Michael Initiated Ring Closure (MIRC) reaction on in situ generated benzylidenecyclohexane-1,3-diones for the construction of chromeno[3,4-b] quinoline derivatives

Article abstract of DOI:10.1016/j.tetlet.2012.02.114

One-pot synthesis of chromeno[3,4-b]quinoline derivatives have been achieved in good yields through Michael Initiated Ring Closure (MIRC) by employing three-component condensation of aromatic aldehydes, 3-aminocoumarins, and cyclic 1,3-diketones in the presence of catalytic amount of p-toluenesulfonic (p-TSA) acid in ethanol under reflux condition. The salient features of this protocol are: simple reaction procedure, shorter reaction time, good yields, avoidance of aqueous work-up, and column-chromatographic separation. The merit of this process is highlighted by its high bond efficiency of producing three new bonds and one stereocenter in a single operation.

Full text of DOI:10.1016/j.tetlet.2012.02.114

Tetrahedron Letters 53 (2012) 2345–2351
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Michael Initiated Ring Closure (MIRC) reaction on in situ generated
benzylidenecyclohexane-1,3-diones for the construction of
chromeno[3,4-b]quinoline derivatives
⇑
Abu T. Khan , Deb Kumar Das
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781 039, India
a r t i c l e i n f o
a b s t r a c t
Article history:
One-pot synthesis of chromeno[3,4-b]quinoline derivatives have been achieved in good yields through
Michael Initiated Ring Closure (MIRC) by employing three-component condensation of aromatic alde-
hydes, 3-aminocoumarins, and cyclic 1,3-diketones in the presence of catalytic amount of p-toluenesul-
fonic (p-TSA) acid in ethanol under reflux condition. The salient features of this protocol are: simple
reaction procedure, shorter reaction time, good yields, avoidance of aqueous work-up, and column-
chromatographic separation. The merit of this process is highlighted by its high bond efficiency of pro-
ducing three new bonds and one stereocenter in a single operation.
Received 13 December 2011
Revised 22 February 2012
Accepted 25 February 2012
Available online 5 March 2012
Keywords:
Multicomponent reaction
3-Aminocoumarin
Ó 2012 Elsevier Ltd. All rights reserved.
Cyclic 1,3-dicarbonyl compounds
Aromatic aldehydes
p-Toluenesulfonic (p-TSA)
Chromeno[3,4-b]quinoline derivatives
The Michael Initiated Ring Closure (MIRC) reaction represents an
elegant approach, which has been used extensively for the con-
struction of cyclopropane rings,1 carbocyclic compounds,2 and
small/medium sized nitrogen3 or oxygen4 containing heterocyclic
compounds. The MIRC reaction strategy can also be cleverly
achieved through one-pot multicomponent reaction, which is gain-
ing interest to the synthetic organic chemists in recent times.5
Multi-component reactions (MCRs) play an important role in the
modern synthetic organic chemistry as they generally occur in a
single pot and exhibit high atom-economy and selectivity.6 They
also provide a powerful synthetic tool for the synthesis of diverse
and complex molecules as well as small and drug-like heterocy-
cles.7 We have perceived that cyclic 1,3-diketones may react with
various aromatic aldehydes in the presence of a suitable acid cata-
lyst to generate benzylidenecyclohexane-1,3-dione derivatives,
which might be reacted instantly with carbon nucleophile such as
3-aminocoumarin through Michael type reaction followed by ring
closure reaction leading to chromeno[3,4-b]quinoline derivatives.
The similar synthetic strategy has also been demonstrated by oth-
ers for the construction of 4-aza-2,3-didehydropodophyllotoxin8a
and tricyclic dihydropyridine analogues,8b and pharmacological
properties of these compounds have also been studied. Compounds
containing 3-aminocoumarin framework are found in many natural
products and some of them are used as antibiotic and antiviral
agent.9,10 For example, novobiocine is a 3-aminocoumarin derived
antibiotic which acts as an ATP-competitive inhibitor of the gyrase
B subunit, blocking the negative super-coiling of relaxed DNA.9d,10
On the other hand, the pyrido[2,3-c]coumarin skeleton constitutes
the backbone of santiagonamine (B), an alkaloid (Fig. 1).11 As a re-
sult, there is a continuing effort to prepare this class of compounds
for biological studies.p-Toluenesulfonic acid (p-TSA) is a readily
available chemical which has been used extensively in place of min-
eral acids. In recent times, it was also used as an efficient acid cat-
alyst for the synthesis of 4(3H)-quinazolinones,12 the regiospecific
nitration of phenols13 and the carbonylation of formaldehyde.14
As a part of our ongoing efforts to develop multi-component reac-
tions to access potentially bioactive scaffolds,15 we would like to re-
port one-pot three-component reaction for the synthesis of
chromeno[3,4-b]quinoline derivatives through MIRC reaction using
condensation of aromatic aldehydes, cyclic 1,3-dicarbonyl com-
pounds and 3-aminocoumarins under reflux condition in ethanol
using p-TSA catalyst as shown in Scheme 1.
Me2N
N
O
O
OMe
⇑
Corresponding author. Tel.: +91 361 2582305; fax: +91 361 2582349.
E-mail address: atk@iitg.ernet.in (A.T. Khan).
Figure 1. The naturally occurring biologically active alkaloid santiagonamine (B).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2012.02.114

2346
A. T. Khan, D. K. Das / Tetrahedron Letters 53 (2012) 2345–2351
R1
CHO
X
R1
O
X
NH2
O
1
p-TSA
Ethanol/reflux
72- 82%
R3
R2
O
O
O
( )n
N
H
X = H/Br/NO2
O
R2
3
4
( )n
O
R3
n = 0, R2 = R3 = H
n = 1, R2 = R3 = H Me/
2
Scheme 1. One-pot three-component condensation reaction for the synthesis of chromeno[3,4-b]quinoline derivatives.
Table 1
Optimization of reaction conditions for the synthesis of chromeno[3,4-b]quinoline derivative 4aa
Entry
Catalyst
Solvent
Catalyst (mol %)
Reaction condition
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
p-TSA
p-TSA
p-TSA
p-TSA
p-TSA
p-TSA
p-TSA
ZnCl2
EtOH
EtOH
EtOH
EtOH
MeOH
CH3CN
H2O
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
n-BuOH
n-BuOH
5
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
12
12
7
54
68
77
78
62
66
42
38
28
24
26
22
00
00
75
10
20
30
20
20
20
20
20
20
20
20
20
0
7
12
12
10
12
12
12
12
24
24
24
4.5
SiO2
Et3N
Piperidine
Acetic acid
HCl
No catalyst
p-TSA
20
a
Reaction conditions: benzaldehyde, dimedone and 3-aminocoumarin were taken in 1:1:1 ratio.
Isolated yields.
b
Table 2
Scope of various substituted chromeno[3,4-b]quinoline derivativesa
Entry
Aldehyde
1,3-Cyclic diketones
3-Aminocoumarin
Product
Time (h)
7
Yieldb
77
CHO
O
NH2
O
O
O
1
O
O
O
O
O
N
H
4a
Cl
CHO
Cl
O
NH2
O
O
2
8
78
O
O
O
N
H
4b
Br
CHO
Br
O
NH2
O
O
3
8
82
O
O
O
N
H
4c

A. T. Khan, D. K. Das / Tetrahedron Letters 53 (2012) 2345–2351
2347
Table 2 (continued)
Entry
Aldehyde
1,3-Cyclic diketones
3-Aminocoumarin
Product
Time (h)
Yieldb
CHO
O
NH2
F
O
O
4
7
73
78
82
O
O
F
O
O
N
H
O
O
4d
CHO
O
O
NH2
O
Cl
O
Cl
5
8
O
O
O
O
N
H
4e
Me
CHO
Me
NH2
O
6
7
O
O
N
H
O
4f
OMe
CHO
OMe
O
NH2
O
O
7
8
72
O
O
O
N
H
O
4g
CHO
O
O
O
NH2
O
OMe
MeO
OMe
O
O
O
O
8
8
7
7
74
79
77
O
O
O
MeO
OMe
OMe
O
O
N
H
4h
CHO
NH2
O
9
O
O
O
N
H
4i
NO2
CHO
NO2
NH2
O
10
O
O
O
N
H
4j
(continued on next page)

2348
A. T. Khan, D. K. Das / Tetrahedron Letters 53 (2012) 2345–2351
Table 2 (continued)
Entry
Aldehyde
1,3-Cyclic diketones
3-Aminocoumarin
Product
Time (h)
Yieldb
76
CHO
O
NH2
NO2
O
O
O
11
7
O
O
NO2
O
N
H
O
O
O
4k
Me
CHO
Me
O
Br
NH2
O
Br
O
O
12
7
81
O
N
H
4l
Cl
CHO
Cl
O
Br
NH2
O
Br
O
O
O
O
13
7
74
O
O
N
H
4m
Br
CHO
Br
O
Br
NH2
O
Br
O
14
15
16
8
7
7
76
79
72
O
O
O
O
O
O
O
O
N
H
O
4n
NO2
CHO
NO2
O
O
O
Br
NH2
O
Br
O
N
H
O
4o
Br
CHO
Br
O2N
NH2
NO2
O
O
O
O
N
H
4p
Cl
CHO
Cl
NH2
O
O
17
7
77
O
O
N
H
4q

A. T. Khan, D. K. Das / Tetrahedron Letters 53 (2012) 2345–2351
2349
Table 2 (continued)
Entry
Aldehyde
1,3-Cyclic diketones
O
3-Aminocoumarin
Product
Time (h)
Yieldb
CHO
NH2
Br
O
O
18
7
76
O
O
Br
O
N
H
O
4r
CHO
Cl
O
NH2
O
O
O
O
19
7
70
O
O
O
O
N
H
O
O
4s
CHO
O
NH2
O
20
12
00
O
N
H
4t
a
Reaction conditions: aromatic aldehyde, 1,3-cyclic ketone and 3-aminocoumarin were taken in 1:1:1 ratio in presence of 20 mol % of p-TSA in ethanol under reflux
conditions.
b
Isolated yields.
To find the optimal conditions, a mixture of benzaldehyde
(1.0 mmol), dimedone (1 mmol) and 3-aminocoumarin (1.0 mmol)
was refluxed for 12 h in ethanol in the presence of 5 mol % p-tolu-
enesulfonic acid and it provided the desired chromeno[3,4-b]quin-
oline derivative 4a in 54% yield (Table 1, entry 1). The same
reactions were also carried out successively using 10, 20, and
30 mol % p-TSA (Table 1, entries 2–4) to afford the desired product
4a in 68%, 77%, and 78% yields, respectively. It was noted that the
yield of the product 4a did not increase significantly by increasing
the amount of catalyst from 20% to 30%. For scrutinizing the suit-
able solvent system, the similar reactions (entries 5–7) were con-
ducted in methanol, acetonitrile and water under otherwise
identical reaction conditions, respectively and the highest yields
and the shortest reaction times were obtained in ethanol. To exam-
ine the efficacy of the catalyst, several reactions were carried out in
the presence of other acidic and basic catalysts (entries 8–11),
respectively. From these observations, it seems to us that p-tolu-
enesulfonic acid (p-TSA) is an optimal catalyst. We have also exam-
ined the reactions with protic acids such as acetic acid and conc.
hydrochloric acid (entries 12 and 13). The reactions were very
sluggish and incomplete even after 24 h of refluxing when the
same reaction was carried out in presence of protic acid (Table 1,
entries 12 and 13). We presume that p-toluenesulfonic acid pro-
vides a more optimal balance between the unprotonated fraction
of amine and a protonated fraction of 1,3-diketone. The results
are summarized in Table 1. To verify the role of temperature, we
have carried out two reactions in the solvent n-butanol (bp 116–
119 °C) with and without catalyst (entries 14 and 15). It is worth-
while to mention that the same reaction was complete relatively
faster in n-butanol. Since the yield has not increased significantly
and cost of the n-butanol is higher as compared to ethanol, all
the reactions were performed in ethanol.
aromatic ring such as Me, OMe, Cl, Br, F, and NO2 with dimedone
and 3-aminocoumarin. The reaction time and percentage yield of
the products (4b–k) are shown in Table 2 (entries 2–11). It is inter-
esting to note that the pure products of all these reactions can be
obtained just by recrystallization of the crude materials from eth-
anol by avoiding aqueous work-up and tedious column-chromato-
graphic separation.
For verifying the generality of the present approach, other
substituted 3-aminocoumarins such as 6-bromo-3-aminocouma-
rin and 6-nitro-3-aminocoumarin17 were also examined with aro-
matic aldehyde and dimedone under identical reaction conditions
to provide the desired chromeno[3,4-b]quinoline products (Table
2, entries 12–16). Furthermore, the reactions with 1,3-cyclohexadi-
one and 1,3-cyclopentadione with 3-aminocoumarin and aromatic
aldehyde were also performed (Table 2, entries 17–19). When
To explore the synthetic scope and the generality of the present
protocol,16 various reactions were performed with a wide variety
of aromatic aldehydes containing different substituents in the
Figure 2. Single crystal X-ray structure 4b (CCDC 827568).

2350
A. T. Khan, D. K. Das / Tetrahedron Letters 53 (2012) 2345–2351
R
O
R
NH2
CHO
O
O
O
O
O
p-TSA
3
( )
O
O
MIRC
R
1
NH2
O
2
O
)
s
e
A
a
o
i
l
i
v
h
p
y A
e
(Pathway B via
X nitrogen nucleophile)
l
R
c
wa
u
h
t
n
a
R
n
P
o
(
b
r
a
c
O
H
O
p-TSA
O
H+
O
O
NH
2O
O
O
NH2
C
O
N
O
H
B
H
H
O
O
R
R
O
O
_
O
H
H2O
O
N
H
HO
O
O
O
N
H
D
N
H
4
OH
O
O
5
Scheme 2. Proposed mechanism for the formation of products catalyzed by p-TSA.
aliphatic aldehydes such as acetaldehyde, or butyraldehyde was
treated with cyclic 1,3-diketones and 3-aminocoumarin in the
presence of p-TSA under identical reaction conditions, the desired
product was not obtained (Table 2, entry 20). It was also noted that
the similar transformation fails while the reaction was carried out
with acyclic 1,3-diketone such as benzoylacetone.
Finally, the structure of one of the representative compounds
such as 12-(4-chlorophenyl)-9,10-dihydro-9,9-dimethyl-7H-chro-
meno[3,4-b]quinoline-6,11(8H,12H)-dione (4c) was confirmed
unambiguously by single crystal X-ray diffraction analysis (see
the Supplementary data) (Fig. 2).
new bonds (two C–C and one C–N) and one stereocenter are formed
in the course of reactions. This method is quite general which
works for a wide variety of aromatic aldehydes, cyclic 1,3-dike-
tones and different substituted 3-aminocoumarins. Shorter reac-
tion times, environmentally benign, superior atom economy, the
easy accessibility of the catalyst and its cost effectiveness, simplic-
ity of the procedure and good to excellent yields are some of the
most significant features of the present protocol. The biological
study of these compounds is under investigation and their asym-
metric synthesis will be reported in due course of time.
The formation of the product may be explained as follows: The
first step is believed to be the condensation reaction between aro-
matic aldehyde (1) with dimedone (2) to give Knoevenagel product
A, benzylidenecyclohexane-1,3-dione,18 which can act as a suitable
Michael acceptor as shown in Scheme 2. We have also tried to iso-
late the intermediate A by performing the reaction of dimedone
and p-chlorobenzaldehyde in the presence of 10% p-TSA. But we
did not get the intermediate A. Still we may believe that the inter-
mediate A reacts with 3-aminocoumarin (3) at the position 4 of the
coumarin ring to provide reactive intermediate C, which undergoes
intra-molecular ring closure reaction followed by dehydration to
give the desired chromeno[3,4-b]quinoline 4 as shown in Pathway
A in Scheme 2. However, we did not obtain the product 5, which
may be possible by the nucleophilic attack of NH2 group of 3-
aminocoumarin to Knoevenagel adduct (A) as shown in Pathway
B. Thus in this reaction we observed selective behavior of 3-amino-
coumarin as C-nucleophile rather than acting as N-nucleophile. It
is reported by Kadutskii and Kozlov that reaction of aromatic
amines, formaldehyde, and dimedone provides spirosubstituted
piperidines,19 which we did not observe in our present study.
In conclusion, we have disclosed the synthesis of novel hetero-
cyclic compounds chromeno[3,4-b]quinoline derivatives (4a–r)
using a high-yielding one-step multicomponent Michael Initiated
Ring Closure (MIRC) reaction. It is worth mentioning that the three
Acknowledgments
D.K.D. is thankful to IIT Guwahati for his research fellowship.
The authors are grateful to the Department of Science and Technol-
ogy, New Delhi for financial assistance for creating single XRD
facility in the Department of Chemistry under FIST program. The
authors also acknowledge to the Director, IIT Guwahati for provid-
ing laboratory facility. We are also thankful to the referee for his
valuable suggestions and comments.
Supplementary data
Supplementary data (X-ray crystallographic data (CIF files) of 4c
spectral data of all compounds and copies of 1H and 13C NMR spec-
tra of products) associated with this article can be found, in the on-
line version, at doi:10.1016/j.tetlet.2012.02.114.
References and notes
1. (a) Lebel, H.; Marcoux, J.-F.; Molinaro, C.; Charette, A. B. Chem. Rev. 2003, 103,
977–1050; (b) Reissig, H.-U.; Zimmer, R. Chem. Rev. 2003, 103, 1151–1196; (c)
Kulinkovich, O. G. Chem. Rev. 2003, 103, 2597–2632.
2. Dumez, E.; Durand, A.-C.; Guillaume, M.; Roger, P.-Y.; Faure, R.; Pons, J.-M.;
Herbette, G.; Dulcére, J.-P.; Bonne, D.; Rodriguez, J. Chem. Eur. J. 2009, 15,
12470–12488.

A. T. Khan, D. K. Das / Tetrahedron Letters 53 (2012) 2345–2351
2351
3. (a) Fioravanti, S.; Morea, S.; Morreale, A.; Pellacani, L.; Tardella, P. A.
Tetrahedron 2009, 65, 484–492; (b) Raveendran, A. E.; Paul, R. R.; Suresh, E.;
Nair, V. Org. Biomol. Chem. 2010, 8, 901–905.
4. (a) Wang, Q.-F.; Hou, H.; Hui, L.; Yan, C.-G. J. Org. Chem. 2009, 74, 7403–7406;
(b) Altieri, E.; Cordaro, M.; Grassi, G.; Risitano, F.; Scala, A. Tetrahedron 2010, 66,
9493–9496.
14. Li, T.; Souma, Y.; Xu, Q. Catal. Today 2006, 111, 288–291.
15. (a) Khan, A. T.; Lal, M.; Khan, M. M. Tetrahedron Lett. 2010, 51, 4419–4424;
(b) Khan, A. T.; Das, D. K.; Khan, M. M. Tetrahedron Lett. 2011, 52, 4539–
4540; (c) Khan, A. T.; Lal, M.; Ali, S.; Khan, M. M. Tetrahedron Lett. 2011, 52,
5327–5332.
16. General procedure for the synthesis of chromeno[3,4-b]quinoline:
A mixture of aromatic aldehyde (1.0 mmol), cyclic 1,3-diketone (1.0 mmol), and
3-aminocoumarin (1.0 mmol)17 was taken in 3 mL of ethanol into a 25 mL
round bottomed flask. Then, the catalyst anhydrous p-toluenesulfonic acid
(0.034 g, 0.2 mmol) was added into it and the reaction mixture was refluxed in
an oil bath. The progress of the reaction was monitored by checking TLC time to
time. After the completion of the reaction, the solid precipitate appeared slowly
under hot conditions at the stipulated time mentioned in the Table 2. Then the
reaction mixture was brought to room temperature and the solid precipitate
was filtered off on a Büchner funnel. The precipitate was washed with cold EtOH
(1 mL) and it was dried finally on vacuum pump. The yields of the pure
products, chromeno[3,4-b]quinoline derivatives, are shown in the Table 2.
Spectrocopic data of the chromeno[3,4-b]quinoline derivatives: 9,10-Dihydro-
9,9-dimethyl-12-phenyl-7H-chromeno[3,4-b]quinoline-6,11(8H,12H)-dione (4a).
Yellow solid (285 mg, 77%); [Found: C, 77.68; H, 5.76; N, 3.83. C24H21NO3
(371.15) requires C, 77.61; H, 5.70; N, 3.77%]; mp 237–239 °C; Rf (30% ethyl
acetate/hexane) 0.33; mmax (KBr) 3290 (NH), 1713 (C@O), 1623 (C@O), 1595
(C@C), 1567, 1504 cmÀ1; dH (400 MHz, CDCl3) 7.66 (1H, d, J = 8.0 Hz), 7.41 (2 H,
d, J = 7.6 Hz), 7.35 (1H, d, J = 7.2 Hz), 7.30 (1H, d, J = 8.4 Hz), 7.26–7.19 (3 H, m),
7.14–7.10 (2H, m), 5.59 (1 H, s), 2.49 (1H, d, J = 16.4 Hz), 2.42 (1H, d, J = 16.4 Hz),
2.30 (1H, d, J = 16.4 Hz), 2.22 (1H, d, J = 16.4 Hz), 1.11 (3 H, s), 0.95 (3H, s); dc
(100 MHz, CDCl3) 195.28, 157.66, 150.70, 148.93, 144.16, 129.34, 128.79,
128.30, 127.16, 126.77, 125.29, 124.22, 121.94, 119.20, 116.91, 108.99, 50.89,
41.54, 36.74, 32.94, 29.42, 27.31; HRMS (ESI): MH+, found 372.1596. C24H21NO3
requires 372.1594.
5. (a) Tranchant, M.-J.; Dalla, V. Tetrahedron 2006, 62, 10255–10270; (b) Wang, Q.
F.; Song, H. K.; Chen, J.; Yan, C. G. J. Comb. Chem. 2009, 11, 1007–1010; (c)
Tarrade, A.; Dauban, P.; Dodd, R. H. J. Org. Chem. 2003, 68, 9521–9524; (d)
Cardillo, G.; Gentilucci, L.; De Matteis, V. J. Org. Chem. 2002, 67, 5957–5962.
6. (a) Ruijter, E.; Scheffelaar, R.; Orru, R. V. A. Angew. Chem., Int. Ed. 2011, 50,
6234–6246; (b) Dömling, A. Chem. Rev. 2006, 106, 17–89; (c) Zhu, J. Eur. J. Org.
Chem. 2003, 1133–1144; (d) Dömling, A.; Ugi, I. Angew. Chem., Int. Ed. 2000, 39,
3168–3210; (e) Zhu, J.; Bienaymé, H. Multicomponent Reactions; Wiley-VCH:
Weinheim, Germany, 2006; (f) Tietze, L. F.; Brasche, G.; Gericke, K. M. Domino
Reactions in Organic Synthesis; Wiley-VCH: Weinheim, Germany, 2006.
7. (a) Lie´by-Muller, F.; Constantieux, T.; Rodriguez, J. J. Am. Chem. Soc. 2005, 127,
17176–17177; (b) Chebanov, V. A.; Saraev, V. E.; Desenko, S. M.; Chernenko, V.
N.; Knyazeva, I. V.; Groth, U.; Glasnov, T. N.; Kappe, C. O. J. Org. Chem. 2008, 73,
5110–5118; (c) Sunderhaus, J. D.; Dockendorff, C.; Martin, S. F. Org. Lett. 2007,
9, 4223–4226.
8. (a) Kamal, A.; Suresh, P.; Mallareddy, A.; Kumar, B. A.; Reddy, P. V.; Raju, P.;
Tamboli, J. R.; Shaik, T. B.; Jain, N.; Kalivendi, S. V. Bioorg. Med. Chem. 2011, 19,
2349–2358; (b) Carroll, W. A.; Agrios, K. A.; Altenbach, R. J.; Buckner, S. A.;
Chen, Y.; Coghlan, M. J.; Daza, A. V.; Drizin, I.; Gopalakrishnan, M.; Henry, R. F.;
Kort, M. E.; Kym, P. R.; Milicic, I.; Smith, J. C.; Tang, R.; Turner, S. C.; Whiteaker,
K. L.; Zhang, H.; Sullivan, J. P. J. Med. Chem. 2004, 47, 3180–3192.
9. (a) Santana, L.; Uriarte, E.; Gonzalez-Diaz, H.; Zagotto, G.; Soto-Otero, R.;
Mendez-Alvarez, E. J. Med. Chem. 2006, 49, 1149–1156; (b) Rivkin, A.; Adams, B.
Tetrahedron Lett. 2006, 47, 2395–2398; (c) Yamaguchi, T.; Fukuda, T.; Ishibashi,
F.; Iwao, M. Tetrahedron Lett. 2006, 47, 3755–3757. and references cited
therein; (d) Burlison, J. A.; Neckers, L.; Smith, A. B.; Maxwell, A.; Blagg, B. S. J. J.
Am. Chem. Soc. 2006, 128, 15529–15536.
17. 3-Aminocoumarin and substituted 3-aminocoumarins were prepared by
following to the reported literature: (a) Kudale, A. A.; Kendall, J.; Warford, C.
C.; Wilkins, N. D.; Bodwell, G. J. Tetrahedron Lett. 2007, 48, 5077–5080; (b)
Valizadeh, H.; Shockravi, A. Heterocycl. Commun. 2004, 10, 475–478; (c)
Beccalli, E. M.; Contini, A.; Trimarco, P. Eur. J. Org. Chem. 2003, 3976–3984.
18. (a) Dandia, A.; Arya, K.; Khaturia, S.; Jain, A. K. Monatsh Chem. 2010, 141, 979–
985; (b) Margaretha, P.; Polansky, O. E. Monatsh Chem. 1970, 101, 824–828; (c)
Karade, N. N.; Budheyar, V. H.; Shinde, S. V.; Jadhav, W. N. Lett. Org. Chem. 2007,
4, 16–19; (d) Mulongo, G.; Mbabazi, J.; Nnamuyombu, P.; Mpango, G. B. Res. J.
Chem. Sci. 2011, 5, 80–84.
10. Gellert, M.; O’Dea, M. H.; Itoh, T.; Tomizawa, Z. I. Proc. Natl. Acad. Sci. U.S.A.
1976, 73, 4474–4478.
11. Valencia, E.; Patra, A.; Freyer, A. J.; Shamma, M.; Fajardo, V. Tetrahedron Lett.
1984, 25, 3163–3166.
12. Narasimhulu, M.; Mahesh, K. C.; Reddy, T. S.; Rajesh, K.; Venkateswarlu, Y.
Tetrahedron Lett. 2006, 47, 4381–4383.
13. Anuradha, V.; Srinivas, P. V.; Aparna, P.; Rao, J. M. Tetrahedron Lett. 2006, 47,
4933–4935.
19. Kozlov, N. G.; Kadutskii, A. P. Tetrahedron Lett. 2008, 49, 4560–4562.