Facile synthesis of 9-acetyl/formyl/cyano-substituted pyrano[2,3-f]flavones and chromones using the baylis-hillman reaction

Article abstract of DOI:10.1080/00397910903069681

Condensation of 8-formyl-7-hydroxyflavones (2a-f) and 8-formyl-7-hydroxy-2- (2'-furyl)-3-methylchromone (2g) with methyl vinyl ketone (3), acrolein (4), and acrylonitrile (5) in the presence of diazabicyclo[2.2.2]octane (DABCO) under an N₂ atmosphere at room temperature using Baylis-Hillman reaction conditions afforded 9-acetyl/formyl/cyano-substituted pyrano2,3-f]flavones (6a-f, 7a-f, 8a-f) and chromones (6g, 7g, 8g).

Full text of DOI:10.1080/00397910903069681

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Facile Synthesis of 9-Acetyl/Formyl/
Cyano-Substituted Pyrano[2,3-f]flavones
and Chromones Using the Baylis–Hillman
Reaction
S. Satyanarayana Reddy a & G. L. David Krupadanam a
a Department of Chemistry, Osmania University, Hyderabad, India
Published online: 07 Apr 2010.
To cite this article: S. Satyanarayana Reddy & G. L. David Krupadanam (2010) Facile Synthesis of
9-Acetyl/Formyl/Cyano-Substituted Pyrano[2,3-f]flavones and Chromones Using the Baylis–Hillman
Reaction, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 40:9, 1292-1304, DOI: 10.1080/00397910903069681
To link to this article: http://dx.doi.org/10.1080/00397910903069681
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Synthetic Communications1, 40: 1292–1304, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903069681
FACILE SYNTHESIS OF 9-ACETYL/FORMYL/
CYANO-SUBSTITUTED PYRANO[2,3-f]FLAVONES
AND CHROMONES USING THE BAYLIS–HILLMAN
REACTION
S. Satyanarayana Reddy and G. L. David Krupadanam
Department of Chemistry, Osmania University, Hyderabad, India
Condensation of 8-formyl-7-hydroxyflavones (2a–f) and 8-formyl-7-hydroxy-2-(20-furyl)-
3-methylchromone (2g) with methyl vinyl ketone (3), acrolein (4), and acrylonitrile (5) in
the presence of diazabicyclo[2.2.2]octane (DABCO) under an N2 atmosphere at room
temperature using Baylis–Hillman reaction conditions afforded 9-acetyl=formyl=
cyano-substituted pyrano2,3-f]flavones (6a–f, 7a–f, 8a–f) and chromones (6g, 7g, 8g).
Keywords: Acrolein; acrylonitrile; DABCO; 8-formyl-7-hydroxyflavones; ketone; methyl vinyl
INTRODUCTION
Substituted flavones, isoflavones, chromones, chalcones, and flavanones have
been recognized as important classes of bioactive heterocyclics. Many of the natural
and synthetic substituted flavones have biological activities such as vasodilatory,
diuretic, antioxidant, anticancer, anti-HIV, antiviral, anti-inflammatory, antiallergic,
central nervous system, and bacteriocidal activities.[1–5] Marketed flavonoid drugs
include flavoxate and demiflin, which are used as diuretics[6] and coronary vasodilators[7]
respectively. In view of the diverse bioactivity, new flavones with a pyran ring fused at
7,8-positions are now designed and synthesized starting from 8-formyl-7-hydroxyfla-
vones by the application of the Baylis–Hillman reaction.
The carbon–carbon bond formation and functional group transformations are
the most fundamental reactions for the construction of a molecular framework and
hence represent the forefront of research in organic chemistry. In recent years, there
have been increased applications of Baylis–Hillman coupling reactions in carbon–
carbon bond-forming reactions.[8–10] The Baylis–Hillman reaction involves the
coupling reaction of carbon electrophiles (e.g., aldehydes, alkoxy carbonyl ketones,
aldimines, and k-deficient olefins) and activated alkenes (e.g., acrylic esters, acryloni-
triles, vinyl ketones, vinyl sulfones, acrolein, and vinyl phosphates) catalyzed by ter-
tiary amines (e.g., DABCO or tertiary phosphines).[11] The Baylis–Hillman reaction
possesses two important features: atom economy and generation of functional
Received March 11, 2009.
Address correspondence to G. L. David Krupadanam, Department of Chemistry, Osmania
University, Hyderabad 500 007, A.P., India. E-mail: davidkrupa@hotmail.com
1292

PYRANO[2,3-f ]FLAVONES AND CHROMONES
1293
groups. This reaction also has been used to synthesize cyclic compounds starting
from suitably substituted electrophiles.[12–17]
RESULTS AND DISCUSSION
In this article, we report the synthesis of new 9-acetyl-pyrano[2,3-f]flavones
(6a–f), 9-acetyl-2-(20-furyl)-3-methyl-pyrano[2,3-f]chromone (6g), 9-formyl-pyrano
[2,3-f]flavones (7a–f), 9-formyl-2-(20-furyl)-3-methyl-pyrano[2,3-f]chromone (7g),
9-cyano-pyrano[2,3-f]flavones (8a–f), and 9-cyano-2-(20-furyl)-3-methyl-pyrano[2,3-f]
chromone (8g) by the Baylis–Hillman reaction of 8-formyl-7-hydroxyflavones=
chromone (2a–f, 2g) with methyl vinyl ketone (3), acrolein (4), and acrylonitrile (5).
7-Hydroxyflavones (1a–f) and 7-hydroxy-2-(20-furyl)-3-methylchromone (1g)
were prepared by using the modified Baker–Venkataraman transformation.[18,19]
Upon the Duff reaction[20,21] with hexamethylenetetramine (HMT) in glacial acetic
acid, these gave 8-formyl-7-hydroxyflavones (2a–f) and 8-formyl-7-hydroxy-2-(20-
furyl)-3-methylchromone (2g) (Scheme 1), which are characterized from their
spectral data.
8-Formyl-7-hydroxyflavones (2a–f), on reaction with methyl vinyl ketone (3) in
the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a catalyst in chloroform
Scheme 1. Synthesis of 9-acetyl=formyl=cyano substituted pyrano[2,3-f ]flavones (6a–f, 7a–f, 8a–f) and
chromones (6g, 7g, 8g).

1294
S. S. REDDY AND G. L. D. KRUPADANAM
solvent under an N2 atmosphere at room temperature, afforded new 9-acetyl-
pyrano[2,3-f]flavones (6a–f) in quantitative yields (Scheme 1). 9-Acetyl-3-methyl-
pyrano[2,3-f]flavone (6a) is characterized from its spectral data. In its infrared
(IR) spectrum, the 9-acetyl carbonyl showed absorption at 1665 cmꢀ1 and the
C O of flavone at 1615 cmꢀ1. Its ultraviolet (UV) (MeOH) spectrum showed bands
=
1
at 332 nm (log e 3.8), 290 nm (log e 4.0), and 241 nm (log e 4.2). In the H NMR
spectrum of 6a, the 8-OCH2 protons of the new pyran ring appeared as a doublet
at d 5.04 (J ¼ 1.5 Hz) as a result of the allylic coupling with H-10. H-10 overlapped
with H-20,60 at d 7.57, and methyl protons of 9-COCH3 appeared at d 2.35 as a
singlet. These three signals suggest that a new fused pyran ring was formed at the
7,8-position of the flavone. The aromatic H-5 appeared as a doublet at d 8.07
(J ¼ 9.0 Hz), and H-6 appeared at d 6.83 as a doublet (J ¼ 9.0 Hz). Phenyl protons
H-30,40,50 appeared as a multiplet at d 7.48, H-20,60 appeared as a multiplet at d
7.57, and 3-CH3 appeared at d 2.09 as a singlet. In the 13C NMR spectrum of
9-acetyl-3-methyl-pyrano[2,3-f ]flavone (6a), the signals from the 9-COCH3 carbonyl
appeared at d 195.4, those from CH3 appeared at d 25.1, those from 8-OCH2
appeared at d 64.8, and those from the olefinic carbons C-9 and C-10 appeared at
d 133.1 and 129.8 respectively. The other carbon signal assignments are d 159.5
Scheme 2. Mechanism of formation of 9-acetyl-pyrano[2,3-f ]flavones=chromone (6a–g).

PYRANO[2,3-f ]FLAVONES AND CHROMONES
1295
=
(C-2), 116.9 (C-3), 177.5 (C O at C-4), 117.8 (C-4a), 126.3 (C-5), 114.3 (C-6), 160.1
(C-6a), 108.9 (C-10a), 153.3 (C-10b), 129.3 (C-10), 128.6 (C-20,60), 128.8 (C-30,50),
130.3 (C-40), and 11.6 (C-3-CH3). In the electron impact (EI) mass spectrum of 6a,
the base peak appeared at m=z 331[M ꢀ 1]þ (100%) due to formation of pyrilium
ions, and other prominent ions appeared at m=z 173 (15%) and 289 (8%). Using
similar reaction conditions, 9-acetyl-2-(20-furyl)-3-methyl-pyrano [2,3-f]chromone
(6g) was synthesized from 8-formyl-7-hydroxy-2-(20-furyl)-3-methyl chromone (2g)
(Scheme 1).
Similar to methyl vinyl ketone, other electron-deficient olefins [e.g., acrolein (4)
and acrylonitrile (5)] were reacted with 2a–g under the Baylis–Hillman reaction
conditions as before to give 7a–g and 8a–g respectively (Scheme 1). Ethyl acrylate
and methyl acrylate reagents did not give good results because they are relatively
more electron-rich olefins than methyl vinyl ketone, acrolein, and acrylonitrile.
The reaction of methyl vinyl ketone (3) with DABCO by a Michael reaction
generates an enolate (9), which reacts with the formyl group of the 8-formyl-7-
hydroxyflavones=chromone (2a–g) to give an intermediate, the Baylis–Hillman
adducts 10a–g. The intramolecular nucleophilic substitution involving the 7-OH of
flavones=chromone leads to the removal of the DABCO and a pyran ring formation
to give 11a–g. The loss of H2O in the presence of DABCO gives rise to 9-acetyl-
pyrano[2,3-f]flavones=chromones (6a–g) (Scheme 2).
EXPERIMENTAL
All melting points are uncorrected and were determined on a Polmon instru-
ment (model MP 96). IR spectra were recorded on a Fourier transform (FT)–IR
spectrometer (Perkin-Elmer model 337), and UV spectra were determined on a
Schimadzu UV-vis 1601 spectrophotometer. The 1H NMR (300 MHz) and 13C
NMR (75.5 MHz) spectra were recorded on a Varian Gemini spectrometer using
CDCl3 solution with tetramethylsilane (TMS) as internal standard (chemical shifts
in d ppm). The mass spectra were recorded on a VG Micromass 7070-H instrument
and VG Autospec mass spectrometer.
General Procedure for the Synthesis of 7-Hydroxyflavones (1a–f) and
7-Hydroxy-2-(20-furyl)-3-methylchromone (1g) by Modified Baker–
Venkataraman Transformation
A mixture of respropiophenone (1.66 g) or resacetophenone (1.52 g, 10 mmol),
aroyl=furoyl chlorides (3.08 g, 22 mmol), and anhydrous potassium carbonate
(10.0 g) in dry acetone was refluxed for 8 h. The acetone was removed from the
solution under reduced pressure, and the residue was treated with ice-cold water
(200 mL). The solution was neutralized with dilute HCl, and the crude ester
7-aroyloxy-3-methylflavone that separated out was filtered. The crude ester was
hydrolyzed with methanolic potassium hydroxide (KOH; 8%, 100 mL) by refluxing
for half an hour. The methanol was distilled under reduced pressure, and the
reaction mass was treated with ice-cold water (200 ml) and filtered. The filtrate
was neutralized with cold dil. HCl to obtain a solid. The crude product was

1296
S. S. REDDY AND G. L. D. KRUPADANAM
recrystallized from methanol to give 7-hydroxyflavones (1a–f) and 7-hydroxy-2-
(20-furyl)-3-methylchromone (1g) in 70–80% yield. Compounds 1a and 1c–g were
previously reported in the literature.[22–24]
7-Hydroxy-20-chloro-3-methylflavone (1b). Recrystallized from methanol
as light brown needles. Mp 229 ꢁC (78% yield); IR (KBr): 3270 cmꢀ1 (OH),
1
1630 cmꢀ1 (C O); UV (MeOH): 296 nm (log e 4.5), 244 nm (log e 4.9); H NMR
=
(CDCl3): d 7.99 (d, J ¼ 9.0 Hz, H-5), 7.47–7.59 (m, H-30,40,50,60), 6.91 (dd, J ¼ 9.0 Hz,
2.1 Hz, H-6), 6.78 (d, J ¼ 2.1 Hz, H-8), 3.35 (bs, 7-OH), 1.89 (s, 3-CH3); 13C NMR
=
(CDCl3 þ DMSO-d6): d 175.2 (C-4, C O), 161.7 (C-7), 158.0 (C-8a), 155.9 (C-2),
131.5 (C-10), 128.2 (C-40), 127.0 (C-30,50), 126.6 (C-20,60), 124.9 (C-5), 114.2 (C-4a),
113.5 (C-6), 112.8 (C-3), 100.2 (C-8), 9.6 (3-CH3); EIMS: m=z 286 (Mþ.) (100),
251 (M-Cl) (90), and 137 (15). Anal. calcd. for C16H11ClO3: C, 67.03; H, 3.87. Found
C, 66.95; H, 3.72%.
General Procedure for Synthesis of 8-Formyl-7-hydroxyflavones
(2a–f) and 8-Formyl-7-hydroxy-2-(20-furyl)-3-methylchromone (2g)
Using the Duff Reaction
Hexamethylenetetramine (HMT) (5.6 g, 40 mmol) was added to a solution of
7-hydroxyflavones (1a–f) (2.52 g, 10 mmol) dissolved in glacial acetic acid (50 mL),
and the resulting solution was heated on a water bath for 6 h. The reaction mixture
was treated with dil. HCl (1:1) followed by further heating for 30 min. It was diluted
to 500 mL with cold water and left overnight in a refrigerator. The reaction mixture
was extracted with ether, and the ether solution was then washed with 10% sodium
bicarbonate solution and water. Concentration of the ether extract gave 8-formyl-7-
hydroxyflavones (2a–f) in 55–65% yield; these were recrystallized from benzene as
pale yellow crystals. Similarly, 8-formyl-7-hydroxy-2-(20-furyl)-3-methylchromone
(2g) was synthesized. Compounds 2a and 2e–g were previously reported in the
literature.[24–26]
8-Formyl-7-hydroxy-20-chloro-ꢀ31-methylflavone (2b). Pale yellow solid.
Mp 169 ꢁC (56% yield); IR: 1665 cm (8-CHO), 1647 cmꢀ1 (flavone C O); UV
=
(MeOH): 296 nm (log e 4.4), 262 nm (log e 4.6), 214 nm (log e 4.9); 1H NMR
(CDCl3): d 12.42 (s, 7-OH), 10.41 (s, 8-CHO), 8.35 (d, J ¼ 9.0 Hz, H-5), 7.39–7.60
(m, H-30, 40, 50, 60), 6.99 (d, J ¼ 9.0 Hz, H-6), 1.95 (s, 3-CH3); 13C NMR (CDCl3):
=
d 192.1 (8-CHO), 176.3 (C-4, C O), 167.1 (C-7), 162.3 (C-8a), 157.8 (C-2), 134.8
(C-40), 133.3 (C-20), 131.6 (C-5), 131.3 (C-10), 130.8 (C-30), 130.1 (C-50), 126.9
(C-60), 120.4 (C-4a), 115.8 (C-6), 115.0 (C-3), 108.4 (C-8), 10.8 (C-3-CH3); ESIMS:
m=z 315 [M þ H]þ and 316 [M þ 2]. Anal. calcd. for C17H11ClO4: C, 64.88; H,
3.52. Found C, 64.71; H, 3.66%.
8-Formyl-7-hydroxy-40-chloro-ꢀ31-methylflavone (2c). Pale yellow solid.
Mp 177 ꢁC (62% yield); IR: 1672 cm (8-CHO), 1651 cmꢀ1 (flavone C O); UV
=
(MeOH): 302 nm (log e 4.6), 270 nm (log e 4.6), 230 nm (log e 4.8), 216 nm (log e
1
4.8); H NMR (CDCl3): d 12.43 (s, 7-OH), 10.53 (s, 8-CHO), 8.34 (d, J ¼ 9.0 Hz,
13
H-5), 7.58 (d, J ¼ 8.8 Hz, H-20,60), 7.51 (d, J ¼ 8.7 Hz, H-30, 50), 6.98 (d, J ¼ 9.0 Hz,
=
H-6), 2.18 (s, 3-CH3); C NMR (CDCl3): d 191.9 (8-CHO), 177.3 (C-4, C O),

PYRANO[2,3-f ]FLAVONES AND CHROMONES
1297
167.2 (C-7), 159.6 (C-8a), 158.9 (C-2), 135.1 (C-40), 135.0 (C-5), 130.9 (C-10), 130.0
(C-30,50), 129.0 (C-20,60), 118.8 (C-4a), 116.0 (C-6), 114.9 (C-3), 108.3 (C-8), 11.5
(C-3-CH3); ESIMS: m=z 315 [Mm þ H]þ and 316 [M þ 2]. Anal. calcd. for
C17H11ClO4: C, 64.88; H, 3.52. Found C, 64.63; H, 3.70%.
8-Formyl-7-hydroxy-40-methoxy-3-ꢀm1 ethylflavone (2d). Pale yellow crys-
tals. Mp 165 ꢁC (65% yield); IR: 1660 cm (8-CHO), 1631 cmꢀ1 (flavone C O);
=
1
UV (MeOH): 316 nm (log e 4.7), 238 nm (log e 4.8), 214 nm (log e 5.0); H NMR
(CDCl3): d 12.41 (s, 7-OH), 10.55 (s, 8-CHO), 8.36 (d, J ¼ 9.0 Hz, H-5), 7.58 (d,
J ¼ 8.6 Hz, H-20, 60), 7.03 (d, J ¼ 8.6 Hz, H-30,50), 6.99 (d, J ¼ 9.0 Hz, H-6), 3.93 (s,
40-OCH3), 2.21 (s, 3-CH3); 13C NMR (CDCl3 þ DMSO-d6): d 191.2 (8-CHO),
0
=
175.8 (C-4, C O), 166.1 (C-7), 160.4 (C-4 ), 159.1 (C-8a), 156.8 (C-2), 133.9 (C-5),
129.6 (C-20,60), 124.0 (C-10), 116.6 (C-4a), 114.7 (C-6), 114.1 (C-3), 113.3 (C-30,50),
107.7 (C-8), 54.6 (C-40-OCH3), 10.7 (C-3-CH3); EIMS: m=z 310 (Mþ.) (100) and
165 (8). Anal. calcd. for C18H14O5: C, 69.67; H, 4.55. Found C, 69.84; H, 4.48%.
General Procedure for the Synthesis of 9-Acetyl/formyl/
cyano-pyrano[2,3-f]flavones (6a–f, 7a–f, 8a–f) and 9-Acetyl/formyl/
cyano-2-(20-furyl)-3-methyl-pyrano[2,3-f]chromones (6g, 7g, 8g)
Methyl vinyl ketone (3) or acrolein (4) or acrylonitrile (5) (15 mmol) and DABCO
(0.86 g, 7.68mmol) were added to a solution of 8-formyl-7-hydroxyflavones=chromone
(2a–f, 2g) (10 mmol) in CHCl3 (50 mL). The mixture was stirred at room temperature
under an N2 atmosphere for 72h. The chloroform was then evaporated, and the solid
residue was chromatographed over silica gel (60–120 mesh) by elution with petroleum
ether and ethyl acetate (9:1) to give 9-acetyl=formyl=cyano-pyrano[2,3-f]flavones (6a–f,
7a–f, 8a–f) and chromones (6g, 7g, 8g) in good yields.
9-Acetyl-3-methyl-pyrano[2,3-f ]flavone (6a). Recrystallized from chloro-
ꢀ1
form as white crystals. Mp 192 ꢁC (81% yield); IR: 1665 cm (C O, 9-COCH3),
=
1615 cmꢀ1 (flavone C O); UV (MeOH): 332 nm (log e 3.8), 290 nm (log e 4.0),
=
1
241 nm (log e 4.2); H NMR (CDCl3): d 8.07 (d, J ¼ 9.0 Hz, H-5), 7.57 (m, 3H,
H-20, 60; H-10), 7.48 (m, H-30, 40, 50), 6.83 (d, J ¼ 9.0 Hz, H-6), 5.04 (d, J ¼ 1.5 Hz,
8-OCH2), 2.35 (s, 9-COCH3), 2.09 (s, 3-CH3); 13C NMR (CDCl3): d 195.4 (9-
=
COCH3), 177.5 (C-4, C O), 160.1 (C-6a), 159.5 (C-2), 153.3 (C-10b), 133.1 (C-9),
130.3 (C-40), 129.8 (C-10), 129.3 (C-10), 128.8 (C-30,50), 128.6 (C-20,60), 126.3 (C-5),
117.8 (C-4a), 116.9 (C-3), 114.3 (C-6), 108.9 (C-10a), 64.8 (C-8-OCH2), 25.1 (C-9-
COCH3), 11.6 (C-3-CH3); EIMS: m=z 331 (M ꢀ 1) (100), 289 (8), and 173 (15). Anal.
calcd. for C21H16O4: C, 75.89; H, 4.85. Found C, 76.02; H, 4.96%.
9-Acetyl-20-chloro-3-methyl-pyrano[2,3-f]flavone
(6b). Recrystallized
ꢀ1
from chloroform as white needles. Mp 165 ꢁC (73% yield); IR: 1654 cm (C O,
=
9-COCH3), 1612 cmꢀ1 (flavone C O); UV (MeOH): 318 nm (log e 3.9), 285 nm
=
(log e 4.1), 231 nm (log e 4.5); 1H NMR (CDCl3): d 8.13 (d, J ¼ 9.0 Hz, H-5),
7.40–7.62 (m, H-30,40,50,60; H-10), 6.89 (d, J ¼ 9.0 Hz, H-6), 5.08 (d, J ¼ 1.5 Hz,
8-OCH2), 2.37 (s, 9-COCH3), 1.91 (s, 3-CH3); 13C NMR (CDCl3): d 195.4
=
(9-COCH3), 177.2 (C-4, C O), 159.7 (C-6a), 158.3 (C-10b), 153.5 (C-2), 133.6
(C-9), 131.9 (C-10), 131.5 (C-40), 130.9 (C-30), 130.3 (C-10), 129.8 (C-50), 129.4

1298
S. S. REDDY AND G. L. D. KRUPADANAM
(C-20), 127.0 (C-5), 126.3 (C-60), 119.9 (C-4a), 117.2 (C-3), 114.5 (C-6), 109.1 (C-10a),
64.8 (C-8-OCH2), 25.1 (C-9-COCH3), 11.0 (C-3-CH3); EIMS: m=z 366 (Mþ.) (100),
331 (90), 313 (10), 289 (20), 215 (30), and 173 (80). Anal. calcd. for C21H15ClO4: C,
68.77; H, 4.12. Found C, 68.59; H, 4.07%.
9-Acetyl-40-chloro-3-methyl-pyrano[2,3-f]flavone
(6c). Recrystallized
ꢀ1
from chloroform as white needles. Mp 186 ꢁC (75% yield); IR: 1662 cm (C O,
=
9-COCH3), 1623 cmꢀ1 (flavone C O); UV (MeOH): 326 nm (log e 3.9), 281 nm
=
(log e 4.6), 237 nm (log e 4.2); 1H NMR (CDCl3 þ DMSO-d6): d 8.07 (d, J ¼ 9.0 Hz,
H-5), 7.41–7.69 (m, H-20,30,50,60; H-10), 6.88 (d, J ¼ 9.0 Hz, H-6), 5.07 (d, J ¼ 1.5 Hz,
8-OCH2), 2.40 (s, 9-COCH3), 2.09 (s, 3-CH3); 13C NMR (CDCl3): d 195.3 (09-
=
COCH3), 177.3 (C-4, C O), 159.6 (C-6a), 158.9 (C-2), 153.2 (C-10b), 136.5 (C-4 ),
131.5 (C-9), 130.1 (C-30, 50), 129.8 (C-10), 129.5 (C-10), 129.0 (C-20, 60), 126.1
(C-5), 118.1 (C-4a), 116.9 (C-3), 114.5 (C-6), 108.9 (C-10a), 64.8 (C-8-OCH2), 25.0
(C-9-COCH3), 11.5 (C-3-CH3); ESIMS: m=z 367 [M þ H]þ and 369. Anal. calcd.
for C21H15ClO4: C, 68.77; H, 4.12. Found C, 68.96; H, 4.01%.
9-Acetyl-40-methoxy-3-methyl-pyrano[2,3-f]flavone (6d). Recrystallized
ꢀ1
from chloroform as white solid. Mp 197 ꢁC (78% yield); IR: 1661 cm (C O,
=
9-COCH3), 1624 cmꢀ1 (flavone C O); UV (MeOH): 330 nm (log e 3.9), 298 nm
=
1
(log e 4.0), 238 nm (log e 4.1); H NMR (CDCl3): d 8.11 (d, J ¼ 9.0 Hz, H-5), 7.62
(s, H-10), 7.55 (d, J ¼ 8.6 Hz, H-20,60), 7.03 (d, J ¼ 8.6 Hz, H-30,50), 6.89 (d,
13
J ¼ 9.0 Hz, H-6), 5.12 (d, J ¼ 1.5 Hz, 8-OCH2), 3.92 (s, 40-OCH3), 2.43 (s, 9-COCH3),
=
2.14 (s, 3-CH3); C NMR (CDCl3): d 195.4 (9-COCH3), 177.5 (C-4, C O), 161.0
(C-40), 160.0 (C-6a), 159.3 (C-2), 153.1 (C-10b), 130.2 (C-20, 60), 129.7 (C-10),
129.2 (C-9), 126.4 (C-5), 125.3 (C-10), 117.0 (C-4a), 116.7 (C-3), 114.1 (C-6), 113.9
(C-30,50), 108.8 (C-10a), 64.6 (C-8-OCH2), 55.3 (C-40-OCH3), 24.9 (C-9-COCH3),
11.6 (C-3-CH3); ESIMS: m=z 363 [M þ H]þ and 385[M þ Na]þ. Anal. calcd. for
C22H18O5: C, 72.92; H, 5.01. Found C, 72.63; H, 5.17%.
9-Acetyl-pyrano[2,3-f]flavone (6e). Recrystallized from chloroform as
ꢀ1
ꢀ1
white solid. Mp 174 ꢁC (80% yield); IR: 1659 cm (C O, 9-COCH3), 1631 cm
=
=
(flavone C O); UV (MeOH): 337 nm (log e 3.9), 283 nm (log e 4.2), 249 nm (log e
1
4.5); H NMR (CDCl3): d 8.12 (d, J ¼ 9.0 Hz, H-5), 7.86 (m, H-20, 60; H-10), 7.57
(m, H-30,40,50), 6.93 (d, J ¼ 9.0 Hz, H-6), 6.77 (s,H-3), 5.15 (d, J ¼ 1.5 Hz,
8-OCH2), 2.52 (s, 9-COCH3); 13C NMR (CDCl3): d 195.3 (9-COCH3), 174.9 (C-4,
0
=
C O), 159.6 (C-2), 153.3 (C-6a), 151.9 (C-10b), 131.3 (C-9), 130.2 (C-4 ), 129.6
(C-10), 128.8 (C-20,60), 128.4 (C-30,50), 128.3 (C-10), 126.2 (C-5), 118.8 (C-4a),
114.8 (C-6), 109.1 (C-10a), 106.3 (C-3), 64.9 (C-8-OCH2), 24.6 (C-9-COCH3); ESI
MS: m=z 319 [M þ H]þ. Anal. calcd. for C20H14O4: C, 75.46; H, 4.43. Found C,
75.68; H, 4.29%.
9-Acetyl-20-chloro-pyrano[2,3-f ]flavone (6f). Recrysꢀta1llized from chloro-
form as white needles. Mp 157 ꢁC (73% yield); IR: 1661 cm (C O, 9-COCH3),
=
1634 cmꢀ1 (flavone C O); UV (MeOH): 343 nm (log e 3.8), 287 nm (log e 4.1),
=
245 nm (log e 4.2); 1H NMR (CDCl3 þ DMSO-d6): d 7.98 (d, J ¼ 9.0 Hz, H-5),
7.35–7.78 (m, H-30,40,50,60; H-10), 6.87 (d, J ¼ 9.0 Hz, H-6), 6.46 (s, H-3), 5.01 (d,
J ¼ 1.5 Hz, 8-OCH2), 2.38 (s, 9-COCH3); 13C NMR (CDCl3): d 195.5 (9-COCH3),
=
177.2 (C O at C-4), 159.7 (C-2), 158.3 (C-6a), 153.5 (C-10b), 133.6 (C-9), 131.9

PYRANO[2,3-f ]FLAVONES AND CHROMONES
1299
(C-10), 131.5 (C-40), 131.0 (C-30), 130.3 (C-10), 129.8 (C-50), 129.4 (C-20), 127.0 (C-5),
126.4 (C-60), 119.9 (C-4a), 114.5 (C-6), 109.1 (C-10a), 106.4 (C-3), 64.8 (C-8-OCH2),
25.1 (C-9-COCH3); ESIMS: m=z 353 [M þ H]þ. Anal. calcd. for C20H13ClO4: C,
68.10; H, 3.71. Found C, 67.92; H, 3.84%.
9-Acetyl-2-(20-furyl)-3-methyl-pyrano[2,3-f ]chromone
(6g). Recrystal-
lized from chloroform as pale yellow solid. Mp 186 ꢁC (72% yield); IR: 1663 cmꢀ1
ꢀ1
=
=
(C O, 9-COCH3), 1620 cm (chromone C O); UV (MeOH): 321 nm (log e 3.9),
1
252 nm (log e 4.1); H NMR (CDCl3): d 8.09 (d, J ¼ 9.0 Hz, H-5), 7.78 (s, H-10),
7.72 (dd, J ¼ 1.5 Hz, 0.8 Hz, H-50), 6.98 (dd, J ¼ 3.7 Hz, 0.8 Hz, H-30), 6.82 (d,
J ¼ 9.0 Hz, H-6), 6.62 (dd, J ¼ 3.7 Hz, 1.5 Hz, H-40), 5.18 (d, J ¼ 1.5 Hz, 8-OCH2),
2.51 (s, 9-COCH3), 2.30 (s,3-CH3); 13C NMR (CDCl3): d 195.2 (9-COCH3), 176.7
0
0
=
(C-4, C O), 159.3 (C-6a), 152.3 (C-2), 150.0 (C-10b), 146.8 (C-2 ), 145.0 (C-5 ),
134.8 (C-9), 129.6 (C-10), 126.0 (C-5), 116.5 (C-4a), 115.6 (C-3), 114.4 (C-30),
114.0 (C-6), 112.0 (C-40), 108.5 (C-10a), 64.7 (C-8-OCH2), 24.9 (C-9-COCH3), 9.8
(C-3-CH3); ESIMS: m=z 323 [M þ H]þ and 345 [M þ Na]þ. Anal. calcd. for
C19H14O5: C, 70.80; H, 4.38. Found C, 71.03; H, 4.14%.
9-Formyl-3-methyl-pyrano[2,3-f ]flavone (7a). Recrystallized from chloro-
form as pale yellow crystals. Mp 149 ꢁC (78% yield); IR: 1673cmꢀ1 (9-CHO),
1628cmꢀ1 (flavone C O); UV (MeOH): 331 nm (log e 3.9), 285 nm (log e 4.0),
=
1
238 nm (log e 4.3); H NMR (CDCl3): d 9.57 (9-CHO), 8.08 (d, J ¼ 9.0 Hz, H-5),
7.55 (m, H-20, 60; H-10), 7.48 (m, H-30, 40, 50), 6.83 (d, J ¼ 9.0 Hz, H-6), 5.09 (d,
J ¼ 1.5 Hz, 8-OCH2), 2.07 (s, 3-CH3); 13C NMR (CDCl3): d 189.4 (9-CHO), 177.4
=
(C-4, C O), 160.3 (C-6a), 159.9 (C-2), 153.3 (C-10b), 133.6 (C-9), 133.0 (C-10), 130.4
(C-40), 130.2 (C-10), 128.9 (C-5), 128.8 (C-30,50), 128.6 (C-20,60), 118.0 (C-4a), 116.9
(C-6), 114.5 (C-3), 108.9 (C-10a), 63.9 (C-8-OCH2), 11.6 (C-3-CH3); FABMS: m=z
319 [M þ H]þ. Anal. calcd. for C20H14O4: C, 75.46; H, 4.43. Found C, 75.23; H, 4.65%.
9-Formyl-20-chloro-3-methyl-pyrano[2,3-f ]flavone
(7b). Recrystallized
from chloroform as a pale yellow solid. Mp 157 ꢁC (72% yield); IR: 1673 cmꢀ1
(9-CHO), 1628 cmꢀ1 (flavone C O); UV (MeOH): 326 nm (log e 3.8), 284 nm (log
=
e 4.4), 238 nm (log e 4.2); 1H NMR (CDCl3): d 9.59 (s, 9-CHO), 8.18 (d, J ¼ 9.0 Hz,
H-5), 7.43–7.62 (m, H-30,40,50, 60; H-10), 6.92 (d, J ¼ 9.0 Hz, H-6), 5.14 (d, J ¼ 1.5 Hz,
8-OCH2), 1.91 (s, 3-CH3); 13C NMR (CDCl3 þ DMSO-d6): d 189.3 (9-CHO), 177.1
=
(C-4, C O), 160.0 (C-6a), 158.3 (C-10b), 153.4 (C-2), 139.7 (C-9), 133.5 (C-10), 132.3
(C-10), 131.8 (C-20), 130.6 (C-40), 130.8 (C-30), 130.5 (C-5), 130.2 (C-50), 127.1 (C-60),
119.9 (C-4a), 117.2 (C-3), 114.6 (C-6), 109.0 (C-10a), 63.9 (C-8-OCH2), 10.9
(C-3-CH3); FABMS: m=z 353 [M þ H]þ. Anal. calcd. for C20H13ClO4: C, 68.10;
H, 3.71. Found C, 68.49; H, 3.84%.
9-Formyl-40-chloro-3-methyl-pyrano[2,3-f ]flavone
(7c). Rꢀe1crystallized
from chloroform as a white solid. Mp 161 ꢁC (75% yield); IR: 1670 cm (9-CHO),
1628 cmꢀ1 (flavone C O); UV (MeOH): 328 nm (log e 3.9), 280 nm (log e 4.0),
=
1
235 nm (log e 4.2); H NMR (CDCl3): d 9.62 (s, 9-CHO), 8.17 (d, J ¼ 9.0 Hz, H-5),
8.03 (d, J ¼ 8.7 Hz, H-20,60), 7.59 (s, H-10), 7.46 (d, J ¼ 8.7 Hz, H-30,50), 6.92 (d,
J ¼ 9.0 Hz, H-6), 5.15 (d, J ¼ 1.5 Hz, 8-OCH2), 2.14 (s, 3-CH3); 13C NMR (CDCl3)
=
(50.3 M Hz): d 188.9 (9-CHO), 176.9 (C-4, C O), 159.4 (C-6a), 158.6 (C-2), 152.8
(C-10b), 135.8 (C-9), 132.9 (C-10), 130.7 (C-40), 129.8 (C-10) 129.7 (C-30,50), 128.4

1300
S. S. REDDY AND G. L. D. KRUPADANAM
(C-20,60), 127.7 (C-5), 117.4 (C-4a), 116.3 (C-3), 114.0 (C-6), 108.4 (C-10a), 63.2
(C-8-OCH2), 10.9 (C-3-CH3); LSIMS: m=z 353 [M þ H]þ, 375 [M þ Na]þ. Anal.
calcd. for C20H13ClO4: C, 68.10; H, 3.71. Found C, 67.96; H, 3.88%.
9-Formyl-40-methoxy-3-methylpyrano[2,3-f ]flavone (7d). Recrystallized
from chloroform as a pale yellow solid. Mp 174 ꢁC (81% yield); IR: 1668 cmꢀ1
(9-CHO), 1622 cmꢀ1 (flavone C O); UV (MeOH): 330 nm (log e 4.0), 299 nm (log
=
e 4.1), 237 nm (log e 4.3); 1H NMR (CDCl3): d 9.60 (s, 9-CHO), 8.15 (d, J ¼ 9.0 Hz,
H-5), 7.67 (s, H-10), 7.59 (d, J ¼ 8.6 Hz, H-20,60) 7.03 (d, J ¼ 8.6 Hz, H-30,50), 6.89 (d,
J ¼ 9.0 Hz, H-6), 5.15 (d, J ¼ 1.5 Hz, 8-OCH2), 3.89 (s, 40-OCH3), 2.14 (s, 3-CH3);
13
0
=
C NMR (CDCl3): d 189.3 (9-CHO), 177.5 (C-4, C O), 161.1 (C-4 ), 160.2
(C-6a), 159.9 (C-2), 153.2 (C-10b), 133.8 (C-10), 130.7 (C-5), 130.3 (C-20,60), 130.1
(C-9), 125.2 (C-10), 117.3 (C-4a), 116.9 (C-3), 114.3 (C-6), 114.0 (C-30,50), 108.8
(C-10a), 63.8 (C-8-OCH2), 55.4 (C-40-OCH3), 11.7 (C-3-CH3); ESIMS: m=z 349
[M þ H]þ and 371 [M þ Na]þ. Anal. Calcd. for C21H16O5: C, 72.41; H, 4.63. Found
C, 72.74; H, 4.30%.
9-Formyl-pyrano[2,3-f ]flavone (7e). Recrystallized from chloroform as a
white solid. Mp 169 ꢁC (73% yield); IR: 1676 cmꢀ1 (9-CHO), 1632 cmꢀ1 (flavone
1
=
C O); UV (MeOH): 338 nm (log e 3.9), 288 nm (log e 4.1), 242 nm (log e 4.4); H
NMR (CDCl3): d 9.76 (s, 9-CHO), 8.16 (d, J ¼ 9.0 Hz, H-5), 7.90 (m, H-20,60),
13
7.81 (s, H-10), 7.58 (m, H-30,40,50), 6.96 (d, J ¼ 9.0 Hz, H-6), 6.78 (s, H-3), 5.18 (d,
=
J ¼ 1.5 Hz, 8-OCH2); C NMR (CDCl3): d 189.3 (9-CHO), 177.5 (C-4, C O),
160.2 (C-6a), 160.0 (C-2), 153.2 (C-10b), 133.6 (C-9), 133.0 (C-10), 130.4 (C-40),
130.3 (C-10), 128.8 (C-5), 128.8 (C-30,50), 128.7 (C-20,60), 118.0 (C-4a), 114.5 (C-6),
108.9 (C-10a), 106.8 (C-3), 63.9 (C-8-OCH2); LSIMS: m=z 305 [M þ H]þ and 327
[M þ Na]þ. Anal. calcd. for C19H12O4: C, 74.99; H, 3.97. Found C, 75.13; H, 3.80%.
9-Formyl-20-chloro-pyrano[2,3-f ]flavone (7f). Recrystallized from chloro-
form as a pale yellow solid. Mp 153 ꢁC (70% yield); IR: 1668 cmꢀ1 (9-CHO),
1622 cmꢀ1 (flavone C O); UV (MeOH): 341 nm (log e 3.8), 291 nm (log e 4.0),
=
1
235 nm (log e 4.3); H NMR (CDCl3): d 9.60 (9-CHO), 8.18 (d, J ¼ 9.0 Hz, H-5),
7.61 (s, H-10), 7.42–7.65 (m, H-30,40,50,60), 6.93 (d, J ¼ 9.0 Hz, H-6), 6.61 (s, H-3),
5.14 (d, J ¼ 1.5 Hz, 8-OCH2); 13C NMR (CDCl3): d 189.3 (9-CHO), 177.0 (C-4,
=
C O), 160.0 (C-6a), 158.3 (C-2), 153.5 (C-10b), 138.3 (C-9), 133.6 (C-10), 131.9
(C-10), 131.7 (C-20), 131.6 (C-40), 130.9 (C-30), 130.5 (C-5), 130.2 (C-50), 127.0
(C-60), 119.9 (C-4a), 114.5 (C-6), 109.1 (C-10a), 106.5 (C-3), 63.8 (C-8-OCH2);
ESIMS: m=z 339 [M þ H]þ. Anal. calcd. for C19H11ClO4: C, 67.37; H, 3.27. Found
C, 67.41; H, 3.22%.
9-Formyl-2-(20-furyl)-3-methyl-pyrano[2,3-f ]chromone (7g). Recrystal-
lized from chloroform as pale yellow needles. Mp 161 ꢁC (78% yield); IR: 1668 cmꢀ1
(9-CHO), 1626 cmꢀ1 (chromone C O); UV (MeOH): 333 nm (log e 3.9), 240 nm
=
1
(log e 4.3); H NMR (CDCl3): d 9.73 (9-CHO), 8.15 (d, J ¼ 9.0 Hz, H-5), 7.76 (s,
H-10), 7.72 (dd, J ¼ 1.5 Hz, 0.8 Hz, H-50), 7.06 (dd, J ¼ 3.7 Hz, 0.8 Hz, H-30), 6.88
(d, J ¼ 9.0 Hz, H-6), 6.65 (dd, J ¼ 3.7 Hz, 1.5 Hz, H-40), 5.16 (d, J ¼ 1.5 Hz,
8-OCH2), 2.34 (s, 3-CH3); 13C NMR (CDCl3 þ DMSO): d 188.5 (9-CHO), 176.3
0
0
=
(C-4, C O), 157.1 (C-6a), 155.4 (C-2), 152.3 (C-10b), 150.5 (C-5 ), 144.3 (C-2 ),
139.7 (C-9), 131.7 (C-10), 128.4 (C-5), 117.8 (C-4a), 116.2 (C-30), 113.8 (C-3), 112.7

PYRANO[2,3-f ]FLAVONES AND CHROMONES
1301
(C-6), 110.7 (C-40), 108.3 (C-10a), 62.1 (C-8-OCH2), 8.1 (C-3-CH3); ESIMS: m=z 309
[M þ H]þ and 331 [M þ Na]þ. Anal. calcd. for C18H12O5: C, 70.13; H, 3.92. Found C,
70.27; H, 3.55%.
9-Cyano-3-methyl-pyrano[2,3-f ]flavones (8a). Recrystallized frꢀo1m chloro-
form as white crystals. Mp 183 ꢁC (76% yield); IR (KBr): 2212 cm
=
(9-CN),
1614 cmꢀ1 (flavone C O); UV (MeOH): 331 nm (log e 3.8), 289 nm (log e 4.0),
1
240 nm (log e 4.2); H NMR (CDCl3): d 8.15 (d, J ¼ 9.0 Hz, H-5), 7.49–7.68 (m,
13
H-20,30,40,50,60; H-10), 6.93 (d, J ¼ 9.0 Hz, H-6), 4.97 (d, J ¼ 1.5 Hz, 8-OCH2), 2.16
=
(s, 3-CH3); C NMR (CDCl3): d 177.3 (C-4, C O), 160.3 (C-6a), 158.1 (C-2),
152.5 (C-10b), 132.8 (C-10), 132.1 (C-10), 130.5 (C-40), 130.3 (C-5), 128.8 (C-30,50),
128.6 (C-20,60), 118.0 (C-4a), 117.3 (9-CN), 116.0 (C-3), 114.3 (C-6), 108.7 (C-9),
102.4 (C-10a), 64.7 (C-8-OCH2), 11.6 (C-3-CH3); FABMS: m=z 316 [M þ H]þ. Anal.
calcd. for C20H13NO3: C, 76.18; H, 4.16; N, 4.44. Found C, 76.36; H, 4.01; N, 4.73%.
9-Cyano-20-chloro-3-methyl-pyrano[2,3-f ]flavone
(8b). Recrystallized
from chloroform as white crystalls. Mp 176 ꢁC (67% yield); IR (KBr): 2213 cmꢀ1
(9-CN), 1624 cmꢀ1 (flavone C O); UV (MeOH): 329 nm (log e 3.9), 281 nm (log e
=
1
4.4), 235 nm (log e 4.2); H NMR (CDCl3): d 8.21 (d, J ¼ 9.0 Hz, H-5), 7.43–7.66
13
(m, H-30,40,50,60; H-10), 6.97 (d, J ¼ 9.0 Hz, H-6), 4.99 (d, J ¼ 1.5 Hz, 8-OCH2),
=
1.97 (s, 3-CH3); C NMR (DMSO-d6): d 175.9 (C-4, C O), 158.0 (C-6a), 152.1
(C-10b), 151.7 (C-2), 143.1 (C-10), 132.2 (C-10), 131.4 (C-40), 131.3 (C-30), 131.0
(C-20), 129.8 (C-5), 129.3 (C-50), 127.6 (C-60), 118.9 (C-4a), 116.6 (9-CN), 116.0
(C-3), 114.6 (C-6), 108.8 (C-9), 103.2 (C-10a), 64.2 (C-8-OCH2), 10.7 (C-3-CH3);
FABMS: m=z 350 [M þ H]þ. Anal. calcd. for C20H12ClNO3: C, 68.68; H, 3.46; N,
4.00. Found C, 68.42; H, 3.75; N, 3.93%.
9-Cyano-40-chloro-3-methyl-pyrano[2,3-f ]flavone
(8c). Recrystallized
from chloroform as white needles. Mp 181 ꢁC (73% yield); IR (KBr): 2216 cmꢀ1
(9-CN), 1625 cmꢀ1 (flavone C O); UV (MeOH): 335 nm (log e 4.0), 269 nm (log e
=
1
4.1), 239 nm (log e 4.6); H NMR (CDCl3): d 8.05 (d, J ¼ 9.0 Hz, H-5), 7.43–7.70
13
(m, H-20,30,50,60; H-10), 6.89 (d, J ¼ 9.0 Hz, H-6), 5.07 (d, J ¼ 1.5 Hz, 8-OCH2),
=
1.98 (s, 3-CH3); C NMR (CDCl3): d 177.2 (C-4, C O), 159.0 (C-6a), 158.2
(C-2), 152.6 (C-10b), 132.0 (C-40), 131.9 (C-10), 130.1 (C-30,50), 129.0 (C-20, 60),
128.8 (C-10), 127.0 (C-5), 118.2 (C-4a), 117.2 (9-CN), 114.5 (C-6), 114.1 (C-3),
108.6 (C-9), 102.4 (C-10a), 64.6 (C-8-OCH2), 11.5 (C-3-CH3); LSIMS: m=z 350
[M þ H]þ. Anal. calcd. for C20H12ClNO3: C, 68.68; H, 3.46; N, 4.00. Found C,
68.83; H, 3.67; N, 4.12%.
9-Cyano-40-methoxy-3-methylpyrano[2,3-f ]flavone (8d). Recrystallized
from chloroform as pale yellow needles. Mp 187 ꢁC (75% yield); IR (KBr):
2214 cmꢀ1 (9-CN), 1627 cmꢀ1 (flavone C O); UV (MeOH): 321 nm (log e 3.9),
=
1
278 nm (log e 4.0), 242 nm (log e 4.2); H NMR (CDCl3): d 8.15 (d, J ¼ 9.0 Hz,
H-5), 7.59 (m, H-20,60; H-10) 7.05 (d, J ¼ 8.6 Hz, H-30,50), 6.92 (d, J ¼ 9.0 Hz, H-6),
4.98 (d, J ¼ 1.5 Hz, 8-OCH2), 3.93 (s, 40-OCH3), 1.98 (s, 3-CH3); 13C NMR (CDCl3):
0
=
d 177.4 (C-4, C O), 161.1 (C-4 ), 160.2 (C-6a), 158.0 (C-2), 152.3 (C-10b), 132.1
(C-10), 130.3 (C-20, 60), 130.2 (C-5), 124.9 (C-10), 117.3 (C-4a), 117.1 (9-CN), 116.0
(C-3), 114.1 (C-6), 114.0 (C-30,50), 108.5 (C-9), 102.1 (C-10a), 64.5 (C-8-OCH2),

1302
S. S. REDDY AND G. L. D. KRUPADANAM
55.4 (C-40-OCH3), 11.7 (C-3-CH3); ESIMS: m=z 346 [M þ H]þ and 368 [M þ Na]þ.
Anal. calcd. for C21H15NO4: C, 73.04; H, 4.38; N, 4.06. Found C, 72.91; H, 4.14;
N, 4.43%.
9-Cyano-pyrano[2,3-f ]flavone (8e). Recrystallizꢀed1 from chloroform as pale
yellow solid. Mp 173 ꢁC (71% yield); IR (KBr): 2211 cm (9-CN), 1622 cmꢀ1 (flav-
1
=
one C O); UV (MeOH): 337 nm (log e 3.8), 291 nm (log e 4.0), 255 nm (log e 4.6); H
NMR (CDCl3): d 8.17 (d, J ¼ 9.0 Hz, H-5), 7.49–7.68 (m, H-20,30,40,50,60; H-10), 6.92
(d, J ¼ 9.0 Hz, H-6), 6.77 (s, H-3), 4.96 (d, J ¼ 1.5 Hz, 8-OCH2); 13C NMR (CDCl3):
=
d 177.4 (C-4, C O), 160.1 (C-2), 159.5 (C-6a), 153.2 (C-10b), 130.3 (C-10), 129.7
(C-40), 129.3 (C-10), 128.8 (C-20,60), 128.6 (C-30,50), 126.3 (C-5), 117.8 (C-4a), 116.9
(9-CN), 114.3 (C-6), 108.9 (C-9), 106.8 (C-10a), 106.7 (C-3), 64.8 (C-8-OCH2);
FABMS: m=z 302 [M þ H]þ. Anal. calcd. for C19H11NO3: C, 75.74; H, 3.68; N,
4.65. Found C, 75.53; H, 3.80; N, 4.76%.
9-Cyano-20-chloro-pyrano[2,3-f ]flavone (8f). Recrystallized from chloro-
form as a white solid. Mp 189 ꢁC (65% yield); IR (KBr): 2213cmꢀ1 (9-CN),
1622cmꢀ1 (flavone, C O); UV (MeOH): 334 nm (log e 3.8), 285 nm (log e 4.2),
=
1
246 nm (log e 4.7); H NMR (CDCl3): d 8.17 (d, J ¼ 9.0 Hz, H-5), 7.38–7.60 (m,
13
H-30,40,50,60; H-10), 6.91 (d, J ¼ 9.0 Hz, H-6), 6.78 (s, H-3), 4.94 (d, J ¼ 1.5 Hz,
=
8-OCH2); C NMR (CDCl3): d 177.3 (C-4, C O), 160.3 (C-2), 158.1 (C-6a), 152.5
(C-10b), 135.1 (C-10), 132.8 (C-20), 132.0 (C-40), 130.6 (C-10), 130.3 (C-30), 128.8
(C-50), 128.6 (C-5), 128.6 (C-60), 118.0 (C-4a), 117.3 (9-CN), 114.3 (C-6), 108.6
(C-9), 106.4 (C-3), 102.3 (C-10a), 64.7 (C-8-OCH2); FABMS: 336 [M þ H]þ. Anal.
calcd. for C19H10ClNO3: C, 67.97; H, 3.00; N, 4.17. Found C, 68.09; H, 3.16; N, 4.31%.
9-Cyano-2-(20-furyl)-3-methyl-pyrano[2,3-f ]chromone
(8g). Recrystal-
lized from chloroform as a white solid. Mp 175 ꢁC (72% yield); IR (KBr):
2212 cmꢀ1 (9-CN), 1621 cmꢀ1 (chromone C O); UV (MeOH): 342 nm (log e 3.9),
=
260 nm (log e 4.3); 1H NMR (CDCl3): d 8.10 (d, J ¼ 9.0 Hz, H-5), 7.72 (dd,
J ¼ 1.5 Hz,0.8 Hz, H-50), 7.66 (s, H-10), 7.05 (dd, J ¼ 3.7 Hz, 0.8 Hz, H-30), 6.88 (d,
13
J ¼ 9.0 Hz, H-6), 6.65 (dd, J ¼ 3.7 Hz,1.5 Hz, H-40), 4.98 (d, J ¼ 1.5 Hz, 8-OCH2),
=
2.32 (s, 3-CH3); C NMR (CDCl3 þ DMSO-d6): d 178.1 (C-4, C O), 161.4
(C-6a), 157.8 (C-10b), 153.2 (C-2), 149.4 (C-50), 144.7 (C-20), 131.1 (C-10), 129.1
(C-5), 117.5 (C-4a), 116.3 (9-CN), 115.2 (C-30), 114.4 (C-6), 113.4 (C-3), 111.5
(C-40), 110.3 (C-9), 102.6 (C-10a), 63.8 (C-8-OCH2), 9.0 (C-3-CH3); ESIMS: m=z
306 [M þ H]þ and 328 [M þ Na]þ. Anal. calcd. for C18H11NO4: C, 70.82; H, 3.63;
N, 4.59. Found C, 70.64; H, 3.78; N, 4.33%.
ACKNOWLEDGMENTS
One of the authors (S. S. R.) thanks the Council for Scientific and Industrial
Research, New Delhi, India, for financial support and grants of junior and senior
research fellowships. Our sincere thanks go to the director of the Indian Institute
of Chemical Technology (IICT), Hyderabad, India, for providing spectral data
and library facilities.

PYRANO[2,3-f ]FLAVONES AND CHROMONES
1303
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