Diacylation of coumarins by silver-catalyzed decarboxylative cross-coupling

Article abstract of DOI:10.1016/j.tet.2014.12.029

A mild silver-catalyzed decarboxylative acylation of coumarins has been developed by using α-oxocarboxylic acids as acyl sources. This protocol provides an efficient and straightforward access to aroyl substituted coumarins in moderate to excellent yields with good selectivities. Furthermore, the reaction conditions were also applicable to quinolinones and naphthoquinones, affording the corresponding acylated heterocyclic compounds.

Full text of DOI:10.1016/j.tet.2014.12.029

Tetrahedron xxx (2014) 1e7
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Diacylation of coumarins by silver-catalyzed decarboxylative
cross-coupling
*
Hua Wang, Shi-Liu Zhou, Li-Na Guo, Xin-Hua Duan
Department of Chemistry, School of Science and MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi’an Jiaotong
University, Xi’an 710049, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A mild silver-catalyzed decarboxylative acylation of coumarins has been developed by using
a-ox-
Received 13 August 2014
Received in revised form 30 November 2014
Accepted 8 December 2014
Available online xxx
ocarboxylic acids as acyl sources. This protocol provides an efficient and straightforward access to aroyl
substituted coumarins in moderate to excellent yields with good selectivities. Furthermore, the reaction
conditions were also applicable to quinolinones and naphthoquinones, affording the corresponding
acylated heterocyclic compounds.
Ó 2014 Published by Elsevier Ltd.
Keywords:
Decarboxylation
Acylation
Radical
Silver-catalyzed
Substituted coumarins
1. Introduction
Coumarins are widely used in pharmaceuticals, agrochemicals,
organic materials, and in other areas due to their remarkable bi-
ological activities and optical properties.1 For examples, Armillar-
isin A, Warfarin, and Acenocoumarol with containing carbonyl
groups in coumarins usually used clinically as antibiotic, antico-
agulant, and anticoagulant agents (Scheme 1).1a As a result, many
effective methods for the synthesis of coumarins have been de-
veloped over the past several years.2 Among these methods, the
synthesis of substituted coumarins is more attractive because of
their extensive existence as core structures in natural products and
pharmaceuticals. Recently, the transition metal-catalyzed direct
regioselective C-3 or C-4 functionalization of simple coumarins
provided an efficient way to obtain substituted coumarins. For
example, palladium-catalyzed C-4 regioselective arylation of cou-
marins using arylboronic acids and simple arenes was extensively
developed by Jafarpour, Li and Hong.3aec Lately, the direct C-3
functionalization of coumarins has also been documented in the
literature.3deh However, most of these approaches are mainly fo-
cused on monosubstituted coumarins, the corresponding 3,4-
disubstituted coumarins are less explored.4 Therefore, the de-
velopment of a general procedure for the synthesis of poly-
substituted coumarins using environmentally friendly and
inexpensive reagents is still highly desirable.
Scheme 1. Biologically active coumarins containing carbonyl groups.
In recent years, the application of readily available and stable car-
boxylic acids instead of expensive and sensitive organometallic re-
agents is highly attractive for organic chemists.5 Up to now, great
progress has been made for the construction of CeC and C-hetero-
atom bonds through the transition metal-catalyzed decarboxylative
cross-coupling reactions.6 More recently, Goossen,7a,b Ge,7c,d and
others7fej including our group7e have also developed a series of
novel palladium-catalyzed decarboxylative acylation reactions us-
ing
recently discovered that silver-catalyzed decarboxylative coupling
of -oxocarboxylic acids with alkenes could also be applied to the
a-oxocarboxylic acids as acyl sources. In this regard, our group
a
synthesis of heterocycles and organofluorine compounds through
tandem radical process.8aec Herein we report a mild synthetic
method for preparation of monosubstituted and polysubstituted
coumarins through direct decarboxylative cross-coupling reactions.
2. Results/discussion
We began our investigation by treatment of coumarin (1a) with
phenylglyoxylic acid (2a) in the presence of AgNO3 (10 mol %) and
* Corresponding author. E-mail address: duanxh@mail.xjtu.edu.cn (X.-H. Duan).
http://dx.doi.org/10.1016/j.tet.2014.12.029
0040-4020/Ó 2014 Published by Elsevier Ltd.
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H. Wang et al. / Tetrahedron xxx (2014) 1e7
Table 2
K2S2O8 (2 equiv) in different solvents (Table 1). As expected, the
reaction proceeded smoothly at room temperature in DMSO/H2O
(1:1), affording the desired 3,4-diacylcoumarin 3a in 68% yield,
along with 24% yield of 3-acylcoumarin 3a0 (entry 1).9 Screening of
solvents revealed that the reactions were fully suppressed in
CH3CN/H2O, DCM/H2O, and acetone/H2O (entries 2e4). For the
different oxidants, both Na2S2O8 and (NH4)2S2O8 resulted in satis-
factory yields (entries 5 and 6), while oxone was ineffective (entry
7). Various catalysts were also examined, but none of them gave
better results than AgNO3 (entries 8e10). Further optimization
found that no reaction took place in the absence of catalyst or ox-
idant (entries 11 and 12).
,b
Scope of a
-oxocarboxylic acidsa
Under the optimal reaction conditions, we explored the scope
of the reaction with a variety of
Both electron-rich and electron-poor
a
-oxocarboxylic acids 2 (Table 2).
-oxocarboxylic acids 2
a
could successfully afford the corresponding products 3 or 30 in
moderate to good yields with excellent functional group toler-
ance (3bek). Phenylglyoxylic acids containing electron-rich
groups at the para position of the aromatic ring, such as 2b and
2c led to the 3,4-diacylcoumarins 3b and 3c in moderate yields
along with a considerable amount of monoacylcoumarins 30. In-
terestingly, phenylglyoxylic acids with p-substituted electron-
withdrawing groups gave the 3-acylcoumarins 3d0eg0 as major
products, which perhaps arises from the nucleophilicities of the
in situ generated acyl radicals (vide infra). Notably, when the
more sterically congested o-substituted phenylglyoxylic acids
2hej were used, the 3,4-diacylcoumarins were selectively ob-
tained (3hej). Furthermore, multisubstituted phenylglyoxylic
acid 2k was also suitable for the reaction, giving the desired
diacylated coumarin 3k in 85% yield. These results demonstrated
that the steric effect was of crucial importance for the selectivity
of the reaction. Finally,
b-naphthyloxoacetic acid and 2-
a
Reaction conditions: AgNO3 (10 mol %), 1a (0.2 mmol, 1 equiv), 2 (0.48 mmol, 2.4
thienylglyoxylic acid were selectively monoacylated in moder-
equiv), K2S2O8 (0.4 mmol, 2 equiv), DMSO/H2O (1:1, 2 mL), room temperature, 24 h.
ated yields (3l0 and 3m0).
b
Yields of 30 are given in parentheses.
Next, other coumarins were also investigated with o-methyl-
phenylglyoxylic acid 2h as reactant (Table 3). In general, we found
that coumarins with electron-donating groups on the phenyl ring
reacted smoothly to give the corresponding diacylated coumarins
in high yields (4a, 4c, 4d, and 4f). By contrast, coumarins containing
electron-withdrawing groups, such as 7-chloro- and 6,8-
dichlorocoumarin, led to the desired products 4e and 4g in some-
what lower yields. When the 6-nitrocoumarin was used, only
a trace amount of the product 4b was observed. These results im-
plied that the electronic effect of the R group on the phenyl ring of
coumarins was quite significant. It is noteworthy that 5,8-
dimethylcoumarin only furnished monoacylated product 4h0
probably due to the steric effect. Gratifyingly, coumarin having
methyl group on C-4 position afforded the monoacylated product
4i in 43% yield.
Table 1
Optimization of the reaction conditionsa
Entry
Oxidant (equiv)
Solvent
Yieldb (%)
68 (24)c
Trace
Finally, a series of other heterocyclic compounds were also ex-
amined under the optimal conditions (Table 4). When 1-methyl-2-
quinolinones were treated with 2a, the diacylated quinolinones
were obtained in somewhat low yields because of the low con-
version (5a and 5b). Moreover, chromone was also suitable for this
reaction, affording the desired product 5c in 36% isolated yield.
Unfortunately, 2-phenyl-4-chromone was ineffective in this system
(5d). 2,6-Dimethylquinone reacted with 2a to give the 5e in 56%
yield. Notably, substituted 1,4-naphthoquinone performed well,
leading to the monoacylated naphthoquinone in high yields (5f and
5g). For 2-hydroxy-1,4-naphthoquinone, the 5h was obtained,
which was formed by acylation of the C]C and CeO bonds of the
naphthoquinone.
1
2
3
4
5
6
7
K2S2O8 (2)
K2S2O8 (2)
K2S2O8 (2)
K2S2O8 (2)
Na2S2O8 (2)
(NH4)2S2O8 (2)
Oxone
K2S2O8 (2)
K2S2O8 (2)
K2S2O8 (2)
d
DMSO/H2O (1:1)
CH3CN/H2O (1:1)
DCM/H2O (1:1)
Acetone/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
n.r.d
Trace
65 (20)c
64 (21)c
n.r.d
8e
9f
10g
11
12h
61 (22)c
51 (16)c
50 (17)c
n.r.d
K2S2O8 (2)
n.r.d
a
Reaction conditions: AgNO3 (10 mol %), 1a (0.2 mmol, 1 equiv), 2a (0.48 mmol,
2.4 equiv), oxidant (0.4 mmol, 2 equiv), solvent (2 mL), room temperature, 24 h.
b
Yield of isolated product.
Yield of 3a0 is given in parentheses.
c
To further probe the mechanism of the reaction, we conducted
the reaction of 3a0 with 2a under the standard conditions
(Scheme 2). The desired product 3a was isolated in 73% yield, along
with 19% of 3a0 was recovered. This result indicated that 3a0 should
be an intermediate product in this transformation. Furthermore,
d
n.r.¼no reaction.
e
10 mol % of Ag2CO3 was used.
f
10 mol % of AgOAc was used.
10 mol % of Ag2O was used.
Without a catalyst.
g
h
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H. Wang et al. / Tetrahedron xxx (2014) 1e7
3
Table 3
Scope of coumarinsa
Scheme 2. Direct decarboxylative coupling of 3-acylcoumarin 3a0 with 2a.
Scheme 3. Proposed mechanism.
cases of acyl radicals having electron-withdrawing groups (Table 2,
2deg), the corresponding monosubstituted coumarins 30 were
obtained as major products, which might be attributed to the less
nucleophilicities of the acyl radical.
3. Conclusion
In summary, we have developed a direct acylation of coumarins
by Ag-catalyzed decarboxylative cross-coupling reactions. These
methods allow efficient access to various 3,4-diacylcoumarins or 3-
acylcoumarins bearing a wide range of functional groups under
mild conditions. In addition, the excellent selectivity of the reaction
could be controlled by using a series of o-substituted
a-oxo-
carboxylic acids.
the yields of 3a were also decreased dramatically by addition of
radical scavengers, such as TEMPO and BHT, which implies that the
reaction probably proceeded via free radical process. Based on
these results and previous studies,8a,b a possible reaction mecha-
nism was proposed as shown in Scheme 3. The reaction is initiated
by the silver-catalyzed oxidative decarboxylation of 2a by persul-
fate to form the acyl radical I,10 which attacks the C]C bond of
coumarin 1a to give the radical intermediate II. The radical II was
then oxidized to the corresponding carbocation followed by the
loss of Hþ, affording the 3-acylcoumarin 3a0. Finally, the resulting
3a0 would then readily couple with nucleophilic acyl radical I10 to
give the diacylated coumarin 3a and regenerate the catalyst. In the
4. Experimental section
4.1. General information
All reactions were carried out under an atmosphere of nitrogen
with the strict exclusion of air. Column chromatography was car-
ried out on silica gel. 1H NMR and 13C NMR spectra were recorded at
400 MHz and 100 MHz in solvents as indicated. Chemical shift are
reported in parts per million (ppm) from CDCl3 using TMS as in-
ternal standard. IR spectra were recorded on an FT-IR spectrometer
and only major peaks are reported in cmꢀ1. HRMS were obtained on
a Q-TOF micro spectrometer. Melting points were determined on
a microscopic apparatus and were uncorrected.
Table 4
,b
Scope of heterocyclic compoundsa
4.2. Starting materials
Coumarin 1a was commercial available and the other coumarin
derivatives 1 were synthesized according to the literature, and the
NMR spectroscopies were in full accordance with the data in the
literature.2g Phenylglyoxylic acid 2a was commercial available.
Other
a-oxocarboxylic acids 2 were prepared from the corre-
sponding methyl ketones according to the reported procedure.11
4.3. General procedure for the decarboxylative acylation of
coumarins with a-oxocarboxylic acids
a
Reaction conditions: AgNO3 (10 mol %), heterocyclic compounds (0.2 mmol, 1
A 10 mL oven-dried Schlenk-tube was charged with AgNO3
(3.4 mg, 10 mol %), coumarin (1, 0.2 mmol, 1.0 equiv), and K2S2O8
(108 mg, 0.4 mmol, 2.0 equiv). The tube was evacuated and back-
equiv), 2a (0.48 mmol, 2.4 equiv), K2S2O8 (0.4 mmol,
2 equiv), DMSO/H2O
(1:1, 2 mL), room temperature, 24 h.
b
The ratio given in parentheses corresponds to 3,4-diacyl quinolinone 5b and 3-
acyl quinolinone 5b’, the ratio was determined by 1H NMR.
filled with nitrogen (three times).
a-Oxocarboxylic acids (2,
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4
H. Wang et al. / Tetrahedron xxx (2014) 1e7
0.48 mmol, 2.4 equiv) in DMSO/H2O (1:1) 2 mL were added by
syringe. The tube was then sealed and the mixture was stirred for
24 h at room temperature. Upon completion of the reaction, the
mixture was diluted with EtOAc, filtered through a pad of Celite,
and the filtrate was then removed under vacuo. The residue was
purified with chromatography column on silica gel (gradient eluent
of EtOAc/petroleum ether: 1:30 to 1:15) to give the corresponding
products 3 or 4 in yields listed in Tables 2 and 3.
d
¼189.3, 188.1, 162.2 (d, JCeF¼257.8 Hz), 161.5 (d, JCeF¼253.3 Hz),
158.5 (d, JCeF¼2.7 Hz), 155.7, 154.5, 136.7 (d, JCeF¼9.1 Hz), 135.2 (d,
JCeF¼8.9 Hz), 134.0, 130.6, 127.0, 125.9 (d, JCeF¼11.7 Hz), 125.1, 124.9
(d, JCeF¼3.5 Hz), 124.5 (d, JCeF¼3.4 Hz), 124.4, 123.7 (d, JCeF¼2.7 Hz),
117.5, 117.0 (d, JCeF¼21.7 Hz), 116.6 (d, JCeF¼2.1 Hz), 116.1 (d,
JCeF¼22.4 Hz) ppm; IR (KBr): ymax 1732, 1663, 1609, 1455,
1239 cmꢀ1; HRMS (ESI) calcd for C23H12F2NaO4 [MþNa]þ 413.0596,
found 413.0599.
4.3.1. 3,4-Dibenzoyl-chromen-2-one (3a). A white solid, mp
147e149 ꢁC, Rf 0.2 (EtOAc/petroleum ether¼1:10); 1H NMR
4.3.7. 3,4-Bis-(2-chloro-benzoyl)-chromen-2-one (3j). A white solid,
mp 158e160 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10); 1H NMR
(400 MHz, CDCl3):
d
¼7.89e7.88 (d, J¼7.2 Hz, 2H), 7.82e7.80 (d,
(400 MHz, CDCl3):
d
¼7.92e7.89 (dd, J¼8.0, 1.6 Hz, 1H), 7.69e7.65
J¼7.2 Hz, 2H), 7.68e7.56 (m, 3H), 7.50e7.41 (m, 5H), 7.29e7.23 (m,
2H); 13C NMR (100 MHz, CDCl3):
¼192.9, 191.4, 158.3, 154.1, 153.3,
136.0, 135.3, 135.0, 134.1, 133.7, 129.8, 129.4, 129.0, 128.6, 127.3, 125.2,
(m, 1H), 7.53e7.27 (m, 10H), 13C NMR (100 MHz, CDCl3):
d
¼191.5,
d
190.9, 158.2, 156.0, 154.6, 137.4, 134.4, 134.3, 134.1, 134.0, 132.8,
132.6, 131.9, 131.7, 130.4, 130.0, 127.7, 127.1, 125.3, 122.9, 117.5,
117.3 ppm; IR (KBr): ymax 1737, 1605, 1239 cmꢀ1; HRMS (ESI) calcd
for C23H12Cl2NaO4 [MþNa]þ 445.0005, found 445.0007.
124.8, 117.4, 116.8 ppm; IR (KBr): ymax 1727, 1668, 1598, 1249 cmꢀ1
;
HRMS (ESI) calcd for C23H14NaO4 [MþNa]þ 377.0784, found 377.0784.
4.3.2. 3,4-Bis-(4-methyl-benzoyl)-chromen-2-one (3b). A white
solid, mp 189e191 ꢁC, Rf 0.2 (EtOAc/petroleum ether¼1:10); 1H
4.3.8. 3,4-Bis-(2,4-dimethyl-benzoyl)-chromen-2-one (3k). A white
solid, mp 137e139 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10); 1H
NMR (400 MHz, CDCl3):
d
¼7.78e7.76 (d, J¼8.0 Hz, 2H), 7.73e7.70
NMR (400 MHz, CDCl3):
d¼7.62e7.58 (m, 1H), 7.48e7.42 (m, 3H),
(d, J¼8.4 Hz, 2H), 7.65e7.61 (m, 1H), 7.48e7.46 (d, J¼8.0 Hz, 1H),
7.32e7.30 (dd, J¼8.4, 1.6 Hz, 1H), 7.24e7.20 (m, 1H), 7.07 (s, 1H),
7.28e7.21 (m, 6H), 2.40 (s, 3H), 2.39 (s, 3H); 13C NMR (100 MHz,
7.01e6.99 (m, 3H), 2.43 (s, 3H), 2.33 (s, 3H), 2.31 (s, 3H), 2.27 (s, 3H);
CDCl3):
d
¼192.3, 190.8, 158.4, 154.0, 152.8, 146.4, 145.3, 133.5, 133.4,
13C NMR (100 MHz, CDCl3):
d
¼193.6, 192.4, 158.4, 154.0, 152.6,
132.9, 130.0, 129.7, 129.3, 127.3, 125.1, 124.8, 117.4, 116.9, 21.9,
21.8 ppm; IR (KBr): ymax 1728, 1667, 1604, 1562, 1253 cmꢀ1; HRMS
(ESI) calcd for C25H18NaO4 [MþNa]þ 405.1097, found 405.1099.
144.8, 143.3, 141.1, 139.9, 133.4, 133.3, 133.2, 132.6, 131.7, 131.6, 127.3,
126.7, 125.1, 125.0, 117.2, 117.1, 21.6, 21.5, 21.4, 20.8 ppm; IR (KBr):
ymax 1731, 1665, 1607, 1248 cmꢀ1; HRMS (ESI) calcd for C27H22NaO4
[MþNa]þ 433.1410, found 433.1411.
4.3.3. 3,4-Bis-(4-methoxy-benzoyl)-chromen-2-one (3c). A white
solid, mp 202e204 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:5); 1H
4.3.9. 3-Benzoyl-chromen-2-one (3a0).2c Rf 0.3 (EtOAc/petroleum
NMR (400 MHz, CDCl3):
d
¼7.85e7.79 (m, 4H), 7.64e7.60 (m, 1H),
ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼8.09 (s, 1H), 7.90e7.88
d
7.47e7.45 (d, J¼8.0 Hz, 1H), 7.30e7.21 (m, 2H), 6.92e6.87 (m, 4H),
(d, J¼7.2 Hz, 2H), 7.68e7.60 (m, 3H), 7.51e7.47 (t, J¼8.0 Hz, 2H),
3.86 (s, 3H), 3.85 (s, 3H); 13C NMR (100 MHz, CDCl3):
d¼190.9,189.4,
7.43e7.41 (d, J¼8.4 Hz, 1H), 7.38e7.34 (td, J¼7.6, 0.8 Hz, 1H); 13C
165.1, 164.5, 158.4, 153.9, 152.0, 133.3, 132.5, 132.2, 128.9, 128.3,
127.2, 125.0, 124.7, 117.3, 116.9, 114.3, 113.9, 55.6, 55.5 ppm; IR (KBr):
ymax 1727, 1598, 1506, 1254, 1169 cmꢀ1; HRMS (ESI) calcd for
NMR (100 MHz, CDCl3):
133.6, 129.6, 129.2, 128.6, 127.0, 125.0, 118.2, 117.0 ppm.
d
¼191.7, 158.4, 154.8, 145.4, 136.2, 133.8,
C
25H18NaO6 [MþNa]þ 437.0996, found 437.0994.
4.3.10. 3-(4-Methyl-benzoyl)-chromen-2-one (3b0).2c Rf 0.3 (EtOAc/
petroleum ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼8.06 (s, 1H),
d
4.3.4. 3,4-Bis-(4-fluoro-benzoyl)-chromen-2-one (3d). A white
solid, mp 176e178 ꢁC, Rf 0.2 (EtOAc/petroleum ether¼1:10); 1H
7.80e7.78 (d, J¼8.0 Hz, 2H), 7.67e7.58 (m, 2H), 7.42e7.40 (d,
J¼8.4 Hz,1H), 7.37e7.33 (m,1H), 7.29e7.27 (d, J¼8.0 Hz, 2H), 2.43 (s,
NMR (400 MHz, CDCl3):
d
¼7.94e7.91 (m, 2H), 7.87e7.83 (m, 2H),
3H), 13C NMR (100 MHz, CDCl3):
d
¼191.2, 158.5, 154.7, 145.0, 144.9,
7.69e7.65 (m, 1H), 7.50e7.48 (d, J¼8.4 Hz, 1H), 7.29e7.23 (m, 2H),
133.6, 133.5, 129.8, 129.3, 129.1, 127.3, 124.9, 118.2, 116.9, 21.8 ppm;
7.18e7.09 (m, 4H); 13C NMR (100 MHz, CDCl3):
d¼191.2, 189.8, 166.8
IR (KBr): ymax 1726, 1662, 1607, 1241 cmꢀ1; HRMS (ESI) calcd for
(d, JCeF¼257.5 Hz),166.4 (d, JCeF¼255.4 Hz),158.1, 154.1, 153.1,133.9,
132.6 (d, JCeF¼9.8 Hz), 132.3 (d, JCeF¼9.6 Hz), 131.8 (d, JCeF¼2.8 Hz),
127.2, 125.3, 124.5, 117.6, 116.6 (d, JCeF¼22.3 Hz), 116.5, 116.0 (d,
JCeF¼22.0 Hz) ppm; IR (KBr): ymax 1728, 1669, 1597, 1245,
1155 cmꢀ1; HRMS (ESI) calcd for C23H12F2NaO4 [MþNa]þ 413.0596,
found 413.0596.
C
17H13O3 [MþH]þ 265.0859, found 265.0862.
4.3.11. 3-(4-Methoxy-benzoyl)-chromen-2-one
(3c0).12a Rf
0.4
¼8.03
(EtOAc/petroleum ether¼1:5); 1H NMR (400 MHz, CDCl3):
d
(s, 1H), 7.90e7.88 (d, J¼9.2 Hz, 2H), 7.66e7.58 (m, 2H), 7.42e7.40 (d,
J¼8.4 Hz, 1H), 7.37e7.30 (td, J¼7.6, 0.8 Hz, 1H), 6.97e6.95 (d,
J¼8.8 Hz, 2H), 3.89 (s, 3H); 13C NMR (100 MHz, CDCl3):
¼190.0,
d
4.3.5. 3,4-Bis-(2-methyl-benzoyl)-chromen-2-one (3h). A white
solid, mp 147e149 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10); 1H
164.3,158.6,154.6,144.6,133.3,132.2,129.0,127.6,124.9,118.3,116.9,
113.9, 55.6 ppm; IR (KBr): ymax 1716, 1606, 1246, 1174 cmꢀ1; HRMS
(ESI) calcd for C17H12NaO4 [MþNa]þ 303.0628, found 303.0624.
NMR (400 MHz, CDCl3):
d
¼7.66e7.62 (m, 1H), 7.58e7.56 (d,
J¼8.0 Hz, 1H), 7.51e7.49 (d, J¼7.6 Hz, 1H), 7.46e7.41 (m, 2H),
7.38e7.32 (m, 2H), 7.29e7.18 (m, 5H), 2.50 (s, 3H), 2.31 (s, 3H); 13
NMR (100 MHz, CDCl3):
C
4.3.12. 3-(4-Fluoro-benzoyl)-chromen-2-one (3d0).12b Rf 0.3 (EtOAc/
d¼194.2, 193.1, 158.3, 154.2, 153.3, 141.2,
petroleum ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼8.11 (s, 1H),
d
139.5,136.1,134.2,133.7,133.6,132.9,132.5,132.4,131.8,130.7,127.4,
126.0, 125.6, 125.1, 125.0, 117.4, 117.1, 21.5, 20.7 ppm; IR (KBr): ymax
1731, 1668, 1600, 1242 cmꢀ1; HRMS (ESI) calcd for C25H19O4
[MþH]þ 383.1278, found 383.1291.
7.94e7.90 (m, 2H), 7.69e7.61 (m, 2H), 7.43e7.41 (d, J¼8.4 Hz, 1H),
7.39e7.35 (td, J¼7.6, 0.8 Hz, 1H), 7.18e7.14 (m, 2H); 13C NMR
(100 MHz, CDCl3):
d
¼190.1, 166.2 (d, JCeF¼254.7 Hz), 158.5, 154.8,
145.7, 133.8, 132.6 (d, JCeF¼2.9 Hz), 132.3 (d, JCeF¼9.5 Hz), 129.2,
126.8, 125.1, 118.1, 117.0, 116.0, 115.8 (d, JCeF¼22.0 Hz) ppm; IR (KBr):
ymax 1708, 1661, 1598, 1244, 1160 cmꢀ1; HRMS (ESI) calcd for
4.3.6. 3,4-Bis-(2-fluoro-benzoyl)-chromen-2-one (3i). A white solid,
mp 163e165 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10); 1H NMR
C
16H9FNaO3 [MþNa]þ 291.0428, found 291.0430.
(400 MHz, CDCl3):
d
¼8.09e8.05 (td, J¼7.6, 2.0 Hz, 1H), 7.72e7.50
(m, 4H), 7.47e7.45 (dd, J¼8.4, 0.4 Hz, 1H), 7.35e7.26 (m, 3H),
4.3.13. 3-(4-Chloro-benzoyl)-chromen-2-one (3e0).2c Rf 0.3 (EtOAc/
7.24e7.19 (m, 1H), 7.10e7.05 (m, 2H); 13C NMR (100 MHz, CDCl3):
petroleum ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼8.13 (s, 1H),
d
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H. Wang et al. / Tetrahedron xxx (2014) 1e7
5
7.83e7.81 (d, J¼8.8 Hz, 2H), 7.69e7.61 (m, 2H), 7.47e7.45 (d,
J¼8.8 Hz, 2H), 7.43e7.41 (d, J¼8.4 Hz, 1H), 7.39e7.35 (td, J¼8.0,
0.8 Hz,1H); 13C NMR (100 MHz, CDCl3):
21.5, 20.7, 15.6 ppm; IR (KBr): ymax 1731, 1669, 1569, 1243 cmꢀ1
;
HRMS (ESI) calcd for C26H21O4 [MþH]þ 397.1434, found 397.1435.
d¼190.5, 158.4,154.8,146.0,
140.3, 134.6, 133.9, 130.9, 129.3, 128.9, 126.6, 125.1, 118.1, 117.0 ppm;
4.3.20. 7-Methoxy-3,4-bis-(2-methyl-benzoyl)-chromen-2-one
IR (KBr): ymax 1714, 1662, 1608, 1242 cmꢀ1; HRMS (ESI) calcd for
(4d). A white solid, mp 173e175 ꢁC, Rf 0.3 (EtOAc/petroleum
C
16H10ClO3 [MþH]þ 285.0313, found 285.0320.
ether¼1:8); 1H NMR (400 MHz, CDCl3):
¼7.57e7.55 (d, J¼7.6 Hz,
d
1H), 7.45e7.41 (m, 2H), 7.36e7.32 (t, J¼7.6 Hz, 1H), 7.30e7.16 (m,
5H), 6.91 (d, J¼2.4 Hz, 1H), 6.83e6.80 (dd, J¼8.8, 2.4 Hz, 1H), 3.91 (s,
4.3.14. 3-(4-Bromo-benzoyl)-chromen-2-one (3f0).9c Rf 0.3 (EtOAc/
petroleum ether¼1:10); 1H NMR (400 MHz, DMSO-d6):
d
¼8.47 (s,
3H), 2.56 (s, 3H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl3):
d¼194.6,
1H), 7.89e7.86 (m, 3H), 7.77e7.73 (m, 3H), 7.51e7.49 (d, J¼8.4 Hz,
193.6,164.5,158.7,156.6,154.9,141.1,138.7,137.0,134.2,133.5,132.6,
132.5,131.9,131.5,129.9,128.7,125.9,125.5,120.9,113.8,110.6,101.0,
1H), 7.45e7.41 (t, J¼7.6 Hz, 1H); 13C NMR (100 MHz, DMSO-d6):
d
¼191.0, 158.1, 154.3, 146.1, 135.3, 133.8, 131.8, 131.5, 129.9, 128.1,
56.0, 21.5, 20.5 ppm; IR (KBr): ymax 1724, 1669, 1615, 1258 cmꢀ1
;
125.9, 125.0, 118.3, 116.4 ppm; IR (KBr): ymax 1713, 1663, 1608,
1243 cmꢀ1; HRMS (ESI) calcd for C16H9BrNaO3 [MþNa]þ 350.9627,
found 350.9634.
HRMS (ESI) calcd for
435.1202.
C
26H20NaO5 [MþNa]þ 435.1203, found
4.3.21. 7-Chloro-3,4-bis-(2-methyl-benzoyl)-chromen-2-one (4e). A
white solid, mp 168e170 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10);
4.3.15. 3-(4-Iodo-benzoyl)-chromen-2-one (3g0). A white solid, mp
206e208 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10); 1H NMR
1H NMR (400 MHz, CDCl3):
d
¼7.54e7.52 (d, J¼7.6 Hz, 1H), 7.49e7.41
(400 MHz, CDCl3):
d
¼8.13 (s, 1H), 7.86e7.84 (d, J¼8.4 Hz, 2H),
(m, 3H), 7.39e7.35 (td, J¼7.6, 1.2 Hz, 1H), 7.29e7.18 (m, 6H), 2.47 (s,
7.69e7.61 (m, 2H), 7.59e7.57 (d, J¼8.4 Hz, 2H), 7.43e7.41 (d,
3H), 2.28 (s, 3H); 13C NMR (100 MHz, CDCl3):
d
¼193.7, 192.6, 157.7,
J¼8.4 Hz, 1H), 7.39e7.35 (td, J¼7.6, 0.8 Hz, 1H); 13C NMR (100 MHz,
154.4, 152.5, 141.3, 139.8, 139.6, 135.9, 134.0, 133.9, 132.8, 132.6,
132.5, 131.8, 130.7, 128.3, 126.1, 125.8, 125.6, 124.8, 117.7, 115.6, 21.4,
20.7 ppm; IR (KBr): ymax 1737, 1670, 1599, 1256 cmꢀ1; HRMS (ESI)
calcd for C25H17ClNaO4 [MþNa]þ 439.0708, found 439.0706.
CDCl3):
d
¼191.1, 158.4, 154.9, 146.1, 137.9, 135.6, 133.9, 130.8, 129.3,
126.5, 125.1, 118.1, 117.0, 102.0 ppm; IR (KBr): ymax 1713, 1664, 1607,
1579, 1242 cmꢀ1; HRMS (ESI) calcd for C16H9INaO3 [MþNa]þ
398.9489, found 398.9502.
4.3.22. 6,8-Dimethyl-3,4-bis-(2-methyl-benzoyl)-chromen-2-one
4.3.16. 3-(Naphthalene-2-carbonyl)-chromen-2-one (3l0).2c Rf 0.3
(4f). A white solid, mp 209e211 ꢁC, Rf 0.3 (EtOAc/petroleum
(EtOAc/petroleum ether¼1:8); 1H NMR (400 MHz, CDCl3):
d¼8.36
ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼7.55e7.53 (d, J¼8.0 Hz,
d
(s, 1H), 8.14 (s, 1H), 8.01e7.89 (m, 4H), 7.70e7.60 (m, 3H), 7.57e7.53
(m,1H), 7.46e7.44 (d, J¼8.4 Hz,1H), 7.40e7.36 (dd, J¼7.6, 0.8 Hz,1H);
1H),
d
¼7.47e7.45 (d, J¼7.6 Hz, 1H), 7.43e7.40 (t, J¼7.6 Hz, 1H),
7.36e7.26 (m, 3H), 7.22e7.16 (m, 3H), 6.95 (s, 1H), 2.48 (s, 6H), 2.27
13C NMR (100 MHz, CDCl3):
d
¼191.6,158.5,154.8,145.3,136.0,133.6,
(s, 6H); 13C NMR (100 MHz, CDCl3):
d¼194.6, 193.3, 158.6, 153.7,
132.3,132.0,129.7,129.2,128.9,128.6,127.9,127.3,126.9,125.0,124.6,
118.2, 117.0 ppm; IR (KBr): ymax 1719, 1653, 1609, 1196 cmꢀ1; HRMS
(ESI) calcd for C20H12NaO3 [MþNa]þ 323.0679, found 323.0688.
150.8, 141.2, 139.4, 136.3, 136.2, 134.4, 134.3, 133.6, 132.8, 132.4,
132.3, 131.7, 130.6, 126.5, 125.9, 125.5, 124.6, 124.1, 116.5, 21.5, 20.8,
20.7, 15.5 ppm; IR (KBr): ymax 1734, 1669, 1572, 1236 cmꢀ1; HRMS
(ESI) calcd for C27H22NaO4 [MþNa]þ 433.1410, found 433.1412.
4.3.17. 3-(Thiophene-2-carbonyl)-chromen-2-one (3m0).12a Rf 0.1
(EtOAc/petroleum ether¼1:10); 1H NMR (400 MHz, CDCl3):
4.3.23. 6,8-Dichloro-3,4-bis-(2-methyl-benzoyl)-chromen-2-one
d
¼8.10 (s, 1H), 7.78e7.76 (d, J¼5.2 Hz, 1H), 7.74e7.73 (d, J¼4.0 Hz,
(4g). A white solid, mp 185e187 ꢁC, Rf 0.2 (EtOAc/petroleum
1H), 7.68e7.64 (td, J¼8.4, 1.2 Hz, 1H), 7.61e7.59 (dd, J¼8.0, 1.2 Hz,
1H), 7.42e7.40 (d, J¼8.0 Hz, 1H), 7.38e7.34 (t, J¼7.6 Hz, 1H),
ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼7.70e7.69 (d, J¼2.4 Hz,
d
1H), 7.50e7.43 (m, 3H), 7.40e7.37 (t, J¼7.2 Hz, 1H), 7.29e7.18 (m,
7.18e7.16 (t, J¼4.8 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d¼182.9,
5H), 2.40 (s, 3H), 2.24 (s, 3H); 13C NMR (100 MHz, CDCl3):
d¼193.0,
158.2, 154.6, 144.7, 142.8, 135.7, 135.1, 133.7, 129.1, 128.4, 126.9,
125.0, 118.1, 116.9 ppm; IR (KBr): ymax 1726, 1635, 1607, 1410,
1245 cmꢀ1; HRMS (ESI) calcd for C14H8NaO3S [MþNa]þ 279.0086,
found 279.0089.
191.8, 156.7, 150.8, 148.5, 141.5, 140.2, 135.2, 134.2, 133.7, 133.4,
133.0, 132.9, 132.6, 132.0, 131.3, 130.4, 126.5, 126.1, 125.7, 125.1,
123.4, 119.0, 21.3, 20.8 ppm; IR (KBr): ymax 1745, 1671, 1555,
1228 cmꢀ1; HRMS (ESI) calcd for C25H16Cl2NaO4 [MþNa]þ 473.0318,
found 473.0317.
4.3.18. 6-Methyl-3,4-bis-(2-methyl-benzoyl)-chromen-2-one (4a). A
white solid, mp 182e184 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10);
4.3.24. 5,8-Dimethyl-3-(2-methyl-benzoyl)-chromen-2-one (4h0). A
white solid, mp 156e158 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10);
1H NMR (400 MHz, CDCl3):
d
¼7.56e7.54 (d, J¼7.6 Hz, 1H), 7.47e7.41
(m, 3H), 7.37e7.33 (m, 2H), 7.28e7.26 (d, J¼7.6 Hz, 1H), 7.23e7.16
1H NMR (400 MHz, CDCl3):
d
¼8.40 (s, 1H), 7.46e7.40 (m, 2H),
(m, 3H), 7.12 (s, 1H), 2.48 (s, 3H), 2.31 (s, 3H), 2.27 (s, 3H); 13C NMR
7.37e7.35 (d, J¼7.6 Hz,1H), 7.32e7.30 (d, J¼7.6 Hz,1H), 7.25e7.22 (t,
(100 MHz, CDCl3):
d
¼194.3, 193.1, 158.5, 153.2, 152.4, 141.2, 139.4,
J¼7.6 Hz, 1H), 7.07e7.05 (d, J¼8.0 Hz, 1H), 2.54 (s, 3H), 2.53 (s, 3H),
136.2,135.1,134.8,134.2,133.7,132.8,132.4,132.3,131.7,130.6,127.0,
126.0, 125.6, 124.5, 117.1, 116.8, 21.4, 20.9, 20.7 ppm; IR (KBr): ymax
1723, 1677, 1560, 1242 cmꢀ1; HRMS (ESI) calcd for C26H20NaO4
[MþNa]þ 419.1254, found 419.1254.
2.43 (s, 3H); 13C NMR (100 MHz, CDCl3):
d
¼194.2,158.2,154.0,143.9,
138.3,137.1, 135.5, 135.0,131.7,129.5,125.9,125.6, 125.4,124.0, 117.0,
20.7, 18.1, 15.3 ppm; IR (KBr): ymax 1736, 1594, 1232 cmꢀ1; HRMS
(ESI) calcd for C19H17O3 [MþH]þ 293.1172, found 293.1178.
4.3.19. 8-Methyl-3,4-bis-(2-methyl-benzoyl)-chromen-2-one (4c). A
white solid, mp 167e169 ꢁC, Rf 0.3 (EtOAc/petroleum ether¼1:10);
4.3.25. 3-Benzoyl-7-hydroxy-4-methyl-chromen-2-one (4i). A white
solid, mp 200e202 ꢁC, Rf 0.2 (EtOAc/petroleum ether¼1:5); 1H
1H NMR (400 MHz, CDCl3):
d
¼7.58e7.56 (dd, J¼7.6, 0.8 Hz, 1H),
NMR (400 MHz, acetone-d6):
d
¼8.00e7.98 (m, 2H), 7.78e7.76 (dd,
7.52e7.47 (m, 2H), 7.44e7.40 (td, J¼7.6, 1.2 Hz, 1H), 7.38e7.34 (td,
J¼7.6, 1.2 Hz, 1H), 7.28e7.27 (d, J¼7.6 Hz, 1H), 7.22e7.14 (m, 5H),
2.52 (s, 3H), 2.50 (s, 3H), 2.31 (s, 3H); 13C NMR (100 MHz, CDCl3):
J¼8.8, 1.2 Hz, 1H), 7.70e7.66 (td, J¼8.0, 1.2 Hz, 1H), 7.56e7.52 (t,
J¼7.6 Hz, 2H), 6.96e6.93 (dd, J¼8.8, 2.4 Hz, 1H), 6.83e6.82 (d,
J¼2.4 Hz,1H), 3.00 (s,1H), 2.32 (s, 3H); 13C NMR (100 MHz, acetone-
d
¼194.5, 193.3, 158.4, 153.7, 152.5, 141.1, 139.4, 136.2, 134.8, 134.2,
d6):
d
¼194.3, 162.6, 159.4, 156.0, 151.4, 137.8, 134.7, 130.0, 129.8,
133.6, 133.0,132.4,131.7,130.7,127.0,126.0,125.6,125.1, 124.6,116.8,
128.2, 123.1, 114.1, 113.2, 103.3, 15.9 ppm; IR (KBr): ymax 3271, 1666,
Please cite this article in press as: Wang, H.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.12.029

6
H. Wang et al. / Tetrahedron xxx (2014) 1e7
1598, 1563, 1261 cmꢀ1; HRMS (ESI) calcd for C17H12NaO4 [MþNa]þ
1290 cmꢀ1; HRMS (ESI) calcd for C18H12NaO3 [MþNa]þ 299.0679,
303.0628, found 303.0635.
found 299.0687.
4.4.6. 2-Benzoyl-3-chloro-[1,4]naphthoquinone (5g). A pale yellow
solid, mp 151e153 ꢁC, Rf 0.4 (EtOAc/petroleum ether¼1:10);
4.4. General procedure for the decarboxylative acylation of
heterocyclic compounds with 2a
1H NMR (400 MHz, CDCl3):
d
¼8.24e8.22 (m, 1H), 8.12e8.10 (m, 1H),
7.94e7.91 (m, 2H), 7.84e7.82 (m, 2H), 7.68e7.64 (t, J¼7.6 Hz, 1H),
A 10 mL oven-dried Schlenk-tube was charged with AgNO3
(3.4 mg, 10 mol %), heterocyclic compounds (6, 0.2 mmol, 1.0 equiv),
and K2S2O8 (108 mg, 0.4 mmol, 2.0 equiv). The tube was evacuated
and backfilled with nitrogen (three times). Phenylglyoxylic acid (2a,
0.48 mmol, 2.4 equiv) in DMSO/H2O (1:1) 2 mL was added by sy-
ringe. The tube was then sealed and the mixture was stirred for 24 h
at room temperature. Upon completion of the reaction, the mixture
was diluted with EtOAc, filtered through a pad of Celite, and the
filtrate was then removed under vacuo. The residue was purified
with chromatography column on silica gel (gradient eluent of
EtOAc/petroleum ether: 1:30 to 1:15) to give the corresponding
products 5 in yields listed in Table 4.
7.53e7.49 (t, J¼7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3):
¼189.6,
d
181.2, 177.3, 144.2, 141.6, 134.9, 134.6, 134.5, 131.2, 131.0, 129.3, 129.1,
127.6, 127.1 ppm; IR (KBr): ymax 1685, 1658, 1594, 1277 cmꢀ1; HRMS
(ESI) calcd for C17H10ClO3 [MþH]þ 297.0313, found 297.0314.
4.4.7. Benzoic acid 3-benzoyl-1,4-dioxo-1,4-dihydro-naphthalen-2-yl
ester (5h). A pale yellow solid, mp 142e144 ꢁC, Rf 0.3 (EtOAc/pe-
troleum ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼8.22e8.19 (m,
d
1H), 8.17e8.15 (m, 1H), 7.99e7.96 (m, 4H), 7.86e7.83 (m, 2H),
7.62e7.58 (td, J¼7.6, 1.2 Hz, 2H), 7.49e7.40 (m, 4H); 13C NMR
(100 MHz, CDCl3):
d
¼189.4, 182.9, 178.0, 163.4, 151.0, 135.5, 134.8,
134.7, 134.6, 134.4, 131.5, 130.9, 130.6, 129.3, 128.9, 128.7, 127.2,
127.0 ppm; IR (KBr): ymax 1751, 1682, 1659, 1289, 1227 cmꢀ1; HRMS
(ESI) calcd for C24H14NaO5 [MþNa]þ 405.0733, found 405.0731.
4.4.1. 3,4-Dibenzoyl-1-methyl-1H-quinolin-2-one (5a). A pale yel-
low solid, mp 175e177 ꢁC, Rf 0.2 (EtOAc/petroleum ether¼1:5); 1H
NMR (400 MHz, CDCl3):
d
¼7.87e7.79 (m, 4H), 7.69e7.65 (m, 1H),
4.5. Investigation of the reaction mechanism
7.59e7.55 (m, 1H), 7.53e7.49 (m, 2H), 7.44e7.35 (m, 5H), 7.21e7.17
(td, J¼8.0, 0.8 Hz, 1H), 3.81 (s, 3H); 13C NMR (100 MHz, CDCl3):
When the TEMPO was added to the reaction of 1a with phe-
nylglyoxylic acid 2a under the standard condition, the yield of 3a
was isolated in 41%. This result indicates that the radical in-
termediate might be involved in the catalytic cycle of the reaction;
When the BHT was added to the reaction of 1a with phenylglyoxylic
acid 2a under the standard condition, the yield of 3a was isolated in
38%. This result indicates that the radical intermediate might be
involved in the catalytic cycle of the reaction.
d
¼194.7, 193.6, 159.6, 148.2, 140.3, 136.8, 136.1, 134.5, 133.6, 132.3,
129.9, 129.5, 129.3, 128.8, 128.4, 127.9, 122.9, 117.8, 114.8, 29.8 ppm;
IR (KBr): ymax 1643, 1595, 1451, 1235 cmꢀ1; HRMS (ESI) calcd for
C
24H17NNaO3 [MþNa]þ 390.1101, found 390.1101.
4.4.2. Isolated as unseparable mixture of 5b and 5b0 (ratio 77:23). 1H
NMR (400 MHz, CDCl3):
d
¼7.88e7.84 (m, 2H), 7.81e7.79 (dd, J¼8.0,
1.2 Hz, 2H), 7.59e7.50 (m, 2H), 7.44e7.37 (m, 4H), 7.29e7.22 (m,
3H), 7.01e6.99 (dd, J¼0.8, 8.4 Hz, 1H), 3.88 (s, 0.7H), 3.79 (s, 2H),
Acknowledgements
2.77 (s, 0.7H), 2.53 (s, 2H); 13C NMR (100 MHz, CDCl3):
d¼194.9,
193.9, 159.8, 148.4, 143.5, 140.5, 137.0, 136.6, 136.1, 134.4, 133.4,
129.9, 129.8, 129.3, 128.8, 128.4, 128.3, 127.8, 126.1, 124.4, 123.3,
115.6, 115.0, 37.3, 29.8, 23.9, 22.4 ppm.
Financial support from National Natural Science Foundation of
China (Nos. 21102110, 21102111) and the Fundamental Research
Funds of the Central Universities (Nos. 2012jdhz28, xjj2012100) are
greatly appreciated.
4.4.3. 2,3-Dibenzoyl-chromen-4-one (5c). Rf 0.2 (EtOAc/petroleum
ether¼1:10); 1H NMR (400 MHz, CDCl3):
¼8.29e8.26 (dd, J¼7.6,
d
Supplementary data
1.2 Hz,1H), 7.96e7.94 (m, 2H), 7.91e7.89 (m, 2H), 7.82e7.78 (m,1H),
7.69e7.64 (m, 1H), 7.59e7.49 (m, 5H), 7.46e7.43 (t, J¼7.6 Hz, 2H);
13C NMR (100 MHz, CDCl3):
d
¼191.6, 187.3, 175.9, 158.5, 155.1, 136.8,
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2014.12.029.
135.1, 134.7, 134.2, 133.7, 130.1, 129.2, 128.8, 128.6, 126.5, 126.3,
126.0, 124.2, 118.4 ppm; IR (KBr): ymax 1680, 1648, 1464, 1377,
1239 cmꢀ1; HRMS (ESI) calcd for C23H14NaO4 [MþNa]þ 377.0784,
found 377.0786.
References and notes
1. For review, see: (a) Sandhu, S.; Bansal, Y.; Silakari, O.; Bansal, G. Bioorg. Med.
Chem. 2014, 22, 3806 For recent examples, see: (b) Li, B.; Pai, R.; Di, M.; Aiello,
D.; Barnes, M. H.; Butler, M. M.; Tashjian, T. F.; Peet, N. P.; Bowlin, T. L.; Moir, D. T.
J. Med. Chem. 2012, 55, 10896; (c) Anand, P.; Singh, B.; Singh, N. Bioorg. Med.
Chem. 2012, 20, 1175; (d) Zou, Q.; Fang, Y.; Zhao, Y.; Zhao, H.; Wang, Y.; Gu, Y.;
Wu, F. J. Med. Chem. 2013, 56, 5288; (e) Jagtap, A. R.; Satam, V. S.; Rajule, R. N.;
Kanetkar, V. R. Dyes Pigment 2009, 82, 84; (f) Chang, C.-H.; Cheng, H.-C.; Lu, Y.-J.;
Tien, K.-C.; Lin, H.-W.; Lin, C.-L.; Yang, C.-J.; Wu, C.-C. Org. Electron. 2010, 11, 247.
2. For selected examples, see: (a) Joule, J. A.; Mills, K. In Heterocyclic Chemistry
Blackwell: Oxford, UK, 2000; (b) Jia, C.; Piao, D.; Oyamada, J.; Lu, W.; Kitamura, T.;
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Shu, X.-Z.; Ji, K.-G.; Shaukat, A.; Liu, X.-Y.; Liang, Y.-M. J. Org. Chem. 2011, 76,
342; (f) Kim, D.; Min, M.; Hong, S. Chem. Commun. 2013, 4021; (g) Wei, J.; Wang,
P.; Jia, Q.; Huang, J.; Du, Z.; Zhang, K.; Wang, J. Eur. J. Org. Chem. 2013, 4499; (h)
Mi, X.; Wang, C.; Huang, M.; Zhang, J.; Wu, Y.; Wu, Y. Org. Lett. 2014, 16, 3356.
3. (a) Khoobi, M.; Alipour, M.; Zarei, S.; Jafarpour, F.; Shafiee, A. Chem. Commun.
2012, 2985; (b) Li, Y.; Qi, Z.; Wang, H.; Fu, X.; Duan, C. J. Org. Chem. 2012, 77,
2053; (c) Min, M.; Hong, S. Chem. Commun. 2012, 9613; (d) Min, M.; Kim, Y.;
Hong, S. Chem. Commun. 2013, 196; (e) Mi, X.; Huang, M.; Zhang, J.; Wang, C.;
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Khoobi, M.; Shafiee, A. Chem. Commun. 2013, 10935; (g) Cao, X.-H.; Pan, X.;
4.4.4. 2-Benzoyl-3,5-dimethyl-[1,4]benzoquinone (5e). A pale yel-
low solid, mp 74e76 ꢁC, Rf 0.4 (EtOAc/petroleum ether¼1:10); 1H
NMR (400 MHz, CDCl3):
d
¼7.86e7.83 (m, 2H), 7.64e7.60 (t,
J¼7.6 Hz, 1H), 7.50e7.46 (t, J¼7.6 Hz, 2H), 6.62 (d, J¼1.6 Hz, 1H), 2.12
(d, J¼1.2 Hz, 3H), 1.93 (s, 3H); 13C NMR (100 MHz, CDCl3):
¼193.1,
d
187.6, 185.6, 146.3, 142.0, 141.5, 135.6, 134.5, 132.8, 129.1, 129.0, 16.1,
13.2 ppm; IR (KBr): ymax 1676, 1652, 1323, 1241 cmꢀ1; HRMS (ESI)
calcd for C15H12NaO3 [MþNa]þ 263.0679, found 263.0672.
4.4.5. 2-Benzoyl-3-methyl-[1,4]naphthoquinone (5f). A pale yellow
solid, mp 139e141 ꢁC, Rf 0.4 (EtOAc/petroleum ether¼1:10); 1H
NMR (400 MHz, CDCl3):
d
¼8.17e8.15 (m, 1H), 8.07e8.05 (m, 1H),
7.92e7.90 (m, 2H), 7.81e7.41 (m, 2H), 7.65e7.61 (t, J¼7.6 Hz, 1H),
7.52e6.48 (t, J¼7.6 Hz, 2H), 2.06 (s, 3H); 13C NMR (100 MHz, CDCl3):
d
¼193.7, 184.8, 183.4, 144.3, 143.9, 135.6, 134.5, 134.2, 134.1, 131.8,
131.5, 129.1, 126.7, 126.4, 13.6 ppm; IR (KBr): ymax 1664, 1595,
Please cite this article in press as: Wang, H.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.12.029

H. Wang et al. / Tetrahedron xxx (2014) 1e7
7
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Chen, X.; Liu, J.; Gui, Q.; Xie, K.; Li, M.; Tan, Z. Chem. Commun. 2013, 1560; (g)
Park, J.; Kim, M.; Sharma, S.; Park, E.; Kim, A.; Lee, S. H.; Kwak, J. H.; Jung, Y. H.;
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Catal. 2013, 355, 1517; (j) Li, Z.-Y.; Li, D.-D.; Wang, G.-W. J. Org. Chem. 2013, 78,
10414.
4. For selected examples leading to 3,4-disubstituted coumarins, see: (a) Kadni-
kov, D. V.; Larock, R. C. Org. Lett. 2000, 2, 3643; (b) Kadnikov, D. V.; Larock, R. C.
J. Org. Chem. 2003, 68, 9423; (c) Zhang, L.; Meng, T.; Fan, R.; Wu, J. J. Org. Chem.
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Eur. J. Org. Chem. 2012, 480; (e) Kim, S.; Kang, D.; Lee, C.-H.; Lee, P. H. J. Org.
Chem. 2012, 77, 6530.
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Goossen, L. J.; Rodríguez, N.; Goossen, K. Angew. Chem., Int. Ed. 2008, 47, 3100;
(c) Satoh, T.; Miura, M. Synthesis 2010, 3395; (d) Rodríguez, N.; Goossen, L. J.
Chem. Soc. Rev. 2011, 40, 5030; (e) Shang, R.; Liu, L. Sci. China Chem. 2011, 54,
1670; (f) Dzik, W. I.; Lange, P. P.; Goossen, L. J. Chem. Sci. 2012, 3, 2671; (g)
Cornella, J.; Larrosa, I. Synthesis 2012, 653.
6. For selected examples, see: (a) Myers, A. G.; Tanaka, D.; Mannion, M. R. J. Am.
Chem. Soc. 2002, 124, 11250; (b) Goossen, L. J.; Deng, G.; Levy, L. M. Science
2006, 313, 662; (c) Forgione, P.; Brochu, M.-C.; St-Onge, M.; Thesen, K. H.;
Bailey, M. D.; Bilodeau, F. J. Am. Chem. Soc. 2006, 128, 11350; (d) Miyasaka, M.;
Fukushima, A.; Satoh, T.; Hirano, K.; Miura, M. Chem.dEur. J. 2009, 15, 3674; (e)
Zhang, F.; Greaney, M. F. Org. Lett. 2010, 12, 4745; (f) Dai, J.-J.; Liu, J.-H.; Luo, D.-
F.; Liu, L. Chem. Commun. 2011, 677; (g) Messaoudi, S.; Brion, J.-D.; Alami, M.
Org. Lett. 2012, 14, 1496; (h) Zhang, Y.; Patel, S.; Mainolfi, N. Chem. Sci. 2012, 3,
3196.
7. For some selected examples, see: (a) Goossen, L. J.; Rudolphi, F.; Oppel, C.;
Rodríguez, N. Angew. Chem., Int. Ed. 2008, 47, 3043; (b) Goossen, L. J.; Zim-
mermann, B.; Knauber, T. Angew. Chem., Int. Ed. 2008, 47, 7103; (c) Fang, P.; Li,
M.; Ge, H. J. Am. Chem. Soc. 2010, 132, 11898; (d) Li, M.; Ge, H. Org. Lett. 2010, 12,
3464; (e) Wang, H.; Guo, L.-N.; Duan, X.-H. Org. Lett. 2012, 14, 4358; (f) Yang, Z.;
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Duan, X.-H. Chem. Commun. 2014, 7382 For other related examples reported in
our group, see: (d) Zhang, S.; Guo, L.-N.; Wang, H.; Duan, X.-H. Org. Biomol.
Chem. 2013, 11, 4308; (e) Wang, H.; Guo, L.-N.; Duan, X.-H. Org. Biomol. Chem.
2013, 11, 4573; (f) Wang, H.; Yang, H.; Li, Y.; Duan, X.-H. RSC Adv. 2014, 4, 8720.
9. Aroyl substituted coumarins were useful biologically active molecules and
useful synthetic intermediates in organic synthesis. For selected examples, see:
ꢀ
(a) Perez-Cruz, F.; Vazquez-Rodriguez, S.; Matos, M. J.; Herrera-Morales, A.;
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Biomol. Chem. 2013, 11, 158.
10. For the pioneering work on the decarboxylation of a-oxocarboxylic acids under
Ag (I)/persulfates, see: (a) Anderson, J. M.; Kochi, J. K. J. Am. Chem. Soc. 1970, 92,
1651; (b) Anderson, J. M.; Kochi, J. K. J. Org. Chem. 1970, 35, 986; (c) Fontana, F.;
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Dnyanoba, N.; Nagahama, M.; Inaba, T.; Nishino, Y.; Miura, K.; Kosaka, S.; Fukao,
J.; Kawasaki, I.; Ohta, S. Heterocycles 2005, 65, 2411.
Please cite this article in press as: Wang, H.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.12.029