Synthesis and biological activity of some 3, 5-diarylisoxazoline derivatives: Reaction of substituted chalcones with hydroxylamine hydrochloride

Article abstract of DOI:10.1155/2010/426383

A series of 3-aryl-5-styrylisoxazoline/ 3,5-diarylisoxazoline derivatives were synthesized by the reaction of appropriately substituted chalcones and hydroxylamine hydrochloride in presence of alkali in ethanol. The synthesized heterocycles have been characterized on the basis of their chemical properties and spectroscopic data. These compounds were tested for biological activity against a variety of test organisms.

Full text of DOI:10.1155/2010/426383

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2010, 7(1), 203-209
http://www.e-journals.net
Synthesis and Biological Activity of Some
3, 5-Diarylisoxazoline Derivatives:
Reaction of Substituted Chalcones with
Hydroxylamine Hydrochloride
VANDANA SHARMA* and K.V. SHARMA
Department of Engineering Chemistry,
Mahakal Institute of Technology, Ujjain 456664, India.
vandanak_sharma@yahoo.co.in
Received 12 April 2009; Accepted 6 June 2009
Abstract:
A series of 3-aryl-5-styrylisoxazoline/ 3,5-diarylisoxazoline
derivatives were synthesized by the reaction of appropriately substituted
chalcones and hydroxylamine hydrochloride in presence of alkali in ethanol.
The synthesized heterocycles have been characterized on the basis of their
chemical properties and spectroscopic data. These compounds were tested for
biological activity against a variety of test organisms.
Keywords: Chalcones, Hydroxylamine hydrochloride, 3,5-Diarylisoxazoline, 3-Aryl-5-styrylisoxazoline.
Introduction
Among five membered heterocycles, isoxazoline represents a class of compounds of great
importance in biological chemistry. For instance, isoxazoline posses biological activities1-8
like insecticidal, antibacterial, antibiotic, antitumour, antifungal, antituberculosis, anti
inflammatory and analgesic. Isoxazoline also serves as anti-influenza virus activity9, inhibition
of human leukocyte elastase and cathepsin G10. In fact, valdecoxib an isoxazoline derivative is
now widely used in the market as anti-inflammatory drug11. Benzfuran isoxazolines serves as
protein tyrosine phosphatase 1B inhibitors12.
Some fluorinated methyliminobenzoxazolines and their derivatives have been patented as
plant protecting acaricides, fungicides and insecticides13. Keeping in view the biological and
medicinal importance of chalcones and isoxazolines, we have synthesized some isoxazolines
starting from substituted 1,5-diaryl-2,4-pentadiene-1-one and hydroxylamine hydrochloride.

204
VANDANA SHARMA et al.
Experimental
General procedures
Melting points were determined by the open tube capillary method and are uncorrected. The
purity of the compounds was controlled by thin layer chromatography (TLC). IR spectra
were recorded as KBr pellets on Perkin-Elmer spectrum RX1 spectrophotometer. Carbon,
hydrogen and nitrogen were estimated by Thermo Finnigan FLASH EA 1112 elemental
analyzer. Mass spectra were measured on JEOL SX 102/DA-6000 mass spectrometer. 3,5-
Diarylisoxazoline derivatives were prepared according to the reported methods.
Synthesis of 1,5-diaryl-2,4-pentadiene-1-one (1)
To a mixture of acetophenone (8.12 mL) and cinnamaldehyde (8.8 mL) in ethanol (110 mL)
a solution of NaOH (10 g in 20 mL of water) was added. The reaction mixture was stirred
for 4 h and then kept over night at room temperature. After cooling in ice, the reaction
mixture was acidified with aqueous HCl (10%). The resulting precipitate was washed with
distilled water and dried. The resulting crude was crystallized from ethanol to obtained
yellow crystalline product.
Synthesis of 3-aryl-5-styrylisoxazoline (1a)
To a mixture of 1,5-diaryl-2,4-pentadiene-1-one (1 g) and hydroxylamine hydrochloride
(0.5 g in 5 mL water) in ethanol (25 mL) a solution of sodium hydroxide (1.1 g in 10 mL
water) was added. The reaction mixture was refluxed for 4 h. It was allowed to cool at room
temperature and then kept overnight in the freezer. A white crystalline solid separated. It
was filtered, washed with distilled water and dried. The product was crystallized from
ethanol to afford white crystals.
Synthesis of 1-(4'-chlorophenyl)-5-phenyl-2,4-pentadiene-1-one (2)
To a mixture of p-chloroacetophenone (9.03 mL) and cinnamaldehyde (8.82 mL) in ethanol
(110 mL) a solution of NaOH (10 g in 20 mL water) was added. The reaction mixture was
stirred for 4 h. It was then kept overnight at room temperature. After cooling in ice, the
reaction mixture was acidified with aqueous HCl (10%). The resulting yellow solid was
filtered, washed well with distilled water and dried. The product on crystallization from
ethanol afforded yellow needles.
Synthesis of 3-(4'-chlorophenyl)-5-styrylisoxazoline (2a)
To a mixture of 1-(4'-chlorophenyl)-5-phenyl-2,4-pentadiene-1-one (1 g) and hydroxylamine
hydrochloride (0.5 g in 5 mL water ) in ethanol (25 mL) a solution of sodium hydroxide (1.1 g
in 10 mL water) was added. The reaction mixture was refluxed for 4 h. It was allowed to cool
to room temperature and then kept overnight in freezer. A white crystalline solid separated. It
was filtered, washed with distilled water and dried. The product was crystallized from ethanol
to afford white crystal.
Synthesis of 1-(4'-methylphenyl)-5-phenyl-2,4-pentadiene-1-one (3)
To a mixture of p-methylacetophenone (9.31 mL) and cinnamaldehyde (8.82 mL) in ethanol
(110 mL) a solution of NaOH (10 g in 20 mL water) was added. The reaction mixture was
stirred for 4 h. It was then kept overnight at room temperature. After cooling in ice, the
reaction mixture was acidified with aqueous HCl (10%). The resulting yellow solid was
filtered, washed well with distilled water and dried. The product on crystallization from
ethanol afforded yellow needles.

Synthesis and Biological Activity of Some 3, 5-Diarylisoxazoline Derivatives
205
Synthesis of 3-(4'-methylphenyl)-5-styrylisoxazoline (3a)
To a mixture of 1-(4'-methylphenyl)-5-phenyl-2,4-pentadiene-1-one (1 g) and hydroxylamine
hydrochloride (0.5 g in 5 mL water ) in ethanol (25 mL) a solution of sodium hydroxide (1.1 g
in 10 mL water) was added. The reaction mixture was refluxed for 4 h. It was allowed to cool
to room temperature and then kept overnight in freezer. A white crystalline solid separated. It
was filtered, washed with distilled water and dried. The product was crystallized from ethanol
to afford white crystal.
Synthesis of 3-(4'-methoxyphenyl)-5-phenyl-2,4-pentadiene-1-one (4)
To a mixture of p-methylacetophenone (10.55 mL) and cinnamaldehyde (8.8 mL) in ethanol
(110 mL) a solution of NaOH (10 g in 20 mL water) was added. The reaction mixture was
stirred for 4 h. It was then kept overnight at room temperature. After cooling in ice, the
reaction mixture was acidified with aqueous HCl (10%). The resulting yellow solid was
filtered, washed well with distilled water and dried. The product on crystallization from
ethanol afforded yellow needles.
Synthesis of 3-(4'-methoxyphenyl)-5-styrylisoxazoline (4a)
To a mixture of 1-(4'-methoxyphenyl)-5-phenyl-2,4-pentadiene-1-one (1g) and hydroxylamine
hydrochloride (0.5 g in 5 mL water) in ethanol (25 mL) a solution of sodium hydroxide (1.1 g
in 10 mL water) was added. The reaction mixture was refluxed for 4 h. It was allowed to cool
to room temperature and then kept overnight in freeze. A white crystalline solid separated. It
was filtered, washed with distilled water and dried. The product was crystallized from ethanol
to afford white crystal.
Synthesis of 3-phenyl-5-(2-hydroxyphenyl) isoxazoline (5)
To a mixture of 2-hydroxychalcone (2 g) and hydroxylamine hydrochloride (1 g in 10 mL
water) in ethanol (110 mL) a solution of NaOH (10 g in 20 mL of water) was added in
ethanol (50 mL) .The reaction mixture was refluxed for 4 h and then kept over night at room
temperature. After cooling in ice, the reaction mixture was acidified with aqueous HCl
(10%). The resulting precipitate was washed with distilled water and dried. The resulting
crude was crystallized from ethanol to obtained white crystalline product.
Synthesis of 3-(4'-methylphenyl)-5-(2-hydroxyphenyl) isoxazoline (6)
To a mixture of 2-hydroxy-4'-methoxychalcone (2 g) and hydroxylamine hydrochloride (1 g
in 10 mL water) in ethanol (110 mL) a solution of NaOH (10 g in 20 mL of water) in ethanol
(50 mL) was added.The reaction mixture was refluxed for 4 h and then kept over night at
room temperature. After cooling in ice, the reaction mixture was acidified with aqueous HCl
(10%). The resulting precipitate was washed with distilled water and dried. The resulting
crude was crystallized from ethanol to obtained white crystalline product.
1,5-Diaryl-2,4-pentadiene-1-one (1)
Compound (1) was obtained as yellow crystals in 85% yield, m.p. 99-100 ◦C; IR, υmax: 3200,
2920, 1650, 1600, 1590, 1580, 1540, 1350, 1290, 1250, 1200, 1100, 1030, 1000, 820, 760
,730, 690, 6000 and 480 cm-1; MS, m/z: 234, 233, 157, 131, 103, 77. Anal. Calcd. for
C17H14O: C, 87.17; H, 5.98, Found: C, 87.20; H, 5.88%.
3-Aryl-5-styrylisoxazoline (1a)
◦
Compound (1a) was obtained as white crystals in 80% yield, m.p. 171-172 C; IR, υmax
:
3200, 2900, 1610, 1580, 1560,1500, 1440, 1410, 1360, 1260, 1060, 990, 960, 930, 760, 750,
700 and 580 cm-1; MS, m/z: 249, 248, 172, 171, 146,103, 77, 69. Anal. Calcd. for C17H15NO:
C, 81.88; H, 6.02; N, 5.66, Found: C, 81.88; H, 6.02; N, 5.62;%.

206
VANDANA SHARMA et al.
1-(4'-Chlorophenyl)-5-phenyl-2,4-pentadiene-1-one (2)
◦
Compound (2) was obtained as yellow crystals in 75% yield, m.p. 139-140 C; IR, υmax
:
3010, 2910, 1650,1590, 1580,1570,1450, 1400, 1350, 1290, 1260, 1200, 1150, 1100, 1030,
1015, 990, 820, 730, 690, 670 and 480 cm-1; MS, m/z: 268, 267, 232, 190, 178, 166, 152,
112, 76. Anal. Calcd. for C17H13ClO: C, 75.58; H, 4.83 Found: C, 76.28; H, 4.29%.
3-(4'-Chlorophenyl)-5-styrylisoxazoline (2a)
Compound (2a) was obtained as white crystals in 78% yield, m.p.173-174 ◦C; IR, υ max:3020,
2930, 1610, 1590, 1550, 1530, 1490,1450, 1420, 1400, 1380, 1350, 1260, 1100, 1010, 980,
910, 860, 840, 820, 750, 690, 550, 530, 500 and 450 cm1; MS, m/z:286, 285, 250, 209, 183,
173, 148, 114, 79, 78, 71. Anal. Calcd. for C17H14ClNO: C, 71.32; H, 4.89; N, 4.89. Found:
C, 71.36; H, 4.78; N, 4.92%.
1-(4'-Methylphenyl)-5-phenyl-2,4-pentadiene-1-one (3)
◦
Compound (3) was obtained as yellow crystals in 71% yield, m.p. 88-89 C; IR, υmax:3020,
2920, 1650, 1600, 1580, 1560, 1450, 1350, 1290, 1260, 1190, 1160, 1120, 1030, 1020,
1000, 940, 880, 750, 730,, 690 and 600 cm-1; MS, m/z: 248, 247, 233, 179, 171, 153, 145,
102, 91, 76. Anal. Calcd. for C18H16O: C, 87.09; H, 6.45; N. Found: C, 87.13; H, 6.43%.
3-(4'-Methylphenyl)-5-styrylisoxazoline (3a)
Compound (3a) was obtained as white crystals in 65% yield, m.p. 138-139 ◦C; IR, υmax:3020,
2920, 1610, 1600, 1580, 1560, 1510, 1510, 1490, 1450, 1430, 1390, 1350, 1260, 1190, 180, 980,
950, 910, 830, 810, 750, 700, 620, 550, 530 and 460 cm-1; MS, m/z: 261, 260, 246, 184, 169, 158,
143, 92, 89, 74,66. Anal. Calcd. for C18H17NO: C, 82.13; H, 6.46; N, 5.32 Found: C, 82.66; H,
5.79; N, 5.36%.
3-(4'-Methoxyphenyl)-5-phenyl-2, 4-pentadiene-1-one (4)
◦
Compound (4) was obtained as yellow crystals in 76% yield, m.p. 83-84 C; IR, υmax:3020,
2940, 1650, 1600, 1590, 1510, 1450, 1420, 1360, 1310, 1290, 1260, 1175, 1120, 1030, 1010,
960, 820, 760, 740, 690, 640, 600 and 510 cm-1; MS, m/z: 264, 263, 233, 187, 179, 161, 153,
107, 102,76. Anal. Calcd. for C18H17O2: C, 81.81; H, 6.06; Found: C, 81.83; H, 6.09%.
3-(4'-Methoxyphenyl)-5-styrylisoxazoline (4a)
Compound (4a) was obtained as white crystals in 72% yield, m.p. 109-110 ◦C; IR, υmax:3020,
2930, 1610, 1590, 1560, 1515, 1490, 1450, 1430, 1350, 1260, 1180, 1120, 1040, 1030, 980,
910, 835, 750, 700, 620 and 550 cm-1; MS, m/z: 239, 238, 208, 162, 136, 131, 67, 62, 54, 36,
28. Anal. Calcd. for C18H17NO2: C, 77.42; H, 6.09; N,5.02. Found: 77.88; H, 5.46; N,
5.05%.
3-Phenyl-5-(2-hydroxyphenyl) isoxazoline (5)
Compound (5) was obtained as white crystals in 65% yield, m.p. 149-150 ◦C; IR υmax: 3200
(-OH stretching vibration) 1610, 1590, 1570, 1500, 1460, 1450, 1360, 1290, 1270, 1190,
1170, 1110, 1050, 1000, 960, 935, 875, 840, 765, 750, 690, 610, 530 and 480 cm-1; MS,
m/z:239, 238, 222, 162, 153, 143, 93, 76, 68. Anal. Calcd. For C15H13NO2: C, 75.31; H,
5.43; N, 5.85. Found: C, 75.29; H, 5.46; N, 5.92%.
3-(4'-Methylphenyl)-5-(2-hydroxyphenyl) isoxazoline (6)
Compound (6) was obtained as white crystals in 75% yield, m.p. 138-139 ◦C; IR, υmax: 3200
(-OH stretching vibration) 1610, 1590, 1570, 1500, 1460, 1450, 1360, 1290, 1260, 1180,
1155, 1110, 1085, 1050, 980, 960, 935, 920, 875, 840, 765, 750, 690, 610, 530 and 480 cm-1;

Synthesis and Biological Activity of Some 3, 5-Diarylisoxazoline Derivatives
207
MS, m/z:253, 252, 238, 236, 161, 159, 144, 90, 75, 67, 58. Anal. Calcd. For C16H15NO2: C,
75.88; H, 5.92; N, 5.53. Found: C, 75.86; H, 5.92; N, 5.55%.
Results and Discussion
Keeping in view the biological activity and medicinal importance of chalcones and isoxazolines,
we synthesized some isoxazolines starting from substituted 1,5-diaryl-2,4-pentadiene-1-ones
and hydroxylamine hydrochloride. Substituted 1,5-diaryl-2,4-pentadiene-1-ones (1-4) have been
prepared by variedly substituted acetophenones and cinnamaldehyde by Claisen-Schmidt
condensation. These substituted 1,5-diaryl-2,4-pentadiene-1-ones and substituted 2-
hydroxychalcones were refluxed with hydroxylamine hydrochloride in presence of alkali in
ethanol for 4 h to afford the corresponding 3-aryl-5-styrylisoxazoline (1a-4a) (Scheme 1) and
3,5-diarylisoxazolines (5,6)(Scheme 2) respectively. The structures of all new compounds have
been elucidated by elemental analyses, mass and IR spectral measurements.
R
R
NaOH
Ethanol
+
O
O
CH
3
O
Substituted acetophenone
Substituted-1,5-diaryl-2-4-pentadiene-1-one
Substituted-1,5-diaryl-2,4-petadiene-1-one
Cinnamaldehyde
(1-4)
R
R
NaOH
H2NOH.HCl
+
Ethanol
O
N
Substituted-1,5-diaryl-2,4-petadiene-1-one Hydroxylamine hydrochloride
Substituted-1,5-diaryl-2-4-pentadiene-1-one
O
3-aryl-5-styrylisoxazoline
(1-4)
(1a-4a)
1,1a: R=H; 2,2a: R=Cl; 3,3a: R=CH3; 4,4a: R= OCH3
Scheme 1. Synthesis of substituted 1,5-diaryl-2,4-pentadiene-1-ones and 3-aryl-5-
styrylisoxazoline derivatives.
R
N
N aO H
R
H 2 N O H .H C l
O
+
E thonal
O
R'
R'
Sbstituted-3,5-diaryl isooxazoline
Substituted-3,5-diarylisoxazoline
H ydroxylam ine Hydrochloride
Sustituted-2-hydroxy chalcone
Substituted-2-hydroxy chalcone
(5,6)
5: R=H; R'=OH, 6:= R=CH3; R'=OH
Scheme 2. Synthesis of substituted-3,5-diarylisoxazoline derivatives
IR spectra of 1,5-diaryl-2,4-pentadiene-1-ones give absorption peak at 1650 cm-1 due to
C=O group, this lowering in frequency is due to extended conjugation. A group of three bands
were found in the region 1600-1500 cm-1. This is due to the absorption of aromatic nucleus and
olefinic double bond. The IR spectra of isoxazolines show no carbonyl absorption peaks at
1610 cm-1 and 1260 cm-1 due to C= N and C–O–N stretching frequencies respectively.

208
VANDANA SHARMA et al.
Biological activity
The synthesized 3-aryl-5-styrylisoxazoline (1a-4a) and 3,5-diarylisoxazolines (5, 6) have been
subjected to in vitro antimicrobial activity against various plant and human pathogenic bacteria
and fungi. Antimicrobial activity was carried out against gram positive coccus Staphylococcus
aureus, Micrococcus luteus, gram positive rod Bacillus megatherium and gram negative rod
Pseudomonas aeruginosa, Proteus vulgaris and Klebsiella pneumoniae. Candida albicans,
Saccharomyces cerevisiae yeast fungus and Aspergillus niger, Penicillium notatum soil fungi
were used for microbial activity. The results are summarized in the Table 1.
Table 1. Antimicrobial activity of 3-aryl-5-styrylisoxazoline and 3,5-diarylisoxazoline
derivatives.
Culture
Compd. No.
A
B
C
D
E
F
G
H
I
J
3
6
4
1
4
3
4
5
5
4
5
7
5
4
5
3
5
2
2
1a
2
2a
3
5
5
5
5
2
7
8
10
10
2
3
3
2
9
3
5
3
3
3a
4
2
5
4
2
10
10
4a
5
7
6
5
6
4
5
4
10
8
2
3
5
6
(Diameter of inhibition zone measured in mm, paper disc 5 mm, inhibition zone measured
excluding paper disc diameter)
A= Staphylococcus aureus;
D= Pseudomonas aeruginosa; E= Proteus vulgaris;
G= Aspergillus niger;
J= Saccharomyces cerevisiae.
B= Micrococcus luteus; C= Bacillus megatherium;
F= Klebsiella pneumoniae;
H= Penicillium notatum; I= Candida albicans;
It can be concluded from the observation that, these substituted 3-aryl-5-
styrylisoxazoline (1a-4a) and 3,5-diarylisoxazolines (5, 6) possess moderate antimicrobial
and antifungal activity. The larger inhibition growth was observed when all the compounds
were tested against gram positive coccus Staphylococcus aureus and soil fungi Penicillium
notatum. However, moderate inhibition growth was observed when all the compounds were
tested with Micrococcus luteus, Candida albicans and Saccharomyces cerevisiae. The
compounds were found to be inactive against gram negative bacteria Pseudomonas
aeruginosa, Proteus vulgaris and Klebsiella pneumoniae.
In conclusion, we have synthesized a systematically substituted series of new 3-aryl-5-
styrylisoxazoline (1a-4a) and 3,5-diarylisoxazolines (5, 6) derivatives for structure-activity
relationship studies. These substituted derivatives are very stable compounds, which renders
them beneficial substances for biological or pharmacological trials.
Acknowledgements
Authors are thankful to School of Studies in Chemistry, Vikram University, Ujjain (India),
RSIC, CDRI, Lucknow (India), Mahakal Institute of Pharmaceutical Studies, Ujjain (India)
for providing spectral and analytical data.

Synthesis and Biological Activity of Some 3, 5-Diarylisoxazoline Derivatives
209
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