One-step synthesis of (1-iodovinyl) arenes from trimethylsilyl ethynylarene through iodotrimethylsilane-mediated hydroiodation

Article abstract of DOI:10.1016/j.tetlet.2012.05.004

One-step access to (1-iodovinyl) arenes from trimethylsilyl ethynylarenes is described. The method is superior to a conventional multi-step approach, and is enhanced by the Sonogashira reaction that provides ready access to a variety of trimethylsilyl ethynylarenes.

Full text of DOI:10.1016/j.tetlet.2012.05.004

Tetrahedron Letters 53 (2012) 3585–3589
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Tetrahedron Letters
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One-step synthesis of (1-iodovinyl) arenes from trimethylsilyl ethynylarene
through iodotrimethylsilane-mediated hydroiodation
⇑
Akihiro H. Sato, Shigenori Mihara, Tetsuo Iwasawa
Department of Materials Chemistry, Faculty of Science and Technology, Ryukoku University, Otsu, Shiga 520-2194, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
One-step access to (1-iodovinyl) arenes from trimethylsilyl ethynylarenes is described. The method is
superior to a conventional multi-step approach, and is enhanced by the Sonogashira reaction that pro-
vides ready access to a variety of trimethylsilyl ethynylarenes.
Received 15 March 2012
Revised 20 April 2012
Accepted 2 May 2012
Available online 8 May 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Vinyl halides
Iodotrimethylsilane
One-step synthesis
Hydroiodation
Alkene
Vinyl halides are important building blocks in organic synthe-
sis.1 They are readily converted into various functional groups by
halogen–metal exchange and are significant for carbon–carbon
bond forming reactions by way of transition-metal catalyzed
we encountered the unforeseen reaction (Eq. 1). Although we in-
tended the demethylation of the ethereal methyl group, instead
a-vinyl iodide was isolated in high yield. We immediately began
exploring the scope and utility of this transformation. Herein we
report a simple synthesis of (1-iodovinyl)arenes from both ethy-
nylarenes as well as trimethylsilyl ethynylarenes (Scheme 1). Com-
mercially available TMSI was useful for the direct transformation
cross-coupling reactions.2–4
a-Vinyl iodides are especially impor-
tant5; the sterically unhindered terminal-olefin and weakly
bonded iodine are highly reactive and incredibly useful toward
the synthesized complex molecules.6 Despite the utility of
a-vinyl
of both of these functional groups into styrene-type a-vinyl iodide
iodides, their synthetic availability still remains a challenge, be-
cause of the inherent difficulty in hydroiodation.7 The stoichiome-
tric addition of hydrogen iodide (HI) to terminal alkynes is one way
units in high yield and in one step. Our synthetic protocol does not
require operations for desilylation, which is superior to the con-
ventional step-by-step approach.6,11,14 To the best of our knowl-
edge, so far such a direct synthesis has not been reported. In
addition, the protocol is enhanced by Sonogashira reaction that
readily makes trimethylsilyl ethynylarenes from aryl halides.17
Thus, it provides a rapid access to (1-iodovinyl) arenes.
to prepare a-vinyl iodides; however, the generation and transfer of
hygroscopic and gaseous HI are inconvenient and difficult to per-
form.8–10 As an alternative hydrometalation exists, although it re-
quires several reaction steps.11
The pioneering work for synthesis of
a-vinyl iodides from al-
kynes via addition of HI was reported by Ishii and co-workers: HI
was generated in situ from mixing of chlorotrimethylsilane, so-
dium iodide, and water in acetonitrile.12 And continuous efforts
have aimed to refine this initial method.13 More recently, Ogawa
and co-workers developed a novel hydroiodation of alkynes using
an iodine/hydrophosphine binary system.14 However, there is still
room for improvement, especially in terms of its scale;15 the sys-
tem worked using 0.2 mmol of starting alkynes.
ð1Þ
Recently we have developed the synthesis of unsymmetrically
functionalized pyrene derivatives.16 In the course of our study,
The hydroiodation of 1-ethynyl-4-methylbenzene (1) is exam-
ined in Table 1.18,19 TMSI was employed as a 1 M CH2Cl2 solution,
utilization of neat TMSI was not successful.20 To the mixture of the
alkyne (1 mmol) and TMSI (1.2 equiv) was added H2O (20 equiv) at
⇑
Corresponding author. Tel.: +81 77 543 7461; fax: +81 77 543 7483.
E-mail address: iwasawa@rins.ryukoku.ac.jp (T. Iwasawa).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.05.004

3586
A. H. Sato et al. / Tetrahedron Letters 53 (2012) 3585–3589
Table 2
Evaluation of the reactivity of 2 via Scheme 1a
Entry
Solvent
(CH3)3SiI (equiv)
Temp. (°C)
Yield (%)
1
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
Toluene
Hexane
CH3CN
1.0
1.2
1.5
2.0
4.0
1.5
1.5
1.5
1.5
1.5
1.5
ꢀ78
ꢀ78
ꢀ78
ꢀ78
ꢀ78
ꢀ45
ꢀ20
0
ꢀ78
ꢀ78
ꢀ20
58
88
88
64
60
66
63
58
74
70
30
2b
3
4
5
6
7
8
9
10
11
Scheme 1. Synthesis of (1-iodovinyl)arenes from 1 and 2.
low temperature, the reaction was allowed to warm to 0 °C.21 Entry
1 illustrates a high yielding transformation when the reaction was
carried out at ꢀ78 °C. The resulting 1-(1-iodovinyl)-4-methylben-
zene was isolated in 88% yield and the Markovnikov addition prod-
uct’s structure was confirmed by 1H NMR. Over the course of the
reaction the starting alkyne completely disappeared in TLC moni-
toring, additionally the corresponding isomer of b-vinyl iodide
was not observed. For entries 2–4, the reaction at ꢀ45 °C gave a
comparable 87% yield, but decreased at ꢀ20 °C and 0 °C.22 The con-
centration of the reaction was increased in entries 5 (3.3 mL
CH2Cl2) and 6 (1 mL) and gave comparable yields to entry 1
(8 mL). For entry 7, use of CH3OH instead of H2O resulted in only
20% yield. For entry 8, addition of H2O (20 equiv) to the solvent
in advance gave 70% yield. Other solvents were explored in entries
9–13, the hydroiodation in toluene and hexane properly occurred
with 81% and 71% yields, respectively. On the other hand, metha-
nol, acetonitrile, and THF were not successful giving multi-spots
on TLC monitoring. In marked contrast to the pioneering work,12,23
it is presumed that the non-polar and non-coordinated solvents are
best for this transformation.
a
Reaction conditions: alkyne 2 (1 mmol), solvent (8 mL), 1 M (CH3)3SiI in CH2Cl2,
H2O (20 mmol).
b
The starting alkyne was recovered in 3%.
underwent
a-vinyl iodation, yet the yields decreased in 80% and
54% (entries 2 and 3); presumably due to the sterically hindered al-
kyl groups for desilylation process. For entries 2 and 3, unreacted
alkynes were recovered in 13% and 45%, and the prolonged reac-
tion time did not increase the yields.
Preliminary mechanistic investigations were performed through
deuteration experiments. Deuterioiodation of 1 was carried out
with D2O, and the deuterium was incorporated under several con-
ditions (Table 4). In each case the major product was (E)-adduct5b
(entries 1–3). For entry 4, when D2O was added in advance, a similar
selectivity to entry 1 was observed. As a matter of form, deuterium
and iodine add to the alkyne with anti-selectivity. Interestingly, this
result is the opposite selectivity to Ishii’s pioneering work which re-
ported that DI adds to alkynes with complete syn-selectivity.12 Sub-
Next, we examined the reaction of ((4-tert-butylphenyl)ethy-
nyl)trimethylsilane (2) with TMSI to give
a-vinyl iodides (Table
2). Alkyne 2 was prepared via Sonogashira reaction. For entries
1–5, the equivalent of TMSI was varied, 1.5 equiv proved appropri-
ate to consume all of 2 and to achieve a high yielding transforma-
tion (entry 3). For entry 2, unreacted alkyne was recovered in 3%
when 1.2 equiv TMSI was used. For entries 6–8, the elevated tem-
peratures to ꢀ45, ꢀ20, and 0 °C were not successful. Other solvents
were explored in entries 9–11, toluene, hexane, and acetonitrile
gave 74%, 70%, and 30%, respectively. Thus, the optimum condi-
tions in Table 2 are close to those in Table 1.
Table 3
Effect of the trialkylsilyl groups on the hydroiodation of 2a
Table 3 illustrates different trialkylsilyl patterns tested. Like tri-
methylsilyl ethynylarene, triethyl-, and triisopropylsilyl substrates
Entry
R
Yield (%)
Recovered alkyne (%)
1
CH3
CH2CH3
CH(CH3)2
88
80
54
0
13
45
2
3b
Table 1
Evaluation of the reactivity of 1 conducted via Scheme 1a
a
Reaction conditions: alkyne (1 mmol), CH2Cl2 (8 mL), 1 M (CH3)3SiI in CH2Cl2
(1.5 mmol), H2O (20 mmol).
Entry
Solvent
Temp. (°C)
Yieldb (%)
b
Prolonged reaction time did not increase the yield.
1
2
3
4
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2/H2O (4% v/v)
Toluene
Hexane
CH3CN
CH3OH
THF
ꢀ78
ꢀ45
ꢀ20
0
ꢀ78
ꢀ78
ꢀ78
ꢀ78
ꢀ78
ꢀ78
ꢀ20
ꢀ78
ꢀ78
88
87
74
49
82
74
20
70
81
71
24
0
Table 4
Deuterioiodation of 1a
5c
6d
7e
8
9
10
11
12
13
Entry
Solvent
Yieldb (%)
% Db
0
(E)-3
(Z)-3
a
Reaction conditions: alkyne 1 (1 mmol), solvent (8 mL), 1 M (CH3)3SiI in CH2Cl2
1
2
3
4
CH2Cl2
Toluene
Hexane
CH2Cl2/H2O (4% v/v)
59
62
71
53
23
16
2
87
80
89
86
(1.2 mmol), H2O (20 mmol). All reactions were performed in accordance with the
representative procedure in Ref.21, unless otherwise stated.
b
Purified yields after silica gel column chromatography (hexane containing
12
5% v/v triethylamine).
c
a
3.3 mL of CH2Cl2 as a solvent was used.
1.0 mL of CH2Cl2 as a solvent was used.
CH3OH was added instead of H2O.
Reaction conditions: alkyne 1 (1 mmol), CH2Cl2 as a solvent (8 mL), 1 M
(CH3)3SiI in CH2Cl2 (1.2 mmol), D2O (20 mmol).
d
Determined by 1H NMR in Ref.12,5b
e
b

A. H. Sato et al. / Tetrahedron Letters 53 (2012) 3585–3589
3587
Table 5
Deuteration experiments of 2a
Entry
Solvent
Yieldb (%)
4
(E)-5
(Z)-5
1
2
3
CH2Cl2
Toluene
Hexane
83
71
61
2
3
3
2
3
3
a
Reaction conditions: alkyne 2 (1 mmol), CH2Cl2 as a solvent (8 mL), 1 M (CH3)3SiI in CH2Cl2 (1.5 mmol), D2O (20 mmol). The deuterium was incorporated better than 95%.
b
Determined by 1H NMR in Ref..12,5b
sequently, deuteration experiments of 2 were carried out, and the
results are summarized in Table 5. For entries 1–3, 4 was formed
along with the same and small amounts of (E)-5 and (Z)-5. The pro-
portions of (E) to (Z) between Tables 4 and 5 make a sharp contrast:
thus a-vinyl iodations of 1 and 2 were treated with the blends of
D2O and H2O (each 10 equiv) (Schemes 2 and 3). There is clearly a
difference between 1 and 2: the (E) isomer was preferred to (Z) in
1,24 while an equal mixture of (E) and (Z) was observed in 2. In addi-
tion, protonation preferentially occurred in 1, while deuteration in
2. Although it is difficult to give the details of the mechanism in 2 at
the present moment, these outcomes indicate that 2 considerably
Scheme 3.
(10 equiv).
a-Vinyl iodation of 2 with a mixture of D2O (10 equiv) and H2O
differs from 1 in the reaction pathway to
a-vinyl iodation. As for
20 in 70% yield. Both vinyl compounds 18 and 20 are solid materi-
als, and likely to be more stable than liquids. For entry 13, the de-
sired 2-(1-iodovinyl)biphenyl was observed in 57% yield, however
the corresponding isomers that are 3-(1-iodovinyl)biphenyl and
4-(1-iodovinyl)biphenyl were too unstable to isolate. For entry
14, the reaction did not proceed29 and the starting 22 was recovered
in >90%. The influence of representative functional groups was also
checked, however, 1-ethynyl-4-(trifluoromethyl)benzene, 1-
chloro-4-ethynylbenzene, 1-bromo-4-ethynylbenzene, and 2,5-
bis((trimethylsilyl)ethynyl)pyridine were not successful for the
the plausible pathway in Scheme 3, initial addition of HI to 2 would
give hydroiodinated iodotrimethylsilylalkene with 1:1 (E)/(Z) ratio.
This intermediate could then undergo desilylation reaction with
another HI, finally giving the desired compound.25–27
Table 6 represents outcomes of this method for several alkynes
listed in Figure 1. For entries 1–6, the commercially available ethy-
nylarenes were employed,14,28 and converted into the correspond-
ing a-vinyl iodides in moderate to good yields. Generally, a-vinyl
iodides are not stable;5a,11a 1-(1-iodovinyl)-4-methoxybenzene in
entry 5 immediately decomposed at ambient temperature in ca.
15 min.14 We made attempts to evaluate this method for other
alkynes, however, unfortunately, other alkynes gave unstable prod-
Table 6
29
ucts (these are described in Supplementary data).
For entries 6
Evaluation of the reactivity of several alkynes for the a
-vinyl iodationa
and 7, different starting alkynes gave the identical products, and
interestingly the former resulted in 45% yield and the latter in 92
Entry
Alkyne
Product
Yieldb (%)
1
2
3
4
5
6
8
9
(1-Iodovinyl)benzene
78
72
71
60
78
45
92
93
71
68
82
70
57i
0
%. These would reflect the individual mechanism of
which was implied in deuterium experiments in Schemes 2 and 3,
and it is a great advantage to approach -vinyl iodides from another
a-vinyl iodation
1-(1-iodovinyl)-4-pentylbenzene
1-(1-Iodovinyl)-2-methoxybenzene
1-(1-Iodovinyl)-3-methoxybenzene
1-(1-Iodovinyl)-4-methoxybenzene
1,4-Bis(1-iodovinyl)benzene
1,4-Bis(1-iodovinyl)benzene
1,3-Bis(1-iodovinyl)benzene
1-(1-Iodovinyl)-3-methoxybenzene
1-(1-Iodovinyl)-3-methoxybenzene
18
10
11
12
13
14
15
16
16
17
19
21
22
a
synthetic route. For entry 8, 15 was successfully prepared in 93%
yield. For entry 9, the reaction at 1 mmol scale gave the product
in 71% isolated yield, and entry 10 was conducted at 5 mmol scale
(1.02 g) of alkyne 16 giving 68% yield: this is a valuable process be-
cause the product of 1-(1-iodovinyl)-3-methoxybenzene cannot be
prepared through hydroiodation.5a,10e,11a,12 For entry 11, pyrene 17
leads to 18 in 82% yield, in which TMSI easily cleaved trimethylsilyl
group at R1 substituent. For entry 12, pyrene 19 bearing trimethyl-
silyl ethynyl groups at 3,8-positions gave the corresponding vinyl
d
7c,
8c,
d
9
10e
11f
12d,
20
g
13h
14j
2-(1-Iodovinyl)biphenyl
3-(1-Iodovinyl)benzenamine
a
Reaction conditions: alkyne 1 (1 mmol), CH2Cl2 (8 mL), 1 M (CH3)3SiI in CH2Cl2
(1.5 mL), H2O (20 mmol).
b
Isolated yields, unless otherwise noted.
c
The reactions were conducted at ꢀ20 °C.
d
3 mL of 1 M (CH3)3SiI in CH2Cl2 was used.
e
5 mmol (1.02 g) of the starting alkyne was used.
The reactions were conducted at 0 °C.
The reactions were conducted at room temperature.
f
g
h
The starting alkyne was recovered in 39%.
i
Determined by 1H NMR.
Scheme 2.
a-Vinyl iodation of 1 with a mixture of D2O (10 equiv) and H2O
j
The starting alkyne was recovered in >90%.
(10 equiv).

3588
A. H. Sato et al. / Tetrahedron Letters 53 (2012) 3585–3589
Figure 1. Compounds 8–22.
4. Galli, C.; Rappoport, Z. Acc. Chem. Res. 2003, 36, 580–587.
hydroiodination. In addition, unfortunately, several attempts to
transform alkyl-substituted terminal and internal alkynes did not
5. (a) Morrill, C.; Funk, T. W.; Grubbs, R. H. Tetrahederon Lett. 2004, 45, 7733–
7736; (b) Chen, Z.; Jiang, H.; Qi, C. Chem. Commun. 2010, 46, 8049–8051.
6. For representative transformations where vinyl iodides are used in synthesis of
complex molecules, see: Liu, X.; Henderson, J. A.; Sasaki, T.; Kishi, Y. J. Am.
Chem. Soc. 2009, 131, 16678. and references cited therein..
7. (a) Stone, H.; Schecher, H. Org. Syn. Coll. 1963, N, 543; (b) Stewart, L. J.; Gray, D.;
Pagni, R. N.; Kabalka, G. W. Tetrahedron Lett. 1987, 28, 4497; (c) Reddy, Ch. K.;
Periasamy, M. Tetrahedron Lett. 1919, 1990, 31.
8. Kropp, P. J.; Craword, S. D. J. Org. Chem. 1994, 59, 3102–3112.
9. (a) Hudrlik, P. F.; Kulkarni, A. K.; Jain, S.; Hudrlik, A. M. Tetrahedron 1983, 39,
877–882; (b) Griesbaum, K.; El-Abed, M. Chem. Ber. 1973, 106, 2001–2008; (c)
Fahey, R. C.; Lee, D.-J. J. Am. Chem. Soc. 1968, 90, 2124–2131; (d) Stacey, F. W.;
Harris, J. F., Jr. Org. React. (N.Y.) 1963, 13, 150–376; (e) Hennion, G. F.; Welsh, C.
E. J. Am. Chem. Soc. 1940, 62, 1367–1368.
give the corresponding a
-vinyl iodides.30
In summary, commercially available TMSI was found to convert
trimethylsilyl ethynylarenes into (1-iodovinyl)arenes in one-step.
Under the optimized reaction conditions, the reaction occurred
quickly under routine conditions, and was readily amenable to
scale up. Deuteration experiments suggest that the reaction path-
way of a-vinyl iodation is different between 1 and 2. This approach
afforded a wide variety of new and potentially useful (1-iodovi-
nyl)arenes. The synthetic utility of (1-iodovinyl)arenes is clear
and we hope that our straightforward and versatile methodology
finds widespread use in organic synthesis. Application and com-
plete mechanistic elucidation are ongoing for further development
of this reaction and will be reported in due course.
10. For the synthetic methods of a-vinyl iodides except the methods from alkynes,
see: (a) Byrd, L. R.; Caserio, M. C. J. Org. Chem. 1972, 37, 3881; (b) Lee, K.;
Wiemer, D. F. Tetrahedron Lett. 1993, 34, 2433; (c) Furrow, M. E.; Myers, A. G. J.
Am. Chem. Soc. 2004, 126, 5436; (d) Krafft, M. E.; Cran, J. W. Synlett 2005, 1263;
(e) Spaggiari, A.; Vaccari, D.; Davoli, P.; Torre, G.; Prati, F. J. Org. Chem. 2007, 72,
2216–2219.
11. (a) Gao, F.; Hoveyda, A. H. J. Am. Chem. Soc. 2010, 132, 10961–10963; (b) Miller,
R. B.; McGarvey, G. J. Org. Chem. 1979, 44, 4623.
Acknowledgment
12. Kamiya, N.; Chikami, Y.; Ishii, Y. Synlett 1990, 675–676.
We are very grateful to Professor Michael P. Schramm at the
California State University Long Beach for helpful discussion.
13. (a) Gao, Y.; Harada, K.; Hata, T.; Urabe, H.; Sato, F. J. Org. Chem. 1995, 60, 290–
291; (b) Campos, P. J.; García, B.; Rodríguez, M. A. Tetrahedron Lett. 2002, 43,
6111–6112; (c) Shimizu, M.; Toyoda, T.; Baba, T. Synlett 2005, 2516–2518; (d)
Moleele, S. S.; Michael, J. P.; de Koning, C. B. Tetrahedron 2006, 62, 2831–2844.
14. Kawaguchi, S.; Ogawa, A. Org. Lett. 2010, 12, 1893–1895.
Supplementary data
15. (a) Mullard, A. Nature Rev. Drug Discov. 2011, 10, 643–644; (b) Prinz, F.;
Schlange, T.; Asadullah, K. Nature Rev. Drug Discov. 2011, 10, 712.
16. Sato, A.H.;Maeda, M.; Mihara, S.; Iwasawa, T.Tetrahedron Lett. 2011,52, 6284–6287.
17. (a) Sonogashira, K.; Toda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 16, 4467; (b)
Sonogashira, K. In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I.,
Eds.; Pergamon Press: New York, 1991; Vol. 3, p 521; (c) Sonogashira, K. In
Metal-Catalyzed Cross-Coupling Reactions; Diederich, F., Stang, P. J., Eds.; Wiley-
VCH: Weinheim, Germany, 1998; p 203.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2012.05.004.
References and notes
1. (a) Ruan, J.; Xiao, J. Acc. Chem. Res. 2011, 44, 614–626; (b) Ma, D.; Cai, Q. Acc.
Chem. Res. 2008, 41, 1450–1460; (c) Littke, A. F.; Dai, C.; Fu, G. C. J. Am. Chem.
Soc. 2000, 122, 4020–4028.
18. Hydrohalogenation of 1-ethynyl-4-methylbenzene was attempted with TMSBr
and TMSCl, however, TMS-Br gave only trace amounts of
a-vinyl bromide and
TMS-Cl did not serve at all as source of hydrochlorination. In both
a
2. (a) Negishi, E. Organometallics in Organic Synthesis; Wiley: New York, 1980; (b)
Wakefield, B. J. The Chemistry of Organolithium Compounds; Pergamon Press:
Oxford, UK, 1974; (c) Brandsma, L.; Verkruijsse, H. Preparative Polar
Organometallic Chemistry 1; Springer: Berlin, 1987; (d) Wakefield, B. J.
Organolithium Methods; Academic Press: London, 1988; (e) Brandsma, L.
Preparative Polar Organometallic Chemistry 2; Springer: Berlin, 1990; (f)
Willard, P. G. In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I.,
Eds.; Pergamon Press: Oxford, UK, 1991; Vol. 1, p 1; (g) Schlosser, M. In
experiments, most of the starting alkyne remained.
19. (a) Walsh, R. Acc. Chem. Res. 1981, 14, 246–252; (b) Doncaster, A. M.; Walsh, R.
J. Phys. Chem. 1979, 83, 3037–3040.
20. We purchased the seal-tubed TMSI (5 g) in neat form from Tokyo Chemical
Industry Co., LTD, and it included a portion of Al metal inside the tube for
inhibiting the decomposition of TMSI. 5 g of TMSI was added to 24 mL of dried
CH2Cl2 along with the Al metal as a solid, thus providing colorless 1 M CH2Cl2
solution of TMSI for our experimental usage. The Al metal would not have a
crucial role for the reactivity of the TMSI solution: actually, the reactivity of the
freshly prepared TMSI solution was not influenced by with or without the
metal. The stock solution in the presence of the Al metal was stable for at least
two weeks, although it turned to slightly red colored solution.
Organometallics in Synthesis
A Manual; Schlosser, M., Ed., 2nd ed.; Wiley:
Chichester, UK, 2002; pp 1–352.
3. (a) Neumann, H.; Seebach, D. Chem. Ber. 1978, 111, 2785; (b) Evans, D. A.;
Crawford, T. C.; Thomas, R. C.; Walker, J. A. J. Org. Chem. 1976, 41, 3947.

A. H. Sato et al. / Tetrahedron Letters 53 (2012) 3585–3589
3589
21. The representative procedure for the
a
-vinyl iodation: To a solution of alkyne
22. The reaction at ꢀ20 and 0 °C consumed the starting alkyne, and the crude
(1 mmol) in anhydrous CH2Cl2 (8 mL) at ꢀ78 °C was added appropriate amount
of TMSI (1 M in CH2Cl2) dropwise over 8 min. After 15 min stirring, H2O was
added, and the mixture was allowed to warm to 0 °C over 50 min, and followed
by additional stirring for 10 min. The reaction was quenched at 0 °C with
saturated aqueous sodium thiosulfate, stirred for 30 min, and allowed to warm
to ambient temperature. To the mixture was added CH2Cl2 and organic phases
were washed with brine, and then dried over Na2SO4, and concentrated to give
a crude product. Purification by silica gel column chromatography (Hexane
containing 5 % v/v triethylamine) gave a desired (1-iodovinyl)arene. Analytcal
Data for 10 in Table 6, entry 11; 1H NMR (400 MHz, CDCl3) d: 8.41 (d, J = 9.5 Hz
1H), 8.34 (d, J = 9.5 Hz, 1H), 8.18 (d, J = 9.2 Hz, 1H), 8.12 (d, J = 7.7 Hz, 1H), 8.06
(d, J = 9.2 Hz, 1H), 7.85 (d, J = 7.7 Hz, 1H), 7.82 (s, 1H), 6.49 (s, 1H), 6.41 (s, 1H),
products contained unclear byproducts.
23. In Ishii’s system, acetonitrile was reported as an essential solvent for the
vinyl iodation.
a-
24. No isomerization between (E)-3 and (Z)-3 was observed under the condition in
Scheme 2.
25. (a) Alzeer, J.; Vasella, A. Helv. Chim. Acta 1995, 78, 177–193; (b) Corey, E. J.;
Kirst, H. A. Tetrahedron Lett. 1968, 9, 5041–5043.
26. We consider the result in Scheme 3 would not be ascribed to isotope effect. If
this is the case of isotope effect, then 4 should be a minor product.
27. The result in Scheme 3 was reproducible: the second experiment gave yields of
46% for 4, each 11% for (E)-5, (Z)-5, and 7.
28. (a) Takács, A.; Farkas, R.; Kollár, L. Tetrahedron 2008, 64, 61–66; (b) Bartoli, G.;
Cipolletti, R.; Antonio, D. G.; Giovannini, R.; Lanari, S.; Marcolini, M.;
Marcantoni, E. Org. Biomol. Chem. 2010, 8, 3509–3517.
3.34–3.29 (m, 4H), 1.86-1.80 (m, 4H), 1.53–1.47 (m, 4H), 1.02–0.98 (m, 6H). 13
C
NMR (100 MHz, CDCl3) d: 138.3, 137.8, 136.9, 131.7, 130.0, 129.6, 129.1, 128.1,
128.0, 127.3, 125.9, 125.82, 125.80, 125.2, 124.8, 123.2, 122.8, 104.0, 34.4, 34.2,
33.8, 33.7, 23.3, 23.2, 14.4. MS (FAB) m/z = 339 [MꢀI]+. Anal. Calcd for C26H27I:
C, 66.96; H, 5.84. Found: C, 67.02; H, 5.65.
29. A lot of other (1-iodovinyl)arenes proved not to isolate due to the unstable
compounds: see Supplementary data.
30. These are summarized in Supplementary data.