Synthesis and crystal structure of isoxazoline derivatives bearing a 1,2,4-triazole moiety

Article abstract of DOI:10.1007/s00706-012-0722-8

Novel isoxazoline derivatives bearing a 1,2,4- triazole moiety have been synthesized starting from 2-bromo-1-phenylethanone. Chalcones were obtained by aldol condensation of 1-phenyl-2-(1H-1,2,4-triazol-1- yl)ethanone and 4-substituted benzaldehydes using

Full text of DOI:10.1007/s00706-012-0722-8

Monatsh Chem (2012) 143:1523–1528
DOI 10.1007/s00706-012-0722-8
ORIGINAL PAPER
Synthesis and crystal structure of isoxazoline derivatives bearing
a 1,2,4-triazole moiety
•
Zhi-Qiang Dong Fang-Ming Liu Sheng-Qin Chen
•
Received: 17 May 2011 / Accepted: 9 January 2012 / Published online: 7 February 2012
Ó Springer-Verlag 2012
Abstract Novel isoxazoline derivatives bearing a 1,2,4-
triazole moiety have been synthesized starting from
2-bromo-1-phenylethanone. Chalcones were obtained by
aldol condensation of 1-phenyl-2-(1H-1,2,4-triazol-1-
yl)ethanone and 4-substituted benzaldehydes using piperi-
dine as catalyst. Finally, 1,3-dipolar cycloaddition of the
chalcones and a variety of aldoximes in the presence of
chloramine-T afforded the title compounds. The structural
identities of these compounds were confirmed on the basis
of IR, NMR, mass spectral, and elemental analysis data and
by X-ray analysis of a typical example of the new class of
isoxazoline analogs.
inhibitor [8], and antibacterial [9] activity. Owing to their
reputed chemotherapeutic applications, the design and
synthesis of new and unique isoxazoline derivatives have
enthused many organic chemists [10, 11]. In addition, 1,2,4-
triazole is also an important structural motif in the design of
new drugs [12]. Use of 1,2,4-triazole derivatives as prom-
ising antimicrobial, antibacterial, antihypertensive, and
antifungal agents has been described and discussed in sev-
eral publications [13–16]. Furthermore, some 1,2,4-triazole
derivatives, for example fluconazole and itraconazole, are
commercially available antifungal agents [17, 18]. Taking
into consideration the important biological activity of azole
derivatives and the combination principles of drug design,
we herein report the synthesis of some new isoxazoline
derivatives with a 1,2,4-triazole moiety. The synthetic route
is shown in Scheme 1.
Keywords Isoxazoline Á 1,2,4-Triazole Á
Crystal structure Á 1,3-Dipolar cycloaddition
Introduction
Results and discussion
The 1,3-dipolar cycloaddition reaction is one of the most
important classes of organic reaction and is a versatile
preparative method for the synthesis of five-membered
heterocycles involving the [3 ? 2] principle [1, 2]. Cyclo-
addition of nitrile oxides to alkenes affords isoxazolines
with a variety of biological activity and which have also
been used as useful intermediates in organic synthesis [3].
Isoxazoline derivatives have been reported to have a variety
of pharmacological activity, for example antimicrobial
[4, 5], antidepressant [6], antifungal [7], phosphodiesterase
The starting compounds 2-bromo-1-phenylethanone (1) and
1-phenyl-2-(1H-1,2,4-triazol-1-yl)ethanone (2) required for
the study were prepared in accordance with reported
methods [19, 20]. The intermediate chalcones 3a–3d were
synthesized via the Claisen–Schmidt condensation between
2 and substituted benzaldehydes in the presence of piperi-
dine. Finally, compounds 3a–3d underwent 1,3-dipolar
cycloaddition with benzaldoximes in the presence of chlo-
ramine-T in MeOH under reflux leading to the formation of
cycloadducts 4a–4l.
A variety of analytical techniques, including IR, NMR,
mass spectrometry, elemental analysis, and X-ray crystal-
lography, were used to confirm the structural identity of the
final products. The target compounds were correctly ana-
lyzed for their molecular structure. Their infrared spectra
Z.-Q. Dong Á F.-M. Liu (&) Á S.-Q. Chen
College of Material and Chemical Engineering,
Hangzhou Normal University, Hangzhou 310036,
Zhejiang, People’s Republic of China
e-mail: fmliu859@sohu.com
123

1524
Z.-Q. Dong et al.
Scheme 1
O
N
HC
R1
O
C
O
C
HN
N
N
N
CH2
CH2Br
N
Piperidine
Et3N
1
2
N
O
OH
R1
O
N
N
O
N
R2
R1
N
Chloramine T; CH3OH
N
N
N
R2
4f
Cl Cl
Cl CH3
3a, R1 = H; 3b, R1 = Cl;
3c, R1 = OCH3; 3d, R1 = CH3
4a 4b 4c 4d 4e
R
1 = H
H
H
Cl
H
R2 = H
Cl CH3
4g
4h 4i
4j
4k
4l
R1 = OCH3 OCH3 OCH3 CH3 CH3 CH3
R2 =
H
Cl
CH3
H
Cl
CH3
Fig. 1 Molecular structure
of 4c
contained strong bands at 1,693 and 1,632 cm-1 because of
The identities of the title compounds were further con-
firmed by single-crystal X-ray crystallographic studies. The
crystal structure of compound 4c is shown in Fig. 1. The
crystal data and structure refinement are shown in Table 1.
Selected bond lengths and angles are listed in Table 2.
There are two five-membered rings, the isoxazoline ring
(plane 1) and the 1,2,4-triazole ring (plane 2) in the
molecular structure. All atoms are nearly coplanar, with
1
the presence of C=O and C=N double bonds. Their H
NMR spectra contained three singlets at 8.43–8.33,
8.04–7.90, and 6.47–6.32 ppm which could be attributed to
the two triazole-H and the isoxazoline-H, respectively. In
addition, the presence of a multiplet at 7.94–6.62 ppm was
ascribed to the aromatic protons. In the mass spectra,
molecular ion peaks of all target compounds were obtained
from EI-MS, but the abundance of molecular ion peaks was
very weak.
˚
˚
existing mean deviations of 0.0931 A and 0.0038 A for
plane 1 and plane 2, respectively. The isoxazoline ring is
123

Synthesis and crystal structure of isoxazoline derivatives
1525
5-dihydroisoxazol-5-yl]phenylmethanone derivatives 4a–4l
by 1,3-dipolar cycloaddition reaction. The molecular con-
formation of the title compounds was confirmed by X-ray
crystallography.
Table 1 Crystal data and structure refinement for compound 4c
Empirical formula
Formula weight
Temperature/K
C25H20N4O2
408.45
293(2)
˚
Wavelength/A
0.71073
Crystal system
Space group
Triclinic
Experimental
P-1
˚
a/A
7.9603(7)
11.6857(9)
12.1472(9)
103.256(2)
100.117(2)
99.210(3)
1,058.82(15)
2
Reactions were monitored by TLC. Melting points were
determined by use of a Mettler FP-5 melting point appa-
ratus. Elemental analysis was performed with a Perkin–
Elmer 2400 elemental analyzer. IR spectra were recorded
as KBr pellets on a Bruker Equinox 55 FT-IR spectro-
photometer. NMR spectra were recorded on a Bruker
400 MHz spectrometer using TMS as internal reference.
Mass spectra were acquired with an Agilent 5975 instru-
ment (EI, 70 eV). X-ray diffraction data were collected on
a Hitachi F-4500 R-Axis Spider diffractometer. The ben-
zaldoximes were synthesized according to a reported
procedure [21].
˚
b/A
˚
c/A
a/°
b/°
c/°
3
˚
V/A
Z
D
calc/g cm-3
1.281
Crystal size/mm
0.45 9 0.22 9 0.16
3.34–27.48
0.084
h range/°
l/mm-1
Reflections collected
Data/restraints/parameters
Final R indices [I[2r(I)]
10,514
4816/0/281
R1 = 0.0418
xR2 = 0.1107
R1 = 0.0916
xR2 = 0.1598
General procedure for preparation of 1-phenyl-3-
(4-substituted phenyl)-2-(1H-1,2,4-triazol-1-yl)-
propen-1-ones 3a–3d
R indices (all data)
The syntheses were carried out according to a known
procedure [22]. 1-Phenyl-2-(1H-1,2,4-triazol-1-yl)ethanone
(2, 3.74 g, 0.02 mol) and the appropriate benzaldehyde
(0.02 mol) were heated under reflux in the presence of
1 cm3 piperidine for 7 h under a nitrogen atmosphere with
80 cm3 toluene in an apparatus equipped with a water
separator. The solvent was evaporated under reduced
pressure and the residue was chromatographed on a silica
gel column with ethyl acetate–petroleum ether 1:1 as eluent
to afford the corresponding chalcones 3a–3d.
˚
Table 2 Selected bond lengths/A and angles/° of compound 4c
O(1)-C(7)
O(2)-C(8)
O(2)-N(4)
N(1)-C(9)
N(3)-C(10)
N(4)-C(18)
C(11)-C(18)
C(8)-C(11)
1.212(2)
1.425(2)
1.449(2)
1.313(3)
1.313(3)
1.282(2)
1.503(3)
1.538(2)
C(8)-O(2)-N(4)
C(9)-N(1)-N(2)
C(10)-N(2)-N(1)
C(10)-N(3)-C(9)
C(18)-N(4)-O(2)
C(6)-C(7)-C(8)
O(2)-C(8)-C(11)
N(4)-C(18)-C(11)
108.38(13)
101.69(16)
109.69(16)
102.43(17)
108.12(15)
120.80(15)
104.53(14)
113.98(16)
1,3-Diphenyl-2-(1H-1,2,4-triazol-1-yl)propen-1-one (3a)
Colorless crystals, yield 76%; m.p.: 129.8–130.6 °C
(125–127 °C [23]).
3-(4-Chlorophenyl)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)-
propen-1-one (3b)
characterized by the torsion angles (enumerated clock-
wise and starting with O(2)-N(4)-C(18)-C(11)): -3.4(2)°,
16.4(2)°, -22.37(17)°, -22.41(17)°, -12.68(19)°, and it
adopts an envelope conformation with atom C(8) deviating
from the plane defined by O(2), N(4), C(18), C(11) of
Colorless crystals, yield 81%; m.p.: 121.3–122.7 °C
(115–116 °C [23]).
3-(4-Methoxyphenyl)-1-phenyl-2-(1H-1,2,4-triazol-1-
yl)propen-1-one (3c, C18H15N3O2)
˚
0.1422 A. In addition, plane 1 and plane 2 are almost
Colorless crystals, yield 75%; m.p.: 80.5–81.5 °C; 1H NMR
(400 MHz, CDCl3): d = 8.21, 8.15 (2s, 2H, triazole-H),
7.84 (s, 1H, C=CH), 7.81–6.91 (m, 9H, Ar–H), 3.82 (s, 3H,
OCH3) ppm; 13C NMR (100 MHz, CDCl3): d = 191.15,
152.93, 145.27, 142.79, 142.63, 136.84, 132.68, 131.45,
130.26, 129.86, 129.28, 128.68, 128.07, 55.51 ppm; IR
perpendicular to each other with a dihedral angle of 96°.
The distances of the plane 1 centroid from plane 2 and the
˚
˚
phenyl ring (C(12)-C(17)) are 3.282 A and 3.986 A,
respectively.
In conclusion, we have obtained
a
series of
3,4-bis(4-substituted phenyl)-5-(1H-1,2,4-triazol-1-yl)-4,
123

1526
Z.-Q. Dong et al.
(KBr): ꢀm = 1,643, 1,492, 1,446, 1,414 cm-1; MS: m/z =
[3-(4-Methylphenyl)-4-phenyl-5-(1H-1,2,4-triazol-1-yl)-
4,5-dihydroisoxazol-5-yl]phenylmethanone
305 (M?).
(4c, C25H20N4O2)
3-(4-Methylphenyl)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)-
propen-1-one (3d, C18H15N3O)
Colorless crystals, yield 42%; m.p.: 204–205 °C; 1H NMR
(400 MHz, CDCl3): d = 8.43, 7.93 (2s, 2H, triazole-H),
7.09–7.55 (m, 14H, Ar–H), 6.45 (s, 1H, isoxazoline-H),
2.34 (s, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d = 186.81, 151.49, 143.58, 138.98, 134.08, 132.39,
131.16, 131.02, 130.10, 129.68, 128.79, 128.71, 128.68,
127.89, 126.79, 126.38, 58.83, 21.71, 21.64 ppm; IR
1
Colorless crystals, yield 77%; m.p.: 112.6–114.0 °C; H
NMR (400 MHz, CDCl3): d = 8.21, 8.15 (2s, 2H, triazole-
H), 7.84 (s, 1H, C=CH), 7.82–6.91 (m, 9H, Ar–H), 2.36 (s,
3H, CH3) ppm; 13C NMR (100 MHz, CDCl3): d = 191.05,
152.75, 145.16, 142.56, 142.52, 136.59, 132.91, 131.51,
130.39, 129.95, 129.38, 128.72, 128.11, 21.64 ppm; IR
(KBr): m = 1,693, 1,632 cm-1; MS: m/z = 408 (M?).
ꢀ
(KBr): m = 1,641, 1,489, 1,442, 1,412 cm-1; MS: m/z =
ꢀ
289 (M?).
[4-(4-Chlorophenyl)-3-phenyl-5-(1H-1,2,4-triazol-1-yl)-
4,5-dihydroisoxazol-5-yl]phenylmethanone
General procedure for preparation of [3,4-bis-
(4-substituted phenyl)-5-(1H-1,2,4-triazol-1-yl)-
4,5-dihydroisoxazol-5-yl]phenylmethanones 4a–4l
(4d, C24H17ClN4O2)
Colorless crystals, yield 45%; m.p.: 156–158 °C; 1H NMR
(400 MHz, CDCl3): d = 8.38, 7.96 (2s, 2H, triazole-H),
6.93–7.89 (m, 14H, Ar–H), 6.40 (s, 1H, isoxazoline-H)
ppm; 13C NMR (100 MHz, CDCl3): d = 186.69, 152.24,
143.51, 141.98, 134.71, 134.24, 132.43, 131.38, 130.35,
130.01, 129.67, 129.00, 128.97, 128.74, 127.92, 126.59,
To a solution of chalcone 3 (1 mmol) in 50 cm3 methanol
the appropriate benzaldoxime (2 mmol) and 0.562 g
chloramine-T (2 mmol) were added. The reaction mixture
was kept under reflux for 7 h. After the mixture had cooled
to room temperature, the separated solid was isolated by
filtration and the filter liquor was evaporated under reduced
pressure. The resulting crude product was purified by col-
umn chromatography with ethyl acetate–petroleum ether
4:1 as eluent and the solid product obtained was recrys-
tallized from petroleum ether–acetone 1:15 to afford the
desired products 4a-4l. White single crystals of compound
4c were obtained from petroleum ether and acetone after
slow evaporation at room temperature.
58.33, 21.47 ppm; IR (KBr): m = 1,695, 1,630 cm-1; MS:
ꢀ
m/z = 428 (M?).
[3,4-Bis(4-chlorophenyl)-5-(1H-1,2,4-triazol-1-yl)-4,5-
dihydroisoxazol-5-yl]phenylmethanone
(4e, C24H16Cl2N4O2)
Colorless crystals, yield 42%; m.p.: 144–145 °C; 1H NMR
(400 MHz, CDCl3): d = 8.36, 7.94 (2s, 2H, triazole-H),
6.88–7.92 (m, 13H, Ar–H), 6.38 (s, 1H, isoxazoline-H)
ppm; 13C NMR (100 MHz, CDCl3): d = 186.78, 152.16,
143.23, 139.37, 134.12, 132.18, 131.33, 131.00, 129.51,
129.25, 128.71, 128.65, 128.34, 127.89, 126.26, 124.25,
[3,4-Diphenyl-5-(1H-1,2,4-triazol-1-yl)-4,5-dihydro-
isoxazol-5-yl]phenylmethanone (4a, C24H18N4O2)
55.99, 21.62 ppm; IR (KBr): m = 1,696, 1,629 cm-1; MS:
ꢀ
Colorless crystals, yield 38%; m.p.: 171–172 °C; 1H NMR
(400 MHz, CDCl3): d = 8.41, 7.93 (2s, 2H, triazole-H),
7.11–7.91 (m, 15H, Ar–H), 6.47 (s, 1H, isoxazoline-H)
ppm; 13C NMR (100 MHz, CDCl3): d = 186.83, 151.56,
143.65, 139.04, 134.16, 132.49, 131.23, 131.09, 130.03,
129.76, 128.88, 128.78, 128.72, 127.96, 126.86, 126.46,
m/z = 462 (M?).
[4-(4-Chlorophenyl)-3-(4-methylphenyl)-5-(1H-1,2,4-
triazol-1-yl)-4,5-dihydroisoxazol-5-yl]phenylmethanone
(4f, C25H19ClN4O2)
Colorless crystals, yield 48%; m.p.: 163–165 °C; 1H NMR
(400 MHz, CDCl3): d = 8.39, 7.91 (2s, 2H, triazole-H),
6.86–7.58 (m, 13H, Ar–H), 6.36 (s, 1H, isoxazoline-H),
2.36 (s, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d = 186.68, 152.19, 143.38, 141.79, 134.16, 132.35,
131.24, 130.21, 130.04, 129.59, 129.08, 128.88, 128.64,
127.77, 126.41, 57.89, 21.64, 21.53 ppm; IR (KBr):
58.81, 21.60 ppm; IR (KBr): m = 1,690, 1,636 cm-1; MS:
ꢀ
m/z = 394 (M?).
[3-(4-Chlorophenyl)-4-phenyl-5-(1H-1,2,4-triazol-1-yl)-
4,5-dihydroisoxazol-5-yl]phenylmethanone
(4b, C24H17ClN4O2)
m = 1,698, 1,629 cm-1; MS: m/z = 442 (M?).
ꢀ
Colorless crystals, yield 38%; m.p.: 191–192 °C; 1H NMR
(400 MHz, CDCl3): d = 8.37, 7.90 (2s, 2H, triazole-H),
6.78–7.59 (m, 14H, Ar–H), 6.46 (s, 1H, isoxazoline-H)
ppm; 13C NMR (100 MHz, CDCl3): d = 186.76, 151.48,
143.56, 139.10, 134.09, 132.41, 131.16, 131.06, 130.08,
129.66, 128.73, 128.68, 128.59, 127.88, 126.75, 126.39,
[4-(4-Methoxyphenyl)-3-phenyl-5-(1H-1,2,4-triazol-
1-yl)-4,5-dihydroisoxazol-5-yl]phenylmethanone
(4g, C25H20N4O3)
Colorless crystals, yield 35%; m.p.: 130–131 °C; 1H NMR
(400 MHz, CDCl3): d = 8.34, 7.95 (2s, 2H, triazole-H),
6.77–7.94 (m, 14H, Ar–H), 6.35 (s, 1H, isoxazoline-H),
3.78 (s, 3H, OCH3) ppm; 13C NMR (100 MHz, CDCl3):
58.78, 21.58 ppm; IR (KBr): m = 1,691, 1,632 cm-1; MS:
ꢀ
m/z = 428 (M?).
123

Synthesis and crystal structure of isoxazoline derivatives
1527
d = 186.79, 151.45, 143.44, 138.97, 133.99, 132.41,
131.15, 131.00, 130.09, 129.58, 128.68, 128.64, 128.59,
127.87, 126.79, 126.31, 57.77, 55.43, 21.39 ppm; IR
(KBr): ꢀm = 1,692, 1,633 cm-1; MS: m/z = 424 (M?).
[3,4-Bis(4-methylphenyl)-5-(1H-1,2,4-triazol-1-yl)-4,5-
dihydroisoxazol-5-yl]phenylmethanone (4l, C26H22N4O2)
Colorless crystals, yield 39%; m.p.: 146–147 °C; 1H NMR
(400 MHz, CDCl3): d = 8.38, 8.04 (2s, 2H, triazole-H),
6.62–7.90 (m, 13H, Ar–H), 6.34 (s, 1H, isoxazoline-H),
2.31 (s, 3H, CH3), 2.18 (s, 3H, CH3) ppm; 13C NMR
(100 MHz, CDCl3): d = 186.81, 152.18, 143.56, 139.07,
134.16, 132.37, 131.09, 130.11, 129.91, 129.68, 128.74,
128.66, 128.59, 127.74, 126.68, 126.37, 58.79, 21.69,
[3-(4-Chlorophenyl)-4-(4-methoxyphenyl)-5-(1H-1,2,4-
triazol-1-yl)-4,5-dihydroisoxazol-5-yl]phenylmethanone
(4h, C25H19ClN4O3)
Colorless crystals, yield 37%; m.p.: 136–138 °C; 1H NMR
(400 MHz, CDCl3): d = 8.33, 7.92 (2s, 2H, triazole-H),
7.17–7.59 (m, 13H, Ar–H), 6.33 (s, 1H, isoxazoline-H),
3.79 (s, 3H, OCH3) ppm; 13C NMR (100 MHz, CDCl3):
d = 186.71, 151.78, 143.56, 139.01, 133.88, 132.53,
131.26, 131.11, 130.22, 129.49, 128.53, 128.51, 128.44,
127.72, 126.64, 126.18, 57.89, 55.32, 21.45 ppm; IR
21.64, 21.58 ppm; IR (KBr): m = 1,695, 1,630 cm-1; MS:
ꢀ
m/z = 422 (M?).
X-Ray crystallography
CCDC-800915 contains the supplementary crystallo-
graphic data for compound 4c. These data can be obtained
free of charge from the Cambridge Crystallographic Data
Centre (CCDC) via e-mail: deposit@ccdc.cam.ac.uk.
(KBr): m = 1,696, 1,632 cm-1; MS: m/z = 458 (M?).
ꢀ
[4-(4-Methoxyphenyl)-3-(4-methylphenyl)-5-(1H-1,2,4-
triazol-1-yl)-4,5-dihydroisoxazol-5-yl]phenylmethanone
(4i, C26H22N4O3)
Colorless crystals, yield 31%; m.p.: 127–129 °C; 1H NMR
(400 MHz, CDCl3): d = 8.36, 7.91 (2s, 2H, triazole-H),
7.10–7.94 (m, 13H, Ar–H), 6.32 (s, 1H, isoxazoline-H),
3.78 (s, 3H, OCH3), 2.32 (s, 3H, CH3) ppm; 13C NMR
(100 MHz, CDCl3): d = 186.86, 151.44, 143.69, 139.83,
138.97, 134.11, 132.36, 131.07, 131.00, 130.06, 129.77,
128.76, 128.67, 127.91, 126.78, 126.47, 58.76, 55.47,
Acknowledgments We are grateful to the Key SCI-Tech Innova-
tion Team of Zhejiang Province (2010R5 0017) for financial help.
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21.72, 21.61 ppm; IR (KBr): m = 1,697, 1,633 cm-1; MS:
ꢀ
m/z = 438 (M?).
[4-(4-Methylphenyl)-3-phenyl-5-(1H-1,2,4-triazol-1-yl)-
4,5-dihydroisoxazol-5-yl]phenylmethanone
(4j, C25H20N4O2)
Colorless crystals, yield 36%; m.p.: 156–157 °C; 1H NMR
(400 MHz, CDCl3): d = 8.37, 7.97 (2s, 2H, triazole-H),
7.28–7.93 (m, 14H, Ar–H), 6.39 (s, 1H, isoxazoline-H),
2.19 (s, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d = 186.82, 151.46, 143.63, 138.97, 134.01, 132.96,
132.36, 131.08, 129.89, 129.68, 128.78, 128.69, 128.58,
127.87, 126.74, 126.31, 58.74, 21.71, 21.61 ppm; IR
9. Dighade SR, Patil SD, Chincholkar MM, Dighade NR (2003)
Asian J Chem 15:450
10. Al HG, Kerbal A, Bennani B, Baba MF, Daoudi M, Ben HT
(2008) Arkivoc 12:42
(KBr): m = 1,692, 1,632 cm-1; MS: m/z = 408 (M?).
ꢀ
[3-(4-Chlorophenyl)-4-(4-methylphenyl)-5-(1H-1,2,4-
triazol-1-yl)-4,5-dihydroisoxazol-5-yl]phenylmethanone
(4k, C25H19ClN4O2)
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Colorless crystals, yield 32%; m.p.: 166–168 °C; 1H NMR
(400 MHz, CDCl3): d = 8.35, 7.90 (2s, 2H, triazole-H),
7.26–7.56 (m, 13H, Ar–H), 6.36 (s, 1H, isoxazoline-H),
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d = 186.75, 151.39, 143.51, 139.97, 138.88, 132.74,
132.19, 131.02, 129.78, 129.52, 128.63, 128.52, 128.39,
127.68, 126.59, 126.18, 58.66, 21.67, 21.60 ppm; IR
(KBr): ꢀm = 1,694, 1,631 cm-1; MS: m/z = 442 (M?).
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