Spectral characterization and crystal structure of some 2,6-diarylthian-4-one hydrazone derivatives

Article abstract of DOI:10.1016/j.molstruc.2014.07.080

A series of cis and trans 2,6-diarylthian-4-one hydrazone derivatives (11-16) have been synthesized and characterized by ¹H, ¹³C and two dimensional NMR spectroscopy. For the 2r,6t-diphenylthian-4-one N-isonicotinoylhydrazone (14) X-ray diffraction have also been recorded. The coupling constants suggested that the cis-hydrazones (11-13), which have the phenyl groups in cis orientation, largely exist in chair conformations with equatorial orientation of the phenyl groups 11C. Analysis of the vicinal coupling constants of trans-hydrazones (14-16) suggests that boat forms 14B must make significant contributions to it and the relative population is 58%. Moreover, in solution chair conformations 14C and 14C′, may contribute to 14. The NOESY and X-ray diffraction of 14 gives definite evidence for the contribution of 14C.

Full text of DOI:10.1016/j.molstruc.2014.07.080

Journal of Molecular Structure 1076 (2014) 554–563
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Spectral characterization and crystal structure of some
2,6-diarylthian-4-one hydrazone derivatives
c
a,
C. Sankar a,b, , S. Umamatheswari , K. Pandiarajan
⇑
⇑
a Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India
b Department of Chemistry, TRP Engineering College, Irungalur, Tiruchirappalli 626 126, Tamil Nadu, India
c Department of Chemistry, Govt. Arts College for Women, Pudukkottai, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
All the compounds were synthesized
in good yields, and fully characterized
by NMR.
Compounds 11–14 largely exist in
chair conformations with equatorial
orientation of the phenyl groups.
In solid state the compounds 14–16
exists in boat forms, but in solution
chair conformation also may
contribute.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 March 2014
Received in revised form 21 July 2014
Accepted 31 July 2014
Available online 7 August 2014
A series of cis and trans 2,6-diarylthian-4-one hydrazone derivatives (11–16) have been synthesized and
characterized by 1H, 13C and two dimensional NMR spectroscopy. For the 2r,6t-diphenylthian-4-one
N-isonicotinoylhydrazone (14) X-ray diffraction have also been recorded. The coupling constants
suggested that the cis-hydrazones (11–13), which have the phenyl groups in cis orientation, largely exist
in chair conformations with equatorial orientation of the phenyl groups 11C. Analysis of the vicinal
coupling constants of trans-hydrazones (14–16) suggests that boat forms 14B must make significant
contributions to it and the relative population is 58%. Moreover, in solution chair conformations 14C
and 14C0, may contribute to 14. The NOESY and X-ray diffraction of 14 gives definite evidence for the
contribution of 14C.
Keywords:
Thian-4-ones
Isoniazid
Hydrazones
Conformation
Single crystal
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
on chemical shifts and coupling constants [1–10]. Such, studies
have furnished information about the dependence of NMR spectral
NMR spectral studies of heterocyclic compounds have helped in
understanding the influence of electronic and conformation effects
parameters such as chemical shifts and couplings constants on
electronegativities of heteroatoms. 1H and 13C NMR techniques
have been extensively applied in deriving stereo-dynamical infor-
mation about a wide variety of systems. 1H chemical shifts are
influenced by electronic, steric and magnetic anisotropic effects
whereas 13C chemical shifts are largely influenced by electronic
and steric effects only. Vicinal coupling constant values have been
⇑
Corresponding authors. Address: Department of Chemistry, TRP Engineering
College, Irungalur, Tiruchirappalli 626 126, Tamil Nadu, India. Tel.: +91 9944585257
(C. Sankar).
E-mail addresses: sankschem@gmail.com (C. Sankar), prof.kprajan@yahoo.com
(K. Pandiarajan).
http://dx.doi.org/10.1016/j.molstruc.2014.07.080
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
555
Scheme 1. Schematic diagram showing the synthesis of title compounds 11–16.
the 2r,6c-diarylthian-4-one and their derivatives are known to
exist in chair conformation with equatorial orientations of the phe-
nyl groups. It has been shown that the substituent in the phenyl
ring does not change the conformation of the heterocyclic ring.
From X-ray crystallographic diffraction study [16], it was found
that the 2r,6c-diphenythian-4-one adopts chair conformation with
phenyl groups in the equatorial positions. The crystal structure of
2r,6t-diphenylthian-4-one has been reported [17].
In view of these findings and in further stage of our work on the
synthesis of heterocycles, here we report the spectral characteriza-
tion and crystal structure of isoniazide hydrazone compounds
derived from 2r,6c-diphenythian-4-one (5–7) and 2r,6t-diphenyl-
thian-4-one (8–10) (Scheme 1).
Table 1
Crystal data and structure refinement for compound 14.
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system, space group
Unit cell dimensions
C23 H21 N3OS
387.49
293(2) K
0.71073 Å
Monoclinic, P21/c
a = 9.4089(9) Å alpha = 90°
b = 13.6000(14) Å beta = 96.905(5)°
c = 16.1335(14) Å gamma = 90°
2049.5(3) Å3
Volume
Z, Calculated density
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Limiting indices
Reflections collected/unique
Completeness to theta
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
Largest diff. peak and hole
CCDC NO
4, 1.256 Mg/m3
0.176 mmꢁ1
816
0.20 ꢂ 0.16 ꢂ 0.16 mm
1.96–25.00°
The synthesized compounds 11–16 were characterized by
FT-IR, 1H & 13C, 2D (COSY, NOESY, HSQC and HMBC) NMR
spectroscopy and X-ray diffraction techniques.
ꢁ11 6 h 6 11, ꢁ16 6 k 6 16, ꢁ19 6 l 6 19
18,301/3607 [R(int) = 0.0648]
25.00% 100.0 %
Semi-empirical from equivalents
0.9780 and 0.9675
Full-matrix least-squares on F2
3607/0/265
Experimental
1.060
Material methods and physical measurements
R1 = 0.0426, wR2 = 0.1107
R1 = 0.0596, wR2 = 0.1245
0.310 and ꢁ0.252 e Åꢁ3
697,344
Isoniazide was purchased from Sigma–Aldrich and used as such
as. All other chemicals were used as Analytical grade. Reactions
were monitored by TLC. All the reported melting points were mea-
sured in open capillaries and are uncorrected. Elemental analyzes
were performed on an Elementar Vario EL III CHNS analyzer. IR
spectra were recorded on an AVATAR 330 FT-IR Thermo Nicolet
spectrometer in KBr pellets.
used for the conformational analysis as it can give an idea about
the orientation of the substituents [11].
Several NMR spectral studies have been reported on 2,6-diaryl-
thian-4-one derivatives [12–15]. In these studies information has
been gained about the conformation of the thian-4-one ring. For
NMR measurements were made in DMSO-d6 for all compounds
in 5 mm NMR tubes. 1H NMR spectra was recorded for 11 on a

556
C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
Table 2
Melting points, yields, elemental analysis and IR stretching frequency of 11–16.
Compd.
m.p. (°C)
Yield (%)
Elemental analysis
Calculated (%)
IR stretching frequencies (cmꢁ1
)
Found (%)
C
C@N
C@O
CAH (aliphatic & aromatic)
C
H
N
H
N
11c
12
13
14t
15t
16t
205–208
215–217
230–232
200–201
177–179
212–214
90
85
80
90
85
78
71.23
72.26
67.09
71.23
72.19
67.03
5.42
6.16
5.63
5.42
6.02
5.59
10.84
10.11
9.39
10.84
10.11
9.38
71.20
72.22
67.12
71.20
72.30
67.10
5.39
6.20
5.67
5.39
5.95
5.61
10.79
10.07
9.43
10.79
10.08
9.40
1600
1621
1603
1634
1600
1607
1645
1665
1650
1684
1655
1661
3183–2917
3183–2900
3170–2890
3054–2895
3024–2849
3040–2835
The crystallographic data are summarized in Table 1. The structure
was solved by SIR-92 [18] and refined by Full matrix least square
with SHELXL-97 [19]. All the non-hydrogen atoms were fixed geo-
metrically. Data center allocated the deposition number CCDC
697342.
Synthesis of the compounds
Synthesis of 2r,6c-diarylthian-4-ones (5–7)
All the parent 2r,6c-diarylthian-4-ones were prepared by the
procedure of refluxing solution of sodium acetate (5 g), 4,40-disub-
stituted dibenzalacetone (5 g) and ethanol (40 mL), the hydrogen
sulphide gas was passed for 6–8 h [20]. After the completion of
the reaction, the contents were cooled to 0 °C and the resinous
mass formed was removed from the supernatant liquid by decan-
tation. The supernatant liquid was kept at 0 °C for 1 day when col-
orless crystals of 2r,6c-diarylthian-4-one separated. The solid was
filtered off and washed with water, dried and recrystallized from
pet.ether (b.p 60–80 °C) to get the pure compound.
Fig. 1. Numbering of carbons, conformation and non-bonded interaction of the
compound.
Synthesis of 2r,6t-diarylthian-4-ones (8–10)
Bruker DRX-500 NMR spectrometer operating at 500.03 MHz for
1H and 125.75 MHz for 13C. For 14–16 these spectra were recorded
on Bruker AMX 400 NMR spectrometer operating at 400.13 MHz
for 1H and 100.62 MHz for 13C.
All the parent 2r,6t-diarylthian-4-ones were prepared by the
procedure of refluxing solution of sodium acetate (7.5 g), 4,40-
disubstituted dibenzalacetone (5 g) and ethanol (40 mL), the
hydrogen sulphide gas was passed for 15–45 min [21]. After the
completion of the reaction, the contents were cooled to 0 °C and
the resinous mass formed was removed from the liquid by decan-
tation. The supernatant liquid was kept at 0 °C for 1 day when col-
orless crystals of 2r,6c-diarylthian-4-one separated. The solid was
filtered off and washed with water, dried and recrystallized from
pet.ether (b.p 60–80 °C) to get the pure compound.
X-ray crystallography
Single crystal X-ray diffraction data were collected at ambient
temperature on BRUKER axis Kappa apex CCD diffractometers
using graphite monochromated Mo K
a (k = 0.71073 Å) radiation.
Table 3
1H chemical shifts (ppm) of hydrazones 11–16.
Protons
Compounds
Parent
11
12
4.17
2.76
2.87
2.35
3.92
4.12
8.73
13
4.20
2.76
2.87
2.35
3.92
4.13
8.71
14
4.43
15
4.35
16
4.34
H-2a
H-3a
H-3e
H-5a
H-5e
H-6
4.84
2.73
2.69
2.73
2.69
4.84
–
4.33
3.00
3.07
2.94
3.58
4.38
8.72
7.71
7.47
2.95
3.27
3.11
3.24
4.63
8.70
7.70
7.53
7.43
7.36
2.89
3.23
3.11
3.19
4.57
8.70
7.69
7.39
7.29
7.16
2.90
3.21
3.09
3.18
4.55
8.71
7.70
7.43
7.33
6.90
H-a
H-b
o-H, o0-H
–
7.46
7.72
7.21, 7.35
7.71
7.51, 7.51
m-H, m0-H
7.32
7.38
7.05,
7.09
–
7.41
p-H, p0-H
p-OCH3
p-CH3
–
–
–
–
–
–
7.26
–
–
–
–
–
3.73
–
–
–
–
–
2.29
11.20
2.26
10.96
ANHACO
11.17
11.17
10.95
10.95

C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
557
Table 4
reaction mixture was cooled and a solid mass was formed. The
solid mass was filtered off and washed with cold mixture of etha-
nol and water. The crude product was recrystallized from ethanol.
The purity of the compounds was checked by TLC.
Correlations in the COSY and NOESY spectra of 11.
Protons
Correlations in the COSY
spectrum
Correlations in the NOESY
spectrum
11.17 (amide
NH)
–
3.58 (H-5e), 7.71 (H-b)
Results and discussion
8.72 (H-
a)
7.71 (H-b)
7.71 (H-b)
7.71 (H-b)
8.72 (H-
a
)
8.72 (H-
NH)
4.38 (H-2), 4.33 (H-6)
a), 11.17 (amide
Numbering and designing of atoms
7.48, 7.46 (o-H,
o0-H)
7.38 (m-H, m0-H)
The title compounds were synthesized through the condensa-
tion of key intermediate cis- and trans-thian-4-ones with isoniaz-
ide (INH) Scheme 1. The physical data for hydrazones 11–16 are
given in Table 2.
The numbering of the carbons of the thiane ring for 11 and 14 is
shown in Fig. 1. The ipso carbons of the aryl groups at C-2 and C-6
are designated as C-20 and C-60. The other carbons of the aryl group
at C-2 are denoted as o, m and p-carbons and those of the aryl
group at C-4 are denoted as o0, m0 and p0-carbons. The carbons of
2.94 (H-3a), 2.66 (H-5a)
–
7.38 (m-H, m0-
H)
7.48, 7.46 (o-H, o0-H),
7.31(p-H, p0-H)
7.38 (m-H, m0-H)
3.01(H-3a)
7.31(p-H, p0-H)
4.38 (H-2a)
2.94 (H-3e)
–
2.94 (H-3e), 7.48 (o-H),
2.66 (H-5a), 4.38 (H-2),
7.48 (o-H)
4.38 (H-2a)
3.01 (H-3a)
2.66 (H-5a)
2.94 (H-3e)
3.58 (H-5e), 4.33 (H-6)
–
2.94 (H-3e), 3.58 (H-5e),
7.46 (o0-H)
2.66 (H-5a), 4.33 (H-6),
11.17(NH)
3.58 (H-5e), 7.46(o0-H)
3.58 (H-5e)
4.33 (H-6)
2.66 (H-5a)
2.66 (H-5a)
the pyridine ring are designated using Greek letters
The protons are denoted accordingly. For example, the benzylic
proton at C-2 is denoted as H-2, and that at C- is denoted as H-
and so on. For the cis isomer 11 the methylene protons at C-3
a, b and c.
a
a
are denoted as H-3a and H-3e and those at C-5 are denoted as H-
5a and H-5e assuming chair conformation for the thiane ring. For
the trans compounds the methylene protons at C-3 are denoted
as H-3c and H-3t those at C-5 are denoted as H-5c and H-5t.
Table 5
Correlations in the HSQC spectrum of 11.
Carbons (ppm)
Correlations in the HSQC spectrum
162.4
162.2
–
–
IR spectral studies
150.0
8.72 (H-a)
141.0
121.7
140.5, 140.4
127.5
127.3
128.7, 128.6
127.7
48.1
46.6
43.8
–
The important IR stretching frequencies of 11–16 are given in
Table 2. In IR spectra, the presence of C@N stretching frequency
around 1600 and 1634 cmꢁ1 confirm the hydrazone formation.
The bands observed in the region of 3256–3298 cmꢁ1 are due to
NAH stretching frequency of hydrazone analogues while the
absorption band in the region 3070–2800 cmꢁ1 are ascribed to aro-
matic and aliphatic CAH stretching frequencies. The band observed
in the region of 1645–1685 cmꢁ1 are due to C@O stretching fre-
quency of amide carbonyl group.
7.71 (H-b)
–
7.46 (o-H)
7.48 (o0-H)
7.38 (m-H, m0-H)
7.31 (p-H, p0-H)
4.38 (H-2a)
4.33 (H-6a)
2.94 (H-3e), 3.01 (H-3a)
2.66 (H-5a), 3.58 (H-5e)
36.1
NMR spectroscopy
General procedure for synthesis of 2,6-diarylthian-4-one N-
Proton and 13C NMR spectral analysis of compound (11)
In order to analysis the spectral assignments of synthesized
novel compounds 11–16, we have chosen compounds 11 and 14
as the representative compounds. The 1H and 13C signals for the
isonicotinoylhydrazone (11–16)
A
mixture of 2,6-diarylthian-4-one (1 mmol), isoniazid
(1.5 mmol) is the presence of few drops of acetic acid in methanol
was refluxed about 2–3 h. After the completion of reaction the
Table 6
13C chemical shifts (ppm) of hydrazones 11–16.
Carbons
Compounds
11
12
13
14t
15t
16
AC@O
C-2
163.0
48.6
161.6
49.1
162.1
49.2
162.3
43.6
162.2
43.3
162.7
43.5
C-3
44.4
40.9
40.9
40.4
40.6
41.2
C-4
C-5
162.7
36.6
160.5
33.9
161.3
33.9
161.7
36.1
162.0
36.1
162.6
36.8
C-6
47.1
47.9
47.8
41.8
41.5
41.7
C-
C-b
a
150.5
122.3
141.5
140.5
140.4
127.5, 127.3
128.7, 128.7
128.2
–
150.7
122.1
141.3
136.9
136.5
126.6
127.8
128.7
150.2
121.6
141.0
138.5,
141.2
129.6, 128.5
128.1
131.6, 131.5
150.0
121.7
140.5
142.6
140.5
127.6, 127.5
128.5, 128.4
127.2
–
150.0
121.7
139.5
141.0
150.5
122.3
141.5
135.0
C-
!
C-20
C-60
137.6
132.9
o-C, o0-C
m-C, m0-C
p-C, p0-C
p-OCH3
p-CH3
127.5, 127.3
129.0, 129.0
136.7 136.3
–
129.2, 129.1
114.4, 114.3
159.1 158.8
55.6
–
21.04, 21.05
–
20.6
–

558
C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
be a doublet of doublet. However, the small vicinal coupling J6a,5e is
not resolved. There is one triplet at 2.66 ppm corresponding to one
proton. This must be due to H-5a. The doublet of doublet at
2.94 ppm is due to H-3e. The proton chemical shifts are given in
Table 3. For confirming these assignments 1HA1H COSY and NOESY
spectra were recorded and the observed correlations in the 1HA1H
COSY and NOESY spectra are given in Table 4.
In order to assign the 13C signals unambiguously HSQC spec-
trum has been recorded for 11. The observed correlations in the
HSQC spectrum are given in Table 5. The two weak signals at
162.4 and 162.2 ppm have no correlation in the HSQC spectrum.
Obviously, the signal at 162.4 ppm is due to C-4 and that at
162.2 ppm is due to the carbonyl carbon. There are three other
weak signals at 141.0, 140.5 and 140.4 ppm. These signals have
no correlation in the HSQC spectrum. These signals are due to
the ipso carbons of the phenyl groups and pyridine ring. The signals
in the range 30–50 ppm could be assigned to the heterocyclic ring
carbons. Among the four signals for the heterocyclic ring carbons,
Fig. 2. NOESY correlation of compound 11.
two upfield signals could be assigned to the
to the C@NANHACOAPy groups). Among these two signals, the
upfield signal could be assigned to the syn -carbon [23,24]. The
a-carbons (carbons a
remaining compounds were assigned by comparison with 11 and
14 using known effects [22] of the Cl, CH3 and OCH3 substituents
in the aryl rings. In the 1H NMR spectrum of 11 there is a sharp sin-
glet at 11.17 ppm, corresponding to one proton. This should be due
to the amide NH proton. There are two doublets at 8.72 and
7.71 ppm, each corresponding to two protons. These should be,
a
other signals are confirmed based on the observed HSQC correla-
tions. The observed 13C chemical shifts of 11 are given in Table 6.
Analysis of coupling constants
In compound 11 the protons H-5a, H-5e and H-6a form an AMX
system and the various coupling constants involving them could be
determined directly from the spectral data. Protons H-3a, H-3e and
H-2a form an ABX system. The coupling constants J2a,3a and J2a,3e
are calculated using second-order [25] analysis. The conformation
of the thiane ring can be deduced from the vicinal coupling con-
stants. The coupling constants of 11 are as follows;
respectively, due to the
a and b protons of the pyridine ring. There
are two doublets at 7.48 and 7.46 ppm, each corresponding to two
protons. These signals should be due to the ortho protons (o-H, o0-
H). The quartet at 7.38 ppm, corresponding to four protons, should
be due to the meta protons (m-H, m0-H). This quartet has formed by
the overlap of two triplets. There is a multiplet at 7.31 ppm, corre-
sponding to two protons. This signal should be due to the para pro-
tons (p-H, p0-H).
There are two doublet of doublets at 4.38 and 4.33 ppm, each
corresponding to one proton. By comparison with 2r,6c-diphenyl-
thian-4-one oxime [12] the signal at 4.38 ppm is assigned to the
benzylic proton H-2a and that at 4.33 ppm is assigned to the ben-
zylic proton H-6a. There is one doublet at 3.58 ppm corresponding
to one proton and the coupling constant observed for the signal is
13.0 Hz. Hence, this signal must be due to H-5e. This signal should
J2a;3a ¼ 11:81 Hz; J2a;3e ¼ 2:18 Hz;
J6a;5e ¼ 2:0 Hz; J6a;5a12:50 Hz; J5a;5e ¼ 13:0 Hz
The coupling constant values and position of the chemical shits
were used to predict the conformation of the compound. The obser-
vations of large vicinal coupling constant values between 11.81 Hz
(3J2a,3a) and 12.50 Hz (J6a,5a) and of small value of the vicinal cou-
pling constant 2.0 Hz (J6a,5e) and 2.18 Hz (J2a,3e) for the protons of
Fig. 3. NOESY spectrum of compound 11.

C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
559
C-6 and C-2 of compound 11 should largely exist in chair conforma-
tion 11C with equatorial orientations of phenyl groups at C-2 and C-
6 Fig. 1. Two geometrical isomers are possible (Z and E), but the
position of chemical shift value of H-5e proton is about 0.89 ppm
deshielded than the parent ketone (Table. 3) which indicates that
NANHACOAPy bond is syn to C-5 which is confirmed from the
observed NOESY correlation between NH proton signal at
11.17 ppm and H-5e proton signal at 3.58 ppm. The deshielding is
due to the non-bonding interaction between H-5e proton and
NAH proton of hydrazide moiety as shown in Fig. 1. Only one signal
is observed for each kind of proton and carbon. The signal due to NH
proton of hydrazide moiety at 11.17 ppm has NOE with the H-b.
Such a NOE is possible only in the Z-isomer (Figs. 2 and 3). Hence,
11 exist in the Z form (about the COANH bond) and E form
(C@NANH bond) almost exclusively.
Fig. 5. Torsional angles for the thiane ring of compound 14.
Single-crystal X-ray analysis of 2r,6t-diphenylthian-4-one N-
isonicotinoylhydrazone (14)
Compound 14 crystallizes into a monoclinic lattice with P21/c.
Crystal data and structure refinement of compound 14 is shown
in Table 1. The ORTEP diagram (Fig. 4) of 14 and displacement
ellipsoids are drawn at 50% probability level. In the solid state
the configuration is Z about (O)CANH bond. The thiane ring adopts
boat conformation. The observed torsional angles for the thiane
ring are shown in Fig. 5. The observed torsional angles suggest that
the boat is a classical boat and not a twist-boat. The molecule is
stabilized by intermolecular hydrogen bonds between the amide
NH of one molecule and the pyridine nitrogen of another molecule.
The type of hydrogen bonding is shown in Fig. 6. The details about
the geometries of the intermolecular hydrogen bond are given in
Table 7.
1H and 13C NMR spectral analysis of compound (14–16)
The structure of compounds 14–16 are established using
1H NMR spectral data. In the 1H NMR spectrum of (Fig. 7) 2r,
6t-diphenylthian-4-one N-isonicotinoylhydrazone (14), there is a
sharp singlet at 10.59 ppm, corresponding to one proton. This
should be due to the amide NH proton. There are two doublets at
8.70 and 7.70 ppm, each corresponding to two protons. These
Fig. 6. Packing diagram of compound 14.
signals must be, respectively, due to the
a and b protons of pyridine
ring. There are two doublets at 7.53 and 7.43 ppm, each corre-
sponding to two protons. These signals are due to the ortho protons
(o-H and o0-H). There is quartet centered at 7.36 ppm, correspond-
ing to four protons. This signal is an overlap of two triplets and it
should be due to the meta protons (m-H and m0-H). There is quartet
at 7.28 ppm, corresponding to two protons. This signal should be
due to the para protons of the phenyl groups.
There are two doublet of doublets at 4.63 and 4.43 ppm, each
corresponding to one proton. These signals are due to the benzylic
protons. In the solid state 14 exists in boat conformations 14B
(Fig. 8). In solution chair conformations 14C and 14C0 (Fig. 8) also
may contribute. Hence, the methylene protons at C-3 are denoted
as H-3c and H-3t. Proton H-3c is cis to H-2 and proton H-3t is trans
to H-2. Similarly, the methylene protons at C-5 are denoted as H-5c
and H-5t.
Though 8 lines are observed for the benzylic protons, only 14
lines are observed for the methylene protons. Careful examination
showed that one line for the methylene protons has merged with
solvent signal and one line is a merged line for two protons. The
frequencies of the two merged lines and the line merging with
the solvent were calculated from the spectral data.
Table 7
Hydrogen bonds for 14 [Å and °].
D–H...A
d(D–H)
0.82(2)
d(H...A)
2.48(2)
d(D...A)
<(DHA)
161(2)
N(2)AH(2)...N(3)#1
3.266(3)
Symmetry transformations used to generate equivalent atoms: #1ꢁx,ꢁy,ꢁz.
Fig. 4. ORTEP diagram of compound 14.

560
C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
The observed chemical shifts of the methylene protons are 3.27,
141.0 and 140.5 ppm. These signals have no correlation in the
HSQC spectrum. The signal at 162.3 ppm shows correlation with
H-b and the amide NH proton. Hence, this signal should be due
to the carbonyl carbon.
In the HMBC spectrum the signal at 141.0 ppm has correlation
with H-a. Hence, this signal should be due to C-a. The signal at
142.6 ppm has correlation with benzylic proton H-2. Therefore,
this signal can be assigned to C-20. Obviously, the signal at
140.5 ppm can be assigned to C-60. In the HSQC spectrum the signal
at 43.6 ppm shows correlation with benzylic proton H-2. Obvi-
ously, the signal at 43.6 ppm is due to C-2.
Similarly the signal at 41.8 ppm shows correlation with H-6.
Therefore this signal must be assigned to C-6. The signal at
36.1 ppm shows correlation with H-5c and H-5t. Hence, this signal
should be due to the C-5. The 13C chemical shifts and the observed
correlations in the HSQC and HMBC spectra of 14 are given in
Tables 6 and 9 respectively.
3.23, 3.14 and 2.95 ppm. From the observed correlations in the
1HA1H COSY spectrum it is seen that protons at 4.63, 3.23 and
3.14 ppm form one set of coupling protons. In the NOESY spectrum
(Fig. 9) there is correlation between the methylene proton at
3.23 ppm and the NH proton of amide. The vicinal coupling con-
stant for this methylene proton is about 4 Hz, corresponding to
cis coupling. Obviously, the proton at 3.23 ppm is H-5c. From the
observed coupling constants the signals at 3.27, 3.14 and
2.77 ppm are assigned to H-3t, H-5t and H-3c, respectively.
Observed proton chemical shifts are given in Table 3. The observed
correlations in the 1HA1H COSY and NOESY spectra of 14 are given
in Table 8. It is seen that the observed correlations are consistent
with the assignments mode. The doublet at 7.53 ppm has nOes
with H-2, H-3c and H-3t. Hence, the doublet at 7.53 ppm must
be due to ortho protons (o-H) of the phenyl ring at C-2. Likewise,
the doublet at 7.43 ppm has strong NOE with H-6 and H-5c. Hence,
the doublet at 7.43 ppm must be due to ortho proton (o-H) of the
phenyl ring at C-6.
In the 13C NMR spectrum of compound 14, there is a weak sig-
nal at 161.7 ppm. This signal has no correlation in the HSQC spec-
trum. In the HMBC spectrum this signal shows correlation with
amide NH proton, H-5, H-2 and H-6 protons. Hence, this signal
must be due to C-4. There are four weak signals at 162.3, 142.6,
Analysis of coupling constants
In compound 14 the protons H-2, H-3c and H-3t form a three
spin system and protons H-6, H-5t and H-5c form another three
spin system. Both systems are of ABX types. The vicinal coupling
constants were determined using second-order analysis. The con-
Fig. 7. 1H NMR spectrum of compound 14.

C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
561
Fig. 8. Possible conformation of compound 14.
Fig. 9. NOESY spectrum of compound 14.
J2,3t and J5t,6 are lower than 12.0 Hz [26]. Hence, in solution chair
conformations 14C and 14C0 may contribute to 14. From the
observed vicinal coupling constants the relative populations of
14C, 14C0 and 14B were calculated as 14%, 28% and 58% (Fig. 8)
[27]. This conformation was further confirmed by NOESY spectrum.
In the NOESY spectrum of compound 14 (Fig. 9), the signal due
to NH proton of amide group at 10.59 ppm has strong nOes with
formation of the thiane ring can be deduced from the vicinal
coupling constants. The coupling constants of 14 are as follows;
J5t;6 ¼ 10:73 Hz; J5c;6 ¼ 3:46 Hz; J3t;2 ¼ 9:25 Hz; J3c;2 ¼ 4:19 Hz
If 14 exists in solution as boat form 14B, the vicinal coupling con-
stant J3t,2 and J5t,6 must be around 12.0 Hz. The observed values of

562
C. Sankar et al. / Journal of Molecular Structure 1076 (2014) 554–563
Table 8
Correlations in the COSY and NOESY spectra of 14.
Protons
Correlations in the COSY spectrum
Correlations in the NOESY spectrum
10.95 (amide NH)
–
3.23 (H-5c), 7.70 (H-b)
7.70 (H-b)
8.70 (H-
a)
7.70 (H-b)
7.70 (H-b)
7.53 (o-H)
8.70 (H-
a)
8.70 (H-a)
2.95 (H-3c), 3.27 (H-3t)
7.36 (m-H, m0-H)
4.43 (H-2)
4.63 (H-6), 3.14 (H-5t)
–
7.43 (o0-H)
7.36 (m-H, m0-H)
7.53 (o-H), 7.43 (o0-H)
7.28 (p-H, p0-H)
7.36 (m-H, m0-H)
2.95 (H-3c), 3.27 (H-3t)
3.27 (H-3t),
7.36 (m-H, m0-H)
7.28 (p-H, p0-H)
4.43 (H-2)
2.95 (H-3c)
–
2.95 (H-3c), 7.53 (o-H)
4.38 (H-2)
4.43 (H-2)
7.53 (o-H)
3.27 (H-3t)
3.23 (H-5c)
3.14 (H-5t)
4.63 (H-6)
2.95 (H-3c), 4.43 (H-2)
3.14 (H-5t)
3.14 (H-5t), 4.63 (H-6)
3.14 (H-5t)
2.95 (H-3c), 4.43 (H-2), 7.53 (o-H), 4.63 (H-6)
4.63 (H-6)
4.63 (H-6)
3.24 (H-5e), 7.43 (o0-H)
Table 9
Correlations in the HSQC and HMBC spectra of 14.
Chemical shifts (ppm)
Correlations in the HSQC spectrum
Correlations in the HMBC spectrum
162.3
161.7
–
–
10.95 (amide NH), 7.70 (H-a)
4.63 (H-6), 4.43 (H-2), 3.24(H-5e), 3.14(H-5a), 3.23 (H-3e), 2.95 (H-3a)
150.0
8.70 (H-
a)
7.70 (H-b)
121.7
140.5
7.70 (H-b)
–
8.70 (H-
8.70 (H-
a
a
)
)
142.6
141.0
127.6, 127.5
–
–
7.36 (m-H, m0-H), 4.43 (H-2)
7.36 (m-H, m0-H), 4.63 (H-6)
7.26 (p-H, p0-H), 7.36 (m-H, m0-H),
4.63 (H-6), 4.43 (H-2)
7.53 (o-C) ,7.43 (o0-C)
128.5, 128.4
127.2
43.6
40.4
36.1
7.36 (m-C)
7.26 (p-C, p0-C)
4.43 (H-2)
3.23 (H-3e), 2.89 (H-3a)
3.24 (H-5e), 3.14(H-5a)
4.63 (H-6)
7.26 (p-H, p0-H)
-
7.53 (o-H), 4.63 (H-6), 3.23 (H-3e), 2.95 (H-3a)
4.43 (H-2)
4.63 (H-6), 3.23 (H-3e), 2.95 (H-3a)
7.43 (o0-H), 3.24 (H-5e), 3.14 (H-5a)
41.8
the b-proton of the pyridine ring. It is obviously that 14 exist as 14
Z in solution.
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Condensation of 2r,6c-diarythian-4-one (5–7) and 2r,
6t-diarythian-4-one (8–10) with isonicotinoylhydrazide gives
2r,6c-diarythian-4-one N-isonicotinoylhydrazone (11–13) and
2r,6t-diarythian-4-one N-isonicotinoylhydrazone (14–16). The
compounds (11–13) the thiane ring adopts chair conformation
11C with equatorial orientations of the phenyl groups. This com-
pound exists in Z form about the (O)CANH bond. In solid state
14 has Z configuration about the (O)CANH bond. The thiane ring
adopts boat conformation. The observed torsional angles suggest
that the boat is a classical boat and not a twist-boat. In solution
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tions 14B and chair conformations 14C and 14C0 and also the
configuration about the (O)CANH bond is Z.
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and single crystal X-ray diffraction. We also thankful to CECRI,
Karaikudi for elemental analysis.
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