α- and β-stannyl trifluoromethylbutenoates: Regioselective preparation and use in copper(I)-catalyzed allylation and propargylation reactions

Article abstract of DOI:10.1002/adsc.200900828

The palladium-free hydrostannylation of ethyl 4,4,4-trifluorobutynoate 1 with tributyltin hydride at room temperature is highly regio- and stereoselective, providing good yields of β-trifluoromethyl (Z)-a- or (Z)-β-stannylacrylates 2. Vinylstannanes 2 undergo a copper(I)-catalyzed coupling reactions with allylic or propargylic bromides leading selectively to good yields of the corresponding allylated or propargylated products without allylic or allenic transposition.

Full text of DOI:10.1002/adsc.200900828

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DOI: 10.1002/adsc.200900828
a- and b-Stannyl Trifluoromethylbutenoates: Regioselective
Preparation and Use in Copper(I)-Catalyzed Allylation and
Propargylation Reactions
Yvan Carcenac,a Khalid Zine,a Jean-Claude Kizirian,a Jꢀrꢁme Thibonnet,a
Alain DuchÞne,a Jean-Luc Parrain,b,* and Mohamed Abarbria,*
a
Laboratoire de Physicochimie des Matꢀriaux et de Biomolꢀcules, EA 4244, Facultꢀ des Sciences de Tours, Parc de
Grandmont, 37200 Tours, France
Fax : (+33)-(0)247-367-073; e-mail: mohamed.abarbri@univ-tours.fr
Institut des Sciences Molꢀculaires de Marseille, iSm2 UMR CNRS 6263, Campus Scientifique de Saint Jꢀrꢁme,
b
Aix-Marseille Universitꢀ, 13397 Marseille, France
Fax : (+33)-(0)491-289-126; e-mail: jl.parrain@univ-cezanne.fr
Received: November 28, 2009; Published online: April 7, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200900828.
Abstract: The palladium-free hydrostannylation of
ethyl 4,4,4-trifluorobutynoate 1 with tributyltin hy-
dride at room temperature is highly regio- and ste-
reoselective, providing good yields of b-trifluoro-
methyl (Z)-a- or (Z)-b-stannylacrylates 2. Vinyl-
stannanes 2 undergo a copper(I)-catalyzed coupling
reactions with allylic or propargylic bromides lead-
ing selectively to good yields of the corresponding
allylated or propargylated products without allylic
or allenic transposition.
species were prepared and alkylated with electro-
philes specific to the carbon attached to the metal. Vi-
nylstannanes bearing a perfluoroalkyl group also
opened the way for the preparation of these types of
compounds.[10] In this context, the preparation of new
vinyltin reagents bearing perfluorylalkyl group and
another functionalities is highly desirable.
However, to the best of our knowledge, no free pal-
ladium-catalyzed hydrostannylation of 1 has yet been
described. We recently reported the preparation of
(Z)-ethyl 3-perfluoroalkyl-3-magnesiated crotonates
from (Z)-ethyl 3-perfluoroalkyl-3-iodoenoates by an
iodine-magnesium exchange reaction with isopropyl-
magnesium bromide.[11] These new reagents reacted
with a wide range of electrophiles, leading to poly-
functional products bearing a fluoroalkyl group.[12] As
a continuation of our previous research on methods
for preparing various derivatives bearing the trifluoro-
Keywords: allylation; copper(I)-catalyzed cross cou-
pling; ethyl trifluorobutynoate; propargylation; re-
gioselective hydrostannylation
Organic compounds containing one or more fluorine methyl group, we report here the first highly regiose-
atoms have received increasing attention in medicinal, lective free-metal hydrostannylation of ethyl 4,4,4-tri-
agricultural and material sciences.[1] They often confer fluorobutynoate 1[13] without any additive, followed
significant changes in their chemical and physical by copper(I)-catalyzed allylation and propargylation.
properties. The introduction of
a
fluorine or
We investigated the hydrostannation of 1 to pre-
perfluoroalkyl group into organic compounds often pare a or b-stannylvinyl esters 2. We initially focused
ACHTUNGTRENNUNG
dramatically changes their structure, stability, reactivi- on the selection of an efficient solvent and a suitable
ty and biological activity.[2] The development of a temperature for a highly regio- and stereoselective
simple method to obtain perfluoroalkylated building hydrostannylation reaction of alkynoate 1 with n-
blocks for their subsequent utilization in the synthesis Bu3SnH (Scheme 1 and Table 1). A number of sol-
of Rf-containing compounds is therefore essential to vents were tested and the results are summarized in
organofluorine chemistry.[3,4]
Table 1.
As shown in Table 1, the hydrostannation of 1 was
Perfluoroalkylated vinylmetals constitute an impor-
tant class of these building blocks. Perfluoroalkylated very dependent on the choice of solvent. Thus, using
vinylmetals have been demonstrated in which lithi- ether, dichloromethane or toluene as solvents, a mix-
um,[5] magnesium,[6] zinc,[7] silver[8] and palladium[9] ture of a- and b-regioisomers was obtained (entries 3,
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Yvan Carcenac et al.
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of this vinyl iodide are in full agreement with the
spectral values reported in the literature.[15]
The mechanism and the solvent effects observed
are not very clear at this time. Nevertheless, some of
our unpublished experimental results have proved
that the alkyne 1, bearing two electron-withdrawing
groups, exhibits unusual reactivity. An ionic mecha-
nism cannot explain the regioselectivity observed in
methanol. Furthermore, if we compare the addition of
Bu3SnH to ethyl propiolate the opposite regioisomer
should be observed, as for the alkynyl triflones de-
scribed by Fuchs et al.[16] Ethyl trifluorobutynoate 1
spontaneously reacted with tetrahydrofuran through a
radical mechanism and without a radical initiator to
provide the THF adduct. In fact, the extremely elec-
tron-deficient sp-hybridized alkyne moiety engenders
efficient trapping of all radical intermediates. Indeed,
we believe that small amounts of dioxygen certainly
serve to initiate the process. Nevertheless, attempts
conducted in a controlled atmosphere (glove box)
and in the dark led to identical results. The stability
of the two radicals possibly explains the regioselectivi-
ty of the reaction.
Scheme 1. Hydrostannation of ethyl 4,4,4-trifluorobutynoate
1.
Table 1. Hydrostannation of ethyl 4,4,4-trifluorobutynoate 1
in various solvents and temperatures.
Entry Solvent
T
[8C]
a/b
(Z)-b/ (Z)-a/ Yield
(E)-b
(E)-a
[%][a]
1
2
3
4
5
6
7
8
hexane
hexane
Et2O
DCM
CH3CN 20
MeOH
MeOH
toluene 20
À40
20
20
>5/95 75/25
>5/95 75/25
–
–
97
98
98
97
99
96
97
96
30/70
80/20
95/5
100/0
100/0
–
100/0
100/0
85/15
85/15
85/15
100/0
20
À40 100/0
–
20
95/5
–
40/60
100/0
[a]
Combined yield of a- and b-regioisomers related to
Bu3SnH.
Theoretical calculations are currently being tested
in order to propose a realistic mechanism describing
the solvent effect. Our preliminary results indicate
4 and 8, Table 1). Very interestingly, the hydrostanna- that in the presence of methanol there would be a hy-
tion of 1 in hexane provided the b-stannylated prod- drogen bond with the carbonyl of ester of 1 (2 kcal/
uct with high regioselectivity (>95%) and excellent mol more stable). The addition of a tributylstannyl
yield (>97%) (entries 1 and 2, Table 1).
radical to this complex would thus provide two radi-
The observed stereoselectivity was in favour of the cals in the a- and b-positions (Scheme 2). We found
(Z)-isomer (Z-2b/E-2b=75/25). Surprisingly, total a- that the radical in the b-position was more stable that
regioselectivity of the hydrostannylation of 1 at the radical in the a-position by 3–4 kcalmolÀ1. In
À408C was observed in MeOH, providing a-tributyl- hexane and in the absence of methanol, the radical in
stannylacrylate 2a as the sole regioisomer in a nearly the a-position is more stable than the radical in the b-
quantitative yield (entry 6, Table 1). In this case, the position (1.9 kcal/mol).
stereoselectivity was also largely in favour of the (Z)-
isomer (Z-2a/E-2a=85/15). Temperature had no sig- vinyltin reagents 2 using a known coupling reaction
nificant effect on the regioselectivity. Similarly, the re- procedure. Although Stille reported that Pd(PPh3)4
Attention was next directed to the reactivity of the
ACHTUNGTRENNUNG
action of 1 with n-Bu3SnH in acetonitrile selectively alone catalyzed the coupling reaction of vinylstan-
afforded the corresponding (Z)-2a product, together nanes and allyl bromides,[17] no coupling reaction be-
with a small amount of b-isomer (<5%) (entry 5, tween 2 and allyl bromides was observed using these
Table 1). It should be noted that in all cases, hydro- experimental procedures. In contrast, on the basis of
stannylation of 1 by Bu3SnH was performed without transmetallation from the organotin compound to the
using a radical initiator or a transition metal catalyst. organocopper intermediate,[10a,18] we investigated a
These results suggest that the ratio of a:b adducts palladium-free cross-coupling of vinylstannane 2b
depends very strongly of the nature of the solvent. with allyl bromide in the presence of a catalytic
The regioselectivity of vinylstannanes 2 was deduced amount of CuI (10 mol%). A very clean reaction was
without ambiguity from NMR data, especially from
the chemical shifts and JH,F coupling patterns. The Z
stereochemistry of 2a and 2b was assigned taking into
3
account that the JSn,H coupling constant observed in
1
the H NMR spectra was over 70 Hz, which indicates
À À À
the existence of trans H C C Sn linkages in these
compounds.[14] Moreover, an iododestannylation reac-
tion of 2b provided the corresponding vinyl iodide
1
with the Z configuration in which the H NMR values Scheme 2. Molecular structures of expected intermediates.
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Adv. Synth. Catal. 2010, 352, 949 – 954

a- and b-Stannyl Trifluoromethylbutenoates: Regioselective Preparation and Use
Scheme 3. Copper(I)-catalyzed allylation reaction.
observed and good yield of the desired product was 2 under the same conditions as described above.
obtained. It was discovered that the reaction was Indeed, compounds (Z)-2a and (Z)-2b underwent re-
complete within 15 h using 10 mol% of CuI at 508C action with propargyl bromides to provide the 2 or 3-
(Scheme 3). The use of CuBr instead of CuI provided propargylated products 3l–p with reasonable to good
similar results. To investigate the scope of the copper- yields and with a clean E configuration of the double
allylated reaction, a variety of allyl bromides were bond, demonstrating again that the copper(I) catalyst
tested to react with (Z)-2a and (Z)-2b, and the results coupling reaction occurred with retention of configu-
are summarized in Table 2.
Vinyltin reagents (Z)-2a and (Z)-2b reacted homocoupling or allenic product was detected.
smoothly in the presence of a catalytic amount of a Propargyl bromides substituted in the terminal po-
ration (Scheme 4 and Table 2, entries 12–16) and no
copper(I) salt with a range of allylic bromides, leading sition were used, and they reacted well with (Z)-2b
to the expected allylated products 3a–k with excellent and (Z)-2a, providing the expected products 3m–o
yields. Interestingly, we found that the use of an equi- (entries 13–15, Table 2). The presence of a trimethyl-
molar amount of copper salt led to moderate yields of silyl group as substituent in the terminal alkyne was
coupling products (<60%). No coupling reaction was well tolerated (entry 13, Table 2).
observed in the absence of Cu(I) catalyst, and the
To the best of our knowledge, there is no report in
starting material was integrally recovered. Equally, no the literature on the reactions of vinyltin reagents
homocoupling product (dienes) was observed under with propargyl halides. A plausible mechanism is pro-
the conditions employed.[18d]
posed for the copper(I)-catalyzed coupling reaction
In the case of 3a–k, the coupling reaction occurred and would proceed as follows. Copper(I) iodide
with retention of configuration of the C(2)=C(3) would transmetallate the vinyltin reagent (Z)-2,[10a,17]
double bonds of 2 and the starting allyl bromides. leading to a vinylcopper species, which then would
These results indicated that the presumed intermedi- react with allylic or propargylic bromide to generate a
ate copper reagent formed after catalytic transmetal- copperACHTUNTRGNEUNG(III) intermediate. Finally, via a reductive elim-
lation of vinyltin reagents with copper iodide was con- ination step, the expected diene or enyne 3 would be
figurationally stable and reacted stereoselectively obtained giving the Cu(I) active species.
with allylic bromides substrates. The (Z)-2a- and (Z)-
2b-derivatives were allowed to react with crotyl bro-
mide under similar conditions, and the reaction pro-
duced a cross-coupled product without allylic transpo-
sition, and the configuration of the starting reagent
was conserved (entries 4 and 10, Table 2). Interesting-
ly, geranyl bromide also reacted with (Z)-2a and (Z)-
2b affording the expected trifluorotrienes 3f and 3k in
good yields and with retention of the olefinic configu-
rations (entries 6 and 11, Table 2), thus providing a
new, efficient entry to this important class of com-
pounds.
To investigate the scope and limitations of the
copper-catalyzed reaction, attention was next directed
to the copper (I)-catalyzed propargylation reaction of (Z)-2b.
Scheme 4. Copper(I)-catalyzed propargylation of (Z)-2a and
Adv. Synth. Catal. 2010, 352, 949 – 954
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951

Yvan Carcenac et al.
Yield [%]
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Table 2. Copper (I)-catalyzed allylation and propargylation of (Z)-2a and (Z)-2b.
Entry
2
Allyl/Propargyl Bromides
Product 3
1
(Z)-2b
3a
92
2
3
4
5
(Z)-2b
(Z)-2b
(Z)-2b
(Z)-2b
3b
3c
3d
3e
91
68
75[a]
66
6
(Z)-2b
(Z)-2a
(Z)-2a
(Z)-2a
(Z)-2a
(Z)-2a
(Z)-2b
(Z)-2b
(Z)-2b
(Z)-2a
(Z)-2a
3f
3g
3h
3i
77
7
70
8
84
9
58
10
11
12
13
14
15
3j
74[b]
73
3k
3l
55[c]
65
3m
3n
3o
3p
62
78
16
67
[a]
(E)-5/(Z)-5=90/10.
(E)-4/(Z)-4=90/10.
20 mol% of CuI were used.
[b]
[c]
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Adv. Synth. Catal. 2010, 352, 949 – 954

a- and b-Stannyl Trifluoromethylbutenoates: Regioselective Preparation and Use
(10 mol%) in DMF (8 mL), and the resulting suspension
In summary, we have investigated the transition
metal-free catalyzed hydrostannylation of ethyl 4,4,4-
trifluorobut-2-ynoate. The hydrostannylation took
place smoothly in the absence of additive, providing
regioselectively high yields of the corresponding a- or
b-stannylated alkenoates depending on the nature of
the solvent used. These new reagents readily undergo
copper(I)-catalyzed coupling reactions with allylic
and propargylic bromides to provide good yields of
the corresponding allyl- or propargylacrylate esters
bearing a b-trifluoromethyl group. This method pro-
vided a new efficient entry to this important class of
compounds. Investigations into the synthesis of new
acrylic esters containing a trifluoromethyl group using
other electrophiles are currently in progress
was stirred for 3 h at 508C. Ethyl acetate (10 mL) and 1M
aqueous KF (5 mL) were added, and the reaction mixture
was stirred for two more hours. The mixture was then ex-
tracted three times with ether, and the combined organic
layers were washed with saturated aqueous NH4Cl and
brine, dried over anhydrous MgSO4 and concentrated under
reduced pressure. The residue was purified by silica gel
column chromatography, using petroleum ether/diethyl
ether (100:0 to 98:2) as eluent.
(E)-Ethyl
3-trifluoromethyl-6-methylhepta-2,5-dienoate
(3c): 68% isolated yield; colourless oil; 1H NMR (CDCl3,
200 MHz): d=6.31 (s, 1H), 5.09 (t, J=6.3 Hz, 1H), 4.24 (q,
J=7.2 Hz, 2H), 3.42 (d, J=7.0 Hz, 2H), 1.71 (s, 3H), 1.68
(s, 3H), 1.31 (t, J=7.1 Hz, 3H); 13C NMR (CDCl3,
50 MHz): d=164.6, 145.0 (q, JC,F =27.8 Hz), 134.6, 123.3 (q,
J
J
C,F =273.6 Hz), 121.9 (q, JC,F =6.0 Hz), 118.7, 60.9, 25.7 (q,
C,F =3.6 Hz), 25.5, 17.7, 14.0; 19F NMR (CDCl3, 376 MHz):
d=À68.9; IR (neat): n=2983, 2932, 1730, 1676, 1308, 1203,
1170: MS (EI): m/z (%)=236 (63), 191 (62), 188 (67), 165
(100), 93 (87); HR-MS (EI): m/z=236.1020, calcd. for
C11H15F3O2 (M+): 236.1024.
Experimental Section
General Procedure for the Synthesis of Stannylvinyl
(E)-Ethyl 3-trifluoromethylhex-2-en-5-ynoate (3l): 63%
isolated yield; colourless oil; 1H NMR (CDCl3, 200 MHz):
d=6.42 (s, 1H), 4.27 (q, J=7.2 Hz, 2H), 3.67 (d, J=2.6 Hz,
2H), 2.03 (t, J=2.6 Hz, 1H), 1.33 (t, J=7.2 Hz, 3H);
Esters 2a, b
n-Bu3SnH (790 mg, 2.71 mmol) was slowly added to a solu-
tion of ethyl 4,4,4-trifluorobutynoate (500 mg, 3.01 mmol) in
20 mL of solvent, at room temperature. The mixture was
stirred for 2 h and the solvent was then evaporated under
reduced pressure. The residue was purified by silica gel
column chromatography using petroleum ether as an eluent,
and products (Z)-2a, b were isolated as colourless oils.
13C NMR (CDCl3, 50 MHz): d=164.0, 139.8 (q, JC,F
=
29.8 Hz), 123.8 (q, JC,F =5.5 Hz), 122.7 (q, JC,F =273.5 Hz),
77.9, 69.2, 61.4, 15.8, 14.0; 19F NMR (CDCl3, 470 MHz): d=
À68.7; IR (neat): n=3314, 2961, 2928, 2128, 1730, 1677,
1377, 1186 cmÀ1; MS (EI): m/z (%)=178 (100), 161 (28),
133 (29), 113 (21), 102 (26); HR-MS (EI): m/z=206.0558,
calcd. for C9H8F3O2 (M+): 206.0555.
(Z)-Ethyl
4,4,4-trifluoro-2-tributylstannyl-but-2-enoate
(2a): 82% isolated yield; colourless oil; 1H NMR (CDCl3,
200 MHz): d=6.85 (q, JH,F =7.6 Hz, JSn,H =72 Hz, 1H), 4.22
(q, J=7.1 Hz, 2H), 1.60–0.80 (m, 30H); 13C NMR (CDCl3,
50 MHz): d=171.1, 151.7, (q, JC,F =6.7 Hz), 134.8 (q, JC,F
=
=
C,F =271.0 Hz), 61.4, 28.7 (2JSn,C
Acknowledgements
34.6 Hz), 123.0 (q,
J
20.0 Hz), 27.1 (3JSn,C =64.3 Hz), 14.2, 13.5, 11.7 (1JSn,C =357–
19F NMR
(CDCl3,
376 MHz):
d=À62.4;
We thank MESR and CNRS for financial support.
348 Hz);
119Sn NMR (CDCl3, 149 MHz): d=À26.2; IR (neat): n=
2958, 2924, 2873, 2856, 1716, 1465, 1278, 1231, 1145 cmÀ1
;
MS (EI): m/z (%)=401 (M+À57, 100), 253 (38), 177 (38),
101 (43), 57 (42); HR-MS (EI): m/z=458.1460, calcd. for
C18H33F3O2Sn (M+): 458.1455.
References
[1] a) R. Filler, Y. Kobayashi, Biomedicinal Aspects of Flu-
orine Chemistry, Kodansha, Tokyo, 1982; b) M. Hud-
licky, Chemistry of Organo Fluorine Compounds, Ellis
Horwood, New York, 1976.
[2] a) B. E. Smart, Chem. Rev. 1996, 96, 1555–1555; b) G.
Resnati, V. A. Soloshonok, Tetrahedron 1996, 52, 1–1;
c) Organofluorine Chemistry: Principle and Commer-
cial Applications, (Eds.: R. E. Banks, B. E. Smart, J. C.
Tatlow), Plenum Press, New York, 1994.
[3] a) M. Prakesh, D. Grꢀe, S. Chandrasekhar, R. Grꢀe,
Eur. J. Org. Chem. 2005, 1221–1232; b) K. Mikami, Y.
Itoh, M. Yamanaka, Chem. Rev. 2004, 104, 1–16.
[4] a) D. J. Burton, Organofluorine chemistry: techniques
and synthons, (Ed.: R. D. Chambers), Springer Verlag,
Berlin, Heidelberg, 1997; b) J. H. Steenis, A. Gen, J.
Chem. Soc. Perkin Trans. 1 2002, 2117–2133; c) G. K. S.
Prakash, A. K. Yudin, Chem. Rev. 1997, 97, 757–786;
d) I. Ojima, Chem. Rev. 1988, 88, 1011–1030.
(Z)-Ethyl
4,4,4-trifluoro-3-tributylstannylbut-2-enoate
(2b): 70% isolated yield; colourless oil; 1H NMR (CDCl3,
200 MHz): d=6.93 (q, JH,F =2.3 Hz, JSn,H =73.0 Hz, 1H),
4.26 (q, J=7.1 Hz, 2H), 1.60–0.85 (m, 30H); 13C NMR
(CDCl3, 50 MHz): d=166.6, 156.7 (q, JC,F =34.5 Hz), 134.3
(q, JC,F =9.5 Hz), 126.6 (q, JC,F =272.9 Hz), 61.4, 28.9 (2JSn,C
=
19.6 Hz), 27.3 (3JSn,C =65 Hz), 14.1, 13.6, 11.8 (1JSn,C =368–
355 Hz);
19F NMR
(CDCl3,
376 MHz):
d=À62.0;
119Sn NMR (CDCl3, 149 MHz): d=À33.0; IR (neat): n=
2958, 2923, 2873, 2855, 1720 cmÀ1; MS (EI): m/z (%)=401
(M+À57, 100), 235 (38), 179 (53), 129 (29), 57 (34); HR-MS
(EI): m/z=458.1459, calcd. for C18H33F3O2Sn (M+): 458.1455
General Procedure for the Cross-Coupling
Allylations and Propargylations
A solution of allyl bromide or propargyl bromide (2 mmol)
in DMF (2 mL) was added to a mixture of (Z)-ethyl 4,4,4-
trifluoro-3-tributylstannylbut-2-enoate (2 mmol) and CuI
[5] a) K. Uneyama, C. Noritake, K. Sadamune, J. Org.
Chem. 1996, 61, 6055–6057; b) H. Watanabe, F. Yan, T.
Adv. Synth. Catal. 2010, 352, 949 – 954
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Yvan Carcenac et al.
COMMUNICATIONS
Sakai, K. Uneyama, J. Org. Chem. 1994, 59, 758–761;
c) H. Watanabe, F. Yamashita, K. Uneyama, Tetrahe-
dron Lett. 1993, 34, 1941–1944; d) P. A. Morken, H.
Lu, A. Nakamura, D. J. Burton, Tetrahedron Lett. 1991,
32, 4271–4274.
Knochel, Angew. Chem. 1998, 110, 1801–1803; Angew.
Chem. Int. Ed. 1998, 37, 1701–1703.
[12] J. Thibonnet, A. DuchÞne, J.-L. Parrain, M. Abarbri, J.
Org. Chem. 2004, 69, 4262–4264.
[13] a) G. Priꢀ, J. Thibonnet, M. Abarbri, A. DuchÞne, J.-L.
Parrain, Synlett 1998, 839–841; b) B. C. Hamper, Org.
Synth. 1991, 70, 246–255.
[6] T. Kobayashi, T. Nakagawa, H. Amii, K. Uneyama,
Org. Lett. 2003, 5, 4297–4300.
[14] a) K. Tatsuta, T. Yamaguchi, Tetrahedron Lett. 2005, 46,
5017–5020; b) M. Delmas, J.-C. Maire, J. Santamaria, J.
Organomet. Chem. 1969, 16, 405–409; c) T. N. Mitchell,
A. Amamria, H. Killing, D. Rutschow, J. Organomet.
Chem. 1983, 241, C45-C47; d) B. L. Chenard, C. M.
Van Zyl, J. Org. Chem. 1986, 51, 3561–3566.
[15] a) G. Priꢀ, M. Abarbri, J. Thibonnet, J.-L. Parrain, A.
DuchÞne, New J. Chem. 2003, 27, 432–441; b) F.
Camps, R. Canela, J. Coll, A. Messeguer, A. Roca, Tet-
rahedron 1978, 34, 2179–2182.
[7] a) C. R. Davis, D. J. Burton, Organozinc Reagents,
(Eds.: P. Knochel, P. Jones), Oxford, 1999, pp 57–76;
b) G.-Q. Shi, X.-H. Huang, F. Hong, J. Org. Chem.
1996, 61, 3200–3204; c) P. A. Morken, D. J. Burton, J.
Org. Chem. 1993, 58, 1167–1172, and references cited
therein.
[8] a) R. E. Banks, R. N. Haszeldine, D. R. Taylor, G.
Webb, Tetrahedron Lett. 1970, 5215–5218; b) W. Miller,
R. H. Snider, R. J. Hummel, J. Am. Chem. Soc. 1969,
91, 6532–6534.
[9] a) T. Fuchikami, A. Yamanouchi, I. Ojima, Synthesis
1984, 766–768; b) T. Fuchikami, A. Yamanouchi,
Chem. Lett. 1984, 1595–1598.
[10] a) Y. Wang, D. J. Burton, Org. Lett. 2006, 8, 1109–1111;
b) Y. Wang, L. Lu, D. J. Burton, J. Org. Chem. 2005, 70,
10743–10746; c) J. H. Chae, T. Konno, M. Kanda, T.
Ishihara, T. Yamanaka, J. Fluorine Chem. 2003, 120,
185–193.
[16] J. Chen, G.-Q. Lin, Z.-M. Wang, H.-Q. Liu, Synlett
2002, 1265–1268.
[17] J. Chen, G.-Q. Lin, Z.-M. Wang, H.-Q. Liu, Synlett
2002, 1265–1268.
[18] a) M. Cai, G. Chen, W. Hao, Synthesis 2007, 1197–
1203; b) E. Piers, J. G. K. Yee, P. L. Gladstone, Org.
Lett. 2000, 2, 481–484; c) E. Piers, E. J. McEachern,
P. A. Burns, Tetrahedron 2000, 56, 2753–2765; d) E.
Piers, J. G. K. Yee, P. L. Gladstone, E. J. McEachern,
Tetrahedron 1998, 54, 10609–10626; e) E. Piers, M. A.
Romero, J. Am. Chem. Soc. 1996, 118, 1215–1216, and
references cited therein.
[11] a) M. Abarbri, J. Thibonnet, L. Bꢀrillon, F. Dehmel, M.
Rottlander, P. Knochel, J. Org. Chem. 2000, 65, 4618–
4634; b) L. Boymond, M. Rottlꢃnder, G. Cahiez, P.
954
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