Direct construction of novel dispiro heterocycles through 1,3-dipolar cycloaddition of azomethine ylides

Article abstract of DOI:10.1016/j.tetlet.2011.08.014

The 1,3-dipolar cycloaddition of 2-oxo-(2H)-acenaphthylen-1-ylidene- malononitrile and 2-fluoren-9-ylidene-malononitrile as dipolarophiles have been investigated for the first time with the azomethine ylides generated in situ from N-substituted isatin and

Full text of DOI:10.1016/j.tetlet.2011.08.014

Tetrahedron Letters 52 (2011) 5333–5337
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Tetrahedron Letters
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Direct construction of novel dispiro heterocycles through 1,3-dipolar
cycloaddition of azomethine ylides
⇑
Anshu Dandia , Anuj K. Jain, Dharmendra S. Bhati
Center for Advance Studies, Department of Chemistry, University of Rajasthan, Jaipur 302 004, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The 1,3-dipolar cycloaddition of 2-oxo-(2H)-acenaphthylen-1-ylidene-malononitrile and 2-fluoren-9-yli-
dene-malononitrile as dipolarophiles have been investigated for the first time with the azomethine ylides
generated in situ from N-substituted isatin and sarcosine to furnish novel dispiro heterocycles. The struc-
ture and relative stereochemistry of both types of cycloadducts were confirmed by single crystal X-ray
diffraction, as well as with the help of 1H, 13C, and HMBC spectroscopic methods.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 1 June 2011
Revised 1 August 2011
Accepted 2 August 2011
Available online 7 August 2011
Keywords:
1,3-Dipolar cycloaddition
Azomethine ylides
Dispiroheterocycles
Regioselectivity
Five-membered nitrogen heterocycles, especially highly substi-
tuted pyrrolidines feature widely in pharmaceuticals, natural alka-
loids, organocatalysts and are also useful building blocks in
organic synthesis.1 1,3-Dipolar cycloaddition of azomethine ylides
to electron-deficient alkenes provides an efficient approach for
constructing pyrrolidine rings with high selectivity.2 The extensive
use of isatin as a precursor for 1,3-dipolar cycloaddition stems from
the fact that a wide variety of azomethine ylides with primary and
secondary amines can be generated and trapped with suitable
dipolarophiles.3
Spirooxindole unit is a privileged heterocyclic motif that forms
the core of a large family of alkaloid and natural products with
strong bioactivity profiles and interesting structural properties.4–6
Significant recent advances in the synthesis of this fused heterocy-
clic system have led to an intense interest in the development of
related compounds as potential medicinal agents or biological
probes. For example, Alstonisine a natural alkaloid was firstly iso-
lated from Alstonia muelleriana7 and several biomimetic analogues
of Alstonisine have been investigated.8 Further, Strychnofoline has
been found to inhibit mitosis in a number of cell lines including
mouse melanoma B16, Ehrlich, and Hepatom HW165.9 Chitosenine
is another structurally interesting natural product, which exhibits
short-lived inhibitory activity of ganglionic transmission ‘in vivo’
in rats and rabbits.10
The synthesis of spiro-oxindoles via 1,3-dipolar cycloaddition
reaction of azomethine ylides derived from isatin with various type
of chalcons,11 Baylis–Hillman and Morita–Baylis–Hillman adducts
of isatin has been reported.12–14 To the best of our knowledge, only
a few methods are reported involving gem-dicyano olefin segment
as the dipolarophiles.15,16 But, the synthesis of dispiropyrrolidine
oxindoles using 2-oxo-(2H)-acenaphthylen-1-ylidene-malononitri-
le Knoevenagel adduct (1), as dipolarophiles in 1,3-dipolar cycload-
dition reaction of azomethine ylides has not been studied so far. As a
part of our own interest for the synthesis of biologically important
spirooxindole derivatives,17 we report herein the efficient synthesis
of novel dispiropyrrolidine oxindole framework via the one-pot
multicomponent condensation of azomethine ylide with the Knoe-
venagel adduct (1).
The Knoevenagel adduct (1) was prepared via modification of the
previously reported method.18 Utilization of our modified method
reduced the reaction time with a concomitant increase in the yield.
This adduct was reacted smoothly with the non-isolated azome-
thine ylides (dipole 4a–d) generated in situ by the decarboxylative
condensation of isatin 2a–d and sarcosine 3 in refluxing toluene for
Table 1
Synthetic results of dispiropyrrolidine oxindoles 5a–d
Entry
Products
R
Time (h)
Yieldsa (%)
Mp (°C)
The unique structural array and the highly pronounced pharma-
cological activities of pyrrolidines as well as spirooxindole moities
have made them attractive synthetic targets.
1
2
3
4
5a
5b
5c
5d
H
6
7
7
6
78
74
73
79
198–200
214–216
204–206
222–224
C6H5CH2
CH2@CH–CH2
CH„C–CH2
⇑
Corresponding author. Tel.: +91 9414073436; fax: +91 141 2609549.
E-mail address: dranshudandia@yahoo.co.in (A. Dandia).
a
Isolated yield.
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.08.014

5334
A. Dandia et al. / Tetrahedron Letters 52 (2011) 5333–5337
O
O
+
HOOC
N
H
N
R
CN
CN
3
2a-d
O
CN
O
O
N
CN
R
N
N
5a-d
1
N
R
O
CN
CN
dipole 4a-d
O
N
N
R
O
5' a-d
Scheme 1. Synthesis of dispiropyrrolidine oxindoles 5a–d.
the appropriate time (Table 1).The reaction mixture was cooled at
room temperature. The solid precipitate was filtered and recrystal-
lized from acetone to furnish dispiropyrrolidine oxindoles 5a–d in a
regioselective manner (Scheme 1). The structures of cycloadducts
were confirmed through spectroscopic and elemental analyses.19
The IR spectrum of dispiropyrrolidine oxindole derivative 5a
showed two peaks at 1714 and 1726 cmÀ1 due to the oxindole ring
carbonyl and acenaphthenequinone ring carbonyl respectively.
The 1H NMR spectrum of 5a demonstrated a singlet at d 2.10 for
the –NCH3 protons and another singlet at d 10.77 for –NH proton
of oxindole ring. The –N–CH2 protons of the pyrrolidine moiety res-
onate as a singlet at d 4.31 ppm. The 13C NMR spectrum of 5a dem-
onstrated signals at d 176.24 and 197.24 ppm due to oxindole and
acenaphthenequinone ring carbonyls. The two spiro carbons reso-
nated at d 61.26 and 78.22 ppm. The mass spectrum of 5a showed
a molecular ion peak at 405.1 (M+H)+.
The regiochemistry of 5a was established by HMBC studies. Het-
eronuclear Multiple Bond Coherence (HMBC) spectrum 5a as a rep-
resentative example adds a good support for the established
structure. It reveals that the 1,3-coupling of the CN groups (appear-
ing at d 115.5 and d 115.9) correlates with the methylene CH2
(appearing at d 4.31 ppm) which clearly shows the regiochemistry
of the cycloaddition reaction. There is no evidence for the formation
of theother regioisomer as theformationof otherregioisomerwould
result in retarding the strong 1,3 coupling between CN groups and
methylene CH2, which is not the case. Finally, the regio- and ste-
reo-chemical outcome of the cycloaddition was determined unam-
biguously by single crystal X-ray analysis of cycloadduct 5c (Fig. 2).20
Although the detailed mechanism of the above reaction is not
fully clarified, the formation of regioisomer 5a could be explained
as follows: decarboxylative condensation of the isatin 2a with
sarcosine 3 gives the azomethine ylide (dipole 4a) which then
N
CN
HN
CN
Path A
O
O
SOI
O
O
N
CN
CN
HN
O
NH
N
CN
CN
O
Path B
CN
CN
O
NH
N
O
Figure 1. Mode of approach of azomethine ylide 4a.
Figure 2. ORTEP diagram of compound 5c.

A. Dandia et al. / Tetrahedron Letters 52 (2011) 5333–5337
5335
O
O
+
HOOC
N
H
N
R
CN
CN
3
2a-d
O
CN
NC
N
R
N
7a-d
N
6
N
R
O
CN
CN
dipole 4a-d
N
N
R
O
7' a-d
Scheme 2. Synthesis of dispiropyrrolidine oxindoles 7a–d.
Encouraged by these results, we have extended this reaction to
other dipolarophiles such as 2-fluoren-9-ylidene-malononitrile un-
der similar conditions to furnish the respective dispiropyrrolidine
oxindole derivatives 7a–d as single product with good yields
(Scheme 2, Table 2). The structure of dispiropyrrolidine oxindole
derivatives 7a–d was confirmed through spectroscopic and ele-
mental analyses.19
The IR spectrum of dispiropyrrolidine oxindole derivative 7a
showed a peak at 1714 cmÀ1 due to the oxindole carbonyl group.
The 1H NMR spectrum of 7a demonstrated a characteristic singlet
at d 2.15 for the –NCH3 protons and another singlet at d 10.79 for –
NH proton of oxindole ring. The 13C NMR spectrum of 7a showed
two peaks at d 65.48 and 76.99 ppm due to the two spiro carbons.
The amide carbonyl carbon resonated at d 176.70 ppm. These ob-
served chemical shift values are in accordance with the structure
of the compound 7a. Moreover, the presence of a molecular ion
peak at 403.1 (M+H)+ in the mass spectrum of 7a confirmed the
structure of the cycloadduct 7a.
Table 2
Synthetic results of dispiropyrrolidine oxindoles 7a–d
Entry
Products
R
Time (h)
Yieldsa (%)
Mp (°C)
1
2
3
4
7a
7b
7c
7d
H
6
7
7
6
74
76
71
72
218–220
222–224
210–212
214–216
C6H5CH2
CH2@CH–CH2
CH„C–CH2
a
Isolated yield.
undergoes 1,3-dipolar cycloaddition reaction with the dipolaro-
phile (1) regioselectively as shown in Figure 1 (path A). The regi-
oselectivity in the product formation can be explained by
considering the secondary orbital interaction (SOI) of the orbital
of the carbonyl group of dipolarophile 1 with those of the ylide
4a as shown in Figure 1. Accordingly, the observed regioisomer
5a via path A is more favourable because of the secondary orbital
interaction which is not possible in path B.15,16,21
Figure 3. ORTEP diagram of compound 7b.

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A. Dandia et al. / Tetrahedron Letters 52 (2011) 5333–5337
precipitate was then filtered and washed from ethanol to afford Knoevenagel
The relative regiochemistry of cycloadduct 7a was established by
adduct (yield 88%, mp: 244–246 °C).
Heteronuclear MultipleBond Coherencestudies. Based onthe HMBC
spectrum of 7a and the observation of the 1,3-coupling of the CN
groups (appearing at d 115.7 and d 115.9) correlates with the meth-
ylene CH2 (appearing at d 4.39 and d4.44 ppm), which clearly shows
the regiochemistry of the cycloadduct 7a. Finally, the regio- and
stereo-chemical outcome of the cycloaddition was determined
unambiguously by single crystal X-ray analysis of cycloadduct 7b (
Fig. 3).20
19. General procedure: A mixture of sarcosine (10 mmol), N-substituted isatin
(10 mmol) and preformed Knoevenagel adduct (10 mmol) in dry toluene
(20 mL) containing molecular sieves (1000 mg, 3A) was refluxed with stirring
for appropriate time (Tables 1 and 2). After completion of the reaction, as
indicated by TLC, the reaction mixture was cooled at room temperature. The
solid precipitate was filtered off, washed with toluene, dried and recrystallized
from acetone to furnish dispiropyrrolidine oxindoles in high regeoselectivity.
Spectral data
Compound (5a): yellow solid; mp 198–200 °C; IR (KBr): 3406, 2234,
1726,1714, 1608, 1462 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.10 (s, 3H),
;
In conclusion, we have successfully developed the regioselec-
tive version of bioactive pyrrolidines ring containing two cyano
groups, which, not only diversifies the existing 1,3-dipolar cycload-
dition of azomethine ylides but also is valuable in the synthesis of
novel dispiropyrrolidine oxindoles framework. Transformation of
the cyano group to other functionalities is currently under investi-
gation in our research group and anticipated to furnish other new
pyrrolidine derivatives. Further investigation of the mechanism
and the reaction scope are ongoing in our laboratory and will be re-
ported in due course.
4.31 (s, 2H), 6.48 (d, 1H, J = 7.8 Hz, Ar-H), 6.73 (t, 1H, J = 7.5 Hz, Ar-H), 7.00–
6.93 (m, 2H, Ar-H), 7.82–7.76 (m, 2H, Ar-H), 8.02 (t, 2H, J = 7.5 Hz, Ar-H),
8.08(d, 1H, J = 8.4 Hz, Ar-H), 8.24 (d, 1H, J = 8.1 Hz, Ar-H), 10.77 (br s, 1H, NH,
D2O exchangeable), 13C NMR (75 MHz, DMSO-d6): 34.2, 61.7, 78.3, 110.7,
115.5, 115.9, 121.1, 122.5, 123.5, 125.1, 126.3, 127.6, 128.9, 129.4, 129.8, 130.1,
131.1, 133.4, 142.3, 143.3, 176.2, 197.2; MS (ESI) m/z: 405 [M+H]+. Anal. Calcd
for C25H16N4O2: C, 74.25; H, 3.99; N, 13.85. Found: C, 74.42; H, 4.14; N, 13.98.
Compound (5b): yellow solid; mp 214–216 °C; IR (KBr): 3414, 2250,
1720,1706, 1612, 1466 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.12 (s, 3H),
;
4.33 (s, 2H), 4.72 (ABq, 2H, J = 12.8 Hz), 6.52 (d, 1H, J = 7.5 Hz, Ar-H), 6.72 (t, 1H,
J = 7.8 Hz, Ar-H), 6.86 (d, 1H, J = 7.8 Hz, Ar-H), 6.97 (t, 1H, J = 7.6 Hz, Ar-H),
7.23–7.16 (m, 3H, Ar-H) 7.12 (d, 2H, J = 7.8 Hz, Ar-H), 7.88–7.80 (m, 2H, Ar-H),
8.07 (t, 2H, J = 8.1 Hz, Ar-H), 8.12 (d, 1H, J = 8.4 Hz, Ar-H), 8.20 (d, 1H, J = 7.8 Hz,
Ar-H), 13C NMR (75 MHz, DMSO-d6): 34.6, 48.3, 61.8, 78.9, 113.2, 115.6, 116.1,
122.1, 123.5, 124.7, 126.3, 127.3, 127.6, 128.9, 129.1, 129.7, 130.8, 131.1, 132.5,
133.7, 134.4, 136.9, 143.8, 144.3, 177.6, 197.8; MS (ESI) m/z: 495 [M+H]+. Anal.
Calcd for C32H22N4O2: C, 77.72; H, 4.48; N, 11.33. Found: C, 77.52; H, 4.26; N,
11.18.
Acknowledgments
Financial assistance from the UGC (34-349/08/SR) and Council
for Scientific and Industrial Research (01/2248/08/EMR-II) New
Delhi is gratefully acknowledged. We are also thankful to the Cen-
tral Drug Research Institute (CDRI), Lucknow, for the elemental and
spectral analyses.
Compound (5c): yellow solid; mp 204–206 °C; IR (KBr): 3422, 2252, 1722,
1710, 1602, 1468 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.08 (s, 3H), 4.32 (s,
;
2H), 4.36–4.44 (m, 2H), 5.16 (d, 1H, J = 12.8 Hz), 5.28 (d, 1H, J = 12.0 Hz), 5.78–
5.84 (m, 1H), 6.47 (d, 1H, J = 7.5 Hz, Ar-H), 6.74 (t, 1H, J = 7.8 Hz, Ar-H), 6.82 (d,
1H, J = 7.6 Hz, Ar-H), 6.94 (t, 1H, J = 7.8 Hz, Ar-H), 7.82–7.76 (m, 2H, Ar-H), 8.02
(t, 2H, J = 7.5 Hz, Ar-H), 8.08 (d, 1H, J = 8.4 Hz, Ar-H), 8.24 (d, 1H, J = 8.1 Hz, Ar-
H), 13C NMR (75 MHz, DMSO-d6): 33.9, 46.2, 62.7, 78.4, 110.8, 114.9, 115.3,
115.8, 121.6, 122.5, 123.9, 126.8, 127.3, 127.9, 128.6, 129.1, 129.6, 130.7, 131.4,
133.1, 133.5, 134.3, 142.1, 144.8, 177.3, 198.1; MS (ESI) m/z: 445 [M+H]+. Anal.
Calcd for C28H20N4O2: C, 75.66; H, 4.54; N, 12.60. Found: C, 75.42; H, 4.34; N,
12.78.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2011.08.014.
Compound (5d): yellow solid; mp 222–224 °C; IR (KBr): 3418, 2248, 1720,
1712, 1608, 1460 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.06 (s, 1H), 2.11 (s,
;
3H), 4.31 (s, 2H), 4.58–4.64 (m, 2H), 6.46 (d, 1H, J = 7.6 Hz, Ar-H), 6.72 (t, 1H,
J = 7.8 Hz, Ar-H), 6.78 (d, 1H, J = 7.5 Hz, Ar-H), 6.91 (t, 1H, J = 7.6 Hz, Ar-H),
7.80–7.71 (m, 2H, Ar-H), 8.07 (t, 2H, J = 7.6 Hz, Ar-H), 8.09 (d, 1H, J = 8.0 Hz, Ar-
H), 8.22 (d, 1H, J = 8.2 Hz, Ar-H), 13C NMR (75 MHz, DMSO-d6): 34.1, 42.8, 62.3,
71.9, 77.5, 84.3, 110.9, 115.7, 116.1, 120.9, 122.8, 124.3, 126.8, 127.7, 127.9,
128.4, 129.3, 129.9, 130.2, 131.6, 133.1, 133.9, 141.7, 144.2, 177.6, 198.2; MS
(ESI) m/z: 443 [M+H]+. Anal. Calcd for C28H18N4O2: C, 76.01; H, 4.10; N, 12.66.
Found: C, 75.82; H, 4.33; N, 12.47.
References and notes
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S.; Raghunathan, R. Tetrahedron Lett. 2008, 49, 4618; (c) Kumar, R. S.; Perumal,
S. Tetrahedron Lett. 2007, 48, 7164.
Compound (7a): white solid; mp 218–220 °C; IR (KBr): 3436, 2262, 1714,
1612 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.15 (s, 3H), 4.40 (ABq, 2H,
;
4. Trost, B. M.; Brennan, M. K. Synthesis 2009, 18, 3003.
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Caprasse, M.; Angenot, L. Planta Med. 1982, 45, 123.
J = 12.0 Hz), 5.88 (d, 1H, J = 7.8 Hz, Ar-H), 6.43 (t, 1H, J = 7.8 Hz, Ar-H), 6.52 (d,
1H, J = 7.8 Hz, Ar-H), 6.96 (t, 1H, J = 7.8 Hz, Ar-H), 7.47–7.35 (m, 2H, Ar-H),
7.60–7.50 (m, 2H, Ar-H), 7.88–7.75 (m, 3H, Ar-H), 8.10 (d, 1H, J = 7.2 Hz, Ar-H),
10.79 (br s, 1H, NH, D2O exchangeable), 13C NMR (75 MHz, DMSO-d6): 34.4,
41.0, 60.3, 65.4, 76.9, 110.1, 115.7, 115.9, 120.5, 120.8, 121.7, 122.3, 125.9,
126.7, 127.5, 127.9, 128.8, 130.5, 135.9, 139.9, 142.1, 143.3, 143.7, 176.7; MS
(ESI) m/z: 403 [M+H]+. Anal. Calcd for C26H18N4O: C, 77.59; H, 4.51; N, 13.92.
Found: C, 77.76; H, 4.32; N, 14.04.
10. Sakai, S.; Aimi, N.; Yamaguchi, K.; Yamanaka, E.; Haginiwa, J. J. Chem. Soc.,
Perkin Trans. 1 1982, 1257.
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Tetrahedron Lett. 2006, 47, 829; (b) Babu, A. R. S.; Raghunathan, R. Tetrahedron
Lett. 2007, 48, 6809; (c) Kumar, R. R.; Perumal, S.; Senthilkumar, P.; Yogeeswari,
P.; Sriram, D. J. Med. Chem. 2008, 51, 5731; (d) Liu, H.; Dou, G.; Shi, D. J. Comb.
Chem. 2010, 12, 633; (e) Murugan, R.; Anbazhagan, S.; Narayanan, S. S. Eur. J.
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Lett. 2008, 49, 2611.
Compound (7b): white solid; mp 222–224 °C; IR (KBr): 3430, 2256, 1722,
1606 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.13 (s, 3H), 4.42 (ABq, 2H,
;
J = 12.4 Hz), 4.68 (ABq, 2H, J = 12.0 Hz), 5.82 (d, 1H, J = 7.8 Hz, Ar-H), 6.39 (t, 1H,
J = 7.8 Hz, Ar-H), 6.51 (d, 1H, J = 7.8 Hz, Ar-H), 6.92 (t, 1H, J = 7.8 Hz, Ar-H), 7.21-
7.14 (m, 3H, Ar-H) 7.08 (d, 2H, J = 7.5 Hz, Ar-H), 7.51–7.38 (m, 2H, Ar-H), 7.62–
7.57 (m, 2H, Ar-H), 7.92–7.74 (m, 3H, Ar-H), 8.14 (d, 1H, J = 7.8 Hz, Ar-H), 13C
NMR (75 MHz, DMSO-d6): 34.1, 41.3, 49.2, 60.8, 65.7, 76.3, 109.8, 115.5, 115.8,
116.1, 121.3, 122.2, 123.7, 124.9, 125.2, 126.4, 127.8, 127.9, 128.2, 130.7, 135.4,
139.1, 143.4, 143.9, 144.4, 176.3; MS (ESI) m/z: 493 [M+H]+. Anal. Calcd for
14. Basavaiah, D.; Reddy, B. S.; Badsara, S. S. Chem. Rev. 2010, 110, 5447.
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C
33H24N4O: C, 80.47; H, 4.91; N, 11.37. Found: C, 80.66; H, 4.72; N, 11.14.
Compound (7c): white solid; mp 210–212 °C; IR (KBr): 3428, 2268, 1718,
1622 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.14 (s, 3H), 4.36 (ABq, 2H,
;
J = 12.4 Hz), 4.44–4.38 (m, 2H), 5.22 (d, 1H, J = 12.0 Hz), 5.28 (d, 1H,
J = 12.4 Hz), 5.80–5.76 (m, 1H), 5.92 (d, 1H, J = 7.8 Hz, Ar-H), 6.44 (t, 1H,
J = 7.5 Hz, Ar-H), 6.58 (d, 1H, J = 7.8 Hz, Ar-H), 7.02 (t, 1H, J = 7.8 Hz, Ar-H),
7.48–7.42 (m, 2H, Ar-H), 7.67–7.62 (m, 2H, Ar-H), 7.94–7.78 (m, 3H, Ar-H), 8.18
(d, 1H, J = 7.5 Hz, Ar-H), 13C NMR (75 MHz, DMSO-d6): 34.3, 41.7, 47.8, 60.1,
65.6, 76.1, 110.3, 115.6, 115.9, 116.6, 119.1, 120.9, 122.3, 122.8, 124.6, 126.2,
127.4, 127.9, 128.3, 129.8, 133.3, 136.1, 138.2, 141.5, 143.4, 143.9, 176.1; MS
(ESI) m/z: 443 [M+H]+. Anal. Calcd for C29H22N4O: C, 78.71; H, 5.01; N, 12.66.
Found: C, 78.56; H, 4.82; N, 12.44.
18. A mixture of acenapthalenequinone (10 mmol) and malononitrile (10 mmol) in
absolute ethanol (20 mL) were taken in a conical flask and immersed in water
bath of an ultrasonic cleaner. The flask was positioned 0.5 cm above the
bottom of the bath at room temperature for 30 min. The resulting orange
Compound (7d): white solid; mp 214–216 °C; IR (KBr): 3436, 2262, 1716,
1612 cmÀ1 1H NMR (300 MHz, DMSO-d6): d 2.08 (s, 1H), 2.12 (s, 3H), 4.39
;
(ABq, 2H, J = 12.8 Hz), 4.65–4.61 (m, 2H), 5.83 (d, 1H, J = 7.5 Hz, Ar-H), 6.45 (t,
1H, J = 7.6 Hz, Ar-H), 6.53 (d, 1H, J = 7.8 Hz, Ar-H), 6.96 (t, 1H, J = 7.6 Hz, Ar-H),

A. Dandia et al. / Tetrahedron Letters 52 (2011) 5333–5337
5337
7.42–7.34 (m, 2H, Ar-H), 7.62–7.49 (m, 2H, Ar-H), 7.83–7.74 (m, 3H, Ar-H), 8.12
(d, 1H, J = 7.5 Hz, Ar-H), 13C NMR (75 MHz, DMSO-d6): 34.2, 41.8, 43.1, 60.2,
65.7, 71.2, 77.1, 85.7, 109.9, 115.9, 116.3, 121.8, 122.3, 124.7, 123.5, 126.9,
127.6, 128.5, 128.8, 131.7, 135.6, 140.3, 142.4, 143.3, 145.9, 176.8; MS (ESI) m/
z: 441 [M+H]+. Anal. Calcd for C29H20N4O: C, 79.07; H, 4.58; N, 12.72. Found: C,
79.26; H, 4.36; N, 12.94.
20. The crystal structures (5c: CCDC 827499; 7b: CCDC 833828) have been
deposited at the Cambridge Crystallographic Data Center and is available on
request from the Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax:
+44-1223-336033;
e-mail:
deposit@ccdc.cam.ac.uk,
http://
www.ccdc.cam.ac.uk/deposit.
21. Pardasani, R. T.; Pardasani, P.; Chaturvedi, V.; Yadav, S. K.; Saxena, A.; Sharma, I.
Heteroatom Chem. 2003, 14, 36.