From vinyl sulfides, sulfoxides and sulfones to vinyl zirconocene derivatives

Article abstract of DOI:10.1016/j.tet.2003.08.074

An easy and straightforward new method for the preparation of sp ² zirconocene derivatives from a wide range of heterosubstituted alkenes such as vinyl sulfides, sulfoxides and sulfones is described. In all cases, a complete isomerization of the stereochemistry is observed and only the E-isomer is obtained. The reactivity of the resulting vinylic organometallic can be increased by a transmetalation reaction into organocopper, organozinc or organopalladium species and, therefore, several carbon-carbon formation were easily realized.

Full text of DOI:10.1016/j.tet.2003.08.074

Tetrahedron 60 (2004) 1329–1337
From vinyl sulfides, sulfoxides and sulfones to
vinyl zirconocene derivatives
*
Shahera Farhat, Irena Zouev and Ilan Marek
Department of Chemistry, Institute of Catalysis Science and Technology, Technion-Israel Institute of Technology, Technion City,
Haifa 32000, Israel
Received 11 July 2003; accepted 6 August 2003
Abstract—An easy and straightforward new method for the preparation of sp2 zirconocene derivatives from a wide range of
heterosubstituted alkenes such as vinyl sulfides, sulfoxides and sulfones is described. In all cases, a complete isomerization of the
stereochemistry is observed and only the E-isomer is obtained. The reactivity of the resulting vinylic organometallic can be increased by a
transmetalation reaction into organocopper, organozinc or organopalladium species and, therefore, several carbon–carbon formation were
easily realized.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
organometallic derivatives was not addressed (except for
vinyl aryl sulfide) and was therefore a very interesting
challenge to solve.
Although numerous methods for the preparation of sp2
organometallic derivatives are known in the literature and
widely used in synthesis,1 there are still some very
challenging synthetic transformations such as the prep-
aration of vinylic organometallics from oxygen- and sulfur
heterosubstituted alkenes. As the importance of the
sulfoxide and sulfone moieties stem from their application
in carbon–carbon bond formations, including asymmetric
synthesis, and this in turn derive from key aspects of their
properties and reactivity, outstanding applications were
found in organic synthesis.2 In these applications, sulfoxides
and sulfones are, therefore, mostly synthetic tools, which
must be disposed of at the end of the sequence.3 As a
potentially very interesting transformation, the preparation
of organometallic derivatives from vinyl sulfoxides or
sulfones should be synthetically very useful since further
functionalization will increase the complexity of the carbon
skeleton. The only reported example was the transformation
of vinyl phenyl sulfide into vinyl lithium derivatives via
reductive metalation.4 This method involves the reductive
lithiation of alkenyl phenyl sulfides by means of 0either a
stoichiometric amount of radical anion lithium p,p -di-tert-
butylbiphenylide (LDBB) or an excess of lithium metal in
the presence of a catalytic amount of p,p0-di-tert-butylbi-
phenyl (DBB; 5% mol).5 Such transformations failed on
vinyl alkyl sulfides.5,6 Although conceptually simple, the
transformation of sulfur heterosubstituted alkenes into
In this paper, we would like to report in full our results
concerning these transformations.6
Over the past two or three decades, organozirconium
derivatives have emerged as being synthetically useful
reagents or intermediates in organic synthesis and their
incredible efficiency, coupled to their unique ability to
promote unusual transformations have aroused the imagin-
ation of chemists.7 As particular example, we were recently
interested by a side product, originally described by
Negishi,8 obtained when the diallyl ether 2 (R¼C3H5) was
treated with the zirconacyclopropane 1a (easily prepared by
the treatment of Cp2ZrCl2 with two equiv of n-BuLi in THF,
and also called Negishi Reagent).9 Instead of producing the
desired zirconabicycle, the reaction gave the allylzircono-
cene derivative 4 via the addition product 3 followed by a
b-elimination as described in Scheme 1.
This originally unwanted side reaction has proved to be a
synthetically useful route to allylzirconocene derivatives, as
nicely demonstrated by Hanzawa and Taguchi.
*
Corresponding author. Tel.: þ972-4-829-3709; fax: þ972-4-829-3709;
e-mail address: chilanm@tx.technion.ac.il
Scheme 1.
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.08.074

1330
S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
Therefore, several allylic,10 allenic,11 g12- and g,g-alkoxy
allylic13 zirconium species were prepared.14 So, although
the direct insertion of organometallic derivatives into the
carbon-ether bond is impossible, a two-step mechanism
allows their easy preparations. This strategy was also
developed for the selective cleavage of allylic ether
derivative.15 However, this concept of addition-b-elimin-
ation was only sporadically used for the preparation of vinyl
zirconium derivatives. The initial report, published by
Takahashi et al., was the preparation of 5 by reaction of
2-chloroalkene derivatives16 with 1a. Recently, Ichikawa and
Minamisuccessfullyappliedthisstrategy17 forthesynthesisof
fluorinated vinyl zirconium moieties 6 (Scheme 2).
Scheme 3.
stereochemistry of the initial vinyl sulfide, the reaction is
.99% stereoselective but not stereospecific, producing only
the E-vinyl zirconium in good overall yields. No, stereo-
isomerization of 7c into 7a was observed in the process,
which indicates that zirconocene 1a is not a catalyst for the
isomerization of thioenol ether. This isomerization can be
explained by a carbometallative ring expansion between 1a
and 7a–c to lead to the corresponding five-membered ring
zirconacycle 11 which may produce the three-membered
zirconacyclopropane 13, since facile equilibration among
three- and five-membered zirconacycle have been already
discussed for skeletal rearrangements.19 If we consider the
ligand exchange described in Scheme 2, the addition–
b-elimination should lead to different geometrical isomers
of the corresponding vinyl zirconium derivatives 8 when
starting from the E- or Z-isomers of vinyl sulfides (7a and
7c, respectively). Therefore, more complicated interme-
diates are most probably involved during the complexation
between the thioenol ethers 7a–c and the zirconocene 1a
since we have a complete isomerization reaction. Our first
hypothesis was that the initial step proceeds via a dipolar
zirconate species20 represented by 12, followed by an
isomerization reaction leading to the trans zirconacyclo-
propane 13.21 Then, after a b-elimination step, the
corresponding E-vinyl zirconium should be obtained.
Although this mechanistic interpretation was attractive, a
stereochemical problem remains for the elimination reac-
tion since an angle of 1808 (anti-elimination) or 08 (syn-
elimination) is usually required for an elimination reaction.
In this case, an angle of 1208 is expected in the
zirconacyclopropane 13 (Scheme 4).
Scheme 2.
In both cases, a good leaving group was used (halide or
tosyloxy groups) for the b-elimination reaction and no
information on the stereochemical outcome of this reaction
was disclosed.18 On the other hand, when the difluoroolefin
bears a substituent with a lower leaving-group propensity
than that a fluorine (i.e., OPh or OMEM), the preferential
elimination of fluoride occurs in low yield (respectively, 17
and 32% yield).17
2. Results and discussions
So, we reasoned that the combined addition–b-elimination
mechanism could be an interesting way to prepare specific
vinylic organometallic derivatives from sulfur-heterosub-
stituted olefins. Indeed, from the mechanistic interpretation
given in Scheme 2, the combination of an olefinic moiety
(complexation with 1a) with a vinylic heteroatom (leaving
group present in the b-position of the zirconacyclopropane)
should lead to the corresponding sp2 organometallic
derivatives via an addition–elimination sequence.
Our first attempt was directed to the preparation of vinylic
zirconocene from vinyl phenyl sulfide; when 7a was added
to a slight excess of 1a, generated by thermal decomposition
of 1 in THF, and stirred at room temperature for few hours,
the expected vinyl zirconocene 8 was obtained in excellent
yield as determined by its hydrolyzed product 9.
Now, if we consider the carbometallative ring expansion to
produce the corresponding five-membered zirconacycle 11,
the carbon–heteroatom bond of the sp3 metallated center C1
should isomerize to produce the most stable intermediate.
Such isomerization could be due to an interaction between
the sulfur moiety and the zirconium atom,22 which would
produce a weakness of the C1–Zr bond and would facilitate
the isomerization. Thus, whatever the stereochemistry of the
starting material, a conformation is always possible in
which C1–SR is antiperiplanar to C2–C3 in 11. The
elimination reaction or decarbozirconation, occurs in a
concerted way to give the E-vinyl zirconium 8. Unfortu-
nately, neither the zirconacyclopentane nor the zirconacy-
clopropane have been trapped as intermediates. On the other
hand, Cp2ZrEt2 14 is known to give zirconocene-ethylene
complex Cp2Zr(CH2vCH2) 14a in a similar way to 1a, but
The formation of a discrete organometallic was first checked
by deuteriolysis and iodinolysis to give 9 and 10 in 80 and
78% yields, respectively (Scheme 3). The reaction also
proceeds efficiently from the alkyl vinyl sulfide 7b, and 9
and 10 are respectively obtained in 83 and 75% yields after
hydrolysis or iodinolysis. Thus, no difference has been
found in this reaction between alkyl and aryl sulfide. When
the same reaction was now performed on the Z-isomer of the
aryl vinyl sulfide 7c, followed by the addition of iodine, only
the E-vinyl iodide 10 was obtained. So, whatever be the

S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
1331
Scheme 6.
Scheme 4.
Thus, from these mechanistic studies, we believe that the
unique formation of the E-isomer results from a carbome-
tallative ring expansion into zirconacyclopentane followed
by an elimination reaction.
the behavior of the ethylene ligand is very different, in most
cases, from the butene moiety of the zirconocene–butene
complex 1b.23 Indeed, the ethylene ligand reacts with
various unsaturated compounds and as it is usually
incorporated in the reaction products, we were interested
to see if it could be also incorporated into the vinyl sulfide
7b. Cp2ZrEt2 was easily prepared by treatment of 2 equiv.
of EtMgBr (and by also 2 equiv. of EtLi to check that there
is no salt effects) with Cp2ZrCl2 to furnish 14, which was
then treated with 7b at room temperature. The addition
product 15 is rapidly observed by analysis by gas
chromatography of aliquots after hydrolysis, which is
followed by the elimination reaction to give the vinyl
zirconium species 8 and ethylene. Both of the intermediates
and the product were trapped by hydrolysis (Scheme 5).
Although the formation of the vinyl zirconium 8 is
slower in this particular case (only 2–3 h were
necessary for the formation of 8 from 7b and 1a), we
can clearly see that the addition product 15 undergoes a
subsequent b-elimination reaction to give the expected
product 8 (Table 1).
The scope of the reaction can be broader since vinyl
zirconocenes can be transmetallated into more reactive
species as described in Scheme 6.24
Indeed, addition of a catalytic amount of copper chloride in
the presence of lithium chloride25 leads to the corresponding
E-vinyl copper derivative. The latter reacts either via a SN20
process with allyl chloride (17 in 65% yield) or in a 1,4-
addition manner with cyclohexanone in the presence of
TMSCl26 (18 in a non-optimized 55% yield). The
palladium-catalyzed cross-coupling reaction of 8 with aryl
iodide opens a new route to further functionalization as
shown by the formation of 19 in 68% yield. Finally, the
transmetalation of the vinyl zirconium 8 to zinc bromide
followed by the addition of allylmagnesium bromide leads
to new bismetallated species (20 after hydrolysis in 73%
yield).27
We were then interested to extend this methodology to the
transformation of vinyl sulfoxides into vinylic organome-
tallic derivatives. Indeed, the stereogenic sulfur atom in
sulfoxides is configurationally stable at room temperature
and thus sulfoxides may be chiral based on this property
alone.28 Therefore, reactions of chiral sulfoxides found
extensive applications in Asymmetric Synthesis.29 How-
ever, in most cases, once the new chiral centers are created,
sulfoxides have to be removed in subsequent chemical
steps. Although the replacement of sulfoxide moiety in
vinyl sulfoxide by hydrogen atom can be performed by
using different metals such as Na/Hg or activated zinc,30 the
transformation of vinyl sulfoxide into vinylic organome-
tallic derivatives was unknown.
Scheme 5.
When E-vinyl sulfoxide 21 was treated with 1.5 equiv. of 1a
in THF at 278 8C and warning up the reaction mixture to
room temperature, we obtained the corresponding sulfides
7a instead of the expected vinyl zirconium derivative 8.
Therefore, vinyl sulfoxides are reduced with 1a into the
corresponding vinyl sulfide with concomitant formation of
the insoluble polymer [Cp2ZrvO]n (Scheme 7).
Table 1. Apparition of 9 after b-elimination of 15 followed by hydrolysis
Reaction time
16 (%)
9 (%)
20 min
2 h
3 h
90
70
50
30
10
30
50
70
10 h
Low-valent group 4 organometallic derivatives such as

1332
S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
Scheme 7.
bis(trimethyl)phosphine zirconium derivatives are know to
reduce CO2 into CO and Cp2ZrO polymer.31 Thus,
Bu2ZrCp2 1 is also a very mild reducing agent of sulfoxides
into sulfides with formation of the easily removable
[Cp2ZrO]n by simple filtration at the end of the sequence.
As shown in Table 2, the scope of the reaction is relatively
broad.
Scheme 8.
and Z-21 into the vinyl sulfide 7a and 7c, respectively,
without any isomerization of the double bond and then, the
second equivalent of 1a transforms the vinyl sulfides 7a,c
into the corresponding organometallics with a complete
isomerization of the double bond as discussed in Schemes 3
and 4. Reaction of E-8 with iodine led in both cases to the
E-vinyl iodide 10 in good overall yields.
Diaryl, aryl–vinyl, aryl–alkyl sulfoxides were reduced in 1
to 2 h at room temperature in good to excellent yields
(entries 1–6). Trisubstituted vinyl sulfoxides undergo also
the transformation in good isolated yield. Whatever the
stereochemistry of the vinyl sulfoxide (compare entries 2
and 3), the reduction occurs into the corresponding vinyl
sulfide without isomerization of the double bond. Finally,
even sulfoxide bearing two stereogenic centers on its carbon
skeleton as in entry 5 can be reduced without any change in
the stereochemical purity of the substrate. In this particular
case, 2 equiv. of 1a were used.
Finally, we turned our attention to vinyl sulfones. Indeed,
although sulfones were extensively used for the creation of
carbon–carbon bonds, the transformation into vinylic
organometallic derivatives was simply unknown. To date,
the available method for the replacement of sp2 sulfone falls
roughly into three categories: those resulting in replacement
of the sulfone by hydrogen (reductive desulfonylation),32
those in which the sulfone removal is accompanied by a
C–C bond formation (alkylative desulfonylation)33 and
finally those in which the sulfone is a good leaving group
towards b-elimination reaction with formation of the
sulfinate moiety (RSO22).34 When E-22a–c were treated
with Bu2ZrCp2 1a in THF at room temperature, a very fast
reaction was observed which lead to the expected alkenes 9
in excellent isolated yields after hydrolysis, whatever the
nature of the group on the starting sulfone (R¼Ph, Tol, Me,
Scheme 9). By reaction with iodine, E-10 was isolated from
E-22a in 70% yield.
However, our main research goal was the preparation of
vinyl zirconocene derivatives from vinyl sulfoxides and not
its reduction. As sulfoxides can be easily transformed into
sulfides and sulfides can be further transformed into vinylic
organometallics, the expected vinylic organometallic
derivatives have been obtained in a single-pot operation
from sulfoxides by treatment with 2 equiv. of Bu2ZrCp2 as
described in Scheme 8.
The first equivalent of 1a reduces the vinyl sulfoxides E-
Table 2. Reduction of sulfoxides into sulfides with Bu2ZrCp2
Entry
1
Sulfoxides
PhS(O)Ph
Sulfides
PhSPh
Yielda%
95
2
3
80
81
Scheme 9.
When the Z-vinyl sulfone 22a is treated with 1a, a complete
isomerization also occurs as determined by the reaction of
the resulting vinyl organometallic derivatives with iodine.
Only the E-isomer of 10 was isolated with good chemical
yield. In order to probe the formation of zirconacyclopen-
tane 23 as reactive intermediates, the same reaction between
E-22c and Et2ZrCp2 14 was repeated (as described in
Scheme 4 but with sulfone instead of sulfide). Here again,
the addition product 23 was rapidly formed at room
temperature as determined by its hydrolyzed or deuter-
iolysis products 24 and 24(d), respectively. Then, 23
disappear over time in favor of 8 (Scheme 10).
4
5
85
73
C12H25S(O)Tol
C12H25STol
6
92
a
Yield of isolated products after purification by column chromatography.

S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
1333
On the other hand, it is well known that transition metal
catalyzedisomerizationofterminalolefinsintointernalolefins
and in general a mixture of 1-alkenes, (E)- and (Z)-2-alkenes,
reflecting the thermodynamic equilibrium, is obtained.35
Some low-valent titanocene derivatives are highly effective
and stereoselective in favor of the (E)-2-isomer.36 When non-
conjugateddienessuchas33containingone ortwo substituted
vinyl groups are treated with zirconocene 1a, a regioisome-
rization of the less-substituted double bond occurs and lead to
the formation of the conjugated diene–zirconocene com-
plexes 34 (Scheme 11, path A).37
Scheme 10.
In order to extend the scope of the reaction, several
polysubstituted vinyl sulfones were prepared and trans-
formed into the corresponding vinylic organometallic
derivatives as described in Table 3.
When b,b-disubstituted vinyl sulfones were treated with
zirconocene 1a, the expected products 25, 27 and 29 were
obtained in reasonably good yields (Table 3, entries 1, 3 and
5, respectively). The presence of an organometallic species
was proved by trapping experiments either with MeOD
(Table 1, entry 2 of unknown stereochemistry) or with
iodine (Table 3, entry 4). Two geometrical isomers were
obtained for the vinyl iodide 28 starting from two isomers
for the corresponding vinyl sulfones. a,b-Disubstituted
vinyl sulfones also undergo the transformation but only
when one of the substituents is an aromatic group (either in
a- or b-position as described in Table 3, entries 6–8). Only
the E-isomer is obtained in these three cases. When the two
substituents are alkyl groups, the reaction leads to several
isomers, most probably due to subsequent isomerization of
the resulting olefin (Table 3, entry 9). Interestingly, among
all the isomers formed, no terminal double bond was
detected. Finally, when cyclohexenyl sulfone was treated
with 1a, only a 40% yield of the cyclic organometallic was
formed after iodinolysis (Table 3, entry 10).
Scheme 11.
We have recently used this concept of isomerization for the
stereoselective preparation of dienyl zirconocene 36
derivatives in a single-pot operation for substituted enol
ether 35 (Scheme 11, Path B).38
Therefore, we have examined the case of 4-phenyl-sulfonyl-
pent-3-enylbenzene 37, as dialkyl substituted vinyl sulfone,
but with also an aromatic group in a remote position of the
alkyl chain to see if we have an isomerization reaction. The
reaction of 37 with 1a lead to the expected trans isomer 38 but
also to the isomerized product 39 in a 1:2 ratio, respectively, in
60% combined yield as described in Scheme 12.
From this study, we can deduce that b,b0-disubstituted—as
well as a,b-disubstituted vinyl sulfones (but only when one
substituent is aromatic) undergo the transformation but
surprisingly not when substituents are alkyl groups.
Apparently, the phenyl group induces a particular stabiliz-
ation of the zirconacycle intermediate that leads to a
complete stereoselective formation of the E-vinyl zirconium
whereas in its absence, an isomerization occurs and,
therefore, a loss of stereoselectivity.
Scheme 12.
Here again, no traces of terminal olefin that could result
from the isomerization to the opposite side of the molecule
were detected. The isomerization occurs towards the most
stable isomer in which the double bond is conjugated with
the phenyl ring. More surprisingly, when iodine was added
at the end of the reaction to potentially trap organometallic
derivatives, no iodinated products were detected. On the
other hand, when terminal vinyl sulfone 40 with the same
remote aromatic ring was treated with 1a, no isomerization
reaction was found; only 41 was formed in 67% yield
(Scheme 13).
Table 3. Preparation of polysubstituted vinyl zirconocenes
Entry
R1
Oct
Oct
Oct
Oct
Ph
Ph
Me
Ph
hept
(CH2)4
R3
R2
Eþ
Products
Yield (%)a
1
2
3
4
5
6
7
8
9
10
H
H
H
H
H
Bu
Bu
Me
Me
Bu
H
H
H
H
H
H3Oþ
MeOD
H3Oþ
I2
H3Oþ
H3Oþ
H3Oþ
H3Oþ
H3Oþ
I2
25
26
27
28
29
30
30
31
/
70
60
68
67
64
70
60
65
/
Me
Ph
Et
Me
(CH2)4
32
40
a
Yields after purification by column chromatography.
Scheme 13.

1334
S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
From this experiment, we can conclude that alkyl
substituents in a- and b-position of the olefin induce the
isomerization process. As nothing is known on the exact
nature of our intermediate, we must await further investi-
gations to elucidate completely the mechanism of this
reaction, but should arise most probably from the destabi-
lization of the zirconacyclopropane intermediate (such as 13
in Scheme 4, compare Schemes 12 and 13).
3. Experimental
All our starting materials (vinyl sulfides,39 vinyl sulfox-
ides40 and vinyl sulfones41) were prepared by conventional
methods described in the above references.
3.1. General procedure for the transformation of
heterosubstituted alkenes into vinylic zirconocenes
Based on the reported data, we reasoned that a-substituted
vinyl sulfones might undergo the isomerization towards the
most stable alkene via a mechanism similar to the one
described in Scheme 11. Indeed, 37 can react with 1a to
form the zirconacyclopropane 37a, which undergo via a
double allylic C–H bond activation (transformation of 37a
to 37e by formation of two h3-allyl intermediates 37b,d).
Once 37e is formed, the zirconocene must be released (the
sulfonyl moiety can eventually induce this release by
intramolecular chelation) and induce the reduction of the sp3
alkyl sulfone into 39 (see Scheme 14).
A solution of n-butyllithium in hexane (1.6 M, 3.4 equiv.,
3.4 mmol) was added slowly to a solution of bis(cyclopen-
tadienyl)zirconium dichloride (1.7 equiv., 1.4 mmol) in dry
THF (7 ml) at 278 8C. After the solution was stirred for 1 h
at 278 8C, heterosubstituted alkene was added (1 equiv.,
1 mmol) as solution in 3 ml of dry THF at 278 8C. The
reaction mixture was allowed to warm to room temperature
and stirred for 3–5 h. The quantitative formation of the
adduct was checked by gas chromatography. Then, the
solution was cooled to 220 8C, and the electrophile was
added. The reaction was warmed to room temperature and
the mixture was diluted with ether and with an aqueous
solution of HCl (1 M) [in case of transmetalation with CuCl,
a mixture of saturated aqueous solution of NH4Cl (2 equiv.)
and aqueous solution of NH4OH (25%, 1 equiv.) was used].
The aqueous phase was then extracted three times with
ether. The combined organic phases were then washed
successively with a solution of saturated aqueous sodium
hydrogen carbonate, brine and water (in case of addition of
iodine as electrophile, aqueous Na2S2O3 was used), dried
over MgSO4, and evaporated under reduced pressure. The
residue was finally purified by column chromatography on
silica gel.
Scheme 14.
Note. Reaction of vinyl sulfoxides E-21 and Z-21 according
to the above mentioned procedure produced the correspond-
ing vinyl sulfide.7a,c. By using 2.5 equiv. of Cp2ZrCl2 and
5 equiv. of n-BuLi, the desired vinyl zirconium derivative is
obtained.
Although several pendant questions have to be solved to
confirm this mechanistic hypothesis, we have already
confirmed that zirconocene 1a reduces efficiently primary
sp3 alkyl sulfone into the corresponding alkane. When
iodine was added at the end of the reaction, minor amount of
the alkyl iodide was formed confirming that primary alkyl
sulfone undergo reductive desulfonylation most probably
via single-electron transfer process.
The reaction of b,b0- and a,b-disubstituted vinyl sulfones
was carried out by using an excess of Cp2ZrCl2 (2 equiv.)
with 4 equiv. of n-BuLi.
1-Decene (9). Purification by column chromatography on
silica gel (eluent: hexane) gave a colorless liquid in 85%
yield, spectrally identical with an authentic sample
commercially available. 1H NMR (200 MHz, CDCl3) d
(ppm) 0.86 (t, 3H, J¼6.4 Hz), 1.42 (m, 12H), 2.00 (m, 2H),
4.93 (m, 2H), 5.78 (m,1H).
In conclusion, by using zirconocene 1a, we have been able
for the first time to develop an easy and straightforward new
method for the preparation of sp2 zirconocene derivatives
from a wide range of heterosubstituted alkenes such as vinyl
sulfides, sulfoxides and sulfones. In all cases, a complete
isomerization of the stereochemistry is observed and only
the E-isomer is obtained. The reactivity of the resulting
vinylic organometallic can be increased by a transmetala-
tion reaction into organocopper, organozinc or organopal-
ladium species and therefore, several carbon–carbon
formation were easily realized. When more substituted
vinyl sulfones such as b,b0-disubstituted- or a,b-disubsti-
tuted (with at least one substituent aromatic) were used, this
method also leads to the corresponding organometallic
derivatives. On the other hand, when a,b-disubstituted vinyl
sulfones have only alkyl groups, an isomerization occurs to
give a mixture of isomers. This isomerization can be used
for the preparation of the most stable olefin if an aromatic
group is present in the carbon skeleton.
(E)-1-Deuterio-1-decene (9d).42 Purification by column
chromatography on silica gel (eluent: hexane) gave a
colorless liquid in 83% yield: 1H NMR (200 MHz,
CDCl3) d (ppm) 0.87 (t, 3H, J¼6.56 Hz), 1.25 (m, 12H),
1.97–2.07 (m, 2H), 4.87–5.00 (d, 1H, J¼16.85 Hz), 5.72–
5.87 (m, 1H). 13C NMR (50 MHz, CDCl3) d (ppm)
14.21, 22.84, 29.16–29.86 (4C), 32.07, 33.92, 113.47 (t),
139.27.
(E)-1-Iodo-1-decene (10).43 Purification by column chro-
matography on silica gel (eluent: hexane) gave a yellow
liquid in 55–78% yield, spectrally identical with an
1
authentic sample. H NMR (200 MHz, CDCl3) d (ppm)

S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
1335
0.86 (t, 3H, J¼5.89 Hz), 1.09–1.34 (m, 12H), 1.96–2.15
(m, 2H), 5.98 (d, 1H, J¼15.3 Hz), 6.41–6.56 (m, 1H). 13C
NMR (50 MHz, CDCl3) d (ppm) 14.19, 22.79, 28.51–29.83
(4C), 32.03, 36.16, 74.29, 146.98.
J¼6.69 Hz), 1.24 (m, 15H), 1.77–2.11 (m, 2H), 4.88–5.02
(m, 2H), 5.64–5.87 (m, 1H). 13C NMR (50 MHz, CDCl3)
d (ppm) 14.07, 22.67, 29.34–31.92 (8C), 31.92, 117.5,
135.6.
(E)-1,4-Tridecadiene (17).44 The general procedure was
performed as described above. When the formation of the
vinyl zirconium was complete (checked by GC), 0.12 ml of
allyl chloride (1.5 mmol, 1.5 equiv.), copper chloride
(0.1 mmol, 10 mg, 0.1 equiv.) and lithium chloride
(2 mmol, 85 mg, 2 equiv.) were added at 0 8C. Then, the
solution was stirred at 50 8C for 5 h. After usual treatment,
the residue was purified by column chromatography on
silica gel (eluent: hexane) to give a colorless liquid in 65%.
1H NMR (200 MHz, CDCl3) d (ppm) 0.88 (t, 3H,
J¼6.56 Hz), 1.11–1.25 (m, 12H), 1.98 (m, 2H), 2.73 (m,
2H), 4.89–5.05 (m, 3H), 5.34–5.45 (m, 1H), 5.71–5.83 (m,
1H).
1-(Propylthio)-2-ethyl-decane (16). The general procedure
was performed using EtLi or EtMgBr instead of n-BuLi.
The starting material was the vinyl propyl sulfide 7b. The
reaction mixture was quenched with aqueous solution of
HCl (1 M) after 1 h stirring at room temperature. The major
product, 3-(propylthio)-ethyl-decane 16, was purified by
column chromatography on silica gel (eluent: hexane) to
1
give a yellow liquid. H NMR (200 MHz, CDCl3) d (ppm)
0.81–1.00 (m, 9H), 1.25–1.64 (m, 19H), 2.41–2.48 (m,
4H). 13C NMR (50 MHz, CDCl3) d (ppm) 10.83, 13.51,
14.07, 22.67, 23.12, 25.66, 26.73, 29.36, 29.64, 29.99,
31.92, 32.82, 35.03, 36.83, 39.54.
2-(20-Deuterioethyl)-1-(10-deuteriodecyl) methyl sulfone
(24). The general procedure was performed using EtLi or
EtMgBr instead of n-BuLi. The starting material was the
vinyl methyl sulfone E-22c. The reaction mixture was
quenched with MeOD after stirring for 1 h at room
temperature after adding the starting material at 278 8C.
After usual work up, two products were obtained. The minor
product was E-1-deuterio-1-decene 9d 0 and the major
product was 2-(20-deuterioethyl)-1-(1 -deuteriodecyl)
methyl sulfone 24, which was purified by column
chromatography on silica gel (hexane/ethyl acetate, 4/1) to
(E)-1-Cyclohexanone-1-decene (18). The general pro-
cedure was performed as described above. When the
formation of the vinyl zirconium was complete (checked
by GC), 2-cyclohexene-1-one (2.5 equiv., 1.35 mmol,
0.13 ml), TMSCl (2.6 equiv., 1.41 mmol, 0.18 ml), copper
chloride (0.1 equiv., 0.054 mmol, 5 mg) and lithium
chloride (2 equiv., 1.08 mmol, 46 mg) were added at room
temperature. Then, the solution was stirred at 60 8C for 6 h.
After usual treatment, the residue was purified by column
chromatography on silica gel (eluent: hexane/ethyl acetate
1
1
(30:1) to give a colorless liquid in 50% yield: H NMR
give a yellow liquid. H NMR (200 MHz, CDCl3) d (ppm)
(200 MHz, CDCl3) d (ppm) 0.85 (t, 3H, J¼6.79 Hz), 1.23
(m, 12H), 1.68 (m, 4H), 1.83–2.14 (m, 3H), 2.15–2.41 (m,
4H), 5.33–5.40 (m, 2H). 13C NMR (50 MHz, CDCl3) d
(ppm) 14.048, 22.63, 23.87, 28.84–29.67 (4C), 31.34,
31.62, 31.86, 41.51, 41.54, 47.71, 130.02, 132.93, 211.27.
0.84 (t, 5H, J¼6.54 Hz), 1.07–1.55 (m, 17H), 1.96–2.05
(m, 1H), 2.86 (s, 3H). 13C NMR (50 MHz, CDCl3) d (ppm)
9.83 (t), 13.98–34.91 (9C), 41.71, 57.99 (t). HRMS (ESI,
methanol) Calcd for C13H26D2O2S (MHþ) 273.432, Found
273.4453.
(E)-1-Phenyl-1-decene (19).45 The general procedure was
performed as described above. When the formation of the
vinyl zirconium was complete (checked by GC), phenyl
iodide (0.26 g, 1.3 mmol, 1.3 equiv.), copper chloride
(0.15 g, 1.5 mmol, 1.5 equiv.) and 5% of Pd(PPh3)4
(60 mg, 0.05 mmol) were added at room temperature. The
solution was heated for 3 hr at 50 8C. After usual treatment,
the residue was purified by column chromatography on
silica gel (eluent: hexane) to give a colorless liquid in 68%
Butyl-1-decene (25).47 Purification by column chromato-
graphy on silica gel (eluent: hexane) gave a yellow liquid in
70% yield: 1H NMR (200 MHz, CDCl3) d (ppm) 0.86 (t, 6H,
J¼6.67 Hz), 1.14–1.51 (m, 16H), 1.93–1.97 (m, 4H), 4.67
(s, 2H). 13C NMR (50 MHz, CDCl3) d (ppm) 22.50–42.78
(12C), 108.34, 150.39.
2-Butyl-1-deuterio-1-decene (26). Purification by column
chromatography on silica gel (eluent: hexane) gave a yellow
1
1
yield. H NMR (200 MHz, CDCl3) d (ppm) 0.88 (t, 3H,
liquid in 60% yield: H NMR (200 MHz, CDCl3) d (ppm)
J¼7.1 Hz), 1.29–1.52 (m, 12H), 2.15–2.25 (m, 2H), 6.17–
6.29 (m,1H), 6.34–6.42 (d, 1H, J¼15.99 Hz), 7.17–7.37
(m, 5H). 13C NMR (50 MHz, CDCl3) d (ppm) 14.06, 22.67,
29.26, 29.28, 29.41, 29.50, 31.91, 33.05, 125.92 (2C),
126.72, 128.44 (2C), 129.75, 131.24, 138.04.
0.87 (t, 6H, J¼5.06 Hz), 1.24 (m, 16H), 1.94–2.01 (m, 4H),
4.69 (s, 1H). 13C NMR (50 MHz, CDCl3) d (ppm) 14.08–
42.72 (12C), 108.37 (t), 150.37.
2-Methyl-1-decene (27).48 Purification by column chroma-
tography on silica gel (eluent: hexane) gave a yellow liquid
in 68% yield: 1H NMR (200 MHz, CDCl3) d (ppm) 0.86 (t,
3H, J¼6.93 Hz), 1.17–1.50 (m, 12H), 1.69 (s, 3H), 1.98 (t,
2H, J¼7.59 Hz), 4.65 (s, 2H).
4-Methyl-1-dodecene (20).46 The general procedure was
used as described above. When the formation of the vinyl
zirconium was complete (checked by GC), zinc dibromide
(1.9 equiv., 1.9 mmol, 0.43 g) was added at room tempera-
ture followed by addition of allylmagnesium bromide
(1.9 equiv., 1.9 mmol, 0.85 M in ether, 2.24 ml) at
230 8C. Then, the mixture was warmed to room tempera-
ture for 3 h. After usual treatment, the residue was purified
by column chromatography on silica gel (eluent: hexane) to
2-Methyl-1-iodo-1-decene (28).49 Purification by column
chromatography on silica gel (eluent: hexane) gave a yellow
liquid in 67% yield as a mixture of two isomers in a 1 to 1
1
ratio. H NMR (200 MHz, CDCl3) d (ppm) 0.86 (t, 3H,
J¼6.46 Hz), 1.17–1.38 (m, 12H), 1.79 (s, 3H, the second
isomer was singlet at 1.85 ppm), 2.17 (t, 2H, J¼7.82 Hz),
5.79 (s, 1H, the second isomer was singlet at 5.82 ppm).
1
give a colorless liquid in 73% yield. H NMR (200 MHz,
CDCl3) d (ppm) 0.83 (t, 3H, J¼3.39 Hz), 0.86 (t, 3H,

1336
S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
a-Butylstyrene (29).50 Purification by column chromato-
graphy on silica gel (eluent: hexane) gave a yellow liquid in
2-Phenylthio-3-ethyl-4-hydroxyl-4-phenyl-1-butene
(Table 2, entry 6). The general procedure was used as
described above, 2.5 equiv. of Cp2ZrCl2 and 5 equiv. of n-
BuLi were used. After usual work up the residue was
purified by column chromatography on silica gel (eluent:
hexane/ ethyl acetate, 3/1) to give yellow liquid in 92%
1
64% yield: H NMR (200 MHz, CDCl3) d (ppm) 0.86 (m,
3H), 1.07–1.53 (m, 4H), 2.49 (t, 2H, J¼6.98 Hz), 5.05 (s,
1H), 5.25 (s, 1H), 7.13–7.43 (m, 5H).
E-b-Methylstyrene (30).51 Purification by column
chromatography on silica gel (eluent: hexane) gave a
colorless liquid in 70% yield: 1H NMR (200 MHz,
CDCl3) d (ppm) 1.87–1.90 (d, 3H, J¼5.92 Hz), 6.15–
6.32 (m, 1H), 6.37–6.46 (d, 1H, J¼16.03), 7.15–7.36 (m,
5H).
yield. H NMR (200 MHz, CDCl3) d (ppm) 0.87 (t, 3H,
1
J¼7.25 Hz), 1.60–1.80 (m, 2H), 2.13 (s, 1H), 2.39–2.49
(m, 1H), 4.64 (s, 1H), 4.89–4.92 (d, 1H, J¼5.92 Hz), 4.99
(s, 1H), 7.24–7.36 (m, 10H).
E-b-Ethyl styrene (31).52 Purification by column chroma-
tography on silica gel (eluent: hexane) gave a colorless
liquid. Isolated yield 65% (0.095 g).1H NMR: d 7.21 (d,
J¼7 Hz, 2H), 7.09 (d, J¼7 Hz, 2H), 6.33 (d, J¼16 Hz, 1H)
6.25–6.11 (m, 1H), 2.19 (q, J¼6.8 Hz, 2H), 0.95 (t, 6.8 Hz,
3H).
Acknowledgements
This research was supported by the Israel Science
Foundation (grant 79/01-2) and by the Fund for the
Promotion of Research at the Technion.
1-Iodo-1-cyclohexene (32).53 The general procedure was
performed. With an excess of Cp2ZrCl2 (3 equiv.) and
n-BuLi (6 equiv.). After usual work up the residue was
purified by column chromatography on silica gel (eluent:
hexane) to give yellow liquid in 40% yield. 1H NMR
(200 MHz, CDCl3) d (ppm) 0.79–0.90 (m, 2H), 1.58–1.73
(m, 2H), 2.06–2.11 (m, 2H), 2.47 (m, 2H), 6.29–6.32 (m,
1H).
References and notes
1. For monographs, see (a) Schlosser, M. Organometallics.
Synthesis; 2002. (b) Furstner, A. Active Metals. VCH:
Weinheim, 1996. (c) Negishi, E. Organometallics in Organic
Synthesis. Wiley-Interscience: New York, 1980.
2. (a) Magnus, P. D. Tetrahedron 1977, 33, 2019. (b) Patai, S.;
Rappoport, Z.; Stirling, C. J. M. The Chemistry of Sulphones
and Sulphoxides. Wiley: Chichester, 1988. (c) Simpkins, N. S.
Sulphones in Organic Synthesis. Pergamon, 1993.
Pentyl-3-enylbenzene (38).54 Colorless liquid. 1H NMR: d
7.19–7.07 (m, 5H), 5.34–5.26 (m, 1H), 2.52–2.69 (m, 2H),
2.32 (q, J¼6.5 Hz, 2H), 1.62 (d, J¼4.8 Hz, 3H).
Propyl-1-enylbenzene (39).55 Colorless liquid. 1H NMR: d
7.24–7.21 (m, 5H), 6.22 (d, J¼15.9 Hz, 1H), 6.16–6.11 (m,
1H), 2.28–2.37 (m, 4H), 0.88 (t, J¼6 Hz, 3H).
Butyl-3-enyl-benzene (41).56 Slight yellow liquid. Isolated
yield 67% (0.085 g).1H NMR: d 7.26–7.15 (m, 5H), 5.85–
5.83 (m, 1H), 5.06–4.94 (m, 2H), 2.67 (t, J¼7.2 Hz, 2H),
2.34 (q, J¼7.2 Hz, 2H).
3. (a) Cuvigny, T.; Herve du Penhoat, C.; Julia, M. Tetrahedron
Lett. 1983, 24, 4311. (b) Julia, M.; Lauron, H.; Stacino, J. P.;
Verpeaux, J. N.; Jeannin, Y.; Dromzee, Y. Tetrahedron 1986,
42, 2475. (c) Fabre, J. L.; Julia, M.; Verpeaux, J. N. Bull. Soc.
Chim. Fr. 1985, 762. (d) Baldwin, J. E.; Adlington, R. M.;
Ichikawa, Y.; Kneale, C. J. J. Chem. Soc. Chem. Commun.
1988, 702. (e) Trost, B. M. Bull. Chem. Soc. Jpn 1988, 61, 107.
(f) Backvall, J. E.; Chinchilla, R.; Najera, C.; Yus, M. Chem.
Rev. 1998, 98, 2291.
4. (a) Cohen, T.; Doubleday, M. D. J. Org. Chem. 1990, 55,
4784. (b) Cohen, T.; Bhupathy, M. Acc. Chem. Res. 1989, 22,
152.
Reduction of sulfoxides into sulfides
5. (a) Foubelo, F.; Gutierrez, A.; Yus, M. Tetrahedron Lett. 1990,
40, 8173. (b) Yus, M. Chem. Soc. Rev. 1996, 155.
Diphenyl sulfide (Table 2, entry 1). Purification by
column chromatography on silica gel (eluent: hexane)
gave a colorless liquid in 95% yield, spectrally identical
with an authentic sample. 1H NMR (200 MHz, CDCl3)
d (ppm) 7.24–7.38 (m). 13C NMR (50 MHz, CDCl3)
d (ppm) 127.07 (2C), 129.22 (4C), 131.18 (4C), 131.23
(2C).
6. Farhat, S.; Marek, I. Angew. Chem. Int. Ed. 2002, 41, 1410.
7. Titanium and Zirconium in Organic Synthesis. Marek, I., Ed.;
Wiley-VCH: Weinheim, 2002.
8. Rousset, C. J.; Swanson, D. R.; Lamaty, F.; Negishi, E.
Tetrahedron Lett. 1989, 30, 5105.
9. For reviews, see (a) Negishi, E.; Takahashi, T. Bull. Chem.
Soc. Jpn 1988, 71, 755. (b) Negishi, E.; Takahashi, T. Acc.
Chem. Res. 1994, 27, 124. (c) Negishi, E.; Kondakov, D. Y.
Chem. Soc. Rev. 1996, 26, 417.
3-Phenylthio-3-hexene (Table 2, entry 4). Purification by
column chromatography on silica gel (eluent: hexane) gave
colorless liquid in 85% yield. 1H NMR (200 MHz, CDCl3) d
(ppm) 0.97–1.06 (m, 6H), 2.06–2.30 (m, 4H), 5.81 (t, 1H,
J¼7.32 Hz), 7.13–7.31 (m, 5H).
Dodecyl tolyl sulfide (Table 2, entry 5).57 Purification by
column chromatography on silica gel (eluent: hexane) gave
a colorless liquid in 73% yield. 1H NMR (200 MHz, CDCl3)
d (ppm) 0.87 (t, 3H, J¼6.74 Hz), 1.20–1.63 (m, 20H), 2.30
(s, 3H), 2.77–2.89 (m, 2H), 7.05–7.25 (m, 4H).
10. (a) Ito, H.; Taguchi, T.; Hanzawa, Y. Tetrahedron Lett. 1992,
33, 1295. (b) Hanzawa, Y.; Kiyono, H.; Tanaka, N.; Taguchi,
T. Tetrahedron Lett. 1997, 38, 4615.
11. (a) Ito, H.; Nakamura, T.; Taguchi, T.; Hanzawa, Y.
Tetrahedron Lett. 1992, 33, 3769. (b) Ito, H.; Motoki, Y.;
Taguchi, T.; Hanzawa, Y. J. Am. Chem. Soc. 1993, 115, 8835.
(c) Ito, H.; Ikeuchi, Y.; Taguchi, T.; Hanzawa, Y.; Shiro, M.
J. Am. Chem. Soc. 1994, 116, 5469. (d) Hanzawa, Y.; Kiyono,
H.; Tanaka, N.; Taguchi, T. Tetrahedron Lett. 1997, 38, 4615.

S. Farhat et al. / Tetrahedron 60 (2004) 1329–1337
1337
12. Ito, H.; Taguchi, T.; Hanzawa, Y. Tetrahedron Lett. 1992, 33,
7873.
Chim. Fr. 1985, 772. (c) Baldwin, J. E.; Adlington, R. M.;
Ichikawa, Y.; Kneale, C. J. J. Chem. Soc. Chem. Commun.
1988, 702.
13. (a) Ito, H.; Taguchi, T. Tetrahedron Lett. 1997, 38, 5829. (b)
Sato, A.; Ito, H.; Taguchi, T. J. Org. Chem. 2000, 65, 918. (c)
Ito, H.; Kuroi, H.; Ding, H.; Taguchi, T. J. Am. Chem. Soc.
1998, 120, 6623. (d) Ito, H.; Sato, A.; Taguchi, T. Tetrahedron
Lett. 1999, 40, 3217.
34. (a) Trost, B. M. Bull. Chem. Soc. Jpn 1988, 61, 107. (b)
Backvall, J. E.; Chinchilla, R.; Najera, C.; Yus, M. Chem. Rev.
1998, 98, 2291.
35. (a) Tolman, C. A. J. Am. Chem. Soc. 1972, 94, 2994. (b)
Bingham, D.; Hudson, B.; Webster, B. D. E.; Wells, P. B.
J. Chem. Soc., Dalton Trans. 1974, 1521. (c) Bingham, D.;
Webster, D. E.; Wells, P. B. J. Chem. Soc., Dalton Trans.
1974, 1514.
14. (a) Hanzawa, Y.; Ito, H.; Taguchi, T. Synlett 1995, 299. (b) Ito,
H.; Nakamura, T.; Taguchi, T.; Hanzawa, Y. Tetrahedron
1995, 51, 4507.
15. Ito, H.; Taguchi, T.; Hanzawa, Y. J. Org. Chem. 1993, 58, 774.
16. Takahashi, T.; Kotora, M.; Fischer, R.; Nishihara, Y.;
Nakajima, K. J. Am. Chem. Soc. 1995, 117, 11039.
17. (a) Ichikawa, J.; Fujiwara, M.; Nawata, H.; Okauchi, T.;
Minami, T. Tetrahedron Lett. 1996, 37, 8799. (b) Fujiwara,
M.; Ichikawa, J.; Okauchi, T.; Minami, T. Tetrahedron Lett.
1999, 40, 7261.
36. Akita, M.; Yasuda, H.; Nagasuna, K.; Nakamura, A. Bull.
Chem. Soc. Jpn 1983, 56, 554.
37. (a) Swanson, D. R.; Negishi, E. Organometallics 1991, 10,
825. (b) Maye, J. P.; Negishi, E. Tetrahedron Lett. 1993, 34,
3359. (c) Negishi, E.; Maye, J. P.; Choueiry, D. Tetrahedron
1995, 51, 4447.
18. The only available information was found in a footnote (Ref.
[16]) in which a J value of 19 Hz was described (trans
configuration) for a vinyl zirconium without describing the
stereochemistry of the starting material.
38. Chinkov, N.; Majumbar, S.; Marek, I. J. Am. Chem. Soc. 2002,
124, 10282.
39. Normant, J. F.; Alexakis, A.; Commercon, A.; Cahiez, G.;
Villieras, J. C.R. Acad. Sci. 1974, 279, 763.
19. Takahashi, T.; Fujimoto, T.; Seki, T.; Saburi, M.; Uchida, Y.;
Rousset, C. J.; Negishi, E. J. Chem. Soc. Chem. Commun.
1990, 182.
40. (a) Vermeer, P.; Meijer, J.; Eylander, C. Recl. Trav. Chim.
Pays-Bas 1974, 93, 240. (b) Truce, W. E.; Lusch, J. Org.
Chem. 1974, 39, 3174.
20. Negishi, E.; Choueiry, D.; Nguyen, T. B.; Swanson, D. R.;
Suzuki, N.; Takahashi, T. J. Am. Chem. Soc. 1994, 116, 9751.
21. Liard, A.; Marek, I. J. Org. Chem. 2000, 65, 7218.
22. (a) Mintz, E. A.; Ward, A. S.; Tice, D. S. Organometallics
1985, 4, 1308. (b) Ward, A. S.; Mintz, E. A.; Kramer, M. P.
Organometallics 1988, 7, 8.
41. Julia, M.; Lauron, H.; Stacino, J. P.; Verpeaux, J. N.; Jeannin,
Y.; Dromzee, Y. Tetrahedron 1986, 42, 2475.
42. Hoshi, M.; Shirakawa, K. Chem. Commun. 2002, 2146.
43. (a) Boothe, T.; Finn, R.; Vora, M. J. Labelled Compd.
Radiopharm. 1985, 22, 1109. (b) Chen, D. W.; Ochiai, M.
J. Org. Chem. 1999, 64, 6804.
23. (a) Takahashi, T.; Suzuki, N.; Kageyama, M.; Nitto, Y.;
Saburi, M.; Negishi, E. Chem. Lett. 1991, 1579. (b) Takahashi,
T.; Nitto, Y.; Seki, T.; Saburi, M.; Negishi, E. Chem. Lett.
1990, 2259.
44. Kasai, K.; Kotora, M.; Suzuki, N.; Takahashi, T. J. Soc. Chem.
Commun. 1995, 109.
45. Neumann, H.; Seebach, D. Tetahedron Lett. 1976, 4839.
46. Marek, I.; Lefrancois, J. M.; Normant, J. F. Bull. Soc. Chim.
Fr. 1994, 131, 910.
24. Wipf, P.; Jahn, H. Tetrahedron 1996, 52, 12853.
25. Takahashi, T.; Kotora, M.; Kasai, K.; Suzuki, N. Tetrahedron
Lett. 1994, 35, 5685.
47. Barber, J.; Willis, C.; Whitesides, G. J. Org. Chem. 1979, 44,
3603.
26. (a) Nakamura, E.; Kuwajima, I. J. Am. Chem. Soc. 1984, 106,
3368. (b) Corey, E. J.; Boaz, N. W. Tetrahedron Lett. 1985, 26,
6015. (c) Alexakis, A.; Berlan, J.; Besace, Y. Tetrahedron
Lett. 1986, 27, 214.
48. Cahiez, G.; Avedissian, H. Synthesis 1998, 1199.
49. Ma, S.; Negishi, E. J. Org. Chem. 1977, 62, 784.
50. Itami, K.; Nokami, T.; Ioshida, J. J. Am. Chem. Soc. 2001, 123,
5600.
27. Marek, I.; Normant, J. F. Chem. Rev. 1996, 96, 3241.
28. Mislow, K.; Siegel, J. J. Chem. Soc. 1984, 106, 3319.
29. Carreno, C. M. Chem. Rev. 1995, 95, 1717.
30. Holton, R. A.; Crouse, D. J.; Williams, A. D.; Kennedy, R. M.
J. Org. Chem. 1987, 52, 2317.
51. Baxendale, I.; Lee, A.; Ley, S. Synlett 2002, 516.
52. Yao, C.; Chu, C.; Liu, J. J. Org. Chem. 1998, 63, 719.
53. Lee, K.; Wiemer, D. Tetrahedron Lett. 1993, 34, 2433.
54. Kirmse, W.; Kopannia, S. J. Org. Chem. 1998, 63, 1178.
55. Wang, Q.; Deredas, D.; Huynh, C.; Schlisser, M. Chem. A Eur.
J. 2003, 9, 570.
31. Howard, W. A.; Parkin, G. J. Am. Chem. Soc. 1994, 116, 606.
32. Cuvigny, T.; Herve du Penhoat, C.; Julia, M. Tetrahedron Lett.
1983, 24, 4311.
56. Grasa, G.; Moore, Z.; Martin, K.; Stevens, E.; Nolan, S.;
Paquet, V.; Lebel, H. J. Organomet. Chem. 2002, 658, 126.
57. Furman, I.; Whitten, D.; Penner, T.; Ulman, A.; Geiger, H.
Langmuir 1994, 10, 837.
33. (a) Fabre, J. L.; Julia, M.; Verpeaux, J. N. Bull. Soc. Chim. Fr.
1985, 762. (b) Fabre, J. L.; Julia, M.; Verpeaux, J. N. Bull. Soc.