Selenoacetalyzation of 4-formylpyrazoles in the presence of trimethylchlorosilane

Article abstract of DOI:10.1002/hc.21113

The reaction of 3,5-dimethyl-4-formylpyrazoles, bearing various substituents at N-1 atom, with propane-1,3-diselenol and 2-hydroxypropane-1,3- diselenol in the presence of Cyrillic capital letter teCyrillic capital letter emSCl proceeds without heating to

Full text of DOI:10.1002/hc.21113

Heteroatom Chemistry
Volume 00, Number 0, 2013
Selenoacetalyzation of 4-Formylpyrazoles
in the Presence of Trimethylchlorosilane
Lyubov K. Papernaya, Alexandra A. Shatrova,
Ekaterina P. Levanova, Alexandr I. Albanov, Lyudmila V. Klyba,
Elena V. Rudyakova, and Galina G. Levkovskaya
A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
1 Favorsky Street, 664033, Irkutsk, Russia
Received 8 April 2013; revised 18 July 2013
are known [1–3,5–12]. The methods for selenoacetals
ABSTRACT: The reaction of 3,5-dimethyl-4-
preparation are laborious and multistage; they of-
formylpyrazoles, bearing various substituents
ten require hardly available and unstable starting se-
at N-1 atom, with propane-1,3-diselenol and 2-
lenols. For example, the synthesis of 1,3-diselenanes
hydroxypropane-1,3-diselenol in the presence of
has not gained an acceptance due to unavailability
ТМSCl proceeds without heating to chemoselectively
and extreme instability of propane-1,3-diselenol and
give hitherto unknown 2-(pyrazol-4-yl)-1,3-diselenane
its derivatives.
hydrochlorides in high yields. The latter are easily
It is also known that propane-1,3-diselenol in-
transformed to the corresponding free bases—2-
teracts with aliphatic aldehydes in strongly acidic
(pyrazol-4-yl)-1,3-diselenanes. The 15N chemical
media [7,11], and only with benzaldehyde and some
shifts of the pyrazole ring in 2-(pyrazol-4-yl)-1,3-
other aliphatic aldehydes it reacts under milder con-
diselenanes obtained by 2D HMBC-gp (15N-1H)
ditions, that is, in the presence of ZnCl2 [1–3,12].
technique are indicative of the N-2 atom protona-
Alternative methods for the preparation of
ꢀC
tion in hydrochlorides.
2013 Wiley Periodicals,
1,3-diselenanes involve sparse protocols based on
the reaction of substituted 1,2-diselenolanes with
dimethyldiazomethane phosphonate in the pres-
ence of BF3•(С2Н5)2О [8, 13]. UV-irradiation of
1,3-bis(alkylseleno)allenes [9] or their reactions
with diphenyldiazomethane [10]. Open-chained se-
lenoacetals were known to be synthesized from
aldehydes and diphenyldiselenide [14, 15]. It was
also reported on 2-phenyl-1,3-diselenan-5-one and
its reduced analog 2-phenyl-1,3-diselenan-5-ol, but
methods for their preparation were multistage and
did not involve the corresponding diselenols [6]. It
should be emphasized that the methods reported
only cover limited representatives of aromatic se-
lenoacetals, predominantly those bearing the phenyl
substituents.
Inc. Heteroatom Chem. 00:1–10, 2013; View this
article online at wileyonlinelibrary.com. DOI
10.1002/hc.21113
INTRODUCTION
Selenoacetals represent universal reagents in or-
ganic synthesis and play a pivotal role in the develop-
ment of organoselenium and theoretical chemistry
[1–7]. However, at the present time, a limited num-
ber of selenoacetal derivatives, especially cyclic ones,
Correspondence to: Lyubov K. Papernaya; е-mail: papern@
irioch.irk.ru.
Contract grant sponsor: Russian Foundation of Basic Research.
Contract grant number: 10-03-00256а.
Heteryl-1,3-diselenanes were unknown until
our investigations. Earlier, we synthesized 2-(1,3-
diselenan-2-yl)thiophenes in 12%–57% yields from
ꢀC
2013 Wiley Periodicals, Inc.
1

2
Papernaya et al.
Me
N
O
Me
2'
6'
1'
TMSCl
Se
HCl
+
N
Se Se
+
N
HSe(CH2)3SeH
Me
Se
4'
N
R
1a–e
'
r.t., 5–10 min
3'
2
5
5, up to 10%
Me
R
3a–e, 82–90%
R = Me (a), Pr(b), i-Pr (c), allyl (d), Bn (e)
SCHEME 1 Synthesis of 2-(pyrazol-4-yl)-1,3-diselenane hydrochlorides 3a–e.
TABLE 1 Optimization of Se–Se Acetalization Conditions in
the Reaction of Aldehyde 1e and Diselenol 2 in the Presence
of TMSCl
propane-1,3-diselenol and thiophene carbaldehydes
[16]. It was found that even under mild conditions
[–5 to 5◦С, trimethylchlorosilane (ТМSСl) as a cat-
alyst], selenoacetalyzation was accompanied by the
formation of oligomeric products.
Molar Ratio
1e:2: TMSCl
Solvent
(mL)
Yield
Entry
3e (%)a,b
1.
2.
3.
4.
1:1:6
1:1:4
1:1:1
1:1:4
Neat
Neat
Neat
87
86
69
88
RESULTS AND DISCUSSION
CH2Cl2, 2
In the present work, we have studied for the first time
the reaction of formylpyrazoles 1a–e with propane-
1,3-diselenol 2 and 2-hydroxypropane-1,3-diselenol
6, which became available owing to the preparation
methods developed in our earlier study [16]. ТМSСl
was used as a catalyst.
aYield refers to isolated pure products.
bReaction time is 5 min, room temperature.
It should be underlined that the direction
of the reaction between pyrazole carbaldehy-
des and diselenols was not obvious. So, we
found that the reaction of pyrazole carbalde-
hydes with mercaptoethanol in the presence of
ТМSСl afforded predominantly open-chained bis(2-
hydroxyethyl)dithioacetals even under equimolar ra-
tio of the reagents [17], unlike similar reactions of
aromatic aldehydes leading to 1,3-oxathiolanes [18].
Here, we have shown that the interaction of
propane-1,3-diselenol 2 with aldehydes 1а–e un-
der equimolar ratio in four- to sixfold excess of
TMSCl at room temperature (5–10 min) furnishes
novel heterocyclic compounds, 4-(1,3-diselenan-2-
yl)-pyrazoles, formed as hydrochlorides 3a–e in
82%–90% yields (Scheme 1). The reaction was ac-
companied by the exothermic effect.
Taking into account the results of previously
studied reactions of bisfunctional mercaptoethanol
with aldehydes 1 [17] and nitrobenzaldehydes [19],
we have selected the optimal conditions for the re-
actions of diselenol 2 with formylpyrazoles 1. To
diminish the possibilities of side transformations
of the starting diselenol 2, the reaction mixtures
were not heated and, therefore, all reactions were
conducted at room temperature. The application of
СН2Сl2 as an additional solvent (along with TMSCl)
did not practically affect the yield of diselenane 3e
(88%) (Table 1). The decrease of TMSCl content up
to equimolar ratio led to the drop in the yield of the
target diselenane 3e (Table 1).
The formation of both open-chained bis(3-
selanylpropyl)diselenoacetals and the adducts of dis-
elenol 2 to the allyl moiety of pyrazole carbaldehyde
1d was not observed in the course of reaction under
optimal conditions.
Hitherto unknown hydrochlorides 3d and 3e
were isolated as individual compounds and char-
acterized by physical and chemical methods; hy-
drochlorides 3а–c were used in further transforma-
tions without isolation (Table 2).
In the nuclear magnetic resonance (NMR) spec-
tra of hydrochlorides 3d and 3e, the resonance sig-
nals of the methyl group protons are broadened
due to the protonation of N-2 atom and are low-
field shifted relative to their positions in the spec-
trum of bases 4. Besides, the signals С3-Me are
low-field shifted as compared with protons of the С5-
Me group. Chemical shifts of nitrogen atom of the
pyrazole ring, measured by the HMBC-gp (15N-1H)
method, are indicative of the N-2 atom protonation
in hydrochlorides 3d and 3e. So, the resonance sig-
nal of compounds 3d and 3e is high-field shifted by
80–90 ppm as compared with chemical shifts of free
bases 4d and 4e.
Heteroatom Chemistry DOI 10.1002/hc

Selenoacetalyzation of 4-Formylpyrazoles in the Presence of Trimethylchlorosilane
3
TABLE 2 Acetalization of Aldehydes 1a–e with Diselenol 2
in the Presence of TMSCl (Molar Ratio 1:2:TMSCl = 1:1:6)
chromatography. Its formation was due to the high
instability of the starting diselenol 2.
Previously, we have shown [20] that even cooled
propane-1,3-diselenol undergoes self transforma-
tions. Physicochemical properties and NMR spectra
of 1,2-diselenolane 5 are close to those reported in
the literature [21].
The structure of the diselenanes synthesized 4a–
e was proved by IR and NMR spectroscopy and
chromato-mass spectrometry.
Product Yield Product Yield
Entry Aldehydes
3а–e
(%) a,b
4a–e
(%) a,b
Me
N
Me
O
N
Me
c
1.
3а
4а
61
Me
In 1Н NMR spectra, 1,3-diselenane fragment
of compounds 4а–e is present as a six-membered
cycle having a chair conformation (with equato-
rial orientation of the pyrazole substituent). In 2D
HMBC-gp (77Se-1H) correlation spectra, cross-peaks
of equatorial protons are observed at 4ꢁ(6ꢁ) – and 5ꢁ-
carbons with Se atoms. The alteration of optimized
values JSe-H noticeably effects the relative intensity
of these cross-peaks: the lowest value of the con-
stant (∼10 Hz) leads to the increase of intensity
of cross-peaks from equatorial proton in the posi-
tion 5ꢁ of the ring and, on the contrary, the highest
value (∼30 Hz) increases the intensity from equato-
rial protons in the positions 4ꢁ(6ꢁ)ꢁ. This fact as well as
spin–spin cross-coupling constants (measured in 1D
N
Me
O
N
Pr
c
c
2.
3.
3b
3c
4b
4c
67
56
Me
N
Me
O
N
i-Pr
Me
N
Me
O
N
Allyl
4.
5.
3d
3e
90
87
4d
4e
83
72
Me
N
Me
N
Bn
spectra) indicate that the highest value of the con-
aYield refers to isolated pure products.
2
stant (∼30 Hz) relates to J77Se-С4 (6 )-Н, while the
ꢁ
ꢁ
bReaction time is 5 min; Molar ratio 1:2:TMSCl = 1:1:6.
3
77
cNot isolated.
ꢁ
lowest value is attributed to J Se-С5 -Н. The ab-
sence of the spin–spin interaction of selenium atom
3
with С2-Нax, as well as disappearance of lower J
ꢁ
value (∼10 Hz) at substitution of С-5 equatorial pro-
Me
Me
2'
2'
6'
ton by the ОН group (compound 7b) points that the
selenium atom interacts only with cycle equatorial
protons.
6'
1'
1'
SiO2
Se
Se
HCl
N
N
N
Se
Se
4'
4'
5'
5'
N
3'
3'
In continuation of this research, we have
studied the reaction of pyrazole carbaldehydes
1 with 1,3-diselanyl-2-propanol 6. The introduc-
tion of additional НО-functional group in dise-
lenol significantly extends the possibilities of hete-
rocyclization involving different functional groups
and can furnish the corresponding diselenanes or
oxaselenolanes.
It has been found that the interaction of aldehy-
des 1b and 1c with diselenol 6 under optimal condi-
tions of diselenanes 3 synthesis is carried out analo-
gously, but with substantially lower selectivity. The
formation of a six-membered diselenane cycle is due
to the higher stability of this heterocycle (as com-
pared with oxaselenolane) and higher nucleophilic-
ity of the HSe groups.
Me
Me
R
R
4a–e
3a–e
SCHEME 2 Synthesis of 2-(pyrazol-4-yl)-1,3-diselenanes
4a–e.
In the infrared (IR) spectra of hydrochlorides
3а–e, a broad absorption band, typical for the (NH+)
group, is observed at 2613–2202 cm−1
.
Hydrochlorides 3d and 3e are readily dehy-
drochlorided by the column chromatography on
silica gel to afford free bases—2-(pyrazol-4-yl)-1,3-
diselenanes 4d and 4e (Scheme 2).
Similarly, 1,3-diselenanes 4а–c were isolated by
the column chromatography on silica gel of the
corresponding reaction mixtures containing mainly
unpurified hydrochlorides 3а–c. Apart from com-
pounds 4а–e, 1,2-diselenolane 5 (in up to 10% yield)
was isolated from the reaction mixtures by column
Hydrochlorides of pyrazolyldiselenanes formed
in the reactions were not isolated as individual com-
pounds, but were transformed into 2-(pyrazol-4-yl)-
1,3-diselenan-5-ols 7b and 7c (Scheme 3).
Heteroatom Chemistry DOI 10.1002/hc

4
Papernaya et al.
Me
N
Me
2'
O
6'
1'
HO
+
TMSCl
SiO2
Se
N
Se
Se
8
HCl
HSe-CH2-CH-CH2-SeH
OH
+
N
HO
r.t.,
5–10 min
Se
4'
N
R
5'
Me
3'
Me
R
6
1b and 1c
R = Pr(b), i-Pr (c)
Me
2'
6'
1'
HO
SiO2
Se
N
HO
Se
Se
8
+
Se
4'
5'
N
3'
Me
R
7b and 7c
SCHEME 3 Synthesis of 2-(pyrazol-4-yl)-1,3-diselenan-5-ols 7b and 7c.
Together with the target compound 7 (18%–
20% yields), 1,2-diselenolan-4-ol 8 (15%–20% yield)
formed via intramolecular cyclization of the start-
ing diselenol 6 (Scheme 3) was identified among the
reaction products (NMR). Besides, unreacted initial
aldehyde 1 and diselenol 6 remain in the reaction
mixtures.
The structure of 1,2-diselenolan-4-ol 8 was un-
ambiguously proved by spectral methods. The NMR
and GC–MS data corresponded to those published
earlier [22].
tion. Second, there is no need to employ any water-
absorbing agents in the reaction, since water evolv-
ing during the synthesis reacts with Me3SiCl to give
hexamethyldisiloxane and hydrogen chloride that fa-
vors the formation of products 4 and 7. In their turn,
hexamethyldisiloxane and excess Me3SiCl are easily
separated from the products after the reaction com-
pletion. Under the mild condition proposed by us
(absence of strong bases, room temperature), the re-
actions of diselenols trimethylsilylation can not be
probably realized and silicon–selenium ethers are
not formed. The latter were not detected in the reac-
tion mixtures and products.
The drop of the reaction temperature (up to
◦
–15 С) or sixfold decrease of the molar excess of
Me3SiCl (to 0.5) did not increase the yields of com-
pounds 7b and 7c.
Taking into account the conditions of the exper-
iment, we believe that Me3SiCl acts as Lewis acid in
this process. The initially formed complex is further
transformed to diselenol adduct like in [17].
We do not exclude the formation of α-
chloroether НSeСН2СНXСН2SeCHRCl (Х = Н,
ОН), reported for the reaction of formaldehyde with
alkanethiols, the further intramolecular cyclization
of which leads to the target diselenoacetals.
The lower selectivity of the reaction as well
as lower yields of 2-(pyrazol-4-yl)-5-hydroxy-1,3-
diselenanes 7b and 7c are likely due to both the
competitive reaction of diselenol 6 cyclization to
diselenolane 8 and steric and electron effects in
1,3-diselanyl-2-propanol 6 induced by the hydroxyl
group.
The presence of the hydroxyl group in diselenol 6
leads to the increase of a part of conformer with ad-
jacent HSe groups and, hence, to the increase of 1,2-
diselenolan-4-ol 8 yield (15%–20%) and decrease of
pyrazolyl-1,3-diselenan-5-ol 7 amount. Besides, the
electron-negative inductive effect of the ОН group
in 1,3-diselanyl-2-propanol 6 decreases the nucle-
ophilicity of the SeH group and reduces the ability of
6 to interact with the carbonyl group of compounds
1b and 1c.
The structural study (1Н NMR, see the Experi-
mental) of products 7 has shown that the OH moiety
in compounds 7 is in equatorial position toward the
diselenane cycle. Such location of the substituents
ensures its most remoteness from bulky selenium
atoms.
At the same time, it was reported on a 10:90 mix-
ture of equatorially and axially oriented OH group in
phenyl-substituted hydroxydiselenan-5-ol [6].
The behavior of pyrazolyl-substituted 1,3-
diselenanes 4а–e under the electron ionization (EI)
and chemical ionization (CI) has been investigated.
Under EI, all the compounds are studied form the
The application of Me3SiCl in the aldehydes ac-
etalyzation offers some obvious advantages. First,
this catalyst ensures the mild conditions of the reac-
Heteroatom Chemistry DOI 10.1002/hc

Selenoacetalyzation of 4-Formylpyrazoles in the Presence of Trimethylchlorosilane
5
TABLE 3 Main Characteristic Ions of 4-(1,3-Diselenan-2-yl)-3,5-dimethyl-N-substituted-1Н-pyrazoles 4а–e in the EI Mass
Spectra (70 ev)
am/z (I, % from Total Ion Current)
Ion/Compound
4а
4b
4c
4d
4ec
M +•
324 (9)
202 (42)
(4)
(4)
121 (8)
80 (4)
352 (8)
230 (31)
(16)
(16)
149 (2)
108 (7)
352 (6)
230 (24)
(6)
(6)
149 (3)
108 (4)
350 (9)
228 (22)
(3)
(3)
147 (15)
106 (5)
400 (5)
278 (22)
(2)
(2)
197 (2)
156 (1)
[M − C3H6Se]+•, А
[A − СНR1 R2]+, B, m/z 187
[A − СR1 R2]+•, C, m/z 188b
[A − HSe]+, D
[D − MeCN]+, E
aSe isotope.
bion C is imposed on ion B.
cm/z 91 (17) [C7H7]+
stable molecular ion (Wм) 5%–9% (Table 3). The
main direction of the molecular ion fragmenta-
tion involves the formation of the odd electron ion
[М − C3H6Se]+• (ion А, Scheme 4, Table 3). How-
ever, unlike thienyl-substituted 1,3-diselenanes [16],
the further fragmentation of ion А is accompanied
by either the N−С bond cleavage at N-1 atom of the
pyrazole ring to afford ions B and C, or the elimina-
tion of radical HSe• (ion D) [23].
Further decomposition of ion D, independent
of the nature of the substituent at the nitrogen
atom, proceeds with the elimination of the MeCN
molecule to generate ion E. It becomes possible if
ion D is stabilized due to the expansion of the five-
membered cycle to a six-membered one, owing to the
methyl group in the position 5 of the pyrazole ring
(Scheme 4). In Table 3, the main characteristic ions
and their abundances under EI for 1,3-diselenanes
4а–e are given.
As expected, for compound 4e, the competitive
direction of fragmentation caused by benzyl decom-
position is realized [ion m/z 91 (17%)].
The 1,3-diselenanes 4 are readily protonated by
methane in the gas phase. In the CI mass spectra
of these compounds, peak clusters of ions М +· and
protonated molecular ions are characterized by max-
imum abundance (Table 4).
Along with the main direction of fragmentation
caused by elimination of the C3H6Sе molecule, in the
spectra CI mode, the peaks of ions [M − C2HSe2]+
and [M − C3H5Se2]+ are observed. These peaks can
be generated both in the course of ionization and
due to the decomposition of [М + Н]+ or М+•. Be-
sides, the peaks of cluster ions [M + C2H5]+ and
Se
H
Me
−CHR1R2.
N
N
H
B
Me
Me
+.
Se
Se
+.
Se
+.
Me
Me
Se
H
H
N
N
Me
Me
N
N
N
N
−CR1R2
−HSe.
−C3H6Se
N
R1
R2
R1
R2
C
4 M+.
А
+
[C6H6NR1R2]
−MeCN
N
E
R1
R2
D
R1 = R2 = H (4a); R1 = H, R2 = Et (4b); R1 = R2 = Me (4c); R1 = H, R2 = vinyl (4d); R 1 = H, R2 = Ph (4e)
SCHEME 4 Pyrazolyl-substituted 1,3-diselenanes 4а–e under the EI.
Heteroatom Chemistry DOI 10.1002/hc

6
Papernaya et al.
TABLE 4 Mass Spectra Positive Mode CI (Methane) of 4-(1,3-Diselenan-2-yl)-3,5-dimethyl-N-substituted-1Н-pyrazoles 4a–e
am/z (I., % from Total Ion Current)
Ion/Compound
4a
4b
4c
4d
4e
b[M + H]+
325 (55)
324 (55)
203 (10)
139 (7)
125 (5)
123 (5)
353 (6)
365 (2)
231 (1)
245 (2)
167 (2)
165 (2)
353 (39)
352 (39)
230 (9)
167 (13)
227 (9)
151 (7)
381 (4)
393 (1)
259 (1)
271 (1)
195 (4)
193 (4)
353 (38)
352 (38)
230 (7)
167 (13)
227 (7)
151 (8)
381 (5)
393 (1)
259 (1)
271 (1)
195 (4)
193 (4)
351 (57)
350 (57)
228 (7)
165 (6)
225 (7)
149 (6)
379 (6)
391 (2)
258 (1)
270 (1)
193 (2)
191 (2)
401 (49)
400 (49)
278 (8)
215 (9)
201 (9)
199 (9)
429 (5)
441 (2)
307 (1)
319 (1)
243 (1)
241 (1)
M +•
[M − C3H6Se] +•
[M − C2HSe2]
[M − C3H3Se2]
[M − C3H5Se2]
[M + C2H5]+
[M + C3H5]+
[(M + C2H5) – C3H6Se]+
[(M + C3H5) – C3H6Se]+
[(M + C2H5) – C2H2Se2]+
[(M + C2H5) – C3H4Se2]+
aSe isotope.
bIon [M + H]+ is imposed on ion М +•
.
[M + C3H5]+ as well as products of their degradation
[(M + C2H5) − C3H4Se2]+ and [(M + C3H5) −
C2H2Se2]+ appear in the spectra (Table 4).
(Shimadzu, Kyoto, Japan, quadruple mass analyzer,
34–650 Da). The samples were introduced using the
system of direct introduction (DI-50). Temperatures
of ions source and samples introduction were se-
lected to ensure qualitative mass spectrum and to
exclude thermal destruction of the samples. Mass
spectra of CI of positive ions were registered on
an Agilent 5975С instrument (Agilent Technologies,
Santa Clara, CA). Methane was used as the gas
reagent. The samples were introduced via an Agi-
lent 6890N chromatograph (Agilent Technologies)
and separated on a chromatographic column HP-
5MS (30 m × 0.25 mm × 0.25 μm) at constant rate
of the flow; helium was used as a gas carrier.
Aldehydes 1а–e were prepared by the formy-
lation with the Wilsmeier–Haack reagent [24] of
the corresponding 1,3,5-trisubstituted pyrazoles syn-
thesized from 3,5-dimethylpyrazole, halogen alkyls,
allyl bromide, and 4-fluoronitrobenzene under the
conditions of indoles alkylation [25]. Diselenol 2 was
synthesized via the original protocol of reductive
cleavage of the Se–Se bond of polytrimethylenedise-
lenide (selenokole) in the system hydrazine hydrate-
KOH [16]. 1,3-Diselanyl-2-propanol 6 was prepared
according to the method [21]. Other materials were
obtained from commercial sources (Sigma-Aldrich
Milwaukee, WI). The reaction course and the com-
pounds purity were controlled by thin layer chro-
matography (TLC) on Silica gel 60 F 254 Merk with
CHCl3–MeOH = 95:5 as an eluent.
Thus, it has been established that all the stud-
ied compounds of 4 under EI form a stable molec-
ular ion, the fragmentation character of which does
not depend on the nature and structure of saturated
and aromatic heterocycles. The main direction of de-
composition during EI and CI is determined by the
formation of stable cation-radical [M – C3H6Se]+•
.
CONCLUSIONS
In conclusion, the interaction of
a series 4-
formylpyrazoles bearing various substituents at
1-N atom with propane-1,3-diselenol 2 and 2-
hydroxypropane-1,3-diselenol 6 has been studied for
the first time. It has been found that in the pres-
ence of ТМSCl, the reaction proceeds without heat-
ing to chemoselectively afford hitherto unknown
bicyclic derivatives, 2-(pyrazol-4-yl)-1,3-diselenane
hydrochlorides, which are easily transformed to the
corresponding 1,3-diselenanes 4a–e and 7b and 7c.
EXPERIMENTAL
General
1Н, 13С, 77Se, and 15N NMR spectra were run
on a Bruker DPX-400 MHz spectrometer (Bruker
BioSpin, Rheinstetten, Germany) (1Н, 400.13 MHz;
13С, 100.62 MHz; 77Se, 76.31 MHz, and 15N, 40.56
MHz) for solutions in СDCl3 using TMS (1Н, 13C),
Me2Se (77Se), and СН3NO2 (15N) as internal stan-
dards. IR spectra were recorded on a Bruker Vertex
70 (Eftlinger, Germany) in thin layer (compounds
3а–e) or in KBr pellets (4а–e, 7b, and 7c). Mass spec-
tra of EI were recorded on a QP-5050 A instrument
General Procedure for the Synthesis of
2-(Pyrazol-4-yl)-1,3-Diselenane Hydrochlorides
3а–e
Propane-1,3-diselenol 2 (0.404 g, 2 mmol) was drop-
wise added on stirring to a mixture of pyrazole
Heteroatom Chemistry DOI 10.1002/hc

Selenoacetalyzation of 4-Formylpyrazoles in the Presence of Trimethylchlorosilane
7
(С-5), 143.4 (С-3). 15N NMR (40.56 MHz, CDCl3): δ,
carbaldehyde 1 (2 mmol) and TMSCl (1.304 g, 12
–186.0 (1-N), –170.1 (2-N). 77Se NMR (76.31 MHz,
mmol) at room temperature. The reaction proceeded
for 5–10 min and was accompanied by self-heating
and separation of the reaction mixture into two lay-
ers. The reaction was controlled by TLC. The crude
product formed as solid 3а–c or viscous substance
3d and 3e was separated from the liquid part. Un-
purified hydrochlorides 3а–c with an admixture of
1,2-diselenolane were separated on the column to
give pure product 4а–с. For purification, crude prod-
uct 3d,e was washed with hexane (three times) and
dried in vacuum.
2
2
ꢁ
ꢁ
CDCl3): δ, 349.1 (dd, JSe,H-4 eq
=
JSe,H-6 eq = 31.0,
3
ꢁ
JSe,H-5 eq = 9.8, Se). Anal calcd for C16H21ClN2Sе2:
С, 44.21; H, 4.87; Cl, 8.16; N, 6.44; Sе, 36.33. Found:
С, 44.08; H, 4.91; Cl, 8.19; N, 6.38; Sе, 36.44.
General Procedure for Preparation of 4-(1,3-
Diselenan-2-yl)-3,5-Dimethyl-N-Substituted-1Н-
Pyrazoles 4а–e
Hydrochlorides 3а–e were passed through the col-
umn 450 × 15 mm (Silica gel 60, 70–230 mesh),
CHCl3–MeOH = 95:5 as an eluent. The product was
additionally recrystallized from hexane to give com-
pounds 4а–e as white crystals.
4-(1,3-Diselenan-2-yl)-3,5-dimethyl-1-prop-2-en-1-
yl-1Н-pyrazole hydrochloride 3d. Yellow oil; yield
0.695 g (90%). IR (neat, ν, cm−1): 2958, 2939,
2613–2202 br (NH+), 1696, 1570, 1468, 1420, 1301,
1246, 1112, 995, 752, 662, 625, 570. 1Н NMR (400.13
2
3
4-(1,3-Diselenan-2-yl)-1,3,5-trimethyl-1Н-pyrazole
4а. Yield 0.429 g (61%), melting point (mp) 93–
95◦С. IR (KBr, ν, cm−1): 2920, 2865, 1552, 1473,
1428, 1413, 1386, 1375, 1302, 1250, 1228, 1195,
1118, 881, 849, 757, 727, 655, 630, 624, 582, 568,
548. 1Н NMR (400.13 MHz, CDCl3): δ, 1.98 (dtt,
ꢁ
ꢁ
ꢁ
ꢁ
MHz, CDCl3): δ, 2.02 (m, J5 ax,5 eq = 14.8, J5 ax,4 ax
ꢁ
3
2
ꢁ
ꢁ
ꢁ
ꢁ
= J5 ax,6 ax = 12.7, 1Н, H-5 ax), 2.21 (m, J5 eq,5 ax
=
14.8, 1Н, H-5ꢁ eq), 2.49 (s, 3H, Me-5), 2.59 (s, 3H,
2
2
ꢁ
ꢁ
ꢁ
ꢁ
Me-3), 2.91 (m, J4 ax,4 eq
=
J6 ax,6 eq = 13.7, 2Н,
2
ꢁ ꢁ ꢁ
ꢁ
ꢁ
2
ꢁ
H-4 eq, H-6 eq), 3.18 (dd, J4 ax,4 eq = J6 ax,6 eq = 13.7,
2Н, H-4ꢁ ax, H-6ꢁ ax), 5.09 (d, 3J = 5.4, 2H, СН2N), 5.28
2
3
J5 ax,5 eq = 14.9, 3J5 ax,4 ax = J5 ax,6 ax = 12.5, 3J5 ax,4 eq
ꢁ
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(d, Jtrans = 17.1, 1Н, СН2 = ), 5.38 (d, Jcis = 10.2, 1Н,
ꢁ
2
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3
3
= J5 ax,6 eq = 2.5, 1Н, H-5 ax), 2.18 (dtt, J5 eq,5 ax
=
СН2 = ), 5.42 (s, 1H, Н-2 ), 5.96 (ddt, J = 5.4, J =
3
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3
14.9, J5 eq,4 ax = J5 eq,6 ax = 5.0, J5 eq,4 eq = J5 eq,6 eq
10.2, J = 17.1, 1Н, СН =). 13С NMR (100.62 MHz,
= 2.3, 1Н, H-5ꢁ eq), 2.28 (s, 3H, Me-3), 2.33 (s,
CDCl3): δ, 9.8 (Ме-5), 10.1 (Ме-3), 13.9 (1JSe-C
=
2
2
73.6, С-2ꢁ ), 24.4 (С-5ꢁ ), 25.4 (1JSe-C = 62.5, С-4ꢁ , C-6ꢁ ),
50.6 (СН2N), 118.6 (С-4), 120.7 (СН2 = ), 128.9
(СН = ), 142.3 (С-5), 143.0 (С-3). 15N NMR (40.56
MHz, CDCl3): δ, –188.8 (N-1), –171.4 (N-2). 77Se
ꢁ
ꢁ
ꢁ
ꢁ
3H, Me-5), 2.83 (ddd, J4 ax,4 eq
=
J6 ax,6 eq = 13.6,
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
J5 ax 4 eq
,
= J5 ax,6 eq = 5.0, 3J4 eq,5 eq = J6 eq,5 eq = 2,3,
ꢁ
ꢁ
2
2
ꢁ
ꢁ
ꢁ
ꢁ
2Н, Н-4 eq, H -6eq), 3.09 (ddd, J4 ax,4 eq = J6 ax,6 eq
=
ꢁ
ꢁ
3
3
ꢁ
ꢁ
ꢁ
ꢁ
13.6, J5 eq,4 ax = J5 eq,6 ax = 5.0, 2Н, H-4 ax, H-6 ax),
3.65 (s, 3H, Me-N), 5.43 (s, 1H, H-2ꢁ ax). 13С NMR
(100.62 MHz, CDCl3): δ, 10.3 (Ме-5), 12.0 (Ме-3),
2
ꢁ
NMR (76.31 MHz, CDCl3): δ, 348.9 (dd, JSe, H-4 eq
=
JSe,H-6 eq = 31.5, 3JSe,H-5 eq = 10.3, Se). Anal calcd for
2
ꢁ
ꢁ
18.5 (1JSe-C = 74.0, С-2ꢁ ), 25.04 (С-5ꢁ ), 25.4 (1JSe-C
=
C12H19ClN2Sе2: С, 37.47; H, 4.98; Cl, 9.22; N, 7.28;
Sе, 41.05. Found: С, 37.21; H, 4.86; Cl, 9.41; N, 7.06;
Sе, 41.48.
63.3, С-4ꢁ , C-6ꢁ ), 35.7 (Me-N), 115.22 (С-4), 137.58
(С-5), 145.01 (С-3). 15N NMR (40.56 MHz, CDCl3):
δ, –185.0 (N-1), –83.3 (N-2). 77Se NMR (76.31 MHz,
2
2
ꢁ
ꢁ
CDCl3): δ, 347.5 (dd, JSe,H-4 eq
=
JSe,H-6 eq = 31.0,
4-(1,3-Diselenan-2-yl)-3,5-dimethyl-1-benz-1-yl-
1Н-pyrazole hydrochloride 3e. Yield 0.796 g (87%).
IR (film, ν, cm−1): 2954, 2925, 2609–2140 br (NH+),
1701, 1561, 1497. 1454, 1429, 1301, 1245, 1112, 752,
703, 662, 570. 1Н NMR (400.13 MHz, CDCl3): δ, 2.00
3JSe,
= 9.8, Se). MS (EI): m/z (Irel, %) = 324
H-5ꢁeq
(19), 323 (3), 322 (17), 321 (7), 320 (11), 319 (3), 318
(4), 204 (18), 203 (19), 202 (100), 201 (63), 200 (50),
199 (48), 198 (29), 197 (11), 196 (3), 187 (10), 186
(3), 185 (6), 184 (3), 163 (9), 160 (3), 158 (3), 149 (6),
136 (9), 135 (3), 123 (10), 122 9180, 121 (28), 120
(3), 119 (4), 109 (6), 107 (4), 95 (3), 94 (8), 93 (7), 92
(3), 91 (5), 82 (4), 81 (10), 80 (10), 78 (3), 77 (4), 66
(28), 56 (27), 55 (4), 54 (4), 53 (6), 52 (4), 51 (8), 43
(4), 42 (21), 41 (30), 40 (7), 39 (36). Anal calcd for
C10H16N2Se2: C, 37.28; H, 5.01; N, 8.70; Se, 49.02.
Found: C, 37.32; H, 5.03; N, 8.73; Se, 48.92.
2
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(dtt, J5 ax,5 eq = 14.9, J5 ax,4 ax
=
J5 ax,6 ax = 12.4,
ꢁ
3
2
3
ꢁ
ꢁ
ꢁ
ꢁ
J5 ax,4 eq
=
J5 ax, 6 eq = 2.5, 1Н, H-5 ax), 2.19 (dtt,
3
3
3
ꢁ
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
J5 eq,5 ax = 14.9, J5 eq,4 ax = J5 eq,6 ax = 2.5, J5 eq,4 eq
ꢁ
ꢁ
ꢁ
=
J5 eq,6 eq = 4.9, 1Н, H-5 eq), 2.44 (s, 3H, Me-5),
2
2
ꢁ
ꢁ
ꢁ
ꢁ
2.61 (s, 3H, Me-3), 2.89 (ddd, J4 ax,4 eq
=
J6 ax,6 eq
ꢁ
ꢁ
2
ꢁ
ꢁ
= 13.8, 2Н, H-4 eq, H-6 eq), 3.18 (ddd, J4 ax,4 eq
=
ꢁ
ꢁ
2
ꢁ
ꢁ
J6 ax,6 eq = 13.8, 2Н, H-4 ax, H-6 ax), 5.36 (s, 1H,
Н-2ꢁ ), 5.63 (d, 2H, СН2N), 7.33–7.42 (m, 5Н, Ph).
13С NMR (100.62 MHz, CDCl3): δ, 10.4 (Ме-5), 10.5
(Ме-3), 14.2 (1JSe,C = 75.5, С-2ꢁ ), 24.6 (С-5ꢁ ), 25.7
(1JSe,C = 62.1, С-4ꢁ , C-6ꢁ ), 52.3 (СН2N), 119.1 (С-4),
128.2 (Сm), 129.2 (Ср), 129.4 (Со), 132.6 (Сi), 142.4
4-(1,3-Diselenan-2-yl)-3,5-dimethyl-1-propyl-1Н-
pyrazole 4b. Yield 0.469 g (67%), mp 75–77◦С.
IR (KBr, ν, cm−1): 2952, 2899, 2875, 1549, 1466,
Heteroatom Chemistry DOI 10.1002/hc

8
Papernaya et al.
2
2
3
1436, 1421, 1383, 1248, 1113, 847, 757, 725, 652,
ꢁ
ꢁ
Se,H-6 eq
ꢁ
(dd, J
= J
= 30.3, JSe,H-5 eq = 10.3,
Se,H-4 eq
626, 606, 572. 1Н NMR (400.13 MHz, CDCl3): δ,
Se). MS (EI): m/z (Irel, %) = 354 (5), 353 (3), 352
(17), 351 (3), 350 (14), 349 (5), 348 (10), 346 (30),
232 (19), 231 (15), 230 (100), 229 (22), 228 (50), 227
(23), 226 (23), 225 (3), 215 (5), 213 (3), 191 (4), 190
(6), 189 (8), 188 (26), 187 (33), 186 (17), 185 (20),
184 (11), 183 (6), 177 (5), 164 (5), 160 (3), 158 (3),
149 (19), 135 (11), 133 (3), 122 (7), 121 (5), 119 (4),
109 (13), 108 (26), 107 (9), 106 (4), 105 (4), 97 (3),
95 (8), 94 (10), 93 (6), 92 (3), 91 (5), 80 (5), 79 (5),
78 (6), 77 (10), 68 (7), 67 (6), 66 (11), 65 (3), 54 (3),
53 (6), 52 (14), 51 (5), 43 (19), 42 (34), 41 (44), 40
(5), 39 (30). Anal calcd for C12H20N2Se2: C, 41.15;
H, 5.76; N, 8.00; Se, 45.09. Found: C, 41.25; H, 5.75;
N, 8.02; Se 44.98.
3
3
0.90 (t, J = 7.3, 3Н, МеСН2СН2), 1.77 (sextet, J
2
ꢁ
ꢁ
= 7.3, 2Н, МеСН2СН2), 2.00 (dtt, J5 ax,5 eq = 15.0,
3
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3
ꢁ
J5 ax,4 ax
=
ꢁJ5 ax,6 ax = 12.7, J5 ax,4 eq
=
J5 ax,6 eq
=
ꢁ
2
ꢁ
ꢁ
ꢁ
2.5, 1Н, H-5 ax), 2.19 (dtt, J5 eq,5 ax = 15.0, J5 eq,4 ax
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
=
J5 eq,6 ax = 4.9, J5 eq,4 eq = J5 eq,6 eq = 2.5, 1Н,
H-5ꢁ eq), 2.29 (s, 3H, Me-3), 2.33 (s, 3H, Me-5), 2.85
ꢁ
ꢁ
(ddd, 2J4 ax,4 eq = J6 ax,6 eq = 13.6, 2H, Н-4 eq, H-6 eq),
2
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
2
2
ꢁ
ꢁ
ꢁ
ꢁ
3.10 (ddd, J4 ax,4 eq
=
J6 ax,6 eq = 13.6, 2Н, Н-4 ax
,
H-6ꢁ ax), 3.87 (t, 2H, СН2N), 5.44 (s, 1H, H-2ꢁ ax). 13С
NMR (100.62 MHz, CDCl3): δ, 10.4 (Ме-5), 12.3
(Ме-3), 11.2 (MeСН2СН2), 18.9 (1JSe-C = 73.6, С-2ꢁ ),
23.6 (СН3СН2СН2), 25.3 (С-5ꢁ ), 25.7 (1JSe-C = 62.5,
С-4ꢁ , C-6ꢁ ), 50.5 (СН2N), 115.1 (С-4), 137.2 (С-5),
145.3 (С-3). 15N NMR (40.56 MHz, CDCl3): δ, –174.4
(N-1), –86.2 (N-2). 77Se NMR (76.31 MHz, CDCl3):
4-(1,3-Diselenan-2-yl)-3,5-dimethyl-1-prop-2-en-1-
yl-1Н-pyrazole 4d. Yield 0.576 g (83%), mp 87–
89◦С. IR (KBr, ν, cm−1): 2902, 2879, 1641, 1549,
1467, 1422, 1379, 1305, 1247, 1195, 1113, 995,
923, 849, 756, 725, 635, 572. 1Н NMR (400.13
2
2
3
ꢁ
ꢁ
ꢁ
δ, 347.7 (dd, JSe, H-4 eq = JSe,H-6 eq = 30.6, JSe,H-5 eq
= 10.7, Se). MS (EI): m/z (Irel, %) = 354 (6), 353 (3),
352 (17), 351 (4), 350 (14), 349 (7), 348 (10), 347 (3),
346 (4), 232 (18), 231 (15), 230 (100), 229 (29), 228
(51), 227 (30), 226 (23), 225 (6), 215 (6), 214 (3), 202
(3), 201 (5), 200 (3), 199 (4), 191 (5), 190 (3), 189 (5),
188 (14), 187 (14), 186 (9), 185 (10), 184 (6), 183 (4),
177 (6), 175 (4), 173 (3), 160 (4), 158 (4), 151 (6),
150 (7), 149 (35), 147 (3), 146 (4), 137 (4), 135 (8),
133 (3), 123 (5), 122 (14), 121 (28), 119 (5), 109 (11),
108 (18), 107 (7), 106 (3), 105 (4), 95 (6), 94 (8), 93
(7), 92 (3), 91 (5), 82 (3), 81 (6), 80 (21), 79 (7), 78
(6), 77 (8), 68 (5), 67 (6), 66 (9), 65 (5), 56 (3), 55 (5),
54 (7), 53 (12), 52 (18), 51 (14), 50 (3), 44 (36), 43
(25), 42 (68),41 (97), 40 (11), 39 (75). Anal calcd for
C12H20N2Se2: C, 41.15; H, 5.76; N, 8.00; Se, 45.09.
Found: C, 41.27; H, 5.78; N, 8.03; Se, 44.92.
2
3
ꢁ
ꢁ
ꢁ
ꢁ
MHz, CDCl3): δ, 1.99 (dtt, J5 ax,5 eq = 14.8, J5 ax,4 ax
3
3
3J
= 2.6,
3
ꢁ ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
5ꢁax,6ꢁeq
=
J5 ax,6 ax = 12.7, J5 ax,4 eq
=
ꢁ
2
ꢁ
ꢁ
1Н, H-5 ax), 2.18 (dtt, J5 eq, 5 ax = 14.8, J5 eq,4 ax
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
=
J5 eq,6 ax = 4.8, J5 eq,4 eq = J5 eq,6 eq, = 2.5, 1Н,
Н-5ꢁ eq), 2.29 (s, 3H, Me-5), 2.31 (s, 3H, Me-3), 2.83
ꢁ
2
2
ꢁ
ꢁ
ꢁ
ꢁ
(ddd, J4 ax,4 eq
=
J6 ax,6 eq = 13.6 Hz, 2Н, H-4 eq
,
ꢁ
ꢁ
ꢁ
3
H-6 eq), 3.09 (ddd, 2Н, H-4 ax, H-6 ax), 4.56 ꢁ(dt, J =
4
5.4, J = 1.5, 2H, СН2N), 5.44 (s, 1H, Н-2 ax), 4.96
(ddd, Jtrans = 16.1, 1Н, СН2 = ) and 5.15 (ddd, Jcis
2
4
= 12.0, J ∼ J = 1.5, СН2 = ), 5.96 (ddt, 1, СН =).
13С NMR (100.62 MHz, CDCl3): δ, 10.2 (Ме-5), 12.2
(Ме-3), 18.5 (1JSe-C = 73.5, С-2ꢁ ), 25.1 (С-5ꢁ ), 25.5
(1JSe-C = 62.7, С-4ꢁ , C-6ꢁ ), 51.6 (СН2N), 115.5 (C-4),
116.9 (СН2 = ), 132.8 (СН = ), 137.5 (С-5), 145.6
(С-3). 15N NMR (40.56 MHz, CDCl3): δ, –176.3 (N-1),
–81.9 (N-2). 77Se NMR (76.31 MHz, CDCl3): δ, 348.3
4-(1,3-Diselenan-2-yl)-3,5-dimethyl-1-(1-methy-
lethyl)-1H-pyrazole 4c. Yield 0.392 g (56%), mp
113–115◦С. IR (KBr, ν, cm−1): 2985, 2975, 2927,
1552, 1482, 1422, 1377, 1277, 1243, 1123, 1079,
2
2
3
ꢁ
ꢁ
ꢁ
(dd, JSe, H-4 eq = JSe, -H-6 eq = 30.6, JSe,5 -Heq = 10.2,
Se). MS (EI): m/z (Irel, %) = 352 (5), 350 (15), 349
(3), 348 (13), 347 (5), 346 (8), 344 (3), 230 (9), 229
(9), 228 (51), 227 (17), 226 (27), 225 (17), 224 (11),
189 (6), 187 (5), 186 (3), 185 (3), 175 (6), 162 (5),
161 (4), 158 (3), 148 (24), 147 (100), 145 (5), 135 (3),
133 (6), 132 (4), 131 (3), 121 (6), 120 (6), 119 (4),
118 (3), 117 (3), 109 (3), 108 (3), 107 (7), 106 (15),
105 (4), 104 (3), 95 (3), 94 (4), 93 (6), 92 (5), 91 (5),
80 (6), 79 (7), 78 (6), 77 (9), 67 (3), 66 (7), 65 (5), 55
(7), 54 (7), 53 (7), 52 (10), 51 (9), 50 (3), 42 (21), 41
(78), 40 (7), 39 (60). Anal calcd for C12H18N2Sе2: С,
41.39; H, 5.21; N, 8.05; Sе, 45.35. Found: С, 41.25;
H, 5.24; N, 8.07; Sе 45.53.
883, 854, 821, 751, 724, 641, 572, 546 cm−1 1Н
.
NMR (400.13 MHz, CDCl3): δ, 1.41 (d, 3J = 6.6,
2
3
ꢁ
ꢁ
ꢁ
ꢁ
6Н, Ме2СН), 1.99 (dtt, J5 ax,5 eq = 14.9, J5 ax,4 ax
=
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
J5 ax,6 ax = 12.6, J5 ax,4 eq = J5 ax,6 eq = 2.5, 1Н, H-
ꢁ
2
3
3
ꢁ
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
5 ax), 2.19 (dtt, J5 eq,5 ax = 14.9, J
= J5 eq,6 ax
5 eq,4 axꢁ
= 5.0, 3J5 eq,4 eq = J5 eq,6 eq = 2.3, 1Н, H-5 eq), 2.30 (s,
ꢁ
ꢁ
ꢁ
ꢁ
2
ꢁ
ꢁ
3H, Me-3), 2.34 (s, 3H, Me-5), 2.84ꢁ (ddd, J4 ax,4 eq
2
ꢁ
ꢁ
ꢁ
=
J6 ax,6 eq = 13.6, 2Н, Н-4 eq, H-6 eq), 3.09 (ddd,
ꢁ ꢁ
2
ꢁ ꢁ ꢁ
2
ꢁ
J4 ax,4 eq = J6 ax,6 eq = 13.6, 2Н, Н-4 ax, H-6 ax), 4.30
(heptete, 1H, Me2СН-N), 5.45 (s, 1H, H-2ꢁ ax). 13С
NMR (100.62 MHz, CDCl3): δ, 10.3 (Ме-5), 12.5
(Ме-3), 19.0 (1JSe-C = 73.6, С-2ꢁ ), 22.4 (Ме2СН),
25.3 (С-5ꢁ ), 25.7 (1JSe-C = 62.9, С-4ꢁ , C-6ꢁ ), 49.4
(Me2СН-N), 114.8 (С-4), 136.2 (С-5), 145.1 (С-3).
15N NMR (40.56 MHz, CDCl3): δ, –163.4 (N-1), –92.
4 (N-2). 77Se NMR (76.31 MHz, CDCl3): δ, 348.0
1-Benzyl-4-(1,3-diselenan-2-yl)-3,5-dimethyl-1Н-
pyrazole 4e. Yield 0.572 g (72%), mp 83–85◦С.
Heteroatom Chemistry DOI 10.1002/hc

Selenoacetalyzation of 4-Formylpyrazoles in the Presence of Trimethylchlorosilane
9
IR (KBr, ν, cm−1): 2932, 2919, 2895, 2876, 1557,
135◦С. IR (KBr, ν, cm−1): 3211, 2976, 2956, 2927,
1554, 1497, 1433, 1390, 1382, 1328, 1288, 1192,
1117, 1026, 997, 905, 842, 725, 652. 1Н NMR (400.13
1494, 1454, 1433, 1416, 1362, 1320, 1244, 1189,
1113, 850, 757, 741, 727, 708, 572, 452. 1Н NMR
2
3
ꢁ
ꢁ
3
(400.13 MHz, CDCl3): δ, 1.96 (dtt, J5 ax,5 eq = 14.9,
MHz, CDCl3): δ, 0.89 (t, J = 7.5, 3Н, МеСН2СН2),
3
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
J5 ax,4 ax
=
ꢁJ5 ax,6 ax = 12.4, J5 ax,4 eq
=
J5 ax,6 eq
=
2.34 (s, 3H, Me-5), 2.31 (s, 3H, Me-3), 1.76 (sextet,
ꢁ
2
3
2
2.5, 1Н, H-5 ax), 2.15 (dtt, J5 eq,5 ax = 14.9, J5 eq,4 ax
3J = 7.5, 2Н, МеСН2СН2), 2.77 (dd, J4 ax,4 eq
=
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3
3
3
2
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
=
J5 eq,6 ax = 2.5, J5 eq,4 eq
=
J5 eq,6 eq = 4.9, 1Н,
J6 ax, 6 eq = 13.0, J4 eq,5 ax
=
J6 eq,5 ax = 3.1, 2Н,
Н-5ꢁ eq), 2.25 (s, 3H, Me-5), 2.33 (s, 3H, Me-3), 2.83
H-4 eq, H-6 eq), 3.10 (dd, J4 ax,4 eq = J6 ax,6 eq = 13.0,
ꢁ
ꢁ
2
2
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(ddd, 2J4 ax,4 eq = J6 ax,6 eq = 13.8, 2Н, H-4 eq, H-6 eq),
J5 ax,4 ax = J5 ax,6 ax = 10.9, 2Н, H-4 ax, H-6 ax), 3.87
2
3
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
2
2
3
3.08 (ddd, J4 ax,4 eq
=
J6 ax,6 eq = 13.8, 2Н, H-4 ax
,
(t, 3J = 7.5, 2H, СН2N), 4.31 (tt, 3J5 ax,4 ax = J5 ax,6 ax
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
H-6ꢁ ax), 5.16 (s, 2H, СН2N), 5.44 (c, 1H, Н-2ꢁ ax), 7.03
(m, 2Н, Но), 7.21 (m,1Н, Нp), 7.26 (m, 2Н, Нm).
13С NMR (100.62 MHz, CDCl3): δ, 10.4 (Ме-5), 12.3
(Ме-3), 18.5 (1JSe-C = 73.9, С-2ꢁ ), 25.0 (С-5ꢁ ), 25.5
(1JSe-C = 62.3, С-4ꢁ , C-6ꢁ ), 52.7 (СН2N), 115.8 (C-4),
126.5 (Сm), 127.4 (Ср), 128.6 (Со), 136.8 (Сi), 137.6
(С-5), 145.7 (С-3). 15N NMR (40.56 MHz, CDCl3):
δ, –177.3 (N-1), –82.9 (N-2). 77Se NMR (76.31 MHz,
= 10.9, J5 ax,4 eq = J5 ax,6 eq = 3.1, 1Н, H-5 ax), 5.42
(s, 1H, H-2ꢁ ax). 13С NMR, (100.62 MHz, CDCl3): δ,
10.3 (Ме-5), 11.1 (МеСН2СН2), 12.3 (Ме-3), 18.0
(1JSe-C = 72.7, С-2ꢁ ), 23.5 (МеСН2СН2), 30.2 (1JSe-C
= 65.2 Hz С-4ꢁ , C-6ꢁ ), 50.4 (СН2N), 67.5 (C-5ꢁ ), 112.6
(С-4), 137.1 (С-5), 145.3 (С-3). 15N NMR, (40.56
MHz, CDCl3): δ, –170.5 (N-1), –84.8 (N-2). 77Se
ꢁ
3
3
ꢁ
ꢁ
ꢁ
ꢁ
2
ꢁ
NMR (76.31 MHz, CDCl3): δ, 385.5 (d, JSe,4 -Heq
=
2
2
2
ꢁ
ꢁ
ꢁ
CDCl3): δ, 348.3 (dd, JSe,H-4 eq
=
JSe,H-6 eq = 30.6,
JSe,6 -Heq = 28.7, Se). Anal. calcd for C12H20N2OSe2:
C, 39.36; H, 5.50; N, 7.65; Se, 43.12. Found: С, 39.40;
H, 5.47; N, 7.59; Sе, 43.17.
3
ꢁ
JSe, H-5 eq = 10.3, Se). MS (EI): m/z (Irel, %):400 (7),
398 (7), 397 (3), 396 (3), 280 (8), 279 (10), 278 (48),
277 (16), 276 (23), 275 (14), 274 (9), 273 (3), 198
(3), 197 (14), 156 (7), 92 (9), 91 (100), 78 (3), 77 (6),
66 (4), 65 (15), 51 (3), 43 (4), 41 (12), 39 (12). Anal
calcd for C16H20N2Se2: C, 48.25; H, 5.06; N, 7.03; Se,
39.65. Found: С, 48.31; H, 5.08; N, 7.05; Sе, 39.56.
1,2-Diselenolane 5 was isolated by column chro-
matography (Silica gel 60, 70–230 mesh, CHCl3 as
eluent) of the reaction mixtures prepared from 4-
formylpyrazoles 1а–c with propane-1,3-diselenol 2
in the presence of TMSCl. The solvent of first frac-
tions was removed under reduced pressure, and then
the solid residue was dried in vacuum. Yield 0.030–
0.045 g (7–10%). Light yellow crystals, mp 66–67◦С
(literature data [20]: mp 65–67◦С). Spectral charac-
teristics correspond to the previously published ones
[20].
2-(1-Isopropyl-3,5-dimethyl-1H-pyrazol-4-yl)-1,3-
diselenan-5-ol 7c. Yield 0.135 g (18.4%), mp 87–
89◦С. IR (KBr, ν, cm−1): 3210, 2974, 2931, 1551,
1499, 1430, 1390, 1328, 1288, 1192, 1116, 1024, 997,
842, 725, 652. 1Н NMR (400.13 MHz, CDCl3): δ,
3
1.38 (d, J = 6.6, 6Н, Ме2СН), 2.29 (s, 3H, Me-3),
2
2
ꢁ
ꢁ
ꢁ
ꢁ
2.32 (s, 3H, Me-5), 2.73 (dd, J4 ax,4 eq = J6 ax,6 eq
=
ꢁ
ꢁ
3
3
ꢁ
ꢁ
ꢁ
ꢁ
12.4, J4 eq,5 ax = J6 eq,5 ax = 3.3, 2Н, H-4 eq, H-6 eq),
2
2
3
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3.07 (dd, J4 ax,4 eq
=
J6 ax,6 eq = 12.4, J5 ax,4 x =
ꢁ ꢁ
3
ꢁ
ꢁ
J5 ax,6 ax = 10.9, 2Н, H-4 ax, H-6 ax), 4.28 (heptet,
3
3
3J = 6.6, 1H, СНN), 4.29 (tt, J5 ax,4 ax = J5 ax,6 ax
=
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3
3
ꢁ
ꢁ
ꢁ
ꢁ
10.9, J5 ax,4 eq
=
J5 ax, 6 eq = 3.3, 1Н, H-5 ax), 5.40
(s, 1H, H-2ꢁ ax). 13С NMR (100.62 MHz, CDCl3): δ,
10.2 (Ме-5), 12.4 (Ме-3), 18.1 (1JSe-C = 72.7, С-2ꢁ ),
22.2 (Ме2СН), 30.2 (1JSe-C = 65.6, С-4ꢁ , C-6ꢁ ), 49.3
(МеСН), 67.4 (C-5ꢁ ), 112.2 (С-4), 136.0 (С-5), 145.1
(С-3). 15N NMR (40.56 MHz, CDCl3): δ, –160.6 (N-1),
–90.8 (N-2). 77Se NMR (76.31 MHz, CDCl3): δ, 385.6
Reactions of 3,5-Dimethyl-4-Formylpyrazoles
1b, 1c with 1,3-Diselenanyl-2-Propanol 6
2
2
ꢁ
ꢁ
(d, JSe,H-4 eq = JSe, H-6 eq = 28.7, Se). Anal calcd for
C12H20N2OSe2: C, 39.36; H, 5.50; N, 7.65; Se, 43.12.
Found: С, 39.30; H, 5.52; N, 7.63; Se, 43.18.
To a mixture of aldehyde 1b (1c) (2 mmol) and TM-
SCl (12 mmol, 1.304 g), 1,3-diselenanyl-2-propanol
6 (2 mmol, 0.436 g) was dropwise added on stirring
at room temperature. The reaction proceeded for 5–
10 min and was accompanied by self-heating and
separation of the reaction mixture into two layers.
The liquid part was removed under reduced pressure
and compounds 7b and 7c were isolated by column
chromatography on silica gel (eluent CHCl3–CH3OH
= 99:1) as white crystals.
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Heteroatom Chemistry DOI 10.1002/hc