Allyl stannanes as electrophiles or nucleophiles in the palladium-catalyzed reactions with alkynes

Article abstract of DOI:10.1016/j.jorganchem.2003.07.027

The reactivity of the allyl stannanes can be inverted by changing the oxidation state of the catalyst from Pd(II) to Pd(0). Whereas with Pd(II) an anti nucleophilic attack of the allyl stannane on the alkyne takes place, the reaction with Pd(0) proceeds by oxidative addition to form (η³-allyl)palladium complexes leading to a formal syn addition to the alkyne. This mechanistic proposal is supported by DFT calculations.

Full text of DOI:10.1016/j.jorganchem.2003.07.027

Journal of Organometallic Chemistry 687 (2003) 410ꢀ419
/
www.elsevier.com/locate/jorganchem
Allyl stannanes as electrophiles or nucleophiles in the palladium-
catalyzed reactions with alkynes
Bele´n Mart´ın-Matute, Elena Bunuel, Mar´ıa Me´ndez, Cristina Nieto-Oberhuber,
˜
Diego J. Ca´rdenas, Antonio M. Echavarren *
Departamento de Qu´ımica Orga´nica, Universidad Auto´noma de Madrid, Cantoblanco, 28049 Madrid, Spain
Received 2 June 2003; accepted 30 July 2003
Dedicated to Professor J.P. Geneˆt on the occasion of his 60th birthday in recognition of his contributions in organopalladium chemistry and organic
synthesis
Abstract
The reactivity of the allyl stannanes can be inverted by changing the oxidation state of the catalyst from Pd(II) to Pd(0). Whereas
with Pd(II) an anti nucleophilic attack of the allyl stannane on the alkyne takes place, the reaction with Pd(0) proceeds by oxidative
addition to form (h3-allyl)palladium complexes leading to a formal syn addition to the alkyne. This mechanistic proposal is
supported by DFT calculations.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Palladium; Allyl stannanes; Electrophiles; Nucleophiles
1. Introduction
this transformation, the usually nucleophilic allyl stan-
nanes [7] behave formally as electrophiles. An oxidative
addition to form complexes 5b has been proposed to
take place in the Pd(0)-catalyzed carboxylation of allyl
stannanes with CO2 [8]. Complexes of type 5 are
believed to be formed by transmetallation of (h3-
allyl)palladium complexes with hexamethylditin [9].
However, palladium complexes of type 5 have never
been isolated as stable species [10].
We have recently found that substrates 6 react in the
presence of PdCl2, PtCl2, or other electrophilic metal
complexes to form dienes 8 (Scheme 2) [11,12]. In this
reaction, the metal triggers the anti attack of the allyl
stannane to the (h2-alkyne)metal complex as shown in 7
[13,14].
Allyl stannanes are important reagents in the Stille
reaction [1]. In this cross coupling, the organic electro-
phile Rꢀ
/
X (Xꢁhalide, triflate) reacts with the Pd(0)Ln
/
complex by oxidative addition to give electrophilic
RPd(L)2X complexes, which transmetallate with the
allyl stannanes [2,3].
Recently, Shirakawa et al. found that the palla-
dium(0)-catalyzed reaction of allyl stannanes 1 with
alkynes 2 affords allylstannylation products 3 (Scheme
1) [4]. This transformation is also catalyzed by Ni(cod)2
[5]. It was proposed that the palladium-catalyzed
allylstannylation of alkynes could proceed by oxidative
cyclometallation to form a palladacyclopentene complex
4, which would undergo b-tin elimination, followed by
reductive elimination [4]. An alternative mechanism was
also considered, in which an oxidative addition of the
allyl stannanes to Pd(0) would give (h3-allyl)palladium
complexes 5a as key intermediates (Scheme 1) [4,6]. In
Recently a new cyclization was developed based on
the regioselective Pd(0)-catalyzed addition of R3Siꢀ
/
?
SnR3 to alleneynes [15]. This transformation was
proposed to proceed by cyclization of the alkynes with
allyl stannanes, formed as intermediate species by the
Pd(0)-catalyzed stannylation of the allenes. More sim-
ply, substrates of type 6 could also undergo cyclization
promoted by Pd(0). Therefore, we decided to explore
this alternative with the aim to determine if an oxidative
* Corresponding author. Fax: ꢂ34-91-397-3966.
E-mail address: anton.echavarren@uam.es (A.M. Echavarren).
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.07.027

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411
Scheme 1.
Scheme 2.
addition of allyl stannanes to Pd(0) to give (h3-
allyl)palladium complexes actually takes place.
2. Results and discussion
The cyclization of substrates of type 6 can be
performed with Pd(0) catalysts. Thus, disulfone 9
reacted in 1,4-dioxane at 50 8C with Pd2(dba)3×
/dba
(2.5 mol%) to give Z-alkenyl stannane 10 in 63%
isolated yield (Scheme 3). The reaction of 9 with
Pd(PPh3)4 (5 mol%) gave 10 in 55% yield. Stannanes
of type 10 were quite labile and suffered facile proto-
destannylation. However, treatment of the cyclization
mixture with I2 allowed for the isolation of the
corresponding alkenyl iodides. Under these conditions,
substrate 9 afforded iodide 11 in 85% yield. The Z
configuration of 11 was demonstrated by NOE experi-
ments. Similarly, 12 (1.2:1 E/Z) gave carbocycle 13
(85%). A lower yield (74%) was obtained with Pd(PPh3)4
(5 mol%).
Allyl stannane 14, which is similar to 9, failed to
undergo cyclization reaction under the above condi-
tions. However, reaction with a catalyst prepared in situ
from Pd(MeCN)2Cl2 and P(C6F5)3 (2 equiv/Pd), fol-
lowed by treatment with I2 gave 15, albeit in only 35%
yield. Under these conditions it was expected that a
Pd(0) complex may be involved, since heating PdCl2
with phosphines is known to give Pd(0)Ln complexes
[16]. On the other hand, cyclization of ether 16, followed
by reaction with I2 afforded heterocycle 17 (43%).
Similarly, cyclization of ether 18 (4.3:1 mixture of
isomers), followed by reaction with I2 afforded 19
Scheme 3.
(72%). Reaction of 18 with Pd(MeCN)2Cl2 and
P(C6F5)3 gave 19 in 34% yield. By using Pd(MeCN)2Cl2
as pre-catalyst, the cyclization of 18 proceeded in 42%
yield. Substrate 20, with the alkyne substituted with an
ester group, reacted with the Pd(MeCN)2Cl2 in benzene
to give 21 in 40% yield. The E configurations of the
exocyclic alkene of 17 was corroborated by NOE
experiments. The assignment of the configuration of
21 was based on the observation of a weak correlation
peak in the NOESY spectrum between the methyl
hydrogens of the ethyl ester and the C-2 methylene
hydrogens.
No cyclization reaction was observed with simple 1,6-
enynes such as 22 by using Pd2(dba)3×
/dba as the
catalyst. Allyl silanes 23 and 24, the silyl analogues of
12 and 14, also failed to cyclize under the conditions of
Scheme 3.

412
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/
Reaction of 25 with Pd2(dba)3×/dba (2.5 mol%) led to
destannylated 26 [11b] in 73% yield after 1 h at 65 8C.
The same result was obtained in the presence of
P(C6F5)3 or i-Pr2NEt. Indeed, destannylation of the
expected stannane 27 was observed in the crude reaction
mixtures. However, reaction with the catalyst prepared
in situ from Pd(MeCN)2Cl2 and P(C6F5)3 (two equiva-
lents/Pd), followed by treatment with I2 gave a 1:3.5
mixture of 26 [11] and 28 (53% yield) (Scheme 4). The
configuration of 28 was secured as shown on the basis of
NOE experiments. This configuration does not corre-
spond to the most stable isomer, since Z-alkenyl iodide
28 is 0.7 (AM1) or 1.2 (PM3) kcal molꢃ1 less stable than
the E-isomer. Formation of 28, with a Z geometry at
the exocyclic alkene, is not consistent with the results of
Scheme 3 and suggests that this is an example of a
Pd(II)-catalyzed transformation, which proceeds by the
anti attack of the allyl stannane to the (h2-alkyne)metal
complex, as shown in 29, to give intermediate 30 [11].
Cleavage of the Pdꢀ
/
C bond by the electrophilic
Scheme 5.
Bu3SnCl then gives 27. This result indicates that,
although Pd(0)Ln may be formed by the reduction of
Pd(MeCN)2Cl2 by the phosphine [16], nevertheless some
of the initially formed Pd(L)2Cl2 complex is able to
trigger the Pd(II)-catalyzed process. This is in agreement
with our recent observation of a Pd(II)-catalyzed
process under similar conditions [17].
allyl stannanes 31 might evolve, via palladium complex
32, to give bicycle 33, the result of an oxidative
cyclometallation (cycle A). A b-tin elimination would
then afford alkenylpalladium complex 34, which would
give the final carbo- or heterocycles 35 by trans to cis
isomerization and reductive elimination. Alternatively,
an oxidative addition of 31 to Pd(0) would give an
According to the mechanistic proposals made by
Shirakawa et al. [4], the results of Scheme 3 can be
explained by the oxidative cyclometallation (via inter-
mediates of type 4) or the oxidative addition (via
intermediates of type 5) mechanisms (Scheme 5). Thus,
(allyl)(tributylstannyl)ꢀ
the alkyne onto the Pdꢀ
give complexes 34 or 37, respectively. Finally, a Cꢀ
CꢀC reductive elimination accounts for the formation
of 35 (cycle B, Scheme 5).
/
Pd(II) complex 36. Insertion of
C bond or PdꢀSn bond would
Sn or
/
/
/
/
In the cyclization of 25 (Scheme 4), the Pd(0)-
promoted reaction of 25 would have formed intermedi-
ates 38 or 39. However, 38, the result of an oxidative
cyclometallation, cannot further evolve since the b-tin
elimination is not possible. On the other hand, forma-
tion of the Cꢀ
C bond between the h3-allyl and the
/
alkyne from complex 39 is difficult for geometrical
reasons. For these reasons, 25 evolves through a Pd(II)-
catalyzed pathway as shown in Scheme 4.
Scheme 4.
To distinguish between the pathways shown in

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413
Scheme 6. Energies in kcal molꢃ1 at the B3LYP/6-31G(d) and
LANL2DZ level including ZPE correction. Values in parentheses
correspond to activation energies.
Fig. 1. Reaction coordinate for the transformation of complex 44 into
46 by oxidative addition. Energies (Eꢂ
ZPE) are given in kcal molꢃ1
/
.
Scheme 5 we recurred to DFT calculations on model
With regards to the insertion, the evolution of 46 to 47
(Fig. 2) was found to take place smoothly with a rather
low activation energy (10.5 kcal molꢃ1). Although the
compounds 40ꢀ48 using maleic anhydride as a model
/
for dba ligand (Scheme 6). The cyclometallation product
42a was located as a minimum of almost the same
energy of 41a (ꢂ
/
0.6 kcal molꢃ1). However, the
transformation is moderately endothermic (ꢂ4.1 kcal
/
molꢃ1), substitution of the acetylene ligand by buthy-
nedial, to mimic dimethyl acetylenedicarboxylate, led to
corresponding transition state TS41a
molꢃ1 above 41a. When Lꢁ
lies 36.1 kcal
PH3, the reaction is more
42a
ꢀ
/
an exothermic (ꢃ
into the alkyne (Eaꢁ
therefore more facile than the alternative insertion of the
allyl into the alkyne to give 48 (Eaꢁ
21.6 kcal molꢃ1),
17.5 kcal
/
5.0 kcal molꢃ1) insertion of SnMe3
favorable thermodynamically, but the activation energy
is even higher. These calculations indicate that a
cyclometallation of an alkyne with an alkene involving
Pd(0) is not a favorable process.
On the other hand, formation of the oxidative
product 46 from complex 44 is slightly endothermic
(3.8 kcal molꢃ1) and the activation energy to reach the
/
8.8 kcal molꢃ1). This insertion is
/
although the transformation is exothermic (ꢃ
/
molꢃ1).
corresponding transition state TS44
is much lower
46
ꢀ
(10.0 kcal molꢃ1) than that of the cyclometallation
process. In this transition state, the allyl stannane,
initially in a perpendicular arrangement to the coordi-
nation plane, rotates to an arrangement similar to 46
(Fig. 1). The inverse process, which would show a lower
activation energy (6.2 kcal molꢃ1) corresponds to the
reductive elimination in the palladium-catalyzed reac-
tion of allyl electrophiles with hexamethylditin [9].
Unexpectedly, starting from 43a with a more electron-
withdrawing maleic anhydride ligand, the oxidative
3. Summary
In summary, these results demonstrate that the
reactivity of the allyl stannanes can be inverted by
changing the oxidation state of the catalyst from Pd(II)
to Pd(0). DFT calculations suggest that the reaction
with Pd(0) proceeds by oxidative addition to form (h3-
allyl)palladium complexes. Importantly, the stereoche-
mical outcomes of the Pd(II)- and Pd(0)-catalyzed
processes are complementary: intermediates of type 49
are involved with Pd(II) (Scheme 7), while in the present
Pd(0)-catalyzed reaction, the intermediate is a palladiu-
m(II) complex with the configuration shown in 50. The
stannanes and iodides that result from 50 have signifi-
addition to give 45a was more favorable (Eaꢁ6.1 kcal
/
molꢃ1). On the other hand, reaction from 43b is almost
thermoneutral, but the activation energy is similar to
that of 440
/
46.

414
B. Mart´ın-Matute et al. / Journal of Organometallic Chemistry 687 (2003) 410ꢀ419
/
Fig. 2. Alternative pathways for the evolution of complex 46 by insertion reactions. Energies (Eꢂ .
ZPE) are given in kcal molꢃ1
/
4.1. Synthesis of stannanes
Stannanes 9, 12, and 14 and silanes 23 and 24 were
prepared as previously described [11].
Scheme 7.
4.2. Synthesis of stannane 16 (Scheme 3)
cant synthetic potential for the construction of functio-
nalized molecules.
4.2.1. 4-(Tri-n-butylstannyl)-2-buten-1-ol
(i). To a solution of cis-2-buten-1,4-diol (40 g, 454
mmol), pyridine (36.7 ml, 454 mmol), and DMAP (500
mg, 4.1 mmol) in CH2Cl2 (100 ml) at 0 8C was added
Ac2O (43.6 ml, 463 mmol) and the mixture was stirred at
23 8C for 16 h. After extractive work-up (CH2Cl2) and
4. Experimental
The NMR determinations were carried out at 23 8C.
Rf were determined on TLC aluminum sheets coated
with 0.2 mm GF254 silica gel. Elemental analyses were
performed at the SIdI (UAM). All reactions were
carried out under an atmosphere of Ar. Solvents were
purified, dried by standard methods and degassed prior
to use.
chromatography (SiO2; 9:1 to 1:1, hexaneꢀ
monoacetate was obtained as a colorless oil (8.55 g,
15%): 1H-NMR (300 MHz, CDCl3) d 5.82ꢀ
5.74 (m,
1H), 5.60ꢀ5.51 (m, 1H), 4.60 (d, Jꢁ6.7 Hz, 2H), 4.18
(d, Jꢁ
6.5 Hz, 2H), 2.01 (s, 3H); 13C-NMR (75 MHz,
/
EtOAc) the
/
/
/
/
CDCl3) d 171.12 (C), 133.31 (CH), 125.16 (CH), 60.02
(CH2), 58.09 (CH2), 20.83 (CH3). (ii). To a suspension of

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415
CuCN (2.73 g, 30.7 mmol) in THF (50 ml) at ꢃ
was added n-BuLi (26 ml, 61.51 mmol; 2.4 M in
hexanes) and the mixture was stirred at ꢃ60 8C for 3
h. The resulting pale yellow solution was cooled down to
78 8C before adding n-Bu3SnH (17.9 g, 61.51 mmol).
/
78 8C
solution was cooled down to ꢃ
/
78 8C before adding n-
Bu3SnH (3.924 g, 13.48 mmol). After 15 min 2-methyl-2-
/
vinyloxirane (510 mg, 6.06 mmol) was added and the
mixture was stirred at ꢃ40 8C for 16 h. The mixture
/
ꢃ
/
was warmed up to 23 8C, and a solution of saturated
aqueous NH4Cl (pH 8) was added. After extractive
work-up (Et2O) and chromatography (SiO2; 20:1, hex-
ane/Et3N), the stannyl alcohol [18] was obtained as a
colorless oil (1.84 g, 80%): 1H-NMR (300 MHz, CDCl3)
After 15 min a solution of cis-4-acetyloxy-2-buten-1-ol
(2.00 g, 15.37 mmol) in THF (10 ml) was added and the
mixture was stirred at ꢃ40 8C for 16 h. The mixture
/
was warmed up to 23 8C, and a solution of saturated
aqueous NH4Cl (pH 8) was added. After extractive
work-up (Et2O) and chromatography (SiO2; 10:1,
d 5.65ꢀ
(m, 17H), 1.09 (t, Jꢁ
13C-NMR (75 MHz, CDCl3; DEPT) d 128.90 (C),
126.73 [2J(13Cꢀ
Sn)ꢁ22.1 Hz; CH], 69.80 (CH2), 29.16
[3J(13Cꢀ 10.5 Hz; CH2], 27.35 [2J(13Cꢀ
Sn)ꢁ Sn)ꢁ26.3
Hz; CH2], 16.69 (CH3), 13.52 (CH3), 10.81
[1J(13Cꢀ119 122.1 Hz, 1J(13Cꢀ117
Sn)ꢁ Sn)ꢁ115.7 Hz;
CH2], 9.51 [1J(13Cꢀ119 155.7 Hz, J(13Cꢀ117
Sn)ꢁ
149.4 Hz; CH2]. Anal. Calc. for C17H36OSn×0.5H2O: C,
53.15, H, 9.72. Found: C, 53.59; H, 9.77%.
/
5.58 (m, 1H), 3.97 (d, Jꢁ
/
5.6 Hz, 2H), 1.77ꢀ
/1.23
/
5.6 Hz, 1H), 0.91ꢀ
/
0.82 (m, 15H);
hexaneꢀ
colorless oil (3.84 g, 70%): 1H-NMR (300 MHz, CDCl3)
d 5.72 (dtt, Jꢁ10.9, 9.3, 1.2 Hz, 1H), 5.30 (dtt, Jꢁ10.9,
6.7, 1.2 Hz, 1H), 4.17 (br t, Jꢁ6.7 Hz, 2H), 1.76 [dd,
Jꢁ9.3, 1.2 Hz, Sn)ꢁ25.6 Hz,
1J(1Hꢀ117
1J(1Hꢀ119
Sn)ꢁ35.2 Hz, 2H], 1.54ꢀ1.19 (m, 12H), 1.14
(t, Jꢁ5.7 Hz, 1H), 0.93ꢀ
0.74 (m, 15H); 13C-NMR (75
MHz, CDCl3; DEPT) d 132.55 (CH), 122.37 (CH),
58.48 (CH2), 29.09 [3J(13Cꢀ
Sn)ꢁ10.7 Hz; CH2], 27.33
[2J(13Cꢀ119 27.4 Hz, 2J(13Cꢀ117
Sn)ꢁ Sn)ꢁ18.9 Hz;
CH2], 13.69 (CH2), 10.98 (CH3), 9.32 [1J(13Cꢀ
Sn)ꢁ
330.4 Hz; CH2].
/
EtOAc) the stannyl alcohol was obtained as a
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
1
/
Sn)ꢁ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
4.3.2. 4-(Tri-n-butylstannyl)-2-methyl-2-buten-1-yl
propargyl ether (18)
To a suspension of NaH (80 mg, 2.00 mmol; 60% in
mineral oil) in DMF (5 ml) a solution of 4-(tri-n-
butylstannyl)-2-methyl-2-buten-1-ol (685 mg, 1.82
mmol) in DMF (3 ml) was added at 0 8C and the
mixture was stirred at 23 8C for 15 min. Propargyl
bromide (330 mg, 1.82 mmol) was added and the
mixture was stirred for 16 h at 23 8C. After extractive
4.2.2. 4-(Tri-n-butylstannyl)-2-buten-1-yl propargyl
ether (16)
To a suspension of NaH (111 mg, 2.73 mmol; 60% in
mineral oil) in DMF (5 ml) a solution of 4-(tri-n-
butylstannyl)-2-buten-1-ol (900 mg, 2.49 mmol) in DMF
(3 ml) was added at 0 8C and the mixture was stirred at
23 8C for 15 min. Propargyl bromide (444 mg, 2.97
mmol) was added and the mixture was stirred for 16 h at
work-up (Et2Oꢀ
/
H2Oꢀice) and chromatography (SiO2;
/
23 8C. After extractive work-up (Et2Oꢀ
chromatography (SiO2; 10:1, hexaneꢀEtOAc) the title
product was obtained as a yellowish oil (342 mg, 35%):
1H-NMR (300 MHz, CDCl3) d 5.88ꢀ
5.77 (m, 1H),
5.27ꢀ5.17 (m, 1H), 4.14 (d, Jꢁ2.4 Hz, 2H), 4.10 (dd,
Jꢁ6.9, 1.3 Hz, 2H), 2.41 (t, Jꢁ2.4 Hz, 1H), 1.79 [dd,
Jꢁ9.3, 0.8 Hz, Sn)ꢁ25.6 Hz,
1J(1Hꢀ117
1J(1Hꢀ119
Sn)ꢁ34.9 Hz, 2H], 1.53ꢀ1.43 (m, 6H),
1.35ꢀ1.24 (m, 6H), 0.91ꢀ
0.84 (m, 15H); 13C-NMR (75
MHz, CDCl3; DEPT) d 134.25 (CH), 118.83 [2J(13Cꢀ
Sn)ꢁ22.1 Hz; CH], 80.12 (CH), 74.07 (C), 65.03 (CH2),
56.86 (CH2), 29.11 [3J(13Cꢀ
Sn)ꢁ10.5 Hz; CH2], 27.33
[2J(13Cꢀ
Sn)ꢁ27.4 Hz; CH2], 13.69 (CH3), 11.18 (CH2),
9.37 (CH2). HRMSꢀ
EI Calc. for C15H27OSn [Mꢂ ꢃ
/
H2Oꢀ
/
ice) and
20:1, hexaneꢀEtOAc), the stannane 18 was obtained as
a yellowish oil (401 mg, 27%; 63% based on recovered
1
starting material) (4.3:1 mixture of isomers): H-NMR
/
/
/
(300 MHz, CDCl3) d 5.66 (br t, Jꢁ
major isomer), 5.58 (br t, Jꢁ8.7 Hz, 1H, minor isomer),
4.10 (d, Jꢁ2.8 Hz, 2H, minor isomer), 4.04 (d, Jꢁ2.8
Hz, 2H, major isomer), 3.96ꢀ3.92 (m, 2H), 2.40 (t,
Jꢁ2.8 Hz, 1H, minor isomer), 2.38 (t, Jꢁ2.8 Hz,
1H, major isomer), 1.83ꢀ1.23 (m, 17 H), 0.96ꢀ0.77
(m, 15H); 13C-NMR (75 MHz, CDCl3; DEPT) (mixture
of isomers) Sn)ꢁ23.1 Hz;
129.63 [2J(13Cꢀ
/9.1 Hz, 1H,
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
d
/
/
/
/
CH], 125.08 (C, major isomer), 124.86 (C, minor
isomer), 80.37 (CH, minor isomer), 80.24 (CH, major
isomer), 76.19 (CH2), 73.90 (C, minor isomer), 73.74
/
/
/
/
Bu]: 343.1084. Found: 343.1080.
(C, major isomer), 56.56 [4J(13Cꢀ
minor isomer], 56.44 (CH2, major isomer),
29.14 Sn)ꢁ10.5 Hz; CH2], 27.33
[3J(13Cꢀ
[2J(13Cꢀ
Sn)ꢁ27.4 Hz; CH2], 13.66 (CH3), 10.95
(CH2), 9.51 [1J(13Cꢀ
Sn)ꢁ157.8 Hz; CH2, major iso-
/
Sn)ꢁ7.4 Hz; CH2,
/
4.3. Synthesis of stannane 18 (Scheme 3)
4.3.1. 4-(Tri-n-butylstannyl)-2-methyl-2-buten-1-ol
/
/
/
/
/
/
mer], 9.37 (CH2, minor isomer) (several signals of the
minor isomer are missing due to overlapping). Anal.
Calc. for C20H38OSn: C, 58.13, H, 9.27. Found: C,
58.49; H, 9.67%.
To a suspension of CuCN (603 mg, 6.74 mmol) in
THF (20 ml) at ꢃ78 8C was added n-BuLi (5.6 ml,
13.48 mmol; 2.4 M in hexanes) and the mixture was
stirred at ꢃ60 8C for 3 h. The resulting pale yellow
/
/

416
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/
4.4. Synthesis of ethyl 4-[4-(tri-n-butylstannyl)-2-
methyl-2-buten-1-yloxy]-2-butynoate (20) (Scheme 3)
aqueous NH4Cl (pH ) was added. After extractive
work-up (Et2O) and chromatography (SiO2; 20:1,
hexaneꢀEt3N) the stannane was obtained as a colorless
/
To a solution of i-Pr2NH (1.28 mmol) in THF at ꢃ
40 8C, n-BuLi (1.28 mmol) was added dropwise, and the
/
oil (1.7 g, 72%): 1H-NMR (300 MHz, CDCl3) d 4.56 [br
4
s, J(1Hꢀ
/
Sn)ꢁ
/
8.9 Hz, 1H], 4.48ꢀ
7.7 Hz, 1H), 2.54 (d, Jꢁ
0.8 Hz, 1J(1Hꢀ
Sn)ꢁ29.9 Hz, 2H], 1.59ꢀ
1.39 (m, 6H), 1.36ꢀ1.23 (m, 6H), 1.35ꢀ1.23 (m, 15H);
13C-NMR (75 MHz, CDCl3; DEPT) d 169.53 (C),
145.96 (C), 106.50 [3J(13Cꢀ
Sn)ꢁ19.9 Hz; CH2], 52.48
(CH3), 50.62 (CH), 37.34 (CH2), 29.06 [3J(13Cꢀ
Sn)ꢁ
9.5 Hz; CH2], 27.61 [2J(13Cꢀ
Sn)ꢁ24.2 Hz; CH2], 18.74
(CH2), 13.66 (CH3), 9.42 [1J(13Cꢀ
Sn)ꢁ151.5 Hz; CH2].
/
4.42 (m, 1H), 3.73 (s,
mixture was stirred at ꢃ
/
40 8C for 1 h. To the resulting
6H), 3.63 (t, Jꢁ
/
/7.7 Hz, 2H),
solution 18 (1.16 mmol), was added at ꢃ
/
40 8C. The red
1.75 [br d, Jꢁ
/
/
/
/
solution was stirred for 2 h, and then ClCO2Et (2.56
mmol) was added rapidly. After 2 h, the reaction was
allowed to warm to room temperature (r.t.), and was
quenched with NH4Cl (pH 8). After usual workup
/
/
/
/
/
/
(Et2O) and chromatography (15:1, hexaneꢀ
/
EtOAc),
stannane 20 was obtained (253 mg, 45%) as a colorless
/
/
/
/
1
oil: IR (neat) 1717, 1245 cmꢃ1; H-NMR (300 MHz,
Anal. Calc. for C21H40O4Sn: C, 53.07; H, 8.48. Found:
C, 52.69; H, 8.59%.
CDCl3) d 5.67 (t, Jꢁ
2H), 4.16 (s, 2H), 3.95 (s, 2H), 1.72 (d, Jꢁ
1.61 (s, 4H), 1.50ꢀ1.41 (m, 4H), 1.33ꢀ1.22 (m, 10H),
0.91ꢀ
0.73 (m, 15H); 13C-NMR (75 MHz, CDCl3) d
153.3, 130.4 [2J(13Cꢀ
Sn)ꢁ22.4 Hz], 124.7, 83.9, 76.7,
73.7, 62.0, 55.3, 29.7 [3J(13Cꢀ
Sn)ꢁ9.8 Hz; CH2], 27.3
[2J(13Cꢀ
Sn)ꢁ26.8 Hz], 14.0, 13.7, 11.1, 9.6
[1J(13Cꢀ119 157.7 Hz; 1J(13Cꢀ117
Sn)ꢁ Sn)ꢁ150.6 Hz;
/
9.3 Hz, 1H), 4.22 (q, Jꢁ/7.3 Hz,
/8.9 Hz, 2H),
/
/
4.5.3. 2-[(Tri-n-butylstannyl)methyl]-1-propen-3-ol
[19]
/
/
/
To a solution of n-BuLi (54.67 mmol, 23.3 ml; 2.35 M
in hexanes) and TMEDA (7.62 g, 65.6 mmol) in Et2O
(26 ml) at 0 8C was added dropwise 2-methyl-1-propen-
3-ol (1.71 g, 23.7 mmol). Upon completion of the
addition, THF (11 ml) was added and stirring was
continued for 24 h at 23 8C. The reaction mixture was
cooled to 0 8C, and then n-Bu3SnCl (8.5 g, 26.15 mmol)
was added rapidly. The resulting clear solution was
stirred at 23 8C for 15 min. The reaction mixture was
added to Et2O (400 ml), washed with saturated aqueous
CuSO4, H2O, and saturated aqueous solution of NaCl.
The organic phase was dried over MgSO4. After
/
/
/
/
/
/
/
/
CH2] (one carbon signal was not observed); FAB-MS
m/z (%): 486 [Mꢂ, 13].
4.5. Synthesis of stannane 25 (Scheme 4)
4.5.1. Dimethyl-1-(2-chloromethyl-2-propenyl)malonate
To a suspension of NaH (705 mg, 17.6 mmol; 60% in
mineral oil) in DMF (50 ml) dimethyl malonate (2.28 g,
17.28 mmol) was added at 0 8C and the mixture was
stirred at 23 8C for 30 min. 3-Chloro-2-chloromethyl-1-
propene (2.28 g, 17.3 mmol) was added and the mixture
was stirred for 17 h at 23 8C. After extractive work-up
purification by chromatography (SiO2; 9:1, hexaneꢀ
EtOAc) the stannane was obtained as a colorless oil
(4.82 g, 56%): 1H-NMR (300 MHz, CDCl3) d 4.76ꢀ
4.69
(m, 1H), 4.65ꢀ4.59 (m, 1H). 3.96 (br d, Jꢁ6.4 Hz, 2H),
1.75 [d, Jꢁ 29.3 Hz, 2H], 1.51ꢀ
1.2 Hz, J(13Cꢀ
1.40 (m, 6H), 1.36ꢀ1.22 (m, 6H), 0.93ꢀ0.79 (m, 15H);
13C-NMR (75 MHz, CDCl3; DEPT) d 149.42 (C),
104.30 [3J(13Cꢀ
Sn)ꢁ17.9 Hz; CH2], 67.13 (CH2),
29.03 [3J(13Cꢀ 8.4 Hz; CH2], 27.3 [2J(13Cꢀ
Sn)ꢁ Sn)ꢁ
27.4 Hz; CH2], 15.03 [1J(13Cꢀ
Sn)ꢁ117.8 Hz; CH2],
13.69 (CH3), 9.51 [1J(13Cꢀ119
Sn)ꢁ159.9 Hz,
1J(13Cꢀ117
Sn)ꢁ152.6 Hz; CH2]; FAB-MS m/z (%):
385 [Mꢂ ꢃ
15, 3], 343 (4), 177 (100).
/
/
/
/
1
(Et2O) and chromatography (SiO2; 5:1, hexaneꢀ
/EtOAc)
/
/
Sn)ꢁ
/
/
the malonate was obtained as a colorless oil (1.21 g,
32%): 1H-NMR (300 MHz, CDCl3) d 5.20 (s, 1H), 5.01
/
/
(s, 1H), 4.0 (br s, 2H), 3.74 (s, 6H), 3.67 (t, Jꢁ
/
7.7 Hz,
7.7 Hz, 2H); 13C-NMR (75 MHz,
/
/
1H), 2.80 (d, Jꢁ
/
/
/
/
/
CDCl3) d 169.06 (C), 141.39 (C), 116.68 (CH2), 52.67
(CH3), 50.14 (CH), 47.45 (CH2), 32.03 (CH2). Anal.
Calc. for C9H13ClO4: C, 48.99; H, 5.94. Found: C,
48.63, H, 6.11%
/
/
/
/
/
/
/
4.5.2. Dimethyl-1-(2-propenyl-2-tri-n-
butylstannyl)malonate
To a suspension of CuCN (974 mg, 10.87 mmol) in
4.5.4. 2-[(Tri-n-butylstannyl)methyl]-3-chloro-1-
propene
To a stirred solution of 2-[(tri-n-butylstannyl)methyl]-
1-propen-3-ol (600 mg, 1.66 mmol), i-Pr2EtN (858 mg,
6.64 mmol) in THF (10 ml) was added at 0 8C followed
by the addition of mesyl chloride (288 mg, 1.98 mmol).
The mixture was stirred at 23 8C for 2 h before adding
LiCl (352 mg, 8.3 mmol). The mixture was stirred for 16
THF (30 ml) at ꢃ
21.74 mmol; 2.5 M in hexanes) and the mixture was
stirred at ꢃ60 8C for 3 h. The resulting pale yellow
solution was cooled down to ꢃ78 8C before adding n-
/
78 8C was added n-BuLi (8.7 ml,
/
/
Bu3SnH (6.32 g, 21.74 mmol). After 15 min a solution of
dimethyl-1-(2-chloromethyl-2-propenyl)malonate (1.1 g,
4.98 mmol) in THF (10 ml) was added and the mixture
h at r.t. After extractive work-up (Et2Oꢀ
/aqueous
NaHSO3) and chromatography (SiO2; 20:1, hexaneꢀ
/
was stirred at ꢃ
warmed up to 23 8C, and a solution of saturated
/
40 8C for 16 h. The mixture was
Et3N) the stannane was obtained as a colorless oil
1
(525 mg, 84%): H-NMR (300 MHz, CDCl3) d 4.84 [br

B. Mart´ın-Matute et al. / Journal of Organometallic Chemistry 687 (2003) 410ꢀ
/419
417
4
4
s, J(1Hꢀ
/
Sn)ꢁ
/
8.9 Hz, 1H], 4.71 [br s, J(1Hꢀ
0.8 Hz, 4J(1Hꢀ
Sn)ꢁ3.24 Hz, 2H],
29.1 Hz, 2H], 1.59ꢀ
1.24 (m, 6H), 0.99ꢀ0.77 (m, 6H),
7.3 Hz, 9H); 13C-NMR (75 MHz, CDCl3;
DEPT) d 145.63 [2J(13Cꢀ
Sn)ꢁ21.1 Hz; C], 109.82
[3J(13Cꢀ
Sn)ꢁ18.9 Hz; CH2], 50.14 (CH2), 29.03
[3J(13Cꢀ 10.5 Hz; CH2], 27.33 [2J(13Cꢀ
Sn)ꢁ Sn)ꢁ27.4
Hz; CH2], 15.84 [1J(13Cꢀ
Sn)ꢁ115.8 Hz; CH2], 13.69
(CH3), 9.65 Sn)ꢁ162.1 Hz;
[1J(13Cꢀ119
1J(13Cꢀ117
Sn)ꢁ153.6 Hz; CH2].
/
Sn)ꢁ
/
8.9
4.6. Palladium(0)-catalyzed cyclizations
Hz, 1H], 3.95 [d, Jꢁ
/
/
/
1
0.8 Hz, J(1Hꢀ
/
Sn)ꢁ
/
/
4.6.1. General procedure: reaction of 9 with Pd2(dba)3×
dba to give tributyl-(Z)-[4,4-bis(phenylsulfonyl)-2-
vinylcyclopentylidenemethyl)]stannane (10)
A solution of 9 (90 mg, 0.13 mmol) in 1,4-dioxane (5
ml) was added to a flask containing Pd2(dba)3×dba (4
mg, 3.6 10ꢃ3 mmol). The mixture was stirred for 2 h at
/
1.89 [d, Jꢁ
1.44 (m, 6H), 1.36ꢀ
0.89 (t, Jꢁ
/
/
/
/
/
/
/
/
/
/
/
/
/
60 8C under Ar. After evaporation of the solvent and
/
/
chromatography (SiO2; 10:1 hexaneꢀ
10 was obtained as a colorless oil (55 mg, 63%): H-
NMR (300 MHz, CDCl3) d 8.07ꢀ8.01 (m, 4H), 7.73ꢀ
7.67 (m, 2H), 7.61ꢀ7.53 (m, 4H), 5.70 (br s, 1H), 5.65
(ddd, Jꢁ16.9, 9.3, 8.1 Hz, 1H), 5.11ꢀ5.04 (m, 2H), 3.60
(dt, Jꢁ17.8, 2.0 Hz, 1H), 3.37ꢀ3.282 (m, 1H), 2.98 (dt,
Jꢁ17.8, 1.6 Hz, 1H), 2.86 (ddd, Jꢁ15.0, 8.9, 1.2 Hz,
1H], 2.56 (dd, Jꢁ15.0, 8.1 Hz, 1H), 1.57ꢀ1.39 (m, 6H),
1.36ꢀ1.18 (m, 6H), 0.95ꢀ
0.83 (m, 15H); 13C-NMR (75
/EtOAc), stannane
/
/
1
/
/
/
/
/
/
/
4.5.5. Dimethyl-1-(2-propenyl-2-tri-n-butylstannyl)-1-
propargyl malonate (25)
/
/
/
/
/
/
/
/
MHz, CDCl3; DEPT) d 156.17 (C), 139.57 (CH), 137.09
(C), 136.18 (C), 134.57 (CH), 134.46 (CH), 131.13 (CH),
131.06 (CH), 126.66 (CH), 123.89 (CH), 116.64 (CH2),
91.64 (C), 48.46 (CH), 42.22 (CH2), 38.32 (CH2), 29.06
(CH2), 27.33 (CH2), 13.72 (CH3), 11.02 (CH2) (one C is
missing due to overlapping).
4.5.5.1. Method A. To a suspension of NaH (84 mg, 2.1
mmol; 60% in mineral oil) in DMF (10 ml) dimethyl-1-
(2-propenyl-2-tri-n-butylstannyl) malonate (1.0 g, 2.1
mmol) was added at 0 8C and the mixture was stirred at
23 8C for 15 min. Propargyl bromide (374 mg, 2.52
mmol; 80% in toluene) was added and the mixture was
stirred for 4 h at 23 8C. After extractive work-up (Et2O/
H2O/ice) the organic phase was dried over MgSO4,
filtered and the solvent evaporated. Stannane 25 was
obtained as a colorless oil (984 mg, 92%).
4.6.2. General procedure: reaction of 9 with Pd2(dba)3×
/
dba, followed by iodination to give (Z)-1-iodomethylene-
4,4-bis(phenylsulfonyl)-2-vinylcyclopentane (11)
A solution of 9 (90 mg, 0.13 mmol) in 1,4-dioxane (5
ml) was added to a flask containing Pd2(dba)3×
/dba (4
mg, 3.6 10ꢃ3 mmol). The mixture was stirred for 2 h at
60 8C under Ar. The reaction mixture was cooled down
to 0 8C and a solution of I2 (35 mg, 0.13 mmol) in 1,4-
dioxane (3 ml) was added. The mixture was stirred for 2
h at 23 8C. The solvent was evaporated and MeOH (6
ml) and KF (90 mg, 1.55 mmol) were added to the flask.
The mixture was stirred at 23 8C for 16 h. The solvent
was evaporated and Et2O was added. The resulting
suspension was filtered off and the filtrate was evapo-
rated and purified by chromatography (SiO2; 7:3
4.5.5.2. Method B. To a suspension of NaH (47 mg, 1.16
mmol; 60% in mineral oil) in DMF (5 ml), dimethyl-
propargyl malonate (180 mg, 1.1 mmol) was added at
0 8C and the mixture was stirred at 23 8C for 30 min. 2-
[(Tri-n-butylstannyl)methyl]-3-chloro-1-propene
mg, 1.1 mmol) was added and the mixture was stirred
for 16 h at 23 8C. After extractive workup (Et2OꢀH2Oꢀ
ice) and chromatography (SiO2; 20:1, hexaneꢀEt3N),
stannane 25 was obtained as a colorless oil (366 mg,
(400
/
/
/
hexaneꢀ
85%): m.p. 128ꢀ
8.10ꢀ8.06 (m, 2H), 7.97ꢀ
2H), 7.64ꢀ7.57 (m, 4H), 6.02 (t, Jꢁ
(ddd, Jꢁ17.4, 9.7, 7.7 Hz, 1H), 5.19ꢀ
(dt, Jꢁ
2H), 2.73 (dd, Jꢁ
/
EtOAc) to yield 11 as a white solid (43 mg,
130 8C; 1H-NMR (300 MHz, CDCl3) d
7.95 (m, 2H), 7.76ꢀ7.69 (m,
1
65%): H-NMR (300 MHz, CDCl3) d 4.66 [d, Jꢁ
Hz, 4J(1Hꢀ
Sn)ꢁ9.1 Hz, 1H], 4.50 [d, Jꢁ1.4 Hz,
4J(1Hꢀ
Sn)ꢁ9.1 Hz, 1H], 3.73 (s, 6H), 2.89 (d, Jꢁ2.8
Hz, 2H), 2.72 [s, J(1Hꢀ
3.6 Hz, 2H], 2.02 (t, Jꢁ
Sn)ꢁ30.3 Hz, 2H], 1.57ꢀ
1.21 (m, 6H), 0.98ꢀ0.79 (m, 15H);
13C-NMR (75 MHz, CDCl3; DEPT) d 170.48 (C),
144.09 [2J(13Cꢀ 21.0 Hz; C], 109.71 [3J(13Cꢀ
Sn)ꢁ
Sn)ꢁ10.5 Hz; CH], 79.45 (CH), 71.67 (C), 57.03 (C),
52.64 (CH3), 39.15 (CH2), 29.00 [3J(13Cꢀ
Sn)ꢁ10.5 Hz;
CH2], 27.36 [2J(13Cꢀ
Sn)ꢁ27.3 Hz; CH2], 22.70 (CH2),
19.99 [1J(13Cꢀ119 351.5 Hz, J(13Cꢀ117
Sn)ꢁ
Hz; CH2], 13.66 (CH3), 9.39 [1J(13Cꢀ119
Sn)ꢁ
1J(13Cꢀ117
Sn)ꢁ117.9 Hz; CH2]; HRMS-EI Calc. for
C24H4104Sn [Mꢂꢂ
1]: 523.2026. Found: 523.2037.
/
1.4
/
/
/
/
/
/
/
/
/
/
/
/
2.0 Hz, 1H), 5.67
4
/
Sn)ꢁ
2.8 Hz, 1H), 1.57 [s, J(1Hꢀ
1.39 (m, 6H), 1.35ꢀ
/
/
/
/
5.14 (m, 2H), 3.53
1
/
/
/
/
17.4, 2.0 Hz, 1H), 3.27 (m, 1H), 3.02ꢀ
/
2.92 (m,
17.7, 6.1 Hz, 1H); 13C-NMR (75
/
/
/
MHz, CDCl3; DEPT) d 149.01 (C), 136.01 (C), 135.67
(C), 135.06 (CH), 134.75 (CH), 131.07 (CH), 130.85
(CH), 128.98 (CH), 128.78 (CH), 117.02 (CH2), 91.89
(C), 82.13 (CH), 73.82 (CH), 49.50 (CH), 40.30 (CH2),
/
/
/
/
/
/
36.81 (CH2); HRMS-FAB Calc. for [Mꢂꢂ
1]: 514.9847.
/
/
/
1
/
/
/
Sn)ꢁ
/
332.2
Found: 514.9823. Anal. Calc. for C20H19IO4S2: C, 46.70,
H, 3.72; S, 12.47. Found: C, 46.80; H,3.61; S, 12.58%.
The structure was confirmed by the following NOE
correlation.
/
/149.9 Hz,
/
/
/

418
B. Mart´ın-Matute et al. / Journal of Organometallic Chemistry 687 (2003) 410ꢀ419
/
4.6.6. (E)-3-Iodomethylene-4-methyl-4-
vinyltetrahydrofuran (19)
Yellowish oil. 1H-NMR (300 MHz, CDCl3) d 6.04 (t,
Jꢁ
(dd, Jꢁ
1H), 4.43 (dd, Jꢁ
/
2.0 Hz, 1H), 5.89 (dd, Jꢁ
10.5, 1.2 Hz, 1H), 5.23 (dd, Jꢁ
12.9, 2.0 Hz, 1H), 4.40 (dd, Jꢁ
/
17.4, 10.5 Hz, 1H), 5.24
17.4, 1.2 Hz,
12.9,
8.7
/
/
/
/
2.0 Hz, 1H), 3.79 (d, Jꢁ
/
8.7 Hz, 1H), 3.70 (d, Jꢁ
/
Hz, 1H), 1.43 (s, 3H); 13C-NMR (75 MHz, CDCl3;
DEPT) d 154.42 (C), 139.35 (CH), 115.08 (CH2), 82.23
(CH2), 75.06 (CH2), 66.21 (CH), 50.93 (C), 19.65 (CH3).
4.6.3. (Z)-1-Iodomethylene-2-isopropenyl-4,4-
bis(phenylsulfonyl)cyclopentane (13)
1
White solid: mp 146ꢀ
CDCl3) d 8.08ꢀ
7.70 (m, 2H), 7.64ꢀ
1H), 4.88ꢀ4.81 (m, 1H), 4.81 (br s, 1H), 3.55 (dt, Jꢁ
17.4, 2.6 Hz, 1H), 3.27ꢀ3.19 (m, 1H), 3.00 (m, 1H), 2.95
(ddd, Jꢁ15.4, 9.3, 1.6 Hz, 1H), 2.96 (dd, Jꢁ15.4, 7.7
Hz, 1H), 1.67 (br t, Jꢁ
1.0 Hz, 3H); 13C-NMR (75
MHz, CDCl3; DEPT) d 148.95 (C), 142.65 (C), 136.99
(C), 135.68 (C), 134.98 (CH), 134.67 (CH), 130.96 (CH),
130.79 (CH), 128.93 (CH), 128.76 (CH), 114.15 (CH2),
91.90 (C), 74.71 (CH), 53.32 (CH), 41.47 (CH2), 37.04
(CH2), 19.16 (CH3). Anal. Calc. for C21H21IO4S2: C,
47.73, H, 4.01; S, 12.14. Found: C, 47.39; H, 4.03; S,
12.04%.
/
148 8C; H-NMR (300 MHz,
/
8.05 (m, 2H), 8.00ꢀ
/
7.96 (m, 2H), 7.77ꢀ
/
/
7.56 (m, 4H), 6.15 (br t, Jꢁ
/
2.6 Hz,
4.6.7. (Z)-Iodo-(4-methyl-4-vinyldihydrofuran-3-
ylidene)acetic acid ethyl ester (21)
/
/
IR (neat) 1704, 1244 cmꢃ1 1H-NMR (500 MHz,
;
/
/
/
CDCl3) d 5.82 (dd, Jꢁ
10.7, 0.5 Hz, 1H), 5.17 (d, Jꢁ
16.6 Hz, 1H), 4.66 (d, Jꢁ16.6 Hz, 1H), 4.16 (q, Jꢁ
Hz, 2H), 3.64 (dd, Jꢁ12.2, 8.8Hz, 2H), 1.49 (s, 3H),
1.26 (t, Jꢁ
7.1 Hz, 3H); 13C-NMR (125 MHz, CDCl3) d
/
17.5, 10.7 Hz, 1H), 5.25 (dd, Jꢁ
17.2 Hz, 1H), 4.84 (d, Jꢁ
7.1
/
/
/
/
/
/
/
/
168.1 (C), 163.7 (C), 138.9 (CH), 116.4 (CH2), 81 (CH2),
79.7 (C), 76 (CH2), 62.7 (CH2), 53.7 (C), 19.2 (CH3),
14.1 (CH3). The structure was confirmed by COSY,
NOESY, HMBC, and HMQC experiments. The follow-
ing NOE correlation allowed to determine the config-
uration. HRMS-CI Calc. for C11H16O3I [Mꢂꢂ
1]:
323.0144. Found: 323.0131.
/
4.6.4. (Z)-Iodomethylene-4,4-bis(methoxycarbonyl)-2-
vinylcyclopentane (15)
1H-NMR (300 MHz, CDCl3) d 6.17 (m, 1H), 5.66
(ddd, Jꢁ
1H), 5.09 (q, Jꢁ
3.33 (q, Jꢁ6.9 Hz, 1H), 3.08 (dt, Jꢁ
2.95 (dt, Jꢁ15.1, 1.3 Hz, 1H), 2.77 (dq, Jꢁ
1H), 2.22 (dd, Jꢁ
7.7, 6.1 Hz, 1H); 13C-NMR (75 MHz,
/
16.6, 9.7, 6.9 Hz, 1H), 5.14 (dt, Jꢁ
1.6 Hz, 1H), 3.72 (s, 3H), 3.71 (s, 3H),
16.2, 2.0 Hz, 1H),
8.5, 1.2 Hz,
/
5.7, 1.2 Hz,
/
/
/
/
/
/
CDCl3) d 171.4, 171.3, 151.4, 136.7, 116.1, 72.9, 59.4,
52.9, 52.8, 48.9, 42.8, 39.5; HRMS-EI Calc. for
C12H15O4I [Mꢂ]: 350.0015. Found: 350.0003.
4.6.8. (Z)-3-Iodomethylene-5-methylenecyclohexane-
1,1-dicarboxylic acid dimethyl ester (28)
To a flask containing Pd(MeCN)2Cl2 (2.5 mg, 0.01
mmol) and (C6F5)3P (10.4 mg, 0.02 mmol) a solution of
dimethyl-1-(2-propenyl-2-tri-n-butylstannyl)-1-propar-
gyl malonate (100 mg, 0.195 mmol) in benzene (5 ml)
was added. The mixture was stirred at 70 8C for 30 h. A
solution of I2 (54 mg, 0.21 mmol) in benzene (3 ml) was
added at 0 8C and the mixture was stirred for 2 h at
23 8C. The solvent was evaporated and MeOH (6 ml)
and KF (50 mg, 0.9 mmol) were added to the flask. The
mixture was stirred at 23 8C for 16 h. The solvent was
evaporated and Et2O was added. The resulting suspen-
sion was filtered off and the filtrate was evaporated and
purified by chromatography (SiO2; hexane) to yield a
mixture of dimethyl 3,5-dimethylenecyclohexane-1,1-
dicarboxylate (27) and (E)-dimethyl 3-iodomethylene-
5-methylenecyclohexane-1,1-dicarboxylate (28) as a col-
orless oil (33 mg, 53%, 1:3.5 mixture). 26: 1H-NMR (300
MHz, CDCl3) d 4.78 (br s, 4H), 3.70 (s, 6H), 2.84 (s,
2H), 2.74 (s, 4H); 13C-NMR (75 MHz, CDCl3; DEPT) d
170.90 (C), 142.40 (C), 111.22 (CH2), 56.81 (C), 52.57
(CH3), 42.84 (CH2), 39.21 (CH2); APCI-MS (m/z):
4.6.5. (E)-3-Iodomethylene-4-vinyltetrahydrofuran (17)
1H-NMR (500 MHz, CDCl3) d 6.08 (q, Jꢁ
/
1.8 Hz,
17.4, 10.1, 7.6 Hz, 1H), 5.18 (dt, Jꢁ
17.2, 1.2 Hz, 1H), 5.14 (dt, Jꢁ10.2, 1.0 Hz, 1H), 4.31
(dt, Jꢁ13.0, 1.7Hz, 1H), 4.21 (dd, Jꢁ13.0, 1.7 Hz, 1H),
3.94 (dd, Jꢁ 8.8, 3.0 Hz,
1H), 5.70 (ddd, Jꢁ
/
/
/
/
/
/
8.8, 6.2 Hz, 1H), 3.84 (dd, Jꢁ
/
1H), 3.32 (m, 1H); 13C-NMR (125 MHz, CDCl3) d
152.5 (C), 134.7 (CH), 116.9 (CH2), 73.4 (CH2), 71.8
(CH2), 69.3 (CH), 51.6 (CH); FAB-MS m/z (%): 235
[Mꢂ ꢃ
1, 14], 219 (34), 167(100). The structure was
/
confirmed by COSY and NOESY experiments. The
following NOE correlation allowed to determine the
configuration.

B. Mart´ın-Matute et al. / Journal of Organometallic Chemistry 687 (2003) 410ꢀ
/419
419
225.3 [Mꢂꢂ
/
1]. 28: 1H-NMR (300 MHz, CDCl3) d 6.08
(b) H. Yoshida, E. Shirakawa, T. Kurahashi, Y. Nakao, T.
Hiyama, Organometallics 19 (2000) 5671.
(t, Jꢁ1,2 Hz, 1H), 4.82 (br s, 2H), 3.73 (s, 6H), 2.97 (br
/
[7] Nucleophilicity of allyl stannanes: H. Mayr, T. Bug, M.F. Gotta,
N. Hering, B. Irrgang, B. Janker, B. Kempf, R. Loos, A.R. Ofial,
G. Remennikov, H. Schimmel, J. Am. Chem. Soc. 123 (2001)
9500.
s, 2H), 2.92 (br s, 2H), 2.76 (br s, 2H); 13C-NMR (75
MHz, CDCl3; DEPT) d 150.54 (C), 144.00 (C), 140.94
(C), 112.12 (CH2), 75.74 (CH), 56.31 (C), 52.69 (CH3),
44.39 (CH2), 39.57 (CH2), 39.17 (CH2). The structure
was confirmed by COSY and NOESY experiments.
[8] (a) M. Shi, K.M. Nicholas, J. Am. Chem. Soc. 119 (1997) 5057;
(b) See also: R.J. Franks, K.M. Nicholas, Organometallics 19
(2000) 1458.
[9] (a) N.A. Bumagin, A.N. Kasatkin, I.P. Beletskaya, Izv. Akad.
Nauk. SSSR Ser. Khim. (Engl. Transl.) (1984) 588;
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[10] Formation of related platinum complexes by the oxidative
addition of allyltrimethylstannane to Pt(0): A. Christofides, M.
Ciriano, J.L. Spencer, F. Gordon, A. Stone, J. Organomet. Chem.
178 (1979) 273.
5. Calculations
The calculations were performed with Gaussian 98
[20]. The geometries of all complexes here reported were
optimized applying density functional theory (DFT) at
the generalized gradient approximation using the
B3LYP hybrid functional [21]. The standard 6-31G(d)
basis set was used for C, H, O, and P. The LANL2DZ
basis set, which includes the relativistic effective core
potential (ECP) of Hay and Wadt [22] and employs a
split-valence (double-j) basis set, was used for Pd and
Sn. Energies include zero-point energy (ZPE) correction.
Harmonic frequencies were calculated at the same level
to characterize the stationary points and to determine
the zero-point energies. The starting approximate geo-
metries for the transition states (TS) were graphically
located.
[11] (a) C. Ferna´ndez-Rivas, M. Me´ndez, A.M. Echavarren, J. Am.
Chem. Soc. 122 (2000) 1221;
(b) C. Ferna´ndez-Rivas, M. Me´ndez, C. Nieto-Oberhuber, A.M.
Echavarren, J. Org. Chem. 67 (2002) 5197.
[12] Intermolecular reaction of allyl stannanes with alkynes with ZrCl4
as catalyst: (a) N. Asao, Y. Matsukawa, Y. Yamamoto, Chem.
Commun. (1996) 1513; (b) Y. Matsukawa, N. Asao, Y. Yama-
moto, Tetrahedron 55 (1999) 3779.
[13] M. Me´ndez, A.M. Echavarren, Eur. J. Org. Chem. (2002) 15.
[14] Review of cyclization of enynes catalyzed by transition metals: C.
Aubert, O. Buisine, M. Malacria, Chem. Rev. 102 (2002) 813.
[15] S. Shin, T.V. RajanBabu, J. Am. Chem. Soc. 123 (2001) 8416.
[16] (a) C. Amatore, E. Blart, J.P. Geneˆt, A. Jutand, S. Lemaire-
Audoire, M. Savignac, J. Org. Chem. 60 (1995) 6829;
(b) G. Papadogianakis, J.A. Peters, L. Maat, R.A. Sheldon, J.
Chem. Soc. Chem. Commun. (1995) 1105.
[17] C. Nevado, L. Charruault, M. Michelet, C. Nieto-Oberhuber,
Acknowledgements
M.P. Munoz, M. Me´ndez, M.N. Rager, J.-P. Geneˆt, A.M.
˜
Echavarren, Eur. J. Org. Chem. (2003) 706.
[18] B.H. Lipshutz, E.L. Ellsworth, S.H. Dimock, P.C. Peuter,
Tetrahedron Lett. 30 (1989) 2065.
We are grateful to the MCyT (Project BQU2001-
0193-C02-01) for support of this research. We acknowl-
edge the MCyT for predoctoral fellowships to B.M.-M.
and C.N.-O., the Centro de Computacio´n Cient´ıfica
(UAM) for computation time, and Johnson Matthey
PLC for a generous loan of PtCl2.
[19] For the synthesis of the trimethylstannyl derivative see: B.M.
Trost, S.A. King, J. Am. Chem. Soc. 112 (1990) 408.
[20] Gaussian 98 (Revision A.7): M.J. Frisch, G.W. Trucks, H.B.
Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, V.G.
Zakrzaweski, J.A. Montgomery, R.E. Stratmann, J.C. Burant,
S. Dapprich, J.M. Millam, A.D. Daniels, K.N. Kudin, M.C.
Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B.
Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A.
Petersson, P.Y. Ayala, Q. Cui, K. Morokuma, D.K. Malick, A.D.
Rabuck, K. Raghavachari, J.B. Foresman, J. Ciolowski, J.V.
Ortiz, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I.
Komaromi, R. Gomperts, R.L. Martin, D.J. Fox, T. Keith,
M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, C. Gonzalez, M.
Challacombe, P.M.W. Gill, B.G. Johnson, W. Chen, M.W.
Wong, J.L. Andres, M. Head-Gordon, E.S. Replogle, J. Pople,
Gaussian, Inc., Pittsburgh, PA, 1998.
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