A convenient method of facilitating aryl-aryl bond-formation reactions in the synthesis of biquinoline- and quinoline-bearing chromene derivatives

Article abstract of DOI:10.1055/s-0032-1317488

A method to derive functionalized biquinoline- and quinoline-bearing chromene bicyclic systems through aryl-aryl bond formation in a one-pot synthesis is described. The X-ray structure analysis provides insight into the mode of orientation of the molecules and opens the way to the synthesis of various hybrid molecules by making use of suitable substituents at R ¹, R², and R³. Copyright

Full text of DOI:10.1055/s-0032-1317488

2858▌
LETTER
lAetteCr onvenient Method of Facilitating Aryl–Aryl Bond-Formation Reactions in
the Synthesis of Biquinoline- and Quinoline-Bearing Chromene Derivatives
Biquinoline- and Quinoline-Bearing Chromene Derivatives
Mathan Sankaran,a Kumarasamy Chandraprakash,a Chokkalingam Uvarani,a Kailasam Natesan Vennila,b
Devadasan Velmurugan,b Palathurai Subramaniam Mohan*a
a
School of Chemical Sciences, Bharathiar University, Coimbatore 641046, India
Fax +91(422)2459845; E-mail: psmohan59@gmail.com
b
Centre for Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600025, India
Received: 25.08.2012; Accepted: 26.09.2012
aryl bond formation have been reported. In addition to the
Abstract: A method to derive functionalized biquinoline- and quin-
synthesis, the X-ray crystal structures of 5f and 5g have
oline-bearing chromene bicyclic systems through aryl–aryl bond
provided insight into structural orientation of these bicy-
clic systems. Some representative examples of biquino-
formation in a one-pot synthesis is described. The X-ray structure
analysis provides insight into the mode of orientation of the mole-
cules and opens the way to the synthesis of various hybrid mole- line systems previously described are shown in Figure 1
cules by making use of suitable substituents at R1, R2, and R3.
and we have decided to use these analogues as model
compounds for preparing 3a–j and 5a–g with the chloro
and NH-substituents suitably placed as additional func-
tional moieties. These results are interesting but suggest
that there is still scope for structural functional modifica-
tions that will generate more valuable output in terms of
efficacy in polymeric materials. In this class of quinoline-
based bicycles, the presence of two donor atoms and the
flexibility of the two quinolines or quinoline-chromene
units linked together by a single aryl bond provide the
possibility of coordination to metal ions in a variety of
modes.
Key words: one-pot synthesis, quinoline, chromene, sulfuric acid,
p-toluenesulphonic acid
In recent years there has been an upsurge of interest from
the chemical community in the design and construction of
structurally versatile biquinoline scaffolds for use in poly-
mer and organometallic chemistry.1 These studies have
included several polycyclic heterocyclic systems such as
biquinolines or chromenes comprising bicyclic systems
that were recognized as valuable entities in transition-
metal coordination chemistry, crystal engineering for gen-
erating a wide variety of molecular architectures,2–5 as
building blocks for supramolecular complexes, and for the
construction of (porous) metal frameworks.6–10 The gener-
ation of such frameworks is a promising approach that can
be used in the search for stable microporous metal-organic
networks that exhibit reversible guest exchange and pos-
sibly selective catalytic activity.11–14 They are also used as
ligands for the preparation of metal complexes with bio-
logical activities such as antibacterial, antifungal, anti-
malarial, and antitumor agents, and as hydrogenation
catalysts.15,16 In addition to the aforementioned signifi-
cance, polyquinolines possess n-type electrically conduct-
ing properties along with good thermal, mechanical, and
oxidative attributes.17,18 Although there are a few reports
on the preparation of bicyclic quinolines,19–25 most suffer
drawbacks such as low yield, formation of by-products,
the use of highly reactive coupling reagents, and compet-
itive reductions in the presence of protonic sources.26,27 To
overcome these difficulties, we describe herein an effi-
cient, one-pot synthesis of some new biquino-
line/chromene-bearing quinoline systems linked through
an aryl–aryl bond. To the best of our knowledge, no exam-
ples of such cyclization for the formation of biquinoline-
and quinoline-bearing chromene systems accompanying
We initiated our experiment by using 1b and 2a (Table 1,
entry 1) with concentrated H2SO4 (0.2 equiv) in methanol,
and found that the product was obtained in 48% isolated
yield (Table 1, entry 1). The yield of the product was im-
proved to 59% when 0.5 equivalent of H2SO4 was added
to the reaction media (Table 1, entry 2), however, little
improvement was observed when the amount of catalyst
H2SO4 was increased further (1 equiv, Table 1, entry 3).
Identical results were obtained by increasing the amount
of catalyst in n-BuOH (Table 1, entries 4 and 5). The re-
action was then examined in different types of solvents,
and the results show that solvents such as acetic acid af-
forded an excellent yield of the product (ca. 88%; Table 1,
entries 6–10). During optimization studies, p-toluenesul-
fonic acid (PTSA) was tried under the same reaction con-
ditions, which showed a significant reactivity for this
reaction in acetic acid (Table 1, entry 10). A moderate to
low yield of the corresponding product was obtained
when MeCN or n-BuOH (Table 1, entries 11 and 12) were
used as solvents with PTSA catalyst.
The starting precursor 4-substituted 3-acetylquinolin-2-
ones 1a–d and 3-acetylcoumarin-2-ones 4a and 4b were
synthesized according to a previously described proce-
dure.28,29 In this context, Scheme 130 illustrates the syn-
thetic approach to the biquinoline systems and their
derivatives 3a–j, starting from the appropriate 2-amino-
benzophenone/2-aminoacetophenones 2a–d with 3-
acetylquinolin-2-ones 1a–d, followed by cyclization to
SYNLETT 2012, 23, 2858–2864
Advanced online publication: 07.11.2012
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9
3
6
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5
2
1
4
1
4
3
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2
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DOI: 10.1055/s-0032-1317488; Art ID: ST-2012-D0711-L
© Georg Thieme Verlag Stuttgart · New York

LETTER
Biquinoline- and Quinoline-Bearing Chromene Derivatives
2859
Table 1 Optimization of Reaction of 3-Acetyl-6-chloro-4-phenyl-
quinolin-2(1H)-one (1b) and o-Aminobenzophenone (2a)a for the
Formation of 3a
R2N
N
N
NR2
Entry Catalyst
(equiv)
Solvent
Temp Time Yield
(°C)
(h)
16
13
12
10
9
(%)b
48
59
64
65
68
82
88
85
77
82
56
45
R = H, Me
1
1
2
concd H2SO4 (0.2)
MeOH
MeOH
MeOH
n-BuOH
n-BuOH
AcOH
AcOH
AcOH
AcOH
AcOH
MeCN
n-BuOH
80
N
concd H2SO4 (0.5)
concd H2SO4 (1)
concd H2SO4 (0.5)
concd H2SO4 (1)
concd H2SO4 (0.2)
concd H2SO4 (0.5)
concd H2SO4 (1)
PTSA (0.2)
80
Br
Br
3
80
N
4
120
120
120
120
120
120
120
80
2
5
6
6
N
N
R
N
7
5
8
5
3
9
9
N
N
10
11
12
PTSA (0.5)
8
Br
Br
PTSA (0.5)
8
4
R = H, t-Bu
PTSA (0.5)
80
10
R3
N
R4
a Reaction conditions: 1b (1 mmol), 2a (1 mmol), catalyst.
R1
b Isolated yield.
R2
N
O
the corresponding biquinoline via the Friedländer conden-
sation under the given conditions (Table 2, entries 1–
10).31 Most of the products were readily filtered off direct-
ly from the reaction medium, although a few required pu-
rification by column chromatography on silica gel
(hexane–ethyl acetate).
H
5
Figure 1 Representative examples of model compounds 1–4 and the
derived analogue 5
R3
R4
R1
R1
O
O
O
R2
R4
R2
H+
R3
NH2
2a–d
N
Me
+
AcOH, reflux
N
O
N
H
H
R1 = Ph, Me
3a–j
1a–d
R
R
R
2 = NO2, Cl, H
3 = Ph, Me
4 = Cl, NO2, H
Scheme 1 Synthesis of biquinoline analogues 3a–j
R2
N
R3
O
O
R3
H+
R2
NH2
Me
+
AcOH, reflux
R1
O
O
R1
O
O
4a–b
2a–d
5a–g
R
R
R
1 = OMe, H
2 = Me, Ph
3 = NO2, Cl, H
Scheme 2 Synthesis of quinoline-bearing chromenes 5a–g
© Georg Thieme Verlag Stuttgart · New York
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M. Sankaran et al.
LETTER
Similarly, Scheme 232 illustrates the synthesis of quino- 2.6 ppm) and the ‘NH2’ in o-aminoketone derivatives
line-bearing chromene systems 5a–g from the appropriate were no longer present. A singlet at δ = 8.63 ppm was at-
2-aminoacetophenone/2-aminobenzophenone 2a–d with tributed to the proton adjacent to the NO2 group at C′-5,
3-acetylchromen-2-ones 4a and 4b. The bicyclic and a singlet at δ = 7.98 ppm was assigned to the proton
chromene-quinoline systems 5a–g were also generated by adjacent to the ring carbon (C′-3). The signals resonating
a similar straightforward approach to that depicted in between δ = 7.34–8.64 ppm were assigned to entire aro-
Scheme 1. After completion of the reaction (TLC analysis matic region, and a signal around δ = 12.88 ppm was at-
of the reaction mixture), the residue was purified by col- tributed to the amide function, which was further
13
umn chromatography to afford the products 5a–g confirmed by C NMR spectra in which the peak at δ =
(Scheme 2 and Table 2, entries 11–17). All the com- 161.36 ppm was attributed to the amide C=O function.
pounds were then recrystallized from tetrahydrofuran The presence of this amide moiety was also evident in the
(THF)/methanol (5:1). The majority of compounds were IR spectrum, in which the stretching frequency due to ace-
soluble in common organic solvents (THF, CHCl3, tyl group was absent. The 13C NMR spectra of 3g gave
CH2Cl2) at concentrations of more than 10 mg/mL. The signals for 25 carbons, which is in accordance with the
1
synthesized molecules were characterized by IR, H and proposed structure. The structure was also confirmed by
13C NMR, mass spectroscopy and elemental analysis; fur- mass spectra (m/z 514 [M]+) and elemental analyses data.
thermore, in two cases, the characterization was unambig- The structures of compounds 5f and 5g were unambigu-
uously determined by single-crystal X-ray crystallo- ously determined by single-crystal XRD studies (Figure 2
graphic analysis.
The 1H NMR spectrum of analogue 3g exhibited aromatic
peaks, and signals associated with the acetyl group (δ =
and Figure 3).33 The assignment of 1H and 13C NMR sig-
nals for 5g was also achieved by using the same straight-
forward approach as described for 3g.
Table 2 Synthesis of Biquinoline/Quinoline-Bearing Chromene Analogues 3a–j and 5a–ga
Entry
3-Acetylquinolines/
3-acetylchromenes
o-Amino ketones
Product
Yield (%)b
Ph
N
Ph
O
Ph
O
Ph
Cl
Cl
Cl
Me
Me
Me
1
3a
85
Cl
N
H
O
NH2
N
H
O
Ph
N
Ph
O
O
Ph
Ph
O2N
O
NH2
Cl
2
3
4
5
3b
3c
3d
3e
88
84
68
82
N
H
N
H
O
Ph
N
Ph
O
O
Ph
Cl
Ph
Cl
O
Cl
N
H
NH2
N
H
O
Ph
Ph
O
O
Ph
NO2
Ph
O2N
Me
O
NH2
N
N
H
N
H
O
Ph
N
Me
O
O
Ph
Me
Me
O
N
H
NH2
N
H
O
Synlett 2012, 23, 2858–2864
© Georg Thieme Verlag Stuttgart · New York

LETTER
Biquinoline- and Quinoline-Bearing Chromene Derivatives
2861
Table 2 Synthesis of Biquinoline/Quinoline-Bearing Chromene Analogues 3a–j and 5a–ga (continued)
Entry
3-Acetylquinolines/
3-acetylchromenes
o-Amino ketones
Product
Yield (%)b
Ph
N
Me
O
O
Ph
NO2
Me
O2N
Me
6
O
NH2
3f
77
N
H
N
H
O
Ph
N
Ph
O
O
Ph
NO2
Ph
O2N
O2N
O2N
O2N
O2N
Me
Me
Me
Me
O
NH2
O2N
O2N
O2N
7
8
3g
3h
3i
72
76
75
66
N
H
N
H
O
O
O
Me
N
Ph
O
O
Me
Ph
O
N
H
NH2
Ph
N
H
Ph
N
Ph
O
O
Ph
O
9
N
H
NH2
N
H
Ph
N
Ph
O
O
Ph
Cl
Ph
Cl
O
O2N
10
3j
N
H
NH2
N
H
O
Ph
N
Ph
O
O
NO2
O2N
O
Me
11
12
13
14
5a
5b
5c
5d
81
86
82
82
NH2
O
O
O
O
O
O
Ph
Ph
O
Cl
Cl
O
Me
Me
N
NH2
MeO
MeO
O
O
O
MeO
MeO
O
Me
Me
O
N
NH2
O
O
O
O
Ph
N
Ph
O
Me
NH2
O
O
O
© Georg Thieme Verlag Stuttgart · New York
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M. Sankaran et al.
LETTER
Table 2 Synthesis of Biquinoline/Quinoline-Bearing Chromene Analogues 3a–j and 5a–ga (continued)
Entry
15
3-Acetylquinolines/
3-acetylchromenes
o-Amino ketones
Product
Yield (%)b
Me
Me
O
O
5e
74
Me
N
O
O
O
O
NH2
O
O
O
O
Ph
Ph
Cl
Cl
O
Me
16
17
5f
76
82
N
NH2
O
Ph
N
Ph
O
O
O
Me
5g
NH2
MeO
O
MeO
O
O
a Reaction conditions: o-aminobenzophenone (0.4 mmol), 3-acetylquinolin-2-one/3-acetylchromene-2-one (0.4 mmol), H2SO4, 120 °C.
b Isolated yield.
A plausible reaction mechanism is described in Scheme 3.
chromene frameworks promoted by acid-catalyzed cycli-
zation of 4-substituted quinoline-2-one and chromen-2-
one. This strategy represents an efficient aryl bond forma-
In conclusion, we have developed an efficient method for
the construction of biquinoline- and quinoline-substituted
H
H
R1
O
O
R1
O
O
R1
O
O
H
R2
R2
R2
CH2
H
Me
CH2
+
N
H
N
H
N
H
1
R3
R3
O
O
R1
R4
R4
R2
R1
O
H2C
R2
O
NH2
NH2
O
N
H
O
N
2
H
H
R3
R3 OH
R4
H
R4
H
R1
R1
R2
R2
O
NH2
N
H
OH
O
– H2O
– H2O
N
O
N
H
H
R3
R4
R1
R2
N
O
N
H
3
Scheme 3 Plausible reaction mechanism for the formation of biquinoline
Synlett 2012, 23, 2858–2864
© Georg Thieme Verlag Stuttgart · New York

LETTER
Biquinoline- and Quinoline-Bearing Chromene Derivatives
2863
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Figure 2 ORTEP diagram of compound 5f
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Figure 3 ORTEP diagram of compound 5g
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Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett. SupngIoipf
omitrSartunpIfopmnigrtir
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References and Notes
nitrobenzophenone (2d; 1 mmol) in acetic acid (20 mL),
appropriate 3-acetyl-6-nitro-4-phenylquinolin-2(1H)-one
(1d; 1 mmol) was added, followed by the addition of a
catalytic amount of H2SO4 (0.5 equiv). The reaction mixture
was heated to reflux for 3–5 h and the course of the reaction
was monitored by TLC. After cooling to r.t., the mixture was
poured into crushed ice (500 g) and the resulting residue was
filtered to afford the desired product, which was purified by
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© Georg Thieme Verlag Stuttgart · New York
Synlett 2012, 23, 2858–2864

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M. Sankaran et al.
LETTER
silica gel column chromatography (hexane–EtOAc, 7:3 v/v)
to afford the target compound (72%) as a pale-yellow solid.
Mp 254–258 °C. IR (KBr): 3311.18, 2865.7, 1822.4,
1653.66, 1532.17, 1334.5, 1258.32, 1069.33, 897.70,
703.89 cm–1. 1H NMR (400 MHz, DMSO-d6): δ = 12.88 (s,
1 H, Q-NH), 8.63 (d, J = 2.5 Hz, 1 H, ArH), 8.42–8.45 (m,
2 H, ArH), 8.11 (d, J = 9.0 Hz, 1 H, ArH), 7.98 (d, J =
2.5 Hz, 1 H, ArH), 7.61–7.65 (m, 5 H, ArH), 7.46 (dd, J =
1.5, 8 Hz, 2 H, ArH), 7.33–7.36 (m, 5 H, ArH). 13C NMR
(100 MHz, DMSO-d6): δ = 161.36, 158.77, 150.02, 149.08,
145.87, 143.61, 142.16, 136.31, 134.45, 132.98, 131.69,
129.88, 129.58, 129.04, 128.77, 125.86, 123.93, 113.33,
119.71, 117.21. MS: m/z = 514 [M + H]. Anal. Calcd for
C30H18N4O5: C, 70.03; H, 3.53; N, 10.89. Found: C, 69.98;
H, 3.55; N, 10.92%.
After cooling to r.t., the mixture was poured into crushed ice
(500 g); the resulting residue was filtered to afford the
desired product, which was purified by silica gel column
chromatography (hexane–EtOAc, 8:2 v/v) to afford the
target compound (82%) as a pale-green solid. Mp 216–
220 °C. IR (KBr): 3059.51, 1718.26, 617.02, 1583.27,
1502.28, 1358.6, 1237.11, 1187.94, 1021.12, 834.06,
703.89 cm–1; 1H NMR (400 MHz, DMSO-d6): δ = 8.99 (s,
1 H, C4-H), 8.40 (s, 1 H, C4–H), 8.22 (d, J = 8.50 Hz, 1 H,
ArH), 7.97 (d, J = 8.50 Hz, 1 H, ArH), 7.76 (t, J = 8.00 Hz,
1 H, ArH), 7.51–7.60 (m, 6 H, ArH), 6.95 (d, J = 2.00 Hz,
1 H, ArH), 6.93 (dd, J = 2.50, 10.00 Hz, 1 H, ArH). 13
C
NMR (100 MHz, DMSO-d6): δ = 163.46, 160.80, 156.23,
152.16, 148.69, 148.52, 143.82, 138.22, 130.08, 129.76,
129.74, 129.48, 128.53, 128.38, 126.65, 126.26, 125.79,
122.57, 121.81, 113.41, 113.19, 100.31, 55.86; MS: m/z =
379 [M + H]. Anal. Calcd for C25H17NO3: C, 79.14; H, 4.52;
N, 3.69. Found: C, 7.19; H, 4.49; N, 3.71%.
(31) Xuegang, C.; Dongfang, Q.; Liang, M.; Xanxiang, C.;
Yanhou, G.; Zhiyuan, X.; Lixiang, W. Transition Met.
Chem. 2006, 31, 639.
(32) 7-Methoxy-3-(4-phenylquinolin-2-yl)-2H-chromen-2-
one (5g): To a stirred suspension of 2-aminobenzophenone
(2a; 1 mmol) in acetic acid (20 mL), appropriate 3-acetyl-7-
methoxy-2H-chromen-2-one (4b; 1 mmol) was added,
followed by the addition of a catalytic amount of H2SO4
(0.5 equiv). The reaction mixture was heated to reflux for 3–
5 h, then the course of the reaction was monitored by TLC.
(33) Cif files for 5f and 5g have been deposited with the
Cambridge Crystallographic Data Centre as CCDC-895741
(5f) and 890933 (5g). Copies of the data can be obtained,
free of charge, on application to CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK. [Fax: +44(1223)336033 or e-
mail: deposit@ccdc.cam.ac.uk].
Synlett 2012, 23, 2858–2864
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