A facile stereoselective synthesis of (E)-1,2-disubstituted vinylstannanes via hydromagnesiation of alkylarylacetylenes

Article abstract of DOI:10.1016/j.jorganchem.2004.04.041

Hydromagnesiation of alkylarylacetylenes 1 in diethyl ether gave (E)-α-arylvinyl Grignard reagents 2, which reacted with trialkylstannyl chlorides 3 in diethyl ether to afford stereoselectively (E)-1,2-disubstituted vinylstannanes 4 in high yields.

Full text of DOI:10.1016/j.jorganchem.2004.04.041

Journal of Organometallic Chemistry 689 (2004) 2531–2534
www.elsevier.com/locate/jorganchem
A facile stereoselective synthesis of (E)-1,2-disubstituted
vinylstannanes via hydromagnesiation of alkylarylacetylenes
*
Mingzhong Cai , Jun Xia, Guiqin Chen
Department of Chemistry, Jiangxi Normal University, Nanchang 330027, PR China
Received 11 February 2004; accepted 21 April 2004
Abstract
Hydromagnesiation of alkylarylacetylenes 1 in diethyl ether gave (E)-a-arylvinyl Grignard reagents 2, which reacted with trial-
kylstannyl chlorides 3 in diethyl ether to afford stereoselectively (E)-1,2-disubstituted vinylstannanes 4 in high yields.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Hydromagnesiation; Alkylarylacetylene; Vinyl Grignard reagent; Tin; Vinylstannane; Stereoselective synthesis
1. Introduction
cohols via the hydromagnesiation of alkynylsilanes
[10]. Herein, we wish to report that (E)-1,2-disubstituted
vinylstannanes could be conveniently synthesized via the
hydromagnesiation of alkylarylacetylenes, followed by
the reaction with trialkylstannyl chlorides.
Vinylstannanes are pivotal intermediates in a wide
range of carbon–carbon bond forming reactions [1].
Due to their synthetic utility, a variety of methods have
been developed for their preparation including those in-
volving carbonyl addition chemistry [2]; transmetalla-
tion of vinylmetallic species [3]; metallometallation of
alkynes [4]; and the hydrostannylation of alkynes in-
duced by either radical initiators [5] or Lewis acid [6]
or transition metal catalysts [7]. The radical-induced
procedure often gives a mixture of the trans- and cis-hy-
drostannylation products, since the isomerization of the
alkenyltin products occurs in the presence of tin radicals
[8]. The transition metal catalyzed hydrostannylation re-
action of alkynes proceeds via the cis-hydrostannylation
pathway [7]. Hydromagnesiation has emerged as a un-
ique hydrometallation with some attractive features
such as the high regioselectivity and stereoselectivity ob-
served with alkylarylacetylenes [9]. Recently, we have re-
ported the stereoselective syntheses of (E)-disubstituted
alkenes, (E)-a-selenenylvinylsilanes and (E)-allylic al-
2. Results and discussion
Alkylarylacetylenes 1 were prepared according to the
literature procedure [11]. Hydromagnesiation of alkyla-
rylacetylenes 1 at 25 ꢁC in diethyl ether for 1 h gave
(E)-a-arylvinyl Grignard reagents 2, which reacted with
trialkylstannyl chlorides 3 in ether to afford stereoselec-
tively (E)-1,2-disubstituted vinylstannanes 4 in high
yields (Scheme 1). Interestingly, the intermediates 2 in
THF were found to possess very low reactivity with tri-
alkylstannyl chlorides and only trace of products 4
were obtained at 60 ꢁC after 8 h. Even in the presence
of CuI, the Mg/Sn exchange reaction in THF proceed-
ed slowly at room temperature and the yields were less
than 15% after 24 h. However, when diethyl ether was
used as the solvent, the Mg/Sn exchange reaction pro-
ceeded smoothly at room temperature and the corre-
sponding (E)-1,2-disubstituted vinylstannanes were
*
Corresponding author. Fax: +86-791-851-7500.
E-mail address: caimz618@sina.com (M. Cai).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.04.041

2532
M. Cai et al. / Journal of Organometallic Chemistry 689 (2004) 2531–2534
Ph
H
Cp TiCl (5 mol%)
Ph
SnBu3
n-C4H9
H
n-C4H9
H
2
2
1. -78˚C, BuLi/THF
2.H O
2
R
Ar
i-BuMgBr
+
Et O, 0~25˚C
2
1
5
4a
Ar
Ar
1
R
R
H
R
SnCl (3)
3
SnR1
Scheme 2.
Et O, 25˚C
2
H
MgBr
3
2
4
trometer using CDCl3 as solvent. Mass spectra were
determined on a Finnigan 8230 mass spectrometer.
Microanalyses were measured using a Yanaco MT-3
CHN microelemental analyzer.
Scheme 1.
obtained in high yields. The typical results are summa-
rized in Table 1.
3.1. General procedure for the synthesis of (E)-1,2-
disubstituted vinylstannanes 4a–h
1
Investigations of the crude products 4 by H NMR
spectroscopy (400 MHz) showed their isomeric purities
of more than 97%. One olefinic proton signal of com-
pounds 4a–h splits characteristically into one triplet at
d=5.73–5.84 with coupling constant J=7.0 Hz, which
indicated that the hydromagnesiation to the alkylaryl-
acetylenes had taken place with strong preference for
the addition of the magnesium atom at the carbon ad-
jacent to the aryl group. We observed that the Mg/Sn
exchange reaction on intermediates 2 occurs with total
retention of the configuration. The configuration of
compound 4a could be confirmed from compound 5
which was obtained by treatment of 4a with n-butyl-
lithium in THF followed by hydrolysis, a reaction
which occurs stereoselectively (Scheme 2) [12]. The
stereochemistry of compound 5 was easily established,
To a solution of isobutylmagnesium bromide (4.5
mmol) in diethyl ether (7 ml) was added Cp2TiCl2 (50
mg, 0.2 mmol) at 0 ꢁC under Ar, and the mixture was
stirred for 30 min at that temperature. To this solution
was added alkylarylacetylene 1 (4.0 mmol) and the mix-
ture was stirred for 1 h at 25 ꢁC. Then, a solution of tri-
alkylstannyl chloride 3 (5.0 mmol) in diethyl ether (2 ml)
was added dropwise over 20 min at 0 ꢁC and the mixture
was stirred for 2 h at 25 ꢁC, quenched with sat. aq
NH4Cl (25 ml) and extracted with Et2O (2·40 ml).
The organic layer was washed with sat. aq NH4Cl (25
ml) and water (3·30 ml) and dried (MgSO4). Removal
of the solvent under reduced pressure gave an oil, which
was purified by column chromatography on silica gel us-
ing light petroleum (for 4a–f) or light petroleum–diethyl
ether (20:1) (for 4g–h) as eluent.
1
since H NMR spectrum (400 MHz) of 5 gives rise to
a doublet at d=6.45 with a coupling constant of 11.6
Hz, which is consistent with a Z-configuration.
In summary, our results showed that the hydromag-
nesiation–stannylation sequence of the alkylarylacety-
lenes has the advantages of readily available starting
materials, straightforward and simple procedures, mild
reaction conditions, and high yields.
3.1.1. (E)-1-Phenyl-1-tributylstannyl-1-hexene (4a)
IR(film): m (cmÀ1) 3073, 2957, 2926, 2854, 1593, 1571,
1
1486, 1464, 1376, 1071, 700. H NMR: d 7.30–6.94 (m,
5H), 5.76 (t, J=7.0 Hz, 1H), 2.15–2.02 (m, 2H), 1.56–
1.24 (m, 16H), 0.97–0.83 (m, 18H). MS: m/z 449 (M+,
2.4), 393 (100), 392 (51), 391 (82), 389 (49), 337(43),
279 (44), 117 (64), 91 (44). Anal. Calc. for C24H42Sn:
C, 64.14; H, 9.35. Found: C, 63.87; H, 9.18%.
3. Experimental
Diethyl ether was distilled from sodium immediate-
ly prior to use. IR spectra were obtained on a Perkin–
1
Elmer 683 instrument as neat films. H NMR spectra
were recorded on a Bruker AC-400 (400 MHz) spec-
3.1.2. (E)-1-Phenyl-1-trimethylstannyl-1-hexene (4b)
IR(film): m (cmÀ1) 3073, 2957, 2924, 2872, 1593, 1572,
1487, 1466, 1187, 856, 764, 700. H NMR: d 7.32–6.96
1
Table 1
Synthesis of (E)-1,2-disubstituted vinylstannanes 4a–h
Entry
R
Ar
R1
Product
Yield (%)a
1
2
3
4
5
6
7
8
n-C4H9
n-C4H9
n-C4H9
n-C4H9
n-C6H13
n-C6H13
n-C6H13
n-C6H13
Ph
Ph
n-C4H9
CH3
4a
4b
4c
4d
4e
4f
87
90
82
85
88
91
84
86
4-ClC6H4
4-ClC6H4
Ph
n-C4H9
CH3
n-C4H9
CH3
Ph
4-CH3OC6H4
4-CH3OC6H4
n-C4H9
CH3
4g
4h
aIsolated yield based on the alkylarylacetylene 1 used.

M. Cai et al. / Journal of Organometallic Chemistry 689 (2004) 2531–2534
2533
(m, 5H), 5.81 (t, J=7.0 Hz, 1H), 2.09–2.03 (m, 2H),
1.39–1.24 (m, 4H), 0.86 (t, J=6.8 Hz, 3H), 0.13 (s,
9H). MS: m/z 323 (M+, 4.3), 309 (81), 307 (75), 117
(100), 115 (62), 91(67), 41 (37). Anal. Calc. for
C15H24Sn: C, 55.73; H, 7.43. Found: C, 55.52; H, 7.26%.
175 (18), 147(55), 121 (100), 41 (36). Anal. Calc. for
C27H48OSn: C, 63.91; H, 9.47. Found: C, 63.69; H,
9.22%.
3.1.8. (E)-1-(4-Methoxyphenyl)-1-trimethylstannyl-1-
octene (4h)
3.1.3. (E)-1-(4-Chlorophenyl)-1-tributylstannyl-1-hex-
ene (4c)
IR(film): m (cmÀ1) 3074, 2924, 2855, 1602, 1571, 1505,
1466, 1378, 1243, 1172, 1039, 865, 824, 766. 1H NMR: d
6.89–6.82 (m, 4H), 5.76 (t, J=7.0 Hz, 1H), 3.81 (s, 3H),
2.08–2.01 (m, 2H), 1.35–1.15 (m, 8H), 0.86 (t, J=7.2 Hz,
3H), 0.10 (s, 9H). MS: m/z 381 (M+, 4.0), 367 (20), 217
(18), 161 (12), 147 (100), 121(93), 115 (21), 91 (29). Anal.
Calc. for C18H30OSn: C, 56.69; H, 7.87. Found: C,
56.44; H, 7.61%.
IR(film): m (cmÀ1) 3076, 2925, 2871, 1607, 1587,
1485, 1464, 1377, 1091, 1014, 869, 844, 690. 1H
NMR: d 7.24 (d, J=8.4 Hz, 2H), 6.86 (d, J=8.4 Hz,
2H), 5.77 (t, J=7.0 Hz, 1H), 2.05–1.99 (m, 2H),
1.49–1.24 (m, 16H), 0.95–0.83 (m, 18H). MS: m/z 483
(M+, 1.2), 427 (87), 425 (63), 179 (84), 177 (100), 175
(67), 151 (79), 125 (71), 115 (74). Anal. Calc. for
C24H41ClSn: C, 59.63; H, 8.49. Found: C, 59.47; H,
8.32%.
3.2. The synthesis of (Z)-1-phenyl-1-hexene (5)
BuLi (1 ml, 1.1 M hexane solution) was added to a
THF (5 ml) solution of 4a (1.0 mmol) at À78 ꢁC. After
stirring for 30 min, the mixture was hydrolyzed with sat-
urated aq. NH4Cl and extracted with CH2Cl2 (2·15
ml). The organic extract was washed with water (2·10
ml), dried with MgSO4, filtered, and concentrated under
vacuum. The residue was purified by column chroma-
tography on silica gel, eluting with light petroleum to
give (Z)-1-phenyl-1-hexene 5 (yield: 79%) as a colorless
oil. IR(film): m (cmÀ1) 2926, 2855, 1647, 1595, 1498,
3.1.4. (E)-1-(4-Chlorophenyl)-1-trimethylstannyl-1-hex-
ene (4d)
IR(film): m (cmÀ1) 3075, 2957, 2858, 1609, 1588,
1485, 1466, 1187, 1091, 1014, 871, 844, 816, 768. H
1
NMR: d 7.29 (d, J=8.4 Hz, 2H), 6.90 (d, J=8.4 Hz,
2H), 5.84 (t, J=7.0 Hz, 1H), 2.08–2.01 (m, 2H),
1.40–1.25 (m, 4H), 0.89 (t, J=6.8 Hz, 3H), 0.15 (s,
9H). MS: m/z 358 (M+, 7.8), 343 (100), 341 (77), 339
(41), 165 (45), 151 (78), 115 (52). Anal. Calc. for
C15H23ClSn: C, 50.42; H, 6.44. Found: C, 50.20; H,
6.23%.
1
1378. H NMR: d 7.34–7.20 (m, 5H), 6.45 (d, J=11.6
Hz, 1H), 5.70 (dt, J=11.6, 7.2 Hz, 1H), 2.36–2.29 (m,
2H), 1.46–1.32 (m, 4H), 0.93 (t, J=7.2 Hz, 3H). Anal.
Calc. for C12H16: C, 90.00; H, 10.00. Found: C, 89.73;
H, 9.84%.
3.1.5. (E)-1-Phenyl-1-tributylstannyl-1-octene (4e)
IR(film): m (cmÀ1) 3073, 3012, 2924, 2857, 1604, 1593,
1572, 1487, 1464, 1377, 1071, 873, 757, 700. 1H NMR: d
7.30–6.94 (m, 5H), 5.78 (t, J=7.0 Hz, 1H), 2.09–2.03 (m,
2H), 1.51–1.22 (m, 20H), 0.93–0.86 (m, 18H). MS: m/z
477 (M+, 1.3), 421 (94), 419 (73), 307 (46), 179 (56),
177(61), 117 (100), 91 (79). Anal. Calc. for C26H46Sn:
C, 65.41; H, 9.64. Found: C, 65.22; H, 9.47%.
Acknowledgement
We thank the National Natural Science Foundation
of China (Project No. 20062002) and the Natural Sci-
ence Foundation of Jiangxi Province in China for finan-
cial support.
3.1.6. (E)-1-Phenyl-1-trimethylstannyl-1-octene (4f)
IR(film): m (cmÀ1) 3073, 2924, 2855, 1607, 1594,
1572, 1486, 1466, 1378, 1188, 852, 765, 700. 1H
NMR: d 7.32–6.95 (m, 5H), 5.81 (t, J=7.0 Hz, 1H),
2.08–2.02 (m, 2H), 1.39–1.21 (m, 8H), 0.88 (t, J=6.8
Hz, 3H), 0.13 (s, 9H). MS: m/z 351 (M+, 2.8), 337
(57), 335 (54), 117 (100), 115 (59), 104 (47), 91(67).
Anal. Calc. for C17H28Sn: C, 58.12; H, 7.98. Found:
C, 57.87; H, 7.82%.
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