Ultrasound promoted greener synthesis of spiro[indole-3,5′-[1,3]oxathiolanes in water

Article abstract of DOI:10.1016/j.ultsonch.2009.08.003

An aqueous mediated novel synthesis of substituted 2′amino-4′benzoyl-2′-methyl spiro[indole 3,5′-[1,3]oxathiolane]-2(1H)-ones (2a-f) was carried out from the reaction of spiro [indole-3,2′-oxiranes] (1a-f) with thioacetamide in the presence of LiBr as cat

Full text of DOI:10.1016/j.ultsonch.2009.08.003

Ultrasonics Sonochemistry 17 (2010) 399–402
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Ultrasonics Sonochemistry
journal homepage: www.elsevier.com/locate/ultsonch
Ultrasound promoted greener synthesis of spiro[indole-3,50-[1,3]oxathiolanes
in water
*
Anshu Dandia , Ruby Singh, Sumit Bhaskaran
Department of Chemistry, University of Rajasthan, Jaipur 302 004, India
a r t i c l e i n f o
a b s t r a c t
An aqueous mediated novel synthesis of substituted 20amino-40benzoyl-20-methyl spiro[indole 3,50-
[1,3]oxathiolane]-2(1H)-ones (2a–f) was carried out from the reaction of spiro [indole-3,20-oxiranes]
(1a–f) with thioacetamide in the presence of LiBr as catalyst. The reaction was carried out under both
microwaves and sonication and results were also compared with conventional method. In general,
improvement in rate and yields observed when reaction was carried out under sonication as compared
to microwave irradiation and conventional method.
Article history:
Received 10 June 2009
Received in revised form 29 July 2009
Accepted 6 August 2009
Available online 9 August 2009
Keywords:
Spiro-oxirane
Water
Ó 2009 Elsevier B.V. All rights reserved.
Sonication
Spiro-oxathiolane
1. Introduction
tion of 4,40-dimethoxythiobenzophenone, xanthene thione and
admantane-2-thione with 2-vinyloxirane [14], by condensation
Heterocyclic rings have played an important role in medicinal
chemistry, serving as key template central to the development of
numerous important therapeutic agents. Among the many five-
membered heterocycles studied, 1,3-oxathiolanes are one such
class of heterocycles which attracted much attention as they have
been reported to possess a wide range of biological activities
including anti-viral [1], anticonvulsant [2], antiulcer [3] and anti-
fungal activity [4]. In addition they also showed antihepatitis
of glyoxylic acid ester with 2,5-dihydroxy-1,4-dithianes [15], by
the reaction of 1,3-thiazole-5(4H)-thiones with 1,2-epoxy cyclo-
alkanes [16] and the reaction of epoxides with sulfur and carbon
monoxide [17], by the reaction of benzoyloxy acetaldehyde and
p-dithiane-2,5-diol [18], by the reaction of oxirane and carbon
disulphide [19] etc.
Many of these methods suffer from several limitations such as,
longer reaction time, unsatisfactory yield, harsh reaction condition
and excessive use of reagents and catalyst. In order to over came
these limitations and in vision of the requirement of green chem-
istry it is therefore important to find convenient method for the
preparation of these compounds.
In the last few years the development of synthetic protocols
employing ultrasound irradiation has determined an epoch-mak-
ing change in organic reactions and activates poorly reactive sub-
strates [20]. The notable features of the ultrasound approach are
enhanced reaction rates, formation of purer products in high
yields, easier manipulation and considered as processing aid in
terms of energy conservation and waste minimization compared
with traditional methods [21]. Further, among alternatives, water
is very begin solvent for organic transformation offers, green
chemistry benefits and expedite the synthesis of diverse heterocy-
cles [22].
B
virus, anti-HIV and anti-HBV activity [5]. 1,3-oxathiolane
derivatives are novel precursors of 20,3-dideoxy-30-oxa-400thioribo-
nucleosides which also show anti-viral activities [6]. Spirocyclic
indolines represent important scaffolds for drug discovery [7].
These heterocycles offer well-defined substituent vectors and their
conformational rigidity, small size, and polarity confers favorable
physical properties for oral bioavailability. On the other hand oxin-
dole derivatives have been identified as a novel inhibitor of micro-
tubule assembly [8], utilized as glycine receptor [9], nonpeptidyl
growth-hormones secretagogues [10], muscarinic receptor modu-
lators [11] and identified as privileged scaffold for the discovery
of ligands for G-protein coupled receptor [12].
The common methods used for the preparation of 1,3-
oxathiolanes include the reaction of aromatic thioketone with
monosubstituted oxirane [13], xanthene thione and by the reac-
As a part of our interest in the synthesis of a wide range of
heterocyclic systems, and in a continuation of using green chemis-
try tools for heterocyclic synthesis [23], we performed the novel
synthesis of spiro[indole-oxathiolanes] (2a–f) by the reaction of
* Corresponding author. Tel.: +91 9414455452.
E-mail addresses: dranshudandia@yahoo.co.in, drrubychem@yahoo.com (A.
Dandia).
1350-4177/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ultsonch.2009.08.003

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A. Dandia et al. / Ultrasonics Sonochemistry 17 (2010) 399–402
H3C
O
NH2
S
O
R
O
Thioacetamide
O
C
R
X
X
C
LiBr, H2O,
)))))
N
H
O
N
O
H
1
2
Scheme 1.
spiro[indole-oxiranes] (1a–f) with thioacetamide in presence of
LiBr under ultrasound irradiation and employing water as the reac-
tion medium for the first time. In fact, as clearly stated by Sheldon,
it is generally recognized that ‘‘The best solvent is no solvent and if
a solvent (diluent) is needed it should preferably be water [24]”. To
the best of our knowledge no report is available in the literature
using ultrasonic assisted method for this transformation (Scheme
1).
It appears that in the present heterogeneous system sonochem-
ical activation is mainly a consequence of the mechanical effects of
cavitation [30], a liquid jet propagates towards the phase boundary
at a velocity of several hundred meters per second, and hits the
surface violently. At a liquid–liquid interface, the mutual injection
of droplets results in emulsification. On a solid, the intense physi-
cal stresses produce particle breakage, the importance of which de-
pends, inter alia, on the lattice energy of the solid [31]. In addition,
cavitation greatly accelerates mass transport [32] and repassiva-
tion by reaction products is made less important or even avoided
[33]. Further, there are certain cases being reported, in which son-
ication induces a specific reactivity under both homogeneous and
heterogeneous conditions [34]. Since purely mechanical effects
cannot explain such qualitative changes, cavitation must have di-
rect chemical consequences.
In continuation of our earlier interest on microwave-assisted
reactions we have also carried out the synthesis of 2a under micro-
wave irradiation using water/DMF as a solvent (Table 1). The role
of DMF can be explained as energy transfer agent and homogenizer
to increase the reaction temperature [35]. There was no apprecia-
ble increase in yield, thus the effect of microwaves on the synthesis
of spiro derivative in not as efficient as ultrasound, but still better
than the thermal method in which the mixture of products was
formed.
2. Results and discussion
The required precursors spiro[indole-3,20-oxirane]30 benzoyl-
2(1H)-ones (1a–f) were synthesized by our improved method
involving the reaction of 3-aroylmethyllene indol-2-one with
alkaline H2O2 under microwave irradiation in 2–3 min at 240 W
[25].
To synthesize spiro[indole-1,3-oxathiolane] (2a), the reaction of
1a with the thioacetamide in presence of LiBr has been carried out
both under low intensity ultrasonic (LIU) laboratory cleaning bath
(which is more economic) and high intensity ultrasound probe sys-
tem (HIU) for comparative studies [26]. Although, it is well estab-
lished that LIU from an ultrasonic cleaner has considerably less
power and the energy of ultrasound is not uniformly available from
the ultrasonic bath [27] when compared to HIU from a direct
immersion horn [28]. This can lead to reproducibility problems
due to the lower power involved for LIU [29]. In the present case,
reaction was facile using both instruments but excellent yield in
shorter reaction time with reproducible results was achieved using
(HIU) sonicator as compared to (LIU) ultrasonic bath. Hence, other
Hence, a series of spiro[indole1,3-oxathiolanes] (2a–f) was
synthesized under sonication using water as solvent. To find the
specific effect of ultrasound on this (HIU) the reaction was also
carried out under same conditions in absence of ultrasound irradi-
ation (Table 1). It was observed that the reaction time increased
considerably and the yield of the product decreased due to
formation of mixture of products. Thus, ultrasound irradiation
was found to have beneficial effect on the synthesis of spiro
[indole-oxathiolanes].
compounds listed in Table
irradiations.
2 were synthesized under HIU
Table 1
Comparative study for synthesis of spiro[indole-1,3-oxathiolane] 2a.
The plausible mechanism for present investigation involves
nucleophilic attack of bromide ion at less substituted C-3 position
of the spiro epoxide [36] leading to the formation of intermediate
(3 and 4). Further, sulfur being a better nucleophile than nitrogen
atom so in the next step cyclization leads to formation of oxathio-
lane ring [37] (Scheme 2).
S. no.
Reaction condition
Method
Time (min/h)
Yield (%)
1
2
3
4
5
6
Water
Water
Water
DMF
THF
Water
US bath (LIU)
Sonicator (HIU)
MW
MW
Stirring
50 min
7 min
20 min
15 min
5 h
80
84
76
70
50
37
The structure of the all synthesized compounds (2a–f) was
established by their spectral and analytical studies.
Stirring
5 h
Table 2
Synthesis of 20amino-40benzoyl-20-methyl spiro[indole-3,50-[1,3]oxathiolane]-2(1H)-ones (2a–f) under sonication and conventional conditions.
Compound
X
R
Ultrasonic irradiation
Time (min)
Conventional
Time (h)
M.P. (°C)
Yield (%)
Yield (%)
2a
2b
2c
2d
2e
2f
H
5-Cl
H
5-Br
5-F
5-CH3
H
H
4-F
H
4-Cl
3-Cl
7
6
5
6
7
8
84
87
86
87
82
86
5
5
5
5
5
5
60
64
58
61
59
62
235 [38]
265
225
250
240
270

A. Dandia et al. / Ultrasonics Sonochemistry 17 (2010) 399–402
401
H3C
NH2
C
S
O
O
C
O
C
O
N
H
O
Br
N
O
H
(3)
(1)
H3C
NH2
CH3
S
H2N
C
O
O
S
C
C
O
O
N
O
Br
H
N
O
H
(2)
(4)
Scheme 2.
4.1.2. Reaction under ultrasound irradiation
(i) Reaction under HIU irradiation using sonicator: A mixture of
spiro[indole-3,20-oxiran]30-benzoyl-2(1H)-one (1a)
(2 mmol),
3. Conclusion
In conclusion we have developed an effective methodology for
the synthesis of spiro derivatives. This new methodology offers
several advantages such as simple procedure, low cost, easy
work-up, short reaction times and milder conditions. In addition
this series may prove new classes of biological active compound
for biomedical screening, which is in progress.
LiBr (.2 mmol) and thioacetamide (2 mmol) in 10 ml water were
taken in a flask. The flask was attached to a 12 mm tip diameter
probe and the reaction mixture was sonicated for the specified
period at 50% power of the processor and 230 W output in
a 4 s pulse mode. At the end of the reaction period, TLC was
checked and the flask was detached from the probe and the con-
tent was transferred into a beaker. The formed solid was filtered
off, washed thoroughly with water to obtain the pure compound
2a.
4. Experimental
Melting points were determined on a Toshniwal apparatus.
The purity of compounds was checked on thin layers of silica
gel in various non-aqueous solvent systems, for e.g. benzene:eth-
ylacetate (9:1), benzene:dichloromethane (8:2). IR spectra (KBr)
were recorded on a Magna FT IR–550 spectrophotometer and
1H NMR and 13C NMR spectra were recorded on Bruker DRX-
300 using CDCl3 at 300.15 and 75.47, respectively. TMS was used
as internal reference. Mass spectrum of representative compound
was recorded on Kratos 50 mass spectrometer at 70 eV. The
microwave-assisted reactions were carried out in a multimode
MW oven (Panasonic-NN-781JF) operating at 1000 W generating
2450 MHz frequency and ultrasonic bath (Bandelin Sonorex)
operating at 230 V generating 33 kHz output frequency. HIU
irradiation was provided by an ultrasonic processor probe system
(Processor SONOPROS PR-1000MP, OSCAR ULTRASONICS made)
operating at 20 kHz, 750 W with 6 mm/12 mm tip diameter
probes.
(ii) Reaction under LIU irradiation using ultrasound bath: A mix-
ture of spiro compound (1a) (2 mmol), LiBr (.2 mmol) and thioace-
tamide (2 mmol) in 10 ml water were taken in a conical flask,
which was immersed in water bath of an ultrasonic cleaner. The
flask was positioned 0.5 cm above the bottom of the bath at room
temperature until the completion of the reaction (monitored by
TLC). The formed solid was filtered off, washed with water to afford
the spiro compound 2a.
4.1.3. Microwave mediated synthesis
(i) Using DMF: A mixture of spiro compound (1a) (2 mmol), LiBr
(.2 mmol) and thioacetamide (2 mmol) with few drops of DMF
contained in a beaker was placed in the microwave oven and irra-
diated for appropriate time (Table 1) The reaction mixture was
cooled and poured onto crushed ice. The precipitate thus filtered,
washed with water and recrystallized from ethanol.
(ii) Using water: A mixture of spiro compound (1a) (2 mmol),
LiBr (.2 mmol) thioacetamide (2 mmol) and water as a solvent in
open borosil beaker was irradiated inside microwave oven at
640 W till the completion of reaction (TLC). An oily product was
formed which was solidified on standing, washed with water and
recrystallized from ethanol.
4.1. Synthesis of 20amino-40benzoyl-20-methyl spiro[indole-3,50-
[1,3]oxathiolane]-2(1H)-ones (2a–f)
4.1.1. Conventional synthesis
A mixture of spiro[indole-3,20-oxirane]30-benzoyl-2(1H)-ones
(2 mmol), LiBr (.2 mmol) in 10 ml THF was stirred at room temper-
ature for 5 min, then thioacetamide (2 mmol) was added to the
solution and resulting mixture was further stirred at room temper-
ature for 5 h. Progress of the reaction was monitored by TLC. After
completion of reaction, the solvent was removed under reduced
pressure and the residue was purified on a silica gel column to give
2a.
Compound 2a: IR (KBr, cmꢀ1) Vmax 3250–3460 (NH and NH2) 1715
(C@O), 1695 (C@O); 1H NMR (300 MHz, CDCl3) dH: 2.24 (s, 3H,
CH3), 5.12 (s, 1H, CH), 6.23–7.87 (m, 11H, Ar–H, NH2), 8.15 (bs,
IH, NH); 13C NMR (74.46 MHz, CDCl3) dC: 32.3 (CH3). 61.7 (CH),
89.7 (spiro carbon), 114.21–142.3 (aromatic carbons), 177.3
(C@O), 199.8 (C@O), MS (m/z): 340.09 (100.0%), 341.09 (21.9%),
342.08 (4.4%), 342.09 (2.8%), Anal. calc. for C18H16N2O3S: C,
63.51; N, 8.23; S, 9.42; Found C, 63.21; N, 8.20; S, 9.40.

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A. Dandia et al. / Ultrasonics Sonochemistry 17 (2010) 399–402
[3] J.C. Aloup, J. Bouchaudon, D. Farge, J. Deregnaucourt, M. Hardy-Houis, J. Med.
Compound 2b: IR (KBr, cmꢀ1) Vmax 3255–3470 (NH and NH2)
Chem. 30 (1987) 24.
1717 (C@O), 1690 (C@O); 1H NMR (300 MHz, CDCl3) dH: 2.23 (s,
3H, CH3), 5.14 (s, 1H, CH), 6.24–7.89 (m, 10H, Ar–H, NH2), 8.18
(bs, IH, NH); 13C NMR (74.46 MHz, CDCl3) dC: 31.9 (CH3). 61.9
(CH), 90.1 (spiro carbon), 114.21–142.3 (aromatic carbons),
177.7(C@O), 197.8 (C@O), MS (m/z): 374.05 (M+). Anal. calc. for:
C18H15ClN2O3S: C, 57.68; H, 4.03; N, 7.47; S, 8.55. Found C, 57.88;
H, 4.01; N, 7.45; S, 8.52.
[4] H. Miyauchi, T. Tanio, N. Ohashi, Bioorg. Med. Chem. Lett. 6 (1996) 2377.
[5] J. Nokami, K.RyokumeJ. Inada, Tetrahedron Lett. 36 (1995) 6099.
[6] W. Wang, H. Jim, T.S. Mansour, Tetrahedron 35 (1994) 4739.
[7] (a) A.H. Abdel-Rahman, E.M. Keshk, M.A. Hanna, Sh.M. El-Bady, Bioorg. Med.
Chem. 12 (2006) 2483;
(b) S.L. Zhu, S.J. Ji, Z. Yong, Tetrahedron 63 (2009) 9365;
(c) T.H. Kang, K. Matsumoto, Y. Murakami, H. Takayama, M. Kitajima, N. Aimi,
Watanabe, Eur. J. Pharmacol. 444 (2002) 39.
[8] M.M. Khafagy, A.H.F.A. El-Wahas, F.A. Eid, A.M. EI-Agrody, Farmaco 55 (2002)
715.
Compound 2c: IR (KBr, cmꢀ1) Vmax 3257–3468 (NH and NH2)
1716 (C@O), 1699 (C@O), cmꢀ1 1H NMR (300 MHz, CDCl3) dH:
:
[9] F.M. Hershenson, K.A. Prodan, R.L. Kochman, J.L. Bloss, C.R. Mackerer, J. Med.
Chem. 20 (1977) 1448.
[10] (a) P.E. Maligres, I. Houpis, K. Rossen, A. Molina, J. Sagar, V. Upadhyay, K.M.
Wells, R.A. Reamer, J.E. Lynch, D. Askin, R.P. Volante, P.J. Reider, Tetrahedron 53
(1997) 10983;
2.22 (s, 3H, CH3), 5.15 (s, 1H, CH), 6.30–7.89 (m, 10H, Ar–H,
NH2), 8.16 (bs, IH, NH); 13C NMR (74.46 MHz, CDCl3) d 33.3
(CH3). 62.7 (CH), 89.2 (spiro carbon), 118.2–145.3 (aromatic car-
bon), 179.2 (C@O), 198.6 (C@O), MS (m/z): 358.08 (M). Anal. calc.
for C18H15FN2O3S; C, 60.32; H, 4.22; N, 7.82; S, 8.95. Found C,
60.11; H, 4.24; N, 7.86; S, 8.91.
(b) B.L. Palucki, S.D. Feighner, S.-S. Pong, K.K. Mckee, D.L. Hrenuik, C. Tan, A.D.
Howard, L.H.Y. Van der Ploeg, A.A. Patchett, R.P. Nargund, Bioorg. Med. Chem.
Lett. 11 (2001) 955.
[11] J.M. Elliott, H. Broughton, M.A. Cascieri, G. Chicchi, I.T. Huscroft, M. Kurtz, A.M.
Macleod, S. Sadowski, G.I. Stevenson, Bioorg. Med. Chem. Lett. 8 (1998) 1851.
[12] K. Bondensgaard, M. Ankersen, H. Thogersen, B.S. Hansen, B.S. Wulff, R.P.
Bywater. J. Med. Chem. 47 (2004) 888.
Compound 2d: IR (KBr, cmꢀ1) Vmax 3270–3480 (NH and NH2)
1719 (C@O), 1698 (C@O), cmꢀ1 1H NMR (300 MHz, CDCl3) dH:
:
2.28 (s, 3H, CH3), 5.10 (s, 1H, CH), 6.28–7.84 (m, 10H, Ar–H, NH2),
8.18 (bs, IH, NH); 13C NMR (74.46 MHz, CDCl3) d 34.3 (CH3). 61.7
(CH), 85.7 (spiro carbon), 119.21–147.3 (aromatic carbon, 179.3
(C@O), 192.8 (C@O): Anal. calc. for C18H15BrN2O3S: C, 51.56; H,
3.61; N, 6.68; S, 7.65. Found C, 51.26; H, 3.60; N, 6.70; S, 7.61.
Compound 2e: IR (KBr, cmꢀ1) Vmax 3275–3465 (NH and NH2)
[13] J. Du, J. Du, Synth. Commun. 34 (2004) 1925.
[14] C. Fu, A. Linden, H. Heimgartner, Halvtica Chimica Acta 84 (2001) 3319.
[15] A. Fedrov, C. Fu, A. Linden, H. Heimgartner, J. Eur. Org. Chem. (2005) 1613.
[16] J.L. Kraus, G. Attardo, Synthesis (1991) 1046.
[17] Z.A. Hozien, A.E.-W.A.O. Sarhan, O.S. Mohamed, Heterocyclic Commun.
(1999) 269.
5
[18] N. Kihara, Y. Nakawaki, T. Endo, J. Org. Chem. 60 (1995) 473.
[19] R.F. Schinazi, A. McMillan, D. Cannon, R. Mathis, R.M. Lioyd, A. Peck, J.P.
Sommadosi, M.St. Clair, J. Wilson, P.A. Furman, Antimicrob. Agents Chemother.
36 (1992) 2423.
[20] (a) G. Cravotto, P. Cintas, Chem. Soc. Rev. 35 (2006) 17;
(b) H. Xu, W.-M. Liao, H.F. Li, Ultrason. Sonochem. 14 (2007) 779.
[21] (a) S.Y. Wang, S.J. Ji, T.P. Loh, Synlett 15 (2003) 2377;
(b) T.J. Mason, J.P. Lorimer, Applied Sonochemistry, The Uses of Power
Ultrasound in Chemistry and Processing, Wiley VCH, Verlag Gmbh, 2002.
[22] (a) K. Aplander, D. Hidestal, K. Katebzadeh, U.M. Lindstrom, Green Chem. 8
(2006) 22;
1720 (C@O), 1700 (C@O) cmꢀ1 1H NMR (300 MHz, CDCl3) dH:
:
2.29 (s, 3H, CH3), 5.15 (s, 1H, CH), 6.33–7.89 (m, 9H, Ar–H, NH2),
8.15 (bs, IH, NH) 13C NMR (74.46 MHz, CDCl3) d 34.3 (CH3). 61.7
(CH), 89.1 (spiro carbon), 124.21–150.3 (aromatic carbon, 175.3
(C@O), 197.8 (C@O), MS (m/z): 392.04 (100.0%). Anal. calc. for
C18H14ClFN2O3S: C, 55.03; H, 3.59; N, 7.13; S, 8.16. Found C,
55.23; H, 3.58; N, 7.15; S, 8.13.
Compound 2f: IR (KBr, cmꢀ1) Vmax 3280–3468 (NH and NH2)
(b) C.-J. Li, Organic reactions in aqueous media with a focus on C–C bond
formations, Chem. Rev. 105 (2005) 3095.
1717 (C@O), 1694 (C@O) cmꢀ1 1H NMR (300 MHz, CDCl3) dH:
:
[23] (a) A. Dandia, K. Arya, Bioorg. Med. Chem. Lett. 18 (2008) 114;
(b) A. Dandia, R. Singh, S. Khaturia, J. Fluorine Chem. 128 (2007) 524;
(c) A. Dandia, R. Singh, S. Khaturia, Bioorg. Med. Chem. 14 (2006) 1303;
(d) A. Dandia, R. Singh, P. Sarawgi, Org. Prepar. Proc. Int. 37 (2005) 397;
(e) A. Dandia, K. Arya, M. Sati, S. Gautam, Tetrahedron 60 (2004) 5253;
(g) A. Dandia, R. Singh, P. Sarawgi, J. Fluorine Chem. 125 (2004) 1835;
(h) A. Dandia, M. Sati, K. Arya, A. Loupy, Green Chem. 4 (2002) 599.
[24] R.A. Sheldon, J. Mol. Catal. A 107 (1996) 75.
[25] A. Dandia, R. Singh, M. Saha, A. Shivpuri, Pharmazie 57 (2002) 4.
[26] S.R. Soudagar, S.D. Samant, Ultrason. Sonochem. 2 (1995) S49.
[27] C.C. Nascentesa, M. Kornb, C.S. Sousac, M.A.Z. Arruda, J. Braz. Chem. Soc. (12)
(2001) 57.
2.25 (s, 3H, CH3), 2.27(s, 3H, CH3), 5.17 (s, 1H, CH), 6.30–7.80 (m,
11H, Ar–H, NH2), 8.13 (bs, IH, NH); 13C NMR (74.46 MHz, CDCl3)
d 32.0 (CH3). 61.7 (CH), 89.2 (spiro carbon), 119.21–150.3 (aro-
matic carbon), 176.3 (C@O), 197.8 (C@O). Anal. calc. for
C19H17ClN2O3S: C, 58.68; H, 4.41; N, 7.20; S, 8.25. Found C, 58.49;
H, 4.42; N, 7.23; S, 8.22.
Presence and position of NH and NH2 protons were confirmed
by deuterium exchange.
[28] G. Cravotto, A. Demetri, G.M. Nano, G. Palmisano, A. Penoni, S. Tagliapietra,
Eur. J. Org. Chem. 22 (2003) 4438.
Acknowledgements
[29] (a) B. Pugin, Ultrasonics 25 (1987) 50;
Financial assistance from the C.S.I.R (01/2248/08/EMR-II)(9/
149/398/2005/EMR-I), New Delhi are gratefully acknowledged.
We are also thankful to the Regional Sophisticated Instrumentation
Centre Chandigarh, and Central Drug Research Institute, Lucknow,
for the elemental and spectral analyses.
(b) Nathan A. Ross, Richard A. Bartsch, J. Org. Chem. 68 (2003) 360;
(c) T.J. Mason, Chem. Soc. Rev. 26 (1997) 443.
[30] L.A. Crum, Ultrason. Sonochem. 2 (1995) S147.
[31] T. Ando, T. Kimura, Ultrasonics 28 (1990) 326.
[32] L.C. Hagenson, L.K. Doraiswamy, Chem. Eng. Sci. 53 (1997) 131.
[33] (a) A. Benhacene, P. Labbé, C. Petrier, G. Reverdy, New J. Chem. 9 (1995) 989;
(b) J. Klima, C. Bernard, C. Degrand, J. Electroanal. Chem. 367 (1994) 297.
[34] P. Cintas, J.-L. Luche, Green Chem. 6 (1999) 116.
[35] H. Marquez, A. Plutin, Y. Rodriguez, E. Perez, A. Loupy, Synth. Commun. 30
(2000) 1067.
References
[36] A. Shamsuzzaman, A. Salim, Tetrahedron Lett. 38 (1997) 5707.
[37] K. Sharma, K. Saleem, A. Salim, Indian J. Chem. 41B (2002) 2676.
[38] N. Dhaka, Ph.D. Thesis, Rajasthan University, Jaipur, 2008.
[1] N. Nguyen-Ba, N. Lee, L. Chan, B. Zacharie, Bioorg. Med. Chem. Lett. 10 (2003)
2223.
[2] M. Rajopadhye, F.D. Popp, J. Med. Chem. 31 (1988) 1001.