Table 1 Hydroesterification of vinyl acetatea
Run
Acid
Conv.b (%)
Ester yieldc (%)
Ester distribution 2b/2b9/2n/2n9
Acetal yield (%)
1
2
a
Wang resin–SO3Hd
CH3SO3H
91
100
70.4
60.8
72.2/0.2/27.2/0.2
66.4/5.9/21.7/5.9
4.8
21.0
Procedure and conditions: Vinyl acetate 10 mmol, MeOH 1.0 mL, Pd2(dba)3 0.01 mmol (0.02 mmol with respect to Pd), DTBPMB
0.02 mmol, acid 0.092 mmol, initial CO pressure 6 kg cm22, 60 uC, 1.5 h. Conversion of vinyl acetate. Total yield of 2b, 2b9, 2n and 2n9.
b
c
d
Derived from Argonaut 800351 Wang resin. SO3H content 5 0.37 mmol g21 (by ICP analysis) for this particular sample.
Table 2 Reaction of vinyl acetate: Catalyst recyclinga
Ester TON for Ester distribution Acetal
Recycle yield (%) esters 2b/2b9/2n/2n9 yield (%)
could be successfully extended to vinyl acetate (Table 1). Thus
hydroesterification of vinyl acetate with methanol in the presence
of the Argonaut 800351-derived sulfonic acid gave 70% carbonyla-
tion yield (2b + 2b9 + 2n + 2n9) with a very minor extent of
methanolysis that afforded hydroxyl esters (2b9, 2n9) as compared
with the reaction using CH3SO3H. In addition, the formation of
the acetal byproduct was also suppressed.
Pristine 82.1
32.8 6 102 76.2/0.6/22.7/0.5
35.8 6 102 72.1/0.6/26.6/0.7
33.4 6 102 74.6/0.4/24.7/0.3
33.9 6 102 73.8/0.4/25.3/0.4
5
6
4
5
1
2
3
a
89.4
83.5
84.9
Procedure and conditions: Vinyl acetate 40 mmol, MeOH 4.0 mL,
The resin–Pd complex recovered by stripping the volatiles
retains the activity to allow repeated use as summarized in Table 2,
suggestive of the stability of the catalyst system.
Pd2(dba)3 0.005 mmol (0.01 mmol with respect to Pd), DTBPMB
0.01 mmol, Wang resin-SO3H (derived from Argonaut 800351 Wang
resin) 0.048 mmol, initial CO pressure 10 kg cm22, 40 uC, 24 h.
In summary, this communication discloses the high performance
of the DTBPMB ligand and favorable effect of the polymeric
sulfonic acid resin of low loading of the SO3H functionality to
synthesize branched esters starting with styrene and vinyl acetate.
The research was conducted under the entrustment contact
between the New Energy and Industrial Technology Development
Organization and the Japan Chemical Innovation Institute.
groups may interact with the palladium species to prevent the
H–Pd species formation or coordination of the phosphine ligand.7
Since PS–SO3H-30 and -100 were synthesized by treating
commercial polystyrene beads with chlorosulfonic acid in dichloro-
methane, the sulfonation may not have uniformly proceeded. To
further confirm the effect of acid density, we prepared another type
of polymeric sulfonic acids by the reaction of Wang resins with
propanesultone (Scheme 3), which is envisioned to afford more
uniformly sulfonated resins.§
Hirohito Ooka,*a Tsutomu Inoue,a Shinichi Itsunob and
Masato Tanaka*c
aOdawara Research Center, Nippon Soda Co. Ltd., 345 Takada,
Odawara, Kanagawa 250-0280, Japan.
The reaction of styrene (styrene 20 mmol, MeOH 2.0 mL,
Pd2(dba)3 (0.01 mmol with respect to Pd metal), DTBPMB 5
0.01 mmol, CO 5 6 atm, room temperature, 18 h) was carried out
in the presence of a new resin derived from Algonaut 800351
Wang resin (0.25 g corresponding to 0.13 mmol of SO3H;
SO3H/Pd 5 13) to give 97% yield of the esters with selectivity for
1b of 86%. Likewise another resin derived from Aldrich 47703-6
Wang resin (0.25 g corresponding to 0.053 mmol of SO3H;
SO3H/Pd 5 5.3) gave 95% yield and 87% 1b selectivity.
E-mail: h.oooka@nippon-soda.co.jp; Fax: +81(0)465 422180;
Tel: +81(0)465 423511
bDepartment of Materials Science, Toyohashi University of Technology,
1-1 Hibarigaoka, Tenpakucho, Toyohasi 441-8580, Japan
cChemical Resources Laboratory, Tokyo Institute of Technology,
4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
E-mail: m.tanaka@res.titech.ac.jp; Fax: +81(0)45 924 5279;
Tel: +81(0)45 924 5244
Notes and references
Vinyl acetate has been a substrate that does not conform to
hydroesterification successfully since the reaction usually accom-
panies side reactions such as alcoholysis of the acetate functionality
and the formation of acetals coming from acetaldehyde.3 Very
recently a patent application has disclosed a new catalyst system
that can circumvent these drawbacks by using a limited quantity of
a sulfonic acid promoter in conjunction with DTBPMB ligand.3c
We have found that the new procedure of hydroesterification using
the polymeric sulfonic acids, DTBPMB and a palladium complex
{ The reaction did not work under the same conditions in the absence of
acid promoters. Camphor- and p-toluene-sulfonic acids used in place of
methanesulfonic acid displayed similar activity and selectivity, but the
performance of trifluoromethanesulfonic acid was much poorer.
{ Synthesis of PS–SO3H-30 and -100: To a suspension of 1 g of commercial
polystyrene crosslinked with 1% divinylbenzene (50–100 mesh) in
dichloromethane was added a solution of 30 or 100 mL of chlorosulfonic
acid in dichloromethane (5 mL) at 0 uC and the mixture was stirred for
30 min at room temperature. After overnight standing, the mixture was
treated with acetic acid (1.0 mL) and was filtered. The resulting resin was
washed successively with water, tetrahydrofuran and dichloromethane and
was dried at room temperature.
§ Synthesis of Wang resin–SO3H: A sample of Algonaut 800351 Wang
resin (2.0 g, OH loading 5 1.22 mmol g21) was added to a suspension of
sodium hydride (4.9 mmol; washed with hexane (2 mL, three times)) in
N-methylpyrrolidone (20 mL). After heating the mixture for 1 h at 60 uC,
propanesultone (12.2 mmol) was added and the mixture was further heated
for another 60 min at the same temperature, left to stand overnight and was
treated with methanol. The filtered off resin was washed successively with
Scheme 3 Derivation of a Wang resin to the corresponding sulfonic acid.
1174 | Chem. Commun., 2005, 1173–1175
This journal is ß The Royal Society of Chemistry 2005