1974
K. Tanemura, T. Suzuki / Tetrahedron Letters 54 (2013) 1972–1975
Table 6
reaction of 4-phenylbutyric acid with benzyl alcohol gave benzyl
4-phenylbutyrate (65%) and dibenzyl ether (23%) (entry 12). The
reactions with secondary alcohols afforded the undesired alkenes
as well as the corresponding esters (entries 15 and 16). Relatively
sterically crowded benzoic acid, pivalic acid, phenol, and 1-
adamantanol were also converted into the corresponding esters
in good yields (entries 13, 14, 17, and 18).
For these reactions, the hydrolysis of the produced esters was
restricted. The irreversibility of esterification was confirmed by
the following experiment. A mixture of octyl 3-phenylpropionate
(2 mmol), water (20 mmol), and S-PPR (50 mg) in heptane (4 mL)
was heated at 110 °C. After 2 h, the starting material was recovered
in 90%. A large amount of the recovery of the octyl ester is a con-
sequence of the structure of S-PPR. The hydrophobic surface of pyr-
ene units of S-PPR prevents the approach of water molecules to
catalytically important SO3H groups.
Recycle experiments for esterification of 3-phenylpropionic acid and transesterifica-
tion of methyl 3-phenylpropionate
Entry
Yieldsa (%)
3rd
1st
2nd
4th
5th
1b
2c
3d
4e
98
90
97
88
99
94
81
92
99
93
59
90
99
91
40
89
98
90
23
89
a
Isolated yields.
b
Reagents and conditions: 3-phenylpropionic acid 2.0 mmol, 1-octanol
2.0 mmol, heptane 4 mL, S-PPR 50 mg, temp. 110 °C, 2 h.
c
Reagents and conditions: 3-phenylpropionic acid 2.0 mmol, 1-octanol
2.0 mmol, S-PPR 50 mg, temp. 110 °C, 2 h.
d
Reagents and conditions: methyl 3-phenylpropionate 2.0 mmol, 1-octanol
3.0 mmol, heptane 4 mL, S-PPR 100 mg, temp. 110 °C, 4 h.
e
Reagents and conditions: methyl 3-phenylpropionate 2.0 mmol, 1-octanol
3.0 mmol, S-PPR 100 mg, temp. 110 °C, 4 h.
Esterification was also carried out without heptane to give
the corresponding esters in good to excellent yields as shown in
Table 4.
Next, we examined transesterification of carboxylic esters with
alcohols in the presence of S-PPR. The results are summarized in
Table 5. The reaction of methyl 3-phenylpropionate with 1.5 equiv.
of 1-octanol gave octyl 3-phenylpropionate in 97% yield (entry 1).
When 1.0 equiv. of 1-octanol was employed, the yield was reduced
(8 h, 84%) (entry 2). The reactions of various carboxylic esters with
alcohols afforded the corresponding esters in good yields (entries
3–9).25 Transesterification without the solvent gave the corre-
sponding esters in good yields (entries 10–15).27
was recycled without significant loss of activities with and without
heptane for esterification of carboxylic acids with alcohols (Table 6,
entries 1 and 2). On the other hand, activities of S-PPR gradually
decreased on recycling for transesterification in heptane (entry
3). The IR spectrum showed that SO3H groups of S-PPR were ester-
ified by the produced MeOH. The intensity of the characteristic
absorption at 3421 cmÀ1 assigned to OH vibration of the SO3H
groups decreased and the new absorptions at 2920, 2850, 1457,
and 1362 cmÀ1 due to the methyl groups appeared. For transeste-
rification without heptane, S-PPR was recycled without significant
loss of activities (entry 4).
In order to check the reusability of the catalyst, S-PPR was
removed by filtration and used for the next experiment. S-PPR
In conclusion, we devised the efficient procedure for esterifica-
tion of carboxylic acids with equimolar amounts of alcohols with
and without heptane. In addition, transesterification of carboxylic
esters with alcohols was carried out under neat conditions. For
these reactions, S-PPR can be easily recovered by filtration and
reused. The dehydrating system such as a Dean-Stark apparatus
is not necessary. Activities of S-PPR were higher than those of con-
ventional sulfonated polymers such as Amberlyst 15 and Nafion
NR50. From these features, this method will become an environ-
mentally benign procedure.
Table 5
Transesterification between various esters and alcohols catalyzed S-PPR with and
without heptanea
Entry Ester
Alcohol
Times
(h)
yieldb
(%)
COOMe
1
2c
n-C8H17OH
4
8
97
84
Ph
COOMe
COOMe
COOMe
COOMe
OH
3
8
24
16
88
77
91
Ph
Ph
Cl
OH
OH
4d
Ph
Acknowledgment
5d
Ph
We thank the Research Promotion Grant (NDUF-12-11) from
Nippon Dental University.
6
n-C8H17OH
n-C8H17OH
12
24
91
84
References and notes
7e
COOMe
COOEt
1. Ishihara, K. Tetrahedron 2009, 65, 1085–1109.
8
n-C8H17OH
n-C8H17OH
6
97
87
Ph
2. Franklin, A. S. J. Chem. Soc. Perkin Trans. 1 1998, 2451–2465.
3. Franklin, A. S. J. Chem. Soc. Perkin Trans. 1 1999, 3537–3554.
4. Manabe, K.; Sun, X.-M.; Kobayashi, S. J. Am. Chem. Soc. 2001, 123, 10101–10102.
5. Ishihara, K.; Ohara, S.; Yamamoto, H. Science 2000, 290, 1140–1142.
6. Saigo, K.; Usui, M.; Kikuchi, K.; Shimada, E.; Mukaiyama, T. Bull. Chem. Soc. Jpn.
1977, 50, 1863–1866.
7. Shiina, I.; Mukaiyama, T.; Miyoshi, S.; Miyashita, M. Chem. Lett. 1994, 515–518.
8. Izumi, J.; Shiina, I.; Mukaiyama, T. Chem. Lett. 1995, 141–142.
9. Otera, J.; Dan-oh, N.; Nozaki, H. J. Org. Chem. 1991, 56, 5307–5311.
10. Wakasugi, T.; Misaki, T.; Yamada, K.; Tanabe, Y. Tetrahedron Lett. 2000, 41,
5249–5252.
9
n-C3H7COOEt
14
COOMe
COOMe
COOMe
COOMe
10f
n-C8H17OH
4
8
88
84
82
Ph
Ph
Ph
OH
11f
Ph
12d,f
16
OH
13f
n-C8H17OH
12
93
COOEt
14f
15f
n-C8H17OH
n-C8H17OH
6
92
87
11. Iida, A.; Osada, J.; Nagase, R.; Misaki, T.; Tanabe, Y. Org. Lett. 2007, 9, 1859–
1862.
Ph
n-C3H7COOEt
14
12. Gacem, B.; Jenner, G. Tetrahedron Lett. 2003, 44, 1391–1393.
13. Ishihara, K.; Nakagawa, S.; Sakakura, A. J. Am. Chem. Soc. 2005, 127, 4168–4169.
14. Sakakura, A.; Nakagawa, S.; Ishihara, K. Tetrahedron 2006, 62, 422–433.
15. Recent reports by Ishihara et al. (a) Sakakura, A.; Koshikari, Y.; Ishihara, K.
Tetrahedron Lett. 2008, 49, 5017–5020; (b) Sakakura, A.; Koshikari, Y.; Akakura,
M.; Ishihara, K. Org. Lett. 2012, 14, 30–33; (c) Koshikari, Y.; Sakakura, A.;
Ishihara, K. Org. Lett. 2012, 14, 3194–3197.
a
Reagents and conditions: ester 2.0 mmol, alcohol 3.0 mmol, heptane 4 mL, S-
PPR 100 mg, temp. 110 °C.
b
Isolated yield.
2.0 mmol, 1-octanol was used.
The reaction was conducted at 80 °C.
S-PPR 200 mg.
c
d
e
16. Liu, Y.; Lotero, E.; Goodwin, J. G., Jr. J. Catal. 2006, 242, 278–286.
17. Gelbard, G. Ind. Eng. Chem. Res. 2005, 44, 8468–8498.
f
Without heptane.