Para substituted benzaldehydes as expedient reagents for the oxidative aromatization of hydroquinoline

Article abstract of DOI:10.1002/jhet.1117

A Cannizzaro-type reaction of tetrahydro-5(1H)-quinolinones with para substituted benzaldehydes in the presence of a base formed the corresponding quinoline and aryl methanol rather than arylidene derivatives because of the oxidation of tetrahydroquinoline and reduction of benzaldehydes as a result of unprecedented hydride transfer from tetrahydroquinoline to arylaldehydes. The reaction proceeds best with the participation of substituents with +M effect in substrate molecule.

Full text of DOI:10.1002/jhet.1117

Month 2013
Para Substituted Benzaldehydes as Expedient Reagents for the Oxidative
Aromatization of Hydroquinoline
*
Poulomi Majumdar, Anita Pati, Rajani K. Behera, and Ajaya Kumar Behera
Organic Synthesis Laboratory, School of Chemistry, Sambalpur University, Jyoti-Vihar, Burla 768019, Sambalpur
Odisha, India
*
E-mail: ajaykumar.behera@yahoo.com
Received May 29, 2011
DOI 10.1002/jhet.1117
Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com).
A Cannizzaro-type reaction of tetrahydro-5(1H)-quinolinones with para substituted benzaldehydes in the
presence of a base formed the corresponding quinoline and aryl methanol rather than arylidene derivatives
because of the oxidation of tetrahydroquinoline and reduction of benzaldehydes as a result of unprecedented
hydride transfer from tetrahydroquinoline to arylaldehydes. The reaction proceeds best with the participation
of substituents with +M effect in substrate molecule.
J. Heterocyclic Chem, 00, 00 (2013).
INTRODUCTION
RESULTS AND DISCUSSION
Literature survey reveals a plethora of protocols for
oxidative aromatization of 1,4-dihydropyridines into the
corresponding pyridines. Numerous oxidants were used in
the aromatization of 1,4-dihydropyridines such as nitric acid
[1,2], nitrous acid in situ formed by action of acids to NaNO2
[3], nitrogen oxides [4], metallic nitrates [5], chromium(VI)
oxidants [6], CrO2 [7], manganesse and iron(III) salts [8],
mercury(II) and Tl(III) salts [9], SnCl4 [10], Pb(OAc)4
[11], K2S2O8 [12], S8 [13], O2 [14], I2 [15], and hypervalent
iodine reagents [16], and non-metallic oxidants [17],
among others [18]. Some catalytical methods employing
stoichiometric amount have been developed such as RuCl3/
O2 [19], Fe(ClO4)3/O2 [20], Pd/C [21], activated charcoal/
O2 [22], Co(II)naphthenate/O2 [23], and Co(OAc)2/H2O2
[24–26]. However, many of these systems suffer from
disadvantages such as use of expensive transition metal
oxidants, strong oxidative conditions, and tedious workup.
We reported herein a new protocol for oxidative aromatiza-
tion of tetrahydro-5(1H)-quinolinones 3 from readily avail-
able reactants, and this article should also be of practical
value because the aromatization process will produce medic-
inally important quinoline moiety [27–29]. Moreover, they
are valuable precursors [30] for the synthesis of medicinally
important compounds such as nonsteroidal androgen recep-
tor agonists [31], the antimalarial drug chloroquine [32],
and martinellines with antibacterial activity [33].
In pursuance of our interest in developing methods for
the synthesis of new heterocylic systems having potential
biological activities [34], we synthesized tetrahydro-5
(1H)-quinolinones 3a–t, by the treatment of dimedone with
various chalcones 2 and ammonium acatate in the presence
of catalytic amount of acetic acid according to the proce-
dure reported in literature [35] (Scheme 1).
We planned to synthesize the arylidene derivative 4 by
the reaction of the hydroquinolinone 3 with para substi-
tuted benzaldehydes and sodium acetate in acetic acid
(Scheme 2) so as to install different heterocyclic moieties
by exploiting the a,b-unsaturated carbonyl unit in the
expected product 4.
During the course of structural elucidation of the product
formed in the reaction, we observed that the spectral data
of the isolated product did not match with the expected
structure 4 for the product. These data led us to assign
structure 5 to a product, which is a quinolin-5-one deriva-
tive. Thus, according to this criterion, the following survey
of results and discusssion is divided into two parts.
The first endeavor started on refluxing equimolar
mixture of tetrahydro-5(1H)-quinolinones 3a (Ar═Ar0═Ph),
benzaldehyde, and sodium acetate in acetic acid with a view
to procure the corresponding benzylidene derivative 4a
(Ar═Ar0═Ar00═Ph). The formation of benzylidene deriva-
tive 4a was primarily ruled out on the basis of its mass and
© 2013 HeteroCorporation

P. Majumdar, A. Pati, R. K. Behera, and A. K. Behera
Vol 000
Scheme 1. Synthesis of tetrahydro-5(1H)-quinolinones 3a–t.
the formation of exocyclic olefinic bond in conjugation
with carbonyl function present in structure 4a. The
shifting of the C═O band to a higher-frequency region
is due to the oxidative aromatization of the ring.
In 1H NMR spectra, the disappearance of the double dou-
blet, doublet, and two singlets at d 5.30 (dd, 1H, C3–H),
4.74 (d, 1H, C4–H), 1.02 (s, 3H, Me), and 1.10 (s, 3H, Me)
of 3a and the appearance of four separate sharp singlets at
1.16 (s, 6H, 2ꢁMe), 2.55 (s, 2H, C6–H), 3.20 (s, 2H, C8–H),
and 7.51 (s, 1H, C3–H) (Fig. 1) are agreeable to the structure 5a
as the product. Therefore, the tetrahydroquinolinone 3a,
instead of undergoing condensation with substituted
benzaldehydes, undergoes a Cannizaro type of redox reaction
with arylaldehydes in the presence of a base to form the
corresponding dihydroquinoline and aryl methanol because
of the oxidation of tetrahydroquinoline and reduction of
arylaldehydes. This transformation is believed to proceed via
unprecedented hydride shift from dihydroquinoline to arylal-
dehydes (Path A) (Scheme 3). The alternative mechanism
(Path B) may also be possible for the formation of dihydro-
quinolinone 5 and aryl methanol. This anomalous result led
us to carry out a series of experiments to ascertain the mech-
anism of the aromatization of the terahydroquinolinone 3.
In the second criterion, we investigated the aforesaid reac-
tion conditions with 1,4-dihydropyridine 6 and hydroquinoline
7 [35] (Scheme 4) in order to postulate a mechanism for
the aromatization of tetrahydro-5(1H)-quinolinones 3
and substituent effect on this particular reaction.
Scheme 2. Synthesis of dihydro-5(6H)-quinolinones 5a–t from 3a–t.
In fact, in both cases, the starting materials were
regenarated rather than achieving the expected aromatized
products 8 and 9. The possible explanation for this failure
of the reaction is the steric effect of the carboethoxy group
substituted at b position of the hydropyridine rings and
phenyl ring at g position.
In order to establish the role of benzaldehyde, we refluxed
hydroquinoline 3 in acetic acid with stoichometric amount of
sodium acatate with the aim of obtaining in situ oxidized
hydroquinoline derivative 5. However, this reaction resulted
in the same starting hydroquinoline 3, suggesting the
necessity of an arylaldehyde for oxidation. Thus, the
oxidative aromatization of 3 was unexpectedly successful
as per the reaction condition illustrated in Scheme 2 on the
basis of the mechanism demonstrated in Scheme 3.
Under similar reaction conditions, tetrahydropyrido[2,3-d]
pyrimidin-4(1H)-one 11 (Scheme 5) underwent successful
oxidative aromatization to afford 12 in good yield. The
PMR spectrum of 11 in DMSO solution displayed two sepa-
rate double doublet at d 3.78 (J6a, 6b = 16.4 Hz, J6a, 5 = 7.6 Hz)
and 3.89 (J6b, 6a = 16.4 Hz, J6b, 5 = 7.6 Hz) for each one
proton at C6 and a triplet at d 4.74 (J = 7.6 Hz) for C5–H
indicating that pyridopyrimidine derivative 11 is in pyrido
[2,3-d]pyrimidin-4(1H)-one 110 form in DMSO (Fig. 2),
whereas in PMR spectrum of 12, two double doublets and a
triplet disappeared and a singlet for C3–H appeared at d 8.03.
elemental analyses. The mass spectra shows a peak at
m/z 328, which is compatible with [M + 1]+ ion peak
of quinolin-5-one 5a (Ar═Ar0═Ph). Further, the
structure 5a for the product was supported by its IR
spectrum with the dissappearence of –NH stretching fre-
quency and a hypsochromic shift of carbonyl stretching
frequency from 1656 to 1693 cmꢀ1, which eliminates
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
Para Substituted Benzaldehydes as Expedient Reagents for the
Oxidative Aromatization of Hydroquinoline
Figure 1. 1H NMR spectra of (a) tetrahydro-5(1H)-quinolinone 3a. (b) Dihydro-5(6H)-quinolinone 5a in CDCl3.
Scheme 4. Results for aromatization of 1,4-dihydropyridine 6 and
hydroquinoline 7 with arylaldehydes.
Scheme 3. Proposed mechanism for aromatization.
Inspection of Table 1 reveals that p-methoxyphenyl,
p-chlorophenyl, p-bromophenyl, and phenyl groups at a
position and p-chlorophenyl, p-bromophenyl, p-anisyl, and
aryl at g position of hydroquinolinone 3 bring about the
oxidation reaction effectively in the presence of aryl
aldehyde as an oxidant. The yield of the product is enhanced
by the electron-releasing groups at para position of the
benzene rings, whereas the electron withdrawing groups
decrease the yield. The effectiveness of the reaction
could be explained on the basis of +M effect of the
substituents, and the order of the reactivity in para
The strategies of this reaction also came out successfully
with sodium ethoxide in ethanolic medium.
To investigate the scope of the substituent effect of this
reaction, were explored various para substituted aryl
groups in 3. In general, all the reactions with different
substituents were very clean, and the aromatized products
were obtained in moderate to good yields; however, very
low yield of the product was obtained in case of para
nitrophenyl substituent (Table 1).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

P. Majumdar, A. Pati, R. K. Behera, and A. K. Behera
Vol 000
Table 1
Aromatization of hydroquinoline 3 to hydroquinoline 5.
Scheme 5. Aromatization of tetrahydropyrido[2,3-d] pyrimidin-4(1H)-
one 11 to 2,3-dihydropyrido[2,3-d]pyrimidin-4(1H)-one 12.
Yieldsd
e/f/g/h/i
Entry
Ar
Ar0
Products
1.
2.
3.
4.
5.
6.
7.
8.
Ph
Ph
Ph
Ph
p-ClC6H4
p-ClC6H4
Ph
(5a)a
(5b)a
(5c)a
(5d)a
(5e)a
(5f)b
(5g)a
(5h)b
(5i)a
53/52/59/20/30
59/58/61/13/32
50/50/55/10/28
56/56/59/12/31
56/56/57/10/27
43/42/45/8/22
60/59/61/20/35
51/52/55/11/27
53/51/55/10/25
52/54/56/12/22
50/48/53/10/20
53/54/56/12/21
—
p-ClC6H4
p-OMeC6H4
p-BrC6H4
Ph
p-ClC6H4
p-OMeC6H4
p-BrC6H4
Ph
p-ClC6H4
p-OMeC6H4
p-BrC6H4
Ph
p-ClC6H4
p-OMeC6H4
p-BrC6H4
Ph
p-ClC6H4
p-ClC6H4
9.
p-OMeC6H4
p-OMeC6H4
p-OMeC6H4
p-OMeC6H4
p-NO2C6H4
p-NO2C6H4
p-NO2C6H4
p-NO2C6H4
p-BrC6H4
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
(5j)b
(5k)a
(5l)a
(5m)a
(5n)c
(5o)c
(5p)c
(5q)a
(5r)b
(5s)b
(5t)b
—
—
—
55/56/57/11/25
47/44/50/12/23
56/57/59/18/29
45/47/50/12/23
p-BrC6H4
p-BrC6H4
p-BrC6H4
p-ClC6H4
p-OMeC6H4
p-BrC6H4
aReactions were carried out for 8 h.
bReactions were carried out for 10 h.
cReactions were carried out for 13 h.
Figure 2. Amino imino tautomerism of pyridopyrimidine derivative 11.
dIsolated yields. Isolated yield e: in the presence of benzaldehyde. f:
in the presence of p-methoxybenzaldehyde. g: in the presence of p-
chlorobenzaldehyde. h: in the presence of p-nitro benzaldehyde. i: in the
presence of p-N,N-dimethyl amino benzaldehyde.
substituted aryl groups at a position of hydroquinoline
is p-OMe > p-Cl > p-Br > H.
checked purity of the products by TLC on silica gel G (BDH)
by using toluene–ethyl acetate (4:1) as irrigant. We recorded IR
spectra with a Shimadzu FTIR Prestige-21 spectrophotometer in
potassium bromide (KBr) by using diffuse reflected spectra
(DRS) technique. NMR spectra were recorded on a VARIAN
200 or 400 MHz (1H, 200 or 400 MHz; 13C, 100 MHz) and
BRUKER AVANCE III 500 MHz (500 Hz for 1H, 125 MHz
for 13C) NMR spectrometer in deuteriochloroform (CDCl3)
or dimethyl sulfoxide (DMSO-d6), unless otherwise stated.
Chemical shifts are expressed in parts per million downfield
from tetramethylsilane as an internal standard. The mass spectra
were taken on API 2000 LC-MS mass spectrometer. Elemental
analyses were performed by Flash 2000 CHN elemental
analyzer and were in agreement with the calculated values
within ꢃ0.4%. All the reagents and solvents used were of the
best grade available and were used without further purification.
Literature methods were used for the preparation of chalcones 2
[36], diethyl 2, 6-dimethyl-4-phenyl-1, 4-dihydropyridine-3, 5-
dicarboxylate 6 [35], ethyl 2, 7, 7-trimethyl-5-oxo-4-phenyl-1,
4, 5, 6, 7, 8-hexahydroquinoline-3-carboxylate7 [35], and 1, 3-
diphenylthiobarbituric acid 10 [37]. The appropriate time for the
preparation and yield of the oxidative aromatized product 5 with
the use of different arylaldehydes as oxidant are given in Table 1.
General procedure for 2,4-disubstituted 7,8-dihydroquinoline-
5(1H)-ones (3a–t). To a solution of dimedone (0.28 g, 2 mmol)
1 and chalcone (2 mmol) 2 in ethanol (10 mL), ammonium
acetate (3.06 g) and 3–4 drops of acetic acid were added and
refluxed with stirring till solid product 3 occurred. The reaction
mixture was allowed to cool, the solid product was filtered, and
it was washed thoroughly with water and recrystallized from
The efficacy of the oxidant has been further studied by
using different p-substituted benzaldehydes such as p-N,
N-dimethyl amino benzaldehyde, p-chlorobenzaldehyde,
p-methoxybenzaldehyde, p-nitrobenzaldehyde, and benz-
aldehyde. It has been observed that the substituents attached
to para position of the benzene ring with –I effect increases
the yield of the oxidized product, and the following order
of reactivity of p-substituated benzaldehydes is given as p-Cl
p-OMe ꢂ H > p-N(Me)2 > p-NO2.
CONCLUSIONS
In summary, we have for the first time reported a new
protocol for oxidative aromatization of tetrahydro-5(1H)-
quinolinones 3 and tetrahydropyrido[2,3-d]pyrimidin-4
(1H)-one 11 by using p-substituated benzaldehydes as oxi-
dants. The yield of product basically depends on the substi-
tuents with +M effect attached to para position of benzene
rings connected to the a and g positions of hydroquinolinone
moiety and the substituents with –I effect attached to the
aryl aldehydes.
EXPERIMENTAL
General information.
We took melting points in open
capillaries by using sulfuric acid bath and are uncorrected. We
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
Para Substituted Benzaldehydes as Expedient Reagents for the
Oxidative Aromatization of Hydroquinoline
ethanol. We checked purity of the products by TLC on silica gel
G (BDH) by using toluene–ethyl acetate (4:1) as irrigant.
4,6,7,8-Tetrahydro-7,7-dimethyl-2,4-diphenyl-5(1H)-
quinolinone (3a) [38–41]. The reaction was carried out
following the general procedure with chalcone 2a (0.42 g,
2 mmol). The pale yellow solid product 3a thus obtained after
10 min was filtered and recrystallized from ethanol. The yield
was 65%. mp 213 ꢄC. Rf: 0.38 (toluene/ethyl acetate, 4:1).
Anal. Calcd for C23H23NO: C, 83.89; H, 6.99; N, 4.26. Found:
C, 83.75; H, 6.63; N, 3.98.
4,6,7,8-Tetrahydro-2-(4-chlorophenyl)-7,7-dimethyl-4-
phenyl-5(1H)-quinolinone (3b) [38,39]. The reaction was carried
out following the general procedure with chalcone 2b (0.48 g,
2 mmol). The pale yellow solid product 3b thus obtained after
20min was filtered and recrystallized from ethanol. The yield was
66%. mp 220 ꢄC. Rf: 0.35 (toluene/ethyl acetate, 4:1). Anal. Calcd
for C23H22NOCl: C, 76.03; H, 6.06; N, 3.86. Found: C, 75.89; H,
5.74; N, 3.75.
4,6,7,8-Tetrahydro-2-(4-methoxyphenyl)-7,7-dimethyl-4-
phenyl-5(1H)-quinolinone (3c) [41]. The reaction was carried
out following the general procedure with chalcone 2c (0.48 g,
2 mmol). The yellow solid product 3c thus obtained after
20 min was filtered and recrystallized from ethanol. The yield
was 55%. mp 208 ꢄC. Rf: 0.28 (toluene/ethyl acetate, 4:1).
Anal. Calcd for C24H25NO2: C, 80.22; H, 6.96; N, 3.90.
Found: C, 79.98; H, 6.67; N, 3.84.
4,6,7,8-Tetrahydro-2-(4-bromophenyl)-7,7-dimethyl-4-phenyl-5
(1H)-quinolinone (3d) [38–40]. The reaction was carried out
following the general procedure with chalcone 2d (0.57 g, 2 mmol).
The yellow solid product 3d thus obtained after 20 min was filtered
and recrystallized from ethanol. The yield was 62%. mp 266 ꢄC. Rf:
0.26 (toluene/ethyl acetate, 4:1). Anal. Calcd for C23H22NOBr: C,
67.65; H, 5.39; N, 3.43. Found: C, 67.42; H, 5.14; N, 3.20.
4,6,7,8-Tetrahydro-4-(4-chlorophenyl)-7,7-dimethyl-2-phenyl-
5(1H)-quinolinone (3e) [38–41]. The reaction was carried out
following the general procedure with chalcone 2e (0.48 g, 2 mmol).
The pale yellow solid product 3e thus obtained after 5 min was
filtered and recrystallized from ethanol. The yield was 59%. mp
198 ꢄC. Rf: 0.45 (toluene/ethyl acetate, 4:1). Anal. Calcd for
C23H22NOCl: C, 76.03; H, 6.06; N, 3.86. Found: C, 75.78; H,
5.78; N, 3.72.
4,6,7,8-Tetrahydro-4-(4-chlorophenyl)-2-(4-methoxyphenyl)-
7,7-dimethyl-5(1H)-quinolinone (3g) [40]. The reaction was
carried out following the general procedure with chalcone 2g
(0.54 g, 2 mmol). The yellow solid product 3g thus obtained after
20 min was filtered and recrystallized from ethanol. The yield was
50%. mp 230 ꢄC. Rf: 0.30 (toluene/ethyl acetate, 4:1). Anal. Calcd
for C24H24NOCl: C, 76.39; H, 6.37; N, 3.71. Found: C, 76.10; H,
6.14; N, 3.46.
4,6,7,8-Tetrahydro-2-(4-bromophenyl)-4-(4-chlorophenyl)-
7,7-dimethyl-5(1H)-quinolinone (3h). The reaction was carried
out following the general procedure with chalcone 2h (0.64 g,
2 mmol). The white solid product 3h thus obtained after 15 min
was filtered and recrystallized from ethanol. The yield was 56%.
mp 264 ꢄC. Rf: 0.50 (toluene/ethyl acetate, 4:1). IR (KBr, DRS):
nmax 3334 (–NH), 3080, 3032 (–CH, Ar–H), 2949, 2870 (–CH,
–CH3), 1651 (C═O), 1487, 1587 (–C═C–, aromatic ring), 1390
1
(–C–N), 821 cmꢀ1. H NMR (CDCl3, 400 MHz): d 1.03 (s, 3H,
Me), 1.10 (s, 3H, Me), 2.21–2.44 (m, 4H, 4H at C6 and C8),
4.74 (d, 1H, J4, 3 = 5.5 Hz, H-4), 5.23 (dd, 1H, J3, 4 = 5.5 Hz, J3,
NH = 2 Hz, H-3), 5.71 (bs, 1H, NH), 7.22–7.58 (m, 8H, PhH);
13C NMR (CDCl3, 100 MHz): d 27 (Me), 29.31 (Me), 31.96 (C-
7), 37.70 (C-8), 42.01 (C-6), 50.72 (C-4), 107.04 (C-3), 108.42
(═C–C═O), 124.60, 126.35, 127.96, 128.95, 130.12, 131.24,
132.09, 136.57 (eight peaks, Ph–C), 147.60 (C-2), 150.68 (═C–
NH), 195.56 (C═O). ES-MS m/z 443 [M + 1]+ (22.90%), 408
(67%), 328 (56.70%), 252 (100%). Anal. Calcd for
C23H21NOClBr: C, 62.44; H, 4.75; N, 3.17. Found: C, 62.22;
H, 4.49; N, 2.92.
4,6,7,8-Tetrahydro-4-(4-methoxyphenyl)-7,7-dimethyl-2-phenyl-
5(1H)-quinolinone (3i) [39,41]. The reaction was carried out following
the general procedure with chalcone 2i (0.48 g, 2 mmol). The pale
yellow solid product 3i thus obtained after 10 min was filtered and
recrystallized from ethanol. The yield was 42%. mp 204 ꢄC. Rf: 0.26
(toluene/ethyl acetate, 4:1). Anal. Calcd for C24H25NO2: C, 80.22; H,
6.96; N, 3.90. Found: C, 79.98; H, 6.67; N, 3.84.
4,6,7,8-Tetrahydro-2-(4-chlorophenyl)-4-(4-methoxyphenyl)-
7,7-dimethyl-5(1H)-quinolinone (3j). The reaction was carried out
following the general procedure with chalcone 2j (0.54 g, 2 mmol).
The yellow solid product 3j thus obtained after 15 min was filtered
and recrystallized from ethanol. The yield was 53%. mp 230 ꢄC.
Rf: 0.35 (toluene/ethyl acetate, 4:1). Anal. Calcd for C24H24NO2Cl:
C, 73.28; H, 6.11; N, 3.56. Found: C, 73.05; H, 5.85; N, 3.34.
4,6,7,8-Tetrahydro-2,4-bis(4-methoxyphenyl)-7,7-dimethyl-
5(1H)-quinolinone (3k) [40]. The reaction was carried out
following the general procedure with chalcone 2k (0.54 g,
2 mmol). The yellow solid product 3k thus obtained after 10 min
was filtered and recrystallized from ethanol. The yield was 42%.
mp 204 ꢄC. Rf: 0.23 (toluene/ethyl acetate, 4:1). Anal. Calcd for
C25H27NO3: C, 77.12; H, 6.94; N, 3.60. Found: C, 76.95; H,
6.66; N, 3.55.
4,6,7,8-Tetrahydro-2,4-bis(4-chlorophenyl)-7,7-dimethyl-5
(1H)-quinolinone (3f). The reaction was carried out following
the general procedure with chalcone 2f (0.55 g, 2 mmol). The
white solid product 3f thus obtained after 15 min was filtered
and recrystallized from ethanol. The yield was 69%. mp 250 ꢄC.
Rf: 0.45 (toluene/ethyl acetate, 4:1). IR (KBr, DRS): nmax 3336
(–NH), 3066 (–CH, Ar–H), 2949, 2870 (–CH, –CH3), 1654
(C═O), 1487, 1587 (–C═C–, aromatic ring), 1388 (–C–N),
821 cmꢀ1 1H NMR (CDCl3, 500 MHz): d 1.03 (s, 3H, Me),
.
1.12 (s, 3H, Me), 2.21–2.44 (m, 4H, 4H at C6 and C8), 4.72 (d,
1H, J4, 3 = 5.5 Hz, H-4), 5.23 (dd, 1H, J3, 4 = 5.5 Hz, J3,
NH = 2 Hz, H-3), 5.71 (bs, 1H, NH), 7.22–7.58 (m, 8H, PhH)
(H-4), 5.3 (dd, 1H, J3, 4 = 5.2 Hz, J3, NH = 2 Hz, H-3), 5.84 (bs,
1H, NH), 7.12–7.43 (m, 10H, PhH); 13C NMR (CDCl3,
125 MHz): d 27.40 (Me), 29.35 (Me), 32.41 (C-7), 37.72 (C-8),
42 (C-6), 50.74 (C-4), 107 (C-3), 108.40 (═C–C═O), 147.65
(C-2), 150.70 (═C–NH), 126.03, 127.94, 128.55, 130.07,
131.05, 132.1, 136.50, 139.02 (eight peaks, Ph–C), 195.45
(C═O); ES-MS m/z 398 [M + 1]+ (16.05%), 361 (40.36%), 360
(95.68%), 252 (100%). Anal. Calcd for C23H21NOCl2: C, 69.52;
H, 5.29; N, 3.53. Found: C, 69.22; H, 5.24; N, 3.28.
4,6,7,8-Tetrahydro-2-(4-bromophenyl)-4-(4-methoxyphenyl)-
7,7-dimethyl-5(1H)-quinolinone (3l). The reaction was carried out
following the general procedure with chalcone 2l (0.60 g, 2 mmol).
The pale yellow solid product 3l thus obtained after 20 min was
filtered and recrystallized from ethanol. The yield was 50%. mp
233 ꢄC. Rf: 0.40 (toluene/ethyl acetate, 4:1). IR (KBr, DRS): nmax
3311 (–NH), 3068 (–CH, Ar–H), 2947, 2868 (–CH, –CH3),
1656 (C═O), 1489, 1585 (–C═C–, aromatic ring), 1392 (–C–
1
N), 825 cmꢀ1. H NMR (CDCl3, 500 MHz): d 1.03 (s, 3H, Me),
1.11 (s, 3H, Me), 2.11–2.46 (m, 4H, 4H at C6 and C8), 3.76 (s,
3H, –OMe), 4.85 (d, 1H, J4, 3 = 5 Hz, H-4), 5.20 (dd, 1H, J3,
4 =5.2Hz, J3, NH = 2 Hz, H-3), 5.79 (bs, 1H, NH), 7.32 (dd, 2H,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

P. Majumdar, A. Pati, R. K. Behera, and A. K. Behera
Vol 000
J=6.5Hz, J=2Hz, Ar–H), 7.36 (dd, 2H, J=6.5 Hz, J =2Hz, PhH),
7.47 (dd, 2H, J=6.5Hz, J = 2 Hz, PhH), 8.10 (dd, 2H, J=6.5Hz,
J=2Hz, PhH); 13C NMR (CDCl3, 125MHz): d 27 (Me), 29.29
(Me), 32.43 (C-7), 37.68 (C-8), 42.21 (C-6), 50.70 (C-4), 55
(OMe), 107.02 (C-3), 108.41 (═C–C═O), 119.09, 125.23, 128.95,
130.46, 131.92, 132.09, 134.53 (seven peaks, Ph–C), 147.63 (C-2),
150.71 (═C–NH), 155.03 (Ph–C), 195.95 (C═O). ES-MS m/z 439
[M + 1]+ (16.30%), 407 (25.28%), 327 (61.03%), 252 (100%).
Anal. Calcd for C24H24NO2Br: C, 65.75; H, 5.48; N, 3.20. Found:
C, 65.54; H, 5.26; N, 2.94.
4,6,7,8-Tetrahydro-7,7-dimethyl-4-(4-nitrophenyl)-2-phenyl-
5(1H)-quinolinone (3m) [39,41]. The reaction was carried out
following the general procedure with chalcone 2m (0.51 g,
2 mmol). The golden yellow solid product 3m thus obtained after
40min was filtered and recrystallized from acetic acid. The yield
was 36%. mp 242 ꢄC. Rf: 0.36 (toluene/ethyl acetate, 4:1). Anal.
Calcd for C23H22N2O3: C, 73.80; H, 5.88; N, 7.49. Found: C,
73.57; H, 5.66; N, 7.29.
(19.90%), 373 (56.06%), 252 (100%). Anal. Calcd for
C24H24N2O4: C, 71.29; H, 5.94; N, 6.93. Found: C, 71.06;
H, 5.72; N, 6.68.
4,6,7,8-Tetrahydro-2-(4-bromophenyl)-7,7-dimethyl-4-(4-
nitrophenyl)-5(1H)-quinolinone (3p) [40]. The reaction was
carried out following the general procedure with chalcone 2p
(0.66 g, 2 mmol). The golden yellow solid product 3p thus
obtained after 55 min was filtered and recrystallized from
ethanol. The yield was 42%. mp 272 ꢄC. Rf: 0.33 (toluene/
ethyl acetate, 4:1). Anal. Calcd for C23H21N2O3Br: C, 60.93;
H, 4.64; N, 6.18. Found: C, 60.7; H, 4.41; N, 5.91.
4,6,7,8-Tetrahydro-4-(4-bromophenyl)-7,7-dimethyl-2-
phenyl-5(1H)-quinolinone (3q). The reaction was carried out
following the general procedure with chalcone 2q (0.57 g, 2 mmol).
The pale yellow solid product 3q thus obtained after 25 min
was filtered and recrystallized from ethanol. The yield was
60%. mp 260 ꢄC. Rf: 0.28 (toluene/ethyl acetate, 4:1). IR (KBr,
DRS): 3230 (–NH), 3056 (–CH, Ar–H), 2956, 2861 (–CH, –
CH3), 1662 (C═O), 1496, 1583 (–C═C–, aromatic ring), 1383
4,6,7,8-Tetrahydro-2-(4-chlorophenyl)-7,7-dimethyl-4-(4-
nitrophenyl)-5(1H)-quinolinone (3n). The reaction was carried
out following the general procedure with chalcone 2n (0.57 g,
2 mmol). The golden yellow solid product 3n thus obtained after
25min was filtered and recrystallized from ethanol. The yield was
39%. mp 274 ꢄC. Rf: 0.33 (toluene/ethyl acetate, 4:1). IR (KBr,
DRS): nmax 3356 (–NH), 3068 (–CH, Ar–H), 2953, 2875 (–CH, –
CH3), 1654 (C═O), 1485, 1593 (–C═C–, aromatic ring), 1392 (–
1
(–C–N), 825 cmꢀ1. H NMR (CDCl3, 500 MHz): d 0.99 (s, 3H,
Me), 1.08 (s, 3H, Me), 2.07–2.36 (m, 4H, 4H at C6 and C8),
4.74 (d, 1H, J4, 3 = 6.1 Hz, H-4), 5.35 (dd, 1H, J3, 4 = 6.1 Hz, J3,
NH = 2 Hz, H-3), 5.96 (bs, 1H, NH), 7.10–7.41 (m, 9H, PhH);
13C NMR (CDCl3, 125 MHz): d 28.01 (Me), 29.12 (Me), 34.34
(C-7), 40.99 (C-8), 43.92 (C-6), 53.65 (C-4), 108.15 (C-3),
110.13 (═C–C═O), 119.09, 128.99, 130.02, 131.05, 131.99,
132.44, 136.09, 138.23 (eight peaks, Ph–C), 147.46 (C-2),
153.127 (═C–NH), 196.42 (C═O). ES-MS m/z 409 [M + 1]+
(22.90%), 328 (46.07%), 253 (100%). Anal. Calcd for
C23H22NOBr: C, 67.65; H, 5.39; N, 3.43. Found: C, 67.4; H,
5.19; N, 3.17.
1
C–N), 1336 (–NO2), 831 cmꢀ1. H NMR (CDCl3, 500 MHz): d
1.03 (s, 3H, Me), 1.14 (s, 3H, Me), 2.20 (d, 1H, J8e, 8a = 16.5Hz),
2.29 (d, 1H, J8a, 8e = 16.5 Hz), 2.33 (d, 1H, J6e, 6a = 16.4Hz), 2.46
(d, 1H, J6a, 6e = 16.5Hz) (4H at C-6 and C8), 4.88 (d, 1H, J4,
3 = 5 Hz, H-4), 5.21 (dd, 1H, J3, 4 = 5 Hz, J3, NH = 2 Hz, H-3), 5.75
(bs, 1H, NH), 7.36–8.15 (m, 8H, PhH); 13C NMR (CDCl3,
125 MHz): d 27.03 (Me), 28.99 (Me), 32.42 (C-7), 37.62 (C-8),
42.16 (C-6), 50.71 (C-4), 107 (C-3), 108.40 (═C–C═O), 122,
127.49, 128.65, 131.21, 132.57, 134.08 (six peaks, Ph–C), 145
(Ph–C), 146.35 (Ph–C), 147.61 (C-2), 150.99 (═C–NH), 195.06
(C═O). ES-MS m/z 407 (5.55%), 406 (19.75%), 405 (41.36%),
404 (100%), 403 (48.15%), 189 (55.56%). Anal. Calcd for
C23H21N2O3Cl: C, 67.65; H, 5.15; N, 6.86. Found: C, 67.34; H,
4.90; N, 6.67.
4,6,7,8-Tetrahydro-4-(4-bromophenyl)-2-(4-chlorophenyl)-
7,7-dimethyl-5(1H)-quinolinone (3r). The reaction was carried
out following the general procedure with chalcone 2r (0.64 g,
2 mmol). The white solid product 3r thus obtained after 15 min
was filtered and recrystallized from ethanol. The yield was 67%.
mp 250 ꢄC. Rf: 0.48 (toluene/ethyl acetate, 4:1). IR (KBr, DRS):
nmax 3339 (–NH), 3082, 3031 (–CH, Ar–H), 2949, 2873 (–CH,
–CH3), 1652 (C═O), 1485, 1587 (–C═C–, aromatic ring), 1391
1
(–C–N), 824 cmꢀ1. H NMR (CDCl3, 400 MHz): d 1.03 (s, 3H,
4,6,7,8-Tetrahydro-2-(4-methoxyphenyl)-7,7-dimethyl-4-
(4-nitrophenyl)-5(1H)-quinolinone (3o). The reaction was
carried out following the general procedure with chalcone 2o
(0.56 g, 2 mmol). The golden yellow solid product 3o thus
obtained after 45 min was filtered and recrystallized from
ethanol. The yield was 40%. mp 218 ꢄC. Rf: 0.28 (toluene/
ethyl acetate, 4:1). IR (KBr, DRS): nmax 3360, 3288 (–NH),
3074 (–CH, Ar–H), 2954, 2837 (–CH, –CH3), 1658 (C═O),
1490, 1593 (–C═C–, aromatic ring), 1388 (–C–N), 1338
Me), 1.12 (s, 3H, Me), 2.10 (d, 1H, J8e, 8a = 16.2 Hz), 2.21 (d,
1H, J8a, 8e = 16.2 Hz), 2.26 (d, 1H, J6e, 6a = 16.2 Hz), 2.38 (d,
1H, J6a, 6e = 16.2 Hz) (4H at C-6 and C-8), 4.76 (d, 1H, J4,
3 = 5.2 Hz, H-4), 5.25 (dd, 1H, J3, 4 = 5.2 Hz, J3, NH = 2 Hz, H-3),
5.78 (bs, 1H, NH), 7.09–7.41 (m, 8H, PhH); 13C NMR (CDCl3,
100 MHz): d 27.99 (Me), 30.04 (Me), 32 (C-7), 37.99 (C-8),
43.55 (C-6), 51.33 (C-4), 107.98 (C-3), 109.56 (═C–C═O),
120.22, 126.21, 127.92, 128.95, 131.22, 132.10, 135.24, 136.97
(eight peaks, Ph–C), 147.56 (C-2), 152.22 (═C–NH), 196.77
(C═O). ES-MS m/z 443 [M + 1]+ (21.34%), 362 (34.56%), 327
(56.89%), 252 (100%). Anal. Calcd for C23H21NOClBr: C,
62.44; H, 4.75; N, 3.17. Found: C, 62.21; H, 4.52; N, 2.95.
4,6,7,8-Tetrahydro-4-(4-bromophenyl)-2-(4-methoxyphenyl)-
7,7-dimethyl-5(1H)-quinolinone (3s). The reaction was carried out
following the general procedure with chalcone 2s (0.60 g,
2 mmol). The pale yellow solid product 3s thus obtained after
20 min was filtered and recrystallized from ethanol. The yield
was 52%. mp 223 ꢄC. Rf: 0.41 (toluene/ethyl acetate, 4:1). IR
(KBr, DRS): nmax 3299 (–NH), 3065 (–CH, Ar–H), 2943, 2868
(–CH, –CH3), 1654 (C═O), 1491, 1585 (–C═C–, aromatic
(–NO2), 1186, 1033 (–C–O–C–), 829 cmꢀ1
.
1H NMR
(CDCl3, 400 MHz): d 1.02 (s, 3H, Me), 1.10 (s, 3H, Me),
2.11–2.46 (m, 4H, 4H at C6 and C8), 3.82 (s, 3H, –OMe),
4.87 (d, 1H, J4, 3 = 5 Hz, H-4), 5.20 (dd, 1H, J3, 4 = 5 Hz, J3,
NH = 2 Hz, H-3), 5.80 (bs, 1H, NH), 7.30 (dd, 2H, J = 6.5 Hz,
J = 2 Hz, PhH), 7.36 (dd, 2H, J = 6.5 Hz, J = 2 Hz, PhH), 7.50
(dd, 2H, J = 6.5 Hz, J = 2 Hz, PhH), 8.13 (dd, 2H, J = 6.5 Hz,
J = 2 Hz, PhH); 13C NMR (CDCl3, 100 MHz): d 26.97 (Me),
28.56 (Me), 32.32 (C-7), 37.44 (C-8), 42.10 (C-6), 50.23
(C-4), 55 (OMe), 107 (C-3), 108.42 (═C–C═O), 120.01,
122, 127.53, 128.79, 130.99 (five peaks, Ph–C), 145.01
(Ph–C), 146.56 (Ph–C), 147.56 (C-2), 152.56 (═C–NH),
155.32 (Ph–C), 195.27 (C═O). ES-MS m/z 405 [M + 1]+
ring), 1180, 1031 (–C–O–C–), 1390 (–C–N), 825 cmꢀ1
.
1H
NMR (CDCl3, 400 MHz): d 0.96 (s, 3H, Me), 1.08 (s, 3H, Me),
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
Para Substituted Benzaldehydes as Expedient Reagents for the
Oxidative Aromatization of Hydroquinoline
2.9–2.10 (m, 4H, 4H at C6 and C8), 3.70 (s, 3H, –OMe), 4.82 (d,
1H, J4, 3 = 5.2 Hz, H-4), 5.26 (dd, 1H, J3, 4 = 5.2 Hz, J3, NH = 2 Hz,
H-3), 5.81 (bs, 1H, NH), 7.09–7.40 (m, 8H, PhH); 13C NMR
(CDCl3, 100 MHz): d 27.56 (Me), 29 (Me), 31.99 (C-7), 38.13
(C-8), 42.98 (C-6), 52.08 (C-4), 55.02 (OMe), 107.99 (C-3),
110.15 (═C–C═O), 119.21, 126.12, 128.95, 130.43, 131.90,
132.18, 134.55 (seven peaks, Ph–C), 147.56 (C-2), 151.25
(═C–NH), 155.15 (Ph–C), 196.05 (C═O). ES-MS m/z 439
[M + 1]+ (20.08%), 358 (45.23%), 328 (60.09%), 252 (100%).
Anal. Calcd for C24H24NO2Br: C, 65.75; H, 5.48; N, 3.20.
Found: C, 65.52; H, 5.26; N, 2.95.
4,6,7,8-Tetrahydro-2,4-bis(4-bromophenyl)-7,7-dimethyl-5
(1H)-quinolinone (3t) [40]. The reaction was carried for out
following the general procedure with chalcone 2t (0.73 g,
2 mmol). The pale yellow solid product 3t thus obtained after
10 min was filtered and recrystallized from ethanol. The yield
was 59%. Anal. Calcd for C23H21NOBr2: C, 56.67; H, 4.31; N,
2.87. Found: C, 56.46; H, 4.08; N, 2.62.
2H, H-8), 3.74 (s, 3H, –OMe), 7.20–7.44 (m, 9H, PhH), 7.52
(s, 1H, H-3); 13C NMR (CDCl3, 100 MHz): d 28.56 (Me),
32.72 (C-7), 47.81 (C-8), 53.83 (C-6), 55.14 (OMe), 119.05
(Ph–C), 121.90 (C-3), 123.57 (═C–C═O), 127.27, 128.03, 128.11,
129.12, 131.16, 137.15 (six peaks, Ph–C), 157.56 (═C–N═),
158.43 (Ph–C), 163.52 (C═N), 198.80 (C═O). ES-MS m/z 358
[M + 1]+ (59.16%), 326 (43.09%), 250 (63.90%), 205 (100%).
Anal. Calcd for C24H23NO2: C, 80.67; H, 6.44; N, 3.92. Found: C,
80.44; H, 6.19; N, 3.69.
7,8-Dihydro-2-(4-bromophenyl)-7,7-dimethyl-4-phenyl-5
(6H)-quinolinone (5d). The reaction was carried out following the
general procedure with tetrahydro-5(1H)-quinolinone 3d (0.41 g,
1 mmol). We obtained the pale yellow solid product 5d after
purification by silica chromatography using toluene as eluent. mp
170 ꢄC. Rf: 0.43. IR (KBr, DRS): nmax 3064, 2976 (–CH, Ar–H),
2865 (–CH, –CH3 and –CH2), 1692 (C═O), 1571 (–C═N), 1531,
1492 (–C═C–, aromatic ring), 835 cmꢀ1 1H NMR (CDCl3,
.
400 MHz): d 1.64 (s, 6H, 2ꢁ Me), 2.59 (s, 2H, H-6), 3.26 (s,
General procedure for 7,7-dimethyl-2,4-diaryl-7,8-
2H, H-8), 7.27–7.54 (m, 9H, PhH), 7.56 (s, 1H, H-3); 13C
dihydroquinolin-5(6H)-one (5). To
a
solution of 2,4-
NMR (CDCl3, 100 MHz): d 28.85 (Me), 32.76 (C-7),
disubstituted hydroquinolin-5(1H,4H,6H)-one (2 mmol) 3 in
acetic acid (3 mL), anhydrous sodium acetate (2 mmol) and
benzaldehyde (2 mmol) were added and refluxed on hot plate at
140 ꢄC for appropriate time. The reaction mixture was allowed
to cool at room temperature. The suspension was poured
into ice-cold water and neutralized with sodium bicarbonate. We
purified the gummy solid thus obtained by silica chromatography
using toluene as eluent to give 5.
7,8-Dihydro-7,7-dimethyl-2,4-diphenyl-5(6H)-quinolinone
(5a) [42]. The reaction was carried out following the general
procedure with tetrahydro-5(1H)-quinolinone 3a (0.33 g,
1 mmol). We obtained the pale yellow solid product 5a after
purification by silica chromatography using toluene as eluent.
mp 118 ꢄC. Rf: 0.49. Anal. Calcd for C23H21NO: C, 84.40; H,
6.42; N, 4.28. Found: C, 84.17; H, 6.17; N, 4.07.
7,8-Dihydro-2-(4-chlorophenyl)-7,7-dimethyl-4-phenyl-5
(6H)-quinolinone (5b). The reaction was carried out following the
general procedure with tetrahydro-5(1H)-quinolinone 3b (0.36 g,
1 mmol). We obtained the pale yellow solid product 5b after
purification by silica chromatography using toluene as eluent. mp
154 ꢄC. Rf: 0.42. IR (KBr, DRS): nmax 3057, 2988 (Ar–H), 2872
(–CH, –CH3 and –CH2), 1697 (C═O), 1583 (–C═N), 1531, 1490
(–C═C–, aromatic ring), 837 cmꢀ1. 1H NMR (CDCl3, 400 MHz):
d 1.65 (s, 6H, 2ꢁ Me), 2.49 (s, 2H, H-6), 3.20 (s, 2H, H-8), 7.30–
7.50 (m, 9H, PhH), 7.57 (s, 1H, H-3); 13C NMR (CDCl3,
100 MHz): d 28.90 (Me), 32.70 (C-7), 47.80 (C-8), 53.83
(C-6), 121.89 (C-3), 123.85 (═C–C═O), 127.23, 127.79,
128.11, 128.87, 130.15, 131.16, 136.10, 140.45 (eight peaks,
Ph–C), 153.22 (C-4), 159.45 (═C–N═), 163.67 (C═N),
198.85 (C═O). ES-MS m/z 362 [M + 1]+ (54.07%), 326 (45.09%),
206 (100%). Anal. Calcd for C23H20NOCl: C, 76.45; H, 5.54; N,
3.88. Found: C, 76.20; H, 5.31; N, 3.64.
47.85 (C-8), 52.99 (C-6), 121.89 (C-3), 122 (Ph–C), 123.87
(═C–C═O), 127.25, 128.11, 128.87, 129.02, 131.16, 134.13,
138.32 (seven peaks, Ph–C), 152.13 (C-4), 159.48 (═C–N═),
163.60 (C═N), 198.79 (C═O). ES-MS m/z 407 [M+ 1]+
(58.09%), 206 (100%). Anal. Calcd for C23H20NOBr: C, 67.98;
H, 4.93; N, 3.45. Found: C, 67.76; H, 4.68; N, 3.21.
7,8-Dihydro-4-(4-chlorophenyl)-7,7-dimethyl-2-phenyl-5
(6H)-quinolinone (5e) [41]. The reaction was carried out following
the general procedure with tetrahydro-5(1H)-quinolinone 3e (0.36 g,
1 mmol). We obtained the pale yellow solid product 5e after
purification by silica chromatography using toluene as eluent. mp
156 ꢄC. Rf: 0.40. Anal. Calcd for C23H20NOCl: C, 76.45; H,
5.54; N, 3.88. Found: C, 76.22; H, 5.29; N, 3.63.
7,8-Dihydro-2,4-bis(4-chlorophenyl)-7,7-dimethyl-5(6H)-
quinolinone (5f). The reaction was carried out following the
general procedure with tetrahydro-5(1H)-quinolinone 3f
(0.40 g, 1 mmol). We obtained the pale yellow solid product 5f
after purification by silica chromatography using toluene as
eluent. mp 140 ꢄC. Rf: 0.42. IR (KBr, DRS): nmax 3064, 2956
(–CH, Ar–H), 2870 (–CH, –CH3 and –CH2), 1683 (C═O),
1581 (–C═N), 1531, 1489 (–C═C–, aromatic ring), 834 cmꢀ1. 1H
NMR (CDCl3, 400 MHz): d 1.62 (s, 6H, 2ꢁ Me), 2.58 (s, 2H,
H-6), 3.19 (s, 2H, H-8), 7.34–7.51 (m, 8H, PhH), 7.65 (s, 1H,
H-3); 13C NMR (CDCl3, 100 MHz): d 28.92 (Me), 32.71 (C-7),
47.81 (C-8), 53.69 (C-6), 121.21 (Ph–C), 121.65 (C-3), 123.78
(═C–C═O), 128.54, 128.99, 129.21, 130.23, 132.12,
135.32, 136.10 (seven peaks, Ph–C), 153.43 (C-4), 159.41
(═C–N═), 163.90 (C═N), 198.89 (C═O). ES-MS m/z 396
[M + 1]+ (30.6%), 325 (45.09%), 205 (100%). Anal. Calcd
for C23H19NOCl2: C, 69.87; H, 4.81; N, 3.54. Found: C,
69.64; H, 4.56; N, 3.33.
7,8-Dihydro-4-(4-chlorophenyl)-2-(4-methoxyphenyl)-7,7-
dimethyl-5(6H)-quinolinone (5g). The reaction was carried out
following the general procedure with tetrahydro-5(1H)-
quinolinone 3g (0.38g, 1 mmol). We obtained the pale yellow
solid product 5g after purification by silica chromatography using
toluene as eluent. mp 145ꢄC. Rf: 0.48. IR (KBr, DRS): nmax 3061,
2954 (–CH, Ar–H), 2868 (–CH, –CH3, and –CH2), 1685 (C═O),
1581 (–C═N), 1529, 1490 (–C═C–, aromatic ring), 1174, 1024
7,8-Dihydro-2-(4-methoxyphenyl)-7,7-dimethyl-4-phenyl-5
(6H)-quinolinone (5c). The reaction was carried out following
the general procedure with tetrahydro-5(1H)-quinolinone 3c
(0.36 g, 1 mmol). We obtained the pale yellow solid product 5c
after purification by silica chromatography using toluene
as eluent. mp 165 ꢄC. Rf: 0.49. IR (KBr, DRS): nmax 3059, 2951
(–CH, Ar–H), 2864 (–CH, –CH3 and –CH2), 1681 (C═O),
1602, 1573 (–C═N), 1529, 1492 (–C═C–, aromatic ring),
(–C–O–C–), 831cmꢀ1 1H NMR (CDCl3, 400 MHz): d 1.55
.
1147, 1022 (–C–O–C–), 842 cmꢀ1
.
1H NMR (CDCl3,
(s, 6H, 2ꢁ Me), 2.47 (s, 2H, H-6), 3.18 (s, 2H, H-8), 3.82 (s, 3H,
400 MHz): d 1.60 (s, 6H, 2ꢁ Me), 2.48 (s, 2H, H-6), 3.17 (s,
–OMe), 7.30–7.5 (m, 8H, PhH), 7.58 (s, 1H, H-3); 13C NMR
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

P. Majumdar, A. Pati, R. K. Behera, and A. K. Behera
Vol 000
(CDCl3, 100MHz): d 28.92 (Me), 32.56 (C-7), 47.82 (C-8), 51.99
(C-6), 55.6 (OMe), 119 (Ph–C), 122.01 (C-3), 123.53 (═C–C═O),
128.23, 128.69, 129.53, 129.67, 133.14, 136.27 (six peaks, Ph–C),
153.22 (C-4), 155.32 (Ph–C), 159.40 (═C–N═), 163.68 (C═N),
198.89 (C═O). ES-MS m/z 392 [M + 1]+ (53.05%), 206 (100%).
Anal. Calcd for C24H22NO2Cl: C, 73.66; H, 5.63; N, 3.58. Found:
C, 73.43; H, 5.38; N, 3.33.
7,8-Dihydro-2,4-bis(4-methoxyphenyl)-7,7-dimethyl-5(6H)-
quinolinone (5k). The reaction was carried out following the
general procedure with tetrahydro-5(1H)-quinolinone 3k (0.39 g,
1 mmol). We obtained the pale yellow solid product 5k after
purification by silica chromatography using toluene as eluent.
mp 206 ꢄC. Rf: 0.49. IR (KBr, DRS): nmax 3083, 2960 (–CH,
Ar–H), 2968 (–CH, –CH3, and –CH2), 1685 (C═O), 1604,
1577 (–C═N), 1531, 1490 (–C═C–, aromatic ring), 1186, 1022
7,8-Dihydro-2-(4-bromophenyl)-4-(4-chlorophenyl)-7,7-
dimethyl-5(6H)-quinolinone (5h). The reaction was carried
out following the general procedure with tetrahydro-5(1H)-
quinolinone 3h (0.44 g, 1 mmol). We obtained the pale yellow
solid product 5h after purification by silica chromatography using
toluene as eluent. mp 215 ꢄC. Rf: 0.38. IR (KBr, DRS): nmax
3068, 2954 (–CH str, Ar–H), 2868 (–CH, –CH3, and –CH2),
1683 (C═O), 1589 (–C═N), 1533, 1487 (–C═C–, aromatic
1
(–C–O–C–), 833 cmꢀ1. H NMR (CDCl3, 400 MHz): d 1.56 (s,
6H, 2ꢁ Me), 2.50 (s, 2H, H-6), 3.19 (s, 2H, H-8), 3.80 (s, 6H,
–OMe), 7.19–7.46 (m, 9H, PhH); 13C NMR (CDCl3, 100 MHz):
d 28.87 (Me), 32.77 (C-7), 47.81 (C-8), 53.87 (C-6), 55.65
(OMe), 119.06 (Ph–C), 120.90 (Ph–C), 122 (C-3), 123.94 (═C–
C═O), 128.37, 128.78, 129.10, 131.22 (four peaks, Ph–C),
153.27 (C-4), 159.40 (═C–N═), 159.99 (Ph–C), 161.02 (Ph–
C), 163.59 (C═N), 199 (C═O). ES-MS m/z 388 [M + 1]+
(41.77%), 326 (56.65%), 205 (100%). Anal. Calcd for
C25H25NO3: C, 77.52; H, 6.46; N, 3.62. Found: C, 77.29; H,
6.24; N, 3.40.
ring), 826 cmꢀ1 1H NMR (CDCl3, 400 MHz): d 1.48 (s, 6H,
.
2ꢁ Me), 2.48 (s, 2H, H-6), 3.18 (s, 2H, H-8), 7.28–7.55 (m,
9H, PhH, and H-3); 13C NMR (CDCl3, 100 MHz): d 29.04
(Me), 32.55 (C-7), 47.65 (C-8), 53.76 (C-6), 121.02 (Ph–C),
21.71 (C-3), 123.65 (═C–C═O), 128.11, 129.81, 130.15,
132.21, 133.09, 135.32, 136.19 (seven peaks, Ph–C), 153.54
(C-4), 159.54 (═C–N═), 163.78 (C═N), 199 (C═O). ES-MS
m/z 441 [M + 1]+ (54.86%), 326 (25.76%), 205 (100%). Anal.
Calcd for C23H19NOClBr: C, 62.73; H, 4.32; N, 3.18. Found:
C, 62.50; H, 4.07; N, 2.96.
7,8-Dihydro-2-(4-bromophenyl)-4-(4-methoxyphenyl)-7,7-
dimethyl-5(6H)-quinolinone (5l). The reaction was carried
out following the general procedure with tetrahydro-5(1H)-
quinolinone 3l (0.44 g, 1 mmol). We obtained the pale yellow
solid product 5l after purification by silica chromatography using
toluene as eluent. mp 154 ꢄC. Rf: 0.51. IR (KBr, DRS):
nmax 3077 (–CH, Ar–H), 2870 (–CH, –CH3, and –CH2),
1690 (C═O), 1573 (–C═N), 1529, 1492 (–C═C–, aromatic
7,8-Dihydro-4-(4-methoxyphenyl)-7,7-dimethyl-2-phenyl-5
(6H)-quinolinone (5i). The reaction was carried out following
the general procedure with tetrahydro-5(1H)-quinolinone 3i
(0.36 g, 1 mmol). We obtained the pale yellow solid product 5i
after purification by silica chromatography using toluene as
eluent. mp 148 ꢄC. Rf: 0.49. IR (KBr, DRS): nmax 3070, 2954 (–
CH, Ar–H), 2868 (–CH, –CH3, and –CH2), 1691 (C═O), 1606,
1577 (–C═N), 1529, 1512 (–C═C–, aromatic ring), 1111, 1029
ring), 1175, 1019 (–C–O–C–), 823 cmꢀ1 1H NMR (CDCl3,
.
400 MHz): d 1.63 (s, 6H, 2ꢁ Me), 2.50 (s, 2H, H-6), 3.20
(s, 2H, H-8), 3.77 (s, 3H, –OMe), 7.24–7.46 (m, 8H, PhH),
7.53 (s, 1H, H-3); 13C NMR (CDCl3, 100 MHz): d 29.07
(Me), 32.88 (C-7), 48 (C-8), 53.89 (C-6), 55.09 (OMe),
120.04 (Ph–C), 121.78 (C-3), 123.86 (═C–C═O), 127.80,
128.09, 129.65, 130.15, 131.98, 135 (six peaks, Ph–C), 154
(C-4), 159.96 (═C–N═), 161.03 (Ph–C), 163.67 (C═N),
199.02 (C═O). ES-MS m/z 437 [M + 1]+ (43.09%), 206
(100%). Anal. Calcd for C24H22NO2Br: C, 66.06; H, 5.05;
N, 3.21. Found: C, 65.84; H, 4.86; N, 2.99.
7,8-Dihydro-7,7-dimethyl-4-(4-nitrophenyl)-2-phenyl-5(6H)-
quinolinone (5m). The reaction was carried out following the
general procedure with hydroquinolin-5(1H,4H,6H)-one 3m
(0.37 g, 1 mmol). The same starting compound 3m was obtained
instead of oxidized product 5m.
1
(–C–O–C–), 825 cmꢀ1. H NMR (CDCl3, 400 MHz): d 1.52 (s,
6H, 2ꢁ Me), 2.49 (s, 2H, H-6), 3.15 (s, 2H, H-8), 3.76 (s, 3H,
–OMe), 7.11–7.43 (m, 10H, PhH); 13C NMR (CDCl3,
100 MHz): d 28.95 (Me), 32.54 (C-7), 47.81 (C-8), 52.69 (C-6),
55.23 (OMe), 118 (Ph–C), 122.01 (C-3), 124.03 (═C–C═O),
127.41, 127.87, 128.21, 128.87, 131.32, 135.15 (six peaks, Ph–
C), 154 (C-4), 159.32 (═C–N═), 160.45 (Ph–C), 163.88
(C═N), 198.96 (C═O). ES-MS m/z 358 [M + 1]+ (56.87%), 206
(100%). Anal. Calcd for C24H23NO2: C, 80.67; H, 6.44; N,
3.92. Found: C, 80.47; H, 6.25; N, 3.69.
7,8-Dihydro-2-(4-chlorophenyl)-4-(4-methoxyphenyl)-7,7-
dimethyl-5(6H)-quinolinone (5j). The reaction was carried
out following the general procedure tetrahydro-5(1H)-quinolinone
3j (0.39 g, 1 mmol). We obtained the pale yellow solid
product 5j after purification by silica chromatography using
toluene as eluent. mp 136 ꢄC. Rf: 0.51. IR (KBr, DRS): nmax
3037 (–CH, Ar–H), 2870 (–CH, –CH3, and –CH2), 1683
(C═O), 1610, 1579 (–C═N), 1529, 1490 (–C═C–, aromatic
7,8-Dihydro-2-(4-chlorophenyl)-7,7-dimethyl-4-(4-nitro
phenyl)-5(6H)-quinolinone (5n). The reaction was carried out
following the general procedure with tetrahydro-5(1H)-
quinolinone 3n (0.40 g, 1 mmol). The same starting compound 3n
was obtained instead of oxidized product 5n.
7,8-Dihydro-2-(4-methoxyphenyl)-7,7-dimethyl-4-(4-nitro
phenyl)-5(6H)-quinolinone (5o). The reaction was carried out
following the general procedure with tetrahydro-5(1H)-
quinolinone 3o (0.39 g, 1 mmol). The same starting compound
3o was obtained instead of oxidized product 5o.
7,8-Dihydro-2-(4-bromophenyl)-7,7-dimethyl-4-(4-nitro
phenyl)-5(6H)-quinolinone (5p). The reaction was carried
out following the general procedure with tetrahydro-5(1H)-
quinolinone 3p (0.44 g, 1 mmol). The same starting
compound 3p was obtained instead of oxidized product 5p.
7,8-Dihydro-4-(4-bromophenyl)-7,7-dimethyl-2-phenyl-5
(6H)-quinolinone (5q). The reaction was carried out following
the general procedure with tetrahydro-5(1H)-quinolinone 3q
(0.45 g, 1 mmol). We obtained the pale yellow solid product
ring), 1124, 1035 (–C–O–C–), 819 cmꢀ1 1H NMR (CDCl3,
.
400 MHz): d 1.69 (s, 6H, 2ꢁ Me), 2.84 (s, 2H, H-6), 3.26 (s,
2H, H-8), 3.85 (s, 3H, –OMe), 7.31–7.51 (m, 9H, PhH); 13C
NMR (CDCl3, 100 MHz): d 29 (Me), 32.65 (C-7), 48.03 (C-
8), 53.89 (C-6), 55.6 (OMe), 119.05 (Ph–C), 121.98 (C-3),
123.76 (═C–C═O), 127.80, 128.23, 128.88, 130.15, 130.22,
134.15 (six peaks, Ph–C), 153.237 (C-4), 159.66 (═C–N═),
161.04 (Ph–C), 163.80 (C═N), 198.90 (C═O). ES-MS m/
z 392 [M + 1]+ (40.09%), 325 (41.08%), 205 (100%). Anal.
Calcd for C24H22NO2Cl: C, 73.66; H, 5.63; N, 3.58. Found:
C, 73.4; H, 5.42; N, 3.37.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
Para Substituted Benzaldehydes as Expedient Reagents for the
Oxidative Aromatization of Hydroquinoline
5q after purification by silica chromatography using toluene as
eluent. mp 155 ꢄC. Rf: 0.44. IR (KBr, DRS): nmax 3066, 2961
(–CH, Ar–H), 2870 (–CH, –CH3, and –CH2), 1684 (C═O),
peaks, Ph–C), 153.52 (C-4), 159.65 (═C–N═), 164.06 (C═N),
198.98 (C═O). ES-MS m/z 486 [M + 1]+ (59.08%), 325
(44.67%), 206 (100%). Anal. Calcd for C23H19NOBr2: C,
56.91; H, 3.92; N, 2.89. Found: C, 56.69; H, 3.71; N, 2.64.
2,3,5,8-Tetrahydro-1,3,5,7-tetraphenyl-2-thioxopyrido[2,3-
1573 (–C═N), 1521, 1489 (–C═C–, aromatic ring), 833 cmꢀ1
.
1H NMR (CDCl3, 400 MHz): d 1.55 (s, 6H, 2ꢁ Me), 2.43 (s,
2H, H-6), 3.20 (s, 2H, H-8), 7.15–7.46 (m, 9H, PhH), 7.50 (s,
1H, H-3); 13C NMR (CDCl3, 100 MHz): d 28.91 (Me), 32.67
(C-7), 47.82 (C-8), 53.85 (C-6), 121.91 (C-3), 123.76 (═C–
C═O), 127.20, 127.81, 128.21, 129.54, 130.06, 132.04,
135.43, 136.78 (eight peaks, Ph–C), 153.30 (C-4), 159.56
(═C–N═), 163.70 (C═N), 199 (C═O). ES-MS m/z 407
[M + 1]+ (52.33%), 206 (100%). Anal. Calcd for C23H20NOBr:
C, 67.98; H, 4.93; N, 3.45. Found: C, 67.77; H, 4.71; N, 3.22.
7,8-Dihydro-4-(4-bromophenyl)-2-(4-chlorophenyl)-7,7-
dimethyl-5(6H)-quinolinone (5r). The reaction was carried out
following the general procedure with tetrahydro-5(1H)-
quinolinone 3r (0.44 g, 1 mmol). We obtained the pale yellow
solid product 5r after purification by silica chromatography
using toluene as eluent. mp 193 ꢄC. Rf: 0.41. IR (KBr, DRS):
nmax 3069 (–CH, Ar–H), 2873 (–CH, –CH3, and –CH2), 1683
(C═O), 1574 (–C═N), 1511, 1490 (–C═C–, aromatic ring),
d]pyrimidin-4(1H)-one (11). To
a
solution of 1, 3-
diphenylthiobarbituric acid (0.60 g, 2 mmol) 10 and chalcone
(0.42 g, 2 mmol) 2a in ethanol (20 mL), ammonium acetate
(3.08 g) and two drops of acetic acid was added. The reaction
mixture was stirred under reflux for 4 h. The reaction mixture
was cooled and poured into ice-cold water. The pale yellow
solid 11 thus obtained was filtered, washed, dried, and
recrystallized from ethanol. The yield was 65%. mp 175 ꢄC. Rf:
0.33. IR (KBr, DRS): nmax 3147 (N-H), 1662 (C═O), 1593,
1568 (–C═C–, aromatic ring), 1298 (C═S) cmꢀ1 1H NMR
.
(DMSO-d6, 400 MHz) d 3.78 (dd, 1H, J6a, 6b = 16.4 Hz, J6a,
5 = 7.6 Hz, H-6), 3.89 (dd, 1H, J6b, 6a = 16.4 Hz, J6b, 5 = 7.6 Hz,
H-6), 4.74 (t, 1H, J = 7.6 Hz, H-5), 6.94–8.35 (m, 20H, PhH);
13C NMR (DMSO-d6, 100 MHz): d 49 (C-5), 84 (═C–C═O),
100.01 (C-6), 121 (Ph–C), 123.10 (Ph–C), 124.21 (Ph–C),
125.6 (Ph–C), 126.09 (Ph–C), 127.21 (Ph–C), 128.62–129.02
(closely spaced six peaks), 131.99 (Ph–C), 134.03 (Ph–C),
134.65 (Ph–C), 142.43 (Ph–C), 146.23 (C-7), 152 (═C–NH),
171 (C═O), 193 (C═S). ES-MS m/z 486 [M + 1]+ (59.08%).
Anal. Calcd for C31H23N3OS: C, 76.70; H, 4.74; N, 8.66.
Found: C, 76.33; H, 4.56; N, 8.34.
2,3-Dihydro-1,3,5,7-tetraphenyl-2-thioxopyrido[2,3-d]
pyrimidin-4(1H)-one (12). To a solution of 2-thioxopyrido[2,3-d]
pyrimidin-4(1H)-one (0.98g, 2 mmol) 11 in acetic acid (2mL),
anhydrous sodium acetate (2mmol) and arylaldehyde (2mmol)
were added and refluxed on hot plate at 140 ꢄC for 5 h. The
reaction mixture was cooled and poured into ice-cold water. The
solid thus obtained was filtered, washed, and dried. We obtained
The pale yellow solid product 12 after purification by silica
chromatography using toluene as eluent. The yield was 57%. mp
213 ꢄC. Rf: 0.38. IR (KBr, DRS): nmax 3059, 3028 (–CH, Ar–H),
1689 (C═O), 1597 (–C═N), 1543, 1490 (–C═C–, aromatic ring).
1H NMR (500 MHz, CDCl3): (d) 7.06–7.91 (m, 20H, PhH), 8.03
(s, 1H, H-3); 13C NMR (CDCl3, 125 MHz): d 105 (═C–C═O),
110.21 (C-6), 122.02 (Ph–C), 123.22 (Ph–C), 124.4 (Ph–C),
125.71 (Ph–C), 126.67 (Ph–C), 127.18 (Ph–C), 128.64–129.02
(closely spaced six peaks), 131.94 (Ph–C), 134 (Ph–C), 134.54
(Ph–C), 142.03 (Ph–C), 149.13 (C-7), 152.10 (C-5), 164.23
(═C–NH), 172.12 (C═O), 193.13 (C═S). ES-MS m/z 484
[M + 1]+ (56.98%). Anal. Calcd for C31H21N3OS: C, 77.02; H,
4.35; N, 8.70. Found: C, 76.78; H, 4.10; N, 8.47.
1
830 cmꢀ1. H NMR (CDCl3, 400 MHz): d 1.59 (s, 6H, 2ꢁ Me),
2.50 (s, 2H, H-6), 3.18 (s, 2H, H-8), 7.22–7.50 (m, 9H, PhH, and
H-3); 13C NMR (CDCl3, 100 MHz): d 28.99 (Me), 32.75 (C-7),
47.81 (C-8), 53.83 (C-6), 121.91 (C-3), 123.86 (═C–C═O),
124.01, 128.21, 129.20, 129.65, 130.15, 131.96, 134.14, 137
(eight peaks, Ph–C), 153.31 (C-4), 159.64 (═C–N═), 164
(C═N), 198.96 (C═O). ES-MS m/z 441 [M + 1]+ (55.01%),
325 (45.09%), 205 (100%). Anal. Calcd for C23H19NOClBr: C,
62.73; H, 4.32; N, 3.18. Found: C, 62.50; H, 4.07; N, 2.95.
7,8-Dihydro-4-(4-bromophenyl)-2-(4-methoxyphenyl)-7,7-
dimethyl-5(6H)-quinolinone (5s). The reaction was carried out
following the general procedure with tetrahydro-5(1H)-
quinolinone 3s (0.44 g, 1 mmol). We obtained the pale yellow
solid product 3s after purification by silica chromatography
using toluene as eluent. mp 139 ꢄC. Rf: 0.48. IR (KBr, DRS):
nmax 3059, 2962 (–CH, Ar–H), 2870 (–CH, –CH3, and –CH2),
1685 (C═O), 1571 (–C═N), 1511, 1485 (–C═C–, aromatic
ring), 1156, 1024 (–C–O–C–), 839 cmꢀ1 1H NMR (CDCl3,
.
400 MHz): d 1.61 (s, 6H, 2ꢁ Me), 2.57 (s, 2H, H-6), 3.22 (s,
2H, H-8), 3.82 (s, 3H, –OMe), 7.19–7.50 (m, 8H, PhH), 7.54
(s, 1H, H-3); 13C NMR (CDCl3, 100 MHz): d 29.05 (Me),
32.95 (C-7), 48 (C-8), 53.89 (C-6), 55.21 (OMe), 120 (Ph–C),
122.01 (C-3), 123.99 (═C–C═O), 124.29 (Ph–C), 128.10,
128.88, 129.25, 130.15, 131.99, 136.22 (six peaks, Ph–C),
153.24 (C-4), 158.23 (Ph–C), 160.12 (═C–N═), 163.65
(C═N), 199.06 (C═O). ES-MS m/z 437 [M + 1]+ (55.87%), 205
(100%). Anal. Calcd for C24H22NO2Br: C, 66.06; H, 5.05; N,
3.21. Found: C, 65.81; H, 4.83; N, 2.98.
Acknowledgments. This work was supported by University
Grant Commission (UGC), New Delhi. P.M. is grateful to
University Grant Commission (UGC), New Delhi for Research
Fellowship. The authors thank FIST, DST for providing
infrastructural facility, and SAIF (IIT Madras) and NISER,
Bhubaneswar for providing NMR spectral data.
7,8-Dihydro-2,4-bis(4-bromophenyl)-7,7-dimethyl-5(6H)-
quinolinone (5t). The reaction was carried out following the
general procedure with tetrahydro-5(1H)-quinolinone 3t (0.49 g,
1 mmol). We obtained the pale yellow solid product 5t after
purification by silica chromatography using toluene as eluent.
mp 185 ꢄC. Rf: 0.38. IR (KBr, DRS): nmax 3076 (–CH, Ar–H),
2961 (–CH, –CH3, and –CH2), 1686 (C═O), 1570 (–C═N),
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet