, in the case of Formula I, R4, represents a polymeric
support. Suitable polymeric supports include silica polymer and styrene
polymer. See, for example, P. Tundo, "Silica Gel as a Polymeric Support
for Phase-transfer Catalysts", Journal of the Chemical Society Chemical
Communications, 1977, pages 641-642 and S. L. Regen and J. J. Besse,
"Liquid-Solid-Liquid Triphase Catalysis. . ." Journal of the American
Chemical Society, (July, 1979), volume 101, pages 4059-4063. One
quaternary phosphonium group or more than one quaternary phosphonium group
may~be attached to the polymeric support.
4 -
1~8~i~5
Another ~ubclass of u~eful ~uaternary phosphonium ~alt i~ that
wherein more than one quaternary phosphonium group is attached to a multi-
valent, stsble, organic group. Thi~ subcla~s may be repre~ented by the
formula
~ R2
Q - ~ 5 ~3 (III)
R3
wherein Q is a multivalent, stable organic group, R2, R3 and A~ ~re as pre-
viously de~cribed with respect to Formula I and Formula II, Rs i~ R4 of
Formula I or -0-Ar of Formula II and n is the valence of Q.
Specie~ of other subclasses of quaternary phosphonium salt wherein
the organic groups attached to the phosphorous atom of the phosphonium group
are stable and do not seriously interfere with the formation of aromatic
haloformate, may be used in the invention.
Exa~ples o~ ~atis~actory quaternary phosphonium salt~ include:
tetrabutylpho~phonium br~mide
(hexadecyl)trimethylphosphonium chloride
benzyl(tris(trifluoromethyl)phosphonium bromide
(16-chlcrohexadecyl)tripentylpho~phonium bromide
(methyl)(phenyl)(phenoxy)benzylphosphonium chloride
tris(4-butylphenyl)methylphosphonium chloride
tris(butylbenzyl)phosphonium bromide
tris(4-phenylbutyl)dodecylphosphonium chloride
benzyltriethylphosphonium chloride
(2-phenylethyl)tripropylpho~phonium chloride
benzyltriisopropylpho~phonium chloride
(2,4-dichlorophenyl)tributylphosphonium chloride
butyltriphenylpho~phonium bromide
-- 5 --
1~98~5
benzyltriphenylphosphonium chloride
(3-bromopropyl)triphenylphosphonium bromide
(chloromethyl)triphenylphosphonium chloride
cyclopropyltriphenylpho~phonium bromide
ethyltriphenylphosphonium bromide
(methoxymethyl)triphenylpho~phonium chloride
methyltriphenylphosphonium bromide
propyltriphenylphosphonium bromide
(phenoxy)triphenylphosphonium chloride
tetramethylenediphenylphosphonium chloride
(o-isopropoxyphenyl)triphenylphosphonium chloride
p-xylylenebi~(triphenylphosphonium bromide)
Only one quaternary phosphonium salt or 8 mixture of quaternary
phosphonium salts may be used.
The preferred quaternary phosphonium salts for use in the inven-
tion are those of ~ormula I wherein Rl, R2, R3, are all unsubstituted phenyl
and wherein R4 i8 either unsubstituted alkyl containing from 1 to 4 carbon
atoms or benzyl. Especially preferred are benzyltriphenylphosphonium
chloride and benzyltriphenylphosphonium bromide.
Ths qua~ernary phosphonium salt catalyst may itself be introduced
to the process or a precursor of the quaternary phosphonium salt catalyst
may be introduced.
One type of precursor which may be used i~ a compound which is
not a quaternary phosphonium salt, but which is con~erted to the quaternary
phosphonium salt catalyst in the reaction medium. An example of thi~ type
of precursor is tertiary phosphine oxide represented by the structure
-- 6 --
1198~5
R2
Rl- - P _ O (I~)
R3
wherein Rl, R2 and R3 are as previously described with respect to Formula I.
Although it is not desired to be bound by any theory, it i3 believed that
the conversion may be represented as follows:
lR2 IR /X
Rl ---p _ O + X~X--> ~1--P + C2
R3 R3
R2 lR2
Rl P ~ ArOH ~ Rl ~ P~ - O - Ar X~ + HX
R3 R3
in which the tertiary phosphine oxide first reacts with carbonic dihalide
to form a trisubstituted phosphine dihalide and carbon dioxide and then the
trisubstituted phosphine dihalide reacts with aromatic alcohol to form
quaternary phosphonium halide of Formula II. In the above reactions, each
X represents halo or halide as the case may be, and they may be the ~ame or
differen~ according to the carbonic dihalide employed; ArOH represents aro-
matic alcohol, and Rl, R2, and R3 are as described with respect to Formula I.
An example of a precursor of this type is triphenylphosphine oxide.
Another type of precursor which may be used iB a quaternary phos-
phonium salt in which at least one of the organic groups is converted to a
different organic group in the reaction medium. Examples of these precursors
include allyltriphenylphosphonium halide and vinyltriphenylphosphonium
halide in which the unsaturated groups are hydrohalogenated to haloalkyl
group~.
~844S
Yet another type of precursor which may be used is a quaternary
phosphonium salt in which the anion, which is other than halide or the
anion of an aromatic alcohol, is replaced in the reaction medium by halide
or the anion of an aromatic alcohol. An example of a precursor of this
type i8 benzyltriphenylphosphonium nitrate.
Although the varîous types of precursors have been described
individually, it will be appreciated that the precursor may share the char-
acteristicR of more than one type, as exemplifiet by vinyltriphenylphospho-
nium nitrate. Similarly, although the precursors have been illustrated as
~0 being converted to monofunctional quaternary phosphonium salts used in the
invention, it will be evident that the principles are applicable to pre-
cursors which will be converted to compounds having more than one ~uater-
nary phosphonium salt group.
The amount of quaternary phosphonium salt cataly~t which may be
used in the invention is subject to wide variation. ln general, the amount
is a catalytic amount, that is, an amount sufficient to catalyze the halo-
formate-forming reaction. From purely chemical considerations, no theo-
retical upper limit upon the amount of quaternary phosphonium salt utilized
probably exist~, but practical ccnsiderations, such as the need to bring
the reactants and the catalyst together in a reasonable volume and the
desirability to ~eparate the catalyst from the product, suggest that the
amount of salt u~ed at least approximately approach as little as is con-
venient to achieve the desired results. In liquid phase reactions, the
equivalent ratio of the quaternary phosphonium salt to the aromatic alcohol
ulti~ately to be converted is typically in the range of from about 0.001:1 -
to about 0.5:1. From about 0.005:1 to about 0.1:1 is preferred. In vapor
phase reaction~, however, the ratio may be very small, since a considerable
amount of aromatic alcohol vapor may be passed over the catalyst.
1198445
In conductin~ the reaction, it i8 preferred that acid acceptors
such as sodium hydroxide, sodium carbonate and the like, be essentially
absent. Although small amounts may be present, the amount should not be
80 great as will markedly interfere with the removal of hydrogen halide
from the vicinity of the reaction mixture.
The reaction itself may be conducted either continously or batch-
wi~e, but batchwise reactions are more usual. The hydrogen halide may be
allowed to accumulate in the vicinity of the reaction mixture and removed
at a lster time, or it may be removed continuously or semicontinuously.
The manner in which carbonic dihalide, aromatic alcohol and cata-
lyst are brought together for reaction under ~ubstantially anhydrous condi-
tions may be widely varied. For example, a vapor phase reaction may be
used in which carbonic dihalide vapor and aromatic alcohol vapor are passed
over the catalyst. A batch operation may be used in which the aromatic
alcohol is in 8 liquid phase together with dissolved catalyst, and to which
carbonic dihalide i~ added. In a variation of this method, the catalytic
amount of the catalyst is ~lurried in the liquid aromatic alcohol to which
carbonic dihalide is added. The carbonic dihalide and aromatic alcohol may
be fed continuously or intermittently to a reaction mixture containing the
cataly~t. The haloformate msy be allowed to accumulate in the reaction
mixture or it may be removed continuously or semicontinuously as desired.
Makeup catalyst may be sdded as needed.
In liquid phase operations, if the aromatic alcohol is a solid,
it is preferred that a liquid pool of preformed haloformate product con-
taining a catalytic amount of the catalyst as a slurry or a~ a solution
be made first, then molten or solid aromatic alcohol be fed into the
pool and carbonic dihalide added either during or after addition of the
~19844S
aromatic alcohol. The reaction iB advantageouqly carried out in such a
manner that carbonic dihalide i~ continuously pa~sed into the reaction mix-
ture while unreacted carbonic dihalide and hydrogen halide are removed.
The carbonic dihalide removed from the reaction mixture can easily be con-
densed and reintroduced into the reaction mixture while the ~ore volatile
hydrogen halide is removed from the system. By carrying out the reaction
in this preferred manner, a atoichiometric deficiency of carbonic dihalide
with respect to the aromatic alcohol used is maintained in the liquid phase
reaction mixture until approximately the end of the reaction when substan-
tially all of the aromatic alcohol has been converted. This means thatthe equivalent ratio of carbonic dihalide to the aromatic alcohol iB in the
liquid pha~e of the reaction zone is below the stoichiometric equivalent
ratio during most of the reaction. Unless modified by the addition of fur-
ther quantities of aromatic alcohol, the ratio increases during the course
of the reaction as the conversion of the aromatic alcohol increases. Pref- -
erably, the equivalent ratio of carbonic dihalide to aromatic alcohol pres-
ent in the liquid phase reaction mixture i8 in the range of from about 0.01:1
to about 0.95:1 until 80 percent of the aromatic alcohol has been converted.
After completion of the reaction, it i~ generally advantageous to eliminate
the remaining carbonic dihalide by blowing with nitrogen or other suitable
gas or by reducing the pressure sufficiently to cause the remaining carbonic
dihalide to be re~oved by distillation.
One of the advantages of the invention is that the process can be
conducted in the sbsence of inert solvent. However, where the aromatic
alcohol is a solid, it may be desirable to use an inert solvent in which
the aromatic alcohol dissolve~ and in which the carbonic dihalide, aromatic
alcohol and catalyst will react to forn aromatic haloformate.
-- 10 --
1~98~45
Substantially any ~olvent or mixture of solvents may be used 80
long as they are inert to the reactants and the reaction products at the
reaction temperature and below. ~xamples of ~uitable solvents are the aro-
matic hydrocarbon solvents such as ben~ene, toluene and xylene. Chlorinated
alîphatic solvents such as methylene chloride, chloroform carbon tetrachlo-
ride, trichloroethylene and perchloroethylene may be used. Similarly, chlo-
rinated aromatic solvents such as chlorobenzene, o-dichlorobenzene, and
o-chlorotoluene are useful. The preferred inert solvents are toluene and
xylene.
The weight ratio of inert solvent to the dissolved solids employed
is subject to wide variation. Generally9 the amount of solvent should be
sufficient to solvate the reactants and the aromaeic haloformate product at
the reaction temperature. The weight ratio of inert solvent to the dis-
solved solids i8 usually in the range of from about 0.5:1 to about 100:1.
From about 1:1 ~o about 3:1 is preferred.
- When a liquid phase reaction is used, the reaction mixture is
generally agitated, as for example, by ~tirring.
Although the process may be conducted at a temperature in the
range of from about 60C to the temperature where carbonate forms in a sub-
stantial amount, a generally useful temperature range is from about 60-C
to about 200C. The preferred temperature range is from about 80C to
about 160C. The phra~e "temperature at which carbonate forms in a sub-
stantial amount" means that temperature above 60C at which the equivalent
ratio of aromatic carbonate produced to aromatic haloformate produced has
increased to about 0.15:1.
The reaction is generally conducted at ambient aemospheric pres-
sure although greater or lesser pressures may be used where desired.
1~9844S
In many cases, depending on the amounts and identities of the
materials present in the liquid phase reaction mixture, quaternary phospho-
nium salt precipitates from the liquid phase reac~ion mixture as the con-
centration of aromatic alcohol is reduced below the level necessary to
completely solubili~e the quaternary phosphonium salt. Frequently the
product haloformate is obtained in high purity by mere removal of precipi-
tated quaternary phosphonium salt from the liquid pha~e. In such circum-
stances further processing steps, such as distillation, recrystallization
and the like, which are directed to purification of the product, may often
be omitted. Such further proce~sing steps, however, may be used when and
as desired. The recovered precipitated quaternary phosphonium salt can be
reused as is, or washed prior to reuse. Examples of suitable materials
which may be used for washing include hexane, heptane, benzene, toluene,
xylene, cyclohexane, methylene chloride, ethylene dichloride, chloroben7ene
and other materials in which aromatic haloformate is soluble but in which
~he quaternary phosphonium salt is relatively in~oluble.
Aromatic haloformates produced by the process of the invention
find many uses. They are especially u~eful a8 intermediates in the produc-
tion of pesticides and herbicides, especially those of the carbamate type.
In the illustrative examples which follow, all parts are parts
by weight and all percentage~ are percentages by weight unless otherwise
specified. The reactions are conducted under substantially anhydrous
conditio~s.
EXAMPLE I
A 250 milliliter, 3-necked, round bottom flask equipped with a
magnetic stirring bar, a thermometer, a phosgene di r tube, an isopropanol
- 12 -
44~
solid carbon dioxide cooled reflux condenser snd an electric heating mantle
is charged with 76.1 grams o-i~opropoxyphenol of 90.9 percent purity (0.431
mole) and 3.89 gram6 (0.01 mole) benzyltriphenylphosphonium chloride. The
charged materials are heated with ~tirring to 118C. As the temperature
increase~, the benzyltriphenylphosphonium chloride dissolves. Over a
period of 50 minutes while the temperature is in the range of from 118-C to
154C, 58.5 grsms (0.59 mole) of phosgene is added. During the reaction,
evolved hydrogen chloride escapes through the condenser. Benzyltriphenyl-
phosphonium chloride beginH to precipitate from the liquid phase near com-
pletion of the conversion of the o-isopropoxyphenol. Upon completion of the
addition, the reaction mixture i8 ~tirred for an additional 50 minutes while
excess phosgene refluxes and while the temperature is in the range of from
135C to 141C. The mixture is dega~sed u8ing vacuum and cooled. Precipi-
tated benzyltriphenylphosphonium chloride is separated from the liquid phase
by filtration. Analysi~ by gas liquid chromatography shows the filtrate to
contain 86.5 percent o-isopropoxyphenyl chloroformate and less than 0.05 per-
cent bis (o-i~opropoxyphenyl) carbonate. The yield of o-isopropoxyphenyl
chloroformate is 97.1 percent based on the o-isopropoxyphenol charged.
After wsshing the precipitate with cyclohexane and drying, the recovery of
benzyltriphenylphosphonium chloride is determined to be g3.3 percent.
EXAMPLE II
A 250 milliliter, 3-necked, round bottom flask equipped as in
Example I i8 charged with 75.3 grams (0.501 mole) 2-sec-butylphenol and
3.89 grams (0.1 mole) benzyltriphenylpho~phonium chloride. The charged
materials are heated with ~tirring to 124-C. As the temperature increases,
the benzyltriphenylphosphonium chloride dissolves. Over a period of 100
- 13 -
11~8a~45
minutes while the temperature is in the range of from 124-C to 150C, 62.5
grams (0.632 mole) of phosgene is added. During the reaction, evolved
hydrogen chloride escapes through the conden~er. Benzyltriphenylphospho-
nium chloride begins to precipitate from the liquid phase near completion
of the conversion of the 2-sec-butylphenol. Upon completion of the addition,
the reaction mixture is ~tirred for an additional 30 minutes while excesfi
phosgene refluxes and while the temperature is maintained at about 150-C.
The mixture is degassed using vacuum and cooled. Precipitated benzyltri-
phenylpho3phonium chloride is separated from the liquid phase by filtration.
Analysis by gas liquid chromatography shows the filtrate to contain 99.0
percent 2-sec-butylphenyl chloroformate, 0.7 percent bis (2-sec-butylphenyl)
carbonate and 0.1 percent 2-sec-butylphenol. The yield of 2-sec-butylphenyl
chloroformate is 95.4 percent based on the 2-sec-butylphenol charged. After
washing the precipitate with toluene and drying, the recovery of benzyltri-
phenylphosphonium chloride is determined to be 97.7 percent. The recovered
benzyltriphenylphosphonium chloride is indistinguishable by infrared spec-
troscopy from the benzyltriphenylphosphonium chloride originally charged.
EXAMPLE III
A 250 milliliter, 3-necked, round bottom flask equipped as in
Example I is charged with 94.3 grams (1.002 moles) phenol and 7.78 grams
(0.02 mole) benzyltriphenylphosphonium chloride. The charged materials are
heated with stirring to 133-C. AB the temperature increases, the benzyl-
triphenylphosphonium chloride dissolves. Over a period of 3 1/2 hours
while the temperature is in the range of from 133-C to 153-C, phosgene in
excess is added. During the reaction, evolved hydrogen chloride escapes
through the condenser. Benzyltriphenylphosphonium chloride begins to
1198445
precipitate from the liquid phase near completion of the conversion of the
phenol. Upon completion of the addition, the reaction mixture is stirred
for an additional 30 minutes while excess phosgene refluxes and while the
temperature is maintained in the range of from 145-S to 150 C. The mixture
is degassed u~ing vacuu~ and cooled. Precipitated benzyltriphenylphosphonium
chloride i~ separated from the liquid phase by filtration. Analysis by gas
liquid chromatography shows the filtrate to contain 88.4 percent phenyl
chloroformate, 10.9 percent diphenyl carbonate and 0.7 percent phenol. The
yield o~ phenyl chloroformate is 82.0 percent based on the phenol charged.
After washing the precipitate with n-hexane and drying, the recovery of
benzyltriphenylphosphonium chloride is determined to be 93.2 percent. The
recovered benzyltriphenylphosphonium chloride is indistinguishable by infra-
red spectroscopy from the benzyltriphenylphosphonium chloride originally
charged.
13XAn~ lV
A 250 milliliter, 3-necked, round bottom flask eq~ipped as in
Example I is charged with 47.1 grams (0.50 mole) phenol and 3.88 grams
(0.01 mole) benzyltriphenylphosphonium chloride. The charged materials are
heated with stirring to 129-C. As the temperature increases, the benzyl-
triphenylpho~phonium chloride dis~olves. Over a period of 2 hours while
the temperature is in the range of from 123C to 141-C, 69 grams (0.70
mole) of phosgene is added. During the reaction, evolved hydrogen chloride
escapes through the condenser. Benzyltriphenylphosphonium chloride begins
to precipitate from the liquid ph2se near completion of the conversion of
the phenol. Upon completion of the addition, the reaction mixture is stirred
for an additional 20 minutes while excess phosgene refluxes and while the
- 15 -
~1~8~45
temperature i8 maintained in the range of from 131-C to 137~. The ~ix-
ture i8 deg&ssed using vacuum and cooled. Precipitated benzyltriphenyl-
phosphonium chloride is separated from the liquid phase by filtration.
Analysi~ by gas liquid chromatography ~hows the filtrate to c~ntain 96.4
percent phenyl chloroformate, 3.4 percent diphenyl carbonate and 0.2
percent phenol. The yield of phenyl chloroformate is 91.8 percent based
on the phenol charged. After washing the precipitate and drying, the
recovery of benzyltriphenylphosphonium chloride i8 determined to be 90.3
percent.
EXAMPLE Y
A 250 milliliter, 3-necked, round bottom flask equipped as in
Example I is charged with 48.7 grams (Q.517 mole) of phenol. No phospho-
nium salt is charged. The chsrged phenol is heated with stirring to 97C.
Over a period of 30 minutes while the temperature is in the range of from
97-C to 153C, 17.5 gr~ms 10.177 mole) of phosgene is added. Phosgene i8
observed to be accumulating, 80 no further addition of phosgene is made.
During the reaction, evolved hydrogen chloride escapes through the con-
denser. Upon completion of the addition, the reaction mixture is stirred
for an additionfll 12.1 hours while phosgene refluxes and while the tem-
perature i~ maintained in the ran8e of from 148C to 160-C. The reac-
tion mixture i~ degassed using a flow of nitrogen and cooled. Analysis
by ga~ liquid chromatography ~hows the liquid to contain 8.0 percent
phenyl chloroformate, 11.4 percent diphenyl carbonate and 80.7 percent
phenol. The yield of phenyl chloroformate i~ 4.5 percent based on the
phenol charged.
- 16 -
~1984~5
EXAMPLE VI
A 250 milliliter, 3-necked, round bottom flask equipped as in
Example I is charged with 47.0 grams (0.499 mole) phenol and 2.78 gr~ms
(0.01 mole~ triphenylphosphine o~ide. The charged materials are heated
with stirring to 137DC. As the temperature increases, the triphenylphos- -
phine oxide dissolves. Over a period of 2 hours while the temperature is
in the range of from 134C to 139DC, 64 grams (0.65 mole) of phosgene is
added. During the reaction, evolved hydrogen chloride escapes through the
condenser. Upon completion of the addition, the reaction mixture is stirred
for an additional 15 minutes while excess phosgene refluxes and while the
temperature i8 maintained at about 139C. No precipitation of solid i8
observed. The mixture is degassed using vacuum and cooled. Analysis by
gas liquid chromatography shows the liquid to contain 97.2 percent phenyl
chloroformate, 2.7 percent diphenyl carbonate and 0.1 percent phenol. The
yield of phenyl chloroformate i8 91.8 percent based on the phenol charged.
EXAMPLE VII
Phosphonium-based polystyrene resin which is polystyrene cross-
linked with 1 percent divinylbenzene wherein 17 percent of the phenyl
groups are substituted with a group represented by the formula
CH2cH2cH2cH3
--CH2-P~-CH2CH2CH2cH3 cle
CH2CH2CH2CH3
is obtained from S.L. Regen of Marquette University. The preparation of
this pho3phonium-based polystyrene resin i8 described by S. L. Regen and
J. J. Besse, "Liquid-Solid-Liquid Triphase Catalysis..." Journal of the
, (July, 1979), volume 101, pages 4059-4063.
~19~34~5
A 25~ milliliter, 3-~erked, round bottom flask equipped as in
~xample I is charged with 47.2 gram~ (0.502 mole) phenol and 4.32 grams
(0.005 mole phosphonium groups) of the above phosphonium-based polystyrene
resin. The charged materials are heated wieh stirring to 143C. Over a
period of 3 hours while the temperature is in the range of from 133-C to
143 C, 66 grams (0.67 mole) of phosgene i~ added. During the reaction,
evolved hydrogen chloride escapes through the condenser. Vpon completion
of the addition, the reaction mixture is ~tirred for an additional 25 min-
utes while excess phoagene refluxes and while the temperature is maintained
in the range of from 136-C to 139C. The mixture is degassed using vacuum
and cooled. Phosphonium-based polystyrene re~in i~ separated from the
liquid phase by filtration. Analysis by gas liquid chromatography ~hows
the filtrate to contain 97.0 percent phenyl chloroformate, 3.0 percent
diphenyl carbonate and less thsn 0.05 percent phenol. The yield of phenyl
chloroformate is 91.8 percent based on the phenol charged. After wa~hing
the separated solids with toluene and drying, the recovery of phosphonium-
based polystyrene resin is determined to be 97.5 percent.
Although the present invention has been described with reference
to specific details of certain embodi~ents thereof, it is not intended that
such details should be regarded as limitations upon the scope of the inven-
tion except insofar as they are included in the accompanying claims.
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