Chemistry Letters 2001
477
References and Notes
1
a) D. Seebach, Synthesis, 1969, 17. b) B. T. Grobel and D.
Seebach, Synthesis, 1977, 357. c) R. K. Olsen and J. O. Currie,
“The Chemistry of the Thiol Group,” ed. by S. Patai, Wiley,
New York (1974), p.519. d) H. Hauptman and W. F. Walter,
Chem. Rev., 62, 347 (1962).
2
3
4
a) A. G. Brook, J. M. Duff, P. F. Jones, and N. R. Davis, J. Am.
Chem. Soc., 18, 431 (1967). b) E. J. Corey, D. Seebach, and R.
Freedman, J. Am. Chem. Soc., 18, 434 (1967).
a) A. F. Patrocinio, I. R. Correa, Jr., and P. J. S. Moran, J. Chem.
Soc., Perkin Trans. 1, 21, 3133 (1999). b) K. Yamamoto, A.
Hayashi, S. Suzuki, and J. Tsuji, Organometallics, 6, 979 (1987).
Satisfactory elemental analyses and spectral data were obtained for
compounds 1b and 2a–d. For example, 2a: colorless crystals; mp
55.5 °C; 1H NMR (CDCl3, δ) 0.01 (s, 6H), 0.08 (s, 9H), 1.8–2.1
(m, 2H), 2.3–2.5 (m, 2H), 2.6–2.9 (m, 2H), 7.0–7.2 (m, 1H),
7.25–7.35 (m, 2H), 7.75–8.0 (m, 2H); 13C NMR (CDCl3, δ) –5.8,
–0.9, 25.2, 25.4, 47.5, 125.1, 128.3, 129.4, 141.0; 29Si NMR
(CDCl3, δ) –17.8, –6.0 ; MS (70 eV) m/z 326 (M+); Anal. Calcd for
C15H26S2Si2: C, 55.15; H, 8.02%. Found: C, 55.04; H, 7.99%. 2d:
pale yellow crystals; mp 101 °C; 1H NMR (CDCl3, δ) 0.01 (s, 6H),
0.10 (s, 9H), 1.8–2.1 (m, 2H), 2.3–2.5 (m, 2H), 2.7–3.05 (m, 2H),
2.94 (s, 6H), 6.72 (d, J = 9 Hz, 2H), 7.68 (d, J = 9 Hz, 2H); 13C
NMR (CDCl3, δ) –5.7, –0.8, 25.2, 25.4, 40.6, 47.0, 112.4, 128.3,
130.0, 148.1; 29Si NMR (CDCl3, δ) –18.1, –6.6; MS (70 eV) m/z
369 (M+); Anal. Calcd for C17H31NS2Si2: C, 55.22; H, 8.45; N,
3.79%. Found: C, 54.80; H, 8.20; N, 3.91%.
Interestingly, photolysis8 of 2a in isopropyl alcohol gave
phenyl(trimethylsilyl)(isopropoxydimethylsilyl)methane (89) in
7% yield along with
a simple reduction product,
benzylpentamethyldisilane (6, 28%). Photolysis of an ethanol
solution of 2a produced ethoxy-derivative 910 and 6 in 5% and
46% yields, respectively, whereas photolysis of 2a in hexane
gave only 6 (18%) as a volatile product.
It is well-known that methyl migration of (trimethylsilyl)-
carbene occurs easily,11 however, no methyl-migrated com-
pound was found in the photoproducts. Therefore, phenyl-
(silyl)carbene [Ph(R3Si)C:] was not considered as a common
intermediate of the reaction. The results showed that silene is
formed during the photolysis of 2a, even though its yield is low.
The plausible mechanism of the photoreaction of 2a is shown in
Scheme 2. The first step should be the cleavage of a C–S bond
to give biradical 10. The simple reduction to produce benzyl-
disilane 6 would then take place through path A and would
include intermolecular and/or intramolecular hydrogen abstrac-
tion. However, the 1,2-migration of trimethylsilyl moiety fol-
lowed by a second C–S bond cleavage gives silene 11 as an
intermediate (path B). Silene 11 reacts with alcohol to form the
corresponding adduct. Formation of 9-d in the photolysis of an
EtOD solution of 2a supports the existence of 11. However, the
d-content was only about 50% determined by GC–MS. The
result showed other pathway should be included in the forma-
tion mechanism of 9.
5
6
H. Sakurai, M. Kira, and M. Ochiai, Chem. Lett., 1972, 87.
Crystal data for 2a: colorless prisms, C15H26S2Si2, monoclinic,
space group P21/n, a = 14.525(2) Å, b = 9.0510(13) Å, c =
15.146(2) Å, β = 107.771(3)°, V = 1896.2(5) Å3, Z = 4, fw
326.66, Dcalcd = 1.144 g/cm3, absorption coefficient = 0.395
mm–1, F(000) = 704, Mo Kα, λ = 0.71073 Å, T = 296 K, Bruker
AXS/CCD diffractometer, crystal size 0.1 × 0.1 × 0.5 mm3,
2θmax = 50°, 9670 reflections collected, 3336 [R(int) = 0.0401]
independent reflections, 172 parameters, GOF = 0.875, R1
=
0.0427, wR2 = 0.0945 for 1838 unique reflections observed (I >
2σ(I)) and R1 = 0.0928, wR2 = 0.1097 for all 3336 unique reflec-
tions. Selected lengths (Å) and bond angles (°): Si1–Si2 =
2.341(1), Si1–C1 = 1.925(3), S1–C1 = 1.810(3), S2–C1 =
1.818(3), C1–C2 = 1.526(4), C1–Si1–Si2 = 113.9(1), C2–C1–S1
= 113.6(2), C2–C1–S2 = 112.8(2), S1–C1–S2 = 109.8(1).
Crystal data for 2d: a pale yellow prisms, C17H27NS2Si2, mono-
clinic, space group P21/n, a = 9.1874(12) Å, b = 10.1539(14) Å,
c = 22.852(3) Å, β = 92.283(2)°, V = 2130.2(5) Å3, Z = 4, fw
365.70, Dcalcd = 1.140 g/cm3, Absorption coefficient = 0.360
mm–1, F(000) = 784, Mo Kα, λ = 0.71073 Å, T = 296 K, Bruker
AXS/CCD diffractometer, crystal size 0.1 × 0.3 × 0.5 mm3, 2θmax
= 50°, 10862 reflections collected, 3739 [R(int) = 0.0408] inde-
pendent reflections, 199 parameters, GOF = 0.901, R1 = 0.0470,
wR2 = 0.1029 for 2279 observed unique reflections (I > 2σ(I)) and
R1 = 0.0887, wR2 = 0.1150 for all 3739 unique reflections.
Si1–Si2 = 2.351(1), Si1–C1 = 1.926(3), S1–C1 = 1.822(3), S2–C1
= 1.829(3), C1–C2 = 1.520(4), C1–Si1–Si2 = 113.8(1), C2–C1–S1
= 113.2(2), C2–C1–S2 = 112.7(2), S1–C1–S2 = 109.2(2).
7
8
9
Products 8 and 9 were isolated by gel permeation chromatogra-
1
phy eluting with chloroform and characterized by H, 13C, and
29Si NMR, and MS spectroscopic data. The yields of 5–9 were
determined by GLC, using decane as an internal standard.
8: a colorless oil, 1H NMR (CDCl3, δ) 0.01 (s, 9H), 0.02 (s, 3H),
0.08 (s, 3H), 1.08 (d, J = 6 Hz, 3H), 1.11 (d, J = 6 Hz, 3 H), 1.54
(s, 1H), 3.93 (sept, J = 6Hz, 1H), 6.9–7.05 (m, 3H), 7.1–7.2 (m,
2H); 13C NMR (CDCl3, δ) –0.21, –0.16, 0.3, 25.76, 25.81, 30.7,
65.0, 123.2, 127.9, 129.0, 142.2; 29Si NMR (CDCl3, δ) 1.5, 11.5;
HRMS m/z found 265.1426, calcd for C15H28OSi2–Me,
265.1443.
10 N. Shimizu, C. Kinoshita, E. Osajima, F. Hayakawa, and Y.
Tsuno, Bull. Chem. Soc. Jpn., 64, 3280 (1991).
11 G. Maas, “The Chemistry of Organic Silicon Compounds Vol.
2,” ed. by Z. Rappoport and Y. Apeloig, Wiley, New York
(1998), p.703.
One of us (S.T.) thanks RIKEN for sponsoring the Special
Postdoctoral Researchers Program.