2170
A. Kawachi et al. / Journal of Organometallic Chemistry 695 (2010) 2167e2171
Dispensing System (Glass Contour) under nitrogen atmosphere. All
reactions were carried out under inert gas atmosphere.
ꢀ4.49 (Me), 50.38 (OMe), 126.29 (CH),129.07 (C), 131.73 (CH), 132.49
(CH),135.64 (C),137.57 (CH). 29Si{1H} NMR (C6D6,
for C9H13BrO2Si: C, 41.39; H, 5.02. Found: C, 41.04; H, 5.14%.
d
) ꢀ17.5. Anal. Calc.
4.2. Synthesis
4.2.4. o-(Dimesitylboryl)[dimethoxy(phenyl)silyl]benzene (4a)
tert-BuLi in pentane (1.59 M, 6.80 mL, 10.8 mmol) was added
dropwise to a solution of 2a (3.58 g, 11.1 mmol) in Et2O (20 mL) at
ꢀ78 ꢁC over 25 min. The reaction mixture was stirred at the same
temperature for 2 h to form a yellow suspension of 3a. To the
suspension was added a solution of fluorodimesitylborane (3.10 g,
11.6 mmol) in Et2O (10 mL) at ꢀ78 ꢁC over 35 min. The reaction
mixture was stirred at ꢀ60 ꢁC for 24 h and then allowed to warm
to ambient temperature over 1.5 h. Then the solvents were
removed in vacuo. The residue was diluted in hexane (100 mL) and
filtered through a glass fiber pad to remove inorganic salts. The
filtrate was concentrated in vacuo. The residue (5.22 g) was sub-
jected to column chromatography on silica gel using hex-
aneeCH2Cl2 (3/1) as eluent (Rf ¼ 0.33) to give 4a (3.53 g, 74% yield)
as white solids.
4.2.1. Chloro(dimethoxy)phenylsilane
To a solution of palladium(II) dichloride (25 mg) and phenyl-
silane (6.2 mL, 50 mmol) in benzene (100 mL) was added methanol
(4.1 mL, 100 mmol) at 0 ꢁC over 2 min. A gas evolution immediately
occurred. The reaction mixture was stirred at 0 ꢁC until the gas
evolution ceased, resulting in formation of (dimethoxy)phenyl-
silane. Carbon tetrachloride (5.0 mL, 52 mmol) was added to the
reaction mixture at room temperature over 2 min. Palladium(II)
dichloride (30 mg, 0.17 mmol) was added by one portion to the
reaction mixture at room temperature, and the reaction mixture
was heated at 50 ꢁC for 30 min. Further palladium(II) dichloride
(29 mg, 0.16 mmol) was added to the reaction mixture at 50 ꢁC,
resulting in a gas evolution. After the gas evolution ceased, the
reaction mixture was cooled to room temperature. Then the
solvents were removed in vacuo. The residue (11.0 g) was subjected
to bulb-to-bulb distillation (64e66 ꢁC (bath temp.)/3.5 mmHg) to
afford chloro(dimethoxy)phenylsilane (9.78 g, 96% yield) as
a colorless oil.
m.p. 117e118.5 ꢁC (in air). 1H NMR (C6H6,
d) 1.4e2.6 (br, 18H),
3.33 (s, 6H), 6.3e6.9 (br, 4H), 7.14e7.22 (m, 5H), 7.36 (d, 3J ¼ 8 Hz,
2H), 7.49 (d, 3J ¼ 8 Hz, 1H), 7.91 (d, 3J ¼ 8 Hz, 1H). 13C NMR (CDCl3,
d)
21.20 (CH3), 23.0e24.0 (br, CH3), 50.48 (OMe), 127.24 (CH),
127.6e129.0 (C), 128.27 (CH), 128.33 (CH), 129.36 (CH), 129.55 (CH),
132.93 (CH), 133.01 (C), 134.16 (CH), 135.75 (CH), 136.83 (C),
138.2e139.3 (br, C), 141.0e142.8 (br, C), 157.38 (C). 11B{1H} NMR
4.2.2. o-Bromo[dimethoxy(phenyl)silyl]benzene (2a)
A solution of n-BuLi in hexane (1.54 M, 32.0 mL, 49 mmol) was
added dropwise to a solution of 1,2-dibromobenzene (5.1 mL,
42 mmol) in THFeEt2O (80 mL/80 mL) over 1 h at ꢀ110 ꢁC (ethanol/
liq. N2 slush bath). After the reaction mixture was stirred at the
same temperature for 40 min, chloro(dimethoxy)(phenyl)silane
(8.59 g, 42 mmol) was added dropwise to the reaction mixture over
15 min at ꢀ110 ꢁC. The reaction mixture was stirred at the same
temperature for further 1.5 h and then allowed to warm to ambient
temperature. After the solvents were removed in vacuo, the residue
was diluted with hexane (70 mL) and filtered through a glass fiber
pad to remove inorganic salts. The filtrate was concentrated in
vacuo to give an oil (15.4 g). The oil was subjected to column
chromatography on silica gel using hexaneeAcOEt (20/1) as eluent
(Rf ¼ 0.30) to give 2a (11.9 g, 87% yield) as a colorless oil.
(C6D6,
d
) 74 (br). 29Si{1H} NMR (C6D6,
d
) ꢀ28.2. Anal. Calc. for
C32H37BO2Si: C, 78.03; H, 7.57. Found: C, 77.84; H, 7.90%.
4.2.5. o-(Dimesitylboryl)[dimethoxy(methyl)silyl]benzene (4b)
tert-BuLi in pentane (1.58 M, 3.50 mL, 5.5 mmol) was added
dropwise to a solution of 2b (1.40 g, 5.4 mmol) in Et2O (10 mL) at
ꢀ78 ꢁC over 15 min. The reaction mixture was stirred at the same
temperature for 2 h to form a yellow suspension of 3b. To the
suspension was added a solution of fluorodimesitylborane (1.47 g,
5.5 mmol) in Et2O (5 mL) at ꢀ78 ꢁC over 12 min. The reaction
mixture was stirred at ꢀ60 ꢁC for 24 h and then allowed to warm to
ambient temperature over 1.5 h. Then the solvents were removed in
vacuo. The residue was diluted in hexane (30 mL) and filtered
through a glass fiber pad to remove inorganic salts. The filtrate was
concentrated in vacuo. The residue (2.38 g) was subjected to
column chromatography on silica gel using hexaneeCH2Cl2 (2/1) as
eluent (Rf ¼ 0.35) to give crude 4b (961 mg), which was again
subjected to column chromatography on silica gel using hex-
aneeCH2Cl2 (2.5/1) as eluent (Rf ¼ 0.15) to give pure 4b (829 mg,
39% yield) as white solids.
1H NMR (C6D6,
d
) 3.51 (s, 6H), 6.84 (ddd, 3J ¼ 8 Hz and 8 Hz,
4J ¼ 2 Hz, 1H), 7.07 (dd, 3J ¼ 8 Hz and 8 Hz, 1H), 7.22e7.24 (m, 3H),
7.36 (d, 3J ¼ 8 Hz,1H), 7.89 (m, 2H), 8.08 (dd, 3J ¼ 8 Hz, 4J ¼ 2 Hz,1H).
13C NMR (CDCl3,
d) 50.79 (OMe), 126.36 (CH), 127.75 (CH), 129.57
(C), 130.27 (CH), 131.71 (C), 132.13 (CH), 132.67 (CH), 134.18 (C),
134.83 (CH), 138.58 (CH). 29Si{1H} NMR (C6D6,
d
) ꢀ32.0. Anal. Calc.
for C14H15BrO2Si: C, 52.02; H, 4.68. Found: C, 51.82; H, 5.01%.
m.p. 112.0e114.0 ꢁC (in air). 1H NMR (C6H6,
d
) ꢀ0.10 (s, 3H),
4.2.3. o-Bromo[dimethoxy(methyl)silyl]benzene (2b)
1.6e2.5 (br, 18H), 3.1e3.4 (br, 6H), 6.6e6.9 (br, 4H), 7.27 (ddd,
3J ¼ 7 Hz and 7 Hz, 4J ¼ 1 Hz, 2H), 7.51 (d, 3J ¼ 7 Hz, 1H), 7.90 (d,
A solution of n-BuLi in hexane (1.55 M, 20.0 mL, 31 mmol) was
added dropwise to a solution of 1,2-dibromobenzene (3.6 mL,
30 mmol) in THFeEt2O (60 mL/60 mL) over 30 min at ꢀ110 ꢁC
(ethanol/liq. N2 slush bath). After the reaction mixture was stirred
at the same temperature for 40 min, chloro(dimethoxy)(methyl)
silane (4.3 mL, 32 mmol) was added dropwise to the reaction
mixture over 30 min at ꢀ110 ꢁC. The reaction mixture was stirred at
the same temperature for further 1.5 h and then allowed to warm to
ambient temperature. After the solvents were removed in vacuo,
the residue was diluted with hexane (70 mL) and filtered through
a glass fiber pad to remove inorganic salts. The filtrate was
concentrated in vacuo to give an oil (7.56 g). The oil was subjected
to bulb-to-bulb distillation (57e62 ꢁC (bath temp.)/0.15 mmHg) to
give 2b (6.29 g, 80% yield) as a colorless oil.
3J ¼ 7 Hz, 1H). 13C NMR (CDCl3,
d
) ꢀ4.98 (Me), 21.23 (CH3),
22.0e24.1 (CH3), 48.9e50.3 (br, OMe), 127.2e127.9 (br, CH), 128.53
(CH), 129.43 (CH), 133.26 (CH), 134.95(CH), 138.19 (C), 138.0e144.0
(br, C), 157.07 (C). 11B{1H} NMR (CDCl3 ) 74 (br). 29Si{1H} NMR
d
(CDCl3
Found: C, 75.39; H, 8.46%.
d
) ꢀ12.4. Anal. Calc. for C27H35BO2Si: C, 75.34; H, 8.20.
4.2.6. o-(Dimesitylboryl)(phenylsilyl)benzene (1a)
A solution of 4a (514 mg, 1.0 mmol) in THF (3 mL) was added
dropwise to a suspension of LiAlH4 (41 mg, 1.1 mmol) in THF (1 mL)
at 0 ꢁC over 4 min, and the reaction mixture was stirred at room
temperature for 3 h. The reaction mixture was concentrated in vacuo
to yield milky oil of 9a. The oil was vigorously stirred in hexane
(5 mL) to form a white suspension. BF3$OEt2 (0.70 mL, 5.5 mmol) was
added to the white suspension at room temperature, and the reac-
tion mixture was stirred at the same temperature for 2 h. Then the
1H NMR (C6D6,
d
) 0.53 (s, 3H), 3.45 (s, 6H), 6.83 (ddd, 3J ¼ 8 Hz and
8 Hz, 4J ¼ 2 Hz, 1H), 7.03 (ddd, 3J ¼ 8 Hz and 8 Hz, 4J ¼ 1 Hz, 1H), 7.41
(d, 3J ¼ 8 Hz,1H), 7.88 (dd, 1J ¼ 8 Hz,4J ¼ 1 Hz,1H). 13C NMR (CDCl3,
d)