Cooperative N-heterocyclic carbene (NHC)-Lewis acid-mediated regioselective umpolung formal [3 + 2] annulations of alkynyl aldehydes with isatins

Article abstract of DOI:10.1039/c4ob00145a

A novel and regioselective umpolung synthesis of spirooxindoles has been developed by cooperative NHC-Lewis acid-mediated formal [3 + 2] annulations of alkynyl aldehydes with isatins. In most cases, the reactions proceeded via a³-d³ umpolung of alkynyl aldehydes resulting in spirooxindole butenolides. In a few cases, spirooxindole furan-3(2H)-ones were formed as the major products via an a¹-d¹ umpolung process by controlling the reaction temperature. These newly formed spirooxindoles could provide promising candidates for chemical biology and drug lead discovery.

Full text of DOI:10.1039/c4ob00145a

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Page 1 of 17
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DOI: 10.1039/C4OB00145A
Cooperative N-heterocyclic carbene (NHC)/Lewis acid-mediated regioselective
umpolung formal [3+2] annulations of alkynyl aldehydes with isatins
Yu Zhang, Yingyan Lu, Weifang Tang, Tao Lu* and Ding Du*
State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China
Pharmaceutical University, Nanjing, 210009, P. R. China. Email: lut163@163.com (T. Lu) and
ddmn9999@cpu.edu.cn (D. Du)
A novel and regioselective umpolung synthesis of spirooxindoles has been developed
by cooperative NHC/Lewis acid-mediated formal [3+2] annulations of alkynyl
aldehydes with isatins. In most cases, the reactions proceeded via a3-d3 umpolung of
alkynyl aldehydes resulting in spirooxindole butenolides. In few cases, spirooxindole
furan-3(2H)-ones were formed as major products via a1-d1 umpolung process by
controlling the reaction temperature. These newly formed spirooxindoles could
provide promising candidates for chemical biology and drug lead discovery.
N-Heterocyclic carbenes (NHCs) are efficient organocatalysts which can promote a
large number of umpolung transformations of different types of aldehydes.[1] The
most-investigated NHC-catalyzed umpolung reactions are involved in a1-d1 umpolung
of aldehydes (such as Benzoin condensation[2] and Stetter reaction[3]) and a3-d3
umpolung of enals[4] which have offered unconventional access to a variety of organic
molecules with diverse skeletons. In recent years, alkynyl aldehydes 1 have emerged
as novel substrates applied in NHC-catalyzed reactions (Scheme 1). Following the
pioneering work of redox esterification of alkynyl aldehydes 1,[5] much emphasis has
been laid on the application of ,-unsaturated acyl azoliums generated from the
sequential a3-d3 umpolung of Breslow intermediate[6] and -protonation of allenonate
equivalent (eq. 1, Scheme 1).[7] In contrast, few attention has been paid to
NHC-catalyzed  -nucleophilic additions of allenonate intermediate which could be
potentially employed as formal 1,3-dipoles to undergo formal [3+m] annulations (eq.

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2, Scheme 2). Until recently, She[8] and Snyder[9] reported a -d umpolung annulations
of alkynyl aldehydes with ketones[8a, 9] and nitrosobenzenes[8b] respectively by a
cooperative NHC/Lewis acid catalysis strategy[10] which has proved critical for some
transformations. However, it is still in demand to further explore novel a3-d3
umpolung annulations of alkynyl aldehydes.
3
3
O
ZH
R1
1
O
H
R'
O
Z
NHC
R
R1
NHC
(1)
OH
Z = O R1
or NH
R'
X
R1
, -unsaturated
acyl azoliums
R
NHC
Breslow intermediate
H+
a3-d3
umpolung
O
Y
O
OH
X
Y
R1
NHC
(2)
3
1
formal [3+m]
annulations
R1
NHC
R1
formal
1,3-dipoles
allenonate equivalent
Scheme 1 Two reaction modes of alkynyl aldehydes with NHC catalysis.
Spirooxindoles[11] represent interesting and attractive frameworks for synthesis
owing to their biological activities and applications for drug lead discovery. Most
spirooxindoles are characterized by a spiro fusion at the 3-position of oxindole ring
with diverse heterocycle motifs (Scheme 2). Furan-2-(5H)-one is a privileged
heterocyclic structure existing in various natural products with a broad range of
biological activities.[12] Thus, fusion of oxindole core with furan-2-(5H)-one motif
could give rise to spirooxindole butenolides which may provide promising candidates
for chemical biology and drug lead discovery. However, the synthesis of
spirooxindoles butenolides is still a challenge and only a few protocols have been
documented.[13] Since isatins[13d, 14] are usually used as privileged molecules in design
and synthesis of spiro-fused cyclic compounds due to the highly reactive C-3 carbonyl
group, we envisioned that the cooperative NHC/Lewis acid-catalyzed umpolung
annulations of alkynyl aldehydes 1 with isatins 2 might afford spirooxindoles
butenolides. Actually, two regioisomers 3 and 4 via two different umpolung processes
(a3-d3 and a1-d1) were observed (Scheme 2). Nevertheless, regioselective a3-d3
umpolung of alkynyl aldehydes could be achieved in most cases by controlling the

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1
1
reaction conditions and N-substituents of isatins 2. In few cases, a -d umpolung
products could also be obtained as major products by lowering the reaction
temperature. As a continuation of our exploration of NHC-catalyzed chemistry of
alkynyl aldehydes to synthesize diverse heterocycles,[7d, 7h] we herein wish to report
the regioselective umpolung formal [3+2] annulations of alkynyl aldehydes 1 with
isatins 2 for the synthesis of spirooxindoles 3 and 4.
Scheme 2 The cooperative NHC/Lewis acid-catalyzed umpolung annulations of
alkynyl aldehydes 1 with isatins 2
Our explorations began with examining the efficiency of several carbene precursors
A-H for the reaction of 3-phenylpropioaldehyde 1a with N-Bn substituted isatin 2a
(Table 1). The reaction did not work at all in the presence of NHCs derived from
precursors A-G even if LiCl was used as a Lewis acid (entry 1). Fortunately, a
mixture of a3-d3 umpolung product 3a and a1-d1 umpolung product 4a was obtained in
lower combined yield when carbene precursor H was employed in the presence of
LiCl (entry 3). Subsequent screening of various bases showed that DIPEA was the
optimal one resulting in 43% yield and high regioselectivity (entries 4-8). However,
further examination of a variety of Lewis acids and solvents failed to improve the
yield and regioselectivity (entries 9-14). At this point, we assumed that N-substituents
of isatins 2 might have certain impact on the yield and regioselectivity. We then tried
other three different N-substituted isatins 2b-d (entries 15-18). Surprisingly, the

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reaction of N-Me substituted isatin 2d with 1a in 1,4-dioxane at 40℃exclusively
afforded a3-d3 umpolung product 3d in 75% yield which was finally established as our
optimal reaction conditions for following substrate scope exploration (entry18). The
structure of the products was established by spectroscopic analysis and further
confirmed by X-ray crystallography of 3d (Figure 1). [15]
Table 1 Optimization of the reaction conditions and evaluation of N-substituents of
isatins 2a
O
Ph
O
O
Catalyst (20 mol%)
Base (1.0 equiv)
O
O
O
Ph
O
O
O
+
H
+
Additive (1.1 equiv)
Solvent
N
N
R2
Ph
N
R2
R2
1a
2
3
4
Entry R2, 2
Cat. Base
Sol.
Add.
Temp. Time Yield of
(oC) (h) 3, 4 (%)b
none or LiCl 40
1
Bn, a A-G DBU
THF
THF
THF
10
a, 0, 0
2
DBU
DBU
none
40
40
40
40
40
40
40
40
40
40
40
40
65
25
25
40
40
8
a, 0, 0
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bn, a
Bz, b
Boc, c
Me, d
Me, d
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
3
LiCl
1
a, 10, 21
a, <10, 37
a, <10,34
a, 14,19
a, 42, 0
a, 43, 0
a, 0, 0
4
tBuOK THF
tBuOLi THF
Cs2CO3 THF
LiCl
1.5
1.5
21
3
5
LiCl
6
LiCl
7
Et3N
THF
LiCl
8
DIPEA THF
DIPEA THF
DIPEA THF
DIPEA THF
DIPEA DCM
DIPEA DMF
LiCl
2
9
LiBF4
Mg(tBuO)2
Ti(iPrO)4
LiCl
40
4
10
11
12
13
14
15
16
17
18
a, 15, 15
a, 11, 0
7
5
a, 26, <10
a, 15, 39
a, 37, 0
b, <10, 0
c, <10, 0
d, 38, 15
d, 75, 0
LiCl
7.5
24
1.5
1
DIPEA 1,4-dioxane LiCl
DIPEA THF
DIPEA THF
DIPEA THF
LiCl
LiCl
LiCl
24
24
DIPEA 1,4-dioxane LiCl

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[a]
All reactions were performed on a 0.3 mmol scale with 2.5 equiv. of 1a, 1.0 equivD. OoIf: 120.,102309/C4OB00145A
mol % of a carbene precursor, 1.0 equiv. of a base, 1.1 equiv. of an additive and 200 mg of 4 Å
[b]
MS in 0.1
M
in
a
solvent under N2.
Isolated yield based on 2. DBU
= 2,4,6-(CH3)3C6H2; DIPEA
=
=
1,8-diazabicyclo[5.4.0]-undec-7-ene;
Mes
N,N-diisopropylethylamine.
Figure 1 X-ray crystal structure of 3d.
After establishing the optimized conditions, we focused on expansion of the
reaction scope (Table 2). Firstly, the variation of isatins 2 was evaluated. A wide range
of isatins 2 except 2m were found suitable for the a3-d3 umpolung [3+2] annulations
to get spirooxindole butenolides 3e-l in 30-90% yield at 40℃ or 65℃ (entries 2-10).
In few cases, spirooxindoles 4f-h and 4j formed via a1-d1 umpolung pathway were
obtained as major products by lowering the reaction temperature to 10℃ (entries 3-5
and entry 7). Subsequently, a variety of alkynyl aldehydes 1 were tested to evaluate
the generality of this protocol. Alkynyl aldehydes 1b-g with substituents at 3- or
4-positions of phenyl rings were tolerant to the reaction, only affording a3-d3
umpolung products in 41-83% yield (entries 11-16). The reaction of
3-(2-chlorophenyl)propiolaldehyde 1h did not work perhaps owing to the steric effect
of hindered 2-Cl group (entry 17). Surprisingly, 3-heteroaromatic-substituted alkynyl

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3
3
aldehyde 1i and 3-aliphatic-substituted alkynyl aldehyde 1j were also subject to a -d
umpolung process in moderate yield (entries 18-19).
Table 2 Scope of the reaction a
O
R1
O
R3
O
H
(20 mol%)
O
R3
O
R3
O
R1
O
DIPEA (1.0 equiv)
O
H
+
+
O
N
LiCl (1.1 equiv)
1,4-dioxane
R1
N
N
Me
1
Me
4
2
Me
3
T
Time
(h)
24
48
10
12
7
Yield of
Entry
R1, 1
R3, 2
(℃)
40
65
65
65
40
65
65
3, 4 (%)b, c
1
Ph, a
Ph, a
Ph, a
Ph, a
Ph, a
Ph, a
Ph, a
Ph, a
Ph, a
Ph, a
H, d
d, 75, 0
2
4-Cl, e
5-F, f
e, 90, 0
3
f, 67, 0 (<10, 45)
4
5-Cl, g
5-Br, h
5-Me, i
6-Cl, j
g, 53, 15 (<5, 47)
h, 30, 33 (0, 42)
i, 47d, 0
5
6
24
10
72
2
7
j, 63, 0 (<10, 46)
k, 37, 0
8
7-Me, k
7-Cl, l
4,6-Me2, m
H, d
65
65
65
65
10
65
40
65
65
40
10
10
9
l, 40, 14
10
11
12
13
14
15
16
17
18
20
20
72
20
48
30
72
24
26
48
m, trace, 0
n, 71, 0
(4-Me)Ph, b
(4-OMe)Ph, c
(4-F)Ph, d
(4-Cl)Ph, e
(3-Me)Ph, f
(3-Cl)Ph, g
(2-Cl)Ph, h
2-furyl, i
H, d
o, 42, 0
H, d
p, 33, 0
H, d
q, 63, 0
H, d
r, 83, 0
s, 41 e, 0
H, d
H, d
t,trace, 0
H, d
u, 56, 0
19
Ph(CH2)2, j
H, d
v, 58, 0
[a]
All reactions were performed on a 0.3 mmol scale with 2.5 equiv. of 1, 1.0 equiv. of 2, 20
mol % of H, 1.0 equiv. of DIPEA, 1.1 equiv. of LiCl and 200 mg of 4 Å MS in 0.1 M in
[b]
[c]
1,4-dioxane, under N2.
Isolated yield based on 2.
Isolated yield in the parentheses was
obtained under 10℃. [d] 70% conversion, [e] 61% conversion.
Preliminary enantioselective studies of the formal [3+2] annulation between alkynyl
1a and isatin 2d has also been undertaken using I as the chiral carbene precursors, and
a3-d3 umpolung product 3d was obtained as the single regioisomer in 78% yield with a
promising 73% e.e. value (Scheme 3).

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O
N
Cl
N
O
N
Mes
O
O
I
(20 mol%)
O
Ph
O
DIPEA (1.0 equiv)
O
H
+
LiCl (1.1 equiv)
1,4-dioxane, 40 oC
N
N
Ph
Me
3d
Me
1a
2d
78% yield, 73% ee
Scheme 3 Preliminary enantioselective studies of the annulation of alkynyl 1a and
isatin 2d.
A plausible mechanism for the regioselective umpolung annulations is proposed
based on the model reaction of alkynyl aldehyde 1a with isatin 2f. Initially, NHC 4
was generated upon deprotonation of carbene precursor H with DIPEA followed by
addition to alkynyl 1a to produce Breslow intermediate 5. Coordination of LiCl with
isatin 2f enhanced the electrophility of 3-carbonyl of 2f by lowering LUMO energy.
This alkali metal salt effect has been observed to promote new C-C bond formation in
10b]
many NHC-catalyzed reactions.[8a,
For a3-d3 umpolung process (path a),
concurrent coordination of LiCl to isatin 2f and Breslow intermediate facilitated the
nucleophilic addition of -carbon anion of allenolate equivalent to the activated
carbonyl as shown in 6. Subsequent intramolecular cyclization afforded the formal
[3+2] adduct 3f accompanied with release of NHC 4 for next catalytic cycle. For a1-d1
umpolung process (path b), the annulation occurred via Benzoin-type addition of
Breslow intermediate to the carbonyl of 2f, followed by intramolecular Michael
addition and release of NHC 4 to give product 4f.

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Scheme 4 Proposed mechanism for the regioselective umpolung annulation of alkynyl
aldehyde 1a and isatin 2f.
In summary, we have described regioselective umpolung formal [3+2] annulations of
alkynyl aldehydes 1 with isatins 2 to give spirooxindole butenolides 3 in moderate to
high yields via a3-d3 umpolung process. In few cases, a1-d1 umpolung spirooxindoles
4 could be obtained as major products in moderate yields by controlling the reaction
temperature. Further investigation on an enantioselective synthesis of this protocol
and exploration of new chemistry of alkynyl aldehydes are currently underway.
Experimental section
General Methods. All reactions were carried out under an atmosphere of nitrogen in
dry glassware, and were monitored by analytical thin-layer chromatography (TLC),
which was visualized by ultraviolet light (254 nm). All solvents were obtained from
commercial sources and were purified according to standard procedures. Purification
of the products was accomplished by flash chromatography using silica gel (200~300

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mesh). All NMR spectra were recorded with a spectrometer at 300 MHz or 500 MHz
(1H NMR) in CDCl3: chemical shifts (δ) are given in ppm, coupling constants (J) in
Hz, the solvent signals were used as references (residual CHCl3 in CDCl3: δH = 7.26
ppm, δc = 77.0 ppm). The e.e. value was determined by chiral HPLC.
General experimental procedure
To an oven-dried 25 mL three-necked glassware was charged with alkynyl aldehyde
1 (0.75 mmol), isatin 2 (0.3 mmol), LiCl (14 mg, 0.33 mmol), carbene precursor H
(16 mg, 0.06 mmol) and 200 mg of 4 Å MS. Then THF (3 mL) was added followed
by addition of DIPEA (39 mg, 0.3 mmol). The resulting mixture was stirred at certain
temperature under nitrogen atmosphere for a period of time. After completion of the
reaction as monitored by TLC, the mixture was cooled to room temperature. The
solvent was evaporated under reduced pressure and the residue was purified by
chromatography on silica gel to afford the products 3 and 4.
3a. White solid, MP: 140-141℃. 1H NMR (500M, CDCl3): δ 6.88-7.33 (m, 14H), 6.65
(s, 1H), 5.12 and 4.76 (2×d, J = 14.4 Hz, 2H). 13C NMR (125M, CDCl3): δ 171.2,
170.0, 163.1, 143.5, 134.7, 131.8, 131.4, 129.1, 128.9, 128.1, 127.6, 125.1, 123.9,
123.8, 116.9, 110.4, 86.5, 44.6. HRMS (ESI) calcd for C24H18NO3 (M+H)+: 368.1281,
found 368.1283. IR (KBr): ν 3089, 3062, 1768, 1733, 1610, 1489, 1359, 1298, 1240,
1186, 1026 cm-1.
4a. White solid, MP: 227-228℃. 1H NMR (300M, CDCl3): δ 7.96 (d, J = 7.3 Hz, 2H),
7.53-7.67 (m, 3H), 7.04-7.39 (m, 8H), 6.79 (d, J = 7.8 Hz, 1H), 6.24 (s, 1H), 5.07 and
13
4.89 (2×d, J = 15.9 Hz, 2H). C NMR (75M, CDCl3): δ 196.8, 187.9, 169.1, 144.3,
134.7, 133.4, 131.1, 128.9, 128.1, 127.8, 127.6, 127.1, 123.9, 123.8, 123.4, 110.2,
100.4, 89.3, 44.3. HRMS (ESI) calcd for C24H18NO3 (M+H)+: 368.1281, found
368.1283. IR (KBr): ν 3128, 2921, 1729, 1693, 1605, 1564, 1488, 1340, 1168, 1046
cm-1.
1
3d. White solid, MP: 194-195℃. H NMR (300M, CDCl3): δ 7.46 (m, 1H), 7.36 (m,

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1H), 7.24-7.29 (m, 2H), 7.08-7.20 (m, 4H), 6.99 (d, J = 7.8 Hz, 1H), 6.66 (s, 1H), 3.31
(s, 3H). 13C NMR (75M, CDCl3): δ 171.2, 169.9, 162.9, 144.4, 131.9, 131.5, 129.2,
128.9, 126.9, 125.0, 124.0, 123.8, 116.9, 109.5, 86.4, 27.1. HRMS (ESI) calcd for
C18H14NO3 (M+H)+: 292.0968, found 292.0967. IR (KBr): ν 3127, 2932, 1775, 1727,
1611, 1574, 1493, 1470, 1448, 1422, 1368, 1348, 1303, 1235, 1200, 1136, 1099, 1058,
1006 cm-1.
1
3e. White solid, MP: 196-197℃. H NMR (300M, CDCl3): δ 6.86-7.35 (m, 8H), 6.66
(s, 1H), 3.27 (s, 3H). 13C NMR (75M, CDCl3): δ 170.9, 169.3, 162.0, 145.9, 133.0,
132.9, 131.4, 129.2, 129.0, 126.5, 124.8, 120.5, 118.3, 107.7, 86.0, 27.3. HRMS (ESI)
calcd for C18H13ClNO3 (M+H)+: 326.0578, found 326.0583. IR (KBr): ν 3188, 2874,
1767, 1731, 1609, 1461, 1335, 1241, 1199, 1124, 1011 cm-1.
3f. White solid, MP: 173-175℃. 1H NMR (300M, CDCl3): δ 7.14-7.35 (m, 8H), 6.66 (s,
1H), 3.30 (s, 3H). 13C NMR (75M, CDCl3): δ 170.7, 169.7, 162.4, 159.6 (d, JC-F
=
243.0 Hz, 1C), 140.3, 131.6, 129.3, 128.6, 126.8, 118.3 (d, JC-F = 23.0 Hz, 1C), 116.9,
113.1 (d, JC-F = 25.0 Hz, 1C), 110.3, 110.2, 85.9, 27.2. HRMS (ESI) calcd for
C18H13FNO3 (M+H)+: 310.0874, found 310.0876. IR (KBr): ν 3145, 2987, 1772, 1735,
1614, 1492, 1270, 1206 cm-1.
4f. White solid, MP: 159-160℃. 1H NMR (300M, CDCl3): δ 7.90 (d, J = 7.3 Hz, 2H),
7.62 (m, 1H), 7.50-7.55 (m, 2H), 7.13 (m, 1H), 6.93 (m, 1H), 6.87 (m, 1H), 6.14 (s,
1H), 3.19 (s, 3H). 13C NMR (75M, CDCl3): δ 196.2, 187.9, 168.5, 159.3 (d, JC-F
=
241.0 Hz, 1C), 141.2, 133.5, 128.9, 127.8, 127.5, 124.9 (d, JC-F = 8.3 Hz, 1C), 117.5 (d,
JC-F = 24.0 Hz, 1C), 112.2 (d, JC-F = 25.5 Hz, 1C), 109.9 (d, JC-F = 7.5 Hz, 1C), 100.3,
88.8, 26.9. HRMS (ESI) calcd for C18H13FNO3 (M+H)+: 310.0874, found 310.0876. IR
(KBr): ν 2956, 2922, 2852, 1734, 1700, 1608, 1569, 1493, 1382, 1270, 1162, 1105,
1046 cm-1.

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1
3g. White solid, MP: 197-198℃. H NMR (300M, CDCl3): δ 7.31-7.39 (m, 2H),
7.20-7.24 (m, 2H), 7.06-7.11 (m, 3H), 6.86 (d, J = 8.5 Hz, 1H), 6.60 (s, 1H), 3.25 (s,
3H). 13C NMR (75M, CDCl3): δ 170.7, 169.6, 162.3, 142.9, 131.9, 131.6, 129.5, 129.4,
128.6, 126.9, 125.4, 117.1, 110.5, 85.8, 27.3. HRMS (ESI) calcd for C18H13ClNO3
(M+H)+: 326.0578, found 326.0583. IR (KBr): ν 3182, 3050, 2841, 1779, 1732, 1610,
1488, 1338, 1229, 1104, 1007, 928 cm-1.
1
4g. White solid, MP: 186-187℃. H NMR (300M, CDCl3): δ 7.88-7.90 (m, 2H), 7.61
(m, 1H), 7.50-7.55 (m, 2H), 7.39 (dd, J = 8.2, 2.2 Hz, 1H), 7.15 (d, J = 2.2 Hz, 1H),
13
6.86 (d, J = 8.5 Hz, 1H), 6.21 (s, 1H), 3.26 (s, 3H). C NMR (75M, CDCl3): δ 196.2,
188.3, 168.2, 143.6, 133.8, 131.2, 129.1, 128.8, 128.0, 127.6, 125.2, 124.6, 110.2,
100.4, 88.6, 27.1. HRMS (ESI) calcd for C18H13ClNO3 (M+H)+: 326.0578, found
326.0582. IR (KBr): ν 3192, 3089, 2856, 1737, 1688, 1604, 1567, 1491, 1451, 1348,
1106 cm-1.
3h. White solid, MP: 207-208℃. 1H NMR (300M, CDCl3): δ 7.52 (dd, J = 8.3, 2.0 Hz,
1H), 7.34 (m, 1H), 7.20-7.24 (m, 3H), 7.05-7.08 (m, 2H), 6.81 (d, J = 8.5 Hz, 1H), 6.60
(s, 1H), 3.24 (s, 3H).13C NMR (75M, CDCl3): δ 170.6, 169.5, 162.6, 143.4, 134.8,
131.8, 129.3, 128.7, 128.2, 126.9, 125.8, 117.2, 116.6, 110.9, 85.9, 27.3. HRMS (ESI)
calcd for C18H13BrNO3 (M+H)+: 370.0073, found 370.0079. IR (KBr): ν 3156, 3088,
3892, 1733, 1688, 1604, 1565, 1488, 1374, 1172, 1103 cm-1.
1
4h. White solid, MP: 201-202℃. H NMR (300M, CDCl3): δ 7.81-7.84 (m, 2H), 7.55
(m, 1H), 7.43-7.49 (m, 3H), 7.21 (d, J = 1.6 Hz, 1H), 6.75 (d, J = 8.4 Hz, 1H), 6.14 (s,
1H), 3.18 (s, 3H). 13C NMR (75M, CDCl3): δ 196.2, 188.0, 168.4, 144.3, 134.1, 133.6,
129.1, 127.9, 127.6, 127.2, 125.5, 115.9, 110.6, 100.4, 88.6, 26.9. HRMS (ESI) calcd
for C18H13BrNO3 (M+H)+: C18H13BrNO3, found 370.0075. IR (KBr): ν 3155, 2898,
1774, 1734, 1608, 1486, 1336, 1288, 1103, 1006 cm-1.

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1
3i. White solid, MP: 194-195℃. H NMR (300M, CDCl3): δ 7.13-7.36 (m, 6H), 6.99
(m, 1H), 6.87 (m, 1H), 6.64 (s, 1H), 3.28 (s, 3H), 2.27 (s, 3H). 13C NMR (75M, CDCl3):
δ 171.2, 169.9, 162.9, 141.9, 133.9, 132.2, 131.4, 129.2, 128.9, 127.0, 125.7, 123.8,
116.8, 109.2, 86.5, 27.1, 20.9. HRMS (ESI) calcd for C19H16NO3 (M+H)+: 306.1125,
found 306.1128. IR (KBr): ν 3167, 2886, 1779, 1726, 1611, 1498, 1347, 1202, 1105,
1005 cm-1.
1
3j. White solid, MP: 197-198℃. H NMR (300M, CDCl3): δ 7.31-7.39 (m, 2H),
7.20-7.23 (m, 2H), 7.05-7.10 (m, 3H), 6.86 (d, J = 8.3 Hz, 1H), 6.60 (s, 1H), 3.25 (s,
3H). 13C NMR (75M, CDCl3): δ 170.7, 169.3, 162.3, 142.7, 131.9, 131.6, 129.5, 129.3,
128.7, 126.9, 125.5, 117.1, 110.4, 85.7, 27.2. HRMS (ESI) calcd for C18H13ClNO3
(M+H)+: 326.0578, found 326.0581. IR (KBr): ν 3175, 2902, 1779, 1732, 1610, 1488,
1337, 1228, 1104, 1006 cm-1.
1
4j. White solid, MP: 184-185℃. H NMR (300M, CDCl3): δ 7.88-7.91(m, 2H), 7.62
(m, 1H), 7.50-7.55 (m, 2H), 7.39 (dd, J = 8.5, 2.0 Hz, 1H), 7.16 (d, J = 1.8 Hz, 1H),
13
6.86 (d, J = 8.5 Hz, 1H), 6.21 (s, 1H), 3.26 (s, 3H). C NMR (75M, CDCl3): δ 196.2,
188.0, 168.5, 143.9, 133.6, 131.2, 129.1, 128.8, 127.9, 127.6, 125.2, 124.5, 110.2,
100.3, 88.7, 27.0. HRMS (ESI) calcd for C18H13ClNO3 (M+H)+: 326.0578, found
326.0582. IR (KBr): ν 3088, 2875, 1736, 1685, 1607, 1567, 1489, 1346, 1173, 1104,
1047 cm-1.
3k. White solid, MP: 189-190℃. 1H NMR (300M, CDCl3): δ 13C NMR (75M, CDCl3):
δ 7.25-7.38 (m, 3H), 7.12-7.18 (m, 3H), 6.92-6.99 (m, 2H), 6.62 (s, 1H), 3.54 (s, 3H).
13C NMR (75M, CDCl3): δ 171.2, 170.6, 162.9, 141.9, 135.6, 131.3, 129.1, 128.9,
126.9, 124.2, 123.9, 122.8, 121.1, 116.8, 85.9, 30.4, 18.9. HRMS (ESI) calcd for
C19H16NO3 (M+H)+: 306.1125, found 306.1129. IR (KBr): ν 3183, 2856, 1762, 1716,
1617, 1449, 1359, 1198, 1114, 1043 cm-1.

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1
3l. White solid, MP: 165-167℃. H NMR (300M, CDCl3): δ 7.31-7.38 (m, 4H),
7.00-7.14 (m, 4H), 6.65 (s, 1H), 3.66 (s, 3H). 13C NMR (75M, CDCl3): δ 170.7, 170.2,
162.5, 140.3, 134.1, 131.6, 129.3, 128.6, 126.9, 126.4, 124.7, 123.5, 117.1, 116.7, 85.5,
30.5. HRMS (ESI) calcd for C18H13ClNO3 (M+H)+: 326.0578, found 326.0582. IR
(KBr): ν 3249, 2912, 1759, 1731, 1610, 1463, 1336, 1205, 1115, 1051 cm-1.
3n. White solid, MP: 181-182℃. 1H NMR (300M, CDCl3): δ 7.44 (t, J = 7.8 Hz, 1H),
7.15 (d, J = 7.5 Hz, 1H), 6.96-7.09 (m, 6H), 6.59 (s, 1H), 3.27 (s, 3H), 2.27 (s, 3H).
13C NMR (75M, CDCl3): δ 171.4, 170.0, 162.8, 144.3, 142.1, 131.8, 129.9, 126.9,
126.0, 124.9, 123.9, 115.8, 109.3, 86.2, 27.0, 21.3. HRMS (ESI) calcd for C19H16NO3
(M+H)+: 306.1125, found 306.1128. IR (KBr): ν 3188, 2895, 1762, 1733, 1607, 1467,
1364, 1235, 1190, 1000 cm-1.
1
3o. White solid, MP: 200-201℃. H NMR (300M, CDCl3): δ 7.45 (m, 1H), 6.98-7.17
13
(m, 5H), 6.76 (d, J = 8.4 Hz, 2H), 6.53 (s, 1H), 3.75 (s, 3H), 3.30 (s, 3H). C NMR
(75M, CDCl3): δ 171.5, 170.1, 162.3, 162.1, 144.3, 131.8, 128.7, 124.9, 124.2, 124.0,
121.2, 114.6, 114.3, 109.4, 86.0, 55.3, 27.0. HRMS (ESI) calcd for C19H16NO4 (M+H)+:
322.1074, found 322.1078. IR (KBr): ν 3185, 2885, 1763, 1725, 1607, 1511, 1269,
1190, 1005 cm-1.
3p. White solid, MP: 190-191℃. 1H NMR (500M, CDCl3): δ 7.52 (t, J = 7.7 Hz, 1H),
7.23 (d, J = 7.3 Hz, 1H), 7.15-7.18 (m, 3H), 6.99-7.04 (m, 3H), 6.65 (s, 1H), 3.35 (s,
13
3H). C NMR (75M, CDCl3): δ 170.9, 169.8, 164.3 (d, JC-F = 252.2 Hz, 1C), 161.6,
144.3, 132.1, 129.2, 129.1, 124.9, 124.1, 123.5, 116.8, 116.5 (d, JC-F = 21.9 Hz, 1C),
109.5, 86.2, 27.0. HRMS (ESI) calcd for C18H13FNO3 (M+H)+: 310.0874, found
310.0880. IR (KBr): ν 3165, 2927, 1752, 1722, 1612, 1508, 1368, 1239, 1208, 1006
cm-1.
1
3q. White solid, MP: 165-166℃. H NMR (300M, CDCl3): δ 7.46 (m, 1H), 6.97-7.25
13
(m, 7H), 6.63 (s, 1H), 3.29 (s, 3H). C NMR (75M, CDCl3): δ 170.8, 169.7, 161.5,

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144.3, 137.7, 132.1, 129.5, 128.2, 127.3, 125.0, 124.1, 123.4, 117.4, 109.5, 86.2, 27.1.
HRMS (ESI) calcd for C18H13ClNO3 (M+H)+: 326.0578, found 326.0585. IR (KBr): ν
3168, 3087, 2887, 1757, 1609, 1468, 1346, 1234, 1202, 1098, 1004 cm-1.
1
3r. White solid, MP: 165-166℃. H NMR (300M, CDCl3): δ 7.45 (m, 1H), 6.96-7.15
(m, 6H), 6.81 (d, J = 6.6 Hz, 1H), 6.62 (s, 1H), 3.29 (s, 3H), 2.23 (s, 3H). 13C NMR
(75M, CDCl3): δ 171.3, 169.9, 163.1, 144.3, 138.9, 132.2, 131.9, 129.0, 127.8, 124.9,
124.0, 123.8, 116.6, 109.3, 86.3, 27.0, 21.3. HRMS (ESI) calcd for C19H16NO3 (M+H)+:
306.1125, found 306.1128. IR (KBr): ν 3136, 2895, 1771, 1727, 1610, 1470, 1356,
1193, 1006 cm-1.
3s. White solid, MP: 157-158℃. 1H NMR (300M, CDCl3): δ 7.47 (m, 1H), 7.32 (d, J =
7.8 Hz, 1H), 7.08-7.21 (m, 4H), 6.93-7.00 (m, 2H), 6.64 (s, 1H), 3.29 (s, 3H). 13C NMR
(75M, CDCl3): δ 170.7, 169.6, 161.4, 144.3, 135.2, 132.2, 131.3, 130.6, 130.5, 127.1,
124.9, 124.8, 124.2, 123.2, 118.2, 109.5, 86.3, 27.1. HRMS (ESI) calcd for
C18H13ClNO3 (M+H)+: 326.0578, found 326.0582. IR (KBr): ν 3145, 3068, 2890, 1773,
1727, 1612, 1471, 1347, 1101, 1008 cm-1.
1
3u. White solid, MP: 174-175℃. H NMR (300M, CDCl3): δ 7.33-7.40 (m, 2H), 7.21
(m, 1H), 7.05 (m, 1H), 6.84 (d, J = 7.2 Hz, 1H), 6.69 (m, 1H), 6.14 (s, 1H), 3.45 (s,
1H), 3.22 (s, 3H). 13C NMR (75M, CDCl3): δ 171.5, 156.9, 144.6, 143.4, 139.8, 130.5,
125.7, 123.7, 123.1, 119.8, 117.5, 108.5, 83.9, 72.7, 70.1, 26.4. HRMS (ESI) calcd for
C16H11NNaO4 (M+Na)+: 304.0580, found 304.0587. IR (KBr): ν 3258, 3146, 2879,
1726, 1616, 1493, 1371, 1293, 1216, 1140, 1009 cm-1.
1
3v. White solid, MP: 137-138℃. H NMR (300M, CDCl3): δ 7.44 (m, 1H), 7.17-7.26
(m, 3H), 7.05-7.14 (m, 4H), 6.93 (d, J = 7.8 Hz, 1H), 6.12 (s, 1H), 3.26 (s, 3H),
2.74-2.91 (m, 2H), 2.34 (m, 1H), 2.18 (m, 1H). 13C NMR (75M, CDCl3): δ 171.8,
169.9, 167.7, 144.4, 139.4, 131.7, 128.6, 128.1, 126.5, 124.5, 123.8, 122.6, 117.3,
109.2, 87.7, 32.4, 28.4, 26.9. HRMS (ESI) calcd for C20H18NO3 (M+H)+: 320.1281,

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DOI: 10.1039/C4OB00145A
found 320.1288. IR (KBr): ν3258, 3132, 3067, 2856, 1768, 1722, 1613, 1466, 1365,
1190, 1104, 1005 cm-1.
Acknowledgements
We thank the National Natural Science Foundation of China (No. 21002124),
Jiangsu Provincial Natural Science Foundation of China (No. BK20131305),
Fundamental Research Funds for the Central Universities (No. JKZD2013002) and
the Project Program of State Key Laboratory of Natural Medicines of China
Pharmaceutical University (No. JKGQ201101) for financial support.
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CCDC 987924 contains the supplementary crystallographic data for compound 3d. The data
can be obtained free of charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. For details of the crystallographic data see Supporting
Information.