A diastereoselective synthesis of novel multifunctional thianes

Article abstract of DOI:10.1080/10426500802625727

The reaction of 2,2′-thiobis(1,3-diarylprop-2-en-1-ones) with malononitrile in the presence of sodium ethoxide under both thermal and solvent-free microwave conditions afforded a series of hitherto unknown 2e,6e-diaroyl-3e,5e-diaryl-4,4-dicyanothianes dia

Full text of DOI:10.1080/10426500802625727

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A Diastereoselective Synthesis
of Novel Multifunctional
Thianes
B. Vinosha a , S. Renuga a , M. Gnanadeebam a & S.
Perumal b
a Department of Chemistry , Fatima College ,
Madurai, India
b School of Chemistry , Madurai Kamaraj University ,
Madurai, India
Published online: 03 Nov 2009.
To cite this article: B. Vinosha , S. Renuga , M. Gnanadeebam & S. Perumal
(2009) A Diastereoselective Synthesis of Novel Multifunctional Thianes,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:11, 2980-2988, DOI:
10.1080/10426500802625727
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Phosphorus, Sulfur, and Silicon, 184:2980–2988, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802625727
A Diastereoselective Synthesis of Novel Multifunctional
Thianes
B. Vinosha,1 S. Renuga,1 M. Gnanadeebam,1 and S.
Perumal2
1Department of Chemistry, Fatima College, Madurai, India
2School of Chemistry, Madurai Kamaraj University, Madurai, India
The reaction of 2,2ꢀ-thiobis(1,3-diarylprop-2-en-1-ones) with malononitrile in the
presence of sodium ethoxide under both thermal and solvent-free microwave
conditions afforded a series of hitherto unknown 2e,6e-diaroyl-3e,5e-diaryl-4,4-
dicyanothianes diastereoselectively in good yields via a double Michael addition.
The structures of all the compounds have been elucidated by IR, 1H NMR, 13C
NMR, and elemental analysis.
Keywords Malononitrile; Michael addition; microwave irradiation; thianes; 2,2ꢀ-
thiobis(1,3-diarylprop-2-en-1-ones)
INTRODUCTION
In continuation of our work on the synthesis of novel heterocyclic
compounds1 employing 2,2ꢀ-thio/2,2ꢀ-sulfonyl-bis(1,3-diarylprop-2-en-
1-ones), we herein report a green, as well as conventional thermal ap-
proach, to the synthesis of multisubstituted thianes. The synthesis of
thianes assumes importance since naturally occurring six-membered
sulfur heterocycles are scant.2 Moreover the thiane ring plays a key
role in the biological activities of drugs such as cephalosporins3 and
dithiathromboxane.4 They also display several pharmacological proper-
ties such as anti-inflammatory,5 antihypertensive,6 antiulcer,7 antimi-
crobial,8 antibacterial,9 and analgesic10 activities in addition to their
use in industry as bleaching11 and antiwear12 agents and stabilizing
agents in color photography.13 Moreover, the title compounds possess
Received 20 October 2008; accepted 13 November 2008.
S.R. and M.G. thank UGC for funds under Major Research Project. S.R., M.G., and
B.V. thank the Secretary and the Principal, Fatima College, Madurai, India for providing
facilities.
Address correspondence to S. Renuga, Department of Chemistry, Fatima College,
Madurai 625018, India. E-mail: s.renuga@gmail.com
2980

Diastereoselective Synthesis of Thianes
2981
gem-dicyano groups, which provide scope for the synthesis of spiro het-
erocycles.14 It is also pertinent to note that though the syntheses of a
large number of a variety of heterocycles by microwave-assisted syn-
thesis have been reported, there is no report on the synthesis of thianes
using microwave irradiation.
RESULTS AND DISCUSSION
In the present investigation, 2,6-diaroyl-3,5-diaryl-4,4-dicyanothianes
were obtained in good yields by the reaction of the 2,2ꢀ-thiobis(1,3-
diarylprop-2-en-1-ones) 1 in DMF with malononitrile in the presence
of sodium ethoxide at room temperature for 1 h (Scheme 1).
Alternatively the same reaction was carried out under solvent-free
microwave irradiation in order to effect a green synthesis and to see
whether there is any product/stereoselectivity, as it is not uncommon
to get different products from reactions under solvent-free microwave
SCHEME 1 Synthesis of 2e, 6e-diaroyl-3e, 5e-diaryl-4,4-dicyanothianes.

2982
B. Vinosha et al.
TABLE I Yields and Reaction Time for Conventional Heating and Mi-
crowave Reactions
Microwave
irradiation
Conventional at
ambient temp.
No.
Compd.
Yield (%)
Time (min)
Yield (%)
Time (min)
1
2
3
4
5
6
7
8
9
2a
2b
2c
2d
2e
2f
2g
2h
2i
86
79
66
66
83
91
93
92
81
82
5
5
5
5
5
5
5
5
5
5
82
76
65
83
79
85
84
82
79
73
60
60
60
60
60
60
60
60
60
60
10
2j
irradiation and in solution under conventional heating.15–19 In addi-
tion, microwave reactions often proceed more rapidly than conventional
thermal reactions with diminished decomposition of the products and
enhanced yields.
In a typical reaction, 2,2ꢀ-thiobis(1,3-diarylprop-2-en-1-ones) 1, mal-
ononitrile, and solid sodium ethoxide were mixed thoroughly in a
borosilicate boiling tube, kept in a silica bath, which in turn was placed
in a microwave oven (750 W and frequency of 2450 MHz) and irradi-
ated at power level 4 of a total scale of 6. Completion of the reaction
(TLC) requires 5 min of microwave irradiation in one stretch without
intermittent cooling. The reaction mixture, after workup, afforded good
yields of the same thianes obtained under thermal conditions described
above (Scheme 1).
The results obtained in the present study regarding thermal ver-
sus microwave reactions in the synthesis of the title compounds are
shown in Table I. It is clear that the microwave-assisted synthesis
afforded better yields in all the cases, except one giving 2d, and the
reaction time is also many-fold shorter than the conventional method.
It also has the obvious advantages of the absence of solvent and easy
workup.
The thianes, 2a–2j, obtained were characterized by elemental anal-
1
ysis, IR, H NMR, and 13C NMR spectroscopic data. The elucidation
1
of the structure of 2 is discussed by taking 2h as an example. The H
NMR spectrum of 2h displayed two 2H doublets at 4.24 (J = 10.8 Hz)

Diastereoselective Synthesis of Thianes
2983
and 5.62 ppm (J = 10.8 Hz) assignable to H-3,5 and H-2,6 of the thi-
ane ring, respectively, on the basis of substituent effects and analogy
with the chemical shifts of similar compounds.1g The thiane 2h also
has signals for the aromatic protons between 7.11 and 7.85 ppm and
tolyl methyl protons as a singlet at 2.27 ppm. The coupling constant
of the doublets (J = 10.8 Hz) of H-3,5 and H-2,6 indicates the diaxial
relationship between the vicinal hydrogens, which points to the equa-
torial orientations of the aryl groups at C-3,5 and aroyl groups at C-2,6.
Thus the compound is characterized as 2e,6e-diaroyl-3e,5e-diaryl-4,4-
dicyanothianes. In its 13C NMR spectrum, 2h showed two signals at
112.9 and 113.8 for the diastereotopic cyanide groups besides the other
expected signals. The other thianes also showed similar spectroscopic
features as 2h.
The formation of thianes displays a double Michael addition of the
carbanion, generated from malononitrile, in distinct steps to the thiobis
compound 1.
CONCLUSION
The present work describes the synthesis of multisubstituted thianes
by conventional solution chemistry and solvent-free, microwave-
assisted synthesis. Though both the methods afforded the same
products, the yields are higher with great diminution in reaction time
under the solvent-free, microwave irradiation procedure. Further util-
ity of the multifunctional thianes, as synthons in the synthesis of spiro
heterocycles, currently is being explored in our group.
EXPERIMENTAL
The melting points are uncorrected. A domestic microwave oven
(IFB, model electron of 750 W capacity and microwave frequency of
2450 MHz) was employed for microwave irradiation. IR spectra were
recorded on a Shimadzu instrument with KBr pellet. NMR spectra
were recorded at 20◦C on a Bruker AMX 300 instrument operating at
1
300 MHz for H and 75 MHz for 13C. Solutions (in CDCl3) were ap-
proximately 0.05 M, and chemical shifts were referenced internally to
TMS in all cases and expressed in δ scale (ppm). Elemental analyses
were performed on a Perkin-Elmer 2400 Series II Elemental CHNS
Analyzer. The Michael acceptor 1 was obtained by the method in the
literature.20

2984
B. Vinosha et al.
General Procedure for the Synthesis of
2e,6e-Diaroyl-3e,5e-diaryl-4,4-dicyanothianes: Synthesis of
2e,6e-Dibenzoyl-4,4-dicyano-3e,5e-diphenylthiane (2a)
Method 1: By the Solvent-Free Microwave Irradiation Method
Malononitrile (0.5 g, 5 mmol) was added dropwise with stirring into
solid sodium ethoxide prepared by dissolving sodium metal (0.12 g, 5
mmol) in absolute ethyl alcohol (4 mL) and evaporating the solvent. To
this mixture, 2,2ꢀ-thiobis(1,3-diphenylprop-2-en-1-one) (2.2 g., 5 mmol)
was added and thoroughly mixed in a mortar. The mixture was then
transferred into a borosilicate boiling tube, immersed in a silica bath,
and kept in a domestic microwave oven at power level 4 (400 W) for
5 min. The completion of the reaction was followed by TLC. The re-
action mixture was first washed with water, then with ethyl alcohol,
and crystallized from an ethyl alcohol:chloroform mixture (3:2, 50 mL)
to give 2e,6e-dibenzoyl-4,4-dicyano-3e,5e-diphenylthiane as a colorless
solid, mp 282–284 ◦C; IR (KBr) ν 1678, 2250 cm−1; 1H NMR (300 MHz,
CDCl3) δH 4.30 (d, 2H, J = 10.5 Hz), 5.72 (d, 2H, J = 10.5 Hz), 7.28–7.62
(m,14H), 7.73 (dd, 2H, J = 3.3, 5.7 Hz), 7.91 (d, 4H, J = 7.8 Hz); 13C NMR
(75 MHz, CDCl3) δC 46.3, 48.8, 52.7, 113.0, 113.4, 128.6, 128.8, 128.9,
129.1, 130.9, 134.3, 135.0, 135.2, 192.2. Anal. Calcd for C33H24N2O2S:
C, 77.32; H, 4.72; N, 5.46. Obsd: C, 77.48; H, 4.74; N, 5.43%.
Method 2: By the Conventional Thermal Method
Malononitrile (0.5 g, 5 mmol) was added dropwise with stirring into
a solution of sodium ethoxide prepared by dissolving sodium metal
(0.12 g, 5 mmol) in absolute ethyl alcohol (4 mL). To this mixture,
a solution of 2,2ꢀ-thiobis(1,3-diphenylprop-2-en-1-one) (2.2 g, 5 mmol)
in dimethylformamide (40 mL) was added with stirring and kept at
room temperature for 1 h. The reaction mixture was then poured into
water, and the separated solid was filtered and crystallized from an
ethyl alcohol:chloroform mixture (3:2, 50 mL) to give 2e,6e-dibenzoyl-
4,4-dicyano-3e,5e-diphenylthiane 2a.
2e,6e-Dibenzoyl-3e,5e-di(p-chlorophenyl)-4,4-dicyanothiane
(2b)
Obtained as a colorless solid, mp 262–264◦C; IR (KBr) ν 1673, 2254
cm−1; 1H NMR (300 MHz, CDCl3) δH 4.31 (d, 2H, J = 10.5 Hz), 5.67 (d,
2H, J = 10.5 Hz), 7.29–7.73 (m, 14H), 7.92 (d, 4H, J = 7.5 Hz); 13C NMR
(75 MHz, CDCl3) δC 46.2, 48.5, 51.9, 112.6, 113.4, 128.6, 129.1, 129.4,
130.0, 133.6, 134.6, 135.6, 191.8. Anal. Calcd for C33H22Cl2N2O2S: C,
68.16; H, 3.81; N, 4.82. Obsd: C, 67.98; H, 3.79; N, 4.84%.

Diastereoselective Synthesis of Thianes
2985
3e,5e-Di(o-anisyl)-2e,6e-dibenzoyl-4,4-dicyanothiane (2c)
Obtained as a colorless solid, mp 244–246◦C; IR (KBr) ν 1673, 2250
1
cm−1; H NMR (300 MHz, CDCl3) δH 3.91 (s, 6H), 5.12 (broad signal,
2H), 5.72 (broad signal, 2H), 6.78–7.59 (m, 14H), 7.93 (d, 4H, J = 7.5
Hz); 13C NMR (75 MHz, CDCl3) δC 47.0, 48.0, 55.9, 111.6, 114.1, 120.7,
128.6, 128.8, 130.2, 134.1, 135.2, 192.6. Anal. Calcd for C35H28N2O4S:
C, 73.41; H, 4.93; N, 4.89. Obsd: C, 73.58; H, 4.94; N, 4.91%.
2e,6e-Dibenzoyl-4,4-dicyano-3e,5e-di(p-nitrophenyl)thiane
(2d)
Obtained as a colorless solid, mp 260–262◦C; IR (KBr) ν 1345, 1527,
1
1675, 2254 cm−1; H NMR (300 MHz, CDCl3) δH 4.48 (d, 2H, J = 10.5
Hz), 5.74 (d, 2H, J = 10.5 Hz), 7.49–7.73 (m,10H), 7.94 (d, 4H, J = 7.5
Hz), 8.23 (d, 4H, J = 8.7 Hz); Anal. Calcd for C33H22N4O6S: C, 65.77;
H, 3.68; N, 9.30. Obsd: C, 65.95; H, 3.69; N, 9.35%.
2e,6e-Di(p-chlorobenzoyl)-4,4-dicyano-3e,5e-diphenylthiane
(2e)
Obtained as a colorless solid, mp 236–238◦C; IR (KBr) ν 1682, 2246
1
cm−1; H NMR (300 MHz, CDCl3) δH 4.29 (d, 2H, J = 10.5 Hz), 5.64
(d, 2H, J = 10.5 Hz), 7.31–7.55 (m, 14H), 7.84 (d, 4H, J = 8.7 Hz);
13C NMR (75 MHz, CDCl3) δC 46.3, 48.6, 52.4, 112.7, 113.7, 128.7,
129.2, 129.4, 129.6, 130.0, 133.2, 135.0, 141.1, 191.0. Anal. Calcd for
C33H22Cl2N2O2S: C, 68.16; H, 3.81; N, 4.82. Obsd: C, 68.28; H, 3.79; N,
4.79%.
2e,6e-Di(p-chlorobenzoyl)-4,4-dicyano-3e,5e-di
(p-fluorophenyl)thiane (2f)
Obtained as a colorless solid, mp 288–290◦C; IR (KBr) ν 1680, 2250
1
cm−1; H NMR (300 MHz, CDCl3) δH 4.29 (d, 2H, J = 10.5 Hz), 5.56
(d, 2H, J = 10.5 Hz), 7.00–7.50 (m, 12H), 7.86 (d, 4H, J = 8.7 Hz); 13
C
NMR (75 MHz, CDCl3) δC 46.2, 48.6, 51.6, 112.5, 113.5, 116.3, 116.6,
129.5, 130.0, 130.5, 130.6, 130.8, 132.9, 141.4, 190.7. Anal. Calcd for
C33H20Cl2F2N2O2S: C, 64.19; H, 3.26; N, 4.54. Obsd: C, 64.01; H, 3.24;
N, 4.56%.

2986
B. Vinosha et al.
2e,6e-Di(p-chlorobenzoyl)-3e,5e-di(p-chlorophenyl)
-4,4-dicyanothiane (2g)
Obtained as a colorless solid, mp 238–240◦C; IR (KBr) ν 1680, 2250
cm−1; 1H NMR (300 MHz, CDCl3) δH 4.26 (d, 2H, J = 10.2 Hz), 5.56 (d,
2H, J = 10.2 Hz), 7.31–7.47 (m, 12H), 7.85 (d, 4H, J = 8.1 Hz). Anal.
Calcd for C33H20Cl4N2O2S: C, 60.94; H, 3.10; N, 4.31. Obsd: C, 60.85;
H, 3.12; N, 4.29%.
2e,6e-Di(p-chlorobenzoyl)-4,4-dicyano-3e,5e-di
(p-methylphenyl)thiane (2h)
Obtained as a colorless solid, mp 240–242◦C; IR (KBr) ν 1688, 2250
cm−1; 1H NMR (300 MHz, CDCl3) δH 2.27 (s, 6H), 4.24 (d, 2H, J = 10.8
Hz), 5.62 (d, 2H, J = 10.8 Hz), 7.11 (d, 4H, J = 7.8 Hz); 7.37 (d, 4H,
J = 7.8 Hz), 7.42 (d, 4H, J = 8.4 Hz), 7.85 (d, 4H, J = 8.4 Hz); 13C
NMR (75 MHz, CDCl3) δC 21.1, 46.2, 49.0, 52.1, 112.9, 113.8, 128.5,
129.3, 129.9, 130.0, 132.1, 133.2, 139.5, 141.0, 191.1. Anal. Calcd for
C35H26Cl2N2O2S: C, 68.96; H, 4.30; N, 4.60. Obsd: C, 69.14; H, 4.28; N,
4.63%.
4,4-Dicyano-2e,6e-di(p-methylbenzoyl)-3e,5e-diphenylthiane
(2i)
Obtained as a colorless solid, mp 266–268◦C; IR (KBr) ν 1688, 2250
cm−1; 1H NMR (300 MHz, CDCl3) δH 2.39 (s, 6H), 4.30 (d, 2H, J = 10.5
Hz), 5.73 (d, 2H, J = 10.5 Hz), 7.22–7.54 (m, 14H), 7.83 (d, 4H, J = 7.5
Hz); 13C NMR (75 MHz, CDCl3) δC 21.7, 46.1, 48.9, 52.7, 112.9, 113.7,
128.7(6), 128.8(1), 129.0, 129.3, 129.6, 132.5, 135.3, 145.5, 191.6. Anal.
Calcd for C35H28N2O2S: C, 77.75; H, 5.22; N, 5.18. Obsd: C, 77.60; H,
5.19; N, 5.21%.
4,4-Dicyano-2e,6e-di(p-methylbenzoyl)-3e,5e-di
(p-chlorophenyl)thiane (2j)
Obtained as a colorless solid, mp 248–250◦C; IR (KBr) ν 1688, 2250
cm−1; 1H NMR (300 MHz, CDCl3) δH 2.41 (s, 6H), 4.27 (d, 2H, J = 10.8
Hz), 5.64 (d, 2H, J = 10.8 Hz), 7.25–7.44 (m, 12H), 7.82 (d, 4H, J = 8.0
Hz); 13C NMR (75 MHz, CDCl3) δC 21.8, 46.0, 48.6, 52.0, 112.3, 113.4,
128.8, 129.4, 129.8, 130.0, 132.2, 133.7, 135.5, 145.9, 191.2. Anal. Calcd
for C35H26Cl2N2O2S: C, 68.96; H, 4.30; N, 4.60. Obsd: C, 68.80; H, 4.32;
N, 4.58%.

Diastereoselective Synthesis of Thianes
2987
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