A new efficient Pd-catalyzed synthesis of diphenyl carbonate with heteropolyacid as a cocatalyst

Article abstract of DOI:10.1016/S0022-328X(01)00870-1

A new catalytic system, Pd-Mn-HPA (heteropolyacid), has been found to be very efficient in the oxidative carbonylation of phenol to diphenyl carbonate (DPC) with CO and oxygen at low pressure in the absence of solvent. Synergistic effect between W-Mo-heteropolyacid and Mn(OAc)₂ was observed for regenerating the Pd(II) species from Pd(0). The ratio of W-Mo in heteropolyacid, efficiency of the heteropolyacid salts and the roles of tetrabutylammonium bromide and molecular sieves have been investigated in detail. Using suitable components of the catalyst system, 53% yield of DPC with a Pd turnover number of 827 can be attained.

Full text of DOI:10.1016/S0022-328X(01)00870-1

Journal of Organometallic Chemistry 630 (2001) 11–16
www.elsevier.com/locate/jorganchem
A new efficient Pd-catalyzed synthesis of diphenyl carbonate with
heteropolyacid as a cocatalyst
Guochuan Yin, Chengguo Jia, Tsugio Kitamura, Teizo Yamaji *, Yuzo Fujiwara *
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu Uni6ersity, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
Received 29 November 2000; received in revised form 23 January 2001; accepted 17 February 2001
Abstract
A new catalytic system, Pd–Mn-HPA (heteropolyacid), has been found to be very efficient in the oxidative carbonylation of
phenol to diphenyl carbonate (DPC) with CO and oxygen at low pressure in the absence of solvent. Synergistic effect between
W–Mo–heteropolyacid and Mn(OAc)2 was observed for regenerating the Pd(II) species from Pd(0). The ratio of W–Mo in
heteropolyacid, efficiency of the heteropolyacid salts and the roles of tetrabutylammonium bromide and molecular sieves have
been investigated in detail. Using suitable components of the catalyst system, 53% yield of DPC with a Pd turnover number of
827 can be attained. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Heteropolyacid; Diphenyl carbonate; Phenol; Oxidative carbonylation; Synergistic effect
1. Introduction
Pd(II) species with oxygen was confirmed to be very
slow, which results in an aggregation of Pd(0) to form
Pd black, which is more difficult to be reoxidized to the
Pd(II) species than Pd(0). Therefore, the efficient redox
cocatalysts are essential to achieve rapid reoxidation of
Pd(0). In the Wacker process [11], copper salts were
chosen to regenerate Pd(II) with high efficiency. In the
DPC synthesis reaction, the efficiency of palladium is
lower than that in the Wacker process when copper
salts were used [6]. Until now, the catalytic system with
high efficiency is very scare, and the systems with
higher yield of DPC and higher efficiency of Pd are
usually run under high pressure or crucial reaction
conditions. From the industrial point of view, it is
necessary to seek a novel catalytic system with high
efficiency that can be performed under mild conditions.
Heteropolyacids are broadly utilized in the catalytic
reactions because of their high stability and redox
reversibility. It was reported that heteropolyacids could
act as the redox cocatalysts in the some palladium-cata-
lyzed reactions [12,13]. Recently, we reported a hetero-
polyacid-catalyzed partial oxidation of methane [14].
Using heteropolyacid as cocatalyst, we investigated the
synthesis of DPC by the oxidative carbonylation of
phenol with the Pd(OAc)2 catalyst under low pressure
in the absence of solvent. A part of this work has
appeared in a preliminary communication [15]. Here,
Diphenyl carbonate (DPC), an important precursor
of polycarbonates, is industrially obtained from phos-
genation of phenol, accompanied by the formation of
chlorinated waste [1]. In recent years, there has been an
increasing demand for a safer and environmentally
benign process for the DPC synthesis. Oxidative car-
bonylation of phenol with CO and oxygen in one-step
is an attractive process for the synthesis of DPC, where
H2O is the sole byproduct and the use of highly toxic
phosgene can be avoided Eq. (1):
(1)
In the previous literature, many metal compounds
were chosen as catalysts for the oxidative carbonylation
reaction [2–10], and palladium was thought to be the
most active. In this reaction, the efficient regeneration
of the Pd(II) species from Pd(0) is the crucial step for
the high yield of DPC and high turnover number
(TON) of Pd. However, direct oxidation of Pd(0) to the
* Corresponding authors. Tel.: +81-92-642-4374; fax: +81-92-
651-5606.
E-mail address: yamaji@csef-kyushu-u.ac.jp (Y. Fujiwara).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00870-1

12
G. Yin et al. / Journal of Organometallic Chemistry 630 (2001) 11–16
major side products are phenysalicylate and 4-phenoxy
phenol, which have been identified by the GC-MS
spectra. Control experiments show that, the side prod-
ucts are not formed from a subsequent reaction of
DPC, and that the DPC can be slightly hydrolyzed to
phenol and carbon dioxide under the reaction
conditions.
we report the details of this heteropolyacid-assisted
oxidative carbonylation reaction.
2. Results and discussion
2.1. Efficiency of oxidati6e carbonylation with 6arious
heteropolyacid cocatalysts
Interestingly, the combinations of some P–Mo–W-
containing heteropolyacids with Mn(OAc)2 as the bi-
component cocatalyst give higher yields than with
Mn(OAc)2 as the sole cocatalyst (entries 6 and 7).
Particularly, yield can be improved to 18.9% with TON
of 295 when H3PW6Mo6O40 is combined with
Mn(OAc)2 as the cocatalyst (entry 7), despite the fact
that H3PW6Mo6O40 as the sole cocatalyst is inactive. A
low yield (13.1%) is obtained with Mn(OAc)2 combined
with simple H3PW12O40 and H3PMo12O40 as the cocata-
lyst (entry 9). These results probably suggest that, there
is the synergistic effect existing between Mn(OAc)2 and
some P–W–Mo-containing heteropolyacids for regen-
erating the Pd(II) species. Although H3PW6Mo6O40 is
inactive under the present conditions, it can assist the
regeneration of the Pd(II) species with high efficiency
when it is combined with Mn(OAc)2 as the bicompo-
nent cocatalyst. In addition, H4SiW6Mo6O40 shows the
same activity as those of the P–W–Mo-containing
heteropolyacids (entry 10). The synergistic effect was
not observed when the combination of vanadium-con-
taining heteropolyacids with Mn(OAc)2 as the bicom-
ponent cocatalyst was used (entry 11).
In a flow system and under low pressure, some
heteropolyacids have been investigated as the redox
cocatalysts for the oxidative carbonylation of phenol to
DPC with the Pd(OAc)2 catalyst in the absence of
solvent. The results are summarized in Table 1. From
the data in Table 1, one can see that, without redox
cocatalyst in the system, Pd(OAc)2 is also slightly active
for the oxidative carbonylation of phenol to DPC,
although the yield of DPC is only 0.3% based on
phenol with TON of 5 based on Pd after 3 h (entry 1).
These results show that the regeneration of Pd(II)
species from Pd(0) with oxygen is a slow reaction under
the present conditions. In the present work, a 1.4%
yield can be obtained with TON of 22 when
H3PVMo11O40 is used as the cocatalyst (entry 2).
H5PV2Mo10O40 is more active than H4PVMo11O40;
yield can be improved to 4.4% with a TON of 69 (entry
3). H3PW6Mo6O40 is inactive as the cocatalyst (entry 4),
which means that H3PW6Mo6O40 is incapable of regen-
erating the Pd(II) species from Pd(0) under the present
conditions, although in previous literature [16], the
PdSO4ꢀH3PW6Mo6O40 catalyst showed good activity in
the oxidation of cyclic olefins to the corresponding
cyclic ketones with oxygen in the aqueous solution.
Mn(OAc)2 is a good cocatalyst, and yield can reach
12.9% with a TON of 202 (entry 5). In all cases, the
2.2. Effect of the ratio of W–Mo in heteropolyacid
The influence of the ratio of W–Mo in heteropoly-
acids (H3PWxMo12−xO40) on the catalytic activity is
Table 1
Oxidative carbonylation of phenol to DPC with various heteropolyacids as a cocatalyst a
c
Entry
Cocatalyst
DPC yield (%) b
TON
DPC selectivity (%) d
1
2
–
0.3
1.4
5
22
\99.9
99
H4PVMo11O40
3
4
5
6
7
8
9
10
11
H5PV2Mo10O40
H3PW6Mo6O40
Mn(OAc)2
H3PW11MoO40+Mn(OAc)2
H3PW6Mo6O40+Mn(OAc)2
H3PW4Mo8O40+Mn(OAc)2
4.4
0.4
69
6
97.4
\99.9
97
97.5
97
96.8
98.0
97.4
98.6
12.9
16.4
18.9
12.4
13.1
18.2
10.2
202
256
295
194
205
284
159
e
H3PW12
H4SiW6Mo6O40+Mn(OAc)2
H5PV2Mo10 40+Mn(OAc)2
O40+H3PMo12O40+Mn(OAc)2
O
a Phenol 0.5 mol, Pd(OAc)2 0.16 mmol, Mn(OAc)2 0.32 mmol, heteropolyacid 0.047 mmol, tetrabutylammonium bromide 3 mmol, M.S. 7 g,
8 atm, CO 500 ml min−1, O2 35 ml min−1, 80 °C, 3 h.
b GC yield based on charged phenol.
c TON based on Pd.
d DPC percentage in the products evaluated from the peak areas on GC and the products identified by GC-MS spectroscopy.
e H3PW12O40 and H3PMo12O40, 0.03 mmol, respectively.

G. Yin et al. / Journal of Organometallic Chemistry 630 (2001) 11–16
13
2.3. Effect of tetrabutylammonium bromide
Tetrabutylammonium bromide (TBAB) is neither a
catalyst for the oxidative carbonylation of phenol, nor
a cocatalyst for the regeneration of the Pd(II) species.
However, it is very essential for the catalytic system
(Table 2). Only a trace amount of the product is formed
(entry 1) without the addition of TBAB in the reaction
mixtures. Higher yield of DPC (14.4%) can be obtained
with 0.75 mmol TBAB, and the yield can reach 22.1%
with TON of 345 when 4.5 mmol TBAB are added in
the reaction mixtures. It was thought that, the reaction
of ammonium halide and phenol could produce ammo-
nium phenoxide which was advantageous for the coor-
dination of phenol to the Pd(II) species in the oxidative
carbonylation process [2,5]. In addition, in the previous
patents [11,18], sodium phenolate added to the reaction
mixtures could improve the yield of DPC. However,
under the present conditions, yield of DPC decreases
sharply to 1.7% and a considerable amount of benzo-
quinone is formed in the reaction when sodium pheno-
late is added to the reaction mixtures (entry 6).
Probably sodium phenoxide makes the oxidization of
phenol to benzoquinone easy and causes the decrease in
DPC. However, the role of TBAB is still not clear
although it improves the reaction greatly.
Fig. 1. The influence of the ratio of W–Mo in H3PWxMo12−xO40 on
the reaction. Conditions: phenol (0.5 mol); Pd(OAc)2 (0.16 mmol);
Mn(OAc)2 (0.32 mmol); heteropolyacid (0.047 mmol); tetrabutylam-
monium bromide (3 mmol); M.S. (7 g), pressure (8 atm); CO (500 ml
min−1); O2 (35 ml min−1); 80 °C; 3 h.
shown in Fig. 1. The combination of H3PMo12O40
(x=0) with Mn(OAc)2 as the bicomponent cocatalyst
gives only a 5% yield. Yield can increase remarkably
with heteropolyacids containing W and Mo. A satisfac-
tory yield of 18.9% can be obtained when the ratio of
W–Mo is 6:6 (x=6). The yield drops to 15% when
H3PW12O40 (x=12) is used as one of the cocatalysts.
Thus, judging from the no synergistic effect of a simple
mixture of H3PW12O40 and H3PMo12O40 (Table 1, entry
9), the presence of polyanions with W–Mo-mixed addi-
tional atoms is responsible for improving the yield. It
has been reported that the redox potential and catalytic
performance can be changed by the W–Mo mixed
coordination (H3PWxMo12−xO40) [17]. Therefore, the
synergistic effect is likely to be associated with the
change in the redox properties of the polyanions.
2.4. The role of molecular sie6es
It was confirmed by the control experiments that
water could react with DPC (hydrolysis) to produce
phenol and CO2. Thus, 3 A powder molecular sieves
(M.S.) are added to remove water formed during the
reaction. The results are listed in Table 3. In the present
catalytic system, without M.S. added to the reaction
mixtures, yield is only 0.5% (entry 1). When 14 g M.S.
are added to the reaction mixtures, yield was improved
to 19.3% with TON of 301 (entry 4). However, putting
too many M.S. to the reaction mixtures can cause a
Table 2
Effect of tetrabutylammonium bromide on the catalytic system a
c
Entry
Tetrabutylammonium bromide (mmol)
DPC yield (%) b
TON
DPC selectivity (%) d
1
2
3
4
5
6
–
Trace
14.4
19.2
18.9
22.1
0.75
1.5
3.0
4.5
225
300
295
345
27
98.2
99.3
97
\99.9
97
e
f
3.0
1.7
a Phenol 0.5 mol, Pd(OAc)2 0.16 mmol, Mn(OAc)2 0.32 mmol, H3PW6Mo6O40 0.047 mmol, M.S. 7 g, 8 atm, CO 500 ml min−1, O2 35 ml
min−1, 80 °C, 3 h.
b GC yield based on charged phenol.
c TON based on Pd.
d DPC percentage in the products evaluated from the peak areas on GC and the products identified by GC-MS spectroscopy.
e Sodium phenolate 4.7 mmol added.
f A considerable amount of benzoquinone was obtained.

14
G. Yin et al. / Journal of Organometallic Chemistry 630 (2001) 11–16
Table 3
Effect of M.S. on DPC yield a
c
Entry
M.S. (g)
DPC yield (%) b
TON
DPC selectivity (%) d
1
2
3
4
5
6
7
8
9
–
3.5
7
14
0.5
8.6
18.9
19.3
5.4
1.2
20.5
0.8
8
134
295
301
84
19
320
12
97
96.1
97
98.2
85.9
90.2
99.5
95.2
97
28
Pd(OAc)2/M.S. (1 g)
Pd(OAc)2/M.S. (1 g)+M.S. (7 g)
7 e
Na2SO4 (7 g)
0.4
6
a Phenol 0.5 mol, Pd(OAc)2 0.16 mmol, Mn(OAc)2 0.32 mmol, H3PW6Mo6O40 0.047 mmol, tetrabutylammonium bromide 3 mmol, 3 A powder
M.S. used, 8 atm, CO 500 ml min−1, O2 35 ml min−1, 80 °C, 3 h.
b GC yield based on charged phenol.
c TON based on Pd.
d DPC percentage in the products evaluated from the peak areas on GC and the products identified by GC-MS spectroscopy.
e 3 A pellets M.S. used.
dium catalyst is influenced greatly by the gas flow rate.
This is in good agreement with the report that high
TON of Pd is usually obtained under high pressure
(high gas concentration in the reaction solution) [3,8].
Probably, low gas flow rate of oxygen is insufficient for
the regeneration of the Pd(II) species in time.
decrease in the activity of the catalytic system; only
5.4% yield is obtained with 28 g M.S. (entry 5). A
decrease in the DPC yield by adding too many M.S. is
possibly because these M.S. make the molten phenol
very viscous, decreasing the chance of reoxidation of
Pd(0) by the cocatalyst. Using supported catalyst,
Pd(OAc)2–M.S., only 1.2% yield is obtained with
90.2% selectivity (entry 6). However, when combining
the supported catalyst with 7 g M.S., the yield can be
improved to 20.5% with 99.9% selectivity (entry 7).
Further, when powder M.S. is used in the reaction, less
than 1 ppm palladium could be detected in the reaction
solution after the reaction (entry 8), indicating that all
the palladium was precipitated to M.S. during the
course of the reaction. However, when 7 g pellets M.S.
are used as the dehydrating agent, yield is only 0.8%. In
addition, when anhydrous Na2SO4, which cannot act as
a support for Pd(OAc)2, is used as the dehydrating
agent, yield is only 0.4% (entry 9). This may be because
of the surface-active effects but may also simply be
because of the fact that it is a far less active dehydrating
agent than the fully activated M.S. All these results
clearly suggest that the M.S. acts both as a support to
Pd and as the dehydrating agent in the reaction.
2.6. Efficiency of salts of heteropolyacids as cocatalyst
Oxidative carbonylation of phenol with salts of het-
eropolyacids combined with Mn(OAc)2 as the bicompo-
nent cocatalyst has also been investigated. The results
are summarized in Table 4. Under the same reaction
conditions, activities of ammonium salts of hetero-
polysacids are generally higher than those of the hetero-
polyacids
as
the
cocatalysts
(entries
1–3).
(TBA)4SiW6Mo6O40 (TBA: tetrabutylammonium) as
one of the cocatalysts gives 22.7% yield of DPC with
TON of 354. At the gas flow rate of CO (670 ml
min−1) and O2 (47 ml min−1), yields can reach 41.2
2.5. Time course of oxidati6e carbonylation
Time course of oxidative carbonylation is shown in
Fig. 2. The DPC yield increases obviously with an
increasing the reaction time for the first 5 h after ehich
the yield increases slow down. After 9 h, a 31.7% yield
of DPC can be obtained with a TON of 495. Yield can
be improved to 37.3% with TON of 583 when the gas
flow rate is increased from CO (500 ml min−1) and O2
(35 ml min−1) to CO (670 ml min−1) and O2 (47 ml
min−1), which suggests that the efficiency of the palla-
Fig. 2. Time course of oxidative carbonation. Conditions: phenol (0.5
mol); Pd(OAc)2 (0.16 mmol); Mn(OAc)2 (0.32 mmol); H3PW6Mo6O40
(0.047 mmol); tetrabutylammonium bromide (3 mmol); M.S. (7 g);
pressure (8 atm); CO (500 ml min−1); O2 (35 ml min−1); 80 °C.

G. Yin et al. / Journal of Organometallic Chemistry 630 (2001) 11–16
15
Table 4
Oxidative carbonylation of phenol to DPC with various salts of heteropolyacids as a cocatalyst a
c
d
Entry
Salts of heteropolyacids
DPC yield (%) b
TON
DPC selectivity (%)
1
2
3
4
5
6
7
8
9
(TBA)3PW6Mo6O40
(TBA)4SiW6Mo6O40
(TBA)4SiWMo11O40
(TBA)3PW6Mo6O40
(TBA)4SiW6Mo6O40
20.8
22.7
20.8
29.5
41.2
43.8
53
10.5
11.7
10.3
325
354
325
460
643
684
827
164
175
161
99.2
99.5
99
98.9
99.4
99.7
99.8
99
e
e
e
(TBA)4SiWMo11O40
f
(TBA)4SiWMo11O40
g
PdHPW6Mo6O40
g
PdH2SiW6Mo6O40
PdH2SiMo12O40
97.4
98
g
10
a Phenol 0.5 mol, Pd(OAc)2 0.16 mmol, Mn(OAc)2 0.32 mmol, salt of heteropolyacid 0.047 mmol, tetrabutylammonium bromide 3 mmol, M.S.
7 g, 8 atm, CO 500 ml min−1, O2 35 ml min−1, 80 °C, 3 h.
b GC yield based on charged phenol.
c TON based on Pd.
d DPC percentage in the products evaluated from the peak areas on GC and the products identified by GC-MS spectroscopy.
e CO 670 ml min−1 and O2 47 ml min−1, 9 h.
f Tetrahydrofuran 15 ml added, CO 670 ml min−1 and O2 47 ml min−1, 9 h.
g Salt of heteropolyacid 0.16 mmol, without Pd(OAc)2.
Scheme 1. A possible mechanism for the oxidative carbonylation of phenol with CO and oxygen with Pd–Mn–HPA catalyst system.
proposed in Scheme 1. The Pd(II) species would be
reduced to Pd(0) during the DPC formation from two
molecules of phenol and one molecule of CO. The
Pd(0) thus formed would then be reoxidized by Mn(III)
to form Pd(II) and Mn(II), and in turn Mn(II) would
be reoxidized to Mn(III) by heteropolyacid (HPA-n)
which is thus reduced to H2(HPA-n). Finally, H2(HPA-
n) would be oxidized to HPA-n by O2.
and 43.8% with TON of 643 and 684 after 9 h, when
(TBA)4SiW6Mo6O40 and (TBA)4SiWMo11O40 were used
as the cocatalysts, respectively (entries 5 and 6). Fur-
ther, the yield of DPC can be improved up to 53% with
TON of 827 when 15 ml tetrahydrofuran are added as
the solvent in the reaction mixture (entry 7). Probably,
tetrahydrofuran added as the solvent can decrease the
viscosity of the reaction solution and increase the
chance of regeneration of the active Pd species by the
cocatalyst. To the best of our knowledge, the present
catalytic system is the first one in which heteropolyacids
(HPA) are used as the cocatlysts to give good results in
the synthesis of DPC, and the efficiency of present
catalytic system is higher than most of the reported
catalytic systems for the oxidative carbonylation. Fur-
ther, in this system, higher yield of DPC with a higher
efficiency of Pd is attained under low pressure. How-
ever, low yields were obtained when palladium salts of
heteropolyacids are used as the catalysts (entries 8–10).
3. Conclusions
Heteropolyacids, combined with Mn(OAc)2 as the
bicomponent cocatalyst, were found to assist in the
oxidative carbonylation of phenol with CO and oxygen
to diphenyl carbonate (DPC) with Pd(OAc)2 as the
catalyst under low pressure and in the absence of
solvent. The efficient synergistic effect for regenerating
the Pd(II) species from Pd(0) is observed when some
heteropolyacids are combined with Mn(OAc)2 as the
bicomponent cocatalyst. Tetrabutylammonium bromide
and M.S. are essential for the efficient oxidative car-
bonylation, and M.S. act as both the dehydrating agent
and a support for palladium. Tetrabutylammonium
salts of heteropolyacids usually show higher efficiencies
in regenerating the Pd(II) species than heteropolyacids,
respectively. Under the present conditions, 53% yield of
2.7. Multistep electron transfer catalytic cycle
The results in Table 1 show that there is a synergistic
effect existing between some heteropolyacids and
Mn(OAc)2 for the regeneration of the Pd(II) species. A
possible mechanism of the multistep electron transfer is

16
G. Yin et al. / Journal of Organometallic Chemistry 630 (2001) 11–16
DPC based on phenol can be obtained with a Pd TON
of 827.
Acknowledgements
Guochuan Yin and Chengguo Jia thank the Japan
Society for the Promotion of Science for the research
fellowships (Nos. P99108 and P98430).
4. Experimental
Salts of heteropolyacids were gifted generously from
Teijin Ltd. All other reagents were obtained from com-
mercial sources and used as received. Molecular sieves
(M.S.) were activated at 450 °C in air for 10 h before
use. All the reactions are run in a flow system.
References
[1] D. Freitag, U. Grico, P.R. Muller, W. Nouvertne, in: H.F. Mark
(Ed.), Polycarbonate in Encyclopedia of Polymer Science and
Engineering, vol. 11, Wiley, New York, 1987 (649pp.).
[2] J.E. Hallgren, G.M. Lucas, J. Organomet. Chem. 212 (1981) 135.
[3] M. Takagi, H. Miyagi, T. Yoneyama, Y. Ohgomori, J. Mol.
Catal. A 129 (1998) L1.
[4] M. Goyal, R. Nagahata, J. Sugiyama, M. Asai, M. Ueda, K.
Takeuchi, Catal. Lett. 54 (1998) 29.
[5] H. Ishii, M. Ueda, K. Takeuchi, M. Asai, J. Mol. Catal. 144
(1999) 369.
A typical reaction procedure is as follows: Pd(OAc)2
0.036 g (0.16 mmol), Mn(OAc)2·4H2O 0.078 g (0.32
mmol), heteropolyacid 0.047 mmol, tetrabutylammo-
nium bromide 1 g (3 mmol), 3 A powder M.S. 7 g and
hot phenol 47 g (0.5 mol) were charged in a 100 ml
stainless steel autoclave which was kept at 60 °C. The
autoclave was then sealed. With mechanical stirring at
800 rpm, a gas mixture (6.5 mol% O2 and 93.5 mol%
CO) was introduced into the autoclave at a flow rate of
535 ml min−1 and the autoclave was heated to 80 °C.
The pressure of the autoclave was kept at 8 atm with
continuous gas flow for the desired time. After the
reaction, the pressure was reduced to the atmospheric
pressure, and the gas mixture was exchanged with
nitrogen. Next, the hot reaction solution was removed
into a receiver and 30 ml EtOAc were used to wash the
autoclave. Finally, the solutions were combined and
analyzed by GC with a capillary column (DB-1, 15
m×¥ 0.53 mm, J & W Scientific). The products were
identified by GC-MS spectra. The major side products
were phenysalicylate and 4-phenoxy phenol. The yield
of DPC is based on the charged phenol and determined
by GC using diphenyl as an internal standard and is
listed in the tables. The selectivity is based on the DPC
percentage in the products evaluated from the peak
areas on the GC chart.
[6] M. Goyal, R. Nagahata, J. Sugiyama, M. Asai, M. Ueda, K.
Takeuchi, J. Mol. Catal. A 137 (1999) 147.
[7] A. Vavasori, L. Toniolo, J. Mol. Catal. A 139 (1999) 109.
[8] E.J. Pressman, S.J. Shafer, US Patent 5,898,079 (1999).
[9] H. Kezuka, F. Okuda, JP open (1995) 39247.
[10] H. Buysch, C. Hesse, J. Jentsch, J. Rechner, E. Zirngiebl, Eur.
Patent 0,736,324 A2 (1996).
[11] J. Tsuji, Palladium Reagents and Catalysts, Wiley, New York,
1995.
[12] N. Mizuno, M. Misono, Chem. Rev. 98 (1998) 199.
[13] K. Bergstad, H. Grennberg, J. Ba¨ckvall, Organometallics 17
(1998) 45.
[14] D. Piao, K. Inoue, H. Shibasaki, Y. Taniguchi, T. Kitamura, Y.
Fujiwara, J. Organomet. Chem. 116 (1999) 574.
[15] G.C. Yin, C.G. Jia, T. Kitamura, T. Yamaji, Y. Fujiwara, Catal.
Lett. 69 (2000) 89.
[16] H. Ogawa, H. Fujinami, K. Taya, S. Teratani, Bull. Chem. Soc.
Jpn. 57 (1984) 1908.
[17] K. Urabe, F. Kimura, Y. Izumi, Proc. Int. Congr. Catal. (1981)
1418.
[18] H. Buysch, C. Hesse, J. Jentsch, J. Rechner, E. Zirngiebl,
European Patent 0,736,325 A2 (1996).
.