Efficient one-pot syntheses of 2H-indazolo[2,1-b] phthalazine-triones by catalytic H2SO4 in water-ethanol or ionic liquid

Article abstract of DOI:10.1016/j.tetlet.2009.10.032

Sulfuric acid-catalyzed, three-component, one-pot condensation of phthalhydrazide, aromatic aldehydes and 1,3-dicarbonyl compounds has been reported for the synthesis of a series of 2H-indazolo[2,1-b] phthalazine-triones in water-ethanol or in ionic liqui

Full text of DOI:10.1016/j.tetlet.2009.10.032

Tetrahedron Letters 50 (2009) 7300–7303
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Efficient one-pot syntheses of 2H-indazolo[2,1-b] phthalazine-triones
by catalytic H2SO4 in water–ethanol or ionic liquid
*
Jitender M. Khurana , Devanshi Magoo
Department of Chemistry, University of Delhi, Delhi 110 007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Sulfuric acid-catalyzed, three-component, one-pot condensation of phthalhydrazide, aromatic aldehydes
and 1,3-dicarbonyl compounds has been reported for the synthesis of a series of 2H-indazolo[2,1-b]
phthalazine-triones in water–ethanol or in ionic liquid. The protocol proves to be efficient and environ-
mentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction
medium (ionic liquid).
Received 19 September 2009
Revised 6 October 2009
Accepted 8 October 2009
Available online 13 October 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Dimedone
Cyclohexane-1,3-dione
Phthalhydrazide
H2SO4
Ionic liquid
Water–ethanol
Indazolophthalazine
1. Introduction
In continuation of our efforts to explore newer reactions for the
synthesis of heterocyclic compounds,14 we decided to explore the
Phthalazine derivatives, constituting a bridgehead hydrazine are
reported to possess a multiplicity of pharmacological properties
including anticonvulsant,1 vasorelaxant,2 and cardiotonic3 activi-
ties. Albeit there are methods available for the synthesis of different
phthalazine derivatives,4–8 their broad utility range has accentuated
the need to develop newer synthetic routes for scaffold manipula-
tion of N-heterocycles containing phthalazine moiety. The recent
protocols directed toward designing structural motifs containing
phthalazine ring fragment, usually employ multi-component
condensation of aldehydes and active methylene compounds
(malononitrile, ethyl cyanoacetate, and dimedone) with 2,3-dihy-
dro-1,4-phthalazinedione also known as phthalhydrazide.9–11
These protocols have their own limitations. Furthermore, the use
of water as a promising solvent for organic reactions has received
considerable attention in the arena of organic synthesis owing to
its green credentials.12 Ionic liquids have also proved to be efficient
alternatives to the traditional volatile organic solvents13 owing to
their negligible vapor pressure, recyclability, solvophobic proper-
ties, and to promote association of reactants in solvent cavity during
the activation process. Thus ionic liquids are well suited as reaction
media for MCRs in which the entropy of the reaction is decreased in
transition state.
possibility of synthesizing 2H-indazolo[2,1-b] phthalazine-trione
derivatives by one-pot, three-component condensation of
phthalhydrazide, aromatic aldehydes, and cyclic 1,3-dicarbonyl
compounds in aqueous media and/ or in ionic liquids.
2. Results and discussion
We herein present efficient and environmentally benign proto-
cols for the synthesis of 2H-indazolo[2,1-b] phthalazine-1,6,-
11(13H)-trione derivatives by three-component condensation of
2,3-dihydro-1,4-phthalazinedione (phthalhydrazide), aromatic
aldehydes, and cyclic 1,3-dicarbonyl compounds catalyzed by sulfu-
ric acid in water–ethanol solvent system and also in [bmim]BF4 ionic
liquid.
In order to achieve optimum conditions, we initially investigated
the reaction of phthalhydrazide (1.0 mmol), 4-bromobenzaldehyde
(1.2 mmol), and 5,5-dimethylcyclohexane-1,3-dione (1.0 mmol) in
the presence of acid catalysts such as HCl, HNO3, CH3COOH, and
H2SO4 in different media. Best result was obtained when water–eth-
anol (1:1, v/v) was chosen as the solvent in the presence of catalytic
amount of sulfuric acid under reflux conditions. The reaction affor-
ded 93% of 3,4-dihydro-3,3-dimethyl-13-(4-bromophenyl)-2H-
indazolo[2,1-b] phthalazine-1,6,11(13H)-trione (1a) by a simple
work-up after 30 min. The reaction when repeated under similar
conditions in the presence of HCl, HNO3, and CH3COOH was found
* Corresponding author. Tel.: +91 11 27667725x1384; fax: +91 11 27666605.
E-mail address: jmkhurana@chemistry.du.ac.in (J.M. Khurana).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.10.032

J. M. Khurana, D. Magoo / Tetrahedron Letters 50 (2009) 7300–7303
7301
O
O
O
Ar
O
O
R
[bmim]BF4 / H2O-EtOH
N
N
NH
CHO
Ar
R
H2SO4
NH
O
R
O
R
1a-j (R = CH3)
1k-v (R = H)
R = CH3, H
Scheme 1.
to be sluggish and incomplete. Also, when only water was employed
as the solvent medium under the same reaction protocol, the reac-
tion did not proceed to completion even after 5 h of reflux and only
57% of 1a was isolated. Thus, water–ethanol (1:1, v/v) and catalytic
amount of H2SO4 were chosen as the optimum system to extend the
protocol. Subsequent reactions of variously substituted aromatic
aldehydes with phthalhydrazide and dimedone were attempted un-
der similar conditions. The reactions proceeded smoothly and
equally well for electron-withdrawing as well as electron-donating
substituents on aldehydes to afford the corresponding phthalazine-
triones in excellent yields (Scheme 1). The results are summarized in
Table 1 (entries 1–10, Method A).
To further explore the scope of this protocol, we decided to
investigate the condensation reaction of phthalhydrazide and aro-
matic aldehydes with another cyclic 1,3-dicarbonyl compound,
that is, cyclohexane-1,3-dione. The reaction of 4-bromobenzalde-
hyde (1.2 mmol), phthalhydrazide (1.0 mmol), and cyclohexane-
1,3-dione (1.0 mmol) in H2O–EtOH (1:1, v/v) using H2SO4 as a
catalyst under reflux yielded 89% of 3,4-dihydro-13-(4-bromophe-
nyl)-2H-indazolo[2,1-b] phthalazine-1,6,11(13H)-trione (1 k) after
30 min. Other substituted benzaldehydes also underwent success-
ful condensation with cyclohexane-1,3-dione and phthalhydrazide
yielding novel phthalazine-triones in good yields. (Table 1, entries
11–22, Method A).
molar ratio was attempted in [bmim]BF4 at room temperature
without the aid of a catalyst. TLC analysis showed the reaction to
be incomplete after 6 h and even on heating the reaction mixture
to 80 °C, only 32% of 3,4-dihydro-3,3-dimethyl-13-(4-bromophe-
nyl)-2H-indazolo[2,1-b] phthalazine-1,6,11(13H)-trione (1a) could
be isolated after 8 h. However, the yield of 1a improved remark-
ably to 92% when the three components were heated at 80 °C in
[bmim]BF4 in the presence of catalytic amount of sulfuric acid for
30 min. The reaction was also attempted under similar conditions
in [bmim]Br but only to result in lower yield (80%) of 1a after long-
er reaction time (2.5 h). Other substituted aromatic aldehydes also
underwent condensation successfully under these conditions in
[bmim]BF4 and the corresponding phthalazine derivatives were
obtained in high yields (Table 1, Method B, entries 1–10). Also
when cyclohexane-1,3-dione was used in the place of dimedone,
promising results were obtained (Table 1, Method B, entries 11–
22). Comparative results were obtained by both the methods A
and B. The ionic liquid utilized in method B could be recycled for
subsequent usage. A plausible mechanism for the formation of
2H-indazolo[2,1-b] phthalazine-triones (1a–1v) in the presence
of H2SO4 is proposed in Scheme 2.
3. Conclusion
We decided to investigate the scope of the scheme further by
employing ionic liquids as the reaction media. A reaction of 4-bro-
mobenzaldehyde with phthalhydrazide and dimedone in 1.2:1:1
We have described an efficient one-pot, three-component con-
densation strategy for the synthesis of 2H-indazolo[2,1-b] phthal-
azine-triones. This MCR is proficiently catalyzed by sulfuric acid
Table 1
Synthesis of 2H-indazolo[2,1-b] phthalazine-trione derivatives by the condensation of aldehydes, phthalhydrazide, and 5,5-dimethylcyclohexane-1,3-dione/ cyclohexane-1,3-
dione using H2SO4 as a catalyst
Entry
Ar
Product
Method A
Method B
Time (min)
Yield (%)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
4-BrC6H4
4-ClC6H4
C6H5
1a
1b
1c
1d
1e
1f
1g
1h
1i
30
25
30
30
25
30
30
25
30
35
30
30
30
25
30
25
30
30
30
30
30
30
93
88
86
85
91
92
87
90
88
82
89
92
88
90
80
90
82
84
88
82
88
85
30
30
30
30
30
30
35
30
30
40
35
30
35
30
35
30
35
35
30
30
30
35
92
88
89
88
92
90
88
90
90
83
92
94
91
93
83
90
85
86
90
84
90
86
4-CH3C6H4
2,4-Cl2C6H3
4-O2NC6H4
4-CH3OC6H4
2-Naphthyl
4-FC6H4
3,4-(CH3O)2 C6H3
4-BrC6H4
4-ClC6H4
1j
1k
1l
C6H5
1m
1n
1o
1p
1q
1r
1s
1t
2,4-Cl2C6H3
3,4-(CH3O)2 C6H3
3- O2NC6H4
4-CH3OC6H4
4-CH3C6H4
2-Naphthyl
4-HO C6H4
4-FC6H4
1u
1v
4-(CH3)2N C6H4
Method A: Reaction in EtOH–H2O (1:1) under reflux.
Method B: Reaction in [bmim]BF4 at 80 °C.

7302
J. M. Khurana, D. Magoo / Tetrahedron Letters 50 (2009) 7300–7303
O
O
R
O
O
OH
O
HN
N
N
R'
R'
H
H
R
O
H+
H2SO4
HN
OH
O
OH
H
R
CHR
R'
OH
O
R'
R'
- H2O
O
R'
R
O
N
N
O
R'
R'
Scheme 2.
in water–ethanol (1:1, v/v) under reflux conditions and in ionic li-
quid at 80 °C. Mild reaction conditions, operational simplicity, en-
hanced rates, and high isolated yields of pure products are
significant advantages of the protocol described here.
reduced pressure and dried at 100 °C to recover the ionic liquid for
subsequent use. The crude product was washed well with hot etha-
nol to yield pure 2H-indazolo[2,1-b] phthalazine-trione derivatives.
4.3. Spectral data of all unknown products are given below
4. Experimental
4.1. General
4.3.1. Compound 1g
1H NMR (300 MHz, CDCl3): d = 8.25–8.35 (m, 2H), 7.82–7.85 (m,
2H), 6.84–7.35 (m, 4H), 6.42 (s, 1H), 3.76 (s, 3H), 3.23 and 3.42 (2H,
AB system, J = 19.2 Hz), 2.34 (s, 2H), 1.21 (s, 6H). 13C NMR
(300 MHz, CDCl3): d = 192.23, 159.74, 156.07, 154.28, 150.75,
134.47, 133.47, 129.18, 128.98, 128.51, 128.36, 127.93, 127.71,
118.58, 114.14, 64.59, 55.21, 50.99, 38.07, 34.65, 28.71, 28.51. IR
The products were characterized by IR spectra, 1H NMR, 13C
NMR, and mass spectra. IR spectra were recorded on Perkin–Elmer
FT-IR-1710 instrument. 1H and 13C NMR spectra were recorded on
Bruker Avance Spectrospin 300 MHz using TMS as the internal
standard. Mass spectra were recorded on KC-455-TOF mass spec-
trometer (Micromass, Manchester, and UK). Melting points were
recorded on a Tropical Labequip apparatus and are uncorrected.
(m
max, cmÀ1) (KBr): 2959, 1655, 1626, 1363, 1314, 1267, 700. MS
(ESI): m/z = 402. mp: 218–220 °C.
4.3.2. Compound 1h
1H NMR (300 MHz, CDCl3): d = 8.22–8.39 (m, 2H), 7.75–7.92 (m,
6H), 7.42–7.48 (m, 3H), 6.61 (s, 1H), 3.27 and 3.46 (2H, AB system,
J = 19.2 Hz), 2.33 (s, 2H), 1.236 (s, 6H). 13C NMR (300 MHz, CDCl3):
d = 196.85, 160.64, 159.03, 155.93, 139.34, 138.86, 138.45, 137.99,
137.79, 133.81, 133.67, 133.28, 132.88, 132.77, 132.39, 132.15,
131.65, 131.17, 131.12, 129.14, 122.86, 69.81, 55.63, 42.72, 39.39,
4.2. General procedure for the synthesis of 2H-indazolo[2,1-b]
phthalazine-trione derivatives (1a–1v)
4.2.1. Method A
A mixture of phthalhydrazide (1.0 mmol), aldehyde (1.2 mmol),
5,5-dimethyl-1,3-cyclohexanedione or 1,3-cyclohexanedione
(1.0 mmol), H2SO4 (0.15 mmol), and 10 mL H2O–EtOH (1:1, v/v)
was stirred magnetically under reflux for an appropriate time as
mentioned in Table 1. After completion of the reaction as monitored
by TLC using ethyl acetate–petroleum ether (60:40, v/v), the reac-
tion mixture was allowed to cool to room temperature. The precip-
itate formed was collected by filtration at pump, washed with water,
and dried. The crude product was washed well with hot ethanol to
yield pure 2H-indazolo[2,1-b] phthalazine-trione derivatives.
33.49, 33.10. IR (m
max, cmÀ1) (KBr): 2952, 1665, 1618, 1362, 1306,
1257, 697. MS (ESI): m/z = 422. mp: 251–252 °C.
4.3.3. Compound 1j
1H NMR (300 MHz, CDCl3): d = 8.26–8.36 (m, 2H), 7.83–7.88 (m,
2H), 6.79–7.00 (m, 3H), 6.41 (s, 1H), 3.87 (s, 3H), 3.82 (s, 3H), 3.22
and 3.44 (2H, AB system, J = 19.2 Hz), 2.35 (s, 2H), 1.22 (s, 6H). 13C
NMR (300 MHz, CDCl3): d = 192.24, 156.12, 154.41, 150.76, 149.30,
134.53, 133.52, 129.16, 128.97, 128.79, 127.96, 127.74, 119.31,
118.52, 111.17, 111.05, 64.77, 55.98, 55.82, 50.99, 38.09, 34.64,
28.83, 28.33. IR (m
max, cmÀ1) (KBr): 2959, 1662, 1630, 1361, 1313,
1267, 699. MS (ESI): m/z = 432. mp: 185–186 °C.
4.2.2. Method B
Phthalhydrazide (1.0 mmol), aldehyde (1.2 mmol), 5,5-di-
methyl-1,3-cyclohexanedione/1,3-cyclohexanedione (1.0 mmol),
and H2SO4 (0.15 mmol) were placed in a 10 mL round-bottomed
flask containing 0.5 mL of [bmim]BF4. The mixture was stirred at
80 °C for an appropriate time as mentioned in Table 1. After comple-
tion of the reaction as monitored by TLC using ethyl acetate–petro-
leum ether (60:40, v/v), the reaction mixture was allowed to cool to
room temperature and the reaction was quenched with water
(ꢀ5 mL). The precipitate formed was collected by filtration at pump,
washed with water, and dried. The filtrate was concentrated under
4.3.4. Compound 1m
1H NMR (300 MHz, CDCl3): d = 8.24–8.36 (m, 2H), 7.82–7.85 (m,
2H), 7.31–7.43 (m, 5H), 6.44 (s, 1H), 3.29–3.60 (m, 2H), 2.44–2.62
(m, 2H), 2.23–2.27 (m, 2H). 13C NMR (300 MHz, CDCl3): d = 192.50,
156.01, 154.21, 152.29, 144.35, 136.33, 134.51, 133.52, 129.04,
128.65, 128.07, 127.95, 127.69, 119.64, 64.94, 36.89, 24.47, 22.26.
IR (
MS (ESI): m/z = 344. mp: 222–224 °C.
m
max, cmÀ1) (KBr): 2954, 1659, 1623, 1366, 1304, 1267, 702.

J. M. Khurana, D. Magoo / Tetrahedron Letters 50 (2009) 7300–7303
7303
4.3.5. Compound 1o
132.09, 131.80, 130.27, 124.18, 120.28, 69.25, 41.68, 29.16, 27.02.
IR (
max, cmÀ1) (KBr): 3424, 2899, 1642, 1612, 1371, 1310, 1279,
703. MS (ESI): m/z = 360. mp: 265–266 °C.
1H NMR (300 MHz, CDCl3): d = 8.26–8.36 (m, 2H), 7.83–7.86 (m,
2H), 6.78–7.05 (m, 3H), 6.42 (s, 1H), 3.89 (s, 3H), 3.82 (s, 3H), 3.34–
3.61 (m, 2H), 2.45–2.51 (m, 2H), 2.24–2.30 (m, 2H). 13C NMR
(300 MHz, CDCl3): d = 192.59, 156.11, 154.35, 152.14, 149.29,
148.98, 134.53, 133.51, 129.15, 128.94, 128.77, 127.97, 127.74,
119.62, 119.00, 111.34, 111.15, 64.75, 56.04, 55.83, 36.97, 24.52,
m
4.3.11. Compound 1u
1H NMR (300 MHz, CDCl3): d = 8.25–8.36 (m, 2H), 7.84–7.87 (m,
2H), 7.39–7.43 (m 2H), 6.99–7.04 (m 2H), 6.43 (s, 1H), 3.27–3.62
(m, 2H), 2.45–2.53 (m, 2H), 2.24–2.33 (m, 2H). 13C NMR
(300 MHz, CDCl3): d = 192.37, 160.77, 155.74, 154.16, 152.49,
134.45, 133.53, 132.32, 132.27, 129.77, 129.06, 127.87, 127.38,
22.34. IR (m
max, cmÀ1) (KBr): 2928, 1662, 1627, 1368, 1304, 1267,
699. MS (ESI): m/z = 404. mp: 205–206 °C.
4.3.6. Compound 1p
118.89, 115.49, 115.20, 64.06, 36.72, 24.29, 22.10. IR (m )
max, cmÀ1
1H NMR (300 MHz, CDCl3): d = 8.22–8.40 (m, 2H), 8.14–8.17 (m,
2H), 7.52–7.92 (m, 4H), 6.52 (s, 1H), 3.31–3.65 (m, 2H), 2.46–2.50
(m, 2H), 2.23–2.38 (m, 2H). 13C NMR (300 MHz, CDCl3): d = 192.46,
164.62, 155.99, 154.65, 153.21, 148.53, 138.60, 134.78, 129.62,
128.27, 127.76, 123.69, 121.70, 118.26, 64.25, 36.79, 24.54, 22.23.
(KBr): 2925, 1660, 1621, 1370, 1305, 1284, 702. MS (ESI): m/
z = 362. mp: 258–260 °C.
4.3.12. Compound 1v
1H NMR (300 MHz, CDCl3): d = 8.25–8.34 (m, 2H), 7.80–7.83 (m,
2H), 7.26–7.29 (m, 2H), 6.63–6.66 (m, 2H), 6.40 (s, 1H), 3.35–3.61
(m, 2H), 2.89 (s, 6H), 2.46–2.48 (m, 2H), 2.24–2.28 (m, 2H). 13C
NMR (300 MHz, CDCl3): d = 192.59, 156.12, 154.12, 151.89,
150.64, 134.34, 133.28, 129.39, 128.98, 128.92, 128.21, 127.84,
127.70, 123.41, 119.95, 112.40, 112.26, 64.83, 40.64, 40.36, 37.02,
IR (m
max, cmÀ1) (KBr): 2926, 1662, 1624, 1369, 1305, 1285, 697.
MS (ESI): m/z = 389. mp: 228–230 °C.
4.3.7. Compound 1q
1H NMR (300 MHz, CDCl3): d = 8.25–8.35 (m, 2H), 7.82–7.86 (m,
2H), 7.32–7.37 (m, 2H), 6.83–6.87 (m, 2H), 6.42 (s, 1H), 3.75 (s, 3H),
3.28–3.60 (m, 2H), 2.44–2.49 (m, 2H), 2.23–2.30 (m, 2H). 13C NMR
(300 MHz, CDCl3): d = 192.60, 159.73, 156.05, 154.22, 152.19,
134.48, 133.47, 129.16, 128.94, 128.55, 128.30, 127.93, 127.69,
24.53, 22.39. IR (m
max, cmÀ1) (KBr): 2923, 1661, 1616, 1364, 1305,
1280, 699. MS (ESI): m/z = 387. mp: 256–258 °C.
Acknowledgment
119.65, 114.09, 64.58, 55.23, 36.96, 24.51, 22.34. IR (m )
max, cmÀ1
(KBr): 2950, 1657, 1624, 1365, 1306, 1246, 703. MS (ESI):
m/z = 374. mp: 254–255 °C.
D.M. thanks CSIR, New Delhi, India, for the grant of junior and
senior research fellowships.
4.3.8. Compound 1r
References and notes
1H NMR (300 MHz, CDCl3): d = 8.25–8.36 (m, 2H), 7.81–7.87 (m,
2H), 7.12–7.32 (m, 4H), 6.42 (s, 1H), 3.29–3.60 (m, 2H), 2.44–2.48
(m, 2H), 2.29 (s, 3H), 2.23–2.27 (m, 2H). 13C NMR (300 MHz,
CDCl3): d = 192.49, 156.06, 154.19, 152.12, 138.48, 134.45,
133.44, 133.34, 129.40, 129.17, 128.95, 127.93, 127.73, 127.06,
1. Grasso, S.; DeSarro, G.; Micale, N.; Zappala, M.; Puia, G.; Baraldi, M.; Demicheli,
C. J. Med. Chem. 2000, 43, 2851.
2. Watanabe, N.; Kabasawa, Y.; Takase, Y.; Matsukura, M.; Miyazaki, K.; Ishihara,
H.; Kodama, K.; Adachi, H. J. Med. Chem. 1998, 41, 3367.
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Pharm. Bull. (Tokyo) 1990, 38, 2179.
4. Heine, H. W.; Baclawski, L. M.; Bonser, S. M.; Wachob, G. D. J. Org. Chem. 1976,
41, 3229.
119.80, 64.84, 36.93, 24.49, 22.30, 21.20. IR (m
max, cmÀ1) (KBr):
2924, 1660, 1627, 1369, 1305, 1269, 701. MS (ESI): m/z = 358.
5. Sheradsky, T.; Moshenberg, R. J. Org. Chem. 1986, 51, 3123.
6. Ramtohup, Y. K.; James, M. N. G.; Vederas, J. C. J. Org. Chem. 2002, 67, 3169.
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9. Sayyafi, M.; Seyyedhamzeh, M.; Khavasi, H. R.; Bazgir, A. Tetrahedron 2008, 64,
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10. Shaterian, H. R.; Hosseinian, A.; Ghashang, M. Arkivoc 2009, 59.
11. Ghahremanzadeh, R.; Shakibaei, G. I.; Bazgir, A. Synlett 2008, 1129.
12. (a) Lindstorm, U. M. Chem. Rev. 2002, 102, 2751; (b) Li, C. J.; Chen, L. Chem. Soc.
Rev. 2006, 35, 68; (c) Herreras, C. I.; Yao, X.; Li, Z.; Li, C. J. Chem. Rev. 2007, 107,
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13. (a) Wilkes, J. S. Green Chem. 2002, 4, 73; (b) Zerth, H. M.; Leonard, N. M.;
Mohan, R. S. Org. Lett. 2003, 5, 55; (c) Kumar, A.; Pawar, S. S. J. Org. Chem. 2004,
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(e) Seddon, K. R. J. Chem. Tech. Biotechnol. 1997, 68, 351.
mp: 244–246 °C.
4.3.9. Compound 1s
1H NMR (300 MHz, CDCl3): d = 8.20–8.38 (m, 2H), 7.75–7.91 (m,
6H), 7.41–7.50 (m, 3H), 6.60 (s, 1H), 3.28–3.65 (m, 2H), 2.43–2.47
(m, 2H), 2.21–2.29 (m, 2H). 13C NMR (300 MHz, CDCl3):
d = 192.47, 156.12, 154.32, 152.30, 134.54, 133.68, 133.55,
133.45, 133.19, 129.10, 129.00, 128.65, 128.27, 128.00, 127.75,
127.67, 126.78, 126.32, 126.23, 124.36, 119.72, 65.17, 36.92,
24.55, 22.31. IR (m
max, cmÀ1) (KBr): 2924, 1661, 1626, 1367, 1304,
1264, 701. MS (ESI): m/z = 394. mp: 262–264 °C.
14. a Khurana, J. M.; Kukreja, G.; Bansal, G. J. Chem. Soc., Perkin Trans. 1 2002, 2520;
b Khurana, J. M.; Kukreja, G. J. Heterocycl. Chem. 2003, 40, 677; c Khurana, J. M.;
Agrawal, A.; Kukreja, G. Heterocycles 2006, 68, 1885; d Khurana, J. M.; Arora, R.;
Satija, S. Heterocycles 2007, 71, 2709; e Khurana, J. M.; Sharma, V. Chem.
Heterocycl. Compd. 2008, 309; f Khurana, J. M.; Kumar, S. Tetrahedron Lett. 2009,
50, 4125; g Khurana, J. M.; Magoo, D. Tetrahedron Lett. 2009, 50, 4777.
4.3.10. Compound 1t
1H NMR (300 MHz, CDCl3): d = 8.83 (s, 1H), 8.23–8.35 (m, 2H),
7.83–7.86 (m, 2H), 7.23 (d, 2H, J= 8.7 Hz), 6.78 (d, 2H, J = 8.4 Hz),
6.37 (s, 1H), 3.35–3.60 (m, 2H), 2.46–2.47 (m, 2H), 2.24–2.28 (m,
2H). 13C NMR (300 MHz, CDCl3): d = 197.29, 162.42, 160.57,
158.79, 157.08, 139.25, 138.28, 137.07, 133.73, 133.38, 132.66,