Substituent-controlled domino-Knoevenagel-hetero Diels - Alder reaction - A one-pot synthesis of polycyclic heterocycles

Article abstract of DOI:10.1016/j.tet.2010.07.028

The reaction of 2-(N-alkenyl-N-aryl)amino-4-oxo-4H-1-benzopyran-3- carbaldehyde with dimedone/Meldrum's acid/4-hydroxycoumarin by heating in ethanol in the presence of pyridine produces polycyclic heterocycles bearing pyridine and pyran rings in a one-pot reaction. The effect of substituents on N-atom of the amino function controls the mode of reaction. Terminal alkenes prefer intramolecular Michael type reaction, but non-terminal alkenes favour Diels-Alder reaction, whereas, under similar condition, 2-(N-alkyl-N-allyl) amino-4-oxo-4H-1-benzopyran-3-carbaldehyde undergoes domino-Knoevenagel-hetero Diels-Alder reaction.

Full text of DOI:10.1016/j.tet.2010.07.028

Tetrahedron 66 (2010) 7625e7632
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Substituent-controlled domino-Knoevenagel-hetero DielseAlder reactiond
a one-pot synthesis of polycyclic heterocycles
*
Sourav Maiti, Suman Kalyan Panja, Chandrakanta Bandyopadhyay
Department of Chemistry, R.K. Mission Vivekananda Centenary College, Rahara, Kolkata 700 118, West Bengal, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 June 2010
Received in revised form 13 July 2010
Accepted 13 July 2010
Available online 21 July 2010
The reaction of 2-(N-alkenyl-N-aryl)amino-4-oxo-4H-1-benzopyran-3-carbaldehyde with dimedone/
Meldrum’s acid/4-hydroxycoumarin by heating in ethanol in the presence of pyridine produces poly-
cyclic heterocycles bearing pyridine and pyran rings in a one-pot reaction. The effect of substituents on
N-atom of the amino function controls the mode of reaction. Terminal alkenes prefer intramolecular
Michael type reaction, but non-terminal alkenes favour DielseAlder reaction, whereas, under similar
condition, 2-(N-alkyl-N-allyl)amino-4-oxo-4H-1-benzopyran-3-carbaldehyde undergoes domino-Knoe-
venagel-hetero DielseAlder reaction.
Keywords:
2-Aminochromone-3-carbaldehyde
Intramolecular DielseAlder reaction
Knoevenagel reaction
1-Benzopyran
Ó 2010 Elsevier Ltd. All rights reserved.
Domino reaction
1. Introduction
intramolecular [3þ2] nitrone-olefin cycloaddition reaction.21 We
report herein the DKHDA reaction involving 3, which is controlled
Domino-Knoevenagel-hetero DielseAlder (DKHDA) reaction
has now become a popular tool for the synthesis of polycyclic
heterocycles.1e3 Compounds having an aldehyde functionality and
a suitably placed alkene or alkyne4 moiety can be made to undergo
DKHDA reaction. The active methylene components used for the
Knoevenagel reaction are usually either in the form of 1,3-dicar-
bonyl compounds or as a part of suitable heterocycles. The widely
studied substrates for DKHDA reaction are O-alkenylated sal-
icylaldehydes,5e7 but N-alkenylated analogues are studied a little.
by the substituents on the amine part of 3.
2. Results and discussion
On heating an equimolar mixture of 3 (R2¼aryl; R3¼R4¼H) and
dimedone (4) in ethanol for 4-5 h in the presence of catalytic
amount of pyridine produced compound 5 in good yields (Table 1,
entries 1e4). Formation of 5 may be rationalized by considering the
formation of intermediate 7a, which undergoes intramolecular
Michael type addition of the activated aromatic ring (8) (path a,
Scheme 1). Similar cyclisation process involving the aldehyde
group10,11,18,22 or using the Knoevenagel condensate23 has been
reported earlier. Literature survey revealed that DKHDA reactions
involving allyl moieties having terminal double bond are scarce.
Reaction of 2-allylbenzaldehyde with N,N’-dimethylbarbituric acid
N-Alkenylated-2-formylindole8 and N-alkenylated-
a-aminoacetal-
dehyde9 have been employed in DKHDA reaction.
2-Arylamino-4-oxo-4H-1-benzopyran-3-carbaldehyde (1)10e12
has proved itself to be a very good synthon for the synthesis of
various heterocycles. Although compound 1 was earlier utilized by
converting it into tertiary amines, followed by substitution with
suitable bisnucleophiles,13e16 we have reported deformylative
Mannich reaction on 1 for the synthesis of bischromones,17,18 re-
actions of different amines with 1,19 and conversion of 1 into 1-
benzopyrano[2,3-b]pyridines with different substitutions at their
3-positions.20 N-Alkenylated derivatives 3, obtained by the reaction
of 1 with 2 in the presence of K2CO3, have been utilized for the
synthesis of 1-benzopyrano[2,3-b]pyridines,16 and also used in
in the presence of EDDA,6 and
a,b-unsaturated thiocarbonyl gen-
erated from O-allylsalicylaldehyde5 are reported.
To check the effect of the substituent in the allyl part in the
intramolecular hetero DielseAlder (IHDA) reaction, compound 1
was alkenylated with cinnamyl bromide 2 (R3¼H, R4¼Ph) to form 3
(R3¼H, R4¼Ph). It was then heated with equimolar amount of 4 in
ethanol in the presence of catalytic amount of pyridine, when
a pentacyclic compound 6 (R3¼H, R4¼Ph) was obtained in mod-
erate yields (entries 5 and 6).
To examine the effect of alkyl group in the dienophile part of IHDA
* Corresponding author. Tel.: þ91 03325682049; e-mail address: kantachandra@
rediffmail.com (C. Bandyopadhyay).
reaction system, compound 3 (R3¼R4¼Me) admixed with dimedone
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.07.028

7626
S. Maiti et al. / Tetrahedron 66 (2010) 7625e7632
R3
O
NHR2
CHO
+
R1
R4
Br
2
O
1
K2CO3, NaI (cat.)
CH3CN, reflux, 9 h
R2
N
O
O
R4
R3
R1
CHO
3
R3
N
O
O
R4
O
R2
N
H3C
CH3
O
O
R2 = Aryl
Path a
4
R1
R3
Path b
R1
Z
R4
O
O
O
O
O
CH3
H3C
CH3
H3C
7b
7a
R3 = H
R4 = H, Me
R3 = H, Me
R4 = Me, Ph
R3
R3
N+
R4
O
R4
R2
N
10
O
1
8
Ha
O
O
R4
R3
N
12
14b
14
R1
11
6a
6
O
Hb
6
R1
Z
O
O
Z
R1
H
4
1
O
O
O-
OH
4
O
CH3
H3C
6
CH3
H3C
CH3
H3C
5
8
For 6
a: R1 = Me; R2 = p-C6H4(Me); R3 = H; R4 = Ph
For 5
a: R1 = Me; R3 = R4 = Z = H
1
3
2
4
b
: R = R = H; R = R = Ph
c: R1 = R3 = R4 = Me; R2 = Ph
d: R1 = H; R2 = Ph; R3 = R4 = Me
1
3
4
b
: R = R = R = H; Z = Me
c: R1 = Z = Me; R3 = R4 = H
d: R1 = R3 = R4 = Z = H
1
4
2
3
e
: R = R = Me; R = Ph; R = H
f: R1 = R3 = H; R2 = Ph; R4 = Me
g: R1 = R3 = R4 =H; R2 = Me
1
4
3
e
: R = R = Me; R = Z = H
f: R1 = R3 = Z = H; R4 = Me
1
2
3
4
h
: R = Me; R = Et; R = R = H
Scheme 1.
was heated under reflux in ethanol in the presence of pyridine and
surprisingly, compound 6 (R3¼R4¼Me) was obtained in good yield
(entries 7 and 8). For examining the effect of alkyl group in the allyl
part more precisely in a IHDA reaction, compound 3 (R3¼H, R4¼Me)
wassynthesized, and anequimolarmixture of 3 (R3¼H, R4¼Me) and 4
was reacted similarly. The reaction mixture produced two com-
pounds 5eef (15e17%) and 6eef (55e60%) (entries 9 and 10).
In an attempt to use the terminal alkene in compound 3 (R3¼R4¼H)
as a dienophile in the IHDA reaction, N-aryl moiety was replaced by N-
alkyl group and indeed the reaction of 3 (R2¼Me or Et; R3¼R4¼H) with
4 produced 6g or 6h (entries 11 and 12). The above results clearly
demonstrate the occurrence of twocompetitive reactions (path a and b,
Scheme 1), which are substituent-dependent. Although ene-reaction
was found to be a competitive reaction with DKHDA reaction,1 to the
best of our knowledge here is the first example where intramolecular
Michael reaction competes with DKHDA reaction.
Formation of 6 from 3 and dimedone may be rationalized by
considering the in situ formation of Knoevenagel condensate 7b,
which undergoes intramolecular DielseAlder reaction. The pres-
ence of alkyl or aryl group increases the energy of HOMO of the
dienophile and facilitates inverse electron demand DielseAlder
reaction by interacting with the LUMO of the in situ formed het-
erodiene (path b, Scheme 1).
The cis-stereochemistry of the C/D ring juncture in 6 was con-
sidered on the basis of the small coupling constant values
(JHaeJHb¼3e4 Hz). It is reported in the literature1 that the aromatic

S. Maiti et al. / Tetrahedron 66 (2010) 7625e7632
7627
Table 1
Reaction of 3 with dimedone (4)/Meldrum’s acid (9)/4-hydroxycoumarin (15) in ethanol under reflux in the presence of catalytic amount of pyridine
Entry
3
Active methylene
component
Time
Products (% yielda)
Mp (ꢀC)
R1
R2
R3
R4
1
2
3
4
5
6
7
8
9
Me
H
Me
H
Me
H
Me
H
Ph
Ar
Ar
Ph
Ar
Ph
Ph
Ph
Ph
H
H
H
H
H
H
Me
Me
H
H
H
H
H
Ph
Ph
Me
Me
Me
4
4
4
4
4
4
4
4
4
4.5 h
5 h
5 h
5 h
4 h
4 h
4 h
4.5 h
5 h
5a (85)
5b (80)
5c (70)
5d (80)
6a (63)
6b (58)
6c (74)
6d (72)
5e (15) and
6e (55)
5f (17) and
6f (60)
186e188
212e214
228e230
236e238
238e240
260e262
256e258
268e270
240e242
140e142
254e256
92e94
Me
10
H
Ph
H
Me
4
5 h
11
12
13
14
15
16
17
H
Me
Et
H
H
Me
Me
H
H
H
4
4
9
9
9
9
15
5 h
5 h
5 h
5 h
5 h
5 h
5 h
6g (50)
6h (55)
196e198
80e82
Me
Me
H
H
Me
Me
Ph
Ph
Ph
Ar
Ar
Me
Me
Ph
Ph
Ph
10a (68)
10b (55)
10c (58)
10d (46)
16a (52) and
17a (25)
16b (45) and
17b (27)
19a (80)
19b (76)
230e232
254e256
198e200
184e186
216e218
268e270
290e292
286e288
234e236
226e228
H
H
18
H
Ph
H
Ph
15
4.5 h
19
20
H
Me
Ar
Ph
H
H
H
H
15
15
5 h
4.5 h
‘Ar’ stands for 4-C6H4(Me).
a
isolated yields.
aldehydes and
a
,
b
-unsaturated aliphatic aldehydes give cis product
undergoes retro DielseAlder reaction to form ketene 13, which traps
water to form
-ketoacid 14 and decarboxylates to form 10.6
and aliphatic aldehydes prefer trans product in DKHDA reaction.
exo-Approach of dienophile in the Knoevenagel adduct 7c
(Scheme 2) leads to the trans-isomer 6E, but endo-approach (7d)
gives the cis-fused product 6 (Scheme 2).
The above reaction was then extended using other active meth-
ylene compounds. Compound3 yielded 10, when Meldrum’s acid(9)
was used in place of dimedone (Table 1, entries 13e16) (Scheme 3).
The reaction proceeds through the same pathway as in the case of
the reaction of 3 with 4. Compound 3 and 9 reacted to give 12 via the
condensate 11. Under the reaction condition compound 12
b
Use of 4-hydroxycoumarin (15) as an active methylene com-
pound, the above reaction produced 16 and 17 (entries 17 and 18)
by IDKHDA reaction8 (path a, Scheme 4). As in the previous cases,
the Knoevenagel condensate is formed first, which then interacts
with the dienophile in two ways as shown in 18a and 18b. Com-
pound 16 was formed when
a
,
b-unsaturated ketone moiety in 18a
acted as the heterodiene and 17 was formed when
a,b
-unsaturated
ester moiety in 18b acted as the heterodiene. Compound 18a acts as
better heterodiene than 18b, which is reflected into the higher yield
R2
R2
O
N
O
O
N
H
O
R3
R4
R1
R1
R3
X
H
O
O
R4
O
O
CH3
H3C
CH3
Exo-approach
H3C
6E
7c
R2
N
R2
N
O
H
R4
R3
O
O
R1
H
R1
O
O
O
O
O
6
R3
Endo-approach
7d
CH3
H3C
R4
Scheme 2.

7628
S. Maiti et al. / Tetrahedron 66 (2010) 7625e7632
R2
R2
N
O
O
N
O
O
O
O
H
R4
R3
O
O
3 +
R1
R1
O
O
H
O
O
O
9
O
R3
O
O
R4
CH3
H3C
11
12
R2
N
R2
N
R2
N
O
O
O
O
O
O
H
H
R4
R3
R4
H
R1
R4
R3
R1
R1
R3
H
H
O
H
O
C
O
HO2C
O
O
O
13
O
14
10
For 10
a: R1 = R3 = R4 = Me; R2 = Ph
b: R1 = H; R2 = Ph; R3 = R4 = Me
c: R1 = R3 = H; R2 = R4 = Ph
d: R1 = Me; R2 = p-C6H4(Me); R3 = H; R4 = Ph
Scheme 3.
R2
N
R2
N
O
O
O
O
O
O
O
Path a
O
O
3 +
R1
R1
OH
O
O
O
15
R3
R3
R4
R3 = R4 = H
R4
Path b
18b
18a
R3
R4
R2
N
R2
N
O
O
10
1
4
H
H
O
O
N
R4
R3
R4
R3
R1
R1
H
O
5
6
H
O
R1
Z
O
O
O
O
O
OH
O
O
O
16
17
19
For 16 and 17
a: R1 = Me; R2 = p-C6H4(Me); R3 = H; R4 = Ph
b: R1 = R3 = H; R2 = R4 = Ph
For 19
a: R1 = R3 = R4 = H; Z = Me
b: R1 = Me; R3 = R4 = Z =H
Scheme 4.
of 16 over 17. However, when 3 (R3¼R4¼H) was treated with 15 by
heating in ethanol in presence of pyridine, compound 19 was
produced following the involvement of the aromatic ring (entries
19 and 20) (path b, Scheme 4).
produce hitherto unreported polycyclic heterocycles. The sub-
stituents on the amino function control the mode of the reaction.
4. Experimental
4.1. General
3. Conclusions
The recorded mps are uncorrected. IR spectra were recorded in
KBr on a Beckman IR 20a, 1H NMR spectra on a Bruker 300 MHz
spectrometer in CDCl3 unless stated otherwise, mass spectra on
a Qtof Micro YA 263 instrument and elemental analysis on
In summary, we have reported domino-Knoevenagel-hetero
DielseAlder reaction of 2-N,N-disubstitutedaminochromone-3-
carbaldehyde 3 with various active methylene compounds to

S. Maiti et al. / Tetrahedron 66 (2010) 7625e7632
7629
a PerkineElmer 240c elemental analyzer. Light petroleum refers to
the fraction with 60e80 ꢀC. All chemicals used are of commercial
grade and are used as such.
5.95; N, 3.24. C27H25NO4 requires C, 75.86; H, 5.89; N, 3.28%]; Rf
(5% EtOAc/C6H6) 0.44; nmax (KBr) 3455, 2957, 2870, 1648,
1610 cmꢁ1
; dH 12.59 (1H, br s, exchangeable, OH), 8.14 (1H, br d, J
7.8 Hz, 4-H), 7.61e7.56 (1H, m, ArH), 7.38e7.36 (2H, m, ArH),
7.20e7.15 (1H, m, ArH), 7.09 (1H, br d, J 6.9 Hz, 10-H), 7.00e6.98
(2H, m, ArH), 6.18e6.09 (1H, m, vinylic-H), 5.42 (1H, d, J 17.4 Hz,
R3), 5.33 (1H, d, J 11.1 Hz, R4), 5.31 (1H, s, 6-H), 4.96 (1H, br d, J
16.5 Hz, NeCH2), 4.70 (1H, br d, J 16.5 Hz, NeCH2), 2.39 (1H, d, J
18.6 Hz, CH2eCMe2), 2.30 (1H, d, J 18.6 Hz, CH2eCMe2) 1.98 (1H,
d, J 16.8 Hz, CH2eCMe2), 1.90 (1H, d, J 16.8 Hz, CH2eCMe2), 1.01
(3H, s, CH3), 0.98 (3H, s, CH3).
4.2. General procedure for synthesis of 5 and/or 6
An ethanolic solution of a mixture of 3 (1 mmol) and 4 (1 mmol)
was heated under reflux for 4e5 h in the presence of catalytic
amount of pyridine (two drops). The reaction mixture was con-
centrated to obtain a solid, which was crystallized from benzene/
light petroleum mixture (60:40) to obtain 5aed or 6aed as faint
yellow or white crystalline solids. But the above reaction with 3
(R3¼H; R4¼Me) under similar conditions produced two com-
pounds, which were separated by column chromatography over
silica gel (100e200 mesh). Compounds 5eef were obtained using
benzene and compounds 6eef were obtained using 10% ethyl ac-
etate in benzene as eluent. On similar treatment, compound 3
(R2¼alkyl, R3¼R4¼H) produced 6geh, which were purified by
chromatography using 50% ethyl acetate in benzene as eluent.
4.2.5. 11-(But-2-en-1-yl)-6,11-dihydro-6-(5,5-dimethyl-3-hydroxy-
2-cyclohexenone-2-yl)-3-methyl-1-benzopyrano[2,3-b]quinoline-
5H-5-one (5e). White crystalline solid, mp 240e242 ꢀC; [found: C,
76.59; H, 6.51; N, 3.00. C29H29NO4 requires C, 76.46; H, 6.42; N,
3.07%]; Rf (5% EtOAc/C6H6) 0.51; nmax (KBr) 3467, 3016, 2890, 1670,
1620 cmꢁ1
; dH 12.68 (1H, br s, exchangeable, OH), 7.94 (1H, br d, J
7.8 Hz, 4-H), 7.41e7.36 (1H, m, ArH), 7.29e7.28 (1H, m, ArH),
7.20e7.15 (1H, m, ArH), 7.01e6.97 (3H, m, ArH), 5.90e5.82 (1H, m,
vinylic H), 5.81e5.71 (1H, m, R3), 5.30 (1H, s, 6-H), 4.89 (1H, br d, J
17.1 Hz, NeCH2), 4.57 (1H, br d, J 17.1 Hz, NeCH2), 2.43 (3H, s,
ArCH3), 2.38 (1H, d, J 18.6 Hz, CH2eCMe2), 2.32 (1H, d, J 18.6 Hz,
CH2eCMe2) 1.96 (1H, d, J 16.8 Hz, CH2eCMe2), 1.89 (1H, d, J 16.8 Hz,
CH2eCMe2), 1.74 (3H, d, J 5.4 Hz, R4), 1.00 (3H, s, CH3), 0.98 (3H, s,
CH3).
4.2.1. 11-Allyl-6,11-dihydro-6-(5,5-dimethyl-3-hydroxy-2-cyclo-
hexenone-2-yl)-3-methyl-1-benzopyrano[2,3-b]quinoline-5H-5-one
(5a). Faint yellow crystals, mp 186e188 ꢀC; [found: C, 76.09; H,
6.11; N, 3.12. C28H27NO4 requires C, 76.17; H, 6.16; N, 3.17%]; Rf (5%
EtOAc/C6H6) 0.49; nmax (KBr) 3458, 2952, 2871, 1645, 1608 cmꢁ1
; dH
12.65 (1H, br s, exchangeable, OH), 7.94 (1H, br s, 4-H), 7.39 (1H, br
d, J 8.4 Hz, 2-H), 7.28e7.26 (1H, m, ArH), 7.20e7.15 (1H, m, ArH),
7.09 (1H, br d, J 7.2 Hz,10-H), 7.01e6.98 (2H, m, ArH), 6.17e6.08 (1H,
m, vinylic-H), 5.41 (1H, d, J 17.4 Hz, R3), 5.33 (1H, d, J 10.8 Hz, R4),
5.31 (1H, s, 6-H), 4.93 (1H, br d, J 16.2 Hz, NeCH2), 4.69 (1H, br d, J
16.2 Hz, NeCH2), 2.42 (3H, s, ArCH3), 2.42e2.29 (2H, m,
CH2eCMe2), 1.97 (1H, d, J 16.8 Hz, CH2eCMe2), 1.90 (1H, d, J 16.8 Hz,
CH2eCMe2),1.01 (3H, s, CH3), 0.98 (3H, s, CH3); dC 197.2,175.8, 172.0,
157.5, 151.2, 138.6, 134.9, 133.6, 132.2, 128.3, 126.9, 126.8, 124.7,
123.6, 121.3, 120.8, 117.1, 116.3, 113.9, 97.9, 50.5, 47.0, 43.4, 31.6, 30.6,
30.2, 26.1, 20.8; m/z 442 (MþHþ), 464 (MþNaþ).
4.2.6. 11-(But-2-en-1-yl)-6,11-dihydro-6-(5,5-dimethyl-3-hydroxy-
2-cyclohexenone-2-yl)-1-benzopyrano[2,3-b]quinoline-5H-5-one
(5f). White crystalline solid, mp 254e256 ꢀC; [found: C, 76.29; H,
6.23; N, 3.10. C28H27NO4 requires C, 76.17; H, 6.16; N, 3.17%]; Rf (5%
EtOAc/C6H6) 0.49; nmax (KBr) 3470, 3016, 2890, 1670, 1625 cmꢁ1
; dH
12.63 (1H, br s, exchangeable, OH), 8.15 (1H, br d, J 7.8 Hz, 4-H), 7.59
(1H, br t, J 7.5 Hz, 2-H), 7.40e7.35 (2H, m, ArH), 7.21e7.16 (1H, m,
ArH), 7.10e6.98 (3H, m, ArH), 5.91e5.83 (1H, m, vinylic H),
5.82e5.71 (1H, m, R3), 5.30 (1H, s, 6-H), 4.91 (1H, br d, J 16.8 Hz,
NeCH2), 4.60 (1H, br d,
J 16.8 Hz, NeCH2), 2.43 (1H, d, J
4.2.2. 11-Allyl-6,11-dihydro-6-(5,5-dimethyl-3-hydroxy-2-cyclo-
hexenone-2-yl)-8-methyl-1-benzopyrano[2,3-b]quinoline-5H-5-one
(5b). Faint yellow crystals, mp 212e214 ꢀC; [found: C, 76.12; H,
6.05; N, 3.13. C28H27NO4 requires C, 76.17; H, 6.16; N, 3.17%]; Rf (5%
19.2 Hz, CH2eCMe2), 2.36 (1H, d, J 19.2 Hz, CH2eCMe2), 1.97 (1H, d,
J 16.8 Hz, CH2eCMe2), 1.90 (1H, d, J 16.8 Hz, CH2eCMe2), 1.75 (3H, d,
J 5.4 Hz, R4), 1.01 (3H, s, CH3), 0.98 (3H, s, CH3).
EtOAc/C6H6) 0.46; nmax (KBr) 3460, 3014, 2892, 1652, 1614 cmꢁ1
;
dH
4.2.7. 8-(4-Methylphenyl)-6-phenyl-1,2,3,4,6,6a,7,8-octahydro-
3,3,12-trimethyldi[1-benzopyrano][2,3-b:40,30-d]pyridine-14H,14bH-
1,14-dione (6a). White crystalline solid, mp 238e240 ꢀC; [found: C,
78.98; H, 6.19; N, 2.58. C35H33NO4 requires C, 79.07; H, 6.26; N,
2.63%]; Rf (10% EtOAc/C6H6) 0.12; nmax (KBr) 3034, 2926, 1665, 1633,
12.61 (1H, br s, exchangeable, OH), 8.13 (1H, br d, J 7.5 Hz, 4-H),
7.60e7.55 (1H, m, ArH), 7.36e7.34 (2H, m, ArH), 6.97 (1H, d, J 8.1 Hz,
10-H), 6.90e6.87 (2H, m, ArH), 6.16e6.07 (1H, m, vinylic-H), 5.41
(1H, d, J 17.1 Hz, R3), 5.32 (1H, d, J 10.5 Hz, R4), 5.27 (1H, s, 6-H), 4.91
(1H, br d, J 17.7 Hz, NeCH2), 4.68 (1H, br d, J 17.7 Hz, NeCH2),
2.50e2.33 (2H, m, CH2eCMe2), 2.24 (3H, s, ArCH3), 2.03e1.85 (2H,
m, CH2eCMe2), 0.99 (6H, s, 2ꢂCH3).
1613, 1542 cmꢁ1
; dH 7.93 (1H, br s, 13-H), 7.37e7.25 (6H, m, ArH),
7.20 (2H, d, J 7.5 Hz, ArH), 7.05 (2H, d, J 7.5 Hz, ArH), 6.87 (1H, d, J
8.1 Hz, 10-H), 5.20 (1H, d, J 9.9 Hz, 6-H), 4.39 (1H, br s, Hb), 3.85 (1H,
br d, J 12.0 Hz, NeCH2), 3.21 (1H, br d, J 12.0 Hz, NeCH2), 2.81e2.76
(1H, m, Ha), 2.47 (1H, d, J 17.1 Hz, 2-CH2), 2.40 (1H, d, J 17.1 Hz,
2-CH2), 2.38 (3H, s, ArCH3), 2.36 (1H, d, J 17.1 Hz, 4-CH2), 2.35 (3H, s,
ArCH3), 2.25 (1H, d, J 17.1 Hz, 4-CH2), 1.17 (3H, s, CH3), 1.13 (3H, s,
CH3); dC 197.8, 174.7, 164.1, 157.4, 150.7, 139.4, 136.8, 134.0, 132.5,
129.9, 129.0, 128.8, 128.3, 127.2, 125.8, 125.5, 123.0, 115.7, 112.9, 96.5,
77.8, 51.4, 50.7, 42.3, 36.2, 32.3, 29.6, 27.8, 25.5, 21.0, 20.7; m/z 532
(MþHþ), 554 (MþNaþ).
4.2.3. 11-Allyl-6,11-dihydro-3,8-dimethyl-6-(5,5-dimethyl-3-hy-
droxy-2-cyclohexenone-2-yl)-1-benzopyrano[2,3-b]quinoline-5H-5-
one (5c). Faint yellow crystals, mp 228e230 ꢀC; [found: C, 76.38; H,
6.35; N, 3.02. C29H29NO4 requires C, 76.46; H, 6.42; N, 3.07%]; Rf (5%
EtOAc/C6H6) 0.50; nmax (KBr) 3450, 2932, 2850, 1660, 1622 cmꢁ1
; dH
12.69 (1H, br s, exchangeable, OH), 7.93 (1H, br s, 4-H), 7.37 (1H, br d,
J 8.4 Hz, 2-H), 7.24 (1H, br d, J 9.0 Hz, 9-H), 6.98e6.86 (3H, m, ArH),
6.16e6.05 (1H, m, vinylic-H), 5.40 (1H, d, J 17.4 Hz, R3), 5.30 (1H, d, J
10.7 Hz, R4), 5.27 (1H, s, 6-H), 4.90 (1H, br d, J 15.6 Hz, NeCH2), 4.67
(1H, br d, J 15.6 Hz, NeCH2), 2.42 (3H, s, ArCH3), 2.41e2.33 (2H, m,
CH2eCMe2), 2.23 (3H, s, ArCH3), 1.97 (1H, d, J 17.7 Hz, CH2eCMe2),
1.91 (1H, d, J 17.7 Hz, CH2eCMe2), 1.10 (3H, s, CH3), 0.98 (3H, s, CH3).
4.2.8. 3,3-Dimethyl-6,8-diphenyl-1,2,3,4,6,6a,7,8-octahydrodi[1-ben-
zopyrano][2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione (6b). White
crystalline solid, mp 260e262 ꢀC; [found: C, 78.77; H, 5.85; N, 2.83.
C33H29NO4 requires C, 78.71; H, 5.80; N, 2.78%]; Rf (10% EtOAc/C6H6)
0.09; nmax (KBr) 3030, 2935, 1670, 1640, 1612, 1545 cmꢁ1
; dH 8.14
4.2.4. 11-Allyl-6,11-dihydro-6-(5,5-dimethyl-3-hydroxy-2-cyclo-
hexenone-2-yl)-1-benzopyrano[2,3-b]quinoline-5H-5-one
(5d). Faint yellow crystals, mp 236e238 ꢀC; [found: C, 75.79; H,
(1H, br d, J 7.2 Hz, 13-H), 7.40e7.16 (12H, m, ArH), 6.96 (1H, br d, J
7.8 Hz, 10-H), 5.22 (1H, d, J 9.6 Hz, 6-H), 4.40 (1H, br s, Hb), 3.89 (1H,
br d, J 12.0 Hz, NeCH2), 3.26 (1H, br d, J 12.0 Hz, NeCH2), 2.77 (1H,

7630
S. Maiti et al. / Tetrahedron 66 (2010) 7625e7632
br d, J 9.6 Hz, Ha), 2.47 (1H, d, J 17.1 Hz, 2-CH2), 2.41 (1H, d, J 17.1 Hz,
2-CH2), 2.36 (1H, d, J 17.4 Hz, 4-CH2), 2.27 (1H, d, J 17.4 Hz, 4-CH2),
1.17 (3H, s, CH3), 1.14 (3H, s, CH3).
(1H, d, J 16.8 Hz, 2-CH2), 2.30 (1H, d, J 16.8 Hz, 2-CH2), 2.25 (1H, d, J
17.4 Hz, 4-CH2), 2.15 (1H, d, J 17.4 Hz, 4-CH2), 1.08 (3H, s, CH3), 1.04
(3H, s, CH3); dC 197.3, 174.0, 164.8, 157.7, 152.5, 131.1, 126.0, 124.2,
123.3, 115.7, 112.2, 95.0, 66.4, 50.9, 49.5, 42.4, 35.9, 32.0, 29.0, 27.9,
24.7; m/z 366 (MþHþ), 388 (MþNaþ).
4.2.9. 1,2,3,4,6,6a,7,8-Octahydro-3,3,6,6,12-pentamethyl-8-phenyldi
[1-benzopyrano][2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione
(6c). White crystalline solid, mp 256e58 ꢀC; [found: C, 76.65; H,
6.58; N, 2.91. C30H31NO4 requires C, 76.73; H, 6.65; N, 2.98%]; Rf (10%
EtOAc/C6H6) 0.06; nmax (KBr) 3000, 2925, 1650, 1646, 1615,
4.2.14. 8-Ethyl-1,2,3,4,6,6a,7,8-octahydro-3,3,12-trimethyldi[1-ben-
zopyrano][2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione (6h). White
crystalline solid, mp 80e82 ꢀC; [found: C, 73.42; H, 6.82; N, 3.48.
C24H27NO4 requires C, 73.26; H, 6.92; N, 3.56%]; Rf (50% EtOAc/
1548 cmꢁ1
; dH 8.07 (1H, br s, 13-H), 7.43e7.36 (2H, m, ArH), 7.28
(1H, br d, J 8.1 Hz, ArH), 7.20e7.17 (3H, m, ArH), 6.86 (1H, d, J 8.1 Hz,
10-H), 4.52 (1H, br s, Hb), 3.89 (1H, dd, J 11.7, 5.4 Hz, NeCH2), 3.68
(1H, t, J 11.7 Hz, NeCH2), 2.39 (3H, s, ArCH3), 2.39e2.05 (5H, m,
2ꢂCH2þHa),1.47 (3H, s, CH3),1.39 (3H, s, CH3),1.02 (3H, s, CH3), 0.94
(3H, s, CH3); dC 195.8, 175.8, 167.2, 155.5, 151.3, 142.3, 133.7, 132.3,
129.2, 126.2, 125.8, 125.4, 122.7, 115.9, 109.7, 98.6, 77.6, 51.6, 48.8,
43.2, 37.9, 31.4, 29.2, 26.7, 26.5, 25.8, 23.3, 20.7; m/z 470 (MþHþ),
492 (MþNaþ).
C6H6) 0.12; nmax (KBr) 2915, 1670, 1646, 1630, 1545 cmꢁ1
; dH 7.93
(1H, br s, 13-H), 7.26 (1H, br d, J 8.4 Hz, 11-H), 7.10 (1H, d, J 8.4 Hz,
10-H), 4.20e4.03 (3H, m, 6-CH2þHb), 3.66 (1H, br d, J 9.6 Hz,
NeCH2), 3.56 (2H, q, J 6.3 Hz, NeCH2Me), 3.28 (1H, br d, J 9.6 Hz,
NeCH2), 2.57e2.52 (1H, m, Ha), 2.37 (3H, s, ArCH3), 2.41e2.13 (4H,
m, 2ꢂCH2), 1.24 (3H, t, J 6.3 Hz, NeCH2CH3), 1.08 (3H, s, CH3), 1.04
(3H, s, CH3).
4.2.10. 1,2,3,4,6,6a,7,8-Octahydro-8-phenyl-3,3,6,6-tetramethyldi[1-
benzopyrano][2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione
(6d). White crystalline solid, mp 268e270 ꢀC; [found: C, 76.54; H,
6.38; N, 2.95. C29H29NO4 requires C, 76.46; H, 6.42; N, 3.07%]; Rf (10%
EtOAc/C6H6) 0.05; nmax (KBr) 3015, 2946, 1674, 1629, 1619,
4.3. General procedure for the synthesis of 10
An equimolar mixture of 3 and 9 was heated under reflux in
ethanol in the presence of catalytic amount of pyridine (two
drops) for 5 h (Table 1). The solvent from the reaction mixture
was removed under reduced pressure and ice-water (10 g) was
added to the residue to afford a solid, which was filtered out. The
solid mass was chromatographed over silica gel using 10% ethyl
acetate in benzene as eluent to obtain 10 as white crystalline
solid.
1573 cmꢁ1
; dH 8.29 (1H, dd, J 7.2, 1.2 Hz, 13-H), 7.44e7.36 (3H, m,
ArH), 7.31e7.25 (2H, m, ArH), 7.20 (2H, br d, J 7.5 Hz, ArH), 6.96 (1H,
br d, J 8.4 Hz, 10-H), 4.53 (1H, br s, Hb), 3.89 (1H, dd, J 11.7, 5.7 Hz,
NeCH2), 3.80 (1H, t,
J 11.7 Hz, NeCH2), 2.33e2.06 (5H, m,
2ꢂCH2þHa),1.48 (3H, s, CH3),1.39 (3H, s, CH3),1.03 (3H, s, CH3), 0.95
(3H, s, CH3).
4.2.11. 1,2,3,4,6,6a,7,8-Octahydro-8-phenyl-3,3,6,12-tetramethyldi[1-
benzopyrano][2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione
(6e). White crystalline solid, mp 140e142 ꢀC; [found: C, 76.39; H,
6.48; N, 2.96. C29H29NO4 requires C, 76.46; H, 6.42; N, 3.07%]; Rf
(10% EtOAc/C6H6) 0.08; nmax (KBr) 3155, 2923, 1650, 1632, 1613,
4.3.1. 1,2,4,4a,5,6-Hexahydro-6-phenyl-4,4,10-trimethyl-1-benzo-
pyrano[2,3-b]pyrano[40,30-d]pyridine-12H,12bH-2,12-dione
(10a). White crystalline solid, mp 230e232 ꢀC; [found: C, 73.87;
H, 5.88; N, 3.50. C24H23NO4 requires C, 74.02; H, 5.95; N, 3.60%]; Rf
(10% EtOAc/C6H6) 0.08; nmax (KBr) 2979, 2928, 1724, 1611, 1554,
1556 cmꢁ1
;
dH 7.94 (1H, br s, 13-H), 7.47e7.42 (2H, m, ArH),
1482 cmꢁ1
; dH 7.94 (1H, br s, 11-H), 7.51e7.46 (2H, m, ArH), 7.38
7.35e7.30 (1H, m, ArH), 7.23e7.17 (3H, m, ArH), 6.82 (1H, d, J 8.4 Hz,
10-H), 4.45e4.40 (1H, m, 6-H), 4.34 (1H, br s, Hb), 3.99 (1H, dd, J
12.3, 3.0 Hz, NeCH2), 3.66 (1H, dd, J 12.3, 5.1 Hz, NeCH2), 2.58e2.53
(1H, m, Ha), 2.35 (3H, s, ArCH3), 2.32 (1H, d, J 15.9 Hz, 2-CH2), 2.27
(1H, d, J 15.9 Hz, 2-CH2), 2.22 (1H, d, J 16.5 Hz, 4-CH2), 2.17 (1H, d, J
16.5 Hz, 4-CH2), 1.45 (3H, d, J 6.3 Hz, 6-CH3), 1.09 (3H, s, CH3), 1.06
(3H, s, CH3).
(1H, br d, J 8.4 Hz, 9-H), 7.31e7.27 (3H, m, ArH), 6.94 (1H, d, J
8.4 Hz, 8-H), 4.07e3.99 (1H, m, 12b-H), 3.90e3.73 (2H, m, NeCH2),
3.41 (1H, dd, J 19.2, 8.0 Hz, 1-CH2), 2.41 (3H, s, ArCH3), 2.43e2.37
(1H, m, 1-CH2), 2.30e2.23 (1H, m, 4a-H), 1.65 (3H, s, CH3), 1.45 (3H,
s, CH3); dC 174.4, 169.8, 157.2, 151.2, 141.6, 134.6, 133.1, 129.5, 127.2,
126.0, 125.0, 122.2, 116.2, 99.1, 81.2, 47.9, 36.9, 32.6, 29.1, 26.5, 24.4,
20.8; m/z 390 (MþHþ), 412 (MþNaþ).
4.2.12. 1,2,3,4,6,6a,7,8-Octahydro-8-phenyl-3,3,6-trimethyldi[1-ben-
4.3.2. 4,4-Dimethyl-1,2,4,4a,5,6-hexahydro-6-phenyl[1-benzo-
pyrano][2,3-b]pyrano[40,30-d]pyridine-12H,12bH-2,12-dione
(10b). White crystalline solid, mp 254e256 ꢀC; [found: C, 73.68;
H, 5.55; N, 3.67. C23H21NO4 requires C, 73.58; H, 5.64; N, 3.73%];
Rf (10% EtOAc/C6H6) 0.08; nmax (KBr) 3025, 2910, 1728, 1618,
zopyrano][2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione
(6f). White
crystalline solid, mp 92e94 ꢀC; [found: C, 76.10; H, 6.07; N, 3.24.
C28H27NO4 requires C, 76.17; H, 6.16; N, 3.17%]; Rf (10% EtOAc/C6H6)
0.06; nmax (KBr) 3115, 2932, 1645, 1628, 1610, 1525 cmꢁ1
; dH 8.15
(1H, br d, J 7.2 Hz, 13-H), 7.45e7.42 (2H, m, ArH), 7.38e7.33 (2H, m,
ArH), 7.25e7.21 (3H, m, ArH), 6.92 (1H, br d, J 8.1 Hz, 10-H),
4.45e4.41 (1H, m, 6-H), 4.36 (1H, br s, Hb), 3.99 (1H, br d, J 11.7 Hz,
NeCH2), 3.66 (1H, dd, J 11.7, 4.8 Hz, NeCH2), 2.63e2.53 (1H, m, Ha),
2.36 (1H, d, J 18.6 Hz, 2-CH2), 2.27 (1H, d, J 18.6 Hz, 2-CH2), 2.23 (1H,
d, J 16.5 Hz, 4-CH2), 2.19 (1H, d, J 16.5 Hz, 4-CH2), 1.46 (3H, d, J
6.0 Hz, 6-CH3), 1.09 (3H, s, CH3), 1.06 (3H, s, CH3).
1575, 1496 cmꢁ1
; dH 8.16 (1H, dd, J 8.7, 1.2 Hz, 11-H), 7.52e7.44
(3H, m, ArH), 7.41e7.27 (4H, m, ArH), 7.04 (1H, br d, J 8.1 Hz, 8-
H), 4.07e4.00 (1H, m, 12b-H), 3.89e3.79 (2H, m, NeCH2), 3.41
(1H, dd, J 19.5, 8.1 Hz, 1-CH2), 2.39 (1H, dd, J 19.5, 9.6 Hz, 1-CH2),
2.31e2.23 (1H, m, 4a-H), 1.65 (3H, s, CH3), 1.45 (3H, s, CH3).
4.3.3. 4,6-Diphenyl-1,2,4,4a,5,6-hexahydro[1-benzopyrano][2,3-b]pyr-
ano[40,30-d]pyridine-12H,12bH-2,12-dione (10c). White crystalline
solid, mp 198e200 ꢀC; [found: C, 76.70; H, 4.91; N, 3.23. C27H21NO4
requires C, 76.58; H, 5.00; N, 3.31%]; Rf (10% EtOAc/C6H6) 0.15; nmax
4.2.13. 1,2,3,4,6,6a,7,8-Octahydro-3,3,8-trimethyldi[1-benzopyrano]
[2,3-b:40,30-d]pyridine-14H,14bH-1,14-dione (6g). White crystalline
solid, mp 196e198 ꢀC; [found: C, 72.40; H, 6.29; N, 3.76. C22H23NO4
requires C, 72.31; H, 6.34; N, 3.83%]; Rf (50% EtOAc/C6H6) 0.09; nmax
(KBr) 3030, 2900, 1717, 1620, 1584, 1516 cmꢁ1
; dH 8.13 (1H, dd, J 8.7,
0.9 Hz, 11-H), 7.50e7.43 (3H, m, ArH), 7.36e7.29 (7H, m, ArH),
7.26e7.24 (2H, m, ArH), 7.06 (1H, br d, J 8.1 Hz, 8-H), 5.36 (1H, d, J
5.7 Hz, 4-H), 3.83e3.78 (2H, m, NeCH2), 3.77e3.69 (1H, m, 12b-H),
3.59 (1H, dd, J 17.4, 7.2 Hz, 1-CH2), 2.73e2.69 (1H, m, 4a-H), 2.53
(1H, dd, J 17.4, 9.3 Hz, 1-CH2); dC 174.8, 170.8, 157.5, 152.9, 143.3,
(KBr) 2912, 1665, 1650, 1618, 1548 cmꢁ1
; dH 8.15 (1H, br d, J 7.8 Hz,
13-H), 7.55e7.35 (1H, m, ArH), 7.27e7.20 (2H, m, ArH), 4.22e4.10
(3H, m, 6-CH2þHb), 3.63 (1H, br d, J 9.3 Hz, NeCH2), 3.27 (1H, br d, J
9.3 Hz, NeCH2), 3.16 (3H, s, NeCH3), 2.55e2.53 (1H, m, Ha), 2.35

S. Maiti et al. / Tetrahedron 66 (2010) 7625e7632
7631
137.8, 132.2, 129.3, 128.8, 128.2, 126.6, 126.0, 125.3, 124.9, 124.8,
116.5, 112.6, 99.7, 80.5, 49.9, 38.3, 33.8, 25.2.
dione (17b). White crystalline solid, mp 286e288 ꢀC; [found: C,
77.78; H, 4.35; N, 2.71. C34H23NO5 requires C, 77.70; H, 4.41; N,
2.67%]; Rf (10% EtOAc/C6H6) 0.31; nmax (KBr) 3046, 2922, 1712,
4.3.4. 1,2,4,4a,5,6-Hexahydro-10-methyl-6-(4-methylphenyl)-4-phe-
nyl[1-benzopyrano][2,3-b]pyrano[40,30-d]pyridine-12H,12bH-2,12-di-
one (10d). White crystalline solid, mp 184e186 ꢀC; [found: C,
76.98; H, 5.54; N, 3.02. C29H25NO4 requires C, 77.14; H, 5.58; N,
3.10%]; Rf (10% EtOAc/C6H6) 0.16; nmax (KBr) 3140, 2980, 1712, 1615,
1645, 1621, 1574 cmꢁ1
; dH 8.14 (1H, br d, J 7.8 Hz, 15-H), 7.72 (1H,
br d, J 7.8 Hz, 2-H), 7.52e7.36 (10H, m, ArH), 7.30e7.27 (2H, m,
ArH), 7.22e7.20 (3H, m, ArH), 6.89 (1H, br d, J 8.4 Hz, 12-H), 4.85
(1H, d, J 10.2 Hz, 8-H), 3.87 (1H, d, J 10.5 Hz, 16b-H), 3.56e3.50
(1H, m, NeCH2), 3.38e3.30 (1H, m, NeCH2), 2.85e2.76 (1H, m,
8a-H).
1612, 1540 cmꢁ1
; dH 7.91 (1H, br s, 11-H), 7.33e7.27 (4H, m, ArH),
7.25e7.18 (4H, m, ArH), 7.13 (2H, d, J 8.1 Hz, ArH), 6.95 (1H, d, J
8.4 Hz, 8-H), 5.35 (1H, d, J 5.1 Hz, 4-H), 3.77e3.68 (3H, m, 12b-
HþNeCH2), 3.57 (1H, dd, J 17.7, 7.2 Hz, 1-CH2), 2.72e2.68 (1H, m,
4a-H), 2.53 (1H, dd, J 17.7, 9.3 Hz, 1-CH2), 2.41 (3H, s, ArCH3), 2.39
(3H, s, ArCH3); m/z 452 (MþHþ), 474 (MþNaþ).
4.5. General procedure for the synthesis of 19
An ethanolic solution of 3 (R3¼R4¼H) (1 mmol) and 4-hydrox-
ycoumarin (15) (1 mmol) was heated under reflux for 4e5 h in the
presence of catalytic amount of pyridine. The reaction mixture was
concentrated to obtain a solid, which was further purified by
crystallization from benzene/light petroleum mixture (60:40) to
obtain 19 as white crystalline solid (Table 1).
4.4. General procedure for the synthesis of 16 and 17
A mixture of 3 (1 mmol) and 4-hydroxycoumarin (15) (1 mmol)
was heated under reflux in ethanol in the presence of catalytic
amount of pyridine (two drops). The completion of the reaction was
monitored by TLC (Table 1). The reaction mixture was concentrated
under reduced pressure and the residual mass was treated with ice-
water (10 g) to afford a solid, which was chromatographed over
silica gel using 10% ethyl acetate in benzene as eluent to produce 16
and 17 as white crystalline solid.
4.5.1. 11-Allyl-6,11-dihydro-6-(4-hydroxy-2-oxo-2H-1-benzopyran-
3-yl)-8-methyl-1-benzopyrano[2,3-b]quinolin-5H-5-one
(19a). White crystalline solid, mp 234e236 ꢀC; [found: C, 75.28; H,
4.48; N, 2.97. C29H21NO5 requires C, 75.15; H, 4.57; N, 3.02%]; Rf (5%
EtOAc/C6H6) 0.57; nmax (KBr) 3415, 3012, 2857, 1645, 1610 cmꢁ1
; dH
13.35 (1H, br s, exchangeable, OH), 8.10 (1H, br d, J 7.8 Hz, 4-H), 8.06
(1H, br d, J 8.1 Hz, 50-H), 7.62e7.56 (1H, m, ArH), 7.46e7.34 (3H, m,
ArH), 7.28e7.23 (1H, m, ArH), 7.15 (1H, br d, J 8.1 Hz, ArH), 7.02 (1H,
br d, J 8.4 Hz, ArH), 6.94 (1H, d, J 9.0 Hz, 1-H), 6.93 (1H, br s, 7-H),
6.17e6.06 (1H, m, vinylic-H), 5.69 (1H, s, 6-H), 5.44 (1H, d, J 17.4 Hz,
R3), 5.33 (1H, d, J 10.5 Hz, R4), 4.88 (1H, ddd, J 17.4, 3.9, 1.8 Hz,
NeCH2), 4.75 (1H, ddd, J 17.4, 4.2, 1.8 Hz, NeCH2), 2.22 (3H, s,
ArCH3).
4.4.1. 14-Methyl-10-(4-methylphenyl)-8-phenyl-8,8a,9,10-tetrahy-
dro-1-benzopyrano[2,3-b]1-benzopyrano[30,40:500,600]pyrano[400,300-d]
pyridine-1H,16H,16bH-1,16-dione (16a). White crystalline solid, mp
216e218 ꢀC; [found: C, 78.21; H, 4.90; N, 2.46. C36H27NO5 requires
C, 78.10; H, 4.92; N, 2.53%]; Rf (10% EtOAc/C6H6) 0.16; nmax (KBr)
3035, 2923, 1725, 1637, 1612, 1542 cmꢁ1
; dH 7.92 (1H, br s, 15-H),
7.68 (1H, br d, J 8.4 Hz, 3-H), 7.48e7.42 (7H, m, ArH), 7.22e7.12 (6H,
m, ArH), 6.85 (1H, d, J 8.4 Hz, 12-H), 5.48 (1H, d, J 9.9 Hz, 8-H), 4.59
(1H, d, J 3.6 Hz, 16b-H), 3.99 (1H, dd, J 12.6, 3.3 Hz, NeCH2), 3.34
(1H, br d, J 12.6 Hz, NeCH2), 2.55e2.53 (1H, m, 8a-H), 2.40 (3H, s,
ArCH3), 2.32 (3H, s, ArCH3); dC 174.7, 164.0, 157.2, 156.2, 152.5, 150.7,
139.1, 137.8, 137.0, 134.1, 132.6, 131.0, 129.9, 129.2, 128.9, 128.2, 127.1,
125.8, 125.5, 123.3, 122.8, 122.4, 116.6, 115.6, 104.3, 95.6, 78.2, 51.1,
35.7, 28.0, 21.0, 20.7; m/z 554 (MþHþ).
4.5.2. 11-Allyl-6,11-dihydro-6-(4-hydroxy-2-oxo-2H-1-benzopyran-3-
yl)-3-methyl-1-benzopyrano[2,3-b]quinolin-5H-5-one (19b). White
crystalline solid, mp 226e228 ꢀC; [found: C, 75.04; H, 4.52; N, 2.99.
C29H21NO5 requires C, 75.15; H, 4.57; N, 3.02%]; Rf (5% EtOAc/C6H6)
0.58; nmax (KBr) 3424, 3022, 2848, 1656, 1618 cmꢁ1
; dH 13.40 (1H, br
s, exchangeable, OH), 8.05 (1H, dd, J 7.8, 0.9 Hz, 50-H), 7.95 (1H, br s,
4-H), 7.46e7.40 (2H, m, ArH), 7.31e7.20 (3H, m, ArH), 7.16e7.12 (2H,
m, ArH), 7.07e6.99 (2H, m ArH), 6.20e6.08 (1H, m, vinylic-H), 5.73
(1H, s, 6-H), 5.45 (1H, d, J 17.1 Hz, R3), 5.34 (1H, d, J 10.5 Hz, R4), 4.90
(1H, ddd, J 17.4, 4.2, 2.1 Hz, NeCH2), 4.76 (1H, ddd, J 17.4, 4.5, 1.2 Hz,
NeCH2), 2.42 (3H, s, ArCH3).
4.4.2. 8,10-Diphenyl-8,8a,9,10-tetrahydro-1-benzopyrano[2,3-b]1-
benzopyrano[30,40:500,600]pyrano[400,300-d]pyridine-1H,16H,16bH-1,16-
dione (16b). White crystalline solid, mp 290e292 ꢀC; [found: C,
77.82; H, 4.47; N, 2.61. C34H23NO5 requires C, 77.70; H, 4.41; N,
2.67%]; Rf (10% EtOAc/C6H6) 0.14; nmax (KBr) 3022, 2936, 1720, 1642,
Acknowledgements
1602, 1552 cmꢁ1
; dH 8.12 (1H, br d, J 6.6 Hz, 15-H), 7.68 (1H, br d, J
6.6 Hz, 3-H), 7.42e7.37 (11H, m, ArH), 7.27e7.16 (4H, m, ArH), 6.94
(1H, br d, J 7.8 Hz, 12-H), 5.50 (1H, d, J 9.6 Hz, 8-H), 4.61 (1H, br s,
16b-H), 4.04 (1H, br d, J 12.3 Hz, NeCH2), 3.39 (1H, br d, J 12.3 Hz,
NeCH2), 2.59e2.57 (1H, m, 8a-H).
We gratefully acknowledge CSIR, New Delhi [Project no. 01
(2206)/07/EMR-II] for financial assistance; Indian Institute of
Chemical Biology, Jadavpur and Indian Association for the Culti-
vation of Science, Jadavpur, Kolkata 700 032 for instrumental help;
the college authority for providing research facilities. SM is thankful
to Subhankar Santra for encouragement.
4.4.3. 14-Methyl-10-(4-methylphenyl)-8-phenyl-8,8a,9,10-tetrahy-
dro-1-benzopyrano[2,3-b]1-benzopyrano[30,20:500,600]pyrano[400,300-d]
pyridine-1H,16H,16bH-1,16-dione (17a). White crystalline solid, mp
268e270 ꢀC; [found: C, 77.96; H, 4.87; N, 2.45. C36H27NO5 requires
C, 78.10; H, 4.92; N, 2.53%]; Rf (10% EtOAc/C6H6) 0.34; nmax (KBr)
Supplementary data
3038, 2924, 1718, 1634, 1609, 1550 cmꢁ1
; dH 7.93 (1H, br s, 15-H),
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.tet.2010.07.028.
7.71 (1H, br d, J 7.8 Hz, 2-H), 7.51e7.38 (7H, m, ArH), 7.22e7.19 (4H,
m, ArH), 7.09 (2H, d, J 8.1 Hz, ArH), 6.89 (1H, d, J 8.4 Hz, 12-H), 4.85
(1H, d, J 10.2 Hz, 8-H), 3.86 (1H, d, J 10.5 Hz, 16b-H), 3.49e3.44 (1H,
m, NeCH2), 3.36e3.28 (1H, m, NeCH2), 2.80e2.74 (1H, m, 8a-H),
2.38 (3H, s, ArCH3), 2.34 (3H, s, ArCH3); m/z 554 (MþHþ).
References and notes
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