Palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of benzylic alcohols with phenols

Article abstract of DOI:10.1016/j.tet.2011.06.060

A palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of benzylic alcohols with phenols to access aryl benzoate derivatives is described. The procedure tolerates a series of functional groups, such as methoxy, nitro, cyano, chloro, fluoro and bromo groups. Thus, it represents a practically alternative method to access aryl benzoate derivatives.

Full text of DOI:10.1016/j.tet.2011.06.060

Tetrahedron 67 (2011) 5878e5882
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification
of benzylic alcohols with phenols
a
b
a
a,
*
Fang Luo , Changduo Pan , Jiang Cheng , Fan Chen
a
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, PR China
Wenzhou Institute of Industry and Science, Wenzhou, 325000, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 May 2011
Received in revised form 10 June 2011
Accepted 21 June 2011
Available online 25 June 2011
A palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of benzylic alcohols with
phenols to access aryl benzoate derivatives is described. The procedure tolerates a series of functional
groups, such as methoxy, nitro, cyano, chloro, fluoro and bromo groups. Thus, it represents a practically
alternative method to access aryl benzoate derivatives.
Ó 2011 Elsevier Ltd. All rights reserved.
1
. Introduction
attention has been paid to the synthesis of aryl benzoate derivatives
despite their importance as building blocks of numerous active
13,14
Esterification is one of the most fundamental and important
compounds.
Very recently, we developed a palladium/NHC-
1
15
reactions in organic synthesis. Although several methods have
catalyzed oxidative esterification of aldehydes with phenols. Lei
been exploited and developed, the search for new environmentally
friendly, atom-efficient methods, which avoid the use of large
amounts of condensing reagents and activators have attracted in-
and Beller developed palladium-catalzyed aerobic oxidative ester-
16
ification of benzylic alcohols, respectively. Herein, we report
a palladium/NHC-catalyzed tandem oxidation/aromatic esterifica-
tion of benzylic alcohols with phenols to access aryl benzoate de-
2
creasing interest. From the atom-economic point of view, the ox-
idative couplings from aldehydes to access esters have received
much attention. However, long-term storage and use of aldehydes
2
rivatives, using O as the clean terminal oxidant.
3
may be troublesome due to their inherent reactivity. An attractive
alternative is the direct catalytic oxidation of alcohols to esters.
2. Result and discussion
4
Corey detailed the two-step oxidation of allylic alcohols to esters
Initial studies were performed by using the reaction of phe-
nylmethanol with 4-nitrophenol under oxygen as the model re-
action, employing Pd(OAc) as the catalyst (Table 1). Only a trace of
5
6
2
in the presence of sodium cyanide and MnO . Chromium and
7
iodine have also been reported to oxidize alcohols to esters.
However, a large excess or stoichiometric amount of a toxic oxidant
was required in the above transformations. In 1987, Murahashi
described a ruthenium-catalyzed oxidative transformation of al-
2
the product was formed in the absence of ligand as determined by
GCeMS (Table 1, entry 1). Various precursors of N-heterocyclic
carbene (NHC) (Fig. 1) were investigated for this reaction. To our
delight, an excellent yield was obtained with L5 (Table 1, entry 6).
When the reaction was carried out under nitrogen, no product was
detected by GCeMS (Table 1, entry 8). This result suggested that the
oxygen played a significant role in the reaction. The choice of sol-
vent was also crucial to the reaction and xylene appeared to be the
best among the solvents (Table 1, entries 6 and 9e11). Moreover,
the base used also had an important effect in the reaction and
8
cohols and aldehydes to esters and lactones. In 2002, Hiroi de-
veloped an oxidative lactonization of 1,4- or 1,5-diols catalyzed by
a novel Ir catalyst.9 Subsequently, Hartwig and Ikariya reported
ruthenium-catalyzed dehydrogenative cyclization of 1,4-diols to
lactones, respectively10 Milstein designed a novel ruthenium
complexes to catalyze dehydrogenation of primary alcohols to es-
ꢀ
11
ters or acetals using a harsh condition (>150 C). Recently, Scheidt
demonstrated a tandem oxidation of alcohols to esters using N-
Na
product was detected by GCeMS in the absence of Pd(OAc)
, entry 6). Conducting the reaction on a 2 mmol scale provided 3aa
in an acceptable 89% yield.
2
CO
3
proved to be the best. In addition, only a trace of the
12
heterocyclic carbenes as catalysts,
which required super-
2
(Table
stoichiometric amounts of MnO as the oxidant. Thus, to develop
2
1
a facile and versatile procedure on such transformation still re-
mains a highly desired goal for organic chemists. Moreover, less
Encouraged by these results, we further pursued the scope of
the process with respect to the phenols. As expected, the reaction
proceeded smoothly with yields ranging from good to excellent and
tolerated various functional groups, such as methoxy, nitro, cyano,
*
Corresponding author. E-mail address: fanchen@wzu.edu.cn (F. Chen).
0
040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.06.060

F. Luo et al. / Tetrahedron 67 (2011) 5878e5882
5879
Table 1
Table 2
Selected results of screening the optimal conditions
Palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of
phenylmethanol with phenols
O
Pd(OAc)
2
, Ligand
R2
+
HO
NO2
OH
base, solvent
O
NO
2
O
Pd(OAc)
2
, L5
2
CH OH
+
1a
2a
3aa
OH
Na CO , xylene, O
2
3
2
O
R
2
Yielda (%)
1a
2
3
Entry
Ligand
Base
Solvent
1
2
3
4
5
6
7
8
9
d
L1
L2
L3
L4
L5
L5
L5
L5
L5
L5
L5
L5
L5
L5
L5
L5
Na
Na
Na
Na
Na
Na
Na
Na
Na
Na
Na
Na
2
2
2
2
2
2
2
2
2
2
2
2
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
3
3
3
3
3
3
Xylene
Xylene
Xylene
Xylene
Xylene
Xylene
Xylene
Xylene
Xylene
DMF
Toluene
1,4-Dioxane
Xylene
Xylene
Xylene
Xylene
Xylene
Trace
10
16
65
82
Entry
Phenol 2
Product 3
Yielda (%)
95
1
2
95
Trace
81
<5
b
c
O
O
F
d
F
OH 2b
3ab
3ac
3ad
3ae
3af
93
91
89
60
70
75
61
64
82
35
10
11
12
13
14
15
16
17
<5
43
30
61
<5
53
43
41
O
O
Cl
K
Cs
2
CO
CO
3
3
4
5
6
7
8
9
2c
Cl
OH
2
3
NaHCO
t-BuOK
d
3
OH
O
2d
a
Cl
O
Cl
All reactions were run with 4-nitrophenol 2a (0.2 mmol), phenylmethanol 1a
(
0.3 mmol), base (0.1 mmol, 0.5 equiv), Pd(OAc)
2
(5 mol %) and ligand (10 mol %) in
ꢀ
dry solvent (2 mL) under O
2
at 130 C for 36 h. Isolated yields.
OH
O
O
b
2e
In the absence of Pd(OAc)
Under air.
2
.
c
Br
Br
d
2
Under N .
O
O
CN
NC
OH 2f
N
N
N
N
N
N
O
O
OH 2g
OH 2h
OH 2i
3ag
3ah
3ai
Cl
L1
Cl
Cl
L3
L2
O
O
N
N
N
N
O
O
OMe
BF
4
L4
Cl
L5
MeO
Fig. 1. Selected imidazolium salts screened.
MeO
O
O
1
1
0
1
2j
3aj
OH
OMe
MeO
chloro, fluoro and bromo groups. Particularly, halogen-substituted
phenols worked well, albeit a lower yield was obtained for bro-
mine (Table 2, entries 2e5). The surviving halogen atom (X¼Cl, Br)
could be valuable for further manipulation. Generally, electron-
deficient phenols reacted with phenylmethanol easily and gave
the products in higher yields than electron-rich phenols (e.g., 2a,
b, 2c and 2d vs 2h, 2i, 2j and 2k). Steric hindrance on phenols with
electron-withdrawing groups had no obvious effect on the reaction
Table 2, entries 3 and 4). Nevertheless, the hindrance on phenols
had a sharp effect on the reaction for those electron-rich analogues
Table 2, entries 9e11). For example, 3ak was obtained in only 35%
OH 2k
3ak
O
OMe
O
12
2l
O
O
3al
88
OH
2
a
Reaction conditions: 1a (0.3 mmol), 2 (0.2 mmol), Pd(OAc)2 (5 mol %), L5
ꢀ
(
(10 mol %) and Na
Isolated yield.
2
CO
3
(0.1 mmol) in dry xylene (2 mL) under O
2
at 130 C for 36 h.
(
yield when 2k was subjected to the procedure.
Next, we turned our attention to the scope of benzylic alcohols,
and the results are shown in Table 3. Once again, the reaction
proceeded smoothly with moderate to good yields and tolerated
various functional groups, such as nitro, cyano, chloro, fluoro,
trifluoromethyl and methoxycarbonyl groups. Generally, the ben-
zylic alcohols possessing electron-withdrawing groups gave
slightly higher yields than those of electron-donating groups
More experiments were carried out to gain preliminary in-
sight into the reaction mechanism. Conversion of benzylic al-
cohol to the aromatic aldehyde was observed under the
standard procedure by GCeMS. Moreover, when naphthalen-1-
ylmethanol 1f was subjected to the standard procedure with-
out L5, 1-naphthaldehyde was isolated in 70% yield (Scheme
1). These results could disclose the possibility of a tandem
oxidation of benzylic alcohol to aromatic aldehyde followed by
an esterification pathway. However, the mechanism in detail
kept unclear in current stage.
18
(
Table 3, entries 9e14). It is worth noting that a saturated ester
was obtained when allyl alcohol was subjected to the procedure
Table 3, entry 14).17
(

5880
F. Luo et al. / Tetrahedron 67 (2011) 5878e5882
Table 3
CH OH
2
CHO
Palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of
benzylic alcohols with phenols
Pd(OAc) (5 mol %)
2
O
2
Pd(OAc) , L5
Na CO3 (0.5 equiv)
ArCH
2
OH
+
OH
Ar
2
Na CO , xylene, O
2
3
2
O
O , xylene
R
a or 2g
2
R
1
3
1f
2
70% yield
Yielda (%)
Scheme
1. Pd(OAc)
2
-catalyzed
oxidation
of
naphthalen-1-ylmethanol
to
Entry
1
Substrate 1
Product 3
1-naphthaldehyde by molecular oxygen.
82
52
alcohols with phenols to access aryl benzoate derivatives. It obvi-
ates the employment of cyanide and super-stoichiometric amounts
of MnO
2 2
. This operationally simple one-pot process uses O as the
2
clean oxidant, producing esters in good to excellent yields.
4
4
. Experimental section
.1. General procedure
3
4
5
80
60
82
1H NMR and 13C NMR spectra were measured on a 500 MHz
1
13
Bruker spectrometer ( H 500 MHz, C 125 MHz), using CDCl
solvent with tetramethylsilane (TMS) as the internal standard at
room temperature. Chemical shifts ( ) are given in parts per million
3
as the
d
relative to TMS, the coupling constants J are given in hertz. Column
chromatography was performed using EM Silica gel 60
(300e400 mesh).
6
7
8
9
83
78
46
80
82
4
.2. Typical experimental procedure of palladium/NHC-
catalyzed tandem benzylic oxidation/oxidative esterification
of benzylic alcohols with phenols
Under oxygen, a reaction tube was charged with phenols
2
(0.2 mmol), benzylic alcohols (0.3 mmol), Pd(OAc) (2.2 mg,
1e
5
mol %), L5 (8.5 mg, 10 mol %), Na
2
CO
3
(10.6 mg, 0.1 mmol) in dry
ꢀ
xylene (2 mL). After the mixture was stirred for 36 h at 130 C, the
solvent was evaporated under reduced pressure and the residue
was purified by flash column chromatography on silica gel to give
the product.
1
0
4
.3. Analytical data of products
4
.3.1. 4-Nitrophenyl benzoate (3aa)19. Pale yellow solid. 1H NMR
(
(
(
CDCl
t, J¼7.5 Hz, 1H), 7.59e7.56 (m, 2H), 7.45 (d, J¼9.0 Hz, 2H). C NMR
CDCl , 125 MHz): 164.2, 155.7, 145.4, 134.2, 130.3, 128.8, 128.6,
3
, 500 MHz):
d
8.36 (d, J¼9.0 Hz, 2H), 8.24e8.22 (m, 2H), 7.71
1
1
1
1
2
3
76
65
61
13
3
d
1
25.3, 122.6.
4
.3.2. 4-Fluorophenyl benzoate (3ab)14h. White solid. 1H NMR
, 500 MHz):
8.19 (d, J¼7.7 Hz, 2H), 7.64 (t, J¼7.4 Hz, 1H), 7.51
(t, J¼7.4 Hz, 2H), 7.19e7.17 (m, 2H), 7.12e7.09 (m, 2H). C NMR
CDCl , 125 MHz):
165.2, 160.3 (d, JCeF¼242.8 Hz), 146.8 (d,
CeF¼2.8 Hz), 133.7, 130.2, 129.3, 128.6, 123.1 (d, JCeF¼8.4 Hz), 116.1
d, JCeF¼23.4 Hz).
(CDCl
3
d
13
(
J
(
3
d
1
4
67
4
(
.3.3. 4-Chlorophenyl benzoate (3ac)20. White solid. 1H NMR
CDCl , 500 MHz):
3
d
8.19 (d, J¼7.5 Hz, 2H), 7.66e7.63 (m, 1H),
a
Reaction conditions: 1 (0.3 mmol), 2 (0.2 mmol), Pd(OAc)
CO (0.1 mmol) in dry xylene (2 mL) under O
2
(5 mol %), L5
at 130 C for 36 h.
13
7
.53e7.50 (m, 2H), 7.40 (d, J¼8.0 Hz, 2H), 7.17 (d, J¼8.0 Hz, 2H).
C
ꢀ
(
10 mol %) and Na
2
3
2
NMR (CDCl
3
, 125 MHz):
d
165.0, 149.4, 133.8, 131.3, 130.2, 129.6,
Isolated yield.
129.2, 128.6, 123.1.
3
. Conclusions
.3.4. 2-Chlorophenyl benzoate (3ad) . White solid. 1H NMR
, 500 MHz): 8.25e8.24 (m, 2H), 7.68e7.65 (m, 1H),
7.55e7.49 (m, 3H), 7.36e7.33 (m, 1H), 7.30e7.28 (m, 2H). C NMR
21
4
In conclusion, we have developed a palladium/NHC-catalyzed
tandem benzylic oxidation/oxidative esterification of benzylic
(CDCl
3
d
13

F. Luo et al. / Tetrahedron 67 (2011) 5878e5882
5881
(
1
CDCl
27.1, 123.9.
3
, 125 MHz):
d
164.3, 147.3, 133.9, 130.4, 128.9, 128.7, 127.8,
2H), 1.30 (t, J¼7.5 Hz, 3H). 13C NMR (CDCl
3
, 125 MHz):
d
164.3, 155.9,
151.5, 145.3, 130.5, 128.3, 126.0, 125.2, 122.7, 29.1, 15.2.
4
.3.5. 3-Bromophenyl benzoate (3ae)22. White solid. 1H NMR
, 500 MHz):
8.19 (d, J¼7.5 Hz, 2H), 7.67e7.64 (m, 1H),
.54e7.51 (m, 2H), 7.42e7.41 (m, 2H), 7.32e7.29 (m, 1H), 7.19e7.17
4.3.16. 4-Nitrophenyl 4-methoxybenzoate (3ea)25. Pale yellow solid.
1
(
CDCl
3
d
H NMR (CDCl
3
, 500 MHz):
d
8.25 (d, J¼9.0 Hz, 2H), 8.08 (d,
7
(
J¼9.0 Hz, 2H), 7.33 (d, J¼9.0 Hz, 2H), 6.94 (d, J¼9.0 Hz, 2H), 3.84 (s,
m, 1H). 13C NMR (CDCl
d
164.7, 151.4, 133.9, 130.5,
3H). C NMR (CDCl
13
3
, 125 MHz):
3
, 125 MHz): d 164.4, 163.9, 156.0, 145.3, 132.5,
130.2, 129.1, 128.7, 125.3, 122.5, 120.6.
125.2, 122.7, 120.7, 114.1, 55.6.
1
4.3.17. 4-Nitrophenyl 1-naphthoate (3fa)28. White solid. 1H NMR
(CDCl , 500 MHz):
9.01 (d, J¼8.5 Hz, 1H), 8.50e8.35 (m, 3H),
8.21e8.15 (m, 1H), 7.96e7.94 (m, 1H), 7.70e7.47 (m, 5H). C NMR
(CDCl , 125 MHz): 164.6, 155.8, 145.5, 135.2, 134.0, 131.8, 131.7,
4
.3.6. 4-Cyanophenyl benzoate (3af)23. Pale yellow solid. H NMR
(
CDCl
3
, 500 MHz):
d
8.12 (d, J¼8.0 Hz, 2H), 7.67 (d, J¼8.2 Hz, 2H),
3
d
13
13
7
.60e7.59 (m, 1H), 7.48e7.45 (m, 2H), 7.30 (d, J¼8.2 Hz, 2H).
C
NMR (CDCl
3
, 125 MHz):
d
164.3, 154.3, 134.2, 133.7, 130.3, 128.8,
3
d
128.7, 122.9, 118.2, 109.9.
128.9, 128.6, 126.7, 125.5, 125.3, 124.6, 124.5, 122.8.
4
5
2
.3.7. Phenyl benzoate (3ag)14a. White solid. 1H NMR (CDCl
00 MHz):
H), 7.45e7.42 (m, 2H), 7.29e7.21 (m, 3H). C NMR (CDCl
25 MHz):
3
3
,
,
4.3.18. 4-Nitrophenyl 4-fluorobenzoate (3ga)25. White solid. 1H
d
8.21 (d, J¼7.5 Hz, 2H), 7.66e7.63 (m, 1H), 7.53e7.50 (m,
NMR (CDCl
3
, 500 MHz): d 8.27e8.25 (m, 2H), 8.17e8.14 (m, 2H),
13
13
7.35e7.33 (m, 2H), 7.16e7.13 (m, 2H). C NMR (CDCl
3
, 125 MHz):
1
d
165.2, 151.0, 133.6, 130.2, 129.6, 129.5, 128.6, 125.9,
d
166.5 (d, JCeF¼255.0 Hz), 163.3155.6, 145.5, 133.0 (d, JCeF¼9.5 Hz),
121.7.
125.3, 124.8 (d, JCeF¼3.0 Hz), 122.6, 116.1 (d, JCeF¼22.0 Hz).
4
5
4
.3.8. p-Tolyl benzoate (3ah)14a. White solid. 1H NMR (CDCl
00 MHz):
8.20 (d, J¼7.0 Hz, 2H), 7.63e7.49 (m, 3H), 7.25e7.09 (m,
H), 2.37 (s, 3H). C NMR (CDCl
3
,
4.3.19. 4-Nitrophenyl 4-chlorobenzoate (3ha)25. White solid. 1
H
d
NMR (CDCl
2H), 7.52 (d, J¼9.0 Hz, 2H), 7.42 (d, J¼9.0 Hz, 2H). C NMR (CDCl
125 MHz): 163.4, 155.4, 145.5, 140.8, 131.6, 129.2, 126.9, 125.3,
22.5.
3
, 500 MHz):
d
8.33 (d, J¼9.0 Hz, 2H), 8.14 (d, J¼9.0 Hz,
13
13
3
, 125 MHz):
d
165.4, 148.7, 135.5,
3
,
133.5, 130.2, 130.0, 129.7, 128.6, 121.4, 20.9.
d
1
4
.3.9. 4-Methoxyphenyl benzoate (3ai)22. White solid. 1H NMR
, 500 MHz): 8.14e8.12 (m, 2H), 7.57e7.54 (m, 1H),
.45e7.42 (m, 2H), 7.06 (d, J¼9.0 Hz, 2H), 6.87 (d, J¼9.0 Hz, 2H), 3.75
s, 3H). 13C NMR (CDCl
, 125 MHz): 165.5, 157.3, 144.4, 133.5, 130.1,
(
CDCl
3
d
4.3.20. Phenyl 4-methoxybenzoate (3eg)14a. Pale yellow solid. 1
NMR (CDCl , 500 MHz):
8.08 (d, J¼8.8 Hz, 2H), 7.36e7.33 (m, 2H),
7.20e7.17 (m, 1H), 7.13e7.12 (m, 2H), 6.90 (d, J¼8.8 Hz, 2H), 3.82 (s,
H
7
(
3
d
3
d
13
129.6, 128.5, 122.4, 114.5, 55.6.
3H). C NMR (CDCl
3
, 125 MHz): d 164.9, 163.9, 151.1, 132.2, 129.4,
1
25.7, 121.9, 121.8, 113.8, 55.5.
4
.3.10. 3-Methoxyphenyl benzoate (3aj)24. Pale yellow liquid. 1
, 500 MHz): 8.14e8.12 (m, 2H), 7.59e7.56 (m, 1H),
H
NMR (CDCl
3
d
4.3.21. Phenyl 4-nitrobenzoate (3ig)14g. White solid. 1H NMR
(CDCl , 500 MHz): 8.33e8.28 (m, 4H), 7.41e7.38 (m, 2H),
7.26e7.23 (m, 1H), 7.18e7.16 (m, 2H). C NMR (CDCl
163.3, 150.9, 150.5, 135.0, 131.3, 129.7, 126.4, 123.7, 121.4.
7.46e7.43 (m, 2H), 7.27e7.24 (m, 1H), 6.77e6.70 (m, 3H), 3.75 (s,
3
d
1
3
13
3
H). C NMR (CDCl
3
, 125 MHz):
d
165.1, 160.5, 151.9, 133.6, 130.2,
3
, 125 MHz):
129.9, 129.6, 128.5, 113.9, 111.9, 107.7, 55.5.
d
.3.11. 2-Methoxyphenyl benzoate (3ak)22. White solid. 1H NMR
CDCl , 500 MHz):
8.22 (d, J¼7.5 Hz, 2H), 7.64e7.61 (m, 1H),
.52e7.49 (m, 2H), 7.25e7.23 (m, 1H), 7.16e7.15 (m, 1H), 7.02e6.98
m, 2H), 3.82 (s, 3H). 13C NMR (CDCl
, 125 MHz): 164.8, 151.4, 140.0,
4.3.22. Phenyl 3-nitrobenzoate (3jg)14a. Pale yellow solid. H NMR
(CDCl , 500 MHz): 9.04 (s, 1H), 8.54e8.49 (m, 2H), 7.38 (t,
J¼8.0 Hz, 1H), 7.48e7.45 (m, 2H), 7.33e7.30 (m, 1H), 7.26e7.23 (m,
1
4
(
7
(
3
d
3
d
13
3
2H). C NMR (CDCl
3
, 125 MHz): d 163.1, 150.5, 148.4, 135.8, 131.4,
133.4, 130.3, 129.5, 128.5, 126.9, 122.9, 120.8, 112.6, 55.9.
129.9, 129.7, 128.0, 126.4, 125.1, 121.4.
1
4
.3.12. Naphthalen-2-yl benzoate (3al)20. White solid. 1H NMR
, 500 MHz):
8.26 (d, J¼7.5 Hz, 2H), 7.90e7.82 (m, 3H),
.70e7.64 (m, 2H), 7.54e7.46 (m, 4H), 7.37e7.35 (m, 1H). C NMR
CDCl , 125 MHz): 165.4, 148.7, 133.9, 133.7, 131.6, 130.2, 129.6,
4.3.23. Phenyl 4-(trifluoromethyl)benzoate (3kg)29. White solid. H
NMR (CDCl , 500 MHz):
8.33 (d, J¼8.0 Hz, 2H), 7.79 (d, J¼8.5 Hz,
2H), 7.45 (t, J¼8.0 Hz, 2H), 7.30 (t, J¼7.5 Hz, 1H), 7.23 (d, J¼8.0 Hz,
(
CDCl
3
d
3
d
13
7
(
13
3
d
2H).
CeF¼32.5 Hz),132.9,130.6,129.6,126.2,125.6 (d, JCeF¼3.8 Hz),123.1
d, JCeF¼271.2 Hz), 121.5.
3
C NMR (CDCl , 125 MHz): d 164.0, 150.7, 135.0 (d,
129.5, 128.6, 127.8, 127.7, 126.6, 125.8, 121.3, 118.7.
J
(
4
.3.13. 4-Nitrophenyl 4-methylbenzoate (3ba)25. Pale yellow solid.
1
4.3.24. Methyl phenyl terephthalate (3lg)14g. White solid. H NMR
(CDCl , 500 MHz):
8.27 (d, J¼8.5 Hz, 2H), 8.16 (d, J¼8.5 Hz, 2H),
7.46e7.43 (m, 2H), 7.29 (t, J¼7.5 Hz, 1H), 7.23 (d, J¼7.6 Hz, 2H), 3.98
1
H NMR (CDCl
H), 7.35e7.33 (m, 2H), 7.27 (d, J¼8.0 Hz, 2H), 2.40 (s, 3H). C NMR
CDCl , 125 MHz): 164.3, 155.9, 145.4, 145.3, 130.4, 129.5, 125.8,
3
, 500 MHz):
d
8.26e8.24 (m, 2H), 8.01 (d, J¼8.0 Hz,
13
2
3
d
(
3
d
13
125.3, 122.7, 21.8.
(s, 3H). C NMR (CDCl
3
,125 MHz): d 166.2,164.4,150.8, 134.5,133.4,
130.1, 129.7, 129.6, 126.1, 121.6, 52.5.
4
.3.14. 4-Nitrophenyl 2-methylbenzoate (3ca)26. Pale yellow solid.
1
4.3.25. Phenyl 4-cyanobenzoate (3mg)14h. Pale yellow solid. 1
NMR (CDCl , 500 MHz):
8.31 (d, J¼8.0 Hz, 2H), 7.82 (d, J¼8.0 Hz,
2H), 7.47e7.44 (m, 2H), 7.32e7.21 (m, 3H). C NMR (CDCl
125 MHz): 163.6, 150.6, 133.5, 132.4, 130.6, 129.7, 126.4, 121.4,
17.8, 117.0.
H NMR (CDCl
H), 7.54e7.51 (m, 1H), 7.42e7.40 (m, 2H), 7.37e7.34 (m, 2H), 2.68
s, 3H). 13C NMR (CDCl
, 125 MHz): 164.6, 155.8, 145.4, 141.9, 133.4,
3
, 500 MHz):
d
8.33 (d, J¼9.0 Hz, 2H), 8.18e8.16 (m,
H
1
(
3
d
13
3
d
3
,
132.2, 131.3, 127.4, 126.1, 125.3, 122.7, 22.0.
d
1
.3.15. 4-Nitrophenyl 4-ethylbenzoate (3da)27. Pale yellow solid. H
, 500 MHz):
8.33 (d, J¼9.0 Hz, 2H), 8.12 (d, J¼8.5 Hz,
H), 7.42 (d, J¼9.0 Hz, 2H), 7.37 (d, J¼8.0 Hz, 2H), 2.77 (q, J¼7.5 Hz,
1
4
NMR (CDCl
2
3
d
4.3.26. 4-Nitrophenyl propionate (3na)30. Pale yellow liquid. 1
NMR (CDCl , 500 MHz):
8.27 (d, J¼7.0 Hz, 2H), 7.29 (d, J¼7.0 Hz,
H
3
d

5882
F. Luo et al. / Tetrahedron 67 (2011) 5878e5882
2
H), 2.64 (q, J¼7.5 Hz, 2H), 1.28 (t, J¼7.5 Hz, 3H). 13C NMR (CDCl
3
,
11. (a) Zhang, J.; Leitus, G.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 2005, 127,
0840; (b) Gunanathan, C.; Shimon, L. J. W.; Milstein, D. J. Am. Chem. Soc. 2009,
31, 3146.
2. (a) Maki, B. E.; Chan, A.; Phillips, E. M.; Scheidt, K. A. Org. Lett. 2007, 7, 371; (b)
Maki, B. E.; Chan, A.; Phillips, E. M.; Scheidt, K. A. Tetrahedron 2009, 65, 3102.
1
1
125 MHz): d 172.0, 155.5, 145.3, 125.2, 122.4, 27.7, 8.9.
1
Acknowledgements
1
3. (a) Moretto, A.; Nicolli, A.; Lotti, M. Toxicol. Appl. Pharmacol. 2007, 219, 196; (b)
Barratt, M. D.; Basketter, D. A.; Roberts, D. W. Toxicol. in Vitro 1994, 8, 823; (c)
James, C.; Snieckus, V. J. Org. Chem. 2009, 74, 4080; (d) Beginn, U.; Zipp, G.;
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We thank the National Natural Science Foundation of China (No.
0972115) and the Natural Science Foundation of Zhejiang Province
2
14. The synthesis of aryl benzoate derivatives using carboxylic acids, anhydrides or
(
Nos. Y4110109 and R4110294).
aldehydes, please see: (a) Luo, F.; Pan, C.; Qian, P.; Cheng, J. Synthesis 2010,
2005; (b) Zhang, L.; Zhang, G.; Zhang, M.; Cheng, J. J. Org. Chem. 2010, 75, 7472;
(
c) Ye, Z.; Wang, W.; Luo, F.; Zhang, S.; Cheng, J. Org. Lett. 2009, 11, 3974; (d)
Supplementary data
Wang, W.; Pan, C.; Chen, F.; Cheng, J. Chem. Commun. 2011, 47, 3978; (e) Dai, J.-
J.; Liu, J.-H.; Luo, D.-F.; Liu, L. Chem. Commun. 2011, 47, 677; (f) Luo, F.; Pan, C.;
Qian, P.; Cheng, J. J. Org. Chem. 2010, 75, 5379; (g) Qin, C.; Wu, H.; Chen, J.; Liu,
M.; Cheng, J.; Su, W.; Ding, J. Org. Lett. 2008, 10, 1537; (h) Rosa, J. N.; Reddy, R. S.;
Candeias, N. R.; Cal, P. M. S. D.; Gois, P. M. P. Org. Lett. 2010, 12, 2686; (i) Ye, Z.;
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Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2011.06.060.
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