Synthesis of some new 3,4-dihydro-2H-1,3-benzoxazines under microwave irradiation in solvent-free conditions and their biological activity

Article abstract of DOI:10.1007/s00044-010-9451-x

A series of some new benzoxazines derivatives have been synthesized using conventional method and solvent-free microwave thermolysis. It was observed that the solvent-free microwave thermolysis is a convenient, rapid, high-yielding, and environmental friendly protocol for the synthesis of benzoxazines when compared with conventional reaction in a solution phase. All the compounds synthesized were tested for anti-inflammatory activity. Compound 3f, 3h, and 3l showed 74.87, 70.39, and 71.89% of inhibition in rat paw edema, 57.38, 54.27, and 55.47% of protection against acetic acid induced writhings, and 0.08, 0.17, and 0.17 of severity index (SI), respectively compared to 82.33, 63.06, and 1.0 values of ibuprofen. The study showed that these compounds are good and safe anti-inflammatory agents and can be used to develop potent and safe anti-inflammatory agents. Springer Science+Business Media, LLC 2010.

Full text of DOI:10.1007/s00044-010-9451-x

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:1147–1153
DOI 10.1007/s00044-010-9451-x
ORIGINAL RESEARCH
Synthesis of some new 3,4-dihydro-2H-1,3-benzoxazines
under microwave irradiation in solvent-free conditions
and their biological activity
•
Mymoona Akhter Shaikh Habibullah
•
•
Syed Misbahul Hasan Mohammad Mumtaz Alam
•
•
N. Akhter Mohammad Shaquiquzzaman
Received: 31 May 2010 / Accepted: 21 September 2010 / Published online: 7 October 2010
Ó Springer Science+Business Media, LLC 2010
Abstract A series of some new benzoxazines derivatives
have been synthesized using conventional method and
solvent-free microwave thermolysis. It was observed that
the solvent-free microwave thermolysis is a convenient,
rapid, high-yielding, and environmental friendly protocol
for the synthesis of benzoxazines when compared with
conventional reaction in a solution phase. All the com-
pounds synthesized were tested for anti-inflammatory
activity. Compound 3f, 3h, and 3l showed 74.87, 70.39,
and 71.89% of inhibition in rat paw edema, 57.38, 54.27,
and 55.47% of protection against acetic acid induced wri-
things, and 0.08, 0.17, and 0.17 of severity index (SI),
respectively compared to 82.33, 63.06, and 1.0 values of
ibuprofen. The study showed that these compounds are
good and safe anti-inflammatory agents and can be used to
develop potent and safe anti-inflammatory agents.
Introduction
The NSAIDs are among the most widely used of all ther-
apeutic agents. They are useful in the treatment of rheu-
matoid arthritis and other inflammatory diseases. However,
long-term use of the NSAIDs has been associated with
gastrointestinal ulceration, bleeding, and nephrotoxicity.
Therefore, an investigation of new anti-inflammatory
agents is still a challenge.
Benzoxazine based heterocyclic compounds forms an
important class of benzfuzed heterocyles with wide spec-
trum of biological activities and are in the development
phase as potential new drugs. Benzoxazines are, therefore,
reported to exhibit anti-inflammatory (Khalaj et al., 2002;
Mashevakaya et al., 2001), analgesic (Gokhan et al., 1999),
antibacterial (Beach and Frechette, 1997), neuroprotective
(Kamei et al., 2006), D2 receptor antagonistic activity (Ilas
et al., 2005), antimycobacterial (Waisser et al., 2003),
antiviral (Wittmann et al., 2000; Pandey et al., 1999),
antifungal (Waisser et al., 2002) etc.
Keywords 1,3-Benzoxazine ꢀ Microwave ꢀ Chalcones ꢀ
Anti-inflammatory ꢀ Analgesic
A cursory look at the literature cited in relation to chal-
cones in recent years indicates that there is a growing interest
in evaluating the pharmaceutically important biological
activities of chalcones and its derivatives, presuming their
role in the prevention of various degenerative diseases and
other human ailments. The compounds with the backbone of
chalcone have been reported to exhibit a wide variety of
pharmacological effects, including anti-inflammatory
(Herencia et al., 1998), antileishmanial (Nielsen et al.,
1998), antibacterial (Liu et al., 2008), antifungal (Tsuchiya
et al., 1994), antitumour (Go et al., 2005), antimalarial
M. Akhter (&) ꢀ S. Habibullah ꢀ M. M. Alam ꢀ
M. Shaquiquzzaman
Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
Jamia Hamdard, New Delhi 110062, India
e-mail: mymoonaakhter@gmail.com;
makhtar@jamiahamdard.ac.in
S. M. Hasan
Pharmacy Department, College of Health Sciences,
P O Box 2994, Sakaka, Kingdom of Saudia Arabia
´
(Mishra et al., 2008; Domınguez et al., 2005; Larsen et al.,
N. Akhter
2005), and anti-TB activity (Chiaradia et al., 2008).
An alternative to conventional heating is microwave
radiation which has been very widely explored by organic
Department of Chemistry, India Institute of Integrated Medicine,
(Center for Scientific and Industrial Research Lab), Sanat Nagar,
Srinagar, Kashmir 190005, India
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Med Chem Res (2011) 20:1147–1153
chemists. Microwave-assisted heating has been shown to
be an invaluable technology in synthesis since it often
dramatically reduces reaction times, typically from days or
hours to minutes or even seconds. Pure products in quanti-
tative yields have been reported with the use of microwave.
Solvent-free reaction techniques have been successfully
coupled with microwave synthesis. Low boiling point, toxic,
and poisonous solvents are often avoided in microwave
synthesis to avoid accidents. The use of microwave for the
synthesis of organic compounds proved to be efficient safe
and environmentally benign techniques with shorter reaction
time. In view of the above findings and in continuation of our
work synthesis of biologically important heterocycles
(Akhter et al., 2009; Hasan et al., 2009) herein we wish to
report a simple, convenient microwave-assisted synthesis of
the title compounds and comparison to the conventional
method of synthesis of 1,3-benzoxazine derivatives.
reaction was followed by TLC (toluene:ethylacetate:formic
acid, 5:4:1), after the completion of reaction, excess of
solvent was distilled off, and the reaction mixture was
cooled to room temperature and poured onto crushed ice.
The solid thus separated was filtered, dried, and crystal-
lized from methanol.
3-(4-Methoxy phenyl)-6-acetyl-3,4-dihydro-2H-1,3-ben-
1
zoxazine (2a) Yield: 64%; mp: 144–46°C; Rf: 0.81; H-
NMR (ppm): 2.52 (3H, s, COCH3), 3.73 (3H, s, OCH3), 4.4
(2H, s, NCH2), 5.3 (2H, s, OCH2N), 6.76 (2H, d,
J = 8.6 Hz, ArH), 7.2 (2H, d, J = 8.6 Hz, ArH), 7.40 (1H,
d, J = 8.1 Hz, H8), 7.56 (1H, d, J = 8.1 Hz, H7), 7.9 (1H,
s, H5); MS m/z: 282 (M?); Anal. Calcd. for C17H17NO3: C,
72.07; H, 6.05; N, 4.94. Found: C, 72.21; H, 6.03; N, 4.93.
3-(4-Methyl phenyl)-6-acetyl-3,4-dihydro-2H-1,3-ben-
zoxazine (2b) Yield: 59%; mp: 134–36°C; Rf: 0.73;
1H-NMR (ppm): 2.15 (3H, s, CH3), 2.51 (3H, s, COCH3),
4.34 (2H, s, NCH2), 5.34 (2H, s, OCH2), 6.71 (2H, d,
J = 8.6 Hz, ArH), 7.12 (2H, d, J = 8.6 Hz, ArH), 7.24
(1H, d, J = 8.1 Hz, H8), 7.76 (1H, d, J = 8.1 Hz, H7), 7.89
(1H, s, H5); MS m/z: 266 (M?); Anal. Calcd. for
C17H17NO2: C, 76.38; H, 6.41; N, 5.24. Found: C, 76.18;
H, 6.40; N, 5.23.
Materials and methods
Chemistry
All the reagents and solvents used were procured from E
Merck (India) Ltd. All the solvents used were dried and
distilled before use. Melting points were determined in
open end capillary tubes using Kjeldhal flask containing
liquid paraffin and are uncorrected. The purity of the
compounds was monitored by ascending thin layer chro-
matography (TLC) on silica gel G (Merck), in the solvent
system toluene–ethyl formate–formic acid (5:4:1) and
ethylacetate:hexane (2:8), the spots were located under
iodine vapors or UV light. IR spectra were recorded in KBr
on Perkin-Elmer 1720 FTIR spectrometer, and proton
nuclear magnetic resonance (1H-NMR) spectra were
recorded on Brucker Avance (300 MHz) spectrometer
using TMS as internal standard in CDCl3/DMSO-d6.
Chemical shifts are reported in parts per million (ppm).
Mass spectra were recorded on Bruker Esquire 300 quad-
rupole ion trap mass spectrometer. Elemental analysis of
all the synthesized compounds was within 0.4%.
Microwave-assisted synthesis was carried out in Micro-
wave oven (900 W).
General procedure for microwave-assisted synthesis of 1,3-
diphenyl-3,4-dihydro-2H-benzo[e][1,3]oxazine-6-yl]
propenone (3)
Compound 2a–b (0.01 mol) was titrated with two flakes of
KOH in a pestle motor and (0.0l mol) of aromatic aldehyde
was added. The contents were mixed throughly and trans-
ferred to a 25 ml beaker. The beaker was placed in a
microwave oven for 4–6 min (900 W) (four pulses each of
1–1.5 min). The reaction conditions for a single reaction
were optimized in terms of power, pulse (time), and
cooling time of reaction mixture. The optimum time for
microwave synthesis was found to be a cycle of 1–2 min of
irradiation followed by 2 min off. The microwave irradi-
ations were repeated 3–4 times giving a total time of
4–6 min to achieve the completion of the reaction.
The reactions were followed by TLC (ethylace-
tate:hexane, 2:8). After completion of the reaction, crushed
ice was added to the reaction mixture in beaker and then
acidified with dilute HCl to obtain the product. The product
obtained was filtered on suction, dried, and crystallized
from methanol.
General procedure for synthesis of 3-phenyl-6-acetyl-3,4-
dihydro-2H-1,3-benzoxazine compounds (2)
General procedure for the synthesis of 1,3-diphenyl-3,4-
dihydro-2H-benzo[e][1,3]oxazine-6-yl] propenone (3)
To a solution of aromatic primary amine (0.025 mol) in
methanol (0.05 mol), formaldehyde was added and the
solution was refluxed for 10 min. To this solution,
4-hydroxy acetophenone (0.025 mol, 3.4 g) was added,
and refluxing was continued for a specified period. The
To a solution of (0.01 mol) 2a–b in ethanol was added
KOH (15%, 3 ml) and refluxed for 10 min, followed by
addition of aromatic aldehyde (0.01 mol). The refluxing
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Med Chem Res (2011) 20:1147–1153
1149
was continued for a specified time with stirring. After
completion of reaction, excess of solvent was distilled off.
The mixture was cooled to room temperature and poured
onto the crushed ice and acidified with dil. HCl. The solid
thus separated was filtered, dried, and crystallized from
methanol.
3-(20-Chlorophenyl)-1-[3-(4-methoxyphenyl)-3,4-dihydro-
2H-benzo[e][1,3]oxazine-6-yl] propenone (3a) mp:
125–27°C; Rf: 0.46; IR (KBr) cm-1: 1322, 1693, 1757;
1H-NMR (ppm): 3.68 (3H, s, OCH3), 4.59 (2H, s, NCH2),
5.5 (2H, s, OCH2), 6.64 (1H, d, J = 8.1 Hz, COCH=), 6.86
(2H, d, J = 8.6 Hz, ArH), 7.21–7.29 (4H, m, ArH), 7.39
(1H, d, J = 8.1 Hz, H8), 7.63 (2H, d, J = 8.6 Hz, ArH),
7.81 (1H, d, J = 8.1 Hz, H7), 7.89 (1H, s, H5), 8.32 (1H, d,
J = 8.1 Hz, =CH–Ar); MS m/z: 404(M?), 406(M ? 2);
Anal. Calcd. for C24H20ClNO3: C, 71.02; H, 4.97; N, 3.45.
Found: C, 71.21; H, 4.96; N, 3.46.
3-(40-Methoxyphenyl)-1-[3-(4-methoxyphenyl)-3,4-dihy-
dro-2H-benzo[e][1,3]oxazine-6-yl] propenone (3b) mp:
123–125°C; Rf: 0.53; IR (KBr) cm-1: 1321, 1696, 1758;
1H-NMR (ppm): 3.83 (3H, s, OCH3), 3.90 (3H, s, OCH3),
4.3 (2H, s, NCH2), 4.95 (2H, s, OCH2), 6.55 (1H, d,
J = 8.6 Hz, COCH=), 6.64 (2H, d, J = 8.6 Hz, ArH),
7.2–7.43 (6H, m, H7, H8, ArH), 7.69 (2H, d, J = 8.6 Hz,
ArH), 7.8 (1H, s, H5), 8.62 (1H, d, J = 8.6 Hz, =CH–Ar);
MS m/z: 400(M?); Anal. Calcd. for C25H23NO4: C, 74.80;
H, 5.77; N, 3.49. Found: C, 74.92; H, 5.76; N, 3.48.
3-(20-Hydroxyphenyl)-1-[3-(4-methoxyphenyl)-3,4-dihy-
dro-2H-benzo[e][1,3]oxazine-6-yl]-propenone (3c) mp:
112–14°C; Rf: 0.47; IR (KBr) cm-1: 1320, 1696, 1769;
1H-NMR (ppm): 3.79 (3H, s, OCH3), 3.99 (2H, s, NCH2),
5.68 (2H, s, OCH2), 6.78 (1H, d, J = 8.1 Hz, COCH=),
6.92–7.2 (4H, m, ArH), 7.32–7.48 (6H, m, H7, H8, ArH),
7.65 (1H, s, H5), 8.56 (1H, d, J = 8.1 Hz, =CH–Ar), 11.07
(1H, s, OH); MS m/z: 386 (M?); Anal. Calcd. for
C24H21NO4: C, 74.40; H, 5.46; N, 3.62. Found: C, 74.56;
H, 5.47; N, 3.61.
(2H, d, J = 8.6 Hz, ArH), 7.11–7.23 (4H, m, ArH), 7.42
(1H, d, J = 8.1 Hz, H8), 7.56 (2H, d, J = 8.6 Hz, ArH), 7.64
(1H, d, J = 8.1 Hz, H7), 7.75 (1H, s, H5), 8.36 (1H, d,
J = 8.1 Hz, =CH–Ar); MS m/z: 404(M?), 406(M ? 2);
Anal. Calcd. for C24H20ClNO3: C, 71.02; H, 4.97; N, 3.45.
Found: C, 70.89; H, 4.98; N, 3.44.
3-(20,40-Dichlorophenyl)-1-[3-(4-methoxyphenyl)-3,4-
dihydro-2H-benzo[e][1,3] oxazine-6-yl] propenone (3f)
mp: 158–60°C; Rf: 0.69; IR (KBr) cm-1: 1316, 1700,
1
1769; H-NMR (ppm): 3.65 (3H, s, OCH3), 4.32 (2H, s,
NCH2), 5.66 (2H, s, OCH2), 6.59 (2H, d, J = 8.6 Hz,
ArH), 6.69 (1H, d, J = 8.1 Hz, COCH=), 6.96 (2H, d,
J = 8.6 Hz, ArH), 7.09–7.18 (3H, m, ArH), 7.42 (1H, d,
J = 8.1 Hz, H8), 7.64 (1H, d, J = 8.1 Hz, H7), 7.75 (1H, s,
H5), 8.16 (1H, d, J = 8.1 Hz, =CH–Ar); MS m/z:
439(M?), 441(M ? 2) Anal. Calcd. for C24H19Cl2NO3: C,
65.47; H, 4.35; N, 3.18. Found: C, 65.62; H, 4.36; N, 3.17.
3-(20-Chlorophenyl)-1-[3-(4-methylphenyl)-3,4-dihydro-
2H-benzo[e][1,3] oxazine-6-yl] propenone (3g) mp:
146–48°C; Rf: 0.73; IR (KBr) cm-1: 1324, 1679, 1757;
1H-NMR (ppm): 2.21 (3H, s, CH3), 4.5 (2H, s, NCH2), 5.51
(2H, s, OCH2), 6.46 (2H, d, J = 8.6 Hz, ArH), 6.90 (2H, d,
J = 8.6 Hz, ArH), 7.18 (1H, d, J = 8.1, COCH=),
7.35–7.51 (6H, m, H7, H8, ArH), 7.60 (1H, s, H5), 8.11 (1H,
d, J = 8.1 Hz, =CH–Ar); MS m/z: 389(M?), 391(M ? 2);
Anal. Calcd. for C24H20ClNO2: C, 73.94; H, 5.17; N, 3.59.
Found: C, 74.08; H, 5.18; N, 3.60.
3-(40-Methoxyphenyl)-1-[3-(4-methylphenyl)-3,4-dihydro-
2H-benzo[e][1,3] oxazine-6-yl] propenone (3h) mp:
100–02°C; Rf: 0.49; IR (KBr) cm-1: 1319, 1681, 1753;
1H-NMR (ppm): 2.10 (3H, s, CH3), 3.53 (3H, s, OCH3),
4.48 (2H, s, NCH2), 5.49 (2H, s, OCH2), 6.66 (2H, d,
J = 8.6 Hz, ArH), 6.89 (1H, d, J = 8.1, COCH=), 7.16
(2H, d, J = 8.6 Hz, ArH), 7.26 (1H, s, H8), 6.37 (2H, d,
J = 8.1 Hz, ArH), 7.59(1H, s, H7), 7.69 (2H, d,
J = 8.1 Hz, ArH), 7.80 (1H, s, H5), 8.06 (1H, d,
J = 8.1 Hz, =CH–Ar); MS m/z: 384(M?); Anal. Calcd. for
C25H23NO3: C, 77.90; H, 6.01; N, 3.63. Found: C, 77.68;
H, 6.00; N, 3.62.
3-(30,40,50-Trimethoxyphenyl)-1-[3-(4-methoxyphenyl)-
3,4-dihydro-2H-benzo[e][1,3] oxazine-6-yl]-propenone
(3d) mp: 108–10°C; Rf: 0.41; IR (KBr) cm-1: 1320,
3-(20-Hydroxyphenyl)-1-[3-(4-methylphenyl)-3,4-dihydro-
2H-benzo[e][1,3]oxazine-6-yl] propenone (3i) mp:
137–40°C; Rf: 0.61; IR (KBr) cm-1: 1322, 1701, 1770;
1H-NMR (ppm): 2.29 (3H, s, CH3), 4.5 (2H, s, NCH2), 5.58
(2H, s, OCH2), 6.73 (1H, d, J = 8.1, COCH=), 6.81–6.94
(4H, m, ArH), 7.29 (1H, d, J = 8.1 Hz, H8), 7.28 (2H, d,
J = 8.5 Hz, ArH), 7.36 (1H, s, H5), 7.40 (2H, d,
J = 8.5 Hz, ArH), 7.72 (1H, d, J = 8.1 Hz, H7), 8.21 (1H,
d, J = 8.1 Hz, =CH–Ar), 11.16 (1H, s, OH); MS m/z:
370(M?); Anal. Calcd. for C24H21NO3: C, 77.61; H, 5.70;
N, 3.77. Found: C, 77.52; H, 5.68; N, 3.76.
1
1698, 1753; H-NMR (ppm) 3.86 (12H, s, 49OCH3), 4.4
(2H, s, NCH2), 5.20 (2H, s, OCH2), 6.62 (1H, d,
J = 8.6 Hz, COCH=), 6.74–6.77 (2H, m, ArH), 6.82 and
7.2 (4H, 29d, J = 8.1 Hz each, ArH), 7.44 (1H, d,
J = 8.1 Hz, H8), 7.64 (1H, d, J = 8.1 Hz, H7), 7.80 (1H,
s, H5), 8.42 (1H, d, J = 8.6 Hz, =CH–Ar); MS m/z: 460
(M?); Anal. Calcd. for C27H27NO6: C, 70.27; H, 5.90; N,
3.03. Found: C, 70.35; H, 5.91; N, 3.02.
3-(40-Chlorophenyl)-1-[3-(4-methoxyphenyl)-3,4-dihydro-
2H-benzo [e] [1,3] oxazine-6-yl] propenone (3e) mp:
134–37°C; Rf: 0.62; IR (KBr) cm-1: 1318, 1707, 1772;
1H-NMR (ppm): 3.74 (3H, s, OCH3), 4.21 (2H, s, NCH2),
5.61 (2H, s, OCH2), 6.60 (1H, d, J = 8.1 Hz, COCH=), 6.94
3-(30,40,50-Trimethoxyphenyl)-1-[3-(4-methylphenyl)-
3,4-dihydro-2H-benzo[e][1,3] oxazine-6-yl] propenone
(3j) mp: 156–58°C; Rf: 0.56; IR (KBr) cm-1: 1321, 1700,
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1
1773; H-NMR (ppm): 2.37 (3H, s, CH3), 3.64 (9H, s,
39OCH3), 4.2 (2H, s, NCH2), 5.6 (2H, s, OCH2), 6.69 (1H,
d, J = 8.1, COCH=), 7.24 (2H, d, J = 8.5 Hz, ArH),
7.29–7.41 (2H, m, ArH), 7.56 (1H, d, J = 8.1 Hz, H8), 7.61
(2H, d, J = 8.5 Hz, ArH), 7.70 (1H, d, J = 8.1 Hz, H7),
7.79 (1H, s, H5), 8.01 (1H, d, J = 8.1 Hz, =CH–Ar); MS
m/z: 444(M?); Anal. Calcd. for C27H27NO5: C, 72.79; H,
6.11; N, 3.14. Found: C, 72.59; H, 6.12; N, 3.13.
administration of the drugs. All the results are expressed as
mean S.E.M.
Analgesic activity
Compounds 3e, 3f, 3h, and 3l were tested for analgesic
activity. Analgesic activity was carried out using acetic
acid induced writhing method (Seigmund et al., 1957) in
Swiss albino mice (25–30 g) of either sex at 20 mg kg-1
body weight. A 1% v/v solution of acetic acid was used as
writhing inducing agent intraperitoneally. The analgesic
effect was studied after 3 h of drug administration. Mice
were divided into groups of six animals each. Number of
writhings were counted for 10 min in control, standard and
test compounds after acetic acid administration and com-
pared. Analgesic activity was measured as percent decrease
in writhings in comparison to control. All the results are
expressed as mean S.E.M.
3-(40-Chlorophenyl)-1-[3-(4-methylphenyl)-3,4-dihydro-
2H-benzo[e][1,3]oxazine-6-yl] propenone (3k) mp:
98–100°C; Rf: 0.44; IR (KBr) cm-1: 1321, 1697, 1765;
1H-NMR (ppm): 2.14 (3H, s, CH3), 4.29 (2H, s, NCH2),
5.60 (2H, s, OCH2), 6.65 (1H, d, J = 8.1, COCH=),
6.82(2H, d, J = 8.5 Hz, ArH), 7.18 (2H, d, J = 8.6 Hz,
ArH), 7.45 (2H, d, J = 8.6 Hz, ArH) 7.61(2H, m, H5, H7),
7.68 (2H, d, J = 8.6 Hz, ArH), 7.78 (1H, s, H5), 8.12 (1H,
d, J = 8.1 Hz, =CH–Ar); MS m/z: 389(M?), 391(M ? 2);
Anal. Calcd. for C24H20ClNO2: C, 73.94; H, 5.17; N, 3.59.
Found: C, 73.78; H, 5.16; N, 3.58.
3-(20,40-Dichlorophenyl)-1-[3-(4-methylphenyl)-3,4-dihy-
dro-2H-benzo[e][1,3]oxazine-6-yl] propenone (3l) mp:
134–36°C; Rf: 0.71; IR (KBr) cm-1: 1319, 1692, 1761;
1H-NMR (ppm): 2.14 (3H, s, CH3), 4.49 (2H, s, NCH2),
5.62 (2H, s, OCH2), 6.65 (1H, d, J = 8.1, COCH=), 7.18
(2H, d, J = 8.6 Hz, ArH), 7.31–7.45 (5H, m, H7, H8, ArH),
7.58 (2H, d, J = 8.6 Hz, ArH), 7.78 (1H, s, H5), 8.12 (1H,
d, J = 8.1 Hz, =CH–Ar); MS m/z: 423(M?), 425(M ? 2);
Anal. Calcd. for C24H19Cl2NO2: C, 67.93; H, 4.51; N, 3.30.
Found: C, 67.98; H, 4.52; N, 3.29.
Acute ulcerogenesis
The studies were carried out on healthy Wistar rats
(150–200 g) at a dose three times the anti-inflammatory
dose viz 60 mg kg-1. The animals were divided into dif-
ferent groups of six each, group I served as control and
received vehicle only and groups II received pure ibuprofen
60 mg kg-1. Other groups were administered test com-
pounds in dose molecularly equivalent to 60 mg kg-1 of
ibuprofen. The ulcerogenic activity was carried out
according to the reported method (Cioli et al., 1979). The
mean score of each treated group minus the mean score of
the control group was considered as the ‘‘severity index’’
(SI) of gastric damage.
Pharmacology
Protocol of animal experiments has been approved by the
Institutional Animal Ethics Committee (IAEC). All the
compounds synthesized were evaluated for their anti-
inflammatory activity; most potent compounds were fur-
ther evaluated for analgesic activity and ulcerogenic
studies.
Results and discussion
3-Phenyl-1-(3-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazin-
6-yl)propenone derivatives described in the study are
shown in Table 1, and the reaction sequence for the prepa-
ration is outlined in Scheme 1. The study compared the
conventional method of synthesis with the microwave-
assisted synthesis of benzoxazine derivatives. It was
observed the use of microwave not only reduces the time of
reaction but also improves the yield in solvent-free condi-
tions. The required intermediate 3-aryl-6-acetyl 1,3-ben-
zoxazine (2a–b) were synthesized by Mannich type
aminomethylation reaction by condensing 4-hydroxy aceto-
phenone with primary aromatic amines in the presence of
formaldehyde. The corresponding chalcone derivatives (3a–
l) were synthesized by base-catalyzed Claisen Schmidt
condensation of the acetyl 1,3-benzoxazines with aromatic
aldehydes. Spectral data of all the newly synthesized
Anti-inflammatory activity
The anti-inflammatory activity was evaluated using carra-
geenan induced rat paw edema method (Winter et al.,
1962). Wistar rats (150–200 g) were divided into groups
of six animals each. Group I served control and was
administered vehicle only, group II received ibuprofen
20 mg kg-1, and other groups received test drugs in dose
molecularly equivalent to the ibuprofen. Drug solutions
were prepared as a homogeneous suspension in aqueous
solution of sodium CMC (0.5% w/v) and were adminis-
tered orally to the animals. The measurement of the hind
paw volume was carried out using a Ugo Basile Plethys-
mometer before any treatment (Vo) and after 3 h of the
123

Med Chem Res (2011) 20:1147–1153
1151
Table 1 Physical constants of the newly synthesized 1,3 benzoxazines derivatives
O
O
R1
R
N
N
R
O
O
2a-b
3a-l
Compd
R
R1
m.p. (°C)
Rf
Conventional method
Microwave method
Time (h)
Yield (%)
Time (min)
Yield (%)
2a
2b
3a
3b
3c
3d
3e
3f
4-OCH3
4-CH3
–
144–46
134–36
125–27
123–25
112–14
108–10
134–37
158–60
146–48
100–02
137–40
156–58
98–100
134–36
0.85
0.71
0.46
0.53
0.47
0.41
0.62
0.69
0.73
0.49
0.61
0.56
0.44
0.71
2
2
64
59
54
45
44
46
57
52
58
41
45
58
39
34
–
–
6
4
6
4
6
6
6
4
6
4
6
4
–
–
–
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-OCH3
4-CH3
2-Cl
8
68
59
60
58
69
69
71
70
67
74
56
57
4-OCH3
2-OH
10
10
12
10
14
11
12
10
8
3,4,5 (OCH3)3
4-Cl
2,4-(Cl)2
2-Cl
3g
3h
3i
4-CH3
4-OCH3
2-OH
4-CH3
3j
4-CH3
3,4,5 (OCH3)3
4-Cl
3k
3l
4-CH3
14
10
4-CH3
2,4-(Cl)2
Scheme 1 Reagents and
conditions: a formaldehyde,
methanol, reflux and b EtOH,
substituted aromatic aldehydes,
25% KOH, reflux
O
NH2
HO
N
CH3
a
+
CH3
O
O
2a-b
R
1
R
b
R1
O
N
O
3a-l
R
compounds were in full agreement with the proposed struc-
tures. In general, Infra Red spectra (IR) revealed C=O and C–
oxazine ring, respectively; two doublets in the range of at d
6.55–7.18 and 8.01–8.62 ppm corresponding to protons of
CO–CH and =CH–Ar of the chalcone moiety, respectively.
All the newly synthesized compounds were screened for
their anti-inflammatory, analgesic activity, and ulcerogenic
effects. The inhibition of swelling in carrageenan induced
edema in rat paw brought about by oral administration of
the drugs is shown in Table 2. The percentages of swelling
of the drugs were calculated using Eq. (1).
N peaks in the range of 1650–1750 and 1280–1340 cm-1
,
respectively. In the Nuclear Magnetic Resonance spectra
(1H-NMR), the signals of the respective protons of the pre-
pared titled compounds were verified on the basis of their
chemical shifts, multiplicities, and coupling constants. The
spectra showed two singlets in the range of d 3.99–4.6 and
4.9–5.68 ppm corresponding to NCH2 and OCH2 groups of
123

1152
Med Chem Res (2011) 20:1147–1153
Ulcerogenic effectb
Table 2 Anti-inflammatory and analgesic evaluation of compound 3a–l
Compd
Anti-inflammatory
Analgesicb
Paw volume SEMa
%Inhibition SEMb
3a
0.24 0.07**
0.26 0.06**
0.29 0.01**
0.25 0.02**
0.22 0.02**
0.17 0.02**
0.26 0.01**
0.19 0.07**
0.33 0.02**
0.29 0.04**
0.24 0.02**
0.19 0.06**
0.67 0.04
63.43 10.54
61.19 10.14
55.72 2.24*
62.18 2.39
67.41 2.76
74.87 3.16
60.44 1.88
70.39 10.09
50.99 2.73**
56.46 5.54*
63.43 2.90
71.89 8.72
–
–
–
–
–
–
–
–
–
3b
3c
3d
3e
52.22 1.69**
0.25 0.12*
3f
57.38 1.17
0.08 0.08**
3g
–
–
3h
54.27 1.2**
0.17 0.11**
3i
–
–
3j
–
–
3k
–
–
3l
55.47 1.06**
–
0.17 0.11**
0.0 0.0
Control
Ibuprofen
0.12 0.03**
82.33 4.45
63.06 2.46
1
0.32
* P \ 0.05; ** P \ 0.01
a
Relative to their respective control and data were analyzed by one-way ANOVA followed by Dunnett’s test for n = 6
Relative to the standard (Ibuprofen) and data were analyzed by one-way ANOVA followed by Dunnett’s test for n = 6
b
(
The most active compounds were also tested for their
gastric irritation, and it was found that these agents were less
irritant to gastric mucosa than the standard as indicated by
the SI. The tested compounds (3e, 3f, 3h, and 3l) showed SI
ranging from 0.08 to 0.25 in comparison to 1.0 of standard.
ꢀ
ꢁ
Inhibition ð%Þ ¼ ðVt ꢁ VoÞcontolꢁ ðVt ꢁ VoÞtreated
=
)
ðVt ꢁ VoÞcontol ꢂ 100
ð1Þ
(Vt and Vo relates to the average volume in the hind paw of
the rats (n = 6) before any treatment and after anti-
inflammatory agent treatment, respectively). All the syn-
thesized compounds tested for anti-inflammatory activity
showed inhibition of edema ranging from 50.99 to 74.87%.
Compound 3f, 3h, and 3l were found to be most potent
compounds with percent inhibition of 74.87, 70.39, and
71.89, respectively. The one-way ANOVA test was
applied, and test compounds were found to be significantly
active compared to the control.
Conclusion
All the compounds have been synthesized by conventional
method and microwave method successfully. It was
observed that the solvent-free microwave thermolysis is a
convenient, rapid, high-yielding, and environmental
friendly protocol for the synthesis of benzoxazines when
compared with conventional reaction in a solution phase.
Further compound, 3f was found to be most active and safe
anti-inflammatory and analgesic agents and could be used
to develop more potent and safe anti-inflammatory and
analgesic agents.
Analgesic activity was carried out on albino mice by
Seigmund et al., 1957 method. Compounds (3e, 3f, 3h, and
3l) showing more than 80% of inhibition of ibuprofen in
swelling induced by carrageenan were further tested for
analgesic activity at the same dose as used for anti-inflam-
matory activity. The percent protection was calculated using
Eq. (2)
Acknowledgments One of the authors Mymooona Akhter is
thankful to UGC for financial support. The authors are grateful to
Janab Abdul Mueed for providing infrastructure and facility to carry
out this work.
Protectionð%Þ ¼ 100
ꢁðno: of writhings in test=no: of writhing in controlÞ
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