tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine and aldehydes at room temperature

Article abstract of DOI:10.1016/j.tetlet.2020.151735

A simple and efficient method is demonstrated for the synthesis of benzimidazoles via cyclocondensation of o-phenylenediamine with aldehydes in the presence of catalytic amount of tert-butyl nitrite. All the reactions were carried out at room temperature while the desired products were obtained in good to excellent yields.

Full text of DOI:10.1016/j.tetlet.2020.151735

Tetrahedron Letters xxx (xxxx) xxx
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
tert-Butyl nitrite catalyzed synthesis of benzimidazoles from
o-phenylenediamine and aldehydes at room temperature
Sadaf Azeez a, Popuri Sureshbabu a, Priyanka Chaudhary a, Shahulhameed Sabiah b,
Jeyakumar Kandasamy a,
⇑
a Department of Chemistry, Indian Institute of Technology (BHU), Varanasi, Uttar Pradesh 221005, India
b Department of Chemistry, Pondicherry University, Pondicherry 605014, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A simple and efficient method is demonstrated for the synthesis of benzimidazoles via cyclocondensation
of o-phenylenediamine with aldehydes in the presence of catalytic amount of tert-butyl nitrite. All the
reactions were carried out at room temperature while the desired products were obtained in good to
excellent yields.
Received 8 January 2020
Revised 4 February 2020
Accepted 11 February 2020
Available online xxxx
Ó 2020 Elsevier Ltd. All rights reserved.
Keywords:
tert-Butyl nitrite
Catalyst
Benzimidazoles
o-Phenylenediamine
COOH
Introduction
O
N
N
N
S
N
Benzimidazole motifs are present in many drugs, bioactive
molecules and natural products [1]. For instance, benzimidazole
derivatives are active pharmacophores which display anti-viral,
anti-microbial, anti-cancer, anti-ulcer and anti-inflammatory prop-
erties (Fig. 1) [1a,2]. On the other hand, benzimidazole derivatives
are well-used in synthetic organic chemistry as building blocks and
ligands [3]. Moreover, benzimidazole based materials and poly-
mers displayed promising applications in different fields, including
optical sensing, energy storage, LED, dyes, etc. [4]. Owing to their
biological and chemical significance, the synthesis of benzimida-
zole derivatives has gained continuous interest in organic chem-
istry [5]. Synthesis of benzimidazoles has been typically achieved
by the condensation of o-phenylenediamine with carbonyl com-
pounds in the presence of different reagents and oxidants
[5g,5m–r]. However, most of the reported methods uses metal
catalysts [5k,l,p,q], stoichiometric amount of oxidants [5h],
higher reaction temperature [5r], etc. In general, organocatalytic
methods are attractive in organic synthesis due to their efficiency
and selectivity [6].
Cl
N
H
MeO
N
O
Bendamistine
(Anti-cancer)
Omeprazole
(Anti-ulcer)
Cl
O
O
S
N
F
O
N
O
NH
NH2
N
H
N
O
Enviradine
(Antiviral)
Flubendazole
(Antimicrobial)
Fig. 1. Pharmacological activities of benzimidazole derivatives.
ical initiator, oxidant, etc. [8]. Over the last few years, our research
work is focused on the chemistry of N-nitrosamines [9] and we
have reported TBN mediated solvent-free synthesis of N-nitrosami-
nes [9a], radical dimerization of thiobenzamide [9f],
transamidation of secondary amides [9e], and nitration of N-alkyl
anilines [9b]. Recently, we have reported the synthesis of
benzotriazoles from o-phenylenediamine using tert-butyl nitrite
[9g]. This method provides excellent yields of benzotriazoles
under neutral conditions while several acid labile functional
groups were found to be stable. In continuation of this work,
tert-Butyl nitrite (TBN) is metal-free multi-tasking reagent
extensively used in various organic transformations [7]. Besides
diazotization and nitration, tert-butyl nitrite has been used as rad-
⇑
Corresponding author.
E-mail address: jeyakumar.chy@iitbhu.ac.in (J. Kandasamy).
https://doi.org/10.1016/j.tetlet.2020.151735
0040-4039/Ó 2020 Elsevier Ltd. All rights reserved.
Please cite this article as: S. Azeez, P. Sureshbabu, P. Chaudhary et al., tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine
and aldehydes at room temperature, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151735

2
S. Azeez et al. / Tetrahedron Letters xxx (xxxx) xxx
here we report TBN catalysed transformation of o-
phenylenediamines into benzimidazoles in the presence of
aldehydes at room temperature (Scheme 1).
condensation in the presence of tert-butyl nitrite (TBN) at room
temperature (Table 1). The reaction was performed with one equiv.
of tert-butyl nitrite in different solvents including dichloro-
methane, acetonitrile, toluene, 1,4-dioxane, methanol, THF, DMF
and DMSO (Table 1, entries 1–8). Among these solvents, the reac-
tion proceeded well in THF by providing the desired product 2-
(4-chlorophenyl) benzimidazole (3a) in 80% yield in 30 mins
(Table 1, entry 6). On the other hand, other solvents provided a
mixture of products containing 1,2-substituted benzimidazole (I)
and benzotriazole (II) in considerable yields. Also, in some solvents
(e.g. DCM, toluene, etc.) the starting materials were remaining un-
reacted. Nevertheless, only a minimum amount of these side prod-
ucts were obtained in THF while compared with other solvents.
Hence, the optimization was carried out in THF by varying the
amount of TBN. The formation of benzotriazole (II) was observed
in high amount when the reaction with 2.0 equiv. of TBN (Table 1,
entry 9). Therefore, the reaction was performed with catalytic
amount of TBN (i.e. 50 mol% to 10 mol%) in THF.
Results and discussion
At the outset, o-phenylenediamine (1a) and 4-chlorobenzalde-
hyde (2a) was chosen as model substrates and subjected to the
O
Our Previous work
O
N
N
(2.0 equiv.)
R1
N
AcCN, 2 h, rt
N
H
NH2
NH2
R1
(30 mol%)
Although
a decrease in benzotriazole (II) formation was
O
O
R1 = EWG/EDG
N
observed with catalytic amount of TBN, the yield of the desired
product was also dropped significantly (Table 1, entries 10–12).
It is also important to note that the 3a was not observed in the
absence of TBN (Table 1, entry 13). Considering the previous report
on TBN mediated thiol oxidation [8d], we performed the
condensation reaction with molecular oxygen (i.e. with oxygen
balloon) in the presence of 50 mol% and 30 mol% of TBN
(Table 1, entries 14 and 15). To our delight, the benzimidazole 3a
N
O2
R1
R
N
H
R
CHO
This work
THF, 2 h, rt
Scheme 1. Synthesis of benzimidazoles.
Table1
Optimization study.a
Cl
CHO
H
N
N
NH2
NH2
NO
N
N
+
Cl
Cl
+
N
H
N
Solvent
N
I
Cl
2a
II
3a
1a
S. No
‘NO’ Source
Mol%
Additives
Solvent
Time (hr)
Yield %b
3a
I
II
1
2
3
4
5
6
7
8
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
TBN
100
100
100
100
100
100
100
100
200
50
30
10
00
50
30
30
30
100
–
–
–
–
–
–
–
–
–
–
–
–
DCMc
CH3CN
Tolunec
1-4 dioxane
MeOH
THF
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1.0
2.0
2.0
2.0
2.0
2.0
2.0
26
22
17
46
77
80
65
62
67
65
59
40
<5
90
90
Trace
83
17
24
23
10
20
<5
5
12
12
<10
<5
<5
<5
<5
<5
<5
Trace
<5
Trace
20
47
16
15
14
10
14
17
21
<5
<5
<5
nr
<5
<5
<10
<5
DMF
DMSO
THF
9
10
11
12
13
14
15
16
17
18
THFc
THFc
THFc
–
THFc
O2
O2
O2
O2
O2
THFc
THF
NOBF4
Isoamyl Nitrite
CF3SO3H
THFc
THF
THFc
Trace
a
b
c
Reaction conditions: Substrate 1a & 2a (1 mmol) and NO-source stirred in appropriate solvents (5 mL) at room temperature.
Isolated yield.
Imine was reminded in the reaction.
Please cite this article as: S. Azeez, P. Sureshbabu, P. Chaudhary et al., tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine
and aldehydes at room temperature, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151735

S. Azeez et al. / Tetrahedron Letters xxx (xxxx) xxx
3
Table 2
Scope of aryl aldehydes.a,b
O
O
N
CHO
N
NH2
NH2
(30 mol%)
O2
N
H
3b-r
R
N
R
N
THF, RT, 2 h
1a
2b-r
N
N
Me
OMe
N
H
N
H
N
H
N
H
3b:
3c:
3d:
3e:
75%
89%
79%
88%
89%
71%
90%
88%
78%
N
N
N
N
NO2
CN
CF3
Br
N
H
N
H
N
H
N
H
3f:
3g:
3h:
3i:
86%
Me
N
N
N
N
F
N
H
N
H
N
H
N
H
NO2
Br
3j:
3k:
3l:
3m:
85%
84%
Cl
Cl
N
N
N
N
N
Cl
S
N
H
N
H
O
N
H
N
H
N
H
3n:
3o:
3p:
3q:
3r:
87%
85%
74%
77%
75%
a
Reaction conditions: Substrate 1a & 2 (1 mmol) and TBN (30 mol%) in THF (5 mL) for 2 h at room temperature.
Isolated yield.
b
was obtained in 90% yield under both the reaction conditions
within 2 h at room temperature.
yields under the optimized conditions (Table 2, 3f-3j). Further-
more, meta-substituted benzaldehydes (3-Br and 3-NO2), sterically
hindered ortho-substituted benzaldehydes (2-Me, 2-Cl and 2,4-di-
Cl) as well as 2-naphthyl aldehyde also participated in the conden-
sation reaction efficiently in the presence of TBN and provided the
desired products in good to excellent yields (Table 2, 3k-3p). Over-
all, it was observed that the reaction proceeds smoothly irrespec-
tive of functional groups at the ortho, para and meta-positions of
the aryl aldehydes. Similar to aryl aldehydes, to our delight hetero-
cyclic aldehydes such as 2-furaldehyde and 3-thiophene aldehyde
also gave the corresponding benzimidazoles 3q and 3r in 75–77%
yields (Table 2, 3q-3r).
After exploring the scope of different aldehydes, a wide range of
functionalized o-phenelenediamines was subjected to the conden-
sation reaction with 4-chlorobenzaldehyde under optimized reac-
tion conditions (Table 3). To our delight, o-phenylenediamines
bearing electron donating groups (e.g. methyl, tert-butyl) and
withdrawing groups (e.g. halogens, nitro, trifluoromethane, car-
bonyl, etc.) underwent cyclization smoothly. These reactions pro-
vided the corresponding benzimidazoles in 82–89% yields within
2 h at room temperature (Table 3, 4a-4g). In addition, o-phenelene-
diamines bearing di-substitutions (i.e. 4,5-di-Me, 3,5-di-Me, 3,4-
di-Me and 4,5-di-Cl) also participated efficiently in the reaction
to provide the desired benzimidazoles in 86–89% yields
(Table 3,4h-4k).
Furthermore, the condensation reaction was carried out with
other nitrosating agents such as nitrosonium tetrafluoroborate
(NOBF4) and isoamylnitrite in the presence of oxygen. The product
3a was not observed with NOBF4 while isoamyl nitrite gave the
benzimidazole 3a in 83% yield (Table 1, entry 16 and 17). In addi-
tion, to understand the involvement of acid in the reaction, we
have attempted the reaction in the presence of CF3SO3H (instead
of TBN) under oxygen atmosphere. However, the product 3a was
obtained only in 17% yield (Table 1, entry 18). Overall, the opti-
mization study indicates that a catalytic amount of TBN (i.e.
30 mol %) in the presence of oxygen is sufficient for the efficient
preparation of benzimidazoles from o-phenylenediamines and aryl
aldehydes.
With optimized conditions in hand, the scope of different aryl
aldehydes was investigated for the preparation of benzimidazoles
(Table 2). Initially, o-phenelenediamine was subjected to the con-
densation reaction with un-substituted as well as electron donat-
ing groups substituted benzaldehydes in the presence of 30 mol%
TBN. All these reactions underwent smoothly to provide the
desired products 3b-3e in 71–79% yield. On the other hand, con-
densation of o-phenelenediamine with electron withdrawing
group functionalized benzaldehydes (e.g. 4-NO2, 4-CN, 4-CF3, 4-F
and 4-Br) provided corresponding benzimidazoles in 84–90%
Please cite this article as: S. Azeez, P. Sureshbabu, P. Chaudhary et al., tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine
and aldehydes at room temperature, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151735

4
S. Azeez et al. / Tetrahedron Letters xxx (xxxx) xxx
Table 3
Scope of o-phenelenediamines.a,b
O
O
N
CHO
NH2
NH2
N
(30 mol%)
O2
Cl
N
H
R
R
THF, RT, 2 h
Cl
2a
1b-1l
4a-4k
N
N
N
Cl
Cl
Cl
Cl
Cl
N
H
N
H
N
H
F3C
4a
4b
4e
4c
: 89%
: 87%
: 85%
N
N
N
Cl
N
H
N
H
N
H
Br
Cl
F
4d
4f
: 85%
: 83%
: 82%
O
N
N
N
Ph
Cl
Cl
Cl
Cl
Cl
N
H
N
H
N
H
: 87%
4g
4h
4k
4i
: 89%
: 85%
Cl
Cl
N
N
N
H
: 86%
N
H
4j
: 88%
a
Reaction conditions: Substrate 1b-1 l & 2a (1 mmol) and TBN (30 mol%) in THF (5 mL) for 2 h at room temperature.
Isolated yield.
b
Table 4
the reaction was carried out with 2.0 equiv. of aliphatic aldehydes
which provided the 1,2-disubstituted benzimidazoles 5a-5c in 86–
88% yields.
Scope of aliphatic aldehydes.a,b
O
O
N
A plausible mechanism for the reaction is depicted in Scheme 2.
In the first step, o-phenylenediamine will react with benzaldehyde
to form the imine intermediate (A). tert-Butyl nitrite (TBN) facili-
tates the formation of cyclic N-nitroso intermediate (B) from imine
(A) via N-nitrosation [10]. The intermediate (B) delivers the desired
product C (i.e. benzimidazole) and nitrous acid (HNO2) in the pres-
ence of oxygen. In the case of formation of 1,2-disubstituted pro-
duct, the intermediate (B) will react with another equivalent of
aldehyde to form intermediate (D) which undergoes rearrange-
ment [11] to generate 1,2-disubstituted product (E) and nitrous
acid (HNO2). Further nitrous acid reacts with tert-butanol to pro-
vide the tert-butyl nitrite (TBN) [12] to resume the catalytic cycle.
(30 mol%)
O2
N
N
NH2
Alkyl
CHO
+
Alkyl
NH2
Alkyl
5a-5c
THF, RT, 2 h
1a
2r-2t
N
N
N
N
8
6
N
CH3
CH3
N
CH3
CH3
7
9
b
c
: 40%b (86%)c
5b
: 37%b (88%)c
5a
: 39% (87%)
5c
cThe reaction was carried out with 2.0 equiv. of aldehyde.
a
Reaction conditions: Substrate 1a (1 mmol) & aldehyde 2r-2 t (1 mmol) and
TBN (30 mol%) in THF (5 mL) for 2 h at room temperature.
b
Isolated yield.
Conclusions
In conclusion, an efficient catalytic method for the preparation
of benzimidazoles from o-phenylenediamine and aldehydes in
the presence of tert-butyl nitrite is demonstrated. All the reactions
were carried out at room temperature in the presence of oxygen as
an oxidant. This current methodology showed a broad substrate
scope while the desired products were obtained in good to excel-
lent yields.
Furthermore, we have investigated condensation of o-phene-
lenediamine with aliphatic aldehydes such as propanal, octanal
and decanal under optimized conditions (Table 4). Interestingly,
these aldehydes provided 1,2-disubstituted benzimidazoles as a
major product in 37–40% yields (Table 4, 5a-5c). It might be due
to high reactivity of alkyl aldehydes over aryl aldehydes. Further,
Please cite this article as: S. Azeez, P. Sureshbabu, P. Chaudhary et al., tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine
and aldehydes at room temperature, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151735

S. Azeez et al. / Tetrahedron Letters xxx (xxxx) xxx
5
NH2
NH2
R
CHO
+
H2O
H2O
t-BuOH
N
R
t-BuONO
+
NH2
t-BuONO
t-BuOH
CHO
A
HNO2
N
N
R
t-BuOH
E
HNO2
R
NO
N
H
R
N
R
N
H
NO
N
N
H
R
H
B
C
N
1/2 O2
R
HO
R
D
Scheme 2. Proposed mechanism of the reaction.
(d) B.C. Patra, S. Khilari, L. Satyanarayana, D. Pradhan, A. Bhaumik, Chem.
Commun. 52 (2016) 7592;
Declaration of Competing Interest
(e) Z.Y. Zhang, H.Y. Zhang, C.J. Jiao, K.Q. Ye, H.Y. Zhang, J.Y. Zhang, Y. Wang,
Inorg. Chem. 54 (2015) 2652.
[5] (a) S.I. Alaqeel, J. Saudi Chem. Soc. 21 (2017) 229;
(b) J. Sharma, P.K. Soni, R. Bansal, A.K. Halve, Curr. Org. Chem. 22 (2018) 2280;
(c) S. Rajasekhar, B. Maiti, M.M. Balamurali, K. Chanda, Curr. Org. Synth. 14
(2017) 40;
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
(d) S. Das, S. Mallick, S. De Sarkar, J. Org. Chem. 84 (2019) 12111;
(e) Z.J. Xu, D.S. Wang, X.L. Yu, Y.C. Yang, D.W. Wang, Adv. Synth. Catal. 359
(2017) 3332;
Acknowledgements
(f) K. Das, A. Mondal, D. Srimani, J. Org. Chem. 83 (2018) 9553;
(g) Z.F. Li, H. Song, R. Guo, M.H. Zuo, C.F. Hou, S.N. Sun, X. He, Z.Z. Sun, W.Y.
Chu, Green Chem. 21 (2019) 3602;
(h) L.H. Du, Y.G. Wang, Synthesis-Stuttgart (2007) 675;
(i) G. Li, R. He, Q. Liu, Z.W. Wang, Y.X. Liu, Q.M. Wang, J. Org. Chem. 84 (2019)
8646;
(j) S. Park, J. Jung, E.J. Cho, Eur. J. Org. Chem. (2014) 4148;
(k) A. Khoshyan, M. Pourtahmasb, F. Feizpour, M. Jafarpour, A. Rezaeifard,
Appl. Organomet. Chem. (2019) 33;
J. K. acknowledges Max-Planck Society-Germany and DST-India
(DST/INT/MPG/P-09/2016) for financial support through Indo-Max
Planck partner group project. S. A. acknowledges the CSIR for
senior research fellowship (09/013(0650)/2016-EMR-I). J.
K
acknowledges Central Instrumentation Facility Center (CIFC)-IIT
BHU for the NMR facilities and S.S. acknowledges Pondicherry
University for Mass analysis.
(l) R. Karimian, S.J. Davarpanah, Appl. Organomet. Chem. (2018) 32;
(m) Z.K. Chen, H.L. Li, G.J. Cao, J.F. Xu, M.Z. Miao, H.J. Ren, Synlett 28 (2017)
504;
(n) M. Karthik, P. Suresh, New J. Chem. 42 (2018) 17931;
(o) T.T. Nguyen, X.T.T. Nguyen, T.L.H. Nguyen, P.H. Tran, Acs Omega 4 (2019)
368;
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tetlet.2020.151735.
(p) Z.Z. Wang, T. Song, Y. Yang, Synlett 30 (2019) 319;
(q) K. Bahrami, M.M. Khodaei, F. Naali, J. Org. Chem. 73 (2008) 6835;
(r) S.S. Panda, S.C. Jain, Synth. Commun. 41 (2011) 729–735;
(s) G. Li, R. He, Q. Liu, Z. Wang, Y. Liu, Q. Wang, J. Org. Chem. 84 (2019) 8646.
[6] (a) V.D. Oliveira, M.F.D. Cardoso, L.D.M. Forezi, Catalysts (2018) 8;
(b) D.W.C. MacMillan, Nature 455 (2008) 304.
References
[1] (a) J.B. Wright, Chem. Rev. 48 (1951) 397;
[7] (a) A. Dahiya, A.K. Sahoo, T. Alam, B.K. Patel, Chem. Asian J. (2019);
(b) P.F. Li, X.D. Jia, Synthesis-Stuttgart 50 (2018) 711;
(c) N.G. Khaligh, Curr. Org. Chem. 22 (2018) 1120.
[8] (a) C.X. Miao, B. Yu, L.N. He, Green Chem. 13 (2011) 541;
(b) H. Zhang, L.L. Qi, Tetrahedron Lett. 59 (2018) 3171;
(c) K.X. He, T. Zhang, S.W. Zhang, Z. Sun, Y.X. Zhang, Y. Yuan, X.D. Jia, Org. Lett.
21 (2019) 5030;
(d) S.L. Yi, M.C. Li, X.Q. Hu, W.M. Mo, Z.L. Shen, Chin. Chem. Lett. 27 (2016)
1505.
[9] (a) P. Chaudhary, S. Gupta, N. Muniyappan, S. Sabiah, J. Kandasamy, Green
Chem. 18 (2016) 323;
(b) M. Marinescu, Chemistry and Applications of Benzimidazole and Its
Derivatives, Intech Open, London, UK, 2019.
[2] (a) Y. Bansal, O. Silakari, Bioorg. Med. Chem. 20 (2012) 6208;
(b) R.S. Keri, A. Hiremathad, S. Budagumpi, B.M. Nagaraja, Chem. Biol. Drug
Des. 86 (2015) 19;
(c) S. Tahlan, S. Kumar, B. Narasimhan, BMC Chem. 13 (2019) 101.
[3] (a) J.M. Praetorius, R.Y. Wang, C.M. Crudden, Organometallics 29 (2010) 554;
(b) V.O. Rodionov, S.I. Presolski, S. Gardinier, Y.H. Lim, M.G. Finn, J. Am. Chem.
Soc. 129 (2007) 12696;
(c) B.N. Li, S.Y. Mai, Q.L. Song, Org. Chem. Front. 5 (2018) 1639;
(d) E. Samolova, D. Premuzic, S. Plociennik, M. Holynska, J. Mol. Struct. 1176
(2019) 366.
(b) P. Chaudhary, S. Gupta, N. Muniyappan, S. Sabiah, J. Kandasamy, J. Org.
Chem. 84 (2019) 104;
(c) P. Chaudhary, S. Gupta, P. Sureshbabu, S. Sabiah, J. Kandasamy, Green
Chem. 18 (2016) 6215;
(d) P. Chaudhary, R. Korde, S. Gupta, P. Sureshbabu, S. Sabiah, J. Kandasamy,
Adv. Synth. Catal. 360 (2018) 556;
[4] (a) W.Y. Hung, L.C. Chi, W.J. Chen, Y.M. Chen, S.H. Chou, K.T. Wong, J. Mater.
Chem. 20 (2010) 10113;
(b) S. Manoharan, S. Anandan, Dyes Pigm. 105 (2014) 223;
(c) G.M. Saltan, H. Dincalp, M. Kiran, C. Zafer, S.C. Erbas, Mater. Chem. Phys.
163 (2015) 387;
Please cite this article as: S. Azeez, P. Sureshbabu, P. Chaudhary et al., tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine
and aldehydes at room temperature, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151735

6
S. Azeez et al. / Tetrahedron Letters xxx (xxxx) xxx
(e) P. Sureshbabu, S. Azeez, P. Chaudhary, J. Kandasamy, Org. Biomol. Chem. 17
(2019) 845;
[11] a) G.M. Martins, T. Puccinelli, R.A. Gariani, F.R. Xavier, C.C. Silveira, S.R.
Mendes, Tetrahedron Lett. 58 (2017) 1969;
(f) S. Chauhan, P. Chaudhary, A.K. Singh, P. Verma, V. Srivastava, J. Kandasamy,
Tetrahedron Lett. 59 (2018) 272;
(g) S. Azeez, P. Chaudhary, P. Sureshbabu, S. Sabiah, J. Kandasamy, Org. Biomol.
Chem. 16 (2018) 8280.
b) J.-P. Wan, S.-F. Gan, J.-M. Wu, Y. Pan, Green Chem. 11 (2009) 1633;
c) D. Saha, A. Saha, B.C. Ranu, Green Chem. 11 (2009) 733;
d) N.H. Cano, J.G. Uranga, M. Nardi, A. Procopio, D.A. Wunderlin, A.N. Santiago,
Beilstein J. Org. Chem. 2 (2016) 2410.
[10] V.M. Wiessler, Angew. Chem. 86 (1974) 817.
[12] W.A. Noyes, Org. Synth. 16 (1936) 7.
Please cite this article as: S. Azeez, P. Sureshbabu, P. Chaudhary et al., tert-Butyl nitrite catalyzed synthesis of benzimidazoles from o-phenylenediamine
and aldehydes at room temperature, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151735