Catalyst-free facile and efficient one-pot synthesis of densely functionalized pyrroles and α-amino ketones

Article abstract of DOI:10.1002/jhet.4227

An efficient catalyst-free one-pot three-component synthesis of penta-substituted pyrroles has been successfully developed. A variety of penta-substituted pyrroles were straightforwardly synthesized from good to excellent yields (78%–93%) by using easily

Full text of DOI:10.1002/jhet.4227

Received: 14 December 2020
DOI: 10.1002/jhet.4227
Accepted: 7 January 2021
A R T I C L E
Catalyst-free facile and efficient one-pot synthesis of
densely functionalized pyrroles and α-amino ketones
Sivarama Krishna Reddy Vanga | Hari Babu Bollikolla
V. V. Satyanarayana Peruri
|
Department of Chemistry, Acharya
Abstract
Nagarjuna University, Guntur, India
An efficient catalyst-free one-pot three-component synthesis of penta-
substituted pyrroles has been successfully developed. A variety of penta-
substituted pyrroles were straightforwardly synthesized from good to excellent
yields (78%–93%) by using easily accessible starting materials under mild con-
ditions. This protocol also provided α-amino ketones in good yields (87%–98%)
without column chromatography.
Correspondence
Hari Babu Bollikolla and V. V.
Satyanarayana, Department of Chemistry,
Acharya Nagarjuna University, Guntur-
522510, Andhra Pradesh, India.
Email: dr.b.haribabu@gmail.com
(H. B. B) and chemperuri@yahoo.co.in
(V. V. S. P)
1 | INTRODUCTION
reaction,[15] Hantzsch synthesis,[16] ring-opening reac-
tions,[17] rearrangement reactions,[18] metal-catalyzed
Pyrrole, the five-membered heteroaromatic, and its deriv-
atives have emerged as a significant class of heterocyclic
compounds due to their wide range of applications in
various fields.[1] Pyrrole derivatives are ubiquitous and
found to be the core structure in many of the natural and
non-natural products.[2] A large number of pyrrole-based
alkaloids have been isolated from marine extracts and
were found to exhibit remarkable biological activities.[3]
Polysubstituted-pyrrole derivatives have been shown to
exhibit diverse biological properties in recent years. Some
of the important biologically active pyrrole derivatives
are shown in Figure 1.
These pyrrole derivatives also demonstrate a range of
biological properties such as antibiotic activity.[4] potent
inhibitors of HMG-CoA reductase,[5] cytotoxic activity.[6]
and antimicrobial,[7] anticancer,[8] antifungal,[9] antiviral,[10]
anti-tubercular,[11] and anti-inflammatory agents.[12] Pyrrole
derivatives are used as conducting polymers.[13] and also
extensively employed in the synthesis of diversely
substituted porphyrins and their derivatives.[14]
reactions,[19] functionalization of pyrroles,[20] cycloaddi-
tions, and iodine-mediated reactions.[21] Also, the reac-
tions of α-amino ketones with suitable reacting partners
provide densely functionalized pyrroles derivatives. It is
one of the simple and efficient methodologies for the syn-
thesis of pyrrole derivatives.[22] This wide range of appli-
cations of pyrrole derivatives has inspired the
development of novel synthetic routes for the synthesis of
penta-substituted pyrroles via α-amino ketones.
α-Amino ketones are another interesting class of com-
pounds that exhibit biological activities. They are also
used as intermediates in the synthesis of biologically rele-
vant molecules.[23] The general methods for the synthesis
of α-amino ketones involve the condensation of diketone
with amine followed by the reduction of the imine func-
tionality, cross-coupling of aldehydes with unactivated
imines, and [(S)-BINAP]PdBr2-catalyzed cross-coupling
reactions of imines with nitriles and silica tungstic acid.
Even though various methodologies have been
reported for the synthesis of α-amino ketones,[24,25] all
these suffer from longer reaction times, expensive
reagents, and use of metal catalysts and toxic solvents,
which may cause harm to the environment. So, there is a
need to develop a simple and environmentally friendly
methodology for the synthesis of α-amino ketones. In
continuation to our work in constructing various
Because of this wide range of applications of pyrroles
in various fields, chemist have continuously endeavored
to synthesize novel, densely functionalized pyrrole deriva-
tives by employing simple and efficient synthetic strate-
gies. Various methodologies have been developed for the
synthesis of substituted pyrroles including the Paal–Knorr
892
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J Heterocyclic Chem. 2021;58:892–899.

VANGA ET AL.
893
FIGURE 1 Representative examples of biologically active pyrroles
important mono.[26] and fused-ring.[27] heterocyclic
compounds [26,27], here we report the design and develop-
ment of a one-pot synthesis of densely functionalized
pyrroles and α-amino ketones.
in 84% yield (Table 1, entry 2). The reaction mediated by
TfOH was completed in 90 min to provide the
corresponding product 2a in 91% yield (Table 1, entry 3).
When the reaction of benzoin (1) and aniline was car-
ried out in presence of molecular iodine in DCE, the
reaction failed to afford the expected product and the
starting materials were recovered. The neat reaction of
benzoin (1) and aniline also could not afford the desired
product (Table 1, entry 4 & 5). Surprisingly, when the
reaction of benzoin (1) and aniline was performed in
acetic acid, the reaction was completed in 30 min. After
completion of the reaction, 3 mL of water was added and
the precipitate thus obtained was filtered, washed with
water, and dried under vacuum to afford the expected
product 2a in 96% yield (Table 1, entry 6). The product
obtained was confirmed by 1H and 13C NMR analysis.
From the above optimization reactions, acetic acid was
found to be the best reagent in the current protocol.
Encouraged with the result obtained, we further decided to
explore the reactivity of benzoin with other aniline deriva-
tives using the present methodology. For this purpose, we
chose various substituted aniline derivatives to test their
scope of reactivity with benzoin. When the reaction of ben-
zoin (1) with 1-naphthylamine under standard conditions
was performed, the reaction proceeded smoothly and
afforded the desired product 2b in 98% yield (Scheme 1).
Further, the reactions of para-substituted anilines such as
2 | RESULTS AND DISCUSSION
In the initial studies, a reaction between benzoin (1) with
aniline in presence of trifluoroacetic acid and 2 mL of
1,2-dichloroethane (DCE) at reflux temperature was per-
formed. The progress of the reaction was monitored by
TLC, and it was observed that after 120 min the starting
materials were completely consumed. After completion
of the reaction, the reaction mixture was subjected to the
usual work-up and the crude reaction mixture obtained
was purified by column chromatography to afford the
desired product 2a in 86% (Table 1, entry 1). The struc-
ture of the product thus obtained was confirmed by the
analysis of 1H and 13C NMR data. Encouraged with
the result obtained, we proceeded for optimization of the
reaction conditions to improve the yield of product 2a.
Therefore we carried out the reactions of benzoin (1) and
aniline in DCE in the presence of other Brønsted acids
such as methane sulfonic acid and triflic acid (TfOH). In
the presence of methane sulfonic acid, the reaction was
completed in 120 min and the product 2a was delivered

894
VANGA ET AL.
TABLE 1 Optimization of reaction
conditions
OH
HN
NH2
O
O
solvent, reagent
1
2a
S. no.
Reagent
CF3COOH
CH3SO3H
TfOH
I2
Solvent
DCE
Temperature (ꢀC)
Reflux
Time (min)
Yielda (%)
1
2
3
4
5
6
120
120
90
86
84
91
-
DCE
Reflux
DCE
Reflux
DCE
Reflux
120
120
30
Neat
100ꢀC
-
-
AcOH
110ꢀC
96
Note: All the reactions were carried out with 1 (1 mmol) and aniline (1 mmol) in 2 ml of solvent.
aYields of pure and isolated product.
SCHEME 1 Acetic acid-
mediated synthesis of
α-aminoketones
4-chloroaniline and 4-bromoaniline were carried out with
benzoin (1) under similar conditions, both the reactions
were completed in 30 min and delivered the products 2c
and 2d in 94% and 92% yields, respectively (Scheme 1).
When the 3-chloro aniline and 3-methoxy aniline were
subjected to reaction with benzoin (1) under standard

VANGA ET AL.
895
SCHEME 2 Designed synthetic
plan for the synthesis of penta-
substituted pyrroles
reaction conditions, the reactions underwent smoothly and
provided the respective products 2e and 2f in 93% and 97%
yields, respectively (Scheme 1). We also examined the reac-
tivity of disubstituted anilines using the current methodol-
ogy. The reaction of 4-bromo 2-methyl aniline under the
optimized reaction conditions gave the corresponding
product 2g in 87% yield. Similarly, the 3,5-dimethylaniline
and 4-methylaniline also provided the expected product 2h
and 2i in 90% and 94% yields, respectively (Scheme 1).
From a literature survey, it was very clear that these
α-amino ketones are very good precursors for the synthe-
sis of densely functionalized heterocyclic derivatives. So,
after synthesizing various substituted α-amino ketones,
we envisioned that these α-amino ketones could be
employed as substrates for the synthesis of penta-
substituted pyrroles. Accordingly, we designed a one-pot
synthetic strategy for the synthesis of penta-substituted
pyrroles from the readily available starting materials
(Scheme 2).
afford the respective products 3c and 3d in 83% and 81%
yields, respectively The meta-substituted anilines
(3-chloroaniline and 3-methoxyaniline) also reacted effi-
ciently and delivered the products 3e and 3f in 86%, and
88% yields, respectively.
Further, we explored the possibility of reactivity of
disubstituted anilines in the current protocol. The reac-
tions of 4-bromo,2-methylaniline and 3,5-dimethylaniline
with benzoin and diethyl acetylene dicarboxylate gave
their respective penta-substituted pyrroles 3g and 3h in
78% and 89% yield, respectively. The reaction of
4-methylaniline also underwent successfully and pro-
vided the product 3i in 87% isolated yield. All the prod-
ucts obtained were well characterized using modern
analytical techniques.
2.1 | Mechanism
We envisaged that the reaction of benzoin (1) with
aniline derivatives in acetic acid would provide the
α-amino ketones, which can be further reacted with
dialkyl acetylene dicarboxylates to provide the densely
functionalized pyrroles. According to the synthetic plan
demonstrated, a one-pot reaction, whose initial step was
the reaction of benzoin (1) with aniline in acetic acid at
110ꢀC for 30 min, gave the α-aminoketone. To this reac-
tion mixture at the same temperature, diethyl acetylene
dicarboxylate was added and the progress of the reaction
was monitored by TLC. The reaction was completed in
30 min, and after the usual work-up and purification by
column chromatography provided diethyl 1,4,5-triphe-
nyl-1H-pyrrole-2,3-dicarboxylate 3a in 91% yield
(Scheme 3).
The plausible reaction mechanism for one-pot synthesis
of penta-substituted pyrroles is shown in Scheme 4. The
initial reaction of benzoin with aniline in the presence of
acetic acid gave the α-aminoketone by dehydration. Thus
obtained α-aminoketone reacted in situ with diethyl acet-
ylene dicarboxylate, and the nitrogen atom of
α-aminoketone underwent Michael addition with diethyl
acetylene dicarboxylate, which in turn underwent intra-
molecular cyclization by reacting with the keto carbon.
The intermediate obtained further underwent aromatiza-
tion by the elimination of water molecule to give the
penta-substituted pyrrole diethyl 1,4,5-triphenyl-1H-pyr-
role-2,3-dicarboxylate (3a).
The one-pot synthetic strategy for the synthesis of
densely functionalized pyrroles was also extended to other
aniline derivatives. Different mono- and di-substituted ani-
line derivatives were allowed to react with benzoin (1) and
diethyl acetylene dicarboxylate under standard conditions;
the details are given in Scheme 3. The reaction of naph-
thylamine with benzoin (1) and diethyl acetylene
dicarboxylate in acetic acid provided the product 3b in
93% yield. When the para-substituted anilines such as
4-chloroaniline and 4-bromoaniline were subjected to the
one-pot reaction, the reactions underwent smoothly to
2.2 | Conclusion
In summary, a facile and efficient methodology was
developed for the synthesis of α-amino ketones from
readily available starting materials mediated by acetic
acid. The current protocol does not require any column
chromatography purification and provides the various
α-amino ketones in high yields. Further, these α-amino
ketones could be effectively exploited in the synthesis of
penta-substituted pyrroles by reacting them with diethyl
acetylene dicarboxylates. The methodology is simple,

896
VANGA ET AL.
SCHEME 3 Synthesis of densely functionalized pyrrole derivatives
easy to handle, and provides an easy access for the syn-
thesis of densely functionalized pyrroles in high yields.
characterized by 1H NMR using a Bruker AMX 400-MHz
NMR instrument using TMS as internal standard (δ in
ppm). 13C NMR was recorded at 100 MHz. The elemental
analysis was done on a Perkin-Elmer 2400 series instru-
ment. All the melting points were determined using the
Meltemp apparatus in open capillaries, and expressed
in ꢀC and are uncorrected.
3 | EXPERIMENTAL
All the chemicals were procured from Avra Chemicals
Pvt. Ltd., Hyderabad, India, and the reactions were moni-
tored by TLC using silica gel-G (Merck grade) as the
General procedure for synthesis of 2a–i: To a mix-
ture of benzoin (1) (1.0 mmol, 0.212 g) and aniline
(1.0 mmol, 0.093 g) was added 2 ml of acetic acid and
adsorbent.
The
synthesized
compounds
were

VANGA ET AL.
897
SCHEME 4 Plausible reaction mechanism for the one-pot synthesis of penta-substituted pyrroles
allowed to heat to 110ꢀC for 30 min. The progress of the
reaction was monitored by TLC. After completion of the
reaction as shown by TLC, the reaction mixture was
diluted with 5 mL of water and the precipitate thus
obtained was filtered and dried under vacuum to obtain
the product 1,2-diphenyl-2-(phenylamino)ethanone (2a)
in 96% yield.
General procedure for synthesis of 3a–i: To a mix-
ture of benzoin (1) (1.0 mmol, 0.212 g) and aniline
(1.0 mmol, 0.093 g) was added 2 mL of acetic acid and
allowed to heat to 110ꢀC for 30 min. The progress of the
reaction was monitored by TLC. After completion of the
reaction as shown by TLC, diethyl acetylene
dicarboxylate (1.0 mmol, 0.170 g) was added to the reac-
tion mixture, which was stirred at the same temperature
for more than 30 min. Then the reaction mixture was
diluted with 5 mL of water. The organic layer was sepa-
rated, washed with water (2 × 10 mL), dried over anhy-
drous Na2SO4, and concentrated under reduced pressure.
The purification of reaction mixture by silica gel column
chromatography using 5% ethyl acetate in hexanes as elu-
ent afforded the product diethyl 1,4,5-triphenyl-1H-pyr-
role-2,3-dicarboxylate (3a) in 91% yield.
(100 MHz, CDCl3): 13.90, 14.05, 60.74, 61.20, 122.71,
123.01, 123.10, 126.70, 127.72, 127.81, 127.92, 128.29,
128.38, 128.56, 129.94, 130.23, 131.13, 133.41, 136.79,
138.20, 160.04, 166.24; Anal. Calcd. for C28H25NO4: C,
76.52; H, 5.73; N, 3.19; O, 14.56; Found: C, 76.64; H,
5.61; N, 3.07.
Diethyl 1-(naphthalen-1-yl)-4,5-diphenyl-1H-pyr-
role-2,3-dicarboxylate (3b)
Yield: 93% as orange solid. m.p., 129–130ꢀC; IR
(cm−1) 1706, 1590, 1520; 1H NMR (400 MHz, CDCl3):
7.85–7.76 (m, 2H), 7.50–7.42 (m, 3H), 7.39–7.29 (m, 2H),
7.27–7.15 (m, 5H), 6.99–6.93 (m, 1H), 6.91–6.80 (m, 4H),
4.30 (q, J = 7.1 Hz, 2H), 3.98–3.84 (m, 2H), 1.24 (t,
J = 7.1 Hz, 3H), 0.82 (t, J = 7.1 Hz, 3H), 13C NMR
(125 MHz, CDCl3):13.50, 14.04, 60.38, 61.26122.75,
123.08, 123.43, 123.60, 124.63, 126.33, 126.68, 127.23,
127.60, 127.79, 127.95, 128.04, 128.93, 129.86, 130.19,
130.58, 131.78, 133.42, 135.19, 137.71, 159.53, 166.4; Anal.
Calcd. for C32H27NO4: C, 78.51; H, 5.56; N, 2.86; O, 13.07;
Found: C, 78.43; H, 5.63; N, 2.77.
Diethyl 1-(4-chlorophenyl)-4,5-diphenyl-1H-pyr-
role-2,3-dicarboxylate (3c)
Yield: 83%; yellow solid. m.p. 119–120ꢀC; IR: (cm−1
)
1
Diethyl 1,4,5-triphenyl-1H-pyrrole-2,3-dicarboxylate
(3a)
1710, 1545, 1520 , H NMR (400 MHz, CDCl3): 7.28–7.23
(m, 2H), 7.22–7.15 (m, 5H), 7.14–7.05 (m, 5H), 6.92–6.87
(m, 2H), 4.26 (q, J = 7.2 Hz, 2H), 4.16 (q, J = 7.2 Hz, 2H),
1.22 (t, J = 7.2 Hz, 3H), 1.18 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3):13.82, 13.95, 60.76, 61.16, 122.83,
123.22, 123.33, 126.75, 126.92, 127.88, 127.92, 128.49,
128.88, 129.19, 129.79, 131.01, 133.04, 133.81, 136.77,
Yield: 91%, yellow solid, m.p. 88–90ꢀC; IR: (cm–1)
1
1712, 1603, 1546; H NMR (400 MHz, CDCl3): 7.31–7.26
(m, 3H), 7.22–7.15 (m, 7H), 7.12–7.01 (m, 3H), 6.87–6.93
(m, 2H), 4.26 (q, J = 7.2 Hz, 2H), 4.14 (q, J = 7.2 Hz, 2H),
1.22 (t, J = 7.2 Hz, 3H), 1.13 (t, J = 7.2 Hz, 3H). 13C NMR

898
VANGA ET AL.
139.26, 159.69, 165.93; Anal. Calcd. for C28H24ClNO4: C,
70.96; H, 5.10; Cl, 7.48; N, 2.96; O, 13.50; Found: C,
70.99; H, 5.07; Cl, 7.39; N, 2.89.
Diethyl 1-(4-bromophenyl)-4,5-diphenyl-1H-pyr-
role-2,3-dicarboxylate (3d)
for C29H26BrNO4: C, 65.42; H, 4.92; Br, 15.01; N, 2.63; O,
12.02; Found: C, 65.55; H, 4.85; Br, 15.13; N, 2.52.
Diethyl 1-(3,5-dimethylphenyl)-4,5-diphenyl-1H-
pyrrole-2,3-dicarboxylate (3h)
Yield: 89%, m.p. 91–92ꢀC; IR (cm−1) 1712, 1603, 1546;
1H NMR (400 MHz, CDCl3): 7.22–7.15 (m, 5H), 7.12–7.01
(m, 3H), 6.94–6.88 (m, 3H), 6.77 (s, 2H), 4.24 (q,
J = 7.1 Hz, 2H), 4.15 (q, J = 7.1 Hz, 2H), 2.22 (s, 6H), 1.20
(t, J = 7.1 Hz, 3H), 1.14 (t, J = 7.1 Hz, 3H), 13C NMR
(400 MHz, CDCl3): 13.90, 14.03, 21.13, 60.71, 61.03,
121.97, 122.94, 123.65, 126.13, 126.58, 127.59, 127.68,
127.84, 129.91, 130.02, 130.40, 131.10, 133.62, 136.48,
137.85, 137.88, 160.26, 166.12; Anal. Calcd. for
C30H29NO4: C, 77.06; H, 6.25; N, 3.00; O, 13.69;
Found: C, 77.20; H, 6.14; N, 3.11.
Yield: 81%; m.p. 124–125ꢀC; IR (cm−1) 1711, 1551,
1491; 1H NMR (400 MHz, CDCl3): 7.40 (d, J = 8.8 Hz, 2H),
7.23–7.15 (m, 5H), 7.14–7.01 (m, 5H), 6.92–6.86 (m, 2H),
4.26 (q, J = 7.2 Hz, 2H), 4.16 (q, J = 7.2 Hz, 2H), 1.22 (t,
J = 6.8 Hz, 3H), 1.18 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3):13.86, 13.96, 60.75, 61.20, 122.21, 122.43,
123.12, 123.37, 126.75, 127.90, 127.94, 129.74, 130.10,
130.99, 131.52, 133.00, 136.84, 137.17, 159.70, 166.04; Anal.
Calcd. for C28H24BrNO4: C, 64.87; H, 4.67; Br, 15.41; N,
2.70; O, 12.35; Found: C, 64.94; H, 4.56; Br, 15.52; N, 2.61.
Diethyl 1-(3-chlorophenyl)-4,5-diphenyl-1H-pyr-
role-2,3-dicarboxylate (3e)
Diethyl
4,5-diphenyl-1-p-tolyl-1H-pyrrole-
2,3-dicarboxylate (3i)
Yield: 86%, m.p. 112–113ꢀC; IR (cm−1) 1712, 1542,
1522, 1H NMR (400 MHz, CDCl3): 7.31–7.36 (m, 1H),
7.24–7.15 (m, 7H), 7.14–7.02 (m, 4H), 6.91 (d, J = 7.0 Hz,
2H), 4.26 (q, J = 7.1 Hz, 2H), 4.16 (q, J = 7.1 Hz, 2H),
1.22 (t, J = 7.1 Hz, 3H), 1.16 (t, J = 7.1 Hz, 3H). 13C NMR
(100 MHz, CDCl3):13.82, 13.95, 60.76, 61.16, 122.83,
123.22, 123.33, 126.75, 126.92, 127.88, 127.92, 128.49,
128.88, 129.19, 129.79, 131.01, 133.04, 133.81, 136.77,
139.26, 159.69, 165.93; Anal. Calcd. For C28H24ClNO4: C,
70.96; H, 5.10; Cl, 7.48; N, 2.96; O, 13.50; Found: C,
70.91; H, 5.03; Cl, 7.54; N, 2.83.
Yield: 87%, yellow solid; m.p. 88–89ꢀC, IR (cm−1
)
1
1708, 1548, 1519; H NMR (400 MHz, CDCl3): 7.25–7.19
(m, 5H), 7.14–7.05 (m, 7H), 6.98–6.88 (m, 2H), 4.28 (q,
J = 7.2 Hz, 2H), 4.18 (q, J = 7.2 Hz, 2H), 2.34 (s, 3H), 1.24
(t, J = 7.1 Hz, 3H), 1.18 (t, J = 7.2 Hz, 3H). 13C NMR
(400 MHz, CDCl3):13.90, 14.02, 21.19, 60.67, 61.11,
122.49, 122.88, 123.04, 126.62, 127.61, 127.75, 127.86,
128.17, 129.00, 129.92, 130.29, 131.11, 133.46, 135.50,
136.81, 138.07, 160.05, 166.24; Anal. Calcd. for
C29H27NO4: C, 76.80; H, 6.00; N, 3.09; O, 14.11;
Found: C, 76.96; H, 5.94; N, 2.98.
Diethyl 1-(3-methoxyphenyl)-4,5-diphenyl-1H-pyr-
role-2,3-dicarboxylate (3f)
ACKNOWLEDGMENTS
Yield: 88%, yellow thick liquid. IR (cm−1) 1706, 1586,
1524; 1H NMR (400 MHz, CDCl3): 7.23–7.14 (m, 6H),
7.12–7.02 (m, 3H), 6.92 (d, J = 7.6 Hz, 2H), 6.86–6.76 (m,
2H), 6.69 (s, 1H), 4.25 (q, J = 7.2 Hz, 2H), 4.16 (q,
J = 7.2 Hz, 2H), 3.66 (s, 3H), 1.21 (t, J = 7.2 Hz, 3H), 1.15
(t, J = 7.2 Hz, 3H), 13C NMR (125 MHz, CDCl3):13.92,
14.04, 55.34, 60.79, 61.15, 114.23, 120.92, 122.42, 123.02,
123.29, 126.69, 127.75, 127.83, 127.90, 128.98, 129.96,
130.28, 131.02, 133.41, 136.56, 139.11, 159.41, 160.05,
166.13; Anal. Calcd. for C29H27NO5: C, 74.18; H, 5.80; N,
2.98; O, 17.04; Found: C, 74.26; H, 5.71; N, 2.88.
We thank Acharya Nagarjuna University, AP, India, for
constant support and providing laboratory facilities.
DATA AVAILABILITY STATEMENT
The data that supports the findings of this study are avail-
able in the supplementary material of this article
ORCID
Hari Babu Bollikolla https://orcid.org/0000-0003-1308-
391X
Diethyl 1-(4-bromo-2-methylphenyl)-4,5-diphenyl-
1H-pyrrole-2,3-dicarboxylate (3g)
REFERENCES
Yield: 78%, white solid; m.p. 126–127ꢀC; IR (cm−1)
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1710,
1596,
1534 cm−1;
1H
NMR
(400 MHz,
CDCl3):7.33–7.25 (m, 2H), 7.23–7.04 (m, 9H), 6.95–6.86
(m, 2H), 4.32–4.22 (m, 2H), 4.14 (q, J = 7.1 Hz, 2H), 1.95
(s, 3H), 1.22 (t, J = 7.1 Hz, 3H), 1.16 (t, J = 7.1 Hz, 3H),
13C NMR (400 MHz, CDCl3):13.90, 14.05, 17.56, 60.74,
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How to cite this article: Vanga SKR,
Bollikolla HB, Peruri VVS. Catalyst-free facile and
efficient one-pot synthesis of densely
functionalized pyrroles and α-amino ketones.
J Heterocyclic Chem. 2021;58:892–899. https://doi.
org/10.1002/jhet.4227
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