Spectral characterization and crystal structure of 5-spiro-(3-methyl-2,6-diphenyltetrahydropyran-4-yl)-4,5-dihydro-[1,3,4]thiadiazole

Article abstract of DOI:10.1016/j.molstruc.2009.09.016

The synthesis of new 1,3,4-thiadiazoline derived from 3-methyl-2,6-diphenyltetrahydropyran-4-one, via the corresponding thiosemicarbazone, is described. The synthesis, spectral characterization and crystal structure of 5-spiro-1,3,4-thiadiazoline of 2,6-d

Full text of DOI:10.1016/j.molstruc.2009.09.016

Journal of Molecular Structure 938 (2009) 142–149
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Spectral characterization and crystal structure of 5-spiro-(3-methyl-2,6-diphenyl-
tetrahydropyran-4-yl)-4,5-dihydro-[1,3,4]thiadiazole
S. Umamatheswari, S. Kabilan *
Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 February 2009
Received in revised form 14 September
The synthesis of new 1,3,4-thiadiazoline derived from 3-methyl-2,6-diphenyltetrahydropyran-4-one, via
the corresponding thiosemicarbazone, is described. The synthesis, spectral characterization and crystal
structure of 5-spiro-1,3,4-thiadiazoline of 2,6-diphenyl-3-methylpyran is reported. Spectral techniques
employed include 1H NMR, C NMR, HOMOCOSY, HSQC, HMBC, NOESY correlation techniques, mass
and IR. The conformation of the compound is established on the basis of H NMR spectral data, MOPAC
calculation and the single crystal X-ray analysis.
2
009
13
Accepted 14 September 2009
Available online 18 September 2009
1
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Thiadiazolines
HOMOCOSY
HSQC
HMBC
NOESY
Crystal structure
1
. Introduction
2. Experimental
Several natural products including antibiotics possess the oxane
pyran) ring skeleton. The pyran nucleus can frequently be recog-
nized in the structure of numerous naturally occurring carbohy-
drates and synthetic compounds with interesting biological and
pharmacological properties [1–4]. Thiosemicarbazones exhibit var-
The IR spectrum was recorded in AVATAR-330 FT-IR spectro-
photometer (Thermo Nicolet) and only noteworthy absorption lev-
els (reciprocal centimeters) are listed. H NMR spectrum was
(
1
recorded at 400 MHz on BRUKER AMX 400 MHz spectrophotome-
ter using CDCl
NMR spectrum was recorded at 100 MHz on BRUKER AMX
as solvent and TMS as internal standard. 13
C
3
ious biological activities and are extensively applied in medicine
2
1
1
particularly in the treatment of tuberculosis [5,6]. The
adiazolines also exhibit biological behavior [7–11].
D
-1,3,4-thi-
3
400 MHz spectrophotometer in CDCl . H– H COSY, phase-sensi-
1
13
tive NOESY and one-bond H– C correlations spectra were re-
corded on BRUKER AMX 500 NMR spectrometer using standard
There are few general routes to obtain 1,3,4-thiadiazolines.
Holmberg and Sandström proposed the reaction between an alde-
hyde or a ketone with substituted thiohydrazides [12]. Evans and
Taylor [13] found that 1,3-dipolar cycloaddition between chloro-
diazabutadiene and thiourea rendered 4-amidine-1,3,4-thiadiazo-
lines. However, the preparation of this heterocyclic ring is mostly
achieved by heterocyclization of thiosemicarbazones [14], as re-
ported by Andreae et al. [15], Somogyi [16] and Kubota et al.
3
parameters. 0.05 M solutions of the sample prepared in CDCl were
used for recording 2D NMR spectra. The tubes used for recording
NMR spectra are of 5 mm diameter. The FAB mass spectrum was
recorded on a JEOLSX 102/DA-6000 mass spectrometer using Ar-
gon/Xenon (6 kV, 10 mA) as the FAB gas. The accelerating voltage
was 10 kV and the spectra recorded at room temperature. The the-
oretical conformation calculation were performed on a personal
computer using PM3 (MNDO Hamiltonian) available in MOPAC
version 7.2 [19]. Unless otherwise stated, all the reagents and sol-
vents used were of high grade and purchased from Fluka and
Merck. All the solvents were distilled prior to use.
[
17]. In view of these findings and in a further stage of our work
on the synthesis of heterocycles [18], here we describe the synthe-
sis, structural and spectral studies of 5-spiro-(3-methyl-2,6-diphe-
nyltetrahydropyran-4-yl)-4,5-dihydro-[1,3,4]thiadiazole.
2.1. X-ray data collection, structure solution and refinement
Single crystals suitable for diffraction were obtained by the slow
*
Corresponding author. Tel.: +91 9944930543.
E-mail address: skabilan08@gmail.com (S. Kabilan).
evaporation of a solution of the compound in ethanol. The colorless
0
022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.09.016

S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
143
O
O
CH3
H C
3
KOH / H O - EtOH
CH3
2
O
+
O
stirred 15 days
O
1
H
H
S
MeOH/H+
Reflux, 2h
H N
2
N
NH2
H
H
CH3
S
NH2
N
N
O
O
HN
O
H C
3
N
N
S
CH3
H
3
C
O
CH
3
CH3
O
O
3
reflux, 10h
O
2
Scheme 1. Schematic diagram showing the synthesis of compound 3.
crystal of the compound having appropriate dimensions of
data. The collected data were reduced using the SAINT program
and structural refinement was carried out by Full-matrix least-
squares on F (SHELXL-97) [20]. Molecular graphics employed in-
clude ORTEP and PLATON [21]. Data center allogated the deposi-
tion number CCDC 697342.
0
.30 Â 0.20 Â 0.20 mm was mounted on a glass fiber with epoxy
2
cement for the X-ray crystallographic study. Bruker axs kappa
apex2 CCD diffractometer equipped with graphite monochromated
Mo Ka
(k = 0.71073 Å) radiation was used for the measurement of
NHAc
N
NH2
N
HN
S
HN
S
CH3
-COCH2
CH3
C H
O
C H
6
5
6
5
C H
O
C H
6
5
6
5
m/z 381
m/z 339
-
CH CO
2
NHAc
CH3
N
N
S
Ac
C H
O
C H
6
5
6
5
NHAc
N
McLafferty
rearrangement
m/z 423
N C NHAc
S
m/z 116
Ac
Ac
N S
N
CH3
CH3
C H
C H
O
C H
6
5
6
5
C H
O
6
5
6
5
m/z 339
m/z 307
Fig. 1. Mass spectral fragmentations of the compound 3.

1
44
S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
2
H C
4.46
in vacuo afford 5-spiro-(3-methyl-2,6-diphenyltetrahydropyran-
4-yl)-4,5-dihydro-[1,3,4]-thiadiazoles 3 which is recrystallized
from 96% ethanol. M.p. 126 °C, yield: 91%.
H
3
1
69.64
N
O
1
42.27
3
. Results and discussion
N
O
2
3
1
68.09
2
3.33
3
3.1. IR spectral studies
S
1
4
N
CH
5
11.62
CH
42.09
8
8.32
3
3
IR spectral data confirms the presence of characteristic groups
4
4
5.48
À1
5
present in the compound. The bands at 1700 cm
and
À1
1
663 cm are for the amide carbonyl groups present in tertiary
78.11
6
2
8
4.40
and secondary amides, respectively. The C@N stretching frequency
appears at 1625 cm . The band at 3251 cm is assigned for the
NH stretching frequency. Aromatic CAH stretching bands occur
in the region 3088 cm . Carbon to carbon stretching vibrations
1
O
À1
À1
1
41.20
139.94
À1
À1
within the ring occurs at 1498 cm
.
Fig. 2. 13C chemical shift values in (d) ppm and carbon numbering of the compound 3.
3.2. Mass spectral analysis of the compound 3
Mass spectra of this heterocyclic compound resemble the ob-
served rupture pattern, although the relative abundance and the
2.2. Synthesis of compound 3
m/z relationship are characteristic for the synthesized compound
3, in agreement with that observed for similar heterocycles derived
Compound 3 was synthesized as shown in Scheme 1. The parent
-methyl-2,6-diphenyltetrahydropyran-4-one 1 was prepared by
from aldehydes [16]. The proposed fragmentation model is pre-
sented in Fig. 1.
3
the literature precedent of Japp and Maitland [22]. The pyran-4-
one further converted into their thiosemicarbazone 2 by condensa-
tion with thiosemicarbazide in the presence of concentrated
3.3. NMR spectral studies of compound 3
Ring closure may be observed by the disappearance in the 13C
NMR spectrum of the signal at 179.70 ppm corresponding to the
thiocarbonyl, the appearance of the signal at 88.32 ppm assigned
to C-4 and the signals of the carbonyl and methyl moieties of the
hydrochloric acid in methanol medium [23]. Compound
0.025 mol) was treated with freshly distilled acetic anhydride
and the mixture was refluxed for 10 h on a water bath (90–
00 °C). The removal of solvent from the cooled reaction mixture
2
(
1
Fig. 3. The HSQC correlation spectrum of the compound 3.

S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
145
Fig. 4. The HMBC correlation spectrum of the compound 3.
is depicted in Fig. 2 with carbon numbering. The 13C chemical shift
values are unambiguously assigned by HSQC and HMBC spectra
CH3
O
H
(Figs. 3 and 4). The HMBC correlations are shown in Fig. 5,
N
respectively.
In the HSQC spectrum of compound 3, the carbon signal at
8
8.32 does not have HSQC correlation whereas there are notable
H
S
H
N
HMBC correlations with H-2a, H-3a, H-5a, H-5e and 3-CH protons
3
H
6
4
which confirm that the signal at 88.32 is for spiro carbon (C-4).
Moreover, the carbon signal at 45.48 ppm having HSQC correla-
tion with two proton signals at 3.46 and 2.42 ppm, respectively,
which confirms that the carbon signal at 45.48 ppm is a methylene
carbon (C-5).
5
N
2
1
Me
3
O
H
O
H
H C
3
1
The H NMR spectral data used to determine the conformation
1
of the compound 3. The H NMR spectral assignments have been
Fig. 5. The HMBC correlations of the compound 3.
made based on the characteristic signal, positions of functional
1
1
groups, spin multiplicity and 2D NMR ( H– H HOMOCOSY, HSQC,
1
HMBC and NOESY) spectral data. The H chemical shift values
acetyl groups incorporated to the molecule. The C@N signal is
around 142.27 ppm. The 13C chemical shift value of compound 3
and the HOMOCOSY correlation of compound 3 are shown in
Fig. 6. The NOESY correlations are shown in Fig. 7. HOMOCOSY
H8.67
2
.21 H C
3
N
O
N
3
O
2
2
.13
1
4
S
N
CH3
5
CH3
2
.42
dd, J = 1.56; J = 13.0 Hz)
.48 (m)
0.74d, J = 6.64 Hz
H5e
H
3
2
(
4
5
3
3
3.48 (m)
H3a
H
5
a
6
2
3
4
.17 (d, J = 10.08 Hz)
H
1
O
4
.68
6a
2a
3
(
dd, J = 10.4, 1.53 Hz)
Ph
Ph
Fig. 6. 1H chemical shift values in (d) ppm with 1H– H HOMOCOSY correlation of the compound 3.
1

1
46
S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
4
.17 (3J2a,3a = 10.08 Hz) with one proton integral each. From the
multiplicity of those signals the higher frequency signal
(4.68 ppm) is assigned as H-6a proton and relatively lower fre-
quency signal is assigned (4.17 ppm) as H-2a proton. Both the sig-
nals are confirmed from its HOMOCOSY (Fig. 6), NOESY (Fig. 7) and
HSQC (Fig. 3) correlation spectra. In the lower frequency region
CH3
H
N
O
2
3
there is a double doublet at 2.42 (J = 13.0 Hz; J = 1.56 Hz) with
one proton integral is assigned as H-5e on the basis of their multi-
plicity and vicinal coupling constant. Consequently, the multiplet
at 3.48 ppm with two protons integral is for H-3a and H-5a, which
is unambiguously assigned from the HSQC correlation spectra. The
two protons linked to C-5 of the pyran nucleus were thus found to
be 1.06 ppm separation. The marked difference between the pro-
tons linked to C-5 would not only result from the inductive effect
exerted by the heteroatoms, but rather due to a spatial effect prob-
ably exerted by the acetyl groups.
H
S
H
N
H
6
4
5
N
2
1
O
CH3
3
H
CH3
H
O
In the NOESY spectrum (Fig. 7), NOE was observed between the
proton linked to the nitrogen atoms and the least shielded methyl
moiety, that is to say, the methyl moiety of the acetamide group
linked to C of the heterocycle; therefore, the methyl moiety that
appears at a higher field is the one belonging to the N-acetyl group.
Considering both acetyl groups, the one located on N-4 of the het-
erocycle is nearer the pyran ring and could present some type of
interaction with the hydrogen atoms in position C-3 and C-5; how-
ever, no NOE effect was observed between the methyl moiety of
this acetyl group and the hydrogen atoms belonging to the pyran
system.
Fig. 7. The NOESY correlation of the compound 3.
and NOESY correlations spectra are shown in Figs. 8 and 9, respec-
tively. The signals appeared as double doublet and multiplet in the
region of 7.21–7.40 ppm with 10 protons integral are due to the
phenyl protons present at C-2 and C-6. Among the two signals
the double doublet at 7.41–7.38 has strong NOE with the double
doublet at 4.68 and doublet at 4.17 ppm (Fig. 8), which suggest
that the double doublet at 7.41–7.38 ppm is due to the ortho pro-
tons of the phenyl groups at C-2 and C-6. Deshielding of the ortho
protons has been attributed to the lone pair of electrons on the
oxygen in the pyran heterocycle. The rest of the phenyl protons
are merged together to give multiplet at about 7.21–7.34 ppm. In
3.4. Conformation of the compound 3
The observed chemical shifts, vicinal coupling constants and
splitting pattern strongly support that the synthesized compound
is in normal chair confirmation with equatorial disposition of the
the higher frequency region there are two signals as double dou-
blet at 4.68 ( J6a,5a = 10.40 Hz; 3
3
J
6a,5e = 1.56 Hz) and doublet at
Fig. 8. The COSY correlation spectrum of the compound 3.

S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
147
Fig. 9. The NOESY correlation spectrum of the compound 3.
phenyl rings present at C-2 and C-6 and methyl group at C-3 posi-
tion of the pyran moiety.
Perusal of Table 2, the benzylic (H-2a and H-6a) protons are not
much affected by the thiadiazoline moiety whereas the axial pro-
tons at C-3 and C-5 are deshielded 0.77 ppm and the equatorial
proton at C-5 is shielded about 0.3 ppm which are due to the aniso-
tropic effect of the carbonyl group present at N-4 of the thiadiazo-
line moiety as shown in Fig. 10.
From these inferences, the carbonyl group of acetyl group at N-
4 of thiadiazoline moiety is oriented in the plane of equatorial pro-
ton of C-5 and equatorial methyl group at C-3 and above the plane
of axial protons at C-3 and C-5. As a result the CAN-acetyl bond
oriented at equatorial.
There are two possible orientations of the N-acetyl group of thi-
adiazoline moiety whether the 4-N-acetyl group at equatorial or
axial. In order to avoid the 1,3-diaxial interaction the N-acetyl
group prefer the equatorial than axial orientation confirmed from
NMR spectral data of the compound 3.
The carbon chemical shift values of the compound 1 and their
parent thiopyran-4-one 3 and difference between them also repro-
duced in Table 1. As a result, the benzylic carbons at C-2 and C-6
are not much affected. An interesting point has been observed for
the compound 3 as C-3 carbon is resonances at shielded region than
the C-5 carbon unlike in parent ketone [24]. This is may be due to the
anisotropic effect exerted by carbonyl group of the thiadiazoline
moiety at N-4 which deshielded the methyl carbon at C-3.
This hypothesis is supported by the optimized energy results
obtained from PM3 calculation. The PM3 calculation was carried
out for both the possible chair conformations Fig. 11 (N-acetyl
group at axial orientation) and Fig. 12 (N-acetyl group at equatorial
1
H NMR spectral data of the compound 3 gives the information
about the orientation of the spiro-C-S bond and C-N-acetyl bond.
The proton chemical shift values of pyran ring protons of com-
pound 3, parent ketone 1 and the difference between them are gi-
ven in Table 2.
H
O
CH3
H
O
Table 1
+
1
3C chemical shift values of 1, 3 and difference between them (d) in ppm.
H
S
N
Compound
C-2
C-3
C-4
C-5
C-6
3-CH
3
H
H
1
3
1
85.97
84.40
1.57
51.65
42.09
9.65
207.09
88.32
118.48
50.16
45.48
4.68
79.39
78.11
1.28
9.48
11.62
À2.14
CH3
H
N
N
–3
-
O
-
CH3
Table 2
1
H chemical shift values of 1, 3 and difference between them (d) in ppm.
Compound
H-2a
H-3a
H-5a
H-5e
H-6a
3-CH
3
+
1
3
1
4.33
4.17
0.16
2.71
3.48
À0.77
4.81
4.68
0.13
0.86
0.74
0.12
3.48
À0.77
2.42
0.29
Fig. 10. Anisotropic effect on H-5e and 3-CH
Àshielding region).
3
protons (+shielding region and
–3

1
48
S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
Table 3
Crystal data and structure refinement of compound 3.
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system, space group
Unit cell dimensions
23 25 3 3
C H N O S
423.52
293(2) K
0.71073 Å
Orthorhombic, P2
a = 11.069(5) Å
b = 14.681(5) Å b = 90°
1 1 1
2 2
a
= 90°
c = 13.910(5) Å
c = 90°
Volume
2260.4(15) Å3
3
Z, calculated density
Absorption coefficient
F(0 0 0)
4, 1.244 mg/m
À1
0.171 mm
896
Crystal size
Theta range for data collection
Limiting indices
Reflections collected/unique
Completeness to theta = 25.00
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
0.30 Â 0.20 Â 0.20 mm
2.30–27.93°
À14 6 h 6 14, À19 6 k 6 19, À18 6 l 6 18
24,921/5423 [R(int) = 0.0348]
99.9%
Fig. 11. The optimized structure of the compound 3 with optimized energy 12.89
kJ/mol).
Semi-empirical from equivalents
0.9665 and 0.9504
(
Full-matrix least-squares on F2
5423/0/290
1.025
Final R indices [I > 2
R indices (all data)
Absolute structure parameter
Largest diff. peak and hole
r
(I)]
R1 = 0.0467, wR2 = 0.1199
R1 = 0.0652, wR2 = 0.1341
0.03(9)
0.442 and À0.200 eA
À3
Fig. 12. The optimized structure of the compound 3 with optimized energy 1.78
kJ/mol).
(
orientation), in which the later optimized at lower energy (1.78 kJ/
mol) than the former (12.89 kJ/mol). The equatorial orientation of
N-acetyl group of thiadiazoline moiety further confirmed from
their selected bond angles and torsion angles derived from PM3
calculation method and X-ray diffraction studies.
Fig. 13. The ORTEP diagram of the compound 3, showing 50% probability
displacement ellipsoids.
3.5. Crystal structure
The compound 3 crystallizes into an orthorhombic lattice with
present at C-5 is in axial and methyl group at C-5 is in equatorial ori-
P2
1
2
1
2
1
symmetry. Crystal data and structure refinement of com-
entation. The sum of the bond angles around N2 atom [347.8 (18)°]
indicates the sp hybridization. The torsion angles C(22)AC(21)A
2
pound 3 is shown in Table 3. The ORTEP diagram of compound 3 is
shown in Fig. 13, displacement ellipsoids is drawn at 50% probability
level. The saturated pyran ring adopts a distorted chair conforma-
tion, as shown by the torsion angles around the bonds involving
the ring atoms. These torsion angles deviate from the ideal value of
N(2)AN(1) [À3.31°] and C(22)AC(21)AN(2)AC(3) [À177.01(3)°]
indicate that atoms C(21) and C(22) lie in the plane of the five-mem-
bered ring (N2AN1AC18AS1AC3). Also the torsion angles
C20AC19AN3AC18 [177.89°], O(2)AC(19)AN(3)AC(18) [À1.25
5
6° reported for the chair conformation of cyclohexane [25]. The
CAC bond lengths of the aryl rings are in the range 1.366 (3)–1.375
4) Å, while the bond angles are in the range 117.8 (2)–122.2 (2)°.
(3)°],
C(19)AN(3)AC(18)AS(1) [6.39°] and
C(19)AN(3)A
C(18)AN(1) [174.47(2)°] indicate that the substituted moiety at
C(18) lie in the plane of the ring to which it is attached. The dihedral
angles (2a)AC(2)AC(3)AS(1) [À173.33°], H(2b)AC(2)AC(3)AS(1)
[À52.80°], H(2a)AC(2)AC(3)AN(2) [À58.93°] and H(4)AC(4)A
C(5)AH(5) [170.94°] which clearly indicates the equatorial orienta-
tion of N-acetyl group. The selected bond length, bond angles and
torsion angles obtained from PM3 calculation data of the compound
3 are in good agreement with XRD-data which are shown in Table 4.
(
The equatorial dispositions of the phenyl groups are revealed by
the torsion angles involving the exo atom and the other three ring
atoms; these vary from À179.0 (4)° to 177.9 (3)°, as observed also
in a pentasubstituted cyclohexan-1-one derivative [26]. Torsion an-
gle of À67.93° and 170.94° perceived by H(5)AC(5)AC(4)AC(23) and
H(4)AC(4)AC(5)AH(5), respectively, confirms the methyl group

S. Umamatheswari, S. Kabilan / Journal of Molecular Structure 938 (2009) 142–149
149
Table 4
References
Geometric parameters of compound 3.
[
1] C.L. Stevens, P. Blumbergs, D.H. Otterbach, J.L. Stronming, M. Matsuhashi, D.N.
Dietzler, J. Am. Chem. Soc. 86 (1964) 2937;
Geometric parameters
XRD
PM3 calculation
Bond length (Å)
C(6)AC(7)
C(6)AC(11)
C(21)AO(3)
C(3)AS(1)
C.L. Stevens, P. Blumbergs, F.A. Daniher, J. Am. Chem. Soc. 85 (1963) 1552.
1.375(4)
1.366(3)
1.213(3)
1.852(2)
1.480(3)
1.263(3)
1.342
1.334
1.268
2.000
1.537
1.303
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[
C(3)AN(2)
C(18)AN(1)
(
1995) 161.
[
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Bond angle (°)
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455.
[7] K. Pan, M.K. Scott, D.H.S. Lee, L.J. Fitzpatric, J.J. Crooke, R.A. Rivero, D.I.
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C(21)AN(2)AN(1)
C(11)AC(6)AC(7)
C(7)AC(6)AC(5)
C(21)AN(2)AN(1)
C(18)AN(1)AN(2)
N(1)AN(2)AC(3)
C(21)AN(2)AN(1)
C(18)AN(1)AN(2)
N(1)AC(18)AN(3)
C(19)AN(3)AC(18)
O(2)AC(19)AN(3)
111.26(17)
117.8(2)
122.2(2)
119.15(18)
111.26(17)
117.39(17)
119.15(18)
111.26(17)
119.48(19)
126.0(2)
112.88
117.21
121.12
120.70
120.02
122.67
120.09
112.88
118.89
124.17
120.69
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[
[
[
[
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C(1)AC12)AC(17)AC(16)
C(5)AO(1)AC(1)AC(12)
C(22)AC(21)AN(2)AN(1)
C(22)AC(21)AN(2)AC(3)
O(2)AC(19)AN(3)AC(18)
C(19)AN(3)AC(18)AS(1)
C(19)AN(3)AC(18)AN(1)
H(2a)AC(2)AC(3)AS
177.9(3)
À179.0(3)
À3.3(4)
178.07
À178.94
À2.26
À177.1(3)
À1.25(3)
6.39(3)
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176.01
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172.10
À175.23
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À62.56
À174.99
1105;
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H(2b)AC(2)AC(3)AS
H(2a)AC(2)AC(3)AN(2)
C(1)AO(1)AC(5)AC(6)
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À172.26
2
402;
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2
4
. Conclusion
Conformation of title compound was carried out using NMR
1
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Chem. 39 (2004) 527;
C. Ramalingan, S. Balasubramanian, S. Kabilan, M. Vasudevan, Med. Chem. Res.
spectral data, X-ray diffraction. The semiempirical molecular orbi-
tal calculation (PM3) also carried out to investigate the conforma-
tional preference of N-acetyl group of 1,3,4-thiadiazoline moiety.
The results show that the title compound exist in chair conforma-
tion with equatorial orientations of two phenyl groups at C-2, C-6,
methyl group at C-3 carbons and N-acetyl group of thiadiazoline
moiety. The results obtained from NMR spectra are in good agree-
ment with those from X-ray crystallography and MOPAC (PM3)
calculation.
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(
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[
[
Authors are thankful to Professor K. Pandiarajan, Head, Depart-
ment of Chemistry, Annamalai University for the facilities pro-
vided. Authors are thankful Council of Scientific and Industrial
Research, New Delhi, India for financial support. The authors would
like to acknowledge NMR research center, IISc-Bangalore and SAIF,
IIT-Madras, respectively, for recording NMR and single crystal XRD.
The authors also acknowledge Dr. M. Ramalingam, Scientist, Prist
University, Thanjavur, for PM3 calculations.
[
[