Solvent free hydrostannation and Stille reactions using ionic liquid supported organotin reagents

Article abstract of DOI:10.1016/j.tet.2013.04.116

Hydrostannation reactions were performed cleanly using ionic liquid supported organotin reagents. These green reducing agents were used both under free radical and palladium-catalyzed conditions. One of the new ionic liquid supported organotin reagents so

Full text of DOI:10.1016/j.tet.2013.04.116

Tetrahedron xxx (2013) 1e5
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Solvent free hydrostannation and Stille reactions using ionic liquid
supported organotin reagents
a
a
b
a,
*
ꢀ
Djibril Faye , Mykhailo Vybornyi , Fabien Boeda , Stephanie Legoupy
a
ꢀ
ꢀ
LUNAM Universite, Universite d’Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 bd Lavoisier, 49045 Angers, France
LUNAM Universite, Universite du Maine, CNRS UMR 6283, IMMM e Institut des Molecules et Materiaux du Mans, Av O. Messiaen, 72085 Le Mans,
b
ꢀ
ꢀ
ꢀ
ꢀ
France
a r t i c l e i n f o
a b s t r a c t
Article history:
Hydrostannation reactions were performed cleanly using ionic liquid supported organotin reagents.
These green reducing agents were used both under free radical and palladium-catalyzed conditions. One
of the new ionic liquid supported organotin reagents so obtained was evaluated successfully in Stille
cross-coupling reactions to give aryl-substituted allylic alcohols in solvent free conditions.
Ó 2013 Published by Elsevier Ltd.
Received 13 February 2013
Received in revised form 22 April 2013
Accepted 24 April 2013
Available online xxx
Keywords:
Hydrostannation
Alkynes
Palladium
Stille reaction
Ionic liquid
1. Introduction
reagents supported on ionic liquid bearing a vinyl moiety. These
compounds were obtained after reaction of a Grignard reagent with
During the past decades, many versatile and efficient synthetic
methods using organotin reagents (Stille coupling, radical re-
actions, allylation reactions.) have emerged as powerful tools for
organic chemists. However, despite such impressive synthetic po-
tential, reactions involving organotin compounds display draw-
backs, such as pollution of products by tin salts and difficulties of
separation at the end of the synthesis. As a result, ongoing efforts
have been devoted to overcome these problems by using solid
phase synthetic methods,1 phosphonium grafted organotins,2 cat-
alytic Stille couplings,3 and other modified organotin reagents.4 As
a part of our ongoing research program on the discovery of po-
tentialities of TSILs (task specific ionic liquids),5 we became in-
terested in investigating the use of organotin reagents supported
on ionic liquids for hydrostannation reaction.
an organotin chloride derivative.5e As it is somehow difficult to
prepare functionalized vinyl Grignard reagents, we report herein
the synthesis of a series of alkenes supported on ionic liquids using
hydrostannation reactions. A preliminary study concerning their
use in Stille cross-coupling reactions is also described in this work.
2. Results and discussion
As an initial assay, hydrostannation reactions under free radical
conditions were investigated using ionic liquid-supported orga-
notin hydride 2. This compound was obtained by reduction of 15c in
presence of sodium borohydride and methanol (Scheme 1).
Vinylstannanes are useful intermediates for organic synthesis.
Among the various methods to obtain vinylstannanes, the most
studied and frequently used one is the addition of a tin hydride
species to an alkyne.6 Following this strategy, Cai et al.7 described
palladium-catalyzed hydrostannation reactions of various alkynes
in ionic liquids. Recently, we reported the synthesis of organotin
Scheme 1. Preparation of organotin hydride supported on ionic liquid.
In a general manner, ionic liquids were isolated with moderate
yields (40e55%) as highlighted in Table 1. The hydrostannation of
phenyl acetylene (Table 1, entry 1) proceeded with no selectivity.
When using propargyl alcohol as substrate (Table 1, entry 2), se-
lectivity was improved in favor of trans-isomer. Unfortunately,
* Corresponding author. Tel.: þ33 2 41735375; fax: þ33 2 41735405; e-mail
address: stephanie.legoupy@univ-angers.fr (S. Legoupy).
0040-4020/$ e see front matter Ó 2013 Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.tet.2013.04.116
Please cite this article in press as: Faye, D.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.04.116

2
D. Faye et al. / Tetrahedron xxx (2013) 1e5
Table 1
Table 3
Hydrostannation reactions under free radical conditions
Palladium-catalyzed hydrostannation reactions
Entry
1
R1
R2
Ratio a/ba
Yield (%)
40
H
H
3a/3b 50:50
Entry
1
R1
R2
Ratio a/ca
Yield (%)
65
2
3
4a/4b 82:18
5a/5b 2:98
42
48
H
H
3a/3c 40:60
2
3
4a/4c 12:88
72
75
4
H
6a/6b 98:2
55
5a
a
Determined by 1H NMR.
4
H
6a/6c 95:5
85
5
6
H
H
7a/7c 5:95
77
50
isomers 3a/3b and 4a/4b could not be separated by silica gel col-
umn chromatography. With a symmetrical alkyne (Table 1, entry 3)
and a sterically demanding alkyne (Table 1, entry 4), one isomer
was mainly obtained, (Z)- and (E)-isomer, respectively.
The reactivity of tin hydride 2 has been evaluated in palladium-
catalyzed hydrostannation reactions with different precatalysts
(3 mol %) under solvent free conditions by using 3-methyl-3-
hydroxybut-1-yne 7 as a benchmark substrate. Results are sum-
marized in Table 2.
8a/8c 62:38
7
H
H
9a/9c 40:60
52
76
8
10a/10c 95:5
Table 2
Precatalyst effect on palladium-catalyzed hydrostannation reactions
a
Determined by 1H NMR.
generation. This species was generated in situ with hyper-
coordinate polymethylhydroxysilane3 (PMHSþfluoride source).
Using our optimized conditions, hydrostannation products were
obtained in moderate to good yields following mild reaction con-
ditions. It should be noted that good regioselectivities were ob-
served with sterically demanding alkynes (Table 3, entries 4 and 8)
leading mainly to one isomer in case of 6a and 10a.
Entry
Precatalyst
Yield (%)
1
2
3
4
5
6
[Pd/C]
d
The influence of the ionic liquid’s counter anion on the hydro-
stannation reaction has been investigated (Scheme 2). It has been
shown that this parameter strongly influences the yield of the re-
action. Indeed, anionic metathesis reactions between bromide and
tetrafluoroborate or hexafluoroantimonate anions have to be ach-
ieved after hydrostannation reaction, otherwise low yields are
obtained (30 and 15%, respectively). This phenomenon is probably
connꢀected to the strength of cationeanion interaction8
[Pd(OAc)2]/2PPh3
[PdCl2]/2PPh3
[Pd(PPh3)4]
18
21
78
85
80
[PdCl2(PPh3)2]
[PdCl2(PPh3)2]a
a
THF was used as co-solvent.
No conversion was observed with Pd/C (Table 2, entry 1). When
using [Pd(OAc)2] or [PdCl2] both with 2 equiv of triphenylphos-
phine (Table 2, entries 2 and 3), the reaction proceeded with only
18e21% conversion. Then, the use of [Pd(PPh3)4] allowed the for-
mation of compound 6a with 78% yield (Table 2, entry 4). In-
terestingly, the highest conversion (85%) was observed when using
[PdCl2(PPh3)2] as precatalyst (Table 2, entry 5). To further optimize
reaction conditions, the influence of a co-solvent was investigated
(Table 2, entry 6). Noteworthy, the use of THF as additive did not
improve the yield.
SbF6 > BF4 > Brꢀ, also confirmed by the 1H chemical shifts of
ꢀ
the proton at C2 position of imidazolium ring.
With these optimized conditions in hand, we decided to in-
vestigate the scope of our catalytic system. Indeed, the hydro-
stannation of a series of alkynes was studied and the results are
depicted in Table 3. We have shown that the palladium-catalyzed
hydrostannation reaction could be done with in situ tin hydride
Scheme 2. Influence of ionic liquid’s counter anion on hydrostannation.
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D. Faye et al. / Tetrahedron xxx (2013) 1e5
3
Finally, we were interested in the reactivity of compound 6a in
Stille cross-coupling reactions. Conditions previously optimized
with brominated substrates5e (130 ꢁC and [Pd(PPh3)4] as pre-
catalyst) were applied (Table 4).
tetramethylstannane. High resolution mass spectra measurements
were recorded on Waters-Micromass GCT Premier spectrometers.
Analytical thin layer chromatography was performed on pre-coated
silica gel 60-F254 plates. The following compounds have been
previously described: 1,5c 15a,9 15b,10 15c,11 15d.12 Compounds 3, 4,
8, and 9 have been isolated as a mixture of regioisomers (NMR data
is provided only for the major product).
Table 4
Stille cross-coupling reactions
4.1.1. General procedure for hydrostannation under radical con-
ditions. To tin hydride 2 (0.494 mg, 1 mmol) in CH3CN (2 mL), the
alkyne substrate (1 mmol) and AIBN (3 mg, 0.019 mmol,
0.01 equiv) were added. After 10 h of reaction at reflux, the mix-
ture was cooled to room temperature and concentrated under
reduced pressure. The residue was purified by silica gel flash
column chromatography (CH2Cl2/MeOH 100/0 to 85/15) to afford
ionic liquids 3e6.
Entry
Aryl bromide
Yield (%)
1
2
15a 81
15b 84
4.1.2. General procedure for precatalyst effect on palladium catalyzed
hydrostannation. To tin hydride 2 (0.494 mg, 1 mmol), the alkyne
substrate (1 mmol) and palladium precatalyst (0.03 mmol) were
added. After 10 h of reaction at room temperature, the solution was
purified by silica gel flash column chromatography (CH2Cl2/MeOH
100/0 to 85/15) to afford ionic liquids 6a.
3
4
15c 67
15d 87
4.1.3. General procedure for palladium catalyzed hydrostannation
with in situ tin hydride generation. To tin chloride 1 (528 mg,
1 mmol) were added 3 M KFaq solution (0.83 mL, 2.5 mmol) and
PMHS (0.15 mL, 2.5 mmol). The resulting solution was allowed to
stir 15mn at room temperature, then the alkyne substrate (1 mmol)
and PdCl2(PPh3)2 (21 mg, 0.03 mmol) were added. After 10 h of
reaction at room temperature, the solution was purified by silica gel
flash column chromatography (CH2Cl2/MeOH 100/0 to 85/15) to
afford ionic liquid 3e10.
At the end of the Stille reaction, desired products 15aed were
isolated with good yields (Table 4, entries 1e4) by simple extraction
with diethylether. As shown in our previous work, the organotin
supported ionic liquid reagent 16 could be recycled without loss of
reactivity.5e
4.1.4. General procedure for anion metathesis. A solution of ionic
liquid 1 or 6a (1.92 mmol) in acetone (25 mL) was stirred with
corresponding salt (1.5 equiv) at room temperature for 24 h. The
reaction mixture was filtered off to remove the insoluble materials.
The acetone was evaporated in vacuo and the product was dried
under reduced pressure to give ionic liquid 11e14.
3. Conclusion
In summary, hydrostannation reactions using ionic liquid-
supported organotin reagents were studied. Both free radical and
palladium-catalyzed conditions have been tested and allowed the
synthesis of eight novel ionic liquid-supported organotin reagents.
The in situ tin hydride generation directly followed by palladium-
catalyzed hydrostannation reaction led to a straightforward ac-
cess to functionalized ionic liquid-supported organotin reagents.
The scope of ionic liquid 6a was evaluated for several Stille cross-
coupling reactions. Overall, the methodologies disclosed in this
paper offer clean synthetic methods to give aryl-substituted allylic
alcohols: no solvent used in both hydrostannation and Stille re-
actions, ease of purification, no tin contamination. Further appli-
cations of organotin reagents supported on ionic liquids are
currently underway in our laboratories and will be disclosed
shortly.
4.1.5. General procedure for Stille cross-coupling reactions. To a so-
lution of ionic liquid 6a (0.173 mmol), Pd(PPh3)4 (3 mol %) and aryl
bromide (0.260 mmol) were added. The mixture was stirred for
24 h at 130 ꢁC. The solution was extracted with diethylether and
concentrated under reduced pressure. The residue was purified by
silica gel column chromatography (CH2Cl2/MeOH 100/0 to 97/3) to
afford aryl-substituted allylic alcohols 15aed.
4.1.6. 1-((Dibutylstannyl)hexyl)-3-ethyl-1H-imidazol-3-ium bromide
(2). To a suspension of NaBH4 (28 mg, 0.75 mmol) in CH2Cl2 (5 mL),
a solution of 1 (132 mg, 0.25 mmol) in mixture of CH2Cl2 (5 mL) and
MeOH (20 m
L) was added slowly at 0 ꢁC. The resulting mixture was
4. Experimental section
4.1. General
stirred for 1 h at room temperature. Water (10 mL) was added to the
reaction mixture, and the aqueous phase was extracted with CH2Cl2
(3ꢂ10 mL). The combined organic phases were then dried over
MgSO4, filtered, and concentrated under reduced pressure to yield
2 (109 mg, 88%) as a yellow viscous oil.
Commercially available reagents and solvents were purified and
dried, when necessary, by standard methods prior to use. 1H
(300 MHz), 13C (75 MHz) NMR spectra were recorded on a Bruker
Avance 300 spectrometer. The compounds studied were measured
in CDCl3 and 1H and 13C chemical shifts, reported in parts per
million, were referred to the central signal of the solvent. 13C NMR
spectra were recorded with complete proton decoupling. The 119Sn
NMR spectra were recorded on a Bruker Avance 400 spectrometer
(149 MHz) and chemical shifts were referred to external
1H NMR (CDCl3):
d
9.97 (s, 1H, CHimidazolium), 7.50 (d, J¼1.9 Hz,
1H, CHimidazolium), 7.35 (d, J¼1.9 Hz, 1H, CHimidazolium), 4.58 (m, 1H,
SneH), 4.36 (q, J¼7.5 Hz, 2H, NeCH2eCH3), 4.26 (t, J¼7.5 Hz, 2H,
NeCH2eCH2), 1.86 (m, 2H, NeCH2eCH2), 1.55 (t, J¼7.5 Hz, 3H,
NeCH2eCH3), 1.21e1.49 (m, 14H, Halkyl), 0.80e0.90 (m, 12H, Halkyl).
13C NMR (CDCl3):
d 136.8, 121.8, 121.7, 53.4, 49.9, 45.1, 33.3, 30.2,
29.7, 27.3, 26.9, 25.7, 15.5, 13.6, 8.1. 119Sn NMR (CDCl3):
d
ꢀ88.4.
HRMS calcd for C19H39N2Sn 415.2135 [MꢀBr]þ; found 415.2132.
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4
D. Faye et al. / Tetrahedron xxx (2013) 1e5
4.1.7. 1-(6-(Dibutyl(styryl)stannyl)hexyl)-3-ethyl-1H-imidazol-3-
ium bromide (3c). 1H NMR (CDCl3):
10.49 (s, 1H, CHimidazolium),
CHimidazolium), 7.31 (m, 2H, CHpyridine), 7.23e6.98 (m, 2H, CHalkene),
4.42 (q, J¼7.3 Hz, 2H, NeCH2eCH3), 4.27 (t, J¼7.5 Hz, 2H,
NeCH2eCH2), 1.99e1.93 (m, 2H, NeCH2eCH2), 1.68 (t, J¼7.3 Hz, 3H,
NeCH2eCH3), 1.56e1.48 (m, 5H, Halkyl), 1.40e1.27 (m, 9H, Halkyl),
d
7.56e7.40 (m, 2H, CHimidazolium), 7.37e7.24 (m, 3H, CHarom),
7.23e7.13 (m, 2H, CHarom), 6.04 (d, J¼2.5 Hz, 1H, CHalkene), 5.42 (d,
J¼2.5 Hz, 1H, CHalkene), 4.44 (q, J¼7.3 Hz, 2H, NeCH2eCH3), 4.30 (t,
J¼7.2 Hz, 2H, NeCH2eCH2), 1.91e1.79 (m, 2H, NeCH2eCH2), 1.61 (t,
J¼7.3 Hz, 3H, NeCH2eCH3), 1.55e1.24 (m,14H, Halkyl),1.05e0.78 (m,
0.95e0.79 (m, 12H, Halkyl). 13C NMR (CDCl3):
d
149.3, 148.0, 136.7,
135.6, 122.2, 121.4, 121.0, 117.9, 50.2, 45.4, 33.6, 30.3, 27.4, 25.8, 25.7,
15.6, 13.8, 10.8, 9.0. 119Sn NMR (CDCl3):
C
d
ꢀ44.4. HRMS calcd for
12H, Halkyl). 13C NMR (CDCl3):
d
154.4, 146.3, 137.3, 132.1, 128.4,
26H44N3Sn 518.2562 [MꢀBr]þ; found 518.2571.
128.2, 128.0, 127.2, 126.9, 121.6, 53.5, 50.1, 45.3, 33.6, 30.3, 29.1, 27.6,
27.3, 26.6, 25.1, 15.7, 13.8, 10.9. 119Sn NMR (CDCl3):
d
ꢀ38.5. HRMS
4.1.13. 1-(6-(Dibutyl(pent-1-en-1-yl)stannyl)hexyl)-3-ethyl-1H-imi-
dazol-3-ium bromide (9c). 1H NMR (CDCl3):
10.37 (s, 1H, CHimida-
calcd for C27H45N2Sn 517.2605 [MꢀBr]þ; found 517.2578.
d
zolium), 7.63 (m, 1H, CHimidazolium), 7.41 (m, 1H, CHimidazolium),
5.76e5.96 (m, 2H, CHalkene), 4.42 (q, J¼7.3 Hz, 2H, NeCH2eCH3),
4.30 (t, J¼7.5 Hz, 2H, NeCH2eCH2), 2.07 (m, 2H, ]CeCH2), 1.88 (m,
2H, NeCH2eCH2), 1.58 (t, J¼7.3 Hz, 3H, NeCH2eCH3), 1.51e1.23 (m,
4.1.8. 1-(6-(Dibutyl(3-hydroxyprop-1-en-1-yl)stannyl)hexyl)-3-
ethyl-1H-imidazol-3-ium (4c). 1H NMR (CDCl3):
d 10.22 (s, 1H, CHi-
midazolium), 7.52 (s, 1H, CHimidazolium), 7.45 (s, 1H, CHimidazolium),
5.89e5.87 (m, 1H, CHalkene), 5.18e5.22 (m, 1H, CHalkene), 4.41 (q,
J¼7.3 Hz, 2H, NeCH2eCH3), 4.33e4.26 (m, 4H, NeCH2eCH2 and
CH2eOH), 2.99 (s, 1H, OH), 1.94e1.86 (m, 2H, NeCH2eCH2), 1.58 (t,
J¼7.3 Hz, 3H, NeCH2eCH3), 1.55e1.41 (m, 6H, Halkyl), 1.39e1.23 (m,
16H, Halkyl), 0.88e0.79 (m, 15H, Halkyl). 13C NMR (CDCl3):
d 149.8,
136.9, 132.0, 128.5, 122.0, 45.3, 39.9, 29.0, 27.3, 25.9, 22.0, 13.7, 9.4.
119Sn NMR (CDCl3):
d
ꢀ50.7. HRMS calcd for C24H47N2Sn 483.2766
[MꢀBr]þ; found 483.2798.
10H, Halkyl), 0.96e0.84 (m, 10H, Halkyl). 13C NMR (CDCl3):
d 155.0,
136.7, 132.0, 128.6, 122.7, 122.0, 68.9, 50.1, 45.3, 33.2, 30.0, 29.1, 27.4,
4.1.14. (E)-1-((Dibutyl(3,3-dimethylbut-1-en-1-yl)stannyl)hexyl)-3-
26.5, 25.5,15.6,13.7, 9.4. 119Sn NMR (CDCl3):
d
ꢀ47.4. HRMS calcd for
ethyl-1H-imidazol-3-ium bromide (10a). 1H NMR (CDCl3):
d 10.67 (s,
C
22H43N2OSn 471.2397 [MꢀBr]þ; found 471.2358.
1H, CHimidazolium), 7.34 (s, 1H, CHimidazolium), 7.24 (s, 1H, CHimidazo-
lium), 5.95 (d, J¼19.3 Hz, 1H, CHalkene), 5.75 (d, J¼19.3 Hz, 1H, CHal-
kene), 4.45 (q, J¼7.3 Hz, 2H, NeCH2eCH3), 4.35 (t, J¼7.5 Hz, 2H,
NeCH2eCH2), 2.01e1.84 (m, 2H, NeCH2eCH2), 1.79e1.65 (m, 6H,
4.1.9. (E)-1-((Dibutyl(1,2-diphenylvinyl)stannyl)methyl)-3-ethyl-1H-
imidazol-3-ium bromide (5a). 1H NMR (CDCl3):
10.48 (s, 1H, CHi-
d
midazolium), 7.64 (s, 1H, CHimidazolium), 7.38 (s, 1H, CHimidazolium), 7.25
(m, 2H, CHarom), 7.13e7.05 (m, 4H, CHarom), 7.00e6.95 (m, 4H,
CHarom), 6.64 (s, 1H, CHalkene), 4.42 (q, J¼7.3 Hz, 2H, NeCH2eCH3),
4.28 (t, J¼7.5 Hz, 2H, NeCH2eCH2), 1.85 (m, 2H, NeCH2eCH2), 1.58
(t, J¼7.3 Hz, 3H, NeCH2eCH3), 1.51e1.40 (m, 6H, Halkyl), 1.34e1.23
H
alkyl), 1.62 (t, J¼7.3 Hz, 3H, NeCH2eCH3), 1.52e1.22 (m, 14H, Halkyl),
1.01e0.80 (m, 15H, Halkyl). 13C NMR (CDCl3):
159.9, 136.1, 130.7,
121.9, 121.7, 119.9, 49.8, 45.2, 32, 29.6, 28.2, 26.8, 25.2, 24.9, 21.9,
d
21.4, 15.5. 119Sn NMR (CDCl3):
d
ꢀ46.4. HRMS calcd for C25H49N2Sn:
497.2918 [MꢀBr]þ; found 497.2964.
(m, 8H, Halkyl), 0.98e0.84 (m, 12H, Halkyl). 13C NMR (CDCl3):
d 149.7,
145.5, 138.1, 136.7, 137.3, 129.0,128.5,127.7, 126.5,126.1, 124.9, 122.7,
121.6, 49.9, 45.1, 33.6, 30.2, 28.8, 27.1, 26.9, 26.4, 25.6, 25.6, 13.5, 9.9.
4.1.15. 1-{6-[Dibutylchlorostannyl]hexyl}-3-ethyl-1H-imidazol-3-
ium tetrafluoroborate (11). 1H NMR (CDCl3):
d 8.85 (s, 1H, CHimida-
119Sn NMR (CDCl3):
d
ꢀ34.8. HRMS calcd for C33H49N2Sn 593.2918
zolium), 7.41 (s, 1H, CHimidazolium), 7.37 (s, 1H, CHimidazolium), 4.27 (q,
J¼7.2 Hz, 2H, NeCH2eCH3), 4.20 (t, J¼7.2 Hz, 2H, NeCH2eCH2), 1.89
(m, 2H, NeCH2eCH2), 1.76e1.52 (m, 9H, Halkyl), 1.46e1.22 (m, 14H,
[MꢀBr]þ; found 593.2910.
4.1.10. (E)-1-((Dibutyl(3-hydroxy-3-methylbut-1-en-1-yl)stannyl)
H
alkyl), 0.91 (t, J¼7.3 Hz, 6H, CH3butyl). 13C NMR (CDCl3):
d 135.1,
hexyl)-3-ethyl-1H-imidazol-3-ium bromide (6a). 1H NMR (CDCl3):
122.2, 121.9, 50.1, 45.4, 31.6, 29.6, 28.2, 26.4, 25.1, 24.3, 21.7, 21.2,
d
10.46 (s, 1H, CHimidazolium), 7.69 (s, 1H, CHimidazolium), 7.53 (s, 1H,
15.1, 13.7. 119Sn NMR (CDCl3):
d 149.7. HRMS calcd for C19H38N2Sn
CHimidazolium), 6.14 (d, J¼19.0 Hz, 1H, CHalkene), 6.07 (d, J¼19.0 Hz,
1H, CHalkene), 4.45 (q, J¼7.4 Hz, 2H, NeCH2eCH3), 4.34 (t, J¼7.5 Hz,
2H, NeCH2eCH2), 2.29 (s, 1H, OH), 1.92 (m, 2H, NeCH2eCH2), 1.60
(t, J¼7.4 Hz, 3H, NeCH2eCH3), 1.56e1.24 (m, 20H, Halkyl), 0.95 (m,
449.1746 [MꢀBF4]þ; found 449.1732.
4.1.16. 1-{6-[Dibutylchlorostannyl]hexyl}-3-ethyl-1H-imidazol-3-
ium hexafluoroantimonate (12). 1H NMR (CDCl3):
d 8.63 (s, 1H,
12H, Halkyl). 13C NMR (CDCl3):
d
165.7, 155.1, 136.7, 122.1, 121.9, 49.9,
CHimidazolium), 7.35 (s, 2H, CHimidazolium), 4.21 (q, J¼7.6, 2H,
NeCH2eCH3), 4.19 (t, J¼7.2 Hz, 2H, NeCH2eCH2), 2.01e1.83 (m, 2H,
NeCH2eCH2), 1.8e1.65 (m, 6H, Halkyl), 1.62 (t, J¼7.6 Hz, 3H,
NeCH2eCH3), 1.50e1.30 (m, 14H, Halkyl), 0.9 (t, J¼7.2 Hz, 6H,
45.2, 32,0, 28.2, 26.8, 25.2, 24.9, 21.4, 15.7, 13.7, 9.4. 119Sn NMR
(CDCl3):
d
ꢀ45.9. HRMS calcd for C24H47N2OSn 499.2710 [MꢀBr]þ;
found 499.2732.
CH3butyl). 13C NMR (CDCl3):
d 135.0, 120.9, 120.1, 50.1, 45.2, 32, 29.2,
4.1.11. 1-(6-(Dibutyl(4-cyanostyryl)stannyl)hexyl)-3-ethyl-1H-imida-
29.1, 26.8, 25.1, 17.6, 15.1, 13.6. 119Sn NMR (CDCl3):
d 156.0. HRMS
zol-3-ium bromide (7c). 1H NMR (CDCl3):
d
10.43 (s, 1H, CHimidazo-
calcd for C19H38N2Sn 449.1746 [MꢀSbF6]þ; found 449.1767.
lium), 7.60e7.57 (m, 2H, CHarom), 7.55 (m, 1H, CHimidazolium), 7.41 (m,
1H, CHimidazolium), 7.22e7.19 (m, 2H, CHarom), 6.02 (d, J¼2.2 Hz, 1H,
CHalkene), 5.53 (d, J¼2.2 Hz, 1H, CHalkene), 4.44 (q, J¼7.3 Hz, 2H,
NeCH2eCH3), 4.33 (t, J¼7.5 Hz, 2H, NeCH2eCH2), 1.94e1.82 (m, 2H,
NeCH2eCH2), 1.56 (t, J¼7.3 Hz, 3H, NeCH2eCH3), 1.52e1.23 (m,
14H, Halkyl), 1.02e0.89 (m, 6H, Halkyl), 0.86 (t, J¼7.3 Hz, 6H, CH3butyl).
4.1.17. (E)-1-(6-(Dibutyl(3-hydroxy-3-methylbut-1-en-1-yl)stannyl)
hexyl)-3-ethyl-1H-imidazol-3-ium tetrafluoroborate (13). 1H NMR
(CDCl3): d 9.08 (s,1H, CHimidazolium), 7.37e7.31 (m, 2H, CHimidazolium),
6.39e6.10 (m, 1H, CHalkene), 5.94e5.72 (m, 1H, CHalkene), 4.32 (q,
J¼7.3 Hz, 2H, NeCH2eCH3), 4.24 (t, J¼7.5 Hz, 2H, NeCH2eCH2),
1.98e1.86 (m, 2H, NeCH2eCH2), 1.78e1.20 (m, 30H, Halkyl), 0.95 (t,
13C NMR (CDCl3):
d 153.6, 151.8, 136.9, 132.2, 129.5, 126.8, 121.9,
119.2, 109.4, 50.1, 45.3, 33.7, 30.3, 29.9, 27.2, 26.6, 25.8, 15.6, 13.7,
J¼7.3 Hz, 6H, CH3butyl). 13C NMR (acetone-d6)
d 158.2, 136.6, 123.5,
123.2,121.4, 72.1, 50.5, 45.7, 34.3, 30.4, 27.8, 26.4,19.5,15.6, 14.0, 9.9.
10.3. 119Sn NMR (CDCl3):
d
ꢀ42.9. HRMS calcd for C28H44N3Sn
542.2563 [MꢀBr]þ; found 542.2568.
119Sn NMR (acetone-d6):
d
ꢀ46.8. HRMS calcd for C24H47N2OSn
499.2710 [MꢀBF4]þ; found 499.2747.
4.1.12. (E)-1-(6-(Dibutyl(2-(pyridin-2-yl)vinyl)stannyl)hexyl)-3-
ethyl-1H-imidazol-3-ium bromide (8a). 1H NMR (CDCl3):
d
10.78 (s,
4.1.18. (E)-1-(6-(Dibutyl(3-hydroxy-3-methylbut-1-en-1-yl)stannyl)
1H, CHimidazolium), 8.58e8.48 (m, 1H, CHpyridine), 7.72e7.60 (m, 1H,
CHpyridine), 7.52e7.41 (m, 1H, CHimidazolium), 7.35 (s, 1H,
hexyl)-3-ethyl-1H-imidazol-3-ium hexafluoroantimonate (14). 1H
NMR (CDCl3):
d 9.75 (s, 1H, CHimidazolium), 7.55 (s, 1H, CHimidazolium),
Please cite this article in press as: Faye, D.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.04.116

D. Faye et al. / Tetrahedron xxx (2013) 1e5
5
Carrera, N.; Salinas-Castillo, A.; Albeniz, A. C.; Espinet, P.; Mallavia, R. J. Orga-
nomet. Chem. 2011, 696, 3316.
7.42 (s, 1H, CHimidazolium), 5.92 (d, J¼19.0 Hz, 1H), 5.71 (d, J¼19.0 Hz,
1H, CHalkene), 4.33 (q, J¼7.3 Hz, 2H, NeCH2eCH3), 4.23 (t, J¼7.5 Hz,
2H, NeCH2eCH2), 1.91e1.71 (m, 2H, NeCH2eCH2), 1.51 (t, J¼7.3 Hz,
3H, NeCH2eCH3), 1.46e1.18 (m, 21H, Halkyl), 0.81 (m, 12H, Halkyl).
2. Poupon, J. C.; Marcoux, D.; Cloarec, J. M.; Charette, A. B. Org. Lett. 2007, 9, 3591.
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(b) Gallagher, W. P.; Terstiege, I.; Maleczka, R. E. J. Am. Chem. Soc. 2001, 123,
ꢀ
13C NMR (CDCl3):
d 125.0, 122.2, 121.3, 50.3, 45.6, 32.6, 29.3, 27.9,
3194; (c) Maleczka, R. E.; Gallagher, W. P. Org. Lett. 2001, 3, 4173; (d) Hernan, A.
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Djibril, F.; Castanet, A.-S.; Legoupy, S. Eur. J. Org. Chem. 2011, 143.
6. (a) Beletskaya, I.; Moberg, C. Chem. Rev. 1999, 99, 3435; (b) Smith, N. D.;
Mancuso, J.; Lautens, M. Chem. Rev. 2000, 100, 3257; (c) Miura, K.; Wang, D.;
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26.8, 25.4, 17.6, 15.1, 13.7. 119Sn NMR (CDCl3):
d
ꢀ45.8. HRMS
calcd for C24H47N2OSn 499.2710 [MꢀSbF6]þ; found 499.2659.
Acknowledgements
We thank CNRS (Centre National de la Recherche Scientifique),
ꢀ
the Universite d’Angers and the Agence Nationale de la Recherche.
ꢀ
We also thank Amelie Durand and Patricia Gangnery for technical
support.
References and notes
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Synthesis 2012, 272.
Please cite this article in press as: Faye, D.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.04.116