Synthesis and biological activity of heterocycles from chalcone

Article abstract of DOI:10.1007/s00044-007-9067-y

The chalcone 3 was synthesized from 3-acetyl-4-hydroxy coumarin and 3-formylchromone by refluxing in ethanol in the presence of a catalytic amount of pyridine. 3 was converted to bipyrazoles 4a-b by treatment with hydrazine and phenylhydrazine. The compounds were screened for their antibacterial activity.

Full text of DOI:10.1007/s00044-007-9067-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2008) 17:318–325
DOI 10.1007/s00044-007-9067-y
ORIGINAL RESEARCH
Synthesis and biological activity of heterocycles
from chalcone
Zeba N. Siddiqui Æ Mohammad Asad Æ
Shagufta Praveen
Received: 6 November 2007 / Accepted: 15 November 2007 / Published online: 2 February 2008
¨
Ó Birkhauser Boston 2008
Abstract The chalcone 3 was synthesized from 3-acetyl-4-hydroxy coumarin and
3-formylchromone by refluxing in ethanol in the presence of a catalytic amount of
pyridine. 3 was converted to bipyrazoles 4a-b by treatment with hydrazine and
phenylhydrazine. The compounds were screened for their antibacterial activity.
Keywords 3 ꢀ Acetyl-4-hydroxycoumarin ꢀ (2E)-1-(4-hydroxy-1-benzopyran-
2-one-3-yl)-3-[1] ꢀ (benzopyran-4-one-3-yl)-2-propen-1-one ꢀ Antibacterial activity
Introduction
Chalcones are important precursors of flavonoids and isoflavonoids (Harborne and
Mabry, 1982). A large number of chalcones have been prepared by Claisen–
Schmidt condensation of aldehydes with methyl ketones under basic conditions
(Claisen et al., 1881). These compounds have shown in vitro antimalarial activity
against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium
falsciparum (Li et al., 1995). Recently authors have reported synthesis of chalcones
under acidic conditions also using perchloric acid and acetic acid (Tuskaev et al.,
2002). A variety of chalcones have been reported for activity as potent tyrosinase
inhibitors, antioxidants and are, thus, used as new depigmentation agents (Nerya
et al., 2004). Nitrogen heterocycles containing chalcone moiety have been reported
as active compounds against herpes simplex virus-1(HSV-1) and human immuno-
deficiency virus 1(HIV-1) (El-Barbary et al., 1994; El-Subbagh et al., 2000). This
class of compounds also exhibits cytotoxic activity towards leukemia cell lines
(Dimmock et al., 1983; Dimmock et al., 1992). Various other chalcones are
reported to exhibit insecticidal, antichinoviral, and antipicorniviral properties
Z. N. Siddiqui (&) ꢀ M. Asad ꢀ S. Praveen
Department of Chemistry, Aligarh Muslim University, Aligarh 202 002, India
e-mail: siddiqui_zeba@yahoo.co.in

Med Chem Res (2008) 17:318–325
319
(Nowakowska et al., 2001). In view of the variety of pharmacological properties
exhibited by chalcones, we were prompted to undertake its synthesis and conversion
to other heterocycles which may show different or better physiological activities. In
continuation of our work on 3-formyl-4-hydroxycoumarin (Siddiqui and Asad,
2006) and 3-formylchromone (Siddiqui et al., 2006), we report herein the synthesis
of chalcone and its conversion to bipyrazoles with nitrogen bases. It is pertinent to
mention that bipyrazoles have been reported to show anti-inflammatory (El-
Khawass and Bistawroos, 1990; Bruno et al., 1993), cytotoxic (Cuadro et al., 1985),
insecticidal (Truboi et al., 1994), herbicidal (Hartfiel et al., 1993), and fungicidal
(Das and Mittra, 1978; Nayak and Mittra, 1980) activities.
Chemistry
Due to the exceptional reactivity of the formyl group in 3-formylchromone as well
as the versatile biological activities of chromone and coumarin derivatives, the
chalcone 3 was synthesized by employing 3-formychromone (1) and 3-acetyl-4-
hydroxycoumarin (2) as starting materials under mild basic conditions.
1'
1''
8''
8'
O
O
O
7'
2'
O
O
O
7''
6''
Hb
2''
6'
2
3'
1
3''
4'
3
5'
4''
5''
C CH3
O
CHO
O
O
Ha
OH
HO
O
1
2
3
The compound was identified on the basis of its spectroscopic data. The infrared
(IR) spectrum showed chromone and coumarin carbonyl groups at 1650 and
1734 cm-1, respectively, in addition to a broad band for the OH group at 3318 cm-
1. The 1H NMR spectrum showed trans olefinic protons Ha and Hb as ortho-coupled
doublets at d 9.10 (J = 15.6 Hz) and 8.18 (J = 15.9 Hz), respectively. The C-20 and
C-50 protons appeared as a singlet and a doublet at d 8.56 and 8.30 (J = 7.8 Hz),
respectively. The remaining three aromatic protons of the chromone unit and the
four protons of coumarin moiety appeared as a multiplet in the region d 7.45–7.93.
The mass spectrum of 3 showed M+ꢀ at m/z 360 as its base peak. The other important
peaks were obtained as shown in Scheme 1a–b.
The condensation of hydrazines with a,b-unsaturated carbonyl compounds
usually gives pyrazolines (Wiley and Jarboe, 1967). Thus, when compound 3 was
treated with nitrogen bases such as hydrazine and phenylhydrazine pyrazolyl
pyrazolines 4a and 4b were obtained, respectively.
The IR spectrum of 4a showed broad bands at 3618, 3456, 3396, and 3269 cm-1
due to the presence of the two OH and NH groups. A sharp and strong absorption
band at 1684 cm-1 indicated a carbonyl group in the compound. Since chromone
carbonyl groups usually appear as sharp absorption bands in the region 1620–
1650 cm-1 (Ellis, 1977), the band at 1684 cm-1 was assigned to coumarin rather
1
than the chromone carbonyl group. The H nuclear magnetic resonance (NMR)

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Med Chem Res (2008) 17:318–325
(a)
O
O
O
O
O
O
O
O
OH
O
O
O
m/z 360
m/z 360
O
O
O
O
O
O
H
+
+
OH
O
O
OH
O
O
O
O
O
O
O
H
O
O
O
O
O
+
+
CH2
OH
OH
m/z 157
H
O
O
C
CH3
OH
O
m/z 204
O
O
O
O
O
(b)
O
m/z 360
RDA
Cleavage
O
O
O
C=O
+
H
O
m/z 240 O
m/z 120
- (CH=C=O)
-CO
O
C=O
O
O
m/z 199
m/z 92
-CO
O
O
m/z 171
Scheme 1 Mass fragmentation of chalcone 3

Med Chem Res (2008) 17:318–325
321
spectrum of 4a did not show the diagnostic singlet of the H-2 olefinic proton for the
chromone moiety. Furthermore, the compound also showed a strong black color
with ferric chloride on a thin-layer chromatography (TLC) plate. Since chromones
usually undergo ring-opening reactions by nitrogen nucleophiles (Kostka, 1973), it
was clear therefore that compound 3 had suffered ring cleavage at the C-2 position
of the chromone unit by attack of the nitrogen bases (hydrazine, phenylhydrazine)
followed by cyclization to form a pyrazole moiety. Furthermore, another molecule
of the nitrogen nucleophile reacted with the a,b-unsaturated ketone unit to form a
pyrazoline moiety (Scheme 2).
The presence of the pyrazoline unit in 4a was clearly established by two double
doublets at (d 3.66, 3.72(Ha); 4.04, 4.09 (Hb) and a multiplet at d 5.15 (Hc). The
broad singlet (D2O exchangeable) at d 6.36 was assigned to the NH proton of
pyrazoline unit. The aromatic region of the spectrum exhibited the eight protons of
coumarin and the phenolic units in the form of a multiplet at d 6.91-7.58. A sharp
singlet integrating for one proton at d 7.81 was assigned to the Hd proton of the
pyrazole moiety. Two broad singlets (D2O exchangeable) at d 10.6 and 12.8 were
due to the two OH groups. Further confirmation of the structure 4a was provided by
mass spectrometry, which showed M+ at m/z 388. The other prominent peaks were
at m/z 370 (M+ꢀ–H2O), 295 [M+ꢀ–Ph(OH)], 360 (M+ꢀ–CO), and 267 (M+ꢀ–C7H4O2).
O
O
NH-NH-R
O
Q
Q
- NHR
H2N
O
O
O
OH
NH-NH-R
Q
Q
Q
O
O
HO
O
O
N
O
H
N
H
HO
NH
N
R
R
N
Q
Q
Q
N
R NH
Ha
Hb
Hd
R N
O
-H2O
H2NNHR
(-H2O)
H Shift
Hc
N
HO
N
R
N
R
N
R
HO
N
HO
N
4a; R = H
4b; R = Ph
O
O
Q =
OH
Scheme 2 Formation of bipyrazoles 4a-b by the reaction of chalcone 3 and hydrazines

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Med Chem Res (2008) 17:318–325
Biological activity
All newly synthesized compounds were screened for antibacterial activity against
Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative
bacteria (Escherichia coli, Salmonella typhimurium). Compound 4a exhibited
strong activity against Gram-positive bacteria and moderate activity against Gram-
negative bacteria as compared to the antibiotic drug chloramphenicol. However
compounds 3 and 4b showed moderate activity against Gram-positive bacteria and
did not show any activity against Gram-negative bacteria. The zone of growth
inhibition ranged from 10 to 25 mm (Table 1).
Summary
A novel chalcone analogue 3 was synthesized under mild basic conditions and in
quantitative yield. Compound 3 was easily converted to the bipyrazoles 4a and 4b
by treatment with hydrazine and phenylhydrazine. All the compounds showed
moderate to strong antibacterial activity against Gram-positive and Gram-negative
bacteria.
Experimental section
Melting points were taken in open capillaries and are uncorrected. The IR spectra
were recorded on a Fourier-transform (FT)-IR spectrometer 2020,1H NMR spectra
on a Bruker DRX-300 spectrometer using tetra methyl silane (TMS) as an internal
standard and the mass spectra on a Jeol SX-120 (FAB). Compound 1 and 2 were
synthesized by reported procedures (Eisenhauer and Link, 1953; Nohara et al.,
1974). The purity of all compounds was checked by TLC plates using silica gel (E.
Merck G254). The plates were run in a chloroform:methanol (3:1) mixture and
visualized by iodine vapors. The elemental analysis data (C, H, and N) were the
same with a variation of 0.4% from calculated values.
Table 1 Antibacterial activity of compounds synthesized
S. no.
Test
microorganisms
Zone of inhibition, size in mm
Compounds
Antibiotic control
chloramp henicol
3
4a
4b
G+
G-
1.
2.
3.
4.
Bacillus subtilis
12
–
25
20
12
–
10
–
33
33
30
30
Staphylococcus aureus
Escherichia coli
–
–
Salmonella typhimurium
–
–
– No activity detected
The compounds were tested at 1000 lg/disc

Med Chem Res (2008) 17:318–325
323
Biological data
Culture media and inoculum
Nutrient (N) (Hi-Media Pvt. Ltd., Mumbai, India) was used to culture the test
bacteria. The microbial culture was grown at 37°C for 18 h and then appropriately
diluted with sterile 0.8% saline solution to obtain a cell suspension of 105 colony
forming unit (CFU)/ml (Aqil and Ahmad, 2003).
Antimicrobial assays
Antibacterial activity of the compounds was assayed by the disc diffusion method
(Bauer et al., 2003) with little modification. Briefly 0.1 ml of diluted inoculum
(105 CFU/ml) of the test organism was spread on nutrient agar plates. Sterile paper
disc was impregnated with 1000 lg of the compounds and a disc without compound
was used as a negative control. The inoculated plates were incubated for the
appropriate temperature and time as described above. The antibacterial activity was
evaluated by measuring the zone of growth inhibition of the test organism around
the disc. Antibiotic chloramphenicol was used as positive control.
Synthesis of (2E)-1-(4-hydroxy-1-benzopyran-2-one-3-yl)-3-[1]
(benzopyran-4-one-3-yl)-2-propen-1-one (3)
To a well-stirred solution of 3-acetyl-4-hydroxycoumarin (4.9 mmol) in ethanol
(30 mL) containing pyridine (0.5 mL) was added 3-formylchromone (4.9 mmol).
The reaction mixture was refluxed in a water bath for 12 h, cooled at room
temperature, and poured into ice-cold water (200 mL). The light yellow solid 3 was
obtained, filtered, washed with water, alcohol, dried, and recrystallized from
chloroform as shining needles (65%); mp 260–262°C; IR (KBr) mmax 3310, 1734,
1650 cm-1; 1H NMR (CDCl3) d 7.45-7.93 (m, 7H, Ar-H), 8.18 (d, 1H, J = 15.9 Hz,
Hb), 8.30 (d, 1H, J = 7.8 Hz, H-50 ), 8.56 (s, 1H, H-20 ), 9.10 (d, 1H, J = 15.6 Hz,
Ha); MS (% rel Int) m/z 360 (M+ꢀ, 100), 342 (30), 240 (5), 204 (90), 199(35),
171(20), 156 (20), 120 (40), 107 (15), 92 (10).
Synthesis of 3-[4-hydroxy-[1]benzopyran-2-one-3-yl]-5-[5-(20-
hydroxyphenylpyrazol-4-yl]- pyrazolin (4a)
Compound 3 (2.7 mmol) was dissolved in alcohol (25mL) and hydrazine hydrate
(5.4 mmol) added to it. The reaction mixture was refluxed in a water bath for
30 min. On cooling at room temperature, a light-green solid 4a was obtained. It was
filtered, washed with ethanol–water, dried, and recrystallized from N,N-dimethyl
formamide (DMF), (79%); mp 162°C; IR (KBr) mmax 3618, 3456, 3396, 3269, 1684,
1
1608, 1578 cm-1; H NMR (DMSO – d6) d 3.72 (dd, 1H, J = 17.7 Hz, 8.1 Hz,

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Med Chem Res (2008) 17:318–325
Hb), 4.09 (dd, 1H, J = 17.1 Hz, 8.7 Hz, Ha), 5.15 (m, 1H, Hc), 6.37 (br s, 1H,
exchangeable, NH), 7.81 (s, 1H, Hd), 6.91 – 8.04 (m, 8H, Ar – H), 10.60 (br s, 1H,
exchangeable, OH), 12.80 (br s, 1H, exchangeable, OH); MS (% rel int) m/z 388
(M+ꢀ, 100), 387 (40), 386 (70), 370((15), 342 (5), 295 (7), 268 (8), 240 (40), 229
(50), 227 (10),161 (20), 159 (5), 134 (25), 136 (25), 118 (20), 107 (10).
Synthesis of 1-phenyl-3-[4-hydroxy-[1]benzopyran-2-one-3-yl]-5-[5-(20
hydroxyphenyl)- 1-phenylpyrazol-4-yl] pyrazolin (4b)
Compound 3 (2.7 mmol) and phenylhydrazine (5.4 mmol) were taken in methanol
(25 mL) and five drops of acetic acid were added. The reaction mixture was
refluxed in a water bath for 45 min. It was cooled at room temperature and poured
into ice-cold water (200 mL), filtered, washed with ethanol–water mixture, and
dried. The yellow solid 4b as obtained was recrystallized from chloroform–benzene
1
(53%); mp 185–190°C; IR (KBr) mmax 3614, 3452, 1710, 1610, 1553 cm-1; H
NMR (DMSO-d6) d 3.74 (m, 1H, Ha), 4.17 (m, 1H, Hb), 5.21 (m, 1H, Hc), 6.75-
7.62 (m, 17H, Ar-H), 7.45 (s, 1H, Hd), 8.04 (d, 1H, J = 7.2 Hz, H-500); MS (% rel
int) m/z 540 (M+ꢀ, 90), 539 (50), 522 (5), 496 (5), 463 (6), 447 (10), 420 (5), 379 (5).
Acknowledgement Financial assistance from UGC, New Delhi, is gratefully acknowledged. The
authors would also like to thank SAIF, CDRI, Lucknow for spectral data, Dr. Iqbal Ahmad, Department
of agricultural microbiology, Aligarh Muslim University, Aligarh for biological screening and Prof. N. U.
Khan, Department of Chemistry, A.M.U. Aligarh for sincere advice.
References
Aqil F, Ahmad I (2003) Broad-spectrum antibacterial and antifungal properties of certain traditionally
used Indian medicinal plants. World J Microbiol Biotechnol 19:653–657
Bauer AW, Kirby WMM, Sherris JC, Turch M (1966) Antibiotic susceptibility testing by a standardized
single disk method. Am J Clin Path 45:493–496
Bruno O, Ranise A, Bonadavalli F, Schenone P, D’Amico M, Felipplli W, Filippelli A, Rossi F (1993)
3,5-Diphenyl-1H-pyrazole derivatives. XI. N-Aryl-5(3)-phenyl-4-(3,5-diphenyl-1-pyrazolyl)-3(5)-
pyrazole amines, 5-substituted 1,6-dihydro-4-phenyl-5-(3,5-diphenyl-1-pyrazolyl)pyrimidines with
antipyretic, antiinflammatory and other activities. Farmaco 48:949–966
Claisen L, Claparede A, Schmidt JG (1881) Condensation of aromatic aldehydes and aliphatic aldehydes
or ketones in the presence of aqueous base. Ber 14:2460, 1459
´
Cuadro AM, Elguero J, Navarro P (1985) Binuclear pyrazoles.I. Synthesis and cytotoxic activity of 1,1-
´
´
dibenzyl and 1,1-dihydroxymethyl 4,4-bispyrazoles. Chem Pharm Bull 33:2535–2540
Das NB, Mittra AS (1978) Heterocyclic fungicides. Part-III. J Indian Chem Soc 55: 829
Dimmock JR, Arora VK, Duffy MJ, Reid RS, Allen TM, Kao GY (1992) Evaluation of some N-acyl
analogues of 3,5-bis (arylidene)-4-piperidones for cytotoxic activity. Drug Des Discovery 8:291–299
Dimmock JR, Raghavan SK, Logan BM, Bigam GE (1983) Antileukemic evaluation of some Mannich
bases derived from 2-arylidene-1,3-diketones. Eur J Med Chem 18:248–254
Eisenhauer HR, Link KP (1953) Studies on 4-hydroxycoumarins.XIII. The mechanism for the reaction of
4-hydroxycoumarin with aliphatic acid chlorides. J Am Chem Soc 75:2044
El-Barbary AA, Khodair AI, Pederson EB, Nielsen C (1994) s-Glucosylated hydantoins as new antiviral
agents. J Med Chem 37:73–77
El-khawass ESM, Bistawroos AE (1990) Synthesis of novel pyrazolylpyrazole, pyrazolylthiadiazole and
pyrazolylthiadiazoline derivatives as potential antiinflammatory agents. Alexandria J Pharm Chem
4:77–79

Med Chem Res (2008) 17:318–325
325
Ellis GP (1977) Chromenes Chromanones and Chromones. Wiley, NY, p. 562
El-Subbagh HI, Abu-Zaid SM, Mahran MA, Badaria FA, Al-Obaid AM (2000) Synthesis and biological
evaluation of certain a, b-unsaturated ketones and their corresponding fused pyridines as antiviral
and cytotoxic agents. J Med Chem 43:2915–2921
Harborne JB, Mabry TJ (1982) The flavonoids: Advances in Research. Chapman and Hall, London, p.
313
Hartfiel U, Dorfmeister G, Franka H, Geisler J, Johann G, Rees R (1993) Substituted (pyrazolyl)
pyrazoles processes for their preparation and their use as broad-leaf weed herbicides. Eur Pat
EP542:388, Chem Abstr 119:180774
Kostka K (1973) Chromone derivatives. VI. Reaction of phenylhydrazine with chromone and x-formyl-
o-hydroxyacetophenone. Rocz Chem 47:305–313
Li R, Kenyon GL, Cohen FE, Chen X, Gong B, Dominguez JN, Davidson E, Kurzban G, Miller RE,
Nuzum EO, Rosenthal PJ, Mckerrow JH (1995) In vitro antimalarial activity of chalcones and their
derivatives. J Med Chem 38:5031–5037
Nayak A Mittra AS (1980) 4,4-Bis-5-pyrazolones and their 4,4-unsaturated products for possible use as
fungicides. J Indian Chem Soc 57:643
Nerya O, Musa R, Khatib S, Tamir S, Vaya J (2004) Chalcones as potent tyrosinase inhibitors: the effect
of hydroxyl positions and numbers. Phytochemistry 65:1389–1395
Nohara A, Umetani T, Sanno Y (1974) A facile synthesis of 4-oxo-4H-1- benzopyran-3-carboxaldehyde
by Vilsmeier reagents. Tetrahedron 30:3553–3561
Nowakowska Z, Wyrzykiewicz E, Kezia B (2001) Synthesis and antimicrobial properties of N-substituted
derivatives of (E)-4-azachalcones. Farmaco 56:325–329
Siddiqui ZN, Asad M (2006) New heterocyclic derivatives of 3-formyl-4- hydroxycoumarin. Indian J
Chem 45B:2704–2709
Siddiqui ZN, Khuwaja G, Asad M (2006) Synthesis of novel heterocycles from 3-(3-alkyl-5-mercapto-
1,2,4-triazolyliminomethyl) chromones. Heterocyclic Commun 12:443–448
Truboi S, Moriie K, Hatsutori, Wada K, Sone S, Oohigata T, Ilo A (1994) Preparation of 1-(phenyl
carbamoyl) pyrazoline derivatives as insecticides. Jpn Kokai Tokkyo Koho JP 06 184:114, Chem
Abstr(1995) 122:105875
Tuskaev VA, Oganesyan ET, Mutsueva SK (2002) Synthesis of 1-phenyl-3-(chromon-3-yl)-2-propen-1-
one derivatives A new group active compounds. Pharma Chem J 36:309–312
Wiley RH, Jarboe CH (1967) The Chemistry of Heterocyclic compounds. Interscience, NY. 22(2):183