An easy synthetic protocol for imidazo-1,4-oxazines and evaluation of their toxicities

Article abstract of DOI:10.1002/hc.21412

Imidazo-1,5-alkynyl alcohol derivatives were synthesized, and they were cyclized to imidazo-1,4-oxazines by means of cesium carbonate. Propargyl-allene isomerization was examined, and the reaction mechanism was proposed. Moreover, cytotoxicity of synthesized molecules against LN405 cell lines was investigated by means of structure-activity relationship (SAR). With SAR study, toxicities of some functional groups have been shown. In addition, two lead compounds were tested against DNA damaging.

Full text of DOI:10.1002/hc.21412

Received: 18 November 2017
DOI: 10.1002/hc.21412
Revised: 26 January 2018
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R E S E A R C H A R T I C L E
An easy synthetic protocol for imidazo-1,4-oxazines and
evaluation of their toxicities
Burak Kuzu1,2
Hasan Genç3
Mehmet Taşpinar4
Meltem Tan1,2
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Nurettin Menges1,2
1Pharmaceutical Chemistry Section, Faculty
of Pharmacy, Van Yüzüncü Yil University,
Van, Turkey
2YYU TEKNOKENT, R&D Lab. SAFF
Chemical Reagent, Van, Turkey
3Faculty of Education, Van Yüzüncü Yıl
University, Van, Turkey
4School of Medicine, Van Yüzüncü Yil
University, Van, Turkey
Abstract
Imidazo-1,5-alkynyl alcohol derivatives were synthesized, and they were cyclized to
imidazo-1,4-oxazines by means of cesium carbonate. Propargyl-allene isomerization
was examined, and the reaction mechanism was proposed. Moreover, cytotoxicity of
synthesized molecules against LN405 cell lines was investigated by means of
structure-activity relationship (SAR). With SAR study, toxicities of some functional
groups have been shown. In addition, two lead compounds were tested against DNA
damaging.
Correspondence
Nurettin Menges and Meltem Tan,
Pharmaceutical Chemistry Section, Faculty
of Pharmacy, Van Yüzüncü Yil University,
Van, Turkey.
K E Y W O R D S
allene, COMET, cyclization of alkyne, heterocyclic compounds, SAR
Emails: nurettinmenges@yyu.edu.tr (N.M.);
meltemtan@yyu.edu.tr (M.T.)
Funding information
YYU-BAP, Grant/Award Number:
TAP-2016-5610 and TAP-2017-6092;
TÜBİTAK, Grant/Award Number: 115Z894
antibiotic, sold under the trade name Levaquin 2, and acorta-
tarin A 3 which is an inhibitor for the production of reactive
1
INTRODUCTION
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oxygen species (ROS)[2] include oxazine cores (Figure 1).
In a few decades, tremendous efforts have been de-
voted to the development of new, efficient, atom-
economic, and no-catalyst methods to achieve important
heterobicyclic molecules.[3b–e] One of these protocol cov-
ers 1,4-oxazine rings. There have been some synthetic
methods for 1,4-oxazines and its bicyclic derivatives
in the literature. Kerwin and coworkers have developed
The design and synthesis of desired and tolerable methods to
attain complex molecules from appropriate starting materi-
als are still challenging work for lots of scientific areas such
as modern synthetic and medicinal chemistry. The methods
which include synthesis of compounds containing nitrogen
and oxygen are of growing importance due to the importance
of some biological activities.[1a–c] Some important heterocy-
clic compounds such as antituberculosis agent 1 (PA-824),
Contract grant sponsor: Scientific and Technological Research Council of Turkey.
Contract grant number: 115Z894.
Contract grant sponsor: Van Yüzüncü Yil University Coordinator of Scientific Research Projects.
Contract grant number: TAP-2016-5610.
Contract grant number: TAP-2017-6092.
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Heteroatom Chemistry. 2018;e21412.
https://doi.org/10.1002/hc.21412
wileyonlinelibrary.com/journal/hc
© 2018 Wiley Periodicals, Inc.
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OCF3
O
N
O
O
O
HO
HO
F
OH
N
O
N
N
N
O2
O
N
O
N
O
H
1
3
2
FIGURE 1 Some important molecules which bear oxazine ring
Ar
Ar
OH
Ar
N
N
O
Ar
N
i
O
N
O
iii
ii
N
Ar
Ar
N
H
Ar
4a-j
5a-j
6a-j
7a-j
MeO
F
Br
MeO
MeO
S
a
c
e
h
g
b
d
f
Br
S
i
j
SCHEME 1 Obtaining of starting materials. (i): (1) SeO2, 1,4-dioxane, reflux, (2) NH4OAc, EtOH, rt. (ii) propargyl bromide, NaH, DMF,
0°C. (iii) NaBH4, MeOH, rt
a method for cyclization of 1,4-alkynyl alcohols using
metal catalyst to reach 1,4-oxazine-imidazole deriv-
atives.[3a] Wang et al[4] have reported a method for hy-
droalkoxylation of 1,5-alkynyl alcohols with NaH to get
1,4-oxazines. Muthusubramanian et al[5a] have published
a paper in which imidazolo-1,4-oxazine derivatives oc-
curred via hydroalkoxylation of 1,5-alkynyl alcohols
by lithium t-butoxide (t-BuOLi). On the other hand,
1,5-alkynyl alcohols were also utilized to synthesize
1,4-diazepinone-imidazole ring system via CuI.[5b] In
this study, we have utilized 1,5-alkynyl alcohols to form
1,4-oxazine-imidazole derivatives with safer base, cesium
carbonate. Formerly used bases such as NaH and t-BuOLi
are toxic and highly water-sensitive. To remove these dis-
advantages, we have synthesized 1,4-oxazine-imidazoles
using cesium carbonate in ethanol.
2
2.1
RESULTS AND DISCUSSION
Chemistry
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Propargylation of NH group and reduction in carbonyl group
at C-2 position of the imidazole ring gave starting materials
7a-j, and these molecules were used to furnish the imidazo-
1,4-oxazine derivatives (Scheme 1).
Another route that we have followed to take starting mate-
rials was acylation of the unsubstituted imidazole ring. This
reaction gave us the imidazole ring derivatized with benzoyl
at C-5 position (Scheme 2). Propargylation and reduction re-
actions were then applied to 10 resulting in N-propargylated
imidazole derivative 12.
Starting materials were attempted to be cyclized with
some of common catalysts and reagents such as AuCl3 and I2
which are well known for hydroalkoxylation in the literature

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O
N
N
N
N
i
ii
iii
+
O
O
OH
Ph
Cl
N
H
N
N
N
H
Ar
Ar
Ar
9
11
12
8
10
SCHEME 2 Another route for hydroalkoxylation of imidazole. (i) pyridine, NaOH, reflux, (ii) and (iii) NaBH4, MeOH, rt
Ph
Ph
I2, NaHCO3
CHCl3
OH
Ph
N
N
OH
Ph
AuCl3
N
N
NR
I
17
7a
SCHEME 3 Attempts for cyclization
I
of hydroalkoxylation
(Scheme 3).[6a–e] Unfortunately, gold (III) chloride did not
give any result. On the other hand, iodine gave a reaction with
alkyne unit to give compound 17.
that middle carbon (C-2), terminal carbon (C-3), and internal
carbon (C-1) resonated at 202.8, 87.4, and 98.1 ppm, respec-
tively (Figure 2). Allene protons between C-1 and C-3 pro-
tons have long-range couplings with 5.6 Hz. C-1 proton and
C-3 protons resonated at 8.22 and 5.62 ppm, respectively.[3c]
There are two possible reactions between allene unit and OH
group which are exo-dig and endo-dig cyclization. However,
the observed chemical shift of middle carbon gives informa-
tion to predict the selectivity of the cyclization reaction. NBO
charges are −0.087, 0.045, and −0.416 for C-1, C-2, and C-3,
respectively.[7] These values show that C-2 of allene unit is
the most reactive side (Figure 2).
The addition of various O-H nucleophiles to C-C multi-
ple bonds represents one of the great methods for preparing
such oxygen-containing heterocycles. However, due to so
many factors including the relatively high bond enthalpies of
most O-H σ-bonds and the modest reactivity of electron-rich
olefins with nucleophiles, an efficient intramolecular hydro-
functionalization reaction remains a challenge. Unfortunately,
poor nucleophilicity of OH group brings some challenges
to cyclize with multiple bonds. So, propargyl group should
be converted to a more reactive group so that cyclization of
propargyl group with OH takes place. Our previous studies
have uncovered that propargyl group can be isomerized to
allene, more reactive than propargyl against nucleophiles.[3c]
This strategy has been also used by Muthusubramanian[5]
and Wang[4] in which t-BuOLi and NaH have been applied.
These bases are hard, toxic, flammable, water-reactive and
corrosive. With these disadvantages, we have chosen cesium
carbonate as a base to convert the propargyl group into the
allene. This reactive intermediate (16a) was also isolated in
good yield (Scheme 4). Two cyclization routes were carried
out under basic condition. One of them was cyclization of
C-2-substituted N-propargylated imidazoles 7a-j(I), and the
other was C-5-substituted N-propargylated imidazole 12(II).
In both cases, we have achieved to form imidazo-1,4-oxazines
in good yields (Scheme 4). In the reaction pathway of I, we
could not isolate 15c which bears 3,4-dimethoxyphenyl rings.
This skeleton might be exposed to oxidation under open air.
Crude NMR data for 15c presented an unidentified mixture.
Allene is a very reactive molecule, and its reactivity can be
seen when analyzed its 13C-NMR spectrum. We have there-
fore isolated allene isomer 16a, and its NMR data showed
With this respect, we have proposed the reaction mecha-
nism as seen in Scheme 5.
Allene-propargyl isomerization occurred by a base (I).
Then, OH group attacks the most reactive carbon of the allene
unit to produce cyclic intermediate (II). Proton abstraction of
methylenic carbon gives imidazooxazine derivatives 15.
2.2
MTT assay: toxicity test and
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SAR studies
To evaluate the cytotoxicities with structure-activity relation-
ship (SAR), synthesized molecules were added into LN405
cell lines. As shown in Figure 3, we have chosen phenyl, sub-
stituted phenyl, its fused analogs, and thiophene derivatives.
We have first analyzed phenyl-substituted imidazo-1,4-
oxazine 13. It did not show any toxicity against LN405
cell lines. Then, we have observed that 15a was no ef-
fect on the cells, as well. After negative results, we have
wanted to check substituent effects and OMe, F, Br, and
Ph groups were selected. 4-Methoxy-substituted imidazo-
1,4-oxazine derivative 15b did present very little toxic ef-
fect. 4-Bromine-substituted derivative 15d decreased cell

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KUZU et al.
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SCHEME 4 Cyclization reaction with cesium carbonate
with F-bonding/interactions.[8–9] Such F-H hydrogen bonds,
π-interactions with aromatic or guanidine groups, multipolar
interactions, and/or F-nitrogen interactions (halogen bond-
ing) are reported.[8]
Biphenyl-substituted imidazo-1,4-oxazine 15f presented
the most toxicity of the selected compounds. This result
might indicate that π-π interactions have occurred in the hy-
drophobic packet resulting in the most toxicity. To understand
the limitations of a bulky phenyl group, we have analyzed the
toxicities of the naphthalene and the pyrene derivatives 15g
and 15j, respectively (Figure 3). Significant loss of toxicity
potency also occurred with the replacement of the biphenyl
moiety by one or more fused phenyl groups. This result might
point that the hydrophobic selectivity pocket might not have
enough space to bind a larger group or that the naphthalene
or pyrene group could not possess a conformation/orienta-
tion that could give maximal hydrophobic interactions. This
observation uncovered that bulky group and its orientation
might be important for exogen-protein interactions in the
studied skeleton.
Replacement of phenyl ring by thiophene, which is a het-
erocyclic aromatic ring having a donor atom, showed little
increase in the toxicity against the cells. While thiophene-
substituted imidazo-1,4-oxazine derivative 15h showed cell
viability down to 92%, cell viability of its brominated deriv-
ative 15i was calculated 96%. Probably, thiophene has hy-
drogen bonding interaction with protein in the packet which
might give more biological effect. Toxicity of brominated
thiophene 15i is lower than unsubstituted thiophene 15h.
FIGURE 2 NBO charges of allene carbon atoms of 16a (values
indicate NBO charges, and values in brackets indicate observed 13C-
NMR chemical shifts of those carbons)
viability up to 91%. 4-Fluorine-substituted compound 15e
decreased cell viability up to 77% (Figure 3). Fluorine is a
unique atom for drug design. Different types of interactions
between fluorine atoms and functional groups of proteins
which have not observed with the other halogens have been
reported. In addition, in biological environments, compounds
with a fluorine substituent behave more differently than
other halogen-substituted compounds.[8] An unusual effect
of the 4-fluorine-substituted compound 15e can be explained

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Ar
OH
Ar
Ar
Ar
Ar
N
N
Ar
N
N
N
N
N
N
Ar
Ar
O
base
H
OH
O
H
7
I
15
II
SCHEME 5 Proposed reaction mechanism
fluorine atom is an electronegative atom, and due to the
electronegativity of it, 15e might bind DNA easier than
the others. For this reason, it can be said that the cytotoxic
effect of 15e at 20 mmol L−1 might occur due to DNA
damaging.
120
100
80
60
100
97
To sum up, an atom-economic and safer method has been
revealed for imidazo-1,4-oxazines. In addition, reactive
intermediate, allene isomer, which is responsible for cy-
clization, was isolated. Moreover, theoretical NBO charges
of allene unit and observed NMR data were analyzed.
Allene isomer is more reactive than its propargyl isomer
and its middle carbon resonated at 202.8 ppm. With these
outcomes, a proposed reaction mechanism was plotted.
Furthermore, cytotoxicities of all synthesized molecules
were studied, and toxicities of some important functional
groups have been discussed. With SAR study, we uncov-
ered that phenyl ring at exact orientation is responsible for
higher toxicity against LN405 cell lines. Furthermore, fluo-
rine atom at the para position of phenyl ring exhibited also
genotoxicity which might be due to specific interactions
between guanidine ring and fluorine which are unique for
fluorine atom.
98
13
96
94
92
91
89
85
40
20
0
77
67
Control 15a
(0.01 %
DMSO)
15b
15d
15e
15f
15g
15h
15i
15j
FIGURE 3 Cytotoxicity against LN405 Cell lines after 72 h.
Numbers show percentage of cell viability at 20 mmol L−1 in DMSO
This might be due to the higher molecular refractivity of
15i than that of 15h that blocks the entering of the mole-
cule into the packet of protein effectively. Finally, we have
observed that all molecules which have a lower concentra-
tion of 20 mmol L−1 in DMSO did not present any toxicity
against LN405 cell lines. This outcome points out that those
molecules are safe at a mentioned concentration according to
toxicity tests.
3
EXPERIMENTAL
General
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2.3
COMET assay: genotoxicity tests
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3.1
|
MTT assay emerged some lead compounds, and we have
evaluated their genotoxicity effects against LN405 cell
lines. Lead compounds were chosen as 15e and 15f which
are the most toxic compounds against LN405 cell lines.
DNA-damaging effect of 15e and 15f was analyzed using
COMET assay. There was no statistically significant re-
sult between control and 15f in terms of DNA damage
(P = 0528). But, the statistical differences between con-
trol and 15e and between 15f and 15e in terms of DNA
damage effects in cells were determined (respectively,
P < 0001 and P < 0001). As a result, the cytotoxicity
effect of 15f at 20 mmol L−1 may not be due to DNA
damaging. Further investigations should be proceeded
to reveal how the cytotoxic effect of this compound at
20 mmol L−1 is displayed. On the other hand, 15e has two
fluorine atoms at the para position of the phenyl ring. The
All reagents used were commercially available unless other-
wise stated, and all solvents were used as received. A Varian
400 spectrometer was used to acquire 400 MHz 1H NMR and
100 MHz 13C NMR spectra. Chemical shifts are reported in
ppm relative to tetramethylsilane (TMS) in chloroform-d or
d6-DMSO. HRMS spectra were recorded using a THERMO
ITQ900 LC/MS spectrometer with ESI method. All spectro-
scopicanalysiswereconductedatVanYüzüncüYilUniversity,
Scientific Research and Application Center. Spectra of all syn-
thesized compounds was given in Supporting information.
3.2
General procedure for 6a-j and 11
|
Imidazole skeletons were synthesized following our pre-
vious article.[10] The imidazole derivatives (10 and 5a-j)

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(1 mmol) were dissolved in the dry DMF (15 mL), and NaH
(1.6 mmol) was added to the solution at 0°C. After the
solution was stirred for 30 minutes, propargyl bromide
(1.4 mmol) was added to the cooled solution. The reaction
was controlled by TLC and was ended. The mixture was
extracted with ethyl acetate (10 × 3 mL) and water (30 mL).
Then, organic layer was treated with anhydrous MgSO4.
Then, the ethyl acetate was evaporated, and the obtained
compound was purified with column chromatography (5:1,
hexane:ethyl acetate).
(m, 2H, Ar-H), 7.74 (s, 1H, Ar-H), 7.64-7.59 (m, 1H,
Ar-H), 7.55-7.51 (m, 2H, Ar-H), 7.45-7.40 (m, 2H, Ar-
H), 7.35-7.30 (m, 1H, Ar-H), 5.33 (d, J = 2.65 Hz, 2H,
CH2), 2.57 (t, J = 2.65 Hz, 1H, CH). 13C NMR (100 MHz,
CDCl3) δ = 183.6, 141.9, 141.8, 136.9, 133.1, 133.0,
131.3, 128.7, 128.1, 127.7, 125.3, 120.9, 77.1, 75.1,
38.7.
3.6
(4-Methoxyphenyl)[4-(4-
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methoxyphenyl)-1-(prop-2-yn-1-yl)-1H-
imidazol-2-yl]methanone (6b)
3.3
General procedure for 7a-j and 12
1
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Light yellow solid, m.p.: 83-85°C; yield: 76%. H NMR
(400 MHz, CDCl3) δ = 8.56-8.52 (m, AA′BB′ system, 2H,
H-15, H-19), 7.80-7.76 (m, AA′BB′ system, 2H, H-10, H-
14), 7.64 (s, 1H, H-2), 7.01-6.93 (m, AA′BB′ system, 4H,
Ar-H), 5.33 (d, J22,24 = 2.58 Hz, 2H, H-22), 3.89 (s, 3H,
OMe), 3.83 (s, 3H, OMe), 2.54 (t, J22,20 = 2.58 Hz, 1H, H-
22). 13C NMR (100 MHz, CDCl3) δ = 182.0, 163.6, 159.2,
142.0, 141.5, 133.7, 129.8, 126.5, 126.0, 119.5, 114.0,
113.4, 77.3, 74.8, 55.5, 55.3, 38.5.
The obtained propargylated imidazole derivatives (11 and
6a-i) (1 mmol) were dissolved in ethanol, and NaBH4
(2 mmol) was added to the solution at room temperature.
The solution was stirred for 2 hours, and the reaction com-
pletion was controlled by TLC. After completion of the re-
action, water (20 mL) was added to reaction flask. Then, the
obtained solid compound was dried at room temperature.
The solid compound was used for next step without any
purification.
Note: Compound 7j was not isolated because of some
unidentified impurities (further cyclization reaction was pro-
gressed in the reaction mixture, See section 3.4)
3.7
(3,4-Dimethoxyphenyl)[4-(3,4-
|
dimethoxyphenyl)-1-(prop-2-yn-1-yl)-1H-
imidazol-2-yl]methanone (6c)
Yellow solid, m.p.: 91-93°C; yield: 81%. 1H NMR
(400 MHz, CDCl3) δ = 8.29 (dd, J15,16 = 2.01 Hz,
J15,19 = 8.43 Hz, 1H, H-15), 8.14 (d, J19,15 = 2.01 Hz, 1H,
H-19), 7.65 (s, 1H, H-2), 7.40 (d, J14,10 = 1.97 Hz, 1H, H-
14), 7.36 (dd, J10,14 = 1.97 Hz, J11,10 = 8.25 Hz, 1H, H-10),
6.96 (d, J = 8.43 Hz, 1H, h-16), 5.32 (d, J22,24 = 2.58 Hz,
2H, H-20), 3.97 (s, 3H, OMe), 3.96 (s, 3H, OMe), 3.94 (s,
3H, OMe), 3.90 (m, 3H, OMe), 2.54 (t, J24,22 = 2.58 Hz,
1H, H-24). 13C NMR (100 MHz, CDCl3) δ = 181.7, 153.4,
149.1, 148.7, 148.3, 142.0, 141.5, 129.6, 126.6, 117.8,
113.4, 111.3, 110.0, 108.4, 77.2, 74.8, 56.1, 56.0, 55.9,
55.8, 38.6. HRMS (ESI) (M + H): C23H23N2O5: 407.1607,
found: 407.1600.
3.4
General procedure for 15a-j and 13
|
N-propargylated C-2- and C-4-substituted imidazole deriva-
tive (12 and 7a-i) (1 mmol) was dissolved in ethanol (5 mL),
and Cs2CO3 (1 mmol) was added to this solution. Then, the
mixture was refluxed for 2 hours. Then, completion of the
reaction was controlled by TLC. After that, the reaction was
extracted with ethyl acetate (10 × 3 mL) and water (20 mL).
The organic layer was dried with MgSO4, and organic phase
was evaporated. Viscous liquid was washed with diethyl
ether to get final product.
For 15j: Compound 6j (1 mmol) was reacted with
NaBH4 (2 mmol) in ethanol (10 mL) and after completion
of the reaction, judged by TLC, Cs2CO3 (1 mmol) was
added to the reaction mixture. Then, the reaction medium
was heated at reflux temperature of ethanol. Crude prod-
uct was concentrated under vacuum and was extracted with
ethyl acetate (10 × 3 mL) and water (20 mL). The organic
layer was dried with MgSO4, and organic phase was evap-
orated. Viscous liquid was washed with diethyl ether to get
final product.
3.8
(4-Bromophenyl)[4-(4-bromophenyl)-1-
|
(prop-2-yn-1-yl)-1H-imidazol-2-yl]methanone
(6d)
Yellow solid, m.p.: 140-141°C; yield: 85%. 1H NMR
(400 MHz, CDCl3) δ = 8.36-8.33 (m, AA′BB′ system,
2H, Ar-H), 7.77 (s, 1H, H-2), 7.72-7.69 (m, AA′BB′ sys-
tem, 2H, Ar-H), 7.67-7.64 (m, 2H, Ar-H), 7.54-7.51 (m,
AA′BB′ system, 2H, Ar-H), 5.35 (d, J22,24 = 2.59 Hz,
2H, H-22), 2.58 (t, J24,22 = 2.59 Hz, 1H, H-24). 13C NMR
(100 MHz, CDCl3) δ = 182.3, 141.7, 140.9, 135.5, 132.8,
131.8, 131.4, 128.5, 126.7, 121.6, 121.1, 76.7, 75.4,
38.9.
3.5
Phenyl[4-phenyl-1-(prop-2-yn-1-yl)-
|
1H-imidazol-2-yl]methanone (6a)
Yellow solid, m.p.: 95-97°C; yield: 71%. 1H NMR
(400 MHz, CDCl3) δ = 8.51-8.49 (m, 2H, Ar-H), 7.87-7.85

KUZU et al.
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H-5), 7.25 (dd, J2,5 = 1.17 Hz, J2,1 = 5.06 Hz, 1H, H-2), 7.16
(dd, J16,17 = 3.88 Hz, J16,15 = 4.93 Hz, 1H, H-16), 7.04 (dd,
J1,5 = 3.57 Hz,J1,2 = 5.06 Hz,1H,H-1),5.30(d,J18,20 = 2.61 Hz,
2H, H-18), 2.55 (t, J20,18 = 2.61 Hz, 1H, H-20). 13C NMR
(100 MHz, CDCl3) δ = 174.5, 141.5, 140.7, 137.1, 136.7, 136.6,
135.9, 128.0, 127.7, 124.5, 123.1, 120.3, 76.8, 75.3, 38.6.
3.9
(4-Fluorophenyl)[4-(4-fluorophenyl)-1-
|
(prop-2-yn-1-yl)-1H-imidazol-2-yl]methanone
(6e)
Yellow solid, m.p.: 110-111°C; yield: 93%. 1H NMR
(400 MHz, CDCl3) δ = 8.57-8.52 (m, AA′BB′ system,
2H, Ar-H), 7.83-7.71 (m, AA′BB′ system, 2H, Ar-H),
7.71 (s, 1H, H-2), 7.21-7.15 (m, 2H, Ar-H), 7.13-7.07
(m, AA′BB′ system 2H, Ar-H), 5.34 (d, J22,24 = 2.61 Hz,
2H, H-22), 2.57 (t, J24,22 = 2.61 Hz, 1H, H-24). 13C NMR
(100 MHz, CDCl3) δ = 181.8, 167.1, 164.6, 163.7, 161.2,
141.7, 141.0, 134.1, 134.0, 133.1, 133.0, 129.2, 129.1,
126.9, 126.8, 120.5, 115.7, 115.5, 115.4, 115.1, 76.9, 75.2,
38.8.
3.13
(5-Bromothiophen-2-yl)[4-(5-
|
bromothiophen-2-yl)-1-(prop-2-yn-1-yl)-1H-
imidazol-2-yl]methanone (6i)
Orange solid, m.p.: 157-159°C; yield: 74%. 1H NMR
(400 MHz, CDCl3) δ = 8.18 (d, J14,15 = 4.15, 1H, H-14),
7.59 (s, 1H, H-7), 7.15 (d, J15,14 = 4.15 Hz, 1H, H-15),
7.09 (d, J5,1 = 3.82 Hz, 1H, H-5), 7.01 (d, J1,5 = 3.82 Hz,
1H, H-1), 5.34 (d, J20,22 = 2.58 Hz, 2H, H-20), 2.57 (t,
J22,20 = 2.58 Hz, 1H, H-22). 13C NMR (100 MHz, CDCl3)
δ = 172.9, 141.6, 140.3, 138.1, 136.4, 136.3, 130.8, 130.5,
125.7, 123.2, 120.2, 111.6, 76.3, 75.6, 38.6. HRMS (ESI)
(M + H): C15H9Br2N2OS2: 454.8523, found: 454.8518.
3.10
(1,1′-Biphenyl]-4-yl)[4-(1,1′-biphenyl-
|
4-yl)-1-(prop-2-yn-1-yl)-1H-imidazol-2-yl]
methanone (6f)
1
Light brown solid, m.p.: 160-162°C; yield: 71%. H NMR
(400 MHz, CDCl3) δ = 8.62-8.59 (m, AA′BB′ 2H, Ar-H),
7.98-7.94 (m, AA′BB′ system, 2H, Ar-H), 7.83 (s, 1H,
H-2), 7.78-7.75 (m, AA′BB′ system, 2H, Ar-H), 7.71-
7.64 (m, 6H, Ar-H), 7.52-7.36 (m, 6H, Ar-H), 5.40 (d,
J32,34 = 2.60 Hz, 2H, H-32), 2.59 (t, J34,32 = 2.60 Hz, 1H,
H-34). 13C NMR (100 MHz, CDCl3) δ = 183.1, 145.6,
142.1, 141.5, 140.7, 140.3, 140.1, 135.6, 132.1, 131.9,
128.9, 128.8, 128.2, 127.4, 127.3, 127.2, 127.0, 126.8,
125.7, 120.9, 77.2, 75.2, 38.8.
3.14
[1-(Prop-2-yn-1-yl)-4-(pyren-2-yl)-1H-
|
imidazol-2-yl](pyren-2-yl)methanone (6j)
1
Light brown solid, m.p.: 194-196°C; yield: 64%. H NMR
(400 MHz, CDCl3) δ = 8.88 (d, J = 9.35 Hz, 1H, Ar-H), 8.61-
8.54 (m, 2H, Ar-H), 8.44-8.23 (m, 10H, Ar-H), 8.15-8.12 (m,
2H, Ar-H), 8.10 (bs, 2H, Ar-H), 8.01-7.94 (m, 2H, Ar-H), 5.68
(d, J = 2.49 Hz, 2H, CH2), 3.71 (t, J = 2.49 Hz, 1H, CH). 13
C
NMR (100 MHz, CDCl3) δ = 186.8, 143.4, 141.7, 133.3, 132.9,
131.3, 131.1, 130.7, 130.6, 130.5, 129.7, 129.2, 129.1, 128.0,
127.8, 127.7, 127.3, 127.2, 126.8, 126.7, 126.5, 125.4, 125.3,
124.9, 124.7, 124.3, 124.2, 124.0, 79.2, 77.2, 38.8. HRMS (ESI)
(M + H): C36H23N2O: 499.1810, found: 499.1827.
3.11
Naphthalen-2-yl[4-(naphthalen-
|
2-yl)-1-(prop-2-yn-1-yl)-1H-imidazol-2-yl]
methanone (6g)
Viscous liquid, brown color. Yield: 79%. 1H NMR (400 MHz,
CDCl3) δ = 9.25 (s, 1H, Ar-H), 8.44 (dd, J = 1.71, 8.64 Hz,
1H, Ar-H), 8.37 (s, 1H, Ar-H), 8.06 (d, J = 8.05 Hz, 1H, Ar-
H), 8.01-7.96 (m, 2H, Ar-H), 7.93-7.89 (m, 4H, Ar-H), 7.86-
7.84 (m, 1H, Ar-H), 7.65-7.56 (m, 2H, Ar-H), 7.52-7.45
(m, 2H, Ar-H), 5.41 (d, J10,12 = 2.58 Hz, 2H, H-10), 2.60 (t,
J12,10 = 2.58 Hz, 1H, H-12). 13C NMR (100 MHz, CDCl3)
δ = 183.5, 142.3, 141.8, 135.6, 134.2, 134.1, 133.6, 133.0,
132.4, 130.5, 130.1, 128.6, 128.4, 128.2, 127.9, 127.8, 127.7,
126.5, 126.3, 126.2, 123.7, 123.6, 121.2,76.7, 75.2, 38.8.
3.15
Phenyl[4-phenyl-1-(prop-2-yn-1-yl)-
|
1H-imidazol-2-yl]methanol (7a)
1
Light brown solid, m.p.: 130-132°C; yield: 95%. H NMR
(400 MHz, d6-DMSO) δ = 7.74-7.65 (m, 3H, Ar-H), 7.37-7.18
(m, 8H, Ar-H), 6.44 (bs, 1H, OH), 5.96 (bs, 1H, CH-O), 4.90
(d, J = 17.76 Hz, AB system, 1H, CH2), 4.49 (d, J = 17.76 Hz,
AB system, 1H, CH2), 2.48 (bs, 1H, CH). 13C NMR (100 MHz,
d6-DMSO) δ = 149.1, 141.9, 139.1, 134.5, 128.9, 128.5, 127.6,
126.8, 126.5, 124.7, 117.3, 78.8, 76.5, 68.7, 35.7.
3.12
[1-(Prop-2-yn-1-yl)-4-(thiophen-2-yl)-
|
1H-imidazol-2-yl](thiophen-2-yl)methanone
(6h)
3.16
(4-Methoxyphenyl)[4-(4-
|
methoxyphenyl)-1-(prop-2-yn-1-yl)-1H-
imidazol-2-yl]methanol (7b)
Brown solid, m.p.: 100-102°C; yield: 80%. 1H NMR (400 MHz,
CDCl3) δ = 8.58 (dd, J17,15 = 1.23 Hz, J17,16 = 3.88 Hz, 1H,
H-17), 7.71 (dd, J15,17 = 1.23 Hz, J15,16 = 4.93 Hz, 1H, H-15),
7.57 (s, 1H, H-7), 7.34 (dd, J5,2 = 1.17 Hz, J5,1 = 3.57 Hz, 1H,
White solid, m.p.: 150-152°C; yield: 94%. 1H NMR
(400 MHz, d6-DMSO) δ = 7.65-7.63 (m, AA′BB′ system,
2H, Ar-H), 7.50 (s, 1H, H-2), 7.28-7.26 (m, AA′BB′ system,

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2H, Ar-H), 6.90-6.87 (m, 4H, Ar-H), 6.30 (bs, 1H, H-6), 5.87
(s, 1H, H-9), 4.86 (dd, J22,24 = 2.53 Hz, J22,22 = 17.79 Hz,
1H, AB system, H-22), 4.75 (dd, J = 2.54 Hz, 17.79 Hz, 1H,
AB system, H-22), 3.73 (s, 3H, OMe), 3.71 (s, 3H, OMe),
3.39 (t, J24,22 = 2.53 Hz, 1H, H-24). 13C NMR (100 MHz, d6-
DMSO) δ = 158.8, 158.3, 149.0, 139.1, 134.1, 127.7, 127.4,
125.9, 115.9, 114.3, 113.9, 79.0, 76.4, 68.4, 55.5, 55.4 35.5.
128.6 (d, J = 8.20 Hz), 126.5 (d, J = 7.91 Hz), 117.2, 115.7
(J = 21.39 Hz), 115.2 (J = 21.35 Hz), 78.8, 76.5, 68.0, 35.6.
3.20
(1,1′-Biphenyl-4-yl)[4-(1,1′-biphenyl-
|
4-yl)-1-(prop-2-yn-1-yl)-1H-imidazol-2-yl]
methanol (7f)
Light yellow solid, m.p.: 149-152°C; yield: 91.3%. 1H NMR
(400 MHz, d6-DMSO) δ = 7.83-7.80 (m, 2H, Ar-H), 7.66-
7.64 (m, AA′BB′ system, 4H, Ar-H), 7.59-7.56 (m, AA′BB′
system, 4H, Ar-H), 7.48-7.41 (m, 6H, Ar-H), 7.35-7.30 (m,
2H, Ar-H), 7.30 (s, 1H, H-10), 6.21 (bs, 1H, H-7), 4.47
(dd, J10,12 = 2.57 Hz, J10,10 = 17.78 Hz, 1H, H-10), 4.38
(dd, J10,12 = 2.57 Hz, J10,10 = 17.78 Hz, 1H, H-10), 2.24 (t,
J12,10 = 2.57 Hz, H-34).13C NMR (100 MHz, d6-DMSO)
δ =148.8, 140.8, 140.7, 140.6, 139.6, 139.1, 138.9, 132.4,
128.8, 128.7, 127.4, 127.3, 127.3, 127.2, 127.1, 126.9, 126.6,
125.2, 116.4, 76.4, 74.4, 68.9, 35.9.
3.17
(3,4-Dimethoxyphenyl)[4-(3,4-
|
dimethoxyphenyl)-1-(prop-2-yn-1-yl)-1H-
imidazol-2-yl]methanol (7c)
White solid, m.p.: 178-180°C; yield: 88%. 1H NMR (400 MHz,
CDCl3) δ = 7.33 (d, J14,10 = 1.83 Hz, 1H, H-19), 7.24 (dd,
J14,10 = 1.83 Hz, J11,10 = 8.27 Hz, 1H, AB system, H-16), 7.18
(s, 1H, H-2), 6.89-6.77 (m, 4H, Ar-H), 5.99 (s, 1H, H-6), 4.38
(dd, J22,24 = 2.54 Hz, J22,22 = 17.78 Hz, 1H, AB system, H-
22), 4.31 (dd, J = 2.54 Hz, 17.78 Hz, 1H, AB system, H-22),
3.95 (s, 3H, OMe), 3.89 (s, 3H, OMe), 3.84 (s, 3H, OMe), 3.78
(s, 3H, OMe), 2.30 (t, J24,22 = 2.54 Hz, 1H, H-24). 13C NMR
(100 MHz, CDCl3) δ = 149.1, 149.0, 148.6, 148.5, 148.1,
139.3, 132.5, 126.6, 118.5, 117.1, 115.4, 111.2, 110.9, 109.3,
108.3, 76.5, 74.3, 68.8, 55.9 (2C), 55.8 (2C), 35.8. HRMS
(ESI) (M + H): C23H25N2O5: 409.1763, found: 409.1751.
3.21
Naphthalen-2-yl[4-(naphthalen-2-yl)-
|
1-(prop-2-yn-1-yl)-1H-imidazol-2-yl]methanol
(7g)
Light brown solid, m.p.: 199-202°C; yield: 94.1%. 1H NMR
(400 MHz, d6-DMSO) δ = 8.28 (bs, 1H, Ar-H), 7.99 (bs, 1H,
Ar-H), 7.94-7.83 (m, 8H, Ar-H), 7.53-7.39 (m, 5H, Ar-H),
6.66 (d, J9,7 = 4.20 Hz, 1H, H-9), 6.20 (d, J7,9 = 4.20 Hz, 1H,
H-7), 5.01 (dd, J10,12 = 2.54 Hz, J10,10 = 17.80 Hz, 1H, AB
system, H-10), 4.88 (dd, J10,12 = 2.54 Hz, J10,10 = 17.80 Hz,
1H, AB system, H-10), 3.41 (t, J12,10 = 2.54 Hz, 1H, H-12).
13C NMR (100 MHz, d6-DMSO) δ = 149.3, 139.5, 139.2,
133.8, 133.2, 132.8, 132.4, 128.4, 128.2, 128.1, 128.0, 127.9,
126.7, 126.6, 126.3, 125.2, 124.6, 123.9, 122.3, 118.2, 78.9,
76.7, 68.9, 35.9.
3.18
(4-Bromophenyl)[4-(4-bromophenyl)-1-
|
(prop-2-yn-1-yl)-1H-imidazol-2-yl]methanol (7d)
1
Light yellow solid, m.p.: 187-189°C; yield: 82%. H NMR
(400 MHz, d6-DMSO) δ = 7.50-7.44 (m, AA′BB′ system,
4H, Ar-H), 7.43-7.40 (m, AA′BB′ system, 2H, Ar-H), 7.22-
7.18 (m, 2H, Ar-H), 7.17 (s, 1H, H-2), 5.99 (bs, 1H, H-7),
4.44 (dd, J22,24 = 2.59 Hz, J22,22 = 17.77 Hz, 1H, AB system,
H-22), 4.26 (dd, J22,24 = 2.59 Hz, J22,22 = 17.77 Hz, 1H, AB
system, H-22), 2.26 (t, J24,22 = 2.59, 1H, H-24). 13C NMR
(100 MHz, d6-DMSO) δ = 148.9, 141.3, 138.0, 131.8, 131.4,
128.9, 126.7, 120.8, 119.6, 118.1, 78.7, 76.7, 67.9, 35.7.
3.22
[1-(Prop-2-yn-1-yl)-4-(thiophen-2-yl)-
|
1H-imidazol-2-yl](thiophen-2-yl)methanol (7h)
Brown solid, m.p.: 145-146°C; yield: 80%. 1H NMR
(400 MHz, d6-DMSO) δ = 7.57 (s, 1H, H-7), 7.47 (dd,
J15,17 = 1.26 Hz, J15,16 = 5.05 Hz, 1H, H-15), 7.34 (dd,
J2,5 = 1.16, J2,1 = 5.06, 1H, H-2), 7.28 (dd, J5,2 = 1.16 Hz,
J5,1 = 3.52 Hz, 1H, H-5), 7.02 (dd, J1,5 = 3.52 Hz,
J1,2 = 5.06 Hz, 1H, H-1), 6.96 (dd, J16,17 = 3.51 Hz,
J16,15 = 5.06 Hz, 1H, H-16), 6.86 (dt, J17,15 = 1.26 Hz,
J17,16 = 3.52 Hz, 1H, H-17), 6.74 (d, J11,13 = 4.4 Hz,
1H, H-3), 6.13 (d, J11,13 = 4.4 Hz, 1H, H-11), 4.94 (dd,
J18,20 = 2.56, 17.78 Hz, 1H, AB system, H-18), 4.85 (dd,
J18,20 = 2.56, 17.78 Hz, 1H, AB system, H-18), 3.45 (t,
J20,18 = 2.56 Hz, 1H, H-20). 13C NMR (100 MHz, d6-
DMSO) δ = 148.1, 145.9, 138.4, 134.8, 128.1, 127.1,
126.1, 124.8, 123.9, 122.0, 116.6, 78.7, 76.7, 65.7, 35.9.
3.19
(4-Fluorophenyl)[4-(4-fluorophenyl)-
|
1-(prop-2-yn-1-yl)-1H-imidazol-2-yl]methanol
(7e)
1
Light orange solid, m.p.: 150-152°C, yield: 96%. H NMR
(400 MHz, d6-DMSO) δ = 7.76-7.73 (m, AA′BB′ system,
2H, Ar-H), 7.65 (s, 1H, H-2), 7.42-7.39 (m, AA′BB′ system,
2H, Ar-H), 7.18-7.12 (m, 4H, AA′BB′ system, Ar-H), 6.48 (d,
J6,9 = 4.92 Hz, 1H, H-6), 5.95 (d, J9,6 = 4.92 Hz, 1H, H-9), 4.91
(dd, J22,24 = 2.55 Hz, J22,22 = 17.83, 1H, AB system, H-22),
4.82 (dd, J22,24 = 2.55 Hz, J22,22 = 17.83, 1H, AB system, H-
22), 3.40 (t, J24,22 = 2.55 Hz, 1H, H-24). 13C NMR (100 MHz,
d6-DMSO) δ = 162.8 (d, J = 38.3 Hz), 160.4 (d, J = 38.2 Hz),
149.0, 138.4, 138.2 (d, J = 2.97 Hz), 131.1 (d, J = 2.93 Hz),

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δ = 142.5, 141.7, 139.1, 134.9, 133.8, 131.1, 128.9, 127.7,
126.7, 125.6, 123.3, 111.1, 102.0, 75.7, 17.5.
3.23
(5-Bromothiophen-2-yl)[4-(5-
|
bromothiophen-2-yl)-1-(prop-2-yn-1-yl)-1H-
imidazol-2-yl]methanol (7i)
3.27
2,8-Bis(4-methoxyphenyl)-6-methyl-
Viscous liquid dark brown, yield: 92%. 1H NMR (400 MHz,
CDCl3) δ = 7.15 (s, 1H, H-7), 6.95 (d, J = 3.83, 1H, Ar-H),
6.94 (d, J = 3.8 0 Hz, 1H, Ar-H), 6.85 (d, J15,14 = 3.80 Hz,
1H, H-15), 6.46 (dd, J14,16 = 1.32 Hz, J14,15 = 3.79 Hz,
1H, H-14), 6.03 (d, J11,12 = 1.32 Hz, 1H, H-11), 4.68 (dd,
J20,22 = 2.61 Hz, J20,20 = 17.81 Hz, 1H, H-20), 4.5 (dd,
J20,22 = 2.61 Hz, J20,20 = 17.81 Hz, 1H, H-20), 2.38 (t,
J22,20 = 2.61 Hz, 1H, H-22). 13C NMR (100 MHz, CDCl3)
δ=147.2, 145.2, 137.5, 133.7, 130.4, 129.7, 124.7, 122.9,
116.3, 112.7, 110.4, 75.9, 75.0, 65.8, 36.4. HRMS (ESI)
(M + H): C15H11Br2N2OS2: 456.8680, found: 456.8666.
|
8H-imidazo[2,1-c][1,4]oxazine (15b)
Brown solid, m.p.: 126-128°C; yield: 80%. 1H NMR
(400 MHz, CDCl3) δ = 7.71-7.67 (m, 2H, AA′BB′, Ar-H),
7.30-7.26 (m, 2H, AA′BB′ system, Ar-H), 7.08 (s, 1H, H-
2), 6.92-6.86 (m, 4H, Ar-H), 6.31 (bs, 1H, H-6), 6.25 (d,
J22,24 = 1.20, 1H, H-22), 3.82 (s, 3H, OMe), 3.79 (s, 3H,
OMe), 1.87 (d, J24,22 = 1.20, 3H, H-24). 13C NMR (100 MHz,
CDCl3) δ = 159.9, 158.6, 142.2, 141.5, 138.9, 129.7, 128.8,
126.7, 126.1, 113.9, 113.8, 109.5, 101.8, 75.3, 55.3, 55.2,
17.4.
3.24
Phenyl[1-(prop-2-yn-1-yl)-1H-
3.28
2,8-Bis(4-bromophenyl)-6-methyl-8H-
|
|
imidazol-5-yl]methanone (11)
imidazo[2,1-c][1,4]oxazine (15d)
Brown viscous liquid, yield: 89%. 1H NMR (400 MHz,
CDCl3) δ = 8.28-8.26 (m, 2H, Ar-H), 7.60-7.56 (m, 1H, Ar-
H), 7.50-7.47 (m, 3H, Ar-H), 7.28 (d, J = 1.04 Hz, 1H, Ar-
H), 5.33 (d, J7,9 = 2.61 Hz, 2H, H-7), 2.53 (t, J9,7 = 2.61 Hz,
1H, H-9). 13C NMR (100 MHz, CDCl3) δ = 184.2, 142.2,
137.0, 132.9, 130.9, 130.8, 129.6, 128.1, 124.9, 76.9, 74.9,
38.5. HRMS (ESI) (M + H): C13H11N2O: 211.0871, found:
211.0869.
Light red solid, m.p.: 155-157°C; yield: 65%. 1H NMR
(400 MHz, CDCl3) δ = 7.62-7.58 (m, 2H, AA′BB′ system,
Ar-H), 7.52-7.45 (m, 4H, AA′BB′ system, Ar-H), 7.27-7.24
(m, 2H, AA′BB′ system, Ar-H), 7.16 (s, 1H, H-2), 6.29
(bs, 1H, H-7), 6.25 (q, J32,34 = 1.18 Hz, 1H, H-22), 1.90 (d,
J34,32 = 1.18 Hz, 3H, H-34). 13C NMR (100 MHz, CDCl3)
δ = 142.6, 140.8, 138.6, 136.3, 132.6, 131.7, 131.6, 129.2,
128.9, 126.5, 126.4, 123.0, 120.6, 110.8, 101.9, 74.8, 17.4.
3.25
Phenyl[1-(prop-2-yn-1-yl)-1H-
3.29
2,8-Bis(4-fluorophenyl)-6-methyl-8H-
|
|
imidazol-5-yl]methanol (12)
imidazo[2,1-c][1,4]oxazine (15e)
Light brown viscous liquid, yield: 93%. 1H NMR (400 MHz,
CDCl3) δ = 7.31 (d, J = 4.35 Hz, 4H, Ar-H), 7.26 (t,
J = 4.35 Hz, 1H, Ar-H), 7.01 (d, J1,4 = 1.34 Hz, 1H, H-
1), 6.84 (d, J4,1 = 1.34 Hz, 1H, H-4), 5.96 (bs, 1H, H-6),
4.69 (dd, J7,9 = 2.60 Hz, J7,7 = 17.75 Hz, 1H, H-7), 4.37
(dd, J7,9 = 2.60 Hz, J7,7 = 17.75 Hz, 1H, H-7), 2.29 (t,
J9,7 = 2.60 Hz, 1H, H-9). 13C NMR (100 MHz, CDCl3)
δ = 148.6, 140.4, 128.4, 127.5, 126.5, 126.0, 120.4, 74.1,
68.8, 35.7. HRMS (ESI) (M + H): C13H13N2O: 213.1028,
found: 213.1019.
Red solid, m.p.: 96-98°C; yield: 83.4%. 1H NMR (400 MHz,
CDCl3) δ = 7.71-7.68 (m, 2H, AA′BB′ system, Ar-H), 7.39-
7.35 (m, 2H, AA′BB′ system, Ar-H), 7.13 (s, 1H, H-2), 7.07-
7.02 (m, 4H, AA′BB′ system, Ar-H), 6.34 (bs, 1H, H-6), 6.28
(q, J22,24 = 1.22 Hz, 1H, H-22), 1.90 (d, J24,22 = 1.22, 3H, H-
24). 13C NMR (100 MHz, CDCl3) δ = 164.2, 163.2, 161.7,
160.8, 142.5, 140.9, 138.8, 133.1, 129.9, 129.2, 126.5, 115.6,
115.4, 110.3, 101.9, 74.8, 17.4.
3.30
2,8-Di(1,1′-biphenyl-4-yl)-6-methyl-
|
8H-imidazo[2,1-c][1,4]oxazine (15f)
3.26
6-Methyl-2,8-diphenyl-8H-
|
White solid, m.p.: 224-226°C; yield: 81%. 1H NMR
(400 MHz, CDCl3) δ = 7.86-7.84 (m, 2H, AA′BB′ sys-
tem, Ar-H), 7.65-7.61 (m, 6H, AA′BB′ system, Ar-H),
7.60-7.57 (m, 3H, Ar-H), 7.51-7.48 (m, 2H, Ar-H), 7.48-
7.44 (m, 2H, Ar-H), 7.44-7.42 (m, 1H, Ar-H), 7.37-7.33
(m, 2H, Ar-H), 7.24 (s, 1H, H-2), 6.46 (s, 1H, H-6), 6.30
(q, J32,34 = 1.20 Hz, 1H, H-32), 1.95 (d, J34,32 = 1.20 Hz,
3H, H-34). 13C NMR (100 MHz, CDCl3) δ = 141.6, 140.8,
140.6, 139.6, 138.9, 136.4, 128.8, 128.7, 127.9, 127.6,
imidazo[2,1-c][1,4]oxazine (15a)
Light red solid, m.p.: 158-160°C, yield: 92%. 1H NMR
(400 MHz, CDCl3) δ = 8.32 (bs, 1H, Ar-H), 7.87-7.85 (m,
2H, Ar-H), 7.82-7.80 (m, 2H, Ar-H), 7.73 (bs, 1H, Ar-H),
7.63 (dd, J = 1.71, 8.56 Hz, 1H, Ar-H), 7.51-7.47 (m, 2H,
Ar-H), 7.46-7.43 (m, 1H, Ar-H), 7.32 (bs, 1H, Ar-H), 6.60
(bs, 1H, CH-O), 6.29 (q, J = 1.13 Hz, 1H, C=CH), 1.92
(d, J = 1.13 Hz, 3H, CH3). 13C NMR (100 MHz, CDCl3)

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127.4, 127.3, 127.2, 127.1, 126.9, 125.4, 125.3, 110.7,
101.9, 75.3, 17.5.
3H, H-42). 13C NMR (100 MHz, CDCl3) δ =143.0, 141.7,
139.0, 132.1, 131.4, 131.2, 131.0, 130.9, 130.5, 130.1, 129.5,
129.0, 128.1, 128.1, 127.5, 127.4, 127.3, 127.1, 127.0, 126.1,
125.8, 125.7, 125.6, 125.5, 125.4, 125.3, 125.2, 124.9, 124.8,
124.7, 124.4, 123.6, 114.2, 101.9, 73.9, 17.4. HRMS (ESI)
(M + H): C39H25N2O: 537.1967, found: 537.1942.
3.31
6-Methyl-2,8-di(naphthalen-2-yl)-8H-
|
imidazo[2,1-c][1,4]oxazine (15g)
Light red solid, m.p.: 162-164°C; yield: 82%. 1H NMR
(400 MHz, d6-DMSO) δ = 8.21 (bs, 1H, Ar-H), 7.97-7.91
(m, 3H, Ar-H), 7.88 (s, 1H, Ar-H), 7.86-7.82 (m, 5H, Ar-
H), 7.58-7.50 (m, 3H, Ar-H), 7.45-7.38 (m, 2H, Ar-H), 6.78
(q, J28,30 = 0.91 Hz, 1H, Ar-H), 6.62 (bs, 1H, H-7), 1.90 (d,
J30,28 = 0.91 Hz, 3H, H-30). 13C NMR (100 MHz, d6-DMSO)
δ = 142.6, 140.8, 139.5, 135.6, 133.7, 133.4, 132.9, 132.4,
131.8, 128.8, 128.6, 128.5, 128.2, 128.1, 128.0, 127.1, 127.0,
126.8, 125.8, 125.6, 123.9, 122.4, 113.0, 102.7, 75.5, 17.3.
3.35
6-Methyl-8-phenyl-8H-imidazo[5,1-c]
|
[1,4]oxazine (13)
Viscous liquid, dark brown, yield: 73%. 1H NMR (400 MHz,
CDCl3) δ = 7.36-7.33 (m, 5H, Ar-H), 7.02 (d, J4,1 = 1.31 Hz,
1H, H-4), 6.85 (d, J1,4 = 1.31 Hz, 1H, H-1), 6.22 (q,
J15,16 = 1.23 Hz, 1H, H-15), 6.21 (bs, 1H, H-6), 1.87 (d,
J16,15 = 1.23 Hz, 3H, H-16). 13C NMR (100 MHz, CDCl3)
δ = 142.8, 138.9, 137.2, 128.8, 128.7, 128.6, 127.2, 115.1,
102.0, 75.9, 17.2. HRMS (ESI) (M + H): C13H13N2O:
213.2600, found: 213.2589.
3.32
6-Methyl-2,8-di(thiophen-2-yl)-8H-
|
imidazo[2,1-c][1,4]oxazine (15h)
Viscous liquid, dark brown, yield: 80%. 1H NMR (400 MHz,
CDCl3) δ = 7. 32 (dd, J15,17 = 1.67 Hz, J15,16 = 4.64 Hz, 1H,
H-15), 7.27 (dd, J5,2 = 1.16 Hz, J5,1 = 3.57 Hz, 1H, H-2),
7.18 (dd, J2,5 = 1.16 Hz, J2,1 = 5.07 Hz, 1H, H-2), 7.09 (s,
1H, H-7), 7.02 (dd, J1,5 = 3.57 Hz, J1,2 = 5.07 Hz, 1H, H-1),
6.95-6.92 (m, 2H, H-16,17), 6.60 (bs, 1H, H-27), 6.27 (q,
J18,20 = 1.20 Hz, 1H, H-18), 1.89 (d, J20,18 = 1.20 Hz, 3H, H-
20). 13C NMR (100 MHz, CDCl3) δ = 142.3, 140,4, 138.2,
137.2, 136.8, 127.5, 126.9, 126.8, 126.7, 123.5, 122.2, 110.1,
101.9, 71.2, 17.4.
3.36
Phenyl[4-phenyl-1-(propa-1,2-dien-1-
|
yl)-1H-imidazol-2-yl]methanone (16a)
Viscous liquid, dark brown, yield: 88%. 1H NMR (400 MHz,
CDCl3) δ = 8.46-8.44 (m, 2H, Ar-H), 8.22 (t, J = 6.6 Hz,
1H), 7.86-7.84 (m, 2H, Ar-H), 7.66 (bs, 1H), 7.61 (tt,
J = 1.30, 7.39 Hz, 1H, Ar-H), 7.53 (tt, J = 1.80, 7.74 Hz,
1H, Ar-H), 7.40 (tt, J = 1.80, 7.74 Hz, 2H, Ar-H), 7.31 (tt,
J = 1.30, 7.39 Hz, 1H, Ar-H), 5.61 (d, J = 6.6 Hz, 2H). 13C
NMR (100 MHz, CDCl3) δ = 202.8, 183.9, 142.4, 141.7,
137.0, 133.0, 132.8, 131.3, 128.7, 128.0, 127.8, 125.3, 118.1,
98.1, 87.4. HRMS (ESI) (M + H): C19H15N2O: 287.1184,
found: 287.1171.
3.33
2,8-Bis(5-bromothiophen-2-yl)-6-
|
methyl-8H-imidazo[2,1-c][1,4]oxazine (15i)
1
Viscous liquid, dark brown, yield: 63%. H NMR (400 MHz,
3.37
(E)/(Z)-[1-(2,3-diiodoallyl)-4-phenyl-
|
CDCl3) δ = 7.04 (s, 1H, H-7), 7.01 (d, J5,1 = 3.84 Hz, 1H, H-
5), 6.96 (d, J1,5 = 3.84 Hz, 1H, H-1), 6.89 (d, J15,14 = 3.81 Hz,
1H, H-15), 6.68 (dd, J14,30 = 0.98 Hz, J14,15 = 3.81 Hz, 1H, H-
14), 6.48 (d, J = 0.98 Hz, 1H, H-11), 6.26 (q, J44,46 = 1.22 Hz,
1H, H-44), 1.91 (d, J46,44 = 1.22 Hz, 3H, H-46). 13C NMR
(100 MHz, CDCl3) δ = 142.6, 141.5, 137.6, 136.1, 130.4,
129.5, 127.6, 127.4, 122.4, 113.9, 110.3, 110.2, 101.8, 71.1,
17.4. HRMS (ESI) (M + H): C15H11Br2N2OS2: 456.8680,
found: 456.8671.
1H-imidazol-2-yl]phenylmethanol (17)
This molecule was synthesized via reaction with 1 eq 7a,
1.1 eq NaHCO3, and 1.1 eq molecular iodine in chloroform
(3 mL). The final mixture was stirred in room temperature
for 18 hours. To complete the reaction, a solution of Na2S2O4
(5 mL) was added, and the mixture was extracted with ethyl
acetate. Organic phase was separated, dried, and evaporated
to get the addition product.
1
Yellow solid, m.p.: 120-122°C; yield: 88%. H NMR
(400 MHz, d6-DMSO) δ = 7.74-7.71 (m, 2H, Ar-H), 7.52
(t, J12,10 = 1.11 Hz, 1H, H-12), 7.46 (s, 1H, H-2), 7.45-7.42
(m, 2H, Ar-H), 7.35-7.30 (m, 4H, Ar-H), 7.26 (tt, J = 1.13,
7.31 Hz, 1H, Ar-H), 7.17 (tt, J = 1.20, 7.36 Hz, 1H, Ar-H),
6.33 (d, J6,9 = 4.96, 1H, H-6), 5.90 (d, J9,6 = 4.96 Hz, 1H,
H-9), 4.94 (dd, J10,12 = 1.11 Hz, J10,10 = 15.84 Hz, 1H, H-
10), 4.78 (dd, J = 1.11, 15.84 Hz, 1H, H-10) 13C NMR
(100 MHz, d6-DMSO) δ = 149.8, 142.0, 139.1, 134.6, 128.9,
128.4, 127.6, 126.9, 126.8, 124.7, 117.3, 99.4, 87.0, 68.4,
3.34
6-Methyl-2,8-di(pyren-2-yl)-8H-
|
imidazo[2,1-c][1,4]oxazine (15j)
Brown solid, m.p.: 212-215°C; yield: 89%. 1H NMR
(400 MHz, CDCl3) δ = 8.89 (d, J = 9.30 Hz, 1H, Ar-H), 8.67
(d, J = 9.30 Hz, 1H, Ar-H), 8.30-8.22 (m, 5H, Ar-H), 8.17-
8.05 (m, 8H, Ar-H), 8.04 (bs, 2H, Ar-H), 7.99-7.95 (m, 1H,
Ar-H), 7.65 (d, J = 7.95 Hz, 1H, H-22), 7.52-7.48 (m, 1H, H-
24), 6.49 (q, J = 1.21 Hz, 1H, H-39), 1.80 (d, J42,24 = 1.21 Hz,

KUZU et al.
11 of 12
|
57.0. HRMS (ESI) (M + H): C19H17I2N2O: 542.9430, found:
542.9415.
of 5 × 105 cells/mL. All the steps of this experiment were
carried out under dim light so as to prevent any additional
DNA damage. Each cleaned microscope slide was precoated
with a layer of 1% normal melting point agarose (Vivantis
LE Agarose) in PBS (Ca2+ and Mg2+ free) and then dried
at room temperature at least overnight. Approximately 104
cells (18 μL) were mixed with 0.75% low melting point
agarose (Sigma) (50 μL) at 37°C, and this suspension was
dropped onto the first agarose layer. The slides were al-
lowed to solidify for 25 minutes at 4°C. The coverslips were
removed, and the slides were immersed in freshly prepared
cold lysis buffer containing 2.5 mol L−1 NaCl, 0.1 mol L−1
EDTA, 0.01 mol L−1 Tris, 1% sodium N-lauroyl sarcosine
(adjusting pH to 10); 1% Triton X-100 and 9 mmol L−1
DL-dithiothreitol, prechilled at 4°C, were added for 1 hour.
The slides were then incubated at 37°C in lysis buffer with
20 μg/mL of Proteinase K (Vivantis) for 2 hours. The slides
were removed from the lysis buffer, drained, and placed in
a horizontal electrophoresis unit filled with fresh neutral
electrophoresis buffer (Tris-borate-EDTA [TBE]), contain-
ing 10 mmol L−1 Tris, 80 mmol L−1 boric acid, 0.5 mol L−1
EDTA (pH = 8.3) at 4°C for 20 minutes incubation so as to
allow the DNA to unwind. Electrophoresis was performed at
room temperature, at 25 V for 20 minutes. After electropho-
resis, the slides were air-dried and subsequently stained with
50 μL of 8 μg/mL ethidium bromide and covered with a cov-
erslip. The images of more than 1000 randomly chosen cells
were visually analyzed. Observations were made at a magni-
fication of 400× using a fluorescent microscope (Olympus,
Japan). Each image was classified according to the intensity
of the fluorescence in the comet tail, and given a value of 0,
1, 2, 3, or 4 (from undamaged class 0 to maximally damaged
class 4).
3.38
MTT toxicity method
|
MTT assay was used to determine the drug sensitivity of the
LN405 glioma cell line. The synthesized molecules stock
solutions (10 mol L−1) were prepared in DMSO and diluted
in the culture medium prior to use. Cells were plated in
96-well plates at 8 × 103 cells/well density in 100 μL me-
dium and incubated overnight for attachment to the surface
of the plate. The cells were treated with synthesized mol-
ecules at various concentrations (0.1, 0.02, 0.01, 0.001, and
0.0001 mol L−1). Control cells were treated with the same
amount of DMSO at synthesized molecules for each experi-
ment. These plates were incubated for 72 hours. Stock MTT
solution was prepared in sterile PBS and filtered through a
0.22-μm filter. At the end of the incubation period, the me-
dium was discarded, and a new medium containing 10-fold
diluted MTT stock solution (5 mg/mL) was added. After 3-
hour incubation time at 37°C, 5% CO2, MTT solution was
gently discarded, and the lysis solution was added into each
well for solubilization of the formazan crystals and shaken
for 15 minutes for homogenization. The absorbance of each
well at 570 nm was measured in a microplate reader. Growth
inhibition was compared between the treated with synthe-
sized molecules samples and the untreated controls and ana-
lyzed using GraphPad Prism 5 software (San Diego, CA).
All the experiments were performed at least four times. The
sensitivity of the treated cells with synthesized molecules
was measured by IC50. The molecules concentration causing
a 50% inhibition in LN405 glioma cell activity was defined
as IC50.
3.39
COMET assay genotoxicity test
ACKNOWLEDGMENTS
|
Single cell gel electrophoresis (COMET) DNA damage was
determined by COMET assay after LN405 cells were treated
with compounds. The applied method is similar to published
protocol in our article.[11] These cells were plated in 25-cm2
flasks at a density of 0.7 × 105 cells/mL and incubated over-
night for attachment to the surface of the flask. After over-
night incubation, compounds with were added to the cells at
0.1 μmol L−1 concentration. Approximately 30%-35% death
ratio, which does not arrive at the level of IC50 dose in cells,
was determined at this concentration according to control
group for 72 hours. Therefore, this concentration value was
chosen to detect DNA damage in COMET assay. The cells
that treated with compounds were incubated for 72 hours.
After incubation time, the cells were treated with trypsin and
then centrifuged at 2833.5 × g for 5 minutes at 4°C, and the
supernatant was discarded. These cells were washed and di-
luted with PBS (Ca2+ and Mg2+ free) yielding a concentration
Financial support from the Scientific and Technological
Research Council of Turkey (TUBITAK, Grant No.
115Z894), Van Yüzüncü Yil University Coordinator of
Scientific Research Projects (TAP-2016-5610 and TAP-
2017-6092), is gratefully acknowledged.
ORCID
Nurettin Menges
http://orcid.org/0000-0002-5990-6275
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SUPPORTING INFORMATION
Additional Supporting Information may be found online in
the supporting information tab for this article.
How to cite this article: Kuzu B, Genç H, Taşpinar
M, Tan M, Menges N. An easy synthetic protocol for
imidazo-1,4-oxazines and evaluation of their
toxicities. Heteroatom Chem. 2018;e21412.
https://doi.org/10.1002/hc.21412
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