Synthesis and spectroscopic studies of some new oxazepine derivatives throughout [2+5] cycloaddition reactions (III)

Article abstract of DOI:10.1007/s11164-012-0877-2

The present work included condensation reactions of o-tolidine with different aromatic aldehydes in absolute ethanol to give Schiff bases (w ₉ -w ₁₂ ) in high yield which, on reaction with maleic and phthalic anhydride by [2+5] cycloaddition reactions in the presence of suitable solvents, give the corresponding [1,3]oxazepine-4,7-dione (w ₉ m-w ₁₂ m) and [1,3]oxazepine-1,5-dione (w ₉ ph-w ₁₂ ph), respectively. The structure of the newly synthesized compounds were monitored by TLC and established on the basis of elemental analysis, FT-IR, and ¹H NMR.

Full text of DOI:10.1007/s11164-012-0877-2

Res Chem Intermed
DOI 10.1007/s11164-012-0877-2
Synthesis and spectroscopic studies of some new
oxazepine derivatives throughout [2+5]
cycloaddition reactions (III)
•
Alaa J. Mahrath Saadon A. Aowda Sabah N. Kamil
•
Received: 12 September 2012 / Accepted: 17 October 2012
Ó Springer Science+Business Media Dordrecht 2012
Abstract The present work included condensation reactions of o-tolidine with
different aromatic aldehydes in absolute ethanol to give Schiff bases (w9–w12) in
high yield which, on reaction with maleic and phthalic anhydride by [2?5]
cycloaddition reactions in the presence of suitable solvents, give the corresponding
[1,3]oxazepine-4,7-dione (w9m–w12m) and [1,3]oxazepine-1,5-dione (w9ph–
w12ph), respectively. The structure of the newly synthesized compounds were
monitored by TLC and established on the basis of elemental analysis, FT-IR, and 1H
NMR.
Keywords Imines ꢀ o-Tolidine ꢀ 1,3-Oxazepine-4,7-dione
Introduction
o-Tolidine is the derivative of benzidine which belongs to an important group of
aromatic compounds containing methyl group in the 3-position of 4,40-diamino
biphenyl [1]. o-Tolidine derivatives possessing diverse biological activities play
important roles as versatile building blocks for the synthesis of natural products and
biologically active compounds [2–9]. In particular are the formation of imine
derivatives, which have great interest due to their proceeding in several important
pathway reactions [10–12]. Moreover, the reactions of imine throughout ring
A. J. Mahrath (&)
Chemistry Department, College of Medicine, Babylon University, Babylon, Iraq
e-mail: aalaamahrath@gmail.com; ajmbioorg@gmail.com
S. A. Aowda
Chemistry Department, College of Science, Babylon University, Babylon, Iraq
S. N. Kamil
Department of Pharmacology, College of Pharmacy, Babylon University, Babylon, Iraq
123

A. J. Mahrath et al.
closing generate a wide range of five-, six-, and seven-member rings of heterocyclic
organic molecules, such as 4-thiazolidinone derivatives [13], 1,2-dihydro-
1-arylnaphtho[1,2-e][1,3]oxazine-3-one derivatives [14–17], and 1,3-oxazepinedi-
ones [14]. Based on these papers, all of these derivatives have attracted considerable
attention in drug synthesis and a wide range of pharmaceutical activities for these
purposes indicate that the synthesis of these compounds is interesting.
Experimental
Materials and methods
The chemicals used in this work were obtained from B.D.H. and they were all pure
grade reagents. All melting points were determined in an open capillary and are
uncorrected. The solvents, ethanol, methanol dichloromethane, tetrahydrofuran,
ether, and acetone were purified according to the literature [18]. The characteriza-
tions of the prepared compounds were accomplished by FT-IR spectra using Perkin
Elmer apparatus with a KBr disk and an interval ranging from 450 to 4,400 cm-1
.
1H NMR spectra were obtained using a Bruker 300 MHz spectrometer in Jordanian
University and Glasgow University. The samples were in (DMSO–d6) and CDCl3
with tetramethylsilane (TMS) as the reference. Elemental analysis was carried out
using a EuroEA Elemental Analyzer/University of Kufa.
General procedure for the synthesis of imines derivatives (w9–w12)
A mixture of 1 mmol of o-tolidine (0.21 g) and 2 mmol of substituted aromatic
aldehyde were heated in the presence of approximately 10–15 ml of absolute
ethanol with drops of glacial acetic acid in a water bath at 70–80 °C for
approximately 30–40 min. The process of reaction was followed by TLC. Then,
filtration or evaporation of the solvent under reduced pressure was followed by
recrystallization from a suitable solvent [19].
40
Synthesis of N4,N -dibenzylidene-3,30-dimethylbiphenyl-4,40-diamine (w9)
2 mmol (0.42 g) of o-tolidine in absolute ethanol was added to 4 mmol (0.4 g) of
benzaldehyde in the presence of drops of glacial acetic acid under refluxing for
40 min, yellow precipitate was observed, and then section filtration yielded 65 % with
m.p. = 156–158 °C. The IR spectra showed that adsorption bands appeared in the
range of 3,004 and 2,901 cm-1, which belong to C–H aromatic and CH3, respectively,
while –C=N appeared at 1,624 cm-1, –C–N appeared at a stretching frequency of
1,167 cm-1, and, besides that, the aromatic C=C appeared at the range
1,417–1,575 cm-1. On the other hand, 1H NMR in DMSO–d6 as a solvent showed a
sharp singlet at d = 8.40 ppm (s, 2H, CH–N), (dd, 4H) aromatic at d = 7.76–
7.74 ppm, (dd, 5H) aromatic at d = 7.55–7.47 ppm, (d, 3H) at d = 7.06–7.04 ppm,
(d, 4H) at d = 6.87–6.75 ppm, and (s, 6H, 2CH3) at d = 2.41–2.28 ppm. Elemental
123

Synthesis and spectroscopic studies
analysis confirmed the molecular formula C28H24N2 (calculated/found): C, 86.56/
87.12; H, 6.23/6.93; N, 7.21/7.87.
Synthesis of bis(4-(dimethylamino)benzylidene)-3,30-dimethylbiphenyl-4,40-
diamine (w10)
2 mmol (0.42 g) of o-tolidine in absolute ethanol was added to 4 mmol (0.6 g) of N,N-
dimethylamino benzaldehyde in the presence of drops of glacial acetic acid under
refluxing for 30 min, yellow-orange precipitate was observed, and then section
filtration yielded 94 % with m.p. = 256–258 °C. The IR spectra showed stretching
absorption bands at 3,010–2,956 cm-1, referring to CH aromatic and aliphatic,
respectively, while imines’ band appeared at about 1,607 cm-1, C=C appeared in the
range 1,521–1,585 cm-1, a medium intensity band appeared at 1,361 cm-1 referring
to N–CH3 and at 1,165 cm-1 referring to C–N. On the other hand, 1H NMR in CDCl3
as a solvent showed an approximately similar chemical shift of compound w9 as
follows: at d = 8.43 ppm (s, 2H, CH=N), d = 7.83–7.85 ppm (d, 2H, Ar),
d = 7.44–7.49 ppm (m, 4H, Ar), d = 6.88–7.26 ppm (dd, 8H, Ar), and two sharp
singlet peaks at d = 2.45–2.46 ppm, referring to (6H, 2CH3–Ar) and (12H, 4CH3–N).
Elemental analysis confirmed the molecular formula C32H34N4 (calculated/found):
C, 80.98/81.54; H, 7.22/7.89; N, 11.80/12.49.
Synthesis of bis[4-(diethylamino)benzylidene]-3,30-dimethylbiphenyl-4,40-
diamine (w11)
2 mmol (0.42 g) of o-tolidine in absolute ethanol was added to 4 mmol (0.7 g) of
4-N,N-diethylamino benzaldehyde in the presence of drops of glacial acetic acid under
refluxing for 35 min, yellow bold precipitate was observed, and then section filtration
yielded 87 % with m.p. = 174–176 °C. The IR spectra showed stretching absorption
bands at 3,103–2,912 cm-1, referring to CH aromatic and aliphaticrespectively, while
imines’ band appeared at about 1,609 cm-1, C=C aromatic appeared in the range
1,587–1,523 cm-1, a medium intensity band appeared at 1,334 cm-1 referring to
N–CH3 and at 1,172 cm-1 referring to C–N. On the other hand, 1H NMR in DMSO–d6
as a solvent showed an approximately similar chemical shift of compound w10 as
follows: at d = 8.33 ppm (s, 2H, CH=N), d = 7.73–7.75 ppm (d, 2H, Ar),
d = 7.38–7.54 ppm (d, m, 5H, Ar), d = 6.75–7.066 ppm (dd, 5H, Ar), and two
peaks overlapping each other at d = 2.54–2.11 ppm, referring to (8H, 4CH2–N) and
(6H, 2CH3–Ar), while (t, 12H, 4CH3–C) appeared at d = 1.04–1.29 ppm. Elemental
analysis confirmed the molecular formula C36H42N4 (calculated/found): C, 81.47/
82.10; H, 7.98/8.62; N, 10.56/11.24.
Synthesis of bis(4-hydroxy-3-methoxy benzylidene) 3,30dimethyl
biphenyl-4,40-diamine (w12)
2 mmol (0.42 g) of o-tolidine in absolute ethanol was added to 4 mmol (0.60 g) of
4-hydroxy 3-methoxy benzaldehyde in the presence of drops of glacial acetic acid
123

A. J. Mahrath et al.
under refluxing for 60 min, a solid yellow mixture was observed after work up, and
the section filtration yielded 67 % with m.p. = 199–200 °C. The IR spectra showed
stretching absorption broad bands at 3,312 cm-1 referring to OH group,
3,018–2,922 cm-1 referring to CH aromatic and aliphatic, respectively, while
imines’ band appeared at about 1,622 cm-1, C=C aromatic appeared in the range
1,429–1,583 cm-1, a medium intensity band appeared at 1,282 cm-1 referring to
C–O and 1,123 cm-1 referring to C–N. On the other hand, 1H NMR in DMSO–d6 as
a solvent showed a chemical shift of compound w12 as follows: at d = 9.73–
9.82 ppm (s, 2H, OH–Ar), d = 8.310 ppm (s, 2H, CH–N=), d = 7.87–7.90 ppm (d,
m, 4H, Ar), d = 7.272–7.67 ppm (m, 4H, Ar), d = 6.72–6.92 ppm (s, 2H, Ar), and
a sharp singlet peak close to DMSO at d = 2.35 ppm (6H, 2CH3–Ar). On the other
hand, a sharp singlet peak was observed at d = 3.73–3.84 ppm (s, 2CH3O–).
Elemental analysis confirmed the molecular formula C32H34N4 (calculated/found):
C, 74.98/75.44; H, 5.87/6.29; N, 5.83/6.51.
Cycloaddition reaction of the imines derivatives with maleic and phthalic
anhydride
General procedure
1 mmol of the desired imines (w9–w12) was dissolved in suitable solvent under N2
flow, followed by drop wise addition of the cyclic anhydride under refluxing
conditions and monitoring with TLC to determine the completion of the reaction.
Filtration or evaporation took place under reduced pressure and the yield was dried
and recrystallized by a proper solvent.
With maleic anhydride
Synthesis of 3,30-(3,30-dimethylbiphenyl-4,40-diyl)bis(2-phenyl-2,3-dihydro-1,3-
oxazepine-4,7-dione)] (w9m)
Reaction of 1 mmol (0.38 g) of compound w9 with 2 mmol (0.20 g) maleic
anhydride in dry CH2Cl2 added drop wise within N2 flow and stirring under
refluxing condition for about 2.5 h. After cooling the reaction mixture, an orange
precipitate was observed and section filtration yielded 87.7 % with m.p. =
214–215 °C. The IR spectra showed the following bands: two stretching strong
absorption bands at 1,712 and 1,627 cm-1 due to (2C=O, ring), 1,489–1,580 cm-1
1
(C=C, aromatic and alkene), 3,051–2,880 cm-1 (C–H, aromatic and alkene). H
NMR clearly showed d = 8.59 ppm (2H, CH, oxazepine rings), at d = 7.97–
8.0 ppm (m, 4H, Ar), d = 7.58–7.61 ppm (d, 2H, Ar), d = 7.4–7.61
ppm (m, 10H, Ar), d = 7.10–7.21 ppm (dd.4H, 2CH=CH), and at d = 2.34 (s,
6H, 2CH3). Elemental analysis of the molecular formula C36H28N2O6 of the
compound w9m (calculated/found): C, 73.96/74.49; H, 4.83/5, 38; N, 4.79/5.40.
123

Synthesis and spectroscopic studies
Synthesis of 3,30-(3,30-dimethylbiphenyl-4,40-diyl)bis(2-(4-(dimethylamino)phenyl)-
2,3-dihydro-1,3-oxazepine-4,7-dione) (w10m)
Reaction of 1 mmol (0.47 g) of compound w10 with 2 mmol (0.20 g) maleic
anhydride in dry CH2Cl2 added drop wise within N2 flow and stirring under
refluxing condition for about 3.0 h. After cooling the reaction mixture, an orange
precipitate was observed and section filtration yielded 89 % with m.p. = 184–
186 °C. The IR spectra showed the following bands: two stretching strong
absorption bands at 1,712 and 1,642 cm-1 due to (2C=O, ring), 1,460–1,539 cm-1
(C=C, aromatic and alkene), 3,047–2,895 cm-1 (C–H, aromatic and alkene), in
addition to stretching frequency at 3,269 cm-1 (CH, chiral). 1H NMR clearly
showed d = 9.66 ppm (2H, CH, oxazepine rings), at d = 7, 25–7, 82 (m, 10H, Ar),
at d = 7.10–7.22 (m, 2H, Ar), d = 6.77–6.84 ppm (m, 2H, Ar), d = 6.18–
6.34 ppm (d, 2H, alkene), d = 6.59–6.68 ppm (d, 2H, alkene), at d = 2.81 ppm
(s, 4CH3–N–), and at d = 2.30 (s, 6H, 2CH3). Elemental analysis of the molecular
formula C40H38N4O6 of the compound w9m (calculated/found): C, 71.63/72.32; H,
5.71/6.37; N, 8.35/8.94.
Synthesis of 3,30-(3,30-dimethylbiphenyl-4,40-diyl)bis[2-(4-(diethylamino)phenyl)-
2,3-dihydro-1,3-oxazepine-4,7-dione] (w11m)
Reaction of 1 mmol (0.53) of compound w11 with 2 mmol (0.20 g) maleic
anhydride in dry THF added drop wise within N2 flow and stirring under refluxing
condition for about 3.3 h. After cooling the reaction mixture, an orange precipitate
was observed and section filtration yielded 55 % with m.p. = 190–192 °C. The IR
spectra showed the following bands: two stretching strong absorption bands at 1,716
and 1,640 cm-1 due to (2C=O, ring), 1,489–1,591 cm-1 (C=C, aromatic and
alkene), 3,027–2,847 cm-1 (C–H, aromatic and aliphatic), in addition to stretching
frequency at 3,275 cm-1 (CH, chiral). 1H NMR in DMSO–d6 clearly showed
d = 9.27 ppm (2H, CH, oxazepine rings), at d = 7.27–7.89 ppm (m, 14H, Ar),
6.33–6.79 ppm (d, 4H, alkene), at d = 2.12 ppm (s, 2CH3–Ar), at d = 2.50–2.720
(m, 8H, 4CH2–C), and at d = 0.85–1.23 ppm (t, 12H, 4CH3–C). Elemental analysis
of the molecular formula C44H46N4O6 of the compound w9m (calculated/found): C,
72.71/73.38; H, 6.38/6.96; N, 7.71/8.31.
Synthesis of 3,30-(3,30-dimethylbiphenyl-4,40-diyl)bis[2-(4-hydroxy-
3-methoxyphenyl)-2,3-dihydro-1,3-oxazepine-4,7-dione] (w12m)
Reaction of 1 mmol (0.48) of compound w12 with 2 mmol (0.20 g) maleic
anhydride in dry THF added drop wise within N2 flow and stirring under refluxing
condition for about 4 h. After cooling the reaction mixture, an orange precipitate
was observed and section filtration yielded 65 % with m.p. = 196–198 °C. The IR
spectra showed the following bands: two stretching strong absorption bands at 1,714
and 1,627 cm-1 due to (2C=O, ring), 1,448–1,570 cm-1 (C=C, aromatic and
alkene), 3,041–2,959 cm-1 (C–H, aromatic and aliphatic), in addition to stretching
frequency at 3,234 cm-1 (CH, chiral). 1H NMR in DMSO–d6 clearly showed
123

A. J. Mahrath et al.
d = 10.45 ppm (s, 2H, OH, phenolic rings), at d = 8.72 ppm (2H, chair, oxazepine
rings), at d = 7.97–7, 99 ppm (d, 2H, Ar), at d = 7.59–7.84 ppm (dd, 4H, Ar), at
d = 7. 49–7.59 ppm (d, 4H, Ar), at d = 6.31–6.35 and 6.48–6.52 ppm (d, d,
2CH=CH–, alkene), at d = 3.53 ppm (s, 6H, 2CH3–O–Ar), and at d = 2.28 ppm (s,
6H, 2CH3–Ar). Elemental analysis of the molecular formula C38H32N2O10 of the
compound w9m (calculated/found): C, 67.45/68.15; H, 4.77/5.31; N, 4.14/4.67.
With phthalic anhydride
Synthesis of 4,40-(3,30-dimethylbiphenyl-4,40-diyl)bis(3-phenyl-3,4 dihydrobenzo
[1,3] oxazepine-1,5-dione) (w9ph)
Reaction of 1 mmol (0.38 g) of compound w9 with 2 mmol (0.30 g) phthalic
anhydride in dry dioxan added drop wise within N2 flow and stirring under refluxing
condition for about 3.5 h. After cooling the reaction mixture, an oily product was
left, after work up with petroleum ether–hexane, a yellow precipitate was observed,
and section filtration yielded 51 % with m.p. = 278–280 °C. The IR spectra
showed the following bands: two stretching strong absorption bands at 1,699 and
1,637 cm-1 due to (2C=O, ring), 1,488–1,587 cm-1 (C=C, aromatic and alkene),
1
3,026–2,856 cm-1 (C–H, aromatic and alkene). H NMR clearly show a chemical
shift at d = 8.38 ppm (s, 3H, Ar), at d = 7.97 ppm (s, 2H, oxazepine ring), at
d = 7.52–7.58 ppm (m, 7H, Ar), at d = 7.12–7.18 ppm (m, 7H, Ar), at
d = 6.72–6.73 ppm (dd.6H, Ar), and at d = 2.36 (s, 6H, 2CH3). Elemental analysis
of the molecular formula C44H32N2O6 of the compound w9m (calculated/found): C,
77.18/77.72; H, 4.71/5.43; N, 4.09/4.65.
Synthesis of 4,40-(3,30-dimethylbiphenyl-4,40-diyl)bis[3-(4-dimethylaminophenyl)-
3,4-dihydrobenzo[1,3]oxazepine-1,5-dione] (w10ph)
Reaction of 1 mmol (0.47 g) of compound w10 with 2 mmol (0.30 g) phthalic
anhydride in dry CH2Cl2 added drop wise within N2 flow and stirring under
refluxing condition for about 5.0 h. After cooling, the reaction mixture was directly
precipitated, after work up with petroleum ether–hexane, a yellow precipitate was
observed, and section filtration yielded 65 % with m.p. = 146–148 °C. The IR
spectra showed two stretching strong absorption bands at 1,718 and 1,645 cm-1 due
to (2C=O, ring), 1,489–1,593 cm-1 (C=C, aromatic and alkene), 3,016–2,924 cm-1
(C–H, aromatic and alkene). 1H NMR clearly showed the formation of product by a
chemical shift at d = 9.78 ppm (s, 2H, charily), at d = 8.73 ppm (s, 2H, Ar), at
d = 7.97–7.99 ppm (d, 2H, Ar), at d = 7.59–7.79 ppm (m, 10H, Ar), at
d = 7.49–7.51 ppm (d, 4H, Ar), at d = 7.37–7.40 ppm (d.4H, Ar), at d = 3.49
(s, 12H, 4CH3–N), and at d = 2.27 ppm (s, 6H, 2CH3–Ar). Elemental analysis of
the molecular formula C48H42N4O6 of the compound w9m (calculated/found): C,
74.79/75.28; H, 5.49/6.04; N, 7.27/7.81.
123

Synthesis and spectroscopic studies
Synthesis of 4,40-(3,30-dimethylbiphenyl-4,40-diyl)bis(3-(4-(diethylamino)phenyl)-
3,4-dihydro benzo[1,3]oxazepine-1,5-dione) (w11ph)
Reaction of 1 mmol (0.53 g) of compound w11 with 2 mmol (0.30 g) phthalic
anhydride in dry THF added drop wise within N2 flow and stirring under refluxing
O
O
Hb
R2
R2
Ha
N
N
Hc
Ha
O
O
R1
R1
O
O
A=1,3-oxazepine-4,7-dione
B=benzo[1,3]oxazepine-1,5-dione
Fig. 1 Two types A and B of [1,3]oxazepine-dione
N
N
N
i
u
q
e
2
W 10
W 9
N
O
N
N
Ethanol/ Reflux 20-60 min
O
N
H 2
N
NH 2
N
O
O
OH
O
1 equi
N
N
HO
O
N
W 11
N
W 12
N
O
N
HO
Scheme 1 Condensation reaction of o-tolidine via aromatic aldehyde in the presence of absolute ethanol
and glacial acetic acid under refluxing condition
123

A. J. Mahrath et al.
Fig. 2
a
FT-IR of bis(4-(dimethylamino)benzylidene)-3,30-dimethylbiphenyl-4,40-diamine (w10),
b FT-IR of bis[3-methoxy-4-hydroxy benzylidene] 3,30-dimethylbiphenyl-4,40-diamine (w12
)
Fig. 3 a 1H NMR in DMSO–d6 of bis(4-(diethylamino)benzylidene)-3,30-dimethyl biphenyl-4,40-diamine
(w11), b 1H NMR in DMSO–d6 of bis[3-methoxy-4-hydroxy benzylidene] 3,30-dimethylbiphenyl-4,40-
diamine (w12
)
condition for about 6.0 h. After cooling, the reaction mixture was an oily product,
many attempts to solidify the product failed, after work up with hexane, some
precipitate was observed, and section filtration yielded 41 % with m.p. = °C. The
123

Synthesis and spectroscopic studies
O
O
O
O
O
N
N
O
O
N
N
O
O
O
O
O
O
O
O
O
O
O
N
N
N
W9
N
N
N
W10
1 equi
O
O
O
O
O
O
O
O
O
N
N
O
2 equi
O
N
N
N
O
O
N
N
O
O
O
O
N
O
Scheme 2 [2?5] Cycloaddition reactions of imine derivative (w9, w10) with maleic and phthalic
anhydride to afforded (w9m, w9ph, w10m, and w10ph)
IR spectra showed the following bands: two stretching strong absorption bands at
1,718 and 1,645 cm-1 due to (2C=O, ring), 1,481–1,595 cm-1 (C=C, aromatic and
alkene), 3,006–2,854 cm-1 (C–H, aromatic and alkene), and a strong absorption
1
band at 1,361 cm-1 (–C–N–) bond. H NMR clearly showed a chemical shift at
d = 9.73 ppm (s, 2H, charily), at d = 8.05–8.31 ppm (s, 2H, Ar), at d = 7.66–
7.87 ppm (m, 4H, Ar), at d = 7.55–7.58 ppm (d, 10H, Ar), at d = 7.27–7.39 ppm
(d.4H, Ar), at d = 6.92–7.02 ppm (d, 2H, Ar), at d = 3.13–3.20 ppm (m, 8H,
4CH2–C), at d = 2.35 ppm (s, 6H, 2CH3–Ar), and at d = 1.57–1.62 ppm (q, 12H,
4CH3–C). Elemental analysis of the molecular formula C52H50N4O6 of the
compound w9m (calculated/found): C, 75.52/76.16; H, 6.09/6.53; N, 6.77/7.29.
Synthesis of 4,40-(biphenyl-4,40-diyl)bis(3-(4-hydroxy-3-methoxyphenyl)-3,4-
dihydro benzo [1,3]oxazepine-1,5-dione) (w12ph)
Reaction of 1 mmol (0.48 g) of compound w12 with 2 mmol (0.30 g) phthalic
anhydride in dry THF added drop wise within N2 flow and stirring under refluxing
condition for about 3.5 h. After cooling, the reaction mixture was an oily product,
after work up with n-hexane, an orange-yellow precipitate was observed, and
section filtration yielded 45 % with m.p. = 185 °C. The IR spectra showed the
123

A. J. Mahrath et al.
O
N
O
O
N
O
O
N
O
N
N
N
O
O
O
reflux in THF
N
O
N
O
W
O
O
ph
O
O
O
O
O
N
1 equi
N
N
N
W11
O
N
HO
OH
O
N
W12
O
O
O
O
O
O
O
O
O
O
N
O
N
O
2 equi
O
O
O
N
O
HO
O
N
OH
O
OH
O
O
HO
O
O
12
Scheme 3 [2?5] Cycloaddition reaction of imine derivatives (w11, w12) with maleic and phthalic
anhydride to afforded (w11m, w11ph, w12m, and w12ph)
following bands: two stretching strong absorption bands at 1,697 and 1,658 cm-1
due to (2C=O, ring), 1,452–1,590 cm-1 (C=C, aromatic and alkene), 3,038–
2,926 cm-1 (C–H, aromatic and alkene), and a strong absorption band at
1
1,301 cm-1 (C–O–C). H NMR clearly showed a chemical shift at d = 9.93 ppm
(s, 2H, HO–phenolic), at d = 8.74 ppm (s, 2H, oxazepine ring), at d = 8.38 ppm
(d, 2H, Ar), at d = 7.65–7.94 ppm (t, 10H, Ar), at d = 7.35–7.52 ppm (dd.4H, Ar),
at d = 7.13 (s, 2H, Ar), at d = 6.93–7.06 ppm (s, 2H, Ar), at d = 3.35 ppm (s, 6H,
2CH3O–Ar), and at d = 2.35 ppm (s, 6H, 2CH3–Ar). Elemental analysis of the
molecular formula C46H36N2O10 of the compound w9m (calculated/found): C,
71.13/71.79; H, 4.67/5.16; N, 3.61/4.21.
Results and discussion
It’s well known that [1,3]oxazepine-4,7-dione or -1,5-dione (Fig. 10 are heterocy-
clic seven-membered rings containing nitrogen, oxygen, and two carbonyl groups.
When R1 and R2=H, the component (A) is known as 2,3-dihydro-1,3-oxazepine-
4,7-dione, whilst B is known as 3,4-dihydrobenzo1,3-oxazepine-1,5-dione. Many
researchers have investigated these types of heterocyclic compounds due to their
important class, which have a variety of biological applications [20–22]. In recent
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Synthesis and spectroscopic studies
Fig. 4
a
FT-IR of bis(4-(dimethylamino)benzylidene)-3,30-dimethylbiphenyl-4,40-diamine (w10),
b FT-IR of 3,30-(3,30-dimethylbiphenyl-4,40-diyl)bis[2-(4-hydroxy-3-methoxyphenyl)-2,3-dihydro-1,3-
oxazepine-4,7-dione] (w12m), c FT-IR of (3.2) synthesis of 4,40-(3,30-dimethylbiphenyl-4,40-diyl)bis[3-
(4-(dimethylamino)phenyl)-3,4-dihydrobenzo[1,3]oxazepine-1,5-dione] (w10ph)
years, great attention has been paid toward the formation of oxazepine rings [23,
24], due to the importance of these compounds as pharmaceutical drugs and in
biological systems. Our interest was in regard to the modification of oxazepine rings
throughout changes in R1 and R2 in the 2 and 3 positions, and these changes might
cause variations in their biologic applications. Therefore, we start to create an imine
derivative by using selective aldehyde with o-tolidine under condensation reactions
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A. J. Mahrath et al.
Fig. 5 a 1H NMR in DMSO–d6) bis[4-(dimethylamino)benzylidene]-3,30-dimethylbiphenyl-4,40-diamine
(w10), b1HNMRinDMSO–d6 of3,30-(3,30-dimethylbiphenyl-4,40-diyl)bis[2-(4-hydroxy-3-methoxyphenyl)-
2,3-dihydro-1,3-oxazepine-4,7-dione] (w12m), c 1H NMR in DMSO–d6 of 4,40-(biphenyl-4,40-diyl)bis(3-(4-
hydroxy-3-methoxyphenyl)-3,4-dihydro benzo [1,3]oxazepine-1,5-dione) (w12ph)
(Scheme 1). All the imines derivatives were monitored by TLC and identified by
1
FT-IR, H NMR, and elemental analysis, with recall to FT-IR spectra in the KBr
disk. In the first stage, the imines derivatives (w9–w12), which were formed by
condensation reactions, were proved according to the disappearance of –NH2
absorption bands in the range 3,465–3,250 cm-1, which belonged to asymmetric and
symmetric stretching frequencies and the appearance of the sharp (strong–medium)
123

Synthesis and spectroscopic studies
Fig. 6 The default structure of (w10m) compound in 3D view (blue color N, red color O, white color H).
(Color figure online)
intense azomethane (C=N–) group in the stretching frequency range at 1,606–
1,624 cm-1, as shown in Fig. 2a, b. On the other hand, 1H NMR in DMSO–d6 as a
solvent confirmed the generation of these compounds, as shown in Fig. 3a, b. For
compound w10, it is obvious that the methyl group appeared in triplet at
d = 2.35 ppm, and a sharp singlet peak appeared at d = 8.32 ppm, which belonged
to 2CH of azomethane groups. This proton was deshielded due to the effect
of nitrogen azomethane and aromatic ring. The rest of the signals at
d = 6.75–7.75 ppm refer to the aromatic protons with details. Also, elemental
analysis gave matching values for the calculated and found molecular formulas of
each compound. The second stage involved a coupling reaction between
azomethane group (imines derivatives) and two carbonyl groups throughout the
[2?5] cycloaddition reaction (concerted reaction) (Schemes 2 and 3). This type of
reaction afforded a seven-membered ring of 1,3-oxazepine-4,7-dione and 1,3-
oxazepine-1,5-dione derivatives (Fig. 1). These molecules are easily identified by
two major observations: firstly, in FT-IR data, two different stretching frequencies
of (C=O) groups in the oxazepine ring which appear at approximately 1,716 and
1,642 cm-1, respectively, and (CH, chiral) appears at C3,200 cm-1 (Fig. 4a, b0;
secondly, in 1H NMR, more than one proton can be distinguished: highly
deshielding proton (Fig. 1) (Ha) observed at a singlet peak at chemical shift
d C8.50 ppm and alkenes’ protons in the same Fig. 1 (Hb and Hc) in 1,3-oxazepine
4,7-dione observed at a lower chemical shift (as a doublet to doublet signal at
approximately d = 6.34–6.53 ppm) than aromatic protons (Fig. 5a–c) [25]. Also,
elemental analysis of the prepared compounds (w9m–w12m) and (w9ph–w12ph)
were in relative agreement with the calculated value. On the other hand, the
geometry of oxazepine derivatives were identified by the ChemDraw software
program, version 10.2008. The default structure of the w10m compound in Fig. 6 in
the 3D view shows the orientation of oxazepine rings in the perpendicular of plane
of symmetry of the biphenyl molecule, which give an indication that there is no
steric factor or hindrance between CH3 at the biphenyl molecule and protons of the
oxazepine ring.
123

A. J. Mahrath et al.
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