Synthesis of functionalized pyrido[1,2-f[phenanthridines from phenanthridine, activated acetylenes, and arylidenemalononitriles

Article abstract of DOI:10.1080/00397911.2011.605240

The zwitterions generated from phenanthiridine and dialkyl acetylenedicarboxylates (DAADs) react with a variety of arylidenemalononitriles, affording substituted pyrido[1,2-f]phenanthridines.

Full text of DOI:10.1080/00397911.2011.605240

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Synthesis of Functionalized
Pyrido[1,2-f]phenanthridines from
Phenanthridine, Activated Acetylenes,
and Arylidenemalononitriles
Hossein Mehrabi a & Mahdi Hatami-pour a
a Department of Chemistry, Rafsanjan Vali-e-Asr University,
Rafsanjan, Iran
Accepted author version posted online: 10 May 2012.Version of
record first published: 08 Nov 2012.
To cite this article: Hossein Mehrabi & Mahdi Hatami-pour (2013): Synthesis of
Functionalized Pyrido[1,2-f]phenanthridines from Phenanthridine, Activated Acetylenes,
and Arylidenemalononitriles, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 43:4, 611-618
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Synthetic Communications1, 43: 611–618, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.605240
SYNTHESIS OF FUNCTIONALIZED PYRIDO[1,2-
f]PHENANTHRIDINES FROM PHENANTHRIDINE,
ACTIVATED ACETYLENES, AND
ARYLIDENEMALONONITRILES
Hossein Mehrabi and Mahdi Hatami-pour
Department of Chemistry, Rafsanjan Vali-e-Asr University, Rafsanjan, Iran
GRAPHICAL ABSTRACT
Abstract The zwitterions generated from phenanthiridine and dialkyl acetylenedicarboxy-
lates (DAADs) react with a variety of arylidenemalononitriles, affording substituted
pyrido[1,2-f]phenanthridines.
Keywords Arylidenemalononitrile; dialkyl acetylenedicarboxylate; phenanthridine;
pyrido[12-f]phenanthridine derivatives; three-component reaction
INTRODUCTION
Nitrogen-containing heterocyclic compounds are widespread in nature, and
their applications to biologically active pharmaceuticals, agrochemicals, and func-
tional materials are becoming more important.[1] Phenanthridine derivatives have
attracted considerable attention in medicinal chemistry and in material science
because of their biological activity and their presence in a variety of significant natu-
ral products and synthetic dyestuffs.[2] The development of new, efficient methods to
synthesize N-heterocycles with structural diversity is one major interest of modern
synthetic organic chemists.[3]
1,4-Dipolar cycloaddition provides an efficient and convenient route for the
synthesis of six-membered heterocyclic compounds. However, these reactions have
received only scant attention when compared to the related 1,3-dipolar cycloaddition
Received February 22, 2011.
Address correspondence to Hossein Mehrabi, Department of Chemistry, Rafsanjan Vali-e-Asr
University, Rafsanjan 77176, Iran. E-mail: mehraby_h@yahoo.com
611

612
H. MEHRABI AND M. HATAMI-POUR
Scheme 1. Reaction of phenanthridine, dialkyl acetylenedicarboxylates, and arylidenemalononitriles.
reactions. Extensive work has been done on the reactivities of 1,4-dipoles derived
from dimethyl acetylenedicarboxylate (DMAD) and nucleophiles such as phos-
phines,[4] isocyanides,[5] dimethoxycarbene,[6] nitrogen heterocycles,[7] and nucleophi-
lic heterocyclic carbenes (NHC).[8] These studies have led to a number of interesting
carbon–carbon bond-forming reactions and heterocyclic constructions.[9] The
addition of quinoline–DMAD zwitterion to aldehydes, diaryl 1,2-diones, and
arylidenemalononitriles has also been reported to afford three-component addition
products.[10]
To the best of our knowledge, there has not been any report on the reaction
between phenantridine and activated acetylenes in the presence of arylidenemalononi-
triles. We herein report a hitherto unknown three-component reaction of phenantridine,
dialkyl acetylenedicarboxylates (DAADs), and arylidenemalononitriles after stirring in
dry dichloromethane for 24 h to afford substituted pyrido[1,2-f]phenanthridines
(Scheme 1, Table 1).
The structures of the products 4a–h were deduced from their elemental analy-
1
1
ses, infrared (IR), H NMR, and 13C NMR spectra. For example, in the H NMR
spectrum of 4c, signals due to the methoxy carbonyl protons were observed as sharp
singlets at d 3.57 and 3.82 ppm. The two methine protons were discernible as two
single signals at d 5.10 and 5.88 ppm. The aromatic protons resonated in the region
d 6.97–8.16 ppm. The 13C NMR spectrum of compound 4c exhibited 27 distinct
signals, in agreement with the proposed structure. In the IR spectrum, the ester car-
bonyl absorptions were observed at 1743 and 1716 cmꢀ1 and 2364 cmꢀ1 for cyanide
1
groups. Also, the H and 13C NMR spectra of the other compounds 4a–h were
similar to those of 4c, except for the aromatic moiety and the ester groups, which
exhibited characteristic signals with appropriate chemical shifts.
Table 1. Reaction of phenantridine, dialkyl acetylenedicarboxylates, and
arylidenemalononitriles
4
R1
R2
Product
a
b
c
4-Br
4-F
Et
Et
4-Br
4-Cl
Me
Me
Et
d
e
4-Cl
f
2,4-Cl2
3-NO2
4-NO2
Me
Me
Me
g
H

FUNCTIONALIZED PYRIDO[1,2-f]PHENANTHRIDINES
613
Scheme 2. Suggested mechanism for formation of compounds 4.
Scheme 3. Reaction between phenanthridine and dialkyl acetylenedicarboxylates.
In the absence of any theoretical studies, the mechanistic details of the reaction
are not fully understood. The initial event is the formation of dipolar species 5 from
phenanthiridin and dialkyl acetylenedicarboxylates. Reaction of 1,4-dipolar cycload-
=
dition of 5 with the electrophilic C C of the arylidenemalononitriles affords
pyrido[1,2-f]phenanthridines. Alternatively, the reaction may take place in two steps.
The zwitterion 5 may add to the arylidenemalononitriles to form the intermediate 6,
which then undergoes cyclization to give the products 4 (Scheme 2).
We also investigate the reaction between phenantridine and dialkyl acetylene-
dicarboxylates. After stirring the reaction mixture in dichloromethane for 24 h and
column chromatography, compounds 7 were obtained in 50–53% yields (Scheme 3).
In summary we report herein a simple route for the synthesis of substituted
pyrido[1,2-f]phenanthridines by one-pot, three-component reaction of phenantri-
dine, dialkyl acetylenedicarboxylates, and arylidenemalononitriles. Not only is the
reaction performed under neutral conditions, but also the substances can be mixed
without any modification or purification.

614
H. MEHRABI AND M. HATAMI-POUR
EXPERIMENTAL
The chemicals used in this work were purchased from Merck and Aldrich
chemical companies. Melting points were determined using a Mettler FP5 apparatus
and are uncorrected. IR spectra were determined using KBr pellets on a Shimadzu
1
recording spectrophotometer, model 435. H and 13C NMR (400 and 100 MHz)
spectra were recorded on a Bruker 400 spectrometer in CDCl3 with tetramethylsilane
(TMS) as internal standard. Elemental analyses were performed using a Carlo Erba
EA 1108 instrument.
Representative Experimental Procedure
Diethyl acetylenedicarboxylate (82.51 mg, 0.50 mmol) in dry dichloromethane
(5 mL) was added dropwise to a mixture of 2-(4-bromobenzylidene)malononitrile
2a (116.0 mg, 0.50 mmol) and phenanthridine (89.5 mg, 0.50 mmol) in dry dichloro-
methane (10 mL) at room temperature. The reaction mixture was stirred for a further
24 h. Removal of the solvent followed by purification of the reaction mixture by
column chromatography (silica gel, 100–200 mesh; 90:10 n-hexane = ethyl acetate)
afforded 4a as a yellow solid, which could be recrystallized from ethyl acetate =
hexane (1:1).
Diethyl-8-(4-bromophenyl)-9,9-dicyano-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4a)
Yield ¼ 198 mg, 34%. Mp ¼ 260–262 ꢁC. IR (KBr) tmax: 3077, 2980, 2364,
1738, 1694, 1589, 1490, 1267, 1122, 728 cmꢀ1 1H NMR (400 MHz, DMSO):
.
d ¼ 8.13 (d, j ¼ 7.6 Hz, 1H), 8.01 (d, j ¼ 7.6 Hz, 1H), 7.67 (d, j ¼ 8 Hz, 2H), 7.60
(dd, j ¼ 7.6 Hz, 2H), 7.53 (d, j ¼ 7.6 Hz, 1H), 7.33 (dd, j ¼ 8 Hz, 3H), 7.13 (dd,
j ¼ 7.6 Hz, 1H), 6.97 (d, j ¼ 7.6 Hz, 1H), 5.88 (s, 1H), 5.09 (s, 1H), 4.36 (q,
j ¼ 7.2, 1H), 4.22 (q, j ¼ 7.2, 1H), 3.98 (q, j ¼ 7.2, 2H), 1.22 (t, j ¼ 7.2, 3H), 0.98
(t, j ¼ 7.2, 3H) ppm. 13C NMR (100 MHz, DMSO): d ¼ 164.4, 163.7, 142.7,
137.9, 135.0, 132.2, 131.1, 130.5, 130.4, 129.3, 128.7, 126.0, 124.9, 124.0, 123.5,
122.9, 122.6, 122.3, 117.0, 113.9, 112.1, 62.9, 61.9, 61.6, 50.7, 46.6, 13.9 ppm. Anal.
calcd. for C31H24BrN3O4 (582.44): C, 63.93; H, 4.15; N, 7.21. Found: C, 63.72; H,
4.17; N, 7.20.
Diethyl-8-(4-fluorophenyl)-9,9-dicyano-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4b)
Yield ¼ 163 mg, 31%. Mp ¼ 261–263 ꢁC. IR (KBr) tmax: 3076, 2983, 2248, 1738,
1699, 1601, 1506, 1446, 1267, 1124, 760 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.12
(d, j ¼ 7.6 Hz, 1H), 8.02 (d, j ¼ 7.6 Hz, 1H), 7.60 (dd, J ¼ 8 Hz, 2H), 7.52 (dd,
j ¼ 7.6 Hz, 1H), 7.39 (dd, j ¼ 7.6 Hz, 2H), 7.35 (dd, j ¼ 8 Hz, 3H), 7.11 (dd, j ¼ 7.6 Hz,
Hz, 1H), 6.98 (d, j ¼ 7.6 Hz, 1H), 5.87 (s, 1H), 5.10 (s, 1H), 4.38 (q, j ¼ 7.2, 1H), 4.21
(q, j ¼ 7.2, 1H), 3.96 (q, j ¼ 7.2, 2H), 1.22 (t, j ¼ 7.2, 3H), 0.97 (t, j ¼ 7.2, 3H) ppm.
13C NMR (100 MHz, DMSO): d ¼ 164.5, 163.7, 161.5, 154.0, 142.2, 138.0, 131.9,
131.0, 130.4, 129.3, 128.6, 126.1, 124.9, 123.9, 123.5, 122.3, 117.0, 116.3, 116.0,

FUNCTIONALIZED PYRIDO[1,2-f]PHENANTHRIDINES
615
114.0, 112.1, 79.6, 62.8, 61.9, 61.6, 50.6, 46.8, 13.9, 13.9 ppm. Anal. calcd. for
C31H24FN3O4 (521.54): C, 71.39; H, 4.64; N, 8.06. Found: C, 71.64; H, 4.61; N, 8.05.
Dimethyl-8-(4-bromophenyl)-9,9-dicyano-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4c)
Yield ¼ 194 mg, 35%. Mp ¼ 224–226 ꢁC. IR (KBr) tmax: 3069, 2952, 2364, 1743,
1716, 1597, 1491, 1438, 1269, 1082, 756 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.16
(d, j ¼ 7.2 Hz, 1H), 8.03 (d, j ¼ 7.6 Hz, 1H), 7.67 (d, j ¼ 8 Hz, 2H), 7.60 (dd, j ¼ 7.6 Hz,
2H), 7.53 (dd, j ¼ 7.2 Hz, 1H), 7.33 (dd, j ¼ 8 Hz, 3H), 7.13 (dd, j ¼ 7.2 Hz, 1H), 6.97
(d, j ¼ 7.2 Hz, 1H), 5.88 (s, 1H), 5.10 (s, 1H), 3.82 (s, 3H), 3.57 (s, 3H) ppm. 13C
NMR (100 MHz, DMSO): d ¼ 164.9, 164.4, 143.0, 137.3, 135.1, 132.3, 131.1,
130.7, 130.3, 129.3, 128.7, 126.0, 125.0, 124.1, 123.6, 122.8, 122.6, 122.3, 116.8,
113.9, 112.0, 79.6, 61.9, 53.9, 53.0, 50.6, 47.0 ppm.
Dimethyl-8-(4-chlorophenyl)-9,9-dicyano-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4d)
Yield 167 mg, 33%. Mp ¼ 224–226 ꢁC. IR (KBr) tmax: 3063, 2985, 2273, 1735,
1706, 1600, 1511, 1443, 1263, 1121, 763 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.13
(d, j ¼ 7.6 Hz, 1H), 8.01 (d, j ¼ 8.0 Hz, 1H), 7.61 (dd, j ¼ 8.0 Hz, 2H), 7.54 (d, j ¼ 8 Hz,
2H), 7.53 (dd, j ¼ 7.6 Hz, 1H), 7.36 (d, j ¼ 8 Hz, 2H), 7.33 (dd, j ¼ 8 Hz, 1H), 7.13 (dd,
j ¼ 7.6 Hz, 1H), 6.92 (d, j ¼ 7.6 Hz, 1H), 5.88 (s, 1H), 5.12 (s, 1H), 3.82 (s, 3H), 3.57
(s, 3H), ppm. 13C NMR (100 MHz, DMSO): d ¼ 165.0, 164.3, 142.1, 136.5, 134.6,
134.0, 131.1, 130.7, 130.3, 129.4, 128.7, 125.9, 124.9, 124.1, 123.5, 122.8, 122.5,
121.1, 116.8, 114.0, 112.7, 78.4, 61.9, 53.9, 52.9, 50.5, 47.0 ppm. Anal. calcd. for
C29H20ClN3O4 (509.94): C, 68.30; H, 3.95; N, 8.24. Found: C, 68.41; H, 3.97; N, 8.21.
Diethyl-8-(4-chlorophenyl)-9,9-dicyano-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4e)
Yield 177 mg, 33%. Mp ¼ 246–247 ꢁC. IR (KBr) tmax: 3073, 2981, 2366, 1738,
1696, 1591, 1492, 1447, 1268, 1092, 762 cmꢀ1. d ¼ 8.13 (d, j ¼ 7.6 Hz, 1H), 8.01 (d,
j ¼ 8 Hz, 1H), 7.60 (d, j ¼ 8.0 Hz, 2H), 7.54 (d, j ¼ 8.0 Hz, 2H), 7.52 (dd, j ¼ 7.6 Hz,
1H), 7.36 (d, j ¼ 8 Hz, 2H), 7.34 (dd, j ¼ 7.6 Hz, 1H), 7.14 (dd, j ¼ 7.6 Hz, 1H),
6.92 (d, j ¼ 7.6 Hz, 1H), 5.88 (s, 1H), 5.11 (s, 1H), 4.36 (q, j ¼ 7.2, 1H), 4.22 (q,
j ¼ 7.2, 1H), 3.98 (q, j ¼ 7.2, 2H), 1.22 (t, j ¼ 7.2, 3H), 0.98 (t, j ¼ 7.2, 3H), ppm.
13C NMR (100 MHz, DMSO): d ¼ 164.7, 163.3, 159.2, 151.1, 143.6, 137.7, 131.9,
131.3, 130.6, 129.1, 128.6, 126.5, 125.0, 123.9, 123.6, 122.4, 117.6, 116.9, 116.2,
113.6, 112.1, 77.6, 62.1, 61.9, 61.5, 51.3, 47.2, 13.9, 13.9 ppm.
Dimethyl-9,9-dicyano-8-(2,4-dichlorophenyl)-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4f)
Yield 195 mg, 36%. Mp ¼ 213–214 ꢁC. IR (KBr) tmax ¼ 3072, 2987, 2265, 1736,
1702, 1604, 1504, 1439, 1257, 1118, 760 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.15
(d, j ¼ 6.8 Hz, 1H), 8.04 (d, j ¼ 7.6 Hz, 1H), 7.78 (s, 1H), 7.61 (d, j ¼ 8 Hz, 2H), 7.55

616
H. MEHRABI AND M. HATAMI-POUR
(dd, j ¼ 7.6 Hz, 2H), 7.36 (d, j ¼ 6.8 Hz, 1H), 7.32 (d, j ¼ 8 Hz, 1H), 7.19 (dd,
j ¼ 7.6 Hz, 1H), 7.00 (d, j ¼ 6.8 Hz, 1H), 6.01 (s, 1H), 5.71 (s, 1H), 3.82 (s, 3H),
3.59 (s, 3H), ppm. 13C NMR (100 MHz, DMSO): d ¼ 164.7, 164.4, 143.9, 137.4,
135.5, 134.6, 132.8, 131.1, 130.9, 130.8, 130.3, 130.0, 129.5, 128.7, 128.3, 125.6,
125.1, 124.3, 123.6, 122.8, 122.5, 116.7, 113.4, 112.3, 62.4, 53.9, 53.0, 45.7,
45.6 ppm. Anal. calcd. for C29H19Cl2N3O4 (544.38): C, 63.98; H, 3.52; N, 7.72.
Found: C, 64.03; H, 3.51; N, 7.19.
Dimethyl-9,9-dicyano-8-(4-nitrophenyl)-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4g)
Yield 177 mg, 34%. Mp ¼ 235–237 ꢁC. IR (KBr) tmax: 3063, 2987, 2356, 1734,
1698, 1590, 1497, 1432, 1267, 1091, 760 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.31
(d, J ¼ 8.0 Hz, 2H), 8.16 (d, J ¼ 6.8 Hz, 1H), 8.03 (d, J ¼ 7.6 Hz, 1H), 7.81 (t,
J ¼ 7.6 Hz, 2H), 7.62 (dd, J ¼ 8.0 Hz, 2H), 7.55 (d, J ¼ 6.8 Hz, 1H), 7.38 (dd,
J ¼ 7.6, 1H), 7.16 (dd, J ¼ 7.6 Hz, 1H), 6.59 (d, J ¼ 6.8 Hz, 1H), 5.93 (s, 1H), 5.36
(s, 1H), 3.84 (s, 3H), 3.57 (s, 3H) ppm. 13C NMR (100 MHz, DMSO): d ¼ 164.8,
163.9, 143.2, 137.6, 134.1, 133.5, 131.2, 130.8, 130.1, 129.3, 128.8, 125.0, 124.5,
124.0, 123.3, 122.6, 121.7, 121.5, 116.7, 114.4, 112.0, 76.5, 60.2, 54.2, 52.3, 50.5,
48.1 ppm. Anal. calcd. for C29H20N4O6 (520.49): C, 66.92; H, 3.87; N, 10.76. Found:
C, 66.83; H, 3.89; N, 10.73.
Diethyl-9,9-dicyano-8-(4-nitrophenyl)-9,9a-dihydro-8H-
pyrido[1,2-f]phenanthridine-6,7-dicarboxylate (4h)
Yield 180 mg, 33%. Mp ¼ 233–235 ꢁC. IR (KBr) tmax: 3056, 2991, 2347, 1738,
1694, 1593, 1491, 1428, 1271, 1083, 764 cmꢀ1.1H NMR (400 MHz, DMSO): d ¼ 8.31
(d, J ¼ 8.0 Hz, 2H), 8.15 (d, J ¼ 6.8 Hz, 1H), 8.03 (d, J ¼ 7.6 Hz, 1H), 7.81 (t,
J ¼ 7.6 Hz, 2H), 7.63 (dd, J ¼ 8.0 Hz, 2H), 7.56 (d, J ¼ 6.8 Hz, 1H), 7.38 (dd,
J ¼ 7.6 Hz, 1H), 7.16 (dd, J ¼ 7.6 Hz, 1H), 7.00 (d, J ¼ 6.8 Hz, 1H), 5.94 (s, 1H),
5.36 (s, 1H), 4.35 (q, J ¼ 7.2 Hz, 1H), 4.22 (q, J ¼ 7.2 Hz, 1H), 3.98 (q, J ¼ 7.2 Hz,
2H), 1.23 (t, J ¼ 7.2 Hz, 3H), 0.96 (t, J ¼ 7.2 Hz, 3H) ppm. 13C NMR (100 MHz,
DMSO): d ¼ 164.4, 163.7, 143.3, 137.9, 137.7, 131.2, 130.6, 130.3, 130.0, 129.4,
128.8, 125.8, 125.0, 124.4, 124.2, 123.6, 122.3, 122.2, 117.0, 113.6, 111.9, 79.6,
63.0, 61.9, 61.8, 50.4, 46.4, 13.9, 13.9 ppm. Anal. calcd. for C31H24N4O6 (548.55):
C, 67.88; H, 4.41; N, 10.21. Found: C, 67.96; H, 4.42; N, 10.19.
Tetraethyl-9aH-pyrido[1,2-f]phenanthridine-6,7,8,9-tetracarboxylate
(7a)
Yield ¼ 258 mg, 50%. Mp ¼ 179–181 ꢁC. IR (KBr) tmax: 2981, 2935, 1742, 1701,
1603, 1486, 1443, 1367, 1235, 1029, 762 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.03
(d, J ¼ 7.2 Hz, 1H,), 7.97 (d, J ¼ 7.6 Hz, 1H), 7.53 (dd, J ¼ 7.2 Hz, 1H), 7.48 (dd,
J ¼ 7.2 Hz, 2H), 7.44 (dd, J ¼ 7.2 Hz, 1H), 7.26 (d, J ¼ 7.6 Hz, 1H), 7.05 (d,
J ¼ 7.2 Hz, 1H), 5.68 (s, 1H), 4.25 (q, J ¼ 7.6 Hz, 2H), 4.13 (q, J ¼ 7.6 Hz, 2H),
3.96 (q, J ¼ 7.6 Hz, 2H), 3.90 (q, J ¼ 7.6 Hz, 2H), 1.31 (t, J ¼ 7.6 Hz, 3H), 1.12 (t,
J ¼ 7.6 Hz, 3H), 1.06 (t, J ¼ 7.6 Hz, 3H), 0.88 (t, J ¼ 7.6 Hz, 3H) ppm. 13C NMR

FUNCTIONALIZED PYRIDO[1,2-f]PHENANTHRIDINES
617
(100 MHz, DMSO): d ¼ 166.3, 163.8, 162.8, 161.8, 151.0, 139.6, 137.5, 134.9, 131.4,
130.9, 129.5, 129.3, 129.0, 128.6, 125.4, 124.6, 124.1, 123.1, 110.0, 98.1, 79.6, 62.4,
61.5, 60.9, 56.2, 14.3, 14.1, 14.1, 13.6 ppm. Anal. calcd. for C29H29NO8 (519.54):
C, 67.04; H, 5.63; N, 2.70. Found: C, 67.11; H, 5.67; N, 2.69.
Tetramethyl-9aH-pyrido[1,2-f]phenanthridine-6,7,8,9-
tetracarboxylate (7b)
Yield ¼ 245 mg, 53%. Mp ¼ 273–274 ꢁC. IR (KBr) tmax: 3010, 2954, 1737, 1705,
1604, 1511, 1438, 1358, 1241, 1131 760 cmꢀ1. 1H NMR (400 MHz, DMSO): d ¼ 8.03
(d, 1H, J ¼ 7.2 Hz), 7.97 (d, 1H, J ¼ 7.6 Hz), 7.40–7.53 (m, 4H), 7.25 (d, 1H,
J ¼ 7.6 Hz), 7.15 (d, 1H, J ¼ 7.6 Hz), 5.68 (s, 1H), 3.80 (s, 3H), 3.65 (s, 3H), 3.52
(s, 3H), 3.50 (s, 3H) ppm. 13C NMR (100 MHz, DMSO): d ¼ 165.7, 163.4, 161.1,
160.4, 152.3, 138.4, 136.8, 135.2, 132.9, 130.4, 129.9, 129.1, 128.6, 128.0, 126.7,
125.5, 124.8, 121.3, 107.5, 99.7, 76.6, 56.3, 55.9, 53.6, 52.0 ppm. Anal. calcd. for
C25H21NO8 (463.44): C, 64.79; H, 4.57; N, 3.02. Found: C, 64.72; H, 4.57; N, 3.01.
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