Synthesis, antimicrobial and cytotoxicity study of 1,3-disubstituted-1H- naphtho[1,2-e][1,3]oxazines

Article abstract of DOI:10.1016/j.ejmech.2012.08.018

A series of new 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazines (3 and 7) was synthesized in good yields and the structure was determined with the help of NMR, 2D-NMR, HRMS studies and X-ray crystallography. These compounds were tested in vitro for their

Full text of DOI:10.1016/j.ejmech.2012.08.018

European Journal of Medicinal Chemistry 56 (2012) 195e202
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, antimicrobial and cytotoxicity study of 1,3-disubstituted-1H-naphtho
[1,2-e][1,3]oxazines
,
b
b
Vikas Verma a, Kuldeep Singh a, Devinder Kumar a , Thomas M. Klapötke , Jörg Stierstorfer ,
*
Balasubramanian Narasimhan c, Asif Khurshid Qazi d, Abid Hamid d, Sundeep Jaglan d
a Department of Chemistry, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana, India
b Department of Chemistry, Ludwig-Maximilian University of Munich, Butenandtstr, 5-13 (D), D-81377 Munich, Germany
c Faculty of Pharmaceutical Sciences, M D University, Rohtak 124001, Haryana, India
d CSIR-Indian Institute of Integrative Medicine, Jammu 180001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazines (3 and 7) was synthesized in good
yields and the structure was determined with the help of NMR, 2D-NMR, HRMS studies and X-ray
crystallography. These compounds were tested in vitro for their antibacterial activity against Gram-
positive and Gram-negative bacteria and as well as for antifungal activity. The compounds 3c, 3e, 7a,
7d and 7k showed significant antibacterial activity and 7l showed moderate antifungal activity. The
cytotoxicity of 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazines showed that 3e and 7e are more
effective against breast, lung and colon cell proliferation.
Received 27 June 2012
Received in revised form
9 August 2012
Accepted 12 August 2012
Available online 23 August 2012
Keywords:
Naphthoxazine
Schiff base
Ó 2012 Elsevier Masson SAS. All rights reserved.
Antimicrobial
Cytotoxicity
1. Introduction
2. Results and discussion
There has been a considerable interest in the synthesis of
molecules having 1,3-oxazine moiety due to large spectrum of
pharmacological activities such as antitumour [1], antimicrobial
[2], anti-HIV [3] and antimalarial agent [4]. In particular, naph-
thoxazine derivatives have exhibited therapeutic potential for the
treatment of Parkinson’s disease [5]. Further, the growing interest
in the utilization of hypervalent iodine reagents [6,7] in the
synthesis of new molecules and natural products promoted us to
take up the synthesis of naphthoxazine utilizing particularly
iodobenzene diacetate. Therefore, herein we report efficient
synthesis of 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazine by
2.1. Chemistry
The N-arylidene-1-(a-aminoarylbenzyl)-2-naphthol (2) for the
synthesis of the target molecules was obtained by condensation of
2-naphthol (1) with two equivalents of aromatic aldehydes in
presence of ammonia [8]. Reaction of 2 with iodobenzene diacetate
furnished the naphthoxazine 3 instead of 4 in good yields. The
formation of isomeric naphthoxazine (4) was not observed at all.
The structure of compound 3 was determined with the help of IR,
NMR (1H and 13C), 2D-NMR (COSY and HSQC) and mass spectro-
scopic data. The IR spectrum of 3b was devoid of band due OH
the oxidation of N-arylidene-1-(
a
-aminoarylbenzyl)-2-naphthol
stretching and NMR spectrum exhibited the singlet at d 6.32
with iodobenzene diacetate, antimicrobial and cytotoxicity study.
The structure of newly synthesized 1,3-disubstituted-1H-naphtho
[1,2-e][1,3]oxazine was also confirmed by X-ray crystallography.
assigned to C1-H. The optical purity of the enantiomer of
compound 3 due to C-2 chiral centre was also determined by
chiral HPLC analysis which shows enantiomeric ratio of 49:51
(Scheme 1).
In order to prove the structure of 3, the crystals were developed
by vapour diffusion hexane into a saturated dichloromethane
solution for compound 3b. The X-ray crystallography of naph-
thoxazine 3 confirmed the formation of 3 rather than 4. Bond
* Corresponding author. Department of Chemistry, Guru Jambheshwar University
of Science & Technology, TB#3, Room #102, Hisar 125001, Haryana, India. Fax: þ91
1662 276240.
ꢀ
lengths N1-C1 ¼1.263(2) and N1-C2 ¼ 1.470 (2) A are typical of 3b.
The selected crystal structure data are presented in Tables 1 and 2.
E-mail address: dk_ic@yahoo.com (D. Kumar).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.08.018

196
V. Verma et al. / European Journal of Medicinal Chemistry 56 (2012) 195e202
Molecules are packed by aromatic ring attractive interactions along
the crystallographic b and c axes (Fig. 1).
In order to generalize the formation of the naphthoxazine by the
oxidation of iodobenzene diacetate, other N-arylidene-1-(a-ami-
R1
CHO
MeOH, NH3
R1
N
R1
OH
OH
noarylbenzyl)-2-naphthols (6) were prepared. Acidic hydrolysis of
2 resulted in the formation of aminonaphthols (5, Betti base) [9]
which on condensation with equivalent amount of aromatic alde-
hydes gave compound 6. The compound 6 was treated with iodo-
benzene diacetate to produce naphthoxazine (7) in good yields. The
structure of 7 was determined by IR, NMR (1H and 13C) and mass
spectral data which were in good agreement with the structure of
naphthoxazine of the type 3 (Scheme 2).
The NMR spectra of 2 and 6 also showed that in CDCl3 solution
the compound exhibited equilibrium with two diastereomeric
trans- and cis-oxazine structures (B and C) formed by tautomeric
N,O-proton transfer (Scheme 3) besides the open-chain tautomer
2
1
IBD
MeOH
R1
R1
R1
R1
N
N
O
O
4
3
3
(a) R1 = H; (b) R1 = CH3; (c) R1 = OCH3;
(d) R1 = Cl; (e) R1 = F
Scheme 1. Synthesis of naphthoxazine.
Table 1
ꢀ
ꢀ
Selected bond distances (A) and bond angles ( ) of 1,3-di-p-tolyl-1H-naphtho[1,2-e]
[1,3]oxazine (3b).
O1-C1
O1-C4
N1-C1
N1-C2
1.383(2)
1.379(2)
1.263(2)
1.470(2)
C1-C20
C2-C3
C2-H2
C2-C13
1.473(2)
1.513(2)
0.999(18) C4-C5
1.526(3)
C3-C4
C3-C8
1.360(3)
1.431(2)
1.409(3)
C1-O1-C4
C1-N1-C2
C1-C20-C21 121.97(16) C2-C3-C8
C1-C20-C25 119.64(17) C3-C4-C5
N1-C1-C20 122.37(16) C3-C2-C13
117.47(14) C2-C13-C18 121.95(16) C4-C3-C8
118.19(16)
115.0(12)
119.58(18)
126.37(16)
120.89(14) C2-C3-C4
119.64(15) C4-C5-H5
122.17(16) C4-C5-C6
122.96(16) O1-C1-N1
114.75(14) O1-C1-C20 111.16(15)
N1-C2-C3
N1-C2-C13 106.84(14) C3-C2-H2
N1-C2-H2 107.2(10) C3-C8-C7
C2-C13-C14 119.82(15) C3-C8-C9
113.33(15) C3-C2-H2
109.1(10) O1-C4-C3
109.1(10) O1-C4-C5
119.61(16) C13-C2-H2
122.49(17)
121.97(15)
115.07(16)
105.1(10)
Table 2
Crystallographic data of 1,3-di-p-tolyl-1H-naphtho[1,2-e][1,3]oxazine (3b).
Formula
Formula weight
Temperature (K)
C26H21NO
363.44
173
MoKa 0.71073
Monoclinic
P21/c(No. 14)
5.6617(6)
20.311(2)
16.5089(15)
90
ꢀ
Radiation [A]
Crystal system
Space group
ꢀ
a [A]
ꢀ
b [A]
ꢀ
c [A]
alpha [ꢀ]
beta [ꢀ]
94.551(9)
90
1892.5(3)
4
gamma [ꢀ]
3
ꢀ
V [A ]
Z
D(calc) [g/cm3]
1.276
F(000)
768
4.2e25.8
3591
Theta range for data collection minemax [ꢀ]
Nref
Npar
337
Mu(MoKa) [/mm]
Crystal size [mm]
Tot., uniq. data, R(int)
Dataset
0.077
0.14 ꢁ 0.18 ꢁ 0.39
7182, 3591, 0.029
ꢂ6: 5; ꢂ24: 16; ꢂ20: 16
2463
0.0484, 0.1409, 1.04
where P ¼ (F2o þ 2Fc2)/3
0.03, 0.00
ꢂ0.20, 0.21
Observed data [I > 0.0 sigma(I)]
R, wR2, S
w ¼ 1/[s2(F2o) þ (0.0699P)2]
Max. and av. shift/error
3
ꢀ
Min. and max. resd. dens. [e/A ]
Fig. 1. (a) Molecular structure, (b) packing diagram of 3b.

V. Verma et al. / European Journal of Medicinal Chemistry 56 (2012) 195e202
197
activity against the tested strains compared to reference cipro-
floxacin and fluconazole in case of antibacterial and antifungal
activity, respectively.
R1
R1
R1
i) H2O/HCl
ii) NH4OH
NH2
OH
N
OH
In general, the synthesized compounds were more active
against the Gram-negative E. coli having pMICec value more than
2.07. Among the synthesized compounds 7d and 7e were found to
be more effective against E. coli. Compounds 3c was found to be
more active against B. subtilis (pMICbs ¼ 2.10). In case of antibac-
terial activity against S. aureus compound 3e was found to be more
active one. In general the synthesized compounds were moderately
active against the fungal species under test and Compound 7l was
found to be the effective one against the C. albicans (pMICca ¼ 1.83)
and A. niger (pMICan ¼ 1.53) among the synthesized compounds.
The cytotoxic assay of 1,3-disubstituted-1H-naphtho[1,2-e][1,3]
oxazines based on MTT was performed on panel of human cancer
cell lines (MCF-7, A549, HCT-116 and PC-3). In the present study, 3e
and 7e produced concentration dependent inhibition of cell
proliferation on MCF-7, A549, and HCT-116 cancer cell lines. These
results depicted that both 3e and 7e showed more effectiveness
against breast, lung and colon cell proliferation as reflected by
relative percentage growth inhibition values (Table 4).
5
2
R2
MeOH
CHO
R1
R2
R1
R2
N
N
IBD
MeOH
O
OH
6
7
7
a : R1 = H , R2 = OCH3 ; b : R1 = H, R2 = CH3
c : R1 = H, R2= NO2 ; d : R1= H, R2= Cl
e : R1 = H, R2= F ; f : R1 = H, R2= Br
g : R1 = CH3 , R2 = H ; h : R1 = CH3, R2 = OCH3
i : R1 = CH3 , R2 = NO2 ; j : R1 = CH3, R2 = Cl
k : R1 = CH3 , R2 = F ; l : R1 = CH3, R2 = Br
Scheme 2. Synthesis of naphthoxazine.
2.2.2. Structure activity relationship (SAR) studies
1. Compound 3e having electron withdrawing fluoro group on the
phenyl nucleus at position-3 of 1H-naphtho[1,2-e][1,3]oxazine
was emerged as the most active antibacterial compound
against the S. aureus. The role of electron withdrawing group in
improving antimicrobial activities is supported by the studies
of Sharma et al. [13].
[10]. The major ring forms in all tautomeric equilibria contain the
1,3-diaryl substituent in the trans position. The proportions of the
chain and distereomeric ring forms of the tautomeric equilibria
were determined by integration of well separated OeCHAreN
(ring) and N]CHAr (chain) proton singlets or doublets in the
NMR spectra. The azomethine double bond was having
E
2. In case of antibacterial activity against B. subtilis, compound 3c
having electron donating p-methoxy group on the phenyl
nucleus at position-3 of 1H-naphtho[1,2-e][1,3]oxazine was
found to be the most active one. The role of electron donating
methoxy group in improving antibacterial activity against
B. subtilis is similar to the results obtained by Sharma et al. [14].
3. In case of antibacterial activity against E. coli, compounds 7d, 7e
were found to the most active ones. Here, both 7d, 7e requires
the presence of electron withdrawing halo groups [Cl-7d and
F-7e] at para position of 3-phenyl nucleus and no substitution
at the para position of 1-phenyl nucleus of 1H-naphtho[1,2-e]
[1,3]oxazine. This indicated a fact that the presence of hydrogen
at para position of 1-phenyl nucleus is essential for the
hydrogen bonding of 1H-naphtho[1,2-e][1,3]oxazine at the
target site of Gram-negative E. coli. This result is in contrast to
the antibacterial activity requirements against Gram-positive
bacteria where the presence of electron withdrawing/electron
donating substituent is essential on the phenyl nucleus at
position-3.
configuration.
The probable mechanism consists of attack of iodobenzene
diacetate on 2 or 6 resulting in the formation of intermediate (8)
that may undergo reductive elimination of iodobenzene to produce
either 3/7 or 4. However, the isomeric compound 4 was not formed
probably due to severe steric interaction between two aromatic
rings as it will remain in the plane rather there was formation of the
compounds 3 as one of the aromatic ring disposed out of plane to
overcome this steric interaction in intermediate 8 (Scheme 4).
2.2. Biological section
2.2.1. Antimicrobial & cytotoxic activity
The newly synthesized 1,3-disubstituted-1H-naphtho[1,2-e]
[1,3]oxazines were evaluated for their in vitro antibacterial activity
against Gram-positive Bacillus subtilis [MTCC 2063], Staphylococcus
aureus [MTCC 2901] and Gram-negative Escherichia coli [MTCC
1652] and in vitro antifungal activity against Candida albicans
[MTCC 227] and Aspergillus niger [MTCC 8184]. Double strength
nutrient broth-I.P. and Sabouraud dextrose broth-I.P. [11] were
employed for bacterial and fungal growth respectively. Minimum
inhibitory concentrations [MIC] were determined by means of
4. In case of antifungal activity of 1,3-disubstituted-1H-naphtho
[1,2-e][1,3]oxazine against C. albicans and A. niger a totally
different structural requirement was observed. The compound,
3-(4-bromophenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3] oxazine
(7l) was emerged as the most active compound against the
standard serial dilution [12] and the pMIC values in
sented in Table 3. All the compounds exhibited appreciable in vitro
mM are pre-
R1
R2
R1
R2
R1
R2
H
N
H
N
H
H
O
H
H
O
N
OH
2 or 6
A
C
B
Scheme 3. Ring-chain tautomerism of Schiff base.

198
V. Verma et al. / European Journal of Medicinal Chemistry 56 (2012) 195e202
Table 4
R1
R2
R1
R2
H
N
Cytotoxicity of 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazine against cancer cell
lines.
H
H
O
N
OH
Tissue type
Cell type
Breast
MCF-7
Lung
A549
Colon
Prostrate
PC-3
HCT-116
A
B
Entry
Conc(
mM)
% Growth inhibition
OAc
OAc
Ph I
3a
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
10
20
1
37
26
37
30
26
22
38
16
50
36
42
37
46
36
42
34
39
27
51
29
39
27
32
17
39
36
40
35
37
21
44
20
33
26
e
36
19
36
17
35
22
54
28
50
20
43
19
43
19
43
17
38
17
50
18
40
23
37
17
36
15
41
13
28
16
44
16
32
13
79
70
22
5
16
1
5
3b
3c
3d
3e
7a
7b
7c
7d
7e
7f
24
19
29
27
10
2
51
5
14
8
38
8
14
4
29
3
56
12
29
6
1
19
17
2
OAc
R1
Ph
R2
I
H
H
N
1
O
29
22
23
19
20
14
8.
6
19
9
39
14
11
4
3
1
10.
1
12
8
8
X
R1
R2
R1
R2
N
N
O
O
3/7
4
Scheme 4. Probable mechanism for the formation of naphthoxazine.
7g
7h
7i
8
2
14
7
21
7
both the fungal strains among the synthesized compounds.
According to this the presence of electron withdrawing
p-bromo group (3-phenyl nucleus) and electron donating
p-methyl group (1-phenyl nucleus) of 1H-naphtho[1,2-e][1,3]
oxazine is required for a compound to be effective against
fungal species.
5. The aforementioned antibacterial and antifungal results indi-
cated a fact that different structural requirements are essential
for a compound to be active against different microbial
targets. This is similar to the results obtained by Sortino et al.
[15].
7j
6
3
13
8
19
5
2
0
7k
7l
23
18
10
2
78
e
5-Fluorouracil
Mitomycin-C
e
82
70
6. The cytotoxicity screening results indicated that the presence
of electron withdrawing fluoro group improved the cytotox-
icity activity of synthesized 1,3-disubstituted-1H-naphtho[1,2-
e][1,3]oxazines (3e and 7e). It is important to note a fact here
that the presence of halo substituent at 1-phenyl nucleus of 1H-
naphtho[1,2-e][1,3]oxazine is not essential for the cytotoxic
activity of the synthesized compounds as evidenced by the
activity of compound 7e [3-(4-fluorophenyl)-1-phenyl
substituent] which is having cytotoxic activity equal to that of
compound 3e [1,3-bis(p-fluorophenyl) substituent].
Table 3
The aforementioned findings are summarized in Fig. 2.
In vitro antimicrobial activity of synthesized 1,3-disubstituted-1H-naphtho[1,2-e]
[1,3]oxazine derivatives.
Comp.
pMICsa
pMICbs
pMICec
pMICca
pMICan
3. Conclusion
3a
3b
3c
3d
3e
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
1.43
1.46
1.50
1.51
2.07
1.77
1.75
1.78
1.77
1.75
1.52
1.45
1.78
1.80
1.49
1.47
1.83
2.61a
2.03
2.07
2.10
1.81
1.77
1.77
1.45
1.78
1.77
2.05
1.82
1.75
1.78
1.80
1.79
2.07
1.83
2.61a
2.33
1.46
2.10
2.11
1.47
2.37
2.05
1.78
2.37
2.35
1.52
2.35
2.08
1.80
0.88
2.07
1.83
2.61a
1.73
1.76
1.80
1.81
1.77
1.77
1.75
1.78
1.77
1.75
1.82
1.75
1.78
1.80
1.79
1.77
1.83
2.64b
1.43
1.46
1.50
1.51
1.47
1.47
1.45
1.48
1.47
1.45
1.52
1.45
1.48
1.50
1.49
1.47
1.53
2.64b
In summary, we have synthesized 1,3-disubstituted-1H-naph-
tho[1,2-e][1,3]oxazine (3 and 7) in good yields from Schiff base
utilizing iodobenzene diacetate as reagent. The crystal structure
was determined and it established the formation of 1,3-
disubstituted-1H-naphtho[1,2-e][1,3]oxazine instead of 1,3-
disubstituted-3H-naphtho[1,3-e][1,3]oxazine. All the compounds
exhibited appreciable in vitro activity against the tested microbial
strains. The antibacterial activity of compounds 3a, 3c, 3d, 7a, 7d,
7e, 7g and 7h were found to be more active against E. coli;
compounds 3b, 3c and 7k were found to be more active against
B. subtilis and compound 3e was found to be more active against
S. aureus. Further, the antifungal activity of all the compounds was
found to be moderate against C. albicans and A. niger; compound
7l was found to be more active. The cytotoxic assay (MTT) of
1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazines indicated that
compounds, 3e and 7e showed more effectiveness against
Std.
a
Ciprofloxacin.
Fluconazole.
b

V. Verma et al. / European Journal of Medicinal Chemistry 56 (2012) 195e202
199
p-Fluoro group - Increase cytotoxic activity;
Increase antibacterial activity against S. aureus
and E. coli
Electron withdrawing
group
p-Bromo group - Increase antifungal activity
against C. albicans and A. niger
R
p-Methoxy group - Increase antibacterial activity
against B. subt ilis
Electron donating
group
O
N
p-Methyl group - Increase antifungal activity
against C. albicans and A. niger
Electron donating
group
R
No substitution i.e. p-H
Required for antibacterial activity against E. coli
Fig. 2. Structural requirements for antimicrobial and cytotoxic activity of 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazines (3 and 7).
breast, lung and colon cell proliferation as reflected by relative
percentage growth inhibition values.
4.2.2. 1,3-Di-p-tolyl-1H-naphtho[1,2-e][1,3]oxazine (3b)
mp 172e173 ꢀC; yield: 80%; IR(KBr)
: 3039, 3010, 2916, 2872,
n
1672, 1606, 1512 cmꢂ1; NMR dH (400 MHz, CDCl3): 7.92 (d,
J ¼ 8.0 Hz, 2H, C3-C6H4CH3; ortho protons), 7.73e7.69 (m, 2H, C7-H,
C9-H). 7.64 (d, J ¼ 7.96 Hz, 1H, C5-H), 7.33e7.25 (m, 3H, C6-H, C8-H
and C10-H), 7.19 (d, J ¼ 8.2 Hz, 2H, C1-C6H4CH3; ortho protons), 7.12
(d, J ¼ 7.72 Hz, 2H, C3-C6H4CH3; meta protons), 6.97 (d, J ¼ 7.72 Hz,
00
4. Experimental
4.1. General
2H, C1-C6H4CH3; meta protons), 6.32 (s, 1H, C1-H), 2.29 (s, 3H, C4
-
Melting points were determined in open capillaries and are
0
CH3), 2.16 (s, 3H, C4 -CH3); NMR dC (100 MHz, CDCl3): 151.42,146.83,
uncorrected. FTIR spectra were obtained in KBr on IR Affinity-I
0
0
(Shimadzu) spectrophotometer and are reported in cmꢂ1 1H,
.
141.30,140.83,136.97,131.38,130.20,129.40 (C3 , C5 ),129.37,129.21,
00
00
00
13C NMR and 2D-NMR, COSY (correlation spectroscopy), HSQC
(heteronuclear single-quantum coherence) and HMBC (hetero-
nuclear multiple bond correlation) spectra were scanned on
a Bruker Avance II NMR spectrometer operating at 400 MHz in
CDCl3 and are expressed as ppm with respect to TMS. X-ray
crystallographic data was obtained on a Sapphire CCD diffrac-
tometer. The mass spectra were obtained on AB SCIEX 5600
system.
129.17, 128.97, 128.95, 128.87 (C3 , C5 ), 128.82, 128.53, 127.72 (C2 ,
00
0
0
C6 ), 127.59 (C2 , C6 ), 126.94, 126.05 (C10), 124.64 (C8), 123.06 (C6),
þ
0
00
116.62 (C5), 114.43, 56.63, 21.46 (C4 ), 21.05 (C4 ); HRMS: m/z (M )
calcd. for C26H21NO: 363.1623, found: 364.1745 (M þ H).
4.2.3. 1,3-bis(4-Methoxyphenyl)-1H-naphtho[1,2-e][1,3]oxazine (3c)
mp 158e159 ꢀC; yield: 76%; IR(KBr)
n: 3062, 3003, 2958, 2937,
2902, 2839, 1668, 1606, 1504 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.08
(d, J ¼ 8.72 Hz, 2H, C3-C6H4OCH3; ortho protons), 7.83e7.80 (m, 2H,
C7-H, C9-H). 7.73 (d, J ¼ 8.04 Hz, 1H, C5-H), 7.44e7.25 (m, 5H, C6-H,
C8-H, C10-H and C1-C6H4OCH3; ortho protons), 6.93 (d, J ¼ 8.72 Hz,
2H, C3-C6H4OCH3; meta protons), 6.80 (d, J ¼ 8.56 Hz, 2H, C1-
4.2. General procedure for the synthesis of naphthoxazine (3)
00
The compound 2 (prepared by the reaction of 2-naphthol,
ammonia and appropriate benzaldehyde) [8] (0.01 mol) was
dissolved by warming in methanol (15 mL) and iodobenzene diac-
etate (0.02 mol) was added into it. The reaction mixture was stirred
for 2e3 h at 55e60 ꢀC. The reaction was monitored by TLC using
toluene as eluant. The solid so formed was filtered and washed
with cold methanol followed by ether and crystallized from
dichloromethane.
C6H4OCH3; meta protons), 6.39 (s, 1H, C1-H), 3.84 (s, 3H, C4 -OCH3),
0
3.72 (s, 3H, C4 -OCH3); NMR dC (100 MHz, CDCl3): 161.92, 158.72,
151.06, 146.82, 136.20, 131.34, 130.16, 129.27, 129.13, 128.88, 128.52,
126.90, 124.61, 123.05, 116.59, 114.54, 114.05, 113.48, 56.16, 55.31,
55.13; HRMS: m/z (Mþ) calcd. for C26H21NO3: 395.1521, found:
396.1651 (M þ H).
4.2.4. 1,3-bis(4-Chorophenyl)-1H-naphtho[1,2-e][1,3]oxazine (3d)
mp 202e203 ꢀC; yield: 78%; IR(KBr)
n
: 3061, 3024, 2879,
4.2.1. 1,3-Diphenyl-1H-naphtho[1,2-e][1,3]oxazine (3a)
1672, 1624, 1595 cmꢂ1
; NMR dH (400 MHz, CDCl3): 8.05
mp 170e171 ꢀC; yield: 73%; IR(KBr)
n
: 3061, 3026, 2974, 2933,
(d, J ¼ 8.44 Hz, 2H, C3-C6H4Cl; ortho protons), 7.86e7.82 (m, 2H,
C7-H, C9-H). 7.63e7.61 (m, 1H, C5-H), 7.44e7.34 (m, 5H, C6-H, C8-H,
C10-H and C1-C6H4Cl; ortho protons), 7.29 (d, J ¼ 8.44 Hz, 2H,
C3-C6H4Cl; meta protons), 7.24 (d, J ¼ 8.28 Hz, 2H, C1-C6H4Cl; meta
protons), 6.41 (s, 1H, C1-H); NMR dC (100 MHz, CDCl3): 150.65,
146.66, 141.82, 137.40, 133.27, 131.46, 130.35, 129.90, 129.71, 129.21,
128.97, 128.94, 128.68, 128.48, 127.21, 124.97, 122.89, 116.45, 113.24,
56.30; HRMS: m/z (Mþ) calcd. for C24H15Cl2NO: 403.0531, found:
404.0694 (M þ H).
1656, 1625, 1597 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.15 (d,
J ¼ 7.08 Hz, 2H, C3-C6H5; ortho protons), 7.86e7.82 (m, 2H, C7-H, C9-
H). 7.74 (d, J ¼ 7.88 Hz, 1H, C5-H), 7.50e7.38 (m, 8H, ArH), 7.31e7.19
(m, 3H, ArH), 6.32 (s, 1H, C1-H); NMR dC (100 MHz, CDCl3): 151.39,
146.85, 143.54, 132.10, 131.43, 131.06, 130.16, 129.35, 128.73, 128.56,
128.18, 127.86, 127.62, 127.39, 127.01, 124.73, 123.07, 116.58, 114.10,
57.02; HRMS: m/z (Mþ) calcd. for C24H17NO: 335.1310, found:
336.1397 (M þ H).

200
V. Verma et al. / European Journal of Medicinal Chemistry 56 (2012) 195e202
4.2.5. 1,3-bis(4-Fluorophenyl)-1H-naphtho[1,2-e][1,3]oxazine (3e)
mp 138e139 ꢀC; yield: 71%; IR(KBr)
: 3062, 2929, 1666,
123.32, 123.12, 116.26, 113.45, 57.31; HRMS: m/z (Mþ) calcd. for
C24H16N2O3: 380.1161, found: 381.1334 (M þ H).
n
1600 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.12 (dd, J ¼ 8.36, 5.6 Hz,
2H, C3-C6H4F(ortho protons)), 7.86e7.82 (m, 2H, C7-H, C9-H), 7.65
(d, J ¼ 8.12 Hz, 1H, C5-H), 7.44e7.32 (m, 5H, C6-H, C8-H, C10-H and
C1-C6H4F; ortho protons), 7.10 (t, J ¼ 8.6, 8.56 Hz, 2H, C3-C6H4F;
meta protons), 6.96 (t, J ¼ 8.56 Hz, 2H, C1-C6H4F; meta protons),
6.41 (s, 1H, C1-H); NMR dC (100 MHz, CDCl3): 164.70 (d,
J ¼ 50.15 Hz), 161.97 (d, J ¼ 44.42 Hz), 150.54, 146.70, 139.32 (d,
J ¼ 3.12 Hz), 131.45, 129.96, 129.80 (d, J ¼ 8.74 Hz), 129.59, 129.44
(d, J ¼ 11.30 Hz), 128.66, 128.09 (d, J ¼ 3.01 Hz), 127.15, 124.90,
122.94, 116.48, 115.64 (d, J ¼ 21.33 Hz), 115.27 (d, J ¼ 21.79 Hz),
113.64, 56.17; HRMS: m/z (Mþ) calcd. for C24H15F2NO: 371.1122,
found: 372.1276 (M þ H).
4.3.4. 3-(4-Chlorophenyl)-1-phenyl-1H-naphtho[1,2-e][1,3]oxazine
(7d)
mp 197e198 ꢀC; yield: 82%; IR(KBr)
n: 3066, 3028, 2899, 1674,
1593, 1496 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.07 (d, J ¼ 8.44 Hz,
2H, C3-C6H4Cl; ortho protons), 7.85e7.79 (m, 2H, C7-H, C9-H). 7.70
(d, J ¼ 7.56 Hz, 1H, C5-H), 7.44e7.19 (m, 10H, ArH), 6.45 (s, 1H, C1-H);
NMR dC (100 MHz, CDCl3): 150.49, 146.66, 143.66, 137.63, 131.46,
130.55, 130.08, 129.44, 128.97, 128.77, 128.57, 128.42, 127.84, 127.48,
127.07, 124.82, 123.08, 116.43, 113.89, 57.03; HRMS: m/z (Mþ) calcd.
for C24H16ClNO: 369.0920, found: 370.1177 (M þ H).
4.3.5. 3-(4-Fluorophenyl)-1-phenyl-1H-naphtho[1,2-e][1,3]oxazine
4.3. General procedure for the synthesis of naphthoxazine (7)
(7e)
mp 182e183 ꢀC; yield: 74%; IR(KBr)
n: 3070, 3026, 2931, 1666,
Acidic hydrolysis of appropriate N-arylidene-1-(
phenyl/p-tolyl)-2-naphthols (2) resulted in the formation of 1-(
aminophenyl/p-tolylbenzyl)-2-naphthols (5, Betti base) which on
condensation with equivalent amount of aromatic aldehydes gave
a
-amino-
1595, 1506 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.13 (dd, J ¼ 8.32,
5.8 Hz, 2H, C3-C6H4F; ortho protons), 7.85e7.81 (m, 2H, C7-H, C9-H).
7.71 (d, J ¼ 7.60 Hz, 1H, C5-H), 7.48e7.35 (m, 5H, C6-H, C8-H, C10-H
and C1-C6H5; ortho protons), 7.29 (t, J ¼ 7.68, 7.56 Hz, 2H, C3-C6H4F;
meta protons), 7.25e7.19 (m, 1H, ArH), 7.10 (t, J ¼ 8.56 Hz, 2H, C1-
C6H4F; meta protons), 6.48 (s, 1H, C1-H); NMR dC (100 MHz, CDCl3):
165.91, 163.42, 150.56, 146.69, 143.42, 130.09, 129.84 (d, J ¼ 3.16 Hz),
129.42, 128.77, 128.57, 128.20 (d, J ¼ 3.97 Hz), 127.83, 127.46, 127.06,
124.81, 123.07, 116.56, 115.55 (d, J ¼ 3.16 Hz), 115.10, 113.14, 56.96;
HRMS: m/z (Mþ) calcd. for C24H16FNO: 353.1216, found: 354.1467
(M þ H).
a
-
N-arylidene-1-(a-aminophenyl/p-tolylbenzyl)-2-naphthols (6) [9].
The compound 6 (0.01 mol) was dissolved by warming in methanol
(15 mL) and iodobenzene diacetate (0.02 mol) was added into it.
The reaction mixture was stirred for 2e3 h at 55e60 ꢀC. The
reaction was monitored by TLC using toluene as eluant. The solid so
formed was filtered and washed with cold methanol followed by
ether and crystallized from dichloromethane.
4.3.1. 3-(4-Methoxyphenyl)-1-phenyl-1H-naphtho[1,2-e][1,3]
4.3.6. 3-(4-Fluorophenyl)-1-phenyl-1H-naphtho[1,2-e][1,3]oxazine
oxazine (7a)
(7f)
mp 214e215 ꢀC; yield: 75%; IR(KBr)
n
: 3068, 3020, 2949, 2924,
mp 201e202 ꢀC; yield: 77%; IR(KBr)
n: 3066, 3030, 2899, 2868,
2835, 1664, 1602, 1510 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.06 (d,
J ¼ 8.80 Hz, 2H, C3-C6H4OCH3; ortho protons), 7.84e7.80 (m, 2H, C7-
H, C9-H). 7.72 (d, J ¼ 7.88 Hz, 1H, C5-H), 7.42e7.35 (m, 5H, C6-H, C8-
H, C10-H and C1-C6H5; ortho protons), 7.26e7.25 (m, 2H, C3-C6H5;
meta protons), 7.20e7.16 (m, 1H, C1-C6H5; para protons), 6.92 (d,
J ¼ 8.76 Hz, 2H, C1-C6H4OCH3; meta protons), 6.42 (s, 1H, C1-H),
1674, 1624, 1591, 1512 cmꢂ1; NMR dH (400 MHz, CDCl3): 7.99 (d,
J ¼ 8.44 Hz, 2H, C3-C6H4Br; ortho protons), 7.85e7.80 (m, 2H, C7-H,
C9-H), 7.69 (d, J ¼ 7.36 Hz, 1H, C5-H), 7.55 (d, J ¼ 8.40 Hz, 2H, C3-
C6H4Br; meta protons), 7.44e7.18 (m, 8H, ArH), 6.44 (s, 1H, C1-H);
NMR dC (100 MHz, CDCl3): 150.62, 146.66, 143.32, 142.54, 131.41,
131.38, 129.47, 129.19, 128.79, 128.59, 127.99, 127.85, 127.50, 127.41,
126.66, 125.77, 124.85, 123.09, 116.45, 57.05; HRMS: m/z (Mþ) calcd.
for C24H16BrNO: 413.0415, found: 414.0718 (M þ H).
00
3.84 (s, 3H, C4 -OCH3); NMR dC (100 MHz, CDCl3): 162.01, 151.33,
146.92, 143.73, 131.39, 130.22, 129.34, 129.27, 128.71, 128.56, 127.84,
127.33, 126.98, 124.68, 123.07, 116.62, 114.34, 113.54, 56.89, 55.36;
HRMS: m/z (Mþ) calcd. for C25H19NO2: 365.1416, found: 366.1597
(M þ H).
4.3.7. 3-(Phenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3]oxazine (7g)
mp 175e176 ꢀC; yield: 76%; IR(KBr)
n: 3039, 3010, 2916, 2872,
1672, 1606, 1512 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.15 (d,
J ¼ 7.28 Hz, 2H, C3-C6H5; ortho protons), 7.85e7.81 (m, 2H, C7-H, C9-
4.3.2. 1-Phenyl-3-(p-tolyl)-1H-naphtho[1,2-e][1,3]oxazine (7b)
mp 194e195 ꢀC; yield: 72%; IR(KBr)
n
: 3064, 3028, 3005, 2918,
H). 7.75 (d, J ¼ 7.96 Hz, 1H, C5-H), 7.50e7.37 (m, 6H, C6-H, C8-H, C10
-
2893, 1670, 1606, 1514 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.03 (d,
J ¼ 8.04 Hz, 2H, C3-C6H4CH3(ortho protons)), 7.85e7.79 (m, 2H, C7-
H, C9-H). 7.74 (d, J ¼ 7.96 Hz, 1H, C5-H), 7.44e7.37 (m, 5H, C6-H, C8-
H, C10-H and C1-C6H4CH3; ortho protons), 7.30e7.18 (m, 5H, ArH),
H and C3-C6H5), 7.30 (d, J ¼ 7.76 Hz, 2H, C1-C6H4CH3; ortho
protons), 7.09 (d, J ¼ 7.68 Hz, 2H, C1-C6H4CH3; meta protons), 6.45
0
(s, 1H, C1-H), 2.27 (s, 3H, C4 -CH3); NMR dC (100 MHz, CDCl3):
151.32, 146.76, 140.69, 137.04, 132.11, 131.41, 131.01, 130.15, 129.42,
129.24, 128.54, 128.15, 127.73, 127.61, 127.30, 126.98, 124.70, 123.06,
116.56, 114.28, 56.68, 21.06; HRMS: m/z (Mþ) calcd. for C25H19NO:
349.1467, found: 350.1726 (M þ H).
0
6.46 (s, 1H, C1-H), 2.40 (s, 3H, C4 -CH3); NMR dC (100 MHz, CDCl3):
151.53, 146.85, 143.62, 141.38, 131.37, 130.15, 129.27, 128.90, 128.66,
128.54, 127.84, 127.58, 127.34, 126.96, 124.67, 123.04, 116.61, 114.21,
56.93, 21.47; HRMS: m/z (Mþ) calcd. for C25H19NO: 349.1467, found:
350.1647 (M þ H).
4.3.8. 3-(4-Methoxyphenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3]
oxazine (7h)
4.3.3. 3-(4-Nitrophenyl)-1-phenyl-1H-naphtho[1,2-e][1,3]oxazine
mp 176e177 ꢀC; yield: 81%; IR(KBr)
n: 3068, 3020, 2949, 2924,
(7c)
2835, 1664, 1602, 1510 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.08 (d,
J ¼ 8.76 Hz, 2H, C3-C6H4OCH3; ortho protons), 7.83e7.80 (m, 2H, C7-
H, C9-H). 7.74 (d, J ¼ 8.04 Hz,1H, C5-H), 7.44e7.35 (m, 3H, C6-H, C8-H
and C10-H), 7.29 (d, J ¼ 7.92 Hz, 2H, C1-C6H4CH3; ortho protons),
7.08 (d, J ¼ 7.76 Hz, 2H, C1-C6H4CH3; meta protons), 6.93 (d,
mp 208e209 ꢀC; yield: 72%; IR(KBr)
n: 3059, 3030, 2864, 1674,
1598, 1519, 1346 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.30e8.20 (m,
4H, C3-C6H4NO2), 7.88e7.82 (m, 2H, C7-H, C9-H). 7.69e7.67 (m, 1H,
C5-H), 7.44e7.39 (m, 5H, C6-H, C8-H, C10-H and C1-C6H5; ortho
protons), 7.32e7.21 (m, 3H, C1-C6H5), 6.49 (s, 1H, C1-H); NMR dC
(100 MHz, CDCl3): 149.55, 149.38, 146.46, 142.94, 137.84, 131.62,
129.97, 129.71, 128.88, 128.64, 128.57, 127.89, 127.70, 127.23, 125.07,
00
J ¼ 8.76 Hz, 2H, C3-C6H4OCH3(meta, C3 )), 6.41 (s, 1H, C1-H), 3.84 (s,
00
0
3H, C4 -OCH3), 2.27 (s, 3H, C4 -CH3); NMR dC (100 MHz, CDCl3):
161.91, 151.16, 146.80, 140.88, 136.94, 131.33, 130.17, 129.39, 129.30,

V. Verma et al. / European Journal of Medicinal Chemistry 56 (2012) 195e202
201
129.14, 128.52, 127.69, 126.92, 124.61, 124.57, 123.03, 116.59, 114.47,
113.46, 56.54, 55.31, 21.05; HRMS: m/z (Mþ) calcd. for C26H21NO2:
379.1572, found: 380.1859 (M þ H).
compounds were prepared in double strength nutrient broth e I.P.
(bacteria) or Sabouraud dextrose broth I.P. (fungi). The samples
were incubated at 37 ꢀC for 24 h (bacteria), 25 ꢀC for 7 days
(A. niger) and 37 ꢀC for 48 h (C. albicans), and the results were
recorded in terms of MIC.
4.3.9. 3-(4-Nitrophenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3]oxazine
(7i)
mp 203e204 ꢀC; yield: 75%; IR(KBr)
n: 3064, 3014, 2912, 2873,
4.5. In vitro cytotoxicity assay
1670, 1598, 1519, 1327 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.29e8.21
(m, 4H, C3-C6H4NO2), 7.87e7.76 (m, 2H, C7-H, C9-H). 7.69 (d,
J ¼ 6.72 Hz, 1H, C5-H), 7.42e7.33 (m, 3H, C6-H, C8-H and C10-H), 7.27
(d, J ¼ 7.76 Hz, 2H, C1-C6H4CH3; ortho protons), 7.10 (d, J ¼ 7.76 Hz,
The synthesized 1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxa-
zine were dissolved in DMSO to form stock solutions (1 mM/mL),
which were filter sterilized (0.2 mm) before testing on cell lines.
0
2H, C1-C6H4CH3; meta protons), 6.45 (s, 1H, C1-H), 2.28 (s, 3H, C4 -
Growth medium RPMI-1640, Minimum Essential Medium (MEM),
foetal calf serum (GIBCO), trypsin, penicillin, MTT dye, strepto-
mycin, DMSO and phosphate buffer saline (PBS) chemicals were
used for study. Human breast cancer cell line (MCF-7), lung (A-549),
Prostate (PC-3) and Colon (HCT-116) were procured from European
Collection of cell culture (ECACC), UK. Cells were grown in RPMI-
1640 medium supplemented with 10% FCS and 1% penicillin.
Penicillin was dissolved in PBS and sterilized by filtering through
CH3); NMR dC (100 MHz, CDCl3): 149.41, 146.39, 140.10, 137.88,
137.41, 131.59, 129.97, 129.58, 129.56, 128.60, 128.53, 127.75, 127.33,
127.18, 125.01, 123.28, 123.11, 116.24, 113.63, 56.98, 21.06; HRMS: m/
z (Mþ) calcd. for C25H18N2O3: 394.1317, found: 395.1616 (M þ H).
4.3.10. 3-(4-Chlorophenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3]
oxazine (7j)
mp 170e171 ꢀC; yield: 78%; IR(KBr)
n: 3051, 3016, 2978, 2916,
0.2 mm filter in laminar air flow hood. Cells were cultured in CO2
2879, 2844, 1674, 1597, 1512 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.06
(d, J ¼ 8.48 Hz, 2H, C3-C6H4Cl; ortho protons), 7.84e7.80 (m, 2H, C7-
H, C9-H). 7.71 (d, J ¼ 7.68 Hz, 1H, C5-H), 7.43e7.34 (m, 5H, C6-H, C8-
H, C10-H and C1-C6H4CH3; ortho protons), 7.27 (d, J ¼ 7.92 Hz, 2H,
C1-C6H4CH3; ortho protons), 7.09 (d, J ¼ 7.92 Hz, 2H, C1-C6H4CH3;
incubator (New Brunswick, Galaxy 170R, Eppendorf) with an
internal atmosphere of 95% air and 5% CO2 gas and the cell lines
were maintained at 37 ꢀC. The media was stored at low tempera-
ture (2e8 ꢀC). The medium for cryopreservation contained 20% FCS
and 10% DMSO in growth medium.
0
meta protons) 6.41 (s, 1H, C1-H), 2.27 (s, 3H, C4 -CH3); NMR dC
(100 MHz, CDCl3): 150.41, 146.61, 140.53, 137.19, 137.16, 131.45,
130.61, 130.09, 129.48, 129.34, 128.97, 128.56, 128.40, 127.72, 127.05,
124.80, 123.09, 116.44, 114.09, 56.71, 21.07; HRMS: m/z (Mþ) calcd.
for C25H18ClNO: 383.1077, found: 384.1353 (M þ H).
4.5.1. Cell viability assay
The MTT assay was used to assess the effect of 1,3-disubstituted-
1H-naphtho[1,2-e][1,3]oxazine on cell viability. In each well of a 96-
well plate, 3 ꢁ 103 cells were grown in 100
mL of medium. After 24 h,
1,3-disubstituted-1H-naphtho[1,2-e][1,3]oxazine was added to ach-
4.3.11. 3-(4-Fluorophenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3]oxazine
ieve a final concentration 50e10 mmol/100 mL, respectively. 20 mL of
(7k)
2.5 mg/mL MTT (Organics Research, Inc.) solution in PBS was added
to each well followed by an additional incubation period of at least
4 h to allow for complete bioreduction of MTT to the final formazan
product. After 48 h of treatment, supernatant was removed and
mp 177e178 ꢀC; yield: 74%; IR(KBr)
n: 3057, 3012, 2976, 2918,
2877, 1676, 1600, 1510 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.13 (dd,
J ¼ 8.52, 5.64 Hz, 2H, C3-C6H4F; ortho protons), 7.84e7.81 (m, 2H,
C7-H, C9-H). 7.72 (d, J ¼ 7.84 Hz, 1H, C5-H), 7.44e7.35 (m, 3H, C6-H,
C8-H and C10-H), 7.28 (d, J ¼ 7.92 Hz, 2H, C1-C6H4CH3; ortho
formazan crystals were dissolved in 200 mL of DMSO. Absorbancewas
then measured at 570 nm using an absorbance plate reader (Bio-Rad
Microplate Reader). Data are expressed as the percentage of viable
cells in treated relative to non-treated conditions [16].
0
protons), 7.12e7.08 (m, 4H, ArH), 6.41 (s, 1H, C1-H), 2.27 (s, 3H, C4 -
CH3); NMR dC (100 MHz, CDCl3): 165.89, 150.43, 146.66, 140.62,
137.13, 131.43, 130.12, 129.84 (d, J ¼ 8.73 Hz), 129.47, 129.31, 128.56,
128.27 (d, J ¼ 2.99 Hz), 127.71, 127.03, 124.77, 123.09, 116.46, 115.29
(d, J ¼ 21.86 Hz), 114.17, 56.66, 21.07; HRMS: m/z (Mþ) calcd. for
C25H18FNO: 367.1372, found: 368.1647 (M þ H).
Acknowledgements
The authors thank University Grants Commission, New Delhi for
financial support.
4.3.12. 3-(4-Bromophenyl)-1-p-tolyl-1H-naphtho[1,2-e][1,3]
oxazine (7l)
Appendix A. Supplementary data
mp 156e157 ꢀC;yield:76%;IR(KBr)
n:3051, 3024, 2918,2900,1676,
1593, 1512 cmꢂ1; NMR dH (400 MHz, CDCl3): 8.00 (d, J ¼ 8.40, Hz, 2H,
C3-C6H4Br; ortho protons), 7.84e7.79 (m, 2H, C7-H, C9-H). 7.72 (d,
J ¼ 7.72 Hz, 1H, C5-H), 7.44e7.34 (m, 5H, C6-H, C8-H and C10-H), 7.28 (d,
J ¼ 7.84 Hz, 2H, C1-C6H4CH3; ortho protons), 7.09 (d, J ¼ 7.72 Hz, 2H,
Crystallographic data for 3b has been deposited with the Cam-
bridge Crystallographic Data Centre (No. CCDC 874764).
Appendix B. Supplementary data
0
C1-C6H4CH3; meta protons), 6.41 (s, 1H, C1-H), 2.27 (s, 3H, C4 -CH3);
NMR dC (100 MHz, CDCl3): 150.49, 146.58, 140.49, 137.16, 131.45,
131.36, 131.06, 130.08, 129.47, 129.34, 129.18, 128.56, 127.72, 127.04,
125.69, 124.80, 123.08, 116.43, 114.06, 56.72, 21.07; HRMS: m/z (Mþ)
calcd. for C25H18BrNO: 427.0572, found: 428.0901 (M þ H).
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ejmech.2012.08.
018.
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