Synthesis of 3H-pyrazoles by reaction of methyl and p-tolyl phenylethynyl sulfones with diphenyldiazomethane and their thermal and acid-catalyzed transformations

Article abstract of DOI:10.1134/S107042801506010X

Methyl and p-tolyl phenylethynyl sulfones reacted with diphenyldiazomethane in diethyl ether at 20° C to give 1,3-dipolar cycloaddition products both according and contrary to the von Auwers rule, sulfonyl-substituted 3H-pyrazoles at a ratio of 1 : 1.5 and 1.3 : 1, respectively. On heating in toluene for 2 h, the Auwers adducts underwent van Alphen-Hüttel rearrangement with 1,5-sigmatropic shift of one phenyl substituent to afford sulfonyl-substituted 4H-pyrazoles. Under analogous conditions, the anti-Auwers adducts rearranged into sulfonyl-substituted N-phenyl-1H-pyrazoles containing a small amount of the denitrogenation product, sulfonyl-substituted cyclopropene. The Auwers adducts, as well as 4H-pyrazoles resulting from their thermal rearrangement, were converted in 5-7 days at 20°C into 3,4,4-triphenyl-1H-pyrazol-5(4H)-one by the action of a catalytic amount of sulfuric acid in acetic acid. Under analogous conditions, the regioisomeric anti-Auwers adducts gave rise to 3,4,5-triphenyl-1H-pyrazole with an impurity of 4-(R-sulfonyl)-1,3,5-triphenyl-1H-pyrazoles.

Full text of DOI:10.1134/S107042801506010X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 6, pp. 874–883. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © V.A. Vasin, Yu.Yu. Masterova, E.V. Bezrukova, V.V. Razin, N.V. Somov, 2015, published in Zhurnal Organicheskoi Khimii, 2015,
Vol. 51, No. 6, pp. 890–899.
Synthesis of 3H-Pyrazoles by Reaction of Methyl
and p-Tolyl Phenylethynyl Sulfones with Diphenyldiazomethane
and Their Thermal and Acid-Catalyzed Transformations
V. A. Vasina, Yu. Yu. Masterovaa, E. V. Bezrukovaa, V. V. Razinb, and N. V. Somovc
a Ogarev Mordovian State University, ul. Bol’shevistskaya 68, Saransk, 430005 Russia
e-mail: vasin@mrsu.ru
b St. Petersburg State University, Universitetskii pr. 26, St. Petersburg, 198504 Russia
c Lobachevsky State University of Nizhni Novgorod, pr. Gagarina 23, Nizhni Novgorod, 603950 Russia
Received April 3, 2015
Abstract—Methyl and p-tolyl phenylethynyl sulfones reacted with diphenyldiazomethane in diethyl ether at
20°C to give 1,3-dipolar cycloaddition products both according and contrary to the von Auwers rule, sulfonyl-
substituted 3H-pyrazoles at a ratio of 1:1.5 and 1.3:1, respectively. On heating in toluene for 2 h, the Auwers
adducts underwent van Alphen–Hüttel rearrangement with 1,5-sigmatropic shift of one phenyl substituent to
afford sulfonyl-substituted 4H-pyrazoles. Under analogous conditions, the anti-Auwers adducts rearranged into
sulfonyl-substituted N-phenyl-1H-pyrazoles containing a small amount of the denitrogenation product,
sulfonyl-substituted cyclopropene. The Auwers adducts, as well as 4H-pyrazoles resulting from their thermal
rearrangement, were converted in 5–7 days at 20°C into 3,4,4-triphenyl-1H-pyrazol-5(4H)-one by the action of
a catalytic amount of sulfuric acid in acetic acid. Under analogous conditions, the regioisomeric anti-Auwers
adducts gave rise to 3,4,5-triphenyl-1H-pyrazole with an impurity of 4-(R-sulfonyl)-1,3,5-triphenyl-1H-
pyrazoles.
DOI: 10.1134/S107042801506010X
Functionally substituted 1H-, 3H-, and 4H-pyra-
zoles possess practically important properties, in par-
ticular high biological activity, which stimulates
studies on their synthesis and applications [1–4]. One
of the most efficient methods for the preparation of
pyrazole derivatives is based on 1,3-dipolar cycload-
dition of diazoalkanes to acetylenic compounds [5, 6].
Reactions of diazomethane and monosubstituted diazo-
methanes lead to the formation of 1H-pyrazoles. It is
believed that initially formed unstable 3H-pyrazoles
undergo aromatization to give 1H-pyrazoles via proto-
tropic rearrangement. On the other hand, 3H-pyrazoles
resulting from cycloaddition of disubstituted diazo-
methanes are quite stable. Among such 1,3-dipoles,
diphenyldiazomethane has been studied most thor-
oughly. Reactions of diphenyldiazomethane with un-
symmetrically substituted acetylenes, such as propynal
and phenylpropynal, propynenitrile, methyl but-2-
ynoate, and methyl 3-phenylprop-2-ynoate, were
reported [7–13] to afford mainly two regioisomeric
3H-pyrazoles which were formed according and con-
trary to the von Auwers rule.* Thermal and acid-
catalyzed transformations of these cycloadducts were
studied, and it was found that van Alphen–Hüttel rear-
rangement occurred in each case [14, 15], which led to
the formation of 1H- and/or 4H-pyrazole derivatives
via 1,5-sigmatropic shift of the phenyl substituent. The
regioselectivity of both cycloaddition and isomeriza-
tion of the 3,3-diphenyl-3H-pyrazole derivative is
largely determined by the effect of electron-withdraw-
ing group in the initial dipolarophile [6].
In the present work we examined the addition of
diphenyldiazomethane to acetylenic sulfones 1a and
1b and thermal and acid-catalyzed transformations of
the resulting cycloadducts, sulfonyl-substituted 3H-pyr-
azoles. We have found only one relevant publication
[16] in which the reaction of diphenyldiazomethane
with propynyl phenyl sulfone was described. However,
* In the reaction of diphenyldiazomethane with propynal only
Auwers 3H-pyrazole was obtained [7], whereas in the reaction
with 3-phenylpropynenitrile, only the anti-Auwers adduct was
formed [13].
874

SYNTHESIS OF 3H-PYRAZOLES
875
Scheme 1.
Ph
SO2R
RSO2
Ph
N2
Et2O, 20°C
Ph
SO2R
+
+
Ph
Ph
N
Ph
Ph
N
Ph
Ph
N
N
1a, 1b
2a, 2b
3a, 3b
Hereinafter, R = Me (a), 4-MeC6H4 (b).
there were no data on van Alphen–Hüttel rearrange-
ment of regioisomeric sulfonyl-substituted 3H-pyra-
zoles thus obtained. Dipolarophiles 1a and 1b reacted
with 9-diazofluorene to give only Auwers 3H-pyra-
zoles [17] whose thermal, acid-catalyzed, and photo-
induced transformations were studied.
sulfonyl group [18]. The molecular ion peak in the
mass spectra of these compounds had moderate inten-
sity, and their fragmentation pattern involved elimina-
tion of the sulfonyl group and nitrogen molecule from
the molecular ion. The structure of regioisomers 2 and
3 was finally proved by the X-ray diffraction data for
compound 3a (see figure).
The reactions of acetylenic sulfones 1a and 1b with
diphenyldiazomethane were carried out in diethyl ether
at 20°C for 5–7 days. From compound 1a we obtained
two possible regioisomers 2a and 3a at a ratio of 1:1.5
The relatively low regioselectivity of the cycloaddi-
tion of diphenyldiazomethane to acetylenic sulfones 1a
and 1b, in contrast to complete regioselectivity of the
cycloaddition of 9-diazofluorene [17] to the same
dipolarophiles, is likely to be determined by different
steric structures of these diazo compounds. In the reac-
tion with planar 9-diazofluorene, steric factor is not
significant, and the regioselectivity is controlled exclu-
sively by the electronic factors. The benzene rings in
the diphenyldiazomethane molecule are forced out of
the CN2 plane, which creates some steric hindrances to
approach of the reactant to dipolarophile. Presumably,
some difference in the regioselectivities of the cyclo-
addition of diphenyldiazomethane to dipolarophiles 1a
and 1b is related to different effective volumes of the
phenyl and sulfonyl substituents, on the one hand
(conformational energies of the Ph and SO2Me groups
are 2.80 and 2.50 kcal/mol, respectively [19]), and
of the methylsulfonyl and phenylsulfonyl groups, on
the other.
1
(according to the H NMR data) in favor of the anti-
Auwers adduct. The ratio of regioisomeric pyrazoles
2b and 3b in the reaction with compound 1b was
1.3:1, i.e., the Auwers adduct was the major product
(Scheme 1). All compounds 2a, 2b, 3a, and 3b were
isolated as pure substances, and their structure was
1
confirmed by H and 13C NMR spectroscopy with
account taken of specific spectral features of different
1
regioisomers. Compound 3a showed in the H NMR
spectrum a two-proton signal at δ 8.3 ppm, which was
located at a distance of ~0.7 ppm from the multiplet
corresponding to the other aromatic protons. We
assigned that signal to the ortho protons in the phenyl
ring on C5, and its strong downfield shift may be
rationalized by deshielding effect of the neighboring
N=N fragment (cf. [12]). By contrast, in the spectrum
of 2a all aromatic proton signals are gathered in the
region δ 7.1–7.4 ppm. The proposed assignment is also
supported by the large difference in the chemical shifts
of the SO2Me protons (δΔ = 1.1 ppm). The SO2Me
signal of 3a is located in a stronger field (δ 2.39 ppm)
due to shielding by the geminal phenyl substituents
on C3. Likewise, the CPh2 moiety affects the position
of signals of aromatic protons of the p-tolyl substituent
(two doublets at δ 6.50 and 6.75 ppm) in the spectrum
of 3b; in the spectrum of 2b all aromatic protons
resonated in a weaker field (δ >7.0 ppm).
O1
C20
O2
C19
C18
S1
C8
C1
C6
C2
C22
C21
C16
C3
C17
C9
C7
N2
C11
N1
C4
C12
C13
C5
C10
Compounds 2a, 2b, 3a, and 3b characteristically
displayed in the 13C NMR spectra a signal at δC 110–
113 ppm, which is typical of C3 in 3H-pyrazoles. The
IR spectra of 2a, 2b, 3a, and 3b contained strong
absorption bands at ~1150 and 1320 cm−1 due to sym-
metric and anti-symmetric stretching vibrations of the
C15
C14
Structure of the molecule of 4-(methanesulfonyl)-3,3,5-tri-
phenyl-3H-pyrazole (3a) according to the X-ray diffraction
data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

VASIN et al.
3H-Pyrazoles 2a, 2b, 3a, and 3b were subjected to
876
The structure of 5a and 5b was reliably confirmed
by the 1H and and 13C NMR spectra. The IR spectra of
5a and 5b characteristically displayed a strong absorp-
tion band at ~1800 cm−1 due to stretching vibrations of
the disubstituted cyclopropene double bond [18, 22].
Compounds 6a and 6b were purified by crystal-
lization, and their structure was determined on the
basis of the IR, 1H and 13C NMR, and mass spectra. In
the 13C NMR spectra of 6a and 6b we observed signals
at δC ~80 (C4) and ~180 ppm (C3, C5) which are typical
of 4H-pyrazoles [23].
The results of thermal isomerization of 3H-pyra-
zoles 2a, 2b, 3a and 3b can be satisfactorily explained
in terms of the Woodward–Hoffmann rules [24] as-
suming 1,5-sigmatropic shift of the phenyl group from
C3. However, the directions of this shift in regioiso-
mers 2 and 3 are the opposite: strictly toward N2 in 2
and strictly toward C4 in 3. While interpreting the
regioselectivity of the thermal isomerization of pyra-
zoles 2 and 3 we followed the approach proposed in
[12], according to which the transition states for the
two possible transformations of 2 and 3 are simulated
by polarized nonalternant diazabicyclo[3.1.0]hexatri-
enes C1–C4 (Scheme 4; cf. [25, 26]).
thermolysis in boiling toluene (112°C, 2 h). Two prod-
ucts were obtained from each of compounds 3a and
3b, 1H-pyrazole 4a (4b) and sulfonylcyclopropene 5a,
(5b) at a ratio of 5:1 or 9:1, respectively (according to
1
the H NMR data). Under the same conditions, com-
pounds 2a and 2b were converted into a single prod-
uct, the corresponding 4H-pyrazole derivative 6a or 6b
(Scheme 2).
Scheme 2.
RSO2
Ph
Ph
Ph
PhMe, 112°C
3a, 3b
+
N
Ph
N
Ph
SO2R
Ph
4a, 4b
5a, 5b
Ph
SO2R
Ph
Ph
PhMe, 112°C
2a, 2b
N
N
6a, 6b
Sulfonyl-substituted 1H-pyrazoles 4a and 4b were
isolated in the pure state by silica gel column chro-
matography. Compound 4b was identified by com-
paring its physical constants and spectral character-
istics with those given in [20] where it was synthesized
by a different method. The spectral parameters of 4a
were also satisfactorily consistent with the assumed
structure. In particular, the 13C NMR spectrum of 4a
contained signals at δC ~146 and 152 ppm due to C3
and C5 of the 1H-pyrazole ring (cf. data for model
compounds [12]). Cyclopropenyl sulfones 5a and 5b
Scheme 4.
RSO2
Ph
to N2
4
Ph
N
N
Ph
Ph
C1
SO2R
3
Ph
to C4
1
were identified in the reaction mixtures by H NMR;
N
Ph
the corresponding pure compounds were isolated in the
photolysis of 3H-pyrazoles 3a and 3b. Photolytic trans-
formation of 3H-pyrazoles into cyclopropenes is a well
known reaction [8, 10, 21] involving diazoalkane A
and vinylcarbene B as intermediates (Scheme 3).
N
C2
Ph
SO2R
to N2
Ph
Ph
N
N
C3
Scheme 3.
2
SO2R
Ph
SO2R
to C4
Ph
Ph
Ph
Ph
hν
6
3a, 3b
N
Ph
N
N
N
C4
A
Comparison of the results of thermal isomerization
of 3H-pyrazoles 2 and 3 and their analogs 7 [12], 8 [9],
9 [12], and 11 [13] revealed a general relation. The
presence of an electron-withdrawing substituent on C5
favors the isomerization toward the formation of
SO2R
Ph
Ph
5a, 5b
··
–N2
Ph
B
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

SYNTHESIS OF 3H-PYRAZOLES
877
4H-pyrazole, whereas N-phenyl-1H-pyrazole is formed
as the major product when the same substituent is
present in the 4-position.** In our case, as well as with
cyano-substituted 3H-pyrazole 11, this relation is
clearly fulfilled, whereas lower regioselectivity is ob-
served for 3H-pyrazoles 7, 9, and 10. Presumably, the
SO2R and CN substituents better stabilize negative
charge in the isomerization transition state than do
CHO and CO2Me groups {cf. Hammett constants σ–:
1.13 (SO2Me), 1.0 (CN), 0.74 (CO2Me) [27]}.
Compounds 2 turned out to me appreciably more
stable than their spiro analogs 12.
With the hope of revealing reversibility of the iso-
merization of 3H-pyrazoles 2 into 4H-pyrazoles 6 we
studied thermal transformations of these compounds at
elevated temperature. When 3H-pyrazoles 2a and 2b
were heated in boiling o-xylene (144°C) for 2 h,
mixtures of 4H-pyrazoles 6a and 6b and ~10–15% of
indenes 15a and 15b (denitrogenation products) were
formed, whereas no cyclopropenes 5 were detected.
Thermolysis of 2a and 2b in toluene at 180°C (40 min)
under microwave irradiation afforded indenes 15a and
15b as the major products together with small amounts
of three unidentified compounds. Pure indenes 15a
and 15b were isolated by silica gel column chromatog-
raphy, and their structure was confirmed by spectral
Ph
SO2R
Ph
X
X
Ph
N
N
Ph
Ph
N
Ph
Ph
N
N
N
1
methods. The H NMR spectra of 15a and 15b con-
7, 8
9–11
12a, 12b
tained a singlet at δ 5.41 (5.62) ppm due to 1-H, and
the C1 signal appeared in the 13C spectrum at δC 73.5
and 74 ppm, respectively. A more rigorous proof was
obtained by the NOE experiment for compound 15a,
which displayed long-range spin–spin coupling be-
tween the methyl protons and 1-H.
7, 9, X = MeOCO; 8, 10, X = CHO; 11, X = CN.
However, the thermolysis of known [17] 3H-pyra-
zoles 12a and 12b (analogs of 2) at 80°C afforded
4H-pyrazoles 13 (analogs of 6), in agreement with the
behavior of 3H-pyrazoles 2. On the other hand, unlike
compounds 2, heating of 12 or 13 at 112°C gave
N-aryl-1H-pyrazole derivatives 14 (Scheme 5). This
behavior of compounds 12 was rationalized [17]
assuming that the isomerization of 12 into 13 is revers-
ible at 112°C (but not at 80°C) and that the isomeriza-
tion of 12 into more stable 1H-pyrazoles 14 is irre-
versible.
We believe that 3H-pyrazoles 2a and 2b at elevated
temperature undergo partial or complete denitrogena-
tion through intermediate diradical D whose recom-
bination could give cyclopropene 5 or indene 15.
Furthermore, cyclopropenes 5, like their analogs [28],
are also potential precursors of 15 (Scheme 6). In fact,
all these compounds at 150°C undergo completely
regioselective cyclopropene–indene isomerization
through diradical D [28]. The transformation at 180°C
in 45–60 min yields only indenes 15 as the most stable
products. Presumably, the rate of the isomerization of
5 into 15 at high temperature is higher than the rate of
formation of 15 directly from 3H-pyrazoles 2; there-
fore, cyclopropenes 5 were not detected in the reaction
mixtures under these conditions. It should also be
recognized that in this case the energy barrier to the
Scheme 5.
SO2R
Ph
80°C
N
N
12a, 12b
13a, 13b
Scheme 6.
Ph
Ph
Ph
Δ
SO2R
·
112°C
2a, 2b
5a, 5b
·
–N2
N
N
Ph
SO2R
D
Ph
14a, 14b
Ph
** An exception is 3H-pyrazole 10 [9] which readily undergoes
thermal denitrogenation to the corresponding cyclopropene,
so that van Alphen–Hüttel rearrangement products cannot be
isolated.
SO2R
15a, 15b
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

VASIN et al.
878
Scheme 8.
denitrogenation of 3H-pyrazoles 2a and 2b is lower
than the barrier to their transformation into the corre-
sponding 1H-pyrazoles (analogs of 14), so that the
probability of the latter is low.
Addition of a catalytic amount of sulfuric acid to
a solution of 2a or 2b in glacial acetic acid at 20°C led
to the formation of 1H-pyrazol-5(4H)one 16. The same
compound was obtained from 4H-pyrazoles 6a and
6b under similar conditions (Scheme 7). In this
respect, the behavior of 3H- and 4H-pyrazoles 2 and 6
was fully consistent with the behavior of their analogs
12 and 13 [17].
Ph
Ph
H+, AcOH
3a, 3b
4a, 4b +
N
Ph
N
H
17
as shown in Scheme 9, where the key step is selective
protonation of 2a at the N2 atom with formation of
cation E which isomerizes into protonated 4H-pyrazole
6a. Treatment of the reaction mixture with water
afforded final product 16 as a result of proton transfer,
hydration, and elimination of the corresponding
sulfinic acid.
The acid-catalyzed transformation of 3H-pyrazoles
3a and 3b follows two competing pathways since their
protonation is not as selective as the protonation of
2a and 2b. As a result, 1H-pyrazoles 4 (path a) and 17
(path b) are formed (Scheme 10). Path b involves
intermediate protonated 4H- and 3H-pyrazoles and
N-sulfonyl-1H-pyrazoles. Hydrolysis of the latter
yields compound 17. Examples of reversible con-
current protonation of structurally related 3H-pyra-
zoles at both nitrogen atoms, followed by rearrange-
ment of the protonated forms with formation of dif-
ferent products, were reported in the literature [30] and
were also observed by us previously [17].
In summary, by 1,3-dipolar cycloaddition of di-
phenyldiazomethane to sulfonyl-substituted acetylenes
we have synthesized previously unknown regioiso-
meric sulfonyl-substituted 3,3-diphenyl-3H-pyrazoles
and found that the direction of their thermal isomeriza-
tion at 112°C with phenyl group migration to N2 or C4
is determined by the position of the electron-withdraw-
ing group with respect to the geminal diphenyl moiety.
On heating to 144°C and higher, 3H-pyrazoles lose
nitrogen molecule to give 1-sulfonyl-2,3,3-triphenyl-
cyclopropenes whose cyclopropene–indene isomeriza-
tion affords 1-sulfonyl-2,3-diphenyl-1H-indenes. Due
to reduction of the energy barrier, the acid-catalyzed
van Alphen–Hüttel rearrangement of the Auwers
Scheme 7.
Ph
O
H+, AcOH
Ph
Ph
2a, 2b or 6a, 6b
NH
N
16
The structure of 16 was confirmed by the IR,
1H and 13C NMR, and mass spectra. The IR spectrum
of 16 contained a strong carbonyl stretching vibration
band at 1709 cm–1 and weak absorption bands in the
region 3060–3200 cm–1 due to N–H vibrations [18]. In
addition, the NH proton gave rise to a broadened
1
singlet at δ 9.76 ppm in the H NMR spectrum.
Characteristic signals in the 13C NMR spectrum of 16
were those located at δC 65.3 (C4), 161.7 (C3), and
179.5 ppm (C5=O).
3H-Pyrazoles 3a and 3b in glacial acetic acid in the
presence of a catalytic amount of H2SO4 were con-
verted into the corresponding 1H-pyrazoles 4a and 4b
and 3,4,5-triphenyl-1H-pyrazole 17, the latter being
the major product [ratio 4:17 1:(3.5–4); Scheme 8].
Pure pyrazole 17 was isolated by crystallization from
ethanol and was identified by comparing with pub-
lished data [12, 29]. Pyrazoles 4a and 4b were iden-
tified in the reaction mixtures by 1H NMR.
The formation of pyrazolone 16 from compounds
2a and 2b under acidic conditions may be rationalized
Scheme 9.
Ph
Ph
Ph
SO2R
SO2R
SO2R
NH
H+
Ph
Ph
Ph
Ph
1,5-Ph shift
2a, 2b
Ph
Ph
N
N
N
H
N
N
H
E
H+
6a, 6b
H2O –RSO2H
16
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

SYNTHESIS OF 3H-PYRAZOLES
879
Scheme 10.
RSO2
RSO2
Ph
Ph
H+
1,5-Ph shift
3a, 3b
4a, 4b
–H+
Ph
Ph
a
NH
NH
Ph
N
N
H
F
Ph
Ph
RSO2
Ph
Ph
Ph
RSO2
Ph
RSO2
Ph
1,5-Ph shift
F
Ph
Ph
b
N
N
NH
N
N
H
N
H
SO2R
Ph
SO2R
Ph
Ph
Ph
Ph
Ph
Ph
1,5-SO2R shift
1,5-SO2R shift
–H+
H2O
–RSO3H
17
NH
N
N
Ph
Ph
SO2R
N
N
N
H
3H-pyrazoles occurs at room temperature and yields
3,4,4-triphenyl-1H-pyrazol-5(4H)-one through inter-
mediate 4H-pyrazoles. Under analogous conditions,
regioisomeric anti-Auwers 3H-pyrazoles are convert-
ed into mixtures of 4-sulfonyl-1,3,5-triphenyl- and
3,4,5-triphenyl-1H-pyrazoles. We plan to continue
studies on rearrangements of sulfonyl-substituted 3H-
pyrazoles with the goal of revealing general relations
existing there.
Reactions of compounds 1a and 1b with diphe-
nyldiazomethane (general procedure). A solution of
3.20 g (16.5 mmol) of diphenyldiazomethane in 30 mL
of anhydrous diethyl ether was added to a solution of
15 mmol of compound 1a or 1b in 30 mL of the same
solvent. The mixture was kept for 5–7 days at 20°C
1
with protection from light. According to the H NMR
data, the ratio of 3H-pyrazoles 2a and 3a (from 1a)
was 1:1.5, and of 2b and 3b (from 1b), 1.3:1. Crys-
talline compounds 2 and 3 separated from the reaction
solution. Compound 2 slowly crystallized first, and
then pyrazole 3 separated. The products were suc-
cessively isolated by filtration. Decomposition prod-
ucts of diphenyldiazomethane remained in solution.
Attempts to separate mixtures of 2 and 3 by pre-
parative TLC or column chromatography on silica gel
or alumina were unsuccessful because the sorbent cata-
lyzed chemical transformations leading to multicom-
ponent mixtures of unidentified compounds. 3H-Pyr-
azoles 2a and 2b were completely converted into
1H-pyrazolone 16 on prolonged storage (for 1 month
and more).
EXPERIMENTAL
1
The H and 13C NMR spectra were recorded on
a Jeol JNM-ECX400 spectrometer at 400.1 and
100.6 MHz, respectively, using the residual proton and
carbon signals of the deuterated solvents (δ 7.26 and
2.50 ppm, δC 77.0 and 39.5 ppm for CDCl3 and
DMSO-d6, respectively) as reference. The IR spectra
were recorded in KBr on an InfraLYuM FT-02 spec-
trometer with Fourier transform. The elemental anal-
yses were obtained on a VarioMICRO CHNS analyzer.
The mass spectra (electron impact) were recorded on
a Konik RBK-HRGC5000B-MSQ12 (Konixbert HI-
TECH, S.A.) Analytical TLC was performed on
Sorbfil plates which were eluted with light petroleum
ether–acetone (4:1) and developed in a iodine cham-
ber. Silica gel Merck 60 (0.040–0.063 mm) was used
for column chromatography (eluent light petroleum
ether–acetone, 7 : 1 to 3 : 1). Microwave-assisted
thermal isomerization was carried out in an Anton Paar
Monowave 300 microwave oven (magnetron fre-
quency 2455 MHz).
5-(Methanesulfonyl)-3,3,4-triphenyl-3H-pyra-
zole (2a). Yield 1.62 g (29%), yellow crystals,
mp 154–155°C (from CH2Cl2–petroleum ether). IR
spectrum, ν, cm–1: 1609 w, 1590 w, 1493 m, 1447 m,
1
1323 s, 1146 v.s, 752 m, 694 m, 556 m. H NMR
spectrum (CDCl3), δ, ppm: 3.49 s (3H, CH3), 7.14–
7.16 m (4H, Harom), 7.19–7.21 m (2H, Harom), 7.28–
7.42 m (9H, Harom). 13C NMR spectrum (CDCl3), δC,
ppm: 43.2 (CH3), 110.5 (C3), 128.4 (2C), 128.6, 128.8
(4C), 129.2 (4C), 129.4 (2C), 130.0 (2C), 131.3, 132.5
(2C), 150.6 (C4), 162.0 (C5). Mass spectrum, m/z (Irel,
%): 374 (40) [M]+, 295 (13), [M – SO2CH3], 267 (9)
[M – SO2CH3 – N2], 192 (15), 190 (13), 165 (35), 77
Ethynyl sulfones 1a and 1b [31] and diphenyl-
diazomethane [32] were prepared according to known
methods.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

VASIN et al.
880
(100), 51 (35). Found, %: C 70.60; H 4.82; N 7.41;
S 8.67. C22H18N2O2S. Calculated, %: C 70.57; H 4.85;
N 7.48; S 8.56. M 374.46.
151.1 (C4), 158.0 (C5). Mass spectrum, m/z (Irel, %):
450 (52) [M]+, 385 (49), 295 (9) [M – Ts], 267 (49)
[M – Ts – N2], 266 (95), 252 (97), 189 (97), 166 (100),
91 (89), 77 (82), 65 (94), 51 (69). Found, %: C 75.18;
H 4.91; N 6.32; S 7.06. C28H22N2O2S. Calculated, %:
C 74.64; H 4.92; N 6.22; S 7.12. M 450.55.
4-(Methanesulfonyl)-3,3,5-triphenyl-3H-pyra-
zole (3a). Yield 2.84 g (51%), yellow crystals,
mp 161–162°C (from CH2Cl2–petroleum ether). IR
spectrum, ν, cm–1: 1582 w, 1566 w, 1489 m, 1455 m,
1312 v.s, 1146 v.s, 953 m, 775 s, 702 v.s, 544 s.
1H NMR spectrum (CDCl3), δ, ppm: 2.39 s (3H, CH3),
7.36–7.42 m (10H, Harom), 7.59–7.62 m (3H, Harom),
X-Ray analysis of pyrazole 3a. A yellow transpar-
ent prismatic single crystal of 3a (0.31 × 0.26×
0.16 mm) was grown from a solution in chloroform–
llight petroleum ether (1:2). Total of 37041 reflection
intensities were measured at 293(2) K on an Oxford
Diffraction Xcalibur Gemini S automatic four-circle
diffractometer (MoKα radiation, λ 0.71073 Å, graphite
monochromator, Sapphire III CCD detector; ω-scan-
ning, θ 3.45–30.5°, –13 ≤ h ≤ 14, –29 ≤ k ≤ 29, –13 ≤
l ≤ 13). Averaging of equivalent reflections left
5841 independent reflections (Rint 0.0242), including
5010 reflections with I > 2σ(I). The unit cell param-
eters were determined, and the reflection intensities
were measured, using CrysAlisPro software [33].
A correction for absorption was applied empirically by
the SCALE3 ABSPACK algorithm [33]. Monoclinic
crystals, space group P21/c; unit cell parameters: a =
9.8194(4), b = 20.4689(7), c = 9.6034(3) Å; β =
96.044(3)°; V = 1919.48(12) A3; M 374.44; Z = 4;
dcalc = 1.296 g/cm3; μ = 0.188 mm–1; F(000) = 784.
The structure was solved by the direct method and was
refined against F2 by the full-matrix least-squares
procedure in anisotropic approximation for non-hydro-
gen atoms using SHELX97 [34] and WinGX [35].
Number of variables 316, goodness of fit 1.12; residual
electron density ρmin/ρmax –0.177/0.412 ē Å–3. Final
divergence factors R1 = 0.0618 [for reflections with
I > 2σ(I)], wR2 = 0.1757 (for all independent reflec-
tions). Hydrogen atoms were placed into geometrically
calculated positions and were refined according to the
riding model [U(H) = 1.5Ueq(C) for methyl groups,
U(H) = 1.2Ueq(C) for other hydrogens]; weight scheme
w = 1/[σ2(Fo2) + (0.0742P)2 + 0.3640P], where P =
(Fo2 + 2 F2c)/3. The molecular structure of 3a was
plotted using ORTEP-3 program [36]. The crystallo-
graphic data for compound 3a were deposited to the
Cambridge Crystallographic Data Centre (entry
no. CCDC 1055415).
13
8.31–8.33 m (2H, Harom). C NMR spectrum (CDCl3),
δC, ppm: 43.8 (CH3), 113.4 (C3), 128.6, 128.9 (4C),
129.0 (2C), 129.2 (4C), 129.3 (2C), 131.0 (2C), 131.9,
133.1 (2C), 148.0 (C4), 157.3 (C5). Mass spectrum, m/z
(Irel, %): 374 (15) [M]+, 295 (8) [M – SO2CH3], 267
(41) [M – SO2CH3 – N2], 263 (100), 252 (96), 239
(79), 189 (99), 165 (94), 132 (97), 119 (85), 77 (72),
51 (69). Found, %: C 70.48; H 4.81; N 7.32; S 8.52.
C22H18N2O2S. Calculated, %: C 70.57; H 4.85; N 7.48;
S 8.56. M 374.46.
5-(4-Methylbenzenesulfonyl)-3,3,4-triphenyl-3H-
pyrazole (2b). Yield 2.98 g (44%), yellow crystals,
mp 151–152°C (from CH2Cl2–petroleum ether). IR
spectrum, ν, cm–1: 1597 w, 1559 w, 1489 m, 1443 m,
1316 m, 1154 v.s, 718 s, 752 m, 698 m, 583 v.s.
1H NMR spectrum (CDCl3), δ, ppm: 2.45 s (3H, CH3),
7.00–7.04 m (6H, Harom), 7.25–7.37 m (10H, Harom),
7.38–7.43 m (1H, Harom), 7.93 d (2H, Harom, J =
8.4 Hz). 13C NMR spectrum (CDCl3), δC, ppm: 21.9
(CH3), 110.1 (C3), 128.1 (2C), 128.6 (4C), 128.9 (2C),
129.0 (4C), 129.1, 129.2 (2C), 129.6 (2C), 130.1 (2C),
130.7, 132.6 (2C), 136.7, 145.6, 151.4 (C4), 161.7 (C5).
Mass spectrum, m/z (Irel, %): 450 (40) [M]+, 386 (100),
295 (8) [M – Ts], 267 (55) [M – Ts – N2], 266 (98), 252
(97), 190 (98), 166 (97), 91 (73), 77 (87), 65 (86), 51
(62). Found, %: C 74.69; H 4.89; N 6.03; S 7.15.
C28H22N2O2S. Calculated, %: C 74.64; H 4.92; N 6.22;
S 7.12. M 450.55.
4-(4-Methylbenzenesulfonyl)-3,3,5-triphenyl-3H-
pyrazole (3b). Yield 2.12 g (31%), yellow crystals,
mp 153–154°C (from CH2Cl2–petroleum ether). IR
spectrum, ν, cm–1: 1620 w, 1593 w, 1489 w, 1451 w,
1
1327 s, 1157 s, 752 m, 694 v.s, 586 s. H NMR spec-
trum (CDCl3), δ, ppm: 2.22 s (3H, CH3), 6.47 d (2H,
Thermolysis of 3H-pyrazoles 2 and 3 (general
procedure). A solution of 1 mmol of compound 2a, 2b,
3a, or 3b in 35 mL of toluene was heated for 2 h under
reflux. The solvent was removed under reduced pres-
sure, and the crude product was analyzed by 1H NMR.
4H-Pyrazoles 6a and 6b (from 2) were isolated by
crystallization. The ratios of 4a and 5a (from 3a) and
H
arom, J = 8.3 Hz), 6.75 d (2H, Harom, J = 8.1 Hz),
7.38–7.43 m (10H, Harom), 7.50–7.59 m (3H, Harom),
13
7.98–8.01 m (2H, Harom). C NMR spectrum (CDCl3),
δC, ppm: 21.6 (CH3), 112.9 (C3), 127.2 (2C), 128.4
(2C), 128.6 (4C), 128.9, 128.9 (2C), 129.1 (2C), 129.7
(4C), 130.8 (2C), 131.3, 133.5 (2C), 137.4, 144.8,
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SYNTHESIS OF 3H-PYRAZOLES
881
of 4b and 5b (from 3b) were 5:1 and 9:1, respectively
7.52 m (1H, Harom), 7.71–7.73 m (2H, Harom). 13C NMR
spectrum (DMSO-d6), δC, ppm: 43.4 (CH3), 79.0 (C4),
127.6, 128.3 (4C), 128.9 (2C), 129.2 (2C), 129.3 (2C),
129.4 (4C), 131.2, 132.6, 179.1, 180.5 (C3, C5). Mass
spectrum, m/z (Irel, %): 374 (60) [M]+, 373 (68), 295
(100) [M – SO2CH3]+, 294 (95), 267 (59) [M –
SO2CH3 – N2]+, 192 (55), 165 (95), 77 (65), 51 (37).
Found, %: C 70.37; H 4.90; N 7.39; S 8.60.
C22H18N2O2S. Calculated, %: C 70.57; H 4.85; N 7.48;
S 8.56. M 374.46.
(calculated from the intensities of the methyl proton
1
signals in the H NMR spectra). Pure compounds 4a
and 4b were isolated by silica gel column chromatog-
raphy. Cyclopropenes 5a and 5b were identified in the
reaction mixtures by NMR.
4-(Methanesulfonyl)-1,3,5-triphenyl-1H-pyra-
zole (4a). Yield 0.27 g (72%), colorless crystals,
mp 176–177°C (from CH2Cl2–petroleum ether). IR
spectrum, ν, cm–1: 1593 w, 1497 s, 1400 m, 1304 v.s,
1
5-(4-Methylbenzenesulfonyl)-3,4,4-triphenyl-4H-
pyrazole (6b). Yield 0.39 g (87%), colorless crystals,
mp 191–192°C (from CHCl3–petroleum ether). IR
spectrum, ν, cm–1: 1597 w, 1512 w, 1493 m, 1443 m,
1130 s, 791 m, 764 m, 694 m. H NMR spectrum
(CDCl3), δ, ppm: 2.77 s (3H, CH3), 7.24–7.31 m
(4H, Harom), 7.38–7.43 m (4H, Harom), 7.47–7.51 m
(3H, Harom), 7.88–7.90 m (2H, Harom). 13C NMR spec-
trum (CDCl3), δC, ppm: 44.9 (CH3), 120.1 (C4), 125.6
(2C), 127.9, 128.4 (2C), 128.4 (3C), 128.5, 129.1 (2C),
129.4, 130.0 (2C), 131.0 (2C), 131.3, 138.7, 145.7 and
151.6 (C3, C5). Mass spectrum, m/z (Irel, %): 374 (83)
[M]+, 373 (100), 295 (34) [M – SO2CH3], 294 (51),
189 (47), 180 (22), 165 (9), 89 (9), 77 (75), 51 (35).
Found, %: C 70.41; H 4.78; N 7.29; S 8.66.
C22H18N2O2S. Calculated, %: C 70.57; H 4.85; N 7.48;
S 8.56. M 374.46.
1
1331 s, 1149 m, 760 s, 694 s, 671 s, 582 v.s. H NMR
spectrum (CDCl3), δ, ppm: 2.38 s (3H, CH3), 7.18 d
(2H, Harom, J = 8.0 Hz), 7.23–7.26 m (2H, Harom), 7.32–
7.40 m (11H, Harom), 7.49 d (2H, Harom, J = 8.2 Hz),
7.70 d (2H, Harom, J = 8.2 Hz). 13C NMR spectrum
(CDCl3), δC, ppm: 21.8 (CH3), 80.0 (C4), 128.5, 128.6
(2C), 128.8 (2C), 128.9 (4C), 129.2 (2C), 129.3 (4C),
129.7 (2C), 129.8 (2C), 131.7 (2C), 132.2, 136.4,
145.5, 180.9, 181.1 (C3, C5). Mass spectrum, m/z
(Irel, %): 450 (15) [M]+, 386 (20), 295 (14) [M – Ts],
267 (525) [M – Ts – N2]+, 192 (60), 180 (22), 165
(100), 91 (62), 77 (53), 65 (38), 51 (17). Found, %:
C 74.49; H 4.85; N 6.08; S 7.04. C28H22N2O2S. Calcu-
lated, %: C 74.64; H 4.92; N 6.22; S 7.12. M 450.55.
4-(4-Methylbenzenesulfonyl)-1,3,5-triphenyl-1H-
pyrazole (4b). Yield 0.29 g (64%), colorless crystals,
mp 212–213°C (from acetone–petroleum ether); pub-
lished data [20]: mp 214–215°C (from CHCl3–
hexane). IR spectrum, ν, cm–1: 1593 w, 1497 s, 1446 m,
1396 m, 1315 s, 1146 v.s, 764 m, 698 m, 598 m.
1H NMR spectrum (CDCl3), δ, ppm: 2.30 s (3H, CH3),
6.70 d (2H, Harom, J = 8.0 Hz), 7.20–7.29 m (9H,
Harom), 7.32–7.36 m (2H, Harom), 7.40–7.45 m (4H,
Harom), 7.69–7.72 m (2H, Harom). 13C NMR spectrum
(CDCl3), δC, ppm: 21.6 (CH3), 121.3 (C4), 125.4 (2C),
127.3 (2C), 127.9 (2C), 128.1, 128.2 (2C), 128.3,
128.9 (2C), 129.1, 129.1 (2C), 129.8, 130.4 (2C),
131.1 (2C), 131.6, 138.7, 139.7, 143.5, 145.5 and
152.3 (C3, C5). Mass spectrum, m/z (Irel, %): 450 (63)
[M]+, 385 (40), 295 (11) [M – Ts], 293 (30), 267 (27)
[M – Ts – N2], 189 (62), 180 (25), 91 (63), 77 (100), 65
(36), 51 (25). Found, %: C 74.59; H 4.87; N 6.15;
S 7.18. C28H22N2O2S. Calculated, %: C 74.64; H 4.92;
N 6.22; S 7.12. M 450.55.
Transformations of 3H-pyrazoles 2a and 2b
under microwave irradiation. A microreactor was
charged with a solution of 1 mmol of compound 2a or
2b in 35 mL of toluene, and the mixture was subjected
to microwave irradiation for 40 min, maintaining the
temperature at 180°C. The solvent was removed under
reduced pressure (water-jet pump), and the solid
1
residue was analyzed by H NMR. Crystalline indenes
15a and 15b were isolated by silica gel column chro-
matography.
1-(Methanesulfonyl)-2,3-diphenyl-1H-indene
(15a). Yield 42%, light yellow crystals, mp 112–
113°C. IR spectrum, ν, cm–1: 3009 m, 2928 s, 1489 s,
1462 s, 1443 m, 1304 v.s, 1173 s, 1146 s, 1099 s,
1
768 s, 702 s. H NMR spectrum (CDCl3), δ, ppm:
2.34 s (3H, SO2CH3), 5.41 s (1H, 1-H), 7.21–7.32 m
(5H, Harom), 7.32–7.45 m (8H, Harom), 8.00 d (1H,
5-(Methanesulfonyl)-3,4,4-triphenyl-4H-pyra-
zole (6a). Yield 0.30 g (80%), colorless crystals,
mp 254–255°C (from CH2Cl2–petroleum ether;
decomp.). IR spectrum, ν, cm–1: 1497 m, 1331 m,
1311 v.s, 1138 m, 795 m, 768 m, 698 s. 1H NMR spec-
trum (DMSO-d6), δ, ppm: 3.19 s (3H, CH3), 7.30–
7.33 m (4H, Harom), 7.36–7.43 m (8H, Harom), 7.47–
H
arom, J = 7.2 Hz). 13C NMR spectrum (CDCl3), δC,
ppm: 36.0 (CH3), 73.5 (C1), 121.4, 126.9, 128.0 (2C),
128.1, 128.2 (2C), 128.8 (2C), 129.1 (2C), 129.5,
129.8 (2C), 133.5, 133.6, 135.1, 136.1, 145.1, 145.4.
Found, %: C 76.44; H 5.03; S 9.30. C22H18O2S. Calcu-
lated, %: C 76.27; H 5.24; S 9.25.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

VASIN et al.
882
1-(4-Methylbenzenesulfonyl)-2,3-diphenyl-1H-
ppm: 2.32 s (3H, CH3), 7.07 d (2H, Harom, J = 8.1 Hz),
7.14–7.20 m (10H, Harom), 7.40–7.51 m (3H, Harom),
7.68 d (2H, Harom, J = 8.1 Hz), 7.76 d (2H, Harom, J =
7.3 Hz). 13C NMR spectrum (CDCl3), δC, ppm: 21.7
(CH3), 47.7 (C3), 119.1, 124.6, 126.7 (2C), 127.8 (2C),
128.25 (4C), 128.28 (4C), 129.3 (2C), 129.8 (2C),
131.6, 131.9 (2C), 132.1, 137.8, 141.5 (2C), 144.9.
Found, %: C 79.48; H 5.13; S 7.39. C28H22O2S. Cal-
culated, %: C 79.59; H 5.25; S 7.59.
indene (15b). Yield 40%, colorless crystals, mp 129–
130°C (from acetone–petroleum ether). IR spectrum, ν,
cm–1: 1316 s, 1169 s, 1080 m, 814 m, 771 m, 760 m,
694 m, 660 m, 575 v.s. 1H NMR spectrum (CDCl3), δ,
ppm: 2.36 s (3H, CH3), 5.62 s (1H, 1-H), 6.77–6.79 m
(2H, Harom), 6.90 d (1H, Harom, J = 7.2 Hz), 6.99 d (2H,
H
arom, J = 8.1 Hz), 7.05 d (2H, Harom, J = 8.3 Hz),
7.10–7.13 m (2H, Harom), 7.22–7.24 m (3H, Harom),
7.27–7.33 m (4H, Harom), 7.35–7.39 m (1H, Harom),
8.11 d (2H, Harom, J = 7.4 Hz). 13C NMR spectrum
(CDCl3), δC, ppm: 21.7 (CH3), 74.0 (C4), 120.8, 126.5,
126.9, 127.7, 127.9 (3C), 128.3 (2C), 128.7 (2C),
129.3, 129.4 (2C), 130.1 (2C), 132.0, 133.6, 134.2,
135.5, 135.6, 144.5, 145.1, 146.2 (C2, C3). Found, %:
C 79.84; H 5.00; S 7.30. C28H22O2S. Calculated, %:
C 79.59; H 5.25; S 7.59.
Acid-catalyzed transformations of 3H-pyrazoles
2a, 2b, 3a, and 3b and 4H-pyrazoles 6a and 6b
(general procedure). Concentrated sulfuric acid,
0.1 mL, was added to a solution of 1 mmol of com-
pound 2a, 2b, 3a, 3b, 6a, or 6b in 50 mL of glacial
acetic acid, and the mixture was left to stand for 4–
6 days at 20°C. The progress of the reaction was
monitored by TLC. When the reaction was complete,
the mixture was diluted with 250 mL of water, and the
Photolysis of 3H-pyrazoles 3a and 3b (general
procedure). A quartz test tube was charged with a solu-
tion of 1 mmol of compound 3a or 3b in 20 mL of
anhydrous methylene chloride, the test tube was tightly
capped, and the solution was irradiated for 8–10 h with
ultraviolet light using a DRT-400 lamp. The progress
of the reaction was monitored by TLC. The solvent
was removed under reduced pressure, and the residue
1
precipitate was filtered off and analyzed by H NMR.
Pyrazolone 16 was obtained from compounds 2 and 6,
and compounds 3a and 3b were converted into a mix-
ture of 1H-pyrazole 17 and 22–25% of 1H-pyrazole 4a
or 4b. Compounds 16 and 17 were isolated by crystal-
lization from ethanol.
3,4,4-Triphenyl-1H-pyrazol-5(4H)-one (16). Yield
90% (from 2a), 87% (from 6b); colorless crystals,
mp 164–165°C (from EtOH). IR spectrum, ν, cm–1:
3213 w, 3063 w, 1709 v.s (C=O), 1497 w, 748 w,
1
was analyzed by H NMR spectroscopy. Pure cyclo-
propenes 5a and 5b were isolated by column chroma-
tography on silica gel.
1
1-(Methanesulfonyl)-2,3,3-triphenylcyclo-
propene (5a). Yield 67%, colorless crystals, mp 183–
184°C (from CH2Cl2–petroleum ether). IR spectrum, ν,
cm–1: 2916 v.s, 1790 m, 1489 w, 1446 m, 1315 v.s,
1138 s, 960 m, 779 m, 764 s, 702 s, 690 m, 517 m.
1H NMR spectrum (CDCl3), δ, ppm: 2.90 s (3H, CH3),
7.26–7.29 m (2H, Harom), 7.31–7.35 m (4H, Harom),
7.40–7.43 m (4H, Harom), 7.46–7.52 (3H, Harom), 7.87–
7.89 m (2H, Harom). 13C NMR spectrum (CDCl3), δC,
ppm: 44.4 (CH3), 47.7 (C3), 117.8, 124.2, 127.3 (2C),
128.3 (4S), 128.7 (4C), 129.4 (2C), 132.2 (2C), 132.5,
132.7, 141.9. Mass spectrum, m/z (Irel, %): 346 (0.2)
[M]+, 267 (100) [M – SO2CH3], 251 (11), 238 (6), 189
(9), 165 (18). Found, %: C 76.00; H 5.12; S 9.23.
C22H18O2S. Calculated, %: C 76.27; H 5.24; S 9.25.
M 346.44.
694 w. H NMR spectrum (CDCl3), δ, ppm: 7.22–
7.43 m (13H, Harom), 7.62 d (2H, Harom, J = 7.3 Hz),
9.76 br.s (1H, NH). 13C NMR spectrum (CDCl3), δC,
ppm: 65.3 (C4), 127.4 (2C), 128.3 (2C), 128.5 (2C),
129.0 (4C), 129.0 (4C), 130.0, 131.4, 136.4 (2C),
161.7 (C3), 179.5 (C=O). Mass spectrum, m/z (Irel, %):
312 (100) [M]+, 269 (79) [M – HNCO], 252 (61), 194
(69) [M – C6H5CN2H], 180 (91), 166 (98), 165 (99),
152 (39), 139 (47), 77 (99), 51 (91). Found, %:
C 80.47; H 5.13; N 8.68. C21H16N2O. Calculated, %:
C 80.75; H 5.16; N 8.97. M 312.37.
3,4,5-Triphenyl-1H-pyrazole (17). Yield 0.13 g
(44%, from 3a), 0.12 g (41%, from 3b); colorless
crystals, mp 267–268°C (from EtOH); published data
[28]: mp 265–266°C. IR spectrum, ν, cm–1: 3217 w
(NH), 1605 w, 1489 w, 1446 w, 1146 w, 972 w, 771 w,
729 m, 694 v.s, 605 w. 1H NMR spectrum (DMSO-d6),
δ, ppm: 7.16–7.18 m (2H, Harom), 7.27–7.35 m (13H,
1-(4-Methylbenzenesulfonyl)-2,3,3-triphenyl-
cyclopropene (5b). Yield 71%, colorless crystals,
mp 134–135°C (from CH2Cl2–petroleum ether).
IR spectrum, ν, cm–1: 1779 m (C=C), 1489 m, 1319 s,
1304 m, 1292 m, 1154 v.s, 1084 m, 721 s, 702 s, 683 s,
H
arom). 13C NMR spectrum (DMSO-d6), δC, ppm:
116.8, 127.1, 127.4 (6C), 127.6, 128.4 (5C), 128.7
(3C), 130.6 (3C), 133.9. Mass spectrum, m/z (Irel, %):
296 (77) [M]+, 295 (100), 218 (15), 189 (17), 165 (46),
1
571 m, 544 s, 529 m. H NMR spectrum (CDCl3), δ,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 6 2015

SYNTHESIS OF 3H-PYRAZOLES
883
17. Vasin, V.A., Masterova, Yu.Yu., Razin, V.V., and
Somov, N.V., Russ. J. Org. Chem., 2014, vol. 50,
p. 1323.
18. Silverstein, R.M., Webster, F.X., and Kiemle, D.J.,
Spectrometric Identification of Organic Compounds,
New York: Wiley, 2005, 7th ed.
104 (15), 89 (18), 77 (56), 51 (26). Found, %: C 85.02;
H 5.50; N 9.39. C21H16N2. Calculated, %: C 85.11;
H 5.44; N 9.45. M 296.37.
This study was performed in part in the framework
of the base part of state contract no. 2014/134 (project
no. 2312).
19. Eliel, E.L., Wilen, S.H., and Doyle, M.P., Basic Organic
Stereochemistry, New York: Wiley, 2001.
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