Reactions of trifluoro- and hexafluoroacetylacetones with thiobenzoylhydrazine

Article abstract of DOI:10.1007/s11172-012-0120-8

The reaction of thiobenzoylhydrazine with trifluoroacetylacetone leads to the product of condensation at the CH₃C=O bond with the 5-hydroxy-2-pyrazoline structure. The tautomeric transition to the 2,3-dihydro-1,3,4-thiadiazole isomer occurs in

Full text of DOI:10.1007/s11172-012-0120-8

Russian Chemical Bulletin, International Edition, Vol. 61, No. 4, pp. 858—862, April, 2012
858
Reactions of trifluoroꢀ and hexafluoroacetylacetones with thiobenzoylhydrazine
V. V. Alekseyev,a V. V. Pakal´nis,b I. V. Zerova,b and S. I. Yakimovichb
aS. M. Kirov Military Medical Academy,
6 ul. Akad. Lebedeva, 194044 Saint Petersburg, Russian Federation.
Fax: +7 (812) 329 7118. Eꢀmail: alekseyevv.v@mail.ru
bSaint Petersburg State University,
26 Universitetsky prosp., 198504 Saint Petersburg, Russian Federation.
Fax: +7 (812) 428 6939. Eꢀmail: viktoriapakalnis@mail.ru
The reaction of thiobenzoylhydrazine with trifluoroacetylacetone leads to the product of
condensation at the CH3C=O bond with the 5ꢀhydroxyꢀ2ꢀpyrazoline structure. The tautomeric
transition to the 2,3ꢀdihydroꢀ1,3,4ꢀthiadiazole isomer occurs in solution. This isomer underꢀ
goes the cleavage to 2ꢀmethylꢀ5ꢀphenylꢀ1,3,4ꢀthiadiazole and trifluoroacetone. The reaction of
thiobenzoylhydrazine with hexafluoroacetylacetone affords one of diastereomers of [3,5ꢀdiꢀ
hydroxyꢀ3,5ꢀbis(trifluoromethyl)pyrazolidinꢀ1ꢀyl](phenyl)thioketone, which at equilibrium is
transformed in solution into the second diastereomer of the 3,5ꢀdihydroxypyrazolidine form
followed by the elimination of water elements and formation of a tautomeric 5ꢀhydroxyꢀ2ꢀ
pyrazoline—2,3ꢀdihydroꢀ1,3,4ꢀthiadiazole mixture.
Key words: trifluoroacetylacetone, hexafluoroacetylacetone, thiobenzoylhydrazine, 3,5ꢀdiꢀ
hydroxypyrazolidine, 2ꢀpyrazoline, 2,3ꢀdihydroꢀ1,3,4ꢀthiadiazole, ringꢀring tautomerism.
Scheme 1
The products of the reactions of acetylacetone and its
3ꢀalkylꢀsubstituted analogs with thiobenzoylhydrazine
show in solutions a unique equilibrium involving two
heterocyclic forms: of the 5ꢀhydroxyꢀ2ꢀpyrazoline and
2,3ꢀdihydroꢀ1,3,4ꢀthiadiazole structures.1 There are few
examples for similar ringꢀring equilibria, where heteroꢀ
cycles of different nature compete.2—4 In this work we
studied the reactions of thiobenzoylhydrazine 1 with fluorꢀ
inated analogs of acetylacetone, trifluoroꢀ and hexaꢀ
fluoroacetylacetones 2 and 3.
The reaction of thiobenzoylhydrazine 1 with trifluoroꢀ
acetylacetone 2 occurs with 100% regioselectivity at the
MeС=О bond. Due to the intramolecular cyclization of
intermediate hydrazone structure 4a, the condensation
product has 5ꢀhydroxyꢀ2ꢀpyrazoline structure 4b (Scheme 1).
The 1Н NMR spectrum of derivative 4b in CDCl3 deꢀ
tected immediately after dissolution contain two signals
as nonsymmetrical doublets at Н 3.25 and 3.41. Their
intensity is one proton each, and they form a typical AB
system (JАВ = 18.9 Hz). The spectrum also contains
a broadened signal at Н 8.23. These signals should be
ascribed to the diastereotopic protons at the carbon atom
in position 4 of the pyrazoline cycle and to the proton of
the hydroxyl group. The downfield position of the latter is
due to the influence of the adjacent electronꢀacceptor triꢀ
fluoromethyl group. The data of 13С NMR spectroscopy
is completely consistent with the structure proposed
for 4b (see Experimental). The quartet signal at С 93.35
(2JC,F = 33.9 Hz) can be mentioned as the most characꢀ
teristic one. This signal should be attributed to the quaterꢀ
nary carbon atom in position 5 of the heterocycle. The
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 0855—0859, April, 2012.
1066ꢀ5285/12/6104ꢀ0858 © 2012 Springer Science+Business Media, Inc.

Reaction of fluorodiketones with thiohydrazide
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
859
quartet shape of the signal indicates the bond with the
trifluoromethyl group. The spectral characteristics of the
discussed compound 4b are close, to a considerable exꢀ
tent, to the results of the spectral study of the condensaꢀ
tion product of trifluoroacetylacetone with benzoylhydrꢀ
azine.5,6 The Xꢀray structure of study of the latter showed
that this product is formed by the condensation at the
MeС=О bond and is 5ꢀhydroxyꢀ2ꢀpyrazoline bearing the
methyl group in position 3 and the trifluoromethyl group
in position 5.
recovers the current concentration of 1,3,4ꢀthiadiazoꢀ
line 4c, and the cleavage process continues to the comꢀ
plete disappearance of the primary condensation product,
5ꢀhydroxyꢀ2ꢀpyrazoline 4b.
The results of the interaction of thiobenzoylhydrazine 1
with hexafluoroacetylacetone 3 in dioxane (Scheme 2) are
worth detailed discussion. According to the mass spectroꢀ
metric and elemental analysis data, the isolated derivative
corresponded to hydroxyhydrazine 6a, formed due to the
initial addition of polynucleophile 1 to the С=О bond of
one of the trifluoroacetyl groups, or to the product of subꢀ
sequent cyclization at the second carbonyl group, viz., to
the corresponding 3,5ꢀdihydroxypyrazolidine 6b. A cerꢀ
tain argument against the hydroxyhydrazine structure is
the fact that the IR spectrum of the discussed compound
in КВr exhibits no absorption band in the region of stretchꢀ
ing vibrations of the С=О bond (1700—1750 cm–1). The
NMR spectral data certainly show that the reaction afꢀ
fords one of the diastereomers of compound 6b.
1
The shape of the Н NMR spectrum of a solution of
derivative 4b changes on storage. The second set of resoꢀ
nance signals appears in the spectrum. It turned out that
this set does not correspond to possible tautomeric forms,
viz., linear hydrazone (4а) or cyclic 1,3,4ꢀthiadiazolꢀ
ine (4c), but is due to the formation of the structure of the
1,3,4ꢀthiadiazole type: 2ꢀmethylꢀ5ꢀphenylꢀ1,3,4ꢀthiadiꢀ
azole (5). The initial 5ꢀhydroxyꢀ2ꢀpyrazoline 4b completeꢀ
ly disappears with time. Derivative 4b is also transformed
into thiadiazole 5 on its keeping in methanol.
1
The Н NMR spectrum of derivative 6 in CDCl3 reꢀ
This can be explained as follows. A very insignificant
equilibrium transition to the 2,3ꢀdihydroꢀ1,3,4ꢀthiadiazole
form 4c occurs in solutions of the condensation product of
trifluoroacetylacetone with thiobenzoylhydrazine 4b. The
heterocycle formed undergoes conversion to 2ꢀmethylꢀ5ꢀ
phenylꢀ1,3,4ꢀthiadiazole upon the elimination of trifluoꢀ
roacetone. The driving force of the process is the aromatic
character o the formed 1,3,4ꢀthiadiazole cycle. The cleavꢀ
age of the carbon—carbon bond with the substituent in
position 2 of the heterocycle is favored by the fact that the
trifluoroacetone anion is eliminated in which the negative
charge is stabilized by strong electronꢀacceptor properties
of the trifluoromethyl group. The tautomeric transition
corded immediately after dissolution exhibits two nonꢀ
symmetrical doublet signals forming the AB system at
Н 2.61 and 2.63 (JАВ = 16.0 Hz) and three broadened
oneꢀproton singlet signals at Н 4.11, 5.82, and 6.78, whose
position and broadened shape indicate that they belong to
the protons bound to the heteroatoms. In principle, this
does not contradict to linear (6a) or cyclic structure (6b)
of compound 6. Structure 6а has a chirality center, and
dihydroxypyrazolidine 6b has two such centers. This reꢀ
sults in diastereotopicity of the protons of their methylene
groups and, correspondingly, the appearance of the AB
1
system in the Н NMR spectrum. However, linear strucꢀ
ture 6a contains the NH bond of the thioamide type. In
Scheme 2

860
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
Alekseyev et al.
the spectrum the signal of the corresponding proton should
lie in rather downfield region. Thus, the shape of the Н
NMR spectrum of derivative 6 indicates in favor of cyclic
structure 6b.
tained for the reaction product of hexafluoroacetylacetone
and benzoylhydrazine having the 5ꢀhydroxyꢀ2ꢀpyrazoline
structure.7
1
The position of signals forming the second AB system
(Н 3.58 and 3.69) corresponds to 1,3,4ꢀthiadiazoline
heterocycle 8. This is confirmed by a comparison with the
spectral data for the reaction products of thiobenzoylꢀ
hydrazine with a series of aroyltrifluoroacetones formed
by the condensation at the CF3С=О bond and having the
1,3,4ꢀthiadiazoline structure.8 A comparison of the intenꢀ
sity of the signals corresponding to 5ꢀhydroxyꢀ2ꢀpyrazolꢀ
ine 7 and 1,3,4ꢀthiadiazoline 8 is 1 : 3 in favor of the latꢀ
ter form.
The final choice between the presented structures can
be made on the basis of 13С NMR spectroscopic data.
A distinctive feature of hydroxyhydrazine structure 6a
should be the presence of the quartet signal from the carbon
atom of the С=О bond in the trifluoroacetyl group
at С 190 of the carbon spectrum. The experimental
13С NMR spectrum of compound 6 in CDCl3 contains no
similar signal but has two quartet signals at С 81.76
(2JC,F = 29.9 Hz) and 92.50 (2JC,F = 30.9 Hz). They are
assigned to the carbon atoms in positions 3 and 5 of pyrꢀ
azolidine structure 6b.
The intensity of the 1Н NMR signals belonging to diaꢀ
stereomeric 3,5ꢀdihydroxypyrazolidines 6b´ and 6b deꢀ
crease in time and that of the signals from 5ꢀhydroxyꢀ2ꢀ
pyrazoline 7 and 1,3,4ꢀthiadiazoline 8 increases. This proꢀ
cess is related to the elimination of water elements and is
very slow. The signals from 3,5ꢀdihydroxypyrazolidine 6b´
prevailing in the configurational equilibrium are retained
1
The shape of the Н NMR spectrum changes in time
on storage of a solution of isolated derivative 6. First, two
signals as nonsymmetrical doublets at Н 2.64 and 2.67
forming the AB system (JАВ = 16.0 Hz) appear. The very
close position of the already present and newly appeared
signals of two AB systems indicates the formation of the
second diastereomer of 3,5ꢀdihydroxypyrazolidine strucꢀ
ture 6. In several hours, the intensity ratio of the signals of
two AB systems stop changing. Evidently, two diastereoꢀ
meric 3,5ꢀdihydroxypyrazolidines 6b´ and 6b are equiliꢀ
brated. Judging from the intensity of their signals, the
ratio between these isomers is 4 : 1 in favor of the initial
form. The predominant configurational isomer should
rather contain cisꢀarranged bulky trifluoromethyl groups
(6b´), where they can take the equatorial orientation for
the heterocycle as an envelop or a halfꢀchair.
1
in the Н NMR spectrum even in three months. At this
moment, its fraction in a mixture with derivatives 7 and 8
is about 15%. Note that the ratio of cyclic tautomers 7 and
8 remains almost unchanged in time. This means that the
equilibrium between them is established rather rapidly.
The 13С NMR spectrum was recorded for a mixture
obtained after the threeꢀmonth keeping of the initial deꢀ
rivative 6b´. Taking into account that thiadiazoline 8 is
the major component in this mixture, we could rather
reliably reveal the signals belonging to this heterocycle
(see Experimental). The most characteristic ones are the
quartet signals at С 81.23 (2JC,F = 30.9 Hz) and 186.10
(2JC,F = 37.9 Hz) corresponding to the carbon atoms in
position 2 of the heterocycle and the С=О bond of the
trifluoroacetyl group.
The sequence of transformations that occur on storage
in a solution of the isolated product of the reaction of
hexafluoroacetylacetone with thiobenzoylhydrazine of the
dihydroxypyrazolidine structure 6b´ are presented above.
Several processes occur simultaneously.
The primary diastereomer of the dihydroxypyrazolidine
structure 6b´ is rather rapidly transformed into alternative
configurational isomer 6b, and these structures are equilꢀ
ibrated. Water elements are simultaneously eliminated
from these structures to form 5ꢀhydroxyꢀ2ꢀpyrazoline 7.
In turn, 1,3,4ꢀthiadiazoline heterocycle 8 is formed through
the intermediate undetected hydrazone structure. As a reꢀ
sult, the ringꢀring tautomeric equilibrium involving heteroꢀ
cycles 7 and 8 is established.
The mutual transformation of diastereomers 6b´ and
6b can occur only through linear hydroxyhydrazine strucꢀ
ture 6а, which is not detected by NMR spectroscopy.
The 1Н NMR spectrum of compound 6 detected 1 day
after the preparation of the solution shows the formation
of two new exceptionally different structures.
In the 1Н NMR spectrum one of them gives nonsymꢀ
metrical doublet signals at Н 3.51 and 3.71 (AB system,
JАВ = 19.6 Hz) and somewhat broadened singlet signal at
Н 7.83. Another compound give signals at Н 3.58 and
3.69 in the form of nonsymmetrical doublets (AB system,
JАВ = 17.4 Hz) and a broadening signal at Н 6.86. It can
be assumed that water elements are eliminated from diaꢀ
stereomeric 3,5ꢀdihydroxypyrazolidines 6b´ and 6b to
form 5ꢀhydroxyꢀ2ꢀpyrazoline 7, which further undergoes
the equilibrium transition to 1,3,4ꢀthidiazoline tautomer 8
through the intermediate linear structure of the hydrazone
form. Compounds 7 and 8 have chirality centers, and the
hydrogen atoms of their methylene groups are diastereoꢀ
topic, due to which we observed two AB systems in the
1Н NMR spectrum.
After the dihydroxypyrazolidine derivative is kept in
boiling toluene for 4 h, 5ꢀtrifluoromethylꢀ2ꢀphenylꢀ1,3,4ꢀ
thiadiazole (9) was isolated. All processes of transformaꢀ
tion of the heterocycles to other heterocycles are accelerꢀ
ated on reflux in toluene. The high temperature favors the
irreversible cleavage of 1,3,4ꢀthiadiazoline structure 8 with
The signals forming the first AB system (Н 3.51 and
3.71) belonging to 5ꢀhydroxyꢀ2ꢀpyrazoline 7. This follows
from a comparison with the spectral characteristics obꢀ

Reaction of fluorodiketones with thiohydrazide
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
861
fluoroacetylacetone 2 and hexafluoroacetylacetone 3 (Aldrich)
were used without additional purification.
the formation of 1,3,4ꢀthiadiazole 9 and trifluoroacetone.
As mentioned above, similar cleavage also takes place also
for the condensation product of trifluoroacetylacetone with
thiobenzoylhydrazine but at ambient temperature.
A comparison of the results obtained by the study of
the reaction products of thiobenzoylhydrazine with acetylꢀ
acetone5,6,9 and its fluorinated analogs (trifluoroꢀ and
hexafluoroacetylacetones) suggests the following.
As mentioned above, the ringꢀring equilibrium of two
heterocycles is observed for acetylacetone in solutions.
The storage of solutions for a sufficiently prolonged time
is not accompanied by irreversible changes.
For the trifluoroacetylacetone, the 5ꢀhydroxyꢀ2ꢀpyrꢀ
azoline structure is considerably more favorable than
the 1,3,4ꢀthiadiazoline structure; however, the smallest
amounts of this tautomer, which cannot be detected by
NMR spectroscopy, result on storage in the decomposiꢀ
tion of the condensation product to form 1,3,4ꢀthiadiꢀ
azole and trifluoroacetone.
Diastereomeric dihydroxypyrazolidine structures are
possible for the product with hexafluoroacetylacetone. This
is due to an increase in the lifetime of the primary reaction
product of 1,3ꢀdiketone with polynucleophile (hydroxyꢀ
hydrazine), where the strong electronꢀwithdrawing trifluꢀ
oromethyl group prevents the elimination of water eleꢀ
ments and allows the intramolecular addition to the secꢀ
ond CF3С=О bond to occur. The diastereomeric dihyꢀ
droxypyrazolidines that formed eliminate water very slowly
due to the same electronꢀacceptor properties of the triꢀ
fluoromethyl groups. 5ꢀHydroxyꢀ2ꢀpyrazoline formed exꢀ
periences, in turn, the reversible tautomeric transition to
2,3ꢀdihydroꢀ1,3,4ꢀthiadiazole, and the ringꢀring equilibꢀ
rium with comparable amounts of two heterocycles is esꢀ
tablished. This resembles the situation with the acetylꢀ
acetone derivative.
Thus, the replacement of one methyl group in the
1,3ꢀdiketone component for the reaction product with
thiobenzoylhydrazine results in the almost complete disꢀ
appearance of the 5ꢀhydroxyꢀ2ꢀpyrazoline—2,3ꢀdihydroꢀ
1,3,4ꢀthiadiazole equilibrium, and the replacement of the
second methyl group by the trifluoromethyl group sucꢀ
cessfully recovers this equilibrium.
[5ꢀHydroxyꢀ3ꢀmethylꢀ5ꢀ(trifluoromethyl)ꢀ4,5ꢀdihydroꢀ1Нꢀ
pyrazolꢀ1ꢀyl](phenyl)thioketone (4b). Trifluoroacetylacetone 2
(0.462 g, 3 mmol) was added with stirring to a solution of thiobenꢀ
zoylhydrazine (0.456 g, 3 mmol) in methylene chloride (5 mL)
at 20 C. The reaction mixture was kept for 20 min, the solvent
was evaporated under reduced pressure without heating, and the
crystalline residue was washed with cooled methanol and dried
in vacuo. The yield was 0.58 g (67%), m.p. 41 C. Found (%):
С, 49.84; Н, 3.76; N, 9.60. C12H11F3N2OS. Calculated (%):
С, 50.00; Н, 3.85; N, 9.72. 1Н NMR (CDCl3), : 2.86 (s, 3 H, Me);
3.25, 3.41 (both d, 1 H each, H(4), JАВ = 18.9 Hz); 7.27—7.50
(m, 5 H, Ar); 8.23 (s, 1 Н, ОH). 13С NMR (CDCl3), : 15.46
2
(Ме); 43.34 (C(4)); 93.35 (q, C(5), JC,F = 33.9 Hz); 122.55
(q, CF3, 1JC,F = 285.2 Hz); 127.72—129.49 (Ar); 157.68 (C(3));
200.72 (C=S).
2ꢀMethylꢀ5ꢀphenylꢀ1,3,4ꢀthiadiazole (5). A solution of 5ꢀhydrꢀ
oxyꢀ3ꢀmethylꢀ1ꢀthiobenzoylꢀ4,5ꢀdihydroꢀ1Нꢀpyrazole 4b (0.288 g,
1 mmol) in methanol (3 mL) was kept at 20 C for 1 day, the
solvent was evaporated under reduced pressure, and the residue
was recrystallized from benzene and dried in vacuo. The yield
was 0.161 g (67%), m.p. 108 C (Ref. 11: 108 C). 1Н NMR
(CDCl3), : 2.82 (s, 3 H, Me); 7.52 (m, 3 H, Ar); 8.02 (m, 2 H,
Ar). 13С NMR (CDCl3), : 16.16 (Ме); 128.25—131.32 (Ar);
165.18 (C(2)); 169.30 (C(5)).
[(3RS,5SR)ꢀ3,5ꢀDihydroxyꢀ3,5ꢀdi(trifluoromethyl)pyrazolꢀ
idinꢀ1ꢀyl](phenyl)thioketone (6b´). A solution of thiobenzoylꢀ
hydrazine (0.228 g, 1.5 mmol) in anhydrous dioxane (3 mL) was
added dropwise with stirring to a solution of hexafluoroacetylꢀ
acetone 3 (0.312 g, 1.5 mmol) in anhydrous dioxane (5 mL) at
20 C. The reaction mixture was kept until the reaction ceased,
the solvent was evaporated under reduced pressure without
heating, and the crystalline residue was washed with cooled
chloroform and dried in vacuo. The yield was 0.47 g (87%),
m.p. 125—127 C. Found (%): С, 39.80; Н, 2.79; N, 7.54.
C12H10F6N2O2S. Calculated (%): С, 40.01; Н, 2.80; N, 7.78.
MS (EI, 70 eV), m/z (Irel (%)): 360 [M]+ (3), 342 [M – H2O]+
(19), 290 (19), 273 [M – H2O – CF3]+ (100), 231 [M – H2O –
– CH2COCF3]+ (53), 177 (50), 136 (16), 121 [CSPh]+ (72), 104
(47), 77 [Ph]+ (69). 1Н NMR (CDCl3), : 2.61, 2.63 (both d,
1 H each, H(4), JАВ = 16.0 Hz); 4.11 (br.s, 1 H, NH); 5.82 (br.s,
1 Н, ОH); 6.78 (br.s, 1 Н, ОН); 7.46 (m, 3 H, Ar); 7.65 (m, 2 H,
Ar). 13С NMR (DMSOꢀd6), : 37.87 (C(4)); 81.76 (q, C(3),
2
2JC,F = 29.9 Hz); 92.50 (q, C(5), JC,F = 30.9 Hz); 124.25
1
1
(q, CF3, JC,F = 290.2 Hz); 125.55 (q, CF3, JC,F = 285.2 Hz);
127.17—131.32 (Ar); 200.22 (C=S).
[5ꢀHydroxyꢀ3,5ꢀdi(trifluoromethyl)ꢀ4,5ꢀdihydroꢀ1Нꢀpyrꢀ
azolꢀ1ꢀyl](phenyl)thioketone (7) was synthesized in a mixture
with compounds 6b and 8 on keeping for 1 day of a solution of
the reaction mixture of hexafluoroacetylacetone and thioꢀ
benzoylhydrazine in CDCl3. 1Н NMR (CDCl3), : 3.51, 3.71
(both d, 1 H each, H(4), JАВ = 19.6 Hz); 7.37—7.55 (m, 5 H,
Ar); 7.83 (s, 1Н, ОH).
1,1,1ꢀTrifluoroꢀ3ꢀ(2ꢀtrifluoromethylꢀ5ꢀphenylꢀ2,3ꢀdihydroꢀ
1,3,4ꢀthiadiazolꢀ2ꢀyl)propanꢀ2ꢀone (8) was synthesized in a mixꢀ
ture of compounds 6b and 7 on keeping for 1 day of a solution of
the reaction mixture of hexafluoroacetylacetone and thioꢀ
benzoylhydrazine in CDCl3. 1Н NMR (CDCl3), : 3.58, 3.69
(both d, 1 H each, СH2, JАВ = 17.4 Hz); 6.86 (br.s, 1 H, NH);
7.42 (m, 3 H, Ar); 7.56 (m, 2 H, Ar). 13С NMR (CDCl3), :
Experimental
NMR spectra were recorded on a Bruker DXꢀ300 spectromꢀ
eter at 300 (1Н) and 75 MHz (13С) under the conditions of
complete spinꢀspin proton decoupling. An internal standard was
HMDS. The spectra were recorded in DMSOꢀd6 and CDCl3.
IR spectra were recorded on a Perkin Elmer FTꢀIR System Specꢀ
trum spectrometer (KBr) at 400—4000 cm–1. Mass spectra were
measured on an МХ 1321 instrument (EI, 70 eV). The reaction
course and purity of the synthesized compounds were monitored
by TLC on Silufol UVꢀ254 plates (eluent СНСl3). Melting points
were determined in a glass capillary. The starting thiobenzoylꢀ
hydrazine 1 was synthesized using a known procedure.10 Triꢀ

862
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Alekseyev et al.
2
41.17 (CН2); 81.23 (q, C(2), JC,F = 30.9 Hz); 115.31 (q, CF3,
4. S. I. Yakimovich, I. V. Zerova, V. V. Pakal´nis, in Sovremenꢀ
nye problemy organicheskoi khimii [Modern Problems of Orꢀ
ganic Chemistry], Izdꢀvo SPbGU, St. Petersburg, 2010, 217
(in Russian).
1JC,F = 291.2 Hz); 124.56 (q, CF3, JC,F = 286.2 Hz);
127.41—130.88 (Ar); 160.65 (С(5)); 186.10 (q, CОСF3, 2JC,F
1
=
= 37.9 Hz).
5ꢀTrifluoromethylꢀ2ꢀphenylꢀ1,3,4ꢀthiadiazole (9). A solution
of [3,5ꢀdihydroxyꢀ3,5ꢀdi(trifluoromethyl)tetrahydroꢀ1Нꢀpyrꢀ
azolꢀ1ꢀyl](phenyl)thioketone 6b (0.360 g, 1 mmol) in anhydrous
toluene (5 mL) was refluxed for 40 h, the solvent was evaporated
under reduced pressure, and the residue was recrystallized from
hexane and dried in vacuo. The yield was 0.191 g (53%), m.p.
92—93 C. Found (%): С, 46.90; Н, 2.09; N, 12.25. C9H5N2F3S.
Calculated (%): С, 46.96; Н, 2.19; N, 12.17. 1Н NMR (CDCl3),
: 7.52—7.63 (m, 3 H, Ar), 8.03 (d, 2 H, Ar, J = 6.5 Hz).
5. S. I. Yakimovich, I. V. Zerova, K. N. Zelenin, Zh. Org. Khim.,
1997, 33, 418 [Russ. J. Org. Chem. (Engl. Transl.), 1997, 33].
6. V. V. Pakal´nis, I. V. Zerova, S. I. Yakimovich, Vestnik
SPbGU [Bulletin of St. Petersburg University], 2009, 4, 79
(in Russian).
7. V. V. Pakal´nis, I. V. Zerova, S. I. Yakimovich, Zh. Obshch.
Khim., 2007, 77, 1665 [Russ. J. Gen. Chem. (Engl. Transl.),
2007, 77].
8. V. V. Pakal´nis, I. V. Zerova, S. I. Yakimovich, V. V. Alekꢀ
seyev, Khim. Geterotsikl. Soedin., 2008, 765 [Chem. Heteroꢀ
cycl. Compd. (Engl. Transl.), 2008, 44].
1
13С NMR (CDCl3), : 119.79 (q, CF3, JC,F = 273.2 Hz);
2
128.75—132.81 (Ar); 157.02 (q, С(5), JC,F = 38.9 Hz);
172.28 (С(2)).
9. M. T. Toshev, Kh. B. Dustov, S. O. Saidov, S. I. Yakimovꢀ
ich, I. V. Zerova, B. B. Umarov, Koord. Khim., 1992, 18,
1184 [Russ. J. Coord. Chem. (Engl. Transl.), 1992, 18].
10. K. A. Jensen, Ch. Pedersen, Acta Chem. Scand., 1961,
15, 1097.
References
1. K. N. Zelenin, V. V. Alekseyev, V. A. Khrustalev, S. I. Yakiꢀ
movich, V. N. Nikolaev, N. V. Koshmina, Zh. Org. Khim.,
1984, 20, 180 [Russ. J. Org. Chem. (Engl. Transl.), 1984, 20].
2. S. I. Yakimovich, K. N. Zelenin, Zh. Obshch. Khim., 1995,
65, 705 [Russ. J. Gen. Chem. (Engl. Transl.), 1995, 65, 637].
3. K. N. Zelenin, V. V. Alekseyev, K. Pihlaja, V. V. Ovchaꢀ
renko, Izv. Akad. Nauk, Ser. Khim., 2002, 197 [Russ. Chem.
Bull., Int. Ed., 2002, 51, 205].
11. B. Holmberg, Ark. Kemi, 1947, 25A, 1.
Received November 21, 2011;
in revised form February 10, 2012