Tetrazoles: XLIV. Synthesis and chemical properties of 5-substituted 2-triphenylmethyltetrazoles

Article abstract of DOI:10.1023/A:1021672317335

Tritylation of tetrazole and its 5-substituted derivatives with triphenylmethyl chloride under conditions of phase-transfer catalysis regioselectively yields the corresponding 5-substituted 2-trityltetrazoles which can be used to protect N-H bonds in nitrogen-containing heterocycles and O-H bonds in primary alcohols. Thermolysis of 2-trityltetrazoles in benzonitrile leads to 3,6-disubstituted 1,2,4,5-tetrazines. Thermal transformation of the same compounds in dodecane follows a radically different mechanism, resulting in formation of difficultly accessible 8,8-diphenylheptafulvenes. The structure of the latter was proved by X-ray analysis.

Full text of DOI:10.1023/A:1021672317335

Russian Journal of Organic Chemistry, Vol. 38, No. 9, 2002, pp. 1360 1369. Translated from Zhurnal Organicheskoi Khimii, Vol. 38, No. 9, 2002,
pp. 1413 1421.
Original Russian Text Copyright
2002 by Myznikov, Artamonova, Bel’skii, Stash, Skvortsov, Koldobskii.
Dedicated to Full Member of the Russian Academy of Sciences
V.A. Tartakovskii on the 70th Anniversary of His Birth
Tetrazoles: XLIV.* Synthesis and Chemical Properties
of 5-Substituted 2-Triphenylmethyltetrazoles**
L. V. Myznikov1, T. V. Artamonova1, V. K. Bel’skii2, A. I. Stash2,
N. K. Skvortsov1, and G. I. Koldobskii1
1
St. Petersburg State Institute of Technology, Moskovskii pr. 26, St. Petersburg, 198013 Russia
e-mail: koldobsk@tu.spb.ru
2
Karpov Research Physicochemical Institute, Moscow, Russia
Received April 17, 2002
Abstract Tritylation of tetrazole and its 5-substituted derivatives with triphenylmethyl chloride under condi-
tions of phase-transfer catalysis regioselectively yields the corresponding 5-substituted 2-trityltetrazoles which
can be used to protect N H bonds in nitrogen-containing heterocycles and O H bonds in primary alcohols.
Thermolysis of 2-trityltetrazoles in benzonitrile leads to 3,6-disubstituted 1,2,4,5-tetrazines. Thermal trans-
formation of the same compounds in dodecane follows a radically different mechanism, resulting in formation
of difficultly accessible 8,8-diphenylheptafulvenes. The structure of the latter was proved by X-ray analysis.
Temporary protection of the N H bond in tetra-
zoles is necessary when these compounds are used in
the synthesis of drugs [2 8] and complex ligands for
biomimetic studies [9], as well as in the functionaliza-
tion of tetrazole [10 12] and 5-substituted tetrazoles
[13 15]. It was noted that triphenylmethyl group,
whose protective properties are determined mainly by
steric factor, is superior to the other groups which
are commonly used to protect the tetrazole N H bond
[2, 3, 6, 16]. The reason is that introduction of trityl
group into a substrate molecule is always regioselec-
tive and almost is not accompanied by side processes
which could reduce the yield of the tritylation product.
It was shown previously [9, 13, 17] that treatment
of 5-methyl- and 5-aryltetrazoles with triphenylmethyl
chloride or 4,4 -dimethoxytriphenylmethyl chloride
under conditions of phase-transfer catalysis gives the
corresponding N2-trityl derivatives in high yield.
From the preparative viewpoint, advantages of the
phase-transfer procedure are obvious. Unlike non-
catalytic methods, this procedure does not require the
use of anhydrous solvents and inert atmosphere.
Scheme 1.
I, R = H (a), Me (b), PhCH2 (c), PhCH(Et) (d), PhOCH2 (e), 4-CH3OC6H4 (f), Ph (g), 4-ClC6H4 (h), 4-NO2C6H4 (i), CH3S (j),
PhS (k), 3-pyridyl (l), 4-pyridyl (m).
____________
*
For communication XLIII, see [1].
**
This study was financially supported by the Integratsiya
Federal Program (project no. I0667).
1070-4280/02/3809-1360$27.00 2002 MAIK Nauka/Interperiodica

TETRAZOLES: XLIV.
1361
In continuation of our studies in the field of N H
bond protection in tetrazole derivatives, we examined
tritylation of tetrazole and a series of 5-substituted
tetrazoles under conditions of phase-transfer catalysis.
The reactions were carried out at 20 C in a two-phase
system consisting of aqueous sodium hydroxide and
chloroform, and tetrabutylammonium bromide was
used as phase-transfer catalyst. These conditions
ensured a high rate of the process, and the correspond-
ing N2-trityl derivatives were formed in 40 93% yield
(Scheme 1). Presumably, the relatively low yield
(24%) of tetrazole IId is explained by steric effect of
the 5-substituent.
Chemical properties of N-trityltetrazoles have been
studied very poorly. It is known that treatment of
5-methyl-2-trityl- and 5-(2-biphenylyl)-2-trityltetra-
zoles with acetic, trifluoroacetic, hydrochloric, and
sulfuric acids results in removal of the trityl protection
[2, 3, 6, 13]. 2-Trityltetrazoles prepared by tritylation
with triphenylmethyl chloride on a polymeric support
[15] and 2-(4,4 -dimethoxytriphenylmethyl)-5-phenyl-
tetrazole [9] are deprotected in a similar way. 2-Trityl-
tetrazoles IIa IIm follow the above general relations.
They undergo smooth deprotection to the correspond-
ing 5-substituted tetrazoles by the action of 15%
hydrochloric acid at 20 C. On the other hand, 2-trityl-
tetrazoles are relatively stable in weakly alkaline and
neutral media, so that they can be used as reagents
for protection of N H bonds in nitrogen-containing
heterocycles and O H bonds in alcohols.
action of dimethyl sulfate even on heating to 100 C.
Less sterically crowded compounds, e.g., 5-substituted
2-tert-butyltetrazoles smoothly react with dimethyl
sulfate at 60 C [18]. Thus, the use of 2-trityltetrazoles
is expected to be most efficient in the protection of
O H bonds in primary alcohols which are insuf-
ficiently stable in basic medium.
Studies of thermal transformations of nitrogen-
containing heterocycles constitute a promising and
extensively developing field in heterocyclic chemistry
[19 22]. Beginning with the first Huisgen works, i.e.,
over a period of more than 40 years, tetrazoles have
persistently become the most interesting subjects of
these studies. Just the results obtained by studying
thermolysis of 2,5-substituted tetrazoles [23, 24] made
it possible to formulate a general and fundamental
concept of formation of 1,3-dipoles and their parti-
cipation in 1,3-dipolar cycloaddition and 1,5-electro-
cyclization processes [25]. From the preparative view-
point, thermolysis of 2,5-disubstituted tetrazoles is
a universal method for preparation of various hetero-
cycles, from pyrazoles, 1,2,4-triazoles, and 1,3,4-oxa-
diazoles to 3H-1,3,4-benzotriazepines [26 28].
The reactivity of 1,3-dipoles generated by thermol-
ysis of 2,5-disubstituted tetrazoles strongly depends
on the substituent in position 2 of the heteroring and
properties of the reaction medium. The effect of these
factors is clearly seen in the thermolysis of 5-sub-
stituted 2-trityltetrazoles. Heating of tetrazoles IIf IIh
in benzonitrile at 150 C leads to formation of the cor-
responding 3,6-disubstituted 1,2,4,5-tetrazines Va Vc
in 41 72% yield (Scheme 3).
Heterocyclic substrates having an N H bond can
be tritylated with 2-trityltetrazoles in acetonitrile at
80 C. Analogous reactions with alcohols occur on
heating at the boiling point (Scheme 2).
Scheme 3.
Scheme 2.
V, R = 4-MeO (a), H (b), 4-Cl (c).
Analogous results were obtained previously [29]
while studying thermolysis of 5-phenyltetrazole in
mesitylene, as well as on treatment of the same com-
pound with p-toluenesulfonyl chloride in pyridine
[30]. It should be noted that in the first case the only
product was 3,6-diphenyl-1,2,4,5-tetrazine, while in
the latter process 3,6-diphenyl-2,3-bis(p-tolylsul-
fonyl)-1,2,4,5-tetrazine was formed in addition to
3,6-diphenyl-1,2,4,5-tetrazine. Presumably, thermal
transformations of 5-phenyltetrazole, its N-sulfonyl
derivatives, and 5-substituted 2-trityltetrazoles follow
III, Ht = 1-imidazolyl (a), 1-benzimidazolyl (b), 1-benzo-
triazolyl (c); IV, R = Me (a), Et (b), Pr (c).
It is important that the tritylation of alcohols occurs
in neutral medium and that secondary hydroxy groups
are not involved. The low reactivity of 2-trityltetra-
zoles toward secondary alcohols is likely to result
from steric hindrances in the reagent, created by the
triphenylmethyl group. For example, 5-phenyl-2-trityl-
tetrazole does not undergo quaternization by the
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

1362
MYZNIKOV et al.
to 1,4-dihydrophthalazine. It is known that 1,4-di-
hydrophthalazines are widely used in the synthesis of
o-quinodimethanes [31, 32]. Thus there are reasons
to believe that thermolysis of 2-trityltetrazoles results
in formation of o-quinodimethanes. It should be noted
1
that the data of elemental analysis, UV, IR, and H
and 13C NMR spectroscopy, and mass spectrometry
for all products obtained by thermolysis of tetrazoles
IIb and IIf IIh do not contradict possible o-quinodi-
metane structures. On the other hand, the thermolysis
products are characterized by high thermal stability
and low reactivity, e.g., in the cycloaddition with
tetracyanoethylene. These properties are inconsistent
with the generally accepted views, according to which
o-quinodimethanes are highly reactive intermediates
generated by thermolysis of of benzocyclobutenes,
1,4-dihydrophthalazines, and some other substrates
[32]. Although some fairly stable o-quinodimethanes
have been reported in the recent years [33, 34], these
cases are likely to be an exception rather than a rule.
Fig. 1. Structure of the molecule of 1-methyl-8,8-diphenyl-
heptafulvene (VIa) according to the X-ray diffraction data.
The above discrepancies were eliminated by the
results of X-ray diffraction study of the thermolysis
products obtained from 5-methyl- and 5-phenyl-2-
trityltetrazoles. It was shown that thermal transforma-
tion of 5-substituted 2-trityltetrazoles leads not to
o-quinodimethanes but to isomeric 1-substituted
8,8-diphenylheptafulvenes VIa VIe (Scheme 4).
Scheme 4.
VI, R = Me (a), Ph (b), 4-CH3OC6H4 (c), 4-ClC6H4 (d),
4-pyridyl (e).
The corresponding X-ray diffraction data are given
below. Figures 1 and 2 show molecular structures of
heptafulvenes VIa and VIb, and the principal bond
lengths and bond angles are presented in Table 1.
For comparison, Table 1 also contains published data
for 1-isopropyl-8,8-dicyano- and 8,8-dicyano-1,6-di-
methylheptafulvenes VIIa and VIIb [35, 36], which
are the closest structural analogs of VIa and VIb.
The seven-membered ring in molecules VIa and
VIb has a deep boat conformation, whereas the same
ring in 8,8-dicyanofulvene is almost planar [37]. The
conformations of the different compounds can be
Fig. 2. Structure of the molecule of 1,8,8-triphenylhepta-
fulvene (VIb) according to the X-ray diffraction data.
a common mechanism involving intermediate forma-
tion of the corresponding 1,3-dipoles, whose dimeriza-
tion leads to tetrazines.
Quite surprising results were obtained while study-
ing thermolysis of 2-trityltetrazoles in dodecane at
180 C. Formerly, we proposed that this process leads
to formation of the corresponsing o-quinodimethanes
[17]. Here, the following considerations were taken
into account. Thermal transformation of 2-trityltetra-
zoles is likely to include cleavage of the heteroring
and subsequent loss of nitrogen molecule to give
1,3-dipole. The latter undergoes 1,6-electrocyclization
compared using the angles
, , , and , which are
shown in Figs. 3 and 4 and given in Table 2. Analysis
of these data indicates that the angle changes only
slightly in going from one structure to another, while
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

TETRAZOLES: XLIV.
consderable differences are observed in the angle ,
1363
(a)
depending on the substituent in position 1. It
attains its maximal value for compound VIIb having
a phenyl group in that position. By contrast, the angle
appreciably decreases. The depth of the boat along
the other axis is characterized by the dihedral angle .
In this case, the maximal deviation from planarity is
also typical of structure VIIb. The most appreciable
differences are observed in the C1 C7 and C7 C8
bond lengths. The C1 C7 bond becomes longer while
the exocyclic double C7 C8 bond becomes shorter
as the boat depth increases. The reason is increase of
the torsion angles C1 C7 and C6 C7, which reduces
the degree of overlap of p-orbitals. The bond lengths
and angles indicate an insignificant contribution of di-
polar structure, which was assumed for unsubstituted
8,8-dicyanoheptafulvene on the basis of its large
dipole moment, 7.5 D [37]. The substituents at the
exocyclic double bond do not lie in one plane, and
the maximal deviation is observed for compound
VIIb. An analogous effect was noted previously
for 8,8-dicyano-1-isopropylheptafulvene [35].
(b)
The C7 and C8 atoms are characterized by a small
degree of pyramidality. The C7 atom in molecule VIa
is located above the plane formed by the adjacent
carbon atoms (the corresponding deviation is 0.05 ),
Fig. 3. Projections of the molecule of 1-methyl-8,8-di-
phenylheptafulvene (VIb) with respect to different planes:
(a) angle and (b) angles , and
,
.
whereas the C8 atom lies in that plane. By contrast,
the C7 atom in VIb lies in the plane formed by the
neighboring carbon atoms, while C8 deviates from it
Thus, detailed analysis of our present experimental
data and available information on the thermolysis of
2,5-disubstituted tetrazoles and on the method for
preparation of 1,3,5-cycloheptatrienes allowed us to
propose a probable mechanism of thermal transforma-
tions of 5-substituted 2-trityltetrazoles into 1-sub-
stituted 8,8-diphenylheptafulvenes (Scheme 6). In the
first stage, cleavage of the tetrazole ring occurs with
loss of nitrogen molecule to give 1,3-dipole A. Its
1,6-electrocyclization yields 1,4-dihydrophthalazine B.
The key stage in the further transformations is the
conversion of 1,4-dihydrophthalazine B into 3,4-di-
hydro-3H-pyrazole C. The latter gives rise to final
8,8-diphenylheptafulvene through intermediate D,
following the known scheme [39, 40].
by 0.02
.
Our results show that both electronic and steric
factors should be taken into account in order to inter-
pret structural parameters and reactivity of substituted
8,8-diphenylheptafulvenes. According to Komatsu
et al. [38], [4+2]-cycloaddition of 8,8-diphenylhepta-
fulvene to tetracyanoethylene in benzene at 20 C in
4.5 h gives the corresponding product in 62% yield.
The reactions of 1-methyl-8,8-diphenylheptafulvene
(VIa) and 1,8,8-triphenylheptafulvene (VIb) with
tetracyanoethylene under the same conditions gave
only 54 and 65% of the corresponding cycloadducts
in 30 days (Scheme 5).
To conclude, it should be noted that thermolysis
of 5-substituted 2-trityltetrazoles may be regarded as
a new method for preparation of difficultly accessible
1-substituted 8,8-diphenylheptafulvenes.
Scheme 5.
EXPERIMENTAL
The IR spectra were recorded on a UR-20 spec-
trometer in KBr. The IR spectrum of VIb was taken
on a Perkin Elmer Spectrum BX-1000 instrument.
The electron spectrum of VIb was measured on
VIII, R = Me (a), Ph (b).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

1364
MYZNIKOV et al.
Scheme 6.
1
a Perkin Elmer Lambda 40 spectrophotometer. The
mass spectra (70 eV) were run on an MKh-1321 mass
X-ray absorption by the sample (0.066 cm ) was
introduced.
spectrometer. The 1H and 13C NMR spectra were
recorded on a Bruker AC-200 instrument in DMSO-d6
(compounds IIa IIm, IIIa, Va Vc, VIa, VIc, VIe,
and VIIIa) or CDCl3 (VIb, VId, and VIIIb).
Crystals of compound VIa, suitable for X-ray
analysis, were obtained by recrystallization from
2-propanol. Pink prisms, mp 114 115 C, crystal habit
0.46 0.10 0.06. The unit cell parameters and reflec-
tion intensities were measured on an Enraf Nonius
CAD-4 diffractometer (MoK -irradiation, /2 scan-
ning). Tetragonal crystals: a = 32.493 (5), c =
5.844(1) ; V = 6170.1(17) 3; dcalc = 1.164 g/cm3;
space group I41/a; Z = 16. The structure was solved
by the direct method; R = 0.025, Rw = 0.058 [from
1672 reflections with I > 2 (I)]. A correction for
Crystals of VIb were obtained by recrystallization
from acetonitrile. Yellow prisms, mp 106 108 C,
crystal habit 0.56 0.40 0.20. Triclinic crystals:
a = 6.2680(10), b = 8.444(2), c = 17.677
;
=
,
3
93.48, = 98.88(3), = 93.51(3) ; V = 920.3(3)
dcalc = 1.164 g/cm3; space group P-1; Z = 2. The
structure was solved by the direct method: R = 0.0291,
Rw = 0.0739 [from 2198 reflections with I > 2 (I)].
A correction for X-ray absorption by the sample
1
(0.066 cm ) was introduced.
2-Trityltetrazole (IIa). A mixture of 2.5 mmol of
5-phenyltetrazole, 0.2 mmol of tetrabutylammonium
bromide, 10 ml of 10% aqueous sodium hydroxide,
and 10 ml of chloroform was stirred for 15 min at
20 C. A solution of 3 mmol of triphenylmethyl
(a)
(b)
Fig. 4. Projections of the molecule of 1,8,8-triphenylheptafulvene (VIb) with respect to different planes: (a) angle
(b) angles , and
and
,
.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

TETRAZOLES: XLIV.
1365
chloride in 20 ml of chloroform was added, and the
mixture was stirred for 4 h at 20 C. The organic phase
was separated, washed with 5 ml of 10% aqueous
sodium hydroxide and water (2 10 ml), dried over
sodium sulfate, and evaporated to dryness. Yield
0.53 g (67%), mp 212 C (from ethyl acetate). IR spec-
Table 1. Principal bond lengths d and bond angles
in molecules VIa, VIb, VIIa, and VIIb
Parameter
Bond
VIa
VIb
VIIa
VIIb
d,
1.348(6) 1.346(2) 1.361(9)
1.425(7) 1.440(2) 1.443(12) 1.420(8)
1.329(6) 1.339(3) 1.347(15) 1.338(8)
1.432(6) 1.431(3) 1.426(14) 1.410(8)
1.339(5) 1.341(3) 1.343(11) 1.335(7)
1.466(5) 1.478(2) 1.474(9)
1.477(6) 1.494(2) 1.471(8)
1.347(5) 1.342(2) 1.367(8)
1.522(7) 1.489(2) 1.535(8)
1
trum, , cm : 910, 930, 960, 1010, 1020, 1040, 1090,
C1 C2
C2 C3
C3 C4
C4 C5
C5 C6
C6 C7
C7 C1
C7 C8
C1 C9
1.342(8)
1140, 1150, 1170, 1190, 1280, 1330, 1390, 1450,
1
1500, 1600, 2940, 3040, 3080. H NMR spectrum, ,
ppm: 6.90 7.40 m (15H, Harom), 8.90 s (1H, CH).
Found, %: C 76.51; H 5.28; N 17.61. C20H16N4. Cal-
culated, %: C 76.92; H 5.13; N 17.95.
Tetrazoles IIb IIm were synthesized by a similar
procedure.
1.460(8)
1.470(7)
1.361(8)
1.507(11)
5-Methyl-2-trityltetrazole (IIb). Yield 60%,
mp 178 C [11] (from ethyl acetate). IR spectrum, ,
1
cm : 890, 910, 930, 1010, 1030, 1040, 1090, 1170,
Angle
, deg
1190, 1290, 1330, 1360, 1390, 1450, 1500, 1520,
1
1600, 2970, 3040, 3070. H NMR spectrum, , ppm:
C2C1C7 124.4(4) 118.84(14) 122.8(5)
C2C1C9 117.7(5) 121.60(14) 119.9(5)
C7C1C9 117.7(5) 119.53(12) 117.3(5)
C1C2C3 128.2(5) 127.66(16) 130.3(7)
C4C3C2 127.1(6) 126.26(19) 125.4(9)
121.8(5)
120.9(6)
117.2(5)
129.5(5)
125.2(5)
3.10 s (3H, CH3), 6.90 7.20 m (6H, Harom), 7.30
7.45 m (9H, Harom).
5-Benzyl-2-trityltetrazole (IIc). Yield 56%,
1
mp 154 C (from ethyl acetate). IR spectrum, , cm :
910, 940, 1005, 1025, 1040, 1095, 1160, 1195, 1290,
1340, 1390, 1460, 1500, 1610, 2860, 2940, 3050,
C3C4C5 126.1(5) 126.12(17) 127.4(10) 127.1(5)
C6C5C4 126.9(5) 125.28(18) 127.4(8)
C5C6C7 127.2(5) 122.84(17) 126.7(7)
C8C7C6 121.5(4) 122.72(13) 118.6(5)
C8C7C1 123.5(4) 124.28(13) 123.2(5)
C6C7C1 114.5(4) 112.99(12) 117.8(5)
128.3(5)
123.2(5)
122.6(4)
122.0(4)
115.2(4)
1
3080. H NMR spectrum, , ppm: 4.60 s (2H, CH2),
7.00 7.50 m (20H, Harom). Found, %: C 80.50;
H 5.54; N 13.96. C27H22N4. Calculated, %: C 80.60;
H 5.47; N 13.93.
5-(1-Phenylpropyl)-2-trityltetrazole (IId). Yield
24%, mp 110 C (from ethyl acetate). IR spectrum, ,
1
cm : 890, 910, 940, 1005, 1050, 1070, 1095, 1160,
a
Table 2. Dihedral angles
VIa, VIb, VIIa, and VIIb
,
,
, and
in molecules
1195, 1240, 1290, 1390, 1450, 1500, 1605, 2890,
1
2950, 2980, 3040, 3080. H NMR spectrum, , ppm:
0.70 0.90 m (3H, CH3), 1.90 2.30 m (2H, CH2),
4.20 4.30 t (1H, CH), 6.90 7.50 m (20H, Harom).
Found, %: C 81.05; H 5.97; N 13.10. C29H26N4. Cal-
culated, %: C 80.93; H 6.05; N 13.02.
Comp. no.
VIa
VIb
VIIa
VIIb
134.4
125.2
137.9
131.9
20.9
24.8
19.5
20.1
39.1
6.1
0.6
5.6
4.0
51.0
37.3
45.3
5-Phenoxymethyl-2-trityltetrazole (IIe). Yield
58%, mp 145 C (from ethyl acetate). IR spectrum, ,
1
cm : 880, 920, 940, 990, 1010, 1030, 1040, 1080,
1150, 1160, 1185, 1195, 1220, 1240, 1270, 1300,
1330, 1360, 1405, 1450, 1500, 1600, 2850, 2930,
2970, 3040, 3090. H NMR spectrum, , ppm: 5.45 s
a
See Figs. 3 and 4.
1
1
(2H, CH2), 6.90 7.40 m (20H, Harom). Found, %:
C 77.65; H 5.31; N 13.49. C27H22N4O. Calculated, %:
C 77.51; H 5.26; N 13.40.
1580, 1600, 2900, 2950, 2990, 3050. H NMR spec-
trum, , ppm: 3.82 s (3H, CH3O), 6.95 7.40 m (17H,
Harom), 8.00 m (2H, Harom). Found, %: C 77.56;
H 5.48; N 13.44. C27H22N4O. Calculated, %: C 77.51;
H 5.26; N 13.40.
5-(4-Methoxyphenyl)-2-trityltetrazole (IIf). Yield
55%, mp 186 C (from ethyl acetate). IR spectrum, ,
1
cm : 910, 940, 1000, 1040, 1070, 1100, 1150, 1170,
5-Phenyl-2-trityltetrazole (IIg). Yield 93%,
1190, 1230, 1280, 1300, 1330, 1390, 1450, 1500,
mp 155 156 C (from butyl acetate); published data
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

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MYZNIKOV et al.
1
[10]: mp 158 160 C. IR spectrum, , cm : 930,
1005, 1030, 1050, 1160, 1195, 1285, 1330, 1380,
7.00 7.50 m (15H, Harom), 7.90 8.10 m (2H, pyri-
dine), 8.70 8.90 m (2H, pyridine). Found, %:
C 77.19; H 4.92; N 17.89. C25H19N5. Calculated, %:
C 77.12; H 4.88; N 17.99.
1
1455, 1480, 1500, 1605, 2870, 2930, 3050, 3075. H
NMR spectrum, , ppm: 7.08 7.48 m (18H, Harom),
8.03 m (2H, Harom).
5-(4-Chlorophenyl)-2-trityltetrazole (IIh). Yield
51%, mp 187 C (from ethyl acetate). IR spectrum, ,
cm : 910, 940, 1010, 1020, 1040, 1100, 1160, 1200,
1270, 1330, 1420, 1450, 1500, 1610, 2860, 2940,
3030, 3070. H NMR spectrum, , ppm: 7.10 7.50 m
1-Tritylimidazole (IIIa). A mixture of 0.2 mmol
of imidazole, 0.2 mmol of 5-phenyl-2-trityltetrazole,
and 0.3 mmol of NaOH in 10 ml of acetonitrile was
heated for 10 h under reflux (80 C). After cooling,
the precipitate was filtered off, and the filtrate was
evaporated to dryness. Yield 0.45 g (72%), mp 212
215 C (from ethyl acetate); published data [41]:
mp 210 212 C.
1
1
(15H, Harom), 8.20 m (4H, Harom). Found, %: C 74.08;
H 4.46; N 13.35. C26H19ClN4. Calculated, %:
C 73.85; H 4.50; N 13.25.
Compounds IIIb and IIIc were synthesized in
5-(4-Nitrophenyl)-2-trityltetrazole (IIi). Yield
a similar way.
43%, mp 203 C (from ethyl acetate). IR spectrum, ,
cm : 910, 940, 1005, 1020, 1040, 1090, 1120, 1170,
1-Tritylbenzotriazole (IIIb). Yield 47%, mp 216
218 C (from ethyl acetate); published data [41]:
mp 214 216 C.
1
1200, 1230, 1280, 1330, 1360, 1450, 1500, 1530,
1
1610, 2900, 2950, 2990, 3050. H NMR spectrum, ,
1-Tritylbenzimidazole (IIIc). Yield 89%, mp 181
ppm: 7.10 7.50 m (17H, Harom), 8.10 m (2H, Harom).
Found, %: C 72.02; H 4.25; N 16.19. C26H19N5O2.
Calculated, %: C 72.05; H 4.39; N 16.17.
1
182 C (from ethyl acetate). H NMR spectrum,
,
ppm: 6.40 6.50 d (1H, CH), 6.75 6.90 t (1H, Harom),
7.05 7.45 m (16H, Harom), 7.60 7.70 d (1H, Harom),
7.80 7.90 s (1H, Harom). Found, %: C 86.59; H 5.49;
N 7.57. C26H20N2. Calculated, %: C 86.67; H 5.55;
N 7.77.
5-Methylthio-2-trityltetrazole (IIj). Yield 60%,
1
mp 139 C (from ethyl acetate). IR spectrum, , cm :
910, 940, 1005, 1030, 1040, 1060, 1090, 1150, 1170,
1190, 1220, 1285, 1300, 1390, 1450, 1500, 1590,
Methyl triphenylmethyl ether (IVa). 5-Phenyl-2-
trityltetrazole, 0.13 mmol, was dissolved in 15 ml of
methanol, and the solution was heated for 3 h under
reflux. The mixture was diluted with 10 ml of 10%
aqueous sodium hydroxide and allowed to settle
down, and the precipitate was filtered off. Yield 1.4 g
(71%), mp 82 C (from 2-propanol) [42].
1
1605, 2860, 2949, 3040, 3070. H NMR spectrum, ,
ppm: 2.64 s (3H, CH3), 6.95 7.40 m (15H, Harom).
Found, %: C 70.35; H 5.16; N 15.66. C21H18N4S.
Calculated, %: C 70.39; H 5.01; N 15.64.
5-Phenylthio-2-trityltetrazole (IIk). Yield 42%,
1
mp 122 C (from ethyl acetate). IR spectrum, , cm :
920, 940, 1010, 1040, 1070, 1100, 1150, 1170, 1190,
1230, 1280, 1300, 1330, 1390, 1450, 1500, 1580,
Ethyl triphenylmethyl ether (IVb). 5-Phenyl-2-
trityltetrazole, 0.13 mmol, was dissolved in 15 ml
of ethanol, and the solution was heated for 4 h under
reflux. The mixture was diluted with 10 ml of 10%
aqueous sodium hydroxide and allowed to settle
down, and the precipitate was filtered off. Yield 45%,
mp 76 C (from 2-propanol) [42].
1
1600, 2900, 2950, 2990, 3050. H NMR spectrum, ,
ppm: 7.00 7.42 m (20H, Harom). Found, %: C 74.39;
H 4.56; N 13.36. C26H20N4S. Calculated, %: C 74.28;
H 4.76; N 13.30.
5-(3-Pyridyl)-2-trityltetrazole (IIl). Yield 40%,
1
mp 167 C (from ethyl acetate). IR spectrum, , cm :
Propyl triphenylmethyl ether (IVc). 5-Phenyl-2-
trityltetrazole, 0.13 mmol, was dissolved in 15 ml
of 1-propanol, and the solution was heated for 18 h
under reflux. The mixture was diluted with 10 ml
of 10% aqueous sodium hydroxide and allowed to
settle down, and the precipitate was filtered off. Yield
36%, mp 54 C (from 2-propanol) [42].
880, 915, 1010, 1030, 1095, 1160, 1195, 1285, 1340,
1420, 1455, 1500, 1610, 2870, 2940, 3050, 3080. H
1
NMR spectrum, , ppm: 7.00 7.60 m (17H, Harom),
8.30 8.50 m (1H, pyridine), 8.60 8.70 d (1H, pyri-
dine), 9.10 9.30 s (1H, pyridine). Found, %: C 77.15;
H 4.93; N 17.93. C25H19N5. Calculated, %: C 77.12;
H 4.88; N 17.99.
3,6-Diphenyl-1,2,4,5-tetrazine (Va). A mixture of
2.6 mmol of 5-phenyl-2-trityltetrazole and 10 ml of
benzonitrile was heated for 5 7 h at 150 C. The
mixture was then evaporated to dryness, and the solid
tarry residue was treated with petroleum ether
5-(4-Pyridyl)-2-trityltetrazole (IIm). Yield 69%,
mp 201 C (from ethyl acetate). IR spectrum, , cm :
1
910, 950, 1000, 1010, 1050, 1095, 1160, 1195, 1215,
1290, 1330, 1370, 1430, 1450, 1500, 1540, 1620,
1
2870, 2940, 3050, 3080. H NMR spectrum, , ppm:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

TETRAZOLES: XLIV.
1367
(3 10 ml). Yield 0.2 g (65%), violet crystals with
mp 189 C (from DMF) [43]. IR spectrum, , cm :
130.1. Found, %: C 94.10; H 5.91. M+ 332. C26H20.
Calculated, %: C 93.97; H 6.03. M 332.
1
810, 820, 900, 990, 930, 1030, 1070, 1090, 1150,
1370, 1440, 1470, 1570, 2965, 3130. H NMR spec-
trum, , ppm: 7.50 7.80 m (3H, Harom), 8.55 8.70 d
(2H, Harom). Found, %: C 71.94; H 4.15; N 23.84.
C14H10N4. Calculated, %: C 71.79; H 4.27; N 23.93.
1-(4-Chlorophenyl)-8,8-diphenylheptafulvene
1
(VIc). Yield 51%, mp 127 C (from 2-propanol). IR
1
spectrum, , cm : 830, 870, 900, 1010, 1080, 1100,
1
1360, 1410, 1495, 1610, 1650, 3040, 3080. H NMR
spectrum, , ppm: 6.15 m (1H, CH), 6.25 7.40 m
(18H, Harom). Found, %: C 84.95; H 5.15. M+ 367.
C26H19Cl. Calculated, %: C 85.13; H 5.18. M 366.5.
3,6-Bis(4-chlorophenyl)-1,2,4,5-tetrazine (Vb).
A mixture of 2.4 mmol of 5-(4-chlorophenyl)-2-trityl-
tetrazole and 10 ml of benzonitrile was heated for
5 7 h at 150 C. After cooling, the violet solid was
filtered off. Yield 0.26 g (77%), violet crystals with
1-(4-Methoxyphenyl)-8,8-diphenylheptafulvene
(VId). Yield 49%, mp 133 C (from 2-propanol). IR
1
spectrum, , cm : 830, 870, 900, 1020, 1070, 1100,
1
mp 303 C (from DMF). IR spectrum, , cm : 810,
1360, 1410, 1460, 1490, 1600, 1640, 3040, 3080.
1H NMR spectrum, , ppm: 3.63 s (3H, CH3O),
6.10 m (1H, CH), 6.20 7.40 m (18H, Harom). Found,
%: C 89.75; H 6.20. C27H22O. Calculated, %:
C 89.50; H 6.08.
830, 910, 990, 930, 1010, 1060, 1090, 1150, 1370,
1
1440, 1470, 1570, 2980, 3110. H NMR spectrum,
, ppm: 7.65 7.80 d (2H, Harom), 8.5 8.65 d (2H,
H
arom). Found, %: C 55.63; H 2.57; Cl 23.22;
N 18.73. C14H8ClN4. Calculated, %: C 55.45; H 2.64;
Cl 23.43: N 18.82.
1-(4-Pyridyl)-8,8-diphenylheptafulvene (VIe).
Yield 45%, mp 133 C (from 2-propanol). IR spec-
1
3,6-Bis(4-methoxyphenyl)-1,2,4,5-tetrazine (Vc)
trum, , cm : 910, 920, 970, 1000, 1040, 1080, 1160,
was obtained in a similar way. Yield 41%, mp 250 C
(from DMF) [43]. IR spectrum, , cm : 835, 910,
1180, 1370, 1420, 1450, 1500, 1600, 3040, 3070,
3090. H NMR spectrum, , ppm: 6.05 6.15 m (1H,
1
1
1020, 1050, 1100, 1110, 1170, 1250, 1295, 1385,
1510, 1590, 2860, 2950, 2990. H NMR spectrum,
CH); 6.42 7.42 m (19H, Harom). Found, %: C 90.12;
H 5.71; N 4.38. C25H19N. Calculated, %: C 90.09;
1
, ppm: 3.95 4.05 s (6H, CH3), 7.10 7.30 d (2H, H 5.70; N 4.21.
arom), 8.45 8.55 d (2H, Harom). Found, %: C 65.41;
H
4-Diphenylmethylene-3-methylbicyclo[3.2.2]-
nona-2,6-diene-8,8,9,9-tetracarbonitrile (VIIIa).
1-Methyl-8,8-diphenylheptafulvene, 0.17 mmol, was
dissolved in 10 ml of benzene, and a solution of
0.17 mmol of tetracyanoethylene in 10 ml of benzene
was added. The mixture was kept for 30 days at room
temperature and evaporated, and the residue was
treated with petroleum ether. Yield 0.26 g (54%),
H 14.71; N 18.97. C16H14N4O2. Calculated, %:
C 65.31; H 14.76; N 19.05.
1-Methyl-8,8-diphenylheptafulvene (VIa).
A mixture of 3 mmol of 5-methyl-2-trityltetrazole and
10 ml of dodecane was heated for 3 h at 170 180 C.
After cooling, the yellow precipitate was filtered off.
Yield 0.63 g (76%), mp 116 C (from 2-propanol). IR
1
mp 142 143 C (from EtOH H2O). IR spectrum,
,
spectrum, , cm : 700, 760, 780, 800, 850, 930, 980,
1
cm : 800, 830, 890, 950, 1000, 1030, 1070, 1160,
1280, 1320, 1370, 1440, 1490, 1570, 1620, 2350,
1030, 1080, 1450, 1500, 1610, 2860, 2930, 3030.
1H NMR spectrum, , ppm: 1.70 s (3H, CH3), 5.80
6.50 m (5H, CH, Harom), 7.00 7.40 m (10H, Harom).
Found, %: C 93.30; H 6.78. M+ 270. C21H18. Cal-
culated, %: C 93.33; H 6.67. M 270.
1
3050, 3440. H NMR spectrum, , ppm: 1.40 s (3H,
CH3), 3.80 t (1H, CH), 4.40 d (1H, CH), 5.75 d
(1H, CH), 6.35 t (1H, CH), 6.70 t (1H, CH), 6.90
7.40 m (10H, Harom). 13C NMR spectrum, , ppm:
24.7, 41.92, 43.65, 46.67, 50.32, 112.31, 112.77,
113.59, 124.91, 127.52, 128.28, 128.36, 128.44,
128.84, 128.97, 129.16, 129.29, 133.18, 138.77,
141.77, 142.25, 148.43. Found, %: C 81.48; H 4.71;
N 13.98. C27H18N4. Calculated, %: C 81.41; H 4.52;
N 14.07.
Heptafulvenes VIb VIe were obtained by a similar
procedure.
1,8,8-Triphenylheptafulvene (VIb). Yield 68%,
mp 107 108 C (from 2-propanol). IR spectrum,
cm : 755, 859, 907, 1043, 1069, 1352, 1440, 1490,
1559, 1600, 1636, 3013. UV spectrum (ethanol),
nm (log ): 240.58 (4.18), 268.85 (4.02), 324.28
(3.76). H NMR spectrum, , ppm: 6.15 m (1H, CH),
6.42 7.42 m (19H, Harom). 13C NMR spectrum,
,
1
,
max
4-Diphenylmethylene-3-phenylbicyclo[3.2.2]-
nona-2,6-diene-8,8,9,9-tetracarbonitrile (VIIIb) was
synthesized in a similar way. Yield 65%, mp 225
1
,
C
1
ppm: 125.7, 125.9, 126.1, 126.2, 126.5, 126.8, 127.2,
127.3, 127.5, 127.9, 128.0, 128.7, 129.0, 129.3,
226 C (from ethyl acetate). IR spectrum, , cm :
855, 965, 1030, 1074, 1280, 1440, 1490, 1600, 2250,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 9 2002

1368
MYZNIKOV et al.
1
3060, 3450, 3650. H NMR spectrum, , ppm: 4.00 t
(1H, CH), 4.65 d (1H, CH), 5.90 d (1H, CH), 6.40 t
(1H, CH), 6.70 t (1H, CH), 6.90 7.50 m (15H, Harom).
13C NMR spectrum, , ppm: 38.02, 39.27, 42.55,
45.84, 108.01, 108.40, 108.54, 109.34, 121.49,
122.59, 123.22, 123.73, 124.48, 125.03, 125.24,
126.14, 127.92, 137.36, 137.46, 140.47, 146.30.
Found, %: C 83.87; H 4.03; N 11.99. C32H20N4. Cal-
culated, %: C 83.48; H 4.35; N 12.17.
15. Matthews, D.P., Green, J.E., and Shuker, A.J.,
J. Combinat. Chem., 2000, vol. 2, no. 1, pp. 19 23.
16. Greene, T.W. and Wuts, P.G.M., Protective Groups
in Organic Synthesis, New York: Wiley, 1999.
17. Artamonova, T.V., Myznikov, L.V., and Koldob-
skii, G.I., Russ. J. Org. Chem., 2001, vol. 37, no. 11,
pp. 1672 1674.
18. Koren, A.O., Gaponik, P.N., Ivashkevich, O.A., and
Kovaleva, T.B., Mendeleev Commun., 1995, no. 1,
pp. 10 11.
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