Full Papers
doi.org/10.1002/ejoc.202100349
139.94 ppm. 29Si NMR (600 MHz, chloroform-d, trace Cr(acac)3): δ
Silylation of Organic Thiols
À 67.83 (s, 0.8Si), À 66.10 (s, 0.6Si), À 66.06 (s, 3Si), À 56.14 (s, 1Si),
À 13.49 (s, 0.04Si), À 11.94 (s, 0.3Si), À 1.87-0.82 (m, 38Si), 0.83 (s,
1Si), 7.85 (s, 0.1Si), 8.99-9.05 (m, 4Si) ppm.
Benzyl thiol: In a pre-dried 100.0 mL round-bottomed flask, benzyl
thiol (3.05 g, 24.56 mmol) and 1 (5.39 g, 24.22 mmol) were mixed in
dry hexanes (15.0 mL) as solvent. Freshly prepared B(C6F5)3 stock
solution was added (0.242 mL, 0.024 mmol) after 5 min stirring. The
total reaction time was 3 h, then the reaction was quenched by
adding neutral alumina. The silylated benzyl thiol product 5 (7.71 g,
contaminated with 4% silicone) was obtained using vacuum
filtration (for full experimentals for 5–7 from benzyl thiol and 8–10
from octyl thiol, including NMR spectra and GC-MS data, see SI).
The evolution of silylated products, as shown in Figure 4 to
Figure 5, involved a separate reaction for each data point (see
Table S5, Figures S6, S7, SI), changing only the ratio of hydrosilane
against disulfide [SiH]/[SiOEt].
Reduction of bis(triethoxysilylpropyl)disulfide S2 using BisH
1: ([SiH]/[SiOEt]=8:6 to give SÀ OSi3(Si)
PhCH2SSiMe(Me3SiO)2 (compound 5): PhCH2SH=1:0.18.
1H NMR (600 MHz, chloroform-d): δ Compound 5 (1 equiv.): 0.12-
0.14 (m, 18H, PhCH2SSiMe(Me3SiO)2), 0.27 (s, 3H, PhCH2SSiMe
(Me3SiO)2), 3.75 (m, 2H, PhCH2SSiMe(Me3SiO)2), 7.20–7.33 (m, 5H
arom); PhCH2SH (0.18 equiv.): 1.76 (t, J=7.53 Hz, 1H, SH), 3.76 (s, 2H,
PhCH2SH) 7.20–7.33 (m, 5H arom); Impurity: 3.60 (s, 0.03H, from
residual benzyl thiol starting material).
To a pre-dried 200 mL round-bottomed flask purged with dry N2
was added bis(triethoxysilylpropyl)disulfide stock solution (0.50 g,
1.05 mmol) and BisH 1 (1.90 g, 8.54 mmol) together with dry
toluene (0.730 g, 7.92 mmol) as solvent. Freshly prepared B(C6F5)3
stock solution was added (0.345 mL, 0.067 mmol) after 5 min
stirring. The total reaction time was 3 h, then the reaction was
quenched by adding neutral alumina (recovered 2.21 g). Note: for
most reactions, bubble formation ceased within 30 min, but 3 h
was used to ensure complete reaction in all titrations.
Reductive Cleavage of Organic Disulfides: Silylation of
dibenzyl disulfide with Bis-H
SÀ OSi3(Si): δ 0.02-0.06 (m, 9H, CH2Si((OSiMe(OSiMe3)2)3), 0.09–0.13
(m, 72H, CH2Si((OSiMe(OSiMe3)2)3 and CH2SSiMe(OSiMe3)2 over-
lapped), 0.27–0.29 (m, 3H, CH2SSiMe(OSiMe3)2), 0.62–0.73 (m, 2H,
SiCH2CH2CH2S), 1.66–1.69 (m, 2H, SiCH2CH2CH2S), 2.45–2.52 (m, 2H,
SiCH2CH2CH2S)(full spectrum in SI);13C NMR (600 MHz, chloroform-d):
δ À 1.86, 2.06, 5.16, 14.53, 21.81, 26.55, 30.07, 77.36, 126.16, 128.58,
138.21 ppm; 29Si NMR (600 MHz, chloroform-d, trace Cr(acac)3): δ
À 66.16–À 65.90 (m, 1Si), À 54.49 (s, 2Si), À 30.67 (s, 1Si), 7.45–7.62
(m, 16Si), 9.40–9.53 (m, 4Si) ppm.
In a pre-dried 100.0 mL round-bottomed flask dibenzyl disulfide
(0.50 g, 2.03 mmol), Bis-H 1 (0.91 g, 4.09 mmol) with dry dichloro-
methane (3.81 g, 44.86 mmol) as solvent were added. Freshly
prepared B(C6F5)3 stock solution was added (0.167 mL, 0.033 mmol)
after 5 min stirring. The total reaction time was 3 h, then the
reaction was quenched by adding neutral alumina. The silylated
benzyl disulfide product 5 was obtained (1.27 g) using vacuum
filtration (for preparation and reductive silylation of dibenzyl
disulfide to 6, 7, of didodecyl disulfide to 13 with 2, and tetrasulfide
14 with 1 see SI). Due to the presence of water, an excess of the
silane was required for complete conversion. Production of
PhCH2SH is due to hydrolysis of 5.
Complete reduction of bis(triethoxysilylpropyl)disulfide S2
using BisH 1: ([SiH]/[SiOEt]=9:6 to give SÀ OSi3(Si)
PhCH2SSiMe(Me3SiO)2
(compound
5):
(PhCH2S)2 :PhCH2SH=
SÀ OSi3(Si): δ 0.03–0.07 (m, 9H, CH2Si((OSiMe(OSiMe3)2)3), 0.10–0.15
(m, 72H, CH2Si((OSiMe(OSiMe3)2)3 and CH2SSiMe(OSiMe3)2 over-
lapped), 0.28–0.30 (m, 3H, CH2SSiMe(OSiMe3)2), 0.64–0.74 (m, 2H,
SiCH2CH2CH2S), 1.69–1.72 (m, 2H, SiCH2CH2CH2S), 2.50–2.54 (m, 2H,
SiCH2CH2CH2S); Silicone impurities (integration relative to SÀ OSi3
(Si)): 0.03–0.07 (m, 13H, overlapped), 0.10–0.15 (m, 84H, over-
lapped), 0.37 (m, 0.3H)(full spectrum in the SI).
82.0:4.1:13.9.
1H NMR (600 MHz, chloroform-d): δ Compound 5 (1 equiv.) see
above; (PhCH2S)2 (0.05 equiv.) δ 3.60 (s, 4H, (PhCH2)2SS), 7.16–7.34
(m, 5H, arom); PhCH2SH (0.17 equiv.) 1.76 (t, J= 7.56 Hz, 1H, SH),
3.76 (s, 2H, PhCH2SH), 7.16–7.34 (m, 5H arom); Silicone impurity:
0.03 (s, 4H) ppm. (full spectrum in SI.)
Each data point in Figure 4 to Figure 5 was obtained from a
separate reaction conducted under identical reaction conditions,
changing only the ratio of hydrosilane against disulfide [SiH]/[SiOEt]
(see Figures S8–S10, SI).
Reduction of bis(triethoxysilylpropyl)disulfide S2 using
dimethylphenylsilane 3 ([SiH]/[SiOEt]=8:6 to give SÀ OSi3
The process described above (Reductive Cleavage of Organic
Disulfides) was followed to prepare silylated SÀ OSi3: bis
(triethoxysilylpropyl)disulfide stock solution (0.50 g, 1.05 mmol);
dimethylphenylsilane (1.15 g, 8.44 mmol); dry toluene (0.501 g,
5.44 mmol) as solvent. Freshly prepared B(C6F5)3 stock solution
(0.672 mL, 0.067 mmol)(recovered 1.44 g).
Reduction of bis(triethoxysilylpropyl)tetrasulfide S4 using
BisH 1 ([SiH]/[SiOEt]=12:6 to give SÀ OSi3(Si)
The process described above was followed: bis(triethoxysilylpropyl)
tetrasulfide S4 stock solution (0.52 g, 0.96 mmol); BisH (2.48 g,
11.1 mmol); dry toluene (0.90 g, 9.77 mmol); B(C6F5)3 stock solution
was added (0.456 mL, 0.089 mmol)(recovered 2.69 g). A separate
reaction was undertaken for each data point in Figures S11–S14,
Table S6, changing only the ratio of hydrosilane against tetrasulfide
[SiH]/[SiOEt].
1H NMR (600 MHz, chloroform-d):
δ
SÀ OSi3: 0.35 (s, 24H,
PhSiMe2CH2CH2CH2Si((OSi(Me)2Ph)3), 0.60–0.71 (m, 2H, CH2CH2CH2Si-
((OSi(Me)2Ph)3), 1.60–1.88 (m, 2H, CH2CH2CH2Si((OSi(Me)2Ph)3), 2.44–
2.82 (m, 2H, CH2CH2CH2Si((OSi(Me)2Ph)3), 7.16–7.57 (m, 20H arom).
Overlapped silicone (integration relative to SÀ OSi3): 0.29 (s, 13H),
0.32 (s, 10H), 0.38–0.43 (m, 10H), 0.52–0.54 (m, 10H); Residual
ethoxy: 1.07–1.14 (m, 0.71H, SiOCH2CH3), 3.60–3.73 (m, 0.52H,
SiOCH2CH3)(full spectrum in the SI).
1H NMR (600 MHz, chloroform-d): δ 0.03–0.06 (m, 9H, CH2Si((OSiMe
(OSiMe3)2)3), 0.11–0.12 (m, 72H, CH2Si((OSiMe(OSiMe3)2)3 and
CH2SSiMe(OSiMe3)2 overlapped), 0.21–0.30 (m, 3H, CH2SSiMe
(OSiMe3)2), 0.64–0.74 (m, 2H, SiCH2CH2CH2S), 1.68–1.74 (m, 2H,
SiCH2CH2CH2S), 2.50–2.55 (m, 2H, SiCH2CH2CH2S); Residual ethoxy:
1.19–1.21 (m, 0.12H, SiOCH2CH3), 3.80 (s, 0.08H, SiOCH2CH3); Silicone
13C NMR (600 MHz, chloroform-d): δ À 0.22, 0.58, 0.65, 0.68, 0.97,
12.78, 13.56, 14.15, 14.58, 21.57, 26.97, 27.72, 28.07, 28.21, 30.13,
32.92, 125.42, 127.82, 128.35, 129.16, 129.36, 133.12, 137.99, 139.43,
Eur. J. Org. Chem. 2021, 2694–2700
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