M. Suginome et al.
Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
325
room temperature over 20 min. The resultant blue-purple suspen-
sion was vigorously stirred for 3 days at room temperature. Under
a nitrogen atmosphere, the supernatant solution was decanted and
the remaining precipitates were centrifuged to allow separation of
the precipitates. The precipitates were washed with hexane. The
combined hexane solution was evaporated in vacuo. Bulb-to-bulb
distillation (90 ꢃC/10 mmHg (bath temperature)) afforded 1a (8.5
g, 74%). 1H NMR (C6D6) ꢁ 0.22 (s, 6H), 0.81 (t, J ¼ 7:2 Hz, 2H),
1.00 (d, J ¼ 6:8 Hz, 6H), 1.02 (d, J ¼ 6:8 Hz, 6H), 1.20 (t, J ¼
6:8 Hz, 2H), 1.91 (m, 2H), 3.29 (septet, J ¼ 6:8 Hz, 1H), 3.47
(septet, J ¼ 6:8 Hz, 1H); 13C NMR (C6D6) ꢁ 1.1, 18.5, 24.0,
25.2, 25.6, 27.2 (br), 49.5, 57.5 (br); 11B NMR (C6D6) ꢁ 53.2;
29Si NMR (C6D6) ꢁ ꢂ15:2 (broad). HRMS Calcd for C11H26BNSi
(Mþ): 211.1927. Found: 211.1922.
Experimental
General. 1H, 11B, and 13C NMR spectra were recorded on a
Varian Gemini 2000 spectrometer (7.0 T magnet) at ambient tem-
perature. 29Si NMR spectra were recorded on a JEOL JNM-
GX400 spectrometer (9.3 T magnet) at ambient temperature.
1H NMR data are reported as follows: chemical shift in ppm
downfield from tetramethylsilane (ꢁ scale), multiplicity (s ¼
singlet, d ¼ doublet, t ¼ triplet, q ¼ quartet, and m ¼ multiplet),
coupling constant (Hz), and integration. 13C NMR chemical shifts
are reported in ppm downfield from tetramethylsilane (ꢁ scale).
All 13C NMR spectra were obtained with complete proton decou-
pling. 11B NMR chemical shifts are reported in ppm downfield
from Et2O BF3 (ꢁ scale). 29Si NMR chemical shifts are reported
in ppm downfield from tetramethylsilane (ꢁ scale). High resolu-
tion mass spectra (HRMS) were recorded on a JEOL JMS-
SX102A spectrometer.
All reactions were carried out under an argon or nitrogen atmo-
sphere. Me2S BH3 and BCl3 were purchased from commercial
sources, and used without further purification. Allylchlorodimeth-
ylsilane, trimethylsilyldiisopropylamine, and 1,1,3,3-tetramethyl-
butyl isocyanide were purchased from commercial sources and
purified by distillation before use. All solvents were distilled
under an argon atmosphere from appropriate drying agents before
use.
Synthesis of Chloro(3-dichloroborylpropyl)dimethylsilane
(4). To a solution of dimethyl sulfide–borane (6.2 mL, 66 mmol)
in dichloromethane (24 mL) placed in a three-necked flask was
added a solution of allylchlorodimethylsilane (3) (20 g, 149
mmol) in dichloromethane (24 mL) dropwise over 40 min at room
temperature. The mixture was stirred for 10 h at room tempera-
ture. The solution was then transferred to a three-necked flask fit-
ted with a dry-ice condenser and a gas inlet. The volatile materials
were evaporated under a vacuum at room temperature. Into the
residue heated at 110 ꢃC was introduced BCl3 (21 mL, 250 mmol)
over 45 min via a gas-inlet tube with vigorous stirring. The mix-
ꢁ
Synthesis of 2-Diisopropylamino-1,1-diphenyl-1-sila-2-bora-
cyclopentane (1b). According to a procedure similar to that for
the synthesis of 1a, 1b was prepared from chloro{3-[chloro(diiso-
propylamino)boryl]propyl}diphenylsilane (2.1 g, 5.2 mmol) over
2 days at room temperature. 1b (0.60 g, 35%) was isolated by
bulb-to-bulb distillation (160–190 ꢃC/0.4 mmHg (bath tempera-
ꢁ
1
ture)). 1b: H NMR (C6D6) ꢁ 0.83 (d, J ¼ 6:8 Hz, 6H), 1.07 (d,
J ¼ 6:8 Hz, 6H), 1.26 (t, J ¼ 6:8 Hz, 2H), 1.37 (t, J ¼ 6:8 Hz,
2H), 2.00 (m, 2H), 3.06 (septet, J ¼ 6:8 Hz, 1H), 3.90 (septet, J ¼
6:8 Hz, 1H), 7.14–7.22 (m, 6H), 7.63–7.66 (m, 4H); 13C NMR
(C6D6) ꢁ 16.6, 22.5, 24.4, 24.7, 26.9, 47.0, 60.9, 128.5, 129.2,
136.4, 138.9; 11B NMR (C6D6) ꢁ 53.3; 29Si NMR (C6D6) ꢁ
ꢂ13:0. HRMS Calcd for C21H30BNSi (Mþ): 335.2241. Found:
335.2240.
Reaction of 1a with Alcohols: A Representative Reaction of
1a with Isopropyl Alcohol. A mixture of 1a (0.10 g, 0.47 mmol)
and isopropylꢃalcohol (0.11 mL, 1.42 mmol) in C6D6 (4 mL) was
heated at 50 C. Periodically, a small portion of the sample was
taken out, and the extent of the reaction was checked by 1H NMR.
No intermediary species, such as 2-isopropoxy-1,1-dimethyl-1-si-
la-2-boracyclopentane, were detected by the 1H NMR observation.
After 24 h, the volatile materials were evaporated under a vacuum.
ꢃ
ꢃ
ture was heated at 110 C for 2 h, and then 1-hexene (27 mmol)
Quick bulb-to-bulb distillation (90 C/10 mmHg (bath tempera-
was added while still heating. The mixture was further stirred at
110 ꢃC for 30 min and then cooled to room temperature. The vola-
tile materials were evaporated under a vacuum. Distillation under
a vacuum (79–93 ꢃC/15 mmHg) afforded 4 (28 g, 87% for 2
steps) as a colorless liquid.
1H NMR (C6D6) ꢁ 0.12 (s, 6H), 0.42 (m, 2H), 1.11 (t, 2H), 1.37
(m, 2H); 13C NMR (C6D6) ꢁ 2.7, 20.2, 22.5, 34.0 (br); 11B NMR
(C6D6) ꢁ 62.1; 29Si NMR (C6D6) ꢁ 30.2.
ture)) of the residue gave 1-dimethylsilyl-3-(diisopropylboryl)pro-
pane (90 mg, 83%). An attempt at further purification of the ma-
terial by distillation was accompanied by slight decomposition.
The material did not give a satisfactory mass spectrum under EI
or FAB ionization conditions. 1H NMR (C6D6) ꢁ 0.05 (d, J ¼
2:8 Hz, 6H), 0.69 (m, 2H), 0.88 (t, J ¼ 7:6 Hz, 2H), 1.09 (d, J ¼
6:0 Hz, 12H), 1.69 (m, 2H), 4.16 (m, 1H), 4.35 (septet, J ¼ 6:0
Hz, 2H); 13C NMR (C6D6) ꢁ ꢂ13:8, 17 (br), 18.2, 20.2, 25.2,
65.5; 11B NMR (C6D6) ꢁ 29.8; 29Si NMR (C6D6) ꢁ 13.9.
Reaction of 1a with Diethylamine: Amino Group Exchange.
To a 0.5 M solution of 1a (1.0 g, 4.7 mmol) in toluene was added
diethylamine (3.0 mL, 29 mmol) at room temperature. The mix-
ture was stirred at 90 ꢃC for one week. Evaporation of the voꢃlatile
materials and bulb-to-bulb distillation under a vacuum (85 C/8
mmHg (bath temperature)) afforded 2-diethylamino-1,1-dimeth-
yl-1-sila-2-boracyclopentane (0.65 g, 75%). 1H NMR (C6D6) ꢁ
0.23 (s, 6H), 0.887 (t, J ¼ 7:2 Hz, 3H), 0.892 (t, J ¼ 7:2 Hz,
2H), 0.96 (t, J ¼ 7:2 Hz, 3H), 1.05 (t, J ¼ 7:2 Hz, 2H), 1.94
(quintet, J ¼ 7:2 Hz, 2H), 2.91 (q, J ¼ 7:2 Hz, 2H), 3.06 (q, J ¼
7:2 Hz, 2H); 13C NMR (C6D6) ꢁ 2.9, 16.1, 17.0, 18.2, 24.2, 44.3,
50.5; 11B NMR (C6D6) ꢁ 54.3; 29Si NMR (C6D6) ꢁ ꢂ17:2. HRMS
Calcd for C9H22BNSi (Mþ): 183.1615. Found: 183.1617.
Synthesis of Chloro{3-[chloro(diisopropylamino)boryl]pro-
pyl}dimethylsilane (2). To a solution of 4 (2.38 g, 11.0 mmol)
in dichloromethane (6.4 mL) was added dropwise a solution N-tri-
methylsilyldiisopropylamine (1.59 g, 11.0 mmol) in dichlorometh-
ꢃ
ane (6.4 mL) over 5 min at ꢂ40 C. The solution was stirred for
10 h while gradually raising the bath temperature (ꢂ40 ꢃC to room
temperature). After concentration of the reaction mixture under a
vacuum, 2 (2.65 g, 86%) was isolated by bulb-to-bulb distillation
ꢃ
1
(100 C/0.2 mmHg (bath temperature)). H NMR (C6D6) ꢁ 0.20
(s, 6H), 0.75–0.79 (m, 2H), 0.91 (d, J ¼ 6:8 Hz, 6H), 1.00–1.13
(br, 6H), 1.18 (t, J ¼ 8:0 Hz, 2H), 1.73 (m, 2H), 3.24–3.43 (bs,
2H); 13C NMR (C6D6) ꢁ 1.8, 20.2, 22.5, 23.2, 26.6 (br), 48.2
(br); 11B NMR (C6D6) ꢁ 38.6; 29Si NMR (C6D6) ꢁ 30.7.
Synthesis of 2-Diisopropylamino-1,1-dimethyl-1-sila-2-bo-
racyclopentane (1a). To a suspension of Na/K alloy, prepared
from Na (2.54 g, 66 mmol) and K (7.7 g, 198 mmol), in hexane
(90 mL) was added 2 (15.5 g, 55 mmol) in hexane (90 mL) at
Reaction of 1a with 1-Octyne. To a mixture of 1a (21.1 mg,
0.10 mmol) and 1-octyne (30 mL, 0.20 mmol) in C6D6 (0.5 mL)
was added a solution of [Pd(acac)2] (0.61 mg, 2.0 mmol) and