A simple synthesis of trisubstituted quinolines through transesterification

Article abstract of DOI:10.1002/jhet.711

An efficient and simple method has been reported for the synthesis of 2,3,4-trisubstituted quinolines through zwitterion intermediate under reflux condition in presence of sulfuric acid. The formed dicarboxylate subsequently undergoes transesterification in various alcohols with good yields. Most of the synthesized compounds are newly reported characterized by spectroscopic method. J. Heterocyclic Chem., (2011). Copyright

Full text of DOI:10.1002/jhet.711

1342
A Simple Synthesis of Trisubstituted Quinolines Through
Transesterification
Vol 48
Dipti R. Patil, Madhukar B. Deshmukh, Sonali M. Salunkhe,
and Prashant V. Anbhule*
Department of Chemistry, Shivaji University, Kolhapur 416 004, Maharashtra, India
*E-mail: pvanbhule@gmail.com
Received June 29, 2010
DOI 10.1002/jhet.711
Published online 19 August 2011 in Wiley Online Library (wileyonlinelibrary.com).
An efficient and simple method has been reported for the synthesis of 2,3,4-trisubstituted quinolines
through zwitterion intermediate under reflux condition in presence of sulfuric acid. The formed dicar-
boxylate subsequently undergoes transesterification in various alcohols with good yields. Most of the
synthesized compounds are newly reported characterized by spectroscopic method.
J. Heterocyclic Chem., 48, 1342 (2011).
INTRODUCTION
use of various Lewis acid catalysts such as boron tribro-
mide [10], anhydrous aluminium trichloride embedded
in polystyrene-divinyl benzene [11]. Bronsted acid cata-
lysts such as hydrochloric, phosphoric, sulfonic, sulfuric,
or p-toluenesulfonic acid [12] or basic catalysts such as
metal alkoxides [13] and metal carbonates [14] also cat-
alyze this conversion.
Quinoline and their derivatives are very important
structural motif not only in medicinal chemistry because
of their wide occurrence in numerous natural products
[1] and drugs [2] but also in polymer chemistry, elec-
tronics, and optoelectronics for their excellent mechani-
cal properties [3]. Because of their enormous impor-
tance, they have become the synthetic targets of many
organic and medicinal chemistry groups [4]. The struc-
tural core of quinoline has generally been synthesized
by various conventional name reactions [5]. There have
been very few reports available on synthesis of 2,3,4-tri-
substituted quinoline derivatives by using 2-aminoaryl
ketones and dialkyl acetylenedicarboxylate, and these
compounds show antiallergic properties [6,7]. However,
synthetic protocols reported so far suffer from high tem-
peratures, prolonged reaction times, harsh reaction con-
ditions, and low yields of the products. Therefore, its
important need to develop efficient method for the syn-
thesis of said bioactive compounds so as to investigate
other biological activity.
These remarkable importance of quinoline derivatives
and as part of continuing efforts toward the development
of new methods for the expeditious synthesis of biologi-
cally relevant heterocyclic compounds [15] enthused us
to develop new methods for quinoline synthesis.
RESULTS AND DISCUSSION
In this article, we report our results involving synthe-
sis of 2,3,4-trisubstituted quinoline and consecutively
transesterification of formed dicarboxylate using variety
of alcohols in presence of sulfuric acid. As a trial case,
the reaction of stoichometric amount of 5-chloro-2-ami-
nobenzophenone with diethyl acetylenedicarboxylate
(DEAD) and catalytic amount of sulfuric acid in reflux-
ing ethanol afforded product as trisubstituted quinoline 4
in 84% yield (Scheme 1).
Likewise, transesterification is a potent and versatile
transformation in various fields of organic synthesis in
industrial and in academic laboratories. For example,
the formation of methyl esters by the transesterification
of naturally occurring oils and fats can be used as diesel
alternatives [8]. It is applicable in the paint industry for
the curing of alkyl resin [9]. It also plays significant
role in polymerization [9]. Transesterification has been
carried out conventionally and most frequently by the
The structure of formed product was confirmed on the
basis of spectroscopic data. The IR spectrum showed the
sharp absorption bands at 1732 and 1718 cmꢀ1 assigned
to the two ester carbonyls. In 1H-NMR spectrum, the
two triplets observed at d 0.96–1.01 and 1.45–1.49 are
due to the two methyl protons of ester moiety, and the
C
V
2011 HeteroCorporation

November 2011
A Simple Synthesis of Trisubstituted Quinolines Through Transesterification
1343
Scheme 1
Scheme 2. Possible mechanism for synthesis of 2,3,4-trisubstituted quinolines.
1
two quartets resonated at d 4.08–4.11 and 4.50–4.58 are
due to the methylene protons of carbonyl ester. While in
13C-NMR spectrum, the two ester carbonyls were
observed at d 164.91, 166.74. Mechanistically, the reac-
tion may involves the initial formation of 1:4 zwitter-
ionic intermediate between ethanol and DEAD which
rearranged to form (III) which further adds to the proto-
nated 2-aminoaryl ketone followed by cyclodehydration
leads to 2,3,4-trisubstituted quinoline derivative as end
product (Scheme 2).
in H-NMR but interestingly it has been observed that
two triplets at d 0.96–1.01 and 1.44–1.48 while two
quartets at d 4.08–4.10 and 4.49–4.56 indicated formed
trisubstituted quinoline product undergoes transesterifi-
cation (Scheme 3).
In view of the interesting results obtained by above
synthesis, we next focused our attention on transesterifi-
cation by variety of alcohols. In most of the alcohols,
we got the desired 2,3,4-trisubstituted quinolines with
effective transesterification.
To verify the generality of the present protocol, the
same reaction was extended by replacement of DEAD
with dimethyl acetylenedicarboxylate (DMAD) in etha-
nol. As expected two singlets for two methoxy protons
The reaction of 2-aminoaryl ketones with terminal
dialkyl acetylenedicarboxylate and various alcohols
afforded quinoline derivatives in good yields. All
these results are summarized in Table 1. It have been
Scheme 3
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Table 1
Synthesis of 2,3,4-trisubstituted quinoline in presence of H2SO4 along with transesterification.
Entry
a
2-Aminoaryl ketones
DEADa/DMADb
Alcohol
Product
Yield (%)
Time (h)
CH3CH2OH
84
6
b
c
d
e
f
CH3CH2OH
CH3CH2OH
CH3OH
86
83
92
81
89
81
79
80
80
84
–
6
7
4.5
CH3OH
6
CH3OH
6
g
h
i
CH3CH2CH2OH
CH3CH2CH2OH
(CH3)2CH-OH
(CH3)2CH-OH
9
5
7
j
12
k
l
7
No reaction
No reaction
–
m
–
–
b
aDEAD, diethyl acetylenedicarboxylate. DMAD, dimethyl acetylenedicarboxylate.

November 2011
A Simple Synthesis of Trisubstituted Quinolines Through Transesterification
1345
H), 7.80–7.85 (m, 1H, Ar-H), 8.32–8.35 (m, 1H, Ar-H); 13C-
NMR (CDCl3) d (ppm) 14.20, 52.38, 62.66, 126.62, 127.51,
128.22, 128.27, 128.79, 129.11, 129.30, 129.41, 130.67,
130.97, 134.63, 147.14, 148.20, 165.41, 167.87; ms: m/z ¼
351 [Mþ].
noted that in case of cyclohexanol and isopropanol with
DMAD transesterification product was not formed,
whereas with benzyl alcohol and 4-methoxy benzyl
alcohol, reactions did not proceed.
Dimethyl-4-phenyl-6-chloroquinoline-2,3dicarboxylate (d).
Yield 92%, mp Obs. 145–152ꢁC (lit. 162.5–163ꢁC [6]); IR
(KBr): 2954, 1726, 1605, 1246, 1054, 832, 703 cmꢀ1 1H-
;
CONCLUSIONS
NMR (CDCl3) d (ppm) 3.64 (s, 3H, AOCH3), 4.07 (s, 3H,
AOCH3), 7.34–7.37 (m, 2H, Ar-H) 7.52–7.54 (m, 3H, Ar-H),
7.59–7.60 (m, 1H, Ar-H), 7.74–7.78 (dd, 1H, Ar-H), 8.26–8.29
(dd, 1H, Ar-H); 13C-NMR (CDCl3) d (ppm) 53.54, 61.78,
99.99, 125.39, 125.42, 128.47, 128.52, 129.14, 129.23, 129.33,
132.01, 132.08, 132.20, 132.24, 133.85, 135.71, 165.00,
167.55.
In conclusion, we have reported quite interesting and
highly efficient strategy for the synthesis of variety of
trisubstituted quinolines. The main practical importance
of this reaction is that formed quinolines undergo trans-
esterification reaction, which make it unique alternative
for the synthesis of bioactive quinoline derivatives. Fur-
ther investigations with other activated alkynes and alco-
hols are in progress.
Dimethyl-4-phenylquinoline-2,3-dicarboxylate
81%, m.p. obs. 126–129ꢁC (lit. 129–130ꢁC [6]); IR (KBr):
2983, 1743, 1723, 1248, 1048, 768,703 cmꢀ1 1H-NMR
(e). Yield
;
(CDCl3) d (ppm) 3.64, (s, 3H, AOCH3), 4.08 (s, 3H, AOCH3),
7.35–7.38 (m, 2H, Ar-H), 7.50–7.52 (m, 3H, Ar-H), 7.60–7.67
(m, 2H, Ar-H), 7.82–7.87 (m, 1H, Ar-H), 8.36–8.38 (d 1H,
Ar-H); 13C-NMR (CDCl3) d (ppm) 52.55, 53. 63.79, 126.70,
127.28, 127.73, 128.33, 128.95, 129.09 129.39, 129.43,
130.28, 131.37, 134.34, 144.52, 146.64, 148.59, 165.20,
167.46.
EXPERIMENTAL
Melting points are uncorrected and were determined in an
open capillary. Infrared spectra (in KBr pellets) were recorded
on a Schimazdu IR-470 FT-IR spectrophotometer. The 1H-
and 13C-NMR spectra were recorded on a Bruker Spectrospin
Avance II-300 MHz spectrophotometer using CDCl3 solvent
and tetramethylsilane as an internal standard. Chemical shifts
are given in the delta scale (d) in ppm. Mass spectra were ana-
lyzed on a Shimadzu QP2010 GCMS. DMAD and DEAD
were purchased from Aldrich chemicals and was used without
further purification. The purity of the compounds was checked
by thin layer chromatography (TLC).
Dimethyl-4-(2-chlorophenyl)-6-chloroquinoline-2,3-dicar-
boxylate (f). Yield 89%, m.p.: obs. >300ꢁC; IR (KBr): 2952,
1729, 1606, 1221, 830, 812, 759, 744. cmꢀ1
;
1H-NMR
(CDCl3) d (ppm) 3.64 (s, 3H, AOCH3), 4.07 (s, 3H, AOCH3),
7.26–7.30 (m, 1H, Ar-H) 7.37–7.40 (m, 1H, Ar-H), 7.40–7.49
(m, 2H, Ar-H), 7.51–7.59 (d, 1H, Ar-H), 7.76–7.79 (m, 1H,
Ar-H), 8.26–8.30 (d, 1H, Ar-H); 13C-NMR (CDCl3) d (ppm)
53.49, 61.79, 124.93, 124.97, 126.81, 127.82, 127.89, 129.74,
129.81, 130.70, 130.76, 130.93, 131.06, 132.21, 132.45,
132.37, 132.44, 132.83, 133.50, 135.96, 144.62, 145.34,
165.24, 166.80; ms: m/z ¼ 389 [Mþ], 391 [Mþ þ 2].
Spectroscopic data of the synthesized compounds. Di-
ethyl-4-phenyl-6-chloroquinoline-2,3-dicarboxylate(a). Yield
84%, m.p. 260–263ꢁC; IR (KBr): 2985, 1732, 1718, 1238,
;
1050, 954, 830, 700 cmꢀ1 1H-NMR (CDCl3) d (ppm) 0.96–
Di-n-propyl-4-phenyl-6-chloroquinoline-2,3-dicarboxylate (g).
Yield 81%, m.p. 136–138ꢁC; IR (KBr): 2945, 1741, 1720,
1.01(t, 3H, ACH2ACH3), 1.45–1.49 (t, 3H, ACH2ACH3),
4.08–4.11(q, 2H, ACH2ACH3), 4.50–4.58 (q, 2H,
ACH2ACH3), 7.33–7.36 (m, 2H, Ar-H), 7.51–7.54 (t, 3H, Ar-
H), 7.58–7.59 (d, 1H, Ar-H ), 7.73–7.77 (dd, 1H, Ar-H) 8.25–
8.28 (d, 1H, Ar-H); 13C-NMR (CDCl3) d (ppm) 13.57, 14.16,
61.67, 62.70, 125.34, 127.91, 128.32, 128.44, 129.05, 129.32,
131.98, 132.17, 134.04, 135.36, 145.44, 147.17, 164.91,
166.74; ms: m/z ¼ 383 [Mþ], 385 [Mþ þ 2].
1
1605, 1218, 1050, 813, 752 cmꢀ1; H-NMR (CDCl3) d (ppm)
0.71–0.76 (t, 3H, ACH2ACH3), 1.00–1.05 (t, 2H,
ACH2ACH3), 1.33–1.45 (m, 2H, AOCH2ACH2ACH3), 1.84–
1.86 (m, 2H, AOCH2ACH2ACH3), 3.95–3.99 (t, 2H,
AOCH2ACH2) 4.40–4.44 (t, 2H, AOCH2ACH2), 7.32–7.35
(m, 2H, Ar-H) 7.51–7.53 (m, 3H, Ar-H), 7.58–7.59 (m, 1H,
Ar-H), 7.73–7.76 (dd, 1H, Ar-H), 8.25–8.28 (dd, 1H, Ar-H);
13C-NMR (CDCl3) d (ppm) 10.29, 21.44, 21.93, 52.49, 68.22,
125.37, 127.71, 128.27, 128.50, 129.01, 129.13, 129.20,
129.30, 131.98, 132.17, 132.22, 133.94, 135.44, 145.42,
145.48, 145.79, 147.32, 164.99, 167.27; ms: m/z ¼ 411[Mþ],
Diethyl-4-phenyl-6-chloroquinoline-2,3-dicarboxylate (b).
Yield 86%, m.p. 259–261ꢁC; IR (KBr): 2941, 1737, 1719,
1
1238, 1051, 831, 701 cmꢀ1; H-NMR (CDCl3) d (ppm) 0.96–
1.01 (t, 3H, ACH2CH3) 1.44–1.48 (t, 3H, ACH2CH3), 4.08–
4.10 (q, 2H, ACH2CH3), 4.49–4.56 (q, 2H, ACH2CH3), 7.33–
7.36 (m, 2H, Ar-H), 7.51–7.59 (m, 4H, Ar-H), 7.73–7.77 (m,
1H, Ar-H), 8.25–8.28 ( dd, 1H, Ar-H); 13C-NMR (CDCl3) d
(ppm) 13.57, 14.16, 52.45, 62.69, 125.34, 125.37, 128.43,
128.49, 129.05, 129.12, 129.21, 129.32, 131.98, 132.04,
132.18, 132.22, 133.93, 134.05, 135.36. 1135.46, 145.45,
145.50, 145.71, 147.16, 147.28, 164.85, 164.92, 166.74,
167.27; ms: m/z ¼ 383[Mþ], 385 [Mþ þ 2].
þ
413 [M þ 2].
Ethyl-n-propyl-4-phenylquinoline-2,3-dicarboxylate (h). Yield
79%, mp 82–85ꢁC; IR (KBr): 2972, 1731, 1229, 1051, 812,
763, 705 cmꢀ1 1H-NMR (CDCl3) d (ppm) 0.94–1.01 (t, 3H,
;
ACH2ACH3), 1.02–1.08 (t, 3H, ACH2ACH3), 1.83–1.90 (m,
2H, AOCH2ACH2ACH3), 4.05–4.14 (q, 2H, AOCH2ACH2)
4.40–4.48 (t, 2H, AOCH2ACH2), 7.35–7.38 (m, 2H, Ar-H),
7.49–7.51 (m, 3H, Ar-H), 7.58–7.62 (m, 2H, Ar-H), 7.81–7.82
(dd, 1H, Ar-H), 8.31–8.34 (dd, 1H, Ar-H); 13C-NMR (CDCl3)
d (ppm) 10.32, 13.59, 21.94, 61.55 68.10, 100.0, 126.59,
128.22, 128.72, 129.00, 129.40, 130.66, 130.89, 147.4, 147.7,
165.5, 168.6; ms: m/z ¼ 363 [Mþ], 365 [Mþ þ 2].
Ethylmethyl-4-phenylquinoline-2,3-dicarboxylate (c). Yield
83%, m.p. 98–99ꢁC IR (KBr): 2997, 1737, 1718, 1308, 1226,
1
1052, 766, 704 cmꢀ1. H-NMR (CDCl3) d (ppm) 1.45–1.49 (t,
3H, ACH2CH3), 3.62 (s, 3H, AOCH3), 4.50–4.58 (q, 2H,
ACH2CH3), 7.26–7.38 (m, 2H, Ar-H), 7.50–7.65 (m, 5H, Ar-
Journal of Heterocyclic Chemistry
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1346
D. R. Patil, M. B. Deshmukh, S. M. Salunkhe, and P. V. Anbhule
Vol 48
REFERENCES AND NOTES
Diisopropyl-4-phenyl-6-chloroquinoline-2,3-dicarboxylate (i).
Yield 80%, m.p. 180–185ꢁC; IR (KBr): 2986, 1737, 1720,
1605, 1209, 830, 707 cmꢀ1 1H-NMR (CDCl3) d (ppm)
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;
0.92–0.98 (m, 6H, ACHA(CH3)2), 1.42–1.44 (m, 6H,
ACHA(CH3)2), 4.03–4.13 (m, 1H, ACHA(CH3)2 ), 5.32–5.42
(m, 1H, ACHA(CH3)2), 7.32–7.36 (m, 2H, Ar-H), 7.51–7.58
(m, 3H, Ar-H), 7.72–7.76 (m,1H, Ar-H), 8.25–8.28 ( dd, 1H,
Ar-H); 13C-NMR (CDCl3) d (ppm) 13.53, 13.58, 21.11, 21.68,
61.69,70.68, 125.30, 125.35, 128.18, 128.44, 129.02, 129.07,
129.42, 131.92, 132.01, 132.17, 132.23, 134.17, 135.21,
145.50, 147.14, 164.50, 166.79; ms: m/z ¼ 411[Mþ], 413 [Mþ
þ 2].
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Dimethyl-4-phenyl-6-chloroquinoline-2,3-dicarboxylate (j).
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(KBr): 3065, 2954, 1727, 1605, 1220, 1144, 1054, 833,
701cmꢀ1 1H-NMR (CDCl3) d (ppm) 3.64 (s, 3H, AOCH3),
;
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Dimethyl-4-phenyl-6-chloroquinoline-2,3-dicarboxylate
(k). Yield 84%, m.p.: Obs. 144–145ꢁC (lit. 62.5–163ꢁC[6]); IR
(KBr): 2954, 1727, 1605, 1220, 1054, 956, 833, 701 cmꢀ1
;
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AOCH3), 7.33–7.36 (m, 2H, Ar-H), 7.52–7.54 (m, 3H, Ar-H),
7.59–7.60 (m, 1H, Ar-H), 7.75–7.78 (dd, 1H, Ar-H), 8.26–8.29
(dd, 1H, Ar-H); 13C-NMR (CDCl3) d (ppm) 52.59, 53.60,
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135.66, 145.45, 147.29, 164.05, 167.28.
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General procedure for said trisubstituted quinolines with
desired transesterification. As a case study, 5-chloro-2-ami-
nobenzophenone (2 mmol) and dimethyl acetylene dicarboxy-
late (DMAD) (2 mmol) in ethanol (5 mL) and sulphuric acid
(0.375 mmol) were heated in oil bath under reflux condition
till completion of reaction monitored by TLC. On cooling to
room temperature (25ꢁC), the reaction mixture was solidified.
It was filtered off, washed with petroleum ether, and recrystal-
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[15] (a) Deshmukh, M. B.; Salunkhe, S. M.; Patil, D. R.; Anb-
hule, P.V. Eu J Med Chem 2009, 44, 2651; (b) Deshmukh, M. B.;
Anbhule, P.V.; Jadhav, S.D.; Mali, A. R.; Jagtap, S. S.; Deshmukh S.
A., Indian J Chem 2007, 42B, 1445; (c) Deshmukh, M. B.; Anbhule,
P. V.; Jadhav, S. D.; Jagtap, S. S.; Patil, D. R.; Salunkhe, S. M.; Sank-
pal, S. A. Indian J Chem 2008, 47B, 792.
Acknowledgments. The authors acknowledge the UGC, New
Delhi for providing the grant to the Department of Chemistry,
Shivaji University, Kolhapur under SAP and one of the authors
(DRP) is thankful to UGC for the award of UGC Research Fel-
lowship in sciences for meritorious students.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet