Synthesis of coumarin-3-carboxylic esters via FeCl3-catalyzed multicomponent reaction of salicylaldehydes, Meldrum's acid and alcohols

Article abstract of DOI:10.1016/j.tet.2014.12.042

A FeCl₃-catalyzed multicomponent reaction was developed for the facile synthesis of coumarin-3-carboxylic ester derivatives in a highly atom-economic and environmentally friendly way. Using simple and cheaply available salicylaldehydes, Meldrum's acid and alcohols as the starting materials, the method needs no extra additives and features wide substrate scope, good functional group tolerance and mild reaction conditions.

Full text of DOI:10.1016/j.tet.2014.12.042

Accepted Manuscript
Synthesis of Coumarin-3-carboxylic Esters via FeCl -Catalyzed Multicomponent
3
Reaction of Salicylaldehydes, Meldrum’s Acid and Alcohols
Xinwei He, Yongjia Shang, Yao Zhou, Zhiyu Yu, Guang Han, Wenjing Jin, Jiaojiao
Chen
PII:
S0040-4020(14)01746-3
10.1016/j.tet.2014.12.042
TET 26263
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 31 October 2014
Revised Date: 5 December 2014
Accepted Date: 12 December 2014
Please cite this article as: He X, Shang Y, Zhou Y, Yu Z, Han G, Jin W, Chen J, Synthesis of
Coumarin-3-carboxylic Esters via FeCl -Catalyzed Multicomponent Reaction of Salicylaldehydes,
3
Meldrum’s Acid and Alcohols, Tetrahedron (2015), doi: 10.1016/j.tet.2014.12.042.
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Synthesis of Coumarin-3-carboxylic Esters
via FeCl3-Catalyzed Multicomponent
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Reaction of Salicylaldehydes, Meldrum’s
Acid and Alcohols
Xinwei He, Yongjia Shang,* Yao Zhou, Zhiyu Yu, Guang Han, Wenjing Jin, Jiaojiao Chen
The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-
Based Materials, Institute of Organic Chemistry, College of Chemistry and Materials Science, Anhui Normal
University, Wuhu, Anhui 241000, China

2
Tetrahedron
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Tetrahedron
journal homepage: www.elsevier.com
Synthesis of Coumarin-3-carboxylic Esters via FeCl3-Catalyzed Multicomponent
Reaction of Salicylaldehydes, Meldrum’s Acid and Alcohols
Xinwei He, Yongjia Shang, Yao Zhou, Zhiyu Yu, Guang Han, Wenjing Jin, Jiaojiao Chen
The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Institute of Organic Chemistry,
College of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A FeCl3-catalyzed multicomponent reaction was developed for the facile synthesis of coumarin-
3-carboxylic ester derivatives in a highly atom-economic and environmentally friendly way.
Using simple and cheaply available salicylaldehydes, Meldrum’s acid and alcohols as the
starting materials, the method needs no extra additives and features wide substrate scope, good
functional group tolerance and mild reaction conditions.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
FeCl3
Coumarin-3-carboxylic esters
Meldrum’s acid
Multicomponent reaction
Salicylaldehydes
Introduction
pharmacological properties of these coumarin derivatives.
Herein, we report the details of our research on this
multicomponent reaction (Scheme 1).
Coumarins are very attractive targets for combinatorial library
synthesis due to their wide range of valuable biological activities
including anticancer,1 anti-HIV,2 anti-acetylcholinesterase,3 anti-
fungal,4 antioxidant,5 antihelmintic,6 antibacterial7 and antiviral8
activities. They are also extensively used in fragrances,
agrochemicals, insecticides and in food and cosmetics as
additives.9 On the other hand, they have also found applications
as photosensitizers, laser dyes, fluorescent indicators, optical
brighteners and photosensitizers.10-13 As a result, the drive to
obtain typically functionalized coumarins in one step from
readily available starting materials with minimal waste, less time
and simple manipulation has been prevalent among the
community of organic chemists.14
Scheme 1. Synthesis of coumarin-3-carboxylic esters via
FeCl3-catalyzed multicomponent reaction of salicylaldehydes,
Meldrum’s acid and alcohols.
Results and discussion
Initially, salicylaldehyde (1a), Meldrum’s acid (2) and ethanol
(3a) were chosen as the starting materials in the model reaction.
Ethanol played both as the reagent and solvent while different
metal salt catalysts were screened (Table 1). Interestingly, when
the FeCl3 were used as the catalyst (Table 1, entry 7), the highest
yield of the product (92% yield) was obtained, and that CuBr2
(Table 1, entry 2) also had good catalytic ability (86% yield).
Here, the yield could not be improved by increasing the amount
of catalyst (Table 1, entries 12 and 13), even while decreasing the
amount of catalyst to 5 mol% could lead to a slightly higher yield
of 93% (Table 1, entry 11). However, the product yield dropped
to 72% by further decreasing the catalyst to 2 mol% (Table 1,
Multicomponent reactions (MCRs) has been one of the best
approaches that meet the requirements of green chemistry as well
as the library development of medicinal scaffolds.15 Previously,
we have reported FeCl3-catalyzed cascade reaction to efficient
approach to functionalized coumarin derivatives.16 In
continuation of our efforts toward the development of novel
methodologies for the synthesis of heterocycles,17 a new
synthetic route to coumarin-3-carboxylic esters has been
explored. To the best of our knowledge, this work presents the
first simple direct route to the important class of coumarin
derivatives, which would facilitate relevant studies on the
———
Corresponding author. Tel.: +86-553-5910129; fax: +86-553-5910126; e-mail: shyj@mail.ahnu.edu.cn

4 c
100
EtOH
DMF
8
8
90
0
entry 9). In the absence of catalyst, the model reaction failed to
ACCEPTED MANUSCRIPT
provide the desired product, while 2-oxo-2H-chromene-3-
carboxylic acid was isolated as the only product in 72% yield
after a prolonged reaction time of 24 h. Therefore, 5 mol% FeCl3
was chosen as catalyst for further optimizing other reaction
conditions.
5
6
70
70
70
70
70
70
70
70
70
70
THF
8
60
60
45
0
7
CH3CN
Toluene
DMSO
Cyclohexane
H2O
8
Table 1. Screen of catalysts. a
8
8
9
8
10
11
12 c
13 c
14 c
8
50
21
40
80
92
8
Entry
1
Catalyst (mol %)
Cu(OAc)2 (10)
CuBr2 (10)
CuSO4 (10)
NiCl2·6H2O (10)
AgNO3 (10)
K3Fe(CN)6 (10)
FeCl3 (10)
Yield (%) b
EtOH
2
EtOH
5
10
86
65
80
10
trace
92
0
EtOH
10
2
a Reaction condition: salicylaldehyde 1a (1.0 mmol), Meldrum’s acid
2 (1.2 mmol), ethanol 3a (1.2 mmol), solvent (3 mL), FeCl3 (0.05
mmol).
3
4
b Isolated yields.
c Ethanol (3 mL) was used as solvent.
5
6
Subsequently, various structural diverse salicylaldehydes 1b-
1j were subjected to the optimum reaction conditions with
Meldrum’s acid 2 and ethanol 3a. The results are summarized in
Table 3. A variety of functional groups in the examined
substituted salicylaldehydes were well tolerated to give good to
excellent yields of ethyl 2-oxo-2H-chromene-3-carboxylate (4aa-
4ja), regardless of their electronic nature or steric hindrance.
Particularly, when the substituents on salicylaldehydes 1 were
strongly electron-donating groups (e.g. -OCH3, -NEt2) at the para
position of the aldehydes (Table 3, entries 3, 4) or strongly
electron-withdrawing groups (e.g. -NO2) at the para position of
the phenol hydroxyl group (Table 3, entry 8), also gave the
desired products in good to excellent yields. Moreover, tert-butyl
group at the 3,5-position of salicylaldehydes 1e participated
successfully in this reaction (Table 3, entry 5). The structure of
the product 4aa was unambiguously confirmed by X-ray
crystallographic analysis (Figure 1).
7
8 c
9
—
FeCl3 (2)
72
70
93
92
90
10
11
12
13
CuBr2 (2)
FeCl3 (5)
FeCl3 (15)
FeCl3 (20)
a
Reaction condition: 1a (1.0 mmol), 2 (1.2 mmol),
3a (3 mL), 70 oC, 8 h.
b Isolated yields.
c 2-oxo-2H-chromene-3-carboxylic acid was obtained
in 72% yield as the only product after 24 h.
To determine the optimum reaction conditions, the effects of
other reaction parameters such as the solvent, temperature, and
reaction time were studied. Several other solvents including
dimethyl formamide (DMF), tetrahydrofuran (THF), acetonitrile,
toluene, dimethylsulfoxide (DMSO), cyclohexane and water
were screened but inferior yields were obtained (Table 2, entries
5-11). So in this reaction alcohol was used both as a solvent and
as one of the reactants as well. In addition, the effect of
temperature and reaction time were also investigated (Table 2,
entries 1-4, and 12-14). It was found that neither decreasing nor
increasing the reaction temperature/time could improve the yield.
Therefore, this reaction could be best performed with 5 mol % of
FeCl3 as catalyst in ethanol at 70 oC for 8 h.
Figure 1. X-ray crystal structure of compound 4aa.18
Table 3. Synthesis of ethyl coumarin-3-carboxylate
derivatives via FeCl3-catalyzed multicomponent reactions of
salicylaldehydes, Meldrum’s acid and ethanol.
Table 2. Optimization of reaction conditions. a
Entry
R1,R2,R3,R4
1a (H, H, H, H)
Product
4aa
Yields (%) b
Entry
1c
Temp. (oC)
Solvent
EtOH
EtOH
EtOH
Time (h)
Yield (%) b
1
2
3
93
89
89
r.t.
50
70
8
8
8
20
60
93
1b (H, CH3, H, H)
1c (H, H, CH3O, H)
4ba
2 c
4ca
3 c

4
Tetrahedron
4dAa CCEPTED MANUSCRIPT1j
4
5
1d (H, H, NEt2, H)
83
80
91
90
89
93
90
21
3e
4je
91
a
Reaction condition: salicylaldehyde 1 (1.0 mmol), Meldrum’s acid 2
1e (C(CH3)3, H, C(CH3)3, H)
1f (H, Cl, H, H)
4ea
4fa
4ga
4ha
4ia
(1.2 mmol), alcohol 3 (3 mL), FeCl3 (0.05 mmol), 70 oC, 6-8 h.
b Isolated yields.
6
7
1g (H, Br, H, H)
In order to understand the reaction mechanism, we examined
the reaction of Meldrum’s acid 2 with ethanol 3a catalyzed by
FeCl3 in 70 C. The esterification product of diethyl malonate
8
1h (H, NO2, H, H)
o
9
1i (H, F, H, H)
was obtained in 93% yield after 4 h. On the basis of the above
observations and our reported work,16 a possible reaction
mechanism is proposed in Scheme 2. First, Meldrum’s acid 2
reacted with alcohol 3 to form the esterification products 5 in the
presence of FeCl3 as a Lewis acid catalyst, and then the
Knoevenagel condensation between 5 and 2-hydroxy aromatic
aldehydes 1 would form the intermediate A, which are readily
10
1j (-CH=CH-CH=CH-, H, H, H)
4ja
a
Reaction condition: salicylaldehyde 1 (1.0 mmol), Meldrum’s acid 2
(1.2 mmol), ethanol 3a (3 mL), FeCl3 (0.05 mmol), 70 oC, 6-8 h.
b Isolated yields.
Subsequently, a series of alcohols such as methyl alcohol
converted to the desired products
transesterification.
4 via intramolecular
(3b), 2-pentanol (3c), benzyl alcohol (3d) and allyl alcohol (3e)
were subjected to the reaction with salicylaldehydes 1 and
Meldrum’s acid 2 (Table 4). We found that both saturated and
unsaturated alcohols gave the desired products, and the allyl
alcohol gave relatively higher yields of the products. To our
delight, good yields of products were also obtained in the case of
benzyl alcohol 3d (Table 4, entries 13-15).
Table 4. FeCl3-catalyzed multicomponent reactions for the
formation of coumarin-3-carboxylic esters. a
Scheme 2. Proposed mechanism for the formation of
coumarin-3-carboxylic esters 4.
Yields
Entry
R1,R2,R3,R4
R5
Product
(%) b
91
Conclusions
1
2
3
4
5
6
7
8
9
1a (H, H, H, H)
CH3 (3b)
3b
4ab
4bb
4cb
4db
4eb
4fb
4gb
4hb
4jb
In conclusion, we have developed a highly efficient and
environmental friendly method for the synthesis of coumarin-3-
carboxylic ester derivatives via FeCl3-catalyzed multicomponent
reactions in good to excellent yields. The notable advantages of
this method are mild reaction conditions, lower amounts of cheap
and nontoxic FeCl3 as catalyst, and the reactant of alcohol as
solvent. It should be noted that this protocol is an expedient and
atom-economic approach to the coumarin-3-carboxylic esters
from easy available starting materials. In addition, operational
simplicity and no need for extra solvent are the attractive features
which make this protocol highly practical for accessing new
coumarin scaffolds.
1b (H, CH3, H, H)
1c (H, H, CH3O, H)
1d (H, H, NEt2, H)
90
88
85
80
89
88
89
90
3b
3b
1e
(C(CH3)3,
H,
3b
C(CH3)3, H)
1f (H, Cl, H, H)
3b
1g (H, Br, H, H)
3b
1h (H, NO2, H, H)
3b
1j
(-CH=CH-
3b
CH=CH-, H, H, H)
4. Experimental SectionGeneral comments
4.1 General comments
pentan-2-yl
10
11
12
13
14
15
16
17
18
19
20
1c
4cc
4fc
88
90
89
73
81
83
90
85
91
90
91
(3c)
1f
1g
1c
1g
1h
1c
1e
1f
3c
Unless otherwise specified, all reagents and starting materials
were purchased from commercial sources and used as received,
and the solvents were purified and dried by standard procedures.
The chromatography solvents were technical grade and distilled
prior to use. Flash chromatography was performed using 200-300
mesh silica gel with the indicated solvent system according to
standard techniques. The 1H and 13C NMR data were recorded on
300 MHz NMR spectrometers, unless otherwise specified.
Chemical shifts (δ) in parts per million are reported relative to the
residual signals of chloroform (7.26 ppm for 1H and 76.1 ppm for
13C). Multiplicities are described as s (singlet), d (doublet), t
(triplet), q (quartet), or m (multiplet), and coupling constants (J)
are reported in hertz. HRMS analysis with a quadrupole time-of-
flight mass spectrometer yielded ion mass/charge (m/z) ratios in
3c
4gc
4cd
4gd
4hd
4ce
4ee
4fe
C6H5CH2 (3d)
3d
3d
CH2=CH-CH2
(3e)
3e
3e
3e
3e
1g
1h
4ge
4he

CDCl3) δ: 8.43 (s, 1H), 7.60 (s, 1H), 7.26-7.33 (m, 2H), 4.43 (q, J
atomic mass units. IR spectra were measured as dry films (KBr),
and peaks are reported in terms of wave number (cm-1).
ACCEPTED MANUSCRIPT
= 7.2 Hz, 2H), 1.41 (t, J = 7.2 Hz, 3H) ppm. 13C NMR (75 MHz,
CDCl3) δ: 162.6, 156.0, 153.4, 147.2, 134.1, 130.1, 128.4, 119.4,
118.8, 118.2, 62.2, 14.2 ppm. IR (KBr) v: 3070, 1755, 1705,
1616, 1560, 1473, 1415, 1367, 1290, 1244, 1211, 1083, 1024,
997, 840, 794, 663, 605 cm-1. HRMS (ESI) calcd for C12H9ClO4
([M+H]+) 253.0267, found 253.0267.
4.2 General procedure for the synthesis of polysubstituted
coumarin-3-carboxylic esters 4.
Anhydrous FeCl3 (0.05 mmol) was added to a stirred solution
of salicyladehyde 1a (1 mmol), Meldrum’s acid 2 (1.2 mmol) in
ethanol (3 mL). The mixture was heated at 70 oC for 8 h in an oil
bath and then cooled down to room temperature. The solvent was
removed under vacuum, and the residue was directly purified by
flash column chromatography on silica gel with ethyl acetate and
petroleum ether (1:6, v/v) as eluting solvent to afford the product
4aa in 93% yield.
4.2.7 Ethyl
6-bromo-2-oxo-2H-chromene-3-carboxylate
1
(4ga).16 White solid, yield 90%, mp 175-177 oC. H NMR (300
MHz, CDCl3) δ: 8.42 (s, 1H), 7.69-7.74 (m, 2H), 7.24 (s, 1H),
4.44 (q, J = 7.2 Hz, 2H), 1.42 (t, J = 7.2 Hz, 3H) ppm. 13C NMR
(75 MHz, CDCl3) δ: 162.6, 155.9, 153.9, 147.0, 136.9, 131.5,
119.4, 119.3, 118.5, 117.3, 62.2, 14.1 ppm. IR (KBr) v: 3070,
1753, 1705, 1616, 1598, 1558, 1477, 1411, 1367, 1290, 1242,
1211, 1024, 794 cm-1. HRMS (ESI) calcd for C12H9BrO4
([M+H]+) 296.9762, found 296.9765.
4.2.1 Ethyl
2-oxo-2H-chromene-3-carboxylate
o 1
16
(4aa)
. White solid, yield 93%, mp 90-91 C. H NMR (300
MHz, CDCl3) δ: 8.52 (s, 1H), 7.60-7.67 (m, 2H), 7.30-7.37 (m,
2H), 4.42 (q, J = 7.2 Hz, 2H), 1.43 (t, J = 7.2 Hz, 3H) ppm. 13C
NMR (75 MHz, CDCl3) δ: 162.9, 156.8, 155.0, 148.6, 134.3,
129.5, 124.8, 118.1, 117.8, 116.6, 61.9, 14.2 ppm. IR (KBr) v:
3062, 1776, 1766, 1606, 1564, 1450, 1375, 1296, 1132, 1033,
962, 775 cm-1. HRMS (ESI) calcd for C12H10O4 ([M+H]+)
219.0657, found 219.0657.
4.2.8 Ethyl 6-nitro-2-oxo-2H-chromene-3-carboxylate (4ha).16
o
1
White solid, yield 89%, mp 192-193 C. H NMR (300 MHz,
CDCl3) δ: 8.58 (s, 1H), 8.56 (s, 1H), 8.51 (d, J = 9.0 Hz, 1H),
7.51 (d, J = 9.3 Hz, 1H), 4.47 (q, J = 7.2 Hz, 2H), 1.44 (t, J = 7.2
Hz, 3H) ppm. 13C NMR (75 MHz, CDCl3) δ: 162.0, 158.3, 155.0,
146.9, 144.2, 128.6, 125.2, 120.5, 118.0, 117.8, 62.5, 14.1 ppm.
IR (KBr) v: 3088, 1780, 1757, 1691, 1618, 1570, 1497, 1348,
1257, 1219, 1095, 1018, 985, 752 cm-1. HRMS (ESI) calcd for
C12H9NO6 ([M+Na]+) 286.0322, found 286.0324.
4.2.2 Ethyl
6-methyl-2-oxo-2H-chromene-3-
o
carboxylate (4ba). White solid, yield 89%, mp 108-109 C.
1H NMR (300 MHz, CDCl3) δ: 8.45 (s, 1H), 7.44 (d, J = 8.4 Hz,
1H), 7.37 (s, 1H), 7.24 (d, J = 8.4 Hz, 1H), 4.40 (q, J = 7.2 Hz,
2H), 2.40 (s, 3H), 1.41 (t, J = 7.2 Hz, 3H) ppm. 13C NMR (75
MHz, CDCl3) δ: 163.0, 156.9, 153.2, 148.5, 135.4, 134.6, 129.1,
118.0, 117.5, 116.3, 61.8, 20.6, 14.2 ppm. IR (KBr) v: 3053,
1761, 1705, 1620, 1575, 1492, 1375, 1296, 1134, 1039, 979, 798
cm-1; HRMS (ESI) calcd for C13H13O4 ([M+H]+) 233.0814, found
233.0814.
4.2.9 Ethyl 6-fluoro-2-oxo-2H-chromene-3-carboxylate (4ia).
o
1
White solid, yield 93%, mp 104-106 C. H NMR (300 MHz,
CDCl3) δ: 8.48 (s, 1H), 7.59 (s, 2H), 7.32 (d, J = 8.4 Hz, 1H),
4.44 (q, J = 7.2 Hz, 2H), 1.42 (t, J = 7.2 Hz, 3H) ppm. 13C NMR
1
1
(75 MHz, CDCl3) δ: 162.7 (d, JCF = 177.4 Hz), 157.1 (d, JCF
=
=
1
1
62.0 Hz), 151.3, 147.4 (d, JCF = 1.8 Hz), 130.5, 122.0 (d, JCF
1
1
24.4 Hz), 119.5, 118.5 (d, JCF = 8.2 Hz), 114.5 (d, JCF = 23.6
Hz), 62.2, 14.2 ppm. IR (KBr) v: 3059, 1751, 1687, 1618, 1571,
1489, 1369, 1294, 1157, 1114, 1026, 993, 796 cm-1; HRMS (ESI)
calcd for C12H10FO4 ([M+H]+) 237.0563, found 237.0562.
4.2.3 Ethyl
7-methoxy-2-oxo-2H-chromene-3-carboxylate
1
(4ca).16 Yellow solid, yield 89%, mp 130-132 oC. H NMR (300
MHz, CDCl3) δ: 8.45 (s, 1H), 7.48 (d, J = 8.7 Hz, 1H), 6.87 (d, J
= 8.7 Hz, 1H), 6.77 (s, 1H), 4.39 (q, J = 7.2 Hz, 2H), 3.86 (s,
3H), 1.38 (t, J = 7.2 Hz, 3H) ppm. 13C NMR (75 MHz, CDCl3) δ:
165.1, 163.7, 157.5, 157.1, 148.9, 130.7, 114.0, 113.6, 111.5,
100.3, 61.6, 56.0, 14.2 ppm. IR (KBr) v: 3053, 1753, 1726, 1714,
1620, 1558, 1506, 1381, 1294, 1172, 1118, 1031, 829, 761 cm-1.
HRMS (ESI) calcd for C13H12O5 ([M+H]+) 249.0763, found
249.0762.
4.2.10 Ethyl 3-oxo-3H-benzo[f]chromene-2-carboxylate (4ja).16
1
Yellow solid, yield 90%, mp 118-119 oC. H NMR (300 MHz,
CDCl3) δ: 9.30 (s, 1H), 8.32 (d, J = 8.1 Hz, 1H), 8.10 (d, J = 9.0
Hz, 1H), 7.93 (d, J = 8.1 Hz, 1H), 7.77 (t, J = 7.5 Hz, 1H), 7.63
(t, J = 7.8 Hz, 1H), 7.46 (d, J = 9.0 Hz, 1H), 4.50 (q, J = 7.2 Hz,
2H), 1.46 (t, J = 7.2 Hz, 3H) ppm. 13C NMR (75 MHz, CDCl3) δ:
162.7, 155.9, 155.0, 143.6, 135.2, 128.3, 128.2, 125.6, 120.5,
115.7, 111.4, 61.1, 13.4 ppm. IR (KBr) v: 3080, 1745, 1697,
1627, 1604, 1568, 1463, 1396, 1296, 1217, 1124, 1095, 742 cm-1.
HRMS (ESI) calcd for C16H12O4 ([M+H]+) 269.0814, found
269.0813.
4.2.4 Ethyl
7-(diethylamino)-2-oxo-2H-chromene-3-
carboxylate (4da).16 Pale brown solid, yield 83%; mp 171-172
1
oC. H NMR (300 MHz, CDCl3) δ: 8.40 (s, 1H), 7.34 (d, J = 9.3
Hz, 1H), 6.60 (d, J = 9.0 Hz, 1H), 6.43 (s, 1H), 4.38 (q, J = 7.2
Hz, 2H), 3.45 (q, J = 7.2 Hz, 4H), 1.38 (t, J =7.2 Hz, 3H), 1.23 (t,
J = 7.2 Hz, 6H) ppm. 13C NMR (75 MHz, CDCl3) δ: 164.2,
158.4, 158.3, 152.8, 149.2, 131.0, 109.5, 108.8, 107.6, 96.6, 61.1,
45.0, 14.3, 12.4 ppm. IR (KBr) v: 3354, 1732, 1699, 1622, 1589,
1514, 1477, 1446, 1354, 1222, 1186, 1103, 1028, 819, 792 cm-1.
HRMS (ESI) calcd for C16H19NO4 ([M+H]+) 290.1392, found
290.1393.
4.2.11 Methyl 2-oxo-2H-chromene-3-carboxylate (4ab). White
solid, yield 91%, mp 118-120 oC. 1H NMR (300 MHz, CDCl3) δ:
8.53 (s, 1H), 7.56-7.64 (m, 2H), 7.27-7.34 (m, 2H), 3.92 (s, 3H)
ppm. 13C NMR (75 MHz, CDCl3) δ: 163.8, 156.9, 155.2, 149.1,
134.4, 129.5, 124.9, 117.9, 117.8, 116.7, 52.9 ppm. IR (KBr) v:
3059, 1745, 1701, 1685, 1616, 1560, 1452, 1363, 1311, 1247,
1215, 1155, 997, 756 cm-1; HRMS (ESI) calcd for C11H9O4
([M+H]+) 205.0501, found 205.0500.
4.2.5 Ethyl 6,8-di-tert-butyl-2-oxo-2H-chromene-3-carboxylate
o
1
4.2.12 Methyl
6-methyl-2-oxo-2H-chromene-3-carboxylate
o 1
(4ea). White solid, yield 80%; mp 115-116 C. H NMR (300
MHz, CDCl3) δ: 8.49 (s, 1H), 7.66 (s, 1H), 7.39 (s, 1H), 4.40 (q,
J = 7.2 Hz, 2H), 1.49 (s, 9H), 1.41 (t, J = 7.2 Hz, 3H), 1.34 (s,
9H) ppm. 13C NMR (75 MHz, CDCl3) δ: 163.3, 156.6, 152.0,
149.9, 147.1, 137.4, 129.7, 123.9, 117.8, 117.0, 61.7, 35.1, 34.6,
31.2, 29.7, 14.2 ppm. IR (KBr) v: 2981, 1739, 1707, 1618, 1577,
1471, 1396, 1286, 1255, 1211, 1035, 979, 796 cm-1; HRMS (ESI)
calcd for C20H27O4 ([M+H]+) 331.1909, found 331.1909.
(4bb). White solid, yield 90%; mp 135-136 C. H NMR (300
MHz, CDCl3) δ: 8.49 (s, 1H), 7.45 (d, J = 8.7 Hz, 1H), 7.37 (s,
1H), 7.24 (d, J = 8.7 Hz, 1H), 3.93 (s, 3H), 2.40 (s, 3H) ppm. 13
C
NMR (75 MHz, CDCl3) δ: 163.8, 156.9, 153.3, 149.2, 149.1,
135.6, 134.7, 129.1, 117.7, 117.5, 116.4, 52.8, 20.6 ppm. IR
(KBr) v: 3064, 1772, 1755, 1622, 1571, 1492, 1436, 1381, 1294,
1132, 1029, 933, 756 cm-1; HRMS (ESI) calcd for C12H11O4
([M+H]+) 219.0657, found 219.0655.
4.2.6 Ethyl 6-chloro-2-oxo-2H-chromene-3-carboxylate (4fa).16
o
1
White solid, yield 91%, mp 174-175 C. H NMR (300 MHz,

6
Tetrahedron
4.2.13 Methyl 7-methoxy-2-oxo-2H-chromene-3-carboxylate
1394, 1296, 1211, 1120, 1103, 1008, 983, 794 cm-1; HRMS (ESI)
ACCEPTED MANUSCRIPT
o
1
(4cb). Yellow solid, yield 88%, mp 226-228 C. H NMR (300
MHz, CDCl3) δ: 8.81 (s, 1H), 7.62 (d, J = 8.7 Hz, 1H), 7.00 (d, J
= 8.7 Hz, 1H), 6.89 (s, 1H), 3.91 (s, 6H) ppm. 13C NMR (75
MHz, CDCl3) δ: 163.1, 151.2, 149.5, 131.7, 130.7, 115.1, 113.7,
100.7, 100.3, 56.3, 52.7 ppm. IR (KBr) v: 3049, 1751, 1681,
1614, 1556, 1473, 1363, 1298, 1205, 1072, 1001, 829, 798 cm-1;
HRMS (ESI) calcd for C12H11O5 ([M+H]+) 235.0606, found
235.0605.
calcd for C15H11O4 ([M+H]+) 255.0657, found 255.0658.
4.2.20 Pentan-2-yl 7-methoxy-2-oxo-2H-chromene-3-
o
1
carboxylate (4cc). White solid, yield 88%, mp 125-126 C. H
NMR (300 MHz, CDCl3) δ: 8.43 (s, 1H), 7.50 (d, J = 9.0 Hz,
1H), 6.85-6.89 (d, J = 8.7 Hz, 1H), 6.80 (s, 1H), 5.10-5.20 (m,
1H), 3.89 (s, 3H), 1.68-1.75 (m, 1H), 1.51-1.60 (m, 1H), 1.36-
1.48 (m, 2H), 1.34 (d, J = 6.3 Hz, 3H), 1.23 (t, J = 6.9 Hz, 3H)
ppm; 13C NMR (75 MHz, CDCl3) δ: 164.1, 162.0, 156.6, 147.5,
138.7, 129.7, 113.7, 112.7, 110.7, 99.4, 71.5, 55.1, 37.1, 17.8,
17.5, 13.0 ppm; IR (KBr) v: 2962, 1749, 1697, 1606, 1556, 1506,
1462, 1377, 1263, 1219, 1170, 1022, 794 cm-1; HRMS (ESI)
calcd for C16H19O5 ([M+H]+) 291.1232, found 291.1232.
4.2.14 Methyl
7-(diethylamino)-2-oxo-2H-chromene-3-
carboxylate (4db).16 Yellow solid, yield 85%, mp 173-174 oC. 1H
NMR (300 MHz, CDCl3) δ: 8.41 (s, 1H), 7.34 (d, J = 9.0 Hz,
1H), 6.59 (d, J = 9.0 Hz, 1H), 6.42 (s, 1H), 3.87 (s, 3H), 3.45 (q,
J = 7.8 Hz, 4H), 1.22 (t, J = 6.6 Hz, 6H) ppm. 13C NMR (75
MHz, CDCl3) δ: 164.9, 158.5, 152.9, 149.6, 131.1, 109.6, 108.3,
107.6, 96.6, 52.2, 45.0, 12.3 ppm. IR (KBr) v: 3502, 1755, 1703,
1618, 1587, 1514, 1446, 1419, 1354, 1224, 1199, 1136, 1078,
796 cm-1; HRMS (ESI) calcd for C15H17NO4 (M+H+) 276.1236,
found 276.1235.
4.2.21 Pentan-2-yl 6-chloro-2-oxo-2H-chromene-3-carboxylate
o
1
(4fc). White solid, yield 90%, mp 139-140 C. H NMR (300
MHz, CDCl3) δ: 8.36 (s, 1H), 7.54-7.59 (m, 2H), 7.28 (d, J = 8.4
Hz, 1H), 5.12-5.26 (m, 1H), 1.68-1.78 (m, 1H), 1.52-1.61 (m,
1H), 1.39-1.46 (m, 2H), 1.36 (d, J = 6.3 Hz, 3H), 0.94 (t, J = 7.2
Hz, 3H) ppm. 13C NMR (75 MHz, CDCl3) δ: 162.1, 156.0, 153.3,
146.5, 133.9, 130.0, 128.4, 119.8, 118.8, 118.2, 73.0, 37.9, 19.8,
18.6, 13.8 ppm. IR (KBr) v: 3097, 1745, 1708, 1625, 1566, 1479,
1363, 1292, 1246, 1118, 1083, 1010, 968, 792 cm-1; HRMS (ESI)
calcd for C15H16ClO4 ([M+H]+) 295.0737, found 295.0735.
4.2.15 Methyl
6,8-di-tert-butyl-2-oxo-2H-chromene-3-
o 1
carboxylate (4eb). White solid, yield 80%, mp 157-159 C. H
NMR (300 MHz, CDCl3) δ: 8.50 (s, 1H), 7.64 (s, 1H), 7.36 (s,
1H), 3.90 (s, 3H), 1.46 (s, 9H), 1.31 (s, 9H) ppm. 13C NMR (75
MHz, CDCl3) δ: 164.0, 156.5, 152.1, 150.5, 147.2, 137.4, 129.9,
123.9, 117.8, 116.6, 52.7, 35.1, 31.2, 29.7 ppm. IR (KBr) v:
2953, 1739, 1718, 1622, 1581, 1467, 1363, 1288, 1240, 1209,
1018, 956, 767 cm-1; HRMS (ESI) calcd for C19H25O4 ([M+H]+)
317.1753, found 317.1754.
4.2.22 Pentan-2-yl 6-bromo-2-oxo-2H-chromene-3-carboxylate
o
1
(4gc). White solid, yield: 89%, mp 147-148 C. H NMR (300
MHz, CDCl3) δ: 8.35 (s, 1H), 7.68-7.74 (m, 2H), 7.22 (d, J = 8.4
Hz, 1H), 5.14-5.20 (m, 1H), 1.69-1.78 (m, 1H), 1.54-1.61 (m,
1H), 1.39-1.46 (m, 2H), 1.33 (d, J = 6.3 Hz, 3H), 0.91 (t, J = 7.5
Hz, 3H) ppm. 13C NMR (75 MHz, CDCl3) δ: 162.1, 155.9, 153.8,
146.4, 136.7, 131.4, 119.9, 119.3, 118.5, 117.2, 73.1, 37.9, 19.9,
18.6, 13.8 ppm. IR (KBr) v: 3091, 1753, 1703, 1624, 1600, 1560,
1475, 1359, 1267, 1209, 1149, 1105, 1010, 968, 792 cm-1;
HRMS (ESI) calcd for C15H16BrO4 ([M+H]+) 339.0232, found
339.0232.
4.2.16 Methyl 6-chloro-2-oxo-2H-chromene-3-carboxylate (4fb).
o
1
White solid, yield 89%, mp 199-200 C. H NMR (300 MHz,
CDCl3) δ: 8.83 (s, 1H), 8.43 (s, 1H), 7.43 (d, J = 9.6 Hz, 1H),
7.29 (d, J = 9.3 Hz, 1H), 3.92 (s, 3H) ppm. 13C NMR (75 MHz,
CDCl3) δ: 163.4, 161.9, 153.5, 150.2, 147.7, 135.6, 134.2, 129.3,
128.4, 118.6, 118.3, 53.1 ppm. IR (KBr) v: 3051, 1753, 1680,
1614, 1560, 1475, 1429, 1384, 1300, 1269, 1205, 1087, 1035,
1001, 798 cm-1; HRMS (ESI) calcd for C11H8ClO4 ([M+H]+)
239.0111, found 239.0111.
4.2.23 Benzyl
7-methoxy-2-oxo-2H-chromene-3-carboxylate
o 1
(4cd). Yellow solid, yield 73%, mp 123-125 C. H NMR (300
MHz, CDCl3) δ: 8.50 (s, 1H), 7.48 (d, J = 9.0 Hz, 2H), 7.33-7.41
(m, 4H), 6.88 (d, J = 9.0 Hz, 1H), 6.81 (s, 1H), 5.37 (s, 2H), 3.89
(s, 3H) ppm; 13C NMR (75 MHz, CDCl3) δ: 165.2, 163.1, 157.6,
149.2, 135.7, 130.7, 128.6, 128.3, 113.7, 111.6, 100.3, 67.2, 56.0
ppm; IR (KBr) v: 2951, 1751, 1689, 1614, 1562, 1500, 1463,
1377, 1305, 1276, 1170, 1116, 1026, 1006, 869, 736 cm-1;
HRMS (ESI) calcd for C18H15O5 ([M+H]+) 311.0919, found
311.0918.
4.2.17 Methyl
6-bromo-2-oxo-2H-chromene-3-carboxylate
o 1
(4gb). White solid, yield 88%, mp 184-185 C. H NMR (300
MHz, CDCl3) δ: 8.82 (s, 1H), 8.43 (s, 1H), 7.36 (d, J = 8.1 Hz,
1H), 7.23 (d, J = 8.1 Hz, 1H), 3.92 (s, 3H) ppm. 13C NMR (75
MHz, CDCl3) δ: 163.4, 161.8, 150.0, 147.5, 138.4, 137.1, 132.4,
131.5, 118.8, 118.5, 117.4, 53.0 ppm. IR (KBr) v: 3051, 1750,
1699, 1616, 1564, 1454, 1438, 1365, 1285, 1209, 1092, 1002,
796, 758 cm-1; HRMS (ESI) calcd for C11H8BrO4 ([M+H]+)
282.9606, found 282.9608.
4.2.24 Benzyl 6-bromo-2-oxo-2H-chromene-3-carboxylate (4gd).
o
1
White solid, yield 81%, mp 186-187 C. H NMR (300 MHz,
CDCl3) δ: 8.43 (s, 1H), 7.70-7.73 (m, 2H), 7.45-7.48 (m, 2H),
7.36-7.42 (m, 4H), 7.23 (s, 1H), 5.39 (s, 2H) ppm. 13C NMR (75
MHz, CDCl3) δ: 162.3, 155.9, 153.9, 147.4, 137.1, 135.1, 131.5,
128.7, 128.5, 128.3, 119.2, 119.1, 118.5, 117.3, 67.7 ppm. IR
(KBr) v: 3091, 3034, 1762, 1693, 1618, 1558, 1473, 1413, 1382,
1288, 1209, 1136, 1072, 985, 792, 744 cm-1; HRMS (ESI) calcd
for C17H12BrO4 ([M+H]+) 358.9919, found 358.9916.
4.2.18 Methyl 6-nitro-2-oxo-2H-chromene-3-carboxylate (4hb).
o
1
White solid, yield 89%, mp 222-224 C. H NMR (300 MHz,
CDCl3) δ: 8.58 (s, 1H), 8.52 (s, 1H), 8.47 (d, J = 8.1 Hz, 1H),
7.48 (d, J = 8.4 Hz, 1H), 3.94 (s, 3H) ppm. 13C NMR (75MHz,
CDCl3) δ: 162.6, 158.3, 147.4, 128.7, 125.2, 120.1, 118.1, 117.7,
53.3 ppm. IR (KBr) v: 3105, 3068, 1780, 1757, 1697, 1618,
1570, 1521, 1477, 1436, 1348, 1305, 1257, 1139, 1095, 1001,
796, 752 cm-1; HRMS (ESI) calcd for C11H8NO6 ([M+H]+)
250.0351, found 250.0350.
4.2.25 Benzyl 6-nitro-2-oxo-2H-chromene-3-carboxylate (4hd).
o
1
White solid, yield 83%, mp 236-237 C. H NMR (300 MHz,
DMSO-d6) δ: 8.98 (s, 1H), 8.96 (s, 1H), 8.51 (d, J = 8.7 Hz, 1H),
7.65 (d, J = 8.7 Hz, 1H), 7.50 (d, J = 6.9 Hz, 2H), 7.34-7.42 (m,
3H), 5.34 (s, 2H) ppm. 13C NMR (75 MHz, DMSO-d6) δ: 162.5,
158.5, 155.5, 148.4, 144.1, 136.0, 129.1, 128.9, 128.6, 128.4,
126.6, 119.6, 118.6, 118.2, 107.5, 67.2 ppm. IR (KBr) v: 3086,
3057, 1755, 1703, 1573, 1498, 1452, 1379, 1290, 1217, 1095,
1002, 862, 796 cm-1; HRMS (ESI) calcd for C17H12NO6 ([M+H]+)
326.0664, found 326.0664.
4.2.19 Methyl 3-oxo-3H-benzo[f]chromene-2-carboxylate (4jb).
o
1
Yellow solid, yield 90%, mp 162-163 C. H NMR (300 MHz,
CDCl3) δ: 9.24 (s, 1H), 8.25 (d, J = 8.4 Hz, 1H), 8.05 (d, J = 9.0
Hz, 1H), 7.89 (d, J = 8.1 Hz, 1H), 7.70 (t, J = 7.2 Hz, 1H), 7.57
(t, J = 7.5 Hz, 1H), 7.39 (d, J = 9.0 Hz, 1H), 3.98 (s, 3H) ppm.
13C NMR (75 MHz, CDCl3) δ: 164.0, 156.8, 155.9, 144.9, 136.2,
130.1, 129.3, 129.2, 129.1, 126.6, 121.4, 116.5, 115.8, 112.2,
52.9, 29.6 ppm. IR (KBr) v: 3051, 1745, 1701, 1602, 1570, 1442,

4.2.26 Allyl 7-methoxy-2-oxo-2H-chromene-3-carboxylate (4ce).
This work was supported by the National Natural Science
Yellow solid, yield 90%, mp 108-109 C. HANMCRCE(30P0TMEHDz, MANUSCRIPT
o
1
Foundation of China (No. 21172001, 21372008), the Program for
the NCET (NCET-10-0004), and the Anhui Provincial Natural
Science Foundation (No. 1308085QB39).
CDCl3) δ: 8.52 (s, 1H), 7.49 (d, J = 8.7 Hz, 1H), 6.89 (d, J = 8.7
Hz, 1H), 6.80 (s, 1H), 595-6.08 (m, 1H), 5.47 (d, J = 17.1 Hz,
1H), 5.31 (d, J = 10.5 Hz, 1H), 4.82 (d, J = 5.7 Hz, 2H), 3.89 (s,
3H) ppm. 13C NMR (75 MHz, CDCl3) δ: 165.2, 163.1, 157.6,
157.1, 149.3, 131.6, 130.8, 118.9, 113.7, 113.6, 111.5, 100.3,
66.1, 56.0 ppm. IR (KBr) v: 3047, 3018, 1755, 1732, 1693, 1616,
1560, 1498, 1419, 1379, 1309, 1230, 1172, 1024, 1008, 943, 860,
792 cm-1; HRMS (ESI) calcd for C14H13O5 ([M+H]+) 261.0763,
found 261.0762.
References and notes
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Nat. Prod. 2001, 64, 683-685. (b) Shen, Q.; Peng, Q.; Shao, J.;
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Chem. 2003, 18, 63-69.
4.2.27 Allyl 6,8-di-tert-butyl-2-oxo-2H-chromene-3-carboxylate
o
1
(4ee). White solid, yield 85%, mp 122-123 C. H NMR (300
MHz, CDCl3) δ: 8.52 (s, 1H), 7.66 (s, 2H), 7.39 (s, 1H), 5.82-
6.01 (m, 1H), 4.81 (d, J = 5.4 Hz, 2H), 4.63 (d, J = 5.7 Hz, 2H),
1.48 (s, 9H), 1.33 (s, 9H) ppm; 13C NMR (75 MHz, CDCl3) δ:
166.0, 163.0, 156.5, 152.1, 150.3, 147.1, 137.4, 131.6, 131.4,
129.8, 124.0, 118.7, 117.8, 116.5, 66.1, 41.4, 31.2, 29.7 ppm; IR
(KBr) v: 2954, 1739, 1710, 1649, 1620, 1579, 1467, 1365, 1282,
1211, 1145, 1010, 993, 796 cm-1; HRMS (ESI) calcd for
C21H27O4 ([M+H]+) 343.1909, found 343.1906.
6. Mahmoud, Z. F.; Sarg, T. M.; Amer, M. E.; Khafagy, S. M.
Pharmazie 1983, 38, 486-487.
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Kumar, A.; Lata, S.; Kumar, A. Int. J. ChemTech. Res. 2010, 2,
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Vliegen, I.; Clercq, E. D.; Neyts, J. Antiviral Res. 2008, 77, 157-
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M. S.; Kheffache, D.; Boutemeur-Kheddis, B.; Hamdi, M. J.
Molecular Liquids 2014, 95, 240–247. (b) Yeh, T.-F.; Lin, C.-Y.;
Chang, S.-T. J. Agric. Food Chem. 2014, 62, 1706–1712. (c)
Dugrand, A.; Olry, A.; Duval, T.; Hehn, A.; Froelicher, Y.;
Bourgaud, F. J. Agric. Food Chem. 2013, 61, 10677–10684. (d)
Wang, Y.-H.; Avula, B.; Nanayakkara, N. P. D.; Zhao, J.; Khan, I.
A. J. Agric. Food Chem. 2013, 61, 4470–4476.
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M. Langmuir 2014, 30, 6669–6677. (b) Yam, V. W. W.; Song, H.
O.; Chan, S. T. W.; Zhu, N.; Tao, C. H.; Wong, K. M. C.; Wu, L.-
X. J. Phys. Chem. C 2009, 113, 11674-11682.
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M.; Madaras, M.; Lenhart, W. C. Inorg. Chem. 2010, 49, 1301-
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(b) Santana, L.; Uriarte, E.; Gonzalez-Diaz, H.; Zagotto, G.; Soto-
Otero, R.; Mendez-Alvarez, E. J. Med. Chem. 2006, 49, 1149-
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(d) Li, J.-M.; Chen, H.-Y.; Zhang-Negrerie, D.; Du, Y.-F.; Zhao,
K. RSC Adv. 2013, 3, 4311–4320. (e) Yoshida, H.; Ito, Y.;
Ohshita, J. Chem. Commun. 2011, 47, 8512-8514; (f) Nakai, K.;
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Tetrahedron 2014, 70, 3762–3769. (b) Qian, W.-Y.; Amegadzie,
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4.2.28 Allyl 6-chloro-2-oxo-2H-chromene-3-carboxylate (4fe).
o
1
White solid, yield 91%, mp 142-143 C. H NMR (300 MHz,
CDCl3) δ: 8.45 (s, 1H), 7.59 (s, 2H), 7.32 (d, J = 8.7 Hz, 1H),
5.95-6.08 (m, 1H), 5.49 (d, J = 16.8 Hz, 1H), 5.34 (d, J = 10.2
Hz, 1H), 4.85 (d, J = 5.1 Hz, 2H,) ppm. 13C NMR (75 MHz,
CDCl3) δ: 162.3, 155.9, 153.5, 147.4, 134.2, 131.3, 130.1, 128.4,
119.2, 118.7, 118.2, 66.5 ppm. IR (KBr) v: 3053, 1766, 1741,
1701, 1643, 1620, 1562, 1479, 1379, 1301, 1251, 1012, 943, 794
cm-1; HRMS (ESI) calcd for C13H10ClO4 ([M+H]+) 265.0267,
found 265.0265.
4.2.29 Allyl 6-bromo-2-oxo-2H-chromene-3-carboxylate (4ge).
o
1
White solid, Yield 90%, mp 154-155 C. H NMR (300 MHz,
CDCl3) δ: 8.44 (s, 1H), 7.73 (s, 2H), 7.23 (s, 1H), 5.97-6.04 (m,
1H), 5.48 (d, J = 16.8 Hz, 1H), 5.33 (d, J = 8.7 Hz, 1H), 4.84 (d,
J = 6.0 Hz, 2H) ppm. 13C NMR (75 MHz, CDCl3) δ: 162.2,
155.8, 153.9, 147.3, 137.0, 131.5, 131.3, 119.2, 118.5, 117.3,
66.5 ppm. IR (KBr) v: 3099, 3053, 1766, 1741, 1699, 1643,
1560, 1477, 1415, 1379, 1247, 1207, 1010, 943, 794 cm-1;
HRMS (ESI) calcd for C13H10BrO4 ([M+H]+) 308.9762, found
308.9760.
4.2.30 Allyl 6-nitro-2-oxo-2H-chromene-3-carboxylate (4he).
o
1
Yellow solid, yield 91%, mp 165-166 C. H NMR (300 MHz,
CDCl3) δ: 8.60 (s, 1H), 8.56 (s, 1H), 8.50 (d, J = 9.3 Hz, 1H),
7.50 (d, J = 9.3 Hz, 1H), 5.95-6.08 (m, 1H), 5.49 (d, J = 17.4 Hz,
1H), 5.35 (d, J = 10.5 Hz, 1H), 4.87 (d, J = 7.2 Hz, 2H) ppm. 13
C
NMR (75 MHz, CDCl3) δ: 161.7, 158.3, 154.8, 147.2, 144.2,
131.0, 128.7, 125.2, 120.2, 119.5, 118.1, 117.7, 66.8 ppm. IR
(KBr) v: 3074, 3055, 1776, 1755, 1693, 1647, 1622, 1568, 1477,
1346, 1255, 1093, 1006, 939, 752 cm-1; HRMS (ESI) calcd for
C13H10NO6 ([M+H]+) 276.0508, found 276.0505.
4.2.31 Allyl 3-oxo-3H-benzo[f]chromene-2-carboxylate (4je).
o
1
Yellow solid, yield 91%, mp 115-116 C. H NMR (300 MHz,
CDCl3) δ: 9.30 (s, 1H), 8.29 (d, J = 8.4 Hz, 1H), 8.09 (d, J = 9.3
Hz, 1H), 7.92 (d, J = 8.1 Hz, 1H), 7.76 (t, J = 7.5 Hz, 1H), 7.59
(t, J = 7.5 Hz, 1H), 7.45 (d, J = 8.7 Hz, 1H), 6.00-6.14 (m, 1H),
5.53 (d, J = 17.4 Hz, 1H), 5.35 (d, J = 11.7 Hz, 1H),4.91 (d, J =
6.9 Hz, 2H) ppm. 13C NMR (75 MHz, CDCl3) δ: 163.2, 156.7,
155.9, 144.7, 136.3, 131.5, 130.1, 129.3, 129.2, 129.1, 126.6,
121.4, 119.1, 116.6, 115.9, 112.1, 66.4 ppm. IR (KBr) v: 3014,
2922, 1745, 1695, 1625, 1600, 1564, 1454, 1392, 1300, 1255,
1134, 1012, 989, 750 cm-1; HRMS (ESI) calcd for C17H13O4
([M+H]+) 281.0814, found 281.0816.
16. He, X.-W.; Yan, Z.-L.; Hu, X.-Q.; Zuo, Y.; Jiang, C.; Jin, L.;
Shang, Y.-J. Synth. Commun. 2014, 44, 1507-1514.
Acknowledgements

8
Tetrahedron
17. (a) He, X.-W.; Shang, Y.-J.; Yu, Z.-Y.; Fang, M.; Zhou, Y.; Han,
0o, V = 1038.3(4) Å3, T = 293 K, Z = 4. Crystallographic data for
compound 4i (CCDC-1011994) reported in this paper can be
ACCEPTED MANUSCRIPT
G.; Wu, F.-L. J. Org. Chem. 2014, 79, 8882-8888. (b) Shang, Y.-
J.; Liao, K.-S.; He, X.-W.; Hu, J.-S. Tetrahedron 2013, 69, 10134-
10138. (c) Wu, J.-P.; Shang, Y.-J.; Wang, C.-E.; He, X.-W.; Yan,
Z.-L.; Hu, M.-M.; Zhou, F.-Y.; RSC Adv. 2013, 3, 4643-4651.
18. Crystallographic data for 4aa: space group P(2)1/c, a = 7.933(2)
Å, b = 15.745(4) Å, c = 8.748(2) Å, α = 90o, β = 108.157(3)o, γ =
found in the ESI. These data can be obtained free of charge from
The
Cambridge
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/data_request/cif.