Mohamed and Brook
1361
when radical traps such as alkenes are present. However, the
photochemical formation of silylenes from TTMSS could not
be observed in the presence of standard silylene traps.
(t, 3H, J= 6), 0.20 (s, 27 H). 13C NMR (50.3 MHz, C6D6)
δ: 70.52, 65.83, 15.52, 9.81, 1.31.
3-Oxo-1-[tris(trimethylsilyl)silyl]butane: Methyl vinyl ketone
(0.46 g, 6.6 mmol), TTMSS (1.9 g, 7.9 mmol), hexane
(10 mL); product was purified on silica gel (petroleum ether,
1.58 g, 80%). IR (neat) ν: 2951, 2895, 1720, 1409, 1356,
Experimental section
1H and 13C NMR spectra were recorded on a Bruker AC-
200 spectrometer with CDCl3 or C6D6 as an internal stan-
dard. IR spectra were recorded on a Biorad spectrometer.
Electron impact (EI) and chemical ionization (CI, NH3) mass
spectra were recorded at 70 eV with a source temperature of
200°C on a VG Instruments analytical ZAB-R mass spec-
trometer equipped with a VG 11–250 data system.
1
1245, 840, 623. H NMR (200 MHz, C6D6) δ: 2.38–2.32
(m, 2 H), 2.05 (s, 3 H), 0.96–0.91 (m, 2 H), 0.08 (s, 27H).
13C NMR (50.3 MHz, C6D6) δ: 209.0, 42.65, 28.99, 1.45,
1.24. MS (EI, m/z (%)): 303 (M+-15, 2.6), 245 (18), 191 (8),
175 (8), 131 (12), 117 (19), 73 (100), 45 (24).
3-Phenyl-1-tris(trimethylsilyl)silylpropane: Allylbenzene
(0.96 g, 8.1 mmol), TTMSS (2.4 g, 9.7mmol), and 20 mL of
hexane was placed in a quartz cell. After 8 h of photolysis,
the reaction mixture was concentrated in vacuo, and the
product purified on silica gel (5% ethyl acetate–hexane) to
give (0.72 g, 75%). MS (EI, m/z): 366 (5.0), 351 (3.0), 293
(40), 219 (8.0), 204 (6.0), 175 (71), 117 (20), 73 (100). IR ν
(cm–1): 3086, 3064, 3028, 2950, 2894, 2856, 1604, 1496,
1453, 1397, 1245, 1069, 835, 746, 695, 623. 1H NMR
(200 MHz, CDCl3) δ: 7.18 (m, 5 H, Ph), 2.61 (t, 2 H, J = 7),
1.68 (dd, 2 H, J = 7 and 4), 0.12 (s, 27 H (CH3)3Si)3).
13C NMR (50.3 MHz, CDCl3) δ: 142.3, 128.4, 128.2, 125.6,
40.49, 30.91, 7.42, 1.15.
Gas chromatographic (GC) analyses were carried out us-
ing a Hewlett–Packard 5890A gas chromatography equipped
with a conventional heated injector, a flame ionization detec-
tor, a Hewlett–Packard 3393A integrator, and a DB-1 mega-
bore capillary column (30 m × 0.54 mm, Chromatographic
Specialties, Inc.). Mass spectra and GC–MS analyses were
recorded on a Hewlett–Packard 5890II gas chromatograph
equipped with a HP-5971A mass selective detector and a
DB-5 fused silica capillary column (30 m × 0.25 mm,
Chromatograph Specialties, Inc.). All syntheses were per-
formed with dry glassware under an atmosphere of anhy-
drous nitrogen. Prior to photolysis, all the solutions were
degassed with dry argon.
With the exception noted below, all reagents were pur-
chased from Aldrich: vinyl acetate, ethyl vinyl ether, methyl
vinyl ketone, allylbenzene, diethyl ether, chlorotrimethylsilane,
MeMgBr, MeLi-Br hexane (Omni solvent), and THF. THF
was distilled from benzophenone ketyl just before to use.
Silicon tetrachloride was purchased from Gelest. (Me3Si)4Si,
(Me3Si)3SiH, and (Me3Si)3Me (14) were prepared by stan-
dard literature routes or are commercially available (Gelest).
Without traps
A solution of TTMSS (0.30 g, 1.2 mmol) in hexane
10 mL was irradiated for 2 h to 20% conversion in the ab-
sence of added trapping agent. GC–MS analysis of the crude
mixture led to many products in which the major product is
(Me3Si)4Si, (4%, refers to GC area%, Table 1).
With alcohols as traps
Photolysis of TTMSS in the presence of methanol for
2.5 h: (Me3Si)3SiH (90%), (Me3Si)2SiH2 (0.8%) MS: 176
(M+), 162, 161, 131,117, 101, 88, 73; (Me3SiO)2Si(H)SiMe3
(1.5%) MS: 280 (6.4), 265 (6.4), 207 (47), 191 (100), 177
(18), 147 (14), 133 (18), 117 (18), 103 (4.3), 73 (21);
(Me3Si)3SiMe (2) (0.3%), (Me3Si)4Si (3) (0.6%).
Prolonged photolysis of TTMSS in the presence of MeOH
over 24 h led to the formation of two products: 3 (92%), un-
identified product (5%), GS–MS: 353 (13), 264 (91), 235
(26), 219 (38), 205 (73), 189 (18), 175 (43), 159 (9), 131
(38), 117 (27), 89 (18), 73 (100), 59 (34), and TTMSS (3%).
A solution of TTMSS (0.248 g, 1.0 mmol) in hexane
(10 mL) was photolyzed in the presence of cyclopentanol
(0.086 g, 1 mmol) for 2.35 h. Six major products were pro-
duced: 3 (2.5%,), 4 (3%, for mass spectral data, see Table 1),
(C5H9O)SiMe3 (1.7%), GC–MS: 158, 143, 129, 115, 101,
75, 73; (Me3SiO)2Si(H)SiMe3 (3.2%), GC–MS: 280, 265,
207, 191, 177, 147, 133, 117, 103, 87, 73, 59. The other two
products could not be identified. Residual starting material
(80%) accounted for the remainder of the products.
Photolyses
With alkenes: hydrosilylation
A mixture of alkene and 1.2 equiv. of silane in a quartz
tube was irradiated for 3 h in a Rayonet photochemical reac-
tor equipped with low pressure mercury lamps emitting
254 nm radiation.
1-[Tris(trimethylsilyl)silyl]ethyl acetate: Vinyl acetate (0.53 g,
62 mmol), TTMSS (1.8 g, 7.4 mmol), hexane (10 mL);
product was purified on silica gel (petroleum ether, 1.64 g,
79%). MS (EI, m/z (%)): 319 (M+-15 (1.0)), 291 (3.2), 275
(4.2), 233 (39), 191 (33), 174 (20), 73 (100), 43 (50). IR
(cm–1) ν: 2954, 2897, 1742, 1247, 1046. 1H NMR
(300 MHz, C6D6) δ: 4.27–4.22 (t, 2H, J= 8), 1.70 (s, 3H),
1.32–1.26 (t, 2H), 0.17 (s, 27 H). 13C NMR (MHz, C6D6)
δ: 170.05, 64.60, 20.78, 8.9, 0.98.
2-(Ethoxy)-1-[tris(trimethylsilyl)silyl]ethane: Ethyl vinyl ether
(0.35 g, 5 mmol), TTMSS (1.5 g, 6 mmol), hexane (10 mL);
product was purified on silica gel (petroleum ether, 1.47 g,
92%). MS (EI, m/z (%)): 305 (M+-15 (1.6)), 275 (0.5), 247
(2.1), 219 (12), 191 (12), 131 (11), 117 (15), 73 (100), 45
(27). IR (neat) ν: 2951, 2895, 2861, 1245, 1122, 1097.
1H NMR (200 MHz, C6D6) δ: 3.53–3.47 (t, 2 H, J= 6), 3.35–
3.28 (q, 2 H, J = 4), 1.28–1.22 (t, 2 H J= 6), 1.15–1.10
Acknowledgements
We gratefully acknowledge the financial support of the
Natural Sciences and Engineering Research Council of
Canada (NSERC). The authors would also like to thank
© 2000 NRC Canada