One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles catalyzed by [NMPH]CH3SO3

Article abstract of DOI:10.1016/j.tetlet.2019.151043

A general method for the synthesis of 1,2,3,4-tetrasubstituted pyrroles by [NMPH]CH₃SO₃ is reported. A full factorial design was performed in order to obtain a more robust and statistically correct optimum condition. The products were obtained in moderate to excellent yields. The developed methodology is very simple, cost-effective, and applicable for tri- and tetra-component reactions.

Full text of DOI:10.1016/j.tetlet.2019.151043

Tetrahedron Letters xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles
catalyzed by [NMPH]CH3SO3
Luana A. Pachechne a, Vinicius F. Pereira a, Guilherme M. Martins b, Edmar Martendal a, Fernando R. Xavier a,
Samuel R. Mendes a,
⇑
a SINCA – Departamento de Química, Universidade do Estado de Santa Catarina, 89219-719 Joinville, SC, Brazil
b Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
A general method for the synthesis of 1,2,3,4-tetrasubstituted pyrroles by [NMPH]CH3SO3 is reported. A
full factorial design was performed in order to obtain a more robust and statistically correct optimum
condition. The products were obtained in moderate to excellent yields. The developed methodology is
very simple, cost-effective, and applicable for tri- and tetra-component reactions.
Ó 2019 Elsevier Ltd. All rights reserved.
Received 3 July 2019
Revised 9 August 2019
Accepted 12 August 2019
Available online xxxx
Keywords:
Ionic Liquid
Multicomponent reaction
Pyrroles
Solventless
Introduction
These strategies can be achieved with several catalysts, such as
CeCl3 7H2O [19], NiCl2 6H2O [20], FeCl3 [21], KI [22], Yb(OTf)3
Ionic liquid (IL) is a low melting point salt with weakly coordi-
nated ions, being in liquid form at temperatures below 100 °C or
even at room temperature, and can be used as solvents and cata-
lysts in organic synthesis [1–3]. These salts offer many advantages,
such as thermal stability, non-volatility, and it can be easily
designed [4–7]. Protic ionic liquids (PILs) are a subset of ionic liq-
uids and have another advantage: they can be easily prepared
through proton transfer from a Brønsted acid to a base [8,9]. In this
sense, N-methyl-2-pyrrolidonium methyl sulfonate, [NMPH]CH3-
SO3, a Brønsted acidic ionic liquid, can be obtained by the stoichio-
metric neutralization reaction between methane sulfonic acid and
N-methyl-2-pyrrolydone [10]. [NMPH]CH3SO3 has been used in
several organic reactions, such as esterification processes [11], to
convert fructose into 5-hydroxymethylfurfural [12], synthesis of
imidazoles [13] and biodiesel [14,15].
[23], ionic liquids [24,25], Cu/C [26], hypervalent iodine [27], I2
[28,29], phosphazenes [30], Amberlyst-15 [31] or in a metal-free
condition [32–36]. Pyrrole derivatives are of great interest in the
field of chemical materials, with technological applications
[37,38], well as in pharmaceutical applications, such as precursors
of bioactive molecules [39,40]. Considering the sustainable chem-
istry, the study of new environmentally friendly synthetic routes
is extremely interesting for modern chemistry. Moreover, the
development of atom economy strategies and metal-free condi-
tions are of great industrial and pharmacological interest [41–44].
Our group has been developing studies focused on clean and
efficient strategies in organic synthesis for a long time [19,45–
48]. Thus, we decided to investigate the synthesis of pyrrole
derivatives via tri-component reaction (Scheme 1, path A) and
tetra-component reaction (Scheme 1, path B) using [NMPH]CH3SO3
as a catalyst, in a metal-free condition.
Additionally, pyrroles and their derivatives are important com-
pounds, being found in a wide variety of natural products [16].
Functionalized pyrroles are typically obtained by classical routes,
Results and discussion
such as the Knorr reaction (b-dicarbonyl with
a-aminoketone),
Paal-Knorr (amines with 1,4-diketone), Clauson-Kaas (2,5-
dimethoxytetrahydrofuran with primary amines), Hantzsch (b-
The limitations of the tri-component reaction were studied. It
was observed that, without the use of the catalyst, using aniline
(1.5 mmol), (E)-(2-nitrovinyl)benzene (1.0 mmol), pentane-2,4-
dione (1.0 mmol), at 75 °C for 2 h, the desired product was not
obtained. Thus, the proposition of the [NMPH]CH3SO3 catalyst for
this reaction is justified. In order to obtain a more robust and
ketoester,
a-haloketone and an amine), among others [17,18].
⇑
Corresponding author.
E-mail address: samuel.mendes@udesc.br (S.R. Mendes).
https://doi.org/10.1016/j.tetlet.2019.151043
0040-4039/Ó 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: L. A. Pachechne, V. F. Pereira, G. M. Martins et al., One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles cat-
alyzed by [NMPH]CH3SO3, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2019.151043

2
L.A. Pachechne et al. / Tetrahedron Letters xxx (xxxx) xxx
Scheme 1. Synthesis of pyrroles catalyzed by [NMPH]CH3SO3.
statistically correct optimum condition, we decided to perform a
full factorial design, whose variables and levels as well as the
answers are shown in Table 1.
Further information about the design can be found in the sup-
plementary materials. Fig. 1, named Pareto chart, indicates that
all variables and their secondary interactions are significant, except
for the ones between temperature and mass of aniline (1 Â 3), time
and mass of aniline (3 Â 4) and catalyst mass and reaction time
(2 Â 4). Information on model validation and how the interpreta-
tion of effects should be conducted are contained in the supple-
mentary material. In Fig. 1, it can also be observed that the
curvature parameter was also significant. This means that one or
more variables may not behave linearly between the chosen lower
and upper levels.
These effects are best visualized by the estimates of response
surfaces generated by the data (Fig. 2). An optimum temperature
range between 75 and 90 °C and a catalyst mass between 30 and
150 mg (Fig 2A) is observed, with a slight tendency towards
30 mg. There is weak evidence of interaction between the mass
of catalyst and temperature of reaction in this range. A significant
interaction can be attributed when the optimum of a variable is a
function of the value of another variable. For instance, at a temper-
ature of 75 °C, the optimum mass of catalyst is 30 mg. Contrarily, at
a temperature of 125 °C, the optimum mass of catalyst is 150 mg.
Fig. 1. Pareto chart of standardized effects generated by the data obtained in the
full factorial design. Effects surpassing the vertical dashed line are considered
statistically larger compared to experimental error at 95% confidence level.
This analysis corroborates the significant 1 Â 2 interaction shown
in the Pareto chart. In the interaction between the temperature
of reaction and the amount of aniline, an optimum response can
be observed when aniline is in the highest evaluated amount,
and temperature in the range of 75–90 °C. The reaction behavior
with respect to excess aniline was already expected, as reported
by Maiti et al. [21] There is no evidence of interaction between
the variables, confirming the result of the non-significant 1 Â 3
interaction in the Pareto chart. The time of reaction was not signif-
icant in the range of 30–90 min at 75–90 °C (Fig 2B).
On the other hand, at higher temperatures, for example 125 °C,
even with 90 min, the reaction is not finished. The formation of
some intermediate may be disadvantageous at elevated tempera-
tures, or the deprotonation of the catalyst (consequently the
Table 1
Combination of the four relevant factors, their levels and the response obtained for each experiment in the full factorial design carried out in this study.a
O
Ph
Me
Me
Ph
O
O
NH2
Ph
[NMPH]CH3SO3
+
+
Me
Me
N
Ph
NO2
Entry
Temperature
(°C)
Catalyst
(mg)
Aniline
(mmol)
Time
(min)
Yield
(%)b
1
2
3
4
5
6
7
8
75
75
75
75
75
75
75
75
100
100
125
125
125
125
125
125
100
125
125
30
1.00
1.50
1.50
1.00
1.00
1.50
1.00
1.50
1.25
1.25
1.50
1.50
1.00
1.00
1.00
1.00
1.25
1.50
1.50
30
30
90
30
90
30
90
90
60
60
30
90
30
90
30
90
60
30
90
86
90
87
24
93
100
31
100
83
85
64
100
52
83
16
55
85
81
100
150
150
150
30
30
150
30
90
90
30
30
9
10
11
12
13
14
15
16
17
18
19
30
30
150
150
90
150
150
a
The reactions were performed using aniline (4thcolumn), b-nitrostyrene (1.0 mmol), 1,3-dicarbonyl compounds (1.0 mmol), [NMPH]CH3SO3 (3rd column), at temperature
(2nd column) and stirred for time (5th column).
b
Conversion by 1H NMR.
Please cite this article as: L. A. Pachechne, V. F. Pereira, G. M. Martins et al., One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles cat-
alyzed by [NMPH]CH3SO3, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2019.151043

L.A. Pachechne et al. / Tetrahedron Letters xxx (xxxx) xxx
3
Fig. 2. Response surfaces generated by the full-factorial experimental design applied in this study to evaluate four variables. Each response surface was plotted with the other
two variables in their optimal value: catalyst mass at 30 mg, time of reaction at 30 min, temperature of reaction at 75 °C and 1.5 mmol of aniline. Response surface for aniline
versus temperature can be found in supplementary material.
protonation of the aniline) can be favored at high temperatures,
which is suggested to be the cause of delay in the reaction pro-
gress. Again, it is verified that the optimal value of a variable is a
function of the value of another variable, which justifies the signif-
icant interaction between temperature and time of reaction
(1 Â 4), as shown in the Pareto chart. In Fig. 2C, it can be verified
that the catalyst range of 30–150 mg can be used only when ani-
line is at its maximum level of 1.5 mmol. When aniline is at its
minimum level, a smaller amount of catalyst should be used, but
even in that condition the yield is not maximized. This strong
interaction is due to the acidic character of the catalyst, which
may protonate the aniline and slows the reaction progress. This
is the strongest interaction observed in this study (2 Â 3, see Fig
1), with an effect that could only be assessed through multivariate
design, in which combinations between variables are evaluated
simultaneously.
The interaction between the time of reaction and the aniline
amount can be observed in Fig. 2D, in which it is verified that
the optimum condition occurs in any time interval of 30–90 min,
but only when aniline is in its level at 1.5 mmol. When aniline is
at the 1 mmol-level, at least 90 min of reaction time is required.
It is suggested, therefore, that the aniline should be involved in
the slow reaction step, since its quantity influences the time
required for the reaction to be completed. Finally, the optimal con-
dition attributed to the reaction is: aniline (1.5 mmol), (E)-(2-nitro-
vinyl)benzene (1.0 mmol), pentane-2,4-dione (1.0 mmol), 30 mg of
[NMPH]CH3SO3, at 75 °C, under magnetic stirring for 30 min.
Thus, in order to explore the scope and the limitations of this
synthetic method, the protocol was extended to other examples
(Scheme 2). The corresponding pyrroles were obtained from differ-
ent b-nitrostyrenes, noting that this protocol tolerates a variety of
aromatic nitrostyrenes containing electron-donating and electron-
withdrawing substituents. Methyl and chloride groups as sub-
stituents provided the corresponding products with good to excel-
lent yields (4b, 4c respectively). However, a lower yield (4d, 44%)
was observed in the case of the aliphatic b-nitrostyrene. The use
of a b-ketoester as the 1,3-dicarbonyl component further extended
the scope of this methodology, and the corresponding product was
obtained in good yield (4e, 81%). Different amines were employed
as well, and the products were obtained in good yields (4f–k), with
exception of 4i from o-Methylaniline, and 4j and 4k from benzylic
and aliphatic amine, respectively. Unfortunately, the catalyst can-
not be recovered at the end of reactions due to the small amount
employed.
Subsequently, we directed our attention to the tetra-component
reactions, from aldehydes (Scheme 3). At first, the reaction condi-
tions employed were the same as those of the reactions from b-
nitrostyrenes. Then, we performed the tetra-component reaction
with benzaldehyde (1.0 mmol), nitromethane (1.0 mL), aniline
(1.5 mmol) and acetylacetone (1.0 mmol). After 30 min under stir-
ring at 75 °C the product 4a was obtained in 87% yield. Encouraged
by this result, we decided to use these reaction conditions also for
tetra-component reactions. The scope of the tetra-component reac-
tion was expanded using other aldehydes and amines (Scheme 3).
Please cite this article as: L. A. Pachechne, V. F. Pereira, G. M. Martins et al., One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles cat-
alyzed by [NMPH]CH3SO3, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2019.151043

4
L.A. Pachechne et al. / Tetrahedron Letters xxx (xxxx) xxx
O
O
R1
R1
Me
Me
R2
R1
O
O
O
O
O
NH2
R2
NH2
R3
[NMPH]CH3SO3
75 °C, 30 min a
[NMPH]CH3SO3
75 °C, 30 min a
CH3NO2
+
Me
+
+
+
+
R1
H
Me
Me
Me
R2
N
N
NO2
R2
R3
________________________________________________________________
________________________________________________________________
Cl
Cl
Me
O
O
O
O
O
O
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
N
N
N
N
N
4c
4f
, 75%
, 83%
4a
, 87%
N
N
N
4a
, 92%
4b
4c
, 82%
, 85%
OMe
O
O
Me
Me
O
Me
Me
O
O
Me
Me
OEt
Me
Me
Me
N
N
4h
, 71%
b
4k
, 69%
N
b
b
4d
, 44%
4e
, 81%
4f
, 94%
NO2
OMe
O
Scheme 3. Synthesis of 1,2,3,4-tetrasubstituted pyrroles from tetra component
reaction. Conditions: The reactions were performed using aldehyde(1.0 mmol),
a
O
O
nitromethane (1.0 mL), acetylacetone(1.0 mmol), amine (1.5 mmol), and [NMPH]
Me
Me
Me
Me
Me
b
CH3SO3 (30 mg), at 75 °C for 30 min. The reaction was performed using aldehyde
(1.3 mmol), nitromethane (1.0 mL), acetylacetone (1.0 mmol), butylamine
(1.0 mmol), and [NMPH]CH3SO3 (30 mg), at 75 °C for 30 min.
Me
Me
N
N
N
4g
, 91%
4h
, 78%
4i
, 62%
Acknowledgments
NO2
Cl
O
O
This study was financed in part by the Coordenação de Aper-
feiçoamento de Pessoal de Nível Superior - Brasil (CAPES) – Finance
Code 001. CNPq, UDESC, FAPESC, FINEP and FITEJ are thanked for
financial support. S.R.M. would like to acknowledge CNPq for fund-
ing, protocol 431391/2016-5.
Me
Me
Me
Me
N
N
4j
, 41%
4k
, 36%
Scheme 2. Synthesis of 1,2,3,4-tetrasubstituted pyrroles catalyzed by [NMPH]CH3-
a
Appendix A. Supplementary data
SO3. Conditions:
The reactions were performed using aniline (1.5 mmol), b-
nitrostyrene (1.0 mmol), 1,3-dicarbonyl compounds (1.0 mmol), 30 mg of [NMPH]
b
CH3SO3, at 75 °C and stirred for 30 min. Reaction time: 2 h.
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tetlet.2019.151043.
Good to excellent yields were obtained for the products from
tetra-component reaction. However, it was observed that the
NO2-deactivated aniline provided lower reaction yield (4h, 71%)
compared to aniline (4a, 87%). However, when the reaction was
performed with butylamine, 4k was obtained in 69%, a better yield
compared to the three-component reaction.
References
[1] P. Wasserscheid, J. Joni, in: Handbook of Green Chemistry, Wiley-VCH Verlag
GmbH & Co. KGaA, Weinheim, Germany, 2010, p. 41.
[2] D. Zhao, M. Wu, Y. Kou, E. Min, Catal. Today 74 (2002) 157–189.
[3] Z.S. Qureshi, K.M. Deshmukh, B.M. Bhanage, Clean Technol. Environ. Policy. 16
(2014) 1487–1513.
Mechanism studies in analogous transformations for the syn-
thesis of pyrrole derivatives have already been widely discussed
[21,49]. Under the conditions studied here, the need for a promoter
was observed. [NMPH]CH3SO3 acts as a facilitator, being able to
activate the 1,3-dicarbonyl substrate functionalities, providing
imine and b-aminocarbonyl intermediates. The promoter facili-
tates the Michael addition to nitrostyrene, with subsequent
intramolecular cyclization and aromatization (by elimination reac-
tion) leading to the pyrrole.
[4] N.V. Plechkova, K.R. Seddon, in: Methods and Reagents for Green Chemistry:
An Introduction, John Wiley & Sons Inc, Hoboken, NJ, USA, 2007, pp. 103–130.
[5] M.J. Earle, K.R. Seddon, Pure Appl. Chem. 72 (2000) 1391–1398.
[6] V. Le Boulaire, R. Grée, Chem. Commun. (2000) 2195–2196.
[7] J. Dupont, R.F. de Souza, P.A.Z. Suarez, Chem. Rev. 102 (2002) 3667–3692.
[8] T.L. Greaves, C.J. Drummond, Chem. Rev. 108 (2008) 206–237.
[9] T.L. Greaves, C.J. Drummond, Chem. Rev. 115 (2015) 11379–11448.
[10] M. Imteyaz Alam, S. De, S. Dutta, B. Saha, RSC Adv. 2 (2012) 6890–6896.
[11] H. Zhang, F. Xu, X. Zhou, G. Zhang, C. Wang, Green Chem. 9 (2007) 1208–1211.
[12] J. Zhang, X. Yu, F. Zou, Y. Zhong, N. Du, X. Huang, ACS Sustain Chem Eng. 3
(2015) 3338–3345.
[13] H.R. Shaterian, M. Ranjbar, J. Mol. Liq. 160 (2011) 40–49.
[14] L. Zhang, M. Xian, Y. He, L. Li, J. Yang, S. Yu, X. Xu, Bioresour. Technol. 100
(2009) 4368–4373.
[15] F.G. Zanin, A. Macedo, M.V.L.R. Archilha, E.P. Wendler, A.A. Dos Santos,
Bioresour. Technol. 143 (2013) 126–130.
Conclusion
[16] C.T. Walsh, S. Garneau-Tsodikova, A.R. Howard-Jones, Nat. Prod. Rep. 23 (2006)
517.
[17] E. Baltazzi, L.I. Krimen, Chem. Rev. 63 (1963) 511–556.
[18] M.A. Yurovskaya, R.S. Alekseyev, Chem. Heterocycl. Compd. 49 (2014) 1400–
1425.
[19] C.C. Silveira, S.R. Mendes, G.M. Martins, S.C. Schlösser, T.S. Kaufman,
Tetrahedron 69 (2013) 9076–9085.
[20] A.T. Khan, M. Lal, P. Ray Bagdi, R. Sidick Basha, P. Saravanan, S. Patra,
Tetrahedron Lett. 53 (2012) 4145–4150.
In conclusion, N-methyl-2-pyrrolidonium methyl sulfonate,
[NMPH]CH3SO3, proved to be an effective catalyst for synthesis of
1,2,3,4-tetrasubstituted pyrroles. Tri and tetra-component reac-
tions provided products in moderate to excellent yields with high
atomic economy. The significant advantages offered by this
method are simple operation, good cost effectiveness, and applica-
ble for tri and tetra-component reactions.
Please cite this article as: L. A. Pachechne, V. F. Pereira, G. M. Martins et al., One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles cat-
alyzed by [NMPH]CH3SO3, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2019.151043

L.A. Pachechne et al. / Tetrahedron Letters xxx (xxxx) xxx
5
[21] S. Maiti, S. Biswas, U. Jana, J. Org. Chem. 75 (2010) 1674–1683.
[22] J. Wu, X. Chen, Y. Xie, Y. Guo, Q. Zhang, G.-J. Deng, J. Org. Chem. 82 (2017)
5743–5750.
[23] G.R. Reddy, T.R. Reddy, S.C. Joseph, K.S. Reddy, C.L.T. Meda, A. Kandale, D.
Rambabu, G.R. Krishna, C.M. Reddy, K.V.L. Parsa, K.S. Kumar, M. Pal, RSC Adv. 2
(2012) 9142–9150.
[24] Y. Luo, B.-Q. Zhang, Y.-H. He, Z. Guan, Zeitschrift für Naturforsch B 70 (2015)
29–38.
[25] H.M. Meshram, B. Madhu Babu, G. Santosh Kumar, P.B. Thakur, V.M. Bangade,
Tetrahedron Lett. 54 (2013) 2296–2302.
[26] N. Yasukawa, M. Kuwata, T. Imai, Y. Monguchi, H. Sajiki, Y. Sawama, Green
Chem. 20 (2018) 4409–4413.
[27] N.C. Jadhav, P.B. Jagadhane, H.V. Patile, V.N. Telvekar, Tetrahedron Lett. 54
(2013) 3019–3021.
[28] J. Chen, D. Chang, F. Xiao, G.-J. Deng, J. Org. Chem. 84 (2019) 568–578.
[29] G.R. Reddy, T.R. Reddy, S.C. Joseph, K.S. Reddy, M. Pal, RSC Adv. 2 (2012) 3387.
[30] F. Palacios, C. Alonso, D. Aparicio, G. Rubiales, J.M. de los Santos, Tetrahedron
63 (2007) 523–575.
[31] P. Radha Krishna Murthi, D. Rambabu, M.V. Basaveswara Rao, M. Pal,
Tetrahedron Lett. 55 (2014) 507–509.
[37] S.J. Evenson, M.J. Mumm, K.I. Pokhodnya, S.C. Rasmussen, Macromolecules 44
(2011) 835–841.
[38] H. Wu, Y. Wang, X. Qiao, D. Wang, X. Yang, H. Li, Chem. Mater. 30 (2018) 6992–
6997.
[39] J.B. Bharate, S. Singh, A. Wani, S. Sharma, P. Joshi, I.A. Khan, A. Kumar, R.A.
Vishwakarma, S.B. Bharate, Org. Biomol. Chem. 13 (2015) 5424–5431.
[40] T.V. Baiju, R.G. Almeida, S.T. Sivanandan, C.A. de Simone, L.M. Brito, B.C.
Cavalcanti, C. Pessoa, I.N.N. Namboothiri, E.N. da Silva Júnior, Eur. J. Med.
Chem. 151 (2018) 686–704.
[41] D. Tzankova, S. Vladimirova, L. Peikova, M. Georgieva, J. Chem. Technol. Metall.
53 (2018) 451–464.
[42] R. Kaur, S.K. Manjal, R.K. Rawal, K. Kumar, J. Pharm. Chem. Chem. Sci. 1 (2017)
17–32.
[43] G.R. Reddy, T.R. Reddy, S.C. Joseph, K.S. Reddy, L.S. Reddy, P.M. Kumar, G.R.
Krishna, C.M. Reddy, D. Rambabu, R. Kapavarapu, C. Lakshmi, T. Meda, K.K.
Priya, K.V.L. Parsa, M. Pal, Chem. Commun. 47 (2011) 7779.
[44] T. Bhaskar Kumar, C. Sumanth, S. Vaishaly, M. Srinivasa Rao, K.B. Chandra
Sekhar, C.L.T. Meda, A. Kandale, D. Rambabu, G. Rama Krishna, C. Malla Reddy,
K. Shiva Kumar, K.V.L. Parsa, M. Pal, Bioorg. Med. Chem. Lett. 22 (2012) 5639–
5647.
[32] D. Zhao, Y. Zhu, S. Guo, W. Chen, G. Zhang, Y. Yu, Tetrahedron 73 (2017) 2872–
2877.
[45] E. Zimmermann, S. Thurow, C. Freitas, S. Mendes, G. Perin, D. Alves, R. Jacob, E.
Lenardão, Molecules 18 (2013) 4081–4090.
[33] A. Kumar, R. Ramanand, N. Tadigoppula, Green Chem. 19 (2017) 5385–5389.
[34] T.V. Kumar, C.R.K. Rao, K. Mukkanti, P.S. Mainkar, Asian J. Chem. 27 (2015)
1457–1461.
[35] M. Hassani, M.R. Naimi-Jamal, L. Panahi, ChemistrySelect. 3 (2018) 666–672.
[36] X. Lin, Z. Mao, X. Dai, P. Lu, Y. Wang, Chem. Commun. 47 (2011) 6620.
[46] S.R. Mendes, S. Thurow, M.P. Fortes, F. Penteado, E.J. Lenardão, D. Alves, G.
Perin, R.G. Jacob, Tetrahedron Lett. 53 (2012) 5402–5406.
[47] G.M. Martins, T. Puccinelli, R.A. Gariani, F.R. Xavier, C.C. Silveira, S.R. Mendes,
Tetrahedron Lett. 58 (2017) 1969–1972.
[48] C. Silveira, C.P. Fortes, M.R. Mendes, S. Curr, Org Chem. 16 (2012) 1540–1548.
[49] H. Saeidian, M. Abdoli, R. Salimi, C. R. Chim. 16 (2013) 1063–1070.
Please cite this article as: L. A. Pachechne, V. F. Pereira, G. M. Martins et al., One-pot multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles cat-
alyzed by [NMPH]CH3SO3, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2019.151043