Synthesis and in vitro antiprotozoal activities of 5-phenyliminobenzo[a] phenoxazine derivatives

Article abstract of DOI:10.1016/j.bmcl.2011.07.112

A series of 5-phenyliminobenzo[a]phenoxazine derivatives were synthesized. The in vitro antiprotozoal activities were evaluated against Plasmodium falciparum K1, Trypanosoma cruzi, Leishmania donovani and Trypanosoma brucei rhodesiense. N,N-Diethyl-5-((4-

Full text of DOI:10.1016/j.bmcl.2011.07.112

Bioorganic & Medicinal Chemistry Letters 21 (2011) 5804–5807
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Bioorganic & Medicinal Chemistry Letters
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Synthesis and in vitro antiprotozoal activities of 5-phenyliminobenzo[a]
phenoxazine derivatives
Xue-Liang Shi a, Jian-Feng Ge a, , Bao-Qiang Liu a, Marcel Kaiser b, Sergio Wittlin b, Reto Brun b,
⇑
Masataka Ihara c,
⇑
a Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, 199 Ren’Ai Road, Suzhou 215123, China
b Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel, Switzerland
c Drug Discovery Science Research Centre, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 5-phenyliminobenzo[a]phenoxazine derivatives were synthesized. The in vitro antiprotozoal
activities were evaluated against Plasmodium falciparum K1, Trypanosoma cruzi, Leishmania donovani and
Trypanosoma brucei rhodesiense. N,N-Diethyl-5-((4-methoxyphenyl)imino)-5H-benzo[a]phenoxazin-9-
Received 8 April 2011
Revised 27 July 2011
Accepted 29 July 2011
Available online 5 August 2011
amine shows IC50 = 0.040
l
mol LÀ1 with a selective index of 1425 against Plasmodium falciparum K1.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Antiprotozoal
Benzo[a]phenoxazine
In vitro
Plasmodium falciparum
Nile blue
Malaria, Chagas disease, leishmaniasis, and African sleeping
sickness are the main tropical diseases caused by protozoans. The
inhabitants in subtropical regions are also exposed to the danger of
infection owing to global warming.
inexpensive antiprotozoal candidates is a challenge for synthetic
chemists, biochemists and medicinal chemists.
The
p-delocalized lipophilic cation (DLC) hypothesis was used
for the selection of the antiprotozoal candidates in our group.7 Qua-
ternary ammonium salts of rhodacyanine and phenoxazinium type
derivatives were prepared for the evaluation of the antiprotozoal
activities. Rhodacyanines, which are easily prepared by several
steps in high yields, show good in vitro activities against P. falcipa-
rum and L. donovani.8 Phenoxazinium and phenothiazinium, which
are water-soluble, inexpensive and high purity dyes, exhibit potent
antiprotozoal activities, especially against P. falciparum K1 (resis-
tant to chloroquine and pyrimethamine) and T. cruzi.9 However,
the cytotoxicities of these compounds against normal L-6 cells were
observed at low concentration. 5-Heterocycliciminobenzo-
[a]phenoxazine derivatives attached with substituted phenyl rings
to the phenoxazinium skeleton were evaluated for the antiproto-
zoal activities, since their corresponding salts are a variant of DLC
candidates; SSJ-183, having a 4-aminopyridine group, showed an
IC50 value against P. falciparum K1 of 7.6 nM and a selectivity index
of >7300. Cure was achieved by three oral doses of SSJ-183 at
100 mg/kg to mice infected with the P. berghei ANKA strain.10 The
synthesis and in vitro antiprotozoal activities of 5-phen-
yliminobenzo[a]phenoxazine derivatives from the corresponding
aniline derivatives is discussed below in details.
Malaria, which is caused by the protozoan parasites of the
genus Plasmodium,1 exists in about 109 countries. About 1.4 billion
people were estimated to be at high risk of Plasmodium falciparum
malaria, and malaria accounted for the reported 863 thousand
deaths among an estimated 243 million cases; According to data
and estimates, only one in five malaria deaths was reported. In
many parts of the world, parasites have developed resistance to a
number of anti-malarial medicines.2 Thus, malaria is looked as a
major threatening disease to the public health. Chagas disease,3
leishmaniasis,4 and African sleeping sickness5 are caused by Try-
panosoma cruzi, Leishmania donovani, and Trypanosoma brucei rho-
desiense, respectively. The lack of interest in pharmaceutical
companies for developing new drugs makes them ‘neglected dis-
eases’, and they are usually treated with medicines, which have
low efficacy and high acute toxicity.6
Developing countries have many patients infected by parasitic
protozoa. Thus, the identification of effective, low-toxicity, and
⇑
Corresponding authors. Tel./fax: +86 0512 6588-4717 (J.-F. Ge), tel./fax: +81 03
5498 6391 (M. Ihara).
The synthetic scheme of benzo[a]phenoxazines (3a–i) is shown
E-mail addresses: ge_jianfeng@hotmail.com (J.-F. Ge), m-ihara@hoshi.ac.jp
(M. Ihara).
in Figure 1.11 The coordinated complex of zinc chloride and
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.07.112

X.-L. Shi et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5804–5807
5805
Figure 1. Synthesis of 5-phenyliminobenzo[a]phenoxazines.11
9-(diethylamino)benzo[a]phenoxazin-7-ium chloride was synthe-
sized by N,N-diethyl-4-nitrosoaniline hydrochloride and 2-naph-
thalenol in refluxing zinc chloride-ethanol solution. It was
converted to the 9-(diethylamino)benzo[a]phenoxazin-7-ium ni-
trate (1) by the treatment with nitric acid.12 5-Phen-
yliminobenzo[a]phenoxazines were obtained by the reaction of 1
and three equivalents amine. Although the main product was
benzo[a]phenoxazine, ammonia solution was used in the reaction
to ensure full conversion of the benzo[a]phenoxazinium salt con-
verted to the benzo[a]phenoxazine (Method A).13 The products
were purified with chromatography. Alternatively, N,N-diethyl-5-
((4-methoxyphenyl)imino)-5H-benzo[a]phenoxazin-9-amine (3c)
and N,N-diethyl-5-((3-methoxyphenyl)imino)-5H-benzo[a]phen-
oxazin-9-amine (3d)14 can be obtained by the reaction of meth-
oxy-aniline with the 9-(diethylamino)-5-(phenylsulfonyl)benzo
[a]phenoxazin-7-ium nitrate (2, Method B). However, the nucleo-
philic abilities of other aniline derivatives with electron-withdraw-
ing groups are too weak to drive the reaction.
100
90
80
70
60
50
40
30
3g
3f
3a
3c
3f
3g
3a
3c
100
200
300
400
500
Temperature (oC)
Figure 3. TGA curves of the selected compounds.
To verify the structure of the 5-phenyliminobenzo[a]phenoxa-
zine, the single crystals of 3i was obtained in methanol solution
(CCDC number: 816443). The crystal structure is shown in Figure 2.
The compound was constructed by the benzo[a]phenoxazine and
phenylimino group with imine bond (N3 = C19, 0.1319(5) nm).
The benzo[a]phenoxazine and phenyl group were in oblique cross-
ing position. TGA (thermogravimetric analysis, Fig. 3) was per-
formed for the selected compounds (3a, 3c, 3f, and 3g) to
evaluate the stability of the title compounds, since imine group
was usually looked as unstable structure. The decomposed temper-
atures of 3a and 3c were around 300–400 °C, while 3f and 3g were
decomposed at 300–340 °C. It was obvious that all the compounds
were stable enough in the ambient temperature.
The in vitro tests were performed at pH 7.4 as microplate assays
using P. falciparum K1, T. cruzi (Tulahuen C4), T. b. rhodesiense
(STIB900), and L. donovani (MHOM-ET-67/L82), and the cytotoxic-
ity was assessed with rat skeletal myoblasts (L-6 cells) as described
previously. The following substances were used as reference stan-
dards: chloroquine (P. falciparum K1), benznidazole (T. cruzi), mel-
arsoprol (T. b. rhodesiense), miltefosine (L. donovani) and
podophyllotoxin (cytotoxicity assay).9c
Antiprotozoal and cytotoxic activities of the title compounds
(3a–i) are shown in Table 1. From the IC50 value to the normal L-
6 cells, the higher IC50 values indicate that benzo[a]phenoxazine
is a less toxic class compound than the reported phenoxazinium
and phenothiazinium.9c,d All compounds show insufficient activi-
ties against T. b. rhodesiense, T. cruzi and L. donovani. The
Figure 2. Crystallographic structure of 3i.

5806
X.-L. Shi et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5804–5807
Table 1
Antiprotozoal and cytotoxic activities (IC50 values,
l
M) of title compounds (3a–i)a
Compd
P. falc.K1
T. cruzi
T.b. rhod.
L. don.
Cytotox. L-6
IC50
IC50
SIb
IC50
SIb
IC50
SIb
IC50
SIb
3a
3b
3c
3d
3e
3f
3g
3h
0.208c
0.253c
0.040
0.045
0.215
0.209
0.135
1.933
0.205
0.148
863c
531c
1425
883
261
617
386
8
>228.7
20.9
20.3
143.2
78.8
76.7
56.9
10.9
143.7
0.886
<0.79
6.42
2.82
0.28
0.71
1.68
0.91
1.34
0.43
NTe
88.5
36.2
14.9
11.3
2.03
3.71
3.84
3.52
0.66
1.00
0.26
0.08
0.42
NTe
20.1
10.7
5.2
8.94
12.54
10.91
13.87
2.41
4.50
179.8
134.2
57.2
39.6
56.2
129.1
51.9
14.6
61.8
0.02
2.9
85.4
23.3
28.6
>205.3
70.5
90.6
0.280
129.2
197.5
184.2
147.1
0.006
<0.25
0.21
3i
302
0.68
Standardsd
NTe
NTe
a
Values indicate the inhibitory concentration of a compound or standard in
independent experiments are shown.
lM, which is necessary to achieve 50% growth inhibition (IC50). Mean values of two
b
Selectivity index = IC50 value for L-6/IC50 value for P. falciparum K1, T. b. rhodesiense, T. cruzi, or L. donovani.
Data was obtained by hydrochloride salts in Ref. 10.
Standards: chloroquine (P. falciparum K1), melarsoprol (T.b. rhodesiense), benznidazole (T. cruzi), miltefosine (L. donovani), and podophyllotoxin (L6 cells, cytotoxicity).
Not tested.
c
d
e
4. Tripathi, K.; Kumar, R.; Bharti, K.; Kumar, P.; Shrivastav, R.; Sundar, S.; Pai, K.
Clin. Chim. Acta 2008, 388, 135.
5. Croft, S. L. Parasitology 1997, 114, S3.
compounds bearing electron withdrawing groups (3e–3i) do not
exhibit improved activity. Notably, compounds 3c and 3d
substituted by methoxyl groups show reasonable activities
against P. falciparum, N,N-diethyl-5-((4-methoxy-phenyl)imino)-
5H-benzo[a]phenoxazin-9-amine (3c) and N,N-diethyl-5-((3-
methoxyphenyl)imino)-5H-benzo[a]phenoxazin-9-amine (3d) show
6. (a) Urbina, J. A.; Docampo, R. Trends Parasitol. 2003, 19, 495; (b) Vieira, N. C.;
Espindola, L. S.; Santana, J. M.; Veras, M. L.; Pessoa, O. D. L.; Pinheiro, S. M.;
Mendonca, A. R.; Lima, M. A. S.; Silveira, E. R. Bioorg. Med. Chem. 2008, 16, 1676;
(c) Bressi, J. C.; Choe, J.; Hough, M. T.; Buckner, F. S.; Voorhis, W. C. V.; Verlinde,
C. L. M. J.; Hol, W. G. J.; Gelb, M. H. J. Med. Chem. 2000, 43, 4135.
7. (a) Chen, L. B. Ann. Rev. Cell. Biol. 1988, 4, 155; (b) Ihara, M. Heterocycles 2011.
doi:10.3987/REV-11-706.
8. (a) Takasu, K.; Inoue, H.; Kim, H.-S.; Suzuki, M.; Shishido, T.; Wataya, Y.; Ihara,
M. J. Med. Chem. 2002, 45, 995; (b) Takasu, K.; Terauchi, H.; Inoue, H.; Kim, H.-
S.; Wataya, Y.; Ihara, M. J. Comb. Chem. 2003, 5, 211; (c) Pudhom, K.; Kasai, K.;
Terauchi, H.; Inoue, H.; Kaiser, M.; Brun, R.; Ihara, M.; Takasu, K. Bioorg. Med.
Chem. 2006, 13, 8550; (d) Takasu, K.; Pudhom, K.; Kaiser, M.; Brun, R.; Ihara, M.
J. Med. Chem. 2006, 49, 4795; (e) Takasu, K.; Morisaki, D.; Kaiser, M.; Brun, R.;
Ihara, M. Heterocycles 2005, 66, 161; (f) Pudhom, K.; Ge, J.-F.; Arai, C.; Yang, M.;
Kaiser, M.; Wittlin, S.; Brun, R.; Itoh, I.; Ihara, M. Heterocycles 2009, 77, 207; (g)
Yang, M.; Aria, C.; Md, A. B.; Lu, J.; Ge, J.-F.; Aria, C.; Pudhom, K.; Takasu, K.;
Kasai, K.; Kaiser, M.; Brun, R.; Yardley, V.; Itoh, I.; Ihara, M. J. Med. Chem. 2010,
53, 368.
IC50 of 0.040 and 0.045 l
mol LÀ1 with a selectivity index of 1425
and 883 against P. falciparum K1, respectively. The results indicate
that 5-phenyliminobenzo[a]phenoxazine bearing the electron
donating group and lone-pair electron would be potential candi-
date for this type anti-malaria compound.
In summary, 5-phenyliminobenzo[a]phenoxazine derivatives
were synthesized, and they were very stable compounds. The
benzo[a]phenoxazine with methoxylphenylimino group in 5-pos-
tion shows good in vitro antiprotozoal activity against P. falciparum
K1.
9. (a) Yang, M.; Ge, J.-F.; Arai, C.; Itoh, I.; Fu, Q.; Ihara, M. Bioorg. Med. Chem. 2009,
17, 1481; (b) Ge, J.-F.; Arai, C.; Ihara, M. Dyes Pigments 2008, 79, 33; (c) Ge, J.-F.;
Arai, C.; Kaiser, M.; Wittlin, S.; Brun, R.; Ihara, M. J. Med. Chem. 2008, 51, 3654;
(d) Lu, Y.-T.; Arai, C.; Ge, J.-F.; Ren, W.-S.; Kaiser, M.; Wittlin, S.; Brun, R.; Lu, J.-
M.; Ihara, M. Dyes Pigments 2011, 89, 44.
10. Ge, J.-F.; Arai, C.; Yang, M.; Md, A. B.; Lu, J.; Ismail, N. S. M.; Wittlin, S.; Kaiser,
M.; Brun, R.; Charman, S.; Nguyen, T.; Morizzi, J.; Itoh, I.; Ihara, M. ACS Med.
Chem. Lett. 2010, 1, 360.
Acknowledgments
We thank Professor Terumi Nakajima and Professor Toshio
Honda, Hoshi University, and Dr. Isamu Itoh, Dr. Hiroyuki Togashi,
and Seiki Sakanoue of Synstar Japan Co., Ltd for their kind encour-
agement. This study was supported by the Creation and Support
Program for Start-ups from Universities, Adaptable and Seamless
Technology Transfer Program through Target-driven R&D, Japan
Science Technology Agency (JST) and the Program for Promotion
of Fundamental Studies in Health Sciences of the National Institute
of Biomedical Innovation (NIBIO). Synthetic part was partly sup-
port by Natural Science Fund (BK2009113, BK2009600) in Jiangsu
Province, China.
11. Compound 3f13 were obtained by the reported procedures. General proce-
dure for the preparation of 3a–e, 3g–i: (Method A13): 9-(Diethylamino)
benzo[a]phenoxazin-7-ium nitrate (1) (2.7 mmol) and corresponding aniline
(8.1 mmol) dissolved in ethanol (40 mL), the mixture was heated to reflux for
72 h with stirring. After cooling to room temperature, the residue was obtained
by filtration. Then the residue was dissolved in 40 mL water, ammonia was
added slowly while stirring until the pH ꢀ9.0. The mixture was stirred for 3 h
at room temperature, and then filtered; the solid was purified by silica column
chromatography eluted with chloroform to afford the product. Compound 3a:
Red solid, yield: 27%, mp: 161–163 °C. 1H NMR (400 MHz, CDCl3) dppm: 8.62–
8.58 (m, 2H), 7.67–7.61 (m, 2H), 7.47 (d, J = 8.9 Hz, 1H), 7.38 (t, J = 7.8 Hz, 2H),
7.11 (t, J = 7.4 Hz, 1H), 6.94 (d, J = 7.8 Hz, 2H), 6.52 (dd, J = 9.0, 2.6 Hz, 1H), 6.30
(s, 1H), 6.25 (d, J = 2.6 Hz, 1H), 3.39 (q, J = 7.1 Hz, 4H), 1.20 (t, J = 7.1 Hz, 6H). 13
C
Supplementary data
NMR (75 MHz, CDCl3) dppm: 156.9, 152.3, 149.9, 148.8, 146.8, 142.5, 133.1,
131.7, 130.5, 130.2, 130.1, 129.3, 125.2, 124.8, 124.1, 123.5, 121.0, 108.6, 98.7,
96.6, 45.1, 12.9. TOF-MS(EI): m/z 393.1842 [M]+. Calcd for m/z 393.1841 [M]+.
Compound 3b: Red solid, yield: 38%, mp: 201–202 °C. 1H NMR (400 MHz,
CDCl3) dppm: 8.59 (td, J = 7.6, 2.2 Hz, 2H), 7.66–7.59 (m, 2H), 7.47 (d, J = 9.0 Hz,
1H), 7.18 (d, J = 7.9 Hz, 2H), 6.84 (d, J = 8.2 Hz, 2H), 6.52 (dd, J = 9.0, 2.7 Hz, 1H),
6.34 (s, 1H), 6.24 (d, J = 2.7 Hz, 1H), 3.39 (q, J = 7.1 Hz, 4H), 2.37 (s, 3H), 1.20 (t,
J = 7.1 Hz, 6H). 13C NMR (75 MHz, CDCl3) dppm: 156.9, 149.9, 149.7, 148.6,
146.9, 142.8, 133.3, 132.9, 131.7, 130.4, 130.1, 129.9, 125.1, 124.8, 124.0,
120.89, 108.5, 98.8, 96.6, 45.1, 21.2, 12.9. TOF-MS(EI): m/z 407.1997 [M]+. Calcd
Supplementary data (CIF file of 3i) associated with this article
can be found, in the online version, at doi:10.1016/
j.bmcl.2011.07.112.
References and notes
1. Snow, R. W.; Guerra, C. A.; Noor, A. M.; Myint, H. Y.; Hay, S. I. Nature 2005, 434,
214.
for m/z 407.1998 [M]+. Compound 3c: Red solid, yield: 43%, mp: 188–190 °C. 1
H
NMR (400 MHz, CDCl3) dppm: 8.62–8.59 (m, 2H), 7.67–7.61 (m, 2H), 7.48 (d,
J = 9.0 Hz, 1H), 6.94(s, 4H), 6.54 (dd, J = 9.0, 2.5 Hz, 1H), 6.42 (s, 1H), 6.27 (d,
J = 2.6 Hz, 1H), 3.85 (s, 3H), 3.41 (q, J = 7.1 Hz, 4H), 1.21 (t, J = 7.1 Hz, 6H). 13C
NMR (75 MHz, CDCl3) dppm: 157.0, 156.5, 150.0, 148.8, 146.9, 144.8, 142.5,
133.0, 131.6, 130.5, 130.1, 130.1, 125.1, 125.0 124.0, 122.4, 114.6, 108.8, 98.6,
96.58, 55.8, 45.1, 12.9. TOF-MS(EI): m/z 423.1950 [M]+. Calcd for m/z 423.1947
2. World Health Organization, World malaria report 2009, http://
www.searo.who.int/LinkFiles/Reports_mal2009_report.pdf; World malaria
report 2010, http://www.who.int/entity/malaria/world_malaria_report_2010/
worldmalariareport2010.pdf.
3. Kraus, J. M.; Verlinde, C. L. M. J.; Karimi, M.; Lepesheva, G. I.; Gelb, M. H.;
Buckner, F. S. J. Med. Chem. 2009, 52, 1639.

X.-L. Shi et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5804–5807
5807
[M]+. Compound 3d: Red solid, yield: 49%, mp: 131–133 °C. 1H NMR (400 MHz,
CDCl3) dppm: 8.62–8.59 (m, 1H), 8.58–8.55 (m, 1H), 7.67–7.60 (m, 2H), 7.48 (d,
J = 9.0 Hz, 1H), 7.28 (d, J = 8.3 Hz, 1H), 6.68–6.65 (m, 1H), 6.54–6.51 (m, 3H),
6.32 (s, 1H), 6.26 (d, J = 2.7 Hz, 1H), 3.82 (s, 3H), 3.40 (q, J = 7.1 Hz, 4H), 1.20 (t,
J = 7.1 Hz, 6H). 13C NMR (75 MHz, CDCl3) dppm: 160.6, 157.0, 153.8, 150.0,
148.7, 146.9, 142.5 133.1, 131.7, 130.5, 130.2, 130.1, 130.1 125.1, 124.8, 124.1,
113.2, 109.5, 108.6, 106.2, 98.8, 96.6, 55.5, 45.1, 12.9. TOF-MS(EI): m/z
423.1946 [M]+. Calcd for m/z 423.1947 [M]+. Compound 3e: Red solid, yield:
17%, mp: 209–210 °C. 1H NMR (400 MHz, CDCl3) dppm: 8.63 (t, J = 7.1 Hz, 2H),
7.69–7.63 (m, 2H), 7.50 (d, J = 9.0 Hz, 1H), 7.45 (d, J = 9.0 Hz, 1H), 7.28–7.24 (m,
1H), 7.04 (t, J = 7.0 Hz, 1H), 6.92 (d, J = 7.8 Hz, 1H), 6.55 (d, J = 9.0 Hz, 1H), 6.27
(s, 1H), 6.09–6.08 (m, 1H), 3.40 (q, J = 7.0 Hz, 4H), 1.20 (t, J = 7.0 Hz, 6H). 13C
NMR (75 MHz, CDCl3) dppm: 157.9, 150.1, 149.3, 149.0 146.8, 142.2, 132.6,
131.8, 130.59, 130.4, 130.2, 127.5, 125.5, 125.5, 124.9, 124.3, 124.1, 122.1,
108.8, 98.6, 96.6, 45.2, 12.8. TOF-MS(EI): m/z 427.1450 [M]+. Calcd for m/z
427.1451 [M]+. Compound 3g: Green solid, yield: 12%, mp: 243–244 °C. 1H NMR
(400 MHz, CDCl3) dppm: 8.64 (d, J = 7.6 Hz, 1H), 8.53 (d, J = 7.6 Hz, 1H), 8.27 (d,
J = 8.6 Hz, 2H), 7.71–7.63 (m, 2H), 7.53 (d, J = 9.1 Hz, 1H), 7.03 (d, J = 8.6 Hz,
2H), 6.59 (d, J = 9.0 Hz, 1H), 6.30 (s, 1H), 6.14 (s, 1H), 3.42 (q, J = 7.0 Hz, 4H),
1.22 (t, J = 7.0 Hz, 6H). 13C NMR (101 MHz, CDCl3) dppm: 158.9, 157.1, 150.1,
149.2, 146.6, 143.3, 141.2, 132.0, 131.5, 130.5, 130.3, 129.9, 125.2, 125.1, 124.8,
123.9, 121.1, 109.0, 97.5, 96.2, 44.9, 12.6. TOF-MS(EI): m/z 438.1695 [M]+. Calcd
for m/z 438.1692 [M]+. Compound 3h: Black solid, yield: 13%, mp: 244–246 °C.
1H NMR (400 MHz, CDCl3) dppm: 8.66 (d, J = 7.9 Hz, 1H), 8.59 (d, J = 7.6 Hz, 1H),
8.38 (s, 1H), 8.16 (d, J = 8.8 Hz, 1H), 7.73–7.65 (m, 2H), 7.55 (d, J = 9.1 Hz, 1H),
7.04 (d, J = 8.7 Hz, 1H), 6.61 (d, J = 9.1 Hz, 1H), 6.32 (s, 1H), 5.97 (d, J = 1.2 Hz,
1H), 3.43 (q, J = 7.0 Hz, 4H), 1.22 (t, J = 7.0 Hz, 6H). TOF-MS(EI): m/z 472.1307
[M]+. Calcd for m/z 472.1302 [M]+. Compound 3i: yield: 6%, mp: 248–249 °C. 1
H
NMR (300 MHz, CDCl3) dppm: 8.68 (d, J = 7.9 Hz, 1H), 8.69–8.57 (m, 2H), 8.39
(dd, J = 8.9, 2.5 Hz, 1H), 7.76–7.66 (m, 2H), 7.60 (d, J = 9.1 Hz, 1H), 7.15 (d,
J = 8.9 Hz, 1H), 6.67 (dd, J = 9.1, 2.6 Hz, 1H), 6.36 (d, J = 2.5 Hz, 1H), 6.10 (s, 1H),
3.45 (q, J = 7.0 Hz, 4H), 1.24 (t, J = 7.1 Hz, 6H). TOF-MS(EI): m/z 463.1642 [M]+.
Calcd for m/z 463.1644 [M]+. General procedure for the preparation of 3c–d:
(Method B14): 9-(Diethylamino)-5-((phenylsulfinyl)oxy)benzo[a]phenoxazin-
7-ium nitrate (0.5 mmol), and corresponding aniline (2.0 mmol) were
dissolved in a solution of ethanol (8 mL) and concentrated hydrochloric acid
(0.1 mL). The mixture was heated to reflux for 2 h with stirring. After cooling to
room temperature, the residue was obtained by filtration. Then the residue
was dissolved in 10 mL water, ammonia was added slowly while stirring until
the pH ꢀ9.0. The mixture was stirred for 3 h at room temperature, and then
filtered; the solid was purified by silica column chromatography eluted with
chloroform to afford the product. Compound 3c: yield: 36%, Compound 3d:
yield: 38% (based on compound 2).
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1952, 74, 573.
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2011, 88, 50.
14. Afanas’eva, G. B.; Postovskii, I. Y. Rss. J. Org. Chem. 1965, 1, 1163.