DBU Acetate Mediated: One-pot Multi Component Syntheses of Dihydropyrano[3,2-c]quinolones

Article abstract of DOI:10.1002/jhet.2506

Three-component reaction involving condensation of 1-methylquinoline-2,4(1H,3H)-dione(1), aromatic aldehydes (2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h) and malononitrile/cyanoaceticester (3a, 3b) in{(1,8-diazabicyclo[5.4.0]-undec-7-en-8-ium acetate)}[DBU][Ac] as ta

Full text of DOI:10.1002/jhet.2506

Month 2015
DBU acetate mediated: one-pot multi component syntheses of
dihydropyrano[3,2-c]quinolones
*
Rajasekar Bhupathi, Bandi Madhu, B. Rama Devi, Ch. Venkata Ramana Reddy, and P. K. Dubey
Department of Chemistry, College of Engineering, Jawaharlal Nehru Technological University Hyderabad, Kukatpally,
Hyderabad, (T.S.), 500 085 India
*
E-mail: rs.bhupathi@gmail.com
Additional Supporting Information may be found in the online version of this article.
Received April 26, 2015
DOI 10.1002/jhet.2506
Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
Three-component reaction involving condensation of 1-methylquinoline-2,4(1H,3H)-dione(1), aromatic
aldehydes 2(a-h) and malononitrile/cyanoaceticester 3(a,b) in{(1,8-diazabicyclo[5.4.0]-undec-7-en-8-ium
acetate)}[DBU][Ac] as task-specific ionic liquid leading to the efficient synthesis of dihydropyrano[3,2-c]
quinolones 4(a-p) is described. This approach is convenient, mild, and affords the products in high yields
without the use of column chromatography.
J. Heterocyclic Chem., 00, 00 (2015).
INTRODUCTION
In literature survey, only a few reactions are reported on
DBU acetate-catalyzed multicomponent reactions. Herein,
we report on the use of DBU acetate as an efficient catalyst
and reaction medium for the synthesis of pyranoquinolones
4(a-p) through the one pot method.
Multicomponent reactions (MCRs) [1] have been used
extensively in recent years for the synthesis of a large
number of heterocyclic, carbocyclic compounds. Such
reactions offer a wide range of possibilities for the efficient
construction of complex molecules in a single procedural
step, thus avoiding the isolation and purification steps of
intermediates, giving high yields, and allowing savings of
both solvents and reagents. In the past decade, there have
been tremendous developments in three-component and
four-component reactions, and great efforts continue to
be made to develop new MCRs.
Pyrano [3,2-c]quinolone structural units are commonly
found in alkaloids showing diverse biological activities like
antibacterial [2], antiinflammatory, [3] and antifungal [4].
The methods available for the synthesis of pyranoquinolones
are fairly elaborate but somewhat inconvenient.
Ionic liquids [5] have attracted much attention because
of their mild reaction conditions, short reaction times and
better yield, solvating ability, and easy recyclability [6].
Various reactions have been reported recently using ionic
liquids as a catalyst, reaction media [7], as rate enhancers
[8], and in peptide synthesis [9]. These solvents are playing
a key role in multicomponent synthesis for preparation of
many heterocyclic compounds. DBU acetate is especially
used as solvent and catalyst for many organic reactions.
Yu et al. [10] reported DBU-based carbonylation of o-
phenylenediamines with CO2 to 2-benzimidazolones under
solvent-free condition. Lima et al. [11] reported DBU-
catalyzed synthesis amides via aminolysis of methyl esters.
RESULTS AND DISCUSSION
A mixture of 1-methylquinoline-2,4(1H,3H)-dione(1),
benzaldehyde 2(a-h), malo nonitrile /ethylcyano acetate
3(a,b) was stirred at 100°C in DBU acetate for 20min. After
simple processing of the reaction mixture, pyranoquinolones
4(a-p) were isolated as products and characterized by IR,
1HNMR,13CMR, and mass spectral data (for details, please
see the Experimental section). When the reaction was carried
out in the absence of DBU acetate, by refluxing the reactants
in ethanol for 2–3h, no progress in the product formation was
observed as found by periodic thin-layer chromatography
(TLC) analysis of the reaction mixture. DBU [12] acetate
required in this reaction was generated in situ by using the
reported procedure.
Initially, a mixture of 1-methylquinoline-2,4(1H,3H)-
dione (1) benzaldehyde (2a), and malononitrile (3a) was
stirred with 5 mL of DBU acetate at room temperature.
TLC showed formation of the product in low yield.
(Scheme 1) Therefore, the same mixture was heated at
100°C for 20 min to accomplish the reaction. After
workup, pyranoquinolones were the only products isolated
in high yield. We noticed that reducing in the quantity of
DBU acetate (3 mL) did not affect the yields (Table 1).
© 2015 HeteroCorporation

R. Bhupathi, B. Madhu, B. R. Devi, C. V. R. Reddy, and P. K. Dubey
Vol 000
Scheme 1. Synthesis of 4 (a-p) from 1, 2(a-h) and 3(a-b).
Table 2
Ionic liquids screened for the synthesis of pyranoquinolones.
The catalyst/reaction medium plays a vital role in deter-
mining the success of the reaction in terms of rate and
yields. Various ionic liquids such as [bmim]Br, [bmim]
BF4, and [bmim]AlCl4 were screened for the synthesis of
pyranoquinolones 4(a-p). Among these ionic liquids,
DBU acetate proved to be the most effective as far as com-
pletion of reaction in short time and yields are concerned
(Table 2). As shown in Chart 1, the ionic liquid [DBU]
[Ac] could be recycled four times without considerable loss
of activity.
Ionic liquid
used
Time (min)
of reaction
Temp
(°C)
Yield (%) of
product 4a
Entry
1
2
3
4
5
[bmim]Br
90
90
90
90
20
100
100
100
100
100
35
46
55
45
90
[bmim]BF4
[bmim]AlCl4
[bmim]SbF6
[DBU][AC]
The synthesis of pyranoquinolones could also be
achieved in a tandem fashion (Scheme 2). Thus, a mixture
of benzaldehyde (2a), malononitrile (3a), and DBU ace-
tate was stirred at 100°C for 20 min. The reaction was
monitored by TLC. After the completion of reaction, as
shown by disappearance of one of the reactants to the
resulting mixture,1-methylquinoline-2,4(1H,3H)-dione
(1) was added in a tandem way without isolating any
product/intermediate and the resulting mixture stirred at
100°C for a further 20 min. At the end of this period,
the mixture was processed to obtain the final product, that
is, pyranoquinolone 4a.
Chart 1. Recyclization of DBU acetate in synthesis of 4a. [Color figure
can be viewed in the online issue, which is available at wileyonlinelibrary.
com.]
Similarly, a mixture of 1, 2a and DBU acetate was
stirred at 100°C for 30 min. The reaction was monitored
Table 1
Synthesis of pyranoquinolones derivatives from 1-methylquinoline-2,4(1H,3H)-dione (1).
S. No
Aldehydes (2)
Active methylene (3)
Product
Time (min)
Yield (%)
m.p (°C)
1.
2.
3.
4.
5.
6.
7.
8.
2a (R = H, R1 = H)
2b (R = F, R1 = H)
3a (X = CN)
3a (X = CN)
3a (X = CN)
3a (X = CN)
3a (X = CN)
3a (X = CN)
3a (X = CN)
3a (X = CN)
3b (X = COOC2H5)
3b (X = COOC2H5)
3b (X = COOC2H5)
3b (X = COOC2H5)
3b (X = COOC2H5)
3b (X = COOC2H5)
3b (X = COOC2H5)
3b (X = COOC2H5)
4a
4b
4c
4d
4e
4f
4 g
4 h
4i
15
18
18
17
20
15
20
20
18
18
20
19
20
16
20
20
90
88
85
86
86
93
85
87
91
90
86
89
85
92
86
88
260-62
240-42
243-45
220-22
190-93
175-177
220-23
>280
210-12
156-60
150-52
160-64
180-82
175-77
218-20
183-85
2c (R = Cl, R1 = H)
2d (R = Br, R1 = H)
2e (R = OCH3, R1 = H)
2f (R = NO2, R1 = H)
2 g (R = CH3, R1 = H)
2 h (R = H, R1 = OH)
2a (R = H, R1 = H)
2b (R = F, R1 = H)
9.
10.
11.
12.
13.
14.
15.
16.
4j
2c (R = Cl, R1 = H)
2d (R = Br, R1 = H)
2e (R = OCH3, R1 = H)
2f (R = NO2, R1 = H)
2 g (R = CH3, R1 = H)
2 h (R = H, R1 = OH)
4 k
4 l
4 m
4n
4o
4p
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Green and efficient, three component reaction
1
Scheme 2. (Alternate synthesis of pyranoquinolones). [Color figure can be
viewed in the online issue, which is available at wileyonlinelibrary.com.]
study of spectral data (IR, H-NMR and mass) showed
it to be 6a (for details of spectral data, please see the
Experimental section). The product thus obtained, that
is, 6a was thus a combination of one unit of 2a and
two units of 1, a case which probably seems to be un-
precedented in the literature.
In the mechanism, the reaction includes a Knoevenagel
condensation catalyzed by DBU acetate between benzalde-
hyde (2) and active methylene group of the cyano com-
pound (3) to yield α, β-unsaturated nitrile intermediate 5.
The latter is then attacked by the carbanion of the
1-methylquinoline-2,4(1H,3H)-dione compound (1) in the
form of Michael addition followed by a keto-enol
tautomerization to furnish the enol intermediate (X).
Nucleophilic addition of the hydroxyl group of interme-
diate (X) to the cyano moiety afforded imine intermedi-
ate, which undergoes enolization to yield the final
product 4.
Mechanism I
A possible mechanism has been proposed for the formation of 4(a-p) from 2(a-h), 3and 1
by TLC. After completion of reaction to the resulting
CONCLUSION
mixture, malononitrile 3a was added in a tandem fash-
ion without isolating the condensed product and then
stirred at R.T. for a further 20 min. At the end of this
period, the mixture was processed to obtain a product,
which surprisingly was not the expected 4a. Careful
We have developed a general and highly efficient method
using DBU acetate as convenient reaction medium for the
three-component synthesis of pyranoquinolones. The products
are isolated in high yield. Easy workup, high yield, and inex-
pensive catalyst are the advantages of the present procedure.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

R. Bhupathi, B. Madhu, B. R. Devi, C. V. R. Reddy, and P. K. Dubey
Vol 000
EXPERIMENTAL
7.11–8.12 (m, 8H, Aromatic hydrogens), 7.48 (s, 2H, -NH2,
D2O exchangeable); 13C-NMR (DMSO-d6, 100MHz): δ
29.34, 58.57, 109.35, 113.28, 115.43, 120.46, 122.64, 122.85,
127.13, 127.43, 128.57, 131.78, 138.78, 144.86, 150.84,
159.32, 160.25; m/z (M++1): 348. Anal. Calcd for
C20H14FN3O2 (347.11): C, 69.16; H, 4.06; N, 12.10; Found:
Melting points were determined in open capillary tubes
and are uncorrected. The progress of the reaction was mon-
itored by TLC performed on silica gel G coated Merck
plastic sheets (Kenilworth, NJ, USA), and spots were ob-
served by exposure to iodine vapor or UV light. IR spectra
were recorded by using KBr disc on a Perkin-Elmer (Wal-
tham, MA, USA) 240c analyzer. 1H NMR spectra were re-
corded on Brucker DPX-400 (Billerica, MA, USA) at
400MHz (chemical shifts in δ, ppm) and mass spectra on
an Agilent (Agilent Technologies, Sta. Clara, CA, USA)
C, 69.65; H, 4.32; N, 12.84.
2-amino-4-(4-chlorophenyl)-6-methyl-5-oxo-5,6-dihydro-
4H-pyrano[3,2-c]quinoline-3-carbonitrile (4c).
(R = Cl,
R1 = H, X =CN) : IR (KBr): 3391, 3302 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 2190 (sharp,
1
medium, -CN), 1671 cmÀ1 (-CO- group, broad); H-NMR
LC-MS instrument giving only M+ values in Q +1 mode.
General procedure for synthesis of pyranoquinolones
4(a-p). A mixture of methylquinoline-2,4(1H,3H)-dione 1
(DMSO d6/TMS): δ 3.54 (s, 3H, -NCH3), 4.72 (s, 1H, -CH),
7.14–8.05 (m, 8H, Aromatic hydrogens), 7.52 (s, 2H, -NH2,
D2O exchangeable); 13C-NMR (DMSO-d6, 100MHz): δ
29.46, 58.64, 109.84, 113.31, 115.87, 120.23, 122.72, 122.21,
127.42, 127.52, 128.82, 131.84, 138.87, 144.43, 150.92, 159.74,
160.19; m/z (M++1): 364. Anal. Calcd for C20H14ClN3O2
(1mM), aldehyde 2a-e(1mmol), malononitrile or ethyl
cyanoacetate 3a-b (1mM), in DBU acetate (3ml) was stirred
at 100°C for 30min. To the resulting oily reaction mixture
was added 5mL of ethanol to force out the crude product
from the polar ionic liquid reaction medium. Then the
precipitated product was filtered and washed with cold
ethanol to afford the pure products. The collected ionic
liquid along with ethanol as filtrate in the filtration flask was
evaporated to remove ethanol, and the obtained ionic liquid
was reused for subsequent reactions. To compensate for the
loss of some acetic acid during the workup procedure, an
amount of acetic acid (2mL) was added after each run. A
volume of DBU (2mL) was added to the ionic liquid filtrate
(363.00): C, 66.03; H, 3.88; N, 11.55; Found: C, 66.56; H,
3.32; N, 11.12.
2-amino-4-(4-bromophenyl)-6-methyl-5-oxo-5,6-dihydro-
4H-pyrano[3,2-c]quinoline-3-carbonitrile (4d).
(R = Br,
R1 =H, X= CN) : IR (KBr): 3390, 3299 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 2194
(sharp, medium, -CN), 1669cmÀ1 (-CO- group, broad); 1H-
NMR (DMSO d6/TMS): δ 3.44 (s, 3H, -NCH3), 4.62 (s, 1H,
-CH), 7.11–7.96 (m, 8H, Aromatic hydrogens), 7.47 (s, 2H, -
NH2, D2O exchangeable); 13C-NMR (DMSO-d6, 100MHz):
δ 29.43, 58.87, 109.74, 113.97, 115.75, 120.32, 122.71,
122.90, 127.54, 127.73, 128.57, 131.66, 138.40, 144.39,
150.57, 159.29, 160.85; m/z (M++1): 408. Anal. Calcd for
C20H14BrN3O2 (407.03): C, 58.84; H, 3.46; Br, 19.57; N,
after three runs.
Procedure for the preparation of 6. A mixture of
benzaldehyde 2a (1 mM),1-methyl quinol ine-2,4(1H,3H)-
dione 1 (1 mM) and DBU acetate (3 mL) was stirred at
100°C for 30min. After completion of the reaction
monitored by TLC, the reaction mixture cooled to room
temperature was added 5mL of ethanol. Then the
precipitated product was filtered and washed with cold
10.29; O, 7.84% Found: C, 58.31; H, 3.91; N, 10.64.
2-amino-4-(4-methoxyphenyl)-6-methyl-5-oxo-5,6-dihydro-
4H-pyrano[3,2-c]quinoline-3-carbonitrile (4e). (R = OCH3,
R1 = H, X = CN) : IR (KBr): 3389, 3291 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 2190
(sharp, medium, -CN), 1665 cmÀ1 (-CO- group, broad);
1H-NMR (DMSO d6/TMS): δ 2.89 (s, 3H, -OCH3), 3.56
(s, 3H,-NCH3),4.45(s,1H,-CH),6.96–7.88(m,8H,Aromatic
hydrogens),7.32(s,2H,-NH2,D2Oexchangeable);13C-NMR
(DMSO-d6, 100MHz): δ 29.31, 50.43, 58.39, 109.22,
113.84, 115.72, 120.91, 122.73, 122.98, 127.24, 127.75,
128.48, 131.53, 138.94, 144.86, 150.84, 159.32, 160.25; m/z
ethanol to afford the pure product 6.
2-amino-6-methyl-5-oxo-4-phenyl-5,6-dihydro-4H-pyrano
[3,2-c]quinoline-3-carbonitrile 4a. (R=H, R1 =H, X=CN) :
IR (KBr): 3391, 3297 (unequal doublet, asymmetric and
symmetric stretchings of –NH2), 2205 (sharp, medium, -CN),
1677cmÀ1 (-CO- group, broad); 1H-NMR (DMSO d6/TMS):
3.52 (s, 3H, -NCH3), 4.51 (s, 1H, -CH), 7.16–8.02 (m, 9H,
Aromatic hydrogens), 7.55 (s, 2H, -NH2, D2O exchangeable);
13C-NMR (DMSO-d6, 100MHz): δ 29.62, 58.31, 109.53,
113.02, 115.27, 120.08, 122.50, 122.52, 127.04, 127.80, 128.68,
131.94, 138.98, 144.57, 150.50, 159.21, 160.13; m/z (M++1):
330. Anal. Calcd for C20H15N3O2 (329.12): C, 72.94; H, 4.59;
(M++1): 360. Anal. Calcd for C21H17N3O3 (359.38): C,
70.18; H, 4.77; N, 11.69; Found: C, 70.54; H, 4.14; N, 11.23.
2-amino-6-methyl-4-(4-nitrophenyl)-5-oxo-5,6-dihydro-
4H-pyrano[3,2-c]quinoline-3-carbonitrile(4f). (R = NO2,
R1 =H, X =CN) : IR (KBr): 3386, 3297 (unequal doublet,
N, 12.76; Found: C, 72.23; H, 4.93; N, 12.35;
2-amino-4-(4-fluorophenyl)-6-methyl-5-oxo-5,6-dihydro-4H-
pyrano[3,2-c]quinoline-3-carbonitrile (4b).
asymmetricandsymmetricstretchingsof–NH2),2220(sharp,
1
medium, -CN), 1675 cmÀ1 (-CO- group, broad); H-NMR
(R=F, R1 =H,
(DMSOd6/TMS):δ3.46(s,3H,-NCH3),4.77(s,1H,-CH),7.06–
8.12 (m, 8H, Aromatic hydrogens), 7.44 (s, 2H, -NH2, D2O
exchangeable); 13C-NMR (DMSO-d6, 100 MHz): δ 29.26,
58.54,109.83,113.92,115.33,120.81,122.32,122.72,127.56,
X =CN) : IR (KBr): 3395, 3299 (unequal doublet, asymmetric
and symmetric stretchings of –NH2), 2197 (sharp,
1
medium, -CN), 1670 cmÀ1 (-CO- group, broad); H-NMR
(DMSO d6/TMS): δ 3.48 (s, 3H, -NCH3), 4.61 (s, 1H, -CH),
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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Green and efficient, three component reaction
127.24,128.54,131.88,138.84,144.21,150.33,159.53,160.43;
149.54, 159.32, 160.43, 167.32; m/z (M++1): 395. Anal.
Calcd for C22H19FN2O4 (394.13): C, 67.00; H, 4.86;
m/z (M++1): 375. Anal. Calcd for C20H14N4O4 (374.35):
C, 64.17; H, 3.77; N, 14.97; Found: C, 64.53; H, 3.23; N, 14.32.
N, 7.10; Found: C, 67.53; H, 4.23; N, 7.94.
2-amino-6-methyl-5-oxo-4-(p-tolyl)-5,6-dihydro-4H-pyrano
Ethyl-2-amino-4-(4-chlorophenyl)6-methyl-5-oxo-5,6-dihydro-
[3,2-c]quinoline-3-carbonitrile (4 g).
(R = CH3, R1 = H,
4H-pyrano[3,2-c]quinoline-3-carboxylate (4 k). (R =Cl, R1 =H,
X = CN) : IR (KBr): 3380, 3290 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 2189
(sharp, medium, -CN), 1656 cmÀ1 (-CO- group, broad);
1H-NMR (DMSO d6/TMS): δ 1.80 (s, 3H, -CH3), 3.21
(s, 3H, -NCH3), 4.12 (s, 1H, -CH), 6.92–7.82 (m, 8H,
Aromatic hydrogens), 7.38 (s, 2H, -NH2, D2O
exchangeable); 13C-NMR (DMSO-d6, 100 MHz): δ
25.84, 29.84, 58.33, 109.23, 113.76, 115.65, 120.95,
122.36, 122.99, 127.26, 127.84, 128.74, 131.21,
138.46, 144.34, 150.67, 159.26, 160.55; m/z (M++1):
X = COOC2H5) : IR (KBr): 3370, 3278 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 1682,
1650 cmÀ1 (-CO- group, broad); 1H-NMR (DMSO d6/
TMS):δ1.16(t,3H,-CH3),3.49(s,3H,-NCH3),4.01(q,2H,
-CH2), 4.96 (s, 1H, -CH), 7.06–8.11 (m, 8H, Aromatic
hydrogens), 7.82 (s, 2H, -NH2, D2O exchangeable); 13C-
NMR (DMSO-d6, 100 MHz): δ 29.23, 35.45, 58.65, 77.32,
111.43, 112.47, 114.66, 122.35, 122.95, 123.45, 125.65,
126.76, 127.46, 127.74, 131.56, 138.52, 145.64, 149.68,
159.75, 160.76, 167.44; m/z (M++1): 411. Anal. Calcd for
344. Anal. Calcd for C21H17N3O2 (343.13): C, 73.45; H,
4.99; N, 12.24; Found: C, 73.91; H, 4.32; N, 12.71.
2-amino-4-(2-hydroxyphenyl)-6-methyl-5-oxo-5,6-dihydro-
C22H19ClN2O4 (410.10):C,64.31;H,4.66;N,7.10;Found:
C,64.71;H,4.13;N,7.61.
Ethyl-2-amino-4-(4-bromophenyl)-6-methyl-5-oxo-5,6-
4H-pyrano[3,2-c]quinoline-3-carbonitrile (4 h).
(R = H,
dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate (4 l).
(R = Br,
R1 = OH, X =CN) : IR (KBr): 3387, 3198 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 2195
(sharp, medium,-CN), 1667 cmÀ1 (-CO- group, broad);
1H-NMR (DMSO d6/TMS): δ 3.44 (s, 3H, -NCH3),
4.14 (s, 1H, -CH), 6.86–7.69 (m, 8H, Aromatic hydrogens),
7.21 (s, 2H, -NH2, D2O exchangeable), 9.44 (s, 1H, -OH,
D2O exchangeable); 13C-NMR (DMSO-d6, 100MHz): δ
29.65, 58.42, 109.65, 113.26, 115.95, 120.47, 122.87,
122.34, 127.22, 127.27, 128.56, 131.76, 138.33, 144.66,
150.87, 159.32, 160.44; m/z (M++1): 346. Anal. Calcd for
C20H15N3O3 (345.11): C, 69.56; H, 4.38; N, 12.17; Found:
R1 =H, X=COOC2H5) : IR (KBr): 3378, 3289 (unequal
doublet, asymmetric and symmetric stretchings of –NH2),
1
1675, 1645cmÀ1 (-CO- group, broad); H-NMR (DMSO
d6/TMS): δ 1.12 (t, 3H, -CH3), 3.46 (s, 3H, -NCH3), 4.04 (q,
2H, -CH2), 4.95 (s, 1H, -CH), 7.04–8.08 (m, 8H,
Aromatichydrogens),7.81(s,2H,-NH2,D2Oexchangeable);
13C-NMR (DMSO-d6, 100MHz): δ 29.43, 35.22, 58.62,
77.54, 111.94, 112.26, 114.84, 122.83, 122.98, 123.32,
125.49, 126.23, 127.83, 127.95, 131.84, 138.22, 145.35,
149.53, 159.82, 160.43, 167.86; m/z (M++1): 455. Anal.
CalcdforC22H19BrN2O4(454.05):C,58.04;H,4.21;N,6.15;
C, 69.12; H, 4.87; N, 12.57.
Found:C,58.72;H,4.82;N,6.82.
Ethyl-2-amino-6-methyl-5-oxo-4-phenyl-5,6-dihydro-4H-
Ethyl-2-amino-4(4-methoxyphenyl)-6-methyl-5-oxo-5,6-
dihydro-4H-pyrano[3,2-c] quinoline-3-carboxylate (4 m).
pyrano[3,2-c]quinoline-3carboxylate (4i).
X = COOC2H5) : IR (KBr): 3375, 3281 (unequal doublet,
(R=H, R1 =H,
(R = OCH3, R1 = H, X = COOC2H5) : IR (KBr): 3368,
3279 (unequal doublet, asymmetric and symmetric
stretchings of –NH2), 1667, 1649 cmÀ1 (-CO- group,
asymmetric and symmetric stretchings of –NH2), 1685,
1655cmÀ1 (-CO- group, broad); H-NMR (DMSO d6/TMS):
1
1
δ 1.11 (t, 3H, -CH3), 3.54 (s, 3H, -NCH3), 3.96 (q, 2H, -CH2),
4.85 (s, 1H, -CH), 7.06–8.09 (m, 9H, Aromatic hydrogens),
7.75 (s, 2H, -NH2, D2O exchangeable); 13C-NMR (DMSO-d6,
100 MHz): δ 29.28, 35.22, 58.84, 77.43, 111.94, 112.87,
114.92, 122.15, 122.79, 123.65, 125.99, 126.22, 127.78, 127.92,
131.35, 138.49, 145.89, 149.98, 159.46, 160.09, 167.82; m/z
(M++1): 377. Anal. Calcd for C22H20N2O4 (376.14): C, 70.20;
broad); H-NMR (DMSO d6/TMS): δ 1.14 (t, 3H, -CH3),
3.45 (s, 3H, -NCH3), 3.92 (s, 3H, -OCH3), 4.01 (q, 2H, -CH2),
4.98 (s, 1H, -CH), 7.02–8.12 (m, 8H, Aromatic hydrogens),
7.91 (s, 2H, -NH2, D2O exchangeable); 13C-NMR (DMSO-d6,
100MHz): δ 29.33, 35.43, 50.33, 58.84, 77.34, 111.25, 112.43,
114.34, 122.39, 122.56, 123.24, 125.53, 126.43, 127.61, 127.84,
131.73, 138.82, 145.74, 149.77, 159.35, 160.64, 167.97; m/z
(M++1): 407. Anal. Calcd for C23H22N2O5 (406.15): C, 67.97;
H, 5.36; N, 7.44; Found: C, 70.73; H, 5.93; N, 7.91.
Ethyl-2-amino-4-(4-fluorophenyl)-6-methyl-5-oxo-5,6-dihydro-
H, 5.46; N, 6.89; Found: C, 67.12; H, 5.92; N, 6.11.
4H-pyrano[3,2-c]quinoline-3-carboxylate (4j). (R=F, R1 =H,
X=COOC2H5) : IR (KBr): 3371, 3280 (unequal doublet,
asymmetric and symmetric stretchings of –NH2), 1680,
Ethyl-2-amino-6-methyl-4-(4-nitrophenyl)-5-oxo-5,6-dihydro-
4H-pyrano[3,2-c]quinoline-3-carboxylate (4n). (R = NO2,
R1 = H, X = COOC2H5) : IR (KBr): 3369, 3285 (unequal
doublet, asymmetric and symmetric stretchings of –NH2),
1653cmÀ1 (-CO- group, broad); H-NMR (DMSO d6/TMS):
1
1
δ 1.13 (t, 3H, -CH3), 3.48 (s, 3H, -NCH3), 3.98 (q, 2H, -
CH2), 4.92 (s, 1H, -CH), 7.05–8.09 (m, 8H, Aromatic
hydrogens), 7.81 (s, 2H, -NH2, D2O exchangeable);
13C-NMR (DMSO-d6, 100 MHz): δ 29.34, 35.32, 58.43,
77.53, 111.82, 112.43, 114.53, 122.23, 122.84, 123.33,
125.24, 126.89, 127.24, 127.45, 131.84, 138.45, 145.34,
1660, 1644cmÀ1 (-CO- group, broad); H-NMR (DMSO
d6/TMS): δ 1.18 (t, 3H, -CH3), 3.46 (s, 3H, -NCH3), 4.05
(q, 2H, -CH2), 4.97(s, 1H, -CH), 7.11–8.16 (m, 8H, Aromatic
hydrogens),7.92(s,2H,-NH2,D2Oexchangeable);13C-NMR
(DMSO-d6, 100MHz): δ 29.77, 35.63, 58.72, 77.42, 111.68,
112.93,114.54,122.46,122.78,123.46,125.84,126.32,127.49,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

R. Bhupathi, B. Madhu, B. R. Devi, C. V. R. Reddy, and P. K. Dubey
Vol 000
127.84,131.54,138.33,145.64,149.48,159.53,160.73,167.49;
131.79, 138.42, 145.64, 149.84, 159.74, 160.56, 167.34;
m/z (M++1): 393. Anal. Calcd for C22H20N2O5 (392.14):
C, 67.34; H, 5.14; N, 7.14; Found: C, 67.87; H, 5.68; N, 7.77.
m/z (M++1): 422. Anal. Calcd for C22H19N3O6 (421.13):
C, 62.70; H, 5.54; N, 9.97; Found: C, 62.11; H, 5.91; N, 9.22.
Ethyl-2-amino-6-methyl-5-oxo-4-(p-tolyl)-5,6-dihydro-4H-
pyrano[3,2-c]quinoline-3-carboxylate (4o).
(R = CH3,
Acknowldegement. The authors are indebted to the
authorities of Jawaharlal Nehru Technological University
Hyderabad for providing laboratory facilities.
R1 =H, X=COOC2H5) : IR (KBr): 3360, 3270 (unequal
doublet, asymmetric and symmetric stretchings of –NH2),
1661, 1640cmÀ1 (-CO- group, broad); 1H-NMR (DMSO d6/
TMS): δ 1.12 (t, 3H, -CH3), 1.41 (s, 3H, -CH3), 3.42 (s, 3H,
-NCH3), 4.01 (q, 2H, -CH2), 4.91 (s, 1H, -CH), 7.04–7.98
(m, 8H, Aromatic hydrogens), 7.86 (s, 2H, -NH2, D2O
exchangeable); 13C-NMR (DMSO-d6, 100MHz): δ 25.83,
29.32, 35.43, 58.54, 77.63, 111.84, 112.11, 114.32, 122.34,
122.54, 123.42, 125.46, 126.67, 127.65, 127.74, 131.64,
138.43, 145.67, 149.32, 159.79, 160.67, 167.85; m/z (M++1):
391. Anal. Calcd for C23H22N2O4 (390.16): C, 70.75; H,
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5.68; N, 7.17; Found: C, 70.98; H, 5.13; N, 7.87.
Ethyl-2-amino-4-(2-hydroxyphenyl)-6-methyl-5-oxo-5,6-
dihydro-4H-pyrano[3,2-c] quinoline-3-carboxylate (4p).
(R = H, R1 = OH, X = COOC2H5) : IR (KBr): 3369, 3278
(unequal doublet, asymmetric and symmetric stretchings of
–NH2), 1669, 1645cmÀ1 (-CO- group, broad); H-NMR
1
(DMSO d6/TMS): δ 1.15 (t, 3H, -CH3), 3.41 (s, 3H, -NCH3),
4.02 (q, 2H, -CH2), 4.79 (s, 1H, -CH), 7.01–7.99 (m, 8H,
Aromatic hydrogens), 7.78 (s, 2H, -NH2, D2O exchangeable),
10.23 (s, 1H, -OH, D2O exchangeable); 13C-NMR (DMSO-d6,
100 MHz):δ29.64,35.73,58.35,77.85,111.64,112.42,114.13,
122.32, 122.53, 123.65, 125.62, 126.78, 127.83, 127.86,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet