Thermolysis of N-aryl enaminoimine hydrochloride derivatives: A short and general method for the synthesis of pyranoquinolin-3-one and pyranoacridin-3-one derivatives

Article abstract of DOI:10.1002/jhet.1703

A short synthesis of 3H-pyrano[3,2-f]quinolin-3-one, 3H-acenaphtho[1,2-b]pyrano-[3,2-f]quinolin-3-one, and 3H-benzo[h]pyrano[3,2-a]acridin-3-one derivatives are described via thermolysis of suitable enaminoimine hydrochloride derivatives.

Full text of DOI:10.1002/jhet.1703

1
306
Thermolysis of N-Aryl Enaminoimine Hydrochloride Derivatives: A Short
Vol 51
and General Method for the Synthesis of Pyranoquinolin-3-one and
Pyranoacridin-3-one Derivatives
Prasanta Patra, Gandhi K. Kar,* and Biswajit Khatua
Department of Chemistry and Biochemistry, Presidency University (formerly Presidency College), 86/1 College Street,
Kolkata 700073, India
*
E-mail: gandhikar41@hotmail.com
Received December 24, 2011
DOI 10.1002/jhet.1703
Published online 17 March 2014 in Wiley Online Library (wileyonlinelibrary.com).
A short synthesis of 3H-pyrano[3,2-f]quinolin-3-one, 3H-acenaphtho[1,2-b]pyrano-[3,2-f]quinolin-3-one,
and 3H-benzo[h]pyrano[3,2-a]acridin-3-one derivatives are described via thermolysis of suitable
enaminoimine hydrochloride derivatives.
J. Heterocyclic Chem., 51, 1306 (2014).
INTRODUCTION
in both aryl amine and chloroaldehyde as part of the sub-
strates. We have used this pathway to achieve the synthesis
of our target compounds.
Coumarins fused to heteroaromatic rings constitute an
important class of non-natural and natural product. Many
natural and synthetic coumarin derivatives [1–12] fused
with naphthalene, aza/oxa/thia-heterocycles have been
reported to possess significant biological activities includ-
ing anti HIV activity, cytotoxity and anticancer activity,
antimicrobial activity, as well as activity against malignant
dermatoses. Chromenoquinoline derivatives [13] have
been reported to act as human progesterone receptor and
have been used therapeutically. Although coming across
the literature, we found a gradual increase on the studies to-
wards the synthesis of pyridocoumarin derivatives since
RESULT AND DISCUSSIONS
Retro synthesis (Figure 1) showed that the required enam-
inoimine hydrochlorides (3) may be a precursor for the
synthesis of pryidocoumarins (4) and such enaminoimine
hydrochlorides can easily be obtained from b-chloroacrolein
derivatives (2) and 6-aminocoumarin (1). A number of
pyranoquinolin-3-one and pyranoacridin-3-one derivatives
have been synthesized using these pathway. Herein, we
report our results.
1
999 and in the last decade, a large number of synthesis
[
14–27] of such compounds have been reported by various
The required choroaldehydes 2(a–f) were prepared via
Vilsmeier–Haack reaction from the corresponding ketones
groups especially by Majumdar et al. [15,20,25–27]. As
a part of our ongoing studies towards the synthesis of novel
coumarin derivatives anchored with heterocyclic rings, we
undertook the challenge towards the synthesis of some
novel polynuclear pyridocoumarin derivatives such as
and POCl /DMF by standard-reported procedure. When
3
these chloroaldehydes were treated with two equivalents
of 6-aminocoumarin (1) in ethanol containing catalytic
conc, HCl produced the anil hydrochlorides (3) in excellent
yields. Thus, 1-chloro-6-methoxy-3,4-dihydronaph- thalen-
2-aldehyde (2d) (1.0 equivalent) on treatment with 6-amino-
coumarin (1) (~2.0 equivalents) in EtOH in presence of HCl
(cat.) at room temperature furnished the intermediate N-aryl
enaminoimine hydrochloride derivative 3d, as a dark red
solid, in 95% yield. Brief heating of the anil hydrochloride
3
[
3
H-pyrano[3,2-f]quinolin-3-one, 3H-acenaphtho[1,2-b]pyrano
3,2-f]quinolin-3-one, and 3H-benzo[h]pyrano[3,2-a]acridin-
-one derivatives. For quite some time, we, in collaboration
with the group of Ray et al, are working on the synthe-
sis of polycyclic azaarenes via thermoysis of N-aryl enami-
noimine hydrochloride derivatives (anil hydrochlorides)
ꢀ
[
28–31]. Such anil hydrochloride derivatives are obtained
derivative (3d) at about 250–260 C for 3–5 min without
by reaction of suitable b-chloro-a,b-unsaturated aldehyde
derivatives and aryl amines. The method has several advan-
tages such as easy availability of starting materials, simple
procedure, short time reaction and generally high yield, and
above all the potential to introduce to various substitutions
any solvent furnished the pyridocoumarin derivative 4d (10-
methoxy-12,13-dihydro-3H-benzo[h]pyrano[3,2-a]acridin-3-
one), in 52% yield, as the only isolable product after usual
work up. The spectral and analytical data of compound 4d
is in well agreement with the assigned structure. We were
©
2014 HeteroCorporation

September 2014 Thermolysis of N-Aryl Enaminoimine Hydrochloride Derivatives: A Short and General
1307
Method for the Synthesis of Pyranoquinolin-3-one and Pyranoacridin-3-one Derivatives
Figure 1. Retrosynthesis of pyridocoumarin derivatives.
EXPERIMENTAL
unable to isolate the other possible isomeric product (5d)
formed (if any) (Scheme 1).
The method is a general one. A series of novel pyrido-
coumarin derivatives 4(a–f) have been synthesized (in
All melting points are uncorrected and were checked with
one-side open glass capillary using a sulphuric acid bath. Solvents
were dried following standard literature procedure. H nmr
1
ꢀ
spectra were recorded on Brucker 500 MHz (at Chemgen Pharma,
5
0–58% yield) via thermal cyclization at 220–320 C of
13
Kolkata) and Brucker 200 MHz (at I.I.T Kharagpur). C nmr
spectra were recorded, respectively, in 50 or 125 MHz nmr
spectrometer (Brucker), respectively. ESI mass spectra were
recorded on a micro mass Q-TOF mass spectrometer (serial no.
YA 263) at IACS, Kolkata; IR spectral data was obtained from
JASCO FT/IR680 PLUS spectrometer. Reactions were monitored
with TLC on pre-coated plates of silica gel GF245 (Merck) and
visualizing under UV light and/or by charring solution.
different anil hydrochloride derivatives 3(a–f). These
anil hydrochlorides were in turn prepared by reaction of
various chloroaldehydeds 2(a–f) and 6-aminocoumarin
(
1) (table-1). In most of the cases, the major/isolated
product is formed via cyclization of anil derivative at C5-
position of the coumarin moiety. However, in few occa-
sions, we were able to isolate the isomeric products that
Preparation of anil hydrochlorides 3(a–f): General
arise via cyclization at C -position of the coumarin ring
7
method.
To a mixture of 6-aminocoumarin (1) (580 mg,
(entries no. 1 and 2). The results have been summarized
3.60 mmol) and the choroaldehyde 2(a–f) (1.8 mmol) in 35–40 mL
in Table 1.
of EtOH, catalytic amount of conc. HCl was added with the help
of capillary tube. The mixture was stirred vigorously at room
The dihydropyrido coumarin 4(c–e) when aromatized
ꢀ
ꢀ
with DDQ in refluxing chlorobenzene at ~140 C for
temperature for 2–4 h and then cooled to 5–10 C. The red to dark
1
2–14 h furnished the fully aromatic 3H-benzo[h]pyrano
red solid separated was filtered, washed with little cold ethanol,
and dried under vacuum to obtain the anil hydrochloride
derivatives 3(a–f) in 81–96% yield. The anil hydrochlorides were
[
(
3,2-a]acridine-3-one derivatives 5(c–e) in excellent yield
Scheme 2)
1
directly used for next step without further purification. H nmr of
In conclusion, we have achieved the synthesis of
the sample could not be recorded because of poor solubility of
these salts.
several 3H-pyrano[3,2-f]quinolin-3-one, 3H-acenaphtho[1,
2-b]pyrano[3,2-f]quinolin-3-one, and 3H-benzo[h]pyrano[3,
ꢀ
Compound 3a: Red solid, yield 81%, mp 218–220 C (d); IR
2-a]acridin-3-one derivatives via an efficient, short, and
(
KBr) nmax: 1726.94 (very strong), 1644.02 (m), 1629.55 (m),
-1
simple method.
3442.31 (broad) cm . Compound 3b: Orange red solid, yield
ꢀ
ꢀ
Scheme 1. (i) EtOH, HCl (cat.), 30–35 C, 3 h. (ii) 250–260 C, 3–4 mins.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1
308
P. Patra, G. K. Kar, and B. Khatua
Vol 51
Table 1
Formation of anilhydrochloride, 3H-pyranoquinolin-3-one, 3H-acenaphtho[1,2-b]-pyrano[3,2-f]quinolin-3-one, and 12,13-dihydro-3H-benzo[h]pyrano
3,2-a]acridin-3-one derivatives.
[
Anil hydrochloride (% of
isolated yield)
Heating temp.
ꢀ
Entry no.
Chloroaldehyde
( C)
Product (s) (% of isolated yield)
1
220–240
2
220–240
3
250–260
4
250–260
5
250–260
6
300–320
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2014 Thermolysis of N-Aryl Enaminoimine Hydrochloride Derivatives: A Short and General
1309
Method for the Synthesis of Pyranoquinolin-3-one and Pyranoacridin-3-one Derivatives
Scheme 2. Aromatization of compounds 4(c–e).
ꢀ
+
8
1
2%, mp 180–182 C (d); IR (KBr) n : 1710.55 (strong),
C H NO : 288.1025 (M +H)]. Compound 4b: Colorless solid,
19 14 2
1
max
-
1
ꢀ ꢀ
yield 10%, mp 240–242 C (CHCl /pet. ether 60–80 C). H nmr
3
(500MHz, CDCl ) d: 2.508(s, 3H), 6.38 (d, 1H, J = 9.5 Hz),
3
6.50 (br s, 1H), 7.14 (d, 1H, J =2.5Hz), 7.49 (d, 1H,
J = 6.5 Hz), 7.50–7.53 (m, 2H), 7.60–7.62 (m, 2H), 7.65 (d, 1H,
729.83 (m), 1745.26 (s), 3290.93 (m), 3442.32 (br) cm .
Compound 3c: Red solid, yield 95%, mp 235–336 C (d);
IR (KBr) nmax: 1719.23 (strong), 1735.62 (s), 1750.83 (m),
090.37 (br) cm . Compound 3d: Red solid, yield 95%,
mp 168–170 C (d); IR (KBr) nmax
421.11 (br) cm . Compound 3e: Red solid, yield 96%, mp
80–182 C (d); IR (KBr) nmax: 1728.05 (strong), 3402.01
broad) cm . Compound 3f: Deep red solid, yield 94%, mp
75–277 C (d); IR (KBr) nmax: 1721.16 (strong), 3403.05
ꢀ
-
1
3
ꢀ
-1
:
1724.05 (strong),
J= 9.0 Hz), 8.40 (s, 1H) ppm; IR (KBr) nmax: 1727.01 (strong) cm .
-
1
ꢀ
3
1
(
2
Compound 4c: Colorless solid, yield 58%, mp 248–250 C
ꢀ
ꢀ
1
3 3
(CHCl /pet. ether 60–80 C). H nmr (400 MHz, CDCl ) d: 3.05 (br
-
1
t, 2H, J= 7.0 Hz), 3.21 (br t, 2H, J= 7.0 Hz), 6.60 (d, 1H,
J= 9.7 Hz), 7.29 (br d, 1H, J= 7.1 Hz), 7.38–7.46 (m, 2H), 7.63 (d,
1H, J= 9.3 Hz), 8.27 (d, 1H, J= 9.2 Hz), 8.29 (s, 1H), 8.42 (d, 1H,
J= 9.7 Hz), 8.55 (br d, 1H, J=7.4Hz) ppm. C nmr (125 MHz,
CDCl ) d: 28.11, 29.19, 112.40, 116.05, 119.64, 123.56, 125.96,
127.52, 127.75, 128.10, 130.18, 132.52, 133.94, 134.44, 138.44,
ꢀ
-
1
(
broad) cm .
13
Thermal cyclization of anil hydrochlorides; preparation of
pyridocoumarins 4(a–f): General method.
.0 mmol of anil hydrochloride derivative 3 (a–f) was taken in a
long-necked hard glass test tube and heated at about 220–320 C
for 3–5 min in a salt bath. The fused mass was extracted
An amount of
3
1
ꢀ
1
39.17, 144.64, 153.31, 153.42, 160.65 ppm. IR (KBr) nmax:
-
1
+
1
732.73 (strong) cm ; hrms (ESI, 70 eV); m/z: 300.0688 (M +H)
+
thoroughly with CHCl
was collected, dried (anhyd. Na SO ), and solvent removed. The
3
and washed with water. The organic layer
[calculated mass for C20
2
H14NO : 300.1025 (M +H)].
ꢀ
Compound 4d: Light yellowish solid, yield 52%, mp 240–242 C
2
4
ꢀ
(CHCl /pet. ether 60–80 C). H nmr (400 MHz, CDCl ) d: 3.02
3 3
1
crude residue thus obtained was further purified by column
chromatography (silica gel/ benzene-ethyl acetate mixture, 5:1) to
furnish the pyridocoumarin derivative 4(a–f) in 50–58% yield. An
analytical sample was prepared by recrystalization from suitable
solvents.
(br t, 2H, J= 7.0 Hz), 3.20 (br t, 2H, J= 7.0 Hz), 3.98 (s, 3H),
6.60 (d, 1H, J= 9.6 Hz), 6.81 (d, 1H, J= 2.0 Hz), 6.98 (dd, 1H,
J= 2.4 and 8.6 Hz), 7.26 (d,1H, J= 9.2 Hz), 8.26 (s, 1H), 8.26
(br s, 1H) 8.42 (d, 1H, J= 10.0 Hz), 8.50 (d, 1H, J=8.4Hz)
3
ppm. C nmr (75 MHz, CDCl ) d: 28.41, 29.19, 55.34, 112.37,
113.01, 113.19, 115.9, 119.39, 123.06, 126.96, 127.39, 127.63,
131.85, 134.18, 138.42, 140.98, 144.66, 153.08, 153.37, 160.80,
161.74 ppm. IR (KBr)nmax: 1730.8 (strong sharp) cm ; hrms
ꢀ
13
Compound 4a: Colorless solid, yield 45%, mp 212–213 C
ꢀ
1
(
6
CHCl
.65 (d, 1H, J = 10.0 Hz), 7.49–7.58 (m, 3H), 7.72 (d, 1H,
J = 9.2 Hz), 8.08 (d, 1H, J = 8.8 Hz), 8.19 (d, 2H, J = 7.2 Hz),
.36 (d, 1H, J = 9.2 Hz), 8.44 (d, 1H, J = 9.6), 8.61 (d, 1H,
3
/ pet. ether 60–80 C). H nmr (200 MHz, CDCl
3
) d:
-1
+
8
(ESI, 70 eV); m/z: 330.1122 (M +H) [calculated mass for
-1
+
J = 8.8 Hz) ppm; IR (KBr) nmax: 1721.16 (strong) cm ; hrms
ESI, 70 eV); m/z: 274.0864 (M +H) [calculated mass for
: 274.0868 (M +H)]. Compound 4a: Colorless solid,
yield 10%, mp 210–212 C (CHCl /pet. ether 60–80 C ) H nmr
C
21
H
16NO
3
: 330.1085 (M +H)]. Compound 4e: Light yellow
+
ꢀ
ꢀ
3
/pet. ether 60–80 C). H
1
(
C
solid, yield 50%, mp 242–244 C (CHCl
nmr (200 MHz, CDCl ) d: 3.00 (br t, 2 H, J = 7.2 Hz), 3.22 (br t,
2H, J = 4.0 Hz), 6.62 (d, 1H, J = 9.8 Hz), 7.32 (s, 1H), 7.42–7.52
(m, 2H), 7.65 (dd, 1H, J = 3.4 and 9.0 Hz), 8.29 (br d, 2H,
+
18
H
12NO
2
3
ꢀ
ꢀ
1
3
(
200 MHz, CDCl ) d: 6.56 (d, 1H, J = 9.6 Hz), 7.51–7.59 (m, 4H),
3
7
8
n
.74 (s, 1H), 7.95 (d, 1H, J = 9.6 Hz), 8.00 (d, 1H, J =8.8 Hz),
J = 6.8), 8.43 (dd, 1H, J = 2.2 Hz and 9.6Hz) ppm.; IR (KBr)
1
.19 (d, 2H, J =8.0Hz), 8.33 (d, 1H, J = 8.8 Hz) ppm; IR (KBr)
n
max: 1717.3 (strong sharp) cm ; hrms (ESI, 70eV); m/z:
-1
+
+
max: 1722.12 (strong) cm ; hrms (ESI, 70 eV); m/z: 274.0860
378.0156 (M +H), 380.0078 (M +2+ H) [calculated mass for
+
+
+
+
(M +H) [calculated mass for C H NO : 274.0866 (M +H)].
C H BrNO : 378.0130 (M +H), 380.0109 (M +2 + H)].
18
12
2
20 13 2
ꢀ
ꢀ
Compound 4f: Light yellow solid, yield 50%, mp 249–251 C
1
Compound 4b: Colorless solid, yield 46%, mp 240–242 C
ꢀ
1
(
2
CHCl
.57(s, 3H), 6.62 (d, 1H, J =9.7Hz), 7.46–7.53 (m, 3H), 7.59
m, 2H), 7.64 (d, 1H, J = 9.2 Hz), 8.27 (d, 1H, J= 9.2Hz), 8.39
3
/ pet. ether 60–80 C) H nmr (200 MHz, CDCl
3
) d:
3
(benzene/EtOAc). H nmr (500 MHz, CDCl ) d: 6.66 (d, 1H,
J = 9.9Hz), 7.68 (d, 1H, J = 8. 9 Hz), 7.78 (br t, 1H,
J = 7.3Hz), 7.84 (br t, 1H, J = 7.2 Hz), 8.03 (d, 1H, J = 8.1 Hz),
8.07 (d, 1H, J = 8.2 Hz), 8.13 (d, 1H, J = 7.0 Hz), 8.38 (d, 1H,
J = 9.0Hz), 8.45 (d, 1H, J = 6.9 Hz), 8.59 (d, 1H, J = 9.4 Hz) ,
(
(
13
s, 1H), 8.45 (d, 1H, J = 9.7 Hz) ppm. C nmr (75 MHz, CDCl3)
2
1
1
1.01, 112.06, 116.12, 119.79, 123.32, 128.41, 128.57, 128.82,
30.76, 131.32, 134.26, 138.30, 139.89, 143.60, 153.59,
60.19, 160.49 ppm; IR (KBr) nmax: 1727.91 (strong) cm ; hrms
-1
8.90 (s, 1H) ppm; IR (KBr) nmax: 1715.23 (strong sharp) cm ;
-1
+
hrms (ESI, 70eV); m/z: 322.0921 (M +H) [calculated mass for
+
+
(ESI, 70 eV); m/z: 288.1013 (M +H) [calculated mass for
C H NO : 322.0868 (M +H)].
22
12
2
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1
310
P. Patra, G. K. Kar, and B. Khatua
Vol 51
Aromatization of dihydropyrido coumarin derivatives
(c–e); preparation of 5(c–e): General method. A mixture
[4] Nakashima, K.; Oyama, M.; Ito, T.; Murata, H.; Linuma,
M. Heterocycles 2011, 83, 1603.
4
[5] Jacobs, A. E.; Christiansen, L. E.; Renson, M. J. Tetrahedron
of 0.30 mmol of dihydropyrido coumarin derivatives 4(c–e)
and 0.31 mmol of DDQ in 25 ml chlorobenzene was refluxed
for 12–14 h under argon atmosphere. The chlorobenzene was
removed under reduced pressure and the residue was taken
up in excess of chloroform and filtered a short path of silica
gel. Removal of the solvent afforded the crude product that
was further purified by column chromatography (silica gel/
benzene-EtAc, 10:1) in 92–95% yield.
1994, 50, 9315.
[6] Tsui, T. W.; Wang, E. C. J Chinese Chemical Soc 2004, 51,
1019 and references 1–7 cited therein.
[7] Fan, H.; Peng, J.; Hamann, M. T.; Hu, J. Chem Rev 2008, 108,
264.
[8] Handy, S. T.; Zhang, Y. Org Prep Proced Int (OPPI) 2005, 37,
411.
[9] Fujikawa, N.; Ohta, T.; Yamaguchi, T.; Fukuda, T.; Ishibashi,
F.; Iwao, M. Tetrahedron 2006, 62, 594. (k) Pla, D.; Albericio, F.;
Alvarez, M. Anticancer Agents Med Chem 2008, 8, 746.
ꢀ
Compound 5c: Light yellow solid, yield 92%, mp 255–257 C
1
(
benzene/EtOAc). H nmr (500 MHz, DMSO-d
6
) d: 6.82 (d, 1H,
[10] Jadhav, V. B.; Nayak, S. K.; Row, T. N. G.; Kulkarni, M. V.
J = 9.8 Hz), 7.86 (dd, 2H, J = 3.8 and 6.0 Hz), 7.98 (d, 1H,
Eur J Med Chem 2010, 45, 3575.
J = 9.4 Hz), 8.01 (s, 2H), 8.09 (dd, 1H, J = 3.5 and 5.9 Hz), 8.53
[11] Suzuki, M.; Yu, D.; Morris-Natschke, S. L.; Smith, P. C.;
Lee, K. Bioorg Med Chem 2007, 15, 6852.
(
d, 1H, J = 9.4 Hz), 9.11 (d, 1H, J = 9.9 Hz), 9.39 (br dd, 1H,
[
12] Lee, M-T.; Yen, C-K.; Yang, W-P.; Chen, H-H.; Liao, C-H.;
Tsai, C-H.; Chen, C. H. Org Lett 2004, 6, 1241.
13] Edwards, J. P.; West, S. J.; Marschke, K. B.; Mais, D. E.;
Gottardis, M. M.; Jones, T. K. J Med Chem 1998, 41, 303.
14] Ajana, W.; Lidia, F.; Mercedes, A.; Joule, J. A. Tetrahedron
1998, 54, 4405.
[15] Majumdar, K. C.; Ghosh, S. K.; Biswasa, P. Monatsh Chem
2000, 131, 967.
J ~ 3.0 and 9.0 Hz), 9.71 (s, 1H) ppm; IR (KBr) nmax: 1736.58
-
1
+
(
strong) cm ; hrms (ESI, 70 eV); m/z: 298.0859 (M +H) [calcu-
[
+
lated mass for C H NO : 298.0868 (M +H)]. Compound 5d:
Light yellow solid, yield 95%, mp 252–254 C (benzene-EtOAc).
H nmr (500 MHz, DMSO-d ) d: 3.98 (s, 3H), 6.80 (d, 1H,
6
20
12
2
ꢀ
[
1
J = 9.8 Hz), 7.44 ( dd, 1H, J = 2.4 and 8.9 Hz), 7.57 (d, 1H,
J = 2.5 Hz), 7.93 (d, 1H, J = 9.0 Hz), 7.94 (d, 1H, J = 9.4 Hz),
[16] Zhang, W.; Pugh, G. Tetrahedron Lett 2001, 42, 5613.
7
.97 (d, 1H, J = 9.0 Hz), 8.46 (d, 1H, J = 9.4 Hz), 9.08 (d, 1H,
[17] Dotsenko, V. V.; Krivokolysko, S. G.; Litvinov, V. P. Chem
J = 9.8 Hz), 9.25 (d, 1H, J = 8.9 Hz), 9.64 (s, 1H) ppm; IR (KBr)
-
1
Heterocycl Compd 2005, 41, 635.
18] Galariniotou, E.; Fragos, V.; Makri, A.; Litinas, K. E.;
Nicolaides, D.N. Tetrahedron 2007, 63, 8298.
19] Kudale, A. A.; Kendall, J.; Miller, D. O.; Collins, J. L.;
n
3
(
2
max: 1730.8 (strong, sharp) cm Hrms (ESI, 70 eV); m/z:
[
+
3
28.00938 (M +H) [calculated mass for C21H14NO : 328.0974
M +H)]. Compound 5e: Light yellow solid, yield 95%, mp
55–257 C (benzene/EtOAc). H nmr (400 MHz, DMSO) d:
.82 (d, 1H, J = 9.7 Hz), 7.98–8.08 (m, 5H), 8.55 (d, 1H,
+
[
ꢀ
1
Bodwell, G. J. J Org Chem 2008, 73, 8437.
[20] Majumdar K. C.; Chattopadhyay, B.; Nath, S. Tetrahedron
Lett 2008, 49, 1609.
[21] Hon, Y. S.; Tseng, T. W.; Cheng, C. Y. Chem Commun 2009,
45, 5618.
6
J = 9.3 Hz), 9.09 (d, 1H, J = 9.8 Hz), 9.46 (d, 1H, J = 9.8 Hz),
-
1
9
.73 (s, 1H) ppm; IR (KBr) nmax: 1718.26 (broad) cm ;
+
hrms (ESI, 70 eV); m/z: 376.0053 (M +H) 378.0078
M +2 + H) [calculated mass for C H BrNO : 375.9973
[
22] Gautam, D. R.; Protopappas, J.; Fylaktakidou, K. C.; Litinas,
K. E.; Nicolaides, D. N.; Tsoleridis, C. A. Tetrahedron Lett 2009, 50, 448.
23] Majumdar, K. C.; Nath, S.; Chattopadhyay, B.; Sinha, B.
Synthesis 2010, 22, 3918.
24] Iaroshenko, V. O.; Ali, S.; Mahmood Babar, T.; Dudkin, S.;
Mkrtchyan, S.; Rama, N. H.; Villinger, A.; Langer, P. Tetrahedron Lett
011, 52, 373.
+
(
(
20 11 2
+
+
M +H), 377.9953 (M +2 + H)].
[
[
Acknowledgment. Financial help was from DST and CSIR, and
New Delhi is gratefully acknowledged. We would also like to
thank CSIR and New Delhi for providing a NET fellowship to
one of the authors (PP).
2
[
[
25] Majumdar, K. C.; Ponra, S.; Taher A. Synthesis 2011, 3, 463.
26] Majumdar, K. C.; Ansary, I.; Samanta, S.; Roy B. Tetrahedron
Lett 2011, 52, 411.
[27] Majumdar, K. C.; Ponra, S.; Ghosh, D.; Abu, T. Synlett 2011,
104.
REFERENCES
[28] Ramesh, D.; Kar, G. K.; Chatterjee, B. G.; Ray, J. K. J Org
Chem 1988, 53, 212.
[
1] Murray, R. D. H.; Mendez, J.; Brown, S. A. The Natural
[29] Kar, G. K.; Karmakar, A. C.; Ray, J. K. Tetrahedron Lett 1989,
30, 223.
Coumarins: Occurrence, Chemistry and Biochemistry; J. Wiley & Sons:
NY, 1982; pp 27–31.
[30] Kar, G. K.; Karmakar, A. C.; Ray, J. K. J Org Chem 1991, 56,
2268.
[31] Pan, D.; Kar, G. K.; Ray, J. K.; Lean, J. M.; Amin, S.;
Chantrapromma, S.; Fun, H. K. J Chem Soc Perkin Trans-I 2001, 2470.
[
2] Fylaktakidou, K. C.; Hadjipavlou-Litina, D. J.; Litinas, K. E.;
Nicolaides, D. N. Curr Pharm Des 2004, 10, 3813.
3] Kothakar, S. A.; Shinde, D. B. Bioorg Med Chem 2006, 16, 6181.
[
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet