Z. Xi et al.
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(2C), 106.79 (2C), 110.41 (2C), 122.94
G
J=8.1 Hz, 4H; CH); 13C NMR (75 MHz, CDCl3, 258C, Me4Si): d=À4.67
(4CH3), 13.85 (2CH3), 22.30 (2CH2), 31.02 (2CH2), 126.56 (4CH), 126.80
(2CH), 127.56 (4CH), 127.79 (4CH), 128.17 (4CH), 129.86 (2CH),
137.75 (2C), 140.37 (2C), 142.39 (2C), 142.47 (2C), 152.69 (2C),
162.65 ppm (2C); HRMS: m/z (%) calcd for C42H46Si2: 606.3138; found:
606.3141.
3i: Yellow liquid (558 mg, 71% yield); 1H NMR (300 MHz, CDCl3,
258C, Me4Si): d=0.30 (s, 12H; CH3), 0.55 (t, J=6.9 Hz, 6H; CH3), 0.74
(t, J=6.9 Hz, 6H; CH3), 1.02–1.13 (m, 20H; CH2), 1.95 (t, J=7.5 Hz,
4H; CH2), 2.33 (t, J=7.5 Hz, 4H; CH2), 5.93 (s, 2H; CH), 7.05–7.08 (m,
4H; CH), 7.29–7.38 (m, 10H; CH), 7.64 ppm (d, J=8.1 Hz, 2H; CH);
13C NMR (75 MHz, CDCl3, 258C, Me4Si): d=À4.75 (4CH3), 13.87
(2CH3), 13.96 (2CH3), 22.41 (2CH2), 22.48 (2CH2), 23.79 (2CH2), 29.70
(2CH2), 31.09 (2CH2), 31.54 (2CH2), 40.68 (2CH2), 54.82 (1C), 119.13
(2CH), 122.16 (2CH), 126.21 (2CH), 126.77 (2CH), 127.59 (4CH),
127.79 (4CH), 129.53 (2CH), 138.66 (2C), 139.98 (2C), 142.54 (2C),
143.59 (2C), 150.64 (2C), 152.18 (2C), 162.84 ppm (2C); MS (MALDI-
TOF): m/z (%) found: 786.3 [M+].
(4CH), 128.19 (4CH), 128.52 (2CH), 128.91 (2CH), 128.99 (4CH),
131.95 (4CH), 139.94 (2C), 143.12 (2C), 154.28 (2C), 163.30 ppm (2C);
MS (MALDI-TOF): m/z (%) found:1238.7 [M+].
4h: Yellow solid (683 mg, 52%); m.p.: 64.0–65.68C; 1H NMR (300 MHz,
CDCl3, 258C, Me4Si): d=0.16 (s, 6H; CH3), 0.30 (s, 6H; CH3), 0.67 (t,
J=7.2 Hz, 6H; CH3), 1.40–1.47 (m, 4H; CH2), 1.83–1.90 (m, 2H; CH2),
2.14–2.22 (m, 2H; CH2), 7.25–7.46 (m, 20H; CH), 7.58–7.60 ppm (m, 8H;
CH); 13C NMR (75 MHz, CDCl3, 258C, Me4Si): d=0.82 (2CH3), 1.84
(2CH3), 14.42 (2CH3), 21.54 (2CH2), 35.45 (2CH2), 92.33 (2C), 97.52
(2C), 106.83 (2C), 110.55 (2C), 123.06 (2C), 126.81 (4CH), 128.09
(4CH), 128.27 (4CH), 128.58 (2 CH), 128.78 (4CH), 128.96 (2CH),
129.10 (4CH), 132.03 (4CH), 139.83 (2C), 140.09 (2C), 143.08 (2C),
154.15 (2C), 163.39 ppm (2C); MS (MALDI-TOF): m/z (%) found:
1315.0 [M+].
4i: Yellow solid (673 mg, 45%); m.p.: 53.3–55.08C; 1H NMR (300 MHz,
CDCl3, 258C, Me4Si): d=0.19 (s, 6H; CH3), 0.33 (s, 6H; CH3), 0.60–0.78
(m, 12H; CH3), 0.83–0.88 (m, 4H; CH2), 1.04–1.26 (m, 12H; CH2), 1.26–
1.45 (m, 4H; CH2), 1.90–2.21 (m, 8H; CH2), 7.25–7.43 (m, 20H; CH),
7.64–7.66 ppm (m, 6H; CH); 13C NMR (75 MHz, CDCl3, 258C, Me4Si):
d=0.79 (2CH3), 1.80 (2CH3), 13.99 (2CH3), 14.27 (2CH3), 21.52 (2CH2),
22.31 (2CH2), 23.56 (2CH2), 29.37 (2CH2), 31.26 (2CH2), 35.37 (2CH2),
40.09 (2CH2), 55.15 (1C), 92.22 (2C), 98.68 (2C), 106.75 (2C), 110.38
(2C), 119.43 (2CH), 122.51 (2CH), 122.92 (2C), 127.14 (2CH), 127.97
(4CH), 128.14 (4CH), 128.45 (2CH), 128.83 (2CH), 128.99 (4CH),
131.88 (4CH), 140.05 (2C), 140.09 (2C), 142.77 (2C), 150.73 (2C), 153.60
(2C), 163.42 ppm (2C); MS (MALDI-TOF): m/z (%) found: 1367.0 [M+
ÀI].
A Typical Procedure for the Synthesis of Silole 3gS from Negishi
Coupling of 3gI
To a solution of 2-iodothiophene (2 mL, 105 mg, 0.5 mmol) in THF, was
added tBuLi (0.63 mL, 1 mmol, 1.6m in pentane) at À788C. After stirring
for 0.5 h, a solution of ZnCl2 (82 mg, 0.6 mmol) in THF (2 mL) was
added. To the formed 2’-thienylzinc chloride, was then added diiodo bis-
silole 3gI (390 mg, 0.5 mmol) and PdACHTNUGRTNEUNG(PPh3)4 (25 mg, 0.005 mmol). The re-
action mixture was heated to 508C, and was kept at this temperature for
4 h before quenching with water and extracted with Et2O. The extract
was washed with brine and dried over MgSO4. The solvent was then
evaporated in vacuum, and the residue thereafter was purified by column
chromatography using silica gel to afford the title products 3gS as orange
solid (582 mg, 84%). M.p.: 180.2–181.98C; 1H NMR (300 MHz, CDCl3,
258C, Me4Si): d=0.50 (s, 12H; CH3), 0.55 (t, J=7.5 Hz, 6H; CH3), 1.12–
1.26 (m, 4H; CH2), 2.13 (t, J=7.5 Hz, 4H; CH2), 6.78–7.01 (m, 6H; CH),
7.15 (s, 4H; CH), 7.24–7.48 ppm (m, 10H; CH); 13C NMR (75 MHz,
CDCl3, 258C, Me4Si): d=À2.96 (4CH3), 14.07 (2CH3), 22.84 (2CH2),
31.52 (2CH2), 125.44 (2CH), 126.02 (2CH), 126.74 (2CH), 127.59
(2CH), 127.80 (4CH), 128.92 (4CH), 129.60 (4CH), 133.03 (2C), 137.93
(2C), 139.01 (2C), 139.71 (2C), 143.08 (2C), 152.57 (2C), 154.90 ppm
(2C); HRMS: m/z (%) calcd for C44H46Si2S2: 694.2580; found: 694.2585.
Synthesis of Siloles 3g–i from Tetra Iodides 4g–i
To a solution of 4g–i (10 mL, 1.0 mmol) in ether at À788C was added
tBuLi (4.0 mmol, 1.5m in pentane). After the reaction mixture was stirred
at À788C for 0.5 h, it was warmed to reflux and maintained for 2 h. The
reaction mixture was cooled to À788C and electrophiles were added.
After reacting at room temperature for 1 h, the mixture was quenched
with water and extracted with Et2O. The extract was washed with brine
and dried over MgSO4. The solvent was then evaporated in vacuo and
the residue thereafter was purified by column chromatography using
silica gel to afford the title products 3g–i.
3g: Colorless wax (382 mg, 72%); 1H NMR (300 MHz, CDCl3, 258C,
Me4Si): d=0.31 (s, 12H; CH3), 0.56 (t, J=7.2 Hz, 6H; CH3), 1.00–1.08
(m, 4H; CH2), 2.33 (t, J=7.2 Hz, 4H; CH2), 5.91 (s, 2H; CH), 7.08 (s,
4H; CH), 7.28–7.35 ppm (m, 10H; CH); 13C NMR (75 MHz, CDCl3,
258C, Me4Si): d=À4.53 (4CH3), 13.88 (2CH3), 22.31 (2CH2), 30.99
(2CH2), 126.72 (2CH), 127.56 (4CH), 127.60 (4CH), 127.76 (4CH),
129.66 (2CH), 138.34 (2C), 142.51 (2C), 142.58 (2C), 152.40 (2C),
162.75 ppm (2C); HRMS: m/z (%) calcd for C36H42Si2: 530.2825; found:
530.2830.
3gD: Colorless wax (394 mg, D=95%, 74% yield); 1H NMR (300 MHz,
CDCl3, 258C, Me4Si): d=0.31 (s, 12H; CH3), 0.56 (t, J=7.2 Hz, 6H;
CH3), 1.01–1.08 (m, 4H; CH2), 2.33 (t, J=7.8 Hz, 4H; CH2), 7.09 (s, 4H;
CH), 7.24–7.39 ppm (m, 10H; CH); 13C NMR (75 MHz, CDCl3, 258C,
Me4Si): d=À4.52 (4CH3), 13.89 (2CH3), 22.32 (2CH2), 30.99 (2CH2),
126.73 (2CH), 127.57 (4CH), 127.60 (4CH), 127.76 (4CH), 138.34 (2C),
142.44 (2C), 142.55 (2C), 152.38 (2C), 162.70 ppm (2C); HRMS: m/z
(%) calcd for C36H40D2Si2: 532.2951; found: 532.2953.
3gI: Yellow wax (414 mg, 53%); m.p.: 55.9–57.68C; 1H NMR (300 MHz,
CDCl3, 258C, Me4Si): d=0.33 (s, 12H; CH3), 0.52 (t, J=7.2 Hz, 6H;
CH3), 1.03–1.11 (m, 4H; CH2), 2.21 (t, J=7.2 Hz, 4H; CH2), 7.08 (s, 4H;
CH), 7.17–7.44 ppm (m, 10H; CH), 13C NMR (75 MHz, CDCl3, 258C,
Me4Si): d=À5.25 (4CH3), 13.90 (2CH3), 22.48 (2CH2), 31.95 (2CH2),
99.90 (2C), 127.36 (2CH), 127.57 (4CH), 128.02 (4CH), 128.26 (4CH),
138.22 (2C), 141.62 (2C), 142.65 (2C), 153.91 (2C), 163.51 ppm (2C);
HRMS: m/z (%) calcd for C36H40Si2I2: 782.0758; found: 782.0765.
Synthesis of a-Lithio Silole 2a from Iodosilole 3aI
To a solution of 3aI (5 mL, 0.5 mmol) in ether at À788C, was added
tBuLi (2.0 mmol, 1.5m in pentane). After the reaction mixture was stirred
at À788C for 0.5 h, the solvent was removed in vacuum. n-Hexane was
added, and the mixture was filtered to remove the insoluble salts (LiI).
After the removal of n-hexane, the final product 2a was obtained by re-
crystallization from hexane as colorless crystals, 2a (190 mg, 92%).
1H NMR (300 MHz, C6D6, 258C): d=0.42 (s, 9H; CH3), 0.73 (s, 6H;
CH3), 1.14 (t, J=6.9 Hz, 6H; CH3), 3.37 (q, J=6.9 Hz, 4H; CH3), 7.18–
7.47 ppm (m, 10H; CH); 13C NMR (75 MHz, CDCl3, 258C, Me4Si): d=
À1.85 (2CH3), 1.64 (3CH3), 14.50 (2CH3), 65.36 (2CH2), 125.45 (1CH),
125.90 (1CH), 127.39 (2CH), 127.85 (2CH), 128.60 (2CH), 128.93
(2CH), 146.35 (1C), 147.83 (1C), 148.07 (1C), 168.24 (1C), 170.42 (1C),
202.19 ppm (1CLi).
X-ray Crystallographic Studies of 2a
As described above, crystals 2a for X-ray analysis were obtained and
sealed in thin-walled glass capillaries. Data collections were performed at
À1108C on a Rigaku RAXIS RAPID IP diffractometer, using graphite-
monochromated MoKa radiation (l=0.71073 ꢁ). The determination of
space group and unit cell parameters was carried out by the Rapid-
AUTO (Rigaku 2000) program package. The raw frame data were pro-
cessed by using Crystal Structure (Rigaku/MSC 2000) to yield the reflec-
tion data file. The structure was solved by the use of the SHELXTL pro-
gram. Refinement was performed on F2 anisotropically for all the nonhy-
drogen atoms by the full-matrix least-squares method. The hydrogen
atoms were placed at the calculated positions and were included in the
3h: White wax (382 mg, 63%); m.p.: 129.7–131.58C; H NMR (300 MHz,
CDCl3, 258C, Me4Si): d=0.31 (s, 12H; CH3), 0.56 (t, J=7.2 Hz, 6H;
CH3), 0.98–1.08 (m, 4H; CH2), 2.33 (t, J=7.5 Hz, 4H; CH2), 5.94 (s, 2H;
CH), 7.18 (d, J=8.1 Hz, 4H; CH), 7.25–7.38 (m, 10H; CH), 7.62 ppm (d,
1126
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Chem. Asian J. 2010, 5, 1120 – 1128