Synthesis and antimicrobial activity of 2-Aryl-4H-3,1-benzoxazin-4-ones

Article abstract of DOI:10.14233/ajchem.2013.12846

Twenty derivatives of 2-aryl-4H-3,1-benzoxazin-4-one synthesized and their potential therapeutically significance tested against two strains of Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and four strains of Gram negative bacteria (Shigella flexnari, Escherichia coli, Salmonella typhi and Pseudomonas aeruginsoa) by agar well diffusion method. The 2-(3-nitrophenyl)-4H-3,1-benzoxazin-4-one (3f) recorded significant antibacterial activity against Bacillus subtilis whereas 2-(4-bromophenyl)-4H-3, 1-benzoxazin-one (3o) exhibited weak antibacterial activity against Staphylococcus aureus. Further 2-(2-methylphenyl)-4H-3,1-benzoxazin-4-one (3b) showed significant activity against Shigella Flexnari, Escherichia coli, Pseudomonas aeruginsoa and Salmonella typhi. The antibacterial activity of synthesized derivatives of 2-aryl-4H-3,1-benzoxazin-4-one was compared to reference standard antibiotics amoxycillin, streptomycin, kanamycin and ciprofloxacin. The present study revealed that 2-aryl-4H-3,1-benzoxazin-4-ones possess good bactericidal activity against a panel of bacteria causing common bacterial diseases and therefore opens the possibility of finding latest clinically useful antibacterial compounds. The synthesized compounds were characterized by 1H NMR, EI, FT-IR and elemental analysis.

Full text of DOI:10.14233/ajchem.2013.12846

Asian Journal of Chemistry; Vol. 25, No. 1 (2013), 152-156
http://dx.doi.org/10.14233/ajchem.2013.12846
Synthesis and Antimicrobial Activity of 2-Aryl-4H-3,1-benzoxazin-4-ones
1
,*
1
2
ZULFIQAR ALI KHAN , SYED ALI RAZA NAQVI , SOHAIL ANJUM SHAHZAD ,
3
4
1
NASIR MAHMOOD , MUHAMMAD YAR and AMEER FAWAD ZAHOOR
1
2
3
4
Department of Chemistry, Government College University, Faisalabad-38000, Pakistan
Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad-22060, Pakistan
Department of Allied Health Sciences and Chemical Pathology, University of Health Sciences, Lahore, Pakistan
Interdisciplinary Research Center in Biomedical Materials, COMSATS Institute of Information Technology, Lahore-54000, Pakistan
*
Corresponding author: Tel: +92 33 26243829, E-mail: zulfiqarchem@gmail.com
Received: 12 October 2011; Accepted: 12 July 2012)
(
AJC-11838
Twenty derivatives of 2-aryl-4H-3,1-benzoxazin-4-one synthesized and their potential therapeutically significance tested against two
strains of Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and four strains of Gram negative bacteria (Shigella
flexnari, Escherichia coli, Salmonella typhi and Pseudomonas aeruginsoa) by agar well diffusion method. The 2-(3-nitrophenyl)-4H-3,1-
benzoxazin-4-one (3f) recorded significant antibacterial activity against Bacillus subtilis whereas 2-(4-bromophenyl)-4H-3,1-benzoxazin-one
(
3o) exhibited weak antibacterial activity against Staphylococcus aureus. Further 2-(2-methylphenyl)-4H-3,1-benzoxazin-4-one (3b)
showed significant activity against Shigella Flexnari, Escherichia coli, Pseudomonas aeruginsoa and Salmonella typhi. The antibacterial
activity of synthesized derivatives of 2-aryl-4H-3,1-benzoxazin-4-one was compared to reference standard antibiotics amoxycillin,
streptomycin, kanamycin and ciprofloxacin. The present study revealed that 2-aryl-4H-3,1-benzoxazin-4-ones possess good bactericidal
activity against a panel of bacteria causing common bacterial diseases and therefore opens the possibility of finding latest clinically useful
1
antibacterial compounds. The synthesized compounds were characterized by H NMR, EI, FT-IR and elemental analysis.
Key Words: 2-Aryl-4H-3,1-benzoxazin-4-ones, Synthesis, Antimicrobial activity, Agar well diffusion method.
biological applications they can be used as starting materials
INTRODUCTION
12
for synthesis of 1,3,4-oxadiazoline-5-thione , quinazolinone
The drawn of a post-antibiotic era is almost upon us. New
13
14
derivatives and triazoles . Like other heterocyclic compounds,
benzoxazinones are used directly or indirectly in many indus-
trial, academic research and clinical applications.
challenges for the control of diseases caused by pathogenic
microbes to our present day antibiotics and reemergence of
devastating diseases such as pyoderma (literally means pus in
the skin and refers to bacterial infections of the skin) leads
one to conclude that new strategies to combat these disease
causing microorganisms must be developed with great deal of
We already explored many classes of compounds for their
potential use in medicinal chemistry as well as their new
15
synthetic methodology developments . Therefore, capable
therapeutic prospective of this class of compounds encouraged
us to synthesize and biologically screen a series of structural
variants of 2-aryl-4H-3,1-benzoxazin-4-one against various
strains of Gram positive and Gram negative bacteria.
1
urgency .
Previous work by the medicinal chemists had led to a
number of drugs related uses being found for benzoxazinone
class of heterocyclic compounds. The family of benzoxazinones
2
-7
EXPERIMENTAL
was found promising as antifungal and antibacterial agents .
8
Benzoxazinone derivatives are used as antiphlogistic drugs .
9
They have also shown antielastase properties . Recently this
IR spectra (KBr discs or MeOH) were recorded on a
Bruker FT-IR IFS48 spectrophotometer. EI mass spectra data
were recorded with various MAT 711 (70 eV) spectropho-
class of compounds reported to show a strong dual inhibitory
11
effect on human neutrophil elastase release . Fenton et al.
10
1
tometers and data are tabulated as m/z. H NMR spectra were
have described plasma lipid altering characteristics of a series
of substituted 4H-3,1-benzoxazin-4-one as high density lipo-
protein elevators for the treatment of patients suffering from
hyperlipoproteinemia and associated diseases. Beside of their
3
recorded in CDCl using Bruker AC400 (300 MHz and 400
MHz) spectrophotometer, respectively. Melting points were
determined on a Büchi 434 melting point apparatus and were
uncorrected. The progress of all reactions was monitored by

Vol. 25, No. 1 (2013)
Synthesis and Antimicrobial Activity of 2-Aryl-4H-3,1-benzoxazin-4-ones 153
2
Anal. calc. for C15H11NO (237.253): C, 75.94; H, 4.67; N,
TLC, which was performed on 2.0 × 5.0 cm aluminum sheets
precoated with silica gel 60F254 to a thickness of 0.25 mm
5.90; found: C, 75.95; H, 4.65; N, 5.88.
2-(2-Nitrophenyl)-4H-3,1-benzoxazin-4-one (3e):Yield:
(
Merck). The chromatograms were visualized under ultra-
16
violet light (254-366 nm) or iodine vapours.All the carboxylic
acids are commercially available (Flulka Aldrich).
70 % (1.87 g, 7.0 mmol); m.p.: 191 ºC (lit. m.p. = 193 ºC);
1
-1
IR (KBr, νmax, cm ): 1768, 1636, 1531, 1346, 1225; H NMR
(400 MHz, DMSO-d ): δ 8.20 (d, 1H, J = 7.8, H-5), 8.14 (d,
16
Synthesis of 2-aryl-4H-3,1-benzoxzin-4-one (3a-3t) :
To a 100 mL round bottom flask containing the solution of
anthranilic acid (1.37 g, 0.01 mol) in pyridine (30 mL) was
cooled to 0 ºC in an ice bath followed by the careful addition
of acid chlorides (2a-2s) (0.02 mol). An exothermic reaction
occurred. The reaction mixture was stirred for 5 min at 0 ºC.
The ice bath was removed and the reaction mixture was
allowed to warm slowly to room temperature. The reaction
mixture was further stirred for 0.5 h at room temperature. The
reaction mixture was poured into ice cold water (200 mL) and
precipitates were filtered off. The residue was washed with
cold water (3 × 60 mL) and dried. Benzoxazin-4-one crystal-
lized from ethanol as white prismatic needles.
6
1H, J = 7.5 Hz, H-6´), 8.08 (d, 1H, J = 7.5, H-3´), 7.99 (t, 1H,
J = 7.8 Hz, H-6), 7.93 (t, 1H, J = 7.5 Hz, H-5´), 7.88 (t, 1H, J
= 7.8 Hz, H-7), 7.72 (d, 1H, J = 7.8, H-8), 7.69 (t, 1H, J = 7.5
+
Hz, H-4´); EIMS: m/z (%) 268 (M , 62), 146 (29), 133 (100),
8 2 4
118 (2), 76 (15). Anal. calcd. for C14H N O (268.224): C,
62.69 %; H, 3.01 %; N, 10.44 %; found: 62.71; 3.02; N, 10.46.
2-(3-Nitrophenyl)-4H-3,1-benzoxazin-4-one (3f):Yield:
16
82 % (2.2 g, 8.2 mmol), m.p.: 165 ºC (lit. m.p. = 166 ºC); IR
-1
(KBr, νmax, cm ): 1756, 1626, 1530, 1474, 1346, 1220, 1036;
1
H NMR (400 MHz, DMSO-d ): δ 8.85 (s, 1H, H-2´), 8.56 (d,
6
1H, J = 7.6 Hz, H-4´), 8.47 (d, 1H, J = 7.6 Hz, H-6´), 8.17 (d,
1H, J = 8.0 Hz, H-5), 7.98 (t, 1H, J = 8.0 Hz, H-6), 7.89 (t, 1H,
J = 8.0 Hz, H-7), 7.80 (d, 1H, J = 8.0 Hz, H-8), 7.66 (t, 1H, J
4-Methyl-N-[2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl]-
benzenesulfonamide (3t) was also synthesized with similar
+
= 7.6 Hz, H-5´); EIMS: m/z (%) 268 (M , 100), 222 (13), 150
17
procedure in which p-toluene sulphonyl chloride was used
8 2 4
(34), 146 (64), 104 (28), 76 (26); Anal. calcd. for C14H N O
instead of acid chloride.
(268.224): C, 62.69 %; H, 3.01 %; N, 10.44; found: C, 62.67,
H, 3.03, N, 10.46.
2-(4-Nitrophenyl)-4H-3,1-benzoxazin-4-one (3g):
2
2.0 g, 8.96 mmol); m.p.: 111 ºC (lit. m.p. = 123 ºC); IR
-Phenyl-4H-3,1-benzoxazin-4-one (3a): Yield: 90 %
16
(
(
-1
1
16
KBr, νmax, cm ): 1764.5, 1616, 1572, 1472; H NMR (400
): δ 8.20 (d, 1H, J = 7.1 Hz, H-5 ), 7.94 (t, 1H,
J = 7.1 Hz, H-7 ), 7.72 (1H, d, J = 7.1 Hz, H-8), 7.64 (t, 1H,
Yield: 78 % (2.01g, 7.8 mmol); m.p.: 198 ºC (lit. m.p. = 203
-1
MHz, DMSO-d
6
ºC); IR (KBr, νmax, cm ): 1768, 1596, 1519, 1437, 1354, 1254;
1
H NMR (400 MHz, DMSO-d6): δ 8.41 (d, 2H, J = 8.9 Hz, H-
J = 7.1 Hz, H-6), 8.15 (d, 2H, J = 7.8 Hz, H-2´,6´), 7.57-7.61
(
3´/5´), 8.30 (1H, d, J = 8.2Hz, H-5), 8.14 (2H, d, J = 8.9 Hz,
H-2´/6´ ), 7.98 (1H, t, J = 8.2 Hz, H-6), 7.77 (d, 1H, J = 8.2
Hz, H-8), 7.67 (t, 1H, J = 8.2 Hz, H-7); EIMS: m/z (%) 268
+
m, 3H, H-3´/4´/5´); EIMS: m/z (%) 223 (M , 100), 146 (16),
1
05 (52), 76 (5 %); Anal. calcd. for C14
5.33; H, 4.06; N, 6.27; found: C, 75.30; H, 4.07; N, 6.30.
-(2-Methylphenyl)-4H-3,1-benzoxazin-4-one (3b):
9 2
H NO (223.227): C,
+
7
(M , 100), 222 (4), 146 (74), 104 (58), 76 (86%). Anal. calcd.
2
8 2 4
for C14H N O (268.224): C, 62.69 %; H, 3.01 %; N, 10.44 %;
16
Yield: 68 % (1.61 g, 6.79 mmol), m.p.: 112 ºC (lit. m.p. =
1
found: C, 62.68; H, 3.02; 10.45.
2-(2-Fluorophenyl)-4H-3,1-benzoxazin-4-one (3h):
-1
14 ºC); IR (KBr, νmax, cm ): 2960, 1758, 1611, 1470, 1218;
1
16
Yield: 53 % (1.27 g, 5.3 mmol); m.p.: 111 ºC (lit. m.p. = 115
H NMR (400 MHz, DMSO-d
6
): δ 8.16 (1H, d, J = 7.8 Hz, H-
), 7.97-7.90 (m, 2H, H-4´/6´), 7.70 (d, 1H, J = 7.8, H-8),
.64 (t, 1H, J = 7.8 Hz, H-6), 7.50 (t, 1H, J = 7.8 Hz, H-7),
.32-7.38 (m, 2H, H-3´/5´), 2.44 (3H, s, CH ); EIMS: m/z 237
-1
5
7
7
ºC); IR (KBr, νmax,cm ): 1772, 1625, 1606, 1477, 1320, 1278;
1
H NMR (400 MHz, CDCl ): δ 8.24 (d, 1H, J = 7.8 Hz, H-5),
3
3
8.11 (t, 1H, J = 7.6 Hz, H-4´), 7.83 (t, 1H, J = 7.8 Hz, H-6),
7.7 (d, 1H, J = 7.8 Hz, H-8), 7.51-7.56 (m, 2H, H-6´/7), 7.27
(t, 1H, J = 7.6 Hz, H-3´), 7.20 (1H, t, J = 7.6 Hz, H-5´); EIMS:
+
(
M , 100), 146 (7), 119 (58), 118 (30), 91 (33 %). Anal. calcd.
(237.253): C, 75.94; H, 4.67; N, 5.90; found:
C, 75.95; H, 4.66; N, 5.88.
-(3-Methylphenyl)-4H-3,1-benzoxazin-4-one (3c):
Yield: 65 % (1.54 g, 6.5 mmol); m.p.: 110-112 ºC; IR (KBr,
for C15H11NO
2
+
241 (M ,100), 213 (9), 197 (98), 146 (85), 95 (70), 76 (15 %).
2
8 2
Anal. calcd. for C14H FNO (241.217): C, 69.71 %; H, 3.34
%; N, 5.81 %; found: C, 69.69; H, 3.36; N, 5.81.
2-(3-Fluorophenyl)-4H-3,1-benzoxazin-4-one (3i):
-1
1
ν
(
max, cm ): 2957, 1757, 1602, 1474, 1321, 1260; H NMR
400 MHz, CDCl ): δ 8.23 (d, 1H, J = 7.8 Hz, H-5), 8.10 (d,
3
Yield: 69 % (1.66 g, 6.9 mmol), m.p.: 133 ºC; IR (KBr, νmax,
1
-1
1
1
1
H, J = 7.5 Hz, H-6´), 7.81 (t, 1H, J = 7.8 Hz, H-6), 7.68 (d,
H, J = 7.8 Hz, H-8), 7.49 (t, 2H, J = 8.1 Hz, H-7/5´), 7.39 (d,
cm ): 1766, 1615, 1477, 1445, 1323, 1260; H NMR (400
MHz, CDCl ): 8.23 (d, 1H, J = 7.8 Hz, H-5), 8.08 (d, 1H, J =
3
H, J = 7.3 Hz, H-4´), 7.37 (s, 1H, H-2´), 2.43 (s, 3H, CH
+
3
);
7.8 Hz, H-8), 7.97-8.012 (m, 1H, H-2´), 7.82 (t, 1H, J = 7.8
Hz, H-7), 7.68 (d, 1H, J = 7.6 Hz, H-6´), 7.51(t, 1H, J = 7.95
Hz, H-5´), 7.46(t, 1H, J = 8.0Hz, H-6), 7.25-7.27 (m, 1H, H-
EIMS: m/z (%) 237 (M , 90), 193 (25), 146 (10), 119 (100),
9
7
1 (35), 76 (5 %). Anal. calcd. for C15
5.94; H, 4.67; N, 5.90; found: C, 75.92; H, 4.66; N, 5.88.
-(4-Methylphenyl)-4H-3,1-benzoxazin-4-one (3d):.
2
H11NO (237.253): C,
+
4´); EIMS: m/z (%) 241 (100 %, M ), 213 (5 %), 197 (76 %),
2
8 2
146 (36 %), 95 (38 %), 76 (5 %). Anal. calcd. for C14H FNO
16
Yield: 86 % (2.04 g, 8.6 mmol); m.p.: 149 ºC (lit. m.p. = 155
(241.217): C, 69.71 %; H, 3.34 %; N, 5.81 %; found: C, 69.72;
H, 3.36; N, 5.83.
-1
ºC); IR (KBr, νmax, cm ): 2963, 1757, 1608, 1473, 1315; 1H
NMR (400 MHz, CDCl ): δ 8.21 (d, 1H, J = 7.9 Hz, H-5), 8.2
d, 2H, J = 8.2, H-2´/6´), 7.79 (t, 1H, J = 7.9 Hz, H-6), 7.64 (d,
3
2-(4-Fluorophenyl)-4H-3,1-benzoxazin-4-one (3j):
16
(
Yield: 97 % (2.34 g, 9.7 mmol); m.p.: 168 ºC (lit. m.p. = 170
-1
1
2
2
H, J = 7.9 Hz, H-8), 7.47 (t, 1H, J = 7.9 Hz, H-7), 7.29 (d,
H, J = 8.2 Hz, H-3´/5´), 2.44 (s, 3H, CH ); EIMS: m/z (%)
37 (95, M ), 193 (31), 146 (10), 119 (100), 91 (42), 76 (3 %).
ºC); IR (KBr, νmax, cm ): 1764, 1601, 1508, 1472, 1321, 1231;
1
3
H NMR (300 MHz, CDCl ): δ 8.30 (d, 1H, J = 6.5 Hz, H-5),
3
8.21 (1H, d, J = 6.5 Hz, H-8), 7.81 (t, 1H, J = 6.5 Hz, H-6),
+

154 Khan et al.
Asian J. Chem.
7
.66 (d, 2H, J = 5.9 Hz, H-2´/6´), 7.54 (t, 1H, J = 6.5 Hz,
2-(2-Methoxyphenyl)-4H-3,1-benzoxazin-4-one (3p):
17
Yield: 75 % (1.9 g, 7.5 mmol); m.p.: 131 ºC (lit. m.p. = 132-
+
H-7), 7.14-7.17 (m, 2H, H-3´/ 5´); EIMS: m/z (%) 241 (M ,
1), 146 (7), 123 (100), 95 (40), 76 (4 %). Anal. calcd. for
NO F (241.217): C, 69.71 %; H, 3.34 %; N, 5.81 %;
found: C, 69.69; H, 3.36; N, 5.82.
-(2-Chlorophenyl)-4H-3,1-benzoxazin-4-one (3k):
-1
3
133 ºC); IR (KBr, νmax, cm ): 1769, 1607, 1490, 1467, 1255;
1
H NMR (400 MHz, CDCl ): δ 8.24 (d, 1H, J = 7.9 Hz, H-5),
3
C
14
H
8
2
7.84 (d, 1H, J = 7.6 Hz, H-6´), 7.79 (d, 1H, J = 7.6 Hz, H-4´),
7.70 (d, 1H, J = 7.9 Hz, H-8), 7.51 (t, 1H, J = 7.9 Hz, H-7),
7.48 (t, 1H, J = 7.9 Hz, H-6), 7.0-7.07 (m, 2H, H-3´/ 5´), 3.93
2
16
Yield: 64 % (1.64 g, 6.4 mmol); m.p.: 136 ºC (lit. m.p. = 138
-1
+
ºC); IR (KBr, νmax, cm ): 1769, 1622, 1474, 1316, 1272, 1225;
1
3
H NMR (300 MHz, CDCl ): δ 8.26 (d, 1H, J = 6.1 Hz, H-5),
(s, 3H, -OCH ); EIMS: 253 (M , 64,), 224 (26), 209 (3), 146
(8), 135 (63), 133 (23), 119 (100), 77 (25), 76 (4 %); Anal.
calcd. for C15 (253.253): C, 71.14; H, 4.38; N, 5.53;
3
7
7
7
7
2
1
.87 (d, 1H, J = 6.8 Hz, H-6´), 7.84 (t, 1H, J = 6.1 Hz, H-7),
.7 (d, 1H, J = 6.1 Hz, H-8), 7.57 (t, 1H, J = 6.1 Hz, H-6),
.51 (d, 1H, J = 6.8 Hz, H-3´), 7.45 (t, 1H, J = 6.8 Hz, H-5´),
H11NO
3
found: C, 71.12; H, 4.40; N, 5.54.
2-(4-Methoxyphenyl)-4H-3,1-benzoxazin-4-one (3q):
+
16
Yield: 94 % (2.38 g, 9.4 mmol), m.p.: 150 ºC (lit. m.p. = 148
.38 (t, 1H, J = 6.8 Hz,H-4´); EIMS: m/z (%) 259 (M , 15),
57 (44), 213 (31), 215 (11), 146 (21), 139 (47), 141 (19),
-1
ºC); IR (KBr, νmax, cm ): 1757, 1606, 1568, 1472, 1259, 1168;
1
13 (6), 146 ( 21), 76 (5); Anal. calcd. for C14
257.672): C, 65.26 %); H, 3.13 %; N, 5.44 %; found: C, 65.24;
H, 3.15; N, 5.46.
-(3-Chlorophenyl)-4H-3,1-benzoxazin-4-one (3l):
H
8
NO
2
Cl
3
H NMR (400 MHz, CDCl ): δ 8.24 (d, 1H, J = 8.5 Hz, H-5),
(
8.2 (d, 1H, J = 8.5 Hz, H-8), 7.82 (t, 1H, J = 8.5 Hz, H-7),
7.63 (d, 2H, J = 8.0 Hz, H-2´/ 6´), 7.45 (t, 1H, J = 8.5 Hz,
2
H-6), 6.99 (d, 1H, J = 8.0 Hz, H-3´/5´), 3.88 (s, 3H, OCH
3
);
EIMS: m/z (%) 253 (M , 23), 209 (5), 146 (3), 135 (100), 107
(8), 76(3), 64 (9 %). Anal. calcd. for C15 (253.253): C,
17
+
Yield: 87 % (2.19 g, 8.5 mmol); m.p.: 153 ºC (lit. m.p. 159-
-1
1
69 ºC); IR (KBr, νmax, cm ): 1761, 1601, 1566, 1473, 1416;
H NMR (400 MHz, CDCl ): δ 8.30 (s, 1H, H-2´), 8.23 (1H,
H11NO
3
1
3
71.14, H, 4.38, N, 5.53; found: C, 71.14; H, 4.39; N, 5.51.
2-(3, 4, 5-Trimethoxyphenyl)-4H-3,1-benzoxazin-4-one
(3r): Yield: 40 % (1.25 g, 4.0 mmol); m.p.: 181 ºC; IR (KBr,
d, J = 7.8 Hz, H-5), 8.17 (d, 1H, J = 8.1 Hz, H-6´), 7.81 (t, 1H,
J = 7.8 Hz, H-7), 7.68 (d, 1H, J = 7.8 Hz, H-8), 7.50-7.55 (m,
-
1
1
2
2
H, H-4´/5´), 7.42 (t, 1H, J = 7.8 Hz, H-6); EIMS: m/z (%)
+
59 (M , 36), 257 (100), 213 (61), 215 (21), 146 (41),139
ν
max, cm ): 1754, 1607, 1504, 1349, 1292, 1131; H NMR
(300 MHz, CDCl ): δ 8.20 (1H, d, J = 8.1 Hz, H-5), 7.80 (t,1H,
J = 8.1 Hz, H-7), 7.66 (d, 1H, J = 8.1, H-8), 7.53 (s, 2H, H-2´
/ 6´), 7.48 (t, 1H, J = 8.1 Hz, H-6), 3.92 (s, 9H, -OCH ); EIMS:
m/z (%) 313 (M , 100), 268 (5), 223 (2),195 (28), 193 (3), 167
(6), 146 (30), 76 (2). Anal. calcd. for C17 (313.305): C,
3
(
67), 141 (21), 113 (14), 111 (43), 76 (10 %); Anal. calcd. for
NO Cl (257.672): C, 65.26 %; H, 3.13 %; N, 5.44 %;
found: C, 65.28; H, 3.12; N, 5.44.
-(4-Chlorophenyl)-4H-3,1-benzoxazin-4-one (3m):
C
14
H
8
2
3
+
2
H15NO
5
16
Yield: 85 % (2.18 g, 8.49 mmol); m.p.: 192 ºC (lit. m.p. =
1
65.17; H, 4.83; N, 4.47; found: C, 65.18; H, 4.82; N, 4.47.
2-(1-Naphthyl)-4H-3,1-benzoxazin-4-one (3s): Yield:
95% (2.59 g, 9.5 mmol); m.p.: 136-137 ºC (lit.17 m.p. = 138-
-1
90 ºC); IR (KBr, νmax, cm ): 1770, 1633, 1484, 1316, 1255;
H NMR (400 MHz, CDCl ): δ 8.01 (d, 1H, J = 7.9 Hz, H-5),
1
3
-1
7.83 (2H, d, J = 7.4 Hz, H-2´/6´), 7.46 (t, 1H, J = 7.9, H-6),
7.34 (d, 1H, J = 7.9 Hz, H-8), 7.27(d, 2H, J = 7.4 Hz, H-3´/
5
2
140 ºC); IR (KBr, νmax, cm ): 1747, 1596, 1510, 1471, 1320,
1
3
1223; H NMR (300 MHz, CDCl ): δ 8.98 (d, 1H, J = 8.6 Hz,
+
´), 7.01 (t, 1H, J = 7.9 Hz, H-7); EIMS: m/z (%) 259 (M ,
H-8´), 8.93 (d, 1H, J = 8.6 Hz, H-2´), 8.37 (d, 1H, J = 7.3 Hz,
H-4´), 8.20 (d, 1H, J = 7.6 Hz, H-5 ), 8.13 (d, 1H, J = 7.6 Hz,
H-8), 8.07 (d, 1H, J = 8.6 Hz, H-5´), 7.99 (t, 1H, J = 8.6 Hz,
H-7´), 7.79 (t, 1H, J = 7.6 Hz, H-7), 7.73-7.65 (m, 3H, H-6/6´/
7), 257 (81), 213 (37), 215 (13), 146 (14), 139 (100), 141
(32), 113 (12), 111 (37), 76 (8 %).Anal. calcd. for C14
8 2
H NO Cl
(
257.672): C, 65.26 %; H, 3.13 %; N, 5.44 % found: C, 65.26;
+
H, 3.14; N, 5.43.
-(2-Bromophenyl)-4H-3,1-benzoxazin-4-one (3n):
3´); EIMS: m/z (%) 273 (M , 20), 153 (4), 146 (7), 155 (100),
2
2
127 (67), 76 (4); Anal. calcd. for C18H11NO (273.285): C,
16
Yield: 87 % (2.63 g, 8.7 mmol); m.p.: 115 ºC (lit. m.p. = 118
79.11; H, 4.06; N, 5.13; found: C, 79.11; H, 4.08; N, 5.11.
4-Methyl-N-[2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl]-
benzenesulfonamide (3t): Yield: 55 % (1.8 g, 4.59 mmol);
-1
ºC); IR (KBr, νmax, cm ): 1767, 1626, 1474, 1315, 1270, 1224;
1
3
H NMR (400 MHz, CDCl ): δ 8.26 (d, 1H, J = 8.0 Hz, H-5),
1
6
-1
7
7
.82-7.86 (m, 2H, H-3´/5´), 7.71 (d, 2H, J = 7.9 Hz, H-8 / 6´),
.56 (t, 1H, J = 8.0 Hz, H-7), 7.42 (t, 1H, J = 7.4, H-4´), 7.35
m.p.: 212 ºC (lit. m.p. = 216 ºC); IR (KBr, νmax, cm ): 1778,
1
3
1704, 1604, 3446, 1570, 1474; H NMR (400 MHz, CDCl ):
+
t, 1H, J = 8.0 Hz, H-6); EIMS: m/z (%) 303 (M , 97), 301
(
(
(
δ 11.92 (s, 1H, NH), 8.17 (d, 1H, J = 8.5 Hz, H-6´ ), 7.97
(d,1H, J = 7.7 Hz, H-5) 7.69 (t, 1H, J = 7.7 Hz, H-7), 7.56 (d,
1H, J = 7.7 Hz, H-8), 7.52 (d, 2H, J = 8.0 Hz, H-2´´/ 6´´), 7.44
(t, 1H, J = 7.7 Hz, H-6´), 7.25 (d, 2H, J = 8.0 Hz, H-3´´/ H-5´´
), 7.21 (t, 1H, J = 8.5 Hz, H-4´) 7.11 (d, 2H, J = 8.5 Hz, H-5´/
100), 257 (33), 259 (32), 222 (4), 183 (47), 185 (45), 146
25), 76 (8 %).Anal. calcd. for C14
; H, 2.67 %; N, 4.64 %; found: C, 55.68; H, 2.66; N, 4.63.
-(4-Bromophenyl)-4H-3,1-benzoxazin-4-one (3o):
8 2
H NO Br (302.123): C, 55.66
%
2
16
+
Yield: 80 % (2.41 g, 8.0 mmol); m.p.: 182 ºC (lit. m.p. = 184
3´), 2.27 (s, 3H, CH3); EIMS: 392.2 (M , 100), 377 (3), 237
-1
1
ºC); IR (KBr, νmax, cm ): 1764, 1619, 1480, 1320, 1256; H
NMR (400 MHz, CDCl ): δ 8.23 (d, 1H, J = 7.8 Hz, H-5),
.16 (d, 2H, J = 8.6 Hz, H-2´/ 6´), 7.81 (t, 1H, J = 7.8, H-7),
16 2 4
(66), 146 (4), 91 (20 %). C H N analysis calcd. for C21H N O
3
(392.429): C, 64.27; H, 4.11; N, 7.14; found: C, 64.28; H,
4.13; N, 7.12.
8
7
5
9
1
.67 (d, 1H, J = 7.8 Hz, H-8), 7.63 (d, 2H, J = 8.6 Hz, H-3´/
+
´), 7.51 (t, 1H, J = 7.8 Hz, H-6); EIMS: m/z (%) 303 (M ,
Antibacterial bioassay: Bactericidal activity was deter-
19
mined by agar well diffusion method . This test was performed
8), 301 (100), 155 (46), 157 (45), 146 (38) 118 (2), 104 (5),
by spreading 18-24 h old pathogenic bacterial culture of all six
bacterial starins viz. Bacillus subtilis, Pseudomonas aeruginsoa,
Staphylococcus aureus, Shigella Flexnari, Escherichia coli and
8 2
02 (5), 76 (42), 64 (5);Anal. calcd. for C14H NO Br (302.123):
C, 55.66; H, 2.67; N, 4.64; found: C, 55.65; H, 2.68; N, 4.65.

Vol. 25, No. 1 (2013)
Synthesis and Antimicrobial Activity of 2-Aryl-4H-3,1-benzoxazin-4-ones 155
4
6
16
Salmonella typhi containing approximately 10 -10 colony
forming units (CFU)/mL on the surface of nutrient agar plates.
The bacterial cells were counted by hemocytometer method
under microscope. In nutrient agar plate wells of 0.85 cm size
were produced with the help of sterilized metallic borer under
aseptic condition in laminar flow chamber. Twenty test samples
after microfiltration with 0.2 microns filters in concentrations
4-one (3a-3s) in moderate to excellent yields (Scheme-I).
The acid chlorides, where not commercially available, were
prepared by the action of thionyl chloride on the appropriate
carboxylic acid. The failure of aliphatic acyl halides to produce
benzoxazinones is probably due to ready hydrolysis of initially
18
formed 2-alkyl-4H-3,1-benzoxazin-4-one .
O
(
100 µg) in DMSO were added in labeled wells. Other wells
COOH
O
were supplemented with reference drugs i.e. Amoxycillin,
Streptomycin and Kanamycin were used as standard reference
drugs (100 µg) serving as the positive controls. The ciprofloxacin
was used as a reference standard (5 µg) in DMSO for
Pseudomonas aeruginsoa. DMSO was also used for the prepa-
ration of solutions of standard antibiotics used in the current
experimental assay. Experimental plates after spreading the
bacterial strains on the separate plates along subsequent
addition of the drugs and samples in the wells were subjected
to incubation at 37 ºC for 24 h and bacterial growth was deter-
mined by measuring the diameter of zone of inhibition in mm.
During antibacterial assay negative control wells were also
used where pure solvents were used instead of the compounds.
The experiment was repeated thrice and the mean values are
recorded to evaluate the antibacterial potential of synthesized
compounds with reference to positive and negative controls.
O
+
Pyridine, 0°C to r.t
R
Cl
NH2
N
R
1
2a-s
3a-s
Compound
R
Compound
R
3a
C
H
6
-
5
3k
3l
o-ClC
m-ClC
p-ClC
o-BrC
p-BrC
6 4
H -
H -
6 4
3b
o-CH
m-CH
p-CH
o-NO
m-NO
p-NO
o-FC H -
3
C
6
H -
4
3c
3 6
C
4
H -
3m
3n
3o
3p
3q
3r
3s
6
H
4
-
-
3
3
3
3
3
d
e
f
3
C
6
H
H
4
-
6
H
H
4
C
-
4
-
4
2
6
6
C
2
H
4
-
o-OCH
p-OCH C H
3 6 4
C
H -
4
6
3
6
g
h
2
C
6
H -
4
-
3,4,5-(OCH ) C H -
2
6
4
3
3
6
3i
m-FC
p-FC H -
6 4
6
H
4
-
1-Naphthyl
3j
Scheme-I: Synthesis of 2-aryl-4H-3,1-benzoxazin-4-ones
Anthranilic acid (1) reacts with p-toluene-sulphonyl
RESULTS AND DISCUSSION
chloride (2t) in the presence of excess of pyridine to give 2-
substituted benzoxazin-4-one (3t) in good yield. This reaction
probably proceeds via a mixed carboxylic acid-sulphonic acid
anhydride intermediate (Scheme-II).
One mole equivalent of anthranilic acid (1) was treated
with two mole equivalent of aryl chlorides (2a-2s) in the
presence of excess of pyridine to give 2-substituted benzoxazin-
TABLE-1
ANTIBACTERIAL ACTIVITY OF 2-ARYL-4H-3,1-BENZOXAZIN-4-ONES (3a-3t) IN COMPARISON TO STANDARD ANTIBIOTICS
AMOXYCILLIN, STREPTOMYCIN, KANAMYCIN AND CIPROFLOXACIN AGAINST GRAM NEGATIVE BACTERIAL STRAINS
Gram negative bacteria (Zone of inhibition in mm)
Entry
Compound No
Shigella flexnari
Escherichia coli
Pseudomonas aeruginsoa
Salmonella typhi
a
1
3a
3b
3c
3d
3e
3f
0
12
0
0
15
0
0
12
15
0
0
13
0
a
2
a
3
a
4
0
0
0
a
5
0
10
0
12
11
0
0
a
6
12
0
0
a
7
3g
3h
3i
12
0
0
a
8
0
0
12
0
a
9
0
12
10
0
0
a
1
1
1
1
1
1
1
1
1
1
2
0
1
2
3
4
5
6
7
8
9
0
3j
0
0
0
a
a
a
a
a
a
a
a
a
a
3k
3l
0
0
0
0
0
10
0
0
3m
3n
3o
3p
3q
3r
3s
11
0
0
0
0
18
15
12
12
0
0
0
0
0
15
0
10
0
0
0
0
0
0
16
0
0
12
0
0
3t
0
0
b
2
1
Amoxycillin
25.0
28.5
25.5
-
19.5
28.5
21.0
-
-
27.5
33.5
20.0
-
b
2
2
2
2
3
4
Streptomycin
b
Kanamycin
-
-
c
Ciprofloxacin
25
a
b
Note: The concentration of test compounds were 100 µg in DMSO; The concentration of amoxycillin, streptomycin and kanamycin was 100 µgin
c
DMSO; The concentration of ciprofloxacin was 5 µg in DMSO

156 Khan et al.
Asian J. Chem.
O
N
O
O
A comparison of bactericidal activity of 2-aryl-4H-3,1-
benzoxazinones with three reference antibiotics is shown in
Table-2. Two compounds 3o and 3s with o-bromophenyl and
1-naphthyl moieties showed weak activity against Staphylo-
coccus aureus (Table-2). All compounds were inactive against
Bacillus subtilis except compound 3f with m-nitrophenyl group
demonstrated significant activity in comparison to reference
standard antibiotics (Table-2).
O
S
O
COOH
S
O HN
Cl Pyridine
0°C to r.t.
+
NH2
CH3
H C
3
1
2t
3t
Scheme-II: Synthesis of 4-methyl-N-[2-(4-oxo-4H-3,1-benzoxazin-2-
yl)phenyl]-benzenesulfonamide
Antibacterial activity: The antibacterial activity of
twenty compounds was assayed in vitro by agar well diffusion
Conclusion
19
method against six bacterial species.Among them four were
gram negative and two were Gram positive bacteria. The results
of bactericidal activities were displayed in Tables 1 and 2.
Most of compounds showed the bactericidal activities against
four strains of Gram negative bacteria (Table-1). The comp-
ounds 3a, 3d, 3k, 3r and 3t had shown no bactericidal activity
against any bacteria (Tables 1 and 2). The compounds 3f, 3s,
Twenty derivatives of 2-aryl-4H-3,1-benzoxazin-4-ones
were synthesized and evaluated for bactericidal activity against
six pathogenic microorganism. In conclusion, 2-aryl-4H-3,1-
benzoxazin-4-ones possess a broad spectrum of activity against
a group of Gram negative bacteria responsible causing most
common bacterial diseases. However, few members were active
against Gram positive bacteria. This study opens the possibility
of finding new clinically effective bactericidal compounds.
3
p, 3m and 3b showed good to moderate activity against
Shigella flexnari. The compounds 3b, 3e, 3g, 3i and 3p showed
weak activity against Escherichia coli. The compound 3n
showed good activity against Pseudomonas aeruginsoa,
whereas other compounds 3b, 3c, 3e, 3f, 3l, 3s, 3p, 3o and 3q
showed moderate to weak activity in comparison to standard
ciprofloxacin. The compound 3b and 3h showed some activity
against Salmonella typhi. The remaining compounds were
inactive against all microorganisms.
ACKNOWLEDGEMENTS
The authors are thankful to Higher Education Commission
of Pakistan (HEC) for munificent financial support under IPFP/
TTS program.
REFERENCES
1
2
.
.
W.M. Kelany and H.M. Galal, J. Am. Sci., 7, 120 (2011).
M.L. Bouillant, J. Favre-Bonvin and P. Ricci, Tetrahedron Lett., 24,
TABLE-2
ANTIBACTERIAL ACTIVITY OF 2-ARYL-4H-3,1-
BENZOXAZIN-4-ONE (3a-3t) COMPARED WITH STANDARD
ANTIBIOTICS AMOXYCILLIN, STREPTOMYCIN AND
KANAMYCIN AGAINST GRAM POSITIVE BACTERIA
5
1 (1983).
M. Ponchet, J. Martin-Tanguy, A. Marais and A. Poupet, Phytochemistry,
3, 1901 (1984).
3
4
5
.
.
.
2
S. Mayama, T. Tani, T. Uneo, K. Hirabayashi, T. Nakashuna, H. Fukamt,
Y. Mizuno and H. Irie, Tetrahedron Lett., 22, 2103 (1981).
M. Hauteville, M. Ponchet, P. Ricci and J. Favre-Bonvin, J. Heterocycl.
Chem., 25, 715 (1988).
Gram positive bacteria
Compound
no.
Entry
(zone of inhibition in mm)
Staphylococcus aureus Bacillus subtilis
6
7
.
.
N.S. El-Din, Acta Pharm., 50, 239 (2000).
a
1
3a
3b
0
0
0
0
A.A. Shalaby,A.M. El-Khamry, S.A. Shiba,A.A.Ahmed andA.A. Hanafi,
Arch. Pharm. (Weinheim), 333, 365 (2000).
C. Belluci, F. Gualtieri and A. Chiarine, Eur. J. Med. Chem., 22, 473
a
2
a
3
3c
3d
0
0
8
.
.
a
4
0
0
(1987).
E. Colson, J. Wallach and M. Hauteville, Biochimie, 87, 223 (2005).
a
5
3e
0
0
9
1
a
6
3f
3g
0
16
0
0. P.-W. Hsieh, H.-P.Yu,Y.-J. Chang and T.-L. Hwang, Eur. J. Med. Chem.,
45, 3111 (2010).
a
7
0
a
8
3h
3i
0
0
11. G. Fenton, C.G. Newton, B.M. Wyman, P. Bagge, D.I. Dron, D. Riddell
and G.D. Jones, J. Med. Chem., 32, 265 (1989).
a
9
0
0
a
1
1
1
1
1
1
1
1
1
1
2
0
1
2
3
4
5
6
7
8
9
0
3j
3k
0
0
12. M.F. Ismail, S.A. Emara and O.E.A. Mustafa, Phosphorus, Sulfur, Silicon
Rel. Elem., 63, 373 (1991).
13. H.M.F. Madkour, Arkivoc, 36 (2004).
a
a
a
a
a
a
a
a
a
a
b
0
0
3l
3m
0
0
14. M.B. Deshmukh, A.W. Suryawanshi,A.R. Mali and S.R.D. Desai, Synth.
Commun., 34, 2655 (2004).
0
0
3n
3o
0
0
15. (a) Z.A. Khan and T. Wirth, Org. Lett., 11, 229 (2009); (b) S.A.R.
Naqvi, T. Matzow, C. Finucane, S.A. Nagra, M.M. Ishfaq, S.J. Mather
and K.J. Sosabowski, Canc. Biother. Radiopharm., 25, 89 (2010); (c)
S.A. Shahzad, C. Venin and T. Wirth, Eur. J. Org. Chem., 3465 (2010);
10
0
0
3p
0
3q
3r
0
0
0
0
(d) Z.A. Khan, N.H. Rama, M.T. Hussain and G.S. Khan, Indian J.
Chem., 46B, 1322 (2007).
3s
3t
10
0
0
0
1
1
6. D.I. Bain and R.K. Smalley, J. Chem. Soc., 1593 (1968).
7. W.C.J. Doyle, US Patent 3970652 (1976); Chem. Abstr., 85, 117997
2
1
Amoxycillin
Streptomycin
Kanamycin
17
19.5
24
15.3
16.0
19.0
b
b
22
(
1976).
8. D.T. Zentmeyer and E.C. Wagner, J. Org. Chem., 14, 967 (1949).
23
1
19. I. Naeem, Z. Saddiqe, A. Patel and C. Hellio, Asian J. Chem., 22, 3596
(2010).
a
b
Note: The concentration of test samples were 100 µg in DMSO The
concentration of standard reference antibiotics (amoxicillin,
streptomycin and kanamycin) was 100µg in DMSO