Ionic liquid catalyzed one-pot multi-component synthesis, characterization and antibacterial activity of novel chromeno[2,3-d]pyrimidin-8-amine derivatives

Article abstract of DOI:10.1016/j.molstruc.2012.02.044

An efficient, simple and convenient method for the one-pot multi-component synthesis of novel chromeno[2,3-d]pyrimidin-8-amine derivatives has been accomplished by starting from α-naphthol, aryl aldehydes, malononitrile and NH₄Cl. The reaction

Full text of DOI:10.1016/j.molstruc.2012.02.044

Journal of Molecular Structure 1017 (2012) 60–64
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Ionic liquid catalyzed one-pot multi-component synthesis, characterization
and antibacterial activity of novel chromeno[2,3-d]pyrimidin-8-amine derivatives
⇑
Sankari Kanakaraju, Bethanamudi Prasanna, Srinivas Basavoju, G.V.P. Chandramouli
Department of Chemistry, National Institute of Technology, Warangal 506 004, AP, India
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient, simple and convenient method for the one-pot multi-component synthesis of novel chro-
Received 13 January 2012
Received in revised form 17 February 2012
Accepted 17 February 2012
Available online 1 March 2012
meno[2,3-d]pyrimidin-8-amine derivatives has been accomplished by starting from
a-naphthol, aryl
aldehydes, malononitrile and NH4Cl. The reaction has been catalyzed by 1-butyl-3-methylimidazolium
tetrafluoroborate [bmim]BF4 ionic liquid. The newly synthesized compounds were characterized by IR,
1H NMR, 13C NMR, mass spectra, and elemental analysis. The structure of compound 4a was confirmed
by single-crystal X-ray diffraction. All the synthesized compounds were evaluated for their in vitro anti-
bacterial activity.
Keywords:
One-pot synthesis
Multi-component reaction
[bmim]BF4
Ó 2012 Elsevier B.V. All rights reserved.
Chromeno[2,3-d]pyrimidin-8-amine
Antibacterial activity
Single-crystal X-ray diffraction
1. Introduction
continue to be made to develop new MCRs [21–23]. Besides, the
ionic liquids have invoked enormous interest as catalyst and
Chromenes are important heterocyclic compounds with a wide
spectrum of biological and pharmacological activities viz. antimi-
crobial [1], antiviral [2], mutagenicity [3], antiproliferative [4],
and anticancer [5]. They also act as CNS agents [6] and antioxidants
[7]. They are also useful in preparing pheromones [8] and antitu-
mor agents [9]. Some of these compounds are employed in making
cosmetics, pigments [10] and potential biodegradable agrochemi-
cals [11].
On the other hand, pyrimidine ring which is an integral part of
various natural products of therapeutic importance plays a pivotal
role in catalyzing both biological and chemical reactions.
Pyrimidine derivatives are important biologically active heterocy-
clic compounds which possess antimalarial [12], antibacterial
[13], fungicidal [14], antitoxoplasma [15], anticancer [16], anti-
inflammatory and antitumor activities [17]. Hence, the synthesis
of molecules containing both chromene and pyrimidine ring was
taken up in the present investigation.
solvent in organic synthesis because of their specific properties
of non-volatility, non-flammability, solvating ability, thermal sta-
bility and easy recyclability [24]. Many organic reactions, including
MCRs, were carried out efficiently in ionic liquids [25–28]. In con-
tinuation of our work on the synthesis of heterocyclic compounds
in ionic liquids [29], we report herein four component synthesis of
novel chromeno[2,3-d]pyrimidin-8-amines using [bmim]BF4 ionic
liquid as catalyst. A study of antibacterial activity of the products
was also conducted.
2. Results and discussion
A mixture of
a-naphthol (1 eq) 1, malononitrile (1 eq) 2, aryl
aldehydes (2 eq) 3a–f and NH4Cl (2 eq) underwent one-pot cyclo-
condensation in the presence of [bmim]BF4 and trace amount of
triethylamine (TEA) in DMF producing compounds 4a–f. To the
best of our knowledge, this type of method was not found in the
literature. The advantage of this method is that the compounds
4a–f were obtained in quantitative yields directly, without the iso-
lation of corresponding iminochromenes (Scheme 1). The reaction
may proceed via an imine 5 formed from 2-amino-4H-chromeno-
3-carbonitrile and arylaldehyde. Imine 5 reacts with NH4Cl to give
amidine 6, followed by cyclization and aromatization to afford the
compounds 4a–f (Scheme 2).
A multi-component reaction (MCR) can create highly complex
molecules from readily available starting materials without the
complicated purification operations. Thus, MCRs are identified as
time-effective and economically favorable processes in diversity
generation [18–20]. Recently, there have been tremendous devel-
opments in three and four component reactions and great efforts
⇑
A full characterization details were provided in experimental
section. The molecular structure of a representative compound
Corresponding author.
E-mail address: gvpc_2000@yahoo.co.in (G.V.P. Chandramouli).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2012.02.044

S. Kanakaraju et al. / Journal of Molecular Structure 1017 (2012) 60–64
61
Scheme 1. General synthetic route of chromeno[2,3-d]pyrimidine-8-amine derivatives 4a–f.
Scheme 2. Plausible mechanism for the synthesis of compounds 4a–f.
Table 1
Synthesis of chromeno[2,3-d]pyrimidin-8-amines 4a–f catalyzed by [bmim]BF4.
S.No
Product 4
R
Time (min)
Yield (%)a
1
2
3
4
5
6
4a
4b
4c
4d
4e
4f
H
90
92, 91, 90, 90b
4-Cl
4-Br
4-Me
4-OMe
2-Cl
105
100
95
110
130
88
86
90
88
87
a
Yield of isolated product.
[bmim]BF4 was reused for four runs.
b
1643 cmꢀ1 for (AC@N), and 1261 cmꢀ1 for (CAOAC). The 1H
NMR spectra of compound 4a showed singlet at d 5.42 ppm for
pyran proton, d 6.96 ppm for ANH2 proton, multiplet at d 7.18–
7.96 ppm assigned for aromatic protons and d 8.38 ppm for ArH-
1. The 13C NMR spectrum is in good agreement with the structure
assigned. Mass spectra of compound 4a gave molecular ion peak at
m/z 402 (M+1)+ corresponding to molecular formula C27H19N3O.
The elemental analysis values are in good agreement with theoret-
ical data. All the compounds 4a–f was screened for their antibacte-
rial activity (Table 4).
Fig. 1. ORTEP representation of compound 4a. Thermal ellipsoids are drawn at 50%
probability level.
4a was confirmed by single-crystal X-ray diffraction (Fig. 1). The
scope and the generality of the present method was further dem-
onstrated by the reaction of various aromatic aldehydes with mal-
ononitrile,
a-naphthol and NH4Cl. In all cases, quantitative yields in
3. Single crystal X-ray diffraction
reasonable reaction times were obtained and ionic liquid could be
reused for four times without evident loss of activity (Table 1).
The IR spectrum of compound 4a exhibited absorption at 3500,
3454 cmꢀ1 for (ANH2), 3058 cmꢀ1 for (aromatic CAH stretching),
The good quality crystals were selected for the single crystal
X-ray diffraction. The data was collected on a Bruker APEX-II CCD
diffractometer at 293(2) K using graphite-monochromated MoK
a

62
S. Kanakaraju et al. / Journal of Molecular Structure 1017 (2012) 60–64
Table 2
Salient crystallographic data and structure refine-
ment parameters of compound 4a.
4a
Empirical formula
Formula weight
Crystal system
Space group
T (K)
C27H19N3O
401.45
Monoclinic
P21/c
293(2)
a (Å)
b (Å)
c (Å)
15.061(5)
10.397(4)
12.850(4)
90.00
Fig. 2. A one dimensional corrugated tape with CAHꢁ ꢁ ꢁO hydrogen bonds.
a
(°)
b (°)
98.131(6)
90.00
c
(°)
Z
4
V (Å)3
1992.0(12)
1.339
840.0
Dcalc (g/cm3)
F (000)
l
(mmꢀ1
)
0.083
h (°)
Index ranges
1.37 to 26.05
ꢀ18 6 h 6 18
ꢀ12 6 k 6 12
ꢀ15 6 l 6 15
20041
N-total
N-independent
N-observed
Parameters
Rint
3933
3199
288
0.0406
R1 (I > 2
r
(I))
0.0829
wR2 (all data)
GOF
CCDC
0.1657
1.183
840878
Fig. 3. A one dimensional tape viewed down c-axis.
hydrogen bond with the pyran ring oxygen atom of the 21 screw
related molecule (C26ꢁ ꢁ ꢁO1; D = 3.303(4) Å, C26AH26ꢁ ꢁ ꢁO1;
h = 135°) (Fig. 2) [33]. These interactions are propagated along
the c-axis and form the one dimensional corrugated tape (Fig. 3).
It is surprising that the amino (ANH2) group has not involved in
any hydrogen bonding.
radiation (k = 0.71073 Å). No absorption correction was applied.
The lattice parameters were determined from least-squares analy-
sis, and reflection data were integrated using the program SHELXTL
[30]. The crystal structure was solved by direct method using
SHELXS-97 and refined by full-matrix least-squares refinement
on F2 with anisotropic displacement parameters for non-H atoms
using SHELXL-97 [31]. The NAH hydrogens were located from
difference Fourier maps. Aromatic and aliphatic CAH hydrogens
were generated by the riding model in idealized geometries. The
software used to prepare material for publication was Mercury
2.3 (Build RC4), ORTEP-3 and X-Seed [32]. Table 2 gives the perti-
nent crystallographic data, and Table 3 gives hydrogen bond
parameters.
5. Antibacterial activity
The antibacterial activity was determined by agar plate disk dif-
fusion method [34] at the concentration of 50 lg per disk. All the
synthesized compounds were tested in vitro for their antibacterial
activity against microorganisms such as Staphylococcus aureus
(NCIM 2079), Bacillus subtilis (NCIM 2439) (Gram positive), Esche-
richia coli (NCIM 2831), and Pseudomonas aerugenosa (NCIM
2863) (Gram negative) strains, using ciprofloxacin as standard
antibacterial. Each test compounds were dissolved in DMSO to
get a concentration of 10 mg/mL. The disk (6 mm in diameter)
4. Crystal structure analysis
Compound 4a crystallizes in the monoclinic P21/c space group
with one molecule in the symmetric unit (Z0 = 1). The phenyl group
which is attached to the pyrimidine ring is not essentially coplanar
with the pyrimidine moiety (torsion angle of N2AC2AC16AC17 is
161.17°). The CAH group of the same phenyl ring which is attached
the pyrimidine ring forms an intramolecular CAHꢁ ꢁ ꢁN hydrogen
bond with pyrimidine nitrogen atom (C21ꢁ ꢁ ꢁN2; D = 2.766(5) Å,
C21AH21ꢁ ꢁ ꢁN2; h = 100°). The crystal structure analysis reveals
that the molecules in the crystal form supramolecular one dimen-
sional (1D) corrugated tapes. The CAH group of the phenyl ring
which is attached to asymmetric center forms a weak CAHꢁ ꢁ ꢁO
was impregnated with 5 lL of each test solution to get 50 lg/disk,
air dried and placed on the agar medium, previously seeded with
0.2 mL of broth culture of each organism for 18 h. The plates were
incubated at 37 °C for 24 h and the inhibition zones were measured
in mm. Disks impregnated with DMSO were used as a control and
ciprofloxacin disks as antibacterial reference standard.
The results of antibacterial activity presented in the Table 4
suggested that amongst all the synthesized compounds 4a–f,
compounds 4a and 4e were found to be highly active against
E. coli. Compounds 4b and 4d exhibited excellent activity against
Table 3
Geometrical parameters of hydrogen bonds in compound 4a.
Compound
DAHꢁ ꢁ ꢁAa
Dꢁ ꢁ ꢁA (Å)
Hꢁ ꢁ ꢁA (Å)
DAHꢁ ꢁ ꢁA (°)
Symmetry code
4a
Intra C21AH21ꢁ ꢁ ꢁN2
C26AH26ꢁ ꢁ ꢁO1
2.766(5)
3.303(4)
2.45
2.58
100
135
–
x, ꢀ1/2ꢀy, ꢀ1/2 + z
a
All of the CAH distances are neutron normalized to 1.083 Å.

S. Kanakaraju et al. / Journal of Molecular Structure 1017 (2012) 60–64
63
Table 4
purified by column chromatography using silicagel (CHCl3:MeOH
9:1) to furnish 4a–f in good yields. The residue aqueous phase
was evaporated under reduced pressure, and the remaining
[bmim]BF4 was rinsed with ether (15 mL), dried under a vacuum,
and reused for four runs (Table 1).
Antibacterial activity of compounds 4a–f.
Compounds
Zone of inhibition (in mm)
S. aureus
B. subtilis
E. coli
(NCIM
2831)
P. aerug
(NCIM 2863)
(NCIM 2079)
(NCIM 2439)
8.1. 7,10-Diphenyl-7H-benzo[7,8]chromeno[2,3-d]pyrimidin-8-amine
(4a)
4a
4b
4c
4d
4e
4f
++
+++
–
+++
–
–
+++
++
++
++
+++
++
+++
++
++
+++
++
++
++
+++
–
++
+++
+++
Yellow solid; mp: 176–178 °C; IR (KBr): 3500, 3454, 3058, 1643,
1261 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 5.42 (s, 1H, pyran
;
++
ACH), 6.96 (s, 2H, ANH2), 7.18–7.96 (m, 15H, ArAH), 8.38 (d, 1H,
ArH-1); 13C NMR (75 MHz, DMSO-d6): d 44.0, 108.2, 118.6, 120.7,
121.8, 126.2, 126.8, 127.1 127.9, 128.7, 129.2, 129.8, 130.2, 130.9,
131.4, 133.4, 135.2, 144.2, 151.6, 159.3, 167.4, 174.9; ms: m/z
402 (M+1)+. Anal. Calcd. for C27H19N3O: C, 80.78; H, 4.77; N,
10.47. Found: C, 80.71%; H, 4.61%; N, 10.52%.
Ciprofloxacin +++
+++
+++
‘–’ inactive (inhibition zone <6 mm); ‘+’ slightly active (inhibition zone 7–9 mm);
‘++’ moderately active (inhibition zone 10–13 mm); ‘+++’ highly active (inhibition
zone >14 mm).
S. aureus. Compounds 4a and 4d were found to be highly active
against P. aerug. Compounds 4c and 4f were found to be more
potent against B. subtilis. Compounds 4c and 4e showed no activity
against S. aureus. Compounds 4a and 4d possessed no activity
against B. subtilis. The rest of tested compounds were found to have
moderate activity.
8.2. 7,10-Di-(4-chlorophenyl)-7H-benzo[7,8]chromeno[2,3-d]pyrimi-
din-8-amine (4b)
Yellow solid; mp: 194–196 °C; IR (KBr): 3505, 3472, 3056, 1640,
1262 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 5.44 (s, 1H, pyran
;
ACH), 6.94 (s, 2H, ANH2), 7.20–8.02 (m, 13H, ArAH), 8.38 (d, 1H,
ArH-1); 13C NMR (75 MHz, DMSO-d6): d 44.2, 108.3, 118.6, 120.9,
122.0, 126.2, 126.6, 127.2, 128.6, 129.1, 130.1, 130.8, 131.0,
131.9, 132.7, 134.1, 136.3, 143.7, 151.8, 159.5, 167.8, 175.0; ms:
m/z 471 (M+1)+. Anal. Calcd. for C27H17Cl2N3O: C, 68.95; H, 3.64;
N, 8.93. Found: C, 68.86%; H, 3.67%; N, 8.99%.
6. Conclusion
In summary, we have developed an efficient protocol for the
synthesis of novel chromeno[2,3-d]pyrimidin-8-amine derivatives
in [bmim]BF4 ionic liquid and compound 4a was confirmed by sin-
gle-crystal X-ray diffraction and all the synthesized compounds
were assayed for their in vitro antibacterial activity.
8.3. 7,10-Di-(4-bromophenyl)-7H-benzo[7,8]chromeno[2,3-d]pyrimi-
din-8-amine (4c)
7. Experimental section
Yellow solid; mp: 234–236 °C; IR (KBr): 3490, 3392, 3052, 1648,
1263 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 5.48 (s, 1H, pyran
;
7.1. General
ACH), 6.96 (s, 2H, ANH2), 7.20–8.06 (m, 13H, ArAH), 8.34 (d, 1H,
ArH-1); 13C NMR (75 MHz, DMSO-d6): d 44.4, 108.8, 118.9, 120.9,
122.0, 122.8, 125.4, 126.4, 126.9, 127.4, 128.7, 129.3, 130.8,
131.7, 132.2, 134.3, 135.1, 144.5, 151.9, 159.6, 168.0, 175.2; ms:
m/z 560 (M+1)+. Anal. Calcd. for C27H17Br2N3O: C, 57.99; H, 3.06;
N, 7.51. Found: C, 57.82%; H, 3.11%; N, 7.43%.
Melting points were recorded in open capillary and were uncor-
rected. Column chromatography was performed using silica-gel
(60–120 mesh size) purchased from Thomas Baker and TLC was
carried out using aluminum sheets pre-coated with silica gel
60F254 purchased from Merck. IR spectra (KBr) were recorded on
a Bruker WM-4(X) spectrometer (577 model). 1H NMR (300 MHz)
and 13C NMR (75 MHz) spectra were recorded on Bruker AC-300
spectrometer in DMSO-d6 with TMS as an internal standard. Mass
spectra (EI-MS) were determined on Perkin Elmer (SCIEX API-2000,
ESI) at 12.5 eV. CHNS analysis was done by Carlo Erba EA 1108
automatic elemental analyzer. The compound 4a was crystallized
from N,N-dimethylformamide and the crystal data was collected
on a Bruker APEX-II CCD diffractometer. All the solvents and chem-
icals used were pure, purchased from commercial sources and
were used without further purification unless otherwise stated.
8.4. 7,10-Di-(4-methylphenyl)-7H-benzo[7,8]chromeno[2,3-d]pyrimi-
din-8-amine (4d)
Yellow solid; mp: 212–214 °C; IR (KBr): 3494, 3390, 3055, 1642,
1260 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 2.24 (s, 6H, ACH3), d
;
5.38 (s, 1H, pyran ACH), 6.88 (s, 2H, ANH2), 7.10–7.86 (m, 13H,
ArAH), 8.30 (d, 1H, ArH-1); 13C NMR (75 MHz, DMSO-d6): d 28.2,
43.4, 108.3, 118.4, 120.6, 121.7, 126.1, 126.9, 127.1, 128.4, 129.0,
129.8, 130.2, 131.2, 132.3, 133.6, 137.2, 140.7, 142.4, 151.3,
159.1, 167.3, 174.8; ms: 430 (M+1)+. Anal. Calcd. for C29H23N3O:
C, 81.09; H, 5.40; N, 9.78. Found: C, 81.14%; H, 5.32%; N, 9.85%.
8. General procedure for the synthesis of 7,10-diaryl-7H-benzo
[7,8]chromeno[2,3-d]pyrimidin-8-amine 4a–f
8.5. 7,10-Di-(4-methoxyphenyl)-7H-benzo[7,8]chromeno[2,3-d]pyr-
imidin-8-amine (4e)
To
a mixture of a-naphthol 1 (1 mmol), malononitrile 2
(1 mmol) and arylaldehydes 3a–f (2 mmol) in 10 mL of DMF,
[bmim]BF4 (2 mmol) and trace amount of TEA (0.2 mL) was added
and the reaction mixture was stirred at 100 °C for 60–90 min. The
progress of the reaction was monitored by TLC and after comple-
tion of the reaction (single spot on TLC), NH4Cl (2 mmol) was
added and the reaction was continued for an additional 30–
40 min. After completion of the reaction, the reaction mixture
was cooled to room temperature and 20 mL of water was added.
The solid separated was filtered, washed with ether, dried and
Yellow solid; mp: 164–166 °C; IR (KBr): 3504, 3482, 3054, 1642,
1262 cmꢀ1; 1H NMR (300 MHz, DMSO-d6): d 3.58 (s, 6H, AOCH3), d
5.40 (s, 1H, pyran ACH), 6.90 (s, 2H, ANH2), 7.12–7.94 (m, 13H,
ArAH), 8.32 (d, 1H, ArH-1); 13C NMR (75 MHz, DMSO-d6): d 44.2,
58.3, 108.4, 116.7, 118.5, 120.7, 121.8, 125.3, 126.2, 126.9, 127.3,
128.7, 129.3, 130.3, 131.4, 134.0, 137.9, 152.3, 159.2, 160.1,
162.3, 168.2, 175.2; ms: m/z 462 (M+1)+. Anal. Calcd. for
C29H23N3O3: C, 75.47; H, 5.02; N, 9.10. Found: C, 75.53%; H,
5.10%; N, 9.03%.

64
S. Kanakaraju et al. / Journal of Molecular Structure 1017 (2012) 60–64
[10] G.P. Ellis, in: A. Weissberger, E.C. Taylor (Eds.), The Chemistry of Heterocyclic
Compounds: Chromenes, Chromanes and Chromones, John Wiley, New York,
1977, pp. 11–139 (Chapter II).
8.6. 7,10-Di-(2-chlorophenyl)-7H-benzo[7,8]chromeno[2,3-d]pyrimi-
din-8-amine (4f)
[11] E.A.A. Hafez, M.H. Elnagdi, A.G.A. Elagamey, F.M.A.A. Ei-Taweel, Heterocycles
26 (1987) 903.
[12] A. Agarwal, K. Srinivas, S.K. Puri, P.M.S. Chauhan, Bioorg. Med. Chem. 13 (2005)
4645.
Yellow solid; mp: 188–190 °C; IR (KBr): 3502, 3486, 3056, 1645,
1260 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 5.42 (s, 1H, pyran
;
ACH), 6.95 (s, 2H, ANH2), 7.15–7.94 (m, 13H, ArAH), 8.36 (d, 1H,
ArH-1); 13C NMR (75 MHz, DMSO-d6): d 38.4, 108.9, 118.7, 120.7,
122.3, 126.2, 126.9, 127.4, 128.5, 129.1, 129.4, 129.8, 130.4,
131.2, 131.8, 132.6, 133.5, 134.4, 135.3, 140.4, 145.2, 151.7,
159.2, 167.8, 174.9; ms: 471 (M+1)+. Anal. Calcd. for C27H17Cl2N3O:
C, 68.95; H, 3.64; N, 8.93. Found: C, 68.88%; H, 3.68%; N, 8.98%.
[13] A. Ali, G.E. Taylor, K. Ellsworth, G. Harris, R. Painter, L.L. Silver, K.J. Young, J.
Med. Chem. 46 (2003) 1824.
[14] Q. Ren, Z. Cui, H. He, Y. Gu, J. Fluorine Chem. 128 (2007) 1369.
[15] M.N.S. Saudi, M.R. Gaafar, M.Z. El-Azzouni, M.A. Ibrahim, M.M. Eissa, Med.
Chem. Res. 17 (2008) 541.
[16] F. Xie, H. Zhao, L. Zhao, L. Lou, Y. Hu, Bioorg. Med. Chem. Lett. 19 (2009) 275.
[17] B. Tozkoparan, M. Ertan, P. Kelicen, R. Demirdamar, II Farmaco 54 (1999) 588.
[18] J. Zhu, H. Bienayme (Eds.), Multicomponent Reactions, Wiley-VCH, Weinheim,
2005.
[19] D.J. Ramon, M. Yus, Angew. Chem. Int. Ed. Engl. 44 (2005) 1602.
[20] I. Marek, Tetrahedron 61 (2005) 11309.
Acknowledgements
[21] C.R. Bohn Rhoden, B. Westermann, L.A. Wessjohann, Synthesis (2008) 2077.
[22] L. Shen, S. Cao, N. Liu, J. Wu, L. Zhu, X. Qian, Synlett (2008) 1153.
[23] (a) A. Alizadeh, A. Rezvanian, Synthesis (2008) 1747;
(b) I. Yavari, M. Sabbaghan, Z. Hossaini, Synlett (2008) 1341.
[24] (a) J.S. Wilkes, Green Chem. 4 (2002) 73;
We are thankful to the Director, National institute of Technol-
ogy, Warangal for providing facilities and financial support. We
are also thankful to University of Hyderabad for providing single
crystal X-ray data collection.
(b) N. Jain, A. Kumar, S. Chauhan, S.M.S. Chauhan, Tetrahedron 61 (2005) 1015.
[25] T. Welton, Chem. Rev. 99 (1999) 2071.
[26] J.S. Yadav, B.V.S. Reddy, S. Shubashree, K. Sadashiv, J.J. Naidu, Synthesis (2004)
2376.
References
[27] M.A.P. Martins, C.P. Frizzo, D.N. Moreira, N. Zanatta, H.G. Bonacorso, Chem.
Rev. 108 (2008) 2015.
[28] N. Isambert, M. del Mar Sanchez Duque, J.-C. Plaquevent, Y. Génisson, J.
Rodriguez, T. Constantieux, Chem. Soc. Rev. 40 (2011) 1347.
[29] (a) M. Maradolla, S.K. Allam, A. Mandha, G.V.P. Chandramouli, Arkivoc xv
(2008) 42;
(b) M. Maradolla, G.V.P. Chandramouli, Phosphorus, Sulfur Silicon Relat. Elem.
186 (2011) 1650.
[30] SHELXTL, Program for the Solution and Refinement of Crystal Structures
(version 6.14), Bruker AXS, Wisconsin, USA, 2000.
[31] G.M. Sheldrick, SHELX-97: Program for the Solution and Refinement of Crystal
Structures, University of Göttingen, Germany, 1997.
[32] (a) C.F. Macrae, I.J. Bruno, J.A. Chisholm, P.R. Edgington, P. McCabe, E. Pidcock,
L. Rodriguez-Monge, R. Taylor, J. van de Streek, P.A. Wood, J. Appl. Cryst. 41
(2008) 466;
[1] M.M. Khafagy, A.H.F.A. El-Wahas, F.A. Eid, A.M. El-Agrody, II Farmaco 57 (2002)
715.
[2] (a) W.P. Smith, L.S. Sollis, D.P. Howes, C.P. Cherry, D.I. Starkey, N.K. Cobley, H.
Weston, J. Scicinski, A. Merritt, A. Whittington, P. Wyatt, N. Taylor, D. Green, R.
Bethell, S. Madar, R.J. Fenton, P.J. Morley, T. Pateman, A.J. Beresford, J. Med.
Chem. 41 (1998) 787;
(b) A.G. Martinez, L.J. Marco, Bioorg. Med. Chem. Lett. 7 (1997) 3165.
[3] K. Hiramoto, A. Nasuhara, K. Michiloshi, T. Kato, K. Kikugawa, Mutat. Res. 47
(1997) 395.
[4] C.P. Dell, C.W. Smith, Chem. Abstr. 119 (1993) 139102d.
[5] (a) J. Skommer, D. Wlodkowic, M. Matto, M. Eray, J. Pelkonen, Leukemia Res. 30
(2006) 322;
(b) D.R. Anderson, S. Hegde, E. Reinhard, L. Gomez, W.F. Vernier, L. Lee, S. Liu, A.
Sambandam, P.A. Snider, L. Masih, Bioorg. Med. Chem. Lett. 15 (2005) 1587;
(c) J.L. Wang, D. Liu, Z. Zhang, S. Shan, X. Han, S.M. Srinvasula, C.M. Croce, E.S.
Alnemeri, Z. Huang, Proc. Natl. Acad. Sci. USA 97 (2000) 7124.
[6] F. Eiden, F. Denk, Arch. Pharm. Weinhein Ger. (Arch. Pharm.) 324 (1991) 353.
[7] P.G. Pietta, J. Nat. Prod. 63 (2000) 1035.
(b) L.J.J. Farrugia, Appl. Cryst. 30 (1997) 565;
(c) L.J.J. Barbour, Supramol. Chem. 1 (2001) 189.
[33] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and
Biology, Oxford University Press, Oxford, UK, 1999.
[34] C.H. Collin, Microbiological Methods, Butterworths, London, 1964. p. 92.
[8] G. Bianchi, A. Tava, Agric. Biol. Chem. 51 (1987) 2001.
[9] S.J. Mohr, M.A. Chirigos, F.S. Fuhrman, J.W. Pryor, Cancer Res. 35 (1975) 3750.