Synthesis and structure of (thio)semicarbazonocyclohexanedicarboxylates. Crystalline and molecular structure of diethyl 4-hydroxy-4-methyl-2-phenyl-6-thiosemicarbazonocyclohexane-1,3-dicarboxylate

Article abstract of DOI:10.1134/S1070428009120070

Diethyl 2-aryl-4-hydroxy-4-methyl-6-(thio)semicarbazonocyclohexane-1,3-dicarboxylates were synthesized, and their structure was determined by ¹H and ¹³C NMR spectroscopy, including the HSQC technique. The molecular and crystalline st

Full text of DOI:10.1134/S1070428009120070

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 12, pp. 1790–1794. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © N.V. Poplevina, A.P. Kriven’ko, O.A. Shchelochkova, A.G. Golikov, S.F. Solodovnikov, 2009, published in Zhurnal Organicheskoi
Khimii, 2009, Vol. 45, No. 12, pp. 1796–1799.
Synthesis and Structure of (Thio)semicarbazonocyclohexane-
dicarboxylates. Crystalline and Molecular Structure of Diethyl
4-Hydroxy-4-methyl-2-phenyl-6-thiosemicarbazonocyclohexane-
1,3-dicarboxylate
N. V. Poplevinaa, A. P. Kriven’koa, O. A. Shchelochkovab,
A. G. Golikova, and S. F. Solodovnikovc
a Chernyshevskii Saratov State University, ul. Astrakhanskaya 83-1, Saratov, 410012 Russia
e-mail: PoplevinaNV@mail.ru
b Saratov State Medical University, Saratov, Russia
с Nikolaev Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
Received April 2, 2009
Abstract—Diethyl 2-aryl-4-hydroxy-4-methyl-6-(thio)semicarbazonocyclohexane-1,3-dicarboxylates were
1
synthesized, and their structure was determined by H and 13C NMR spectroscopy, including the HSQC
technique. The molecular and crystalline structure of diethyl 4-hydroxy-4-methyl-6-thiosemicarbazono-
2-phenylcyclohexane-1,3-dicarboxylate was determined by X-ray analysis.
DOI: 10.1134/S1070428009120070
Polycarbonyl compounds of the dialkyl 2-aryl-4-
hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarbox-
ylate series (β-keto esters) are used as model structures
for stereochemical studies and keto–enol transforma-
tions, as well as intermediate products in the synthesis
of carbo- and heterocyclic systems [1–3]. Their reac-
tions with nitrogen-centered nucleophiles have been
well documented; depending on the nucleophile struc-
ture, these reactions lead to the formation of enamines,
oximes, fused heterocycles, and heterocyclic spiro
compounds whose structure was determined by spec-
tral methods and X-ray analysis [4–7].
Reactions of such β-keto esters with thiosemicar-
bazides have been studied in the recent years [3, 8];
1
however, the available spectral data (IR, H NMR) are
clearly insufficient to unambiguously assign the struc-
Scheme 1.
O
Ar
O
O
O
Ar
O
N
H2NC(=X)NHNH2
OEt
EtO
HO
OEt
EtO
HO
Me
H
N
NH2
Me
X
Ia–Ie
IIa–IIf (A)
O
Ar
O
O
Ar
O
OEt
OEt
EtO
HO
Me
EtO
HO
Me
H
N
H
N
NH2
X
N
H
HN
NH
X
B
C
Ia, IIa, IIb, Ar = Ph; Ib, IIc, Ar = 4-MeOC6H4; Ic, IId, Ar = 3-O2NC6H4; Id, IIe, Ar = 4-HO-3-MeOC6H3;
Ie, IIf, Ar = 2-thienyl; X = S (a), O (b–f).
1790

SYNTHESIS AND STRUCTURE OF (THIO)SEMICARBAZONOCYCLOHEXANE-...
1791
δ, ppm
1.0
1.5
2.0
2.5
3.0
3.5
4.0
60
55
50
45
40
35
30
25
20
δC, ppm
Fig. 1. A fragment of the HSQC spectrum of diethyl 4-hydroxy-4-methyl-2-phenyl-6-thiosemicarbazonocyclohexane-
1,3-dicarboxylate (IIa).
ture of the reaction products (thiosemicarbazone A,
thiosemicarbazide B, or spirane C). Therefore, addi-
tional studies using 13C NMR spectroscopy (including
double resonance techniques) and X-ray analysis are
necessary.
cannot distinguish between thiosemicarbazone A and
spiro structure C. Valuable information was obtained
from the 13C NMR spectrum (DMSO-d6) which con-
tained 10 signals from sp3-hybridized carbon atoms
and one signal assignable to sp2-carbon atom (C6,
δC 151 ppm); this spectral pattern is consistent with
thiosemicarbazone structure A and excludes isomeric
structures B and C where 9 and 11 sp3-carbon atoms
are present, respectively. Detailed signal assignment
was made on the basis of the two-dimensional HSQC
spectrum (Fig. 1). It contained the following cross
peaks: 1-H/C1 (δ 3.63/δC 56.3 ppm), 2-H/C2
(3.05/57.1), 3-H/C3 (3.73/44.6), 5-Hax/C5 (2.26/41.0),
In the present article we present new data on the
structure of the reaction product of diethyl 4-hydroxy-
4-methyl-6-oxo-2-phenylcyclohexane-1,3-dicarbox-
ylate (Ia) with thiosemicarbazide, as well as on reac-
tions of β-keto esters I with semicarbazide, which were
not reported previously. Diethyl 4-hydroxy-4-methyl-
6-thiosemicarbazono-2-phenylcyclohexane-1,3-dicar-
boxylate (IIa) was obtained in 79% yield by reaction
of keto diester Ia with thiosemicarbazide according to
the known procedure [8] (heating in boiling ethanol
using 1.5 equiv of the nucleophile), and its structure
C19
C18
C13
C14
C15
O2
1
was determined on the basis of the H and 13C NMR,
C12
C11
HSQC, and X-ray diffraction data.
O5
O4
1
C17
C4
The H NMR spectrum of IIa (DMSO-d6) con-
C16
C3
tained singlets from three NH protons at δ 6.71, 8.20,
and 10.4 ppm and hydroxy proton at δ 4.61 ppm;
methylene protons on C5 resonated as doublets at
C9
C8
C2
C1
C7
N3
C20
N1
O3
O1
C10
2
C5
N2
δ 2.26 and 3.22 ppm with a coupling constant J of
C6
14 Hz, and the 2-H signal was a doublet at δ 3.05 ppm
with a coupling constant J of 12 Hz; and the 1-H and
3-H protons together with OCH2 protons in the ester
moiety give rise to a multiplet at δ 3.61–3.75 ppm. The
presence of a signal from 1-H rules out one of the
possible structures, thiosemicarbazide B, but we still
S1
Fig. 2. Structure of the molecule of diethyl 4-hydroxy-4-
methyl-2-phenyl-6-thiosemicarbazonocyclohexane-1,3-di-
carboxylate (IIa) according to the X-ray diffraction data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 12 2009

POPLEVINA et al.
1792
and 5-Heq/C5 (3.22/41.0). Thus the above data indicat-
ed that compound IIa in DMSO-d6 has thiosemicarba-
zone structure A.
9.25 ppm), a diffuse doublet from the NH2 group
(δ 5.53–6.28 ppm), and a singlet from the hydroxy
proton (δ 4.34–4.55 ppm). Compound IIb displayed in
the 13C NMR spectrum (DMSO-d6) 10 signals from
sp3-hybridized carbon atoms. The C6 atom resonated at
δC 147 ppm. The HSQC spectrum of IIb (DMSO-d6)
revealed the following cross peaks formed by directly
coupled 1H and 13C nuclei: 1-H/C1 (δ 3.64/δC 56.1 ppm),
2-H/C2 (3.00/57.2), 3-H/C3 (3.64/44.8), 5-Hax/C5
(2.16/40.0), 5-Heq/C5 (3.07/40.0).
Thiosemicarbazone IIa crystallized to form well-
defined crystals, and its molecular conformation was
determined on the basis of the X-ray diffraction data
(Fig. 2). The C5 atom (for atom numbering, see Fig. 2)
has sp2-hybridization: the bond angle N1C5C4 is 116°,
and the C5–N1 bond length is 1.28 Å. The thiosemicar-
bazone fragment is almost planar: the torsion angle
C5N1N2C20 is –178.2°. The cyclohexane ring adopts
a distorted chair conformation, and the torsion angles
C6C1C2C3 (–61.6°) and C1C2C3C4 (61.4°) approach
those in analogous cyclohexane conformer.
We can conclude that products of the reactions of
β-keto diesters I with thiosemicarbazide and semicar-
bazide have (thio)semicarbazone structure.
EXPERIMENTAL
All substituents in the cyclohexane ring, except for
the hydroxy group, occupy equatorial positions. The
hydrogen atoms on C2 and C3, as well as on C3 and C4,
occupy axial positions and are arranged trans with
respect to each others. This follows from the torsion
angles between the corresponding ester fragment and
phenyl substituent: C8C2C3C11 –51.8°, C11C3C4C17
56.5°. Molecules IIa in crystal are characterized by
weak intramolecular hydrogen bond O1–H1 · · · O2
(O2 ···H1 2.47, O1 ···O2 3.09 Å) and intermolecular
hydrogen bonds N2–H2···O2′ (O2′···H2 2.25, N2···O2′
3.08 Å) and N3–H3 ···O4′ (O4′ ···H3 2.23, N3 ···O4′
3.03 Å). Intermolecular hydrogen bonds give rise to
a three-dimensional network. Thus compound IIa has
thiosemicarbazone structure A both in solution in
DMSO-d6 and in the crystalline state.
The IR spectra were recorded in KBr on an FSM-
1201 spectrometer with Fourier transform. The 1H and
13C NMR spectra, and two-dimensional HSQC spectra
were recorded on Bruker AM-200 (200 MHz), Bruker
MSL-400 (400 MHz), and Varian 400 spectrometers
using DMSO-d6 as solvent and tetramethylsilane as
internal reference.
The X-ray diffraction data for a 0.18×0.14×0.12-
mm single crystal of compound IIa were acquired at
room temperature on a Bruker Nonius X8 Apex auto-
matic diffractometer equipped with a two-dimensional
CCD detector (λMoKα irradiation, graphite monochro-
mator, φ-scanning through a step of 0.5°, Bragg angle
range 2.50° ≤ θ ≤ 27.50°). Total of 16745 reflection
intensities were measured over one half of the recipro-
cal space sphere; among these, 5031 reflections were
independent (Rint = 0.0195). Monoclinic crystal sys-
tem; C20H27N3O5S; M 421.51; space group P21/n; unit
cell parameters: a = 9.5131(4), b = 16.8601(6), c =
12.1904(4) Å; β = 101.748(1)°, V = 2195.78(14) Å3;
Z = 4; dcalc = 1.275 g/cm3. No correction for absorption
was introduced, taking into account small value of the
linear absorption coefficient (μ = 0.182 mm–1).
The reactions of β-keto esters Ia–Ie with semicar-
bazide were carried out following a modified proce-
dure. Taking into account instability of semicarbazide
as free base, it was used as hydrochloride, and the free
base was generated by adding potassium hydroxide. As
a result, we isolated the corresponding semicarbazones
IIb–IIe in high yield (81–90%).
The spectral parameters of semicarbazones IIb–IIe
were similar to those of thiosemicarbazone IIa. Their
IR spectra contained absorption bands at 1703–
1726 cm–1, belonging to stretching vibrations of un-
conjugated ester carbonyl groups, two bands due to
primary amino group (3082–3206 cm–1), and a band
corresponding to secondary amino group (3314–
The structure was solved by the direct method
using SHELXS-97 software [9] and was refined by
full-matrix least-squares procedure in anisotropic ap-
proximation for non-hydrogen atoms using SHELXL-
97 software package [10]. All hydrogen atoms were
localized by the Fourier difference syntheses, and their
positions were refined with isotropic thermal param-
eters. The final divergence factors were R = 0.0450,
wR2 = 0.1195 for 3857 reflections with F ≥ 4σ(F) (with
respect to Fhkl; 371 varied parameters) and R = 0.0636,
wR2 = 0.1379 for all independent reflections (5031);
goodness of fit S = 1.058.
1
3364 cm–1). In the H NMR spectra of compounds
IIb–IIe in DMSO-d6 we observed doublets from axial
and equatorial qprotons on C5 (δ 2.11–2.22 and 2.49–
3.11 ppm, J = 14–15 Hz), signals from 2-H (δ 2.90–
3.17 ppm), 1-H, and 3-H (δ 3.49–3.83 and 3.49–
3.80 ppm), a singlet from the NH proton (δ 9.21–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 12 2009

SYNTHESIS AND STRUCTURE OF (THIO)SEMICARBAZONOCYCLOHEXANE-...
1793
Diethyl 4-hydroxy-4-methyl-2-phenyl-6-thio-
semicarbazonocyclohexane-1,3-dicarboxylate (IIa)
was synthesized according to the procedure described
in [8]. Yield 79%, colorless crystals, mp 160–161°C
[8]. Single crystals suitable for X-ray analysis were
obtained by slowly cooling a solution of IIa in ethanol.
1H NMR spectrum, δ, ppm: 0.78 t and 0.90 t (3H each,
CH2CH3, J = 7.0 Hz), 1.23 s (3H, 4-CH3), 2.26 d (1H,
5-Hax, J = 14 Hz), 3.05 d (1H, 2-H, J = 12 Hz), 3.22 d
(1H, 5-Heq, J = 14 Hz), 3.61–3.75 m (4H, 1-H, 3-H,
OCH2), 3.79–3.87 m (2H, OCH2), 4.61 s (1H, OH),
6.71 s (1H, NH), 7.12–7.26 m (5H, Ph), 8.20 s (1H,
NH), 10.4 s (1H, NH). 13C NMR spectrum, δC, ppm:
13.6 and 13.8 (CH2CH3), 28.3 (4-CH3), 44.6 (C3), 55.6
(C1), 56.6 (C2), 59.2 and 59.5 (OCH2), 71.1 (C4); 127,
128, 129, 140 (Carom); 151 (C6), 169 and 170 (C=O),
179 (C=S). HSQC spectrum, δ, ppm/δC, ppm:
0.78/14.0 (CH2CH3), 0.90/14.5 (CH2CH3), 1.23/28.6
(4-CH3), 2.26/41.0 (5-Hax/C5), 3.05/57.1 (2-H/C2),
3.22/41.0 (5-Heq/C5), 3.63/44.6 (3-H/C3), 3.73/56.3
(H1/C1), 3.63/59.9 (OCH2), 3.73/60.1 (OCH2);
7.13/127, 7.20/128, 7.23/129 (CHarom).
(CHarom). Found, %: C 59.38; H 6.72; N 9.76.
C20H27N3O6. Calculated, %: C59.25; H 6.71; N 10.36.
Compounds IIc–IIf were synthesized in a similar
way.
Diethyl 4-hydroxy-2-(4-methoxyphenyl)-4-meth-
yl-6-semicarbazonocyclohexane-1,3-dicarboxylate
(IIc). Yield 90%, colorless crystals, mp 211–212°C
(from EtOH). IR spectrum (KBr), ν, cm–1: 3497 (OH);
3363 (NH); 3088, 3182 (NH2); 1715 (C=O, ester);
1
1672 (C=O, amide); 1561 (C=N). H NMR spectrum,
δ, ppm: 0.87 t and 1.00 t (3H each, CH2CH3, J =
6.8 Hz), 1.23 s (3H, 4-CH3), 2.13 d (1H, 5-Hax, J =
14 Hz), 2.90–2.95 m (1H, 2-H), 3.08 d (1H, 5-Heq, J =
14 Hz), 3.51–3.58 m (2H, 1-H, 3-H), 3.69 s (3H,
OCH3), 3.76 q (2H, OCH2, J = 7.2Hz), 3.82–3.90 m
(2H, OCH2), 4.34 s (1H, OH), 5.66–6.22 br.d (NH2),
6.75 d and 7.15 d (2H each, C6H4), 9.22 s (1H, NH).
Found, %: C 58.60; H 6.74; N 9.77. C21H29N3O7. Cal-
culated, %: C 58.49; H 7.26; N 9.34.
Diethyl 4-hydroxy-4-methyl-2-(3-nitrophenyl)-6-
semicarbazonocyclohexane-1,3-dicarboxylate (IId).
Yield 89%, colorless crystals, mp 207–210°C (from
EtOH). IR spectrum, ν, cm–1: 3477 (OH); 3314 (NH);
3150, 3206 (NH2); 1715–1730 (C=O); 153 (C=N).
1H NMR spectrum, δ, ppm: 0.85 t (3H, CH2CH3, J =
6.8 Hz), 0.98 t (3H, CH2CH3, J = 7.4 Hz), 1.27 s (3H,
4-CH3), 2.22 d (1H, 5-Hax, J = 14 Hz), 3.11 d (1H,
5-Heq, J = 14 Hz), 3.14–3.17 m (1H, 2-H), 3.75–
3.83 m (3H, 1-H, OCH2), 3.85–3.93 m (3H, 3-H,
OCH2), 4.55 s (1H, OH), 5.62–6.16 br.d (NH2); 7.55 t,
7.73 d, 8.04 d, and 8.20 s (4H, C6H4); 9.25 s (1H, NH).
Found, %: C 53.84; H 5.72; N 12.32. C20H26N4O8. Cal-
culated, %: C 55.05; H 5.69; N 12.84.
Diethyl 4-hydroxy-4-methyl-2-phenyl-6-semicar-
bazonocyclohexane-1,3-dicarboxylate (IIb). A solu-
tion of 0.97 g (8.7 mmol) of semicarbazide hydro-
chloride and 0.49 g (8.7 mmol) of potassium hydroxide
in 2 ml of water was added to a solution of 2 g
(5.8 mmol) of compound Ia in 50 ml of ethanol, and
the mixture was heated for 1 h under reflux. After
cooling, the precipitate was filtered off, washed with
water, propan-2-ol, and diethyl ether, and dried under
reduced pressure. Yield 1.97 g (85%), colorless crys-
tals, mp 201–203°C (from EtOH). IR spectrum, ν,
cm–1: 3501 (OH); 3353 (NH); 3088, 3183 (NH2); 1713,
1719 (C=O, ester); 1676 (C=O, amide); 1560 (C=N).
1H NMR spectrum, δ, ppm: 0.83 t and 0.97 t (3H each,
CH2CH3, J = 6.8 Hz), 1.25 s (3H, 4-CH3), 2.16 d (1H,
5-Hax, J = 14 Hz), 2.99–3.04 m (1H, 2-H), 3.10 d (1H,
5-Heq, J = 15 Hz), 3.62–3.68 m (2H, 1-H, 3-H), 3.75 q
(2H, OCH2, J = 6.8 Hz), 3.82–3.92 m (2H, OCH2),
4.36 s (1H, OH), 5.53–6.19 br.d (NH2), 7.13–7.25 m
(5H, Ph), 9.25 s (1H, NH). 13C NMR spectrum, δC,
ppm: 13.7 and 14.0 (CH2CH3), 28.5 (4-CH3), 44.4
(C3), 55.8 (C1), 56.8 (C2), 59.3 and 59.5 (OCH2), 71.0
(C4); 127, 128, 129, 141 (Carom); 147 (C6), 157 (C=O,
amide), 169 and 171 (C=O, ester). HSQC spectrum,
δ, ppm/δC, ppm: 0.80/14.1 (CH2CH3), 0.93/14.5
(CH2CH3), 1.20/29.2 (4-CH3), 2.16/40.0 (5-Hax/C5),
3.00/57.2 (2-H/C2), 3.07/40.0 (5-Heq/C5), 3.64/44.8
(3-H/C3), 3.64/56.1 (1-H/C1), 3.81/59.4 (OCH2),
3.82/60.0 (CH2); 7.16/127, 7.17/128, 7.20/129
Diethyl 4-hydroxy-2-(4-hydroxy-3-methoxy-
phenyl)-4-methyl-6-semicarbazonocyclohexane-1,3-
dicarboxylate (IIe). Yield 90%, colorless crystals,
mp 186–187°C (from EtOH). IR spectrum, ν, cm–1:
3480 (OH); 3441 (OHarom); 3320 (NH); 3150, 3206
1
(NH2); 1726 (C=O), 1545 (C=N). H NMR spectrum,
δ, ppm: 0.89 t and 1.02 t (3H each, CH2CH3, J =
6.8 Hz), 1.23 s (3H, 4-CH3), 2.11 d (1H, 5-Hax, J =
15 Hz), 2.95 d (1H, 2-H, J = 10 Hz), 3.07 d (1H, 5-Heq,
J = 15 Hz), 3.49–3.59 m (2H, 1-H, 3-H), 3.72 s (3H,
OCH3), 3.79 q (2H, OCH2, J = 7.2 Hz), 3.86–3.92 m
(2H, OCH2), 4.30 s (1H, OH), 5.58–6.28 br.d (NH2),
6.56–6.60 m and 6.78 s (3H, Harom), 8.60 s (1H,
OHarom), 9.21 s (1H, NH). Found, %: C 55.41; H 6.58;
N 9.61. C21H29N3O8. Calculated, %: C 55.88; H 6.43;
N 9.31.
Diethyl 4-hydroxy-4-methyl-6-semicarbazono-2-
(2-thienyl)cyclohexane-1,3-dicarboxylate (IIf). Yield
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 12 2009

POPLEVINA et al.
1794
3. Zorina, A.A., Cand. Sci. (Chem.) Dissertation, Perm,
81%, colorless crystals, mp 194°C (from EtOH). IR
spectrum, ν, cm–1: 3502 (OH); 3352 (NH); 3082, 3182
(NH2); 1703, 1722 (C=O, ester); 1680 (C=O, amide);
2006.
4. Sorokin, V.V., Grigor’ev, A.V., Ramazanov, A.K., and
Kriven’ko, A.P., Russ. J. Org. Chem., 2000, vol. 36,
p. 781.
1
1557 (C=N). H NMR spectrum, δ, ppm: 0.96 t and
1.06 t (3H each, CH2CH3, J = 6.8 Hz), 1.24 s (3H,
4-CH3), 2.15 d (1H, 5-Hax, J = 14 Hz), 2.95 d (1H,
2-H, J = 12Hz), 3.08 d (1H, 5-Heq, J = 15 Hz), 3.55 d
(1H, 1-H, J = 12 Hz), 3.86 q (2H, OCH2, J = 7.2 Hz),
3.92–3.98 m (3H, 3-H, OCH2), 4.45 s (1H, OH), 5.58–
6.27 br.d (NH2), 6.86–6.88 m and 7.24 d (3H, C4H3S),
9.24 s (1H, NH). Found, %: C 52.55; H 6.08; N 10.22.
C18H25N3O6S. Calculated, %: C 52.70; H 5.72;
N 10.58.
5. Grigor’eva, E.A., Kriven’ko, A.P., Sorokin, V.V., Rama-
zanov, A.K., and Inozemtseva, O.A., Izv. Vyssh. Uchebn.
Zaved., Ser. Khim. Khim. Tekhnol., 2004, vol. 50, p. 131.
6. Sorokin, V.V., Grigor’ev, A.V., Ramazanov, A.K., and
Kriven’ko, A.P., Khim. Geterotsikl. Soedin., 1999,
p. 757.
7. Sorokin, V.V., Suponitskii, K.Yu., and Kriven’ko, A.P.,
Zh. Strukt. Khim., 2006, vol. 47, p. 598.
8. Shchelochkova, O.A., Grigor’eva, E.A., and Kriven’-
ko, A.P., Izv. Vyssh. Uchebn. Zaved., Ser. Khim. Khim.
Tekhnol., 2006, vol. 49, p. 139.
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