Conformational analysis, spectral and catalytic properties of 1,3-thiazolidines, ligands for acetophenone hydrosilylation with diphenylsilane

Article abstract of DOI:10.1134/S107036321010021X

2-Aryl- and 2-furyl-4-carboxy-1,3-thiazolidines were synthesized. Their spectral properties were studied, and conformational analysis was performed. It was shown that they exist in solution as an equilibrium of neutral and zwitter-ion forms. The influence

Full text of DOI:10.1134/S107036321010021X

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 10, pp. 2007–2021. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.N. Skvortsov, V.M. Uvarov, D.A. de Vekki, E.P. Studentsov, N.K. Skvortsov, 2010, published in Zhurnal Obshchei Khimii, 2010,
Vol. 80, No. 10, pp. 1697–1711.
Conformational Analysis, Spectral and Catalytic Properties
of 1,3-Thiazolidines, Ligands for Acetophenone Hydrosilylation
with Diphenylsilane
A. N. Skvortsova, V. M. Uvarovb, D. A. de Vekkib, E. P. Studentsovb, and N. K. Skvortsovb
a St. Petersburg State Polytechnic University, St. Petersburg, Russia
b St. Petersburg State Technological Institute, Moskovskii pr. 26, St. Petersburg, 190013 Russia
Received December 24, 2009
Abstract―2-Aryl- and 2-furyl-4-carboxy-1,3-thiazolidines were synthesized. Their spectral properties were
studied, and conformational analysis was performed. It was shown that they exist in solution as an equilibrium
of neutral and zwitter-ion forms. The influence of the nature of substitutents and of their location in a benzene
ring of thiazolidines as ligands of rhodium complexes on acetophenone hydrosilylation with diphenylsilane was
examined. Thiazolidines containing donor substituents in the para-position of the benzene ring were found to
be the most effective; maximal asymmetrical induction (55% ее) was reached in the presence of 2-(4-
methoxyphenyl)-4-carboxy-1,3-thiazolidine.
DOI: 10.1134/S107036321010021X
It was reported earlier [1–5] that asymmetrical
hydrosilylation of acetophenone with diphenylsilane
proceeds under nitrogen or argon atmosphere in the
presence of [Rh(COD)Cl]2 and monodentate thiazo-
lidines in situ reaching maximal asymmetrical
induction of 18.6%. On the other hand, it is known [6]
that the presence of water traces at ketone hydro-
silylation in the presence of [Rh(COD)Cl]2 and di-
phosphines accelerates the reaction.
hydride in the presence of dimethylaminopyridine
(DMAP).
Thiazolidines I–XIII and XV are white crystalline
substances, soluble in DMF and DMSO, poorly
soluble in alcohols and tetrahydrofuran and virtually
insoluble in water, diethyl ether, chloroform, acetone,
hexane, toluene etc. The esterification with methanol
or ethanol in the presence of thionyl chloride gives the
corresponding esters, which are well soluble in
nonpolar organic solvents.
In this connection the study of acetophenone
hydrosilylation with diphenylsilane in the presence of
[Rh(COD)Cl]2 and some 2-substituted 1,3-thiazo-
lidines in situ under not inert atmosphere is of un-
doubtful interest. On the other hand, the extension of
the series of thiazolidine compounds is of separate
interest due to their chemo- and radioprotective
properties and low toxicity [7–10].
All the obtained thiazolidines have (R)-amino acid
chirality (С4-ring). During the process of thiazolidine
ring formation the additional asymmetrical center at
С2-atom appears. After one crystallization from
methanol (ethanol) (2R, 4R)- and (2S, 4R)-
diastereomers were obtained, whose ratio for
compounds I–XIII and XV can be determined by
1
Synthesis, conformational analysis, and spectral
parameters of thiazolidines. Synthesis of 2-aryl-
(hetaryl)-4-carboxy-1,3-thiazolidines I–XIII and XV
was carried out by condensation of L-cysteine
hydrochloride and the corresponding aldehydes in
aqueous alcohol in the presence of sodium hydrogen
carbonate [11–14] by the protocols mentioned below;
N-acetyl-2-phenyl-4-carboxy-1,3-thiazolidine XIV was
obtained by acylating thiazolidine I with acetic an-
means of Н NMR spectroscopy from the relationship
between the areas of signals at С2-atom: The proton
signal of the (2R, 4R)-isomer is upfield relative to the
signal of (2S, 4R)-isomer. The identification of
thiazolidine XIV diastereomers by the NMR method is
more difficult and will be discussed below. The ratio
of (2R, 4R)- and (2S, 4R)-diastereomers in
thiazolidines I–IV and VI–XII is ~7:8, in thiazolidines
V, XIII and XV) ~5:9, and in thiazolidine XIV ~3:2.
2007

2008
SKVORTSOV et al.
R'''
R
R'''
R
R''
R'
R''
R'
COOH
Δ
*
+
S
O
NaHCO3
NH2
HS
HCl
*
C
*
*
H
COOH
NH
I−XIII
R'''
R
R''
(CH3CO)2O
DMAP
S
*
R'
*
*
COOH
N
COCH3
XIV
I, XIV, R = R' = R'' = R''' = H; II, R = OH, R' = R'' = R''' = H; III, R = R'' = R''' = H, R' = OH; IV, R = R' = R''' = H, R'' =
OCH3; V, R = R''' = OCH3, R' = R'' = H; VI, R = H, R' = R'' = R''' = OCH3; VII, R = OH, R' = OCH3, R'' = R''' = H; VIII,
R = R''' = H, R' = OCH3, R'' = OH; IX, R = R' = R''' = H, R'' = CH3; X, R = R' = R''' = H, R'' = C2H5; XI, R = R' = R''' = H,
R'' = i-Pr; XII, R = R' = R''' = H, R'' = F; XIII, R = R'' = R''' = H, R' = NO2.
COOH
Δ
S
O
*
+
H3C
H3C
NH+2
*
NaHCO3
C
*
O
O
NH2
HS
HCl
*
H
COOH
N
H
XV
In the 1Н NMR spectrum of compounds I–XIII and
XV there are signals of two nonequivalent protons at
thiazolidine C5-atom at δН 2.8–3.4 ppm, proton H4
signal is observed at δН 3.7–4.3 ppm, proton H2 signal,
at δН 5.3–5.9 ppm. The proton signals of aryl
substituent are registered in the range of δН 6.7–7.6 ppm
(except for thiazolidine XIII, where they appear at δН
7.6–8.2 ppm), and furan ring protons, at δН 5.9–6.4 ppm.
Summary signal of the exchanging imine and carboxy
protons appears before the use of a narrowing filter as
a very broad band of half-width 1 ppm at 3.3–3.6 ppm.
The band location, its strong broadening, the absence
of the separate signals of NH- and COOH-groups and
the absence of proton H2 splitting or significant
broadening allow an assumption that similar to the
majority of amino acids the thiazolidines exist as an
equilibrium of neutral and zwitter-ion forms, being in
dynamic exchange conditions. The spectra of
compounds II, III, VII and VIII contain the band of
analogous large half-width in the range of 9.4–10.3 ppm
corresponding to phenol ОН-proton, also exchanging
protons with carboxy and imino-groups.
NH+2
H2
R
H4
H4
R
H5'
H5
H5'
H5
COO−
COO−
H2
S
S
(2S,4R)-isomer
(2R,4R)-isomer
R = aryl, furyl.
configuration of C2-atom, which on the one hand allows
a conclusion about the conformation of thiazolidine
ring, and on the other hand, to assign signals of two
protons at С5-atom. In (2R, 4R)-diastereomer aryl/furyl
substituent and carboxy group are located on one side
of the ring and suffer a sufficient steric interaction. As
a result, the thiazolidine ring is predominantly in the
conformation, which provides maximum reciprocal
removal of these groups. Then protons H2, H4, and H5
occupy axial position relative to thiazolidine ring, and
the aryl substituent and the carboxy group, equatorial
positions. In (2S, 4R)-diastereomer the substituents are
on different sides of the ring, the steric interaction is
absent. There are no additional limitations for the
conformational mobility of the thiazolidine ring; the
Screening and spin-spin proton coupling constants
in the studied compounds depend strongly on absolute
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CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
2009
corresponding protons can dynamically exchange axial
and equatorial positions.
In the spectra of the (2R, 4R)-diastereomers of the
2-substituted 1,3-thiazolidines the value of the
3
3
coupling constants Jcis and Jtrans comprise on the
average 7 and 9 Hz, the scatter of values for different
compounds is small. Such values indicate the suf-
ficiently rigid fixation of the thiazolidine ring in the
conformation with the large negative cis-angle and the
equatorial carboxy group in complete agreement with
the postulated above steric interaction of carboxy and
aryl/furyl groups. In the spectra of (2S, 4R)-diastereo-
It is known [15] that in the axial position the
screening is greater than in the equatorial. Con-
sequently, in (2R, 4R)-diastereomer the chemical shifts
H2, H4 and H5 must be less, and the chemical shifts H5'
and of aryl/furyl groups protons should be greater than
in the conformationally free (2S, 4R)-diastereomer. It
makes possible to assign proton signal in the range of
3.00-3.15 ppm to the proton H5 (in trans-position
relative to H4), and signal at 3.2–3.4 ppm, to (2R, 4R)-
isomer proton H5' (in cis-position relative to H4). The
proton H5 in (2R, 4R)-diastereomer is shifted upfield
relative to (2S, 4R)-diastereomer similarly to the
signals H2 and H4, and the proton H5' signal is shifted
to the same side as aryl/furyl group protons.
3
3
mers the values Jcis and Jtrans are close to 7 and 4 Hz
in accordance with the conformational mobility of
thiazolidine ring. The values of constants observed for
diastereomers confirm the validity of the assignment of
3
the signals of the protons H5' and H5. The value Jtrans
is on the average more than 4 Hz. This is consistent
with the general rule: In the case of nonrigid ring the
conformation with the equatorial substituent is
somewhat more advantageous.
The thiazolidine ring conformation can be analyzed
3
by means of two vicinal coupling constants Jcis and
3Jtrans between the proton H4 (that corresponds to
cysteine α-proton) and the protons H5' and H5 (β-
protons). The value of the coupling constant depends
on the dihedral angles H4–С4–С5–H5' (cis-angle) and
H4–С4–С5–H5 (trans-angle) values, whose difference
modulus in all the conformations remains approxi-
mately equal to 120°. The typical range of changes of
the angle H4–С4–С5–H5' in 4R-carboxythiazolidines is
from –30° (H4 and H5 in the maximal axial position) to
30° (H4 and H5 in the maximal equatorial position).
Taking into account characteristic angular depen-
dences for the vicinal constants in cyclopentanes [15],
2
The geminal coupling constant J(H5H5') changes
little and comprises for all compounds approximately
10 Hz; its value in (2S, 4R)-diastereomer is more on
the average by 0.3 Hz, which agrees well with the
higher conformational mobility. It should be noted that
3Jtrans is the most sensitive to the nature of the aryl
substituent in (2S, 4R)-diastereomer among all ob-
served constants. The introduction of substituents into
the ortho-position of the benzene ring leads to its
increase (the greatest value 6.0 Hz is observed for
compounds V and XIII, the smallest, 3.8 Hz, for
VIII), i.e. the substituent makes more preferable the
conformation of (2S, 4R)-diastereomer with the
equatorial carboxy group. These regularities are
observed in all spectra of compounds I–XIII, XV and
make it possible to unambiguously identify all dia-
stereomers signals even at their equal concentrations.
The conformational strain of (2R, 4R)-diastereomers is
most probably the reason for the fact that they are
formed in the synthesis in smaller quantities.
3
in this range Jcis has maximum 9 Hz at 0° (2-endo-
conformation) and decreases to 6.5 Hz at the extreme
angle value. The angle H4–С4–С5–H5 changes from
–150° to –90°, respectively, and in this case the
constant 3Jtrans decreases steadily from 8.6 to ~0 Hz. In
thiazolidines the constants are somewhat less owing to
the effect of the electronegative sulfur atom, but their
angular dependence and mutual relationships remain
the same. If one assumes that thiazolidine ring is
conformationally nonrigid, the cis- and trans-angle
may dynamically take all allowed values from –30° to
30° and from –150° to –90°, respectively. In this case
the averaged values of the constants 3Jcis and 3Jtrans will
be approximately 7 and 4 Hz. An increase in the
The signals of aromatic protons of both dia-
stereomers of 2-aryl-4-carboxy-1,3-thiazolidines are
two typical AA'XX' spectra with a “large” AX
constant (9 Hz, ortho-constant) and a “small” constant
4
4
5
(about 2.5 Hz, total effect of JAA', JXX', JAX', meta-
and para-constants).
3
constant Jtrans will indicate the preferred existence of
conformation with the negative cis-angle and the equa-
torial carboxy group, and the decrease in Jtrans value,
The spectrum of the N-acylated derivative XIV
deserves a separate examination. At room temperature
its 1H NMR spectrum contains four sets of signals (the
best distinguishable in the regions of signals of H4 and
COCH3), each corresponding to the initial formula of
3
the conformation with axial carboxy group. An increase
3
3
in the constant Jcis at Jtrans ~4 Hz will correspond to
2-endo-conformation with the zero cis-angle.
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2010
SKVORTSOV et al.
the compound. The reason for this is the hindered rota-
tion of the acetyl group around the amide bond, as a
result of which each diastereomer is represented by a
pair of conformers. The NMR spectra of these con-
formers are distinguished also strongly as the spectra
of diastereomers (Fig. 1). The signals assignment in
this case is performed both using the published data on
the NMR spectroscopy of purified diastereomers of
related compounds and on the basis of the analysis of
NMR spectra at 100°C (at this temperature the
sufficiently fast rotation of acyl group occurs, and the
signals of two conformers are merged) [11, 13, 16].
А: 2R,4R
δ 4.704 ppm
J 8.0, 6.5
B: 2R,4R
δ 5.145 ppm
J 6.8, 3.7
C: 2S,4R
δ 5.107 ppm
J 6.9 Hz
D: 2S,4R
δ 5.337 ppm
J 6.3, 1 Hz
5.4 5.3 5.2 5.1 5.0 4.9 4.8 4.7 4.6
The identification of N-acylthiazolidine diastereo-
mers is the most easily performed through the signals
of protons H4, which are well resolved. The signals of
(2S, 4R)-diastereomer conformers have the coupling
δ, ppm
1
Fig. 1. The fragment of H NMR spectrum of thiazolidine
XIV at room temperature corresponding to the signals of
proton H4 after applying the narrowing digital filter [A, B
3
constants Jtrans 4–9 Hz, for (2S, 4R)-diastereomer
are conformers of (2R, 4R)-diasteromer; C,
conformers of (2S, 4R)-diasteromer].
D are
signals 3Jtrans are no more than 1.6 Hz (Fig. 1). (2R, 4R)-
Diastereomer A (41%) is prevailing in the mixture of
conformers, and the content of the second conformer B
is practically 2 times less (20%). A quantity of (2S,
4R)-diastereomer conformers comprises 21 and 18%
for C and D respectively. Thus, in thiazolidine XIV
(2R, 4R)-diastereomer prevails. It should be noted that
the chemical shifts of the protons H2 and COCH3 for
different diastereomers A and C, or B and D are more
similar to each other, than in the spectra of the
conformers of one diastereomer. It is obvious that A
and C are the conformers with identical orientation of
acyl group relative to carboxy group, and the presence
of acyl group strongly affects the conformation of
thiazolidine. First, zwitter-ion form becomes impossible
group. In contrast to (2S, 4R)-diastereomers of
compounds I–XIII, the values of Jtrans for conformers
3
C and D are close to zero, indicating that the cis-angle
is rigidly fixed near 30°, and the carboxy group is
located in the maximally axial position. The geminal
coupling constant of conformer A increases in the
module to 12 Hz. All protons of thiazolidine XIV
conformers are strongly deshielded in comparison with
the protons of compounds I–XIII, the H2 proton signal
falls into the region 6.1–6.4 ppm, and H4, to 4.7–5.4 ppm.
The smallest deshielding of thiazolidine protons is
observed in the conformer A, and deshielding of the
phenyl ortho-protons in this conformer is, on the
contrary, maximal. The analysis of chemical shifts and
the construction of the simplest molecular models
makes it possible to conclude that in the conformer A
as before exists the typical for (2R, 4R)-diastereomer
conformation with the greatest reciprocal distance
between the carboxy and phenyl groups. In this case
the protons H2, H4, and H5 occupy axial positions, and
the phenyl group and H5', equatorial positions. One of
the fragments of acyl group (С=O or CH3) is
approached to COOH group. When C=O fragment
approaches the COOH group, the repulsion can be
theoretically relieved due to the formation of
intramolecular hydrogen bond, and all three lateral
groups will prove to be in the advantageous equatorial
position. The turn of acyl group by 180° will lead to
unfavorable steric interaction of COOH and CH3
groups and will force them to displace to the axial
1
and in the Н NMR spectrum of thiazolidine XIV the
broadened signal of carboxy group at 13.07 ppm is
observed. Secondly, due to the conjugation of the lone
electron pair of nitrogen and π-orbitals of CO-group
the thiazolidine aminoacyl fragment is flat [16]: The
atoms С2, N, С4 and acyl group approach the
arrangement in the one plane; as a result the acyl group
occupies strictly equatorial position and it interacts
sterically with COOH and aryl group. The strong
overlapping of the H5 and H5' signals prevents the
complete signals assignment for conformers B–D, but
3
3
the coupling constants Jcis and Jtrans can be reliably
determined from the analysis of H4 signals. The value
3
3
of the coupling constants Jcis and Jtrans of conformer
A are close to (2R, 4R)-diastereomers of compounds I–
XIII (rigid ring, equatorial carboxy group), and the
conformer B constants have values, which correspond
to free ring with the preferred axial position of COOH
3
position (with the observed decrease in the Jtrans
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CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
2011
value). In (2S, 4R)-diastereomer there is no
conformations, where the groups R and COOH could
simultaneously occupy equatorial positions not
destroying the coplanarity of thiazolidine aminoacyl
fragment; therefore COOH group is rigidly fixed in the
axial position (3Jtrans is close to zero). Apparently, N-
acylation makes the ring of (2S, 4R)-diastereomer
more strained than that of (2R, 4R)-diastereomer, in
contrast to the isomers of initial thiazolidine I. On the
basis of the above stated and also taking into account
the relative values of the chemical shifts of H2, H4 and
COCH3 in the pair of the conformers, it is possible to
assume with the confidence that in the conformers A
and C the acyl group is oriented to the carboxy group
side by C=O fragment, and in the conformers B and D,
by the CH3 group.
chemical shifts values of the carbon atoms С2 and С4
in (2R, 4R)-diastereomer confirm the above discussed
effect, according to which the substituents at these
atoms (aryl/furyl and carboxy group) in (2R, 4R)-
diastereomer occupy preferably equatorial position.
The IR spectra of thiazolidines contain charac-
teristic stretching vibrations of the groups N–H and O–
H (3410–3450 cm–1), С–Н (2590–3070 cm–1), С=О
and С=С (1550–1725 cm–1).
Hydrosilylation. The acetophenone hydrosilylation
with diphenylsilane followed by hydrolysis of the
formed mixture of silyl ethers isomers XVII is one of
the synthetic approaches to 1-phenylethanol (S)- or
(R)-isomers XIX and is widely used as a model
reaction to evaluate the catalyst efficiency and the
influence of different conditions on the hydrosilylation
of prochiral compounds [18–20]. The main side
reaction of the diphenylsilane addition, which occurs
during the hydrosilylation in the presence of rhodium
complexes, is the formation of enol silyl ether XVI,
which with the subsequent hydrolysis of the reaction
mixture is easily converted into the initial aceto-
phenone.
The 13C NMR spectra of investigated thiazolidines
are identical to the spectra of related compounds, given
in the literature [11, 12, 17]. In (2S, 4R)-diastereomer
the chemical shifts of all the 13C nuclei of thiazolidine
are somewhat less than in (2R, 4R)-diastereomer. The
carboxy carbon nucleus is, on the contrary, more
screened in (2R, 4R)-diastereomer. The greater
SiPh2H
O
SiPh2H
O
H3C
H
H3C
H
H3C
O
H2C
O
SiPh2H
+
Ph SiH
+
+
+
H Si
O
Si
H
2
2
[Rh]
(R)-isomer
XVI
(S)-isomer
XVIII
H2O, H+
XVII
0−5oC
H2O, H+
0−5oC
CH3
CH3
H
H
OH
OH
+
(S)-isomer
(R)-isomer
XIX
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SKVORTSOV et al.
The reaction carried out under not inert atmosphere
process selectivity. The decrease in the target product
yield occurs also at the use of the acylated bidentate
pyridinethiazolidines, which is connected with the
decrease in the donor ability of the thiazolidine
nitrogen atom [2].
(aerobic conditions) leads additionally to 1,1,3,3-
tetraphenyldisiloxane XVIII formation. In this case the
ligand structure in the rhodium complex has the
decisive effect on its yield [21].
The acetophenone hydrosilylation with diphenyl-
silane under not inert atmosphere in the presence of
[Rh(COD)Cl]2 and of the introduced in situ thia-
zolidines I–XV occurs sufficiently slowly, and in all
cases enol silyl ether XVI and siloxane XVIII are
formed along with the main product XVII (see the
table). The acetophenone conversion (the ratio
complex : thiazolidine is 1:10) depends on the stru-
cture of thiazolidine used, but the target product yield
does not exceed 42% after 24 h. At the same time the
yield of compound XVII attains 93–99% after 38–65 h,
when bidentate pyridine-thiazolines were used [2]. If
the reaction is carried out in the presence of pyridine-
oxazolines, the yield reaches 62% after only 18 h [22].
The reaction under aerobic condition has certain
positive effect on the desired product yield. For
example, the yield of ether XVII in the presence of I
under the air atmosphere is equal to 39% vs. 35% with
the reaction under nitrogen atmosphere [2].
The variation in the substituents location and nature
in the benzene ring of thiazolidines I–XIII provides a
possibility to affect the hydrosilylation activity and
chemoselectivity. The presence of only one donor
substituent in ortho-, meta- or para-positions of the
benzene ring (compounds II–IV, IX–XI) or total
absence of substituents makes it possible to reach 48–
65% acetophenone conversion in 24 h, and the yield of
ether XVII reaches 30–42% (see the table). At the
same time in the first reaction stage in the presence of
thiazolidines with electron-donor group the yield of
ether XVII is higher than in the case of ligand
containing unsubstituted phenyl ring (for example,
after 1 h the yield of ether XVII is equal to 20 and
26% in the presence of compounds IV and III,
respectively, vs. 7% with thiazolidine I). The hydro-
silylation selectivity in the presence of meta-sub-
stituted phenylthiazolidine is found to be somewhat
lower (60%), than in the presence of a donor group in
ortho- (~100%) or para-positions (67%).
The maximal acetophenone conversion is observed
with the use of N-acetyl-2-phenyl-4-carboxy-1,3-
thiazolidine (73%); however, the ether XVII yield
(40%) is comparable with that in the presence of 2-
phenyl-, 2(3-[hydroxyphenyl])- or 2(3-tolyl)-4-car-
boxy-1,3-thiazolidines (see the table) and it is by 7%
higher than enol silyl ether yield and by 17% higher
than the by-product, tetraphenyldisiloxane, yield.
Therefore the presence of acyl protection in
thiazolidine affects favorably the hydrosilylation rate
(probably, because of the formation of low-active
zwitter-ion form), but has a negative effect on the
The concurrent reaction, the tetraphenyldisiloxane
formation, depends on the donor substituent location,
but otherwise than depends the hydrosilylation: The
yield of compound XVIII is greater when the benzene
ring donor group is closely located to the thiazolidine
core. For example, the presence of ОН-group in ortho-
or meta-positions leads to 40 and 13% yield of sil-
oxane, respectively. The presence of donor substituents
in para-position leads to a decrease in the yield of
siloxane XVIII (see the table). In this case the increase
in the electron-donor properties of these substituents
Reaction of acetophenone with diphenylsilane in the presence of [Rh(COD)Cl]2 and thiazolidines (24 h, Сc 1 mol %,
complex:thiazolidine, 1:10)
Thiazolidine
Vа
VIа
VIIIа
I
II
III
IV
VII
IX
X
XI
XII XIII XIV XV
Acetophenone conver-
sion, %
60
31
65
48
45
62
30
72
53
49
60
3
28
73
1
21
39
3
traces
31
26
39
13
16
32
8
14
31
18
25 traces
37
35
12
11
42
12
19
30
11
24
36
8
0
3
6
traces 33
0
1
8
XVI
Yield, %
36
11
30
66
28
27
40
19
XVII
40
XVIII
a Reaction time 48 h.
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CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
2013
leads to a gradual decrease in the tetraphenyldisiloxane
yield (for example, to 12 and 8% in the case of methyl
and methoxy groups, respectively).
reaches 66% after 24 h. The high yield of tetra-
phenyldisiloxane in the presence of two donor groups,
one of which is located in the ortho-position relative to
the thiazolidine ring, correlates with its yield in the
case of only one ortho-located substituents. Therefore,
even with the uncoordinated influence of substituents
the presence of one of them in ortho-position of the
benzene ring contributes to tetraphenyldisiloxane
formation.
The fluorine in para-position having strong –I and
weak +М effects causes considerable inhibition both of
the hydrosilylation (conversion 3%) and dehydro-
condensation of diphenylsilane (yield of siloxane
XVIII is 6%). A 4-fold increase in the reaction time in
the presence of thiazolidine XII makes it possible to
reach 29% conversion of acetophenone, but in this
case in the reaction products 1-phenylethanol is
present, and the unreacted diphenylsilane is completely
converted into siloxane XVIII (77%).
The introduction of three methoxy-groups simulta-
neously into ortho-, meta-, and para-positions, prob-
ably, proves to be superfluous despite the fact that
acetophenone conversion after 48 h reaches 62% (in
1 h 16%), yield of ether XVII, 36% (in 1 h, 12%), and
of siloxane XVIII, 11% (in 1 h, 6%). Thus, the
catalysts with thiazolidines containing two and more
substituents in the benzene ring, located in meta- or
para-position, are more effective for hydrosilylation,
than in the dehydrocondensation reactions, in contrast
to thiazolidines, which have at least one group in
ortho-position of the benzene ring.
The acetophenone conversion in the presence of
thiazolidine containing a strong acceptor substituent in
the meta-position, nitro group, proves to be close to its
conversion in the presence of thiazolidine with the
donor substituent, meta-hydroxy group, while the
addition selectivity with the use of nitrophenylthia-
zolidine is almost 100% (see the table). The yield of
siloxane XVIII in the presence of ligand XIII attains
27%, which is greater by 14% than at the use of
hydroxythiazolidine III. This shows that the use of
thiazolidines with the donor substituents in the benzene
ring is more preferable in comparison with the use of
thiazolidines, which contain electron-acceptor groups.
Replacement of aryl substituent in the thiazolidine
ring by methylfuryl group affects negatively both the
hydrosilylation (acetophenone conversion after 150 h
does not exceed 3%) and the dehydrocondensation of
diphenylsilane (siloxane yield is 8%). Thus, an in-
crease in the electron-acceptor properties of the
substituent in position 2 of thiazolidine ring affects
negatively the hydrosilylation.
Uncoordinated influence of donor substituents in
the benzene ring, i.e., the combination of two
methoxy-groups in ortho- and meta-position or of
methoxy-group in meta-position and of hydroxy-group
in ortho- or para-position relative to the thiazolidine
ring in certain cases leads to an increase in aceto-
phenone conversion in comparison with compounds II
and IV, which contain only one substituent. However,
the yield of the desired reaction product in these cases
proves to be similar (31–35%), and only hydrosilyla-
tion selectivity is considerably distinguished. After
24 h the acetophenone conversion in the presence of
ligands II and VII virtually coincided (see the table).
The yields attain 34, 45, and 72% respectively after
48 h with the use of thiazolidines II, V and VIII. At
the same time within 1 h after the beginning of the
reaction the ketone conversion and ether XVII yield
coincided (for example, 26% in the presence of ligand
II and 34% in the presence of ligand VIII). However,
for instance, in the presence of thiazolidine V the
transformation of acetophenone does not occur. After
48 h the yield of siloxane XVIII in the presence of
compounds V and VIII is equal to 18 and 12%,
respectively, whereas in the presence of ligand VII it
The twofold decrease in the thiazolidine
concentration, as a rule, affects negatively the reaction
rate and ether XVII yield. For example, after 24 h the
yield of 1-phenylethanol silyl ether in the case of the
ratio [Rh(COD)Cl]2:thiazolidine (I, III, IX and X),
1:5, is by 15, 17, 3, and 9% less than for the ratio 1:10,
respectively. An increase in the reaction time is, as a
rule, accompanied by 1-phenylethanol appearance in
the reaction medium. It leads to the significant yields
growth of enol XVI and tetraphenyldisiloxane and to
only small change in ether XVII yield.
As a result of the electronic nature variation of the
benzene ring substituents in 2-aryl-4-carboxy-1,3-
thiazolidines, it becomes possible to control the
hydrosilylation enantioselectivity to a greater extent
than the reaction chemoselectivity. The use of a
diastereomers mixture of thiazolidines I–XV to reach
asymmetrical induction during the hydrosilylation is
based on [2], where it has been shown that one
diastereomer participates in the reaction catalyzed by
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SKVORTSOV et al.
rhodium, but the second is not coordinated at all.
Consequently, the presence of the uncoordinating
diasteromer will have a negligible effect on the optical
yield of 1-phenylethanol isomers, since the asym-
metrical induction is underlain by the formation of a
chiral transition state. Furthermore, in the reaction
medium the thiazolidines epimerization on the С2-atom
occurs, and the catalysis occurs with the participation
of epimeric ligand form [2].
Factor analysis. The introduction of substituents
into thiazolidines benzyl moiety was shown above to
influence the equilibrium between thiazolidine ring
conformations, the hydrosilylation rate, and selectivity.
For revealing possible concealed interrelation between
the catalytic activity and structural characteristics of
examined thiazolidines the factor analysis was per-
formed by the main components method [23]. The
chemical shifts of thiazolidine ring protons and vicinal
coupling constants 3J were taken as the active
structural variables, participating in the construction of
main constituents, while geminal coupling constants 2J
were not considered since their dispersion in the
studied compounds was comparable with the error in
the coupling constant determination and it was
considerably random. In view of different dimen-
sionality and substantially distinguished dispersions
value, the selected variables were autoscaled. The
Introduction of the donor substituents into the
benzene ring in the ortho- or para-positions leads to
the preferred formation of (R)-phenylethanol. Also an
increase in the optical yield occurs, the maximum
value of which is observed in the presence of
thiazolidine IV (55% ее). The replacement of methoxy-
group in para-position by the weaker electron-donor
substituent (alkyl group) decreases the optical yield of
alcohol XIX, which, for example, in the presence of
ethylphenylthiazolidine X attains 30% ее. The presence
of donor group in ortho-position (hydroxy-group)
proves to be less effective (16% ее), and its meta-
position (OH group in meta-position reduces the
electron density on the benzene carbon atom bonded
directly to the thiazolidine frame) makes it possible to
obtain alcohol XIX with the opposite configuration in
low optical yield (12% ее).
2
diasteremers ratio, geminal coupling constants J, and
catalytic properties were analyzed as additional passive
variables; they were also autoscaled and projected on
the main components formed by the structural variables.
The combined analysis of (2R, 4R)- and (2S, 4R)-
isomers of thiazolidines I–XIII and XV showed that
the first main component (MC-1) describes 56% of
dispersion, and the sum of two high-order main
components (MC-1 + MC-2) is equal to 89%. In this
case MC-1 reproduces the difference between dia-
stereomers, since its counts (value of the main com-
ponents contribution) for (2R, 4R)- and (2S, 4R)-
isomers have different sign. Changes in the structural
parameters coincide with those examined by means of
conformational analysis: going from (2S)- to (2R)-
The uncoordinated influence of donor substituents
(OH and OCH3) affects negatively the asymmetrical
induction, which in this case does not exceed 3% ее. It
is necessary to note that the configuration of the
alcohol obtained at the uncoordinated influence of the
substituents depends on their strength. For example,
two identical by the strength donor groups (methoxy-
groups) in ortho- and meta-position favor the
formation, insignificant as it is, of (S)-phenylethanol
(1% ее). At the same time the strong donor (methoxy
group) in para-position and the less strong donor
(hydroxy-group) in meta-position act as one donor
substituent in para-position to give (R)-phenylethanol.
configuration is accompanied by the growth of δH
5
,
3
δH5', and Jtrans and by the decrease in the values δH
and δ
4
2
H , which is caused by the steric repulsion of aryl
and carboxy groups in the (R)-isomer. The counts of
the second main component for diastereomers with the
identical aryl substituent are distinguished sub-
stantially, i.e., aryl group substituents have different
effect on the diastereomers conformation. Therefore
(2R, 4R)- and (2S, 4R)-isomers were separately
analyzed (Fig. 2).
Thus, the presence of the donor group in benzene
ring (with the uncoordinated influence of substituents
where one of them must be strong electron donor),
which increases the electron density on the benzene
carbon atom bonded directly the thiazolidine frame, is
optimum for the asymmetrical induction and affords
(R)-isomer of 1-phenylethanol. The opposite con-
figuration of alcohol is predominantly formed in the
presence of substituents, which reduce the electron
density on the mentioned carbon atom.
Each variable (active or additional) is mapped onto
the loading plot as a vector (Figs. 2a, 2b); the identical
direction of vectors indicates the strong positive
correlation of variables, and opposite direction, the
strong inverse correlation. The perpendicular vectors
position shows the absence of correlation. The loads
(projection of vectors on axis, Figs. 2a, 2b) reflect the
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CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
(a) (b)
2015
1.0
0.5
0.0
2.0
1.5
1.0
XIII
δH5'
XV
S/R
3Jcis
XII
III
3Jtrans
0.5
0.0
I
XI
2J
δH
2
δH
5
X
%XVI
conv
IV
VI
–0.5
–1.0
IX
–0.5
%XVIII
%XVII
VII
δH
4
VIII
II
V
–1.0
–1.0
–0.5
0.0
0.5
1.0
–3 –2 –1
0
1
2
3
MC-1 70.57%
MC-1 70.57%
(c)
(d)
1.0
0.5
0.0
XV
2
1
3Jcis
VIII
II
IX
III
I
VII
X
0
–1
–2
–3
–4
%XVI
conv
2J
IV
V
%XVIII
VI
XI
XII
3Jtrans
δH5'
δH
2
–0.5
S/R
δH
5
δH
4
XIII
–1.0
–1.0
–0.5
0.0
MC-1 47.33%
0.5
1.0
–3
–2
–1
0
1
2
MC-1 47.33%
Fig. 2. Plots of (a, b) loads and (c, d) of counts of (a, b) (2S, 4R)-diastereomers and (c, d) (2R, 4R)-diastereomers of thiazolidines
I–XIII. Active variables (bright circles): δH2, δH4, δH5, δH5' are chemical shifts of protons; Jtrans and Jcis are vicinal coupling
2
2
constants. Additional variables (dark rhombs): J are coupling constants JH5-H5'; S/R is the concentrations ratio for (2S, 4R)- and
(2R, 4R)-isomers; (conv) is the conversion of acetophenone; %XVI–%XVIII is the yield of compounds XVI–XVIII.
contribution of MC-1 and MC-2 into the dispersion of
the corresponding variables, and their lengths, the
dispersion portion of variables, described by these
main components.
thiazolidines XIII and XV, due to the special feature
of their NMR spectra, caused by an essential
difference in the properties of substituents in
thiazolidines XIII and XV from the remaining group
of compounds. To the remaining main components
correspond 4% of dispersion, that is within the range
of the experimental error. All the investigated
compounds on the calculation plot are divided into
three clear groups. The first group is formed by
compounds III, V and VII, which contain substituents
It is easy to note that for (2S, 4R)-isomers (Figs. 2a,
2b) MC-1 and MC-2 describe 87% of dispersion of
experimental matrix. The third main component (it is
not shown in Fig. 2) describes an additional 9% of
dispersion, but its contribution is essential only from
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SKVORTSOV et al.
in the ortho-position of the benzene ring of thiazol-
idine. The second group includes thiazolidines XIII
and XV, and the third group includes all the remaining
compounds. All counts with exception of the first
group compounds are approximately located along one
line (main sequence), direction of which is governed
subsequent MC for some compounds have sufficiently
random nature. This is possible, when the steric rep-
ulsion of aryl and carboxy groups has decisive
importance for the dynamic structure of (2R, 4R)-
isomers, and the influence of substituents on the con-
formational mobility is substantially less. Apparently,
a change in the chemical shifts in this case stronger
depends on inductive and other effects, than on the
displacement of the conformational equilibrium. The
described thiazolidines as a whole are lined up along
MC-1 direction. Only nitro-derivative XIII is se-
parately located. Thiazolidines with the para-
substituted benzene ring form very compact group;
compounds with the large number of the benzene ring
substituents (V, VI, VII) deviate from this group into
the range of negative MC-1 counts, and the
unsubstituted phenyl- (I) and meta-hydroxyl-
phenylthiazolidines, into the range of positive MC-2
counts. Structural parameters of (2R, 4R)-isomers, cor-
responding to MC-1, indicate the insignificant
competition between aryl and carboxy groups for
equatorial position, in contrast to (2S, 4R)-isomers.
More negative values of MC-1 correspond to the
conformation with the equatorial aryl group; however,
the load of active variables on the main components is
sufficiently low. There are no expressed correlation
between the structural parameters and catalytic
properties of (2R, 4R)-isomers, since the corresponding
correlation coefficients do not exceed 0.4.
by the variable δH . The motion along this line from the
4
furyl and nitrophenyl thiazolidine derivatives to the
meta- and para-disubstituted derivatives of thiazoli-
dines is accompanied by an increase in MC-1 count and
by a decrease in MC-2 count, and also by an increase in
the values δ
4
H , δH
5
and decrease in δH
and 3Jtrans values.
2
Taking into account the discussed above de-
pendences of these parameters on thiazolidine ring
structure, it is possible to say that the passage from the
preferred conformation with axial aryl and equatorial
carboxyl groups to the conformation with equatorial
aryl and axial carboxyl groups occurs. Simultaneously
content of (2S, 4R)-configuration in the diastereomers
mixture decreases (variable S/R in Fig. 2a) and
catalytic properties are strengthened: acetophenone
conversion and yields of ethers XVI and XVII grow.
The correlation of catalytic properties with the struc-
tural characteristics of thiazolidines reaches ~0.7.
The introduction of substituents into the benzene
ring ortho-position of (2S, 4R)-isomers leads to the
negative counts of MC-1 and MC-2 that corresponds to
a strong decrease in δH5', and also to an increase in δH
2
3
and to decrease in δH and Jcis. Changes in the
5
The sum of the obtained data allows an assumption
that in the catalytic cycle (2S, 4R)-isomers participate,
since the correlation between their structural param-
eters and catalytic properties is expressed to a greater
extent than for (2R, 4R)-isomers. According to the
factor analysis, the catalysis is more effective as the
number of donor substituents in meta- and para-
positions of benzene ring increases, and the intro-
duction of substituents into ortho-position or the presence
of meta-nitro group produces a negative effect.
structural variables in comparison with the compounds
located on the main sequence, indicate significant
interaction of substituents in the ortho-position of the
benzene fragment with thiazolidine ring. This, in
principle, agrees well with the formation of the hydro-
gen bond between the imine group of thiazolidine and
the hydroxy or methoxy group oxygen in the aryl
fragment, for whose formation a complete steric
freedom exists in (2S, 4R)-isomers. Furthermore, for
compounds III, V, and VII the correlation between the
structural parameters and side tetraphenyldisiloxane is
additionally observed (vector, which corresponds to an
increase in tetraphenyldisiloxane yield is clearly
directed to the described group side).
Simultaneously, it is experimentally shown that the
catalysts on the basis of [Rh(COD)Cl]2, in whose
coordination sphere 2-aryl-4-carboxy-1,3-thiazolidines
with an aryl fragment, benzene ring containing donor
substituent in para-position, are included, manifest the
greatest effectiveness for acetophenone hydrosilylation
by diphenylsilane.
The factor analysis for (2R, 4R)-isomers (Figs. 2b,
2d) shows that two high-order main components
describe only 77% of dispersion of set, but in this case
the complete dispersion of active structural variables
for (2R, 4R)-isomers proves to be 2.5 times less than
for (2S, 4R)-isomers. MC-1 and MC-2 satisfactorily
describe active variables, but the load on MC-2 and
EXPERIMENTAL
1
The Н and 13С NMR spectra were registered on
Bruker АС-200 and WM-400 instruments with
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CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
2017
accumulation at operating frequencies 400 (1Н) and
50 (13С) MHz in CDCl3 and (CD3)2SO without
additional references and the frequency stabilization on
the deuterium signal of the solvent. The Lorentz–
Gauss window function was applied to the free
induction decay for refining chemical shifts and the
deter-mination of the spin–spin coupling constants
(initial characteristic lines width in the spectra was
2 Hz), which made it possible to attain the half-width
of the lines of aliphatic protons of 0.4 Hz with the
retention of high signal/noise ratio. The IR spectra
were recorded on a Shimadzu FTIR-8400S spectro-
meter (4000–500 cm–1) from KBr pellets. Melting
points were measured in capillaries with the heating
rate 2 deg min–1.
2-Aryl(hetaryl)-4-carboxy-1,3-thiazolidines I–XV
were prepared by procedures [7, 11–14, 17] and used
in catalysis without additional purification.
2-Phenyl-4-carboxy-1,3-thiazolidine (I). Yield
78%, mp 140–142°С (decomp.) (154–155°С [17, 26],
157–159°С [27], 158-159°С [28, 29], 159–160°С [12,
30–32], 163–165°С [33], 166–171°С [13]). R/S ratio
equals 46/54. IR spectrum, cm–1: (ОН, NH) 3430 br; ν
(CH) 2962, 2928, 2877, 2745, 2704, 2659, 2605, 2558;
2469; ν(С=О, C=С) 1622, 1575; δ(NН) 1494; ν(C=С)
1475; δ(СН) 1450; 1436; 1425; 1381; 1307; ν(CN)
1237, 1210, 1138, 1078; 1014; δ(ОН) 921, 914; 857;
808; 767; δ(СН) 715; 695; 649; 620, 618; 583; 527;
502; 457.
1
(2R, 4R)-isomer. Н NMR [(CD3)2SO], δ, ppm:
3.063 d.d (1H, H5, J 10.3, 8.8 Hz), 3.368 d.d (1H, H5',
J 10.3, 7.2 Hz), 3.876 d.d (1H, H4, J 8.8, 7.2 Hz),
5.487 s (1H, H2), 7.360 m (2H, H3,5, Ph, J 7.5, 1.5 Hz),
7.501 m (2H, H2,6, Ph, J 7.5, 1.5 Hz), 7.316 m (1H, H4,
Ph, J 7.5, 1.5 Hz).
The factor analysis was performed using chemo-
metrics.xla plug-in to MS Excel, which was kindly
supplied by Prof. A.L. Pomerantsev (Institute of
Chemical Physic of Russian Academy of Sciences).
The acetophenone hydrosilylation with diphenylsilane
was carried out in THF solution; molar ratio aceto-
phenone:Ph2SiH2:catalyst:THF equaled 1:1.25:0.01:1.4.
Into a reactor were charged 0.0215 mmol of [Rh(COD)
Cl]2, THF, and acetophenone (Сc 1 mol %), 5- or 10-
fold excess of ligand relative to complex. The mixture
was kept for 5–15 min at room temperature and cooled
to 0°С. To this mixture was added diphenylsilane in
two equal portions. The reaction mixture was kept at
0°С for 2–3 h, after that the temperature was gradually
increased to ambient. The reaction progress was
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.127 d.d (1H, H5, J 10.4, 4.7 Hz), 3.289 d.d (1H,
H5', J 10.4, 7.1 Hz), 4.216 d.d (1H, H4, J 4.7, 7.1 Hz),
5.670 s (1H, H2), 7.316 m (2H, H3,5, Ph, J 7.5, 1.5 Hz),
7.425 m (2H, H2,6, Ph, J 7.5, 1.5 Hz), 7.250 m (1H, H4,
Ph, J 7.5, 1.5 Hz).
2-(2-Hydroxyphenyl)-4-carboxy-1,3-thiazolidine
(II). Yield 96 %, mp 151–154°С (decomp.) (164–166°С
[11], 171°С [34], 174–175°С [35]). R/S ratio equals
46/54. IR spectrum, cm–1: ν(ОН, NH) 3450–3400;
ν(CH) 3100, 2983, 2956, 2925, 2850, 2689, 2563; 2468;
ν(С=О, C=С) 1629, 1625, 1619, 1600, 1599, 1578,
1572, 1566, 1562; δ(NН) 1501; ν(C=С) 1471; δ(СН)
1460, 1454; 1390; 1383; 1332; ν(CN) 1238; 1152;
1097; 1063; 1039; δ(ОН) 937; 862; 783, 768, 758;
679; 489; 420.
1
monitored by Н NMR method. In order to isolate the
hydrolysis product to the reaction mixture was added
1 ml of methanol and after 1 h 5 ml of 1 М HCl solu-
tion, then the mixture was extracted with diethyl ether,
dried over MgSO4, passed through short column with
silica gel, and concentrated. The analysis of enantio-
1
meric composition was made by the Н NMR method
1
after the reaction of the obtained 1-phenylethanol with
(S)-(+)-α-methoxy-α-trifluoro-methylphenylacetyl chlo-
ride by procedure [24]. The enantiomeric excess was
determined by the ratio of methyl groups doublets of
the obtained diastereomers at δН 1.64 [J 6.6 Hz, (S,S)-
isomer] and 1.57 ppm [J 6.6 Hz, (S,R)-isomer], that
corresponds to (S)- and (R)-isomers of 1-phenylethanol.
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.057 d.d (1H, H5, J 10.1, 8.9 Hz), 3.327 d.d (1H,
H5', J 10.1, 6.6 Hz), 3.818 d.d (1H, H4, J 8.9, 7.0 Hz),
5.631 s (1H, H2), 6.782 d.t (1H, H5, Ph, J 7.7, 1.0 Hz),
6.833 d.d (1H, H3, Ph, J 7.7, 1.0 Hz), 7.112 d.t (1H,
H4, Ph, J 7.7, 1.8 Hz), 7.324 d.d (1H, H6, Ph, J 7.7,
1.8 Hz).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
In the experiments commercially available me-
thanol (Merk), diphenylsilane (Acros), chemically pure
acetophenone, THF, diethyl ether, L-cysteine and hydro-
chloric acid were used. [Rh(COD)Cl]2 was obtained as
reported in [25].
ppm: 3.144 d.d (1H, H5, J 10.1, 5.2 Hz), 3.191 d.d (1H,
H5', J 10.1, 6.6 Hz), 4.199 d.d (1H, H4, J 6.6, 5.2 Hz),
5.824 s (1H, H2), 6.741 d.t (1H, H5, Ph, J 7.7, 1.0 Hz),
7.782 d.d (1H, H3, Ph, J 7.7, 1.0 Hz), 7.041 d.t (1H,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 10 2010

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SKVORTSOV et al.
H4, Ph, J 7.7, 1.8 Hz) 7.282 d.d (1H, H6, Ph, J 7.7,
1.8 Hz).
equals 37/63. IR spectrum, cm–1: ν(ОН, NH) 3450–
3400; ν(CH) 3010, 2967, 2937–2920, 2853, 2833;
1735; ν(С=О) 1630; ν(C=С) and δ(NН) 1590, 1576,
1567; δ(NН) 1495; ν(C=С) 1460; 1430; 1384; 1347;
1308; 1281; ν(CN) 1240; 1211; ν(С–О) 1178; 1052;
1027; 949; 880; 862; 824; 800; 746; 700; 628; 442.
2-(3-Hydroxyphenyl)-4-carboxy-1,3-thiazolidine
(III). Yield 83%, mp 165–167°С (decomp.) (178–179°С
[7]). R/S-ratio equals 45/55. IR spectrum, cm–1: ν(ОН, NH)
3424 br; ν(CH) 3087, 3014, 2933, 2840, 2741, 2695,
2622, 2583, 2488; ν(С=О, C=С) 1629, 1626, 1620,
1595, 1591; δ(NН) 1503; ν(C=С) 1490; δ(СН) 1461;
1420; 1392; 1349; 1324, 1317; 1290; ν(CN) 1242;
1197; 1163; 1063; 1009; 995; 971; δ(ОН) 923; 866,
859; 818; 766; 733; 696; 627; 617; 598; 585; 541; 528;
501; 457; 442.
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 2.971 d.d (1H, H5, J 10.0, 9.0 Hz), 3.295 d.d (1H,
H5', J 10.0, 6.7 Hz), 3.699 s (3H, OCH3, C2, Ph), 3.735
s (3H, OCH3, C5, Ph), 3.844 d.d (1H, H4, J 9.0,
6.7 Hz), 5.640 s (1H, H2), 6.840 d.d (1H, H4, Ph, J 8.8,
3.3 Hz), 6.934 d (1H, H3, Ph, J 8.8 Hz), 7.122 d (1H,
H6, Ph, J 3.3 Hz).
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.039 d.d (1H, H5, J 10.3, 8.6 Hz), 3.348 d.d (1H,
H5', J 10.3, 7.2 Hz), 3.865 d.d (1H, H4, J 8.6, 7.2 Hz),
5.401 s (1H, H2), 6.705 d.t (1H, H4, Ph, J 8.2, 1.0 Hz),
6.893 m (1H, H6, Ph, J 7.6, 2.0 Hz), 6.900 m (1H, H2,
Ph, J 1.0, 2.0 Hz), 7.141 m (1H, H5, Ph, J 8.2, 7.6 Hz).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 2.967 d.d (1H, H5, J 10.2, 6.0 Hz), 3.127 d.d (1H,
H5', J 10.2, 6.7 Hz), 3.681 s (3H, OCH3, C2, Ph), 3.724
s (3H, OCH3, C5, Ph), 4.172 d.d (1H, H4, J 6.0,
6.7 Hz), 5.794 s (1H, H2), 6.767 d.d (1H, H4, Ph, J 8.9,
3.3 Hz), 6.877 d (1H, H3, Ph, J 8.9 Hz), 6.976 d (1H,
H6, Ph, J 3.3 Hz).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.097 d.d (1H, H5, J 10.3, 4.6 Hz), 3.257 d.d (1H,
H5', J 10.3, 6.9 Hz), 4.181 d.d (1H, H4, J 4.6, 6.9 Hz),
5.571 s (1H, H2), 6.642 m (1H, H4, Ph, J 8.2, 1.0 Hz),
6.824 m (1H, H6, Ph, J 7.6, 2.0 Hz), 6.834 m (1H, H2,
Ph, J 1.0, 2.0 Hz), 7.094 m (1H, H5, Ph, J 8.2, 7.6 Hz).
2-(3,4,5-Trimethoxyphenyl)-4-carboxy-1,3-thia-
zolidine (VI). Yield 80%, mp 146–148°С (decomp.).
R/S ratio 43/57. IR spectrum, cm–1: ν(ОН, NH) 3434
br; ν(CH) 3070, 2954, 2930, 2854, 2837; 1741;
ν(С=О) 1641; ν(C=С) 1593; δ(NН) 1512; ν(C=С)
1461; 1427; 1377; 1332; 1306; 1256; ν(CN) 1248;
1193; 1161; ν(C–O) and δ(С–О) 1132 s; 1010; 998;
993; 946; 838; 821; 657; 620; 499.
2-(4-Methoxyphenyl)-4-carboxy-1,3-thiazolidine
(IV). Yield 95%, mp 146–148°С (decomp.) (156–158°С
[11], 161–162°С [7], 163–164°С [29], 207–208°С
[36]). R/S ratio equals 47/53. IR spectrum, cm–1: ν(ОН, NH)
3440 br; ν(CH) 2960, 2915, 2839, 2757, 2668, 2605,
2478; ν(С=О, C=С) 1609, 1578; δ(NН) 1512; ν(C=С)
1463; δ(СН) 1440; 1422; 1379; 1307; 1295; 1258,
1247; ν(CN) 1236; 1210; ν(С–О) 1174; 1135; 1028,
1026; δ(ОН) 922; 862; 836; 809; 733; 697; 644; 610;
567; 523; 493.
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.071 d.d (1H, H5, J 9.8, 9.3 Hz), 3.321 d.d (1H,
H5', J 9.8, 6.8 Hz), 3.633 s (3H, OCH3, C4, Ph), 3.763 s
(6H, OCH3, C3,5, Ph), 3.853 d.d (1H, H4, J 9.3, 6.8 Hz),
5.419 s (1H, H2), 6.849 s (2H, H2,6, Ph).
1
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.057 d.d (1H, H5, J 10.0, 8.5 Hz), 3.347 d.d (1H,
H5', J 10.0, 7.2 Hz), 3.739 s (3H, OCH3), 3.856 d.d
(1H, H4, J 8.5, 7.2 Hz), 5.438 s (1H, H2), 6.910 m (2H,
H3,5, Ph, J 9.0, 2.0 Hz), 7.428 m (2H, H2,6, Ph, J 9.0,
2.0 Hz).
ppm: 3.154 d.d (1H, H5, J 10.3, 4.0 Hz), 3.283 d.d (1H,
H5', J 10.3, 7.2 Hz), 3.623 s (3H, OCH3, C4, Ph), 3.751
s (6H, OCH3, C3,5, Ph), 4.290 d.d (1H, H4, J 7.2,
4.0 Hz), 5.561 s (1H, H2), 6.759 s (2H, H2,6, Ph).
2-(2-Hydroxy-3-methoxyphenyl)-4-carboxy-1,3-
thiazolidine VII. Yield 86%, mp 147–149°С
(decomp.) (142–143°С [37]). R/S ratio equals 47/53.
IR spectrum, cm–1: ν(ОН, NH) 3250 br; ν(CH) 3107,
3025, 2987, 2975, 2959, 2944, 2840; ν(С=О, C=С)
1639, 1632; 1605; δ(NН) 1485; 1441; 1345; 1282;
ν(CN) 1237; 1183; 1159; ν(C–O) and δ(С–О) 1078,
1059; 983; 938; δ(ОН) 926; 838; 807; 768; 737; 699;
636; 489.
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.144 d.d (1H, H5, J 10.2, 4.0 Hz), 3.275 d.d (1H,
H5', J 10.2, 7.2 Hz), 3.726 s (3H, OCH3), 4.240 d.d
(1H, H4, J 7.2, 4.0 Hz), 5.583 s (1H, H2), 6.875 m (2H,
H3,5, Ph, J 9.0, 2.0 Hz), 7.358 m (2H, H2,6, Ph, J 9.0,
2.0 Hz).
2-(2,5-Dimethoxyphenyl)-4-carboxy-1,3-thiazolidine
(V). Yield 35%, mp 120–125°С (decomp.). R/S ratio
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 10 2010

CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
2019
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 2.952 d.d (1H, H5, J 10.0, 9.2 Hz), 3.329 d.d (1H,
H5', J 10.0, 6.9 Hz), 3.773 s (3H, OCH3, C3, Ph), 3.824
d.d (1H, H4, J 9.2, 6.9 Hz), 5.658 s (1H, H2), 6.756 d.d
(1H, H5, Ph, J 8.1, 7.7 Hz), 6.897 d.d (1H, H4, Ph,
J 8.1, 1.4 Hz), 6.942 d.d (1H, H6, Ph, J 7.7, 1.4 Hz).
(1С, CH3), 38.2 (1С, C5), 65.80 (1С, C4), 71.77 (1С, C2),
127.06 (2С, C3,5, Ph), 128.95 (2С, C2,6, Ph), 137.52
(1С, C4, Ph), 136.68 (1С, C1, Ph), 172.48 (1С, COO).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 2.264 s (3H, CH3), 3.127 d.d (1H, H5, J 10.3,
4.3 Hz), 3.273 d.d (1H, H5', J 10.3, 7.1 Hz), 4.219 d.d
(1H, H4, J 4.3, 7.1 Hz), 5.614 s (1H, H2), 7.118 m (2H,
H3,5, Ph, J 8.0, 2.0 Hz), 7.307 m (2H, H2,6, Ph, J 8.0,
2.0 Hz). 13С NMR spectrum [(CD3)2SO] δ, ppm: 20.63
(1С, CH3), 37.94 (1С, C5), 64.97 (1С, C4), 71.01 (1С,
C2), 126.77 (2С, C3,5, Ph), 128.67 (2С, C2,6, Ph).
135.95 (1С, C4, Ph), 138.25 (1С, C1, Ph), 173.02 (1С,
COO).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.005 d.d (1H, H5, J 10.2, 5.4 Hz), 3.186 d.d (1H,
H5', J 10.2, 6.7 Hz), 3.761 s (3H, OCH3, C3, Ph), 4.198
d.d (1H, H4, J 5.4, 6.7 Hz), 5.853 s (1H, H2), 6.718 d.d
(1H, H5, Ph, J 8.2, 7.7 Hz), 6.831 d.d (1H, H4, Ph,
J 8.2, 1.5 Hz), 6.912 d.d (1H, H6, Ph, J 7.7, 1.5 Hz).
2-(4-Hydroxy-3-methoxyphenyl)-4-carboxy-1,3-
thiazolidine (VIII). Yield 97%, mp 141–144°С
(decomp.) (164–166°С [11]). R/S ratio equals 48/52.
IR spectrum, cm–1: ν(ОН, NH) 3430–3400; ν(CH)
3053, 3006, 2972, 2925, 2853; 1741; ν(С=О, C=С)
1625, 1622, 1609, 1596; δ(NН) 1519; ν(C=С) 1467;
1452, 1440; 1380; 1334; 1292; 1277; ν(CN) 1248;
1216; 1160; ν и δ(С–О) 1135; 1049; 1028; 1001; 964;
δ(ОН) 919; 862; 847; 820; 797; 762; 652; 618; 561;
496.
2-(4-Ethylphenyl)-4-carboxy-1,3-thiazolidine (X).
Yield 61%, mp 146°С (decomp.). R/S ratio equals
46/54. IR spectrum, cm–1: ν(ОН, NH) 3450–3350;
ν(CH) 2962, 2929, 2867, 2760, 2614, 2473; ν(С=О,
C=С) and δ(NН) 1621, 1574; ν(C=С) 1475; ν(C=С)
and δ(СН) 1434; 1380; 1311; ν(CN) 1237; 1211; 1185;
1140; 1064; 1016; δ(ОН) 922; 860; 829; 771; 643;
610; 486.
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 1.157 t (3H, CH3, J 7.5 Hz), 2.583 m (2H,
CH2CH3, J 7.5 Hz), 3.050 d.d (1H, H5, J 10.0, 8.8 Hz),
3.355 d.d (1H, H5', J 10.0, 7.2 Hz), 3.858 d.d (1H, H4,
J 8.8, 7.2 Hz), 5.452 s (1H, H2), 7.193 m (2H, H3,5, Ph,
J 8.0, 2.0 Hz), 7.402 m (2H, H2,6, Ph, J 8.0, 2.0 Hz).
ppm: 3.045 d.d (1H, H5, J 9.8, 8.9 Hz), 3.323 d.d (1H,
H5', J 9.8, 7.1 Hz), 3.755 s (3H, OCH3, C3, Ph), 3.828
d.d (1H, H4, J 8.9, 7.1 Hz), 5.383 s (1H, H2), 6.717 d
(1H, H5, Ph, J 8.1 Hz), 6.875 d.d (1H, H6, Ph, J 8.1,
2.1 Hz), 7.100 d (1H, H2, Ph, J 2.1 Hz).
1
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.153 d.d (1H, H5, J 10.4, 3.8 Hz), 3.267 d.d (1H,
H5', J 10.4, 7.3 Hz), 3.743 s (3H, OCH3, C3, Ph), 4.276
d.d (1H, H4, J 3.8, 7.3 Hz), 5.513 s (1H, H2), 6.828 d
(1H, H6, Ph, J 8.1 Hz), 6.688 d.d (1H, H5, Ph, J 8.1,
2.3 Hz), 7.009 d (1H, H2, Ph, J 2.3 Hz).
ppm: 1.149 t (3H, CH3, J 7.5 Hz), 2.565 m (2H,
CH2CH3, J 7.5 Hz), 3.126 d.d (1H, H5, J 10.2, 4.5 Hz),
3.275 d.d (1H, H5', J 10.2, 7.1 Hz), 4.220 d.d (1H, H4,
J 4.5, 7.1 Hz), 5.620 s (1H, H2), 7.150 m (2H, H3,5, Ph,
J 8.0, 2.0 Hz), 7.332 m (2H, H2,6, Ph, J 8.0, 2.0 Hz).
2-(4-Isopropylphenyl-4-carboxy-1,3-thiazolidine
(XI). Yield 66%, mp 128–130°С (decomp.). R/S ratio
equals 46/54. IR spectrum, cm–1: ν(ОН, NH) 3400 br;
ν(CH) 2963, 2925, 2888, 2874, 2713, 2596; 2473;
1708; ν(С=О, C=С) and δ(NН) 1580, 1572; ν(C=С)
and δ(СН) 1467, 1425; 1382; 1301; ν(CN) 1235; 1210;
1137; 1063; 1015; δ(ОН) 921; 860; 829; 809; 753;
692; 638; 607; 562; 548; 491; 419.
2-(4-Tolyl)-4-carboxy-1,3-thiazolidine (IX). Yield
90%, mp 154–155°С (decomp.) (144–145°С [32],
185°С [38]). R/S ratio equals 47/53. IR spectrum, cm–1:
ν(ОН, NH) 3440 br; ν(CH) 3025, 2961, 2924, 2872,
2715, 2674, 2614, 2478; ν(С=О, C=С) and δ(NН)
1628, 1579, 1572; ν(C=С) and δ(СН) 1434; 1383;
1309; ν(CN) 1237; 1212; 1184; 1140; 1014; δ(ОН)
921; 861; 815; 785; 724; 641; 606; 561; 476; 409.
1
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 2.287 s (3H, CH3), 3.045 d.d (1H, H5, J 10.1,
8.8 Hz), 3.353 d.d (1H, H5', J 10.1, 7.2 Hz), 3.853 d.d
(1H, H4, J 8.8, 7.2 Hz), 5.433 s (1H, H2), 7.161 m (2H,
H3,5, Ph, J 8.0, 2.0 Hz), 7.377 m (2H, H2,6, Ph, J 8.0,
2.0 Hz). 13С NMR spectrum [(CD3)2SO] δ, ppm: 20.60
ppm: 1.170 t (6H, CH3, J 7.0 Hz), 2.866 m (1H,
CHCH3, J 7.0 Hz), 3.050 d.d (1H, H5, J 9.9, 8.7 Hz),
3.355 d.d (1H, H5', J 9.9, 7.2 Hz), 3.860 d.d (1H, H4,
J 8.7, 7.2 Hz), 5.451 s (1H, H2), 7.224 m (2H, H3,5, Ph,
J 8.0, 2.0 Hz), 7.408 m (2H, H2,6, Ph, J 8.0, 2.0 Hz).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 10 2010

2020
SKVORTSOV et al.
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 1.179 t (6H, CH3, J 7.0 Hz), 2.848 m (1H,
CHCH3, J 7.0 Hz), 3.125 d.d (1H, H5, J 10.4, 4.4 Hz),
3.275 d.d (1H, H5', J 10.4, 7.2 Hz), 4.218 d.d (1H, H4,
J 4.4, 7.2 Hz), 5.621 s (1H, H2), 7.180 m (2H, H3,5, Ph,
J 8.0, 2.0 Hz), 7.338 m (2H, H2,6, Ph, J 8.0, 2.0 Hz).
N-Acetyl-2-phenyl-4-carboxy-1,3-thiazolidine
(XIV). Yield 69%, mp 123–126°С (decomp.) (151–
152°С [33]). R/S ratio equals 61/39. IR spectrum, cm–1:
ν(ОН, NH) 3440 br; ν(CH) 3059, 3027, 2969, 2922,
2841, 2585; ν(С=О) 1725, 1721, 1708; ν(С=О, C=С),
δ(NН) 1604, 1598; δ(СН) 1420, 1408; 1352; ν(CN)
1239, 1200, 1172; 1129; 940; 890; 833; 796; 734, 727,
700; 683; 600; 436; 419.
2-(4-Fluorophenyl)-4-carboxy-1,3-thiazolidine
(XII). Yield 85%, mp 160°С (decomp.) (166°С [7]).
R/S ratio equals 44/56. IR spectrum, cm–1: ν(ОН, NH)
3500–3400; ν(CH) 3025, 2942; ν(С=О, C=С) and
δ(NН) 1639, 1635, 1630, 1619, 1611, 1605; ν(C=С)
and δ(СН) 1513, 1510; 1438; 1381; 1334; 1313, 1311;
1270; ν(CN) 1231; 1167; 1102; 1052; ν(СF) 1003;
878; 864; 846; 832; 815; 792; 608; 547; 529; 507, 419.
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: conformer А (41%) 1.783 s (3H, CH3), 3.071 d.d
(1H, H5, J 12.0, 7.9 Hz), 3.38–3.46 (1H, H5'), 4.704 d.d
(1H, H4, J 7.9, 6.5 Hz), 6.367 s (1H, H2), 7.17–7.39
(3H, Ph), m 7.685 (2H, H2,6, Ph, J 7.5 Hz); conformer
B (20%) 2.045 s (3H, CH3), 3.30–3.46 (2H, H5,5'),
5.145 d.d (1H, H4, J 6.8, 3.7 Hz), 6.153 s (1H, H2),
7.17–7.39 (3H, Ph), m 7.488 (2H, H2,6, Ph, J 7.5 Hz).
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.066 d.d (1H, H5, J 9.9, 9.1 Hz), 3.349 d.d (1H,
H5', J 9.9, 7.1 Hz), 3.868 d.d (1H, H4, J 9.1, 7.1 Hz),
5.490 s (1H, H2), 7.178 m (2H, H3,5, Ph, J 8.6, 3.2; JHF
8.8 Hz), 7.561 m (2H, H2,6, Ph, J 8.6, 3.2; JHF 5.6 Hz).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: conformer C (21%) 1.744 s (3H, CH3), 3.14–
3.19 (1H, H5), 3.30–3.46 (1H, H5'), 5.107 d (1H, H4,
J 6.9 Hz), 6.367 s (1H, H2), 7.17–7.39 (5H, Ph);
conformer D (18%) 1.783 s (3H, CH3), 3.14–3.19 (1H,
H5), 3.30–3.46 (1H, H5'), 5.337 d.d (1H, H4, J 6.3,
1.0 Hz), 6.137 s (1H, H2), 7.17–7.39 (5H, Ph).
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.118 d.d (1H, H5, J 10.2, 4.5 Hz), 3.285 d.d (1H,
H5', J 10.2, 7.0 Hz), 4.191 d.d (1H, H4, J 4.5, 7.0 Hz),
5.658 s (1H, H2), 7.136 m (2H, H3,5, Ph, J 8.6, 3.2; JHF
8.8 Hz), 7.467 m (2H, H2,6, Ph, J 8.6, 3.2; JHF 5.6 Hz).
2-(5'-Methyl-2'-furyl)-4-carboxy-1,3-thiazolidine
(XV). Yield 52%, mp 111°С (decomp.). R/S ratio
equals 36/64. IR spectrum, cm–1: ν(ОН, NH) 3434 br;
2-(3-Nitrophenyl)-4-carboxy-1,3-thiazolidine
(XIII). Yield 20%, mp 150–152°С (decomp.) (151–
153°С [37], 154–156°С [14]). R/S ratio equals 36/64.
IR spectrum, cm–1: ν(ОН, NH) 3460–3410; ν(CH)
3098, 3056, 3006, 2923; ν(С=О, C=С) and δ(NН)
1631, 1625, 1621; ν(NО, C=С) and δ(СН) 1537, 1530;
1395; 1370, 1362; ν(NО2) 1350; 1327; 1298; ν(CN)
1253; 1197; 1138; 1000; 959; 909; ν(СN) 848, 841;
807, 805; 748; 697; 628; 419.
ν
asym(CH) 2978, 2944, 2917; νsym(CH) 2861; ν(CH)
2748, 2590; 1731; 1618, 1615; ν(С=О, C=С) and
δ(NН) 1572, 1568, 1553; δ(СН) 1437; 1380; 1360;
1318; 1290; ν(CN) 1237; 1221; 1166; 1138; 1058;
1021; 1004; 956; 856; 835; 835; 797; 789; 627; 595;
514; 477.
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 2.239 s (3Н, СН3), 2.960 d.d (1H, H5, J 10.0,
8.9 Hz), 3.327 d.d (1H, H5', J 10.0, 7.2 Hz), 3.827 d.d
(1H, H4, J 8.9, 7.2 Hz), 5.528 s (1H, H2), 6.017 d (2H,
H5, furyl, J 3.2 Hz), 6.341 d (1H, H4, furyl, J 3.2 Hz).
13С NMR spectrum [(CD3)2SO] δ, ppm: 13.19 (1С,
CH3), 38.0 (1С, C5), 64.31 (1С, C4), 65.00 (1С, C2),
106.51 (1С, C4, furyl), 108.32 (1С, C3, furyl), 149.19
(1С, C5, furyl), 151.61 (1С, C2, furyl), 172.07 (1С,
COO).
1
(2R, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.116 d.d (1H, H5, J 10.0, 8.9 Hz), 3.348 d.d (1H,
H5', J 10.0, 6.7 Hz), 3.936 d.d (1H, H4, J 8.9, 6.7 Hz),
5.656 s (1H, H2), 7.633 d.d (1H, H5, Ph, J 8.1, 6.7 Hz),
7.947 m (1H, H6, Ph, J 6.7, 2.0, 0.8 Hz), 8.151 m (1H,
H4, Ph, J 8.1, 2.4, 0.8 Hz), 8.431 d.d (1H, H2, Ph, J 2.4,
2.0 Hz).
1
1
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
(2S, 4R)-isomer. Н NMR spectrum [(CD3)2SO], δ,
ppm: 3.092 d.d (1H, H5, J 10.2, 5.5 Hz), 3.317 d.d (1H,
H5', J 10.2, 6.9 Hz), 4.114 d.d (1H, H4, J 5.5, 6.9 Hz),
5.853 s (1H, H2), 7.603 d.d (1H, H5, Ph, J 7.9, 6.6 Hz),
7.853 m (1H, H6, Ph, J 6.6, 2.0, 1.0 Hz), 8.097 m (1H,
H4, Ph, J 7.9, 2.2, 1.0 Hz), 8.270 d.d (1H, H2, Ph, J 2.2,
2.0 Hz).
ppm: 2.209 s (3Н, СН3), 2.970 d.d (1H, H5, J 10.1,
6.0 Hz), 3.268 d.d (1H, H5', J 10.1, 6.8 Hz), 4.088 d.d
(1H, H4, J 6.0, 6.8 Hz), 5.659 s (1H, H2), 5.955 d (2H,
H5, furyl, J 3.1 Hz), 6.193 d (1H, H4, furyl, J 3.1 Hz).
13С NMR spectrum [(CD3)2SO] δ, ppm: 13.19 (1С,
CH3), 37.62 (1С, C5), 63.99 (1С, C4), 64.49 (1С, C2),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 10 2010

CONFORMATIONAL ANALYSIS, SPECTRAL AND CATALYTIC PROPERTIES
2021
106.21 (1С, C4, furyl), 107.21 (1С, C3, furyl), 151.06
(1С, C5, furyl), 152.25 (1С, C2, furyl), 172.44 (1С,
COO).
19. Perspektivy gidrosililirovania (Hydrosilylation Pros-
pects), Lukevits, E., Ed., Riga: Inst. Org. Sinteza Latv.
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Pawluć, P., Advances in Silicon Science, Marciniec, B.,
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ACKNOWLEDGMENTS
This work was financially supported by the Russian
Foundation for Basic Research (grant no. 07-03-
00823а, 09-03-00341а), St. Petersburg Government
(МКN/15-05/005) and Program of President of
Russian Federation (МKN/15-05/005).
21. Uvarov, V.M., de Vekki, D.А., Reshetilovskii, V.P., and
Skvortsov, N.K., Zh. Obshch. Khim., 2010, vol. 80,
no. 1, p. 39.
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