Copper-catalyzed oxidative C-O bond formation of 2-acyl phenols and 1,3-dicarbonyl compounds with ethers: Direct access to phenol esters and enol esters

Article abstract of DOI:10.1021/jo500576x

A copper-catalyzed oxidative coupling of 2-carbonyl-substituted phenols and 1,3-dicarbonyl compounds with a wide range of dibenzyl or dialkyl ethers is described. This protocol provides an efficient preparation of phenol esters and enol esters in good yields with high chemoselectivity. This method represents an alternative protocol for classical esterification reactions.

Full text of DOI:10.1021/jo500576x

Note
pubs.acs.org/joc
Copper-Catalyzed Oxidative C−O Bond Formation of 2‑Acyl Phenols
and 1,3-Dicarbonyl Compounds with Ethers: Direct Access to Phenol
Esters and Enol Esters
Jihye Park, Sang Hoon Han, Satyasheel Sharma, Sangil Han, Youngmi Shin, Neeraj Kumar Mishra,
Jong Hwan Kwak, Cheong Hoon Lee, Jeongmi Lee, and In Su Kim*
School of Pharmacy, Sungkyunkwan University, Suwon 440-746, Republic of Korea
S
* Supporting Information
ABSTRACT: A copper-catalyzed oxidative coupling of 2-
carbonyl-substituted phenols and 1,3-dicarbonyl compounds
with a wide range of dibenzyl or dialkyl ethers is described.
This protocol provides an efficient preparation of phenol esters
and enol esters in good yields with high chemoselectivity. This
method represents an alternative protocol for classical
esterification reactions.
ster groups are the highly important and abundant
1, path D). Recently, efficient Cu-catalyzed and transition-
metal-free protocols for the formation of benzylic esters have
been developed to allow a CDC involving alkylbenzenes as
coupling partners (Scheme 1, path E).11 In the past decade,
copper-catalyzed C−H functionalizations have emerged as
promising new catalytic transformations because copper
catalysts are inexpensive, readily available, insensitive to air,
and easy to handle, compared to other transition-metal
catalysts.5,12 Notably, the combination of copper salts and
peroxides as oxidants was well-known to facilitate the
functionalizations of sp3 carbon, especially the sp3 carbon
atom near to a nitrogen atom.13 In addition, C−H bond
functionalization of ethers and related oxygen-containing
compounds under copper catalysis has been recently ex-
plored.14
E
scaffolds found in natural products, medicinally relevant
molecules, and functional materials.1 The traditional methods
for the synthesis of ester groups rely on the reaction of
preactivated acid derivatives, such as acyl halides, anhydrides,
and activated esters, with alcohols in the presence of a
stoichiometric amount of bases (Scheme 1, path A).2 An
Scheme 1. Synthetic Protocol for the Preparation of Ester
Groups
Recently, we found that dibenzyl ethers can play a key role as
new carbonyl sources for acylation reaction of arene C−H
bonds catalyzed by palladium(II) metal.15 In continuation of
our efforts for the development of catalytic C−H functionaliza-
tions,16 we herein disclose the copper-catalyzed oxidative
esterification of 2-carbonyl-substituted phenols and 1,3-
dicarbonyl compounds with a range of dibenzyl or dialkyl
ethers to afford the corresponding phenol esters and enol
esters. To our knowledge, it is the first method of catalytic
esterfication from the ether oxidation level.
In our initial study, 1-(4-fluoro-2-hydroxyphenyl)ethanone
(1a) and di(2-methylbenzyl)ether (2a) were selected for the
optimization of reaction conditions. After detailed screening of
reaction conditions, we found that the best result was obtained
by using 5 mol % Cu(OAc)2 and 3 equiv of tert-butyl
hydroperoxide (TBHP) in DMSO (1 mL) at 80 °C to afford
our desired product 3a in 74% yield (see Supporting
alternative protocol involves transition-metal-catalyzed coupling
reactions using aryl halides, carbon monoxide, and alcohols
(Scheme 1, path B).3 Recent efforts have been devoted toward
the oxidative coupling between aldehydes and alcohols based
on the use of stoichiometric amounts of metal oxidants
(KHSO5 and MnO2), N-heterocyclic carbene activation, and a
transition-metal-mediated process (Scheme 1, path C).4
Another attractive protocol is the cross dehydrogenative
coupling (CDC)5 between two different alcohols using Ru,6
Rh,7 Ir,8 Pd,9 and Cu10 catalysts, which represents a step
forward toward an economical and sustainable process (Scheme
Received: March 11, 2014
Published: April 24, 2014
© 2014 American Chemical Society
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Note
a
Table 1. Scope of 2-Carbonyl-Substituted Phenols
a
Reaction conditions: 1a−1l (0.3 mmol), 2a (0.6 mmol), Cu(OAc)2 (5 mol %), TBHP (3 equiv), DMSO (1 mL) at 80 °C for 20 h in pressure
b
tubes. Isolated yield by flash column chromatography.
a
Table 2. Scope of 1,3-Dicarbonyl Compounds
a
Reaction conditions: 1m−1t (0.3 mmol), 2a (0.6 mmol), CuI (5 mol %), TBHP (3 equiv), DMSO (1 mL) at 80 °C for 20 h in pressure tubes.
Isolated yield by flash column chromatography.
b
Information for optimization table). Under the optimized
reaction conditions, the scope of 2-carbonyl-substituted
phenols was examined, as shown in Table 1. The coupling of
dibenzylic ether 2a and para-substititued-2-hydroxyacetophe-
nones 1a−1d with electron-rich and electron-deficient groups
was found to be favored to afford the products 3a−3d in high
yields. Notably, sterically hindered naphthol 1e smoothly
reacted with 2a to produce compound 3e in 65% yield. In
addition, it was found that 2-hydroxyacetophenone 1f with a
bromo moiety at the meta position was a suitable substrate for
this transformation, whereas 1g and 1h with electron-donating
groups (Me and OMe) were less reactive under present
reaction conditions. Further examination revealed that 2-
hydroxybenzophenone 1i and 2-hydroxybenzoates 1j and 1k
were well tolerated under current reaction conditions. Finally,
compound 1l with benzothiazole moiety instead of carbonyl
group at the ortho position of phenol underwent smoothly
esterification reaction to provide 3l in 67% yield.
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Note
a
Table 3. Scope of Ethers
a
Reaction conditions: 1c (0.3 mmol), 2b−2l (0.6 mmol), Cu(OAc)2 (5 mol %), TBHP (3 equiv), DMSO (1 mL) at 80 °C for 20 h in pressure
b
c
tubes. Isolated yield by flash column chromatography. Cu(OAc)2 (10 mol %), TBHP (6 equiv).
Scheme 2. Crossover Experiments
In previous literature, 1,3-dicarbonyl compounds were used
as interesting substrates for catalytic C−O bond-formation
reaction in the presence of aldehydes or formamides to yield
the various enol esters or enol carbamates.17 Thus, we sought
to expand our substrate scope from 2-carbonyl-substituted
phenols to 1,3-dicarbonyl compounds because the enol
tautomer of the diketone moiety has structural similarities to
2-acyl phenolic compounds. To our pleasure, ethyl acetoacetate
(1m) was coupled with ether 2a under the standard conditions
to afford our desired product 3m in 54% yield. After further
optimization of reaction conditions, we found that CuI was
found to be a good catalyst in this transformation to afford 3m
in 68% yield (Table 2). In general, the reaction of β-keto esters
1n−1r with 2a afforded the desired products 3n−3r in
moderate to good yields, while α,β-disubstituted keto ester 1s
and 1,3-diketone 1t were less reactive. It should be mentioned
that all reactions furnished the (Z)-enol esters as major
products, which were confirmed by 1H NMR analysis and NOE
experiments.
Subsequently, a series of dibenzyl or dialkyl ethers 2b−2l
were subjected to reaction with 1c (Table 3). Dibenzylic ethers
2b−2i with electron-rich and electron-deficient groups (OMe,
Me, F, Cl, and Br) reacted with 2-hydroxy-4-methoxyaceto-
phenone (1c) to afford the coupling products in moderate to
high yields. Particulary, this process was tolerated by halogen
groups as versatile functionalities for further cross-coupling
reaction. To our pleasure, this process is not limited to
dibenzylic ethers.18 Dialkyl ethers 2j−2l also participated in the
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Note
Scheme 3. Intramolecular Competition Experiments
Scheme 4. Control Experiments
coupling reaction to furnish the corresponding products 4j
(74%), 4k (51%), and 4l (58%).
provided a separable mixture of 4c and 4d in a 2:1 ratio
(Scheme 3, eq 1). In addition, the reaction of 2n with 1c
afforded a product distribution of 3:1 between 4b and 4j
(Scheme 3, eq 2). These results may reveal that the kinetic
stability of radical intermediates derived from ethers primarily
influences the site selectivity.
To further examine the possible mechanism, some related
experiments were performed (Scheme 4). First, the reaction of
dibenzylic ether 2a in the absence of 2-hydroxyacetophenone
under standard reaction conditions was conducted, and the
reaction progress was monitored by GC−MS analysis. After the
reaction was carried out at 80 °C for 3 h, we could observe the
formation of o-tolylaldehyde (2ab) and o-methylbenzyl alcohol
(2ac), as well as ester 2aa (Scheme 4, eq 1).19 Thus, we further
examined the esterification of 1c using 2aa under standard
reaction conditions but observed no formation of the
esterificated compound 3c (Scheme 4, eq 2). In addition,
treatment of 1c with aldehyde 2ab or alcohol 2ac provided the
To gain a mechanistic insight, some crossover experiments
were carried out under standard reaction conditions (Scheme
2). Exposure of ether 2a to equimolar quantities of 2-
hydroxyacetophenone (1b) and phenol (1u) provided a single
product of 3b in 62% isolated yield, but no esterification of 1u
was observed (Scheme 2, eq 1). In addition, competition
experiment between 2-hydroxyacetophenone (1b) and 3-
hydroxyacetophenone (1v) led to no formation of 3v (Scheme
2, eq 2). Thus, no observation of compounds 3u and 3v
indicates that the bidentate coordination of substrate to copper
center might be one of the key factors for the initiation of the
catalytic cycle.
Intramolecular competition experiments using unsymmetric
dibenzylic ether 2m or alkylbenzyl ether 2n were performed to
illustrate the chemoselectivity of this transformation (Scheme
3). Exposure of 2m to 1c under standard reaction conditions
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Note
1H NMR (700 MHz, CDCl3): δ 8.23 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H),
7.88 (d, J = 8.7 Hz, 1H), 7.48 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.35−7.31
(m, 2H), 6.86 (dd, J1 = 8.7, J2 = 2.5 Hz, 1H), 6.72 (d, J = 2.5 Hz, 1H),
3.86 (s, 3H), 2.68 (s, 3H), 2.50 (s, 3H). 13C NMR (175 MHz,
CDCl3): δ 195.8, 165.6, 163.8, 151.6, 141.5, 132.8, 132.5, 131.9, 131.4,
128.3, 126.0, 123.6, 111.7, 109.4, 55.7, 29.3, 21.8. IR (KBr): υ 2932,
2840, 1738, 1677, 1605, 1568, 1497, 1458, 1356, 1288, 1233, 1189,
1125, 1031, 962, 884, 733 cm−1. HRMS (quadrupole, EI) m/z calcd
for C17H16O4 [M]+ 284.1049, found 284.1053.
desired product 3c in high yields, respectively (Scheme 4, eqs 3
and 4). Although it is not clear about the formation of ester 2aa
at this point,20 we believe that the C−O bond of the ester
cannot be cleaved to afford the corresponding aldehyde and
alcohol under the present reaction conditions.
Finally, to understand the generation of the acyl radical
intermediate, the reaction between 1c and 2a with 2,2,6,6-
tetramethyl-1-piperidinyloxy (TEMPO) as a radical scavenger
was conducted.21 A substantial decrease of yield was detected in
a dose-dependent manner (see Supporting Information for
details). These collective data can be explained by a radical
pathway that benzylic or alkyl radicals can be generated by the
radical initiator TBHP under a copper salt. The formed
benzylic or alkyl radicals may be rapidly converted to the
corresponding acyl radicals, which can be trapped by a copper-
substrate complex to give an esterification product. A plausible
reaction mechanism is shown in Supporting Information. First,
Cu(II) catalyst can form complex I with 2-carbonyl-substituted
enol 1. The reactive benzoyl radicals22 derived from ether 2 by
TBHP and a catalytic amount of copper catalyst can react with
complex I by single electron transfer to produce Cu(III)
complex II.23 Finally, reductive elimination of intermediate II
affords the desired product 3 and Cu(I) catalyst, which can be
reoxidized to Cu(II) by TBHP.
2-Acetyl-5-methylphenyl 2-Methylbenzoate (3d). Yield: 66%
1
(53 mg). Pale yellow oil. Rf = 0.17 (n-hexane/EtOAc = 15:1). H
NMR (700 MHz, CDCl3): δ 8.21 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H), 7.78
(d, J = 7.9 Hz, 1H), 7.48 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.35−7.32 (m,
2H), 7.17−7.16 (m, 1H), 7.03 (d, J = 6.3 Hz, 1H), 2.67 (s, 3H), 2.52
(s, 3H), 2.43 (s, 3H). 13C NMR (175 MHz, CDCl3): δ 197.0, 165.8,
149.5, 144.8, 141.5, 132.8, 131.9, 131.3, 130.5, 128.4, 128.3, 126.8,
126.0, 124.5, 29.5, 21.8, 21.4. IR (KBr): υ 2624, 2857, 1737, 1682,
1612, 1456, 1355, 1247, 1219, 1138, 1038, 965, 816, 732 cm−1. HRMS
(quadrupole, EI) m/z calcd for C17H16O3 [M]+ 268.1099, found
268.1098.
2-Acetylnaphthalen-1-yl 2-Methylbenzoate (3e). Yield: 65%
1
(59 mg). Yellow oil. Rf = 0.20 (n-hexane/EtOAc = 15:1). H NMR
(700 MHz, CDCl3): δ 8.44 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H), 8.03 (dd, J1
= 8.4, J2 = 0.7 Hz, 1H), 7.93−7.89 (m, 2H), 7.83 (d, J = 8.6 Hz, 1H),
7.63−7.60 (m, 1H), 7.57−7.54 (m, 2H), 7.43−7.38 (m, 2H), 2.71 (s,
3H), 2.65 (s, 3H). 13C NMR (175 MHz, CDCl3): δ 197.8, 165.4,
146.7, 142.1, 136.4, 133.2, 132.2, 131.5, 128.5, 127.9, 127.8, 127.5,
127.4, 127.2, 126.2, 126.0, 125.2, 123.0, 30.1, 22.0. IR (KBr): υ 2924,
2851, 1738, 1685, 1598, 1463, 1356, 1230, 1191, 1132, 1067, 1018,
813, 731 cm−1. HRMS (quadrupole, EI) m/z calcd for C20H16O3 [M]+
304.1099, found 304.1098.
2-Acetyl-4-bromophenyl 2-Methylbenzoate (3f). Yield: 67%
(67 mg). Colorless oil. Rf = 0.39 (n-hexane/EtOAc = 10:1). 1H NMR
(700 MHz, CDCl3): δ 8.18 (dd, J1 = 7.8, J2 = 1.2 Hz, 1H), 7.95 (s,
1H), 7.68 (dd, J1 = 8.5, J2 = 2.4 Hz, 1H), 7.50 (td, J1 = 7.4, J2 = 1.3 Hz,
1H), 7.36−7.32 (m, 2H), 7.11 (d, J = 8.6 Hz, 1H), 2.66 (s, 3H), 2.53
(s, 3H). 13C NMR (175 MHz, CDCl3): δ 196.2, 165.2, 148.3, 141.8,
136.1, 133.2, 133.0, 132.9, 132.1, 131.3, 127.7, 126.1, 125.8, 119.2,
29.6, 21.8. IR (KBr): υ 2925, 2857, 1738, 1690, 1598, 1470, 1389,
1355, 1286, 1235, 1190, 1134, 1066, 1026, 873, 732 cm−1. HRMS
(quadrupole, EI) m/z calcd for C16H13BrO3 [M]+ 332.0048, found
332.0045.
2-Acetyl-4-methylphenyl 2-Methylbenzoate (3g). Yield: 43%
(35 mg). Colorless oil. Rf = 0.29 (n-hexane/EtOAc = 10:1). 1H NMR
(700 MHz, CDCl3): δ 8.20 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H), 7.65 (s,
1H), 7.48 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.39−7.37 (m, 1H), 7.35−
7.31 (m, 2H), 7.10 (d, J = 8.1 Hz, 1H), 2.66 (s, 3H), 2.53 (s, 3H), 2.42
(s, 3H). 13C NMR (175 MHz, CDCl3): δ 197.8, 165.8, 147.1, 141.5,
135.8, 134.0, 132.8, 131.9, 131.3, 131.0, 130.6, 128.3, 126.0, 123.7,
29.7, 21.8, 20.8. IR (KBr): υ 2924, 2851, 1737, 1686, 1577, 1487,
1355, 1241, 1192, 1133, 1035, 872, 733 cm−1. HRMS (quadrupole, EI)
m/z calcd for C17H16O3 [M]+ 268.1099, found 268.1097.
2-Acetyl-4-methoxyphenyl 2-Methylbenzoate (3h). Yield:
31% (26 mg). Pale yellow oil. Rf = 0.18 (n-hexane/EtOAc = 10:1).
1H NMR (700 MHz, CDCl3): δ 8.20 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H),
7.49 (td, J1 = 7.5, J2 = 1.4 Hz, 1H), 7.35−7.32 (m, 3H), 7.14−7.10 (m,
2H), 3.86 (s, 3H), 2.66 (s, 3H), 2.53 (s, 3H). 13C NMR (175 MHz,
CDCl3): δ 197.4, 166.0, 157.7, 142.8, 141.6, 132.9, 132.0, 131.2, 128.2,
126.0, 124.8, 119.0, 114.5, 55.8, 29.8, 21.8. IR (KBr): υ 2923, 2853,
1736, 1688, 1576, 1486, 1458, 1356, 1283, 1240, 1187, 1134, 1036,
870, 734 cm−1. HRMS (quadrupole, EI) m/z calcd for C17H16O4 [M]+
284.1049, found 284.1053.
In conclusion, a carbonyl-group-assisted copper-catalyzed
oxidative esterification of 2-carbonyl-substituted phenols and
1,3-dicarbonyl compounds with dibenzyl or dialkyl ethers has
been described. Further detailed mechanistic investigations
regarding benzyl ethers as acyl equivalents are in progress.
EXPERIMENTAL SECTION
■
General Procedure for the Esterification of 2-Carbonyl-
Substituted Phenols. To an oven-dried sealed tube charged with 1a
(46.2 mg, 0.3 mmol, 100 mol %), Cu(OAc)2 (2.7 mg, 0.015 mmol, 5
mol %), and TBHP (0.16 mL, 0.9 mmol, 300 mol %, 5.5 M in decane)
in DMSO (1 mL) was added 2a (135.8 mg, 0.6 mmol, 200 mol %).
The reaction mixture was allowed to stir at 80 °C for 20 h. After
cooling at room temperature, the reaction mixture was evaporated
onto silica gel. Purification of the product by column chromatography
(SiO2; n-hexane/EtOAc = 15:1) provided 3a (61 mg, 0.222 mmol) in
74% yield.
2-Acetyl-5-fluorophenyl 2-Methylbenzoate (3a). Yield: 74%
(60 mg). Colorless oil. Rf = 0.17 (n-hexane/EtOAc = 15:1). 1H NMR
(700 MHz, CDCl3): δ 8.20 (dd, J1 = 7.8, J2 = 1.3 Hz, 1H), 7.91 (d, J =
6.3 Hz, 1H), 7.51 (td, J1 = 7.6, J2 = 1.4 Hz, 1H), 7.36−7.32 (m, 2H),
7.09−7.06 (m, 1H), 6.97 (dd, J1 = 8.9, J2 = 2.5 Hz, 1H), 2.67 (s, 3H),
2.53 (s, 3H). 13C NMR (175 MHz, CDCl3): δ 196.0, 165.1, 165.0 (d,
JC−F = 254.3 Hz), 151.2 (d, JC−F = 10.7 Hz), 141.8, 133.2, 132.3 (d,
JC−F = 10.3 Hz), 132.0, 131.4, 127.8 (d, JC−F = 3.1 Hz), 127.7, 126.1,
113.3 (d, JC−F = 21.0 Hz), 111.9 (d, JC−F = 23.9 Hz), 29.6, 21.8. IR
(KBr): υ 2967, 2851, 1740, 1687, 1602, 1491, 1458, 1413, 1356, 1287,
1228, 1145, 1111, 1029, 973, 885, 816, 732 cm−1. HRMS (quadrupole,
EI) m/z calcd for C16H13FO3 [M]+ 272.0849, found 272.0852.
2-Acetylphenyl 2-Methylbenzoate (3b). Yield: 66% (51 mg).
1
Colorless oil. Rf = 0.20 (n-hexane/EtOAc = 15:1). H NMR (700
MHz, CDCl3): δ 8.21 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H), 7.86 (dd, J1 = 7.7,
J2 = 1.6 Hz, 1H), 7.60−7.58 (m, 1H), 7.49 (td, J1 = 7.4, J2 = 1.3 Hz,
1H), 7.38−7.32 (m, 3H), 7.22 (dd, J1 = 8.0, J2 = 1.0 Hz, 1H), 2.67 (s,
3H), 2.55 (s, 3H). 13C NMR (175 MHz, CDCl3): δ 197.7, 165.6,
149.3, 141.6, 133.4, 132.9, 132.0, 131.4, 131.3, 130.2, 128.2, 126.1,
126.0, 124.0, 29.6, 21.8. IR (KBr): υ 2927, 2581, 1737, 1686, 1602,
1574, 1480, 1446, 1356, 1283, 1241, 1190, 1133, 1071, 1028, 954, 837,
733 cm−1. HRMS (quadrupole, EI) m/z calcd for C16H14O3 [M]+
254.0943, found 254.0945.
2-Benzoyl-5-methoxyphenyl 2-Methylbenzoate (3i). Yield:
82% (85 mg). Light yellow solid. Mp = 91−94 °C. Rf = 0.13 (n-
1
hexane/EtOAc = 15:1). H NMR (700 MHz, CDCl3): δ 7.76−7.74
(m, 2H), 7.71 (dd, J1 = 7.8, J2 = 1.2 Hz, 1H), 7.57 (d, J = 8.6 Hz, 1H),
7.47−7.44 (m, 1H), 7.39−7.36 (m, 3H), 7.21 (d, J = 7.7 Hz, 1H), 7.15
(t, J = 7.3 Hz, 1H), 6.88 (dd, J1 = 8.6, J2 = 2.5 Hz, 1H), 6.83 (d, J = 2.4
Hz, 1H), 3.89 (s, 3H), 2.56 (s, 3H). 13C NMR (175 MHz, CDCl3): δ
194.2, 165.1, 163.0, 151.0, 141.3, 138.4, 132.7, 132.6, 132.4, 131.6,
2-Acetyl-5-methoxyphenyl 2-Methylbenzoate (3c). Yield:
96% (82 mg). Pale yellow oil. Rf = 0.26 (n-hexane/EtOAc = 3:1).
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Note
131.1, 129.6, 128.2, 127.8, 125.6, 124.2, 111.3, 109.1, 55.7, 21.7. IR
(KBr): υ 2930, 2835, 1735, 1650, 1605, 1572, 1500, 1448, 1319, 1270,
1233, 1160, 1098, 1028, 912, 881, 848, 732 cm−1. HRMS (quadrupole,
EI) m/z calcd for C22H18O4 [M]+ 346.1205, found 346.1206.
2-(Ethoxycarbonyl)phenyl 2-Methylbenzoate (3j). Yield: 53%
(45 mg). Colorless oil. Rf = 0.29 (n-hexane/EtOAc = 15:1). 1H NMR
(700 MHz, CDCl3): δ 8.26 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H), 8.08 (dd, J1
= 7.8, J2 = 1.6 Hz, 1H), 7.60 (td, J1 = 7.5, J2 = 1.7 Hz, 1H), 7.48 (td, J1
= 7.4, J2 = 1.3 Hz, 1H), 7.37−7.31 (m, 3H), 7.21 (dd, J1 = 8.0, J2 = 1.0
Hz, 1H), 4.24 (q, J = 7.1 Hz, 2H), 2.68 (s, 3H), 1.16 (t, J = 7.1 Hz,
3H). 13C NMR (175 MHz, CDCl3): δ 165.7, 164.8, 150.6, 141.5,
133.6, 132.7, 131.9 (two carbons), 131.5, 128.3, 126.0, 125.9, 124.1,
124.0, 61.2, 21.9, 13.9. IR (KBr): υ 2977, 2928, 2868, 1736, 1720,
1605, 1575, 1452, 1366, 1290, 1241, 1197, 1133, 1078, 1030, 733
cm−1. HRMS (quadrupole, EI) m/z calcd for C17H16O4 [M]+
284.1049, found 284.1053.
Hz, 1H), 7.44 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.29−7.27 (m, 2H), 5.61
(s, 1H), 2.64 (s, 3H), 2.09 (s, 3H), 1.35 (s, 9H). 13C NMR (175 MHz,
CDCl3): δ 163.9, 163.1, 157.9, 141.3, 132.6, 131.8, 131.4, 128.3, 125.8,
110.7, 80.4, 28.0, 21.8, 21.5. IR (KBr): υ 2977, 2932, 1739, 1717, 1668,
1602, 1575, 1456, 1367, 1291, 1211, 1164, 1129, 1041, 1024, 964, 831,
733 cm−1. HRMS (quadrupole, EI) m/z calcd for C16H20O4 [M]+
276.1362, found 276.1372.
(Z)-4-(Benzyloxy)-4-oxobut-2-en-2-yl 2-Methylbenzoate
(3p). Yield: 53% (49 mg). Colorless sticky oil. Rf = 0.33 (n-hexane/
EtOAc = 15:1). 1H NMR (700 MHz, CDCl3): δ 8.08 (dd, J1 = 8.4, J2 =
1.5 Hz, 1H), 7.47−7.45 (m, 1H), 7.30−7.27 (m, 7H), 5.79 (s, 1H),
5.11 (s, 2H), 2.63 (s, 3H), 2.17 (s, 3H). 13C NMR (175 MHz,
CDCl3): δ 163.9, 163.5, 160.5, 141.3, 135.7, 132.6, 131.7, 131.4, 128.4,
128.2, 128.1, 128.0, 125.8, 108.5, 66.0, 21.8, 21.7. IR (KBr): υ 2921,
2852, 1722, 1668, 1602, 1455, 1379, 1331, 1248, 1188, 1131, 1027,
829, 732 cm−1. HRMS (quadrupole, EI) m/z calcd for C19H18O4 [M]+
310.1205, found 310.1205.
(Z)-1-Methoxy-4,4-dimethyl-1-oxopent-2-en-3-yl 2-Methyl-
benzoate (3q). Yield: 68% (56 mg). Colorless oil. Rf = 0.40 (n-
hexane/EtOAc = 15:1). 1H NMR (700 MHz, CDCl3): δ 8.07 (dd, J1 =
8.6, J2 = 1.4 Hz, 1H), 7.44 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.31−7.26
(m, 2H), 5.80 (s, 1H), 3.62 (s, 3H), 2.64 (s, 3H), 1.22 (s, 9H). 13C
NMR (175 MHz, CDCl3): δ 169.5, 164.8, 164.1, 141.1, 132.4, 131.8,
131.1, 128.7, 125.8, 104.2, 51.2, 37.6, 27.4, 21.6. IR (KBr): υ 2972,
2912, 1747, 1724, 1653, 1603, 1459, 1434, 1328, 1270, 1237, 1171,
1087, 1040, 844, 731 cm−1. HRMS (quadrupole, EI) m/z calcd for
C16H20O4 [M]+ 276.1362, found 276.1369.
Benzyl 2-(2-Methylbenzoyloxy)benzoate (3k). Yield: 44% (46
1
mg). Yellow sticky oil. Rf = 0.33 (n-hexane/EtOAc = 15:1). H NMR
(700 MHz, CDCl3): δ 8.18 (dd, J1 = 8.2, J2 = 1.4 Hz, 1H), 8.12 (dd, J1
= 7.9, J2 = 1.6 Hz, 1H), 7.63−7.61 (m, 1H), 7.47 (td, J1 = 7.5, J2 = 1.4
Hz, 1H), 7.36 (td, J1 = 7.7, J2 = 1.1 Hz, 1H), 7.30−7.23 (m, 8H), 5.24
(s, 2H), 2.61 (s, 3H). 13C NMR (175 MHz, CDCl3): δ 192.8, 165.7,
164.6, 150.7, 141.5, 135.4, 133.9, 132.6, 132.0, 131.8, 131.5, 128.4,
128.3, 128.2, 126.0, 125.9, 124.1, 123.8, 67.0, 21.8. IR (KBr): υ 2929,
2851, 1720, 1605, 1574, 1452, 1375, 1288, 1244, 1197, 1072, 1028,
732 cm−1. HRMS (quadrupole, EI) m/z calcd for C22H18O4 [M]+
346.1205, found 346.1204.
2-(Benzo[d]thiazol-2-yl)phenyl 2-Methylbenzoate (3l). Yield:
67% (69 mg). Colorless sticky oil. Rf = 0.48 (n-hexane/EtOAc = 5:1).
1H NMR (700 MHz, CDCl3): δ 8.39−8.37 (m, 2H), 7.94 (d, J = 8.1
(Z)-3-Ethoxy-3-oxo-1-phenylprop-1-enyl 2-Methylbenzoate
(3r). Yield: 51% (48 mg). Pale brown oil. Rf = 0.24 (n-hexane/EtOAc
1
= 15:1). H NMR (700 MHz, CDCl3): δ 8.28 (d, J = 7.8 Hz, 1H),
Hz, 1H), 7.82 (d, J = 7.9 Hz, 1H), 7.58−7.53 (m, 2H), 7.45−7.33 (m,
6H), 2.67 (s, 3H). 13C NMR (175 MHz, CDCl3): δ 165.4, 162.6,
153.0, 148.6, 141.9, 135.4, 133.0, 132.0, 131.8, 131.5, 130.4, 128.3,
126.6, 126.4, 126.2, 126.0, 125.2, 124.0, 123.3, 121.4, 22.0. IR (KBr): υ
2978, 2857, 1740, 1603, 1574, 1482, 1433, 1264, 1240, 1188, 1134,
1104, 1024, 965, 729 cm−1. HRMS (quadrupole, EI) m/z calcd for
C21H15NO2S [M]+ 345.0824, found 345.0831.
7.66−7.64 (m, 2H), 7.50−7.47 (m, 1H), 7.45−7.39 (m, 3H), 7.35−
7.31 (m, 2H), 6.37 (s, 1H), 4.16 (d, J = 7.0 Hz, 2H), 2.66 (s, 3H), 1.19
(t, J = 7.1 Hz, 3H). 13C NMR (175 MHz, CDCl3): δ 164.2, 164.1,
157.9, 141.7, 133.7, 132.9, 131.9, 131.5, 130.9, 128.8 (two carbons),
127.9, 126.0, 106.8, 60.3, 21.8, 14.1. IR (KBr): υ 2979, 2934, 1739,
1716, 1638, 1599, 1578, 1448, 1367, 1331, 1276, 1224, 1162, 1058,
1027, 850, 763, 733 cm−1. HRMS (quadrupole, EI) m/z calcd for
C19H18O4 [M]+ 310.1205, found 310.1208.
2-(Ethoxycarbonyl)cyclohex-1-enyl 2-Methylbenzoate (3s).
Yield: 41% (35 mg). Colorless oil. Rf = 0.34 (n-hexane/EtOAc = 15:1).
1H NMR (700 MHz, CDCl3): δ 8.06 (dd, J1 = 8.4, J2 = 1.4 Hz, 1H),
7.43 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.28−7.26 (m, 2H), 4.06 (q, J = 7.1
Hz, 2H), 2.64 (s, 3H), 2.48−2.45 (m, 2H), 2.38−2.36 (m, 2H), 1.81−
1.78 (m, 2H), 1.73−1.70 (m, 2H), 1.03 (t, J = 7.1 Hz, 3H). 13C NMR
(175 MHz, CDCl3): δ 165.9, 164.8, 155.2, 141.2, 132.5, 131.8, 131.3,
128.5, 125.8, 118.2, 60.4, 29.3, 25.3, 22.1, 21.9, 21.8, 13.9. IR (KBr): υ
2935, 2863, 1731, 1701, 1660, 1602, 1577, 1457, 1372, 1284, 1233,
1187, 1119, 1073, 1055, 1031, 857, 733 cm−1. HRMS (quadrupole, EI)
m/z calcd for C17H20O4 [M]+ 288.1362, found 288.1349.
General Procedure for the Esterification of 1,3-Dicarbonyl
Compounds. To an oven-dried sealed tube charged with 1m (39.0
mg, 0.3 mmol, 100 mol %), CuI (2.9 mg, 0.015 mmol, 5 mol %), and
TBHP (0.16 mL, 0.9 mmol, 300 mol %, 5.5 M in decane) in DMSO (1
mL) was added 2a (135.8 mg, 0.6 mmol, 200 mol %). The reaction
mixture was allowed to stir at 80 °C for 20 h. After cooling at room
temperature, the reaction mixture was evaporated onto silica gel.
Purification of the product by column chromatography (SiO2; n-
hexane/EtOAc = 10:1) provided 3m (51 mg, 0.203 mmol) in 68%
yield.
(Z)-4-Ethoxy-4-oxobut-2-en-2-yl 2-Methylbenzoate (3m).18
Yield: 68% (51 mg). Colorless oil. Rf = 0.26 (n-hexane/EtOAc = 15:1).
1H NMR (700 MHz, CDCl3): δ 8.10 (dd, J1 = 7.7, J2 = 1.2 Hz, 1H),
(Z)-5-Oxohept-3-en-3-yl 2-Methylbenzoate (3t). Yield: 36%
(27 mg). Colorless oil. Rf = 0.21 (n-hexane/EtOAc = 15:1). 1H NMR
(700 MHz, CDCl3): δ 8.08 (d, J = 7.9 Hz, 1H), 7.44 (td, J1 = 7.4, J2 =
1.3 Hz, 1H), 7.30−7.28 (m, 2H), 5.97 (s, 1H), 2.63 (s, 3H), 2.50 (q, J
= 7.2 Hz, 2H), 2.41 (q, J = 7.1 Hz, 2H), 1.18 (t, J = 7.4 Hz, 3H), 1.03
(t, J = 7.2 Hz, 3H). 13C NMR (175 MHz, CDCl3): δ 198.1, 164.1,
161.8, 141.3, 132.6, 131.8, 131.2, 128.3, 125.9, 113.6, 37.0, 28.5, 21.7,
10.5, 7.8. IR (KBr): υ 2975, 2937, 1736, 1699, 1630, 1458, 1377, 1286,
1235, 1166, 1131, 1059, 1019, 843, 733 cm−1. HRMS (quadrupole, EI)
m/z calcd for C15H18O3 [M]+ 246.1256, found 246.1255.
7.45−7.43 (m, 1H), 7.30−7.27 (m, 2H), 5.70 (s, 1H), 4.08 (q, J = 7.0
Hz, 2H), 2.64 (s, 3H), 2.13 (s, 3H), 1.14 (t, J = 7.1 Hz, 3H). 13C NMR
(175 MHz, CDCl3): δ 164.0, 163.8, 159.9, 141.2, 132.6, 131.8, 131.4,
128.2, 125.8, 108.7, 60.0, 21.8, 21.7, 14.0. IR (KBr): υ 2980, 2933,
1720, 1668, 1602, 1576, 1440, 1379, 1287, 1250, 1190, 1132, 1037,
831, 732 cm−1. HRMS (quadrupole, EI) m/z calcd for C14H16O4 [M]+
248.1049, found 248.1053.
(Z)-4-Methoxy-4-oxobut-2-en-2-yl 2-Methylbenzoate (3n).
Yield: 54% (38 mg). Colorless oil. Rf = 0.30 (n-hexane/EtOAc =
15:1). 1H NMR (700 MHz, CDCl3): δ 8.10 (dd, J1 = 7.7, J2 = 1.1 Hz,
1H), 7.44 (td, J1 = 7.4, J2 = 1.4 Hz, 1H), 7.30−7.27 (m, 2H), 5.71 (s,
1H), 3.63 (s, 3H), 2.64 (s, 3H), 2.14 (s, 3H). 13C NMR (175 MHz,
CDCl3): δ 164.1, 164.0, 160.4, 141.2, 132.6, 131.7, 131.3, 128.3, 125.9,
108.2, 51.2, 21.8, 21.6. IR (KBr): υ 2952, 1723, 1675, 1602, 1576,
1436, 1379, 1336, 1288, 1250, 1194, 1133, 1039, 986, 922, 831, 734
cm−1. HRMS (quadrupole, EI) m/z calcd for C13H14O4 [M]+
234.0892, found 234.0883.
2-Acetyl-5-methoxyphenyl Benzoate (4b):10 Yield: 75% (61
mg). Colorless oil. Rf = 0.29 (n-hexane/EtOAc = 3:1). 1H NMR (700
MHz, CDCl3): δ 8.21 (dd, J1 = 8.3, J2 = 1.2 Hz, 2H), 7.89 (d, J = 8.8
Hz, 1H), 7.66−7.64 (m, 1H), 7.54−7.51 (m, 2H), 6.88−6.73 (m, 1H),
6.72 (s, 1H), 3.86 (s, 3H), 2.50 (s, 3H). 13C NMR (175 MHz,
CDCl3): δ 195.6, 165.1, 163.7, 151.7, 133.7, 132.4, 130.3, 129.3, 128.7,
123.5, 112.0, 109.2, 55.7, 29.5. IR (KBr): υ 2923, 1734, 1676, 1604,
1567, 1497, 1425, 1356, 1320, 1237, 1159, 1124, 1056, 1021, 962, 884,
702 cm−1. HRMS (quadrupole, EI) m/z calcd for C16H14O4 [M]+
270.0892, found 270.0891.
(Z)-4-tert-Butoxy-4-oxobut-2-en-2-yl 2-Methylbenzoate
(3o). Yield: 60% (50 mg). Colorless oil. Rf = 0.27 (n-hexane/EtOAc
1
= 15:1). H NMR (700 MHz, CDCl3): δ 8.09 (dd, J1 = 7.7, J2 = 1.1
4740
dx.doi.org/10.1021/jo500576x | J. Org. Chem. 2014, 79, 4735−4742

The Journal of Organic Chemistry
Note
2-Acetyl-5-methoxyphenyl 4-Methoxybenzoate (4c). Yield:
96% (87 mg). Yellow oil. Rf = 0.19 (n-hexane/EtOAc = 3:1). 1H NMR
(700 MHz, CDCl3): δ 8.18−8.15 (m, 2H), 7.88 (d, J = 8.8 Hz, 1H),
7.01−6.99 (m, 2H), 6.86 (d, J = 8.4 Hz, 1H), 6.70 (s, 1H), 3.90 (s,
3H), 3.86 (s, 3H), 2.48 (s, 3H). 13C NMR (175 MHz, CDCl3): δ
195.7, 164.7, 164.1, 163.7, 151.8, 132.5, 132.3, 128.6, 121.6, 113.9,
112.0, 109.2, 55.7, 55.5, 29.7. IR (KBr): υ 2923, 2841, 1731, 1678,
1603, 1510, 1463, 1422, 1357, 1319, 1251, 1161, 1126, 1068, 1025,
964, 845, 761 cm−1. HRMS (quadrupole, EI) m/z calcd for C17H16O5
[M]+ 300.0998, found 300.0996.
55.8, 29.0. IR (KBr): υ 2925, 2581, 1750, 1678, 1607, 1568, 1466,
1436, 1357, 1258, 1236, 1126, 1030, 963, 887, 742 cm−1. HRMS
(quadrupole, EI) m/z calcd for C16H13ClO4 [M]+ 304.0502, found
304.0500.
2-Acetyl-5-methoxyphenyl Butyrate (4j). Yield: 74% (53 mg).
1
Pale yellow oil. Rf = 0.36 (n-hexane/EtOAc = 3:1). H NMR (700
MHz, CDCl3): δ 7.82 (d, J = 8.7 Hz, 1H), 6.81 (dd, J1 = 8.8, J2 = 2.5
Hz, 1H), 6.58 (s, 1H), 3.84 (s, 3H), 2.61 (t, J = 7.4 Hz, 2H), 2.50 (s,
3H), 1.83−1.77 (m, 2H), 1.05 (t, J = 7.4 Hz, 3H). 13C NMR (175
MHz, CDCl3): δ 195.7, 172.0, 163.7, 151.4, 132.4, 123.2, 111.5, 109.3,
55.7, 36.2, 29.1, 18.0, 13.7. IR (KBr): υ 2964, 2875, 1760, 1677, 1606,
1568, 1499, 1425, 1356, 1255, 1241, 1124, 1066, 1025, 966, 813, 749
cm−1. HRMS (quadrupole, EI) m/z calcd for C13H16O4 [M]+
236.1049, found 236.1049.
2-Acetyl-5-methoxyphenyl Octanoate (4k). Yield: 51% (45
mg). Colorless oil. Rf = 0.47 (n-hexane/EtOAc = 3:1). 1H NMR (700
MHz, CDCl3): δ 7.82 (d, J = 8.8 Hz, 1H), 6.81 (dd, J1 = 8.7, J2 = 2.5
Hz, 1H), 6.58 (s, 1H), 3.84 (s, 3H), 2.62 (t, J = 7.4 Hz, 2H), 2.49 (s,
3H), 1.78−1.74 (m, 2H), 1.43−1.25 (m, 8H), 0.88 (t, J = 6.9 Hz, 3H).
13C NMR (175 MHz, CDCl3): δ 195.7, 172.2, 163.6, 151.5, 132.4,
123.2, 111.5, 109.3, 55.7, 34.4, 31.6, 29.2, 29.1, 28.9, 24.5, 22.6, 14.0.
IR (KBr): υ 2926, 2856, 1762, 1678, 1606, 1568, 1500, 1464, 1425,
1356, 1256, 1126, 1068, 1026, 965, 813, 749 cm−1. HRMS
(quadrupole, EI) m/z calcd for C17H24O4 [M]+ 292.1675, found
292.1681.
2-Acetyl-5-methoxyphenyl Isobutyrate (4l). Yield: 58% (41
mg). Colorless oil. Rf = 0.22 (n-hexane/EtOAc = 5:1). 1H NMR (700
MHz, CDCl3): δ 7.81 (d, J = 8.7 Hz, 1H), 6.81 (dd, J1 = 8.7, J2 = 2.5
Hz, 1H), 6.56 (s, 1H), 3.84 (s, 3H), 2.90−2.84 (m, 1H), 2.49 (s, 3H),
1.35−1.34 (m, 6H). 13C NMR (175 MHz, CDCl3): δ 195.8, 175.3,
163.6, 151.5, 132.3, 123.4, 111.5, 109.1, 55.7, 34.2, 29.1, 18.7. IR
(KBr): υ 2975, 2935, 1756, 1678, 1606, 1569, 1500, 1466, 1356, 1319,
1255, 1125, 1066, 1025, 965, 905, 810, 734 cm−1. HRMS (quadrupole,
EI) m/z calcd for C13H16O4 [M]+ 236.1049, found 236.1045.
2-Acetyl-5-methoxyphenyl 4-Fluorobenzoate (4d). Yield:
1
86% (74 mg). Colorless oil. Rf = 0.31 (n-hexane/EtOAc = 3:1). H
NMR (700 MHz, CDCl3): δ 8.24−8.22 (m, 2H), 7.88 (d, J = 8.7 Hz,
1H), 7.25−7.18 (m, 2H), 6.87 (dd, J1 = 8.7, J2 = 2.5 Hz, 1H), 6.71 (s,
1H), 3.87 (s, 3H), 2.49 (s, 3H). 13C NMR (175 MHz, CDCl3): δ
195.6, 166.2 (d, JC−F = 253.6 Hz), 164.2, 163.8, 151.5, 132.9 (d, JC−F
=
9.0 Hz), 132.5, 125.7 (d, JC−F = 2.5 Hz), 123.3, 115.9 (d, JC−F = 22.3
Hz), 111.9, 109.3, 55.7, 29.2. IR (KBr): υ 2939, 2840, 1737, 1677,
1605, 1507, 1425, 1357, 1321, 1257, 1239, 1137, 1126, 1067, 1010,
963, 845, 733 cm−1. HRMS (quadrupole, EI) m/z calcd for C16H13FO4
[M]+ 288.0798, found 288.0796.
2-Acetyl-5-methoxyphenyl 4-Bromobenzoate (4e). Yield:
53% (55 mg). White solid. Mp = 106−108 °C. Rf = 0.36 (n-
hexane/EtOAc = 3:1). 1H NMR (700 MHz, CDCl3): δ 8.07−8.05 (m,
2H), 7.88 (d, J = 8.8 Hz, 1H), 7.66−7.65 (m, 2H), 6.87 (dd, J1 = 8.8, J2
= 2.5 Hz, 1H), 6.71 (d, J = 2.5 Hz, 1H), 3.86 (s, 3H), 2.48 (s, 3H). 13
C
NMR (175 MHz, CDCl3): δ 195.5, 164.5, 163.8, 151.4, 132.6, 132.0,
131.8, 128.9, 128.4, 123.1, 112.0, 109.3, 55.8, 29.1. IR (KBr): υ 2983,
1738, 1679, 1608, 1591, 1486, 1424, 1397, 1357, 1262, 1164, 1127,
1069, 1010, 964, 844, 731 cm−1. HRMS (quadrupole, EI) m/z calcd
for C16H13BrO4 [M]+ 347.9997, found 347.9999.
2-Acetyl-5-methoxyphenyl 3-Methylbenzoate (4f). Yield:
80% (68 mg). Pale yellow oil. Rf = 0.33 (n-hexane/EtOAc = 3:1).
1H NMR (700 MHz, CDCl3): δ 8.03−8.01 (m, 2H), 7.89 (d, J = 8.8
Hz, 1H), 7.46−7.25 (m, 2H), 6.86 (dd, J1 = 8.8, J2 = 2.5 Hz, 1H), 6.71
(s, 1H), 3.85 (s, 3H), 2.49 (s, 3H), 2.44 (s, 3H). 13C NMR (175 MHz,
CDCl3): δ 195.7, 165.3, 163.7, 151.7, 138.5, 134.6, 132.4, 130.8, 129.2,
128.6, 127.4, 123.6, 112.0, 109.2, 55.7, 29.5, 21.3. IR (KBr): υ 2922,
2846, 1735, 1677, 1606, 1568, 1425, 1356, 1321, 1258, 1182, 1125,
1065, 1025, 964, 896, 822, 732 cm−1. HRMS (quadrupole, EI) m/z
calcd for C17H16O4 [M]+ 284.1049, found 284.1052.
2-Acetyl-5-methoxyphenyl 3-Chlorobenzoate (4g). Yield:
63% (57 mg). Pale yellow oil. Rf = 0.15 (n-hexane/EtOAc = 5:1).
1H NMR (700 MHz, CDCl3): δ 8.18 (s, 1H), 8.17−8.08 (m, 1H),
7.89 (d, J = 8.7 Hz, 1H), 7.62−7.60 (m, 1H), 7.46 (t, J = 7.9 Hz, 1H),
6.89−6.71 (m, 1H), 6.71 (s, 1H), 3.87 (s, 3H), 2.49 (s, 3H). 13C NMR
(175 MHz, CDCl3): δ 195.5, 164.0, 163.8, 151.4, 134.8, 133.7, 132.6,
131.2, 130.3, 129.9, 128.4, 123.0, 112.0, 109.3, 55.8, 29.1. IR (KBr): υ
2921, 2851, 1732, 1685, 1601, 1481, 1447, 1356, 1248, 1195, 1175,
1057, 1022, 954, 846, 756, 701 cm−1. HRMS (quadrupole, EI) m/z
calcd for C16H13ClO4 [M]+ 304.0502, found 304.0507.
ASSOCIATED CONTENT
* Supporting Information
Spectroscopic data for all compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: insukim@skku.edu.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research was supported by Basic Science Research
Program through the National Research Foundation of Korea
(NRF) funded by the Ministry of Education, Science and
Technology (No. 2013R1A2A2A01005249).
2-Acetyl-5-methoxyphenyl 2-Naphthoate (4h). Yield: 93%
1
(89 mg). Colorless oil. Rf = 0.34 (n-hexane/EtOAc = 3:1). H NMR
(700 MHz, CDCl3): δ 8.81 (s, 1H), 8.21 (dd, J1 = 8.5, J2 = 1.6 Hz,
1H), 8.00 (d, J = 8.0 Hz, 1H), 7.96 (d, J = 8.6 Hz, 1H), 7.91 (d, J = 1.9
Hz, 2H), 7.64−7.62 (m, 1H), 7.59−7.56 (m, 1H), 6.89 (dd, J1 = 8.8, J2
REFERENCES
■
= 2.5 Hz, 1H), 6.78 (d, J = 2.4 Hz, 1H), 3.87 (s, 3H), 2.51 (s, 3H). 13
C
(1) (a) Rosato, D. V.; Rosato, M. V. Plastic Product Material and
Process Selection Handbook; Elesevier: New York, 2004. (b) Riemensch-
neider, W.; Bolt, H. M. Esters, Organic. Ullmann’s Encyclopedia of
Industrial Chemistry; Wiley-VCH: Weinheim, 2005. (c) Otera, J.
Esterification: Methods, Reaction and Application, 2nd ed.; Wiley-VCH:
Weinheim, 2010.
NMR (175 MHz, CDCl3): δ 195.7, 165.3, 163.8, 151.8, 135.9, 132.5,
132.4, 132.2, 129.6, 128.7, 128.5, 127.8, 126.8, 126.6, 125.5, 123.6,
112.0, 109.3, 55.7, 29.5. IR (KBr): υ 2934, 2840, 1734, 1677, 1606,
1569, 1503, 1464, 1424, 1356, 1262, 1187, 1126, 1068, 952, 819, 732
cm−1. HRMS (quadrupole, EI) m/z calcd for C20H16O4 [M]+
320.1049, found 320.1050.
2-Acetyl-5-methoxyphenyl 2-Chlorobenzoate (4i). Yield: 49%
(45 mg). Pale yellow oil. Rf = 0.11 (n-hexane/EtOAc = 5:1). 1H NMR
(700 MHz, CDCl3): δ 8.20 (dd, J1 = 7.7, J2 = 1.4 Hz, 1H), 7.88 (d, J =
8.8 Hz, 1H), 7.53−7.48 (m, 2H), 7.43−7.40 (m, 1H), 6.88 (dd, J1 =
8.7, J2 = 2.5 Hz, 1H), 6.75 (d, J = 2.4 Hz, 1H), 3.88 (s, 3H), 2.52 (s,
3H). 13C NMR (175 MHz, CDCl3): δ 195.7, 163.8, 163.6, 151.2,
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