Cu(NO3)2-catalysed direct synthesis of 5-substituted 1H-tetrazoles from alcohols or aldehydes

Article abstract of DOI:10.3184/174751917X14815427219248

A simple, convenient and practical protocol to synthesise 5-substituted 1H-tetrazoles from alcohols or aldehydes is reported. Using ammonia and sodium azide as nitrogen sources and Cu(NO₃)₂ as catalyst, benzylic alcohols and benzaldehydes were directly converted into 5-substituted 1H-tetrazoles in a one-pot procedure.

Full text of DOI:10.3184/174751917X14815427219248

JOURNAL OF CHEMICAL RESEARCH 2016
VOL. 41 JANUARY, 25–29
RESEARCH PAPER 25
Cu(NO3)2-catalysed direct synthesis of 5-substituted 1H-tetrazoles from
alcohols or aldehydes
Chuanzhou Taoa,b*, Bin Wanga, Lei Suna, Jiuyin Yia, Dahua Shia,b, Jian Wanga and Weiwei Liua,b
aSchool of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005, P.R. China
bJiangsu Marine Resources Development Research Institute, Lianyungang 222005, P.R. China
A simple, convenient and practical protocol to synthesise 5-substituted 1H-tetrazoles from alcohols or aldehydes is reported. Using
ammonia and sodium azide as nitrogen sources and Cu(NO3)2 as catalyst, benzylic alcohols and benzaldehydes were directly converted
into 5-substituted 1H-tetrazoles in a one-pot procedure.
Keywords: copper-catalysed, 5-substituted 1H-tetrazole, alcohol, aldehyde
Tetrazoles are important compounds with a wide range of
applications in coordination chemistry as a ligand, in materials
science as specialty explosives or photographic materials,
and especially in medicinal chemistry as metabolically stable
surrogates for the carboxylic acid group.1–3 Moreover, tetrazoles
are useful synthons to access more complex heterocycles through
various rearrangements.4,5 Among tetrazoles, 5-substituted
1H-tetrazoles are the most interesting heterocycles and many
synthetic approaches have been developed to assemble such
popular functionality. [3+2] Cycloaddition of organometallic
azides and nitriles, often catalysed by proton donor or Lewis
acids, is one of the most efficient methods to form 5-substituted
1H-tetrazoles. Aluminium azide,6 tin azide7–9 or silicon azide10–13
were usually used as the source of azide, which have some
evident drawbacks: toxic organometallic reactants, difficulties
in removing metal residuals and expensive substances.
H
N
N
N
Cu(NO3)2
NH3 NaN
R
R
CH2OH
CHO
R
,
3
N
Scheme 1 Direct synthesis of 5-substituted 1H-tetrazoles from benzyl
alcohols and benzaldehydes.
Table 1 Copper-catalysed [3+2] cycloaddition of sodium azide with
benzonitrilea
H
+ or
N
2+
Cu
Cu
N
N
CN
NaN3
N
2a
1a
Entry
Catalyst
–
Cu2O
CuCl
CuBr
CuI
CuO
CuCl2
CuSO4
Solvent
Temp./°C
120
120
120
120
120
120
120
120
120
Yield /%b
20
1
2
3
4
5
6
7
8
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
70
79
74
78
56
78
77
92
58
90
87
71
A
major advance in the synthesis of 5-substituted
1H-tetrazoles came with the publication of Sharpless’ work.14,15
They reported a safe and simple protocol using the inorganic
salt, sodium azide as nitrogen source, and 5-substituted
1H-tetrazoles were easily synthesised with zinc salts as catalyst.
Since then, metal-catalysed [3+2] cycloadditions of sodium
azide with nitriles was extensively studied,16–18 especially
with heterogeneous nanocatalysts including nanocrystalline
ZnO,19 ZnS nanospheres,20 CuFe2O4 nanoparticles,21 nano
copper oxide,22 Cu–Zn alloy nanopowder,23 and Cu–MCM–41
nanoparticles.24 Although there are some advantages such as
the simple filtration of catalysts and the ability to reuse them,
these nanocatalysts require advance preparation which would
increase the cost of the procedure. Given that 5-substituted
1H-tetrazoles can be found in many applications in various
fields of science, it still remains an important objective to find
new and more practical protocols for these compounds.
9
Cu(NO3)2·3H2O
10
11
12
13
14
Cu(NO3)2·3H2O
Cu(NO3)2·3H2O
Cu(NO3)2·3H2O
Cu(NO3)2·3H2O
Cu(NO3)2·3H2O
Toluene
NMP
DMSO
DMF
DMSO
110
120
120
100
100
69
aReaction conditions: benzonitrile (1.0 mmol), catalyst (10 mol%), NaN3 (2.0 mmol),
solvent (1.0 mL), 16 h
bIsolated yield
Results and discussion
Herein, we report a simple, convenient and practical protocol
to synthesise 5-substituted 1H-tetrazoles directly from alcohols
or aldehydes (Scheme 1).25,26 Initially, an efficient [3+2]
cycloaddition of sodium azide and nitriles was achieved with
Cu(NO3)2 as catalyst. With ammonia and sodium azide as
nitrogen source and Cu(NO3)2 as catalyst, benzylic alcohols
and benzaldehydes were directly converted into 5-substituted
1H-tetrazoles in a one-pot manner. Copper catalysis has
extensive applications in organic reactions such as the Ullmann
Reaction,27–29 the latest C(sp3)–C bond formations30–33 and
oxidation reactions.34 Easy accessibility of the catalysts and
the operationally simple and cheap nitrogen source make this
protocol highly practically appealing.
Recently, we developed an efficient protocol for the synthesis
of aryl nitriles from the corresponding benzylic alcohols.35
The key point of the Cu-catalysed direct conversion alcohols
or aldehydes into 5-substituted 1H-tetrazoles is to combine an
efficient [3+2] cycloaddition of the inorganic salt sodium azide
and a nitrile. Thus we systematically evaluated copper catalysts
in the cycloaddition of nitriles and NaN3.
We commenced our investigation with benzonitrile 1 and
sodium azide as model substrates, and screened the reaction
parameters in the [3+2] cycloaddition (Table 1). We initially
used DMF as the solvent and tested several copper salts with
different oxidation states. It was found that the cycloaddition
* Correspondent. E-mail: taocz@hhit.edu.cn

26 JOURNAL OF CHEMICAL RESEARCH 2016
Table 2 Copper(II)-catalysed [3+2] cycloaddition of sodium azide with various nitrilesa,b
H
N
Cu(NO3)2 10mol%
NaN3
N
N
R
R
CN
DMF, 120oC, 16h
N
2
1
H
N
H
N
H
H
N
N
N
N
N
N
N
N
N
O2N
O
Cl
N
N
N
N
N
2a, 92%
2b, 65%
2f, 90%
2c, 89%
2d, 93%
Cl
Br
NO2
H
H
N
H
N
N
N
N
N
N
N
N
N
N
F
N
N
N
N
N
H
2e, 91%
2g, 68%
2h, 38%
H
N
H
N
N
N
H
N
N
N
N
N
N
N
N
2k, 62%
2j, 45%
2i, 40%
aReaction conditions: nitrile (1.0 mmol), NaN3 (2.0 mmol), Cu(NO3)2·3H2O (10 mol%), DMF (1.0 mL), 16 h
bIsolated yield
gave the product in 20% yield when no catalyst was added (entry
1), but introduction of catalytic copper salt dramatically increased
the yields. For example, yields of up to 70–79% were obtained
with Cu(I) salts as catalysts (entries 2–5). Although the yields of
the desired product were 56–78% with many Cu(II) salts (entries
6–8), we were pleased to find that Cu(NO3)2 can dramatically
increase the cycloaddition yield to 92% (entry 9). Further
optimisation by changing the solvent did not improve the yield.
The less polar solvent toluene gave a lower yield of 58% (entry
10), nevertheless, other polar solvents gave comparable yields
(87–90%) to DMF (entries 11 and 12). When the temperature
was reduced to 100 °C, the yield decreased to 69–71% (entries
13 and 14).
To extend the scope of the catalysis, we examined a variety of
substrates (Table 2). We found that cycloaddition of aryl nitriles
containing an electron-donating group and sodium azide afforded
tetrazoles with moderate yields (65% for 4-methoxy, 2b). To our
delight, aryl nitriles carrying an electron-withdrawing group can
be smoothly converted to the desired products with excellent
isolatedyields(89–93%). However, arylnitrilescarryinganortho-
substituent were not found to readily participate in the reaction.
For instance, 2-nitrobenzonitrile gave a more moderate isolated
yield of 68% (2g), whereas the yield from 2-chlorobenzonitrile
was low (38%, 2h). Similarly, the yield is only 40% from
naphthalene-1-carbonitrile (2i). Thus, the steric effect has a much
stronger influence than the electronic effect in the cycloaddition
with sodium azide. Furthermore, the method can be applied to
the transformation of unsaturated nitriles to tetrazoles. Although
the isolated yield is 45%, cinnamyl tetrazoles can be formed from
cinnamonitrile without isomerisation of the double bond (2j).
Finally, an aliphatic nitrile was tested, and phenylacetonitrile can
be converted to the desired tetrazole with satisfactory yield (62%)
under the standard conditions (2k).
Having successfully developed an efficient method for the
preparation of nitriles, we next sought to develop a one-pot
protocol to synthesise tetrazoles directly from alcohols or
aldehydes. Our previous study35 has shown that aryl nitriles can
be obtained directly from the corresponding benzylic alcohols or
aldehydes. Thus, we examined whether the same catalytic system
can be applied to the one-pot synthesis of tetrazoles directly
from alcohols or aldehydes (Table 3). Gratifyingly, employing
Cu(NO3)2 as catalyst, benzyl alcohol 3 can be converted to the
desired products with satisfactory isolated yields. It was found that
the electron-poor (4-chlorophenyl, 4-fluorophenyl, 4-nitrophenyl)
substrates gave high yields when compared to electron-rich (i.e.
4-methoxyphenyl) substrates (entries 1–5). Because of the steric
hindrance influence in the [3+2] cycloaddition, low yields were
obtained in some cases (entries 6,7). The yield is only 35% for
NH3
Cu(NO3)2
R-CN
Cu(NO3)2
R-CH=NH
R-CH2OH
R-CHO
4
O2
O2
3
1
A
Cu(NO )
3 2
NaN3
ONO2
ONO2
1 R-CN
Cu
R
Cu
N
N
N3
-
N
+
N
H
Na
B
N
N
N
N
H+
ONO2
N
N
Cu
R
R
N
N
N
N
2
D
NaN3
N
R
N
C
Scheme 2 Proposed mechanism of Cu(NO3)2-catalysis.

JOURNAL OF CHEMICAL RESEARCH 2016 27
Table
3 Copper(II)-catalysed one-pot synthesis of 5-substituted
naphthalen-1-ylmethanol, and 42% for 2-chlorobenzyl alcohol
even with extended reaction times. Cinnamyl tetrazoles could
be obtained from cinnamyl alcohol without isomerisation of
the double bond (entry 8). Furthermore, with benzaldehyde
derivatives 4 as starting materials, the desired products were
obtained with 67–85% isolated yields (entries 9–12). It is
noteworthy that oxidation of the benzylic alcohol, oxidation of
the intermediate of imine and subsequent [3+2] cycloaddition
with sodium azide were realised in a one-pot manner, without
losing catalytic activity of Cu(NO3)2 (Scheme 2).
1H-tetrazoles directly from benzyl alcohols and benzaldehydes
N
HN
Cu(NO3)2 (10 mol%)
Cu(NO3)2 (10 mol%)
N
CHO
CH2OH
(i)
NH
(i)
TEMPO/ 3(aq.)/O2
NH
3(aq.)/O2
N
R
R
R
(ii)
NaN3
(ii)
NaN3
4
3
2
ArCH2OH 3a
ArCHO 4b
Entry
1
Product 2
Yield /%c
86
H
N
N
N
CH2OH
N
A possible reaction mechanism is proposed in Scheme 2.
According our previous report,35 the oxidation of the alcohol to
an aldehyde is catalysed by Cu(NO3)2, and condensation with
ammonia affords a primary imine intermediate A. The second
oxidation affords nitrile 1 with the same catalytic system.
Sharpless suggested that the critical element of the catalysis is
the activation of the nitrile by coordination to the metal ion.15 By
means of coordination to Cu(NO3)2, the electrophilic nitrile was
easily attacked by an azide ion to afford intermediate B which,
through cycloaddition, gives intermediate C. The catalytic cycle
is accomplished by a transmetalation between sodium azide and
C to give intermediate D, followed with acidic workup to afford
the desired products 2.
3a
3b
3c
3d
3e
2a
2b
2d
2e
2c
H
N
N
O
CH2OH
CH2OH
CH2OH
CH2OH
O
2
3
4
5
63
86
81
83
N
N
H
N
N
N
Cl
Cl
N
H
N
N
F
F
N
N
H
N
Conclusion
N
O2N
O2N
N
In summary, we have developed a simple, convenient and
practical protocol to synthesise 5-substituted 1H-tetrazoles using
ammonia and sodium azide as nitrogen source. Initially, [3+2]
cycloaddition of sodium azide and nitriles was realised with the
copper(II) salt, Cu(NO3)2 as catalyst. Under these conditions,
tetrazoles were prepared directly from alcohols or aldehydes, and
the copper salt did not lose its catalytic activity. Easy accessibility
of the catalyst and the operationally simple and cheap nitrogen
source make this protocol highly practically appealing.
Considering the inexpensive nature of this catalytic system and
the simple procedure, the method described in the present report
may be valuable for realistic industrial-scale applications.
N
H
N
6
35d
N
N
CH2OH
N
3f
2i
Cl
Cl
N
N
N
7
8
42d,e
CH2OH
N
H
3g
3h
2h
H
N
CH2OH
N
Experimental
50d
N
All chemicals were obtained from commercial sources and used without
further purification. Flash column chromatography was performed on
silica 300–400 mesh. 1H NMR and 13C NMR spectra were recorded on
a Bruker Avance 400 spectrometer (at 400 and 100 MHz respectively)
at ambient temperature in DMSO-d6. Chemical shifts are reported
in ppm relative to TMS. Melting points were measured on a SGW X-4
microscope melting point apparatus.
N
2j
2a
2b
2d
2e
H
N
N
CHO
9
78
61
82
80
N
N
4a
4b
4c
4d
H
N
N
N
Cu(NO3)2-catalysed synthesis of 5-substituted 1H-tetrazoles; general
procedure
O
CHO
O
Cl
F
10
11
12
N
Cu(NO3)2·3H2O (0.10 mmol), the appropriate nitrile 1 (1.0 mmol), NaN3
(2.0 mmol) and DMF (1 mL) were added to a 50 mL round-bottomed
flask equipped with a magnetic stirrer. The reaction mixture was stirred
in an oil bath at 120 °C for 16 h. After cooling to room temperature, the
reaction was acidified HCl (3 M, pH 1.0). Ethyl acetate (~30 mL) was
added, and stirring was continued until no solid was present. The organic
layer was separated, and the aqueous layer was extracted with ethyl
acetate twice. The combined organic layers were washed with saturated
brine, and concentrated in vacuo. The residue was purified by column
chromatography (silica gel, EtOAc-PE) to afford the product 2.
H
N
N
N
Cl
CHO
N
H
N
N
F
CHO
N
N
aReaction conditions: (i) benzylic alcohol (1.0 mmol), Cu(NO3)2·3H2O (10 mol%), TEMPO
(10 mol%), 25% aq. NH3 (3.0 mmol), DMSO (1.0 mL), O2 (1 atm), 8 h, 80 °C; (ii) NaN3
(2.0 mmol), 120°C, 16 h
Cu(NO3)2-catalysed one-pot synthesis of 5-phenyl-1H-tetrazole
directly from benzylic alcohols; general procedure
bReaction conditions: (i) aldehyde (1.0 mmol), Cu(NO3)2·3H2O (10 mol%), 25% aq. NH3
(3.0 mmol), DMSO (1.0 mL), O2 (1 atm), 8 h, 80 °C; (ii) NaN3 (2.0 mmol), 120 °C, 16 h
cIsolated yield
Cu(NO3)2·3H2O (0.10 mmol), TEMPO (0.10 mmol), the benzylic
alcohol 3 (1.0 mmol) and DMSO (1 mL) were added to a 100 mL
round-bottomed flask equipped with a magnetic stirrer. The vessel
was flushed with O2 and aqueous NH3 (25-28%, 3.0 mmol) was added.
The vessel was sealed and the reaction mixture was stirred in an oil
dReaction time for (ii) is 24 h
eReaction time for (i) is 24 h

28 JOURNAL OF CHEMICAL RESEARCH 2016
bath at 80 °C for 8 h. After cooling to room temperature, the stopper was
removed and NaN3 (2.0 mmol) was added. Stirring was continued in an
oil bath at 120 °C for 16 h. After completion of the reaction, the reaction
was acidified HCl (3 M, pH 1.0). Ethyl acetate (~30 mL) was added,
and the mixture was stirred until no solid was present. The organic
layer was separated, and the aqueous layer was extracted with ethyl
acetate twice. The combined organic layers were washed with saturated
brine, and concentrated in vacuo. The residue was purified by column
chromatography (silica gel, EtOAc-PE) to afford the product 2.
(E)-5-Styryl-1H-tetrazole (2j): M.p. 152–154 °C (lit.40 154–156 °C);
1H NMR (400 MHz, DMSO-d6) δ 7.72 (d, J = 7.0 Hz, 2H), 7.66
(d, J = 16.6 Hz, 1H), 7.49–7.38 (m, 3H), 7.34 (d, J = 16.6 Hz, 1H);
13C NMR (100 MHz, DMSO-d6) δ 155.31, 137.82, 134.86, 129.61,
128.98, 127.47, 110.42.
5-Benzyl-1H-tetrazole (2k): M.p. 120–121 °C (lit.36 121–122 °C);
1H NMR (400 MHz, DMSO-d6) δ 7.37–7.30 (m, 2H), 7.30–7.24 (m,
3H), 4.29 (s, 2H); 13C NMR (100 MHz, DMSO-d6) 154.83, 136.08,
128.91, 128.84, 127.20, 29.06.
Cu(NO3)2-catalysed one-pot synthesis of 5-aryl-1H-tetrazole directly
from benzaldehyde derivatives; general procedure
Acknowledgements
We are grateful to the National Natural Science Foundation
of China (21402062), Natural Science Foundation of Jiangsu
Province (BK20130404, BK20141246), Scientific and
Technological Research Project of Lianyungang (CG1303,
CN1401), and the Project Funded by the Priority Academic
Program Development of Jiangsu Higher Education Institutions,
and Open-end Funds of Jiangsu Key Laboratory of Marine
Pharmaceutical Compound Screening (2015HYB11).
Cu(NO3)2·3H2O (0.10 mmol), the appropriate benzaldehyde derivative
4 (1.0 mmol) and DMSO (1 mL) were added to a 100 mL round-
bottomed flask equipped with a magnetic stirrer. The vessel was
flushed with O2 and aqueous NH3 (25–28%, 3.0 mmol) was added.
The vessel was sealed and the reaction mixture was stirred in an oil
bath at 80 °C for 8 h. After cooling to room temperature, the stopper
was removed and NaN3 (2.0 mmol) was added. Stirring was continued
in an oil bath at 120 °C for 16 h. After completion of the reaction, the
reaction was acidified HCl (3 M, pH 1.0). Ethyl acetate (~30 mL) was
added, and the mixture was stirred until no solid was present. The
organic layer was separated, and the aqueous layer was extracted with
ethyl acetate twice. The combined organic layers were washed with
saturated brine, and concentrated in vacuo. The residue was purified
by column chromatography (silica gel, EtOAc-PE) to afford the
product 2.
Electronic Supplementary Information
The ESI (1H and 13C NMR spectra of the tetrazoles) is available
through:
stl.publisher.ingentaconnect.com/content/stl/jcr/supp-data.
Received 12 September 2016; accepted 11 December 2016
Paper 1604317 DOI: 10.3184/174751917X14815427219248
Published online: 17 January 2017
5-Phenyl-1H-tetrazole (2a): M.p. 214–216 °C (lit.36 215–216 °C);
1H NMR (400 MHz, DMSO-d6) δ 8.12–8.02 (m, 2H), 7.78–7.58 (m,
3H); 13C NMR (100 MHz, DMSO-d6) δ 155.78, 131.70, 129.89, 127.43,
124.65.
References
5-(4-Methoxyphenyl)-1H-tetrazole (2b): M.p. 229–231°C (lit.36
1
M. Hiskey, D.E. Chavez, D.L. Naud, S.F. Son, H.L. Berghout and C.A.
Bome, Proc. Int. Pyrotech. Semin., 2000, 27, 3.
1
230–232 °C); H NMR (400 MHz, DMSO-d6) δ 7.98 (d, J = 8.8 Hz,
2H), 7.16 (d, J = 8.8 Hz, 2H), 3.84 (s, 3H); 13C NMR (100 MHz,
DMSO-d6) δ 161.44, 154.73, 128.60, 116.28, 114.83, 55.42.
2
3
4
5
R.C. Tuites, T.E. Whiteley and L.M. Minsk, US Patent 1,245,614 (1971).
G.I. Koldobskii and V.A. Ostrovskii, Russ. Chem. Rev., 1994, 63, 797.
D. Moderhack, J. Prakt. Chem., 1998, 340, 687.
V. Novakova, J. Roh, P. Gela, J. Kunes and P. Zimcik, Chem. Commun.,
2012, 48, 4326.
5-(4-Nitrophenyl)-1H-tetrazole (2c): M.p. 218–220 °C (lit.36
1
219–221 °C); H NMR (400 MHz, DMSO-d6) δ 8.44 (d, J = 8.9 Hz,
2H), 8.31 (d, J = 8.9 Hz, 2H); 13C NMR (100 MHz, DMSO-d6) δ
156.30, 148.94, 131.98, 128.49, 125.03.
6
7
V. Aureggi and G. Sedelmeier, Angew. Chem. Int. Ed., 2007, 46, 8440.
K. Sisido, K. Nabika, T. Isida and S. Kozima, J. Organomet. Chem., 1971,
33, 337.
5-(4-Chlorophenyl)-1H-tetrazole (2d): M.p. 258–260 °C (lit.36
8
9
J.V. Duncia, M.E. Pierce and J.B. Santella, J. Org. Chem., 1991, 56, 2395.
G. Garipova, A. Gautier and S.R. Piettre, Tetrahedron, 2005, 61, 4755.
1
259–260 °C); H NMR (400 MHz, DMSO-d6) δ 8.06 (d, J = 8.6 Hz,
2H), 7.66 (d, J = 8.6 Hz, 2H); 13C NMR (100 MHz, DMSO-d6) δ
156.09, 135.69, 129.86, 129.01, 124.92.
10 E. Ettenhuber and K. Ruhlmann, Chem. Ber., 1968, 101, 743.
11 T. Jin, F. Kitahara, S. Kamijo and Y. Yamamoto, Tetrahedron Lett., 2008,
49, 2824.
12 J. Bonnamour and C. Bolm, Chem. Eur. J., 2009, 15, 4543.
13 D. Cantillo, B. Gutmann and C.O. Kappe, J. Am. Chem. Soc., 2011, 133,
4465.
14 Z.P. Demko and K.B. Sharpless, J. Org. Chem., 2001, 66, 7945.
15 F. Himo, Z.P. Demko, L. Noodleman and K.B. Sharpless, J. Am. Chem.
Soc., 2003, 125, 9983.
16 U.B. Patil, K.R. Kumthekar and J.M. Nagarkar, Tetrahedron Lett., 2012,
53, 3706.
17 B. Akhlaghinia and S. Rezazadeh, J. Braz. Chem. Soc., 2012, 23, 2197.
18 K.M. Khan, I. Fatima, S.M. Saad, M. Taha and W. Voelter, Tetrahedron
Lett., 2016, 57, 523.
19 M.L. Kantam, K.B. Shiva Kumar and C. Sridhar, Adv. Synth. Catal., 2005,
347, 1212.
5-(4-Fluorophenyl)-1H-tetrazole (2e): M.p. 205–207 °C (lit.36
1
203–205 °C); H NMR (400 MHz, DMSO-d6) δ 8.12 (dd, J = 8.9,
5.4 Hz, 2H), 7.44 (t, J = 8.9 Hz, 2H); 13C NMR (100 MHz, DMSO-d6)
δ 163.38 (d, J = 248.2 Hz), 155.37, 129.29 (d, J = 8.9 Hz), 121.94 (d,
J = 3.1 Hz), 116.41 (d, J = 22.1 Hz).
5-(3-Bromophenyl)-1H-tetrazole (2f): M.p. 149–151 °C (lit.37
1
149–150 °C); H NMR (400 MHz, DMSO-d6) δ 8.22 (d, J = 1.7 Hz,
1H), 8.06 (d, J = 7.7 Hz, 1H), 7.81 (d, J = 8.0 Hz, 1H), 7.62–7.53 (m,
1H); 13C NMR (100 MHz, DMSO-d6) δ 154.99, 134.40, 132.10, 129.87,
126.90, 126.46, 122.88.
5-(2-Nitrophenyl)-1H-tetrazole (2g): M.p. 162–164 °C (lit.38
165–166 °C); 1H NMR (400 MHz, DMSO-d6) δ 8.08 (dd, J = 8.0, 0.8
Hz, 1H), 7.95 (dd, J = 7.7, 1.1 Hz, 1H), 7.87 (td, J = 7.6, 1.1 Hz, 1H),
7.79 (td, J = 8.0, 1.4 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 154.87,
148.79, 133.58, 131.80, 131.53, 124.84, 121.11.
20 L. Lang, B. Li, W. Liu, L. Jiang, Z. Xu and G. Yin, Chem. Commun., 2010,
46, 448.
21 B. Sreedhar, A.S. Kumar and D. Yada, Tetrahedron Lett., 2011, 52, 3565.
22 U. Yapuri, S. Palle, O. Gudaparthi, S.R. Narahari, D.K. Rawat, K. Mukkanti
and J. Vantikommu, Tetrahedron Lett., 2013, 54, 4732.
23 G. Aridoss and K.K. Laali, Eur. J. Org. Chem., 2011, 6343.
24 M. Abdollahi-Alibeik and A. Moaddeli, New J. Chem., 2015, 39, 2116.
25 W.Y. Yin, C.M. Wang and Y. Huang, Org. Lett., 2013, 15, 1850.
26 M.M. Heravi, A. Fazeli, H.A. Oskooie, Y.S. Beheshtiha and H. Valizadeh,
Synlett, 2012, 23, 2927.
27 C.Z. Tao, W.W. Liu, A.F. Lv, M.M. Sun, Y. Tian, Q. Wang and J. Zhao,
Synlett, 2010, 21, 1355.
28 C.Z. Tao, A.F. Lv, N. Zhao, S. Yang, X.L. Liu, J. Zhou, W.W. Liu and J.
Zhao, Synlett, 2011, 22, 134.
5-(2-Chlorophenyl)-1H-tetrazole (2h): M.p. 171–173 °C (lit.39
1
172–174 °C); H NMR (400 MHz, DMSO-d6) δ 7.82 (dd, J = 7.6,
1.7 Hz, 1H), 7.73 (d, J = 8.0 Hz, 1H), 7.65 (td, J = 7.9, 1.3 Hz, 1H), 7.57
(t, J = 7.5 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 153.84, 133.13,
132.44, 132.22, 130.90, 128.27, 124.51.
5-(Naphthalen-1-yl)-1H-tetrazole (2i): M.p. 211–213 °C (lit.39
212–214 °C); 1H NMR (400 MHz, DMSO-d6) δ 8.56 (d, J = 7.7 Hz, 1H),
8.20 (d, J = 8.1 Hz, 1H), 8.13–8.07 (m, 1H), 8.00 (d, J = 7.1 Hz, 1H),
7.74–7.65 (m, 3H); 13C NMR (100 MHz, DMSO-d6) δ 155.09, 133.40,
131.47, 129.93, 128.65, 128.42, 127.71, 126.75, 125.33, 125.09, 121.45.
29 H.J. Xu, Y.Q. Zhao, T. Feng and Y.S. Feng, J. Org. Chem., 2012, 77, 2878.

JOURNAL OF CHEMICAL RESEARCH 2016 29
30 C.T. Yang, Z.Q. Zhang, Y.C. Liu and L. Liu, Angew. Chem. Int. Ed., 2011,
50, 3904.
35 C.Z. Tao, F. Liu, Y.M. Zhu, W.W. Liu and Z.L. Cao, Org. Biomol. Chem.,
2013, 11, 3349.
31 C.T. Yang, Z.Q. Zhang, J. Liang, J.H. Liu, X.Y. Lu, H.H. Chen and L. Liu,
J. Am. Chem. Soc., 2012, 134, 11124.
36 B. Nammalwar, N. P. Muddala, R. Pitchimani and R.A. Bunce, Molecules,
2015, 20, 22757.
32 G. Wang, J. Jiang, X. Bu, J. Dai, J. Xu, Y. Fu and H. Xu, Org. Lett., 2015,
17, 3682.
37 H. Sharghi, S. Ebrahimpourmoghaddam and M.M. Doroodmand, J.
Organomet. Chem., 2013, 738, 41.
33 A. Ebrahim-Alkhalil, Z. Zhang, T. Gong, W. Su, X. Lu, B. Xiao and Y. Fu,
Chem. Commun., 2016, 52, 4891.
34 S.E. Allen, R.R. Walvoord, R. Padilla-Salinas and M.C. Kozlowski, Chem.
Rev., 2013, 113, 6234.
38 R.N. Butler and T.M. McEvoy, J. Chem. Soc., Perkin Trans. 2, 1978, 1087.
39 Z. Wang, Z. Liu and S.H. Cheon, Bull. Korean Chem. Soc., 2015, 36, 198.
40 M. Sridhar, K.K.R. Mallu, R. Jillella, K.R. Godala, C.R. Beeram and N.
Chinthala, Synthesis, 2013, 45, 507.