Trapping the -allylpalladium intermediate from fulvene-derived azabicyclic olefin with soft nucleophiles

Article abstract of DOI:10.1055/s-0030-1258227

A facile method for the synthesis of a new class of disubstituted alkylidenecyclopentenes has been introduced. The methodology involves the palladium-catalyzed ring opening of pentafulvene-derived bicyclic hydrazines with phenols and active methylene compounds, furnishing 1,4-disubstituted alkylidenecyclopentenes in good yield. The utility of multiple points of functionalization was effectively demonstrated by the synthesis of a substituted cyclopentanone and 2-hydrazinofulvene.

Full text of DOI:10.1055/s-0030-1258227

PAPER
3649
Trapping the p-Allylpalladium Intermediate from Fulvene-Derived
Azabicyclic Olefin with Soft Nucleophiles
Rani Rajan, Jubi John, Sreeja Thulasi, Nayana Joseph, K. V. Radhakrishnan,* R. C. Sawant
Organic Chemistry Section of Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology
(NIIST)-CSIR, Trivandrum 695 019, India
Fax +91(471)2491712; E-mail: radhupreethi@rediffmail.com
Received 17 June 2010; revised 29 June 2010
lytic enantioselective intramolecular Conia–Ene reaction
Abstract: A facile method for the synthesis of a new class of disub-
of b-dicarbonyl compounds and alkynes,9 and the stereo-
stituted alkylidenecyclopentenes has been introduced. The method-
selective [3+2] cyclization of activated and deactivated al-
ology involves the palladium-catalyzed ring opening of
lenes with alkenyl Fischer carbene complexes.10 Recently,
pentafulvene-derived bicyclic hydrazines with phenols and active
methylene compounds, furnishing 1,4-disubstituted alkylidenecy- Shi et al. reported the synthesis of trans-substituted alky-
clopentenes in good yield. The utility of multiple points of function-
lidenecyclopentenes via the ring-opening rearrangement
alization was effectively demonstrated by the synthesis of a
of methylenecyclopropyl-substituted alkenyl deriva-
substituted cyclopentanone and 2-hydrazinofulvene.
tives.11
Key words: azabicyclic olefin, palladium, soft nucleophile, alky-
lidenecyclopentene, substituted cyclopentanone, 2-hydrazinoful-
In the context of our general interest in pentafulvene-
derived bicyclic hydrazines, we have unraveled a facile
method for the construction of alkylidenecyclopentenes
through palladium/Lewis acid catalyzed ring opening of
fulvene-derived azabicyclic olefins with hard nucleo-
philes like organostannanes,12 silanes, boronic acids,13
and allylindium reagents.14 All these reactions furnished
trans-4,5-disubstituted 1-alkylidenecyclopent-2-ene de-
rivatives. The reactivity of soft nucleophiles like phenols
and active methylene compounds towards fulvene-
derived azabicyclic olefins under palladium catalysis
remained unexplored. Micouin and co-workers have
reported the palladium-catalyzed ring opening of cyclo-
pentadiene derived bicyclic olefins with soft nucleophiles
towards the synthesis of cis-3,5-disubstituted cyclo-
pentenes.15 Herein we disclose a facile route towards cis-
1,4-disubstituted 5-alkylidenecyclopent-2-enes and the
synthetic transformations of the latter to functionalized
cyclopentanones and substituted fulvenes.
vene
Cyclopentane derivatives are important synthons for a va-
riety of natural products and biologically active mole-
cules;1 hence the synthesis of substituted cyclopentanes
has garnered a great deal of interest.2 Among various sub-
stituted cyclopentanes, alkylidenecyclopentanes hold spe-
cial attention as intermediates in the construction of
biologically interesting molecules including (+)- and (–)-
nigellamine A2,3 guanacastepene A,4 etc. The synthesis of
(+)-allocyathin B2, which has interesting biological activ-
ity, by Trost and co-workers involves an alkylidenecyclo-
pentenone as the key intermediate.5 Some bioactive
molecules containing the alkylidenecyclopentane core are
shown in Figure 1.
H
Our studies started with the reaction of diethyl 7-(diphe-
nylmethylene)-2,3-diazabicyclo[2.2.1]hept-5-ene-2,3-di-
carboxylate (1a) with 4-methoxyphenol (2a) in the
presence of [Pd(allyl)Cl]2 (5 mol%), 1,1¢-bis(diphe-
nylphosphino)ferrocene (dppf, 10 mol%), and sodium hy-
dride (1.0 equiv) in tetrahydrofuran at 60 °C. The reaction
afforded the cis-1,4-disubstituted 5-alkylidenecyclopent-
2-ene 3a in 43% yield (Table 1, entry 1).
H
H
O
hirsutene
β-vetivone
Figure 1 Bioactive molecules containing the alkylidenecyclopen-
tane core
Detailed optimization studies were carried out to find the
best condition for this transformation (Table 1). Among
the different bases examined, potassium carbonate was
found to be more proficient than sodium hydride and po-
tassium tert-butoxide (entries 1–3). We then went on to
optimize the palladium catalyst. The reactions with
Pd2(dba)3·CHCl3 and PdCl2(PPh3)2 afforded the product
in only 38% and 21%, respectively (entries 5 and 6). The
desired product 3a was isolated in 80% yield when the re-
action was performed in presence of Pd(PPh3)4 (entry 8).
However Pd(OAc)2 and PdCl2 gave only trace amounts of
Various methods are known in the literature for the prep-
aration of alkylidenecyclopentane derivatives. Trost has
elegantly utilized trimethylenemethane chemistry for the
synthesis of alkylidenecyclopentanes.6 Other important
strategies7 towards the synthesis of alkylidenecyclopen-
tanes involve the rhodium-catalyzed regioselective ring-
expanding rearrangement of allenylcyclopropane,8 cata-
SYNTHESIS 2010, No. 21, pp 3649–3656
x
x.
x
x
.
2
0
1
0
Advanced online publication: 25.08.2010
DOI: 10.1055/s-0030-1258227; Art ID: Z15610SS
© Georg Thieme Verlag Stuttgart · New York

3650
R. Rajan et al.
PAPER
the expected product (entries 4 and 7). We then turned our This was further generalized with 6,6¢-dialkylfulvene-
attention to other parameters such as ligand and solvent. derived bicyclic hydrazines (Table 3). The adduct 4a was
Ligands 1,2-bis(diphenylphosphino)ethane and triphe- prepared from adamantanone-derived fulvene and 4b
nylphosphine were found to be less efficient compared to from cyclohexanone-derived fulvene, respectively.
1,1¢-bis(diphenylphosphino)ferrocene (entries 8–10). In
We were then interested in extending our investigation to
the case of solvents tested, tetrahydrofuran gave a superi-
another class of soft nucleophile, namely active methyl-
or result compared to acetonitrile and N,N-dimethyl-
formamide (entries 11 and 12). It was interesting to
observe an increase in yield to 96% when the reaction was
performed at room temperature (entry 13). After the opti-
ene compounds. We commenced our investigation with
the reaction of dimethyl malonate (6a) with the bicyclic
alkene 1a in presence of Pd(PPh3)4 as catalyst, 1,1¢-
bis(diphenylphosphino)ferrocene as ligand, and potassi-
mization studies, the best conditions for the reaction were
um carbonate as the base in tetrahydrofuran at room tem-
found to be a 1:1.5 mixture of phenol 2a and bicyclic hy-
perature. The reaction afforded the product 7a in 43%
yield (Table 4, entry 1).
drazine 1a with Pd(PPh3)4 (5 mol%), 1,1¢-bis(diphe-
nylphosphino)ferrocene (10 mol%), and potassium
Table 4 describes our effort towards optimizing different
carbonate (1.0 equiv) in dry tetrahydrofuran as solvent at
parameters. After the optimization studies, a combination
room temperature.
of [Pd(allyl)Cl]2 (5 mol%), 1,1¢-bis(diphenylphosphi-
Table 1 Optimization Studiesa
no)ferrocene (10 mol%), and sodium hydride (1.0 equiv)
was found to be the best conditions for this transforma-
tion.
Ph
Ph
Ph
Ph
OH
NHCO2Et
O
N
CO2Et
catalyst, ligand
To explore the scope and generality of the method, the re-
action was repeated using different fulvene-derived bicy-
clic hydrazines 1 and 4 and active methylene compounds
6. The results of the investigations are summarized in
Table 5.
N
+
CO2Et
base, solvent
60 °C, time
N
CO2Et
OMe
MeO
1a
2a
3a
Entry Catalyst
Ligand Base
Solvent Yieldb
(%)
We propose a plausible mechanism for this trans-
formation16 that involves two stages, the initial one being
the ring opening of the bicyclic alkene (Scheme 1). The
first step of the catalytic cycle involves the formation of
p-allylpalladium intermediate B by the attack of Pd(0) on
the double bond (allylic species), and subsequent oxida-
tive addition to C–N bond leading to the ring opening. In
the second stage, the nucleophile regio- and stereospecif-
ically attacks the p-allylpalladium species B thereby
forming the intermediate C. The reason for the cis stereo-
chemistry can be attributed to a classical mechanistic
pathway involving a double inversion.
1
2
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
Pd(OAc)2
dppf
dppf
dppf
dppf
dppf
NaH
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
43
K2CO3
t-BuOK
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
73
3
38
4
trace
21
5
PdCl2(PPh3)2
6
Pd2(dba)3·CHCl3 dppf
38
7
PdCl2
dppf
dppf
dppe
PPh3
dppf
dppf
dppf
trace
80
8
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
To explore the synthetic utility of the synthesized alky-
lidenecyclopentenes and also to get further confirmation
9
35
R2
10
11
12
13
42
R2
R1O2H2CN
R2
N
R2
MeCN 34
Nu
R1O2C
decomplexation
DMF
THF
50
D
N
N
Pd(0)
CO2R1
CO2R1
96c
R2
a Reaction conditions: alkene 1a (1.5 equiv), phenol 2a (1.0 equiv),
catalyst (5 mol%), ligand (10 mol%) base (1.0 equiv), solvent (2 mL),
60 °C, 16 h.
R2
R2
R1O2H2CN
R2
LnPd
N
Nu
R1O2C
b Isolated yield.
N
CO2R1
CO2R1
c Solvent (4 mL), r.t., 1.5 h.
N
LnPd
C
A
R2
The generality of the new ring-opening reaction was test-
ed by repeating the reaction under the optimized condition
with various phenols. Different fulvene-derived bicyclic
adducts 1a–c were subjected to the desymmetrization
with substituted phenols 2a–e. The results are summa-
rized in Table 2.
R2
R1O2CN
Nu
N
base
NuH
R1O2C
B
PdLn
Scheme 1 Mechanistic rationale
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York

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Trapping a p-Allylpalladium Intermediate
3651
Table 2 Palladium-Catalyzed Reaction of Azabicyclic Olefins with Phenolsa
Entry Alkene
Nucleophile
Product
Yield (%)
96
Ph
Ph
Ph
Ph
Ph
Ph
Ph
OH
CO2Et
CO2Et
HN
N
1
2
3
4
1a
1a
1a
1a
2a
3a
O
N
CO2Et
N
OMe
OH
CO2Et
MeO
Ph
Ph
Ph
CO2Et
HN
2b
2c
2d
3b
3c
3d
88
86
87
O
N
CO2Et
N
CO2Et
N
CO2Et
Ph
Ph
Ph
OH
CO2Et
CO2Et
HN
N
O
N
CO2Et
N
CO2Et
Ph
Ph
Ph
HN
OH
Br
CO2Et
O
N
CO2Et
N
CO2Et
N
CO2Et
Br
Ph
HN
Ph
Ph
Ph
CO2Et
OH
O
N
5
6
1a
1b
2e
2a
3e
3f
78
81
CO2Et
N
CO2Et
N
CO2Et
Ph
Ph
HN
N
OH
Ph
Ph
CO2i-Pr
CO2i-Pr
O
N
CO2i-Pr
N
CO2i-Pr
OMe
OH
MeO
Ph
Ph
Ph
Ph
Ph
Ph
Ph
CO2i-Pr
HN
7
8
1b
1b
1c
1c
2b
2c
2a
2b
3g
3h
3i
80
75
60
55
O
N
CO2i-Pr
N
N
CO2i-Pr
CO2i-Pr
Ph
Ph
Ph
OH
OH
CO2i-Pr
CO2i-Pr
HN
N
O
N
CO2i-Pr
N
CO2i-Pr
Ph
Ph
Ph
CO2t-Bu
HN
O
9
N
CO2t-Bu
N
CO2t-Bu
N
CO2t-Bu
OMe
OH
MeO
Ph
HN
Ph
Ph
CO2t-Bu
10
3j
O
N
CO2t-Bu
N
CO2t-Bu
N
CO2t-Bu
a Reaction conditions: alkene 1 (1.5 equiv), phenol 2 (1.0 equiv), Pd(PPh3)4 (5 mol%), dppf (10 mol%), K2CO3 (1.0 equiv), r.t., 1.5 h.
on the assigned structure, we carried out the hydrogena- carbon tetrachloride–water (1:1:1 ), oxidative cleavage of
tion of 7d over palladium on carbon; the reaction afforded the tetrasubstituted double bonds occurred furnishing the
the reduced product 8 in quantitative yield. When 8 was substituted cyclopentanone 9 in 74% yield (Scheme 2).
treated with a system consisting of ruthenium(III) chlo- This reaction can be viewed as an alternative route to cis-
ride trihydrate and sodium periodate in acetonitrile– a,a¢-disubstituted cyclopentanones.
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York

3652
R. Rajan et al.
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Yield (%)
76
Table 3 Palladium-Catalyzed Reaction of 6,6¢-Dialkylidenefulvene-Derived Alkenes with Phenola
Entry
1
Alkene
Phenol
Product
OH
CO2Et
CO2Et
HN
N
4a
2a
5a
O
N
CO2Et
OMe
N
CO2Et
MeO
OH
CO2Et
HN
N
2
3
4a
4b
2b
2a
5b
5c
73
78
O
CO2Et
N
CO2Et
N
CO2Et
OH
CO2Et
HN
N
O
CO2Et
N
CO2Et
OMe
N
CO2Et
MeO
a Reaction conditions: alkene 4 (1.5 equiv), phenol 2 (1.0 equiv), Pd(PPh3)4 (5 mol%), dppf (10 mol%), K2CO3 (1.0 equiv), r.t., 1.5 h.
Table 4 Optimization Studiesa
Ph
Ph
Ph
Ph
NHCO2i-Pr
NHCO2i-Pr
Chloranil
Ph
Ph
O
N
N
Ph
Ph
CO2i-Pr
xylene, 110 °C
74%
CO2i-Pr
MeO2C
MeO2C
NHCO2Et
CO2Me
catalyst
3f
10
N
N
CO2Et
+
MeO
dppf, base
THF, r.t., 1.5 h
CO2Et
N
Me
CO2
CO2Et
Scheme 3 Synthesis of substituted fulvenes
7a
1a
6a
Entry Nucleophile
Conditions
Yieldb (%)
was refluxed with three equivalents of chloranil in xylene,
the reaction afforded the 2-hydrazino-substituted fulvene
10 in 74% yield (Scheme 3).
1
2
3
CH2(CO2Me)
CH2(CO2Me)
CH2(CO2Me)
Pd(PPh3)4, dppf, K2CO3
Pd(PPh3)4, dppf, NaH
[Pd(allyl)Cl]2, dppf, NaH
43
73
93
In conclusion, we have introduced a facile route towards
the synthesis of a new class of disubstituted alkylidenecy-
clopentenes. The products are obtained in good to excel-
lent yields. The possibility for further functionalization
was effectively demonstrated by the synthesis of substi-
tuted cyclopentanones and 2-hydrazinofulvenes. To the
best of our knowledge this is the first report on the synthe-
sis of 2-hydrazinofulvenes. Efforts for utilizing the devel-
oped methodology towards the synthesis of bioactive
molecules will be reported in due course.
a Reaction conditions: alkene 1a (1.5 equiv), phenol 6a (1.0 equiv),
catalyst (5 mol%), dppf (10 mol%), base (1.0 equiv), THF (2 mL), r.t.,
1.5 h.
b Isolated yield.
MeO2C
MeO2C
NHCO2Et
NCO2Et
MeO2C
MeO2C
NHCO2Et
NCO2Et
Pd/C, H2
EtOAc, r.t., 6 h
100%
All reactions were conducted in oven-dried glassware. Solvents
used for the experiments were distilled or dried as specified. All re-
actions were monitored by TLC (silica gel 60 F254, 0.25 mm, Mer-
ck) until conversion was complete; visualization was effected with
UV and/or by staining with enholm yellow or with basic KMnO4.
Column chromatography used silica gel (100–200 mesh) eluting
with petroleum ether (PE)–EtOAc mixtures. The solvents were re-
moved using a Buchi E.L rotary evaporator. HPLC analyses were
conducted with a LC9101 Recycling Preparative chromatograph.
IR spectra were taken on a Nicolet impact 400d FT-IR spectropho-
tometer. NMR spectra were recorded at 300 and 500 MHz (1H) and
75 and 125 (13C) MHz, respectively on a Bruker DPX-300 and -500
MHz FT-NMR spectrometer. NMR spectra were obtained using
CDCl3 as the solvent with TMS as internal standard. Mass spectra
7d
8
O
MeO2C
MeO2C
NHCO2Et
NCO2Et
RuCl3⋅3H2O, NaIO4
MeCN–CCl4–H2O (1:1:1)
r.t., 5 h, 74%
9
Scheme 2 Synthesis of substituted cyclopentanones
Our next attempt was to oxidize the substituted alky-
lidenecyclopentene to check whether these molecules
could act as precursors for substituted fulvenes. When 3f
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York

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Trapping a p-Allylpalladium Intermediate
3653
Table 5 Palladium-Catalyzed Reaction of Azabicyclic Olefins with Active Methylene Compoundsa
Entry
1
Alkene
Nucleophile
Product
Yield (%)
Ph
Ph
Ph
Ph
Ph
Ph
CO2Me
CO2Me
CO2Et
CO2Et
MeO2C
MeO2C
HN
N
1a
6a
7a
93
N
N
CO2Et
CO2Et
CO2i-Pr
CO2Et
Ph
Ph
Ph
CO2Et
CO2Et
CO2Et
CO2Et
86b
76b
EtO2C
EtO2C
HN
2
3
1a
1b
6b
6b
7b
7c
N
N
N
CO2Et
Ph
Ph
Ph
CO2Et
CO2Et
CO2i-Pr
CO2i-Pr
EtO2C
EtO2C
HN
N
N
N
CO2i-Pr
CO2Me
CO2Me
4
5
4a
4a
6a
6b
7d
7e
79
CO2Et
MeO2C
MeO2C
HN
N
N
CO2Et
CO2Et
N
CO2Et
CO2Et
CO2Et
70b
CO2Et
CO2Et
EtO2C
EtO2C
HN
N
N
CO2Et
N
CO2Et
a Reaction conditions: alkene 1a,b or 4a (1.5 equiv), phenol 6a,b (1.0 equiv), [Pd(allyl)Cl]2 (5 mol%), dppf (10 mol%), NaH (1.0 equiv), r.t.,
1.5 h.
b 60 °C.
were recorded by FAB ionization technique using a Jeol JMS 600H
mass spectrometer.
5-(Diphenylmethylene)-4-(4-methylphenoxy) Diethyl Ester 3b
Light-brown powder; yield: 88%; mp 78–80 °C; Rf = 0.62 (EtOAc–
hexane, 4:6).
Diethyl 1-[cis-5-(Diphenylmethylene)-4-(4-methoxyphen-
oxy)cyclopent-2-enyl]hydrazine-1,2-dicarboxylate(3a);Typical
Procedure
IR (KBr): 3308, 3055, 2974, 2928, 1750, 1715, 1508, 1412, 1227,
1063, 930, 772 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.32–7.10 (m, 10 H), 6.94–6.93
(m, 2 H), 6.68–6.62 (m, 2 H), 6.16–6.08 (m, 2 H), 5.89–5.82 (m, 1
H), 5.61 (s, 1 H), 5.22–5.17 (m, 1 H), 4.06–4.01 (m, 2 H), 3.83–3.77
(m, 2 H), 2.21 (s, 3 H), 1.18–0.97 (m, 6 H).
13C NMR (125 MHz, CDCl3): d = 155.2, 154.7, 153.7, 141.3, 137.9,
133.7, 132.2, 129.9, 129.5, 129.3, 129.1, 128.0, 127.8, 124.7, 115.1,
79.4, 62.7, 62.3, 61.9, 21.0, 14.5, 14.4.
Pd(PPh3)4 (46.0 mg, 0.04 mmol), dppf (44.4 mg, 0.08 mmol), and
K2CO3 (111.8 mg, 0.81 mmol) were added to a Schlenk tube and
placed under vacuum for 15 min. Freshly distilled THF (2 mL) was
degassed and then added to the mixture at r.t.; the soln was stirred
for 15 min. To the Schlenk tube was added 2a (100.0 mg, 0.81
mmol) and 1a (484.8 mg, 1.2 mmol) dissolved in THF (2 mL) and
the soln was stirred at r.t. (TLC monitoring). The solvent was re-
moved under reduced pressure and the residue was subjected to
chromatography (silica gel, EtOAc–hexane, 40:60) to afford 3a
(412 mg, 96%) as a light-brown powder; mp 122–124 °C; Rf = 0.52
(EtOAc–hexane, 4:6).
MS (FAB): m/z [M]+ calcd for C31H32N2O5: 512.23; found: 512.20.
5-(Diphenylmethylene)-4-phenoxy Diethyl Ester 3c
Light-brown powder; yield: 86%; mp 124–126 °C; Rf = 0.62
(EtOAc–hexane, 4:6).
IR (KBr): 3368, 2983, 2928, 1748, 1727, 1599, 1510, 1374, 1231,
1034, 763 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.35–7.28 (m, 3 H), 7.22–7.12 (m,
7 H), 6.68–6.62 (m, 4 H), 6.13–6.09 (m, 2 H), 5.88–5.82 (m, 1 H),
5.60 (s, 1 H), 5.11 (m, 1 H), 4.10–4.03 (m, 2 H), 3.84–3.83 (m, 2 H),
3.69 (s, 3 H), 1.19–1.16 (m, 3 H), 1.05–0.98 (m, 3 H).
13C NMR (125 MHz, CDCl3): d = 156.0, 155.1, 153.7, 149.6, 141.4,
140.0, 138.0, 133.6, 133.0, 132.1, 130.0, 129.4, 129.1, 128.0, 127.8,
124.7, 116.0, 78.3, 62.5, 62.1, 61.8, 55.6, 14.7, 14.4.
IR (KBr): 3308, 3055, 2978, 2932, 1748, 1715, 1597, 1493, 1383,
1227, 1028, 966, 752 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.38–7.16 (m, 12 H), 6.95–6.90
(m, 1 H), 6.82–6.80 (m, 2 H), 6.25–6.21 (m, 2 H), 5.98–5.92 (m, 1
H), 5.72 (s, 1 H), 5.31 (m, 1 H), 4.12 (m, 2 H), 3.91 (m, 2 H), 1.23–
1.09 (m, 6 H).
13C NMR (125 MHz, CDCl3): d = 156.9, 156.2, 154.7, 141.1, 140.3,
135.1, 134.9, 134.6, 134.3, 133.0, 132.6, 129.4, 128.6, 128.1, 127.6,
127.5, 127.3, 121.1, 116.1, 78.8, 62.6, 62.3, 61.7, 14.4, 14.2.
MS (FAB): m/z [M]+ calcd for C31H32N2O6: 528.23; found: 528.90.
MS (FAB): m/z [M]+ calcd for C30H30N2O5: 498.22; found: 498.58.
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York

3654
R. Rajan et al.
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5-(Diphenylmethylene)-4-phenoxy Diisopropyl Ester 3h
Light-brown powder; yield: 75%; mp 114–116 °C; Rf = 0.43
(EtOAc–hexane, 4:6).
4-(4-Bromophenoxy)-5-(diphenylmethylene) Diethyl Ester 3d
Light-brown powder; yield: 87%; mp 130–134 °C; Rf = 0.62
(EtOAc–hexane, 4:6).
IR (KBr): 3308, 3057, 2980, 2859, 1743, 1713, 1585, 1412, 1227,
1063, 930, 772 cm–1.
IR (KBr): 3325, 3054, 2980, 2939, 1748, 1715, 1612, 1508, 1491,
1468, 1385, 1229, 1109, 1036, 963, 752, 702 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.37–7.16 (m, 12 H), 6.72–6.66
(m, 2 H), 6.21–6.15 (m, 2 H), 5.97–5.91 (m, 1 H), 5.70 (s, 1 H),
5.28–5.25 (m, 1 H), 4.14–4.06 (m, 2 H), 3.95–3.90 (m, 2 H), 1.26–
1.04 (m, 6 H).
1H NMR (500 MHz, CDCl3): d = 7.43–7.34 (m, 4 H), 7.29–7.15 (m,
8 H), 6.93–6.90 (m, 1 H), 6.85–6.80 (m, 2 H), 6.50 (s, 1 H), 6.24–
6.12 (m, 2 H), 5.98–5.92 (m, 1 H), 5.34–5.28 (m, 1 H), 4.91–4.85
(m, 1 H), 4.63–4.59 (m, 1 H), 1.32–1.03 (m, 12 H).
13C NMR (125 MHz, CDCl3): d = 156.3, 156.1, 154.7, 147.0, 140.6,
140.1, 135.7, 135.1, 134.0, 133.5, 132.2, 131.9, 128.7, 128.5, 128.1,
127.8, 127.6, 127.5, 127.1, 117.8, 79.3, 63.6, 62.4, 62.2, 14.5, 14.2.
13C NMR (125 MHz, CDCl3): d = 156.9, 155.7, 155.6, 140.9, 135.1,
134.5, 133.9, 132.5, 132.4, 129.2, 128.8, 128.7, 128.2, 128.0, 127.4,
121.0, 78.7, 69.6, 69.4, 62.2, 21.8, 21.7.
MS (FAB): m/z [M]+ calcd for C30H29BrN2O5: 576.13; found:
MS (FAB): m/z [M]+ calcd for C32H34N2O5: 526.25; found: 526.46.
578.22 [M + 2].
5-(Diphenylmethylene)-4-(4-methoxyphenoxy) Di-tert-butyl Es-
ter 3i
Light-brown powder; yield: 60%; mp 94–96 °C; Rf = 0.35 (EtOAc–
hexane, 4:6).
5-(Diphenylmethylene)-4-(1-naphthyloxy) Diethyl Ester 3e
Brown powder; yield: 78%; mp 128–130 °C; Rf = 0.60 (EtOAc–
hexane, 4:6).
IR (KBr): 3364, 3053, 2982, 2930, 1750, 1719, 1595, 1489, 1381,
1231, 1061, 795, 754, 702 cm–1.
IR (KBr): 3333, 3057, 2978, 2932, 1748, 1711, 1504, 1393, 1368,
1238, 1157, 1032, 968, 752 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.33 (d, J = 8.0 Hz, 1 H), 7.81 (d,
J = 8.0 Hz, 1 H), 7.52–7.50 (m, 2 H), 7.42–7.38 (m, 5 H), 7.32–7.24
(m, 4 H), 7.00–6.98 (m, 3 H), 6.63 (d, J = 8.0 Hz, 1 H), 6.36 (br s,
1 H), 6.26 (m, 1 H), 6.07 (m, 1 H), 5.81 (s, 1 H), 5.52 (m, 1 H), 4.15–
4.12 (m, 2 H), 3.97 (m, 2 H), 1.14–1.09 (m, 6 H).
13C NMR (125 MHz, CDCl3): d = 156.5, 156.1, 152.9, 141.1, 140.9,
140.3, 135.4, 134.7, 132.6, 132.1, 128.7, 128.5, 128.0, 127.8, 127.4,
126.2, 125.8, 125.6, 124.9, 122.9, 120.4, 106.3, 79.3, 63.7, 62.6,
61.9, 14.5, 14.3.
1H NMR (500 MHz, CDCl3): d = 7.34–7.12 (m, 10 H), 6.68–6.66
(m, 4 H), 6.35 (s, 1 H), 6.09–6.01 (m, 1 H), 5.84–5.80 (m, 1 H), 5.39
(m, 1 H), 5.09–5.06 (m, 1 H), 3.68 (s, 3 H), 1.34 (s, 9 H), 1.21 (s, 9
H).
13C NMR (125 MHz, CDCl3): d = 155.8, 155.1, 154.9, 141.1, 140.8,
135.0, 134.8, 132.4, 129.8, 129.7, 128.9, 128.8, 128.7, 128.0, 127.6,
127.4, 116.0, 80.8, 80.0, 61.8, 61.6, 55.6, 28.2, 28.1.
MS (FAB): m/z [M]+ calcd for C35H40N2O6: 584.29; found: 584.82.
MS (FAB): m/z [M]+ calcd for C34H32N2O5: 548.23; found: 548.71.
5-(Diphenylmethylene)-4-(4-methylphenoxy) Di-tert-butyl Es-
ter 3j
5-(Diphenylmethylene)-4-(4-methoxyphenoxy) Diisopropyl Es-
Light-brown powder; yield: 55%; mp 156–158 °C; Rf = 0.54
ter 3f
(EtOAc–hexane, 4:6).
Light-brown powder; yield: 81%; mp 148–150 °C; Rf = 0.54
(EtOAc–hexane, 4:6).
IR (KBr): 3337, 3050, 2984, 2938, 1752, 1717, 1506, 1389, 1371,
1226, 1148, 1031, 961, 751 cm–1.
IR (KBr): 3323, 3053, 2980, 2934, 1742, 1713, 1466, 1385, 1225,
1036, 966, 826, 750 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.28–7.20 (m, 3 H), 7.18–7.10 (m,
7 H), 6.67–6.60 (m, 4 H), 6.41 (s, 1 H), 6.11–6.05 (m, 2 H), 5.87–
5.82 (m, 1 H), 5.14–5.10 (m, 1 H), 4.86–4.82 (m, 1 H), 4.54–4.50
(m, 1 H), 3.68 (s, 3 H), 1.18–0.99 (m, 12 H).
13C NMR (125 MHz, CDCl3): d = 155.6, 154.2, 153.9, 140.9, 140.3,
134.9, 134.8, 134.4, 134.0, 132.8, 128.7, 128.0, 127.5, 127.4, 127.3,
114.6, 79.9, 70.2, 69.5, 62.2, 55.3, 22.1, 21.9.
1H NMR (500 MHz, CDCl3): d = 7.44–7.34 (m, 3 H), 7.25–7.15 (m,
7 H), 7.03–7.00 (m, 2 H), 6.75–6.73 (m, 2 H), 6.48 (s, 1 H), 6.20–
6.15 (m, 2 H), 5.96–5.88 (m, 1 H), 5.28–5.20 (m, 1 H), 2.28 (s, 3 H),
1.40 (s, 9 H), 1.28 (s, 9 H).
13C NMR (125 MHz, CDCl3): d = 154.9, 154.8, 153.3, 141.0, 135.1,
135.0, 132.4, 132.2, 130.3, 129.8, 128.9, 128.7, 128.0, 127.7, 127.4,
116.6, 80.4, 79.1, 61.6, 28.2, 21.0.
MS (FAB): m/z [M]+ calcd for C35H40N2O5: 568.29; found: 569.01
[M + 1].
MS (FAB): m/z [M]+ calcd for C33H36N2O6: 556.26; found: 556.46.
5-(Adamantan-2-ylidene)-4-(4-methoxyphenoxy) Diethyl Ester
5a
5-(Diphenylmethylene)-4-(4-methylphenoxy) Diisopropyl Ester
3g
Light-green viscous liquid; yield: 76%; Rf = 0.54 (EtOAc–hexane,
4:6).
Light-brown powder; yield: 80%; mp 94–96 °C; Rf = 0.48 (EtOAc–
hexane, 4:6).
IR (KBr): 3306, 3054, 2909, 2856, 1753, 1707, 1504, 1412, 1302,
1225, 1063, 955, 756 cm–1.
1H NMR (500 MHz, CDCl3): d = 6.88–6.76 (m, 4 H), 6.57 (s, 1 H),
6.25–6.16 (m, 2 H), 5.87 (m, 1 H), 5.38 (m, 1 H), 4.21–4.19 (m, 2
H), 4.07–4.06 (m, 2 H), 3.77 (s, 3 H), 2.81–2.77 (m, 2 H), 1.95–1.92
(m, 12 H), 1.27–1.25 (m, 6 H).
13C NMR (125 MHz, CDCl3): d = 156.4, 155.8, 153.7, 135.1, 133.3,
130.1, 129.9, 121.9, 115.8, 77.7, 62.4, 61.7, 55.8, 40.2, 39.5, 38.5,
38.3, 36.8, 35.3, 34.8, 28.0, 14.7, 14.3.
IR (KBr): 3325, 3054, 2980, 2939, 1748, 1715, 1612, 1508, 1491,
1468, 1385, 1229, 1036, 963, 752, 702 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.28–7.09 (m, 10 H), 6.94–6.92
(m, 2 H), 6.67–6.61 (m, 2 H), 6.40 (s, 1 H), 6.14–6.06 (m, 2 H),
5.88–5.82 (m, 1 H), 5.23–5.16 (m, 1 H), 4.83–4.82 (m, 1 H), 4.53–
4.52 (m, 1 H), 2.21 (s, 3 H), 1.19–0.96 (m, 12 H).
13C NMR (125 MHz, CDCl3): d = 155.7, 154.7, 153.5, 140.9, 132.6,
132.1, 130.2, 130.0, 129.7, 128.7, 128.0, 127.7, 127.4, 127.3, 124.6,
115.1, 79.4, 69.7, 69.4, 62.2, 22.0, 21.8, 20.5.
MS (FAB): m/z [M]+ calcd for C28H36N2O6: 496.26; found: 496.32.
MS (FAB): m/z [M]+ calcd for C33H36N2O5: 540.26; found: 540.46.
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York

PAPER
Trapping a p-Allylpalladium Intermediate
3655
5-(Adamantan-2-ylidene)-4-(4-methylphenoxy) Diethyl Ester
5b
4 H), 3.93–3.89 (m, 2 H), 3.74 (m, 2 H), 3.28–3.22 (m, 1 H), 1.26–
1.19 (m, 6 H), 1.05–0.96 (m, 6 H).
Light-green viscous liquid; yield: 73%; Rf = 0.52 (EtOAc–hexane,
4:6).
13C NMR (125 MHz, CDCl3): d = 168.4, 168.1, 156.4, 154.2, 144.5,
143.8, 142.0, 141.8, 141.3, 141.1, 135.4, 135.1, 135.0, 128.6, 127.0,
62.4, 61.7, 61.3, 53.1, 29.8, 14.5, 14.1.
IR (KBr): 3308, 3057, 2916, 2850, 1758, 1714, 1502, 1414, 1302,
1225, 1063, 968, 750 cm–1.
MS (FAB): m/z [M]+ calcd for C31H36N2O8: 564.25; found: 564.93.
1H NMR (500 MHz, CDCl3): d = 7.07 (d, J = 8.5 Hz, 2 H), 6.83 (d,
J = 8.5 Hz, 2 H), 6.54 (s, 1 H), 6.27–6.26 (m, 1 H), 6.17–6.16 (m, 1
H), 5.88 (m, 1 H), 5.44 (s, 1 H), 4.26–4.18 (m, 2 H), 4.05–4.04 (m,
2 H), 2.80–2.74 (m, 2 H), 2.29 (s, 3 H), 1.97–1.82 (m, 12 H), 1.60–
1.26 (m, 4 H), 1.13–1.11 (m, 2 H).
13C NMR (125 MHz, CDCl3): d = 156.4, 155.8, 153.7, 135.1, 133.1,
130.0, 129.9, 121.9, 115.8, 77.6, 62.4, 61.7, 61.3, 40.2, 39.5, 38.5,
38.3, 36.8, 35.3, 34.8, 28.0, 20.5, 14.7, 14.3.
4-[Bis(ethoxycarbonyl)methyl]-5-(diphenylmethylene) Diiso-
propyl Ester 7c
Viscous liquid; yield: 76%; Rf = 0.63 (EtOAc–hexane, 4:6).
IR (KBr): 3312, 3055, 2981, 2936, 2908, 1726, 1715, 1597, 1489,
1371, 1223, 1061, 754, 705 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.20–7.18 (m, 10 H), 6.14–6.08
(m, 1 H), 5.89–5.88 (m, 1 H), 5.80–5.70 (m, 1 H), 4.89–4.88 (m, 1
H), 4.54–4.40 (m, 2 H), 4.13 (m, 2 H), 3.94 (m, 2 H), 3.29–3.22 (m,
1 H), 1.21–0.83 (m, 18 H).
MS (FAB): m/z [M]+ calcd for C28H36N2O5: 480.26; found: 480.32.
5-Cyclohexylidene)-4-(4-methoxyphenoxy) Diethyl Ester 5c
Light-green viscous liquid; yield: 78%; Rf = 0.72 (EtOAc–hexane,
4:6).
13C NMR (125 MHz, CDCl3): d = 168.1, 167.7, 155.5, 153.6, 141.8,
141.2, 135.1, 134.7, 130.4, 128.7, 128.5, 128.3, 127.9, 127.2, 126.9,
126.6, 69.5, 69.3, 63.9, 61.1, 60.9, 45.4, 26.9, 22.1, 21.9, 14.0, 13.7.
IR (KBr): 3308, 3057, 2916, 2850, 1758, 1714, 1502, 1414, 1302,
1225, 1063, 968, 750 cm–1.
MS (FAB): m/z [M]+ calcd for C33H40N2O8: 592.28; found: 592.93.
1H NMR (500 MHz, CDCl3): d = 6.87–6.68 (m, 4 H), 6.41 (s, 1 H),
6.14–6.10 (m, 2 H), 5.77–5.71 (m, 1 H), 5.29 (s, 1 H), 4.17–4.15 (m,
2 H), 4.02 (m, 2 H), 3.70 (s, 3 H), 2.16 (m, 4 H), 1.56–1.53 (m, 6 H),
1.21–1.09 (m, 6 H).
5-(Adamantan-2-ylidene)-4-[bis(methoxycarbonyl)methyl] Di-
ethyl Ester 7d
Light-brown viscous liquid; yield: 79%; Rf = 0.50 (EtOAc–hexane,
4:6).
13C NMR (125 MHz, CDCl3): d = 156.0, 155.7, 153.4, 132.8, 132.6,
127.1, 125.1, 124.8, 116.0, 64.9, 62.8, 61.8, 60.4, 55.6, 26.0, 25.9,
22.6, 22.2, 21.0, 14.6, 14.2.
MS (FAB): m/z [M]+ calcd for C24H32N2O6: 444.23; found: 445.03
[M + 1].
IR (KBr): 3308, 2980, 2907, 2849, 1728, 1711, 1694, 1504, 1412,
1306, 1219, 1061, 959, 812 cm–1.
1H NMR (500 MHz, CDCl3): d = 6.05–6.01 (m, 1 H), 5.92 (s, 1 H),
5.79–5.76 (m, 1 H), 4.19–4.16 (m, 4 H), 3.92 (d, J = 9.0 Hz, 1 H),
3.75 (s, 6 H), 3.42–3.40 (m, 1 H), 2.79–2.75 (m, 1 H), 2.54–2.50 (m,
1 H), 1.92–1.80 (m, 12 H), 1.25 (s, 6 H).
Diethyl 1-{cis-4-[Bis(methoxycarbonyl)methyl]-5-(diphenyl-
methylene)cyclopent-2-enyl}hydrazine-1,2-dicarboxylate (7a);
Typical Procedure
13C NMR (125 MHz, CDCl3): d = 168.9, 168.7, 156.0, 155.2, 150.8,
137.1, 130.5, 121.8, 62.4, 61.7, 57.4, 52.4, 44.9, 39.2, 38.8, 38.6,
36.7, 35.0, 34.5, 27.7, 14.6, 14.5.
[Pd(allyl)Cl]2 (14.6 mg, 0.04 mmol), dppf (44.4 mg, 0.08 mmol),
and NaH (18.2 mg, 0.76 mmol) were added to a Schlenk tube and
placed under vacuum for 15 min. Freshly distilled THF (2 mL) was
degassed and then added to the mixture at r.t.; the soln was stirred
for 15 min. 6a (100.0 mg, 0.76 mmol) and 1a (460.1 mg, 1.14
mmol) dissolved in THF (2 mL) were added and the mixture was
stirred at r.t. (TLC monitoring). The solvent was removed under re-
duced pressure and the residue was subjected to chromatography
(silica gel, EtOAc–hexane, 40:60) to afford 7a (377 mg, 93%) as a
light-brown viscous liquid; Rf = 0.57 (EtOAc–hexane, 4:6).
MS (FAB): m/z [M]+ calcd for C26H36N2O8: 504.25; found: 505.05
[M + 1].
5-(Adamantan-2-ylidene)-4-[bis(ethoxycarbonyl)methyl] Di-
ethyl Ester 7e
Viscous liquid; yield: 70%; Rf = 0.63 (EtOAc–hexane, 4:6).
IR (KBr): 3311, 2975, 2910, 2849, 1730, 1715, 1698, 1510, 1414,
1306, 1225, 1064, 950, 754 cm–1.
1H NMR (500 MHz, CDCl3): d = 6.07–6.04 (m, 1 H), 5.91 (s, 1 H),
5.79–5.76 (m, 1 H), 4.32–4.14 (m, 8 H), 3.93–3.91 (m, 1 H), 3.47–
3.35 (m, 1 H), 2.80–2.77 (m, 1 H), 2.57–2.54 (m, 1 H), 1.94–1.62
(m, 12 H), 1.27–1.26 (m, 12 H).
13C NMR (125 MHz, CDCl3): d = 168.7, 168.4, 155.9, 155.2, 150.7,
137.3, 130.2, 121.9, 62.8, 62.3, 61.6, 61.3, 57.8, 44.6, 39.2, 39.0,
38.7, 36.7, 34.9, 34.5, 27.7, 14.5, 14.0.
IR (KBr): 3317, 3049, 2981, 2940, 2900, 1730, 1720, 1601, 1489,
1370, 1216, 1061, 750, 705 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.35–7.20 (m, 10 H), 6.15–6.10
(m, 1 H), 5.90 (s, 1 H), 5.78 (m, 1 H), 4.46 (m, 1 H), 4.18–4.10 (m,
4 H), 3.67 (s, 6 H), 3.28 (m, 1 H), 1.26–1.10 (m, 6 H).
13C NMR (125 MHz, CDCl3): d = 168.7, 168.4, 156.5, 156.0, 141.0,
135.1, 134.8, 128.6, 128.1, 127.6, 127.4, 127.0, 126.7, 63.0, 61.7,
61.4, 53.4, 45.2, 28.3, 14.7, 14.5.
MS (FAB): m/z [M]+ calcd for C28H40N2O8: 532.28; found: 533.09
[M + 1].
MS (FAB): m/z [M]+ calcd for C29H32N2O8: 536.22; found: 536.30.
Diethyl 1-{cis-2-(Adamantan-2-ylidene)-3-[bis(methoxycarbon-
yl)methyl]cyclopentyl}hydrazine-1,2-dicarboxylate (8)
Compound 7d (300.0 mg, 0.60 mmol) was dissolved in anhyd
EtOAc. 10% Pd/C (cat.) was added and the mixture was stirred un-
der H2 (1 atm) at r.t. for 6 h (TLC monitoring). When the reaction
was complete, the mixture was filtered through a pad of Celite. The
solvent was removed under reduced pressure and the residue was
subjected to chromatography (silica gel, EtOAc–hexane, 30:70) to
afford 8 (300.0 mg, yield: 100%) as a colorless viscous liquid; Rf =
0.51 (EtOAc–hexane, 4:6).
4-[Bis(ethoxycarbonyl)methyl]-5-(diphenylmethylene) Diethyl
Ester 7b
Viscous liquid; yield: 86%; Rf = 0.50 (EtOAc–hexane, 4:6).
IR (KBr): 3324, 3046, 2975, 2936, 2910, 1730, 1722, 1584, 1493,
1368, 1223, 1061, 760, 705 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.35–7.13 (m, 10 H), 6.11 (m, 1
H), 5.89 (s, 1 H), 5.77 (m, 1 H), 4.45–4.40 (m, 1 H), 4.18–4.10 (m,
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York

3656
R. Rajan et al.
PAPER
IR (KBr): 3312, 2978, 2907, 2849, 1732, 1697, 1616, 1416, 1384,
1220, 1126, 1061, 925, 758 cm–1.
1H NMR (500 MHz, CDCl3): d = 4.25–4.11 (m, 5 H), 3.74 (s, 6 H),
3.50–3.40 (m, 2 H), 2.68–2.63 (m, 2 H), 2.52–2.50 (m, 1 H), 2.32–
2.26(m, 1 H), 2.04 (m, 1 H), 1.81–1.56 (m, 14 H), 1.30–1.23 (m, 6
H).
Industrial Research, New Delhi are greatly acknowledged. R.R.
acknowledges the Council of Scientific and Industrial Research
(CSIR) for a senior research fellowship. The authors thank Dr. R.
Luxmi Varma and Ms. S. Viji, Chemical Sciences and Technology
Division, for NMR and mass spectral analysis.
13C NMR (125 MHz, CDCl3): d = 169.2, 168.4, 156.3, 155.2, 150.6,
128.3, 62.3, 61.8, 61.1, 53.6, 52.4, 40.8, 39.2, 38.4, 36.7, 35.2, 33.6,
29.6, 28.9, 22.5, 14.4, 14.2.
References
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MS (FAB): m/z [M]+ calcd for C26H38N2O8: 506.26; found: 506.81.
Diethyl 1-{cis-3-[Bis(methoxycarbonyl)methyl]-2-oxocyclopen-
tyl}hydrazine-1,2-dicarboxylate (9)
Compound 8 (160.0 mg, 0.32 mmol) was dissolved in MeCN–CCl4
(1:1, 10 mL). NaIO4 (409.0 mg, 1.92 mmol) was added to the soln
and the mixture was stirred. A soln of RuCl3 (7.8 mg, 0.03 mmol)
in H2O (5 mL) was added in one portion and vigorous stirring was
continued for 5 h. The mixture was diluted with H2O (10 mL), it was
extracted with CH2Cl2 (3 × 20 mL), and the combined organic ex-
tracts were filtered through a pad of Celite. The filtrate was concen-
trated under reduced pressure and the residue was subjected to
column chromatography (silica gel, EtOAc–hexanes) afforded 9
(90.0 mg, 74%) as a colorless viscous liquid; Rf = 0.65 (EtOAc–hex-
ane, 4:6).
IR (KBr): 3308, 2984, 2957, 1744, 1713, 1506, 1435, 1415, 1383,
1228, 1161, 1059, 926, 762 cm–1.
1H NMR (500 MHz, CDCl3): d = 4.21–4.10 (m, 4 H), 3.93–3.92 (m,
1 H), 3.77 (s, 6 H), 2.73 (m, 1 H), 2.45 (br s, 1 H), 2.22–2.05 (m, 2
H), 1.86–1.85 (m, 2 H), 1.28–1.26 (m, 6 H).
13C NMR (125 MHz, CDCl3): d = 211.7, 168.5, 168.0, 156.3, 155.4,
62.9, 62.3, 60.4, 52.8, 29.7, 24.3, 22.0, 14.4, 14.2.
MS (FAB): m/z [M]+ calcd for C16H24N2O9: 388.15; found: 388.17.
Diisopropyl 1-[5-(Diphenylmethylene)cyclopenta-1,3-di-
enyl}hydrazine-1,2-dicarboxylate (10)
Compound 3f (53.0 mg, 0.10 mmol) and chloranil (73.8 mg, 0.3
mmol) were dissolved in xylene and heated at 110 °C for 3 h. The
solvent was removed under reduced pressure and the residue was
subjected to chromatography (silica gel, EtOAc–hexane, 20:80) to
afford 10 (30.0 mg, 74%) as a blood-red-colored viscous liquid;
Rf = 0.39 (EtOAc–hexane, 4:6).
(10) (a) Barluenga, J.; Vicente, R.; Barrio, P.; Lopez, L. A.;
Tomas, M. J. Am. Chem. Soc. 2004, 126, 5974.
(b) Barluenga, J.; Vicente, R.; Barrio, P.; Lopez, L. A.;
Tomas, M. J. Am. Chem. Soc. 2006, 128, 7050.
(11) Tang, X.-Y.; Shi, M. J. Org. Chem. 2010, 75, 902.
(12) Anas, S.; Sajisha, V. S.; Mohanlal, S.; Radhakrishnan, K. V.
Synlett 2006, 2399.
(13) Anas, S.; John, J.; Sajisha, V. S.; John, J.; Rajan, R.; Suresh,
E.; Radhakrishnan, K. V. Org. Biomol. Chem. 2007, 5, 4010.
(14) Anas, S.; Sajisha, V. S.; John, J.; Joseph, N.; George, S. C.;
Radhakrishnan, K. V. Tetrahedron 2008, 64, 9689.
(15) Luna, A. P.; Cesario, M.; Bonin, M.; Micouin, L. Org. Lett.
2003, 5, 4771.
IR (KBr): 3312, 3055, 2981, 2936, 2908, 1726, 1715, 1597, 1489,
1371, 1223, 1061, 754, 705 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.36–7.24 (m, 10 H), 6.80–6.66
(m, 1 H), 6.40–6.39 (m, 1 H), 6.14–6.12 (m, 1 H), 4.90–4.83 (m, 2
H), 1.27–1.12 (m, 12 H).
13C NMR (125 MHz, CDCl3): d = 155.9, 154.3, 141.5, 140.5, 138.0,
132.4, 131.8, 130.3, 129.1, 128.4, 127.8, 125.0, 124.2, 70.0, 69.7,
22.2, 22.0.
MS (FAB): m/z [M]+ calcd for C26H28N2O4: 432.20; found: 432.86.
Acknowledgment
(16) Hand Book of Organopalladium Chemistry for Organic
Synthesis, Vol. 2; Negishi, E., Ed.; Wiley-Interscience: New
York, 2002.
Financial assistance from Department of Science and Technology
(DST No: SR/S1/OC-78/2009) and Council of Scientific and
Synthesis 2010, No. 21, 3649–3656 © Thieme Stuttgart · New York