A quick route for the synthesis of 3-Aryl-3,4-dihydro-2H-benz[e]-1,3- oxazin-2-ones

Article abstract of DOI:10.14233/ajchem.2013.14053

N-(2-Hydroxy)-benzyl-arylamines (1) gave substantially pure 3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-one 2 on cyclization with carbonyldiimidazole in DMSO in 20-30 min at 20-25 °C in excellent yields.

Full text of DOI:10.14233/ajchem.2013.14053

Asian Journal of Chemistry; Vol. 25, No. 8 (2013), 4537-4540
http://dx.doi.org/10.14233/ajchem.2013.14053
A Quick Route for the Synthesis of 3-Aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-ones
*
DAVENDER KUMAR SHUKLA, MANJU RANI and ARIF ALI KHAN
University School of Basic & Applied Sciences, Guru Gobind Singh Indraprastha University, Dwarka, New Delhi-110 078, India
*Corresponding author: E-mail: khanaarif@hotmail.com
(Received: 12 May 2012;
Accepted: 15 February 2013)
AJC-13006
N-(2-Hydroxy)-benzyl-arylamines (1) gave substantially pure 3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-one 2 on cyclization with
carbonyldiimidazole in DMSO in 20-30 min at 20-25 ºC in excellent yields.
Key Words: 2H-Benzoxazin-2-ones, 2H-Benz[e]-1,3-oxazin-2-ones, Carbonyldiimidazole, Cyclization, Heterocycles.
having intensity more than 20 % has been given. Infrared
spectrum was recorded on Shimadzu FTIR-8700. Elemental
analysis was carried out using EURO EA 3000 elemental
analyzer. Melting points were recorded in open capillary
method and are uncorrected.
INTRODUCTION
Many important medicines, dyes, insecticides, etc., are
found in the series of heterocyclic compounds, called oxazines1
and thiazines2. They are found mainly in the polycyclic divisions
in which other rings, such as the benzene ring, are fused to the
oxazines or thiazine ring. A considerable number of reports
concerning 1,3-oxazine3-6 derivatives which have undergone
their greatest development in the last few years. This is due to
partially the fact that these compounds show interesting pharma-
cological7-11 activity. Efavirenz12 (Sustiva), a non-nucleoside
reverse transcriptase inhibitor, explored a new dimension for
2H-benzoxazin-2-ones in the field of medicinal world. Thus,
the emphasis of the derivatization of benzoxazinones has got
R
O
N
X
X
H
R-NH2
H
MeOH
25-30 °C
OH
OH
NaBH4
0-5 °C
a new pace to counter HIV in recent times13-15
.
R
H
HN
EXPERIMENTAL
X
R
O
X
N
Salicyldehyde (Spectrochem), sodium borohydride
(Spectrochem), carbonyldiimidazole (GLR scientific), aniline
(CDH), 4-methyl aniline (Thomas Baker), 4-chloroaniline
(CDH), 4-bromo aniline (Spectrochem), 1-naphthylamine
(CDH), 2-amino pyridine (Spectrochem), 3-amino pyridine
(Spectrochem), 4-toluene sulfonamide (CDH) and rafoxinide
(Fluka) were used as received. Solvents were purified by
standard procedures.
CDI
DMSO
20-22 °C
O
OH
2
1
Scheme-I
Synthesis of N-(2-hydroxy)-benzyl-arylamines 1: Schiff
bases were prepared by dissolving aldehyde (0.1 mol) in
methanol, was mixed with aryl amine (0.1 mol) at room tempe-
rature. The mixture was stirred at 20-25 ºC for 0.5 h and poured
in ice water. The separated product was collected by filtration
and re-crystallized with methanol. The re-crystallized Schiff
bases (0.1 mol) were dissolved in methanol, sodium borohy-
dride (0.25 mol) was added lot wise at 0-5 ºC over a period of
1 h. The contents were further stirred for 2-3 h at 25-30 ºC.
The solvent was removed under vacuum, added water to
All reactions and workup were conducted under air, except
when noted otherwise. TLC was performed on MERCK TLC
Silica gel 60 F254 plates and visualized by iodine. Yields refer
to pure isolated substances. NMR spectra were recorded on a
Bruker AV300 MHz spectrophotometer. The chemical shifts
are reported in ppm downfield of internal standard tetramethyl-
silane for 1H and 13C NMR. Mass spectra were recorded on a
Shimadzu GCMS QP2010plus instrument and fragments

4538 Shukla et al.
Asian J. Chem.
precipitate the product. Filter and wash with water to get crude
product. The crude product thus obtained was re-crystallised
with methanol to get 1 as crystalline solid.
120.69, 117.69, 116.39, 50.35; GCMS m/z: 304 mass
fragments, 63.15 (21.1 %), 78.15 (100.0), 90.10 (51.2), 106.05
(64.9), 196.90 (42.8), 303.00 (10.1), 305.00 (9.3).
Synthesis of 3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-
2-ones (2): N-(2-Hydroxy)-benzyl-arylamines 1 (0.01 mol)
dissolved in DMSO (20 mL) was taken in round bottom flask.
Contents were cooled in an ice bath to 20-22 ºC. Carbonyl-
diimidazole (0.011 mol) dissolved in 20 mL DMSO was added
drop wise with constant stirring in 0.5 h at 20-22 ºC. The
reaction mixture was further stirred at 20-22 ºC for 0.5 h. The
reaction was monitored by TLC (EtOAc:hexane 80:20). After
completion of reaction, 1 N HCl (0.02 mol) was added drop
wise over a period of 0.5 h. The reaction mixture was further
stirred for 0.5 h. Filtered and washed the content with 150 mL
water to get white shining material, which was crystallized
from methanol to give compound 2 as white crystalline
material.
3,4-Dihydro-3-(1-naphthyl)-2H-benz[e]-1,3-oxazin-2-
one (2e): Light brown crystalline solid. Yield 2.2 g, 80 %,
m.p. 176-177 ºC (from methanol); elemental analysis calcd.
(%) for C18H13NO2: C, 78.52; H, 4.75; N, 5.08. Found (%): C,
78.17; H, 4.23; N, 4.89; FTIR (cm-1) 1728 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 4.768 (d, 1H, J = 14.7 Hz,
ArCH2N), 4.912 (d, 1H, J = 14.7 Hz, ArCH2N), 7.1780-7.880
(m, 11H, aromatic); 13C NMR (75 MHz, CDCl3): δ 150.39,
150.17, 137.87, 134.83, 129.28, 129.11, 129.06, 128.85,
127.37, 126.68, 125.94, 125.55, 125.12, 124.8, 124.58, 121.88,
117.75, 116.64, 51.61; GCMS m/z: 275, mass fragments,
114.05 (23.61 %), 128.00 (32.0), 141.05 (21.4), 169.05
(100.0), 275.05 (12.5).
3,4-Dihydro-3-pyridin-2-yl-2H-benz[e]-1,3-oxazin-2-
one (2f): White crystalline solid.Yield 1.92 g, 85 %, m.p. 62-
63 ºC (from methanol); elemental analysis calcd. (%) for
C13H10N2O2: C, 69.02; H, 4.45; N, 12.38. Found (%): C, 68.56;
H, 4.12; N, 12.19; FTIR (cm-1) 1722 (>C=O); 1H NMR (300
MHz, CDCl3 Me4Si): δ 5.128 (s, 2H, ArCH2N), 7.187-8.441
(m, 8H, aromatic); 13C NMR (75 MHz, CDCl3): δ 152.97,
150.48, 149.47, 147.4, 137.87, 137.5, 128.97, 125.78, 124.64,
120.56, 119.05, 118.97, 115.95, 46.42; GCMS m/z: 226 mass
fragments, 51.20 (25.92 %), 78.10 (100.0), 106.00 (26.5),
226.00 (20.8).
3,4-Dihydro-3-phenyl-2H-benz[e]-1,3-oxazin-2-one
(2a): White crystalline solid, yield 2.07 g, 92 %; m.p. 141-
142 ºC (from methanol). Elemental analysis calcd. (%) for
C14H11NO2: C, 74.65; H, 4.92; N, 6.22. Found (%): C, 74.36;
1
H, 4.73; N, 6.38. FTIR (cm-1) 1710 (>C=O); H NMR (300
MHz, CDCl3, Me4Si): δ 4.820 (s, 2H, ArCH2N), 7.135-7.406
(m, 9H, aromatic); 13C NMR (75 MHz, CDCl3): δ 150.27,
149.76, 141.61, 129.3, 129.0, 127.19, 125.28, 125.21, 124.33,
117.89, 116.25, 50.48; GCMS m/z: 225.0, mass fragments,
51.20 (26.3 %), 78.15 (100.0), 91.10 (21.5), 106.05 (77.7),
119.00 (82.9), 224.95 (44.8).
3,4-Dihydro-3-pyridin-3-yl-2H-benz[e]-1,3-oxazin-2-
one (2g): White crystalline solid. Yield 1.89 g, 84 %, m.p.
142-143 ºC (from methanol); elemental analysis calcd. (%)
for C13H10N2O2: C, 69.02; H, 4.45; N, 12.38. Found (%): C,
68.77; H, 4.26; N, 12.11; FTIR (cm-1) 1708 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 4.894 (s, 2H, ArCH2N), 7.180-
7.357 (m, 5H, aromatic), 7.785 (d, 1H, J = 8.1 Hz, aromatic),
8.547 (d, 1H, J = 2.4 Hz, aromatic), 8.705 (d, 1H, J = 2.4 Hz,
aromatic); 13C NMR (75 MHz, CDCl3): δ 150.15, 149.55,
148.02, 146.18, 138.23, 132.78, 129.38, 125.36, 124.7, 123.71,
117.36, 116.43, 50.21; GCMS m/z: 226, mass fragments, 51.15
(22.83 %), 78.10 (100.0), 106.00 (63.8), 225.90 (21.1).
3,4-Dihydro-3-pyridin-4-yl-2H-benz[e]-1,3-oxazin-2-
one (2h): White crystalline solid. Yield 1.44 g, 64 %, m.p.
185-186 ºC (from methanol); elemental analysis calcd. (%)
for C13H10N2O2: C, 69.02; H, 4.45; N, 12.38. Found (%): C,
68.67; H, 4.22; N, 12.31; FTIR (cm-1) 1710.7 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 4.899 (s, 2H, ArCH2N), 7.138-
7.207 (m, 3H, aromatic), 7.369-7.421 (m, 3H, aromatic), 8.652
(s, 2H, aromatic); 13C NMR (75 MHz, CDCl3): δ 150.65,
149.46, 149.23, 148.66, 129.52, 125.44, 124.86, 117.62,
117.41, 116.30, 48.53; GCMS m/z: 226.20, mass fragments,
51.15 (19.4 %), 78.10 (100.0), 106.15 (65.4), 226.20 (42.0).
6-Bromo-3,4-dihydro-3-(4-methylphenyl)-2H-benz[e]-
1,3-oxazin-2-one (2i): White crystalline solid. Yield 2.25 g,
71 %, m.p. 170-171 ºC (from methanol); elemental analysis
calcd. (%) for C15H12NO2Br: C, 56.62; H, 3.80; N, 4.40. Found
(%): C, 56.60; H, 3.78; N, 4.36; FTIR (cm-1) 1712 (>C=O); 1H
NMR (300 MHz, CDCl3, Me4Si): δ 2.373 (s, 3H,ArCH3), 4.781
(s, 2H, ArCH2N), 6.991 (d, 1H, J = 8.4 Hz, aromatic), 7.252
(s, 5H, aromatic ), 7.411 (d, 1H, J = 8.4 Hz, aromatic); 13C
3,4-Dihydro-3-(4-methylphenyl)-2H-benz[e]-1,3-
oxazin-2-one (2b): White crystalline solid.Yield 2.1 g, 88 %,
m.p. 116-117 ºC (from methanol); elemental analysis calcd.
(%) for C15H13NO2: C, 75.29; H, 5.47; N, 5.85. Found (%): C,
75.09; H, 5.28; N, 5.46; FTIR (cm-1) 1728 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 2.363 (s, 3H, ArCH3), 4.805 (s,
2H, ArCH2N), 7.121-7.259 (m, 8H, aromatic ); 13C NMR (75
MHz, CDCl3): δ 150.26, 149.73, 139.01, 137.07, 129.84,
128.90, 125.02, 124.56, 124.2, 117.86, 116.14, 50.54, 20.87;
GCMS m/z: 239, mass fragments, 78.05 (22.5 %), 133.00
(100.0), 239.00 (23.1).
3,4-Dihydro-3-(4-chlorophenyl)-2H-benz[e]-1,3-
oxazin-2-one (2c): White crystalline solid.Yield 2.2 g, 85 %,
m.p. 149-150 ºC (from methanol); elemental analysis calcd.
(%) for C14H10NO2Cl: C, 64.75; H, 3.88; N, 5.39. Found (%):
C, 64.21; H, 3.34; N, 5.12; FTIR (cm-1) 1703 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 4.821 (s, 2H, ArCH2N), 7.145-
7.415 (m, 8H, aromatic); 13C NMR (75 MHz, CDCl3): δ 150.21,
149.71, 140.22, 132.74, 129.47, 129.27, 126.62, 126.15,
125.45, 124.60, 117.74, 116.34, 50.44; GCMS m/z: 259, mass
fragments, 78.05 (100.0 %), 89.85 (22.9), 106.00 (96.8),
152.90 (81.5), 154.95 (29.9), 258.95 (29.8).
3,4-Dihydro-3-(4-bromophenyl)-2H-benz[e]-1,3-
oxazin-2-one (2d): White crystalline solid.Yield 2.61 g, 86 %,
m.p. 147-148 ºC (from methanol); elemental analysis calcd.
(%) for C14H10NO2Br: C, 55.28; H, 3.31; N, 4.60. Found (%):
C, 54.88; H, 3.01; N, 4.39; FTIR (cm-1) 1705 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 4.817 (s, 2H, ArCH2N), 7.144-
7.538 (m, 8H, aromatic); 13C NMR (75 MHz, CDCl3): δ 150.2,
149.67, 140.69, 132.9, 132.47, 129.3, 126.92, 125.46, 124.63,

Vol. 25, No. 8 (2013)
A Quick Route for the Synthesis of 3-Aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-ones 4539
NMR (75 MHz, CDCl3): δ 149.69, 148.88, 138.66, 137.36,
131.92, 129.95, 128.10, 125.03, 119.94, 117.99, 116.62, 50.09,
20.92; GCMS m/z: 317.20, mass fragments, 77.10 (13.9 %),
104.10 (10.8), 105.10 (11.4), 133.15 (100.0), 317.20 (8.3).
6-Bromo-3,4-dihydro-3-(4-chlorophenyl)-2H-benz[e]-
1,3-oxazin-2-one (2j): White crystalline solid. Yield 2.02 g,
60 %, m.p. 210-211 ºC (from methanol); elemental analysis
calcd. (%) for C14H9NO2BrCl: C, 49.66; H, 2.68; N, 4.14.
Found (%): C, 49.59; H, 2.65; N, 4.12; FTIR (cm-1) 1707
(>C=O); 1H NMR (300 MHz, CDCl3, Me4Si): δ 4.787 (s, 2H,
ArCH2N), 6.997 (d, 1H, J = 8.4 Hz, aromatic), 7.262-7.340
(m, 3H, aromatic), 7.402-7.458 (m, 3H, aromatic); 13C NMR
(75 MHz, CDCl3): δ 149.63, 148.83, 139.77, 133.13, 132.31,
129.62, 128.21, 126.58, 119.66, 118.21, 117.02, 50.00; GCMS
m/z: 337.20, mass fragments, 51.10 (22.7 %), 77.10 (49.6),
153.10 (100.0), 155.10 (30.0), 184.00 (28.9), 186.00 (25.4),
337.20 (11.5), 339.15 (14.1).
RESULTS AND DISCUSSION
Among previous reported processes, Mindl et al.16 has
studied the kinetics of cyclization of substituted phenyl-N-(2-
hydroxybenzyl)carbamates and their N-methyl analogues.
Yadav et al.17, has reported compounds of this class under
solvent-free microwave irradiation using montmorillonite
K-10 clay as a support.
During our study, we had used phosgene (20 % solution
in toluene) and carbonyldiimidazole18,19 (CDI) as cyclization
reagents. In case of phosgene, apart from handling and hazard,
the reaction requires overnight stirring. The yield obtained was
55-62 % and the compounds need further purification. Effect
of solvent in the study was vital. The reaction time varies as
the polarity of solvent changes. We have used THF and dioxane
with phosgene as cyclization reagent, in case of dioxane the
yield and quality was better than in THF. While cyclization
with carbonyldiimidazole, we have tried toluene, THF, dioxane
and DMSO. Surprisingly, there is no reaction on TLC in case
of toluene, THF and even in dioxane (Table-1). From all these
synthetic manipulations, the condensation of substituted
2-hydroxybenzylamine with carbonyldiimidazole in DMSO
seemed the most reliable for the synthesis of 3-aryl-3,4-
dihydro-2H-benz[e]-1,3-oxazin-2-ones.
6-Bromo-3,4-dihydro-3-pyridin-3-yl-2H-benz[e]-1,3-
oxazin-2-one (2k): White crystalline solid.Yield 2.03 g, 67 %,
m.p. 120-121 ºC (from methanol); elemental analysis calcd.
(%) for C13H9N2O2Br: C, 51.17; H, 2.97; N, 9.18. Found (%):
1
C, 51.11; H, 2.91; N, 9.09; FTIR (cm-1) 1710 (>C=O); H
NMR (300 MHz, CDCl3, Me4Si): δ 4.862 (s, 2H, ArCH2N),
7.022 (d, 1H, J = 8.7 Hz, aromatic), 7.317 (s, 1H, aromatic),
7.381-7.480 (m, 2H, aromatic), 7.768 (d, 1H, J = 8.1 Hz,
aromatic), 8.567 (d, 1H, J = 4.2 Hz, aromatic), 8.690 (d, 1H,
J = 2.1 Hz, aromatic); 13C NMR (75 MHz, CDCl3): δ 149.56,
148.68, 148.23, 146.19, 137.93, 132.82, 132.40, 131.40,
128.24, 123.80, 119.39, 118.22, 117.16, 49.76; GCMS m/z:
304.20, mass fragments, 51.10 (46.1 %), 77.10 (100.0), 156.05
(28.8), 184.05 (38.7), 186.05 (36.9), 207.10 (21.8), 304.20
(21.7).
TABLE-1
STUDY OF SOLVENTS
S.
No.
Cyclization
reagent
Yield
(%)
R
X
Solvent
1
2
3
4
-C6H5
-C6H5
-C6H5
-C6H5
-H
-H
-H
-H
Phosgene
Phosgene
CDI
THF
55.0
72.0
Nil
Dioxane
Toluene
Dioxane
CDI
Nil
3,4-Dihydro-3-[(4-methylphenyl)sulfonyl]-2H-benz[e]-
1,3-oxazin-2-one (2l): White crystalline solid. Yield 1.93 g,
69 %, m.p. 118-120 ºC (from methanol); elemental analysis
calcd. (%) for C15H13NO4S: C, 59.39; H, 4.32; N, 4.62. Found
(%): C, 59.1; H, 4.12; N, 4.24; FTIR 1749 (>C=O); 1H NMR
(300 MHz, CDCl3, Me4Si): δ 2.141 (s, 3H), 4.115 (d, 2H = 6.3
Hz), 6.098 (s, 1H), 6.761 (m, 2H), 6.977 (d, 1H), 7.114 (t, 1H,
J = 7.8 Hz), 7.255 (d, 1H, J = 7.2 Hz), 7.710 (d, 2H, J = 7.8
Hz); 13C NMR (75 MHz, CDCl3): δ 154.39, 143.68, 136.21,
129.95, 129.68, 129.59, 127.1, 122.02, 102.51, 116.06, 44.21,
21.49.
TABLE-2
EXPERIMENTAL DETAILS OF 2
Reaction
time (min)
m.p.
(ºC)
Yield
Entry
R
X
(%)
92.0
88.0
85.0
86.0
80.0
85.0
84.0
64.0
71.0
60.0
67.0
69.0
58.0
-C6H5
-H
-H
-H
-H
-H
-H
-H
-H
-Br
-Br
-Br
-H
–
25
25
25
25
35
30
35
35
25
35
30
45
35
141-142
116-117
149-150
147-148
176-177
62-63
2a
2b
2c
2d
2e
2f
-4-CH3C6H4
-4-ClC6H4
-4-BrC6H4
-1-Napthyl
-2-Aminopyridyl
-3-Aminopyridyl
-4-Aminopyridyl
-4-CH3C6H4
-4-ClC6H4
142-143
185-186
170-171
210-211
120-121
118-120
220-221
2g
2h
2i
3-[3-Chloro-4-(4-chlorophenoxy)phenyl]-6,8-diiodo-
2H-1,3-benzoxazine-2,4(3H)-dione (2m): White crystalline
solid. Yield 0.3 g, 58 %, m.p. 220-221 ºC (from methanol);
elemental analysis calcd. (%) for C20H9NO4Cl2I2: C, 36.84; H,
1.39; N, 2.15. Found (%): C, 36.53; H, 1.28; N, 2.05; FTIR
2j
-3-Aminopyridyl
-4-CH3C6H4SO2
Rafoxinide
2k
2l
2m
1
1701.1, 1766.7 (>C=O); H NMR (300 MHz, DMDO-d6,
Me4Si): δ 7.082-8.620 (m, 9H, aromatic); 13C NMR (75 MHz,
DMDO-d6): δ 159.11, 154.70, 151.87, 146.72, 135.28, 131.26,
130.69, 127.92, 124.15, 120.75, 119.86, 118.61, 117.10, 90.11,
86.67, 41.07, 40.30, 39.46, 39.19, 38.63.
To the best of our knowledge pyridine amine and sulfon-
amide derived 1,3-benzoxazin-2-ones are not yet reported.
Since reactivity of pyridine and sulfonamide derivative towards
a variety of functional group as well as towards microbial
activity is well documented in the literature20,21. Keeping these
things on priority, we are presenting a library of 3-aryl-3,4-
dihydro-2H-benz[e]-1,3-oxazin-2-ones by a simple, quick and
cost effective synthetic route. For the present study, we
prepared the various imines22/N-sulfonylimines23,24 by reacting
variously substituted arylamines/aryl sulfonamide with
We have developed a simple and economically viable
synthetic method for the preparation of various potential
pharmaceutically useful 2H-benzoxazin-2-one derivatives
starting from salicyldehyde and variously substituted amines.
This simple and effective process will help to develop the
compound of this class in future.

4540 Shukla et al.
Asian J. Chem.
10. X. Li, U.H. Manjunatha, M.B. Goodwin, J.E. Knox, C.A. Lipinski,
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18, 2256 (2008).
salicyldehyde. These are further subjected to reduction by
sodium borohydride in alcohol to give resultant N-(2-hydroxy)-
benzyl-arylamines25/sulfonamide 1 (Scheme-I). 3-Aryl-3,4-
dihydro-2H-benz[e]-1,3-oxazin-2-one 2, were prepared by
cyclization of N-(2-hydroxy)-benzyl-arylamines/sulfonamide
1 with carbonyldiimidazole in DMSO in 20-30 min at 20-25
ºC (Table-2).
11. H. Kai,Y. Morioka,Y. Koriyama, K. Okamoto,Y. Hasegawa, M. Hattori,
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ACKNOWLEDGEMENTS
Authors (Manju Rani and Arif Ali Khan) are thankful to
CSIR, New Delhi for financial support.
15. A. Klasek, K. Koristek, J. Polis and J. Kosmrlj, Tetrahedron, 56, 1551
(2000).
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