High, exoselective Diels-Alder reaction in 5.0 M lithium perchlorate in diethyl ether medium: Efficient synthesis of novel heterocyclic derivatives containing a spirobicyclo[2.2.1]heptane system

Article abstract of DOI:10.1016/S0040-4020(00)00433-6

Exocyclic arylidene derivatives have been used as dienophiles in Diels-Alder reactions with cyclopentadiene. A series of novel heterocyclic derivatives containing the spiro bicyclo[2.2.1]heptane system is the outcome of such reactions. The reactions proceed with high exoselectivity in the presence of 5.0 M LPDE medium. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00433-6

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 5241±5245
High, Exoselective Diels±Alder Reaction in 5.0 M Lithium
Perchlorate in Diethyl Ether Medium:
Ef®cient Synthesis of Novel Heterocyclic Derivatives
Containing a Spirobicyclo[2.2.1]heptane System
²
M. Shanmugasundaram and R. Raghunathan
*
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, India
Received 11 February 2000; revised 3 May 2000; accepted 18 May 2000
AbstractÐExocyclic arylidene derivatives have been used as dienophiles in Diels±Alder reactions with cyclopentadiene. A series of novel
heterocyclic derivatives containing the spiro bicyclo[2.2.1]heptane system is the outcome of such reactions. The reactions proceed with high
exoselectivity in the presence of 5.0 M LPDE medium. q 2000 Elsevier Science Ltd. All rights reserved.
6
reactions. In a continuation of our interest in the area of
cycloaddition reactions, we report herein the Diels±
Alder reaction promoted by 5.0 M LPDE medium.
Bicyclo[2.2.1]heptane derivatives ®nd widespread use as
key intermediates in the synthesis of many complex natural
products. Though a plethora of reports are available in the
7
±10
1
literature involving exocyclic methylene serving as dieno-
2
±4
philes in the Diels±Alder reaction, there appear to be few
reports of the exocyclic benzylidene derivatives acting as
dienophiles. While the use of heterogeneous catalyst
Results and Discussion
5
7
The dienophiles (E) 3-arylidene-4-chromanones chosen for
promoted the Diels±Alder reaction involving exocyclic
benzylidene dienophiles, a high degree of stereoselectivity
our study were prepared according to literature procedure.
The Diels±Alder reaction between 1a±c and cyclopenta-
diene 2 with various Lewis acid catalysts at different
temperatures for 24 h in dichloromethane gave a mixture
of exo 3a±c endo 4a±c isomers. (Scheme 1). The stereo-
chemistry of the exo 3a±c and endo 4a±c isomers were
established by difference NOE studies. In the case of exo
5
was not attainable. In the present study, it was of interest to
promote the Diels±Alder reaction involving such dieno-
philes with a high degree of stereoselectivity. In recent
years, the use of 5.0 M lithium perchlorate in diethyl ether
(LPDE) as a medium has attracted considerable attention
due to the enhanced rate and selectivity in Diels±Alder
Scheme 1.
Keywords: Diels±Alder reactions; lithium and compounds; spiro compounds.
*
Corresponding author. Tel.: 191-44-2351269; fax: 191-44-2351294; e-mail: ragharaghunathan@yahoo.com
mshansun@yahoo.com
²
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00433-6

5
242
M. Shanmugasundaram, R. Raghunathan / Tetrahedron 56 (2000) 5241±5245
Table 1. Reaction of (E) 3-arylidene-4-chromanone 1a±c with cyclopentadiene
a
b
Dienophile
Catalyst
T (8C)
Dienophile (%)
Products (%)
exo:endo
1
a
±
±
AlCl
rt
221
rt
2
2
rt
2
2
rt
2
rt
2
rt
rt
2
rt
2
rt
2
rt
rt
2
rt
2
rt
100
100
38
44
50
37
52
57
33
41
41
47
5
42
47
51
55
49
55
2
±
±
±
±
c
3
32
23
19
34
22
20
38
30
37
28
78
22
19
24
21
21
17
82
13
12
15
13
83
70:30
68:32
69:31
82:18
59:41
60:40
74:26
71:29
71:29
73.27
92:8
79:21
75:25
71:29
72:28
75:25
73:27
93:7
21
78
c
2
BF ´OEt
3
21
78
c
TiCl
4
21
d
e
ZnCl
2
21
LPDE
AlCl
1
1
b
3
21
21
21
c
2
BF
3
´OEt
d
2
ZnCl
e
LPDE
ZnCl
d
2
c
51
55
45
50
2
80:20
77:23
73:27
70:30
93:7
21
21
c
2
BF
3
´OEt
e
LPDE
a
Combined isolated yield of products.
Ratio determined by HPLC.
b
c
d
e
1
1
equiv. of catalyst was used with respect to dienophile.
.5 equiv. of catalyst was used with respect to dienophile.
The reaction was performed in a 5.0 M solution of lithium perchlorate in diethyl ether.
isomer 3a, selective irradiation of the H proton at d 1.84
a
caused 14.6% enhancement of the signal for the C hydro-
3
gen at d 4.62, so that the C methine hydrogen should be on
3
It was of further interest to investigate whether the E con®g-
uration of the exocyclic double bond in the dienophile plays
any role in the observed exo/endo selectivity. The reaction
between (Z) 3-benzylidene-4-chromanone12 5 and cyclo-
pentadiene employing various Lewis acid catalysts for
24 h was studied. (Scheme 2). The exo and endo stereo-
chemistry was unequivocally determined on the basis of
difference NOE experiments. The exo adduct 6 in which
the exo position of the norbornene skeleton, whereas in the
case of endo isomer 4a, selective irradiation of the H proton
a
at d 2.20 did not cause any enhancement of the signal for
the C hydrogen at d 3.83. The structure and the stereo-
3
chemistry of the exo isomer 3a was further corroborated
by signal crystal X-ray structure determination of 3a.
1
1
the C proton had the endo orientation the signal due to
3
the C proton at d 3.06 did not show any NOE enhancement
3
From Table 1, it is evident that in the absence of catalyst, no
reaction occurred. While the use of standard Lewis acid
catalysts like AlCl , BF ´OEt , TiCl and ZnCl promoted
when the H proton at d 2.76 was selectively irradiated.
a
However, in the case of endo adduct 7 in which the C3
proton had the exo orientation the signal due to the C proton
3
3
2
4
2
3
the reaction, the quantity of starting material recovered was
great and a low yield of product formation with decreased
stereoselectivity was observed. Even at lower temperatures,
there was no improvement in selectivity. The best result was
obtained when the reaction was carried out in 5.0 M LPDE
medium; high exoselectivity was observed with enhanced
chemical yields.
at d 3.72 showed a 12% enhancement when the H proton at
a
d 1.85 was selectively irradiated.
It is obvious from Table 2 that in the presence of AlCl or
3
BF ´OEt at rt complete con®gurational isomerization of Z
3
2
to E occurs. In the presence of AlCl , 42% of E isomer 1a
3
was isolated, and in the presence of BF ´OEt , 47% of E
2
3
Scheme 2.

M. Shanmugasundaram, R. Raghunathan / Tetrahedron 56 (2000) 5241±5245
5243
Table 2. Reaction of (Z)-3-benzylidene-4-chromanone 5 with cyclopenta-
diene
zinc±copper couple to form exclusively trans-2-phenyl-
cyclopropyl-1-spiro-3-chromanone. In the present study,
the cycloadducts 3a, 4a, 6 and 7 are obtained from the Z
isomer in the presence of 5.0 M LPDE medium.
a
b
Catalyst
T (8C) 1a (%) 5 (%) Products (%)
3a:4a:6:7
c
3
AlCl
BF
rt
rt
rt
42
47
3
±
±
2
21
19
80
76:24:0:0
79:21:0:0
12.5:1.5:56:30
c
2
3
´OEt
In order to establish the generality of the 5.0 M LPDE
promoted Diels±Alder reaction, the reaction of aurone
d
LPDE
14
8
9
a
and (E) 2-(4-nitrobenzylidene)-1-tetralone 11 with cyclo-
pentadiene was studied (Schemes 3 and 4). The structure
and the stereochemistry of the corresponding cycloadducts
was con®rmed by spectroscopic data and difference NOE
studies.
Combined isolated yield of products.
Ratio determined by HPLC.
b
c
d
1
equiv. of catalyst was used with respect to dienophile.
The reaction was performed in a 5.0 M solution of lithium perchlorate
in diethyl ether.
isomer 1a was obtained. The cycloadducts 6 and 7 arising
from the Z isomer were not obtained, and only the cyclo-
adducts 3a and 4a arising from the E isomer are obtained.
However, in the presence of 5.0 M LPDE medium, Z/E
isomerization is suppressed to a considerable extent. The
cycloadducts arising from both the Z (6, 7) and E isomers
It is clear from Table 3 that once again, the best result was
obtained when the reaction was carried out 5.0 M LPDE
medium.
3
Roush and Brown suggested that the exo preference with
conformationally restricted S-cis dienophiles may be due to
the difference in dipole moment in the exo versus endo
transition states. Recently Buano et al. suggested that the
(
3a, 4a) are obtained. It should be mentioned that Donnelly
1
3
4
and Boyle have reported Simmons Smith reaction of (Z)
-benzylidene-4-chromanone with methylene chloride/
3
relative position of substituents, structural factors and
Scheme 3.
Scheme 4.
Table 3. Reaction of aurone 8 and (E) 2-(4-nitrobenzylidene)-1-tetralone 11 with cyclopentadiene
a
b
Dienophile
Catalyst
T (8C)
Dienophile (%)
Products (%)
exo:endo
c
8
AlCl
BF
LPDE
3
rt
rt
rt
rt
rt
rt
33
37
2
50
47
3
12
16
84
20
18
77
77:23
72:28
96:4
85:15
85:15
89:11
c
c
3
´OEt
2
d
c
1
1
AlCl
BF ´OEt
LPDE
3
3
2
d
a
b
c
d
Combined isolated yield of products.
Ratio determined by HPLC.
1 equiv. of catalyst was used with respect to dienophile.
The reaction was performed in a 5.0 M solution of lithium perchlorate in diethyl ether.

5
244
M. Shanmugasundaram, R. Raghunathan / Tetrahedron 56 (2000) 5241±5245
1
3
consequently steric effects present in the dienophile should
in¯uence the stereoselectivity. Nevertheless, numerous
factors such as steric, conformational or electronic effects
can interfere with the stereoselectivity of the Diels±Alder
reaction.
1.5 Hz, 1H); C NMR: d 46.95, 47.37, 47.78, 49.89,
56.49, 73.17, 117.47, 120.29, 121.14, 126.55, 128.11,
128.16, 128.64, 135.44, 135.49, 138.37, 139.10, 161.35,
1
195.34; MS m/z: 302 (M ); Anal. Calcd for C H O : C,
2
83.41; H, 6.00. Found: C, 83.31; H, 5.90.
1
18
2
1
exo-3-Phenylbicyclo[2.2.1]hept-2-spiro-{3 [chroman-endo-
In conclusion, ef®cient synthesis of a series of novel hetero-
cyclic derivatives containing spirobicyclo[2.2.1]heptane
system has been achieved via Diels±Alder reaction
promoted by 5.0 M LPDE medium.
1
21
4 -one]}-5-ene (4a). Colorless oil, IR (CHCl ): 1682 cm ;
3
1
H NMR: d 1.75 (d, Jˆ8.8 Hz, 1H), 2.20 (d, Jˆ8.8 Hz, 1H),
3.17 (bs, 1H), 3.29 (bs, 1H), 3.76 (d, Jˆ12.0 Hz, 1H), 3.79
(
1
d, Jˆ12.0 Hz, 1H), 3.83 (bs, 1H), 5.81 (dd, Jˆ5.4, 2.9 Hz,
H), 6.52 (dd, Jˆ5.4, 2.9 Hz, 1H), 6.85±7.47 (m, 8H), 7.88
1
Experimental
(dd, Jˆ7.9, 1.6 Hz, 1H); MS m/z: 302 (M ); HRMS (EI):
1
M , found 302.1308. C H O : requires 302.1307.
2
1
18
2
General
1
endo-3-(4-Cholorophenyl)bicyclo[2.2.1]hept-2-spiro-{3 -
1
[chroman-exo-4 -one]}-5-ene (3b). Colorless crystals, mp:
All the melting points are uncorrected. IR spectra were
recorded on a JASCO FT/IR-5300. H NMR spectra and
1
21
1
100±1018C; IR (KBr): 1684 cm ; H NMR: d 1.52 (d,
Jˆ8.5 Hz, 1H), 1.82 (d, Jˆ8.5 Hz, 1H), 2.96 (bs, 1H),
3.23 (bs, 1H), 3.57 (d, Jˆ11.9 Hz, 1H), 3.67 (d, Jˆ
11.9 Hz, 1H), 4.57 (d, Jˆ2.9 Hz, 1H), 6.45 (dd, Jˆ5.4,
3.3 Hz, 1H), 6.71 (dd, Jˆ5.4, 3.3 Hz, 1H), 6.88±7.47 (m,
1
3
C NMR spectra were recorded in CDCl using TMS as
3
an internal standard on a JEOL GX 400 spectrometer at 400
and 100.4 MHz, respectively. Mass spectra were recorded
on a Finnigan MAT-8230 GC-Mass spectrometer. HPLC
was carried out in SHIMADZU LC-9A instrument. The
column used was normal phase column with UV detection
at 281 nm. (CLC-CN, 4.6fX150). Elemental analyses were
carried out on a CEST 1106 instrument. Flash column
chromatography was performed on silica gel (SISCO,
1
3
7H), 7.99 (dd, Jˆ8.3, 2 Hz, 1H); C NMR: 46.21, 47.34,
47.70, 49.83, 56.43, 72.91, 117.42, 120.09, 121.17, 128.04,
128.22, 129.89, 132.28, 135.56, 135.78, 137.60, 137.91,
1
137.97, 161.23, 195.00. MS m/z: 336 (M ); Anal. Calcd
for C H O Cl: C, 74.98; H, 5.10. Found: C, 75.10; H, 5.07.
2
1
17
2
2
30±400 mesh).
1
exo-3-(4-Chlorophenyl)bicyclo[2.2.1]hept-2-spiro-{3 [chro-
1
General procedure for the cycloaddition reaction in the
presence of Lewis acid catalyst
man-endo-4 -one]}-5-ene (4b). Colorless oil, IR (CHCl ):
3
2
1 1
1682 cm ; H NMR: d 1.75 (d, Jˆ8.7 Hz, 1H), 2.17 (d,
Jˆ8.7 Hz, 1H), 3.13 (bs, 1H), 3.30 (bs, 1H), 3.72 (d, Jˆ
11.8 Hz, 1H), 3.77 (d, 11.8 Hz, 1H), 3.80 (bs, 1H), 5.81 (dd,
Jˆ5.4, 3.3 Hz, 1H), 6.51 (dd, Jˆ5.4, 3.3 Hz, 1H), 6.86±7.50
Method A. To a stirred mixture of dienophile (1 mmol) in
5
nitrogen atmosphere, Lewis acid catalyst (1 mmol) was
added. After 15 min excess cyclopentadiene (3 mmol) was
added and the mixture was stirred for 24 h. The reaction
mL of dichloromethane at the speci®ed temperature under
1
(m, 7H), 7.89 (dd, Jˆ8.2, 2.0 Hz, 1H); MS m/z: 336 (M );
1
HRMS (EI): M , 336.0921. C21
H
O
17
Cl requires 336.0918.
2
1
endo-3-(4-Nitrophenyl)bicyclo[2.2.1]hept-2-spiro-{3 [chro-
mixture was washed with water, NaHCO solution, brine
3
1
man-exo-4 -one]}-5-ene (3c). Colorless crystals, mp: 139±
and dried. Removal of the solvent under reduced pressure
gave an oily residue, which was subjected to ¯ash column
chromatography (hexane/EtOAc, 9:1). The ®rst fraction
afforded exo isomer and second fraction afforded endo
isomer. The ratio of the exo and endo isomers was deter-
mined by HPLC of the crude reaction mixture.
2
1
1
1408C; IR (KBr): 1684 cm ; H NMR: d 1.60 (d,
Jˆ8.7 Hz, 1H), 1.85 (d, Jˆ8.7 Hz, 1H), 3.04 (bs, 1H) 3.32
(bs, 1H), 3.58 (d, Jˆ11.9 Hz, 1H), 3.69 (d, Jˆ11.9 Hz, 1H)
4.71 (d, Jˆ2.9 Hz, 1H), 6.51 (dd, Jˆ5.4, 3.0 Hz, 1H), 6.75
(dd, Jˆ5.3, 2.9 Hz, 1H), 6.90±7.50 (m, 5H), 7.99 (dd, Jˆ8,
1
3
2
Hz, 1H), 8.07 (d, Jˆ8.1 Hz, 2H); C NMR: d 46.85,
Method B. To a stirred mixture of dienophile (1 mmol) in
2
47.46, 47.61, 49.92, 57.10, 72.71, 117.55, 119.98, 121.45,
123.36, 128.14, 129.42, 135.87, 136.46, 137.67, 146.64,
147.42, 161.20, 194.63; MS m/z: 347 (M ); Anal. Calcd
mL of 5.0 M LPDE under nitrogen atmosphere, cyclo-
1
pentadiene (3 mmol) was added. After 24 h, methylene
chloride (15 mL) and water (25 mL) were added and the
aqueous layer was extracted with 2£10 mL of methylene
chloride. The combined organic extracts were washed
with NaHCO solution, brine and dried (MgSO ). Removal
for C21
72.46; H, 4.88; N, 3.98.
H
17
O
N: C, 72.60; H, 4.93; N, 4.03. Found: C,
4
1
exo-3-(4-Nitrophenyl)bicyclo[2.2.1]hept-2-spiro-{3 [chro-
3
4
1
of the solvent under reduced pressure gave an oily residue,
which was subjected to ¯ash column chromatography
man-endo-4 -one]}-5-ene (4c). Colorless oil, IR (CHCl ):
3
2
1 1
1683 cm ; H NMR: d 1.83 (d, Jˆ8.8 Hz, 1H), 2.23 (d,
(
hexane/EtOAc, 9:1).
Jˆ8.8 Hz, 1H), 3.19 (bs, 1H), 3.36 (bs, 1H), 3.70 (d, Jˆ
1
1.9 Hz, 1H), 3.78 (d, Jˆ11.9 Hz, 1H), 3.95 (bs, 1H), 5.95
1
endo-3-Phenylbicyclo[2.2.1]hept-2-spiro-{3 [chroman-exo-
4
(dd, Jˆ5.4, 3.0 Hz, 1H), 6.53 (dd, Jˆ5.4, 3.0 Hz, 1H),
1
-one]}-5-ene (3a). Colorless crystals, mp: 139±1408C; IR
1 1
6.91±7.52 (m, 5H). 7.88 (dd, Jˆ8.1, 2.0 Hz, 1H), 8.15 (d,
2
1
1
(
KBr): 1682 cm ; H NMR: d 1.53 (d, Jˆ8.8 Hz, 1H), 1.84
Jˆ8.1 Hz, 2H): MS m/z: 347 (M ); HRMS (EI): M , found
H O N requires 347.1158.
17 4
(
d, Jˆ8.8 Hz, 1H), 2.96 (bs, 1H), 3.27 (bs, 1H), 3.61 (d,
347.1152. C21
Jˆ12.1 Hz, 1H), 3.71 (d, Jˆ12.1 Hz, 1H), 4.62 (d, Jˆ
1
exo-3-Phenylbicyclo[2.2.1]hept-2-spiro-{3 [chroman-exo-
2
.4 Hz, 1H), 6.44 (dd, Jˆ5.4, 2.9 Hz, 1H), 6.75 (dd, Jˆ
.4, 2.9 Hz 1H), 6.88±7.46 (m, 8H), 8.01 (dd, Jˆ7.8,
1
21
5
4 -one]}-5-ene (6). Colorless oil, IR (CHCl ): 1684 cm ;
3

M. Shanmugasundaram, R. Raghunathan / Tetrahedron 56 (2000) 5241±5245
5245
1
1
exo-3-(4-Nitrophenyl)bicyclo[2.2.1]hept-2-spiro-{2 [endo-
H NMR: d 1.82 (d, Jˆ8.8 Hz, 1H), 2.76 (d, Jˆ8.8 Hz, 1H),
1
1 -tetralone]}-5-ene (13). Colorless oil, IR(CCl4):
3
.01 (bs, 1H), 3.04 (bs, 1H), 3.06 (d, Jˆ2 Hz, 1H), 4.18 (d,
2
1
1
Jˆ11.5 Hz, 1H), 4.33 (d, Jˆ11.5 Hz, 1H), 6.26 (dd, Jˆ5.8,
1677 cm ; H NMR: d 1.56 (m, 2H), 1.8 (d, Jˆ8.8 Hz,
1H), 2.19 (d, Jˆ8.8 Hz, 1H), 2.85 (m, 2H), 3.17 (bs, 1H),
3.21 (bs, 1H), (4.05, d, Jˆ3.1 Hz, 1H) 5.95 (dd, Jˆ5.4,
3.2 Hz, 1H), 6.51 (dd, Jˆ5.4, 3.2 Hz, 1H), 7.15±7.50 (m,
2
.9 Hz, 1H), 6.58 (dd, Jˆ5.8, 2.9 Hz, 1H), 6.71 (m, 1H), 6.85
1
(d, Jˆ8.3 Hz, 1H), 6.91±7.32 (m, 7H); MS m/z: 302 (M );
HRMS (EI): M , 302.1309. C H O requires 302.1307.
1
2
1
18
2
5
H), 8.08 (d, Jˆ8.1 Hz, 1H), 8.16 (d, Jˆ8.2 Hz, 2H), MS
22 19 3
1
endo-3-Phenylbicyclo[2.2.1]hept-2-spiro-{3 [chroman-
1
1
m/z: 345 (M ); HRMS (EI) M , 345.1368. C H NO
requires 345.1366.
1
endo-4 -one]}-5-ene (7). Colorless oil, IR (CHCl ):
3
2
1 1
1
683 cm ; H NMR: d 1.53 (d, Jˆ8.7 Hz, 1H), 1.85 (d,
Jˆ8.7 Hz, 1H), 2.95 (bs, 1H), 3.11 (bs, 1H), 3.72 (d, Jˆ
3
1
.0 Hz, 1H), 4.48 (d, Jˆ11.7 Hz, 1H), 4.58 (d, Jˆ11.7 Hz,
H), 6.33 (dd, Jˆ5.3, 3.3 Hz, 1H), 6.65 (m, 1H), 6.75 (d,
Acknowledgements
Jˆ8.3 Hz, 1H), 6.79 (dd, Jˆ5.3, 3.0 Hz, 1H), 6.89±7.35 (m,
1
H); MS m/z: 302 (M ); HRMS (EI): M , 302.1311.
1
7
C H O requires 302.1307.
Financial support from UGC, CSIR and the University of
Madras is gratefully acknowledged.
2
1
18
2
1
endo-3-Phenylbicyclo[2.2.1]hept-2-spiro-{exo-2 -aurone}-
5
-ene (9). Colorless crystals, mp: 109±1108C; IR (KBr):
2
1 1
1
705 cm ; H NMR: d 1.63 (d, Jˆ9.3 Hz, 1H), 2.41 (d,
References
Jˆ9.3 Hz, 1H), 3.12 (bs, 1H), 3.34 (bs, 1H), 3.88 (d, Jˆ
3
3
5
1
2
8
Hz, 1H), 6.39 (dd, Jˆ5.6, 3.2 Hz, 1H), 6.75 (dd, Jˆ5.6,
1
. Desimoni, G.; Tacconi, G.; Barco, A.; Pollini, G. P. Natural
1
3
.2 Hz, 1H), 6.84±7.70 (m, 9H); C NMR: d 46.38, 47.64,
2.26, 57.50, 96.51, 113.07, 120.56, 121.58, 124.23, 126.44,
27.76, 128.91, 135.64, 137.64, 138.01, 138.67, 171.55,
Products Synthesis through Pericyclic Reactions; American
Chemical Society: Washington, DC, 1983; pp 119±254.
2
4
3
4
. Fotiadu, F.; Michel, F.; Buono, G. Tetrahedron Lett. 1990, 31,
863.
1
04.16; MS m/z: 288 (M ); Anal. Calcd for C H O : C,
16
2
0
2
3.30; H, 5.60. Found: C, 83.42; H, 5.65.
. Roush, W. R.; Brown, B. B. J. Org. Chem. 1992, 56, 5782.
. Fotiadu, F.; Pardingon, O.; Buono, G.; Corre, M. L.; Hercouret,
1
exo-3-Phenylbicyclo[2.2.1]hept-2-spiro-{endo-2 -aurone}-
A. Tetrahedron Lett. 1999, 40, 867.
. Cativiela, C.; Garcia, J. I.; Mayoral, J. A.; Pires, E.; Brown, R.
Tetrahedron 1995, 51, 9217.
2
1 1
-ene (10). Colorless oil, IR (CHCl ): 1702 cm ; H NMR:
5
3
5
d 1.95 (d, Jˆ9.2 Hz, 1H), 2.56 (d, Jˆ9.2 Hz, 1H), 2.91 (bs,
1
3
9
H), 3.01 (bs, 1H), 3.28 (d, Jˆ1.5 Hz, 1H), 6.32 (dd, Jˆ5.6,
1
H); MS m/z: 288 (M ); HRMS (EI): M , 288.1157.
6
1
6
7
. (a) Grieco, P. A.; Nunes, J. J.; Gaul, M. D. J. Am. Chem. Soc.
990, 112, 4595. (b) Heard, N. E.; Turner, J. J. Org. Chem. 1995,
0, 4302.
.3 Hz, 1H), 6.69 (dd, Jˆ5.6, 3.3 Hz, 1H), 6.82±7.95 (m,
1
C H O requires 288.1151.
2
0
16
2
. Raghunathan, R.; Shanmugasundaram, M.; Bhanumathi, S.;
1
endo-3-(4-Nitrophenyl)bicyclo[2.2.1]hept-2-spiro-{2 [exo-
Padma Malar, E. J. Heteroatom Chem. 1998, 9, 327.
8. Shanmugasundaram, M.; Raghunathan, R.; Padma Malar, E. J.
Heteroatom Chem. 1998, 9, 517.
1
1
1
1
1
-tetralone]}-5-ene (12). Colorless crystals, mp: 124±
2
1
1
268C; IR (KBr): 1678 cm ; H NMR: d 1.3 (m, 2H),
.55 (d, Jˆ8.8 Hz, 1H), 1.81 (d, Jˆ8.8 Hz, 1H), 2.72 (m,
H), 2.96 (m, 1H), 3.02 (bs, 1H), 3.28 (bs, 1H), 4.85 (d,
9
. Shanmugasundaram, M.; Arulananda Babu, S.; Raghunathan,
R.; Padma Malar, E. J. Heteroatom Chem. 1999, 10, 331.
10. Shanmugasundaram, M.; Raghunathan, R. Tetrahedron Lett.
1999, 40, 4869.
11. Puviarasan, K.; Govindasamy, L.; Velmurugan, D.; Raj,
Jˆ3.0 Hz, 1H), 6.39 (dd, Jˆ5.4, 3.0 Hz, 1H), 2.96 (m, 1H),
.02 (bs, 1H), 3.28 (bs, 1H), 4.85 (d, Jˆ3.0 Hz, 1H), 6.39
dd, Jˆ5.4, 3.0 Hz, 1H), 6.72 (dd, Jˆ5.4, 3.0 Hz, 1H),
.19±7.49 (m, 5H), 8.05 (d, Jˆ8.1 Hz, 1H), 8.12 (d,
3
(
S. S. S.; Shanmugasundaram, M.; Raghunathan, R.; Fun, H. Acta
Cryst. C 1998, 961.
7
1
3
Jˆ8.0 Hz, 2H); C NMR: d 27.06, 30.84, 47.31, 47.37,
1
2. Bennett, P.; Donnelly, J. A.; Meaney, D. C.; Boyle, P. O.
4
1
1
8.51, 49.33, 58.83, 123.01, 126.64, 128.38, 128.62,
29.64, 131.72, 133.28, 135.88, 137.63, 143.14, 146.25,
49.75, 199.66; MS m/z: 345(M ); Anal. Calcd for
J. Chem. Soc., Perkin Trans. 1 1972, 1554.
1
1
1
1
3. Donnelly, J. A.; Boyle, P. O. J. Chem. Soc., Chem. Commun.
969, 1060.
4. Varma, R. S.; Varma, M. Tetrahedron Lett. 1992, 40, 5937.
C H NO : C, 76.49; H, 5.55; N, 4.06. Found: C, 76.37;
2
2
19
3
H, 5.49; N, 4.12.