Thermal Rearrangements of 3H- and 4H-Pyrazoles Prepared by Reactions of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate

Article abstract of DOI:10.1134/S1070428018080122

9-Diazofluoren adds in Et₂O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.

Full text of DOI:10.1134/S1070428018080122

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2018, Vol. 54, No. 8, pp. 1189–1199. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © V.А. Vasin, Yu.А. Popkova, Ye.V. Bezrukova, V.V. Razin, N.V. Somov, 2018, published in Zhurnal Organicheskoi Khimii, 2018,
Vol. 54, No. 8, pp. 1178–1188.
Thermal Rearrangements of 3Н- and 4Н-Pyrazoles Prepared
by Reactions of 9-Diazofluoren with Methyl Tetrolate
and Methyl 3-Phenylpropiolate
V. А. Vasin†a, Yu. А. Popkovaa, Ye. V. Bezrukovaa, V. V. Razinb,* and N. V. Somovc
a Ogarev Mordovian State University, Saransk, 430005 Russia
b St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034 Russia
*e-mail: vvrazin@mail.ru
c Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, 603022 Russia
Received August 2, 2017
Abstract—9-Diazofluoren adds in Et2O at 20°С to methyltetrolate in keeping with Auwers rule and non-
regioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3Н-pyrazoles. The
methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-
carboxylate, at 190°С in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°С
in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in
benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aH-
dibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-
phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.
DOI: 10.1134/S1070428018080122
3,3-Disubstituted 3Н-pyrazoles and 4,4-disub-
stituted 4Н-pyrazoles are compounds conformable to
5,5-disubstituted cyclopentadienes, and they may
undergo typical for the latter sigmatropic
rearrangements [1], consisting in 1,5-shift of
substituent from a saturated carbon atom [2–4].
Considerably more examples of such transformations
are known for 3Н-pyrazoles than for 4Н-pyrazoles [5,
6]. Yet the problem of establishing the dependence of
the rearrangement direction on structural features of
initial compounds and external conditions is topical
and remains unsolved up till now, and since the
products proper are practically interesting the research
on this issue continues [7–11].
The main method of synthesis of the mentioned 3Н-
pyrazoles is the 1,3-dipolar cycloaddition of
disubstituted diazomethanes to activated acetylenes,
and the easiest way to 4Н-pyrazoles is the
isomerization of these 3Н-pyrazoles. In the present
study we performed reactions of cycloaddition of 9-
diazofluoren to methyltetrolate and methyl 3-
phenylpropiolate that allowed the preparation of
attractive for investigation spirocyclic 3Н-pyrazoles
and from them disubstituted 4Н-pyrazoles, and to
study their transformations.
The reaction was performed in a closed vessel in
ethyl ether at 20°С without access of light during 1–2
weeks. The reaction of methyltetrolate is characterized
by strict regioselectivity and leads to the formation of
cycloadduct 1 corresponding to Auwers rule, like in
reactions of 9-diazofluoren with acetylene sulfones
[12, 13]. In contrast, the cycloaddition to methyl 3-
phenylpropiolate occurs without regioselectivity: along
with Auwers adduct 2 forms its regioisomer 3, while
their ratio during the course of the reaction changes,
being, according to 1Н NMR, 2 : 1 in the first stage and
6 : 1 by the end. This result is different from the result
of [14], where the formation of unique cycloadduct 2
has been reported (Scheme 1).
A characteristic signal for the structure of 3Н-
13
pyrazole in С NMR spectra of compounds 1–3 is the
peak of the spirocyclic carbon atom at ~110 ppm [12,
13]. The presence of two possible regioisomers 2 and 3
allows for establishing their structure by comparing 1Н
NMR spectra. Luckily the points of comparison,
† Deceased.
1189

VASIN et al.
1190
Scheme 1.
O
C
MeO
Me
N
N2
O
N
Me
C
OMe
Et2O, 20oC
1
O
C
Ph
MeO
N
N
N
O
O
N
Ph
C
Ph
C
MeO
+
OMe
Et2O, 20oC
2
3
chemical shifts of ortho-protons of phenyl ring and
protons of methoxycarbonyl group, are different in the
spectra of regioisomers, and these differences on
qualitative level may be connected with the structural
diversity. So, the most downfield signal (δ 8.35 ppm)
corresponds to the ortho-protons of phenyl group in
isomer 3, because of the deshielding effect of the
adjacent СО2Mе group and the azo-fragment. In
isomer 2 the corresponding signal is considerably
shifted upfield (δ 7.04 ppm). At the same time
in isomer 2 the chemical shift of group СО2Mе (δ
4.07 ppm), suffering deshielding effect of the N=N
fragment, exceeds chemical shift of the same group in
isomer 3 by 0.64 ppm.
To confirm the structure of 3Н-pyrazol 1 we have
registered the 1Н–1Н NOESY spectrum looking for the
cross-peak а corresponding to the interaction of
spatially close protons of methyl group and protons
Н1,8 of fluorenyl residue that was impossible for anti-
Auwers regioisomer of this compound. According to
the structure of compound 1 the signal of protons of
СО2Mе group is present in the 1Н spectrum in the same
position as in the spectrum of compound 2 (Scheme 2).
Hence, we got three 3Н-pyrazoles, two of which,
compounds 1 and 2, belong to derivatives with an
acceptor substituent in the position 5, and 3Н-pyrazol
3, to a derivative with an acceptor substituent in the
position 4.
We established that 3Н-pyrazole 1 at boiling in
toluene (112°C, 2 h) gives a single product: a derivative
of 4Н-pyrazole indazole 4а. It is known that some 3Н-
pyrazoles at thermolysis may undergo fragmentation
with the formation of cyclopropene derivatives [12,
15–17]. In the case in question it did not happen, and this
conclusion was reliably confirmed, when the anticipated
spirocyclic cyclopropene 5a was specially synthesized
by UV irradiation of 3Н-pyrazole 1 in a quartz test
tube in CH2Cl2 (20°C, 4 h), cf. [12] (Scheme 3).
In favor of the structure assigned to 4Н-pyrazole 4а
evidences the presence in the 13С NMR spectrum of
two signals of carbon atoms of dimethylenehydrazine
fragment in a weak field at δ ~176 and 183 ppm and
two signals in a strong field at 28.7 (Mе) and 65.9 ppm
(quaternary carbon atom), cf. [13]. Moreover, in the
UV spectrum of this compound a characteristic
absorption band at 311 nm (log ε 3.96) is detected, cf.
[6]. For cyclopropene 5a a strong absorption band is
characteristic in the IR spectrum at 1863 cm–1 of
stretching vibrations of the multiple bond С=C
comparable by intensity with the absorption band of
the conjugated to it carbonyl group [18, 19]. Besides
that in 13С NMR spectrum the signal of spirocyclic
carbon atom present at ~41 ppm is characteristic [12].
Scheme 2.
Me
O
C
H8
OMe
a
N
N
H1
1
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 8 2018

THERMAL REARRANGEMENTS OF 3Н- AND 4Н-PYRAZOLES PREPARED BY REACTIONS
1191
Scheme 3.
N
MeO2C
Me
CO2Me
N
112oC
Me
C6H5Me
112oC
1
hv
5a
4a
Scheme 4.
N
MeO2C
Ph
Ph
CO2Me
N
C6H6
80oC
MeOH
65oC
2
5b
4b
Scheme 5.
3Н-Pyrazole 2 turned out to be much less stable
thermally compared to its methyl-substituted analog 1.
At boiling in benzene during 8 h a full conversion was
achieved, and no rearrangement took place, only the
fragmentation affording cyclopropene derivative 5b.
Boiling of pyrazole 2 in methanol results in a
rearrangement, similar to that observed for analog 1,
namely, a single product was obtained, 4Н-pyrazole 4b
(Scheme 4). Such result correlates with conclusions of
[17] on the significantly increasing contribution of a
competitive reaction of denitrogenation at the
thermolysis of 3Н-pyrazoles in aprotic solvent
(benzene) compared to their thermolysis in polar
solvent (acetonitrile, methanol, ethanol).
Ph
MeO2C
N
N
C6H6
80oC
5b
3
Δ
6
The structure of 4Н-pyrazole 4b is recognized by
downfield signals in the 13С NMR spectra at 168.7 and
182.7 ppm of dimethylenehydrazine fragment and by
characteristic absorption in UV spectra at 300 (log ε
Fig. 1. Spatial arrangement of methyl 3a-phenyl-3aH-
dibenzo[e,g]indazole-3-carboxylate 4b molecule in the
crystal by XRD data.
Fig. 2. Spatial arrangement of the methyl 2-phenylpyrazolo-
[1,5-f]phenanthridine-3-carboxylate 6 molecule according
to XRD analysis.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 8 2018

VASIN et al.
1192
Scheme 6.
CO2Me
H
N
N
N
Me
Me
N
C6H6
190oC
MeOH
160oC
4a
7a
8a
Scheme 7.
H
N
CO2Me
Ph
MeO2C
N
N
Ph
Ph
N
N
N
C6H6 or C6H5Me
100_140oC
MeOH
160oC
4b
5b +
+
8b
7b
9
3.95) and 308 (log ε 3.68) nm (see above). A strict
confirmation of the structure of 4Н-pyrazole 4b was
obtained by X-ray diffraction (XRD) analysis of its
single crystal (see the table, Fig. 1).
The structure of compound 6 is confirmed by IR,
1Н and 13С NMR spectra and the data of XRD analysis
of its single crystals (see the table, Fig. 2).
Further we investigated thermal transformations of
two 4Н-pyrazoles 4a and 4b that we obtained.
Compound 4a at high temperature (microwave reactor,
benzene, 190C, 40 min) isomerized into indazole 7a, and
at 160°С in methanol fragmentized with the formation
of N-unsubstituted 1Н-pyrazole 8а (Scheme 6).
Cyclopropene 5b was identified by the absorption
band in IR spectrum at 1836 cm–1 and the
characteristic signal of quaternary carbon atom at
~40.5 ppm in the 13С NMR spectrum (see above).
Spirocyclic 3Н-pyrazole 3 at boiling in benzene
during 12 h fully transformed into 1Н-pyrazole 6
(Scheme 5). Yet the fragmentation of compound 3 and
the formation of cyclopropene 5b did not occur.
For the confirmation of the structure of indazole 7а
we applied a correlation HMBC spectrum, which
revealed the coupling of methyl group protons with the
15
atom N through three bonds. As a spectral feature of
compound 7а an unusually downfield chemical shift of
1
these protons in the Н NMR spectrum (δ 3.19 ppm)
should be mentioned. The structure of indazole 7а was
proved also by XRD analysis of its single crystal (see
the table, Fig. 3).
The structure of 3-methylindazole 8а satisfactorily
1
correlates with Н and 13С NMR spectra. For the
assignment of signals DEPT technique was applied.
4Н-Pyrazole 4b at boiling in benzene (80°С) during
12 h partially (conversion 50%) converts into new
3Н-pyrazole 9. In the microwave reactor at
100°С after 1 h the conversion was 70%. Heating in
benzene at 130°С for 20 min resulted in a full
conversion and gave equal amounts of compounds 7b
and 9. Heating of compound 4b in toluene at 135°С
during 2.5 h ends in the formation of a three-
component mixture consisting of compounds 7b, 9,
Fig. 3. Spatial arrangement of the methyl 3-methyl-2H-
dibenzo[e,g]indazole-2-carboxylate 7а molecule according
to XRD analysis.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 8 2018

THERMAL REARRANGEMENTS OF 3Н- AND 4Н-PYRAZOLES PREPARED BY REACTIONS
1193
Scheme 8.
SO2R'
SO2R'
N
N
N
R
R'O2S
R
N
N
N
R
Δ
Δ
14_17
10_13
18_21
R = Ph (10–12, 14–16, 18–20), Me (13, 17, 21); R' = Me (10, 14, 18), Ph (11, 13, 15, 17, 19, 21), 4-MeC6H4 (12, 16, 20).
and cyclopropene 5b in a ratio 3 : 3 : 2 (Scheme 7).
Compound 5b was identified in reaction mixture by
1Н and 13С NMR spectra of an authentic sample.
Indazole 7b was isolated in crystalline form by
flash-chromatography on silica gel. 3Н-Pyrazole 9
was also obtained at keeping 3Н-pyrazole 2 during
6 h in glacial acetic acid at 20°С with a catalytic
quantity of conc. H2SO4 and it was isolated in an
individual state. Heating of 3Н-pyrazole 2 or 4Н-
pyrazole 4b in methanol at 160°С during 20 min
resulted in known indazole 8b [12], analog of
compound 8а.
To establishing the structure of indazoles 7b and 9
IR, 1Н and 13С NMR spectra were applied. The
chemical proof of the structure of indazole 7b, whose
13С NMR spectrum is very close to the spectrum of
indazole 7а, is its conversion into indazole 8b at
hydrolysis with air moisture at storage. Mild
hydrolysis as well as methanolysis (heating in
methanol at 160°С) of compounds 7a and 7b, occurs
comparatively easily due to their being practically
urethanes, and the formed aromatic 1Н-pyrazoles 8a
and 8b operate therewith in these processes as good
leaving groups in the nucleophilic substitution at the
carbonyl carbon atom.
substituted 4Н-pyrazoles 10–13 [12, 13]. Moreover,
the heating of 4Н-pyrazole 13 in methanol at 160°С
resulted in the same indazole 8a, which was obtained
from compound 7a in the same conditions (see above).
The latter fact calls into question the correctness of
the structure determination of thermolysis products of
4Н-pyrazoles 10–13, which previously were attributed
to phenanthridine structures 14–17 basing on XRD
analysis on single crystals of thermolysis products of
pyrazole 10. We performed a repeated solution of the
XRD data massive of this sample and found that it
really possesses the structure of N-sulfonyl-substituted
indazole 18 (see the table, Fig. 4).
These facts make it possible to conclude that
sulfonyl-substituted 4Н-pyrazoles 10–13 at high
temperature behave similar to methoxycarbonyl-
substituted 4Н-pyrazoles 1 and 2 and are converted
respectively into indazoles 18–21, not into
phenanthridines 14–17 [12, 13] (Scheme 8).
C10
C9
C7
C11
C8
C18
C17
C19
C20
Compound 9 is relatively unstable and at storage
also transforms into indazole 8b. The signal of the
quaternary carbon atom of 3Н-pyrazole 9 appears in
the 13С NMR spectrum at ~105 ppm, and of carbonyl
group, at 167 ppm, close to the chemical shifts of the
same groups of a model indazole, distinguished from
C6
C5
C15
C16
C2
C1
N1
C14
C21
O1
C4
C3
C12
S1
C13
N2
compound
9
by the presence of one more
methoxycarbonyl substituent instead of the phenyl
group [17].
O2
C22
At the analysis of 13С NMR spectra of N-
methoxycarbonyl-substituted indazoles 7a and 7b we
discovered their significant similarity to the spectra of
products of high-temperature thermolysis of 3-sulfonyl-
Fig. 4. Spatial arrangement of the 2-(methylsulfonyl)-3-
phenyl-2H-dibenzo[e,g]indazole 18 molecule in the crystal
according to XRD analysis data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 8 2018

VASIN et al.
1194
Scheme 9.
W
N
W
W
N
N
W
R
N
R
W
N
N
N
R
N
R
R
C
B
A
D
E
Hence the previously unexplained formation of 1Н-
pyrazole 8b at maintaining pyrazoles 14–16 in glacial
acetic acid with catalytic amount of conc. H2SO4 [12]
becomes understandable: indeed, the hydrolysis of N-
sulfonyl-substituted 1Н-pyrazoles 18–20 occurs at
diluting reaction mixtures with water when isolating
the reaction products.
rearrangement product, N-acceptor-substituted 1Н-
pyrazole Е, and its precursor, a new 3Н-pyrazole D
remains unobservable in the higher temperature
conditions. And only from 4Н-pyrazole 4b along with
two rearrangement products, a new 3Н-pyrazole D and
1H-pyrazole Е, and also a fragmentation product was
obtained, derivative of cyclopropene formed via
thermally unstable 3Н-pyrazole B (Scheme 9).
Now we can make some conclusions resulting from
our investigation. Firstly, they regard the conclusions
from the study of thermolysis of 3Н-pyrazoles 1–3
derivatives. The rearrangement of these pyrazoles
occurred fully in keeping with the previously
discovered laws [20] and obeyed the directing effect of
the acceptor substituent СО2Mе in the position 5 (of
compound 1 and 2) or 4 (of compound 3). A
significant increase in the rearrangement rate of phenyl
-substituted pyrazole 2 was found compared to its
methyl analog 1. Evidently, in the bipolar intermediate
state of sigmatropic shift to a carbon atom [20] the
stabilizing effect of phenyl group exceeds the effect of
methyl group. At the thermolysis in aprotic solvent
Hence we experimentally demonstrated that for 4Н-
pyrazole 4b at the temperature, exceeding that at
which it is obtained from 3Н-pyrazole, a possibility
exists of rearrangement either to the reverse side, or to
the new 3Н-pyrazole D. Presumably such possibility is
due to the presence of the phenyl substituent: high
mobility of phenyl (comparing to methyl) group assists
the formation of the new 3Н-pyrazole D. On the other
hand, the stabilizing effect of phenyl substituent in
Auwers 3Н-pyrazole В reduces the barrier of transition
in this direction, and the propensity of pyrazole В to
suffer denitrogenation results in cyclopropene С.
Although sulfones 10–12 also contain a phenyl
substituent, at the thermolysis they do not afford the
new 3Н-pyrazole D, because it appears to be thermally
pyrazole
2
unlike pyrazole
1
undergoes
a
denitrogention, not a rearrangement. Evidently, the
process of fragmentation starts with the rupture of the
bond between the spirocyclic carbon atom and the
nitrogen atom, and further cyclopropene 5b forms with
the participation of vinylcarbene derivative, whose
stability is increased due to the phenyl group.
unstable due to
a
higher, comparied to
methoxycarbonyl group, mobility of sulfonyl group in
1,5-sigmatropic rearrangement [21], leading to the
formation of pyrazole Е. Less understandable is the
lack of transformation of sulfones 10–12 in the
direction of pyrazole В and further to cyclopropene С.
Perhaps, the corresponding 3Н-pyrazole В forms, but
it is less prone to denitrogenation and less stable than
the ester analog due to a lower π-acceptor activity of
sulfonyl group and therefore a shift of equilibrium of
reversible reaction occurs in favor of terminal product
Е. In case of 4Н-pyrazole 4а due to the lower mobility
of methyl group the formation of 3Н-pyrazole D
requires a higher temperature, and it brings further its
quick isomerization into pyrazole Е due to the
migration of СО2Mе group. The path in direction of
3Н-pyrazole В is here less feasible than in the case of
The results of the thermolysis investigation of 4Н-
pyrazoles 4a and 4b show their higher thermal stability
compared to their isomeric 3Н-pyrazoles 1 and 2. The
same behavior features of 3Н- and 4Н-pyrazoles were
observed in the series on sulfones we investigated [12,
13]. While comparing the structure of thermolysis
products of related 4Н-pyrazoles 4а, 4b, and 10–13,
differing only in substituents in the positions 3 or/and
4, the high sensitivity should be mentioned of the paths
of thermal transformations of these pyrazoles to the
substituents nature. Indeed, the thermolysis of 4Н-
pyrazoles 4а and 10–13 results in
a
single
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THERMAL REARRANGEMENTS OF 3Н- AND 4Н-PYRAZOLES PREPARED BY REACTIONS
1195
Crystallographic characteristics, parameters of XRD experiment and of refinement of structures of compounds 4b, 5а, 7a,
and 18
Parameter
Empirical formula
4b
5a
7a
18
C22H16N2O2S
372.43
C23H16N2O2
352.38
C18H14N2O2
290.31
C23H16N2O2
352.38
M
T, K
297(2)
297(2)
297(2)
297(2)
Crystal system
Space group
Z
Triclinic
Monoclinic
Monoclinic
Monoclinic
P1–
2
Р 21/с
P 21/c
P 21/c
4
4
4
a, Å
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
ρ, g/cm3
μ, mm–1
8.5710(6)
8.9793(10)
12.5804(11)
93.285(8)
105.762(7)
110.957(8)
857.21(14)
1.365
7.9431(3)
20.4568(5)
9.235793)
90
111.383(4)
90
13.1429(5)
7.0343(3)
19.6302(9)
90
104.766(4)
90
9.2729(2)
21.0531(3)
9.476392)
90
102.771(2)
90
1397.42(9)
1.380
1754.90(13)
1.334
1804.23 (6)
1.371
0.088
0.092
0.086
0.199
Multi-scan method Multi-scan method
Accounting for extinction
0.24128, 1.0
368
Multi-scan method [27]
[27]
608
[27], 0.811, 1.000
736
F(000)
776
Crystal size, mm
0.21 × 0.14 × 0.12 0.23 × 0.138 × 0.115
0.2 × 0.15 × 0.1
0.509 × 0.452 × 0.379
Diffractometer
XtaLAB Pro: Kappa single
MoKα, λ 0.71073 Å
ω -scans
Gemini S, Sapphire3
MoKα, λ 0.71073Å (graphite
monochromator) ω-scans
Radiation
Scanning type
Range of data collection with
respect to θ, deg
3.416–26.371
3.399–28.281
3.373–31.207
3.615–30.504
–10≤h=10
–11=k=10
–15=l=15
7310
–10≤h=10
–27≤k=27
–12≤l=12
22822
–18≤h=19
–10=k=9
–28=l=28
53548
–13≤h=13
–30≤k=30
–13≤l=13
35646
Reflections intervals
Measured reflections
Independent reflections
with I >2σ(I)
3296
3458
5223
5500
2651
2676
3261
4852
Rint
0.0266
0.0365
0.0621
0.0206
Number of refined parameters
308
255
304
244
GOOF
1.095
1.07
1.023
1.127
R-factors with respect
R1 0.0423,
R1 0.0532,
R1 0.063,
R1 0.0516,
to F2>2σ(F2)
wR2 0.1228
wR2 0.1253
wR2 0.15
wR2 0.1317
R1 0.0535,
wR2 0.1289
–0.18/0.176
R1 0.0718,
wR1 0.1358
–0.183/0.205
R1 0.1117,
wR2 0.167
–0.188/0.334
R1 0.0585,
wR2 0.1367
–0.31/0.363
R-factors for all reflections
Residual electron density, e/A3
(Δ/σ)max/(Δ/σ)min
0.027/0.002
0.005/0.000
0.000/0.000
0.001/0
Software
SHELX2014 [25], WINGX [26], CrysAlisPro [27]
phenyl analog 4b, also due to the stability of this
We plan further to perform special investigation of
pyrazole to denitrogention.
post-rearrangements of 4Н-pyrazoles of related structure.
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VASIN et al.
1196
EXPERIMENTAL
Found, %: C 74.38; Н 4.77; N 9.61. С18Н14N2O2.
Calculated, %: C 74.47; Н 4.86; N 9.65.
1H and 13C NMR spectra were recorded on a spec-
trometer JNM-ECX400 Jeol (400.1 and 100.6 MHz
respectively) from solutions of compounds in СDCl3.
As internal refetence at measurements of chemical
shifts signals were used of residual protons (δН 7.26)
and carbon atoms (δС 77.16) of deuterated solvent. IR
spectra were recorded on a Fourier spectrophotometer
InfraLUM FT-02 from pellets with KBr. UV spectra
Methyl 4'-phenylspiro[fluoren-9,3'-pyrazole]-5'-
carboxylate (2). Yield 82%. Light-yellow crystals, mp
143–144°С (ethyl ether) (141°С [14]). IR spectrum, ν,
cm–1: 1701 vs (С=О), 1442 m, 1337 m, 1222 m, 1126
1
m, 756 s, 648 m. Н NMR spectrum, δ, ppm: 4.07 s
(3Н, ОMе), 6.88 d (2Н, Нarom, J 7.7 Hz), 7.01 d (2Н,
Н
arom, J 7.5 Hz), 7.09 t (2Н, Нarom, J 7.7 Hz), 7.17–7.27
m (3Н, Нarom), 7.44 t (2Н, Нarom, J 7.7 Hz), 7.81 d (2Н,
were recorded on
a
two-beam UV-VID
Н
arom, J 7.5 Hz). 13С NMR spectrum, δ, ppm: 52.8
spectrophotometer UV-2600 (Shimadzu) in methanol.
Elemental analysis was performed on a СНNS-
analyzer vario MICRO. Analytic TLC was performed
on Sorbfil plates, eluent light petroleum ether–acetone,
4 : 1, development in iodine vapor. For column chro-
matography silica gel Merck 60 (0.040–0.063 mm)
was applied, eluent light petroleum ether–acetone, 7–
3 : 1.
(ОMе), 110.2 (С3'), 121.3 (2Сarom), 123.9 (2Сarom),
128.2 (2Сarom), 128.5 (2Сarom), 128.6 (2Сarom), 128.7 w
(С5'), 130.2 (2Сarom), 130.6 (2Сarom), 135.2 (2Сarom),
143.6 (2Сarom), 144.7 (Сarom), 159.6 (С4'), 162.1 (C=O).
Found, %: C 78.28; Н 4.47; N 8.06. С23Н16N2O2.
Calculated, %: C 78.39; Н 4.58; N 7.95.
Methyl 5'-phenylspiro[fluoren-9,3'-pyrazole]-4'-
carboxylate (3). Yield 12%. Light-yellow crystals, mp
144–145°С (petroleum ether–ethyl acetate, 8 : 1). IR
spectrum, ν, cm–1: 1725 vs (С=О), 1620 m, 1492 m,
1435 m, 1335 s, 1207 s, 1138 m, 1092 m, 925 m, 752
Methyltetrolate [22], methyl 3-phenylpropiolate
[23], and 9-diazofluoren [24] were obtained by known
methods.
1
Reaction of methyltetrolate and methyl 3-
phenylpropiolate with 9-diazofluoren. General
method. To a solution of 0.5 g (2.6 mmol) of 9-
diazofluoren in 15 mL of anhydrous ethyl ether was
added 2.3 mmol of activated acetylene in 10 mL of the
same solvent. The mixture was kept at 20°С in a
tightly closed flask in darkness for 2 weeks with
s, 690 m. Н NMR spectrum, δ, ppm: 3.43 s (3Н,
ОMе), 6.86 d (2Н, Нarom, J 7.7 Hz), 7.27 t (2Н, Нarom, J
7.3 Hz), 7.48 t (2Н, Нarom, J 7.8 Hz), 7.57–7.62 m (3Н,
Н
arom), 7.86 d (2Н, Нarom, J 7.5 Hz), 8.34–8.36 m (2Н,
Н
arom). 13С NMR spectrum, δ, ppm: 52.3 (ОMе), 110.7
(С3'), 121.1 (2Сarom), 123.3 (2Сarom), 128.2 (2Сarom),
128.7 (2Сarom), 129.6 w (С5'), 129.9 (2Сarom), 130.4
(2Сarom), 131.1 (2Сarom), 132.9 w (Сarom), 135.6
(2Сarom), 143.5 (2Сarom), 159.8 (С4'), 162.8 (C=O).
Found, %: C 78.42; Н 4.67; N 8.01. С23Н16N2O2.
Calculated, %: C 78.39; Н 4.58; N 7.95.
methyltetrolate and
7
days with methyl
phenylpropiolate. We obtained a derivative 3Н-
pyrazole 1 or a mixture of regioisomers 2 and 3 (2 : 1
after 1 day, 6 : 1 after 7 days) respectively. Precipitated
crystals of cycloadducts 1 and 2 were filtered off and
purified by crystallization. Cycloadduct 3 was isolated
by column chromatography on silica gel from the
mother liquor which remained after separation of
crystals of compound 2.
Methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-
carboxylate (4а). A solution of 0.1 g (34 mmol) of 3Н-
pyrazole 1 in 3 mL of anhydrous toluene was boiled
for 2 h till initial compound disappeared according to
TLC. Yield 96 mg (96%), mp 116–117°С (methanol).
UV spectrum (methanol): λmax 311 nm (log ε 3.96). IR
spectrum, ν, cm–1: 1709 vs (С=О), 1551 m, 1455 s,
1362 s, 1342 s, 1250 s, 1200 s, 1076 s, 1053 m, 756 vs,
Methyl 4'-methylspiro[fluoren-9,3'-pyrazole]-5'-
carboxylate (1). Yield 70%, mp 147–148°С (ethyl
ether) IR spectrum, ν, cm–1: 1732 vs (С=О), 1447 m,
1339 s, 1219 m, 1181 m, 1111 m, 1084 m, 748 s, 729
m. 1Н NMR spectrum, δ, ppm: 1.93 s (3Н, Mе), 4.06 s
(3Н, ОMе), 6.67 d (2Н, Нarom, J 7.7 Hz), 7.24 t (2Н,
1
729 s. Н NMR spectrum, δ, ppm: 1.67 s (3Н, Mе),
4.09 s (3Н, ОMе), 7.27 t (1Н, Нarom, J 7.7 Hz), 7.35 t
(1Н, Нarom, J 7.5 Hz), 7.46 t (1Н, Нarom, J 7.5 Hz), 7.46 t
(1Н, Нarom, J 7.7 Hz), 7.78 d (1Н, Нarom, J 7.7 Hz), 7.85
d (1Н, Нarom, J 7.7 Hz), 7.95 d (1Н, Нarom, J 8.0 Hz), 8.07
d (1Н, Нarom, J 7.5 Hz). 13С NMR spectrum, δ, ppm:
28.7 (Mе), 52.5 (ОMе), 65.9 (С3а), 124.2 (Сarom), 124.9
w (Сarom), 126.2 (Сarom), 126.6 (Сarom), 126.8 (Сarom),
Н
arom, J 7.6 Hz), 7.46 t (2Н, Нarom, J 7.7 Hz), 7.81 d
(2Н, Нarom, J 7.6 Hz). 13С NMR spectrum, δ, ppm: 10.7
(Mе), 52.5 (ОMе), 110.0 (С3'), 121.2 (2Сarom), 123.5
(2Сarom), 128.5 (2Сarom), 130.3 (2Сarom), 135.2 (2Сarom),
143.7 (2Сarom), 145.8 (С5'), 162.0 (С4'), 164.1 (C=O).
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THERMAL REARRANGEMENTS OF 3Н- AND 4Н-PYRAZOLES PREPARED BY REACTIONS
1197
128.5 (Сarom), 128.9 (Сarom), 129.0 (Сarom), 131.0 w
(Сarom), 133.3 (Сarom), 133.7 w (Сarom), 136.1 (Сarom),
162.7 (С=О), 167.6 (С2а), 182.7 (С3). Found, %: C
74.60; Н 4.77; N 9.59. С18Н14N2O2. Calculated, %: C
74.47; Н 4.86; N 9.65.
boiled for 8 h. The reaction progress was monitored by
TLC by disappearance of initial compound.
Cyclopropene 5b and 1Н-pyrazole 6 were obtained.
Methyl 3-phenylspiro(cycloprop[2]en-1,9'-fluo-
ren)-2-carboxylate (5b). Yield 95 mg (70%),
colorless crystals, mp 173–174°С (methanol). IR
spectrum, ν, cm–1: 1836 s (С=С), 1709 vs (С=О), 1489
s, 1447 m, 1431 m, 1300 m, 1285 m, 1204 s, 1169 m,
Methyl 3-methylspiro(cycloprop[2]en-1,9'-fluo-
ren)-2-carboxylate (5а). In a tightly closed quartz test
tube a solution of 0.2 g (0.66 mmol) of 3Н-pyrazole 1
in 7 mL of anhydrous CH2Cl2 was irradiated by the
light of a mercury lamp of moderate pressure DRT-
400. After evaporation of solvent the oily residue was
subjected to flash-chromatography on silica gel to
isolate 58 mg (32%) of colorless crystals of compound
5а, mp 119–120°С. IR spectrum, ν, cm–1: 1863 m
(С=Сolefin), 1708 vs (С=О), 1431 m, 1246 m, 1126 w,
1
737 s. Н NMR spectrum, δ, ppm: 3.83 s (3Н, ОMе),
7.20 s (2Н, Нarom, J 7.5 Hz), 7.28 t (2Н, Нarom, J 7.5 Hz),
7.35–7.44 m (5Н, Нarom), 7.52–7.55 m (2Н, Нarom),
7.91 d (2Н, Нarom, J 7.7 Hz). 13С NMR spectrum, δ,
ppm: 40.5 (С3), 52.5 (ОMе), 105.9 (С2), 120.1
(2Сarom), 121.1 (2Сarom), 124.5 (С1), 126.9 (2Сarom),
127.2 (2Сarom), 129.1 (2Сarom), 131.7 (2Сarom), 131.9
(С2), 132.0 (Сarom), 140.5 (Сarom), 145.7 (Сarom), 159.9
(С=О). Found, %: C 85.13; Н 4.89. С23Н16O2.
Calculated, %: C 85.16; Н 4.97.
1
1103 m, 1072 w, 1030 w, 802 m, 741 m, 652 w. Н
NMR spectrum, δ, ppm: 2.41 s (3Н, Mе), 3.75 s (3Н,
ОMе), 7.17 d (2Н, Нarom, J 7.5 Hz), 7.32 t (2Н, Нarom, J
7.4 Hz), 7.41 t (2Н, Нarom, J 7.4 Hz), 7.87 d (2Н, Нarom
,
Methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-
carboxylate (6). Yield 1.35 g (92%), colorless crystals,
mp 177–178oC (benzene). IR spectrum, ν, cm–1: 1717
vs (С=О), 1531 m, 1451 m, 1327 m, 1273 m, 1130 s,
748 m, 706 m. 1Н NMR spectrum, δ, ppm: 3.84 s (3Н,
ОMе), 7.45–7.54 m (4Н, Нarom), 7.56–7.64 m (3Н,
J 7.6 Hz). 13С NMR spectrum, δ, ppm: 10.4 (Mе), 40.8
(С3), 52.4 (ОMе), 106.0 (С2), 120.2 (2Сarom), 120.8
(2Сarom), 126.77 (2Сarom), 126.92 (2Сarom), 133.6 (С1),
140.3 (2Сarom), 146.4 (2Сarom), 160.0 (С=О). Found, %:
C 82.49; Н 5.44. С18Н14O2. Calculated, %: C 82.42; Н
5.38.
Н
arom), 7.76 d (2Н, Нarom, J 8.2 Hz), 8.32 t (2Н, Нarom, J
Methyl 3a-phenyl-3aH-dibenzo[e,g]indazole-3-
carboxylate (4b). A solution of 5.6 mmol of 3Н-
pyrazole 2 in 4 mL of anhydrous methanol was boiled
for 4 h (TLC monitoring). Yield 1.39 g (73%), yellow
crystals, mp 139–140°С (methanol). UV spectrum
(methanol): λmax 300 nm (log ε 3.95). IR spectrum, cm–1:
1728 vs (С=О), 1559 w, 1447 m, 1343 m, 1223 m,
1103 m, 1014 m, 810 w, 760 m, 729 m, 617 w, 428 w.
1Н NMR spectrum, δ, ppm: 3.94 s (3Н, ОMе), 6.70–
6.74 m (2Н, Нarom), 7.11–7.15 (3Н, Нarom), 7.34 t (1Н,
8.3 Hz), 8.66 d (1Н, Нarom, J 8.3 Hz), 8.87 d (1Н,
Н
arom, J 8.2 Hz). 13С NMR spectrum, δ, ppm: 52.0
(ОMе), 107.2 (С4а), 117.1 (СНarom), 121.5 (С4а), 122.6
(СНarom), 123.1 (2Сarom), 125.8 (СНarom), 126.3
(СНarom), 127.9 (Сarom), 128.25 (СНarom), 128.29
(2СНarom), 128.6 (СНarom), 129.0 (2СНarom), 129.3
(СНarom), 129.4 (СНarom), 133.1 (Сarom), 133.5 (Сarom),
137.3 (Сarom), 154.0 (Сarom), 166.7 (С=О). Found, %: C
78.35; Н 4.64; N 7.86. С23Н16N2O2. Calculated, %: C
78.39; Н 4.58; N 7.95.
Нarom, J 7.5 Hz), 7.40 t (1Н, Нarom, J 7.7 Hz), 7.49 t
Methyl 3-methyl-2H-dibenzo[e,g]indazole-2-
carboxylate (7а). A solution of 70 mg of 4Н-pyrazole
4а in 3 mL of anhydrous benzene was heated in a
microwave reactor at 190°С for 40 min. After cooling
the precipitated crystals were filtered off, washed with
10 mL of ethyl ether. Yield 15 mg (21%), mp 184–
185°С. IR spectrum, ν, cm–1: 1747 vs (С=О), 1450 m,
1431 s, 1354 s, 1331 s, 1277 m, 1246 m, 764 s, 725 m.
1Н NMR spectrum, δ, ppm: 3.19 d (3Н, Mе, J 1.2 Hz),
4.07 s (3Н, ОMе), 7.50–7.65 m (4Н, Нarom), 8.20–8.22
m (1Н, Нarom), 8.42 t (1Н, Нarom, J 8.2 Hz), 8.46 m (1Н,
(2Н, Нarom, J 7.7 Hz), 7.81 d (1Н, Нarom, J 8.1 Hz), 7.88
d (1Н, Нarom, J 7.8 Hz), 7.94 t (2Н, Нarom, J 7.7 Hz).
13С NMR spectrum, δ, ppm: 53.3 (ОMе), 74.2 (С3а),
124.1 (Сarom), 125.7 (Сarom), 126.2 (2Сarom), 126.5
(Сarom), 126.8 (Сarom), 128.3 (Сarom), 128.9 (Сarom),
129.0 (Сarom), 129.2 (2Сarom), 129.4 (Сarom), 129.6
(Сarom), 130.5 w (Сarom), 133.1 (Сarom), 133.2 w (Сarom),
133.4 w (Сarom), 136.2 (Сarom), 161.8 (С=О), 168.7
(С2а), 182.7 (С3). Found, %: C 78.58; Н 4.49; N 7.91.
С23Н16N2O2. Calculated, %: C 78.39; Н 4.58; N 7.95.
Thermolysis of 3Н-pyrazoles 2, 3 in benzene.
General method. A solution of 4.2 mmol of 3Н-
pyrazole 2 or 3 in 3 mL of anhydrous benzene was
Н
arom), 8.61 d (1Н, Нarom, J 8.2 Hz). 13С NMR
spectrum, δ, ppm: 14.7 (Mе), 52.2 (ОMе), 116.4 (С3),
123.4 (Сarom), 124.13 (Сarom), 124.15 (2Сarom), 124.22
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 8 2018

VASIN et al.
1198
(2Сarom), 125.1 (Сarom), 126.5 (Сarom), 127.7 (2Сarom),
129.2 (Сarom), 132.1 (Сarom), 139.4 (С4), 148.3 (С2),
151.9 (С=О). Found, %: C 74.49; Н 4.84; N 9.68.
С18Н14N2O2. Calculated, %: C 74.47; Н 4.86; N
9.65.
needle ctystals, mp 186–187°С (petroleum ether–ethyl
acetate, 4 : 1). IR spectrum, ν, cm–1: 3441 br.s, 1759
vs, 1651 s, 1632 s, 1447 s, 1339 vs, 1242 s, 1177 s,
1
1007 s, 833 s, 745 s, 718 s, 617 m, 475 m. Н NMR
spectrum, δ, ppm: 4.01 s (3Н, ОMе), 7.12 t (1Н, Нarom
,
J 8.0 Hz), 7.35 d (1Н, Нarom, J 8.2 Hz), 7.43 t (1Н,
3-Methyl-2H-dibenzo[e,g]indazole (8а). а. A solution
of 0.2 g (0.66 mmol) of 4Н-pyrazole 4а in 5 mL of
anhydrous methanol was heated in a microwave
reactor at 160°С for 20 min. The precipitated crystals
were filtered off. Yield 150 mg (81%), mp 259–260°С.
IR spectrum, ν, cm–1: 3121 br.m, 1613 m, 1547 m,
1524 m, 1443 m, 1316 m, 1161 m, 1046 m, 1007 m,
Нarom, J 8.3 Hz), 7.50–7.54 m (2Н, Нarom), 7.68 t (1Н,
arom, J 8.1 Hz), 8.46 t (2Н, Нarom, J 7.3 Hz), 8.73 d
Н
(1Н, Нarom, J 7.5 Hz). 13С NMR spectrum, δ, ppm: 55.2
(ОMе), 117.5 (Сarom), 123.6 (СНarom), 123.9 (СНarom),
124.2 (СНarom), 124.4 (СНarom), 125.0 (Сarom), 126.9
(Сarom), 127.0 (СНarom), 127.5 (СНarom), 127.8 (СНarom),
129.2 (2СНarom), 129.3 (СНarom), 129.57 (СНarom),
129.61 (2СНarom), 130.1 (Сarom), 132.16 (Сarom), 132.23
(Сarom), 141.0 (С5), 148.4 (С4), 150.9 (С=О). Found,
%: C 78.40; Н 4.63; N 7.97. С23Н16N2O2.
Calculated, %: C 78.39; Н 4.58; N 7.95.
1
752 vs, 725 vs, 613 m, 428 m. Н NMR spectrum
(DMSO-d6), δ, ppm: 2.82 s (СН3), 3.55 t (1Н, Нarom, J
7.9 Hz), 7.65–7.71 m (3Н, Нarom), 8.28 d (1Н, Нarom, J
7.9 Hz), 8.43–8.47 m (1Н, Нarom), 8.76 t (1Н, Нarom, J
7.4 Hz), the proton signals of NH group were not
found. 13С NMR spectrum (DMSO-d6), δ, ppm: 14.6
(СН3), 112.7 (Сarom), 122.2 (СНarom), 123.1 (СНarom),
123.9 (2СНarom), 124.4 (СНarom), 127.0 (СНarom), 127.1
(Сarom), 127.2 (СНarom), 127.5 (СНarom), 128.0 (Сarom),
129.6 (Сarom), hydrogen-free carbon atoms of pyrazole
fragment cannot be identified properly due to quick
tautomeric transformations of compound 8а. Found,
%: C 82.69; Н 5.41; N 11.98. С16Н12N2. Calculated, %:
C 82.73; Н 5.21; N 12.06.
Methyl 3-phenyl-3H-dibenzo[e,g]indazole-3-
carboxylate (9). A solution of 1.48 g (4.2 mmol) of
4Н-pyrazole 4b in 3 mL of anhydrous toluene was
boiled for 2 h, monitoring disappearance of initial
compound by TLC. The solvent was removed at a
lowered pressure, the residue was purified by
crystallization. Yield 92 mg (62%), colorless crystals,
mp 159–160°С (ethyl ether).1 IR spectrum, ν, cm–1:
1736 vs (С=О), 1454 m, 1234 s, 1122 w, 1006 m, 802
1
w, 752 m, 725 m, 520 w, Н NMR spectrum, δ, ppm:
b. In alternative experiment from 0.3 g (0.8 mmol)
of sulfonyl-substituted 4Н-pyrazole 13 [8] at heating in
methanol at 160°С 190 mg (69%) of compound 8а
were obtained.
3.49 s (3Н, ОMе), 7.34–7.39 m (5Н, Нarom), 7.66 t (1Н,
Нarom J 8.2 Hz), 7.78–7.82 m (1Н, Нarom), 7.86–7.90 m
(2Н Нarom), 8.07 t (1Н, Нarom J 8.2 Hz), 8.81–8.87 m
(2Н, Нarom), 9.12–9.15 m (1Н, Нarom J 8.2 Hz). 13С
NMR spectrum, δ, ppm: 53.7 (ОMе), 105.0 (С3), 123.4
(СНarom), 123.9 (СНarom), 124.8 (СНarom), 125.0 (Сarom),
126.7 (Сarom), 128.1 (СНarom), 128.3 (СНarom), 128.5
(СНarom), 128.7 (СНarom), 128.8 (2СНarom), 128.9
(СНarom), 129.3 (СНarom), 129.4 (2СНarom), 131.6
(Сarom), 131.7 (Сarom), 132.4 (С4), 135.8 (Сarom), 153.0
(С5), 167.49 (С=О). Found, %: C 78.35; Н 4.50; N
8.00. С23Н16N2O2. Calculated, %: C 78.39; Н 4.58; N
7.95.
Thermal transformations of 4Н-pyrazole (4b) in
aprotic solvents. In 10 mL of anhydrous benzene or
toluene 0.2 g (0.66 mmol) of 4Н-pyrazole 4b was
heated for desired time. After removing the solvent in
a vacuum the residue was analyzed by NMR. At
boiling in benzene during 12 h a mixture was obtained
of compounds 4b and 9, 1 : 1, after 1 h in benzene at
100°С, 3 : 7; after 20 min of heating in benzene at
130°С a full conversion was observed, compounds 7b
and 9 formed, 1 : 1; in toluene at 135°С after heating
for 2.5 h a mixture was obtained of indazole 7b, 3Н-
pyrazole 9, and cyclopropene 5b, 1.5 : 1.5 : 1, which
were identified in the reaction mixture by 13С NMR
spectra.
Isomerization of 3Н-pyrazole (2) in glacial acetic
acid. To a solution of 1.55 g (4.4 mmol) of compound
2 in 10 mL of glacial acetic acid was added 2 drops of
conc. H2SO4. The mixture was kept at 20°С for 6 h,
then diluted with 50 mL of water. The precipitated
crystals were filtered off and crystallized from
Methyl 3-phenyl-2H-dibenzo[e,g]indazole-2-
carboxylate (7b) was isolated by flash-
chromatography on silica gel from the reaction
mixture, obtained at thermolysis of 4Н-pyrazole 4b in
benzene at 130°С. Yield 80 mg (38%). Colorless
1
In [14] at thermolysis of 3Н-pyrazole 2 in glacial acetic acid a
single product was obtained, mp 159°С, which was erroneously
identified as 1Н-pyrazole 7b
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 8 2018

THERMAL REARRANGEMENTS OF 3Н- AND 4Н-PYRAZOLES PREPARED BY REACTIONS
1199
8. Pérez-Aguilar, M.C. and Valdés, C., Angew. Chem., Int.
Ed., 2013, vol. 52, p. 1.
methanol. We obtained 0.73 g (47%) of 3Н-pyrazole 9,
mp 159–160°С.
9. Hao, L., Hong, J.-J., Zhu, J., and Zhan, Z.-P., Chem.
X-ray diffraction analysis of single crystals of
compounds 4b, 6, 7а, and 18. Crystallographic
characteristics, parameters of XRD experiment and of
structure refinement are compiled in the table, their
spatial arrangement is demonstrated in figures 1–4. In
each case the initial fragment of structure was solved
by the direct method using software SHELX [25].
Positions of the remaining nonhydrogen atoms were
determined by the differential synthesis of electron
density and refined by the least squares method with
respect to |F|2 in an anisotropic approximation for
thermal parameters. In the structure 18 the positions of
hydrogen atoms were determined geometrically, the
parameters were refined in the rider model. The
positions of hydrogen atoms in pyrazole 7а were found
from the differential synthesis of electron density, their
parameters were refined as free in isotropic
approximation in the general least squares method
cycle. Results of XRD investigations of pyrazoles 4b,
7а, 6, and 18 were deposited to Cambridge
Crystallographic Data Centre (CCDC nos. 1515374,
1486265, 1531656, 1530680 respectively). Molecular
graphics was performed with software ORTEP-3 [28].
Eur. J., 2013, vol. 19, p. 5715.
10. Gladow, D., Doniz-Kettenmann, S., and Reissig, H.-U.,
Helv. Chim. Acta, 2014, vol. 97, p. 808. doi 10.1002/
hlca.201400032
11. Pérez-Aguilar, M.C. and Valdés, C., Angew. Chem., Int.
Ed., 2015, vol. 54, p. 13729.
12. Vasin, V.A., Masterova, Yu.Yu., Razin, V.V., and
Somov, N.V., Russ. J. Org. Chem., 2014, vol. 50,
p. 1323. doi 10.1134/S1070428014090152
13. Vasin, V.A., Razin, V.V., Markelova, Yu.A., and
Masterova, Yu.Yu., Russ. J. Org. Chem., 2015, vol. 51,
p. 1418. doi 10.1134/S1070428015100103
14. Van Alphen, J., Rec. Trav. Chim., 1943, vol. 62,
p. 491.
15. Komendantov, M.I., Zavgorodnyaya, A.P., Domnin, I.N.,
and Bekmukhametov, R.R., Zh. Org. Khim., 1986,
vol. 22, p. 1541.
16. Fedorov, A.A., Duisenbaev, Sh.E., Razin, V.V.,
Kuznetsov, M.A., and Linden, E., Russ. J. Org. Chem.,
2007, vol. 43, p. 231. doi 10.1134/S1070428007020145
17. Mataka, S. and Tashiro, M., J. Org. Chem., 1981,
vol. 46, p. 1929.
18. Silverstein, R.M., Webster, F.X., and Kiemple, D.J.,
Spectrometric Identification of Organic Compounds, 7th
Ed., New York: J.Wiley & Sons, Inc., 2005.
ACKNOWLEDGMENTS
19. Razin, V.V., Zh. Org. Khim., 1975, vol. 11, p. 1457.
This study was performed in the framework of the
basic part of State task for high schools and scientific
organizations in the field of research (project
no. 3.6502.2017/BCh).
20. Vasin, V.A., Razin, V.V., Bezrukova, E.V., and Petrov, P.S.,
Russ. J. Org. Chem., 2016, vol. 52, p. 862. doi 10.1134/
S1070428016060178
21. Huisgen, R., Reissig, H.-U., and Huber, H., J. Am.
Chem. Soc., 1979, vol. 101, p. 3647.
22. Trost, B.M., Taft, B.R., Masters, J.T., and Lumb, J.-P.,
J. Am. Chem. Soc., 2011, vol. 133, p. 8502. doi 10.1021/
ja203171x
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