Organic Process Research & Development
Article
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crystalline solid, which decomposes at ∼230 °C. H NMR δ
(500 MHz, CD2Cl2): 2.25 (s, Cp*). 11B NMR δ (160.4 MHz,
1.65 (mc, 1H), 1.88 (mc, 2H), 2.14 (mc, 2H), 3.87 (mc, 1H).
13C{1H} NMR δ (125.8 MHz, CD2Cl2): 11.0, 29.1, 69.1. GC/
MS: m/z = 126 (1, M+), 98 (40, M+ − C2H4), 70 (70,
CD2Cl2): −30,6 [s, B(SiCl3)4 ], 29Si satellites at −30.9 and
−
−30.4. 29Si NMR δ (99.3 MHz, CD2Cl2): 21.6 (q, 4 SiCl3, 1JSi,B
= 89 Hz). For ESI-MS, see SI.
C4H6O+), 55 (100, C4H7 ).
+
2,4,6-Tri-n-pentyl-1,3,5-trioxane (7b)32 − Preparative
Example. A solution of 5.0 mg (4.8 mmol, 0.016 mol %) of 2c
and 0.7 mL of dichloromethane was added to 3.00 g (30.0
mmol) of hexanal under stirring. The solution was cooled to
−20 °C for 24 h. The product was partially crystallized. 2 N
NaOH (10 μL) was under stirring, and the mixture was
warmed to rt. After filtration through silica to remove the
catalyst, residual hexanal and dichloromethane were removed
in vacuo at 50 °C/0.1 mbar. Yield 2.55 g of 7b, purity 96%
Synthesis of 2e. A solution of 249 mg (453 μmol) of
H+B(SiCl3)4 (Bochmann’s acid, 10) in 2.4 mL of dichloro-
−
methane was slowly added to a solution of 305 mg (479 μmol)
of hexakis(trimethylsilyl)germanocene (3b) in 0.8 mL of
dichloromethane at rt in an argon atmosphere. The orange-
colored mixture was allowed to stand for 30 min at rt. Then,
3.6 g of n-heptane was added dropwise to the solution until no
more solid precipitated (∼3.6 g). The mother liquor was
removed by means of a syringe, and the off-white solid was
washed two times with ∼0.8 mL n-pentane and dried in vacuo.
Yield 238 mg (58%) of an off-white crystalline solid, mp 299
°C (dec.).
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(GC), 85%. H NMR δ (500 MHz, CD2Cl2): 0.90 (t, J = 7.0
Hz, 9H, CH3), 1.26−1.44 [m, 18H, CH3−(CH2)3], 1.59−1.66
(m, 6H, CH2−CHO), 4.84 (t, J = 5.0 Hz, 3H, O−CH−O).
13C{1H} NMR δ (125.8 MHz, CD2Cl2): 13.77 (CH3), 22.56
(C5), 23.22 (C4), 31.61 (C3), 34.43 (C2), 101.54 (C1). GC/
MS: m/z = 299 (1, M+), 229 (3, M+ −C5H10), 201 (70, M+ −
C6H10O), 101 (100, C5H11CH2O).
1H NMR δ (500 MHz, CD2Cl2): 0.44 (s, 9H, Si−CH3), 0.49
(s, 18H, Si−CH3), 7.00 (s, 2H, Cp−H). 11B NMR δ (160.4
MHz, CD2Cl2): −30.7 [s, B(SiCl3)4 ], 29Si satellites at −30.4
−
and −30.9. 29Si NMR δ (99.3 MHz, CD2Cl2): −4.50 [s, 1
Si(CH3)3], −3.68 [s, 2Si(CH3)3]. For ESI-MS, see SI.
Oxidative Coupling of Hydrosilanes with Paralde-
hydeStandard Procedure. Hydrosilane (2 mmol),
paraldehyde (101 mg, 0.76 mmol), and 300 mg of CD2Cl2
were mixed. A solution of the catalyst in ∼50 mg of CD2Cl2
was added under stirring. The solution was placed in an NMR
tube and warmed to 50 °C. From time to time, the formation
of the coupling product was monitored by 1H NMR
spectroscopy. See Table 4 for details.
Oxidative Coupling of Triethylsilane (5, R1 = R2 = R3 =
Et) with Hexanal (6, R′ = H, R″ = n-C5H11)−Standard
Procedure. In an NMR tube, 305 mg (2.62 mmol) of
triethylsilane and 282 mg (2.81 mmol, 1.07 equiv) of hexanal
were mixed under an argon atmosphere. A solution of 1.6 mg
(1.5 μmol, 0.059 mol %) of 2c in 853 mg of CD2Cl2 was added
to the tube. The contents of the tube were immediately mixed
by turning the NMR tube upside down several times. The
1,1,3,3-Tetramethyl-1,3-diphenyl-disiloxane6f (Table 4, en-
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tries 1, 6, and 7): H NMR δ (500 MHz, CD2Cl2): 0.35 (s,
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reaction was then monitored by H NMR spectroscopy (see
12H, CH3), 7.3−7.4 (m, 6H, phenyl), 7.5−7.6 (m, 4H,
phenyl). GC/MS: m/z = 286 (10, M+), 271 (100, M+ −CH3),
193 (90), 89 (10).
Figure 2 and Table 2 for results).
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Hexaethyldisiloxane (Table 2, entries 1−6 and 9−11): H
NMR δ (500 MHz, CD2Cl2): 0.60 (q, 3JH,H = 8 Hz, 12H, Si−
1,3-Dimethyl-1,1,3,3-tetraphenyldisiloxane6k (Table 4, entry
2): 1H NMR δ (500 MHz, CD2Cl2): 0.62 (s, 6H, CH3), 7.32−
7.36 (m, 8H, phenyl), 7.38−7.42 (m, 4H, phenyl), 7.53−7.57
(m, 8H, phenyl). GC/MS: m/z = 410 (10, M+), 395 (100, M+
−CH3), 332 (15), 317 (90), 255 (20), 195 (55).
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CH2), 1.01 (t, JH,H = 8 Hz, 18H, Si−CH2−CH3). GC/MS:
m/z = 246 (1, M+), 217 (100, M+ − C2H5), 189 (90, 217-
C2H4), 161 (60, 189-C2H4), 115 (2, Et3Si+).
Di-n-hexyl ether (Table 2, entries 1−6 and 9−11): 1H NMR
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δ (500 MHz, CD2Cl2): 0.95 (t, JH,H = 8 Hz, 6H, 2CH3),
1,3-Dimethyl-1,3-diphenyl-1,3-divinyldisiloxane38
Preparative Example. To a mixture of 6.64 g (44.8 mmol)
of methylphenylvinylsilane and 2.37 g (17.9 mmol) of
paraldehyde (7a) in 1.9 g of dichloromethane was added a
solution of 1.28 mg (1.24 μmol, 0.0028 mol %) of 2c in 130
mg of dichloromethane. The mixture was heated to 50 °C for 2
h, and further, 0.51 g (3.86 mmol) of 7a was added. After 6 h
at 50 °C, the reaction mixture was filtered through a small
amount of silica and volatiles were removed in vacuo. Yield 6.7
g of a colorless liquid, purity 92% (GC), 89%. 1H NMR δ (500
MHz, CD2Cl2): 0.44 (s, 6H, CH3), 5.83 (dd, 3JHH(trans) = 20
1.30−1.45 [m, 12H, 2(−CH2−)3], 1.59 (mc, 4H, O−CH2−
CH2), 3.41 (t, 3JH,H = 6.7 Hz, 4H, 2CH2−O). GC/MS: m/z =
186 (1, M+), 157 (1, M+ −CH3), 85 (100, C6H13+), 43 (70,
+
C3H7 ).
Further coupling reactions (Table 2, entries 2−7 and 9−11)
were performed according to the standard procedure.
Di-2-butyl ether (Table 2, entry 7): H NMR δ (500 MHz,
CD2Cl2): 0.94 (2t, 6H, 2CH3), 1.11 (mc, 6H, CH3), 1.38−
1.59, 3.39 (mc, 2H, 2CH−O). GC/MS: m/z = 130 (1, M+),
115 (2, M+ − CH3), 101 (30, M+ − C2H5), 57 (80, C4H9), 45
(100).
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2
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Di-cyclo-butyl Ether13c (Table 2, Entry 8)Prepara-
tive Example. A mixture of 5.94 g (84.7 mmol) of
cyclobutanone, 10.4 g (89.5 mmol) of triethylsilane, and 4 g
of dichloromethane was prepared and warmed to 45 °C. A
solution of 8.0 mg (9.0 μmol, 0.011 mol %) of 2a in 0.5 mL of
dichloromethane was added to the mixture under stirring. After
3 h at 45 °C, a second portion of 8.0 mg (9.0 μmol, 0.011 mol
%) of 2a in 0.5 mL of dichloromethane was added and heating
was continued for further 6 h. After standing overnight at rt, a
small amount of sodium carbonate was added and the di-cyclo-
butyl ether was isolated by distillation using a Vigreux column.
Hz, JHH(gem) = 3.5 Hz, 1H), 6.08 (dd, JHH(cis) = 15 Hz,
2JHH(gem) = 3.5 Hz, 1H), 6.28 (dd, 3JHH(cis) = 20 Hz,
3JHH(trans) = 15 Hz, 1H, Si−CHCH2), 7.33−7.41 (m, 6H,
phenyl), 7.54−7.58 (m, 4H, phenyl). 13C{1H} NMR δ (125.8
MHz, CD2Cl2): 129.76, 131.55, 135.61, 135.72, 139.38,
139.80. 29Si NMR δ (99.3 MHz, CD2Cl2): −11.69. GC/MS:
m/z = 312 (5, M+), 297 (5, M+ − CH3), 283 (100), 205 (70),
179 (45). For further results, see Table 4, entries 3, 8, and 9.
Triisopropylethoxysilane38 (Table 4, entry 4): H NMR δ
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(500 MHz, CD2Cl2): 1.04−1.09 (m, 21H, isopropyl), 1.19 (t, J
= 7 Hz, 3H, CH3), 3.76 (q, J = 7 Hz, 2H, CH2).
Synthesis of Phenyl-Siloxane CopolymersStandard
Procedure. A solution of 0.75 mg (0.72 μmol, 0.0070 mol %)
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Yield 9.6 g [purity 83% (GC), 75%], bp 75 °C/60 mbar. H
NMR δ (500 MHz, CD2Cl2): 1.48 (qt, J = 10.7, 8.0 Hz, 1H),
J
Org. Process Res. Dev. XXXX, XXX, XXX−XXX