Synthesis of methyl 1,5-diaryl-1H-pyrrole-2-carboxylates via acid-catalyzed ring-opening/ring-closure sequence

Article abstract of DOI:10.1002/jhet.4306

A facile synthesis of methyl 1,5-diaryl-1H-pyrrole-2-carboxylates was reported in this article. Acid-catalyzed reaction of methyl 2-aroyl-1-phenoxycyclopropanecarboxylates with aromatic amines underwent smoothly to give methyl 1,5-diaryl-1H-pyrrole-2-carboxylates in high to excellent yields under mild conditions.

Full text of DOI:10.1002/jhet.4306

Received: 2 March 2021
DOI: 10.1002/jhet.4306
Revised: 10 May 2021
Accepted: 17 May 2021
A R T I C L E
Synthesis of methyl 1,5-diaryl-1H-pyrrole-2-carboxylates via
acid-catalyzed ring-opening/ring-closure sequence
Long Huang1 | Chenghao Luo1 | Panpan Xu2 | Bing Liu1 | Duntie Zhang1
Jing Zhang1 | Denghong Pang1 | Yuefa Gong2
|
1Engineer Center of New Generation
Abstract
Tobacco of China Tabacco, Hubei
Industrial Co. Ltd, Wuhan, People's
Republic of China
2School of Chemistry and Chemical
Engineering, Huazhong University of
Science and Technology, Wuhan, People's
Republic of China
A facile synthesis of methyl 1,5-diaryl-1H-pyrrole-2-carboxylates was reported in this
article. Acid-catalyzed reaction of methyl 2-aroyl-1-phenoxycyclopropanecarboxylates
with aromatic amines underwent smoothly to give methyl 1,5-diaryl-1H-pyrrole-
2-carboxylates in high to excellent yields under mild conditions.
Correspondence
Yuefa Gong, School of Chemistry and
Chemical Engineering, Huazhong
University of Science and Technology,
1037 Luoyu Road, Wuhan 430074,
People's Republic of China.
Email: gongyf@mail.hust.edu.cn
Funding information
National Natural Science Foundation of
China, Grant/Award Number: 21472053
1 | INTRODUCTION
bases, and alkynes with CsF also afforded the muti-
substituted pyrroles [2,8–11]. An alternative example is
Multi-substituted pyrroles are one of the most important
structural motifs in bioactive molecules and functional
materials [1], and have received much attention from
synthetic chemists. A variety of synthetic methods of
multi-substituted pyrroles have established, involving the
classical Knorr reaction, Hantzsch reaction, and Paal–
Knorr condensation reaction [2]. The construction pat-
terns for pyrrole core mainly include [3+2] annulation,
[4+1] annulation, and three-component reactions with
or without transition metal catalysis. Dimethyl ace-
tylenedicarboxylate (DMAD) as a valuable electrophile in
[3+2] annulation, is commonly used to react with
α-amino ketones, or α-amino ketones generated in situ
from the reaction of phenacyl bromides with aliphatic/
aromatic amines, or α-nitroepoxides and primary amines
[3–7]. The reaction of DMAD with β-enamino ketones or
esters, or C-acylimines formed in situ from anilines and
arylglyoxals, or treatment of α-silylaryl triflates, Schiff
Mn(OAc)3-promoted oxidative cyclization reaction of
DMAD with anilines and styrene [12]. Besides DMAD,
another alkyne reagent, the propargylic amine is also
useful for the construction of a pyrrole ring. One-pot
preparation of pyrroles was achieved via copper (II)-
catalyzed [4+1] annulation of propargylic amines with
N,O-acetals, or with alkyl/aryl glyoxylates [13,14]. In
recent years, transition metal-catalyzed reactions of
2-diazoesters are successfully established to prepare pyr-
roles, such as the dual copper and dirhodium-catalyzed
reaction of tert-butyldimethylsilyl-substituted vinyldia-
zoacetate with nitrones, copper-catalyzed condensation
of imines with α-diazo-β-dicarbonyl compounds, copper
(II)-catalyzed reaction of enaminones with 2-diazo-
2-arylacetate, AgOTf-catalyzed reaction of enaminones
with aryl diazoesters, and rhodium(II)-catalyzed in-
tramolecular N─H insertion reactions of δ-amino-
γ,γ-difluoro-α-diazo-β-ketoesters [15–19]. In addition,
J Heterocyclic Chem. 2021;1–11.
wileyonlinelibrary.com/journal/jhet
© 2021 Wiley Periodicals LLC.
1

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HUANG ET AL.
one-pot acid-catalyzed reaction between 2,3-diketoester,
imine, and aldehyde produces fully substituted 3-
aminopyrroles [20].
was carried out as a model in a sealed tube. Firstly, the
catalytic activity of several common Lewis acids and
protic acids was estimated in the solvent 1,2-
dichloroethane (DCE), and the observed results are
listed in Table 1. In the presence of strong Lewis acids
AlCl3 and FeCl3, the conversion of substrate 1a was com-
pleted after 24 h, and the yields of pyrrole 3aa reached
68% and 55%, respectively (Table 1, entries 1 and 2). In
contrast, using BF3ꢀOEt2 as the catalyst, a large amount
of 1a was not consumed during the reaction period, and
the yield of 3aa declined to 24% (Table 1, entry 3). Only
5% yield of 3aa was obtained in the case of ZnCl2, a rela-
tively weak Lewis acid, indicative of a much lower cata-
lytic activity (Table 1, entry 4). The effect of the strength
of protic acids on the above reaction was also assessed.
Although the superacid CF3SO3H can promote the reac-
tion, a lot of 1a was still maintained after 24 h under the
reaction conditions, and the yield of 3aa is only 38%
(Table 1, entry 5). Relatively weaker acid CF3COOH
furnished 3aa in 52% yield (Table 1, entry 6), whereas the
much weaker acid CH3COOH almost cannot promote
the formation of 3aa under the reaction conditions
(Table 1, entry 7). Obviously, the proton transfer
equilibrium between protic acid and aniline has a mar-
ked influence on the reaction. Based on the above
On the other hand, the chemistry of reactive
cyclopropene species generated from 1,2-elimination of alkyl
1-aroyl-1-halocyclopropanecarboxylates has been carefully
studied in our group [21]. The cascade reaction of this reac-
tive cyclopropene species with nucleophilic reagent like
acylhydrazones afforded functionalized pyrroles [22–24]. The
reaction of alkyl 1-aroyl-1-halocyclopropanecarboxylates with
amines was also assessed in the presence of Cs2CO3 [25]. As
an extension of this investigation, the acid-catalyzed reaction
of the substrates with amines has also been performed. As a
consequence, the acid-promoted reaction of alkyl 1-aroyl-
1-chlorocyclopropanecarboxylates with amines gave compli-
cated products, whereas a satisfying result was observed
when alkyl 1-aroyl-1-phenoxycyclopropanecarboxylates was
used as the substrate. The experimental details about the
reaction are described as follows.
2 | RESULTS AND DISCUSSION
In the beginning, the reaction between methyl 2-benzoyl-
1-phenoxycyclopropanecarboxylate (1a) and aniline (2a)
TABLE 1 Survey of the reaction conditions between 1a and 2aa
Entry
1
Acid (equiv)
AlCl3 (1)
Solvent
DCE
T/oC
100
100
100
100
100
100
100
100
100
100
100
80
t/h
24
24
24
24
24
24
24
24
24
24
18
24
96
40
48
24
Yield of 3aa/%
68
55
24
5
2
FeCl3 (1)
DCE
3
BF3ꢀOEt2 (1)
ZnCl2 (1)
DCE
4
DCE
5
CF3SO3H (1)
CF3COOH (1)
CH3COOH (1)
AlCl3 (1)
DCE
38
52
0
6
DCE
7
DCE
8
Toluene
CH3CN
EtOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
59
43
90b
98
98
90
95
95
0
9
AlCl3 (1)
10
11
12
13
14
15
16
AlCl3 (1)
AlCl3 (1)
AlCl3 (0.5)
AlCl3 (0.25)
AlCl3 (0.25)
AlCl3 (0.1)
AlCl3 (0)
80
100
120
120
aUnless otherwise indicated, all the reactions of 1a (0.25 mmol) with 2a (0.3 mmol) were carried out in solvent (2.0 mL) in a sealed tube.
bA mixture of methyl ester and ethyl ester was obtained at the ratio of 2:1.

HUANG ET AL.
3
observations, AlCl3 was chosen as the most suitable cata-
lyst for the following investigation.
investigated. As depicted in Table 2, the electronic prop-
erty of substituents of the amines has no obvious influ-
ence on the reaction yields. The desired pyrroles 3ab–3af
was obtained in 93%–98% yields, despite whether the sub-
stituents at the para position of anilines are electron-
donating 4-MeO and 4-Me groups or electron-
withdrawing 4-Cl, 4-Br, and 4-NO2 groups. However, it is
clear that electron-rich anilines needed a much longer
time to complete the reaction than electron-deficient ani-
lines, indicating that the relatively weak basicity of ani-
line favored the reaction to a certain extent. Besides the
electronic property, the steric hindrance of substituents
on the reaction was also assessed. Anilines 2g-j with
Me, F, Cl, or Br groups at the ortho site were tested. In
the case of o-toluidine, the reaction was almost com-
pleted after 48 h, giving the product 3ga in 96% yield. In
contrast, the reaction of anilines 2h-j was almost finished
within 18 h under the same conditions and produced the
corresponding products 3ha-ja in 95%–98% yields. In
addition, the reaction of m-chloroaniline (2k) proceeded
much faster than that of o-chloroaniline (2i). This obser-
vation really shows a considerable influence of steric hin-
drance on the reaction rate. This opinion was further
supported by the fact that the bulky 2,4,6-trimethylaniline
(2n) gave the corresponding product 3an only in
72% within 24 h. In addition, either electron-deficient
m-nitroaniline (2l) or 1-naphthylamine (2m) with the
fused ring was suitable for the reaction. Therefore, the
above reaction is tolerant of a range of substituent groups
on the aromatic ring of amines.
Since the pyrrole derivative has an ester group at its
ortho position, we expected that some heterocyclic com-
pounds with a big fused ring system would be con-
structed by introducing a functional group like amino at
the ortho position of aromatic amine. Thus, the individ-
ual reaction of o-phenylenediamine, 4,5-dichloro-o-phe-
nylenediamine, and naphthalene-2,3-diamine with 1a
was performed. The reaction proceeded smoothly as we
expected, and the products 3ao-aq containing the
quinoxalinone structure were obtained in the yield of
98%, 87%, and 92%, respectively. Starting from o-
aminobenzyl alcohol, the product 3ar was isolated in a
yield of 65%.
The solvent was then screened under the reaction
conditions using AlCl3 as the catalyst (Table 1, entries
8–11). The experimental results clearly showed that the
solvent property has a great influence on the reaction
yield. In nonpolar solvent toluene, a similar conversion
to DCE was observed (Table 1, entry 8). Aprotic polar
solvent CH3CN disfavored the conversion of 1a,
affording 3aa only in a 43% yield (Table 1, entry 9).
Unexpectedly, the protic polar solvents EtOH or MeOH
made the reaction undergo smoothly, providing the tar-
get pyrroles in up to 90% yields, despite the trans-
esterification during the reaction (Table 1, entries
10 and 11). To avoid the undesired transesterification
reaction in ethanol, methanol was chosen as the suit-
able solvent.
The effect of the amount of AlCl3 on the reaction
was next studied. As listed in Table 1, reducing the
amount of AlCl3 from 1.0 to 0.10 equiv, the above reac-
tion still underwent readily and over 90% yield of 3aa
can be generated by extending the reaction time or rais-
ing the reaction temperature (Table 1, entries 11–15).
In the case of 0.1 equiv AlCl3, the reaction yield
reached 95% (entry 15) when the reaction was con-
ducted at 120ꢁC for 48 h. A controlled experiment
clearly demonstrated that the reaction did not proceed
without AlCl3 (Table 1, entry 16). Considering the
affecting factors on the reaction yields, we chose the
optimal reaction conditions as follows: the reaction of
1a and 2a was carried out in a sealed tube with AlCl3
(0.5 equiv) in methanol at 80ꢁC for 24 h.
The substrate scope suitable for the reaction was
explored under the above optimal reaction conditions.
As shown in Table 2, the electronic property of R1
groups for 1a–g has little influence on the reaction
yields. No matter electron-donating group (such as
4-MeO and 4-Me) or electron-withdrawing group (4-Cl)
on the aromatic ring of R1, the above reactions could
proceed smoothly and the corresponding products 3ba–
3da were produced in excellent yields. However, it
should be noticed that the transformation of 1d,e with
electron-withdrawing R1 group needs a longer reaction
time. In the case of 1e with 4-Br group, the product 3ea
gradually precipitated during the reaction and can be
isolated in 63% yield by filtration. In addition, the
corresponding product 3fa was obtained in an excellent
yield, despite the bulky R1 group of 1f. In the case of 1g
with a heteroaryl group such as thiophene, the desired
product 3ga was given in a yield of 86% in the presence
of 1 equiv of AlCl3 after 48 h.
Based on the observations mentioned above, a plausi-
ble mechanistic pathway depicted in Scheme 1 was pro-
posed for rationalizing the formation of the pyrrole ring
of 3. First, initial coordination of carbonyl group of the
substrate 1 with Lewis acid AlCl3 led to ring-opening of
the strained cyclopropane slowly, giving a reactive carbo-
cation intermediate A. Then, A was quickly attacked by
the nucleophilic aromatic amine to generate the ammo-
nium B, and B was next converted into 4-aminoketone
C through subsequent intramolecular proton migration
On the other hand, the influence of substituents of
aromatic amines (R2) on the reaction was also

4
HUANG ET AL.
TABLE 2 The scope for the acid-catalyzed reaction between 1 and 2a
3aa, 24 h, 98%
3ba, 24 h, 91%
3ca, 24 h, 95%
3da, 36 h, 96%
3ea, 24 h, 63%b
3fa, 20 h, 94%
3ga, 48 h, 86%c
3ab, 24 h, 94%
3ac, 20 h, 95%
3ad, 12 h, 96%
3ae, 15 h, 98%
3af, 10 h, 93%
3ag, 48 h, 96%
3ah, 12 h, 98%
3ai, 18 h, 95%
3aj, 18 h, 96%
3ak, 10 h, 95%
3al, 18 h, 98%
3am, 12 h, 96%
3an, 24 h, 72%
3ao, 8 h, 98%
3ap, 12 h, 87%
3aq, 12 h, 92%
3ar, 24 h, 65%
aUnless otherwise indicated the reactions of 1 (0.25 mmol) with 2 (0.3 mmol) were carried out with AlCl3 (0.125 mmol) and methanol (2.0 mL) in a sealed tube.
bIsolated yield by filtration of the precipitate.
cThe reaction was carried out with 1 equiv AlCl3 (0.25 mmol).
from ammonium to C═C bond, releasing one molecule
of AlCl3. Intramolecular nucleophilic addition of nitro-
gen to carbonyl and elimination of a molecule of water
resulted in the formation of dihydropyrrole D. Finally,
the pyrrole product 3 was generated by 1,2-elimination of
one molecule of phenol from D.

HUANG ET AL.
5
SCHEME 1 Plausible mechanistic
pathways for the formation of 3
3 | CONCLUSIONS
(2.0 mL), and AlCl3 (17 mg, 0.125 mmol). Then, the
mixture was heated and stirred at 100ꢁC for a period.
Progress for the reaction was monitored by TLC until
all the 1a disappeared completely. The reaction mix-
ture was cooled, quenched with 10 mL of saturated
NaCl aqueous solution, and extracted with CH2Cl2
three times. Combined organic layers were dried over
anhydrous Na2SO4 and concentrated under reduced
pressure. The residue was isolated by silica gel column
chromatography using petroleum ether and ethyl ace-
tate as the eluent (v/v 40:1) to afford colorless solid
3aa in 98% yield.
In summary, a novel and practical [4+1] annulation reac-
tion have been developed for the synthesis of various
multi-substituted pyrroles from methyl 2-acyl-1-pheno-
xycyclopropanecarboxylates 1 and aromatic amine in the
presence of AlCl3 as the catalyst. The reaction has the merits
such as transition metal-free, easily available substrate,
excellent yields, and mild conditions. The application study
of the pyrroles as chiral ligand is ongoing in our group.
4 | EXPERIMENTAL
Unless otherwise specified, all other products 3 were
synthesized according to the typical procedure, and the
spectroscopic data are given as follows:
All reagents and solvents are of commercial grade and puri-
fied prior to use when necessary. Reactions are followed by
thin-layer chromatography (TLC) analysis using silica gel
60 Å F-254 thin layer plates. Flash column chromatography
4.1.1 | Methyl 1,5-diphenyl-1H-pyrrole-
2-carboxylate (3aa)
1
was performed on silica gel 60 Å, 10–40 μm. All H NMR
and 13C NMR spectra are recorded on a 400 or 600 MHz
spectrometer with solvent resonances as the internal stan-
dard (1H NMR: CDCl3 at 7.26 ppm; 13C NMR: CDCl3 at
77.0 ppm). The following abbreviations are used to describe
peak patterns where appropriate: s = singlet, d = doublet,
t = triplet, q = quartet, m = multiplet, and br s = broad sig-
nal. All coupling constants (J) are given in hertz. IR spectra
were recorded on an infrared spectrometer. Melting points
were recorded on a melting point detector. High-resolution
mass spectrometry (HRMS) was measured on a quadrupole
time-of-flight mass spectrometer equipped with an
electrospray ionization (ESI) technique.
Colorless solid (total 68 mg, 98%); m.p. 136–137ꢁC; 1H
NMR (400 MHz, CDCl3) δ 7.27–7.23 (m, 3H), 7.13–7.10
(m, 2H), 7.09–7.05 (m, 4H), 7.03–6.98 (m, 2H), 6.34 (d,
J = 4.0 Hz, 2H), 3.61 (s, 3H). 13C NMR (101 MHz, CDCl3)
δ 161.0, 141.4, 139.1, 132.0, 128.9, 128.7, 128.4, 128.1,
128.0, 127.4, 124.7, 118.5, 110.0, 51.1. IR (film) ν 3059,
2948, 1716, 1598, 1534, 1497, 1457, 1406, 1352, 1282,
1233, 1193, 1150, 1094, 1010, 752, 697 cmꢂ1. HRMS (ESI)
m/z calcd for C18H15NO2Na [M + Na]+: 300.0995, found
300.0988.
The substrate 1 was prepared according to the experi-
mental procedures reported in our previous work [21].
4.1 | The typical procedures for the
reaction of 1a with aniline
A
sealed tube was charged with 1a (74 mg,
0.25 mmol), aniline 2a (27 μL, 0.3 mmol), MeOH

6
HUANG ET AL.
4.1.2 | Methyl 5-(4-methoxyphenyl)-
1-phenyl-1H-pyrrole-2-carboxylate (3ba)
Colorless solid (total 75 mg, 96%); m.p. 173–175ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.30–7.23 (m, 3H), 7.12–7.07
(m, 2H), 7.07–7.01 (m, 3H), 6.92 (d, J = 8.6 Hz, 2H), 6.32
(d, J = 4.0 Hz, 1H), 3.61 (s, 3H). 13C NMR (101 MHz,
CDCl3) δ 160.9, 140.1, 138.8, 133.5, 130.5, 130.0, 128.6,
128.6, 128.3, 128.3, 125.0, 118.4, 110.1, 51.2. IR (film) ν
3054, 2992, 2949, 2844, 1714, 1590, 1529, 1494, 1456,
1390, 1347, 1271, 1237, 1192, 1152, 1108, 1083, 1050,
1010, 950, 915, 833, 778, 753, 696 cmꢂ1. HRMS (ESI) m/z
calcd for C18H14ClNO2Na [M + Na]+: 334.0605, found
334.0598.
Colorless solid (total 70 mg, 91%); m.p. 127–129ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.27–7.20 (m, 3H), 7.14–7.08
(m, 2H), 7.05 (d, J = 3.9 Hz, 1H), 6.92 (d, J = 8.7 Hz, 2H),
6.60 (d, J = 8.7 Hz, 2H), 6.26 (d, J = 3.9 Hz, 1H), 3.62 (s,
3H), 3.59 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 161.0,
159.0, 141.4, 139.2, 130.1, 128.8, 128.5, 128.1, 124.5, 124.2,
118.5, 113.6, 109.4, 55.2, 51.1. IR (film) ν 3056, 2989,
2950, 2837, 1701, 1607, 1573, 1536, 1497, 1461, 1399,
1350, 1308, 1249, 1184, 1152, 1092, 1033, 1010, 913, 840,
4.1.5 | Methyl 5-(4-bromophenyl)-1-phenyl-
1H-pyrrole-2-carboxylate (3ea)
793, 757, 696 cmꢂ1
. HRMS (ESI) m/z calcd for
C19H17NO3Na [M + Na]+: 330.1101, found 330.1095.
4.1.3 | Methyl 1-phenyl-5-(p-tolyl)-1H-
pyrrole-2-carboxylate (3ca)
1
Colorless solid (total 56 mg, %); m.p. 191–193ꢁC. H
NMR (400 MHz, CDCl3) δ 7.41–7.33 (m, 3H), 7.29 (d,
J = 8.5 Hz, 2H), 7.21–7.16 (m, 2H), 7.14 (d, J = 4.0 Hz,
1H), 6.94 (d, J = 8.5 Hz, 2H), 6.41 (d, J = 4.0 Hz, 1H),
3.70 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 160.8, 140.0,
138.8, 131.3, 130.9, 130.3, 128.6, 128.3, 125.0, 121.7, 118.4,
110.1, 51.2. IR (film) ν 3052, 2992, 2948, 2842, 1710, 1590,
1526, 1495, 1454, 1386, 1346, 1271, 1236, 1191, 1151,
Colorless solid (total 69 mg, 95%); m.p. 147–149ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.35–7.30 (m, 3H), 7.22–7.17
(m, 2H), 7.14 (d, J = 3.9 Hz, 1H), 7.00–6.93 (m,4H), 6.38
(d, J = 3.9 Hz, 1H), 3.67 (s, 3H), 2.24 (s, 3H). 13C NMR
(101 MHz, CDCl3) δ 161.0, 141.6, 139.2, 137.3, 129.1,
128.8, 128.8, 128.5, 128.1, 124.5, 118.5, 51.1, 21.2. IR (film)
ν 3052, 2986, 2947, 1712, 1592, 1538, 1495, 1460, 1396,
1348, 1311, 1281, 1237, 1189, 1150, 1089, 1010, 950, 915,
824, 774, 751, 697 cmꢂ1. HRMS (ESI) m/z calcd for
C19H17NO2Na [M + Na]+: 314.1151, found 314.1147.
1094, 1070, 1008, 949, 914, 829, 776, 753, 720, 695 cmꢂ1
.
HRMS (ESI) m/z calcd for C18H14BrNO2Na [M + Na]+:
378.0100, found 378.0087.
4.1.6 | Methyl 5-[(1,10-biphenyl)-4-yl]-
1-phenyl-1H-pyrrole-2-carboxylate(3fa)
4.1.4 | Methyl 5-(4-chlorophenyl)-1-phenyl-
1H-pyrrole-2-carboxylate (3da)
Colorless solid (total 83 mg, 94%); m.p. 171–173ꢁC.
1H NMR (400 MHz, CDCl3) δ 7.51 (d, J = 7.3 Hz, 2H),
7.42–7.34 (m, 7H), 7.30 (t, J = 7.3 Hz, 1H), 7.26–7.21 (m,
2H), 7.16 (dd, J = 10.8, 6.2 Hz, 3H), 6.47 (d, J = 4.0 Hz,

HUANG ET AL.
7
1H), 3.70 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 160.9,
141.0, 140.3, 140.0, 139.1, 130.9, 129.1, 128.8, 128.8, 128.6,
128.2, 127.5, 126.9, 126.7, 124.9, 118.6, 110.1, 51.1. IR
(film) ν 3059, 2949, 1720, 1596, 1497, 1460, 1424, 1347,
1307, 1275, 1232, 1189, 1144, 1091, 1042, 1007, 947, 910,
841, 793, 765, 734, 698 cm-1. HRMS (ESI) m/z calcd for
C24H19NO2Na [M + Na]+: 376.1308, found 376.1301.
1711, 1608, 1513, 1458, 1432, 1353, 1300, 1280, 1242,
1184, 1154, 1092, 1020, 1002, 952, 914, 829, 793,
760, 696 cmꢂ1. HRMS (ESI) m/z calcd for C19H17NO3Na
[M + Na]+: 330.1101, found 330.1093.
4.1.9 | Methyl 5-phenyl-1-(p-tolyl)-1H-
pyrrole-2-carboxylate (3ac)
4.1.7 | Methyl 1-phenyl-5-(thiophen-2-yl)-
1H-pyrrole-2-carboxylate (3ga)
Colorless solid (total 69 mg, 95%); m.p. 121–123ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.09–6.94 (m, 10H), 6.31 (dd,
J = 3.9, 0.9 Hz, 1H), 3.60 (s, 3H), 2.26 (s, 3H). 13C NMR
(101 MHz, CDCl3) δ 161.0, 141.5, 137.9, 136.5, 132.1,
129.2, 128.9, 128.4, 128.1, 127.4, 124.6, 118.4, 109.9, 51.1,
21.3. IR (film) ν 3060, 3033, 2948, 2922, 2851, 1713, 1598,
1514, 1458, 1435, 1411, 1351, 1311, 1283, 1231, 1911,
1149, 1111, 1092, 1048, 1008, 949, 914, 822, 797,
757, 699 cmꢂ1. HRMS (ESI) m/z calcd for C19H17NO2Na
[M + Na]+: 314.1151, found 314.1143.
Faint yellow solid (total 61 mg, 86%); m.p. 94–96ꢁC.
1H NMR (400 MHz, CDCl3) δ 7.41–7.31 (m, 3H), 7.24–
7.18 (m, 2H), 7.02 (d, J = 4.1 Hz, 1H), 7.00 (dd, J = 5.1,
0.9 Hz, 1H), 6.72 (dd, J = 5.0, 3.7 Hz, 1H), 6.53 (dd,
J = 3.6, 0.9 Hz, 1H), 6.43 (d, J = 4.1 Hz, 1H), 3.59 (s,
3H).. 13C NMR (101 MHz, CDCl3) δ 160.8, 139.0, 135.1,
133.6, 129.0, 128.9, 127.0, 125.9, 125.6, 124.9, 118.3, 109.6,
51.2. IR (film) ν 3101, 3070, 2990, 2946, 1712, 1540, 1497,
1468, 1431, 1410, 1346, 1265, 1234, 1203, 1141, 1067, 4.1.10 | Methyl 1-(4-chlorophenyl)-5-phenyl-
1042, 1005, 930, 894, 842, 770, 751, 697 cmꢂ1. HRMS 1H-pyrrole-2-carboxylate (3ad)
(ESI) m/z calcd for C16H13NO2SNa [M + Na]+: 306.0559,
found 306.0553.
4.1.8 | Methyl 1-(4-methoxyphenyl)-
5-phenyl-1H-pyrrole-2-carboxylate (3ab)
Colorless solid (total 75 mg, 96%); m.p. 141–143ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.28 (d, J = 8.6 Hz, 2H), 7.20–
7.17 (m, 3H), 7.15 (d, J = 4.0 Hz, 1H), 7.11 (d, J = 8.6 Hz,
2H), 7.10–7.04 (m, 2H), 6.40 (d, J = 4.0 Hz, 1H), 3.69 (s,
3H). 13C NMR (101 MHz, CDCl3) δ 160.9, 141.5, 137.6,
Colorless solid (total 72 mg, 94%); m.p. 154–156ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.20–7.06 (m, 8H), 6.84 (d,
J = 8.8 Hz, 2H), 6.40 (d, J = 4.0 Hz, 1H), 3.78 (s, 3H),
3.69 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 161.0, 159.1,
141.6, 132.1, 131.8, 129.6, 128.9, 128.1, 127.4, 124.7, 118.3,
113.6, 109.8, 55.3, 51.1. IR (film) ν 3061, 3019, 2942, 2840,
134.0, 131.7, 130.0, 129.0, 128.7, 128.3, 127.7, 124.6, 118.8,
110.3, 51.2. IR (film) ν 3089, 3061, 2985, 2946, 2849, 1711,
1596, 1532, 1494, 1458, 1432, 1409, 1356, 1314, 1278,
1236, 1189, 1153, 1090, 1052, 1011, 950, 916, 841, 825,
794, 758, 697 cmꢂ1
.
HRMS (ESI) m/z calcd for
C18H14ClNO2Na [M + Na]+: 334.0605, found 334.0591.

8
HUANG ET AL.
4.1.11 | Methyl 1-(4-bromophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3ae)
Faint yellow solid (total 70 mg, 96%); m.p. 86–88ꢁC.
1H NMR (400 MHz, CDCl3) δ 7.23–7.15 (m, 1H), 7.13–
6.96 (m, 9H), 6.38 (d, J = 4.0 Hz, 1H), 3.60 (s, 3H), 1.81
(s, 3H). 13C NMR (101 MHz, CDCl3) δ 160.8, 141.0, 138.5,
136.3, 132.0, 130.4, 129.1, 128.6, 128.4, 128.1, 127.5, 126.1,
124.2, 118.3, 109.8, 51.1, 17.4. IR (film) ν 3058, 3022,
2983, 2945, 2919, 2848, 1718, 1602, 1535, 1494, 1459,
1406, 1352, 1314, 1284, 1265, 1234, 1186, 1147, 1091,
1045, 1009, 950, 914, 872, 795, 771, 754, 697 cmꢂ1. HRMS
(ESI) m/z calcd for C19H17NO2Na [M + Na]+: 314.1151,
found 314.1147.
1
Yellow solid (total 87 mg, 98%); m.p. 144–146ꢁC. H
NMR (400 MHz, CDCl3) δ 7.44 (d, J = 8.5 Hz, 2H), 7.22–
7.13 (m, 4H), 7.11–6.98 (m, 4H), 6.40 (dd, J = 2.3, 1.6 Hz,
1H), 3.70 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 160.9,
141.5, 138.1, 131.7, 131.6, 130.4, 129.0, 128.3, 127.7, 124.6,
122.1, 118.8, 110.3, 51.2. IR (film) ν 3059, 2947, 1710,
1595, 1529, 1493, 1458, 1434, 1404, 1349, 1314, 1276,
1231, 1191, 1150, 1092, 1069, 1046, 1006, 947, 913,
829, 795, 756, 699 cmꢂ1. HRMS (ESI) m/z calcd for
C18H14BrNO2Na [M + Na]+: 378.0100, found 378.0096.
4.1.14 | Methyl 1-(2-fluorophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3ah)
4.1.12 | Methyl 1-(4-nitrophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3af)
1
Colorless solid (total 72 mg, 98%); m.p. 89–91ꢁC. H
NMR (400 MHz, CDCl3) δ 7.28–7.19 (m, 1H), 7.13–6.92
(m, 9H), 6.36 (dd, J = 3.4, 1.3 Hz, 1H), 3.62 (s, 3H). 13C
NMR (101 MHz, CDCl3) δ 159.7, 158.8, 156.3, 140.6,
130.5, 129.4, 129.1, 129.0, 127.6, 127.1, 126.7, 126.3, 126.2,
123.7, 122.9, 122.8, 117.6, 114.9, 114.7, 109.2, 50.1. IR
(film) ν 3064, 3024, 2951, 2851, 1713, 1592, 1544, 1503,
1460, 1434, 1411, 1352, 1286, 1261, 1237, 1187, 1146,
Faint yellow solid (total 75 mg, 93%); m.p. 123–125ꢁC.
1H NMR (400 MHz, CDCl3) δ 8.10 (d, J = 8.8 Hz, 2H),
7.26 (d, J = 8.8 Hz, 2H), 7.14–7.06 (m, 4H), 7.00–6.92 (m,
2H), 6.36 (d, J = 3.9 Hz, 1H), 3.62 (s, 3H). 13C NMR
(101 MHz, CDCl3) δ 160.9, 147.0, 144.7, 141.5, 131.2,
129.8, 129.0, 128.4, 128.0, 124.7, 123.8, 119.4, 111.0, 51.4.
IR (film) ν 3057, 2958, 1715, 1599, 1527, 1499, 1460, 1434,
1408, 1356, 1287, 1235, 1189, 1153, 1092, 1044, 1011,
952, 916, 860, 796, 753, 699 cmꢂ1. HRMS (ESI) m/z calcd
for C18H14N2O4Na [M + Na]+: 345.0846, found 345.0839.
1111, 1088, 1039, 1007, 948, 916, 819, 794, 755, 699 cmꢂ1
.
HRMS (ESI) m/z calcd for C18H14FNO2Na [M + Na]+:
318.0901, found 318.0895.
4.1.15 | Methyl 1-(2-chlorophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3ai)
4.1.13 | Methyl 5-phenyl-1-(o-tolyl)-1H-
pyrrole-2-carboxylate (3ag)
Faint yellow solid (total 74 mg, 95%); m.p. 126–128ꢁC.
1H NMR (400 MHz, CDCl3) δ 7.42 (d, J = 7.9 Hz, 1H),
7.32–7.26 (m, 1H), 7.23–7.09 (m, 8H), 6.45 (d, J = 3.9 Hz,
1H), 3.69 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 160.8,
141.3, 137.3, 133.7, 131.6, 130.5, 129.7, 129.7, 128.7, 128.2,

HUANG ET AL.
9
127.8, 127.0, 124.5, 118.4, 110.1, 51.2. IR (film) ν 3073,
3032, 3005, 2957, 2850, 2810, 1704, 1585, 1537, 1486,
1459, 1407, 1350, 1286, 1234, 1187, 1148, 1100, 1072,
1036, 1006, 947, 912, 796, 755, 687 cmꢂ1. HRMS (ESI) m/
z calcd for C18H14ClNO2Na [M + Na]+: 334.0605, found
334.0600.
(ESI) m/z calcd for C18H14ClNO2Na [M + Na]+:
334.0605, found 334.0597.
4.1.18 | Methyl 1-(3-nitrophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3al)
4.1.16 | Methyl 1-(2-bromophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3aj)
Faint yellow solid (total 79 mg, 98%); m.p. 159–161ꢁC.
1H NMR (400 MHz, CDCl3) δ 8.16–8.06 (m, 1H), 7.99 (t,
J = 1.8 Hz, 1H), 7.48–7.35 (m, 2H), 7.14–7.07 (m, 4H),
7.01–6.93 (m, 2H), 6.36 (d, J = 4.0 Hz, 1H), 3.62 (s, 3H).
13C NMR (101 MHz, CDCl3) δ 159.8, 146.9, 140.6, 139.0,
133.9, 130.0, 128.0, 128.0, 127.3, 126.9, 123.6, 123.1, 121.9,
118.1, 109.7, 50.2. IR (film) ν 3076, 2951, 2851, 1704,
1601, 1532, 1459, 1406, 1348, 1286, 1260, 1233, 1195,
Colorless solid (total 85 mg, 96%); m.p. 158–160ꢁC. 1H
NMR (400 MHz, CDCl3) δ 7.58 (dd, J = 7.8, 0.6 Hz, 1H),
7.33–7.09 (m, 9H), 6.45 (d, J = 4.0 Hz, 1H), 3.69 (s, 3H).
13C NMR (101 MHz, CDCl3) δ 160.7, 141.1, 138.9, 132.8,
131.6, 130.6, 129.9, 128.8, 128.2, 127.8, 127.7, 124.3, 124.1,
118.4, 110.2, 51.3. IR (film) ν 3071, 3032, 3003, 2956,
2850, 1704, 1580, 1537, 1500, 1482, 1459, 1405, 1349,
1285, 1234, 1187, 1148, 1096, 1065, 1031, 1005, 947, 912,
1151, 1084, 1048, 1020, 956, 919, 869, 806, 759, 698 cmꢂ1
.
HRMS (ESI) m/z calcd for C18H14N2O4Na [M + Na]+:
345.0846, found 345.0839.
796, 755, 690 cmꢂ1
. HRMS (ESI) m/z calcd for
C18H14BrNO2Na [M + Na]+: 378.0100, found 378.0091.
4.1.19 | Methyl 1-(naphthalen-1-yl)-
5-phenyl-1H-pyrrole-2-carboxylate (3am)
4.1.17 | Methyl 1-(3-chlorophenyl)-5-phenyl-
1H-pyrrole-2-carboxylate (3ak)
1
Gray solid (total 78 mg, 96%); m.p. 119–121ꢁC. H
NMR (400 MHz, CDCl3) δ 7.74 (d, J = 8.2 Hz, 2H),
7.37–7.23 (m,4H), 7.22–7.13 (m, 2H), 7.01–6.81 (m,
5H), 6.45 (d, J = 4.0 Hz, 1H), 3.44 (s, 3H). 13C NMR
(101 MHz, CDCl3) δ 160.6, 142.3, 136.2, 133.7, 132.2,
131.9, 128.9, 128.4, 128.3, 128.0, 127.6, 127.3, 126.5,
126.3, 125.8, 125.0, 122.7, 118.4, 110.1, 51.1. IR (film)
ν 3057, 2949, 1717, 1596, 1540, 1505, 1461, 1415,
1351, 1279, 1235, 1185, 1145, 1081, 1026, 974, 936,
913, 866, 800, 777, 752, 696 cmꢂ1. HRMS (ESI) m/z
calcd for C22H17NO2Na [M + Na]+: 350.1151, found
350.1143.
Faint yellow solid (total 74 mg, 95%); m.p. 130–131ꢁC.
1H NMR (400 MHz, CDCl3) δ 7.23 (d, J = 8.1 Hz, 1H),
7.17 (d, J = 7.9 Hz, 1H), 7.14–7.08 (m, 4H), 7.06 (d,
J = 3.9 Hz, 1H), 7.00 (d, J = 6.7 Hz, 3H), 6.32 (d,
J = 3.9 Hz, 1H), 3.61 (s, 3H). 13C NMR (101 MHz, CDCl3)
δ 160.8, 141.5, 140.2, 133.9, 131.6, 129.3, 129.1, 128.9,
128.4, 128.2, 127.7, 127.2, 124.7, 118.8, 110.3, 51.2. IR
(film) ν 3068, 2988, 2945, 2844, 1711, 1585, 1533, 1458,
1432, 1351, 1311, 1278, 1230, 1191, 1145, 1093, 1075,
1047, 1017, 953, 914, 875, 795, 752, 699 cmꢂ1. HRMS

10
HUANG ET AL.
1
4.1.20 | Methyl 1-mesityl-5-phenyl-1H-
pyrrole-2-carboxylate (3an)
Gray powder (total 72 mg, 87%); m.p. 311–312ꢁC. H
NMR (400 MHz, DMSO) δ 11.50 (s, 1H), 7.66–7.49 (m,
5H), 7.41 (s, 1H), 7.18 (d, J = 3.8 Hz, 1H), 7.00 (s, 1H),
6.67 (d, J = 3.8 Hz, 1H). 13C NMR (101 MHz, DMSO) δ
155.3, 134.9, 132.8, 130.2, 130.0, 129.8, 129.6, 127.4, 125.0,
123.4, 123.2, 118.3, 117.8, 116.2, 112.8. IR (film) ν 3317,
3167, 3119, 3048, 3016, 2927, 2890, 2825, 2728, 1662,
1610, 1545, 1496, 1465, 1409, 1371, 1278, 1251, 1174,
1137, 1077, 1035, 1003, 966, 919, 873, 842, 793, 765,
738, 698, 675 cmꢂ1
. HRMS (ESI) m/z calcd for
1
Colorless solid (total 57 mg, 72%); m.p. 107–109ꢁC. H
NMR (400 MHz, CDCl3) δ 7.20–7.14 (m, 4H), 7.13–7.06 (m,
2H), 6.85 (s, 2H), 6.51 (d, J = 4.0 Hz, 1H), 3.69 (s, 3H), 2.28 (s,
3H), 1.87 (s, 6H). 13C NMR (101 MHz, CDCl3) δ 160.6, 140.2,
137.9, 135.8, 135.2, 132.0, 128.7, 128.2, 127.7, 127.5, 123.2,
118.4, 109.8, 51.1, 21.2, 17.7. IR (film) ν 3064, 3027, 2996,
2949, 2918, 2852, 1701, 1600, 1533, 1490, 1457, 1434, 1403,
1352, 1309, 1278, 1259, 1233, 1181, 1144, 1090, 1038, 1008,
937, 912, 860, 793, 750, 696 cmꢂ1. HRMS (ESI) m/z calcd for
C21H21NO2Na [M + Na]+: 342.1465, found 342.1458.
C17H10Cl2N2ONa [M + Na]+: 351.0062, found 351.0055.
4.1.23 | 1-Phenylbenzo[g]pyrrolo[1,2-a]
quinoxalin-4(5H)-one (3aq)
4.1.21 | 1-Phenylpyrrolo[1,2-a]quinoxalin-4
(5H)-one (3ao)
Faint red powder (total 71 mg, 92%); m.p. 292–294ꢁC.
1H NMR (400 MHz, DMSO) δ 11.52 (s, 1H), 7.77 (d,
J = 8.2 Hz, 1H), 7.66 (s, 1H), 7.62–7.50 (m, 5H), 7.38 (t,
J = 7.5 Hz, 1H), 7.32 (s, 1H), 7.26 (t, J = 7.5 Hz, 1H), 7.20
(d, J = 3.8 Hz, 1H), 7.12 (d, J = 8.2 Hz, 1H), 6.65 (d,
J = 3.8 Hz, 1H). 13C NMR (101 MHz, DMSO) δ 155.8,
135.5, 133.6, 130.7, 130.1, 129.6, 129.5, 129.4, 128.1, 127.6,
126.7, 125.5, 125.3, 124.1, 115.9, 114.6, 113.0, 112.5. IR (film)
ν 3326, 3164, 3115, 3034, 2992, 2949, 2904, 2859, 2822, 2781,
1663, 1590, 1571, 1524, 1492, 1471, 1444, 1389, 1342, 1268,
1215, 1179, 1152, 1128, 1074, 1020, 945, 915, 876, 833,
796, 768, 737, 702, 668 cmꢂ1. HRMS (ESI) m/z calcd for
C21H14N2ONa [M + Na]+: 333.0998, found 333.0991.
Faint yellow powder (total 64 mg, 98%); m.p. 244–
246ꢁC. 1H NMR (400 MHz, DMSO) δ 11.35 (s, 1H), 7.50 (s,
5H), 7.31 (d, J = 7.9 Hz, 1H), 7.18–7.12 (m, 2H), 7.00 (d,
J = 8.4 Hz, 1H), 6.78 (t, J = 7.3 Hz, 1H), 6.59 (d, J = 3.8 Hz,
1H). 13C NMR (101 MHz, DMSO) δ 155.7, 134.5, 133.7,
129.9, 129.8, 129.3, 129.3, 125.8, 125.5, 123.7, 121.8, 117.4,
116.9, 115.9, 112.0. IR (film) ν 3320, 3175, 3123, 3034, 2981,
2916, 2855, 2775, 1666, 1611, 1512, 1494, 1462, 1439, 1380,
1262, 1170, 1153, 1070, 1026, 936, 867, 838, 791, 768, 753,
734, 700, 660 cmꢂ1
.
HRMS (ESI) m/z calcd for
C17H12N2ONa [M + Na]+: 283.0842, found 283.0837.
4.1.24 | Methyl 1-[2-(methoxymethyl)
phenyl]-5-phenyl-1H-pyrrole-
2-carboxylate (3ar)
4.1.22 | 7,8-Dichloro-1-phenylpyrrolo[1,2-a]
quinoxalin-4(5H)-one (3ap)

HUANG ET AL.
11
1
Colorless solid (total 52 mg, 65%); m.p. 92–94ꢁC. H
NMR (400 MHz, CDCl3) δ 7.48 (d, J = 7.5 Hz, 1H), 7.40
(t, J = 7.5 Hz, 1H), 7.30 (dd, J = 10.8, 4.2 Hz, 1H), 7.21
(d, J = 7.7 Hz, 1H), 7.19–7.08 (m, 6H), 6.47 (d,
J = 4.0 Hz, 1H), 4.03 (dd, J = 32.6, 12.8 Hz, 2H), 3.67 (s,
3H), 3.15 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 160.8,
141.3, 137.4, 136.6, 131.7, 129.2, 128.8, 128.5, 128.1, 128.1,
127.6, 127.6, 124.8, 118.4, 109.9, 70.1, 58.4, 51.1. IR (film)
ν 3139, 3066, 3033, 2994, 2951, 2926, 2889, 2849, 2825,
2733, 1711, 1601, 1536, 1495, 1458, 1409, 1381, 1351,
1310, 1283, 1265, 1232, 1188, 114, 1096, 1040, 1007,
969, 949, 913, 871, 795, 757, 725, 699 cmꢂ1. HRMS (ESI)
m/z calcd for C19H17NO3Na [M + Na]+: 330.1101, found
330.1094.
[8] J. Vannada, M. Sulthan, D. Arun, R. Dada, S. Yaragorla,
J. Org. Chem. 2020, 85, 6697.
[9] M. Anary-Abbasinejad, K. Chakhati, H. Anaraki-Ardakani,
Synlett 2009, 7, 1115.
[10] Y. Li, J. Shi, Z. Wu, X. Wang, X. Wu, J. Gu, H. Bu, H. Ma, Tet-
rahedron 2014, 70, 2472.
[11] J. R. Hwu, A. Roy, A. Panja, W. Huang, Y. Hu, K. Tan, C. Lin,
K. Hwang, M. Hsu, S. Tsay, J. Org. Chem. 2020, 85, 9835.
[12] J. Zeng, H. Xu, R. Huang, F. Yu, Z. Zhang, Tetrahedron Lett.
2018, 59, 1576.
[13] N. Sakai, H. Hori, Y. Ogiwara, Eur. J. Org. Chem. 2015, 2015, 1905.
[14] N. Sakai, H. Suzuki, H. Hori, Y. Ogiwara, Tetrahedron Lett.
2017, 58, 63.
[15] X. Xu, M. O. Ratnikov, P. Y. Zavalij, M. P. Doyle, Org. Lett.
2011, 13, 6122.
[16] W. W. Tan, N. Yoshikai, Chem. Sci. 2015, 6, 6448.
[17] M. Li, Y. Sun, Y. Xie, Y. Yu, F. Huang, H. Huang, Chem.
Commun. 2020, 56, 11050.
ACKNOWLEDGMENT
[18] K. Luo, S. Mao, K. He, X. Yu, J. Pan, J. Lin, Z. Shao, Y. Jin,
ACS Catal. 2020, 10, 3733.
[19] Y. Wang, S. Zhu, Org. Lett. 2003, 5, 745.
[20] P. M. Truong, M. D. Mandler, M. P. Doyle, Tetrahedron Lett.
2015, 56, 3042.
This work was supported by grants from National Natu-
ral Science Foundation of China (No. 21472053).
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are avail-
able online in the supplementary material of this article.
[21] M. Zhang, Y. F. Gong, W. Z. Wang, Eur. J. Org. Chem. 2013,
2013, 7372.
[22] Z. M. Huang, J. H. Hu, Y. F. Gong, Org. Biomol. Chem. 2015,
13, 8561.
ORCID
[23] Z. M. Huang, Y. F. Gong, RSC Adv. 2016, 6, 22357.
[24] J. H. Hu, M. Zhang, Y. F. Gong, Eur. J. Org. Chem. 2015, 2015,
1970.
Yuefa Gong https://orcid.org/0000-0001-9944-4055
REFERENCES
[25] Y. Q. Zhu, Y. F. Gong, J. Org. Chem. 2015, 80, 490.
[1] V. Estevez, M. Villacampa, J. C. Menendez, Chem. Soc. Rev.
2014, 43, 4633.
[2] R. Yan, J. Luo, C. Wang, C. Ma, G. Huang, Y. Liang, J. Org.
Chem. 2010, 75, 5395.
[3] M. Farahi, F. Tamaddon, B. Karami, S. Pasdar, Tetrahedron
Lett. 2015, 56, 1887.
[4] L. Nagarapu, R. Mallepalli, L. Yeramanchi, R. Bantu, Tetrahe-
dron Lett. 2011, 52, 3401.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
[5] I. R. Siddiqui, D. Kumar, S. Shamim, J. Heterocyclic Chem
2013, 50, E111.
[6] B. Das, G. C. Reddy, P. Balasubramanyam, B. Veeranjaneyulu,
Synthesis 2010, 10, 1625.
[7] D. Zhao, Y. Zhu, S. Guo, W. Chen, G. Zhang, Y. Yu, Tetrahe-
dron 2017, 73, 2872.
How to cite this article: L. Huang, C. Luo, P. Xu,
B. Liu, D. Zhang, J. Zhang, D. Pang, Y. Gong,
J Heterocyclic Chem 2021, 1. https://doi.org/10.
1002/jhet.4306