Stereoselective synthesis of (E)-α-aryltellurenylvinylsilanes via hydromagnesiation reaction of alkynylsilanes

Article abstract of DOI:10.1016/j.jorganchem.2004.02.027

(E)-α-Aryltellurenylvinylsilanes have been synthesized stereoselectively via the hydromagnesiation of alkynylsilanes, followed by the reaction with aryltellurenyl iodides. (E)-α-Aryltellurenylvinylsilanes can undergo the cross coupling reaction with Grign

Full text of DOI:10.1016/j.jorganchem.2004.02.027

Journal of Organometallic Chemistry 689 (2004) 1714–1717
www.elsevier.com/locate/jorganchem
Stereoselective synthesis of (E)-a-aryltellurenylvinylsilanes via
hydromagnesiation reaction of alkynylsilanes
a,
a
b
a
Mingzhong Cai *, Wenyan Hao , Hong Zhao , Jun Xia
a
Department of Chemistry, Jiangxi Normal University, Nanchang 330027, PR China
b
Department of Pharmacy, Guangdong Pharmaceutical College, Guangzhou 510240, PR China
Received 12 January 2004; accepted 17 February 2004
Abstract
(E)-a-Aryltellurenylvinylsilanes have been synthesized stereoselectively via the hydromagnesiation of alkynylsilanes, followed by
the reaction with aryltellurenyl iodides. (E)-a-Aryltellurenylvinylsilanes can undergo the cross coupling reaction with Grignard
reagents in the presence of Ni(PPh3)2Cl2 catalyst to afford (Z)-1,2-disubstituted vinylsilanes in good yields.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Hydromagnesiation; (E)-a-Aryltellurenylvinylsilane; Alkynylsilane; Cross coupling reaction; Stereoselective synthesis
1. Introduction
carbotelluration with tellurides to give (Z)-a-silylvinyl
tellurides in moderate yields. Recently, Fujiwara et al.
[10] reported that trimethylsilylacetylene underwent the
photoinduced addition with carbamotelluroates to af-
ford (E)-b-telluro-b-trimethylsilylacrylamides, but the
yields and stereoselectivity were poor. Hydromagnesia-
tion is one of the most promising organometallic tech-
nique used in organic synthesis and has emerged as an
unique hydrometallation with some attractive features,
such as the high regioselectivity and stereoselectivity
observed with alkynylsilanes [11]. We now wish to re-
port that (E)-a-aryltellurenylvinylsilanes could be syn-
thesized by hydromagnesiation of alkynylsilanes,
followed by treatment with aryltellurenyl iodides.
The trisubstituted alkene moiety is incorporated in
many biologically active compounds occurring in nature
and the stereoselective synthesis of trisubstituted alkenes
is of considerable interest in organic chemistry [1]. Di-
functional group reagents, which have two different
functional groups linked to the olefinic carbon atoms,
for example, Sn–Si [2], Se–Si [3], Zr–Si [4], Te–Zr [5] and
Te–Br [6] combinations, play an important role in or-
ganic synthesis, especially in developing many conve-
nient methods for stereoselective preparation of
trisubstituted alkenes. Vinylsilanes are important syn-
thetic intermediates and have numerous uses in organic
synthesis owing to the versatile reactivity of the silyl
group and the carbon–carbon double bond [7]. Vinylic
tellurides are also important intermediates because the
tellurium moiety can be replaced by different organic
groups always with total retention of the configuration
[8]. However, to date, the difunctional group reagent
containing silicon and tellurium has rarely aroused at-
tention. Kambe and co-workers [9] described that
trimethylsilylacetylene underwent the photo-promoted
2. Results and discussion
Alkynylsilanes 1 were prepared according to the
literature procedure [12]. Hydromagnesiation of alky-
nylsilanes 1 at 25 °C in diethyl ether for 6 h gave (Z)-
a-silylvinyl Grignard reagents 2, which reacted with
aryltellurenyl iodides 3 in THF to afford (E)-a-aryltel-
lurenylvinylsilanes 4 in good yields (Scheme 1). The
typical results are summarized in Table 1.
* Corresponding author. Fax: +86-791-8517500.
E-mail address: caimz618@sina.com (M. Cai).
The hydromagnesiation of alkynylsilanes 1 at 25 °C
in ether is almost 100% regio- and stereoselective as
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.02.027

M. Cai et al. / Journal of Organometallic Chemistry 689 (2004) 1714–1717
1715
R
H
SiMe3
MgBr
Cp TiCl (5 mol%)
R
H
SiMe3
TeAr
2
2
ArTeI (3)
+
SiMe3 i-BuMgBr
R
Et O, 25˚C
THF, 0~30˚C
2
1
4
2
R = n-C4H9, i-C5H11, n-C6H13, PhCH2
Scheme 1.
Table 1
Synthesis of (E)-a-aryltellurenylvinylsilanes 4
Table 2
Synthesis of (Z)-1,2-disubstituted vinylsilanes 5 according to Scheme 2
Entry
R
Ar
Product
Yielda (%)
Entry
R
Ar
R1
Product Yielda (%)
1
2
n-C4H9
n-C4H9
n-C4H9
i-C5H11
i-C5H11
i-C5H11
n-C6H13
n-C6H13
n-C6H13
PhCH2
Ph
4a
4b
4c
4d
4e
4f
78
82
75
79
81
73
77
80
72
68
1
2
3
4
5
n-C4H9
n-C4H9
i-C5H11
Ph
4-ClC6H4 Ph
n-C4H9
5a
5b
5c
5d
5e
74
81
75
77
65
4-ClC6H4
4-CH3C6H4
Ph
3
Ph n-C4H9
4
n-C6H13 4-ClC6H4 Ph
PhCH2 Ph n-C4H9
5
4-ClC6H4
4-CH3C6H4
Ph
a Isolated yield based on the 4 used.
6
7
4g
4h
4i
8
4-ClC6H4
4-CH3C6H4
Ph
9
10
Ni(0)-catalyzed cross coupling reactions with Grignard
reagents [13]. Therefore, we carried out the nickel cat-
alyzed cross coupling reaction of compounds 4 with
Grignard reagents. We observed that when (E)-a-aryl-
tellurenylvinylsilanes 4 were allowed to react with
Grignard reagents in the presence of catalytic amount of
Ni(PPh3)2Cl2 in THF at room temperature, the corre-
sponding (Z)-1,2-disubstituted vinylsilanes 5 were ob-
tained in good yields according to the Scheme 2 and
Table 2.
In conclusion, we have developed a direct route to the
stereoselective synthesis of (E)-a-aryltellurenylvinylsil-
anes by the hydromagnesiation of the alkynylsilanes.
The present method has some attractive advantages of
readily available starting materials, straightforward and
simple procedures, mild reaction conditions and good
yields. The investigation of the synthetic applications of
(E)-a-aryltellurenylvinylsilanes 4 is in progress.
4j
a Isolated yield based on the alkynylsilane 1 used.
previously described [11]. We observed that the Mg/Te
exchange reaction on intermediates 2 occurs with total
retention of the configuration. Investigations of the
1
crude products 4 by H NMR spectroscopy (400 MHz)
showed their isomeric purities to be more than 98%, one
olefinic proton signal of 4a–j splits characteristically into
one triplet with a coupling constant of 2Jð2HÞ ¼ 6:4–7:5
Hz, which indicated that the hydromagnesiation of al-
kynylsilanes had taken place with strong preference for
the addition of the magnesium atom at the carbon ad-
jacent to the silyl group. The stereochemistry for the
obtained compounds 4 was confirmed by the NOESY in
1
the H NMR spectra. An enhancement of the aromatic
protons next to tellurium was observed as the vinylic
proton of 4a was irradiated. There was no correlation
between the vinylic proton and CH3 bonded to the sil-
icon atom. The correlation between the allylic hydro-
gens and CH3 bonded to the silicon atom was also
observed. The NOE results indicate that 4a has the ex-
pected E configuration.
(E)-a-Aryltellurenylvinylsilanes 4 are new difunc-
tional group reagents in which two synthetically versa-
tile groups are linked to the same olefinic carbon atom
and can be considered both as vinylsilanes and vinylic
tellurides. Vinylic tellurides have been employed to effect
3. Experimental
Tetrahydrofuran (THF) was distilled from sodium–
benzophenone immediately prior to use. (Ph3P)2NiCl2
was prepared according to literature [14]. IR spectra
were obtained on a Perkin–Elmer 683 instrument as neat
films. 1H NMR spectra were recorded on a Bruker AC-
400 (400 MHz) spectrometer 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.
3.1. General procedure for the synthesis of (E)-a-
aryltellurenylvinylsilanes (4a–j)
SiMe3
TeAr
SiMe3
R1
R
H
R
H
Ni(PPh ) Cl
3 2
2
R1MgBr
+
THF, r.t.
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
5
4
Scheme 2.

1716
M. Cai et al. / Journal of Organometallic Chemistry 689 (2004) 1714–1717
stirred for 30 min at that temperature. To this solution
was added alkynylsilane 1 (4.0 mmol), and the mixture
was stirred for 6 h at 25 °C. After removal of the ether
under reduced pressure (2 h, r.t./2 Torr), the residue was
dissolved in THF (5 ml), cooled to 0 °C, and a solution
of aryltellurenyl iodide 3 (5.0 mmol) in THF (8 ml) was
added dropwise over 30 min with stirring. The reaction
mixture was brought to 30 °C gradually and stirred for 4
h, quenched with sat. aq NH4Cl (25 ml) and extracted
with Et2O (2 ꢀ 30 ml). The organic layer was washed
with sat. aq Na2S2O3 (20 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 using light petroleum as
eluent.
3.1.5. (E)-1-Trimethylsilyl-1-(4-chlorophenyltelluro)-5-
methyl-1-hexene (4e)
IR (film): m (cmꢁ1) 3069, 2955, 2869, 1629, 1568, 1470,
1383, 1367, 1248, 1089, 1009, 838, 808, 757, 720. 1H
NMR: d 7.56 (d, J ¼ 8:0 Hz, 2H), 7.18 (d, J ¼ 8:0 Hz,
2H), 6.97 (t, J ¼ 7:2 Hz, 1H), 2.29–2.18 (m, 2H), 1.59–
1.51 (m, 1H), 1.33–1.24 (m, 2H), 0.89 (d, J ¼ 6:5 Hz,
6H), 0.18 (s, 9H). MS: m=z 408 (Mþ, 2.8), 74 (10), 73
(100), 45 (9). Anal. Found: C, 46.89; H, 6.05.
C16H25SiClTe Calc.: C, 47.06; H, 6.13%.
3.1.6. (E)-1-Trimethylsilyl-1-(4-methylphenyltelluro)-5-
methyl-1-hexene (4f)
IR (film): m (cmꢁ1) 3065, 3014, 2954, 2869, 1579, 1486,
1467, 1384, 1366, 1246, 878, 836, 796, 752, 690. 1H
NMR: d 7.46 (d, J ¼ 7:8 Hz, 2H), 6.98 (d, J ¼ 7:8 Hz,
2H), 6.38 (t, J ¼ 6:5 Hz, 1H), 2.45–2.32 (m, 2H), 2.31 (s,
3H), 1.56–1.47 (m, 1H), 1.34–1.23 (m, 2H), 0.86 (d,
J ¼ 6:6 Hz, 6H), 0.07 (s, 9H). MS: m=z 388 (Mþ, 3.6), 91
(8.3), 74 (9.3), 73 (100), 45 (8.7). Anal. Found: C, 52.37;
H, 7.15. C17H28SiTe Calc.: C, 52.58; H, 7.22%.
3.1.1. (E)-1-Trimethylsilyl-1-phenyltelluro-1-hexene (4a)
IR (film): m (cmꢁ1) 3065, 2955, 2857, 1574, 1473, 1433,
1
1377, 1248, 838, 729, 691. H NMR: d 7.57–7.04 (m,
5H), 6.36 (t, J ¼ 6:5 Hz, 1H), 2.46–2.23 (m, 2H), 1.38–
1.19 (m, 4H), 0.86 (t, J ¼ 7:2 Hz, 3H), 0.08 (s, 9H). MS:
m=z 360 (Mþ, 6.4), 77 (9.5), 74 (9.6), 73 (100), 45 (9.9).
Anal. Found: C, 49.76; H, 6.52. C15H24SiTe Calc.: C,
50.00; H, 6.67%.
3.1.7. (E)-1-Trimethylsilyl-1-phenyltelluro-1-octene (4g)
IR (film): m (cmꢁ1) 3066, 2926, 2856, 1574, 1473, 1434,
1248, 839, 729, 691. 1H NMR: d 7.69–7.63 (m, 2H),
7.28–7.09 (m, 3H), 6.96 (t, J ¼ 7:5 Hz, 1H), 2.27–2.20
(m, 2H), 1.40–1.25 (m, 8H), 0.88 (t, J ¼ 7:0 Hz, 3H),
0.18 (s, 9H). MS: m=z 388 (Mþ, 2.7), 77 (4.8), 74 (9.8), 73
(100), 45 (6). Anal. Found: C, 52.34; H, 7.07.
C17H28SiTe Calc.: C, 52.58; H, 7.22%.
3.1.2. (E)-1-Trimethylsilyl-1-(4-chlorophenyltelluro)-1-
hexene (4b)
IR (film): m (cmꢁ1) 3068, 2956, 2858, 1629, 1570, 1470,
1
1381, 1248, 1089, 1009, 838, 808, 755. H NMR: d 7.46
(d, J ¼ 8:4 Hz, 2H), 7.14 (d, J ¼ 8:4 Hz, 2H), 6.45 (t,
J ¼ 6:4 Hz, 1H), 2.43–2.38 (m, 2H), 1.48–1.25 (m, 4H),
0.90 (t, J ¼ 7:2 Hz, 3H), 0.11 (s, 9H). MS: m=z 394 (Mþ,
3.4), 81 (11), 74 (10), 73 (100), 45 (10). Anal. Found: C,
45.43; H, 5.67. C15H23SiClTe Calc.: C, 45.69; H, 5.84%.
3.1.8. (E)-1-Trimethylsilyl-1-(4-chlorophenyltelluro)-1-
octene (4h)
IR (film): m (cmꢁ1) 3069, 2955, 2855, 1629, 1571, 1470,
1
1381, 1248, 1009, 839, 808, 757, 721. H NMR: d 7.56
(d, J ¼ 8:4 Hz, 2H), 7.17 (d, J ¼ 8:4 Hz, 2H), 6.97 (t,
J ¼ 7:5 Hz, 1H), 2.29–2.18 (m, 2H), 1.42–1.27 (m, 8H),
0.89 (t, J ¼ 6:2 Hz, 3H), 0.18 (s, 9H). MS: m=z 422 (Mþ,
1.9), 109 (5.3), 74 (10), 73 (100), 45 (8.8). Anal. Found:
C, 48.17; H, 6.41. C17H27SiClTe Calc.: C, 48.34; H,
6.40%.
3.1.3. (E)-1-Trimethylsilyl-1-(4-methylphenyltelluro)-1-
hexene (4c)
IR (film): m (cmꢁ1) 3065, 3014, 2955, 2871, 1579, 1486,
1
1246, 836, 796. H NMR: d 7.39 (d, J ¼ 7:9 Hz, 2H),
6.95 (d, J ¼ 7:9 Hz, 2H), 6.33 (t, J ¼ 6:5 Hz, 1H), 2.38–
2.27 (m, 2H), 2.25 (s, 3H), 1.39–1.21 (m, 4H), 0.81 (t,
J ¼ 7:0 Hz, 3H), 0.02 (s, 9H). MS: m=z 374 (Mþ, 3.7), 91
(11), 74 (9.4), 73 (100), 45 (10). Anal. Found: C, 51.14;
H, 6.78. C16H26SiTe Calc.: C, 51.39; H, 6.96%.
3.1.9. (E)-1-Trimethylsilyl-1-(4-methylphenyltelluro)-1-
octene (4i)
IR (film): m (cmꢁ1) 3065, 3014, 2925, 2855, 1575, 1486,
1
1456, 1378, 1248, 928, 838, 798, 756. H NMR: d 7.75
(d, J ¼ 8:5 Hz, 2H), 7.03 (d, J ¼ 8:5 Hz, 2H), 6.85 (t,
J ¼ 6:9 Hz, 1H), 2.40–2.15 (m, 5H), 1.58–1.21 (m, 8H),
0.89 (t, J ¼ 6:5 Hz, 3H), 0.19 (s, 9H). MS: m=z 402 (Mþ,
2.6), 91 (10), 74 (9.7), 73 (100), 45 (9.3). Anal. Found: C,
53.50; H, 7.22. C18H30SiTe Calc.: C, 53.73; H, 7.46%.
3.1.4. (E)-1-Trimethylsilyl-1-phenyltelluro-5-methyl-1-
hexene (4d)
IR (film): m (cmꢁ1) 3066, 2954, 2869, 1574, 1473, 1433,
1
1384, 1366, 1248, 838, 729, 691. H NMR: d 7.67–7.20
(m, 5H), 6.84 (t, J ¼ 6:5 Hz, 1H), 2.31–2.18 (m, 2H),
1.61–1.21 (m, 3H), 0.89 (d, J ¼ 6:6 Hz, 6H), 0.19 (s, 9H).
MS: m=z 374 (Mþ, 7.6), 117 (10), 77 (11.8), 74 (10), 73
(100). Anal. Found: C, 51.17; H, 6.83. C16H26SiTe Calc.:
C, 51.39; H, 6.96%.
3.1.10. (E)-1-Trimethylsilyl-1-phenyltelluro-3-phenyl-1-
propene (4j)
IR (film): m (cmꢁ1) 3068, 3019, 2955, 1595, 1574, 1473,
730, 690. 1H NMR: d 7.57–6.93 (m, 10H), 6.87 (t, J ¼ 7:0

M. Cai et al. / Journal of Organometallic Chemistry 689 (2004) 1714–1717
1717
Hz, 1H), 3.49 (d, J ¼ 6:8 Hz, 2H), 0.19 (s, 9H). MS: m=z
394 (Mþ, 3.7), 77 (13), 74 (11), 73 (100). Anal. Found: C,
54.61; H, 5.43. C18H22SiTe Calc.: C, 54.88; H, 5.59%.
3.2.5. (Z)-1-Phenyl-3-trimethylsilyl-2-heptene (5e)
IR (film): m (cmꢁ1) 2956, 2859, 1601, 1494, 1453, 1248,
838. 1H NMR: d 7.42–6.88 (m, 5H), 5.87 (t, J ¼ 7:0 Hz,
1H), 3.53 (d, J ¼ 7:2 Hz, 2H), 2.41–2.06 (m, 2H), 1.62–
1.18 (m, 4H), 0.89 (t, J ¼ 5:4 Hz, 3H), 0.12 (s, 9H). MS:
m=z 246 (Mþ, 4.5), 73 (100). Anal. Found: C, 77.82; H,
10.43. C16H26Si Calc.: C, 78.05; H, 10.57%.
3.2. General procedure for the synthesis of (Z)-1,2-
disubstituted vinylsilanes (5a–e)
To a stirred suspension of Ni(PPh3)2Cl2 (0.05 mmol)
and (E)-a-aryltellurenyl-vinylsilanes 4 (1 mmol) in THF
(5 ml) was added a solution of R1MgBr (4 mmol) in
THF (6 ml) under nitrogen at room temperature and the
mixture was stirred for 48 h. The mixture was treated
with sat. aq NH4Cl (10 ml) and extracted with ether
(2 ꢀ 30 ml). The ethereal solution was washed with wa-
ter (3 ꢀ 20 ml) and dried (MgSO4). Removal of the
solvent under reduced pressure gave an oil, which was
purified by column chromatography on silica gel eluting
with light petroleum.
Acknowledgements
We thank the National Natural Science Foundation
of China (Project No. 20062002) and the Natural Sci-
ence Foundation of Jiangxi Province in China for fi-
nancial support.
References
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3.2.1. (Z)-5-Trimethylsilyl-5-decene (5a)
IR (film): m (cmꢁ1) 2954, 2860, 1613, 1465, 1248, 849.
1H NMR: d 5.83 (t, J ¼ 7:0 Hz, 1H), 2.37–1.82 (m, 4H),
1.59–1.11 (m, 8H), 1.08–0.67 (m, 6H), 0.11 (s, 9H). MS:
m=z 212 (Mþ, 5.2), 73 (100). Anal. Found: C, 73.40; H,
13.13. C13H28Si Calc.: C, 73.58; H, 13.21%.
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3.2.2. (Z)-1-Trimethylsilyl-1-phenyl-1-hexene (5b)
IR (film): m (cmꢁ1) 2956, 2858, 1602, 1249, 839. H
1
(b) A. Sun, X. Huang, Synthesis (2000) 775.
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2.42–2.12 (m, 2H), 1.62–1.21 (m, 4H), 0.90 (t, J ¼ 5:4
Hz, 3H), 0.12 (s, 9H). MS: m=z 232 (Mþ, 3.8), 73 (100).
Anal. Found: C, 77.31; H, 10.25. C15H24Si Calc.: C,
77.59; H, 10.34%.
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4741;
3.2.3. (Z)-2-Methyl-6-trimethylsilyl-5-decene (5c)
IR (film): m (cmꢁ1) 2955, 2871, 1612, 1466, 1384,
(c) Y.Z. Huang, X.S. Mo, Tetrahedron Lett. 39 (1998) 1945;
(d) M.J. Dabdoub, V.B. Dabdoub, M.A. Pereira, J. Org. Chem.
61 (1996) 9503.
1
1366, 1249, 835. H NMR: d 5.83 (t, J ¼ 7:0 Hz, 1H),
2.37–1.93 (m, 4H), 1.59–1.09 (m, 7H), 1.05–0.79 (m,
9H), 0.12 (s, 9H). MS: m=z 226 (Mþ, 4.2), 73 (100).
Anal. Found: C, 74.19; H, 13.06. C14H30Si Calc.: C,
74.34; H, 13.27%.
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3.2.4. (Z)-1-Trimethylsilyl1-phenyl-1-octene (5d)
IR (film): m (cmꢁ1) 2955, 2855, 1602, 1573, 1488, 1249,
837. 1H NMR: d 7.34–6.80 (m, 5H), 5.98 (t, J ¼ 7:0 Hz,
1H), 2.46–2.02 (m, 2H), 1.72–1.17 (m, 8H), 0.90 (t,
J ¼ 5:4 Hz, 3H), 0.11 (s, 9H). MS: m=z 260 (Mþ, 3.2), 73
(100). Anal. Found: C, 78.22; H, 10.53. C17H28Si Calc.:
C, 78.46; H, 10.77%.
(b) F. Sato, J. Organomet. Chem. 285 (1985) 53;
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