New Aryl Derivatives of Quinolinedione and Related Heterocyclic Compounds

Article abstract of DOI:10.1002/jhet.2745

The synthesis of new derivatives of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione via palladium/Sphos-mediated Suzuki–Miyaura cross-coupling reaction is reported. The 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione intermediates were prepared in a three-step reaction from 8-hydroxyquinoline. The palladium-catalyzed reactions of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione with a variety of aryl boronic acids provide coupled compounds in high yields. The arylation of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione with 4-bromophenyl boronic acid supplied 6,6′-(1,4-phenylene)bis(7-bromoquinoline-5,8-dione) and (4-(6-(4-(6-chloro-5,8-dihydroquinolin-7-yl)phenyl)-5,8-dihydroquinolin-7-yl)phenyl)boronic acid respectively, in addition to the expected coupled compounds in moderate yields. Also, Pd(0)/PPh₃ allowed the 7-chloro-6-(4-nitrophenyl)quinoline-5,8-dione and 7-chloro-6-phenylquinoline-5,8-dione to be synthesized via Heck reaction. The yields of the synthesized target molecules depend largely on the reaction conditions and the type of ligands employed. Structural assignments of the synthesized compounds were established by spectra and analytical data.

Full text of DOI:10.1002/jhet.2745

Month 2016
New Aryl Derivatives of Quinolinedione and Related
Heterocyclic Compounds
*
*
Samuel Attah Egu, Uchechukwu Chris Okoro, and Efeturi Abraham Onoabedje
Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Enugu State, Nigeria
*
E-mail: efeturi.onoabedje@unn.edu.ng; attahegu@gmail.com
Received April 28, 2016
DOI 10.1002/jhet.2745
Published online 00 Month 2016 in Wiley Online Library (wileyonlinelibrary.com).
The synthesis of new derivatives of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione
via palladium/Sphos-mediated Suzuki–Miyaura cross-coupling reaction is reported. The 6,7-
dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione intermediates were prepared in a three-
step reaction from 8-hydroxyquinoline. The palladium-catalyzed reactions of 6,7-dibromoquinoline-5,8-dione
and 6,7-dichloroquinoline-5,8-dione with a variety of aryl boronic acids provide coupled compounds in high
yields. The arylation of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione with 4-
bromophenyl boronic acid supplied 6,6′-(1,4-phenylene)bis(7-bromoquinoline-5,8-dione) and (4-(6-(4-(6-
chloro-5,8-dihydroquinolin-7-yl)phenyl)-5,8-dihydroquinolin-7-yl)phenyl)boronic acid respectively, in
addition to the expected coupled compounds in moderate yields. Also, Pd(0)/PPh3 allowed the 7-chloro-
6-(4-nitrophenyl)quinoline-5,8-dione and 7-chloro-6-phenylquinoline-5,8-dione to be synthesized via Heck
reaction. The yields of the synthesized target molecules depend largely on the reaction conditions and
the type of ligands employed. Structural assignments of the synthesized compounds were established by
spectra and analytical data.
J. Heterocyclic Chem., 00, 00 (2016).
INTRODUCTION
halogenatedquinoline-5,8-diones (2 and 3) via palladium-
mediated Suzuki–Miyuara and Heck cross-coupling
reactions is reported.
The surge to employ halogenated quinolines as interme-
diates in metal-catalyzed C–C bond formation for con-
struction of complex molecules such as natural products,
pharmaceuticals, and material science motivated investi-
gating facile reaction protocol for functionalization of
structurally related halogenated quinoline-5,8-dione [1–3].
Quinoline-5,8-dione is an active component in various
antimalaria, antimicrobial, anagelsic, cardiovascular,
anticancer, and anti-inflammatory drugs [4]. The recent
increase in microbial infections has generated a renewed
interest in search for new drugs [5]. To this end,
quinoline-5,8-dione had undergone various synthetic
transformations with a view to developing potent
antibacterial and antifungal agents [6–10]. Pd-catalyzed
reaction on similar system has earlier been reported
[11–13]. Also, we have recently reported the synthesis
of new quinolinedione derivatives and related
heterocyclic compounds, which were obtained by
cross-coupling of 6,7-dihaloquinoline-5,8-diones 2,3
and chlorophenothiazines/chlorophenoxaines, respec-
tively [14,15].
RESULTS AND DISCUSSION
The intermediates 6,7-dibromoquinoline-5,8-dione and 6,7-
dichloroquinoline-5,8-dione were prepared in a three-step
reaction starting from 8-hydroxyquinoline 4 (Fig. 1) [16].
The optimization results of the cross-coupling of
6,7-dibromoquinoline-5,8-dione with phenyl boronic acid
(Fig. 2) is given in Table 1.
The combination of Pd(OAc)2 and PPh3 gave insignifi-
cant % yield of 7-bromo-6-phenylquinoline-5,8-dione 5a
even when reaction was run for 2 days. While the use of
Pd(OAc)2/Sphos supplied moderate % yield of same
product, the reaction time was relatively long (8 h). Based
on earlier work of Buchwald and coworkers [17], the yield
of 7-bromo-6-phenylquinoline-5,8-dione was further en-
hanced by water preactivation of the catalyst system. This
was performed by first heating both Pd(OAc)2 (1mol%),
Sphos (3 mol%) in H2O (4mol%) at 80°C in 1,4-dioxane
In continuation of our avid interest in this class of
compounds, the synthesis of some new aryl derivatives of
within
1 min
before
the
introduction
of
6,7-dibromoquinoline-5,8-dione and phenyl boronic acid.
© 2016 Wiley Periodicals, Inc.

S. A. Egu, U. C. Okoro, and E. A. Onoabedje
Vol 000
Figure 1. Synthesis of 6,7-dihaloquinoline-5,8-diones.
combination with Pd(OAc)2 under water preactivation
and similar reaction conditions, also displayed good activ-
ity in the Suzuki-Miyaura cross-coupling of 6,7-
dichloroquinoline-5,8-dione.
Pd(OAc)2/BHDTBBP
allowed the synthesis of 6-(4-bromophenyl)-7-
chloroquinoline-5,8-quinone 6a, (4-(6-(4-(6-chloro-5,8-
dihydroquinolin-7-yl)phenyl)-5,8-dihydroquinolin-7-yl)
phenyl)boronic acid 6b and 7-chloro-6-(3-nitrophenyl)
quinoline-5,8-quinone 5c derivatives. The synthesized de-
rivatives were purified by recrystallization from aqueous
acetone. Derivatives 5b and 6b were isolated by column
chromatography as reddish solids in addition to the desired
coupled products (5a and 6a) from the reaction of 6,7-
dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-
5,8-dione with 4-bromophenylboronic acid, respectively.
The spectral and elemental analyses of 5b and 6b
agreed with structural assignments. Moreover, their
mass spectra furnished their molecular ion fragments
(M+, 100%) with mass/charge ratios of 550.26 and 546.34,
respectively.
Figure 2. Synthesis 6,7-dibromoquinoline-5,8-dione derivatives via
Suzuki-Miyaura cross-coupling.
Table 1
Optimization reaction of 6,7-dibromoquinoline-5,8-dione with phenyl
boronic acid.
Percent
Reaction
time (h)
yieldf (%)
S/N
Reaction conditiona,b
Pd(OAc)2/PPh3
Pd(OAc)2/SPhos
Pd(OAc)2/SPhosc (WAd)
Pd(OAc)2/BHDTBBPe
(WAd)
1
2
3
4
trace
44
56
48
8
2
45
3
aReaction condition: Pd(OAc)2 = 5 mol%; ligand = 10 mol%;
Ar(OH)2 = 1 eq; 6,7-dibromoquinoline-5,8-dione = 1.5 eq; water = 1 mL;
tert-BuOH = 2 mL.
In another development, 7-chloroquinolin-5.8-dione
substrate 7, which was obtained by multistep[19]
bIn reactions 3 and 4, Pd(OAc)2 and ligand in aqueous tert-BuOH were
heated to 80°C (water preactivated) within 60 s before addition of
dibromoquinoline-5,8-dione and phenyl boronic acid.
c2-Dicyclohexylphosphino-2′,6′-dimethoxybiphenyl.
dWA = water activation.
conversion of 8-hydroxyquinoline
4 (Fig. 3), was
coupled with 4-nitroiodobenzene and 4-iodobenzene,
respectively, via Pd(0)/PPh3-catalyzed Heck reaction to
e1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperizine.
fIsolated yields.
supply 7-chloro-6-(4-nitrophenyl)quinoline-5,8-dione
8
and 7-chloro-6-phenylquinoline-5,8-dione 9 in moderate
yields. The structures of all the synthesized compounds
were established by spectral and analytical data.
The preactivation was visually monitored by color change.
Therefore, with water preactivation of catalytic system, the
synthesis of 7-bromo-6-phenylquinoline-5,8-dione was
achieved in a very short time (2h) (Table 1).
CONCLUSION
Interestingly, it was observed that there was no apparent
difference in yield of product when reaction was conducted
under inert and aerobic conditions. The optimized reaction
was employed as a general protocol to synthesized
The palladium-catalyzed Suzuki–Miyaura cross-
coupling of 6,7-dibromoquinoline-5,8-dione and 6,7-
chloroquinoline-5,8-dione, respectively, provides a con-
venient route for synthesizing their aryl derivatives in
good yields. Arylation of 6,7-dibromoquinoline-
5,8-dione and 6,7-chloroquinoline-5,8-dione via water-
preactivated palladium-catalyzed cross-coupling furnished,
6,6′-(1,4-phenylene)bis(7-bromoquinoline-5,8-dione) and
(4-(6-(4-(6-chloro-5,8-dihydroquinolin-7-yl)phenyl)-5,8-
dihydroquinolin-7-yl)phenyl)boronic acid, respectively, in
compounds
6,6′-(1,4-phenylene)bis(7-bromoquinoline-
5,8-dione) 5b, 7-bromo-6-(3-nitrophenyl)quinoline-5,8
dione 5c, 7-bromo-6-phenylquinoline-5,8-dione 5d
(Table 2). Furthermore, a synthesized, non-phosphorus,
air and moisture stable 1,4-bis(2-hydroxy-3,5-di-tert-
butylbenzyl)piperazine (BHDTBBP) ligand [18] in
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

New Aryl Derivatives of Quinolinedione and Related Heterocyclic Compounds
Month 2016
Table 2
Derivatives of 6,7-halogenatedquinoline-5,8-dione.a,b,c
Entry
1
Ar-X
Ar(OH)2
Product
Reaction time (h)
1.30
Yield (%)d
50
2
2
2
1.30
37
3
4
2
2
1.30
2.00
53
51
5
6
3
3
2.30
2.30
50
33
7
3
2.30
56
aReaction condition: Pd(OAc)2 = 2.5 mol%; Sphos = 10 mol%; Ar(OH)2 = 1 eq; 6,7-dibromoquinoline-5,8-dione = 1.5 eq; water = 1 mL;
tert-BuOH = 2 mL. The Pd(OAc)2 and ligand in aqueous tert-BuOH were heated to 80°C (water preactivated) within 60 s before addition of dibromo or
dichloroquinoline-5,8-dione and boronic acid.
bFor reactions 5 and 6, 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperizine (5 mol%) was used in place of Sphos.
cThe reaction of compounds 2 and 3 with 4-bromophenylboronic acid gave product 4a with 4b and 5a with 5b, which were separated by flash column
chromatography by using methanol eluent.
dIsolated yields.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

S. A. Egu, U. C. Okoro, and E. A. Onoabedje
Vol 000
Figure 3. Synthesis of 7-chloro-6-(4-nitrophenyl)quinoline-5,8-dione 6 and 7-chloro-6-phenylquinoline-5,8-dione.
addition to the expected coupled compounds. Also, Pd(0)/
PPh3 allowed the 7-chloro-6-(4-nitrophenyl)quinoline-
5,8-dione and 7-chloro-6-phenylquinoline-5,8-dione to be
synthesized via Heck reaction. The yields of the
synthesized target molecules depend largely on the reaction
conditions and the type of ligands employed.
by TLC and after completion was cooled and filtered to ob-
tain the crude product. This was further recrystallized from
water–acetone to give the desired product. Procedure A
was used as a general method for the synthesis of com-
pounds 5a–5d.
Procedure B. 1,4-Bis(2-hydroxy-3,5-di-tert-butylbenzyl)
piperazine (5mol%) and Pd(OAc)2 (5 mol%) were placed
in a 25-mL three-neck round bottom flask. This was
followed by introduction of water (1mL) and dioxane
(4mL), and the solution was heated for 60s at 80°C under
inert atmosphere. Thereafter, 6,7-chloroquinoline-5,8-dione
(6.60mmol), boronic acid (7.90mmol), K2CO3 (1.4 eq.),
and dioxane (2mL) were added, and the reaction mixture
was heated under reflux with continuous stirring. After
the termination of the reaction, it was cooled to room
temperature, filtered, and recrystallized from water–acetone
to give the desired product. Procedure B was used as a
general method for the synthesis of compounds 6a–6c.
7-Bromo-6-(4-bromophenyl)quinoline-5,8-dione (5a). Proce-
EXPERIMENTAL SECTION
General. All chemicals were purchased from Aldrich
Chemical Company, UK, and were used without further
purification. Otherwise stated, all compounds were
synthesized and characterized in School of Chemistry,
Cardiff University, UK. Melting points were determined
with Fisher–Johns apparatus and are uncorrected.
Ultraviolet and visible spectra were recorded on a Unico-
UV2102 PC spectrophotometer by using matched 1cm
quartz cells and methanol solvent. The absorption
maxima were recorded in nanometers (nm) and figures in
parenthesis are in log ε. The NMR spectra were recorded
on Bruker DPX 500 and Oxford 300. Chemical shifts are
reported in ppm (δ) scale relative to TMS as internal
standard and coupling constants (J) were reported in
hertz (Hz). The following abbreviations were used: s
(singlet); d (doublet); dd (doublet of doublet); t (triplet);
m (multiplet). Mass spectrometric data were obtained on
a Varian 1200 Quadrupole Mass Spectrometer and
Micro-mass Quadro II Spectrometer. Elemental analyses
were obtained on Heraeus CHN-O rapid analyzer.
dure
A
was employed to cross-coupled 6,7-
dibromoquinoline-5,8-dione (200mg, 0.63mmol) with
4-bromophenylboronic acid (250mg, 1.26mmol) to ob-
tain the title product (5a) in 1.5h as red solid after purifi-
cation by flash column chromatography. Yield: 142.1mg
(50% yield); mp 260–262°C. UV-Visible λmax (MeOH):
1
333 (3.236), 350 (2.868), 421 (3.816), 439 (3.111). H
NMR (400MHz, CDCl3): δ 8.8 (dd, 1H, J=1.6, 4.8Hz),
8.4 (dd, 1H, J=1.6, 8.0Hz), 7.7 (dd, 1H, J=4.8,
7.6Hz), 7.4 (d, 2H, J=8.5), 7.3 (2H). Anal. Calcd. for
C15H7Br2NO2: C, 45.84; H, 1.80; N, 3.56. Found: C,
45.90; H, 1.76; N, 3.52
General procedures for Suzuki-Miyaura reaction
Procedure A. SPhos (10 mol%) and Pd(OAc)2 (2.5 mol
%) were placed in a 25-mL three-neck round bottom flask.
This was followed by addition of water (1 mL) and tert-
BuOH (2 mL) and the solution boiled for 60 s at 80°C
under inert atmosphere. Thereafter, 6,7-dibromo-5,8-
quinolin-5,8-dione (0.316 mmol), the boronic acid
(0.631 mmol), K2CO3 (3 eq.), and tert-BuOH (2mL) were
added, and the entire reaction mixture was refluxed with
continuous stirring. The reaction progress was monitored
6,6′-(1,4-Phenylene)bis(7-bromoquinoline-5,8-dione) (5b). Com-
pound 5b was isolated as dark red solid by flash column
chromatography as second product from the reaction
of 6,7-dibromoquinoline-5,8-dione (200mg, 0.63mmol)
with 4-bromophenylboronic (250mg, 1.26mmol). Yield:
147.2mg (37%); mp 327–329°C. UV-Visible λmax
(MeOH): 335 (3.271), 350 (3.123), 441 (3.548), 440
(3.694). 1H NMR (400MHz, CDCl3) δ 8.2 (d, 2H,
J=7.5), 7.6 (dd, 2H, J=8.0, 1.0), 7.1 (s, 4H), 7.0 (dd,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

New Aryl Derivatives of Quinolinedione and Related Heterocyclic Compounds
Month 2016
2H, J=7.0, 1.0). MS (APCI), m/z (% relative intensity):
545.23 (25), 547.26 (51), 550.26 [(100), M+]. Anal. Calcd.
for C24H10Br2N2O4: C, 52.40; H, 1.83; N, 5.09. Found: C,
52.40; H, 1.52; N, 5.21. Note that compounds 5a and 5b
were separated by flash chromatography by using methanol
as eluent.
MS (APCI), m/z (% relative intensity): 545.33 (52),
546.34 [(100), M+]. Anal. Calcd. (found) for
C30H24BClN2O4: C, 65.91; H, 2.95; N, 5.12. Found: C,
65.66; H, 2.60; N, 5.23. Note that compounds 6a and 6b
were separated by flash chromatography by using methanol
as eluent.
7-Bromo-6-(3-nitrophenyl)quinoline-5,8-dione (5c).
Pro-
7-Chloro-6-(3-nitrophenyl)quinoline-5,8-quinone (6c). Pro-
cedure B was employed to couple 6,7-dichloroquinoline-
5,8-dione (130mg, 0.570mmol) with 3-nitrophenylboronic
acid (140mg, 0.86mmol) to supply the title product
(6c) in 2h as reddish solid. Yield: 100mg (56%); mp
355–357°C. UV-Visible λmax (MeOH): 600 (0.265), 620
(0.144), 630 (0.112), 640 (0.077). 1H NMR (400MHz,
DMSO): 8.8 (dd, 1H, J=1.2, 4.4Hz), 8.7 (dd, 1H,
J=1.6, 4.8Hz), 8.6 (s, 1H), 7.8 (2H), 7.7 (dd, 1H,
J=3.2, 7.6Hz), 7.6 (1H). IR νmax cmÀ1: 1678.14 (C=O);
1535.40 (NO2). Anal. Calcd. for C15H7Cl2NO4: C,
57.25; H, 2.24; N, 8.90. Found: C, 57.29; H, 2.32;
N, 8.82.
cedure A was used to coupled 6,7-dibromoquinoline-5,8-
dione (100 mg, 0.316 mmol) with 3-nitrophenylboronic
acid (110 mg, 0.631 mmol) to supply the title product
(5c) in 1.5h as dark reddish solid. Yield: 180.3 mg
(53%); mp 360–362°C. UV-Visible λmax (MeOH): 333
(4.654), 350 (3.879), 421 (3.326), 439 (3.267). 1H
NMR (400 MHz, DMSO): δ 8.8 (s, 1H), 8.2 (1H), 8.1
(1H), 7.7 (1H), 7.6 (s, 1H), 7.5 (1H), 7.3 (1H). IR νmax
cmÀ1: 1651.14 (C=O); 1392.66 (NO2). MS (APCI), m/z
(% relative intensity): 314.06 (10), 315.09 (55), 361.10
[(100), M+ + 2]. Anal. Calcd. for C15H7BrN2O4: C,
50.17; H, 1.96; N, 7.80. Found: C, 50.20; H, 1.94;
N, 7.75.
General procedure for Heck reaction.
Iodobenzene
7-Bromo-6-phenylquinoline-5,8-dione (5d). Procedure A
was apply to coupled 6,7-dibromoquinoline-5,8-dione
(100 mg, 0.316mmol) with phenylboronic acid (80 mg,
0.474 mmol) to afford the title product (5d) in 2h as red
solid. Yield: 141 mg (51%); mp 316–318°C. UV-Visible
λmax (MeOH): 600 (2.536), 620 (2.44), 630 (1.816),
(0.003 mol) and 7-chloroquinoline-5,8-dione substrate
(0.004 mol), Pd(OAc)2 (3 mol%), PPh3 (5 mol%), and
NaHCO3 (330mg) were added to a 50-mL round
bottom flask containing 4 mL of DMF, and the reaction
mixture was refluxed at 180°C. After the reaction
completion as indicated by TLC, it was cooled to room
temperature. The crude product was extracted with hot
toluene (3 × 10mL). The combined organic extract was
dried with sodium sulfate and concentrated in vacuum.
The crude product was purified by flash column
chromatography on silica gel employing petroleum
ether/ethyl acetate.
1
640 (1.341). H NMR (400 MHz, DMSO): 8.8 (1H), 7.9
(dd, 1H, J = 1.2, 8.0 Hz), 7.5 (2H), 7.4 (dd, 1H, J = 1.6,
7.6Hz), 7.2 (m, 3H). Anal. Calcd. for C15H8BrNO2:
C, 57.35; H, 2.57; N, 4.46. Found: C, 57.40; H, 2.71;
N, 4.50.
6-(4-Bromophenyl)-7-chloroquinoline-5,8-quinone (6a). Pro-
cedure B was employed for the reaction of 6,7-dichloro-
5,8-quinolinequinone (1500mg, 6.60mmol) with 4-
bromophenylboronic acid (1600mg, 7.90mmol) to obtain
the title product (6a) in 2.5h as red solid after purification
by flash column chromatography. Yield: 150mg (50%);
mp 326–328°C. UV-Visible λmax (MeOH): 600 (3.411),
620 (2.732), 630 (3.546), 640 (3.255). 1H NMR
(400MHz, DMSO): 8.9 (dd, 1H, J= 1.2, 4.4, Hz), 8.7
(dd, 1H, J=1.6, 8.4Hz), 8.0 (d, 2H, J=7.1), 7.8 (dd, 1H,
J=4.8, 8.4Hz), 6.8 (2H). Anal. Calcd. for C15H7BrClNO2:
C, 51.69; H, 2.02; N, 4.02. Found: C, 51.70; H, 2. 05;
N, 4.10.
(4-(6-(4-(6-Chloro-5,8-dihydroquinolin-7-yl)phenyl)-5,8-dihydro-
quinolin-7-yl)phenyl)boronic acid (6b). Compound 6b was
isolated as dark red solid by flash column chromatography
as second product from the reaction of 6,7-
dichloroquinoline-5,8-dione (1500mg, 6.60mmol) with
4-bromophenylboronic (1600mg, 7.90mmol). Yield:
1191mg (33%); mp 318–320°C. UV-Visible λmax
(MeOH): 222 (3.776), 350 (2.443), 427 (3.836), 440
(3.342). 1H NMR (400MHz, DMSO): 8.2 (d, 2H),
7.9 (2H), 7.5 (m, 2H), 7.3 (4H), 7.2 (m, 4H), 5.8 (s, 2H).
Synthesis of 7-chloro-6-(4-nitrophenyl)quinoline-5,8-dione
(8). The general Heck procedure was used to cross-
coupled 4-iodonitrobenzene with 7-chloroquinolin-5.8-
dione to obtain titled compound as deep green solid in
3 h. Yield, 620mg (57%). mp 251–253°C. UV-Visible
λmax (MeOH): 450 (3.736), 470 (2.144), 550 (2.812),
500 (2.511). 1H NMR (400MHz, DMSO): 9.0 (1H),
8.4 (1H), 8.2 (2H), 7.7 (1H), 7.1 (2H). IR νmax cmÀ1
:
1740.00 (C=O); 1373.40 (NO2). Anal. Calcd. for
C15H7ClN2O4: C, 57.25; H, 2.24; N, 8.90. Found: C,
57.33); H, 2.43; N, 8.78.
Synthesis of 7-chloro-6-phenylquinoline-5,8-dione (9). The
general Heck procedure was used to cross-coupled
iodobenzene with 7-chloroquinolin-5.8-dione to obtain
titled compound as yellowish green solid in 3h. Yield,
460mg (63%). mp 288–290°C. UV-Visible λmax (MeOH):
520 (3.665), 490 (3.736), 450 (2.144), 420 (2.511). 1H
NMR (400MHz, DMSO): 8.8 (1H), 8.7 (1H), 8.3 (2H),
8.2 (2H), 7.7 (m, 1H), 7.6 (m, 1H). IR νmax cmÀ1
:
1738.00 (C=O). Anal. Calcd. for C15H8ClNO2: C,
66.81; H, 2.99; N, 5.19. Found: C, 66.85; H, 2.81;
N, 5.27.
Journal of Heterocyclic Chemistry
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S. A. Egu, U. C. Okoro, and E. A. Onoabedje
Vol 000
[9] Keyari, C. M.; Kearns, A. K.; Duncan, N. S.; Eickholt, E. A.;
Abbott, G.; Beall, H. D.; Diaz, P. J Med Chem 2013, 56, 3806.
[10] Lanfranchi, D. A.; Cesar-Rodo, E.; Bertrand, B.; Huang,
H.-H.; Day, L.; Johann, L.; Elhabiri, M.; Becker, K.; Williams, D. L.
Org Biomol Chem 2012, 10, 6375.
Acknowledgment. We thank Cardiff University, UK, for short-
term research opportunity.
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