Photoinduced cyclization of alkynoates to coumarins with N-Iodosuccinimide as a free-radical initiator under ambient and metal-free conditions

Article abstract of DOI:10.1016/j.tet.2019.01.013

An efficient photoinduced strategy for the preparation of coumarins was developed. In the presence of N-iodosuccinimide (NIS) as a free-radical initiator and under LED (380–385 nm) irradiation and metal-free conditions, the reaction of alkynoates underwen

Full text of DOI:10.1016/j.tet.2019.01.013

Accepted Manuscript
Photoinduced cyclization of alkynoates to coumarins with N-Iodosuccinimide as a
free-radical initiator under ambient and metal-free conditions
Zhihui Wang, Xuezhi Li, Lei Wang, Pinhua Li
PII:
S0040-4020(19)30028-6
https://doi.org/10.1016/j.tet.2019.01.013
TET 30065
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 22 October 2018
Revised Date: 3 January 2019
Accepted Date: 7 January 2019
Please cite this article as: Wang Z, Li X, Wang L, Li P, Photoinduced cyclization of alkynoates to
coumarins with N-Iodosuccinimide as a free-radical initiator under ambient and metal-free conditions,
Tetrahedron (2019), doi: https://doi.org/10.1016/j.tet.2019.01.013.
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Photoinduced Cyclization of Alkynoates
to Coumarins with N-Iodosuccinimide
as a Free-radical Initiator under
Leave this area blank for abstract info.
Ambient and Metal-free Conditions
Zhihui Wang, Xuezhi Li, Lei Wang and Pinhua Li*
Department of Chemistry, Huaibei Normal University. Huaibei, Anhui 235000, People’s Republic of
China

1
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Tetrahedron
journal homepage: www.elsevier.com
Photoinduced Cyclization of Alkynoates to Coumarins with N-Iodosuccinimide
as a Free-radical Initiator under Ambient and Metal-free Conditions
Zhihui Wanga, Xuezhi Lia, Lei Wanga,b and Pinhua Lia*
a Department of Chemistry, Huaibei Normal University, Huaibei, Anhui 235000, People’s Republic of China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Shanghai 200032, People’s Republic of China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
An efficient photoinduced strategy for the preparation of coumarins was developed. In the
presence of N-iodosuccinimide (NIS) as a free-radical initiator and under LED (380–385 nm)
irradiation and metal-free conditions, the reaction of alkynoates underwent smoothly to afford
the corresponding coumarins in high yields at room temperature with broad substrate scope via
free radical intramolecular cyclization and ester rearrangement.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
Alkynoate
Coumarin
N-iodosuccinimide (NIS)
Photoinduced
Dehalogenation
Previous work:
1. Introduction
OMOM
O
O
O
O
(a)
R1
Cu-catal.
R1
R1
R1
R1
R2B(OH)2
Coumarin and its derivatives are privileged oxygen
heterocycles, which are widely distributed throughout the
animals, plants and microorganisms.1 They display a broad
variety of biological and pharmacological activities, such as
anti-HIV,2 anti-coagulant,3 anti-bacterial,4 anti-oxidant,5 anti-
diabetic6 and so on. Furthermore, they are also used as
additives in food and cosmetics,7 and in the preparation of
insecticides, optical brighteners,8 dispersed fluorescence and
laser dyes.9 In general, coumarin core is prepared through a
variety of organic transformations. There are several
superior methods recommended by organic chemists. For
example, Yamamoto established an efficient Cu-catalyzed
hydroarylation from methyl phenylpropiolates with a MOM-
protected hydroxy group at the ortho-position with
arylboronic acids to 4-arylcoumarins (Scheme 1a).10
Iwasawa reported a Pd-catalyzed direct carboxylation of
alkenyl C−H bonds with CO2, leading to a redox-neutral
+
(2.0 mol%)
CO2Me
R2
H
O
OH
(b)
CO2
or
CO
transition-metal catalyst
or transition-metal-free
R2
+
R1
R2
O
OH
+
R1
(c)
Pd-catal.
R2
+
CO
(5.0 mol%)
R2
O
O
H
O
H
O
Au-catal. (5 mol%)
R1
(d)
or Hf(OTf)4 (10 mol%)
R2
R2
O
H
This work:
R1
O
O
O
H
O
(e)
NIS (20 mol%)
hv (380-385 nm)
H
access to coumarins (Scheme 1b).11 In 2017, Yu et al
.
R1
R2
O
disclosed a transition-metal free lactonization of heteroaryl
and alkenyl C−H bonds with CO2 to coumarin derivatives
(Scheme 1b).12 In addition, Alper, Gulías and Wang realized
transition-metal-catalyzed oxidative cyclocarbonylation of
2-vinyphenols with CO in the presence of Pd-, Rh- or Co-
catalyst (Scheme 1b).13 Most recently, Wu discovered a Pd-
catalyzed oxidative carbonylation procedure for the
synthesis of coumarins from phenols, terminal alkynes and
CO (Scheme 1c).14 In 2004, Song and He developed the
intramolecular Friedel–Crafts alkenylations of aryl phenyl
propiolates catalyzed by Hf(OTf)4 or Au(III), independently
R2
O
este
rangem
I
r
rear
spiro
cycliz
ent
ation
R2
R1
Room temperature !
Transition-metal free !
Scheme 1. Synthesis of coumarins
(Scheme 1d).15 Although considerable progress has been
made in this field, the existing methods suffer from
drawbacks such as narrow substrate scope, harsh reaction

2
Tetrahedron
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Table 1. Optimization of the reaction conditionsa
conditions, need of catalyst or high toxic CO as reagent in
the most of cases. Thus, developing a facile, efficient and
metal-free method to synthesize coumarins with broad
functional group tolerance, mild and environmental-friendly
conditions is highly desirable.
Visible light as a rich and green energy source has been
shown to induce large amounts of organic transformations
through electron transfer, energy transfer and hydrogen
transfer processes. Photo-catalytic strategies can provide a
better choice for organic synthesis because it avoids
additional metals, ligands and high temperature. Visible-
light promoted organic reactions have received the
considerable attention, and emerged as a hot research topic
in chemistry during the past few years.16 Recently, Pan and
She reported the visible-light induced synthesis of 3-
halocoumarins from alkynoates, respectively.17 In this
manuscript, we wish to report an alternative and
straightforward route to coumarins from the corresponding
alkynoates via a photoinduced intramolecular cyclization
and ester rearrangement. The reaction underwent smoothly
Entry
Iodine source
C6H5I(1 equiv.)
C6H5I (1 equiv.)
Solvent
Toluene
DCE
Light source
365–370 nm
365–370 nm
Yield (2a/3a, %)b
17/Trace
1
2
0/10
3
C6H5I (1 equiv.)
C6H5I (1 equiv.)
C6H5I (1 equiv.)
C6H5I (1 equiv.)
NIS (1 equiv.)
TBAI (1 equiv.)
I2 (1 equiv.)
CH3CN
DMSO
DMF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
365–370 nm
380–385 nm
254 nm
0/12
0/0
4
5
0/0
6
28/Trace
46/16
0/0
7
8
9
19/15
91/Trace
87/Trace
90/Trace
82/0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
NIS (20 mol%)
NIS (50 mol%)
NIS (35 mol%)
NIS (15 mol%)
NIS (10 mol%)
NIS (5 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
NIS (20 mol%)
with N-iodosuccinimide (NIS) as free-radical initiator under
photo-irradiation, ambient and metal-free conditions, which
generated the desired products in high yields with broad
substrate scope (Scheme 1e).
57/0
25/0
2. Results and discussion
95/0
For the optimization of the reaction conditions, a model reaction
of p-tolyl 3-phenylpropiolate (1a) was chosen and the reaction
was carried out at a 0.20 mmol scale. When the model reaction
was performed in the presence of C6H5I (1.0 equiv.) as the free
radical initiator in toluene at room temperature under LED (365–
370 nm) irradiation in air for 8 h, the desired product 2a was
isolated in 17% yield with a trace amount of product 3-
iodocoumarin (3a) (Table 1, entry 1). The structure of 2a was
Trace/15
Trace/23
0/20
395–405 nm
410–415 nm
420–425 nm
450–455 nm
515–520 nm
520–525 nm
530–535 nm
White light (18 W)
380–385 nm
380–385 nm
380–385 nm
380–385 nm
0/23
0/25
0/25
0/24
1
characterized by H and 13C NMR, and further confirmed by X-
ray single crystal analysis.18 To further evaluate the feasibility of
the reaction, solvent effect was examined, and the results were
listed in entries 2–6 of Table 1. None of 2a was obtained when
the reaction was conducted in DCE (1,2-dichloroethane) or
CH3CN, and only 10–12% yields of 3a was generated (Table 1,
entries 2 and 3). Neither 2a nor 3a was detected as the model
reaction was performed in DMSO or DMF (Table 1, entries 4 and
5). To our delight, 28% yield of 2a was acquired along with a
neglectable amount of 3a when THF was used as solvent (Table
1, entry 6). In order to increase the yield of the desired product,
some iodine sources were screened. An improved yield (46%) of
2a was obtained when N-iodosuccinimide (NIS, 1.0 equiv.) was
used as free radical initiator, with 16% yield of product 3a (Table
1, entry 7). Other iodine sources, such as tetrabuylammonium
iodide (TBAI) and I2 failed to improve the yield of desired
product (Table 1, entries 8 and 9). To improve the yield of the
target product 2a, and reduce the yield of by-product 3a, we tried
to change the amount of NIS added in the reaction, and the
results were summarized in Table 1 (entries 10–15). Surprisingly,
when 20 mol% of NIS was used, the yield of 2a was reached to
91% and almost no by-product 3a was generated (Table 1, entry
10). More than 35 mol% of NIS or less than 20 mol% of NIS was
added, inferior yields of product 2a were found (Table 1, entries
11–15). Considering the influence of the light source on the
reaction, a series of light sources were tested and the optical
wavelength in the range of 380–385 nm is best, yielding 3a in an
almost quantitative yield (Table 1, entry 16). Other light sources,
including 254, 395–405, 410–415, 420–425, 450–455, 515–
520, 520–525, 530–535 nm and white light were no longer
0/22
Trace/23
30/15c
63/12d
78/Tracee
88/0f
aReaction conditions: 1a (0.20 mmol), solvent (2.0 mL) at room
temperature in air under light irradiation for 8 h. bIsolated yield. c2 h.d4
h. e6 h. f10 h.
the effective ones, and almost no 2a was observed (Table 1,
entries 17–25). Further investigation explored that the
optimal reaction time is 8 h (Table 1, entries 26–29).
With the optimized reaction conditions in hand, we then
probed into the generality of reaction. Firstly, some
substituted groups including typical electron-withdrawing
and electron-donating groups on the aromatic rings of the
ester moieties in substrates
Scheme 2. In general, these groups at the para-position of
the benzene rings resulted in high yields of the desired
products (2a–2k). However, when the para-position of the
aromatic ring in the ester moiety is replaced by a strong
electron-withdrawing group (NO2, CHO or CF3), no
products (2u–2w) were observed. Naphthalen-2-yl 3-
1 were surveyed, shown in
phenylpropiolate is also a suitable substrate, forming an
anticipated product 2l in 75%

3
a
a
ACCEPTED MANUSCRIPT
Scheme 2. The scope of phenol moiety in the substrates
Scheme 3. The scope of propiolic acid unit in the substrates
aReaction conditions:
1 (0.20 mmol), NIS (20 mol%), THF (2.0 mL),
room temperature, LED (380–385 nm, 1.5 W) irradiation for 8 h.
methyl-4-propyl-2H-chromen-2-one (2al) were generated in
76% and 71% isolated yields, respectively. When phenyl
propiolate (1m) was used in the reaction, no desired product
(2am) was detected. However, substrates prepared from 3-
(2-thiphenyl) propiolic acid and 3-(3-pyridyl) propiolic acid
showed the negative effect for the reaction, and no any
products were observed (2an and 2ao).
aReaction conditions: 1 (0.20 mmol), NIS (20 mol%), THF (2.0 mL), room
temperature, LED (380–385 nm, 1.5 W) irradiation for 8 h.
To gain insights into the reaction mechanism, the relationship
of optical wavelength with the ratio of 2a/3a was investigated,
shown in Scheme 4, as well as in Table 1. When the model
reaction of 1a was carried out in the presence of NIS (1.1 equiv.)
under the
yield. In addition, when the meta-position of the aromatic
ring in the ester moiety is substituted by a methyl group, two
regio-isomers (2m and 2m’) were generated in 51% and 37%
yields. On the other hand, meta-substituted groups including
MeO, F, Cl and Br on the substrates afforded the expected
Scheme 4. The formation of halogenation productsa
products (2n–2q) in good yields with excellent regio-
selectivity. It is noteworthy that the reaction of 3,5-
dichlorophenyl 3-phenylpropiolate underwent well to
generate the corresponding product 2r in 77% yield under
optimal reaction conditions. Unfortunately, the use of ortho
-
substituted substrates and heterocyclic substrates failed in
this reaction, no any desired products (2s and 2t) were
detected.
We continued our investigation on the scope of propiolic acid
unit in the substrates under the optimized reaction conditions. As
shown in Scheme 3, substrates derived from 3-arylpropiolic acids
t
with the different electron-donating groups (Me, Et, Bu and
MeO) or electron-withdrawing groups (F, Cl and Br) on the
aromatic rings underwent the reaction smoothly to afford the
corresponding products (2aa–2ai) in good yields (81–89%).
Furthermore, phenyl 3-(3,5-dimethylphenyl)propiolate was
performed under the present reaction conditions to produce the
target product 2aj in 85% yield. For substrates from 3-
alkylpropiolic acids, such as 3-ethylpropiolic acid and 3-
propylpropiolic acid, the corresponding products 4-ethyl-7-
methyl-2H-chromen-2-one (2ak) and 7-
aReaction conditions:
temperature, LED irradiation for 8 h.
1 (0.20 mmol), NIS or NBS, THF (2.0 mL), room

4
Tetrahedron
scavenger, was added into the solution of 1a in THF under
ACCEPTED MANUSCRIPT
standard conditions, the reaction was completely inhibited
(Scheme 5a), indicating the conversion may be involved in a free
radical process. According to possibility of 2a from 3a, when
prepared 3a was added to the solvent of THF and irradiated under
LED (380–385 nm) for 8 h, providing 2a in 86% yield (Scheme
5b). However, no 2a was obtained when the reaction was
irradiated with LED light of 420–425 nm. This phenomenon
indicated that C–I bond of 3a was cleavage by LED light (380–
385 nm), but now with LED light (420-425 nm) failed (Scheme
5c). Subsequently, the hydrogen source for 3a to 2a was
examined, and the solvent THF is confirmed to be the hydrogen
transfer reservoir in the reaction from the control experiments of
3a and 1a in d8-THF solution under the irradiation of LED (380–
385 nm), providing d1-2a in 68% and 73 % yield, respectively
(Scheme 5d and 5e). We repeated the reaction again by using d8-
toluene as solvent, and d1-2a was isolated in 36% yield under the
standard reaction conditions, illustrating that the 3-hydrogen
comes from solvent (Scheme 5f, see SI for details).
Based on the experimental results and related
literature,17a a possible mechanism is illustrated in Scheme 6.
Under light (380–385 nm) irradiation, the homolytic
cleavage of
radical and iodine radical, which underwent an addition to
carbon-carbon triple bond of alkynoate to form an
intermediate , followed by an intramolecular radical
addition, providing an intermediate . Then, the obtained
proceeded an intramolecular ester rearrangement to afford
N-iodosuccinimide generated succinimide free
A
B
C
C
intermediate
D
, which reacted with succinimide radical
A
(via in first priority) or alkoxyalkyl radical
①
E
(via
②
in
cycle-run) via a hydrogen atom abstraction, affording
iodination product (Path I). Under LED (380 nm)
continuing irradiation, the iodination could be converted
into the deiodination product through a homolytic
cleavage C–I of vinyl iodide and protonation sequence
3
3
2
Scheme 5. The control experiments
reaction. It should be noted that the formation of
2 via Path
II could be ruled out (1H NMR of d1
-2a in SI).
irradiation of blue LED (420–425 nm) for 8 h, iodination product
(3a) was achieved in 97% yield with a trace amount of
deiodination product (2a) (Scheme 4b). When LED (380–385 nm)
was used, iodination product (3a) and deiodination product (2a)
were achieved in 34% and 55% yields, respectively (Scheme 4a).
On the contrary, when 1a was performed with NIS (20 mol%)
under the irradiation of LED (380–385 nm) for 8 h, 2a was got
95% yield, and no 3a was detected (Table 1, entry 16). The
preliminary results indicated that the wavelength of light and
loading of NIS play important roles in the formation of
deiodination product (2a) and iodination product (3a). The
generality about the formation of iodination products (3) from the
corresponding starting materials (1) in the presence of NIS (1.1
equiv.) under the irradiation of blue LED (420–425 nm) was
examined, listed in Scheme 4, which is in accordance with Han
and Pan’s results.17a Further investigation was extended to
competition of bromination and debromination processes using
N-bromosuccinimide (NBS). The results shown in Scheme 4 also
indicated that bromination products (4) could be obtained in good
yields, and no any debromination products were found when the
reaction started in the presence of NBS (2.0 equiv.) under the
irradiation of LED (380–385 nm). In addition, the chlorination
and dechlorination could not occur even the reaction of 1a was
carried out with NCS (2.0 equiv.) and LED (380–385 nm)
irradiation for prolonged time. These facts demonstrated that the
reactivity order of C–X bond is C–I > C–Br > C–Cl via free
radical pathway, and dehalogenation process is from the
corresponding halogenation products.
Scheme 6. Proposed mechanism
3. Conclusions
In conclusion, we have developed a straightforward method
for the synthesis of coumarins from the corresponding alkynoates
via a photoinduced intramolecular cyclization. The reaction
underwent smoothly with N-iodosuccinimide as free-radical
initiator under irradiation of LED (380–385 nm) and metal-free
conditions at room temperature, providing the desired products in
good to excellent yields with broad substrate scope.
A
preliminary mechanism indicated that this transformation is
involved in a free radical process. Further efforts are being
carried out to investigate the potential application of this
In order to understand the reaction process clearly, when
2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO),
a
radical

5
methodology in our laboratory.
4. Experimental Section
General Considerations
14.90. HRMS (ESI) ([M + H]+) calcd for C17H14O2:
251.1067, found: 251.1069.
ACCEPTED MANUSCRIPT
5.4. 7-(iso-Propyl)-4-phenyl-2H-chromen-2-one (2d):
1
Yellow liquid. H NMR (400 MHz, CDCl3) δ: 7.52–7.51
1
All H NMR and 13C NMR spectra were recorded on a 400
(m, 3H), 7.45–7.43 (m, 2H), 7.41 (d,
(s, 1H), 7.10 (d, = 8.2 Hz, 1H), 6.31 (s, 1H), 3.05–2.95 (m,
1H), 1.29 (d,
= 6.9 Hz, 6H); 13C NMR (100 MHz, CDCl3)
J = 8.3 Hz, 1H), 7.26
MHz Bruker FT-NMR spectrometer (400 MHz or 100 MHz,
respectively). All chemical shifts are given as δ value (ppm) with
reference to tetramethylsilane (TMS) as an internal standard. The
peak patterns are indicated as follows: s, singlet; d, doublet; t,
triplet; m, multiplet; q, quartet. The coupling constants, J, are
reported in Hertz (Hz). High resolution mass spectroscopy data
of the products were collected on an Agilent Technologies 6540
UHD Accurate-Mass Q-TOF LC/MS (ESI).
J
J
δ: 160.91, 155.52, 154.33, 153.95, 135.30, 129.48, 128.70,
128.27, 126.74, 122.73, 116.72, 114.73, 113,95, 34.02,
23.49. HRMS (ESI) ([M + H]+) calcd for C18H16O2:
265.1223, found: 265.1222.
5.5. 7-(tert-Butyl)-4-phenyl-2H-chromen-2-one (2e):
o
Light yellow solid. m.p. 141.7–141.9 C. 1H NMR (400
Aryl alkynoates were prepared according to the reported
method.19 The chemicals and solvents were purchased from
commercial suppliers either from Aldrich (USA) or Shanghai
Chemical Company (China) without further purification. All the
solvents were dried and freshly distilled prior to use. All the
reactions were carried out under air atmosphere. Products were
purified by flash chromatography on 200–300 mesh silica gels,
SiO2.
MHz, CDCl3) δ: 7.51–7.50 (m, 3H), 7.44–7.40 (m, 4H),
7.28–7.25 (m, 1H), 6.29 (s, 1H), 1.35 (s, 9H); 13C NMR (100
MHz, CDCl3) δ: 160.65, 156.09, 155.16, 153.98, 135.08,
129.36, 128.56, 128.11, 126.30, 121.42, 116.14, 113.90,
113,75, 34.86, 30.73. HRMS (ESI) ([M + H]+) calcd for
C19H18O2: 279.1380, found: 279.1380.
5.6. 7-Methoxy-4-phenyl-2H-chromen-2-one (2f):11
Typical procedure for cyclization of alkynoates to coumarins
with N-iodosuccinimide
o
Light yellow solid. m.p. 152.2–152.6 C. 1H NMR (400
MHz, CDCl3) δ: 7.52–7.50 (m, 3H), 7.45–7.42 (m, 2H), 7.38
A 5 mL oven-dried reaction vessel equipped with a magnetic
stirrer bar was charged with p-tolyl 3-phenylpropiolate (1a, 47.2
mg, 0.20 mmol), N-iodosuccinimide (NIS, 9.0 mg, 20 mol%) and
THF (2.0 mL). The reaction vessel was exposed to LED
(380−385 nm, 1.5 W) irradiation at room temperature in air with
stirring for 8 h. After completion of the reaction, the mixture was
concentrated to yield the crude product, which was further
purified by flash chromatography (silica gel, petroleum
ether/ethyl acetate = 20/1) to give the desired product 2a (44.8
mg, 95% yield).
(d,
J = 8.9 Hz, 1H), 6.88 (d, J = 2.4 Hz, 1H), 6.81–6.78 (m,
1H), 6.21 (s, 1H), 3.88 (s, 3H); 13C NMR (100 MHz, CDCl3)
δ: 162.90, 161.08, 155.91, 155.71, 135.46, 129.49, 128.72,
128.27, 127.88, 112.39, 111.73, 101.01, 55.70. HRMS (ESI)
([M + H]+) calcd for C16H12O3: 253.0859, found: 253.0854.
5.7. 8-Phenyl-6H-[1,3]dioxolo[4,5-g]chromen-6-one (2g):22
o
Light yellow solid. m.p. 142.2–144.1 C. 1H NMR (400
MHz, CDCl3) δ: 7.52–7.50 (m, 3H), 7.45–7.39 (m, 2H), 6.88
(s, 1H), 6.82 (s, 1H), 6.23 (s, 1H), 6.05 (s, 2H); 13C NMR
(100 MHz, CDCl3) δ: 161.10, 155.82, 151.27, 151.09,
144.77, 135.60, 129.54, 128.83, 128.17, 112.76, 112.12,
104.28, 102.31, 98.47. HRMS (ESI) ([M + H]+) calcd for
C16H10O4: 267.0652, found: 267.0655.
5. Spectral Data
5.1. 7-Methyl-4-phenyl-2H-chromen-2-one (2a):20
o
1
Light yellow solid. m.p. 89.1–89.8 C. H NMR (400
5.8. 4,7-Diphenyl-2H-chromen-2-one (2h):23
MHz, CDCl3) δ: 7.52–7.50 (m, 3H), 7.44–7.42 (m, 2H), 7.36
(d,
J = 8.2 Hz, 1H), 7.19 (s, 1H), 7.03 (d, J = 8.1 Hz, 1H),
o
Light yellow solid. m.p. 144.4–144.8 C. 1H NMR (400
6.29 (s, 1H), 2.45 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
160.84, 155.51, 154.15, 143.06, 135.26, 129.48, 128.69,
128.27, 126.55, 125.23, 117.28, 116.40, 113,86, 21.45.
HRMS (ESI) ([M + H]+) calcd for C16H12O2: 237.0910,
found: 237.0916.
MHz, CDCl3) δ: 7.63–7.60 (m, 3H), 7.56–7.53 (m, 4H),
7.49–7.39 (m, 6H), 6.36 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ: 160.75, 155.35, 154.53, 144.94, 138.90, 135.15,
129.66, 129.03, 128.84, 128.51, 128.36, 127.27, 127.13,
122.90, 117.81, 115.28, 114.68. HRMS (ESI) ([M + H]+)
calcd for C21H14O2: 299.1067, found: 299.1069.
5.2. 4-Phenyl-2H-chromen-2-one (2b):15b
o
1
5.9. 7-Fluoro-4-phenyl-2H-chromen-2-one (2i):
Light yellow solid. m.p. 89.1–90.7 C. H NMR (400
MHz, CDCl3) δ: 7.57–7.55 (m, 1H), 7.54–7.52 (m, 3H),
o
Light yellow solid. m.p. 119.4–120.0 C. 1H NMR (400
7.51–7.49 (m, 1H), 7.46–7.44 (m, 2H), 7.40 (d,
J = 8.2 Hz,
MHz, CDCl3) δ: 7.55–7.53 (m, 3H), 7.51–7.47 (m, 1H),
1H), 7.25–7.21 (m, 1H), 6.37 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ: 160.59, 155.54, 154.06, 135.06, 131.82, 129.59,
128.76, 128.31, 126.90, 124.07, 118.85, 117.17, 115,04.
HRMS (ESI) ([M + H]+) calcd for C15H10O2: 223.0754,
found: 223.0757.
7.45–7.43 (m, 2H), 7.14–7.11 (m, 1H), 7.00–6.85 (m, 1H),
6.33 (s, 1H); 13C NMR (100 MHz, CDCl3) δ: 164.46 (d,
J
=
252.8 Hz), 160.31, 155.43, 155.27 (d,
129.84, 128.97, 128.73 (d, = 10.0 Hz), 128.31, 115.74 (d,
= 2.7 Hz), 113.91 (d, = 2.6 Hz), 112.17 (d,
104.72 (d,
= 25.3 Hz). HRMS (ESI) ([M + H]+) calcd for
J = 6.2 Hz), 135.02,
J
J
J
J = 22.3 Hz),
J
5.3. 7-Ethyl-4-phenyl-2H-chromen-2-one (2c):
C15H9FO2: 241.0659, found: 241.0662.
Yellow liquid. 1H NMR (400 MHz, CDCl3) δ: 7.52–7.50
5.10. 7-Chloro-4-phenyl-2H-chromen-2-one (2j):24
(m, 3H), 7.44–7.42 (m, 2H), 7.39 (d,
J = 8.2 Hz, 1H), 7.22
(s, 1H), 7.07 (d, J = 8.1 Hz, 1H), 6.29 (s, 1H), 2.76–2.71 (m,
o
1
Light yellow solid. m.p. 176.9–177.1 C. H NMR (400
MHz, CDCl3) δ: 7.55–7.53 (m, 3H), 7.44–7.41 (m, 4H),
7.22–7.19 (m, 1H), 6.36 (s, 1H); 13C NMR (100 MHz,
2H), 1.29–1.25 (m, 3H); 13C NMR (100 MHz, CDCl3) δ:
160.76, 155.44, 154.22, 149.23, 135.21, 129.42, 128.63,
128.20, 126.63, 124.02, 116.51, 116.00, 113,83, 28.62,

6
Tetrahedron
o
1
CDCl3) δ: 159.96, 155.00, 154.51, 137.82, 134.74, 129.88,
Light yellow solid. m.p. 150.4–151.2 C. H NMR (400
ACCEPTED MANUSCRIPT
128.97, 128.28, 127.88, 124.67, 117.60, 117.47, 114.94.
HRMS (ESI) ([M + H]+) calcd for C15H9ClO2: 257.0364,
found: 257.0369.
MHz, CDCl3) δ: 7.56–7.54 (m, 3H), 7.51–7.48 (m, 1H),
7.46–7.43 (m, 3H), 7.35 (d,
J = 8.8 Hz, 1H), 6.41 (s, 1H);
13C NMR (100 MHz, CDCl3) δ: 159.94, 154.57, 152.60,
134.54, 131.84, 129.96, 129.64, 129.08, 128.27, 126.19,
118.71, 116.13. HRMS (ESI) ([M + H]+) calcd for
C15H9ClO2: 257.0364, found: 257.0370.
5.11. 7-Bromo-4-phenyl-2H-chromen-2-one (2k):24
o
1
Light yellow solid. m.p. 138.3–139.9 C. H NMR (400
MHz, CDCl3) δ: 7.57–7.53 (m, 4H), 7.44–7.43 (m, 2H), 7.35
(m, 2H), 6.37 (s, 1H); 13C NMR (100 MHz, CDCl3) δ:
159.84, 155.05, 154.33, 134.67, 129.88, 128.97, 128.28,
127.99, 127.51, 125.84, 120.42, 117.96, 115.16. HRMS
(ESI) ([M + H]+) calcd for C15H9BrO2: 300.9859, found:
300.9864.
5.18. 6-Bromo-4-phenyl-2H-chromen-2-one (2q):15b
o
1
Light yellow solid. m.p. 134.4–135.8 C. H NMR (400
MHz, CDCl3) δ: 7.65–7.63 (m, 1H), 7.60–7.55 (m, 4H), 7.44
(s, 2H), 7.31–7.29 (m, 1H), 6.40 (s, 1H); 13C NMR (100
MHz, CDCl3) δ: 159.94, 154.53, 153.06, 134.72, 134.49,
130.00, 129.34, 129.11, 128.29, 120.65, 119.05, 117.00,
116.12. HRMS (ESI) ([M + H]+) calcd for C15H9BrO2:
300.9859, found: 300.9861.
5.12. 4-Phenyl-2H-benzo[g]chromen-2-one (2l):25
o
1
Light yellow solid. m.p. 134.4–135.8 C. H NMR (400
5.19. 5,7-Dichloro-4-phenyl-2H-chromen-2-one (2r):27
MHz, CDCl3) δ: 8.63–8.61 (m, 1H), 7.87–7.84 (m, 1H),
7.67–7.63 (m, 2H), 7.61 (d,
J = 8.8 Hz, 1H), 7.57–7.54 (m,
3H), 7.51–7.45 (m, 3H), 6.46 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ: 160.74, 156.57, 151.47, 135.64, 134.82, 129.59,
128.86, 128.83, 128.48, 127.63, 127.15, 123.90, 123.36,
122.72, 122.34, 114.52, 114.20. HRMS (ESI) ([M + H]+)
calcd for C19H12O2: 273.0910, found: 273.0909.
Light yellow solid. m.p. 139.2–139.8 C. H NMR (400
MHz, CDCl3) δ: 7.60 (d, = 2.4 Hz, 1H), 7.57–7.55 (m,
3H), 7.43–7.41 (m, 2H), 7.35 (d, = 2.4 Hz, 1H), 6.44 (s,
o
1
J
J
1H); 13C NMR (100 MHz, CDCl3) δ: 158.68, 154.43,
148.58, 134.20, 131.90, 130.16, 129.29, 129.16, 128.26,
125.04, 123.19, 121.16, 116.70. HRMS (ESI) ([M + H]+)
calcd for C15H8Cl2O2: 290.9974, found: 290.9979.
5.13. 6-Methyl-4-phenyl-2H-chromen-2-one (2m):11
o
1
5.20. 4-(p-Tolyl)-2H-chromen-2-one (2aa): 10
Light yellow solid. m.p. 127.7–127.9 C. H NMR (400
MHz, CDCl3) δ: 7.54–7.52 (m, 3H), 7.47–7.43 (m, 2H),
7.37–7.34 (m, 1H), 7.30–7.28 (m, 1H), 7.25 (s, 1H), 6.34 (s,
1H), 2.34 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.84,
155.53, 152.22, 135.27, 133.79, 132.83, 129.51, 128.77,
128.32, 126.61, 118.57, 116.94, 115.05, 20.84. HRMS (ESI)
([M + H]+) calcd for C16H12O2: 237.0910, found: 237.0907.
o
1
Light yellow solid. m.p. 124.3–125.8 C. H NMR (400
MHz, CDCl3) δ: 7.54–7.53 (m, 2H), 7.40 (d, = 8.1 Hz,
J
1H), 7.37–7.32 (m, 4H), 7.25–7.21 (m, 1H), 6.37 (s, 1H),
2.46 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.82,
155.70, 154.19, 139.87, 132.29, 131.79, 129.52, 128.37,
127.02, 124.05, 119.07, 117.27, 114.88, 21.32. HRMS (ESI)
([M + H]+) calcd for C16H12O2: 237.0910, found: 237.0910.
5.14. 8-Methyl-4-phenyl-2H-chromen-2-one (2m’):20
1
5.21. 4-(4-Ethylphenyl)-2H-chromen-2-one (2ab):28
Light yellow liquid. H NMR (400 MHz, CDCl3) δ:
7.53–7.51 (m, 3H), 7.45–7.43 (m, 2H), 7.40 (d,
J = 1.9 Hz,
o
1
1H), 7.32 (d,
J
= 2.0 Hz, 1H), 7.14–7.10 (m, 1H), 6.36 (s,
Light yellow solid. m.p. 125.4–126.8 C. H NMR (400
1H), 2.51 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.86,
156.03, 152.45, 135.52, 133.19, 129.50, 128.74, 128.42,
126.63, 124.74, 123.57, 118.69, 114.85, 15.74. HRMS (ESI)
([M + H]+) calcd for C16H12O2: 237.0910, found: 237.0912.
MHz, CDCl3) δ: 7.56–7.53 (m, 2H), 7.41–7.35 (m, 5H), 7.23
(t,
J
= 8.1 Hz, 1H), 6.37 (s, 1H), 2.75 (q,
J = 7.6 Hz, 2H),
1.31 (t,
J
= 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
160.82, 155.71, 154.18, 146.12, 132.49, 131.77, 128.46,
128.33, 127.06, 124.04, 119.07, 117.26, 114.87, 28.67,
15.34. HRMS (ESI) ([M + H]+) calcd for C17H14O2:
251.1067, found: 251.1069.
5.15. 6-Methoxy-4-phenyl-2H-chromen-2-one (2n):12
o
1
Light yellow solid. m.p. 149.8–150.5 C. H NMR (400
5.22. 4-(4-(tert-Butyl)phenyl)-2H-chromen-2-one (2ac):21
MHz, CDCl3) δ: 7.54–7.52 (m, 3H), 7.47–7.45 (m, 2H), 7.35
(d,
J = 9.0 Hz, 1H), 7.15–7.12 (m, 1H), 6.93 (d, J = 2.9 Hz,
1H), 6.38 (s, 1H), 3.74 (s, 3H); 13C NMR (100 MHz, CDCl3)
δ: 160.90, 155.84, 155.31, 148.54, 135.24, 129.67, 128.89,
128.30, 119.40, 118.95, 118.19, 115.60, 109.96, 55.75.
HRMS (ESI) ([M + H]+) calcd for C16H12O3: 253.0859,
found: 253.0855.
Light yellow solid. m.p. 124.4–125.5 C. H NMR (400
MHz, CDCl3) δ: 7.58–7.52 (m, 4H), 7.41–7.39 (m, 3H), 7.23
(td, J1 = 0.9 Hz, J2 = 7.6 Hz, 1H), 6.37 (s, 1H), 1.39 (s, 9H);
13C NMR (100 MHz, CDCl3) δ: 160.77, 155.61, 154.17,
153.01, 132.22, 131.74, 128.21, 127.08, 125.75, 124.00,
119.03, 117.21, 114.85, 34.79, 31.20. HRMS (ESI) ([M +
H]+) calcd for C19H18O2: 279.1380, found: 279.1381.
o
1
5.16. 6-Fluoro-4-phenyl-2H-chromen-2-one (2o):26
o
1
5.23. 4-(4-Methoxyphenyl)-2H-chromen-2-one (2ad):10
Light yellow solid. m.p. 172.8–173.5 C. H NMR (400
MHz, CDCl3) δ: 7.56–7.54 (m, 3H), 7.46–7.44 (m, 2H),
7.40–7.37 (m, 1H), 7.29–7.24 (m, 1H), 7.19–7.16 (m, 1H),
6.42 (s, 1H); 13C NMR (100 MHz, CDCl3) δ: 160.16, 158.54
o
1
Light yellow solid. m.p. 129.5–129.7 C. H NMR (400
MHz, CDCl3) δ: 7.58–7.53 (m, 2H), 7.43–7.40 (m, 3H),
(d,
J
= 242.2 Hz), 154.65 (d,
J
= 2.7 Hz), 150.20 (d,
= 8.4 Hz),
= 8.2 Hz), 115.98,
= 25.0 Hz). HRMS (ESI) ([M + H]+) calcd for
J
= 1.6
7.27–7.22 (m, 1H), 7.05 (d, J = 8.7 Hz, 2H), 6.36 (s, 1H),
Hz), 134.56, 129.88, 128.97, 128.17, 119.80 (d,
119.20 (d,
112.46 (d,
J
1.39 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.88,
160.83, 155.31, 154.24, 131.77, 129.93, 127.45, 127.00,
124.05, 119.14, 117.33, 114.63, 114.32, 55.43. HRMS (ESI)
([M + H]+) calcd for C16H12O3: 253.0859, found: 253.0861.
J = 24.5 Hz), 118.69 (d, J
J
C15H9FO2: 241.0659, found: 241.0663.
5.17. 6-Chloro-4-phenyl-2H-chromen-2-one (2p):21
5.24. 4-(4-Chlorophenyl)-2H-chromen-2-one (2ae): 10

7
o
1
Light yellow solid. m.p. 185.9–186.8 C. H NMR (400
MHz, CDCl3) δ: 7.59–7.55 (m, 1H), 7.53–7.51 (m, 2H),
7.45–7.40 (m, 4H), 7.27–7.23 (m, 1H), 6.36 (s, 1H); 13C
NMR (100 MHz, CDCl3) δ: 160.40, 154.39, 154.17, 135.96,
133.55, 132.12, 129.77, 129.21, 126.65, 124.27, 118.66,
117.43, 115.37. HRMS (ESI) ([M + H]+) calcd for
C15H9ClO2: 257.0364, found: 257.0369.
161.39, 157.39, 153.62, 142.62, 125.25, 123.74, 117.28,
ACCEPTED MANUSCRIPT
116.80, 111.84, 24.53, 21.46, 12.03. HRMS (ESI) ([M +
H]+) calcd for C12H12O2: 189.0910, found: 189.0913.
5.31. 7-Methyl-4-propyl-2H-chromen-2-one (2al):
o
1
Light yellow solid. m.p. 86.2–86.3 C. H NMR (400
MHz, CDCl3) δ: 7.51 (d,
J
= 8.1 Hz, 1H), 7.13–7.09 (m,
= 7.6 Hz, 2H), 2.44 (s, 3H),
= 7.3 Hz, 3H); 13C NMR (100
5.25. 4-(4-Bromophenyl)-2H-chromen-2-one (2af):11
2H), 6.21 (s, 1H), 2.72 (t,
1.78–1.69 (m, 2H), 1.05 (t,
J
J
o
1
Light yellow solid. m.p. 201.1–202.4 C. H NMR (400
MHz, CDCl3) δ: 7.68 (d, = 8.4 Hz, 2H), 7.57 (td, J1 = 1.4
= 8.4 Hz,
MHz, CDCl3) δ: 161.25, 156.04, 153.77, 142.64, 125.22,
123.96, 117.32, 116.85, 112.77, 33.59, 21.45, 21.32, 13.83.
HRMS (ESI) ([M + H]+) calcd for C13H14O2: 203.1067,
found: 203.1068.
J
Hz, J2 = 7.7 Hz, 1H), 7.45–7.41 (m, 2H), 7.34 (d,
J
2H), 7.27–7.23 (m, 1H), 6.36 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ: 160.37, 154.41, 154.19, 134.04, 132.17, 132.13,
130.00, 126.64, 124.27, 124.15, 118.61, 117.44, 115.35.
HRMS (ESI) ([M + H]+) calcd for C15H9BrO2: 300.9859,
found: 300.9859.
5.32. 3-Iodo-7-methyl-4-phenyl-2H-chromen-2-one (3a):17a
o
1
Light yellow solid. m.p. 164.2–164.5 C. H NMR (400
MHz, CDCl3) δ: 7.58–7.50 (m, 3H), 7.23–7.21 (m, 2H), 7.18
5.26. 4-(m-Tolyl)-2H-chromen-2-one (2ag):10
(s, 1H), 6.94 (q,
J
= 8.3 Hz, 2H), 2.42 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ: 160.54, 157.97, 153.08, 143.67,
138.98, 129.10, 128.73, 127.68, 127.45, 125.67, 117.66,
116.58, 90.51, 21.61. HRMS (ESI) ([M + H]+) calcd for
C16H11IO2: 362.9876, found: 362.9877.
o
1
Light yellow solid. m.p. 134.4–135.8 C. H NMR (400
MHz, CDCl3) δ: 7.56–7.49 (m, 2H), 7.43–7.39 (m, 2H), 7.33
(d, J = 7.6 Hz, 1H), 7.26–7.21 (m, 3H), 6.36 (s, 1H), 2.45 (s,
3H); 13C NMR (100 MHz, CDCl3) δ: 160.71, 155.79,
154.11, 138.65, 135.10, 131.79, 130.34, 128.93, 128.66,
127.02, 125.47, 124.06, 119.00, 117.20, 114.95, 21.38.
HRMS (ESI) ([M + H]+) calcd for C16H12O2: 237.0910,
found: 237.0912.
5.33. 3-Iodo-4-phenyl-2H-chromen-2-one (3b):17a
o
1
Light yellow solid. m.p. 129.9–130.2 C. H NMR (400
MHz, CDCl3) δ: 7.56–7.55 (m, 4H), 7.39–7.37 (m, 1H),
7.25–7.23 (m, 2H), 7.15 (td, J1 = 1.0 Hz, J2 = 7.6 Hz, 1H),
5.27. 4-(3-Fluorophenyl)-2H-chromen-2-one (2ah):29
7.05 (d,
J
= 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ:
160.65, 157.86, 153.12, 138.98, 132.27, 129.26, 128.88,
127.83, 127.76, 124.56, 120.03, 116.58, 92.25. HRMS (ESI)
([M + H]+) calcd for C15H9IO2: 348.9720, found: 348.9722.
o
1
Light yellow solid. m.p. 104.8–106.6 C. H NMR (400
MHz, CDCl3) δ: 7.59–7.55 (m, 1H), 7.54–7.49 (m, 1H), 7.46
(dd, J1 = 1.1 Hz, J2 = 8.0 Hz, 1H), 7.42 (d,
7.27–7.21 (m, 3H), 7.19–7.17 (m, 1H), 6.38 (s, 1H); 13C
NMR (100 MHz, CDCl3) δ: 162.72(d, = 246.98 Hz),
160.35, 154.16, 137.18 (d, = 7.5 Hz), 132.13, 130.69 (d,
= 8.2 Hz), 126.67, 124.30, 124.20 (d, = 3.0 Hz), 118.59,
J = 8.2 Hz, 1H),
5.34. 7-Chloro-3-iodo-4-phenyl-2H-chromen-2-one (3c):17a
o
1
J
Light yellow solid. m.p. 176.6–177.2 C. H NMR (400
J
J
MHz, CDCl3) δ: 7.60–7.53 (m, 3H), 7.39 (s, 1H), 7.24–7.22
J
(m, 2H), 7.12 (dd, J1 = 2.0 Hz, J2 = 8.6 Hz, 1H), 6.99 (d,
J =
8.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ: 159.98,
157.30, 153.27, 138.58, 138.15, 129.48, 129.03, 128.71,
127.68, 125.15, 118.66, 116.82, 92.07. HRMS (ESI) ([M +
H]+) calcd for C15H8ClIO2: 382.9330, found: 382.9327.
117.41, 116.76, 116.56, 115.73, 115.52. HRMS (ESI) ([M +
H]+) calcd for C15H9FO2: 241.0659, found: 241.0665.
5.28. 4-(o-Tolyl)-2H-chromen-2-one (2ai):10
o
1
Light yellow solid. m.p. 114.4–116.8 C. H NMR (400
MHz, CDCl3) δ: 7.54 (td, J1 = 1.5 Hz, J2 = 7.8 Hz, 1H),
7.42–7.39 (m, 2H), 7.35–7.30 (m, 2H), 7.20–7.16 (m, 2H),
7.07 (dd, J1 = 1.4 Hz, J2 = 7.9 Hz, 1H), 6.32 (s, 1H), 2.16 (s,
3H); 13C NMR (100 MHz, CDCl3) δ: 160.71, 156.02,
153.77, 135.27, 134.64, 131.88, 130.46, 129.20, 128.36,
126.88, 126.06, 124.24, 119.39, 117.06, 115.65, 19.69.
HRMS (ESI) ([M + H]+) calcd for C16H12O2: 237.0910,
found: 237.0915.
5.35. 3-Bromo-7-methyl-4-phenyl-2H-chromen-2-one (4a):17b
o
1
Light yellow solid. m.p. 191.1–191.9 C. H NMR (400
MHz, CDCl3) δ: 7.58–7.52 (m, 3H), 7.30–7.27 (m, 2H), 7.20
(s, 1H), 7.01–6.94 (m, 2H), 2.43 (s, 3H); 13C NMR (100
MHz, CDCl3) δ: 157.49, 154.60, 152.52, 143.43, 135.41,
129.21, 128.74, 128.05, 127.26, 125.85, 117.96, 116.87,
111.22, 21.59. HRMS (ESI) ([M + H]+) calcd for
C16H11BrO2: 315.0015, found: 315.0010.
5.29. 4-(3,5-Dimethylphenyl)-2H-chromen-2-one (2aj):21
5.36. 3-Bromo-4-phenyl-2H-chromen-2-one (4b):17b
o
1
o
1
Light yellow solid. m.p. 136.2–137.7 C. H NMR (400
MHz, CDCl3) δ: 7.56–7.51 (m, 2H), 7.40 (d, = 8.0 Hz,
Light yellow solid. m.p. 153.3–153.5 C. H NMR (400
MHz, CDCl3) δ: 7.59–7.51 (m, 4H), 7.41–7.38 (m, 1H),
7.31–7.27 (m, 2H), 7.21–7.12 (m, 1H), 7.09–7.01 (m, 1H);
13C NMR (100 MHz, CDCl3) δ: 157.19, 154.54, 152.39,
135.20, 131.96, 129.28, 128.78, 128.00, 127.54, 124.63,
120.24, 116.70, 112.52. HRMS (ESI) ([M + H]+) calcd for
C15H9BrO2: 300.9859, found: 300.9860.
J
1H), 7.23 (td, J1 = 0.8 Hz, J2 = 7.6 Hz, 1H), 7.15 (s, 1H),
7.05 (s, 2H), 6.35 (s, 1H), 2.40 (s, 6H); 13C NMR (100 MHz,
CDCl3) δ: 160.79, 156.00, 154.16, 138.52, 135.16, 131.74,
131.21, 127.13, 126.12, 124.04, 119.15, 117.21, 114.87,
21.28. HRMS (ESI) ([M + H]+) calcd for C17H14O2:
251.1067, found: 251.1067.
5.37. 3-Bromo-7-chloro-4-phenyl-2H-chromen-2-one (4c):17b
5.30. 4-Ethyl-7-methyl-2H-chromen-2-one (2ak):
o
1
Light yellow solid. m.p. 190.3–192.1 C. H NMR (400
o
1
Light yellow solid. m.p. 87.1–88.0 C. H NMR (400
MHz, CDCl3) δ: 7.51 (d, = 8.1 Hz, 1H), 7.13–7.09 (m,
2H), 6.23 (s, 1H), 2.80 (q, = 7.4 Hz, 2H), 2.44 (s, 3H),
1.32 (t,
= 7.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
MHz, CDCl3) δ: 7.60–7.54 (m, 3H), 7.41 (m, 1H), 7.30–7.26
(m, 2H), 7.17–7.14 (m, 1H), 7.01 (d,
NMR (100 MHz, CDCl3) δ: 156.70, 153.97, 152.65, 137.99,
J
= 7.0 Hz, 1H); 13C
J
J
J

8
Tetrahedron
ACCEPTED MANUSCRIPT
J.; Chen, X. Chem. Soc. Rev. 2016, 45, 3026; s) Corrigan, N.;
Shanmugam, S.; Xu, J.; Boyer, C. Chem. Soc. Rev. 2016, 45,
6165.
134.93, 129.57, 129.00, 128.47, 128.01, 125.29, 119.00,
117.07, 112.60. HRMS (ESI) ([M + H]+) calcd for
C15H8BrClO2: 334.9469, found: 334.9465.
17. a) Ni, S.; Cao, J.; Mei, H.; Han, J.; Li, S.; Pan, Y. Green Chem.
2016, 18, 3935; b) Feng, S.; Li, J.; Liu, Z.; Sun, H.; Shi, H.;
Wang, X.; Xie, X.; She, X. Org. Biomol. Chem. 2017, 15, 8820.
18. X-Ray single crystal structure of 2a (CCDC: 1856166).
Acknowledgements
We gratefully acknowledge the National Natural Science
Foundation of China (21772062, 21572078), and the Young
Talent Key Project of Anhui Province (170808J02) for
financial support.
References and notes
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