1342 Bull. Chem. Soc. Jpn., 78, No. 7 (2005)
Photophysical Properties of Diaryldisilanes
10ꢂ5 M solutions in a quartz cell with path-length of 1 cm. The
fluorescence quantum yields were determined by comparison with
a naphthalene as a standard (ꢂ ¼ 0:23 in cyclohexane).23 3-Meth-
ylpentane (3-MP) was purified by passage over a silver nitrate–
alumina column and was degassed before the fluorescence
measurement. Spectral grade acetonitrile was purchased (Nakalai
Tesque) and degassed before use.
Isomers were separated by preparative GC. trans-3c: colorless
crystals. mp 71–72 ꢁC. 1H NMR ꢆ 0.44 (s, 6H), 1.10–1.16 (m,
4H), 1.58–1.68 (m, 2H), 1.95–2.05 (m, 2H), 2.18 (s, 6H), 7.12
(d, J ¼ 7:8 Hz, 4H), 7.53 (d, J ¼ 7:8 Hz, 4H). 13C NMR ꢆ
ꢂ4:37, 16.01, 21.58, 26.65, 129.10, 134.58, 134.86, 138.47.
29Si NMR ꢆ ꢂ23:67. MS (EI) m=z (relative intensity) 324 (Mþ,
11), 225 (100). UV (ꢂmax ð"Þ in 3-MP) 238.6 nm (20700). Found:
C, 73.78; H, 8.75%. Calcd for C20H28Si2: C, 74.00; H, 8.69%. cis-
3c: a colorless oil. 1H NMR ꢆ 0.46 (s, 6H), 0.95–1.05 (m, 4H),
1.20–1.30 (m, 2H), 1.70–1.90 (m, 2H), 2.12 (s, 6H), 7.04 (d,
J ¼ 7:7 Hz, 4H), 7.46 (d, J ¼ 7:7 Hz, 4H). 13C NMR ꢆ ꢂ3:92,
16.14, 21.55, 26.64, 128.95, 134.47, 134.93, 138.43. 29Si NMR
ꢆ ꢂ23:67. MS (EI) m=z (relative intensity) 324 (Mþ, 13), 225
(100). UV (ꢂmax ð"Þ in 3-MP) 232.0 nm (19300). Found: C,
74.11; H, 8.89%. Calcd for C20H28Si2: C, 74.00; H, 8.69%.
1,2-Dimethyl-1,2-bis(p-trifluoromethylphenyl)-1,2-disilacy-
clohexane (3b): Yield (67%, cis/trans = 1/2.6). Isomers were
separated by preparative HPLC (ODS, CH3CN as eluent). trans-
3b: a colorless oil. 1H NMR ꢆ 0.20 (s, 6H), 0.90–0.96 (m, 4H),
1.44–1.58 (m, 2H), 1.80–1.94 (m, 2H), 7.32 (d, J ¼ 7:8 Hz,
4H), 7.46 (d, J ¼ 7:8 Hz, 4H). 13C NMR ꢆ ꢂ5:17, 15.13, 26.18,
124.71 (q, J ¼ 3:7 Hz), 125.00 (q, J ¼ 271:7 Hz), 131.03 (q,
J ¼ 32:0 Hz), 134.60, 143.12. 29Si NMR ꢆ ꢂ23:07. 19F NMR ꢆ
ꢂ62:38. MS (EI) m=z (relative intensity) 432 (Mþ, 8), 314
(100). UV (ꢂmax ð"Þ in 3-MP) 246.7 nm (13600). Found: C,
55.37; H, 5.23%. Calcd for C20H22F6Si2: C, 55.53; H, 5.13%.
cis-3b: a colorless oil. 1H NMR ꢆ 0.30 (s, 6H), 0.78–0.87 (m,
2H), 0.96–1.07 (m, 2H), 1.6–1.7 (m, 4H), 7.16 (d, J ¼ 8:3 Hz,
4H), 7.32 (d, J ¼ 8:3 Hz, 4H). 13C NMR ꢆ ꢂ4:71, 15.17, 26.24,
124.52 (q, J ¼ 3:7 Hz), 124.90 (q, J ¼ 271:7 Hz), 131.02 (q,
J ¼ 32:0 Hz), 134.80, 142.68. 29Si NMR ꢆ ꢂ22:82. 19F NMR
ꢆ ꢂ62:42. MS (EI) m=z (relative intensity) 432 (Mþ, 9), 314
(100). UV (ꢂmax ð"Þ in 3-MP) 241.1 nm (15000). Found: C,
55.62; H, 5.20%. Calcd for C20H22F6Si2: C, 55.53; H, 5.13%.
1,2-Bis(p-methoxyphenyl)-1,2-dimethyl-1,2-disilacyclohex-
ane (3d): Isomers were separated by preparative HPLC (hexane/
AcOEt = 10/1) to give 466 mg (1.31 mmol, 44% yield) of trans-
3d as colorless solids and 179 mg (0.501 mmol, 17% yield) of
cis-3d as a colorless oil.
1,2-Dimethyl-1,2-diphenyl-1,2-disilacyclohexane (3a). To a
solution of 1,1,2,2-tetraphenyl-1,2-disilacyclohexane (23.8 g, 56.7
mmol) in CH2Cl2 (100 mL) was added TfOH (10 mL, 110 mmol)
ꢁ
dropwise at 0 C over 10 minutes. Upon completion of the addi-
tion, the addition funnel was rinsed with CH2Cl2 (2 ꢃ 2 mL). Af-
ter being stirred at 0 ꢁC for 1.5 h, the solvent was evaporated. The
ꢁ
residue was dissolved in Et2O (100 mL) and cooled to 0 C. To
the resulting solution was added 180 mL (170 mmol) of a 0.94
ꢁ
M solution of MeMgI in Et2O dropwise at 0 C over 1.5 h. Upon
completion of the addition, the addition funnel was rinsed with
Et2O (10 mL), then the reaction mixture was allowed to warm
to room temperature. After being stirred for 1.5 h, the reaction
mixture was hydrolyzed with 10% NH4Cl (100 mL). Then the bi-
phasic mixture was separated and the aqueous layer was extracted
with Et2O (3 ꢃ 100 mL). The combined organic layer was washed
with brine (100 mL) and dried over MgSO4. After filtration and
evaporation, the residue was subjected to silica-gel column chro-
matography (hexane, Rf ¼ 0:29). The collected fraction was con-
centrated to give 12.9 g (43.6 mmol, 77% yield, cis/trans = 1/
2.5) of 1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane 3a as a
colorless oil.16
Isomers were separated by preparative HPLC (ODS, CH3CN as
1
eluent). trans-3a: H NMR ꢆ 0.38 (s, 6H), 1.08 (m, 4H), 1.59 (m,
2H), 1.96 (m, 2H), 7.2–7.3 (m, 6H), 7.55 (dd, J ¼ 7:4, 2.0 Hz,
4H). 13C NMR ꢆ ꢂ4:55, 15.79, 26.54, 128.23, 128.94, 134.47,
138.48. 29Si NMR ꢆ ꢂ23:42. UV (ꢂmax ð"Þ in 3-MP) 237.5
(15200). UV (ꢂmax ð"Þ in acetonitrile) 238.0 nm (14200). cis-
3a: 1H NMR ꢆ 0.42 (s, 6H), 0.9–1.0 (m, 2H), 1.15–1.25 (m,
2H), 1.7–1.85 (m, 4H), 7.15–7.2 (m, 6H), 7.4–7.5 (m, 4H).
13C NMR ꢆ ꢂ4:14, 15.89, 26.57, 128.05, 128.92, 134.80,
138.02. 29Si NMR ꢆ ꢂ23:37. UV (ꢂmax ð"Þ in 3-MP) 233.4 nm
(13700). UV (ꢂmax ð"Þ in acetonitrile) 234.6 nm (13300).
Conversion from 3a to 3b–e. A Typical Procedure, 1,2-Di-
trans-3d: mp 72–73 ꢁC. 1H NMR ꢆ 0.46 (s, 6H), 1.10–1.20 (m,
4H), 1.58–1.72 (m, 2H), 1.96–2.10 (m, 2H), 3.36 (s, 6H), 6.92 (d,
J ¼ 8:3 Hz, 4H), 7.53 (d, J ¼ 8:3 Hz, 4H). 13C NMR ꢆ ꢂ4:17,
16.24, 26.70, 54.64, 114.28, 129.04, 135.85, 160.85. 29Si NMR
ꢆ ꢂ23:80. MS (EI) m=z (relative intensity) 356 (Mþ, 15), 257
(100). UV (ꢂmax ð"Þ in 3-MP) 240.0 nm (31500). Found: C,
67.50; H, 7.90%. Calcd for C20H28O2Si2: C, 67.36; H, 7.91%.
cis-3d: 1H NMR ꢆ 0.48 (s, 6H), 0.98–1.07 (m, 4H), 1.22–1.31
(m, 2H), 1.76–1.91 (m, 2H), 3.30 (s, 6H), 6.84 (d, J ¼ 8:4 Hz,
4H), 7.46 (d, J ¼ 8:4 Hz, 4H). 13C NMR ꢆ ꢂ3:74, 16.37, 26.70,
54.56, 114.13, 128.66, 136.21, 160.81. 29Si NMR ꢆ ꢂ23:90. MS
(EI) m=z (relative intensity) 356 (Mþ, 16), 257 (100). UV (ꢂmax
ð"Þ in 3-MP) 237.4 nm (33900). Found: C, 67.46; H, 7.97%. Calcd
for C20H28O2Si2: C, 67.36; H, 7.91%.
methyl-1,2-bis(p-methylphenyl)-1,2-disilacyclohexane
(3c):
To a solution of 1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane
3a (1.04 g, 3.50 mmol) in CH2Cl2 (7 mL) was added TfOH
(0.62 mL, 7.0 mmol) dropwise at 0 ꢁC to afford a mixture of
cis- and trans-4-OTf. After being stirred for 1.5 h at 0 ꢁC, the sol-
vent was evaporated. The crude 4-OTf was dissolved in Et2O (7
mL) and cooled to 0 ꢁC. To the resulting solution were added
CuCN (31.7 mg, 0.354 mmol, 10.1 mol %) in one portion and
14.5 mL (14 mmol) of a 0.96 M solution of p-methylphenylmag-
nesium bromide in Et2O dropwise over 10 min at 0 ꢁC. Upon
completion of the addition, the addition funnel was rinsed with
Et2O (2 mL); then the reaction mixture was allowed to warm to
room temperature. After being stirred for 1.5 h, the reaction mix-
ture was hydrolyzed with 10% NH4Cl (9 mL). The resulting bi-
phasic mixture was separated and the aqueous layer was extracted
with Et2O (3 ꢃ 30 mL). The combined organic layer was washed
with brine (50 mL) and dried over MgSO4. After filtration and
evaporation, the residue was subjected to column chromatography
on silica gel (hexane/AcOEt = 10/1, Rf ¼ 0:58) followed by
preparative HPLC (hexane/AcOEt = 20/1) to give 687 mg
(2.12 mmol, 61% yield, cis/trans = 1/2.2) of 1,2-bis(p-methyl-
phenyl)-1,2-dimethyl-1,2-disilacyclohexane 3c as a colorless oil.
1,2-Dichloro-1,2-dimethyl-1,2-disilacyclohexane (4-Cl): To
solution of 1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane
a
(2.41 g, 8.13 mmol) in benzene (10 mL) was added AlCl3 (12.1
mg, 0.0906 mmol), and then HCl gas was introduced into this
mixture for 1.3 h at room temperature. Additional AlCl3 (16.9
mg, 0.127 mmol) was added. After being stirred for 2.3 h, hexane
(10 mL) and acetone (2 mL) were added to quench the reaction,
and the resulting acetone/AlCl3 complex was removed by filtra-
tion. Evaporation followed by distillation gave 1.37 g (6.40 mmol,