Reaction of 5-aryloxytetrazoles with dimethyl sulfoxide and DMSO-acetic anhydride. Structure and quantum-chemical calculations of 1- methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole

Article abstract of DOI:10.1007/s11178-005-0293-9

Decomposition of methyl 5-(4-nitrophenoxy)tetrazole-2-carboxylate in dimethyl sulfoxide at room temperature yields a mixture of 1- methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole, 1- and 2-methyl-5-(4- nitrophenoxy)tetrazoles, and 5-(4-nitrophenoxy)tetrazole. Methyl 5-aryloxytetrazole-2-carboxylates containing electron-donor substituents in the aryloxy group do not give rise to the corresponding products under analogous conditions. The reactions of 5-aryloxytetrazoles [Ar = 4-O₂NC ₆H₄, C₆H₅, 2,6-(MeO) ₂C₆H₃] with dimethyl sulfoxide in the presence of acetic anhydride lead to mixtures of 1- and 2-methylsulfanylmethyl-5- aryloxytetrazoles whose yield and ratio depend on the substituent in the aryloxy group. The structure of 1-methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole was studied by X-ray analysis, two-dimensional NMR spectroscopy (HSQC, HMBC, NOESY), and quantum-chemical methods (ab initio, AM1, PM3). A highly selective procedure was developed for the synthesis of 5-(4-nitrophenoxy)tetrazole.

Full text of DOI:10.1007/s11178-005-0293-9

Russian Journal of Organic Chemistry, Vol. 41, No. 7, 2005, pp. 1055–1063. From Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1076–1084.
Original English Text Copyright © 2005 by Dabbagh, Noroozi Pesyan, Bagheri, Takemo, Hayashi.
Reaction of 5-Aryloxytetrazoles with Dimethyl Sulfoxide
and DMSO–Acetic Anhydride. Structure and Quantum-Chemical
Calculations of 1-Methylsulfanylmethyl-5-
(4-nitrophenoxy)tetrazole*
H. A. Dabbagh1, N. Noroozi Pesyan1, A. Bagheri1, S. Takemo2, and H. Hayashi3
1 College of Chemistry, Isfahan University of Technology, 84155, Isfahan, Iran
dabbagh@cc.iut.ac.ir
2 Department of Chemistry, Osaka Prefecture University, 599-8531, Osaka, Japan
3 Department of Natural Product Chemistry, School of Agriculture and Biological Science,
Osaka Prefecture University, 599-8531, Osaka, Japan
Received October 3, 2004
Abstract—Decomposition of methyl 5-(4-nitrophenoxy)tetrazole-2-carboxylate in dimethyl sulfoxide at room
temperature yields a mixture of 1-methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole, 1- and 2-methyl-5-(4-
nitrophenoxy)tetrazoles, and 5-(4-nitrophenoxy)tetrazole. Methyl 5-aryloxytetrazole-2-carboxylates containing
electron-donor substituents in the aryloxy group do not give rise to the corresponding products under analogous
conditions. The reactions of 5-aryloxytetrazoles [Ar = 4-O2NC6H4, C6H5, 2,6-(MeO)2C6H3] with dimethyl
sulfoxide in the presence of acetic anhydride lead to mixtures of 1- and 2-methylsulfanylmethyl-5-aryloxy-
tetrazoles whose yield and ratio depend on the substituent in the aryloxy group. The structure of 1-methyl-
sulfanylmethyl-5-(4-nitrophenoxy)tetrazole was studied by X-ray analysis, two-dimensional NMR spectros-
copy (HSQC, HMBC, NOESY), and quantum-chemical methods (ab initio, AM1, PM3). A highly selective
procedure was developed for the synthesis of 5-(4-nitrophenoxy)tetrazole.
Numerous tetrazole derivatives exhibit versatile
biological activity due to the fact that the tetrazole ring
is a metabolically stable replacement of carboxylic
functionality [1]. Tetrazoles undergo various reactions
such as alkylation and acylation, complex formation
with metals, thermolysis, photolysis, decomposition
with formation of nitrenes, etc. [2–11]. We previously
studied interconversions of 1,5- and 2,5-substituted
tetrazoles [2–4, 12–14] and showed that 1- and
2-alkoxycarbonyltetrazoles occur in equilibrium with
the corresponding imidoyl azides. The state of the
equilibrium depends on the solvent, temperature, and
electron-acceptor power of functional group attached
to the tetrazole ring.
It is known that dimethyl sulfoxide–N,N'-dicyclo-
hexylcarbodiimide (DMSO–DCC) in the presence of
a source of protons is a mild and efficient reagent for
oxidation of alcohols to the corresponding carbonyl
compounds (Pfitzner–Moffatt reaction) [15] and intro-
duction of a methylsulfanylmethyl group into the ortho
position of phenols [16–18]. Subsequently, a number
of other reagents based on DMSO and sulfides have
been proposed for methylsulfanylmethylation of phe-
nols and anilines, e.g., DMSO–acetic anhydride [19],
DMSO–trifluoroacetic anhydride [20], DMSO–oxalyl
chloride (Swern reaction) [21], methyl sulfide–tert-
butyl hypochlorite [22, 23], etc.
In the present work we examined reactions of
5-aryloxytetrazoles [Ar = 4-O2NC6H4, Ph, 2,6-(MeO)2-
C6H3] with DMSO and DMSO–acetic anhydride with
a view to introduce a methylsulfanylmethyl group into
position 1 or 2 of the tetrazole ring. We previously
showed [4, 14] that methyl 5-aryloxytetrazole-2-car-
boxylates readily undergo isomerization to produce
an equilibrium mixture of methyl 5-aryloxytetrazole-
1- and -2-carboxylates and that decarboxylation of the
latter in the solid phase or in a polar solvent (DMSO,
DMF, MeCN) yields 1- and 2-methyl-5-aryloxytetra-
zoles, respectively (Scheme 1). Surprisingly, in the re-
action of methyl 5-(4-nitrophenoxy)tetrazole-2-carbox-
ylate (Ia) with DMSO we isolated 1-methylsulfanyl-
methyl-5-(4-nitrophenoxy)tetrazole (VIa) in 20–30%
* The original article was submitted in English.
1070-4280/05/4107-1055 © 2005 Pleiades Publishing, Inc.

DABBAGH et al.
1056
Scheme 1.
in the aryloxy group failed to produce the correspond-
O
ing methylsulfanylmethyl derivatives VIb–VIf.
OMe
The reaction mechanism resembles that typical of
Swern oxidation. There are three evidences in support
of a concerted addition–elimination path shown in
Scheme 2. First, no 2-methylsulfanylmethyl-5-(4-nitro-
phenoxy)tetrazole (VIIa) is formed in the reaction;
second, methanol is released; and third, carbonyl ab-
sorption band disappears from the IR spectrum. Ionic
intermediates like E can be ruled out; otherwise, a mix-
ture of VIa and VIIa would be obtained (Scheme 3).
N
N
N
N
Solvent
OMe
N
N
N
N
O
OAr
OAr
II
I
–CO2
H2O
Me
N
N
N
N
N
N
N
N
Methylsulfanylmethylation of 5-aryloxytetrazoles
Va, Vb, and Vf in the system dimethyl sulfoxide–
acetic anhydride at 55–60°C (reaction time 24 h)
afforded mixtures of 1- and 2-methylsulfanylmethyl
derivatives VIa, VIb, VIf and VIIa, VIIb, VIIf
(Scheme 4). Here, two very important observations
should be noted. In all cases, methylsulfanylmethyla-
tion at position 1 of the tetrazole ring predominates
over 2-methylsulfanylmethylation: the ratios of the
1- and 2-substituted isomers are 1.5, 1.63, and 1.75 for
Ar = 4-O2NC6H4, C6H5, and 2,6-(MeO)2C6H3, respec-
tively. Electron-withdrawing substituent in the 5-aryl-
oxy group favors the methylsulfanylmethylation proc-
ess: the overall yields of the products are 50, 42, and
or
OAr
N
N
N
N
Me
H
OAr
OAr
III
IV
V
Solvent = DMSO, DMFA, CH3CN; Ar = 4-O2NC6H4 (a),
Ph (b), 4-MeC6H4 (c), 4-MeOC6H4 (d), 2,6-Me2C6H3 (e),
2,6-(MeO)2C6H3 (f).
yield (Scheme 2). In addition, 25% of 1-methyl-5-
(4-nitrophenoxy)tetrazole (IVa), 40% of 2-methyl-5-
(4-nitrophenoxy)tetrazole (IIIa), and 5–15% of
5-(4-nitrophenoxy)tetrazole (Va) were isolated. Other
5-aryloxytetrazoles Ib–If containing donor substituents
Scheme 2.
Me
Me
N
O
O
O
O
O
HO
MeO
O
O
O
Me2SO
N
N
N
N
N
N
N
S
Me
H
S+
Me
S
N
N
N
N
N
CH2
N
–MeOH
N
N
Me
CH2
OAr
OAr
O
OAr
OAr
Ia
A
B
C
N
N
O
S
N
N
N
N
N
–CO2
S
N
Me
Me
OAr
OAr
D
VIa
Scheme 3.
H
O
Me
O
SMe
N
N
N
N
N
N
N
N
SMe
+
N
N
N
N
Me
O
S
OAr
OAr
OAr
VIIa
CH2
E
VIa
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

REACTION OF 5-ARYLOXYTETRAZOLES WITH DIMETHYL SULFOXIDE
1057
Scheme 4.
SMe
N
N
N
N
N
N
Me2SO, Ac2O
SMe
+
N
N
N
N
N
OAr
N
H
O
OAr
VIa, VIb, VIf
OAr
VIIa, VIIb, VIIf
Va, Vb, Vf
Scheme 5.
Me
Me
Me
N
N
O
S
Me
Me
O
Va, Vb, Vf
O
O
O
S
O
+
MeCOO–
N
OAr
–AcOH
N
Me
Me
O
S
Me
Me
S
Me
H2C
S
Me
Me
Me
Me
Me
S
VIa, VIb, VIf
MeCOO–
N
N
N
N
N
N
+
–AcOH
VIIa, VIIb, VIIf
N
N
N
N
OAr
OAr
OAr
N
N
The structure of VIa was also analyzed by X-ray
22% for Ar = 4-O2NC6H4, C6H5, and 2,6-(MeO)2C6H3,
respectively. These data support our previous predic-
tion that the reaction with DMSO of Ia containing
an electron-withdrawing yields only isomer VIa and
that no analogous product is formed from Ib–If. The
formation of 2-substituted isomers may be regarded as
an additional support for the mechanism shown in
Scheme 2. An alternative mechanism (Scheme 5) is
operative in the system DMSO–acetic anhydride; in
this case, a mixture of VI and VII is obtained.
crystallography (Fig. 2). The bond lengths, bond
angles, and torsion angles in molecule VIa are given
in Tables 1–3. The tetrazole ring in VIa is planar, and
the p-nitrophenoxy group deviates from the tetrazole
ring plane so that the torsion angles C5C4O1C3 and
C4O1C3N4 are 68.6(3)° and 8.1(4)°, respectively. The
torsion angle O1C4C5C6 equal to 173.6(2)° implies
steric interaction between the benzene and tetrazole
rings. The N1–C2 and C5–O1 bonds (in the methylsul-
fanylmethyl and p-nitrophenoxy groups) are not
coplanar: the dihedral angle C2N1C3O1 is 5.1(4)°.
Surprisingly, a weak resonance is observed between
the O1 atom and electron-withdrawing nitro group in
the para position of the benzene ring (structure VIa2 in
The structure of 1-methylsulfanylmethyl-5-(4-nitro-
1
phenoxy)tetrazole (VIa) was elucidated by the H and
13C (including two-dimensional HSQC, HMBC,
NOESY techniques), IR, and mass spectra and ele-
mental analysis. The HSQC spectrum shows correla-
tions between the CH3S protons (H1, δ 2.326 ppm) and
C1 (δC 15.53 ppm), SCH2 protons (H2, δ 5.32 ppm) and
C2 (δC 49.21 ppm), H3 (δ 7.70 ppm) and C9, and
H4 (δ 8.36 ppm) and C8. In the HMBC spectrum
(Fig. 1a–1c), a long-range correlation between H1
(δ 2.326 ppm) and C2 (δC 49.21 ppm) was observed,
while no correlations between the same proton and the
other carbon atoms in molecule VIa were found. The
SCH2 protons correlate with both C1 (δC 15.53 ppm)
and C3 (δC 158.56 ppm). The NOESY spectra revealed
couplings between H1 and H2 in the methylsulfanyl-
methyl group and between H3 and H4 in the benzene
Table 1. Bond lengths (d) in the molecule of 1-methylsul-
fanylmethyl-5-(4-nitrophenoxy)tetrazole (VIa)a
Bond
N5–O2
N5–O3
N5–C7
C7–C8
C8–C9
C9–C4
C4–C5
C5–C6
C6–C7
C4–O1
d, Å
Bond
O1–C3
C3–N1
N1–N2
N2–N3
N3–N4
N4–C3
N1–C2
C2–S1
S1–C1
d, Å
1.189(4)
1.198(4)
1.474(3)
1.371(4)
1.375(4)
1.361(3)
1.369(3)
1.375(4)
1.368(4)
1.403(3)
1.324(3)
1.326(3)
1.348(3)
1.287(3)
1.364(3)
1.304(3)
1.453(3)
1.788(3)
1.790(3)
1
ring. Thus, the H–13C HMBC correlation spectra in-
dicate that the methylsulfanylmethyl group is attached
to the N1 atom of the tetrazole ring. The IR, 1H and 13C
NMR, and mass spectral data of compounds VIa, VIb,
VIf, VIIa, VIIb, and VIIf are given in Experimental.
a
Hereinafter, for atom numbering, see Fig. 2.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

DABBAGH et al.
1058
Scheme 6). Instead, the O1 atom is involved in con-
1-H
(a)
jugation with the tetrazole ring (VIa1). The O1–C3
bond [1.324(3) Å] is shorter than C4–O1 [1.402(3) Å,
Table 1]. These findings contradict our earlier conclu-
sion that a strong electron-withdrawing substituent in
position 5 should affect the electron density distribu-
tion over the tetrazole ring [13]. The results obtained
by ab initio, AM1, and PM3 quantum-chemical cal-
culations of molecules VIa and VIIa complement the
experimental X-ray diffraction data (Tables 4–6).
C1
Scheme 6.
C2
SMe
O
N
N
O
N
N
N
O
2-H
(b)
VIa
C1
SMe
O
N
N
N
N
O2N
VIa1
SMe
C2
O
N
N
–O
N
N
N
O
VIa2
2-H
(c)
SMe
O
N
N
N
N
O2N
VIa3
Compound Va was synthesized by Martin and
Weise [24] in an overall yield of less than 10% by
reaction of p-nitrophenol with cyanogen bromide,
followed by treatment of p-nitrophenyl cyanate with
sodium azide. We have developed a new highly selec-
tive procedure for the synthesis of 5-(4-nitrophenoxy)-
tetrazole (Va) via direct nitration of 5-phenoxy-
tetrazole Vb (Scheme 7). Tetrazole Vb was prepared
in 70% yield by the procedure described previously
[4, 13]. The nitration of Vb with fuming nitric acid
C3
Fig 1. HMBC 1H–13C correlation spectra of 1-methylsulfanylmethyl-
5-(4-nitrophenoxy)tetrazole (VIa) (expanded aliphatic region):
(a) 1-H–C2 correlation, (b) 2-H–C1 correlation, and (c) 2-H–C3 cor-
relation.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

REACTION OF 5-ARYLOXYTETRAZOLES WITH DIMETHYL SULFOXIDE
N3
1059
afforded 90% of Va, and the product contained no
impurities of meta and ortho isomers. Obviously, the
presence of a bulky tetrazolyl substituent prevents
nitration of Vb at the ortho position.
N2
H6
H7
N4
O3
C5
N1
H4
C6
C7
C3
N5
H5
O1
C4
C2
C1
O2
Scheme 7.
C8
H8
N
N
S4
C9
N
H3
H2
H9
N
OH
OCN
O
H
BrCN
NaN3
H1
Fig. 2. Structure of the molecule of 1-methylsulfanylmethyl-5-(4-
nitrophenoxy)tetrazole (VIa) according to the X-ray diffraction data.
Vb
N
N
X-Ray analysis of compound (VIa). Crystals of
VIa were obtained by slow evaporation of a solution
of VIa in a mixture of ethyl acetate and cyclohexane at
room temperature. A suitable single crystal was sealed
in a glass capillary. The data were acquired using
a Rigaku RAXIS-Rapid diffractometer and were
processed using Rigaku Rapid-auto program. Empir-
ical corrections for absorption and Lorentz polarization
were applied. Orthorhombic crystals, C9H9N5O3S,
M 267.27. Unit cell parameters at 296(2) K: a =
12.2341(13), b = 7.6350(8), c = 25.428(3) Å; α = β =
γ = 90°; V = 2375.2(5) Å3; space group Pbca (no. 61);
Z = 8; μ = 0.282 mm–1. Total reflection number 19309
(λ = 0.71075 Å); number of independent reflections
2692 (Rint = 0.0630); final divergence factors [I >
2σ(I)]: R1 = 0.0499, wR2 = 0.1330. The structure was
solved by the direct method using Crystal Structure
N
N
O
H
Fuming HNO3
NO2
Va
EXPERIMENTAL
1
The H NMR spectra were recorded on Varian
EM390 (90 MHz), Jeol JNMα-500 (500 MHz), and
Bruker 500 Ultra Shield (500 MHz) spectrometers.
The 13C NMR spectra (125 MHz) were measured on
Jeol JNMα-500 and Bruker 500 Ultra Shield instru-
ments. The mass spectra were obtained using a Fision
Trio 1000 GC–MS system. The IR spectra were re-
corded on Perkin–Elmer 1760X and Shimadzu IR-470
Fourier spectrometers. The elemental compositions
were determined at the Research Institute of Petroleum
Industry (Pazhouheshgah Bld., Qom Road, Tehran,
Iran). The melting points were determined using
a Gallenkamp apparatus and were not corrected. AM1,
PM3, and ab initio (STO-3G) quantum-chemical
calculations were performed using HyperChem Pro 6.0
software with optimization according to the Polak–
Ribier algorithm.
Table 2. Bond angles (ω) in the molecule of 1-methylsul-
fanylmethyl-5-(4-nitrophenoxy)tetrazole (VIa)
Angle
C2S1C1
C3O1C4
C3N1N2
C3N1C2
N2N1C2
N3N2N1
N2N3N4
C3N4N3
O3N5O2
O3N5C7
O2N5C7
N1C2S1
N4C3O1
ω, deg
Angle
N4C3N1
O1C3N1
C9C4C5
C9C4O1
C5C4O1
C4C5C6
C7C6C5
C6C7C8
C6C7N5
C8C7N5
C7C8C9
C4C9C8
ω, deg
099.79(14)
118.43(18)
106.85(18)
129.8(2)00
123.21(19)
106.64(18)
111.41(18)
103.85(19)
123.7(3)00
118.8(3)00
117.5(3)00
114.49(17)
129.8(2)00
111.3(2)
118.9(2)
122.6(2)
116.8(2)
120.3(2)
118.9(2)
118.3(2)
122.8(2)
118.9(2)
118.3(2)
118.5(2)
118.9(2)
2,6-Dimethoxyphenol, 4-methoxyphenol, 4-methyl-
phenol, 2,6-dimethylphenol, phenol, bromine, sodium
cyanide, dimethyl sulfoxide, sodium azide, and fuming
nitric acid were commercial products and were used
without additional purification. Cyanogen bromide
[25] and phenyl cyanate [26] were synthesized by
known methods. The solvents were purified by stand-
ard procedures prior to use.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

DABBAGH et al.
1060
Table 3. Torsion angles (φ) in the molecule of 1-methylsul-
fanylmethyl-5-(4-nitrophenoxy)tetrazole (VIa)
refined with anisotropic temperature factors. The posi-
tions of hydrogen atoms were determined from the
difference Fourier map and were refined isotropically.
The crystallographic data for structure VIa were
deposited to the Cambridge Crystallographic Data
Center (entry no. CCDC-232963) and are available
free of charge upon request to CCDC, 12 Union
Road, Cambridge, UK (fax: +44-1223-336033, e-mail:
deposit@ccdc.cam.ac.uk).
Angle
φ, deg
Angle
φ, deg
C3N1N2N3
C2N1N2N3
N1N2N3N4
N2N3N4C3
C3N1C2S1
N2N1C2S1
C1S1C2N1
N3N4C3O1
N3N4C3N1
C4O1C3N4
C4O1C3N1
N2N1C3N4
C2N1C3N4
N2N1C3O1
C2N1C3O1
C3O1C4C9
–000.8(2)
–177.4(2)
00–0.4(3)
00–0.1(3)
–101.3(3)
–082.9(3)
–073.1(2)
–177.9(3)
–000.6(3)
–008.1(4)
–174.8(2)
00–0.9(3)
–177.2(2)
–178.5(2)
–005.1(4)
–117.3(3)
C3O1C4C5
C9C4C5C6
O1C4C5C6
C4C5C6C7
C5C6C7C8
C5C6C7N5
O3N5C7C6
O2N5C7C6
O3N5C7C8
O2N5C7C8
C6C7C8C9
N5C7C8C9
C5C4C9C8
O1C4C9C8
C7C8C9C4
–068.6(3)
00–0.2(4)
–173.6(2)
00–0.2(4)
–000.7(4)
–179.3(3)
–000.3(4)
–179.9(3)
–179.6(3)
–000.1(4)
00–0.8(4)
–179.2(2)
–000.1(4)
–173.9(2)
–000.4(4)
Methyl 5-aryloxytetrazole-2-carboxylates Ia–If
were synthesized by the procedures reported in [13].
5-(4-Nitrophenoxy)tetrazole (Va). A 100-ml flask
was charged with 10.0 g (62 mmol) of 5-phenoxy-
tetrazole (Vb), and fuming nitric acid was added drop-
wise over a period of 20 min under stirring and cooling
with an ice bath. The cooling bath was removed, and
the mixture was allowed to warm up to 25–30°C
over a period of 20 min and was transferred into a
beaker containing crushed ice under stirring in a hood.
The precipitate was filtered off and recrystallized from
benzene. Yield 90%, mp 160–161°C; published data
[24]: mp 162–163°C, yield <10%. IR spectrum (KBr),
ν, cm–1: 2500–3200 br, s, 1620, 1580, 1530, 1480,
1
Version 2.0 program and was refined by the full-
matrix least-squares procedure with respect to F2 using
SHELXL97 software [27]. Nonhydrogen atoms were
1350, 1200, 1060, 870, 730, 670, 650. H NMR spec-
trum (90 MHz, DMSO-d6), δ, ppm: 14.60 br.s (1H),
8.60 d (2H, J = 9 Hz), 7.75 d (2H, J = 9 Hz).
VIa
VIIa
Fig. 3. Optimized structures of 1- and 2-methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazoles VIa and VIIa (ab initio calculations).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

REACTION OF 5-ARYLOXYTETRAZOLES WITH DIMETHYL SULFOXIDE
1061
Table 4. Selected bond lengths (d, Å) in molecules VIa and VIIa according to AM1, PM3, and ab initio calculations and
experimental data for VIa
AM1
PM3
Ab initio
VIIa
Experiment
(X-ray diffraction)
Bond
VIa
VIIa
1.395
1.379
1.372
1.348
1.369
1.262
1.441
–
VIa
VIIa
1.388
1.357
1.353
1.367
1.350
1.277
1.406
–
VIa
C4–O1
O1–C3
C3–N1
N1–N2
N2–N3
N3–N4
N4–C3
N1–C2
C2–S1
S1–C1
1.403(3)
1.324(3)
1.326(3)
1.348(3)
1.287(3)
1.364(3)
1.304(3)
1.453(3)
1.788(3)
1.790(3)
1.404
1.376
1.419
1.358
1.280
1.332
1.377
1.441
1.773
1.752
1.399
1.358
1.392
1.392
1.266
1.337
1.361
1.474
1.824
1.801
1.412
1.373
1.399
1.399
1.379
1.420
1.342
1.472
1.815
1.796
1.414
1.384
1.386
1.408
1.419
1.382
1.409
–
1.769
1.750
1.824
1.799
1.815
1.796
Table 5. Selected bond angles (ω, deg) in molecules VIa and VIIa according to AM1, PM3, and ab initio calculations and
experimental data for VIa
AM1
PM3
Ab inilio
Experiment
(X-ray diffraction)
Angle
VIa
VIIa
104.20
115.40
–
VIa
VIIa
103.83
120.31
–
VIa
VIIa
097.18
114.39
–
C2S1C1
C3O1C4
C3N1C2
N2N1C2
N1C2S1
O1C3N1
099.79(14)
118.43(18)
129.8(2)00
123.21(19)
114.49(17)
118.9(2)00
104.18
115.14
127.15
126.95
115.75
120.21
104.01
116.63
130.08
123.36
116.33
121.79
98.74
114.81
129.60
122.14
111.58
116.96
123.30
–
123.76
–
119.40
–
126.05
132.56
120.12
Table 6. Selected torsion angles (φ, deg) in molecules VIa and VIIa according to AM1, PM3, and ab initio calculations and
experimental data for VIa
AM1
PM3
Ab initio
Experiment
(X-ray diffraction)
Angle
VIa
179.0
008.2
–179.5–
001.6
125.3
173.5
VIIa
–
VIa
178.5
003.4
–180.0–
002.2
126.9
173.9
VIIa
–
VIa
VIIa
–
C2N1N2N3
C4O1C3N4
N2N1C3O1
C2N1C3O1
C3O1C4C5
O1C4C5C6
–177.4(2)
–008.1(4)
–178.5(2)
–005.1(4)
–068.6(3)
–173.6(2)
174.8
083.5
–172.6–
–
144.3
–172.0–
–
00–3.2–
–178.9–
005.1
109.60
–173.25–
–
044.7
174.5
022.8
176.9
129.5
0–47.73–
175.99
175.8
tate (90:10) as eluent. We isolated 1-methylsulfanyl-
methyl-5-(4-nitrophenoxy)tetrazole (VIa), mp 67–
68°C, 2-methyl-5-(4-nitrophenoxy)tetrazole (IIIa),
mp 89°C, and 1-methyl-5-(4-nitrophenoxy)tetrazole
(IVa), mp 109°C (108– 109°C [4]).
Reaction of 5-(4-nitrophenoxy)tetrazole (Va)
with DMSO in the presence of acetic anhydride.
Compound Va, 0.5 g, was dissolved in 5 ml of acetic
anhydride, and 20 ml of dry DMSO was added drop-
Reaction of methyl 5-(4-nitrophenoxy)tetrazole-
2-carboxylate (Ia) with dimethyl sulfoxide. A mix-
ture of methyl 5-(4-nitrophenoxy)tetrazole-2-carbox-
ylate (Ia) and DMSO (taken as solvent) was stirred for
12 h at room temperature using a magnetic stirrer. The
progress of the reaction was monitored by TLC (cyclo-
hexane–ethyl acetate, 80:20). Excess DMSO was re-
moved, and the residue was passed through a column
charged with silica gel using cyclohexane–ethyl ace-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

DABBAGH et al.
1062
wise over a period of 30 min. The mixture was stirred
for 24 h at 55–60°C, excess DMSO and acetic anhy-
dride were removed under reduced pressure, and the
residue was washed with several 2–3-ml portions of
water. The precipitate was dissolved in 20 ml of
methylene chloride, the solution was dried over
calcium chloride and evaporated, and the residue was
separated by column chromatography on silica gel
using ethyl acetate–cyclohexane (80:20) as eluent to
isolate compounds VIa and VIIa.
spectrum (500 MHz, CDCl3), δ, ppm: 7.31 m (5H),
5.49 s (2H), 2.34 s (3H). 13C NMR spectrum (125 MHz,
CDCl3), δC, ppm: 171.30, 154.73, 130.26, 125.87,
119.55, 56.86, 16.25. Mass spectrum (EI), m/z (Irel, %)
224 (0.64) [M + 2]+, 222 (14) [M]+, 147 (70), 101 (79),
77 (100), 74 (23), 61 (58). Found, %: C 48.8; H 4.7;
N 25.6. C9H10N4OS. Calculated, %: C 48.63; H 4.53;
N 25.2.
2-Methylsulfanylmethyl-5-phenoxytetrazole
(VIIb). Yield 16%. IR spectrum (KBr), ν, cm–1: 3060,
3000, 2920, 1550, 1490, 1310, 1250, 1190, 1160, 750,
1-Methylsulfanylmethyl-5-(4-nitrophenoxy)-
tetrazole (VIa). Yield 30%, mp 67–68°C. IR spectrum
(KBr), ν, cm–1: 3020, 1640, 1610, 1520, 1410, 1350,
1
680. H NMR spectrum (500 MHz, CDCl3), δ, ppm:
7.40 m (5H), 5.32 s (2H), 2.35 s (3H). 13C NMR spec-
trum (125 MHz, CDC13), δC, ppm: 160.18, 154.71,
130.45, 126.89, 119.60, 49.30, 15.96. Mass spectrum
(EI), m/z (Irel, %) 224 (0.64) [M + 2]+, 222 (14) [M]+,
176 (27), 147 (16), 101 (22), 77 (67), 61 (100).
1
1240, 1180, 1160, 1120, 860, 710. H NMR spectrum
(500 MHz, CDC13), δ, ppm: 8.36 m (2H, J = 9.5 Hz),
7.70 d (2H, J = 9.0 Hz), 5.32 s (2H), 2.33 s (3H).
13C NMR spectrum (125 MHz, CDCl3), δC, ppm:
158.56, 157.08, 145.44, 125.89, 119.63, 49.21, 15.53.
Mass spectrum (EI), m/z (Irel, %): 269 (10) [M + 2]+,
267 (47) [M]+, 192 (75), 150 (8), 122 (28), 101 (90),
76 (33), 61 (100). Found, %: C 40.5; H 3.5; N 26.8.
C9H9N5O3S. Calculated, %: C 40.5; H 3.4; N 26.2.
Reaction of 5-(2,6-dimethoxyphenoxy)tetrazole
(Vf) with DMSO in the presence of acetic an-
hydride. Dry DMSO, 10 ml, was added dropwise over
a period of 30 min to a solution of 0.285 g of com-
pound Vf in 4 ml of acetic anhydride. The mixture was
stirred for 40 h at 45–50°C, excess DMSO and acetic
anhydride were removed under reduced pressure, and
the residue was washed with several 2–3-ml portions
of water. The precipitate was dissolved in 20 ml of
methylene chloride, the solution was dried over
calcium chloride and evaporated, and the residue was
separated by column chromatography on silica gel to
isolate compounds VIf and VIIf.
2-Methylsulfanylmethyl-5-(4-nitrophenoxy)-
tetrazole (VIIa). Yield 20%, mp 92–94°C. IR spec-
trum (KBr), ν, cm–1: 3020, 2980, 1620, 1530, 1480,
1
1340, 1240, 1200, 1090, 1000, 870, 740. H NMR
spectrum (500 MHz, CCl4, DMSO-d6), δ: 8.40 d (2H,
J = 9.0 Hz), 7.78 d (2H, J = 9.0 Hz), 5.57 s (2H),
2.26 s (3H). 13C NMR spectrum (125 MHz, CDCl3),
δC, ppm: 159.71, 158.25, 145.90, 126.86, 121.15, 49.62,
15.60. Mass spectrum (EI), m/z (Irel, %): 269 (2.6)
[M + 2]+, 267 (65) [M]+, 192 (36), 191 (40), 122 (30),
101 (32), 75 (28), 61 (100). Found, %: C 40.6; H 3.6;
N 27.4. C9H9N5O3S. Calculated, %: C 40.5; H 3.4;
N 26.2.
1-Methylsulfanylmethyl-5-(2,6-dimethoxyphen-
oxy)tetrazole (VIf). Yield 14%. IR spectrum (KBr), ν,
cm–1: 3010, 3000, 2900, 2840, 1600, 1580, 1510, 1480,
1
1300, 1260, 1180, 1100, 750, 700. H NMR spectrum
(500 MHz, CDCl3), δ, ppm: 7.22 t (1H, J = 8.5 Hz),
6.70 d (2H, J =10 Hz), 5.46 s (2H), 3.85 s (6H), 2.33 s
(3H). 13C NMR spectrum (125 MHz, CDCl3), δC, ppm:
172.01, 152.84, 132.33, 126.92, 105.73, 56.67, 56.52,
16.17. Mass spectrum (EI), m/z (Irel, %) 284 (1.7)
[M + 2]+, 282 (43) [M]+, 207 (34), 179 (27), 165 (70),
122 (52), 107 (88), 101 (100), 77 (47), 61 (68). Found,
%: C 48.2; H 5.3; N 17.6. C11H14N4O3S. Calculated,
%: C 46.8; H 5.0; N 19.8.
Reaction of 5-phenoxytetrazole (Vb) with DMSO
in the presence of acetic anhydride. Dry DMSO,
20 ml, was added dropwise over a period of 30 min to
a solution of 0.5 g of compound Vb in 5 ml of acetic
anhydride. The mixture was stirred for 24 h at 45–
50°C, excess DMSO and acetic anhydride were
removed under reduced pressure, and the residue was
washed with several small portions of water and dis-
solved in 20 ml of methylene chloride. The solution
was dried over calcium chloride and evaporated, and
the residue was separated by column chromatography
on silica gel to isolate compounds VIb and VIIb.
2-Methylsulfanylmethyl-5-(2,6-dimethoxyphen-
oxy)tetrazole (VIIf). Yield 8%. IR spectrum (KBr), ν,
cm–1: 3000, 1590, 1530, 1390, 1370, 1300, 1260, 1180,
1
1110, 760. H NMR spectrum (500 MHz, CDCl3), δ,
ppm: 7.21 t (1H, J = 10 Hz), 6.69 d (2H, J = 10 Hz),
5.46 s (2H), 3.87 s (6H), 2.56 s (3H). 13C NMR spec-
trum (125 MHz, CDCl3), δC, ppm: 178.05, 152.70,
1-Methylsulfanylmethyl-5-phenoxytetrazole
(VIb). Yield 26%. IR spectrum (KBr), ν, cm–1: 3020,
2993, 1510, 1490, 1410, 1200, 1020, 750, 680. 1H NMR
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 7 2005

REACTION OF 5-ARYLOXYTETRAZOLES WITH DIMETHYL SULFOXIDE
1063
11. Hobbs, P.D. and Magnus, P.D., J. Chem. Soc., Perkin
Trans. 1, 1973, p. 469.
12. Dabbagh, H.A. and Modarresi-Alam, A.R., J. Chem.
Res., Synop., 2000, p. 44.
13. Dabbagh, H.A. and Lwowski, W., J. Org. Chem., 2000,
vol. 65, p. 7284.
14. Dabbagh, H.A. and Mansoori, Y., Russ. J. Org. Chem.,
2001, vol. 37, p. 1771.
131.81, 127.12, 105.64, 56.68, 13.58. Mass spectrum
(EI), m/z (Irel, %) 284 (0.6) [M + 2]+, 282 (15)
[M]+, 281 (20), 236 (83), 151 (73), 140 (39), 107 (59),
43 (100).
The authors thank Isfahan University of Tech-
nology for financial support (Research Council Grant
IUT-1CHI821). We also greatly acknowledge Osaka
Prefecture University (Japan) for performing X-ray
analysis.
15. Pfitzner, K.E. and Moffatt, J.G., J. Am. Chem. Soc.,
1963, vol. 85, p. 3027.
16. Burdon, M.G. and Moffatt, J.G., J. Am. Chem. Soc.,
1967, vol. 89, p. 4725.
REFERENCES
17. Pfitzner, K.E., Marino, J.P., and Olofson, R.A., J. Am.
Chem. Soc., 1965, vol. 87, p. 4658.
18. Moffatt, J.G., J. Org. Chem., 1971, vol. 36, p. 1909.
19. Hayashi, Y. and Oda, R., J. Org. Chem., 1967, vol. 32,
p. 457.
20. Huang, S.L., Omura, K., and Swern, D., J. Org. Chem.,
1976, vol. 41, p. 3329.
21. Mancuso, A.J., Huang, S.-L., and Swern, D., J. Org.
Chem., 1978, vol. 43, p. 2480.
22. Gassman, P.G. and Gruetzmacher, G., J. Am. Chem.
Soc., 1973, vol. 95, p. 588.
23. Gassman, P.G. and van Bergen, T.J., J. Am. Chem. Soc.,
1973, vol. 95, p. 590.
1. Singh, H., Chawla, A., Kapoor, V., Paul, D., and
Malkurta, R., Prog. Med. Chem., 1980, vol. 77, p. 151.
2. Dabbagh, H.A. and Karimzadeh, R., Molecules, 2002,
vol. 7, p. 189.
3. Dabbagh, H.A. and Gaelee, S., J. Org. Chem., 1996,
vol. 61, p. 3439.
4. Dabbagh, H.A., Mansoori, Y., Jafari, M., and Rosta-
mi, M., J. Chem. Res., Synop., 2000, p. 442.
5. Huff, B.F., LeTourneau, M.E., Staszak, M.A., and
Ward, J.A., Tetrahedron Lett., 1996, vol. 37, p. 3655.
6. Olofson, R.A. and Kendall, R.V., J. Org. Chem., 1970,
vol. 35, p. 2246.
7. Isida, T., Akiyama, T., Nabika, K., Sisido, K., and Ko-
24. Martin, D. and Weise, A., Chem. Ber., 1966, vol. 99,
p. 317.
sima, S., Bull. Chem. Soc. Jpn., 1973, vol. 46, p. 2176.
8. Nelson, J.H., Schmitt, D.L., Henry, R.A., Moore, D.W.,
25. Hatman, W.W. and Dreger, E.E., Org. Synth., 1943,
and Jonassen, H.B., Inorg. Chem., 1970, vol. 9, p. 2678.
collect. vol. 2, p. 150.
9. Ofele, K. and Kreiter, C.G., Chem. Ber., 1972, vol. 105,
26. Grigate, E. and Putter, R., Chem. Ber., 1964, vol. 97,
p. 529.
p. 3012.
10. Markgraf, J.H., Brown, H.S., Kaplinsky, M.W., and
27. Sheldrick, G.M., SHELXL97, Göttingen: Univ. of Göt-
Peterson, R.G., J. Org. Chem., 1964, vol. 29, p. 2629.
tingen, 1997.
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