The use of iminopyridines as efficient ligands in the palladium(II)-catalyzed cyclization of (Z)-4′-acetoxy-2′-butenyl 2-alkynoates

Article abstract of DOI:10.1016/j.tet.2007.04.006

Iminopyridines were found to be a sort of efficient bidentate ligands for the palladium(II)-catalyzed cyclization of (Z)-4′-acetoxy-2′-butenyl 2-alkynoates in acetic acid to afford the α-(Z)-acetoxyalkylidene-β-vinyl-γ-butyrolactones. The iminopyridine li

Full text of DOI:10.1016/j.tet.2007.04.006

Tetrahedron 63 (2007) 5148–5153
The use of iminopyridines as efficient ligands in the palladium(II)-
catalyzed cyclization of (Z)-40-acetoxy-20-butenyl 2-alkynoates
a
a,b,
Juan Song,a Qi Shen,a, Fan Xu and Xiyan Lu
*
*
aDepartment of Chemistry and Chemical Engineering, Suzhou University, Suzhou, China
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China
Received 23 February 2007; revised 3 April 2007; accepted 4 April 2007
Available online 8 April 2007
Abstract—Iminopyridines were found to be a sort of efficient bidentate ligands for the palladium(II)-catalyzed cyclization of (Z)-40-acetoxy-
20-butenyl 2-alkynoates in acetic acid to afford the a-(Z)-acetoxyalkylidene-b-vinyl-g-butyrolactones. The iminopyridine ligands could not
only inhibit b-hydride elimination but also stabilize the vinyl-palladium intermediate in acetic acid in the reaction.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
a ligand. To solve these problems, a new type of reaction
to construct a-alkylidene-g-butyrolactones has been devel-
oped in which the acetoxy anion served as the nucleophile
and the nitrogen-containing ligands were employed to in-
hibit the b-hydride elimination reaction.6 The stoichiometric
reactions strongly demonstrated that the nitrogen-containing
ligands, like halides, serve to favor b-heteroatom elimina-
tion over b-hydride elimination.6b Similar strategy was
used in the cyclization of the allylic alkynamides7 and the
electron-rich 1,6-enynes.8
The a-methylene-g-butyrolactone ring is an integral build-
ing block of many natural products, especially the sesquiter-
pene lactones in which the conjugated exocyclic double
bond is considered to be responsible for their interesting
biological properties.1 Since the discovery of several natu-
rally occurring cytotoxic or antitumor agents (e.g., eupurotin,
elephantin, vernolepin, etc.) that possess the a-methylene
lactone ring, much interest has been shown in this class of
compounds. Several reviews dealing with the synthesis of
a-methylene lactones have been published.2 Generally, the
a-methylene lactones are synthesized by a-methylenation
of preformed lactones, by oxidation of a-methylenecyclo-
butanones or b-methylenetetrahydrofuran, and from func-
tionalized acyclic precursors.
R
R
Y
X
O
O
O
O
X = OAc, halogen
Y = leaving group
The use of transition metal catalysts in the carbocyclization
of alkenes and alkynes offers the unique means to construct
a variety of synthetically important carbo- and heterocycles
with high efficiency not normally accessible by traditional
methods.3 Our laboratory has developed the facile intra-
molecular enyne cyclization of allylic 2-alkynoates to build
polysubstituted a-alkylidene-g-butyrolactones4 via a Pd(II)
catalyst, initiated by halopalladation (Scheme 1). In these re-
actions, halide ions serve not only as nucleophiles but also as
a ligand to inhibit the b-hydride elimination reaction.5 How-
ever, there exist problems in the way of developing the asym-
metric version of this reaction while halides are used as
Y
R
R
PdX2-LiX
X
O
O
O
O
β-heteroatom
elimination
PdX2-LiX
Y
halopalladation
R
Pd
Y
R
X
insertion
Pd
X
O
O
O
O
Scheme 1. Palladium(II)-catalyzed intramolecular cyclization of allylic
2-alkynoates to yield a-alkylidene-g-butyrolactones.
Keywords: Iminopyridines; b-Hydride elimination; b-Heteroatom elimina-
tion; Palladium(II)-catalyzed reactions; a-Alkylidene-g-lactones.
* Corresponding authors. Tel.: +86 21 54925158; fax: +86 21 64166128;
e-mail addresses: qshen@suda.edu.cn; xylu@mail.sioc.ac.cn
The asymmetric version of this acetoxypalladation ini-
tiated enyne-coupling reaction was achieved while chiral ni-
trogen-containing ligands were employed.6a,7,8 While only
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.04.006

J. Song et al. / Tetrahedron 63 (2007) 5148–5153
Table 1. Pd(OAc)2-catalyzed cyclization of (Z)-40-acetoxy-20-butenyl 2-alkynoatesa
5149
Pd(OAc)2
L
OAc
OAc
AcO
AcO
+
+
HOAc
70 °C
O
O
O
O
O
O
3
2a
1a
O
OAc
O
AcO
O
O
4
Entry
L
Yield (%)
2ab,c
3
4
N
1
82
N
L4
N
2
71
17
27
N
Cl
L5
N
3
4
5
73
80
43
N
OCH3
L6
N
N
L7
N
21
15
N
L8
N
N
6
6
73
L9
7
78
OH
N
L10
(continued)

5150
J. Song et al. / Tetrahedron 63 (2007) 5148–5153
Table 1. (continued)
Entry
L
Yield (%)
2ab,c
3
4
N
N
8
9
9
63
L11
N
N
73
HO
OH
L12
N
N
N
10
20
61
L13
N
11
17
69
N
N
L14
a
Reaction conditions: 1 (0.5 mmol), Pd(OAc)2 (0.027 mmol), and L (0.04 mmol) in HOAc (2.0 mL) at 60 ꢀC.
Isolated yield.
The stereochemistry of the exocyclic double bond in 2a was assigned as (Z)-configuration based on the higher field chemical shift of the methyl group in
b
c
1H NMR spectra for the Z isomer.13
two nitrogen-containing ligands (L1 and L2, Scheme 2)
showed excellent results in the asymmetric cyclization of
enyne (up to 92% ee),6a most of the test ligands gave only
moderate yield and enantioselectivity.6–8 It is therefore still
worth studying the other kinds of ligands for this reaction.
Here, we wish to report the results of using diimines as the
ligands for this reaction and the use of iminopyridines as
the efficient ligands for the non-asymmetric version of this
reaction.
tunable steric and electronic properties. A number of metal
complexes of diimines have been reported in various reac-
tions.9 A lot of works have proved that palladium complexes
are excellent polymerization catalysts.9c,10 There are also
some papers revealing that palladium complexes with di-
imine ligands are highly efficient catalysts for Suzuki
cross-coupling and Heck reactions.11 It occurred to us that
the enyne cyclization might be attained through the use of
palladium catalysts with diimine ligands.
2.1. Screening of the diimine ligands
O
O
O
As indicated in literatures,12 an attractive characteristic of
diimine lies in its flexible alterability of structure, which
leads to different steric and electronic properties. Any fine-
tuned imine may show different catalytic activity in the reac-
tion. In order to investigate which structure of diimine is
effective in the palladium-catalyzed enyne cyclization reac-
tion, we first screened different diimines as the ligands using
a model reaction. Compound 1a was used as the substrate,
which was reacted in the presence of Pd(OAc)2 (10 mol %)
and the ligand (20 mol %) in HOAc at 60 ꢀC. The result is
shown in Table 1.
N
N
N
N
N
N
Ph
Ph
Ph
L1
L2
L3
Scheme 2. Efficient ligands for the cyclization of (Z)-40-acetoxy-20-butenyl
2-alkynoates under Pd(II) catalysis.6a–c
2. Results and discussion
In our previous work, we tried many nitrogen-containing
ligands. It was shown that a diimino structure existed in the
nitrogen ligands have been proved to be efficient for the
palladium(II)-catalyzed enyne cyclization (Scheme 2).6–8
Diimine ligands have received increasing attention recently
due to their special coordination behavior associated with
Three products were observed under different diimine
ligands. Besides the main product of cyclization, a-(Z)-
(10-acetoxyethylidene)-b-vinyl-g-butyrolactone (2a), the
protonolysis product of the vinylic palladium species (3)

J. Song et al. / Tetrahedron 63 (2007) 5148–5153
5151
Table 2. Cyclization of various (Z)-40-acetoxy-20-butenyl 2-alkynoates in
the presence of N-phenyl-2-pyridinealdimine (L4)a
was also observed in the reaction in many cases. As shown in
the proposed mechanism in Scheme 3, there is a competition
between insertion of the olefin into the vinyl-palladium
intermediate II and protonolysis of thevinyl-palladium inter-
mediate II formed by trans-acetoxypalladation of the
carbon–carbon triple bond. As we know, vinyl-palladium
intermediate II was readily protonized in HOAc media.
Therefore, the role of an efficient ligand should not only in-
hibit b-hydride elimination butalso stabilize the intermediate
II in acetic acid to make intramolecular olefinic insertion
possible. Obviously, some iminopyridines (Table 1, entries
1–4) could play this role successfully. The formation of
a two-component adduct 4 emerged as a major byproduct
in some cases (Table 1, entries 2, 3, and 5) may be due to
the high substrate concentration of the reaction. From our
previous experience, the intermolecular reaction could be
suppressed by diluting the reaction system. However, the
use of o-substituted iminopyridines as ligands suppressed
the cyclization of substrate 1a (Table 1, entries 5 and 6).
We also tried to use the compounds with more coordination
sites but were all defeated (Table 1, entries 9 and 11). From
these results, it is clear that pyridinyl group in the imine li-
gand is necessary and only bidentate iminopyridine ligands
are effective in our modeled palladium-catalyzed enyne
cyclization reaction.
R
O
Pd(OAc)2 (10 mol%)
L4(15 mol%)
R
X
OAc
O
N
AcO
Bn
5
HOAc, 60 °C
X
Y
Y
2
1
N
N
Ph
L4
Entry
1
R
X
Y
2
Yielda,b (%)
83
1
2
3
4
5
6
7
8
9
1a
CH3
O
O
O
O
O
O
O
O
O
O
O
2a
1b n-Pr
1c Ph
1d n-C7H15
1e
1f
2b 81
2c 86
2d 76
2e
2f
2g
2h 51
69
CH3OCH2
CH3
CH3
74
NBn
63c
88
1g
H2 NTs
H2
H2 C(COOMe)2 2i
1h CH3
1i CH3
O
a
Reaction conditions: Pd(OAc)2 (10 mol %), L4 (15 mol %), and HOAc
(2 mL) at 60 ꢀC.
Isolated yield.
Hydrolysis product (5) of the cyclization product 2f was obtained in 33%
yield.
b
c
R
R
Pd(OAc)2
OAc
2.3. Role of iminopyridine ligands
AcO
N
N
O
R
O
O
O
Pd(OAc)2
AcO-
With these satisfactory results in hand, we are interested in
studying the role of these iminopyridines (L4–L7, Table 1,
entries 1–4). Our previous work has shown that excess of
halide ions and bipyridine (bpy) ligand can block the usual
b-hydride elimination,5,6 and this role has been confirmed
by a stoichiometric reaction of the palladium complex 6 with
allyl acetate in the presence of different ligands including
halides and the nitrogen ligands. In the above catalytic cycle
of the cyclization of (Z)-40-acetoxy-20-butenyl 2-alkynoates,
the normal b-hydride elimination of intermediate III
(Scheme 3) was also inhibited and b-acetoxy elimination
took place instead. Evidently, the iminopyridine ligands
play a key role here. In order to probe the role of the imino-
pyridines in this reaction, a similar stoichiometric reaction of
the palladium complex 6 with allyl acetates5,6 in the pres-
ence of iminopyridines (L4–L7) was investigated. An inter-
mediate 7 formed by intermolecular olefinic insertion into
the aromatic carbon–palladium bond was postulated. From
the intermediate 7, b-acetoxy elimination leads to 8, while
b-hydride elimination gives 9. The results are summarized
in Table 3. From Table 3, it was shown that, like chloride
ion, pyridine, bipyridine, and phenanthroline (Table 3, en-
tries 2–5), reactions in the presence of iminopyridines
(L4–L7) afford 8 in medium to good yield (Table 3, entries
6–9). While the same reaction was carried out in the absence
of any ligand, the b-hydride elimination product 9 was iso-
lated in 66% yield. Evidently, iminopyridines were also ef-
fective ligands for inhibiting b-hydride elimination in the
cyclization reaction of (Z)-40-acetoxy-20-butenyl 2-alky-
noates. Similar to the role of halide ions and bipyridine
ligand, this might be ascribed to the following: (a) the
presence of iminopyridine ligands makes Pd coordinatively
saturated and the b-hydride elimination not so feasible; (b)
the coordination of iminopyridine ligands to Pd increases
β-deacetoxy
palladation
coordination
R
[Pd]
OAc
OAc
[Pd]
AcO
O
O
O
O
I
III
protonolysis
olefinic
insertion
trans-acetoxy-
palladation
R
O
R
O
[Pd]
H
O
OAc
OAc
N
N
AcO
[Pd] =
AcO
PdLn
O
II
Scheme 3. Proposed mechanism of the cyclization of (Z)-40-acetoxy-20-
butenyl 2-alkynoates catalyzed by Pd(OAc)2/bipyridine.
2.2. Scope of the cyclization reactions of (Z)-40-acetoxy-
20-butenyl 2-alkynoates
In order to study the generality of the method, other
substituted alkynoates (e.g., phenyl, n-alkyl or methoxy-
methyl, etc.), electron-deficient substrates, and electron-
rich substrates (e.g., alkynoates, alkynyl ether, alkynyl
amine, etc.) were investigated using N-phenyl-2-pyridineal-
dimine (L4) as our standard ligand. The results are shown
in Table 2. Both the substrates with electron-deficient
triple bonds (Table 2, entries 1–6) or that with electron-
rich triple bonds (Table 2, entries 7–9) reacted smoothly
to give cyclization products in moderate to good yields.
Furthermore, substrates containing nitrogen atom (Table 2,
entries 6 and 7) gave better results. This might be explained
by the fact that the nitrogen atom could also coordinate to
palladium making the vinyl-palladium intermediate more
stable.

5152
J. Song et al. / Tetrahedron 63 (2007) 5148–5153
4.2. Preparation of (Z)-40-acetoxy-20-butenyl 2-de-
cynoates (1d)
Table 3. Stoichiometric reactions of palladium complex (6) with allyl ace-
tate in the presence of different ligandsa
H
N
H
N
L
OAc
To a solution of 2-decynoic acid (3.36 g, 20 mmol) and (Z)-
1-acetoxy-2-buten-4-ol (2.86 g, 22 mmol) in CH2Cl2
(20 mL) was added dropwise at ꢁ20 ꢀC a solution of 1,3-di-
cyclohexylcarbodiimide (4.13 g, 20 mmol) and 4-(dimethyl-
amino)pyridine (224 mg, 2 mmol) in CH2Cl2 (20 mL) with
stirring. Then the reaction mixture was stirred at room tem-
perature for 10 h. After the reaction was complete, the white
solid was filtered off and the solvent was removed in vacuo.
The residue was then subjected to column chromatography
on silica gel (petroleum ether–ethyl acetate 5:1), affording
1d as an oil. IR (neat): n 2932, 2238, 1744, 1713,
+
O
O
HOAc
rt
Pd
AcO
OAc
2
LnPd
6
7
β-heteroatom
elimin.
β-H elimin.
H
N
H
N
O
O
1373, 1242, 1072 cmꢁ1 1H NMR (300 MHz, CDCl3):
.
OAc
d 5.80–5.76 (m, 2H), 4.76 (d, J¼5.4 Hz, 2H), 4.68 (d,
J¼4.8 Hz, 2H), 2.35 (t, J¼7.2 Hz, 2H), 2.07 (s, 3H),
1.63–1.53 (m, 2H), 1.28–1.42 (m, 8H), 0.88 (t, J¼6.6 Hz,
3H). 13C NMR (75 MHz, CDCl3): d 170.6, 153.3, 128.6,
127.0, 90.2, 72.6, 60.9, 59.8, 31.5, 28.6, 28.5, 27.3,
22.4, 20.7, 18.5, 13.9. MS (m/z): 279 (M+ꢁ1), 151 (100),
81. HRMS: calcd for C16H24O4Na+1 303.1571, found
303.1567.
9
8
Entry
L
L/Pd
Observation
Yieldb (%)
8
9
1
2
3
4
5
6
7
8
9
None
Clꢁ
py
bpy
phen
L4
L5
L6
L7
Pd Y
66
10/1
2/1
1/1
1/1
2/1
2/1
2/1
2/1
Clear solution
Clear solution
Clear solution
Clear solution
Clear solution
Clear solution
Clear solution
Clear solution
75
69
81
77
66
81
66
75
4.3. Typical procedure for the cyclization of (Z)-40-
acetoxy-20-butenyl 2-alkynoates: synthesis of a-(Z)-
(10-acetoxyoctylidene)-b-vinyl-g-butyrolactone (2d)
To a solution of Pd(OAc)2 (6 mg, 0.027 mmol) and imino-
pyridine ligand L4 (7.3 mg, 0.04 mmol) in HOAc (2 mL)
at 60 ꢀC was added 1d (140 mg, 0.5 mmol) with stirring. Af-
ter the reaction was complete as monitored by TLC, ethyl
ether (80 mL) was added. The mixture was washed with sat-
urated NaHCO3 solution (2ꢂ20 mL) and brine (20 mL). The
ether layer was dried (Na2SO4), filtered, and concentrated in
vacuo. The residue was subjected to column chromato-
graphy on silica gel (petroleum ether–ethyl acetate 4:1), af-
fording pure 2d as an oil. IR (neat): n 2932, 1760, 1675,
a
Reaction conditions: complex 6 (0.13 mmol) and allyl acetate (1.3 mmol)
in HOAc (2.0 mL) at room temperature.
Isolated yield based on Pd complex.
b
the electron density of Pd, resulting in increasing stability of
the carbon–palladium bond toward protonolysis.5,6
3. Conclusion
1374, 1212, 1157 cmꢁ1 1H NMR (400 MHz, CDCl3):
.
d 5.88–5.80 (m, 1H), 5.28–5.19 (m, 2H), 4.43 (dd, J¼8.8,
8.4 Hz, 1H), 4.04 (dd, J¼9.2, 3.2 Hz, 1H), 3.79–3.75 (m,
1H), 2.30 (t, J¼8.1 Hz, 2H), 2.27 (s, 3H), 1.50–1.48 (m,
2H), 1.34–1.14 (m, 8H), 0.88 (t, J¼6.6 Hz, 3H). 13C NMR
(75 MHz, CDCl3): d 168.2, 167.5, 160.2, 136.2, 117.3,
114.2, 69.8, 42.0, 33.2, 31.6, 29.3, 28.9, 25.5, 22.5, 20.8,
14.0. MS (m/z): 280 (M+), 238, 154, 136 (100), 109, 95,
57. HRMS: calcd for C16H24O4Na+1 303.1563, found
303.1567.
In conclusion, we have demonstrated an efficient method for
palladium(II)-catalyzed cyclization of (Z)-40-acetoxy-20-but-
enyl 2-alkynoates in acetic acid to afford the a-(Z)-acetoxy-
alkylidene-b-vinyl-g-butyrolactones using iminopyridines
as ligands. The role of iminopyridine ligands in this cycliza-
tion was studied through a stoichiometric reaction. The
results show that the presence of iminopyridine ligands
might inhibit the b-hydride elimination and stabilize the car-
bon–palladium bond to make the reaction more feasible.
These results may be also usable in performing the mecha-
nism of polymerization of alkenes using palladium(II)–
iminopyridine catalysts.10
4.4. General procedure for the stoichiometric reactions
of di-m-acetatobis(2-acetaminophenyl-2C,O)dipalla-
dium(II) (6) with allyl acetate in the presence of
different ligands
4. Experimental
4.1. Materials
To a suspension of complex 6 (80 mg, 0.13 mmol) and the
corresponding ligand in HOAc (1 mL) was added allyl ace-
tate (135 mg, 1.35 mmol). The mixture was stirred at room
temperature for 1.5 h. After separation of palladium by fil-
tration through a short column of silica gel with the aid of
ethyl acetate, the filtrate was concentrated under vacuum
and the residue was subjected to column chromatography
on silica gel (petroleum ether–ethyl acetate 2:1) to afford
products 8 or 9 as shown in Table 3.
The diimine ligands were prepared according to the litera-
tures.12 The known substrates, (Z)-40-acetoxy-20-butenyl
2-alkynoates, were prepared according to the reported pro-
cedure.6b,7,8 The palladium complex 6 was prepared using
the literature procedure.14

J. Song et al. / Tetrahedron 63 (2007) 5148–5153
5153
4.4.1. N-Acetyl-2-allylaniline (8).5 IR (KBr): n 3286, 1657,
1587, 1536, 1482, 1371, 1298, 994, 970, 916, 753 cmꢁ1. 1H
NMR (300 MHz, CDCl3): d 7.83 (d, J¼8.0 Hz, 1H), 7.29–
7.09 (m, 4H), 6.01–5.92 (m, 1H), 5.20–5.06 (m, 2H), 3.39
(d, J¼6.0 Hz, 2H), 2.15 (s, 3H). MS (m/z): 176 (M++1),
175 (M+), 160, 132 (100), 118, 91, 77.
4. (a) Ma, S.; Lu, X. J. Org. Chem. 1991, 56, 5120; (b) Lu, X.;
Zhu, G.; Wang, Z. Synlett 1998, 115; (c) Lu, X.; Ma, S.
Transition Metal Catalyzed Reactions; Murahashi, S.-I.,
Davies, S. G., Eds.; Blackwell Science: Oxford, UK, 1999;
Chapter 6, p 133.
5. Zhang, Z.; Lu, X.; Xu, Z.; Zhang, Q.; Han, X. Organometallics
2001, 20, 3724.
4.4.2. N-Acetyl-2-(3-acetoxy-1-propenyl)aniline (9).5 IR
(KBr): n 3240, 1736, 1652, 1579, 1542, 1455, 1301, 1239,
6. (a) Zhang, Q.; Lu, X. J. Am. Chem. Soc. 2000, 122, 7604; (b)
Zhang, Q.; Lu, X.; Han, X. J. Org. Chem. 2001, 66, 7676; (c)
Lu, X.; Zhang, Q. Pure Appl. Chem. 2001, 73, 247; (d) Zhao,
H.; Ariafard, A.; Lin, Z. Organometallics 2006, 25, 812.
7. Xu, W.; Kong, A.; Lu, X. J. Org. Chem. 2006, 71, 3854.
8. Zhang, Q.; Xu, W.; Lu, X. J. Org. Chem. 2005, 70, 1505.
9. (a) Kundu, A.; Buffin, B. P. Organometallics 2001, 20, 3635;
(b) van Koten, G.; Vrieze, K. Adv. Organomet. Chem. 1982,
21, 151; (c) Yamada, S. Coord. Chem. Rev. 1999, 190–192,
537.
1025 cmꢁ1 1H NMR (300 MHz, CDCl3): d 7.78 (d,
.
J¼8.1 Hz, 1H), 7.41–7.13 (m, 4H), 6.76 (d, J¼15.6 Hz,
1H), 6.22 (m, 1H), 4.76 (dd, J¼6.3, 1.6 Hz, 2H), 2.22 (s,
3H), 2.12 (s, 3H). MS (m/z): 233 (M+), 191, 173, 130
(100), 118, 77, 43.
Acknowledgements
10. (a) Laine, T. V.; Piironen, U.; Lappalainen, K.; Klinga, M.;
€
Aitola, E.; Leskela, M. J. Organomet. Chem. 2000, 606, 112;
We thank Department of Chemistry and Chemical Engineer-
ing, Suzhou University, the National Natural Science Foun-
dation of China (20423001), and State Key Laboratory of
Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences for financial
support.
(b) Chen, R.; Mapolie, S. F. J. Mol. Catal. A: Chem. 2003,
193, 33; (c) Koppl, A.; Alt, H. G. J. Mol. Catal. A: Chem.
2000, 154, 45; (d) Heinze, K. Chem.—Eur. J. 2001, 7, 2922;
(e) Heinze, K.; Jacob, V.; Feige, C. Eur. J. Inorg. Chem.
2004, 2053; (f) Haddleton, D. M.; Kukulj, D.; Radigue, A. P.
ꢀ
Chem. Commun. 1999, 99; (g) Benito, J. M.; Jesus, E.; Mata,
F. J.; Flores, J. C.; Gomez, R. Organometallics 2006, 25,
ꢀ
3045; (h) Chen, Y.-C.; Reddy, K. R.; Liu, S.-T.
J. Organomet. Chem. 2002, 656, 199; (i) Musaev, D. G.;
Morokuma, K. Top. Catal. 1999, 7, 107; (j) Williams, B. S.;
Leatherman, M. D.; White, P. S.; Brookhart, M. J. Am.
Chem. Soc. 2005, 127, 5132; (k) Lin, W.; Brookhart, M.
Organometallics 2004, 23, 6099.
Supplementary data
Characterization data of the substrates, products, and copies
of the 1H NMR spectra of the compounds 1d, 2d, and prod-
ucts of the stoichiometric reaction, 8 and 9 are provided.
Supplementary data associated with this article can be found
in the online version, at doi:10.1016/j.tet.2007.04.006.
11. (a) Yamada, H.; Kawate, T.; Nishida, A.; Nakagawa, M. J. Org.
Chem. 1999, 64, 8821; (b) Pelagatti, P.; Carcelli, M.; Costa, M.;
Ianelli, S.; Pelizzi, C.; Rogolino, D. J. Mol. Catal. A: Chem.
2005, 226, 107.
References and notes
12. (a) L4: Bose, D.; Banerjee, J.; Rahaman, S. H.; Mostafa, G.;
Fun, H.-K.; Bailey Walsh, R. D.; Zaworotko, M. J.; Ghosh,
B. K. Polyhedron 2004, 23, 2045; (b) L5: Siegrist, A. E.;
Meyer, H. R.; Gassmann, P.; Moss, S. Helv. Chim. Acta 1980,
63, 1311; (c) L6: Jovanovic, B. Z.; Misic-Vukovic, M.;
Marinkovic, A. D.; Vajs, V. J. Mol. Struct. 2002, 642, 113;
(d) L7: Bandini, M.; Luque, R.; Budarin, V.; Macquarrie,
D. J. Tetrahedron 2005, 61, 9860; (e) L8: Garcia-Friaza, G.;
Fernandez-Botello, A.; Perez, J. M.; Prieto, M. J.; Moreno,
V. J. Inorg. Biochem. 2006, 100, 1368; (f) L9: Saino, N.;
Kogure, D.; Kase, K.; Okamoto, S. J. Organomet. Chem.
2006, 691, 3129; (g) L10: Paerssinen, A.; Luhtanen, T.;
Klinga, M.; Pakkanen, T.; Leskelae, M.; Repo, T. Eur. J.
Inorg. Chem. 2005, 11, 2100; (h) L11: Scheibe, G. Chem.
Ber. 1923, 56, 148; (i) L12: Reich, B. J. E.; Justice, A. K.;
Beckstead, B. T.; Reibenspies, J. H.; Miller, S. A. J. Org.
Chem. 2004, 69, 1357; (j) L13: Gago, S.; Rodriguez-Borges,
J. E.; Teixeira, C.; Santos, A. M.; Zhao, J.; Pillinger, M.;
Nunes, C. D.; Petrovski, Z.; Santos, T. M.; Kuehn, F. E.;
Romao, C. C.; Goncalves, I. S. J. Mol. Catal. A: Chem.
2005, 236, 1; (k) L14: Schoumacker, S.; Hamelin, O.;
Pecaut, J.; Fontecave, M. Inorg. Chem. 2003, 42, 8110.
13. (a) Torabi, H.; Evans, R. L.; Stavely, H. E. J. Org. Chem. 1969,
34, 3792; (b) Minami, T.; Niki, I.; Agawa, T. J. Org. Chem.
1974, 39, 3236; (c) Tanaka, K.; Tamura, N.; Kaji, A. Chem.
Lett. 1980, 595.
1. (a) Yoshioka, H.; Mabry, T. J.; Timmermann, B. N.
Sesquiterpene Lactones; University of Tokyo Press: Tokyo,
1973; (b) Fishcher, N. H.; Oliver, C. J.; Fishcher, H. D.
Progress in the Chemistry of Natural Products; Herz, B.,
Grisebach, H., Kirby, G. W., Eds.; Springer: New York, NY,
1997; Vol. 38, Chapter 2; (c) Ayres, D. C.; Loike, J. D.
Lignans: Chemical, Biological and Clinical Properties;
Cambridge University Press: Cambridge, UK, 1990; (d)
Gammill, R. B.; Wilson, C. A.; Bryeon, T. A. Synth. Commun.
1975, 6, 245; (e) Lee, K. H.; Huang, E. S.; Piantadosi, C.;
Pagano, J. S.; Geissman, T. A. Cancer Res. 1971, 31, 1649.
2. (a) Grieco, P. A. Synthesis 1975, 67; (b) Hoffmann, H. M. R.;
Rabe, J. Angew. Chem., Int. Ed. Engl. 1985, 24, 94; (c)
Petragnani, N.; Ferraz, H. M. C.; Sliva, G. V. J. Synthesis
1986, 157; (d) Sarma, J. C.; Sharma, R. P. Heterocycles 1986,
24, 441; (e) Shieh, S.-J.; Liang, K.-W.; Li, W.-T.; Shu, L.-H.;
Chandrasekharam, M.; Liu, R.-S. Pure Appl. Chem. 1998, 70,
1111; (f) Paquette, L. A.; Mendez-Andino, J. Tetrahedron
Lett. 1999, 40, 4301; (g) Blaszczyk, E.; Krawczyk, H.;
Janecki, T. Synlett 2004, 2685.
€
3. (a) Trost, B. M.; Krische, M. J. Synlett 1998, 1; (b) Fruhauf, H.-
W. Chem. Rev. 1997, 97, 523; (c) Ojima, I.; Tzamarioudaki, M.;
Li, Z.; Donovan, R. J. Chem. Rev. 1996, 96, 635; (d) Moos,
W. H.; Davis, R. E.; Scwarz, R. D.; Gamzu, E. R. Med. Res.
Rev. 1988, 8, 353; (e) Kang, S.-K.; Kim, K.-J.; Hong, Y.-T.
Angew. Chem., Int. Ed. 2002, 41, 1584.
14. Horino, H.; Inoue, N. J. Org. Chem. 1981, 46, 4416.