Facile synthesis of 7-methoxy-2-aryl-3-phenyl/or-H-8-[2-(4,6-dimethyl-3,5- dicarbethoxy-pyridyl)]-4H-1-benzopyran-4-ones

Article abstract of DOI:10.1080/00397910601133581

Condensation of 8-formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-ones (5a-f) with ethyl-3-aminocrotonate (6) in glacial acetic acid under Hantzsch conditions afforded 7-methoxy-2-aryl-3-phenyl/or-H-8-[2-(4,6-dimethyl-3,5-dicarbethoxy- pyridyl)]-4H-1-benzopyran-4-ones (7a-f) in good yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910601133581

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Facile Synthesis of
7‐Methoxy‐2‐aryl‐3‐phenyl/
or‐H‐8‐[2‐(4,6‐dimethyl‐3,5‐dicarbethoxy‐pyridyl
Anil Kumar Soni a , G. L. David Krupadanam a & G. Srimannarayana a
a Department of Chemistry , Osmania University , Hyderabad, AP, India
Published online: 09 Mar 2007.
To cite this article: Anil Kumar Soni , G. L. David Krupadanam & G. Srimannarayana (2007) Facile Synthesis
of 7‐Methoxy‐2‐aryl‐3‐phenyl/or‐H‐8‐[2‐(4,6‐dimethyl‐3,5‐dicarbethoxy‐pyridyl)]‐4H‐1‐benzopyran‐4‐ones,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
37:5, 795-804, DOI: 10.1080/00397910601133581
To link to this article: http://dx.doi.org/10.1080/00397910601133581
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Synthetic Communicationsw, 37: 795–804, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910601133581
Facile Synthesis of 7-Methoxy-2-aryl-3-
phenyl/or-H-8-[2-(4,6-dimethyl-3,5-
dicarbethoxy-pyridyl)]-4H-1-benzopyran-
4-ones
Anil Kumar Soni, G. L. David Krupadanam,
and G. Srimannarayana
Department of Chemistry, Osmania University, Hyderabad, India
Abstract: Condensation of 8-formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-ones
(5a–f) with ethyl-3-aminocrotonate (6) in glacial acetic acid under Hantzsch con-
ditions
bethoxy-pyridyl)]-4H-1-benzopyran-4-ones (7a–f) in good yields.
afforded
7-methoxy-2-aryl-3-phenyl/or-H-8-[2-(4,6-dimethyl-3,5-dicar-
Keywords: 4H-1-benzopyran-4-ones, pyridylfarones
INTRODUCTION
Substituted flavones, chromones, chalcones, and flavonones have been recog-
nized as important classes of bioactive heterocyclics. 4-Aryl-1,4-dihydropyr-
idines obtained by the Hantzsch synthesis[1] were found to be highly
effective calcium antagonists.[2] For example, nifedipine and its analogs
nicordipine[3] and nimodipine[4] are powerful calcium antagonists, which
lower the frequency of attack of angina pectoris and reduces blood
pressure.[3] Its activity is due to its coronary vasodilatory effect. The
recent interest in dihydropyridines is due to the co-enzyme NADH,
reduced nicotinamide adenine dinucleotide, which has unique activity to
Received July 21, 2006
Address correspondence to G. Srimannarayana, Department of Chemistry, Osmania
University, Hyderabad 500 007 AP, India. E-mail: soni_chem@yahoo.com
795

796
A. K. Soni, G. L. D. Krupadanam, and G. Srimannarayana
reduce stereoselectively unsaturated functional groups such as carbonyl and
conjugated olefins.[5]
In view of the diverse biological activity shown by 1,4-dihydropyridines,
we planned a simple route to synthesize 8-pyridyl-substituted flavones (7a–f).
Synthesis of some of the target molecules by other routes were reported
earlier. Reaction of substituted salicyaldehydes with ethyl-3-aminocrotonate
in acetic acid medium gave coumarin fused to pyridines.[6] Reaction of
chromone-3-carboxaldehyde with methyl acetoacetate and ammonia in
methanol gave 1,4-dihydropyridyl chromones.[7] The synthesis of
chromones fused to pyrano-pyridines fused at 7 : 8 by the reaction of
7-hydroxy-8-formyl-2,3-dimethyl chromones with ethyl-3-aminocrotonate in
acetic acid under Hantzsch conditions.[8] Irradiation of 4-aryl/alkyl-1,4-dihy-
dropyridine derivatives results in the formation of a pyridine product by dehy-
drogenation.[9] Oxygen plays an important role in oxidation. Ceric ammonium
nitrate (CAN) can also oxidize the dihydropyridines to pyridine derivatives
with stirring at room temperature.
In this article, we report the synthesis of 7-methoxy-2-aryl-3-phenyl/
or-H-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-pyridyl)]-4H-1-benzopyran-4-ones
(7a–f) and 8-formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-ones (5a–f).
7-Hydroxy-2-phenyl-4H-1-benzo- pyran-4-ones (1a–f) on reaction with
hexamine (2) in glacial acetic acid (Duff reaction)[10] gave 8-formyl-7-
hydroxy-2-phenyl-4H-1-benzopyran-4-ones (3a–f).
Compounds 3a–f and dimethylsulphate (4) in acetone–K2CO3 medium
refluxed in a steam bath for 6–8 h gave 8-formyl-7-methoxy-2-phenyl-4H-
1-benzopyran-4-ones (5a–f). Compound 5a is characterized from its
spectral data. In MS, it showed a quasi-molecular ion peak at m/z-357. Its
IR spectrum showed peaks due to the aldehyde carbonyl group (C55O) at
1693 cm21 and at 1609 cm21 due to flavone carbonyl group (C55O). Its UV
spectrum showed absorption maxima at 315 nm (log 1 4.26), 256 nm (log 1
4.36), and 229 nm (log 1 4.22). In its 1H NMR spectrum, recorded in
CDCl3 (200 MHz), the H-5 proton resonated at d 8.40 (d, J ¼ 10 Hz)
whereas the H-6 proton resonated at d 7.00 (d, J ¼ 10 Hz). The C-7
methoxy group protons (7-OCH3) appeared at d 4.10 as singlet, and the C-8
carboxaldehyde proton (8-CHO) appeared at d 10.60 as singlet. Aromatic
protons appeared at d 7.10–7.50 (10H) as multiplet. Its 13C NMR spectrum,
recorded in CDCl3 (50.3 M Hz), showed a chemical shift at d 186.05 due to
carbonyl carbon of carboxaldehyde. The peak at d 178.10 is due to flavone
carbonyl carbon. The oxymethine carbons C-2, C-7, and C-8a resonated at d
168.50, 163.20, and 161.05, respectively, and the methoxyl carbon resonated
at d 56.30. Other carbons resonated at d 106.75 (C-3), 128.05 (C-5), 107.05
(C-6), 110.05 (C-8), 117.50 (C-4a), C-10 (129.50), 126.50 (C-20 & C-60),
128.40 (C-30 & C-50), 132.02 (C-40), 131.50 (C-100), 130.75 (C-200 & C-600),
128.05 (C-300 & C-500), and 127.50 (C-400) respectively.
8-Formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-ones (5a–f) were
condensed with 2 equivalent moles of ethyl-3-aminocrotonate (6) in glacial

Facile Synthesis
797
acetic acid under Hantzsch conditions to afford 7-methoxy-2-aryl-3-phenyl/
or-H-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-pyridyl)]-4H-1-benzopyran-4-
ones (7a–f) (Scheme 1). Compound 7a is characterized from its spectral data.
In MS, it showed a quasi-molecular ion peak at m/z-578. Its IR spectrum
showed two peaks at 1731 cm21 due to the ester carbonyl group (C55O)
and 1644 cm21 due to the carbonyl group (C55O) of flavone. Its UV
spectrum showed absorption maxima at 312 nm (log 1 4.69) and 242 nm
1
(log 1 4.93). Its H NMR spectrum, recorded in CDCl3 (200 MHz), showed
the characteristic peaks of the heterocyclic substituted pyridyl ring attached
to the eighth position of the flavone ring. It showed two singlets at d 2.40
and d 2.65 due to the C-4000-methyl and C-6000-methyl of the pyridine ring.
The protons of 3000-O-CH2-CH3 and 5000-O-CH2-CH3 resonate at d 4.45
and d 4.00 as quartets (J ¼ 7.0 Hz). The protons of 3000-O-CH2-CH3 and
5000-O-CH2-CH3 resonate at d 1.48 and d 0.90 as triplets. The C-7 methoxy
group protons (7-OCH3) appeared at d 3.85 as a singlet. The H-5 proton
Scheme 1.

798
A. K. Soni, G. L. D. Krupadanam, and G. Srimannarayana
resonated at d 8.35 as a doublet (J ¼ 10 Hz). Aromatic protons appeared at d
7.05–7.40 (11H) as a multiplet (side phenyl protons and C6-H). Its 13C NMR
spectrum, recorded in CDCl3 (50.3 MHz), showed characteristic peaks of the
newly formed pyridyl ring. The two methyl carbons of the pyridyl ring
appeared at 17.05 (C-4000) and at 23.75 (C-6000). It showed a chemical shift at
d 176.50 due to carbonyl carbon of flavone and carbonyl of carbethoxy
ester carbons at d 168.05 (C-5000-COOEt) and 166.50 (C-3000-COOEt). Sp3
carbons of 7a -COO-CH2-CH3 appeared at 62.05 (C-5000) and at 61.50
(C-3000), and -COO-CH2-CH3 carbons appeared at 14.05 (C-5000) and at 13.10
(C-3000). The pyridyl ring carbons resonated at d 129.05 (C-1000), 161.05
(C-6000), 155.75 (C-4000), 122.02 (C-3000), and 122.02 (C-5000). The oxymethine
carbons C-2, C-7, and C-8a resonated at d 154.50, 149.50, and 143.75, respect-
ively, and the methoxyl carbon resonated at d 56.05. Other Sp2 carbons
resonated at d 109.02 (C-3), 109.02 (C-6), 129.15 (C-5), 116.50 (C-8),
117.50 (C-4a), C-10 (129.50), 127.20 (C-20 & C-60), 128.10 (C-30 & C-50),
131.02 (C-40), 132.75 (C-100), 129.75 (C-200 & C-600), 131.05 (C-300 & C-500),
and 131.02 (C-400).
EXPERIMENTAL
Melting points were determined on a Polmon instrument (model no. MP 96).
IR spectra were recorded on FT-IR Perkin-Elmer 1605 spectrometer, and
1H NMR (200 MHz) and 13C NMR (50.3 MHz) were recorded on a Varian
Gemini 200 spectrometer using TMS as internal standard (chemical shifts in
d ppm). UV spectra were obtained on a Shimadzu UV-visible spectropho-
tometer (model UV-1601). Mass spectra were recorded on a VG micromass
70-70H instrument.
General Procedure
7-Hydroxy-2-phenyl-4H-1-benzopyran-4-ones (1a–f) by Modified
Baker–Venkataraman Transformation
A mixture of resacetophenone (1.52 g, 10 mmol), benzoylchloride (2.80 g,
20 mmol), anhydrous potassium carbonate (10 g), and acetone (200 ml) was
refluxed for 8–10 h by a modified Baker–Venkataraman transformation to
give the intermediate diketone, which on treatment with aqueous potassium
carbonate underwent cyclisation to give 7-benzoyloxy-2-phenyl-4H-1-benzo-
pyran-4-one (not isolated). The 7-benzoyloxy group was further hydrolyzed
by alkali to give 7-hydroxy-2-phenyl-4H-1-benzopyran-4-ones (1a–f) in
70% yield. Compounds 1a–c and 1e are known and were reported in
literature, and 1d and 1f are new. Their analytical and spectral data are
presented here.

Facile Synthesis
Data
799
2-(2-Chlorophenyl)-7-hydroxy-4H-1-benzopyran-4-one (1d): Recrystal-
lized from methanol as pale yellow crystals, mp 2108C (70%); IR (KBr)
3422 (OH) cm21, 1638 (C55O) cm21; UV (MeOH) 242 nm (log 1 3.98),
254 nm (log 1 3.94), and 304 nm (log 1 3.99). MS (EI) Mþ m/z at 272
1
(50%). H NMR (200 MHz) (CDCl3): d 6.55 (s, H-3), 7.00 (dd, J ¼ 10, 2.0,
H-6), 7.10 (s, H-8), 8.00 (d, J ¼ 10.0 Hz, H-5), 7.40–7.60 (m, 4H, aromatic
protons), 10.25 (s, OH). Anal. calcd. for C15H9O3Cl: C, 66.07; H, 3.33;
found C, 66.08; H, 3.34%.
7-Hydroxy-2-(2-phenoxyphenyl)-4H-1-benzopyran-4-one (1f): Recrystal-
lised from methanol as pale yellow coloured crystals, mp 2248C (70%); IR
(KBr) 3406 (OH) cm21, 1632 (C55O) cm21; UV (MeOH) 256 nm (log 1
4.04), 270 nm (log 1 3.99), and 308 nm (log 1 4.22). MS (EI) Mþ m/z at
1
330 (45%). H NMR (200 MHz) (CDCl3): d 6.70 (s, H-3), 7.00 (dd, J ¼ 10
2.0, H-6), 6.95 (s, H-8), 7.95 (d, J ¼ 10.0 Hz, H-5), 7.05–7.65 (m, 8H,
aromatic protons), 10.30 (s, OH). Anal. calcd. for C21H14O4: C, 76.36; H,
4.27; found C, 76.30; H, 4.29%.
General Procedure
8-Formyl-7-hydroxy-2-phenyl-4H-benzopyran-4-ones (3a–f)
A solution of 7-hydroxy-2-phenyl-4H-1-benzopyran-4-ones (10 mmol) (1a–f)
dissolved in glacial acetic acid (50 ml) was treated with hexamethylene tetra-
mmine (40 mmol) (HMT) and heated in a water bath for 6–8 h. The solution
is treated with hot dil. HCl (1 : 1) followed by further heating for 30 min. It
was diluted to 500 ml with water and left overnight in a refrigerator. The
reaction mixture was then extracted with ether, and the ethereal solution was
washed with sodiumbicarbonate solution and water. Concentration of the
dried ether extract furnished crude 8-formyl-7-hydroxy-2-phenyl-4H-1-benzo-
pyran-4-one (3a–f) in 72% yields. These were recrystallized from benzene as
pale yellow crystals. Compounds 3a–c and 3e are known and were reported in
literature, and 3d and 3f are new. Their analytical and spectral data are
presented here.
Data
2-(2-Chlorophenyl)-8-formyl-7-hydroxy–4H-1-benzopyran-4-one (3d):
Recrystallized from methanol as pale yellow crystals, mp 1448C (66%); IR
(KBr) 1675 (aldehyde . C55O) cm21, 1625 (flavone . C55O) cm21; UV
(MeOH) 306 nm (log 1 4.27), 262 nm (log 1 4.41), and 238 nm (log 1

800
A. K. Soni, G. L. D. Krupadanam, and G. Srimannarayana
1
4.50). MS (EI) Mþ m/z at 300 (45%). H NMR (200 MHz) (CDCl3): d 6.60
(s, H-3), 7.00 (d, J ¼ 10.0 Hz, H-6), 8.35 (d, J ¼ 10.0 Hz, H-5), 7.20–7.60
(m, 4H, aromatic protons), 10.50 (s, CHO), 12.45 (s, OH). Anal. calcd. for
C16H9O4Cl: C, 63.91; H, 3.02; found C, 63.93; H, 3.04%.
8-Formyl-7-hydroxy-2-(2-phenoxyphenyl)-4H-1-benzopyran-4-one (3f):
Recrystallized from methanol as pale yellow crystals, mp 1928C (65%); IR
(KBr) 1682 (aldehyde . C55O) cm21, 1633 (flavone . C55O) cm21; UV
(MeOH) 305 nm (log 1 4.50), 257 nm (log 1 4.55), and 233 nm (log 1
1
4.79). MS (EI) Mþ m/z at 356 (55%). H NMR (200 MHz) (CDCl3): d
6.75 (s, H-3), 7.00 (d, J ¼ 10.0 Hz, H-6), 8.35 (d, J ¼ 10.0 Hz, H-5), 7.05–
7.50 (m, 9H, aromatic protons), 10.50 (s, CHO), 12.40 (s, OH). Anal. calcd.
for C22H14O5: C, 73.74; H, 3.94; found C, 73.76; H, 3.96%.
General Procedure
8-Formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-ones (5a–f)
A mixture of 8-formyl-7-hydroxy-2-phenyl-4H-1-benzopyran-4-one (10 mmol)
(3a–f) and dimethylsulphate (10 mmol) dissolved in dry acetone (100 ml) con-
taining anhydrous potassium carbonate was refluxed in a water bath for 6–8 h.
Acetone solution is evaporated and the residual solid poured over crushed ice in
a beaker. On filtration, the crude solid separates and was recrystallized from
benzene to afford 8-formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-ones
(5a–f) as colorless crystals in 85% yields. Compounds 5a–f were characterized
by analytical and spectral data.
Data
2,3-Diphenyl-8-formyl-7-methoxy-4H-1-benzopyran-4-one (5a): Recrys-
tallized from methanol as pale yellow crystals, mp 148C (85%); IR (KBr)
1693 (aldehyde . C55O) cm21
(MeOH) 315 nm (log 1 4.26), 256 nm (log 1 4.36), and 229 nm (log 1
, ; UV
1609 (flavone . C55O) cm21
1
4.49). MS (EI) Mþ m/z at 356 (35%). H NMR (200 MHz) (CDCl3): d
7.00 (d, J ¼ 10.0 Hz, H-6), 8.40 (d, J ¼ 10.0 Hz, H-5), 7.10–7.50 (m, 10H,
aromatic protons), 10.60 (s, CHO), 4.10 (s, 3H, OMe). Anal. calcd. for
C23H16O4: C, 77.52; H, 4.53; found C, 77.53; H, 4.54%.
8-Formyl-7-methoxy-2-(4-methoxyphenyl)-3-phenyl-4H-1-benzopyran-4-
one (5b): Recrystallized from methanol as pale yellow crystals, mp 1958C
(82%); IR (KBr) 1670 (aldehyde . C55O) cm21, 1630 (flavone . C55O)
cm21; UV (MeOH) 315 nm (log 1 4.70), 254 nm (log 1 4.86), and 230 nm

Facile Synthesis
801
(log 1 4.59). MS (EI) Mþ m/z at 386 (45%). 1H NMR (200 MHz) (CDCl3): d
6.80 (d, J ¼ 10.0 Hz, H-6), 8.45 (d, J ¼ 10.0 Hz, H-5), 7.20–7.40 (m, 5H,
aromatic protons), 7.50 (d, 2H, J ¼ 9 Hz, H-20, 60), 7.10 (d, 2H, J ¼ 9 Hz,
H-30, 50), 10.65 (s, CHO), 4.10 (s, 3H, OMe), 3.95 (s, 3H, OMe). Anal.
calcd. for C24H18O5: C, 74.80; H, 4.70; found C, 74.82; H, 4.72%.
8-Formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-one (5c): Recrystal-
lized from methanol as pale yellow crystals, mp 2108C (84%); IR (KBr)
1693 (aldehyde . C55O) cm21
(MeOH) 316 nm (log 1 4.30), 248 nm (log 1 4.55), and 220 nm (log 1
,
1633 (flavone . C55O) cm21
;
UV
1
4.59). MS (EI) Mþ m/z at 280 (60%). H NMR (200 MHz) (CDCl3): d
6.75 (s, 1H), 7.05 (d, J ¼ 10.0 Hz, H-6), 8.35 (d, J ¼ 10.0 Hz, H-5), 7.50–
7.90 (m, 5H, aromatic protons), 10.70 (s, CHO), 4.05 (s, 3H, OMe), 3.95
(s, 3H, 400-OMe). Anal. calcd. for C17H12O4: C, 72.65; H, 4.32; found C,
72.67; H, 4.34%.
2-(2-Chlorophenyl)-8-formyl-7-methoxy-4H-1-benzopyran-4-one
(5d):
Recrystallized from methanol as pale yellow crystals, mp 1958C (78%); IR
(KBr) 1683 (aldehyde . C55O) cm21, 1636 (flavone . C55O) cm21; UV
(MeOH) 304 nm (log 1 4.30), 253 nm (log 1 4.54), and 222 nm (log 1
1
4.58). MS (EI) Mþ m/z at 314 (50%). H NMR (200 MHz) (CDCl3): d
6.85 (s, 1H), 7.05 (d, J ¼ 10.0 Hz, H-6), 8.40 (d, J ¼ 10.0 Hz, H-5), 7.30–
7.70 (m, 4H, aromatic protons), 10.50 (s, CHO), 4.10 (s, 3H, OMe). Anal.
calcd. for C17H11O4Cl: C, 64.86; H, 3.52; found C, 64.90; H, 3.54%.
8-Formyl-7-methoxy-2-(4-methoxyphenyl)-4H-1-benzopyran-4-one (5e):
Recrystallized from methanol as pale yellow crystals, mp 1688C (80%); IR
(KBr) 1685 (aldehyde . C55O) cm21, 1643 (flavone . C55O) cm21; UV
(MeOH) 308 nm (log 1 4.26), 254 nm (log 1 4.40) and 218 nm (log 1 4.46).
MS (EI) Mþ m/z at 310 (48%). 1H NMR (200 MHz) (CDCl3): d 6.65
(s, 1H, H-3), 7.05 (d, J ¼ 10.0 Hz, H-6), 8.40 (d, J ¼ 10.0 Hz, H-5), 8.05
(d, 2H, J ¼ 9 Hz, H-20, 60), 7.05 (d, 2H, J ¼ 9 Hz, H-30, 50), 10.65
(s, CHO), 4.10 (s, 3H, 7-OMe), 3.90 (s, 3H, 400-OMe). Anal. calcd. for
C18H14O5: C, 69.67; H, 4.55; found C, 69.69; H, 4.57%.
8-Formyl-7-methoxy-2-(2-phenoxyphenyl)-4H-1-benzopyran-4-one (5f):
Recrystallized from methanol as pale yellow crystals, mp 1598C (75%); IR
(KBr) 1688 (aldehyde . C55O) cm21, 1632 (flavone . C55O) cm21; UV
(MeOH) 310 nm (log 1 3.93), 261 nm (log 1 3.98), and 225 nm (log 1
1
4.08). MS (EI) Mþ m/z at 372 (45%). H NMR (200 MHz) (CDCl3): d
6.75 (s, 1H), 7.05 (d, J ¼ 10.0 Hz, H-6), 8.45 (d, J ¼ 10.0 Hz, H-5), 7.50–
7.90 (m, 9H, aromatic protons), 10.50 (s, CHO), 4.05 (s, 3H, OMe). Anal.
calcd. for C23H16O5: C, 74.19; H, 4.33; found C, 74.21; H, 4.35%.

802
A. K. Soni, G. L. D. Krupadanam, and G. Srimannarayana
General Procedure
7-Methoxy-2-aryl-3-phenyl/or-H-8-[2-(4,6-dimethyl-3,5-
dicarbethoxy-pyridyl)]-4H-1-benzopyran-4-ones (7a–f)
A mixture of 8-formyl-7-methoxy-2-phenyl-4H-1-benzopyran-4-one (5a–f)
(10 mmol) and ethyl-3-aminocrotonate (6) (20 mmol) in acetic acid (20 ml)
is kept at room temperature for 4 days with constant stirring. It was diluted
to 100 ml with ice-cold water and left overnight at room temperature. The
reaction mixture was then extracted with ethyl acetate to give a crude
product. Crude product on column chromatography over silica gel by
eluting with petroleum ether–ethyl acetate (v/v, 7 : 3) gave 7a–f in 75%
yields. Compounds 7a–f were characterized by analytical and spectral data.
Data
2,3-Diphenyl-7-methoxy-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-pyridyl)]-
4H-1-benzopyran-4-one (7a): Recrystallized from methanol as pale yellow
coloured crystals, mp 1408C (75%); IR (KBr) 1731 (ester . C55O) cm21
,
1644 (flavone . C55O) cm21; UV (MeOH) 312 nm (log 1 4.69), 242 nm
1
(log 1 4.93). MS (EI) Mþ m/z at 577 (35%). H NMR (200 MHz) (CDCl3):
d 8.35 (d, J ¼ 10.0 Hz, H-5), 7.05–7.40 (m, 11H, H-6 merged, aromatic
protons), 3.85 (s, 3H, 7-OMe), 4.45 (q, 2H, J ¼ 7 Hz, 3000-OCH2-CH3), 4.00
(q, 2H, J ¼ 7 Hz, 5000-OCH2-CH3), 2.65 (s, 3H, 6000-CH3), 2.40 (s, 3H, 4000-
CH3), 1.48 (t, 3H, 3000-OCH2-CH3), 0.90 (q, 2H, 5000-OCH2-CH3). Anal.
calcd. for C35H31NO7: C, 72.78; H, 5.41; N, 2.42; found C, 72.80; H, 5.43;
N, 2.44%.
7-Methoxy-2-(4-methoxyphenyl)-3-phenyl-8-[2-(4,6-dimethyl-3,5-dicar-
bethoxy-pyridyl)]-4H-1-benzopyran-4-one (7b): Recrystallized from
methanol as pale yellow crystals, mp 1828C (74%); IR (KBr) 1725
(ester . C55O) cm21, 1603 (flavone . C55O) cm21; UV (MeOH) 315 nm
1
(log 1 4.30), 249 nm (log 1 4.50). MS (EI) Mþ m/z at 507 (25%). H NMR
(200 MHz) (CDCl3): d 8.25 (d, J ¼ 10.0 Hz, H-5), 7.85 (d, 2H, J ¼ 9 Hz,
H-20, 60), 7.10–7.40 (m, 5H, aromatic protons), 6.95 (d, 2H, J ¼ 9 Hz, H-30,
50), 6.75 (d, J ¼ 10 Hz, H-6), 3.95 (s, 3H, 40-OMe), 3.75 (s, 3H, 7-OMe),
4.35 (q, 2H, J ¼ 7 Hz, 3000-OCH2-CH3), 3.95 (q, 2H, J ¼ 7 Hz, 5000-OCH2-
CH3), 2.75 (s, 3H, 6000-CH3), 2.25 (s, 3H, 4000-CH3), 1.45 (t, 3H, 3000-OCH2-
CH3), 1.05 (q, 2H, 5000-OCH2-CH3). Anal. calcd. for C36H31NO8: C, 71.16;
H, 5.47; N, 2.31; found C, 71.18; H, 5.49; N, 2.33%.
7-Methoxy-2-phenyl-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-pyridyl)]-4H-1-
benzopyran-4-one (7c): Recrystallized from methanol as pale yellow
crystals, mp 1758C (78%); IR (KBr) 1718 (ester . C55O) cm21, 1644

Facile Synthesis
803
(flavone . C55O) cm21; UV (MeOH) 310 nm (log 1 4.06), 243 nm (log 1
1
4.38). MS (EI) Mþ m/z at 501 (20%). H NMR (200 MHz) (CDCl3): d
8.30 (d, J ¼ 10.0 Hz, H-5), 7.05 (d, J ¼ 10 Hz, H-6), 6.75 (s, 1H, H-3),
7.60–8.05 (m, 5H, aromatic protons), 4.05 (s, 3H, 7-OMe), 4.50 (q, 2H,
J ¼ 7 Hz, 3000-OCH2-CH3), 4.05 (q, 2H, J ¼ 7 Hz, 5000-OCH2-CH3), 2.55
(s, 3H, 6000-CH3), 2.45 (s, 3H, 4000-CH3), 1.50 (t, 3H, 3000-OCH2-CH3), 1.05
(q, 2H, 5000-OCH2-CH3). Anal. calcd. for C29H27NO7: C, 69.45; H, 5.43; N,
2.79; found C, 69.47; H, 5.45; N, 2.81%.
2-(2-Chlorophenyl)-7-methoxy-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-
pyridyl)]-4H-1-benzopyran-4-one (7d): Recrystallized from methanol as
pale yellow crystals, mp 1728C (72%); IR (KBr) 1725 (ester . C55O)
cm21, 1610 (flavone . C55O) cm21; UV (MeOH) 312 nm (log 1 4.50),
1
237 nm (log 1 4.68). MS (EI) Mþ m/z at 535 (30%). H NMR (200 MHz)
(CDCl3): d 8.25 (d, J ¼ 10.0 Hz, H-5), 7.10 (d, J ¼ 10 Hz, H-6), 6.65
(s, 1H, H-3), 7.30–7.60 (m, 4H, aromatic protons), 3.95 (s, 3H, 7-OMe),
4.45 (q, 2H, J ¼ 7 Hz, 3000-OCH2-CH3), 3.95 (q, 2H, J ¼ 7 Hz, 5000-OCH2-
CH3), 2.60 (s, 3H, 6000-CH3), 2.40 (s, 3H, 4000-CH3), 1.45 (t, 3H, 3000-OCH2-
CH3), 0.90 (q, 2H, 5000-OCH2-CH3). Anal. calcd. for C29H26ClNO7: C,
64.99; H, 4.89; N, 2.61; found C, 65.01; H, 4.91; N, 2.63%.
7-Methoxy-2-(4-methoxyphenyl)-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-
pyridyl)]-4H-1-benzopyran-4-one (7e): Recrystallized from methanol as pale
yellow crystals, mp 1688C (75%); IR (KBr) 1724 (ester . C55O) cm21, 1625
(flavone . C55O) cm21; UV (MeOH) 313 nm (log 1 4.88), 232 nm (log 1
1
4.99). MS (EI) Mþ m/z at 531 (50%). H NMR (200 MHz) (CDCl3): d 8.25
(d, J ¼ 10.0 Hz, H-5), 7.05 (d, J ¼ 10 Hz, H-6), 6.75 (s, 1H, H-3), 7.40–
7.95 (m, 4H, aromatic protons), 4.05 (s, 3H, 40-OMe), 3.95 (s, 3H, 7-OMe),
4.40 (q, 2H, J ¼ 7 Hz, 3000-OCH2-CH3), 3.95 (q, 2H, J ¼ 7 Hz, 5000-OCH2-
CH3), 2.55 (s, 3H, 6000-CH3), 2.40 (s, 3H, 4000-CH3), 1.45 (t, 3H, 3000-OCH2-
CH3), 1.00 (q, 2H, 5000-OCH2-CH3). Anal. calcd. for C30H29NO8: C, 67.79;
H, 5.50; N, 2.64; found C, 67.81; H, 5.52; N, 2.66%.
7-Methoxy-2-(2-phenoxyphenyl)-8-[2-(4,6-dimethyl-3,5-dicarbethoxy-
pyridyl)]-4H-1-benzopyran-4-one (7f): Recrystallized from methanol as
pale yellow crystals, mp 1658C (70%); IR (KBr) 1725 (ester . C55O)
cm21, 1610 (flavone . C55O) cm21; UV (MeOH) 316 nm (log 1 4.88),
1
228 nm (log 1 4.99). MS (EI) Mþ m/z at 593 (45%). H NMR (200 MHz)
(CDCl3): d 8.25 (d, J ¼ 10.0 Hz, H-5), 7.05 (d, J ¼ 10 Hz, H-6), 6.75
(s, 1H, H-3), 7.10–7.60 (m, 9H, aromatic protons), 3.95 (s, 3H, 7-OMe),
4.45 (q, 2H, J ¼ 7 Hz, 3000-OCH2-CH3), 4.00 (q, 2H, J ¼ 7 Hz, 5000-OCH2-
CH3), 2.55 (s, 3H, 6000-CH3), 2.45 (s, 3H, 4000-CH3), 1.42 (t, 3H, 3000-OCH2-
CH3), 1.05 (q, 2H, 5000-OCH2-CH3). Anal. calcd. for C35H31NO8: C, 70.82;
H, 5.26; N, 2.36; found C, 70.84; H, 5.28; N, 2.38%.

804
A. K. Soni, G. L. D. Krupadanam, and G. Srimannarayana
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