Regioselective and Stereoselective Addition of Tetrazole Derivatives to Electron-poor Acetylenic Esters in the Presence of Triphenylphosphine

Article abstract of DOI:10.1002/jhet.2539

Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine and acetylenic esters by tetrazole derivatives leads to the formation of vinyltriphenylphosphonium salts. The cation of these salts undergoes an addition reaction with the counter anion in CH₂Cl₂at room temperature to yield the corresponding stabilized phosphorus ylides. Elimination of triphenylphosphine from the stabilized phosphorus ylides leads to the corresponding electron-poor N-vinyl tetrazoles in fairly high yields. Structures of N-vinyl tetrazoles were determined by IR,¹H NMR,¹³C NMR and single crystal X-ray structure analyses. The reaction is fairly regioselective and stereoselective.

Full text of DOI:10.1002/jhet.2539

Month 2015
Regioselective and Stereoselective Addition of Tetrazole Derivatives to
Electron-poor Acetylenic Esters in the Presence of Triphenylphosphine
a
a,b
c
c
d
*
*
Ali Ramazani, Fatemeh Zeinali Nasrabadi, Katarzyna Ślepokura, Tadeusz Lis, and Sang Woo Joo
aDepartment of Chemistry, University of Zanjan, P.O. Box 45195-313, Zanjan, Iran
bDepartment of Chemistry, Islamic Azad University-East Tehran (Ghiam Dasht) of Branch, Tehran, Iran
cFaculty of Chemistry, University of Wrocław, 14 Joliot-Curie St., 50-383 Wrocław, Poland
dSchool of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, Korea
*
E-mail: aliramazani@gmail.com; swjoo@yu.ac.kr
Additional Supporting Information may be found in the online version of this article.
Received June 17, 2015
DOI 10.1002/jhet.2539
Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine
and acetylenic esters by tetrazole derivatives leads to the formation of vinyltriphenylphosphonium salts. The
cation of these salts undergoes an addition reaction with the counter anion in CH2Cl2 at room temperature to
yield the corresponding stabilized phosphorus ylides. Elimination of triphenylphosphine from the stabilized
phosphorus ylides leads to the corresponding electron-poor N-vinyl tetrazoles in fairly high yields. Structures
of N-vinyl tetrazoles were determined by IR, 1H NMR, 13C NMR and single crystal X-ray structure analyses.
The reaction is fairly regioselective and stereoselective.
J. Heterocyclic Chem., 00, 00 (2015).
INTRODUCTION
important ligands in a number of transition metal catalysts
[21]. N-additions of nucleophiles to the vinyl group of vi-
nylic phosphonium salts leading to the formation of new
alkylidenephosphoranes have attracted much attention as
a very convenient and synthetically useful method in or-
ganic synthesis [22]. Phosphorus ylides are a special type
of zwitterions, which bear a strongly nucleophilic,
electron-rich carbanionlike function adjacent to a phospho-
nium center. The electron distribution around the P+–Cꢀ
bond and its consequent chemical implications have been
probed and assessed through theoretical, spectroscopic
and crystallographic investigations [22]. The nucleophilic-
ity at the ylidic carbon is a factor of essential mechanistic
importance in the use of phosphorus ylides as Wittig re-
agents. These are important reagents in synthetic organic
chemistry, especially in the synthesis of naturally occurring
products and compounds with biological and pharmaco-
logical activity [23]. These ylides are usually prepared by
treatment of a phosphonium salt with a base, and phospho-
nium salts are usually obtained from a phosphine and an al-
kyl halide. Phosphonium salts are also prepared by
Michael addition of phosphorus nucleophiles to activated
olefins and in other ways [24]. The phosphonium salts
are most often converted to the ylide by treatment with a
strong base, although weaker bases can be used if the salt
is acidic enough.
Tetrazole derivates are well known not only as com-
pounds with a high level of biological activity but also as
precursors to a variety of nitrogen containing heterocycles
[1–8]. Various procedures have been developed for their
syntheses. Tetrazoles have a wide range of applications in
materials as specialty explosives and information recording
systems, in pharmaceuticals as lipophilic spacers and car-
boxylic acid surrogates, and in coordination chemistry as
ligands [9]. They form stable complexes with metals [10–
12]. These compounds are useful as oxidizers and effective
agents for regulating plant growth. Tetrazole derivatives
have also fungicidal, antiviral (including HIV) antimicro-
bial, antiinflammatory, antilipemic, anticancer, antihyper-
tensive and antiallergic activity [13]. 5-Substituted
tetrazoles that contain a free N–H bond are also frequently
referred to as tetrazolic acids, and exist as a nearly 1:1 ratio
of 1H- and 2H-tautomeric forms [14]. The free N–H bond
of tetrazoles makes them acidic molecules because of the
ability of the moiety to stabilize a negative charge by elec-
tron delocalization. Tetrazolate anionic species are more
reactive than the corresponding neutral species toward a
variety of electrophiles and alkylating agents [15–20].
Organophosphorus compounds have been extensively
used in organic synthesis as useful reagents and as
© 2015 HeteroCorporation

A. Ramazani, F. Z. Nasrabadi, K. Ślepokura, T. Lis, and S. W. Joo
Vol 000
Acetylenic esters are reactive systems and take part in
many chemical syntheses. The compounds act almost as
Michael acceptors in organic reactions [25–36]. In recent
years, there has been an increasing interest in the applications
of acetylenic esters in multicomponent synthesis, especially
for preparing stabilized phosphorus ylides [25–36].Recently,
we have established a one-pot method for the synthesis of or-
ganophosphorus compounds [37–40]. In this article, we at-
tempt to describe the regioselective and stereoselective
preparation of electron-poor N-vinyl tetrazoles from the acet-
ylenic esters and 5-benzyl-2H-tetrazole in the presence of
triphenylphosphine in fairly good yields.
section). The NMR spectra indicated that solutions of com-
pound 7a, 7c, and 7d (CDCl3 as solvent) contain Z stereo-
isomer as only product. It may be a result from
thermodynamic stability of Z stereoisomer relative to E ste-
reoisomer. The steric and electronic effects in the stereoiso-
mers can be conducted E/Z equilibrium toward Z
stereoisomer in the presence of PPh3 as a nucleophilic cat-
alyst (via addition to electron-poor C¼C of 7a, 7c, and 7d).
The 1H NMR spectrum of the Z stereoisomer of 7a exhib-
ited five signals readily recognized as arising from OMe
groups (δ =3.84, s and δ= 4.04, s), CH2 (δ= 4.31, s),
=CH (δ =6.90, s), and aromatic moieties (δ=7.23–7.34, m).
The 13C NMR spectrum of the Z stereoisomer showed 12
distinct resonances according to expectation. Partial as-
signment of these resonances is given in the Experimental
section. The NMR spectra indicated that solution of com-
pound 7b (CDCl3 as solvent) contains E and Z stereoiso-
mers. Relative population of E and Z isomers was
determined via their 1H NMR spectra (%E= 50.25, %
RESULTS AND DISCUSSION
Reactions are known in which an α,β-unsaturated car-
bonyl compound is produced from phosphonium salts
[25]. Thus, the compound 5 may result from initial addi-
tion of triphenylphosphine 1 to the acetylenic esters 2
and concomitant protonation of the 1:1 adducts by the tet-
razole derivatives 3 to form the corresponding triphenyl-
phosphonium salts 4. Addition of the anion in 4 to the
vinyltriphenylphosphonium cation leads to the formation
of the stabilized phosphorus ylides 5 (Scheme 1) that un-
dergoes intramolecular proton transfer leading to formation
of sterically congested electron-poor N-vinyl tetrazoles 7
via zwitterionic intermediate 6 (Scheme 1). In this reaction,
triphenylphosphine acts as a catalyst. TLC indicated for-
mation of N-vinyl tetrazoles 7 in CH2Cl2 at room tempera-
ture. The mechanism of the reaction outlined earlier has not
been established experimentally. However, a possible ex-
planation [29] is proposed in Scheme 1.
1
Z = 49.75). The H and 13C NMR spectra of compound
7b are similar to those of 7a, except for the ester group,
which exhibits characteristic signals with appropriate
1
chemical shifts (see Spectral Analysis section). The H
NMR spectrum of the Z stereoisomer of 7c exhibited four
signals readily recognized as arising from OMe groups
(δ= 3.87, s and δ= 4.09, s), =CH (δ= 7.01, s), and aromatic
moieties (δ = 7.26–8.22, m). The 13C NMR spectrum of the
Z stereoisomer showed 11 distinct resonances according to
expectation. Partial assignment of these resonances is
1
given in the Experimental section. The H and 13C NMR
spectra of compound 7d are similar to those of 7c, except
for the ester group, which exhibits characteristic signals
with appropriate chemical shifts (see Spectral Analysis
section).
The structures of products 7 were proved by their IR, 1H
NMR and 13C NMR spectral data (see the Experimental
Scheme 1. Synthesis of electron-poor N-vinyl tetrazoles 7a-d from triphenylphosphine 1, dialkyl acetylene dicarboxylate 2 and tetrazole derivatives 3.
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We have also used ethyl phenyl acetylenecarboxylate 8
(Scheme 2) instead of alkyl acetylenecarboxylate 2 in this
reaction. The stabilized phosphorus ylides 10 may result
from initial addition of triphenylphosphine 1 to the
acetylenic ester 8 and concomitant protonation of the 1:1 ad-
duct, followed by attack of the NH-acid anion 9 on the
vinyltriphenylphosphonium cation to form the phosphorane
10 (Scheme 2). In this reaction, triphenylphosphine acts as
a catalyst. TLC indicated formation of the N-vinyl tetrazoles
12a-c in CH2Cl2. The mechanism of the reaction outlined
earlier has not been established experimentally. However, a
possible explanation [29] is proposed in Scheme 2. The
NMR spectra indicated that solution of compound 12a
(CDCl3 as solvent) contains E stereoisomer as major product,
which may result from easier formation of E isomer than Z
isomer. It may be a result from thermodynamic stability of
E stereoisomer relative to Z stereoisomer. The steric and
electronic effects in the stereoisomers 12 can be conducted
E/Z equilibrium toward E stereoisomer in the presence of
PPh3 as a nucleophilic catalyst (via addition to electron-poor
C¼C of 12). Relative population of E and Z isomers was
determined via their 1H NMR spectra (%E=63.13, %
Z=36.87). The 1H NMR spectrum of the E stereoisomer of
12a exhibited five signals readily recognized as arising from
OCH2 group (δ=4.33, q), OMe (δ =3.88, s), CH3 (δ=1.31,
t), =CH (δ=7.28, s), and aromatic moieties (δ=6.87–8.19,
m). The 13C NMR spectrum of the E stereoisomer showed
15 distinct resonances according to expectation. Partial as-
signment of these resonances is given in the Experimental
section. The 1H and 13C NMR signals of the minor stereoiso-
mer Z are similar to those of the major stereoisomer (see
shifts (see Spectral Analysis section). Structure of 12c was
determined by single crystal X-ray structure analysis.
Crystal structure of 12c. The crystal of 12c is built up
from molecules shown in Figure 1. The summary of the
experimental details is given in Table 1. The overall
structure of 12c is similar to that observed in the related
compounds described by us previously and deposited at the
Cambridge Structural Database [41]. Like in these
compounds, two planes (with the atoms N(1) and C(4) being
common) may be distinguished in the molecule of 12c: the
ethyl (2Z)-2-amino-3-phenylacrylate moiety (forming plane
1 with r. m. s. deviation of fitted atoms = 0.08Å) and the rest
of the molecule (plane 2 with r.m. s. = 0.19Å). The dihedral
angle between the least-squares planes 1 and 2, amounting
to 88.4(1)°, reveals that the two planes are almost
perpendicular to each other. However, it has to be noted that
the two rings within the plane 2 (tetrazolyl and C(13) ~C(18)
phenyl) are slightly twisted with each other, which is
reflected in the N(2)–C(12)–C(13)–C(14) torsion angle of
ꢀ18.0(2)°. Moreover, some deviation from the planarity of
the fragment defined here as plane 1, that is, slight twist of
the C(6)–C(11) phenyl ring, is revealed by the value of the
C(4)–C(5)–C(6)–C(7) torsion angle of ꢀ6.4(2)°. This was
previously observed in most of the Z geometrical isomers of
similar structures reported so far [41].
As it was observed for the analogs of 12c [41], the mol-
ecule adopts Z geometry with respect to the double bond
C(4)–C(5), which is reflected in the value of the torsion
angle N(1)–C(4)–C(5)–C(6) of ꢀ3.5(2)° (Table 2). The
carbonyl atom O(1) of the ester group is in antiperiplanar
conformation in relation to the vinyl atom C(5) [O(1)–C
(3)–C(4)–C(5) torsion angle of 176.6(1)°], as also found
for most of the structurally related compounds [41].
1
Spectral Analysis section). The H NMR and 13C NMR
spectra of compounds 12b-c are similar to those of 12a, ex-
cept for the aromatic substituent on the tetrazole ring, which
exhibits characteristic signals with appropriate chemical
Theweakintramolecularhydrogeninteractions:C(5)–H(5)–
O(2) and C(7)–H(7)–N(1), also observed before [41], give rise
Scheme 2. Synthesis of electron-poor N-vinyl tetrazoles 12a-c from triphenylphosphine 1, ethyl phenyl acetylenecarboxylate 8, and tetrazole derivatives 3.
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A. Ramazani, F. Z. Nasrabadi, K. Ślepokura, T. Lis, and S. W. Joo
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Figure 1. Molecular structure of compound 12c, showing the X-ray atom-numbering scheme and intramolecular C–H–O/N hydrogen bonds forming S(5)
and S(6) motifs, respectively (dashed lines). Displacement ellipsoids represent the 50% probability level. [Color figure can be viewed in the online issue,
which is available at wileyonlinelibrary.com.]
Table 1
Crystallographic data of compound 12c
Crystallized from
Empirical formula
Mr
Crystal color, habit
Crystal dimensions [mm]
Radiation type, λ [Å]
Temperature [K]
Crystal system
Space group
Z
θ Range [°]
a [Å]
b [Å]
CH2Cl2/petroleum ether
C18H16N4O2
320.35
colorless, block
0.35 × 0.28 × 0.22
MoKα, 0.71073
120(2)
triclinic
P1
2
4.77–29.99
7.207(2)
11.102(3)
11.372(3)
64.94(3)
89.78(3)
86.86(3)
822.8(4)
1.293
μ [mmꢀ1
F(000) [e]
Scan type
Index range
]
0.088
336
ω and φ
ꢀ10 ≤ h ≤ 8
ꢀ15 ≤ k ≤ 15
ꢀ12 ≤ l ≤ 15
7080
Measured reflections
Independent reflections
Reflections with I > 2σ(I)
Rint
4348
3406
0.020
Refinement on
F2
Data, restraints, parameters
4348, 0, 281
R1 = 0.040a
wR2 = 0.113 a
R1 = 0.052
wR2 = 0.121
1.12
0.0778/0.0
0.31; ꢀ0.21
R (Fo2 > 2σ(Fo2))
c [Å]
α [°]
β [°]
R (all data)
γ [°]
Goodness-of-fit = S
V [Å3]
Weighting parameter a/b
Dx (calc.) [g cmꢀ3
]
Δρ (max; min) [e Åꢀ3
]
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
h
i
h
i
À
Á
À
Á
aR1 = ∑ |Fo| ꢀ |Fc| /∑|Fo|; wR2 ¼ ∑ w F2o ꢀ Fc2 =∑ w Fo2 . Weighting scheme: w = 1/[σ2(Fo2) + (aP)2 + bP] where P = (Fo2 + 2Fc )/3.
2
2
2
|
|
Table 2
Selected interatomic distances [Å], valence angles [°], and torsion angles [°] of 12c.
Bond lengths
N(1)–N(2)
N(1)–N(3)
N(3)–N(4)
N(1)–C(4)
N(2)–C(12)
1.333(2)
1.336(2)
1.318(2)
1.437(2)
1.338(2)
N(4)–C(12)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
1.361(2)
1.492(2)
1.337(2)
1.464(2)
Valence angles
N(2)–N(1)–N(3)
N(2)–N(1)–C(4)
N(3)–N(1)–C(4)
N(1)–N(2)–C(12)
Torsion angles
114.14(8)
123.60(8)
122.16(8)
101.62(8)
N(1)–N(3)–N(4)
N(3)–N(4)–C(12)
C(4)–C(5)–C(6)
105.59(8)
106.78(8)
132.01(9)
C(3)–O(2)–C(2)–C(1)
C(2)–O(2)–C(3)–C(4)
N(2)–N(1)–C(4)–C(5)
O(2)–C(3)–C(4)–N(1)
ꢀ178.7(2)
175.5(1)
100.6(2)
179.0(1)
O(2)–C(3)–C(4)–C(5)
N(1)–C(4)–C(5)–C(6)
C(4)–C(5)–C(6)–C(7)
N(2)–C(12)–C(13)–C(14)
ꢀ3.0(2)
ꢀ3.5(2)
ꢀ6.4(2)
ꢀ18.0(2)
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to five-membered S(5) and six-membered S(6) motifs, respec-
tively (Fig. 1, Table 3). Both of them are formed in plane 1
and stabilize the molecular structure of the compound. Besides,
atom H(7) is involved in intramolecular C(7)–H(7)–π[Cg(1)]
interaction with tetrazolyl ring (see Table 3 for details).
The crystal packing of 12c is dominated by weak
contacts with the atom O(1) playing the
from initial addition of triphenylphosphine 1 to the acetyle-
nic esters 13 and concomitant protonation of the 1:1 adduct,
followed by attack of the NH-acid anion 14 on the
vinyltriphenylphosphonium cation to form the phosphorane
15 (Scheme 3). In this reaction, triphenylphosphine acts as a
catalyst. TLC indicated formation of the N-vinyl tetrazoles
17a-d in CH2Cl2. The mechanism of the reaction outlined
earlier has not been established experimentally. However, a
possible explanation [29] is proposed in Scheme 3.
main accepting role (Table 3). The molecules in the crystal
are joined to each other by
bonds
to form infinite chains along the b axis (Fig. 2), almost
identical to these observed in the ethyl (Z)-2-(3,5-di-
The NMR spectra indicated that solutions of compound
17a–d (CDCl3 as solvent) contain E stereoisomer as only
product. The H NMR spectrum of the E stereoisomer of
1
methyl-1H-pyrazol-1-yl)-3-phenyl-2-propenoate
crystal
[42]. The adjacent chains interact with each other via
contacts, giving rise to layers
parallel to (001) plane. The neighboring layers are con-
nected to each other through centrosymmetric bifurcated
,
17a exhibited six signals readily recognized as arising from
OMe groups (δ= 3.87, s and δ= 3.88, s), =CH (δ = 6.89, d,
3
3JHH =14.0 Hz), –NCH =(δ= 8.45, d, JHH = 14.0 Hz) and
3
aromatic moieties (δ= 7.03, d, 2 H, JHH = 8.75Hz; 8.14,
3
d, 2 H, JHH = 8.75Hz). The 13C NMR spectrum of the E
stereoisomer showed 10 distinct resonances according to
expectation. Partial assignment of these resonances is
bonds resulting in three-dimensional network of hydrogen
contacts in the crystal of 12c. Additional stabilization of
the crystal packing is provided by the centrosymmetric
1
given in the Experimental section. The H and 13C NMR
spectra of compounds 17b-d are similar to those of 17a,
except for the ester group, which exhibits characteristic
signals with appropriate chemical shifts (see Spectral Anal-
ysis Section).
weak
interactions.
We have also used alkyl acetylenecarboxylates 13
(Scheme 3) instead of dialkyl acetylenedicarboxylate 2 in
this reaction. The stabilized phosphorus ylides 15 may result
Table 3
Geometry of proposed
close contacts for 12c.
D–H [Å]
0.96(2)
0.94(2)
0.98(2)
2.36(2)
2.49(2)
2.50(2)
2.730(2)
3.072(2)
3.429(2)
102(1)
120(1)
160(1)
1.00(2)
1.00(2)
0.95(2)
2.60(2)
2.65(2)
2.60(2)
3.418(2)
3.284(2)
3.251(2)
139(2)
121(1)
126(1)
0.94(2)
0.99(2)
2.66(2)
2.98(2)
3.456(2)
3.856(2)
142(2)
149(2)
Symmetry codes: (i) x, yꢀ1, z; (ii) xꢀ1, y, z; (iii) ꢀx, ꢀy + 1, ꢀzꢀ1; (iv) ꢀx + 1, ꢀy, ꢀz;
Cg(1) and Cg(2) are the centroids of the tetrazolyl N(1)–N(2) and phenyl C(6)–C(11) rings, respectively.
Figure 2. A fragment of infinite chains formed along the b axis in the crystal of 12c with adjacent molecules joined by
hy-
drogen bonds (dashed lines). Intramolecular
close contacts are shown with dotted lines. Symmetry codes are given in Table 3. [Color
figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Journal of Heterocyclic Chemistry
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A. Ramazani, F. Z. Nasrabadi, K. Ślepokura, T. Lis, and S. W. Joo
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Scheme 3. Synthesis of electron-poor N-vinyl tetrazoles 17a-d from triphenylphosphine1, alkyl acetylenecarboxylate 13, and tetrazole derivatives 3.
We have also used alkyl acetylenecarboxylates 13
(Scheme 4) instead of dialkyl acetylenedicarboxylate 2 and
5-benzyl-2H-tetrazol in this reaction. The stabilized phos-
phorus ylides 20 and 21 may result from initial addition of
triphenylphosphine 1 to the acetylenic esters 13 and concom-
itant protonation of the 1:1 adduct, followed by attack of the
NH-acid anion 19 on the vinyltriphenylphosphonium cation
to form the phosphorane 20 and 21 (Scheme 4). In this reac-
tion, triphenylphosphine acts as a catalyst. TLC indicated
formation of the N-vinyl tetrazoles 22 and 23 in CH2Cl2.
The mechanism of the reaction outlined earlier has not been
established experimentally. However, a possible explanation
[29] is proposed in Scheme 4. The formation of tautomeric
forms of 22 and 23 may be a result from the reduction of
steric hindrance (benzyl group is less steric than aryl group
and H group is less steric than CO2R group) in their forma-
tion in comparison with the formation of compounds 7, 12,
and 17 (Schemes 1–4).
The NMR spectra indicated that solutions of compound
22a-b and 23a-b (CDCl3 as solvent) contain E isomer of
2H-tautomeric form as major product, which may result
from the easy tautomerism of 1H- and 2H-tautomeric
forms. Relative population of E isomers of 1H- and 2H-
tautomeric forms were determined via their 1H NMR spec-
tra (22a: %E= 58, 23a: %E= 42; 22b: %E= 60, 23b: %
E= 40). The structure of products 22a-b and 23a-b was
1
proved by their IR, H NMR and 13C NMR spectral data
(see the Experimental section).
Scheme 4. Synthesis of electron-poor N-vinyl tetrazoles 22a-b and 23a-b from triphenylphosphine 1, alkyl acetylenecarboxylate 13 and 5-benzyl-2H-
tetrazol 18.
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3
CONCLUSIONS
3JHH =7.25Hz, CH3 of OEt), 1.40 (t, 3 H, JHH =7.25 Hz,
3
CH3 of OEt), 4.26 (q, 2 H, JHH =7.25 Hz, CH2 of OEt),
4.51 (q, 2H, JHH =7.25 Hz, CH2 of OEt), 4.30 (s, 2 H,
In conclusion, we have developed a convenient, one-pot
regioselective and stereoselective method for preparing
electron-poor N-vinyl tetrazoles (7a–c and 12a–b) utilizing
in situ generation of the phosphonium salts. Other aspects
of this process are under investigation.
3
CH2), 6.23 (s, 1 H, C¼CH), 7.23–7.73 (m, 5 H, arom.
CH). 13C NMR (62.5 MHz, CDCl3): δ 13.75, 14.00 (CH3
of OEt), 63.40, 61.78 (CH2 of OEt), 31.78 (CH2),
111.97, 129.78 (2CH), 128.86, 128.77 (4CH), 135.56,
139.31, 160.16 (3C), 163.33, 166.41 (CO of ester). for Z:
3
EXPERIMENTAL
1H NMR (250 MHz, CDCl3): δ 1.31 (t, 3 H, JHH
3
=7.25 Hz, CH3 of OEt), 1.40 (t, 3 H, JHH =7.25Hz, CH3
of OEt), 4.26 (q, 2 H, JHH =7.25 Hz, CH2 of OEt), 4.51
Melting points were measured on an Electrothermal 9100
apparatus and are uncorrected. IR spectra were recorded on a
Shimadzu IR-460 spectrometer (Shimadzu, Kyoto, Japan).
1H and 13C NMR spectra were measured with a Bruker
Spectrospin spectrometer at 250 and 62.5MHz, respectively.
3
3
(q, 2 H, JHH =7.25 Hz, CH2 of OEt), 4.30 (s, 2 H, CH2),
6.88 (s, 1 H, C¼CH), 7.23–7.73 (m, 5 H, arom. CH). 13C
NMR (62.5MHz, CDCl3): δ 13.75, 14.00 (CH3 of OEt),
61.78, 61.22 (CH2 of OEt), 30.09 (CH2), 111.97, 127.19
(2CH), 128.86, 128.77 (4CH), 135.56, 139.31, 160.16
Synthesis of tetrazole derivatives.
Twenty millimolar
benzonitrile derivatives, 15 mL of water, 1.56g sodium
azide, and 1.632 g zinc chloride were added to a three-
necked 50mL round bottomed flask. The reaction
solution was refluxed for 24 h with vigorous stirring.
After the mixture was cooled to room temperature, the
pH value was adjusted to 1.0 with concentrated HCl, and
the solution was stirred for 30 min to form a solid
precipitate. The new precipitate was then filtered, washed
with 1 M/L HCl, and dried in a drying oven at 90°C
overnight to give 5-benzyl-2H-tetrazole as a white
powder; the crude product was recrystallized in ethanol
(60% yield).
(3C), 165.24, 166.41 (CO of ester).
Dimethyl (Z)-2-(5-phenyl-2H-1,2,3,4-tetraazol-2-yl)-2-
butenedioate (7c). White solid, m.p. 86°C, yield 70%. IR
(KBr): 3076.92, 2961.54, 1730.77, 1653.85, 1453.85cmꢀ1
.
1H NMR (250MHz, CDCl3): δ 3.87 (s, 3 H, CH3 of
OMe), 4.09 (s, 3H, CH3 of OMe), 7.01 (s, 1 H, C¼CH),
7.26–8.22 (m, 5H, arom. CH). 13C NMR (62.5MHz,
CDCl3): δ 52.73, 53.95 (CH3 of OMe), 111.56, 131.35
(2CH), 127.43, 129.06 (4CH), 125.89, 139.44, 160.70
(3C), 163.92, 165.69 (CO of ester). C13H12N4O4 (288.09).
Diethyl
(Z)-2-(5-phenyl-2H-1,2,3,4-tetraazol-2-yl)-2-
butenedioate (7d).
Viscous colorless oil, yield 67%. IR
(KBr): 3184.62, 2930.77, 1730.77, 1661.54, 1469.23cmꢀ1
.
General procedure for the preparation of electron-poor
1H NMR (250MHz, CDCl3): δ 1.34 (t, 3H, JHH
3
N-vinyl tetrazoles.
To a magnetically stirred solution of
3
=7.25Hz, CH3 of OEt), 1.44 (t, 3H, JHH =7.25 Hz, CH3
triphenylphosphine (0.262 g, 1 mM) and tetraazol derivatives
(1 mM) in dichloromethane (5mL) was added dropwise a
mixture of acetylenic esters (1 mM) in dichloromethane
(2mL) at ꢀ10°C over 15min. The mixture was allowed to
warm up to room temperature and stirred for 72–120 h at
room temperature. The solvent was removed under reduced
pressure, and the viscous residue was purified by flash
column chromatography (silica gel; petroleum ether–ethyl
acetate). The solvent was removed under reduced pressure,
and the products were obtained. The characterization data of
the compounds are given in the following.
3
of OEt), 4.31 (q, 2H, JHH =7.25Hz, CH2 of OEt), 4.55
(q, 2H, 3JHH =7.25Hz, CH2 of OEt), 6.98 (s, 1H, C¼CH),
7.51–8.2 (m, 5H, arom CH).13C NMR (62.5MHz,
CDCl3): δ 13.83, 14.08 (CH3 of OEt), 61.87, 63.50 (CH2
of OEt), 111.78, 131.32 (2CH), 127.37, 129.07 (4CH),
125.94, 139.45, 160.25 (3C), 163.44, 167.78 (CO of ester).
C15H16N4O4 (316.12).
Ethyl(E,Z)-2-[5-(4-methoxyphenyl)-2H-1,2,3,4-tetraazol-2-
yl]-3-phenyl-2-propenoate (12a). Viscous colorless oil, yield
65%. IR (KBr): 3069.23, 2923.08, 1730.77, 1653.85,
1469.23cmꢀ1. for E: 1H NMR (250MHz, CDCl3):
Dimethyl
(Z)-2-(5-benzyl-2H-1,2,3,4-tetraazol-2-yl)-2-
3
δ=1.31 (t, 3H, JHH =7.25Hz, CH3 of OEt), 3.88 (s, 3H,
butenedioate (7a).
Viscous colorless oil, yield 62%. IR
(KBr): 3038.46, 2946.15, 1746.15, 1661.54, 1446.15cmꢀ1
1H NMR (250MHz, CDCl3): δ 3.84 (s, 3H, CH3 of
3
CH3 of OMe), 4.33 (q, 2H, JHH =7.25Hz, CH2 of OEt),
.
7.28 (s, 1H, C¼CH), 6.87–8.19 (m, 9H, arom. CH). 13C
NMR (62.5MHz, CDCl3): δ 14.20 (CH3 of OEt), 62.37
(CH2 Of OEt), 55.42 (CH3 of OMe), 128.17, 128.96,
129.41, 130.43 (8CH); 114.34, 131.53 (2CH); 161.54,
151.00, 141.28, 119.48, 130.69 (5C), 162.80 (CO of
-
OMe), 4.04 (s, 3H, CH3 of OMe), 4.31 (s, 2H, CH2), 6.90
(s, 1 H, C¼CH), 7.23–7.34 (m, 5H, arom. CH). 13C NMR
(62.5 MHz, CDCl3): δ 52.71, 53.93 (CH3 of OMe), 31.76
(CH2), 111.63, 127.23 (2CH), 128.80, 128.86 (4CH),
135.49, 139.22, 161.49 (3C), 163.87, 165.29 (CO of ester).
C14H14N4O4 (302.10).
1
ester). for Z: H NMR (250MHz, CDCl3): δ 1.37 (t, 3H,
3JHH =7.25Hz, CH3 of OEt), 3.88 (s, 3H, CH3 of OMe),
3
4.44 (q, 2H, JHH =7.25Hz, CH2 of OEt), 8.07 (s, 1H,
Diethyl (E, Z)-2-(5-benzyl-2H-1,2,3,4-tetraazol-2-yl)-2-
C¼CH), 6.87–8.19 (m, 9H, arom. CH). 13C NMR
(62.5MHz, CDCl3): δ 14.20 (CH3 of OEt), 61.79 (CH2 of
OEt), 55.42 (CH3 of OMe), 128.69, 129.10, 129.48,
butenedioate (7b).
Viscous colorless oil, yield 60%. IR
(KBr): 3092.31, 2938.46, 1730.77, 1661.54, 1407.69cmꢀ1
for E: 1H NMR (250 MHz, CDCl3): δ 1.31 (t, 3 H,
.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

A. Ramazani, F. Z. Nasrabadi, K. Ślepokura, T. Lis, and S. W. Joo
Vol 000
3
130.37 (8CH); 114.34, 131.78 (2CH); 161.06, 151.00,
142.12, 125.6, 136.12 (5C), 165.50 (CO of ester).
C19H18N4O3 (350.14).
Ethyl (Z)-2-(5-benzyl-2H-1,2,3,4-tetraazol-2-yl)-3-phenyl-2-
2H, JHH =9Hz, arom CH). 13C NMR (62.5 MHz, CDCl3):
δ 14.22 (CH3 of OEt), 55.43 (CH3 of OMe), 61.43 (CH2 of
OEt), 114.47, 128.91 (4CH), 113.44, 135.18 (2CH),
118.68, 161.91,164.86 (3C), 165.59 (CO of ester).
propenoate (12b).
Viscous colorless oil, yield 70%. IR
C13H14N4O3 (274.11).
(KBr): 3030.77, 2984.62, 1738.46, 1646.15, 1453.85cmꢀ1
.
Methyl (E)-3-(5-phenyl-2H-1,2,3,4-tetraazol-2-yl)-2-propenoate
(17c). White solid, m.p. 146°C, yield 75%. IR (KBr):
1H NMR (250MHz, CDCl3): δ 1.23 (t, 3 H, 3JHH =7.25Hz,
CH3 of OEt), 4.24 (q, 2 H, JHH =7.25Hz, CH2 of
3100, 2923.08, 1730.77, 1653.85, 1461.54 cmꢀ1 1H
.
3
NMR (250 MHz, CDCl3): δ 3.88 (s, 3 H, CH3 of OMe),
OEt), 4.35 (s, 2H, CH2), 8.09 (s, 1 H, C¼CH), 6.68–7.29
(m, 10 H, arom. CH). 13C NMR (62.5 MHz, CDCl3): δ
14.02 (CH3 of OEt), 62.50 (CH2 Of OEt), 31.77 (CH2),
128.64, 128.69, 128.97, 130.18 (8CH), 126.93, 142.16,
131.71 (3CH), 125.56, 130.27, 136.70, 162.20 (4C), 166.28
3
6.93 (d, 1 H, JHH = 14 Hz, HC¼CH), 7.5–8.23 (m, 5 H,
3
arom. CH), 8.42 (d,1 H, JHH = 14 Hz, CH¼CH). 13C
NMR (62.5 MHz, CDCl3): δ 52.46 (CH3 of OMe),
113.38, 135.36, 131.22 (3CH), 127.32, 129.08 (4CH),
126.17, 165.22 (2C), 165.8 (CO of ester). C11H10N4O2
(CO of ester). C19H18N4O2 (334.14).
Preparation of single crystals of ethyl-(Z)-3-phenyl-2-(5-phenyl-
(230.08).
2H-1,2,3,4-tetraazol-2-yl)-2-propenoate (12c).
Colorless
Ethyl (E)-3-(5-phenyl-2H-1,2,3,4-tetraazol-2-yl)-2-propenoate
(17d). White solid, m.p. 128°C, yield 73%. IR (KBr):
single crystals of ethyl-(Z)-3-phenyl-2-(5-phenyl-2H-
1,2,3,4-tetraazol-2-yl)-2-propenoate were obtained from
slow evaporation of its dichloromethane/light petroleum
ether (1:3) solution (20–25°C). The colorless single
crystals were filtered off, washed with a cold mixture of
dichloromethane/light petroleum ether (1:3) and dried at
1
3092.31, 2930.77, 1723.08, 1676.92, 1469.23 cmꢀ1. H
3
NMR (250 MHz, CDCl3): δ 1.38 (t, 3 H, JHH =7.25 Hz,
3
CH3 of OEt), 4.35 (q, 2 H, JHH =7.25, CH2 of OEt),
3
6.94 (d, 1 H, JHH = 14 Hz, HC¼CH), 7.51–8.23 (m, 5 H,
3
arom. CH), 8.42 (d, 1 H, JHH = 14 Hz, CH¼CH).13C
room temperature.
NMR (62.5 MHz, CDCl3): δ 14.21 (CH3 of OEt), 61.49
(CH2 of OEt), 113.90, 135.17, 131.20 (3CH), 127.30,
129.08 (4CH), 126.21, 164.75 (2C), 165.71 (CO of
Ethyl (Z)-3-phenyl-2-(5-phenyl-2H-1,2,3,4-tetraazol-2-yl)-
2-propenoate (12c). White solid, m.p. 96°C, yield 77%. IR
(KBr): 3061.54, 2976.92, 1723.08, 1653.85, 1453.85cmꢀ1
.
ester). C12H12N4O2 (244.10).
1H NMR (250MHz, CDCl3): δ 1.29 (t, 3 H, 3JHH =7.25Hz,
Methyl (E)-3-(5-benzyl-2H-1,2,3,4-tetraazol-2-yl)-2-propenoate
3
CH3 of OEt), 4.33 (q, 2 H, JHH =7.25Hz, CH2 of OEt),
(22a).
White solid, m.p. 75°C, Total yield 77%. IR
3
(KBr): 3084.62, 2930.77, 1723.08, 1661.54, 1446.15cmꢀ1
.
8.17 (s, 1 H, C¼CH), 6.88 (d, 2H, JHH =7.75Hz arom.
3
3
-1H NMR (250MHz, CDCl3): δ 3.85 (s, 3H, CH3 of
OMe), 4.30 (s, 2H, CH2), 6.83 (d, 1H, JHH =14Hz,
CH); 7.34 (d of d, 2 H, JHH =7.75Hz, JHH =7.25Hz,
3
3
arom. CH), 7.25 (t, 1H, JHH = 7.25 Hz, arom. CH),
7.50–8.27 (m, 5 H, arom. CH). 13C NMR (62.5 MHz,
CDCl3): δ 14.10 (CH3 of OEt), 62.56 (CH2 of
OEt), 127.15, 128.97, 129.11, 130.33 (8CH), 130.68,
130.33, 131.81 (3CH), 125.58, 126.96, 142.18, 162.29
HC¼CH), 7.25–7.72 (m, 5H, arom CH), 8.33 (d,1H,
3JHH =14Hz, CH¼CH). 13C NMR (62.5MHz, CDCl3): δ
52.39 (CH3 of OMe), 31.83 (CH2), 113.42, 127.20, 135.27
(3CH), 128.80, 128.87 (4CH), 135.72, 159.06 (2C),
(4C), 165.6 (CO of ester). C18H16N4O2 (320.13).
Methyl (E)-3-[5-(4-methoxyphenyl)-2H-1,2,3,4-tetraazol-2-
165.13 (CO of ester). C12H12N4O2 (244.10).
Methyl (E)-3-(5-benzyl-1H-1,2,3,4-tetraazol-1-yl)-2-propenoate
(23a). Viscous colorless oil, Total yield 77%. IR (KBr):
yl]-2-propenoate (17a).
White solid, m.p. 119°C, yield
3038.46, 2930.77, 1730.77, 1661.54, 1438.46cmꢀ1. -1H
78%. IR (KBr): 3076.92, 2923.08, 1730.77, 1661.54,
1
1476.92 cmꢀ1. H NMR (250 MHz, CDCl3): δ 3.87 (s,
NMR (250MHz, CDCl3): δ 3.81(s, 3H, CH3 of OMe),
3
3 H, CH3 of OMe), 3.88 (s, 3 H, CH3 of OMe), 6.89
4.42 (s, 2H, CH2), 6.81 (d, 1H, JHH =14Hz, HC¼CH),
3
3
3
(d, 1H, JHH =14Hz, HC¼CH), 8.45 (d,1H, JHH =14Hz,
7.02–7.46 (m, 5H, arom CH), 7.78 (d,1H, JHH =14Hz,
CH¼CH), 7.03 (d, 2H, 3JHH =8.75Hz, arom CH), 8.14 (d,
CH¼CH). 13C NMR (62.5MHz, CDCl3): δ 52.42 (CH3
of OMe), 29.37 (CH2), 114.64, 128.10, 130.74 (3CH),
128.37, 129.41 (4CH), 153.3,136,11 (2C), 166.12 (CO of
2H, JHH =8.75Hz, arom CH). 13C NMR (62.5MHz,
3
CDCl3): δ 52.41, 55.42 (CH3 of OMe), 114.46, 128.92
(4CH), 112.92, 135.36 (2CH), 118.64, 161.92,165.32
(3C), 165.62 (CO of ester). C12H12N4O3 (260.09).
Ethyl (E)-3-[5-(4-methoxyphenyl)-2H-1,2,3,4-tetraazol-2-yl]-
2-propenoate (17b). White solid, m.p. 93°C, yield 77%.
IR (KBr): 3107.69, 2930.77, 1738.46, 1615.38,
ester). C12H12N4O2 (244.10).
Ethyl (E)-3-(5-benzyl-2H-1,2,3,4-tetraazol-2-yl)-2-propenoate
(22b). Viscous colorless oil, Total yield 73%. IR (KBr):
3100, 2930.77, 1730.77, 1661.54, 1461.54cmꢀ1. H NMR
1
3
(250MHz, CDCl3): δ 1.34 (t, 3H, JHH =7.25 Hz, CH3 of
1484.62cmꢀ1
.
1H NMR (250MHz, CDCl3): δ 1.37 (t,
3
OEt), 4.3 (q, 2H, JHH =7.25Hz, CH2 of OEt), 4.30
3
3
3H, JHH =7.00Hz, CH3 of OEt), 3.88 (s, 3H, CH3 of
(s, 2H, CH2), 6.82 (d, 1H, JHH =14Hz, HC¼CH),
3
3
OMe), 4.32 (q, 2H, JHH =7.00Hz, CH2 of OEt), 6.89
7.25–7.34 (m, 5H, arom. CH), 8.32 (d, 1H, JHH =14Hz,
3
3
CH¼CH). 13C NMR (62.5MHz, CDCl3): δ 14.17 (CH3 of
(d, 1 H, JHH =14Hz, HC¼CH), 8.39 (d, 1H, JHH =14Hz,
3
CH¼CH), 7.03 (d, 2H, JHH = 9Hz, arom CH), 8.14 (d,
OEt), 61.42 (CH2 of OEt), 31.84 (CH2), 113.92, 135.75,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Synthesis of Fully Substituted Tetrazoles
127,19 (3CH), 128.79, 128.88 (4CH), 135.09, 164.67 (2C),
166.60 (CO of ester). C13H14N4O2 (258.11).
Malhotra, R. K. Prog Med Chem 1980, 17, 151; (c) Ostrovskii, V. A.;
Pevzner, M. S.; Sheherbinin, M. B.; Tselinskii, I. V. Targets Heterocycl Syst
1999, 3, 467; (d) Hiskey, M.; Chavez, D. E.; Naud, D. L.; Son, S. F.;
Berghout, H. L.; Bome, C. A. Proc Int Pyrotech Semin 2000, 27, 3.
[10] Grunert, M.; Weinberger, P.; Schweifer, J.; Hampel, C.;
Stassen, A. F.; Mcreiterand, K.; Linert, W. J Mol Struct 2005, 733, 4113.
[11] Palazzi, A.; Stagni, S.; Selva, S.; Monari, M. J Organomet
Chem 2003, 669, 135.
Ethyl (E)-3-(5-benzyl-1H-1,2,3,4-tetraazol-1-yl)-2-propenoate
(23b). Viscous colorless oil, Total yield 73%. IR (KBr):
1
3100, 2930.77, 1723.08, 1661.54, 1453.85 cmꢀ1. H NMR
3
(250MHz, CDCl3): δ 1.31 (t, 3 H, JHH =7.25Hz, CH3 of
3
OEt), 4.25 (q, 2H, JHH =7.25Hz, CH2 of OEt), 4.38
[12] Kim, Y. J.; Kwak, Y. S.; Lee, Y. S. J Organomet Chem 2000,
603, 152.
3
(s, 2H, CH2), 6.78 (d, 1 H, JHH =14Hz, HC¼CH),
3
[13] Moderhack, D. J. Prakt Chem /Chem-Ztg 1988, 340, 687.
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7.08–7.50 (m, 5H, arom. CH), 7.75 (d, 1H, JHH =14Hz,
CH¼CH). 13C NMR (62.5MHz, CDCl3): δ 14.10 (CH3 of
OEt), 61.47 (CH2 of OEt), 30.89 (CH2), 115.11, 130.57,
128,08 (3CH), 128.39, 129.39 (4CH), 132.92, 153.12
(2C), 164.5 (CO of ester). C13H14N4O2 (258.11).
X-ray crystal-structure determination of 12c (Table 1
and Fig. 1)[43].
The crystallographic measurement was
[17] Albert, A. J Chem Soc B 1966 427.
performed on a κ-geometry Xcalibur PX automated four-
circle diffractometer with graphite-monochromatized
MoKα radiation (λ 0.71073 Å). The data for the crystal
were collected at 120(2) K by using the Oxford-
Cryosystems cooler. A summary of the conditions for the
data collection and the structure refinement parameters
are given in Table 1. The data were corrected for Lorentz
and polarization effects. Data collection, cell refinement,
and data reduction and analysis were carried out with the
Xcalibur PX software (Oxford Diffractiod Ltd.): CrysAlis
CCD and CrysAlis RED, respectively [44]. The structure
was solved by direct methods with the SHELXS-97
program [45] and refined by a full-matrix least-squares
technique with SHELXL-97 [45] and anisotropic thermal
parameters for non-H atoms. All H-atoms were found in
different Fourier maps and were refined isotropically.
Figures were made with the XP program [46].
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day Trans 1985, 2, 81 1555.
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[26] Ramazani, A.; Abbasi Motejadded, A.; Ahmadi, E. Phospho-
rus, Sulfur, Silicon Relat Elem 2006, 181, 233.
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K.; Lis, T. Z Naturforsch 2006, 61b, 1128.
[28] Ramazani, A.; Morsali, A.; Soudi, A. A.; Souldozi, A.;
Strarikova, Z. A.; Yanovsky, A. Z Kristallogr, NCS 2003, 218, 33.
[29] Yavari, I.; Ramazani, A. Synth Commun 1997, 27, 1449.
[30] Ramazani, A.; Bodaghi, A. Tetrahedron Lett 2000, 41, 567.
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Acknowledgments. This work is funded by the grant NRF-2015-
002423 of the National Research Foundation of Korea.
[34] Tofangchi Mahyari, A.; Shajari, N.; Kazemizadeh, A. R.;
Ślepokura, K.; Lis, T.; Ramazani, A. Z Naturforsch 2007, 62b, 829.
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