Imino Diels-Alder reactions: Efficient synthesis of pyrano and furoquinolines catalyzed by ZrCl4

Article abstract of DOI:10.1081/SCC-200036586

Anhydrous zirconium tetrachloride is found to be an efficient catalyst for the Imino Diels-Alder reactions of N-benzylideneanilines with 3,4-dihydro-2H-pyran and 2,3-dihydrofuran to afford pyrano and furo [3,2-c] quinolines in good yields.

Full text of DOI:10.1081/SCC-200036586

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Imino Diels–Alder Reactions:
Efficient Synthesis of Pyrano
and Furoquinolines Catalyzed
by ZrCl
M. Mahesh , Ch. Venkateshwar Reddy , K.
4
a
a
a
a
Srinivasa Reddy , P. V. K. Raju & V. V. Narayana
a
Reddy
a
Organic Chemistry Division‐II , Indian Institute of
Chemical Technology , Hyderabad, 500 007, India
Published online: 10 Jan 2011.
To cite this article: M. Mahesh , Ch. Venkateshwar Reddy , K. Srinivasa Reddy ,
P. V. K. Raju & V. V. Narayana Reddy (2004) Imino Diels–Alder Reactions:
Efficient Synthesis of Pyrano and Furoquinolines Catalyzed by ZrCl , Synthetic
4
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 34:22, 4089-4104, DOI: 10.1081/SCC-200036586
To link to this article: http://dx.doi.org/10.1081/SCC-200036586
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w
SYNTHETIC COMMUNICATIONS
Vol. 34, No. 22, pp. 4089–4104, 2004
Imino Diels–Alder Reactions: Efficient
Synthesis of Pyrano and Furoquinolines
Catalyzed by ZrCl4
M. Mahesh, Ch. Venkateshwar Reddy, K. Srinivasa Reddy,
*
P. V. K. Raju, and V. V. Narayana Reddy
Organic Chemistry Division-II, Indian Institute of Chemical Technology,
Hyderabad, India
ABSTRACT
Anhydrous zirconium tetrachloride is found to be an efficient catalyst
for the Imino Diels–Alder reactions of N-benzylideneanilines with
3,4-dihydro-2H-pyran and 2,3-dihydrofuran to afford pyrano and furo
[
3,2-c] quinolines in good yields.
Key Words: N-benzylideneaniline; 3,4-dihydro-2H-pyran; 2,3-dihydro-
furan; Imino Diels–Alder reaction; Zirconium tetrachloride.
*
Correspondence: V. V. Narayana Reddy, Organic Chemistry Division-II, Indian Insti-
tute of Chemical Technology, Hyderabad 500 007, India; E-mail: vaddu@iict.res.in.
4
089
DOI: 10.1081/SCC-200036586
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

4
090
Mahesh et al.
INTRODUCTION
Many natural products containing pyrano and furoquinoline moieties
are widely distributed in nature and found to be associated with a wide
[1]
[2]
range of biological activities such as psychotropic, antiallergic, anti-
[3]
[4]
inflammatory, and estrogenic activities. The synthesis of pyrano and
furoquinoline derivatives have acquired paramount importance due to their
potential biological activities. Hence, efforts were directed for the synthesis
of these compounds by different methods. Among them the Imino Diels–
Alder reaction catalyzed by Lewis acids between N-benzylideneanilines and
nucleophilic olefins is one of the most useful tools for the synthesis of nitrogen
[5]
containing heterocyclic compounds. Since the pioneering work of Povarov,
this reaction has been extensively studied with use of different Lewis acids
[
6a,6b]
[7a,7b]
[8] [9]
GdCl3, InCl3, LiClO4,
[10]
such as lanthanide salts
protic acids (TFA, p-TsOH), etc. In this quest it was thought of interest to
BF .OEt ,
3
2
1
1
[12]
use less toxic, potential green catalyst like ZrCl to develop new catalytic
4
reactions. The use of ZrCl as an efficient Lewis acid for various trans-
4
[
13]
[14]
formations, such as Friedel–Crafts reaction,
[
asymmetric Diels–Alder reactions,
Diels–Alder reactions,
and Biginelli cyclocondensation,
15]
[16]
has been well documented in the literature. However, its use in Imino
Diels–Alder reaction has not so far been reported.
RESULTS AND DISCUSSION
In the present article, we describe the synthesis and characterization of
di-substituted pyrano and furoquinolines Ia-b, IIa-b, IIIa-b, and IVa-b for
the first time by application of the Imino Diels–Alder reaction using ZrCl4
as a new catalyst. This procedure is simple, efficient, and has general appli-
cation for the synthesis of pyrano and furo[3,2-c] quinolines starting from
respective N-benzylideneanilines as dienes and 3,4-dihydro-2H-pyran(DHP)
or 2,3-dihydrofuran(DHF) as dienophiles to yield pyrano or furo quinolines
respectively (Scheme 2). Reaction of N-benzylideneanilines (1a–k) with
DHP or DHF in the presence of ZrCl (10 mol%) in DCM at ambient tempera-
4
ture resulted in the formation of endo (3a–k) and exo (4a–k) pyrano and
furoquinolines in 72–97% yield (Table 1).
This reaction was carried out in different solvents such as toluene, tetra-
hydrofuran, dichloroethane, acetonitrile, and dichloromethane. The latter
(DCM) was found to be the solvent of choice to obtain better yields of the
product. The structures of the products were characterized by IR, H NMR,
1
1
3
C NMR, and Mass spectroscopic data. The coupling constants of H-5
proton (J4a, 5) in products 3a-i, (5.2–5.8 Hz) and 4a–i (10.4–10.8 Hz) are in

Imino Diels–Alder Reactions
4091
4
Table 1. Synthesis of pyrano and furoquinolines catalyzed by ZrCl .
Imine
c
Product ratio
3 : 4
0
a,b
Entry
R
R
n
Yield(%)
1
1
1
1
1
1
1
1
1
1
1
a
b
c
d
e
f
H
H
H
H
H
H
1
1
1
1
1
1
1
1
1
0
0
82
75
76
75
72
81
78
73
79
95
97
30 : 70
20 : 80
33 : 67
28 : 72
32 : 68
25 : 75
25 : 75
40 : 60
25 : 75
70 : 30
77 : 33
4-F
4-Br
4-OCH
4-CH3
H
3
4-Cl
j
H
4-NO
2
h
i
H
3-Oph
3-Oph
H
4-CH3
H
j
k
H
Cl
a
Isolation yields after purification.
b
Reaction time for all entries is 180 min, 120 min for entry 1f, 90 min for 1j, and 60 min
for 1k.
c
Product ratio is based on isolation by column chromatography.
consonance with endo and exo configurations, respectively. Besides, the coup-
ling constant (J4a, 10b) in all products (2.7–2.9 Hz) indicates the cis junction
between pyran and quinoline rings.
It is of interest that the di-substituted 3-chloro-4-fluoro-N-benzylidenea-
niline (5) and DHP (2a) under the present reaction conditions yielded four
isomers Ia, IIa, IIIa, and IVa in the ratio 50:15:18:17, respectively, in an
overall yield of 69% (Scheme 2) containing a large excess of the endo
Scheme 1.

4
092
Mahesh et al.
Scheme 2.
isomer. It is for the first time that all four isomers are reported and isolated in
pure state from the reaction mixture by column chromatography and charac-
1
terized unequivocally by H NMR spectra and the chemical shifts of the diag-
nostic protons along with the coupling constants are given in Table 2.
As observed in the case of DHP, DHF also acted as a good dienophile
in reaction with 3-chloro-4-fluoro-N-benzylideneaniline (5) to obtain the
expected mixture of four isomers in the ratio of 60 : 12 : 17 : 11 in 93%
yield. All the four compounds (Ib, IIb, IIIb, and IVb) are new, and the
1
structures assigned are in consonance with the H NMR spectra and the
chemical shifts and coupling constants for diagnostic protons are given in
Table 3.
In summary, the results reveal that ZrCl is effective in catalytic amount
4
in Imino Diels–Alder reaction to synthesize pyrano [3,2-c] and furo [3,2-c]-
quinolines under mild reaction conditions in good yields. It is noteworthy to
mention that exo and endo isomers (Ia–b, IIa–b, IIIa–b, and IVa–b) of
compounds are reported for the first time, and the structures are unambigu-
1
13
ously assigned by using H NMR, C NMR, IR, and Mass spectroscopic
data. Further study on the ZrCl catalyzed Imino Diels–Alder reaction is
currently in progress.
4

Imino Diels–Alder Reactions
4093
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d

4
094
Mahesh et al.
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d

Imino Diels–Alder Reactions
4095
EXPERIMENTAL
1
13
H NMR, C NMR spectra were recorded on a Gemini spectrometer
00 MHz, 50 MHz, respectively, in CDCl by using TMS as internal standard.
2
3
IR spectra were recorded on a Nicolet 740 FT IR spectrometer and Mass
spectra on a VG Micro Mass 7070H. The melting points are uncorrected.
N-benzylideneanilines were prepared as per literature procedures.
General Procedure for the Synthesis of Pyrano
and Furo Quinolines
To a solution of the appropriate N-benzylideneaniline (5.5 mmol) in
CH Cl (5 mL) at room temperature was added sequentially DHP or DHF
2
2
(
5.5 mmol), ZrCl (10 mol%) and stirred for a period of time as mentioned
4
in Table 1. After completion of reation as indicated by TLC, the reaction
was quenched and worked up in the usual manner to afford the crude
product, which was purified by column chromatography by using 2–10%
EtOAc in hexane to obtain the pure product.
Spectroscopic Data
ꢀ
ꢀ
ꢀ
3
a. (4aRS , 5RS , 10bRS )-5-phenyl-3, 4, 4a, 5, 6, 10b-hexahydro-2H-
pyrano [3,2-c] quinoline.White crystals, m.p. 131.7–1328C (n-hexane).
2
1 1
IR (KBr): n ¼ 3300, 3010, 2940, 2850, 1480 cm
HNMR (CDCl ): d1.25–
3
1
2
.65 (m, 4H, 3-CH , 4-CH ), 2.15–2.20 (m, 1H, 4a-H), 3.38–3.65 (m, 2H,
2 2
-CH ), 3.80 (s, 1H, 6-H), 4.70 (d, J ¼ 2.7 Hz, 1H, 10b-H), 5.38
2
(
d, J ¼ 5.8 Hz, 1H, 5-H), 6.58 (d, J ¼ 7.8 Hz, 1H, 7-H), 6.80 (t, J ¼ 7.7 Hz,
1
EIMS: m/z (%): M 265(75), 235(16), 220(17), 206(100), 194(40),
H, 9-H), 7.05 (t, J ¼ 7.6 Hz, 1H, 8-H), 7.2–7.4 (m, 6H, 10-H, 5H-Ar).
þ
1
30(46), 91(39).
ꢀ
ꢀ
ꢀ
4
a. (4aRS , 5SR , 10bRS ) 5-phenyl-3, 4, 4a, 5, 6, 10b-hexahydro-2H-
pyrano [3,2-c] quinoline.Viscous liquid;
1
HNMR (CDCl ): d 1.25–1.90 (m, 4H, 3-CH , 4-CH ), 2.1–2.2 (m, 1H,
3
2
2
4
a-H), 3.7 (dt, J ¼ 2.5, 11.6, Hz, 1H, 2-H), 3.9–4.1 (m, 2H, 2-H, 6-H), 4.4
(
d, J ¼ 2.8 Hz, 1H, 10b-H), 4.7 (d, J ¼ 10.8 Hz, 1H, 5-H), 6.5
d, J ¼ 7.0 Hz, 1H, 7-H), 6.7 (t, J ¼ 7.1 Hz, 1H, 9-H), 7.05 (dt, J ¼ 7.2,
(
1
.1 Hz, 1H, 8-H), 7.2 (d, J ¼ 7.2, 1H, 10-H), 7.25–7.40 (m, 5H, 5H-Ar).

4
096
Mahesh et al.
ꢀ
ꢀ
ꢀ
3
1
b. (4aRS , 5RS , 10bRS ) 9-fluoro-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid,
m.p. 169–1708C (n-hexane).
21 1
IR (KBr): n ¼ 3375, 2940, 2830, 1590, 1490, 1220 cm . HNMR (CDCl ): d
3
1
.2–1.6 (m, 4H, 3-CH , 4-CH ), 2.0–2.1 (m, 1H, 4a-H), 3.20–3.35 (m, 1H,
2 2
2
-H), 3.4–3.6 (m, 1H, 2-H), 3.65 (s, 1H, 6-H), 4.5 (d, J ¼ 2.1 Hz, 1H, 10b-
H), 5.1 (d, J ¼ 5.8 Hz, 1H, 5-H), 6.4 (dd, J ¼ 4.3, 8.4 Hz, 1H, 7-H), 6.6 (dt,
J ¼ 2.9, 8.0 Hz, 1H, 8-H), 7.0 (dd, J ¼ 2.9, 9.1 Hz, 1H,10-H), 7.1–7.3
þ
(
m,5H, 5H-Ar). EIMS: m/z (%): M 283 (6), 240 (97), 226 (100), 90 (45).
ꢀ
ꢀ
ꢀ
4
1
b. (4aRS , 5SR , 10bRS ) 9-fluoro-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. Liquid;
1
HNMR (CDCl ): d 1.2–1.8 (m, 4H, 3-CH , 4-CH ), 1.9–2.0 (m, 1H, 4a-H),
3
2
2
3
.5 (dt, J ¼ 2.9, 11.1 Hz, 1H, 2-H), 3.8–4.0 (m, 2H, 2-H, 6-H), 4.2
(
d, J ¼ 2.9 Hz, 1H, 10b-H), 4.5 (d, J ¼ 10.4 Hz, 1H, 5-H), 6.3 (dd, J ¼ 4.4,
8
.9 Hz, 1H, 7-H), 6.7 (dt, J ¼ 2.9, 8.5, Hz, 1H, 8-H), 6.8 (dd, J ¼ 2.9,
.9 Hz, 1H, 10-H), 7.1–7.3 (m, 5H, 5H-Ar).
8
ꢀ
ꢀ
ꢀ
3
1
c. (4aRS , 5RS , 10bRS ) –9-Bromo-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid,
m.p. 1518C (n-hexane).
21 1
IR (KBr): n ¼ 3370, 2940, 2850, 1490 1080.cm . HNMR (CDCl ): d 1.3–
3
1
.4 (m, 1H, 4-H), 1.5–1.6 (m, 3H, 3-CH , 4-H), 2.0–2.2 (m, 1H, 4a-H), 3.3–
2
3
.5 (m, 1H, 2-H), 3.6–3.7 (m, 1H, 2-H), 3.9 (br S, 1H, 6-H), 4.7 (d, J ¼ 2.7 Hz,
1
H, 10b-H), 5.3 (d, J ¼ 5.8 Hz, 1H, 5-H), 6.5 (d, J ¼ 7.8 Hz, 1H, 7-H), 7.2 (dd,
J ¼ 2.6, 7.6 Hz, 1H, 8-H), 7.3–7.4 (m, 5H, 5H-Ar); 7.55 (S, 1H, 10-H). EIMS:
þ
m/z (%): M 343(2.5), 286(3.7), 233(32), 224(42), 194(100), 91(9).
ꢀ
ꢀ
ꢀ
4
1
c. (4aRS , 5SR , 10bRS ) –9-Bromo-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. Viscous liquid;
1
HNMR (CDCl ): d 1.2–1.9 (m, 4H, 3-CH , 4-CH ), 2.0–2.1 (m, 1H, 4a-H),
3
2
2
3
.7 (dt, J ¼ 2.8, 11.2, 1H, 2-H), 4.0–4.1 (m, 2H, 2-H, 6-H), 4.3 (d, J ¼ 2.7 Hz,
H, 10b-H), 4.65 (d, J ¼ 10.6 Hz, 1H, 5-H), 6.4 (d, J ¼ 7.1 Hz, 1H, 7-H), 7.1
1
(
dd, J ¼ 2.5, 7.9 Hz, 1H, 8-H), 7.2–7.4 (m, 6H, 10-H, 5H-Ar).

Imino Diels–Alder Reactions
4097
ꢀ
ꢀ
ꢀ
3
1
d. (4aRS , 5RS , 10bRS ) –9-methoxy-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid,
m.p. 147–1488C (n-hexane).
2
1 1
IR (KBr): n ¼ 3340, 2970, 2860, 1530, 1065 cm
HNMR (CDCl ): d 1.2–
3
1
3
1
.6 (m, 4H, 3-CH , 4-CH ), 2.0–2.1 (m, 1H, 4a-H), 3.3–3.5 (m, 1H, 2-H),
2 2
.5–3.7 (m, 2H, 2-H, 6-H), 3.75 (s, 3H, 9-OCH ), 4.6 (d, J ¼ 2.0 Hz, 1H,
3
0b-H), 5.3 (d, J ¼ 5.2 Hz, 1H, 5-H), 6.5 (d, J ¼ 8.2 Hz, 1H, 7-H), 6.65 (dd,
J ¼ 2.7, 8.2, Hz, 1H, 8-H), 6.9 (d, J ¼ 2.7 Hz, 1H, 10-H), 7.2–7.4 (m, 5H, 5H-
þ
Ar). EIMS: m/z (%): M 295(100), 238(41), 226(30), 161(23), 118(75),
9
2(22).
ꢀ
ꢀ
ꢀ
4
1
d. (4aRS , 5SR , 10bRS ) –9-methoxy-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid,
m.p. 101–1028C (n-hexane).
1
HNMR (CDCl ): d 1.2–1.8 (m, 4H, 3-CH , 4-CH ), 2.0–2.1 (m, 1H, 4a-H),
3
2
2
3
.3–3.5 (m, 1H, 2-H), 3.5–3.7 (m, 2-H, 2-H, 6-H) 3.7 (s, 3H, 9-OCH ), 4.4
3
(d, J ¼ 2.1 Hz, 1H, 10b-H), 4.63 (d, J ¼ 10.5 Hz, 1H, 5-H), 6.5
(d, J ¼ 8.0 Hz, 1H, 7-H), 6.7 (dd, J ¼ 2.8, 8.1, Hz, 1H, 8-H), 6.8
(d, J ¼ 2.8 Hz, 1H, 10-H), 7.2–7.40 (m, 5H, 5H-Ar).
ꢀ
ꢀ
ꢀ
3
1
e. (4aRS , 5RS , 10bRS ) –9-methyl-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid,
m.p. 129–1308C (n-hexane).
21 1
IR (KBr): n ¼ 3365, 2920, 2850, 1610, 1500, 1450 cm . HNMR (CDCl ): d
3
1.2–1.3 (m, 1H, 4-H), 1.4–1.5 (m, 1H, 4-H), 1.5–1.6 (m, 2H, 3-CH ) 2.1–2.2
2
(m, 1H, 4a-H), 2.3 (s, 3H, 9-CH ), 3.3–3.4 (m, 1H, 2-H), 3.5–3.6 (m, 1H,
3
2
-H), 3.7 (br S, 1H, 6-H), 4.6 (d, J ¼ 2.7 Hz, 1H, 10b-H), 5.25
(
d, J ¼ 5.7 Hz, 1H, 5-H), 6.5 (d, J ¼ 7.7 Hz, 1H, 7-H), 6.8 (d, J ¼ 7.5 Hz,
þ
1
H, 8-H), 7.2–7.4 (m, 6H, 10-H, 5H-Ar). EIMS: m/z (%): M 279(13),
17(100), 142(18), 92(8).
2
ꢀ
ꢀ
ꢀ
4
1
e. (4aRS , 5SR , 10bRS ) –9-methyl-5-phenyl-3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. Viscous liquid;
1
HNMR (CDCl ): d 1.3–1.4 (m, 1H, 4-H), 1.4–1.9 (m, 3H, 3-CH , 4-H),
3
2
2
.0–2.1 (m, 1H, 4a-H), 2.3 (s, 3H, 9-CH ), 3.5–3.6 (m, 1H, 2-H), 3.7–3.8
3
(
m, 1H, 2-H); 3.8–4.0 (m, 2H, 2-H, 6-H), 4.4 (d, J ¼ 2.7 Hz, 1H, 10b-H),
.7 (d, J ¼ 10.7 Hz, 1H, 5-H), 6.5 (d, J ¼ 7.1 Hz, 1H, 7-H), 6.9
d, J ¼ 7.2 Hz, 1H, 8-H), 7.3–7.50 (m, 6H, 10-H, 5H-Ar).
4
(

4
098
Mahesh et al.
ꢀ
ꢀ
ꢀ
3
1
f. (4aRS , 5RS , 10bRS ) -5-(4-chloro-phenyl) -3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White crystals,
m.p. 169–1718C (n-hexane).
2
1 1
IR (KBr): n ¼ 3330, 2930, 2840, 1480, 1070 cm
HNMR (CDCl ): d 1.2–1.4
3
(
m, 1H, 4-H), 1.4–1.7 (m, 3H, 3CH , 4-H), 2.0–2.2 (m, 1H, 4a-H), 3.3–3.5
2
(
m, 1H, 2-H), 3.5–3.7 (m, 1H, 2-H), 3.8 (br S, 1H, 6-H), 4.7 (d, J ¼ 2.8 Hz, 1H,
1
0b-H), 5.3 (d, J ¼ 5.6 Hz, 1H, 5-H), 6.6 (d, J ¼ 7.7 Hz, 1H, 7-H), 6.8
(
t, J ¼ 7.8 Hz, 1H, 9-H), 7.1 (t, J ¼ 7.7 Hz, 1H, 8-H), 7.3–7.5 (m, 5H, 10-H, 4H-
þ
Ar). EIMS: m/z (%): M 299 (71), 268(17), 240(100), 229(36), 130(63), 115(20).
ꢀ
ꢀ
ꢀ
4
1
f. (4aRS , 5SR , 10bRS ) -5-(4-chloro-phenyl) -3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White crystals,
m.p. 1228C (n-hexane).
1
HNMR (CDCl ): d 1.3–1.5 (m, 1H, 4-H), 1.6–1.9 (m, 3H, 3-CH , 4-H), 2.0–
3
2
2.1 (m, 1H, 4a-H), 3.7 (dt, J ¼ 2.8, 11.3Hz, 1H, 2-H), 4.0 (br S, 1H, 6-H), 4.1–
4.2 (m, 1H, 2-H), 4.4 (d, J ¼ 2.8 Hz, 1H, 10b-H), 4.7 (d, J ¼ 10.7Hz, 1H, 5-H),
6.55 (d, J ¼ 7.1 Hz, 1H, 7-H), 6.7 (t, J ¼ 7.6 Hz, 1H, 9-H), 7.1 (t, J ¼ 7.7 Hz,
1H, 8-H), 7.2 (d, J ¼ 7.3 Hz, 1H, 10-H), 7.3–7.4 (m, 4H, 4H-Ar).
ꢀ
ꢀ
ꢀ
3
1
g. (4aRS , 5RS , 10bRS ) -5-(4-nitro-phenyl) -3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. Yellow solid;
m.p. 189–1908C (CH Cl -n-hexane).
2
2
2
1 1
IR (KBr): n ¼ 3350, 3300, 1600, 1510, 1300 cm
HNMR (CDCl ): d 1.1–
3
1
3
.25 (m, 1H, 4-H), 1.3–1.7 (m, 3H, 3-CH , 4-H), 3.3–3.5 (m, 1H, 2-H), 3.5–
2
.7 (m, 1H, 2-H), 3.7–3.8 (br, 1H, 6-H), 4.8 (d, J ¼ 2.8 Hz, 1H, 10b-H), 5.3
(
d, J ¼ 5.7 Hz, 1H, 5-H), 6.6 (d, J ¼ 7.6 Hz, 1H, 7-H), 6.8 (t, J ¼ 7.8 Hz,
1
H, 9-H), 7.1 (t, J ¼ 7.8 Hz, 1H, 8-H), 7.4 (d, J ¼ 7.6 Hz, 1H, 10-H), 7.6
1
3
(
(
d, J ¼ 7.8 Hz, 2H, 2H-Ar), 8.2 (d, J ¼ 7.8 Hz, 2H, 2H-Ar). CNMR
CDCl ): d 149.2, 147.7, 144.8, 128.6, 128.0, 124.0, 120.3, 119.4, 115.2,
3
þ
7
2.8, 61.0, 59.4, 39.3, 26.5, 18.4. EIMS: m/z (%): M 310(56), 252(100),
2
H, 5.85; N, 9.03. found: C, 69.44; H, 5.43; N, 9.18.
06(34), 189(21), 130(55), 115(13). Anal. Calcd. for C H N O : C, 69.66;
1
8 18 2 3
ꢀ
ꢀ
ꢀ
4
1
g. (4aRS , 5SR , 10bRS ) -5-(4-nitro-phenyl) -3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. Yellow solid,
m.p. 169–1708C (CH Cl -n-hexane).
2
2
1
HNMR (CDCl ): d 1.3–1.9 (m, 4H, 3-CH , 4-CH ), 2.0–2.1 (m, 1H, 4a-
3
2
2
H), 3.75 (dt, J ¼ 2.0, 11.1, Hz, 1H, 2-H), 4.0–4.1 (m, 2H, 2-H, 6-H), 4.4

Imino Diels–Alder Reactions
4099
(
(
d, J ¼ 2.8 Hz, 1H, 10b-H), 4.85 (d, J ¼ 10.7 Hz, 1H, 5-H), 6.55
d, J ¼ 7.1 Hz, 1H, 7-H), 6.75 (t, J ¼ 7.3 Hz, 1H, 9-H), 7.1 (t, J ¼ 7.6 Hz,
H, 8-H), 7.2 (t, J ¼ 7.8 Hz, 1H, 10-H), 7.6 (d, J ¼ 7.7 Hz, 2H, 2H-Ar), 8.2
d, J ¼ 7.8 Hz, 2H, 2H-Ar).
h. (4aRS , 5RS , 10bRS ) –5-(3-phenoxy-phenyl) -3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. White Solid,
1
(
ꢀ
ꢀ
ꢀ
3
1
m.p. 135–1368C (CH Cl -n-hexane).
2
2
2
1 1
IR (KBr): n ¼ 3350, 2940, 2860, 1580, 1490cm
HNMR (CDCl ): d1.3–1.6
3
(
m,4H, 3-CH , 4-CH ), 2.1–2.2 (m, 1H, 4a-H), 3.3–3.4 (m, 1H, 2-H), 3.8 (s, 1H,
2 2
6
-H), 4.7 (d, J ¼ 2.7 Hz, 1H, 10b-H), 5.3 (d, J ¼ 5.8 Hz, 1H, 5-H), 6.55
(
d, J ¼ 7.8 Hz, 1H, 7-H), 6.8 (t, J ¼ 7.7 Hz, 1H, 8-H), 6.9 (t, J ¼ 7.1 Hz, 1H,
1
0-H), 7.0–7.2 (m, 5H, 9-H, 4H-Ar), 7.3–7.45 (m, 5H, 5H-Ar). CNMR
3
1
(CDCl ): d 157.3, 144.9, 143.3, 129.7, 129.6, 128.0, 127.5, 123.3, 121.6,
3
119.9, 118.8, 118.4, 117.7, 117.2, 114.4, 72.6, 60.5, 59.1, 38.9, 25.4, 18.0.
EIMS: m/z (%):M 356 (4)190(41), 175(49), 127(47), 111(100).
þ
ꢀ
ꢀ
ꢀ
4
1
h. (4aRS , 5SR , 10bRS ) –5-(3-phenoxy-phenyl) -3, 4, 4a, 5, 6,
0b-hexahydro-2H-pyrano [3,2-c] quinoline. Viscous liquid.
1
HNMR (CDCl ): d 1.2–1.25 (m, 1H, 4-H), 1.3–1.4 (m, 1H, 4-H), 1.5–1.6
3
(
(
m, 1H, 3-H), 1.6–1.7 (m, 1H, 3-H), 2.0–2.1 (m, 1H, 4a-H), 3.6–3.7
m, 1H, 2-H), 4.0–4.1 (m, 2H, 2-H, 6-H), 4.35 (d, J ¼ 2.8 Hz, 1H, 10b-H),
4
.7 (d, J ¼ 10.8 Hz, 1H, 5-H), 6.5 (d, J ¼ 7.0 Hz, 1H, 7-H), 6.7
(
t, J ¼ 7.1 Hz, 1H, 8-H), 6.9 (d, J ¼ 7.2, Hz, 1H, 10-H), 7.0–7.4 (m, 10H,
9
-H, 4H-Ar, 5H-Ar).
ꢀ
ꢀ
ꢀ
3
4
i. (4aRS , 5RS , 10bRS ) –9-methyl–5-(3-phenoxy-phenyl) -3, 4,
a, 5, 6, 10b-hexahydro-2H-pyrano [3,2-c] quinoline. Liquid.
2
1 1
IR (neat): n ¼ 3410, 2920, 2820, 1590, 1490, 1240 cm , HNMR (CDCl ): d
3
1
2
.2–1.4 (m, 1H, 4-H), 1.5–1.7 (m, 3H, 3-CH , 4-H), 2.1–2.2 (m, 1H, 4a-H),
2
.3 (S, 3H, 9-CH ), 3.5–3.7 (m, 3H, 2-CH , 6-H), 4.6 (d, J ¼ 2.6 Hz 1H, 10b-
3
2
H), 5.2 (d, J ¼ 5.7 Hz, 1H, 5-H), 6.5 (d, J ¼ 7.6 Hz, 1H, 7-H), 6.8–7.4
þ
(
m, 11H, 8-H, 10-H, 4H-Ar, 5H-Ar). EIMS: m/z (%):M 371(12), 340(11),
14(13), 142(18), 89(100).
3
ꢀ
ꢀ
ꢀ
4
4
i. (4aRS , 5SR , 10bRS ) –9-methyl-5-(3-phenoxy-phenyl) -3, 4,
a, 5, 6, 10b-hexahydro-2H-pyrano [3,2-c] quinoline. Liquid.
1
HNMR (CDCl ): d 1.3–1.4 (m, 1H, 4-H), 1.5–1.9 (m, 3H, 3-CH , 4-H),
3
2
2
.0–2.1 (m, 1H, 4a-H), 2.3 (s, 3H, 9-CH ), 3.6–3.8 (m, 1H, 2-H), 3.8–3.9
3

4
100
Mahesh et al.
(
m, 1H, 2-H), 4.0–4.1 (m, 1H, 6-H), 4 3 (d, J ¼ 2.7 Hz, 1H, 10b-H), 4.7
d, J ¼ 10.6 Hz, 1H, 5-H), 6.5 (d, J ¼ 7.2, 1H, 7-H), 6.8–7.4 (m, 11H, 8-H,
(
1
0-H, 4H-Ar, 5H-Ar).
ꢀ
ꢀ
ꢀ
3
9
j. (3aRS , 4RS , 9bRS ) –4-phenyl-2, 3, 3a, 4, 5, 6,
b-hexahydro-2H-furo [3,2-c] quinoline. White crystals, m.p. 1908C
(
n-hexane).
2
1 1
IR (KBr): n ¼ 3310, 1595, 1475 cm , HNMR (CDCl ): d 1.47–1.59 (m, 1H,
3
3
5
-H), 2.1–2.3 (m, 1H, 3-H), 2.7–2.85 (m, 1H, 3a-H), 3.6–3.9 (m, 3H, 2-CH ,
2
-H), 4.68 (d, J ¼ 2.6 Hz, 1H, 9b-H), 5.22 (d, J ¼ 7.8 Hz, 1H, 4-H), 6.75
(
t, J ¼ Hz, 1H, 7-H), 6.82 (d, J ¼ 7.8 Hz, 1H, 6-H), 7.02 (dt, J ¼ 1.4,
17 17
7
.4 Hz 1H, 8-H), 7.25–7.45 (m, 6H, 9-H, 5H-Ar). Anal. Calcd. for C H N
O: C, 81.24; H, 6.82; N, 5.57. found: C, 81.37; H, 6.42; N, 5.48. EIMS: m/
þ
z (%): M 251(92), 220(19), 206(100), 174(16), 146(22), 130(32), 91(34).
ꢀ
ꢀ
ꢀ
4
9
j. (3aRS , 4SR , 9bRS ) –4-phenyl-2, 3, 3a, 4, 5, 6,
b-hexahydro-2H-furo [3,2-c] quinoline. Light yellow colour liquid;
1
HNMR (CDCl ): d 1.6–1.8 (m, 1H, 3-H), 1.95–2.1 (m, 1H, 3-H), 2.4–
3
2
.5 (m, 1H, 3a-H), 3.75–4.0 (m, 2H, 4-H, 5-H), 4.05–4.1 (m, 2H, 2-CH2),
.57 (d, J ¼ 5.2 Hz, 1H, 9b-H), 6.58 (d, J ¼ 7.4 Hz, 1H, 6-H), 6.77
4
(
t, J ¼ 7.4 Hz, 1H, 7-H), 7.08 (dt, J ¼ 1.4, 7.0, Hz, 1H, 8-H), 7.3–7.5
m, 6H, 9-H, 5H-Ar).
(
ꢀ
ꢀ
ꢀ
3
9
k. (3aRS , 4RS , 9bRS ) –4-(4-chloro-phenyl)-2, 3, 3a, 4, 5, 6,
b-hexahydro-2H-furo [3,2-c] quinoline. White crystals,
m.p. 110–1128C (n-hexane).
2
1 1
IR (KBr): n ¼ 3325, 1610, 1480 cm , HNMR (CDCl ): d 1.45–1.6 (m, 1H,
3
3
2
6
-H), 2.0–2.2 (m, 1H, 3-H), 2.65–2.72 (m, 1H, 3a-H), 3.6–3.8 (m, 3H,
-CH , 5-H), 4.66 (d, J ¼ 2.9 Hz, 1H, 9b-H), 5.21 (d, J ¼ 8.1 Hz, 1H, 4-H),
2
.53 (d, J ¼ 7.4 Hz, 1H, 6-H), 6.77 (t, J ¼ 7.4 Hz, 1H, 7-H), 7.03 (dt,
1
3
J ¼ 1.4, 7.4 Hz, 1H, 8-H), 7.25–7.45 (m, 6H, 9-H, 5H-Ar). CNMR
(
CDCl ): d 144.6, 140.6, 133.2, 130.0, 129.5, 128.7, 128.3, 122.5, 119.3,
3
1
14.9, 66.6, 56.8, 45.5, 24.5. Anal. Calcd. for C H N O Cl C, 71.45; H,
17 16
þ
5.64; N, 4.90. found: C, 71.51; H, 5.59; N, 4.81. EIMS: m/z (%): M 285
15), 240(20), 141(35), 43(100).
(

Imino Diels–Alder Reactions
4101
ꢀ
ꢀ
ꢀ
4
9
k. (3aRS , 4SR , 9bRS ) –4- (4-chloro-phenyl)-2, 3, 3a, 4, 5, 6,
b-hexahydro-2H-furo [3,2-c] quinoline. White crystals,
m.p. 114–1168C (n-hexane).
1
HNMR (CDCl ): d 1.6–1.7 (m, 1H, 3-H), 1.9–2.0 (m, 1H, 3-H), 2.3–2.4
3
(m, 1H, 3a-H), 3.7–3.8 (m, 2H, 4-H, 5-H), 3.9–4.1 (m, 2H, 2-CH ), 4.53
2
(
d, J ¼ 4.8 Hz, 1H, 9b-H), 6.56 (d, J ¼ 7.8 Hz, 1H, 6-H), 6.76 (td, J ¼ 1.1,
7
5
.4 Hz, 1H, 8-H), 7.07(td, J ¼ 1.4, 8.1 Hz, 1H, 7-H), 7.25–7.4 (m, 6H, 9-H,
H-Ar).
ꢀ
ꢀ
ꢀ
Ia. (4aRS , 5RS , 10bRS ) –8-chloro-9-fluoro–5-phenyl-3, 4, 4a, 5,
, 10b-hexahydro-2H-pyrano [3,2-c] quinoline. White needles,
m.p. 1728C (n-hexane).
6
2
1 1
IR (KBr): n ¼ 3350, 2950, 1590, 1450, 1310 cm , HNMR (CDCl ): d 1.2–
3
1
3
.6 (m, 4H, 3-CH , 4-CH ), 2.0–2.2 (m, 1H, 4a-H), 3.3–3.4 (m, 1H, 2-H),
2 2
.5–3.6 (m, 1H, 2-H), 3.7–3.8 (br S, 1H, 6-H), 4.6 (d, J ¼ 2.1 Hz, 1H, 10b-
H), 5.2 (d, J ¼ 5.1 Hz, 1H, 5-H), 6.6 (d, J ¼ 5.8 Hz, 1H, 7-H), 7.2
1
3
(
d, J ¼ 9.5 Hz, 1H, 10-H), 7.3–7.4 (m, 5H, 5H-Ar). CNMR (CDCl ): d
3
1
1
53.2, 150.0, 141.8, 141.8, 140.4, 128.4, 127.7, 126.6, 120.1, 120.1, 120.0,
19.7, 115.3, 115.2, 114.9, 60.8, 59.3, 38.4, 25.1, 17.9 Anal. calcd for
C H N O Cl F: C, 68.03; H, 5.39; N, 4.41. found: C, 68.43; H, 5.75; N,
1
7 17
þ
4
.43. EIMS: m/z (%): M 317(100), 286(12), 272(13), 259(75), 182(29),
41(62), 91(39).
1
ꢀ
ꢀ
ꢀ
IIa. (4aRS , 5RS , 10bRS ) –10-chloro-9-fluoro–5-phenyl-3, 4, 4a,
, 6, 10b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid,
5
m.p.1428C (n-hexane).
1
HNMR (CDCl ): d 1.1–1.2 (m, 1H, 4-H), 1.3–1.4 (m, 1H, 4-H), 1.6–1.8
3
(
(
(
m, 1H, 3-H), 1.8–1.9 (m, 1H, 3-H), 2.3–2.4 (m, 1H, 4a-H), 2.9–3.0
m, 1H, 6-H), 3.4–3.5 (m, 1H, 2-H), 3.5–3.6 (m, 1H, 2-H), 4.35
d, J ¼ 3.9 Hz, 1H, 10b-H), 5.0 (d, J ¼ 5.0 Hz, 1H, 5-H), 6.4 (dd, J ¼ 4.2,
8
.5 Hz, 1H, 7-H), 6.9 (t, J ¼ 8.6 Hz, 1H, 8-H), 7.1–7.4 (m, 5H, 5H-Ar).
ꢀ
ꢀ
ꢀ
IIIa. (4aRS , 5SR , 10bRS ) –8-chloro-9-fluoro–5-phenyl-3, 4, 4a,
, 6, 10b-hexahydro-2H-pyrano [3,2-c] quinoline. White solid, m.p.
0–718C (n-hexane).
5
7
1
HNMR (CDCl ): d 1.3–1.8 (m, 4H, 3-CH , 4-CH ), 2.0–2.1 (m, 1H, 4a-H),
3
2
2
3
.6–3.7 (m, 1H, 2-H), 3.95–4.1 (m, 2H, 2-H, 6-H), 4.3 (d, J ¼ 2.9 Hz, 1H,

4
102
Mahesh et al.
1
0b-H), 4.6 (d, J ¼ 10.2 Hz, 1H, 5-H), 6.55 (d, J ¼ 6.5 Hz, 1H, 7-H), 7.0
(
d, J ¼ 9.5 Hz, 1H, 10-H), 7.3–7.4 (m, 5H, 5H-Ar).
ꢀ
ꢀ
ꢀ
IVa. (4aRS , 5SR , 10bRS ) –10-chloro-9-fluoro–5-phenyl-3, 4, 4a,
, 6, 10b-hexahydro-2H-pyrano [3,2-c] quinoline. Colorless crystals,
5
m.p. 178–1798C (n-hexane).
1
HNMR (CDCl ): d 1.2–2.0 (m, 5H, 3-CH , 4-CH , 4a-H), 3.6–3.8
2
3
2
(
t, J ¼ 12.4 Hz, 1H, 2-H), 4.0 (brs, 1H, 6-H), 4.1 (m, 1H, 2-H), 4.6
d, J ¼ 2.1 Hz, 1H, 10b-H), 4.7 (d, J ¼ 13.9 Hz, 1H, 5-H), 6.3 (dd, J ¼ 4.4,
(
8
.7 Hz, 1H, 7-H), 6.9 (t, J ¼ 8.7 Hz, 1H, 8-H), 7.2–7.4 (m, 5H, 5H-Ar).
ꢀ
ꢀ
ꢀ
Ib. (3aRS , 4RS , 9bRS ) –7-chloro-8-fluoro–4-phenyl-2, 3, 3a, 4, 5,
, 9b-hexahydro-2H-furo [3,2-c] quinoline. White crystals,
m.p. 139–1408C (n-hexane).
6
2
1
1
IR (KBr): n ¼ 3320, 1640, 1480 cm , HNMR (CDCl ): d 1.4–1.5
3
(
(
m, 1H, 3-H), 2.0–2.2 (m, 1H, 3-H), 2.7–2.8 (m, 1H, 3a-H), 3.6–3.8
m, 3H, 2-CH , 5-H), 4.66 (d, J ¼ 2.9 Hz, 1H, 9b-H), 5.14 (d, J ¼ 7.4 Hz,
2
1
7
1
5
4
2
H, 4-H), 6.59 (d, J ¼ 5.9 Hz, 1H, 6-H), 7.1 (d, J ¼ 9.6 Hz 1H, 9-H), 7.3–
1
.5 (m, 5H, 5H-Ar). CNMR (CDCl ): d 153.3, 150.1, 141.5, 128.7, 127.8,
3
3
26.3, 122.4, 122.3, 120.5, 120.3, 117.3, 117.0, 115.7, 87.2, 75.2, 66.9,
7.2, 45.2, 24.3, Anal. Calcd. for C H N O Cl F: C, 67.22; H, 4.98; N,
1
7 15
þ
.61. found: C, 66.51; H, 4.91; N, 4.43. EIMS: m/z (%): M 303 (100),
58(44), 226(8), 198(13), 91(30).
ꢀ
ꢀ
ꢀ
IIb. (3aRS , 4SR , 9bRS ) –7-chloro-8-fluoro–4-phenyl-2, 3, 3a, 4,
, 6, 9b-hexahydro-2H-furo [3,2-c] quinoline. Pale yellow solid,
5
m.p. 1488C (n-hexane).
1
HNMR (CDCl ): d 1.6–1.8 (m, 1H, 3-H), 1.95–2.1 (m, 1H, 3-H), 2.4–2.5
3
(
m, 1H, 3a-H), 3.7 (d, J ¼ 10.7 Hz, 1H, 4-H), 3.75–3.85 (m, 1H, 5-H),
3
.9–4.1 (m, 2H, 2-CH ), 4.50 (d, J ¼ 5.2 Hz, 1H, 9b-H), 6.6 (d, J ¼ 6.3 Hz,
2
1
H, 6-H), 7.1 (d, J ¼ 9.2 Hz 1H, 9-H), 7.3–7.5 (m, 5H, 5H-Ar).
ꢀ
ꢀ
ꢀ
IIIb. (3aRS , 4RS , 9bRS ) –9-chloro-8-fluoro–4-phenyl-2, 3, 3a, 4,
, 6, 9b-hexahydro-2H-furo [3,2-c] quinoline. White solid, m.p. 1198C
n-hexane).
5
(
1
HNMR (CDCl ): d 1.4–1.6 (m, 1H, 3-H), 2.1–2.4 (m, 1H, 3-H), 2.8–3.0
3
(
m, 1H, 3a-H), 3.6–4.0 (m, 3H, 2-CH , 5-H), 4.5 (d, J ¼ 3.3 Hz, 1H, 9b-H),
2

Imino Diels–Alder Reactions
4103
5
.5 (d, J ¼ 8.5 Hz, 1H, 4-H), 6.59 (dd, J ¼ 4.0, 8.9, Hz, 1H, 6-H), 6.95
(t, J ¼ 8.5 Hz 1H, 7-H), 7.3–7.5 (m, 5H, 5H-Ar).
ꢀ
ꢀ
ꢀ
IVb. (3aRS , 4SR , 9bRS ) –9-chloro-8-fluoro–4-phenyl-2, 3, 3a, 4,
, 6, 9b-hexahydro-2H-furo [3,2-c] quinoline. White solid,
5
m.p. 161–1628C (n-hexane).
1
HNMR (CDCl ): d 1.22–1.5 (m, 1H, 3-H), 1.6–1.8 (m, 1H, 3-H), 1.9–2.1
3
(
m, 1H, 3a-H), 2.3–2.4 (m, 1H, 5-H), 3.77 (d, J ¼ 11.1 Hz, 1H, 4-H), 3.9–
4
.1 (m, 2H, 2-CH ), 4.7 (d, J ¼ 4.4 Hz, 1H, 9b-H), 6.43 (dd, J ¼ 4.4,
2
8
.9 Hz, 1H, 6-H), 6,9 (t, J ¼ 8.9 Hz, 1H, 7-H), 7.3–7.5 (m, 5H, 5H-Ar).
ACKNOWLEDGMENTS
The authors are thankful to The Director, IICT, for constant encourage-
ment. M.M and Ch.V.R thank CSIR for award of Senior Research Fellowship.
REFERENCES
1
. (a) Nesterova, I.N.; Alekseeva, L.M.; Andreeva, L.M.; Andreeva, N.I.;
Golovira, S.M.; Granic, V.G. Synthesis and pharmocological activity of
derivatives of 5-(dimethylamino) pyrano [3,2-c] quinoline-2-ones.
Khim. Farm. Zh. 1995, 29 (2), 31(Russ).
2
. Yamada, N.; Kadowaki, S.; Takahashi, K.; Umezu, K. MY-1250, a major
metabolite of the antiallergic drug repirinast induces phosphorylation of a
7
8-Kda protein in rat mast cells. Biochem. Pharmacol. 1992, 44, 1211.
. Faber, K.; Stueckler, H.; Kappe, T. Non-steroidal antiinflamatory agents.
. Synthesis of 4-hydroxy-2-oxo-1,2-dihydroquinolin-3-ylalkanoic acids
by the Wittig reaction of quinistatins. J. Heterocycle. Chem. 1984,
1 (4), 1177.
3
1
2
4
. (a) Akhmed khodzhaeva, Kh.S.; Bessonova, I.A. Some data on the
reaction between chemical structure and estrogenic activity in a series
of quinoline alkaloids. Dokl. Akad. Nauk Uzb. SSR 1982 (9), 34(Russ).
. Povarov, L.S. a,b-Unsaturated ethers and their analogues in reactions of
Diene synthesis. Russ. Chem. Rev. 1967, 36, 656.
5
6
. (a) Makioka, Y.; Shindo, T.; Taniguchi, Y.; Takaki, K.; Fujiwara, Y.
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Received in the USA July 13, 2004