T.F. Bates et al. / Journal of Organometallic Chemistry 625 (2001) 13–22
19
spectroscopic data for 2c and 2d were determined from
a mixture of E and Z isomers.
the solvent under reduced pressure, was heated for 2 h
at 100°C. Flash chromatography afforded 0.78 g (43%)
of 2b. 13C-NMR: 0.2(−); 28.1(+); 28.5(+); 29.3(+);
29.5(+); 35.0(+); 41.0(+); 124.0(−); 162(+). MS,
m/z (relative intensity): 182(8, P), 167(66, M−15),
139(27), 79(34), 73(77), 59(100), 45(38). Molar mass
from high resolution MS Anal. Calc. for C11H22Si:
182.1491. Found: 182.1488.
3.2.1. Preparation of
(trimethylsilyl)methylenecyclohexane (2a)
3.2.1.1.
Using
(ethoxydimethylsilyl)(trimethylsilyl)-
methane (1b). To a solution of (ethoxydimethylsilyl)-
(trimethylsilyl)methane (1b), (1.14 g, 6.0 mmol) in pen-
tane (10 ml) at room temperature (r.t.) was added
tert-BuLi in pentane (3.53 ml, 6.0 mmol, 1.7 M) via
syringe. After stirring for 2 h, the reaction mixture was
cooled to −78°C and cyclohexanone (0.518 ml, 5.0
mmol) was added drop-wise, via syringe. The reaction
mixture was allowed to warm to room temperature
while stirring overnight. The pale yellow solution was
then added to NH4Cl (satd., aq., 12 ml) and the reaction
vessel rinsed with water (12 ml). After extraction of the
combined aqueous portions with pentane (2×10 ml),
the combined organic layers were dried with anhydrous
MgSO4. The crude product, obtained after removal of
the solvent under reduced pressure, was then heated for
2 h at 100°C. Flash chromatography (silica gel–pen-
tane) afforded 0.60 g (71%) of 2a [19]. 13C-NMR:
l=0.6(−); 26.3(+); 28.4(+); 28.8(+); 34.5(+);
40.5(+); 120.3(−); 160.1(+). MS, m/z (relative inten-
sity): 168(18, P), 153(100, M-15), 125(43), 93(22), 73(37),
59(96), 45(25).
In a few instances, the NMR spectrum of the crude
product obtained after work-up revealed small amounts
of an additional compound. Isolation by flash chro-
matography, followed by NMR and MS analysis,
showed this substance to be 1-trimethylsilymethyl cyclo-
heptene, 5. 13C-NMR: l=1.2, 26.7, 27.7, 28.5, 31.0,
32.7, 35.4, 123.6, 142.4. MS, m/z (relative intensity):
182(13, P), 108(17), 79(13), 73(100), 59(30), 45(49).
When the crude product was heated (100°C, 2 h) and
analysed by NMR, only 2b was detected.
3.2.3. Preparation of
3-[(trimethylsilyl)methyleno]cyclohexene (2c)
3.2.3.1. Using (methoxydimethylsilyl)(trimethylsilyl)-
methane (1a). tert-BuLi in pentane (6.47 ml, 11.0 mmol,
1.7 M) was added to a pentane (20 ml) solution of
(methoxydimethylsilyl)(trimethylsilyl)methane (1a) (1.94
g, 11.0 mmol). 2-Cyclohexenone (1.00 ml, 10.0 mmol)
was added at −78°C. The reaction mixture was an
intense yellow prior to hydrolysis. Flash chromatogra-
phy of the crude product obtained upon aqueous work-
up afforded 1.02 g (61%) of 2c [11]. E-isomer: 1H-NMR:
l=0.13 (s, SiMe3), 1.72 (quintet, 2H), 2.11 (t, 2H), 2.42
(t, 2H), 5.27 (b, 1H), 5.81 (m, 1H), 6.07 (m, 1H).
13C-NMR: l=0.04(−), 22.94(+), 25.23(+), 30.26(+),
125.80(−), 130.30(−), 133.08(−), 151.66(+). Z-iso-
In a few instances, the NMR spectrum of the crude
product revealed the presence of small amounts of an
additional compound. Upon subsequent isolation by
chromatography, this was identified as 1-trimethylsily-
methyl cyclohexene (4) [33]. 13C-NMR: l=1.0(−);
22.5(+); 23.0(+); 25.0(+); 28.0(+); 31.0(+);
119.0(+); 135.5(−). MS, m/z (relative intensity):
168(6, P), 94(8), 73(100), 59(10), 45(11).
1
mer: H-NMR: l=0.11 (s, SiMe3), 1.73 (quintet, 2H),
In some experiments involving the synthesis of 2a
(and 2b), when crude product isolated after work-up
was heated (100°C, 2 h), prior to chromatography,
NMR analysis showed absence of 4. This procedure was
therefore adopted as routine in subsequent experiments.
2.08 (t, 2H), 2.37 (t, 2H), 5.21 (b, 1H), 5.90 (m, 1H),
6.34 (m, 1H). 13C-NMR: l=0.40(−), 23.21(+),
25.61(+), 35.43(+), 125.42(−), 128.65(−), 131.53(−),
151.25(+). MS: m/z (relative intensity) 166(31, P),
151(90), 149(34), 123(40), 121(48), 106(57), 91(42),
73(46), 59(100), 45(59), 43(85). The ratio of E/Z-iso-
mers was determined from the ratio of the integrations
of the proton resonances at 5.21 and 5.27 ppm and
found to be 2.0:1. High resolution MS: Anal. Calc. for
C10H18Si: 166.1178. Found: 166.1176.
3.2.1.2. Using (methoxydimethylsilyl)(trimethylsilyl)-
methane (1a). A similar reaction starting with (methoxy-
dimethylsilyl)(trimethylsilyl)methane (1a), (12 mmol) af-
forded 1.15 g (68%) of 2a.
3.2.2. Preparation of (trimethylsilyl)-
3.2.3.2.
Using
(ethoxydimethylsilyl)(trimethylsilyl)-
methylenecycloheptane (2b)
methane (1b). A similar reaction starting with (ethoxy-
dimethylsilyl)(trimethylsilyl)methane (1b), (5.5 mmol)
afforded 0.47 g (56%) of 2c (E/Z=2.3:1)
In a manner similar to that described above for the
formation of 2a, tert-BuLi in pentane (2.61 ml, 12
mmol, 1.7 M) was added to a pentane (20 ml) solution
of (methoxydimethylsilyl)(trimethylsilyl)methane (1a)
(2.12 g, 12 mmol). Cycloheptanone (1.18 ml, 10 mmol)
was added drop-wise at −78°C. Following aqueous
work-up, the crude product, obtained after removal of
3.2.4. 1-Phenyl-2-trimethylsilylethene (2d)
3.2.4.1. Using (methoxydimethylsilyl)(trimethylsilyl)-
methane (1a). tert-BuLi in pentane (3.53 ml, 6.0 mmol,