Disiloxane Synthesis Based on Silicon-Hydrogen Bond Activation using Gold and Platinum on Carbon in Water or Heavy Water

Article abstract of DOI:10.1021/acs.joc.6b00556

Disiloxanes possessing a silicon-oxygen linkage are important as frameworks for functional materials and coupling partners for Hiyama-type cross coupling. We found that disiloxanes were effectively constructed of hydrosilanes catalyzed by gold on carbon in water as the solvent and oxidant in association with the emission of hydrogen gas at room temperature. The present oxidation could proceed via various reaction pathways, such as the hydration of hydrosilane into silanol, dehydrogenative coupling of hydrosilane into disilane, and the subsequent corresponding reactions to disiloxane. Additionally, the platinum on carbon catalyzed hydrogen-deuterium exchange reaction of arylhydrosilanes as substrates in heavy water proceeded on the aromatic nuclei at 80 °C with high deuterium efficiency and high regioselectivity at the only meta and para positions of the aromatic-silicon bond to give the deuterium-labeled disiloxanes.

Full text of DOI:10.1021/acs.joc.6b00556

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Article
Disiloxane Synthesis Based on Silicon-Hydrogen Bond Activation
Using Gold and Platinum on Carbon in Water or Heavy Water
Yoshinari Sawama, Masahiro Masuda, Naoki Yasukawa, Ryosuke Nakatani, Shumma Nishimura, Kyoshiro
Shibata, Tsuyoshi Yamada, Yasunari Monguchi, Hiroyasu Suzuka, Yukio Takagi, and Hironao Sajiki
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b00556 • Publication Date (Web): 29 Apr 2016
Downloaded from http://pubs.acs.org on May 1, 2016
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The Journal of Organic Chemistry
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Disiloxane Synthesis Based on SiliconꢀHydrogen Bond
Activation Using Gold and Platinum on Carbon in Water
or Heavy Water
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Yoshinari Sawama,a* Masahiro Masuda,a Naoki Yasukawa,a Ryosuke Nakatani, a Shumma Nishimura, a
Kyoshiro Shibata, a Tsuyoshi Yamada, a Yasunari Monguchi a Hiroyasu Suzuka,b Yukio Takagic and
Hironao Sajiki a *
a) Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1ꢀ25ꢀ4 Daigakuꢀnishi, Gifu 501ꢀ
1196, Japan
Phone/Fax: (+81)ꢀ58ꢀ230ꢀ8109; email: sawama@gifuꢀpu.ac.jp, sajiki@gifuꢀpu.ac.jp
b) Catalyst Development Center, N. E. Chemcat Corporation, 25ꢀ3 Koshindaira, Bando, Ibaraki 306ꢀ
0608, Japan
c) Catalyst Development Center, N. E. Chemcat Corporation, 678 Ipponmatsu, Numazu, Shizuoka 410ꢀ
0314, Japan
CORRESPONDING AUTHOR
Yoshinari Sawama and Hironao Sajiki
*Eꢀmail: sajiki@gifuꢀpu.ac.jp; sawama@gifuꢀpu.ac.jp
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ABSTRACT
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Disiloxanes possessing a siliconꢀoxygen linkage are important as frameworks for the functional
materials and coupling partners for Hiyamaꢀtype cross coupling. We found that disiloxanes were
effectively constructed of hydrosilanes catalyzed by gold on carbon in water as the solvent and oxidant
in association with the emission of hydrogen gas at room temperature. The present oxidation could
proceed via various reaction pathways, such as the hydration of hydrosilane into silanol,
dehydrogenative coupling of hydrosilane into disilane and the subsequent corresponding reactions to
disiloxane. Additionally, the platinum on carbonꢀcatalyzed hydrogenꢀdeuterium exchange reaction of
arylhydrosilanes as substrates in heavy water proceeded on the aromatic nuclei at 80 °C with high
deuterium efficiency and high regioselectivity at the only metaꢀ and paraꢀpositions of the aromaticꢀ
silicon bond to give the deuteriumꢀlabeled disiloxanes.
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INTRODUCTION
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Siloxane possessing a silicon (Si)ꢀoxygen (O) linkage is an important core of functional materials, such
as liquid crystals and thermosets,1 and bioactive compounds2 (e.g., muscle relaxant2b). Furthermore, aryl
or vinylꢀsubstituted disiloxanes can be Hiyamaꢀtype coupling partners in organic chemistry.3 The
transformation of hydrosilanes to disiloxanes is a straightforward synthetic method, and the direct
disiloxane synthesis based on the InBr3ꢀcatalyzed air oxidation of hydrosilanes4 and the homogeneous
transition metalꢀcatalyzed reduction of carbonyl compounds by hydrosilanes5ꢀ6 have been reported.
Meanwhile, the homogeneous Rh and Re catalytic methods using H2O as a green solvent and oxidant
were also developed.7 Although reusable heterogeneous catalysts are environmentallyꢀfriendly from the
viewpoint of green chemistry, the reported heterogeneous transition metal (Au8, Pt9, Pd10, Ni11 and
Ag12)ꢀcatalyzed oxidations of hydrosilanes using H2O as an additive in organic solvents selectively gave
the corresponding silanol as the main product.13 A recent research finding revealed the carbon nanotubeꢀ
gold nanohybrid catalysts could selectively oxidize the silanes in H2O to silanol and the use of
homogeneous AuCl3 with the ligands directly provided the disiloxane from silane.14 In this report, We
have newly developed the Au/Cꢀcatalyzed direct synthesis of disiloxanes starting from hydrosilanes in
water, and the unprecedented and regioselecitive Pt/Cꢀcatalyzed deuteration of aromatic nuclei of arylꢀ
substituted disiloxanes generated by the oxidative coupling of hydrosilanes in deuterium oxide (D2O,
heavy water).
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RESULTS AND DISCUSSION
We first investigated the catalyst efficiency of the various platinum group metals on carbon (5 mol%)
using dimethylphenylsilane (1a) as a substrate in H2O for 3 h at room temperature under atmospheric
argon (Table 1). While 10% Pd/C, Pt/C, Rh/C and Ru/C effectively produced the desired
diphenyltetramethyldisiloxane (2a) in high yields and the corresponding silanol was not obtained
(Entries 1ꢀ4), the reaction using 10% Au/C most efficiently proceeded to provide 2a in an excellent
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yield (97%) (Entry 5). As a result of the comparison with various types of heterogeneous platinum group
catalysts,15 carbon as a support and 10% metal content were found to be adequate (Entries 2 vs. 6ꢀ9).
Table 1. Catalyst efficiency of disiloxane synthesis using H2O.
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Entry
Catalyst
Yield (%)
87
Conversion (%)
1
10% Pd/C
10% Pt/C
10% Rh/C
10% Ru/C
10% Au/C
10% Cu/C
10% Ag/C
5% Pt/C
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95
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81
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71
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97
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69
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32
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100
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100
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49
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5% Pt/Al2O3
PtO2
trace
24
10
11
charcoal
trace
Various aryldimethylsilanes could be used for the Au/Cꢀcatalyzed direct synthesis of disiloxanes in
H2O (Table 2). 4ꢀMeO, Me, F, Br and CF3ꢀphenylꢀsubstituted silanes (1b-f) were effectively
transformed into the corresponding disiloxanes (2b-f) in excellent yields (Entries 1ꢀ5). Although
hydrogen gas should be generated during the reaction process, TBS ether16 and alkyne moieties within
the molecule could remain without their hydrogenation (Entries 6 and 7). Additionally, 3ꢀ or 2ꢀMeO and
Fꢀphenylꢀsubstituted silanes (1i-l) also underwent the Au/Cꢀcatalyzed oxidation in H2O to give the
disiloxanes (2i-l) (Entries 8ꢀ11). Meanwhile, the stericallyꢀhindered silanes, such as
diisopropylphenylsilane (1m) and triphenylsilane (1n), were transformed into the corresponding silanols
(3m and 3n) even by heating at 60 °C (Entries 12 and 13). Furthermore, dihydromethylphenylsilane (1o)
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underwent the continuous oxidative coupling of the hydrosilane moieties to mainly give a mixture of
tetramers to octamers (2o) (eq. 1). As the result of the reuse test using 1a, Au/C was found to be
reusable at least 5 times without any metal leaching (eq. 2).17
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Table 2. Scope of substrates in the disiloxane synthesis.
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Entry
Substrate
Product
Yield (%)e
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R1 = MeO (1b)
R1 = Me (1c)
R1 = F (1d)
>99
>99
97
2b
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R1 = Br (1e)
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R1 = CF3 (1f)
R1 = TBSOCH2 (1g)
R1 = PhC≡C (1h)
R2 = MeO (1i)
R2 = F (1j)
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R3 = MeO (1k)
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R3 = F (1l)
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13b,d
(1m)
(1n)
97b,c
3m
3n
Ph3SiH
>99b,d
a
b
c
d
e
For 6 h. At 60 °C. For 9 h. For 24 h. 100% conversion yields were achieved in all these
reactions.
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The mechanistic studies were next evaluated. The Au/Cꢀcatalyzed oxidation of 1a in H2 O instead of
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normal H2O gave the Oꢀlabeled 2a, which clearly indicated that H2O played the role as an oxidant
source (eq. 3). When the reaction was stopped for 5 or 15 min., the desired oxidation of 1a to 2a (80 or
86%) proceeded and a small amount of silanol (3a; 15 or 11%) was obtained as the reaction
intermediate (eq. 4). However, the Au/Cꢀcatalyzed dehydration of 3a was comparatively slow and was
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not completed within 3 h even under either atmospheric Ar or H2 (eq. 5), while the Au/Cꢀcatalyzed
oxidation of 1a into 2a was completed within 3 h (Table 1, entry 5). Based on these experimental
results, two kinds of reaction pathways are considerable. Firstly, the silanol was first generated by the
transition metalꢀcatalyzed hydration of hydrosilane,9ꢀ11 and the subsequent dehydration of the silanol
could produce the disiloxane.7a Alternatively, the first dehydrogenative coupling of the hydrosilane to
disilane,19 and the following hydrolytic oxidation20 of the disilane give disiloxane. Actually, the disilane
(4a) was efficiently transformed into the corresponding disiloxane (2a) in a quantitative yield in the
presence of Au/C in H2O (eq. 6). Because the transformation of silanol into disiloxane is slow (eq. 4),
we propose that the present oxidation of hydrosilane (1a) into disiloxane (2a) mainly proceeds via the
latter dehydrogenative coupling of the hydrosilane to the disilane (4a).
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Deuteriumꢀlabeled compounds are widely utilized in various fields, such as analytical studies and
material chemistry (e.g., fiber optics and heavy drugs).18f, 21 We have previously developed the mild and
platinum group metal on carbonꢀcatalyzed multiꢀdeuteration methods of arenes using D2O under
atmospheric hydrogen as an activating agent of the heterogeneous metal surface.18 Therefore, we
presumed that the deuteration of the arene nuclei of the arylꢀsubstituted disiloxane could proceed in D2O
instead of H2O by utilizing H2, HD or D2 gas generated during the transformation of the hydrosilane to
disiloxane. Although 10% Au/C and Rh/C indicated no catalytic activities for the deuteration of the
arene (Table 3, Entries 1 and 2), the use of 10% Ru/C, Pd/C and Pt/C in D2O at 60 °C effectively
catalyzed the oxidative coupling of 1a to disiloxane together with the regioselective deuteration on the
arene nuclei at the metaꢀ and paraꢀpositions to give the hexadeuterated diphenyldisiloxane (5a) (Entries
3ꢀ5).22 The 10% Pt/C was an adequate catalyst (Entry 5) and the reaction at 80 °C provided 5a with the
excellent D contents (Entries 7 vs. 5 and 6). Although the PtO2ꢀcatalyzed regioselective deuteration
using diphenyltetramethyldisiloxane (2a) as a substrate was reported by Matsubara et al., harsh reaction
conditions in a sealed container using microwaves (150 °C) were required.23,24 Although the direct
deuteration of 2a as the sole substrate under the present reaction conditions (10% Pt/C in D2O at 80 °C)
never proceeded (eq. 7, top), the reaction of 2a under atmospheric hydrogen conditions smoothly gave
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the desired deuterated product (5a) with a high D efficiency (eq. 7, bottom), which clearly indicated that
the hydrogen generated during the first oxidative coupling of the hydrosilane (1)25 was essential to
facilitate the oneꢀpot deuteration of the diphenyldisiloxane (2a) to 5a.26
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Table 3. Regioselective deuteration using phenyldimethyl silane (1a) in D2O.
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Entry
D content of phenyl moiety (%)
Yield (%)c
Catalyst
orhto
Average of meta and para
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10% Au/C
10% Rh/C
10% Ru/C
10% Pd/C
10% Pt/C
10% Pt/C
10% Pt/C
0
0
0
0
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>99
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2
0
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80
92
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7b
a At 40 °C. b At 80 °C c 100% conversion yields were achieved in all these reactions.
All the reactions (the oxidative coupling of hydrosilanes into disiloxanes and the following
deuteration of the arene nuclei) of the various arylsilanes (1d, 1j, 1l, 1b, 1i and 1k) bearing an electronꢀ
withdrawing fluoroꢀ or electronꢀdonating methoxy group at the orthoꢀ, metaꢀ or paraꢀ position of the
aromatic ring could effectively proceed to give the corresponding deuteriumꢀlabeled disiloxanes (5d, 5j,
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5l, 5b, 5i and 5k) with high D efficiencies and high regioselectivities at the metaꢀ and paraꢀpositions
from the ArꢀSi bond due to the sterical hindrance (Table 4, Entries 1ꢀ6). The addition of iꢀPrOH as a coꢀ
solvent effectively increased the D efficiencies for the reactions in Table 4. We also revealed that the
platinum group metal on carbon effectively catalyzed the dehydrogenation of secondary and primary
alcohols to generate the corresponding carbonyl products and hydrogen gas,27 and the in situꢀgenerated
hydrogen derived from iꢀPrOH was utilized for the hydrogenation28 and deuteration29 as a catalyst
activator. Namely, hydrogen derived from the hydrosilane and iꢀPrOH synergistically activated the
platinum metal18 to facilitate the desirable deuteration (the comparison of reaction efficiencies with or
without iꢀPrOH and the additive effect were depicted in Supporting Information). Additionally, the
aromatic nuclei of the silanol (6m) derived from 1m were effectively deuterated with the same
regioselectivity and high D efficiency, while the oxidative coupling reaction never proceeded due to the
steric hindrance effect of the bulky diisopropyl substituents on the Si atom.30
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Table 4. Scope of substrates in the regioselective deuterated disiloxane synthesis.
Entry
1a
Substrate
Product
1d
5d: 32%
5j: 18%
2a
1j
1l
3a
5l: 23%
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4a
5a
6a
1b
1i
5b: 30%
5i: 32%
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1k
5k: 20%
5c: 32%
7a
1c
8a
1m
6m: 23%
a
b
iꢀPrOH (0.8 mL) was added as a coꢀsolvent. 100% conversion yields were achieved in all these
reactions.
In conclusion, we have established the heterogeneous Au/Cꢀcatalyzed oxidative coupling of
hydrosilanes using H2O as an oxidant to give the corresponding disiloxanes. Furthermore, the Pt/Cꢀ
catalyzed oneꢀpot deuteration of the arene nuclei accompanied by the transformation of arylhydrosilanes
to diaryldisiloxanes with a unique regioselectivity was developed utilizing the in situꢀgenerated
hydrogen as a catalyst activator. Since the production method of hydrogen as an energy source from
organosilanes is important and the diaryltetramethyldisiloxanes are good coupling reagents for the
Hiyamaꢀtype reaction, the present methods are expected to contribute to various research fields.
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EXPERIMENTAL SECTION
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General information: 10% Pd/C, Pt/C, Rh/C, Ru/C and Au/C were supplied by N. E. Chemcat
Corporation (Tokyo, Japan). All reactions were performed under argon. H2O and D2O were purchased
from commercial sources and used without further purification. ESI high resolution mass spectra
(HRMS) were measured by a hybrid ITꢀTOF mass spectrometer. Substrates (1a and 1mꢀo) were
purchased from commercial suppliers. Substrates (1bꢀl) were prepared according to the literatures in
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reference 1ꢀ3.
Typical procedure for Tables 1 and 2: A mixture of arylhydrosilane (0.25 mmol), 10% Au/C (5 mol%) and
H2O (3 mL) in 15 mLꢀtest tube was stirred using a personal organic synthesizer at room temperature under argon.
After stirring for 3 h, the reaction mixture was passed through a membrane filter (Millipore, Millex, 0.45 µm) to
remove Au/C. The filtrate was extracted with AcOEt (3 mL × 3). The combined organic layers were washed with
brine, dried over Na2SO4 and concentrated in vacuo to give the disiloxane or silanol. (2h was purified by silicaꢀ
gel column chromatography)
Typical procedure for Tables 3 and 4: A suspension of arylhydrosilane (0.25 mmol) and 10% Pt/C (10 mol%)
in D2O (3 mL) and iPrOH (0.8 mL) was stirred in 15 mLꢀtest tube using a personal organic synthesizer at 80 °C
under argon. After stirring for 3 h, the reaction mixture was passed through a membrane filter (Millipore, Millex,
0.45 µm) to remove Pt/C. The filtrate was extracted with AcOEt (3 mL × 3). The combined organic layers were
washed with brine, dried over Na2SO4 and concentrated in vacuo to give the deutrated disiloxane or silanol.
1,3-Diphenyl-1,1,3,3-tetramethyldisiloxane (2a): When using 1a (34.1 mg, 0.25 mmol) in Table 1, entry 5,
1
2a (34.7 mg, 0.12 mmol) was obtained in 97% yield.; Colorless oil; H NMR (500 MHz, CDCl3) δ: 7.55ꢀ7.54
(4H, m), 7.38ꢀ7.34 (6H, m), 0.33 (12H, s); 1H NMR data was identical with that in the reference 31.
1,3-Bis(4’-methoxyphenyl)-1,1,3,3-tetramethyldisiloxane (2b): When using 1b (41.6 mg, 0.25 mmol), 2b
1
(43,1 mg, 0.12 mmol) was obtained in >99% yield.; Colorless oil; H NMR (400 MHz, CDCl3) δ: 7.46 (4H, d, J
1
= 8.4 Hz), 6.89 (4H, d, J = 8.4 Hz), 3.81 (6H, s), 0.29 (12H, s); H NMR data was identical with that in the
reference 32.
1,3-Bis(4’-tolyl)-1,1,3,3-tetramethyldisiloxane (2c): When using 1c (37.6 mg, 0.25 mmol), 2c (39.1 mg, 0.12
mmol) was obtained in >99% yield.; Colorless oil; 1H NMR (500 MHz, CDCl3) δ: 7.44 (4H, d, J = 7.8 Hz), 7.17
(4H, d, J = 7.8 Hz), 2.35 (6H, s), 0.31 (12H. s) ; 1H NMR data was identical with that in the reference 3d.
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1,3-Bis(4’-fuluorophenyl)-1,1,3,3-tetramethyldisiloxane (2d): When using 1d (38.6 mg, 0.25 mmol), 2d
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2
3
1
(39.1 mg, 0.12 mmol) was obtained in 97% yield.; Colorless oil; H NMR (500 MHz, CDCl3) δ: 7.50ꢀ7.47 (4H,
4
5
m), 7.06ꢀ7.02 (4H, m), 0.31 (12H, s); 1H NMR data was identical with that in the reference 33.
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1,3-Bis(4’-bromophenyl)-1,1,3,3-tetramethyldisiloxane (2e): When using 1e (53.8 mg, 0.25 mmol), 2e (51.1
mg, 0.12 mmol) was obtained in 92% yield.; Colorless oil; IR (ATR) cmꢀ1: 2956, 2925, 2854, 1574, 1479, 1408,
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1376, 1255, 1112, 1065, 1008; H NMR (400 MHz, CDCl3): 7.48 (4H, d, J = 8.2 Hz), 7.36 (4H, d, J = 8.2 Hz),
13
0.31 (12H, s); C NMR (100 MHz, CDCl3): 138.3, 134.6, 130.9, 124.2, 0.7; Anal. calcd for C16H20Br2OSi2: C,
43.25; H, 4.54 N, 0. Found: C, 43.21; H, 4.49; N, 0.
1,3-Bis[4’-(trifluoromethyl)phenyl]-1,1,3,3-tetramethyldisiloxane (2f): When using 1f (51.1 mg, 0.25
1
mmol), 2f (46.0 mg, 0.11 mmol) was obtained in 87% yield.; Colorless oil; H NMR (400 MHz, CDCl3) δ:
7.63—7.57 (8H, m), 0.36 (1H, s); 1H NMR data was identical with that in the reference 31.
1,3-Bis(4’-tert-butyldimethylsiloxymethylphenyl)-1,1,3,3-tetramethyldisiloxane (2g): When using 1g (70.1
mg, 0.25 mmol), 2g (65.4 mg, 0.11 mmol) was obtained in 91% yield; Colorless oil; IR (ATR) cmꢀ1: 2956, 2929,
2886, 2857, 1604, 1471, 1462, 1396, 1372, 1255, 1211, 1085, 1019; 1H NMR (400 MHz, CDCl3): 7.51 (4H, d, J
= 8.2 Hz), 7.31 (4H, d, J = 8.2 Hz), 4.74 (4H, s) 0.95 (18H, s), 0.31 (12H, s), 0.10 (12H, s); 13C NMR (100 MHz,
CDCl3): 142.5, 138.2, 133.0, 125.3, 64.9, 26.0, 18.4, 0.9, ꢀ5.2; ESIꢀHRMS m/z: 597.3051 ([M+Na]+); Calcd for
C30H54O3Si4Na: 597.3042.
1,3-Bis(phenylethynyl)-1,1,3,3-tetramethyldisiloxane (2h): When using 1h (59.1 mg, 0.25 mmol), 1h (49.9
1
mg, 0.10 mmol) was obtained in 82% yield; Colorless oil; H NMR (500 MHz, CDCl3) δ: 7.47ꢀ7.45 (4H, m),
7.31ꢀ7.28 (6H, m), 0.39 (12H, s); 1H NMR data was identical with that in the reference 32.
1,3-Bis(3’-methoxyphenyl)-1,1,3,3-tetramethyldisiloxane (2i): When using 1i (41.6 mg, 0.25 mmol), 2i
(42.0 mg, 0.12 mmol) was obtained in 97% yield.; Colorless oil; IR (ATR) cmꢀ1: 2953, 2833, 1570, 1480, 1462,
1403, 1315, 1282, 1246, 1228, 1182, 1113, 1040, 992, 903, 860, 815, 774, 731, 695, 650, 559, 443; 1H NMR
(500 MHz, CDCl3): 7.31—7.28 (2H, m), 7.12 (2H, d, J = 7.5 Hz), 7.08 (2H, d, J = 2.5 Hz), 6. 91 (2H, dd, J = 8.0,
2.5 Hz), 3.78 (6H, s), 0. 34 (12H, s); 13C NMR (125 MHz, CDCl3):159.0, 141.5, 129.1, 125.3, 118.3, 114.8, 55.1,
1.0; ESIꢀHRMS m/z: 369.1309 ([M+Na]+); Calcd for C18H26O3Si2Na: 369.1313.
1,3-Bis(3’-fluorophenyl)-1,1,3,3-tetramethyldisiloxane (2j): When using 1j (38.6 mg, 0.25 mmol), 2j (37.9
mg, 0.12 mmol) was obtained in 94% yield.; Colorless oil; IR (ATR) cmꢀ1: 2959, 1574, 1477, 1404, 1258, 1215,
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1106, 1046; H NMR (400 MHz, CDCl3): 7.35—7.25 (4H, m), 7.20—7.17 (2H, m), 7.06—7.02 (2H, m), 0.33
1
2
3
13
(12H, s); C NMR (100 MHz, CDCl3): 162.6 (d, J = 246.0 Hz), 142.6 (d, J = 3.8 Hz) 129.6 (d, J = 6.6 Hz),
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5
6
7
128.4 (d, J = 2.9 Hz), 119.3 (d, J = 18.1 Hz), 116.2 (d, J = 21.0 Hz), 0.7; ESIꢀHRMS m/z: 321.0927 ([MꢀH]ꢀ);
Calcd for C16H20OSi2F2: 321.0948.
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1,3-Bis(2’-methoxyphenyl)-1,1,3,3-tetramethyldisiloxane (2k): When using 1k (41.6 mg, 0.25 mmol), 2k
(42.0 mg, 0.12 mmol) was obtained in 97% yield.; Colorless oil; IR (ATR) cmꢀ1: 3062, 2955, 2903, 2833, 1588,
1571, 1460, 1428, 1292, 1268, 1233, 1177, 1161, 1130, 1084, 1044, 1023, 908, 831, 784, 756, 718, 701, 646, 577,
485, 452; 1H NMR (500 MHz, CDCl3): 7.54 (2H, dd, J = 7.5, 1.5 Hz), 7.45 (2H, ddd, J = 8.0, 7.5, 1.5 Hz), 6.95
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(2H, t, J = 7.5 Hz), 6. 83 (2H, d, J = 8.0 Hz), 3.76 (6H, s), 0. 35 (12H, s); C NMR (125 MHz, CDCl3): 163.9,
135.3, 131.0, 127.8, 120.4, 109.4, 59.9, 1.6; ESIꢀHRMS m/z: 369.1309 ([M+Na]+); Calcd for C18H26O3Si2Na:
369.1313.
1,3-Bis(2’-fluorophenyl)-1,1,3,3-tetramethyldisiloxane (2l): When using 1l (38.6 mg, 0.25 mmol), 2l (37.1
mg, 0.12 mmol) was obtained in 92% yield.; Colorless oil; IR (ATR) cmꢀ1: 3074, 2960, 2926, 2855, 1674, 1603,
1
1563, 1470, 1439, 1256, 1204, 1155, 1121, 1081, 1060; H NMR (400 MHz, CDCl3): 7.50—7.46 (2H, m),
7.39—7.33 (2H, m), 7.12 (2H, t, J = 7.2 Hz), 6.97 (2H, t, J = 8.4 Hz), 0.40 (12 H, s); 13C NMR (100 MHz,
CDCl3): 166.9 (d, J = 242.8 Hz), 135.0 (d, J = 11.5 Hz), 131.6 (d, J = 8.2 Hz), 125.6 (d, J = 30.5 Hz), 123.8 (d, J
= 2.5 Hz), 114.7 (d, J = 25.4 Hz), 1.3; ESIꢀHRMS m/z: 345.0896 ([M+Na]+); Calcd for C16H20OSi2F2Na:
345.0913.
Oligomer (2o): When using 1o (31.0 mg, 0.25 mmol), 2o (29.8 mg) was obtained.; brown oil; ESIꢀ
HRMS m/z: (tetramer) 585.1382 ([M+Na]+); Calcd for C28H34O5Si4Na: 585.1376, (pentamer) 721.1704
([M+Na]+); Calcd for C35H42O6Si5Na: 721.1720, (hexamer) 857.2062 ([M+Na]+); Calcd for
C42H50O7Si6Na: 857.2064, (heptamer) 993.2347 ([M+Na]+); Calcd for C49H58O8Si7Na: 993.2409,
(octamer) 1129.2744 ([M+Na]+); Calcd for C56H66O9Si8Na: 1129.2753.
Diisopropylsilanol (3m): When using 1m (48.1 mg, 0.25 mmol), 3m (50.5 mg, 0.24 mmol) was obtained in
1
97% yield.; H NMR (500 MHz, CDCl3) δ: 7.56ꢀ7.55 (2H, m), 7.40ꢀ7.35 (3H, m), 1.75 (1H. brs), 1.26ꢀ1.20 (2H,
m), 1.06 (6H, d, J = 7.5 Hz), 0.98 (6H, d, J = 7.5 Hz); 1H NMR data was identical with that in the reference 34.
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Triphenylsilanol (3n): When using 1n (65.1 mg, 0.25 mmol), 3n (68.8 mg, 0.25 mmol) was obtained in >99%
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2
3
1
yield.; H NMR (500 MHz, CDCl3) δ: 7.64ꢀ7.63 (6H, m), 7.45ꢀ7.44 (3H, m), 7.41ꢀ7.38 (6H, m), 2.48 (1H, s); 1H
4
5
NMR data was identical with that in the reference 32.
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1,3-Diphenyl-1,1,3,3-tetramethylpropanedisiloxane (18O-labeled 2a): When using 1a (15.9 mg, 0.12 mmol),
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91% yield of 18O-labeled 2a was obtained based on H NMR using 1,4ꢀdioxane as an internal standard.;
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Colorless oil; H NMR (500 MHz, CDCl3) δ: 7.56ꢀ7.54 (4H, m), 7.38ꢀ7.34 (6H, m), 0.33 (12H, s); ESIꢀHRMS
m/z: 311.1127 ([M+Na]+); Calcd for C16H2218OSi2Na: 311.1144.
Dimethylphenylsilanol (3a): When using 1a (34.1 mg, 0.25 mmol) for 5 min. in eq. 4, 3a (5.7 mg, 0.04 mmol)
1
was obtained in 15% yield.; Colorless oil; H NMR (500 MHz, CDCl3) δ: 7.61ꢀ7.59 (2H, m), 7.40ꢀ7.38 (3H, m),
1.82 (1H, s, br), 0.41 (6H, s); 1H NMR data was identical with that in the reference 30.
1,3-Diphenyl-1,1,3,3-tetramethyldisiloxane-d6 (5a): When using 1a (34.1 mg, 0.25 mmol) in Table 3, entry 7,
1
5a (19.6 mg, 0.07 mmol) was obtained in 54% yield.; Colorless oil; H NMR (500 MHz, CDCl3) δ: 7.56ꢀ7.54
(4H, m), 7.38ꢀ7.34 (0.18H, m), 0.33 (12H, s); 2H NMR (500 MHz, CDCl3) δ: 7.43 (brs); 2H NMR data was
identical with that in the reference 23.
1,3-Bis(4’-fuluoro)-1,1,3,3-tetramethyldisiloxane-d4 (5d): When using 1d (38.6 mg, 0.25 mmol), 5d (13.1
1
mg, 0.04 mmol) was obtained in 32% yield; Colorless oil; H NMR (400 MHz, CDCl3) δ: 7.48 (4H, d, J = 6.4
Hz), 7.05ꢀ7.00 (0.19H, m), 0.31 (12H, s); 2H NMR (500 MHz, CDCl3) δ: 7.08 (brs).
1,3-Bis(3’-fuluoro)-1,1,3,3-tetramethyldisiloxane-d4 (5j): When using 1j (38.6 mg, 0.25 mmol), 5j (7.3 mg,
0.02 mmol) was obtained in 18% yield; Colorless oil; 1H NMR (400 MHz, CD2Cl2) δ: 7.29 (2H, s), 7.18 (2H, dd,
J = 0.8 Hz, 9.0 Hz), 0.32 (12H, s); 2H NMR (500 MHz, CH2Cl2) δ: 7.39 (s, br), 7.11 (s, br).
1,3-Bis(2’-fuluoro)-1,1,3,3-tetramethyldisiloxane-d6 (5l): When using 1l (38.6 mg, 0.25 mmol), 5l (9.5 mg,
1
0.03 mmol) was obtained in 23% yield; Colorless oil; H NMR (400 MHz, CDCl3) δ: 7.48 (2H, d, J = 6.5 Hz),
7.36 (0.18H, m), 7.13ꢀ7.11 (0.1 H, m), 6.98ꢀ6.96 (0.094H, m), 0.40 (12H, s); 2H NMR (500 MHz, CDCl3) δ: 7.41
(brs), 7.18 (brs), 7.02 (brs).
1,3-Bis(4’-methoxyphenyl)-1,1,3,3-tetramethyldisiloxane-d4 (5b): When using 1b (41.6 mg, 0.25 mmol), 5b
1
(13.1 mg, 0.04 mmol) was obtained in 30% yield.; Colorless oil; H NMR (400 MHz, CDCl3) δ: 7.46 (4H, s),
6.90 (0.44H, m), 3.81 (6H, s), 0.29 (12H, s); 2H NMR (500 MHz, CDCl3) δ: 6.95 (brs).
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1,3-Bis(3’-methoxyphenyl)-1,1,3,3-tetramethyldisiloxane-d4 (5i): When using 1i (41.6 mg, 0.25 mmol), 5i
(14.0 mg, 0.04 mmol) was obtained in 32% yield.; Colorless oil; 1H NMR (400 MHz, CDCl3) : 7.12 (2H, s), 7.08
(2H, s), 3.77 (6H, s), 0.33 (12H, s); 2H NMR (500 MHz, CDCl3) δ: 7.35 (s, br), 6.97 (brs).
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1,3-Bis(2’-methoxyphenyl)-1,1,3,3-tetramethyldisiloxane-d4 (5k): When using 1k (41.6 mg, 0.25 mmol), 5k
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(8.8 mg, 0.3 mmol) was obtained in 20% yield.; Colorless oil; H NMR (400 MHz, CDCl3) : 7.53 (2H, s), 6.81
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(2H, s), 3.76 (6H, s), 0. 35 (12H, s), 2H NMR (500 MHz, CHCl3) : 7.40 (s, br), 6.89 (brs).
1,3-Bis(4’-toryl)-1,1,3,3-tetramethyldisiloxane-d10 (5c): When using 1c (37.6 mg, 0.25 mmol), 1c (12.8 mg,
0.04 mmol) was obtained in 32% yield.; Colorless oil; 1H NMR (400 MHz, CDCl3) δ: 7.44 (4H, s), 7.17 (0.43H,
d, J = 7.0 Hz), 2.35 (5.01H, s), 0.30 (12H. s); 2H NMR (500 MHz, CDCl3) δ: 7.22 (brs), 2.32 (m).
Diisopropylphenylsilanol-d3 (6m): When using 1m (48.1 mg, 0.25 mmol), 6m (12.2 mg, 0.06 mmol) was
1
obtained in 23% yield.; Colorless oil; H NMR (400 MHz, CDCl3) δ: 7.56 (2H, s), 7.39ꢀ7.36 (0.12H, m), 1.26—
1.19 (2H, m), 1.06 (6H, d, J = 7.8 Hz), 0.98 (6H, d, J = 7.8 Hz); 2H NMR (500 MHz, CDCl3) δ: 7.42 (brs).
ASSOCIATED CONTENT
Supporting Information
Synthetic method of substrates and spectroscopic data of substrates and products are described.
ACKNOWLEDGMENTS
We thank the N.E. Chemcat Corporation for the kind gift of all heterogeneous catalysts and the
measurement of ICPꢀOES.
REFERENCES
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Ueda, M. Macromolecules 2010, 43, 805ꢀ810; (d) Yang, J.; Cheng, Y.; Xiao, F. Eur. Polym. J. 2012, 48,
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751ꢀ760; (e) Zelcer, A.; Cecchi, F.; Albores, P.; Guillon, D.; Heinrich, B.; Donnio, B.; Cukiernik, F. D.
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(2) (a) (Review) LeVier, R. R.; Chandler, M. L.; S. R. Wendel, S. R. The Pharmacology of Silanes
and Siloxanes. In The Biochemistry of Silicon and Related Problems; (Eds.; Bendz, G.; Lindqvist, I.)
Plenum: Press New York and London, 1978; pp 473ꢀ514; (b) Tse, F. L. S.; Chang, T.; Finkelstein, B.;
Ballard, F.; Jaffe, J. M. J. Pharm. Sci. 1984, 73, 1599ꢀ1602; (c) Bruns, R. F.; Watson, I. A. J. Med.
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(3) (a) Napier, S.; Marcuccio, S. M.; Tye, H.; Whittaker, M. Tetrahedron Lett. 2008, 49, 3939ꢀ3942;
(b) Denmark, S. E.; Butler, C. R. J. Am. Chem. Soc. 2008, 130, 3690ꢀ3704; (c) Sore, H. F.; Boehner, C.
M.; MacDonald, S. J. F.; Norton, D.; Fox, D. J.; Spring, D. R. Org. Biomol. Chem. 2009, 7, 1068ꢀ1071;
(d) Boehner, C. M.; Frye, E. C.; O’Connell, K. M. G.; Galloway, W. R. J. D.; Sore, H. F.; Dominguez, P.
G.; Norton, D.; Hulcoop, D. G.; Owen, M.; Turner, G.; Crawford, C.; Horsley, H.; Spring, D. R. Chem.
Eur. J. 2011, 17, 13230ꢀ13239.
(4) Sridhar, M.; Ramanaiah, B. C.; Narsaiah, C.; Swamy, M. K.; Mahesh, B.; Reddy, M. K. K.
Tetrahedron Lett. 2009, 50, 7166ꢀ7168.
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6011; (b) AriasꢀUgarte, R.; Sharma, H. K.; Morris, A. L. C.; Pannell, K. H. J. Am. Chem. Soc. 2012, 134,
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(9) Chauhan, B. P. S.; Sarkar, A.; Chauhan, M.; Roka, A. Appl. Organometal. Chem. 2009, 23, 385ꢀ
390.
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J.; Park, J. ChemCatChem 2012, 4, 521ꢀ524.
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Int. Ed. 2008, 47, 7938ꢀ7940; (b) Kikukawa, Y.; Kuroda, Y.; Yamaguchi, K.; Mizuno, N, Angew. Chem.
Int. Ed. 2012, 51, 2434ꢀ2437.
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(13) The transformation of hydrosilanes to silanols in water in the absence of organic solvents was
accomplished using the hydroxyapatiteꢀsupported gold nanoparticles (See reference 8a). The use of a
homogeneous Ru or Ir catalyst in an organic solvent including H2O also gave silanols as the main
products, see; (a) Lee, M.; Ko, S.; Chang, S. J. Am. Chem. Soc. 2000, 122, 12011ꢀ12012; (b) Lee, Y.;
Seomoon, D.; Kim, S.; Han, H.; Chang, S.; Lee, P. H. J. Org. Chem. 2004, 69, 1741ꢀ1743; (c) Tan, S.
T.; Kee, J. W.; Fan, W. Y. Organometallics 2011, 30, 4008ꢀ4013.
(14) Liu, T.; Yang, F.; Li, Y.; Ren, L.; Zhang, L.; Xu, K.; Wang, X.; Xu, C.; Gao, J. J. Mater. Chem.
A 2014, 2, 245ꢀ250.
(15) Although Au/C is an optimum catalyst in disiloxane synthesis, various types of Auꢀsupported
catalysts are not easily available. Therefore, the effect of support was examined using easily available
platinum metal catalysts. The reason for the high catalyst activity of Au/C is unclear.
(16) Ikawa, T.; Hattori, K.; Sajiki, H.; Hirota, K. Tetrahedron 2004, 60, 6901ꢀ6911.
(17) The result of the metal leaching is depicted in the Supporting Information. Compared with XRD,
XPS and STEM data between the fresh and used Au/C, the particle size (ca. 33ꢀ35 nm), shape and
oxidation states (zero valency) indicated no major differences as shown in Supporting Information. The
desired disiloxane (2a) and the corresponding silanol (3a) as an intermediate could be obtained by the
use of fresh Au/C in 95% and 5% yields, respectively, for a shortened reaction time (1h). In addition, the
reused Au/C after the first run also indicated the similar catalyst activity to give 92% of 2a and 8% of 3a.
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(18) The hydrogen can activate the transition metal as a weak and bulkꢀlike and/or gaseous reductant
for the partiallyꢀoxidized metal surface, and we developed various deuteration methods using hydrogenꢀ
activated metals, see; (a) Sajiki, H.; Ito, N.; Esaki, H.; Maesawa, T.; Maegawa, T.; Hirota, K.
Tetrahedron Lett. 2005, 46, 6995ꢀ6998; (b) Ito, N.; Watahiki, T.; Maesawa, T.; Maegawa, T.; Sajiki, H.
Adv. Synth. Catal. 2006, 348, 1025ꢀ1028; (c) Esaki, H.; Aoki, F.; Umemura, M.; Kato, M.; Maegawa,
T.; Monguchi, Y.; Sajiki, H. Chem. Eur. J. 2007, 13, 4052ꢀ4063; (d) Ito, N.; Esaki, H.; Maesawa, T.;
Imamiya, E.; Maegawa, T.; Sajiki, H. Bull. Chem. Soc. Jpn. 2008, 81, 278ꢀ286; (e) Ito, N.; Watahiki, T.;
Maesawa, T.; Maegawa, T.; Sajiki, H. Synthesis 2008, 9, 1467ꢀ1478; (f) (Review) Sawama, Y.;
Monguchi, Y.; Sajiki, H. Synlett 2012, 23, 959ꢀ972.
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S.; Miqueu, K.; Amgoune. A.; Bourissou, D. Organometallics 2012, 31, 6001ꢀ6004.
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7744–7765; (b) Herbert, J. M.; J. Labelled Compd. Radiopharm. 2010, 53, 658ꢀ661.
(22) Our recent studies reveals that Pd/C and Pt/C are efficient to promote the direct HꢀD exchange
reactions of aromatic rings and the Au/Cꢀcatalyzed deuteration never proceeds. The reason of the metal
effect is still unclear. Au/C could catalyzed only oxidation of hydrosilanes into disiloxanes in H2O.
(23) Yamamoto, M.; Oshima, K.; Matsubara, S. Org. Lett. 2004, 6, 5015ꢀ5017.
(24) Although PtO2 is an effective catalyst for the direct deuteration of disiloxane according to the
reference 22, hydrogen generated during Pt/Cꢀcatalyzed coupling of hydrosilane into disiloxane is
necessary in the present HꢀD exchange reaction under milder reaction conditions. PtO2 could not
effectively catalyze the coupling reaction of hydrosilane to generate the hydrogen as shown in Table 1.
(25) The generation of hydrogen during the first oxidative coupling of the hydrosilane (1) was
detected by an indicator tube for hydrogen (Kitagawa Komyo Rikagaku Kogyo, Tube No. 137U).
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The Journal of Organic Chemistry
(26) When the HꢀD exchange reaction using dimethylphenylhydrosilane (1a) at 80 oC was terminated
for 30 min, the mixture of the deuterated silanol and disiloxane (5a) was obtained in low deuterium
contents, which indicated that the regioselective deuteration could proceed on both the silanol and
disiloxane.
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(27) (a) Sawama, Y.; Morita, K.; Yamada, T.; Nagata, S.; Yabe, Y.; Monguchi, Y.; Sajiki, H. Green
Chem. 2014, 16, 3439–3443; (b) Sawama, Y.; Morita, K.; Asai, S.; Kozawa, M.; Tadokoro, S.;
Nakajima, J.; Monguchi, Y.; Sajiki, H. Adv. Synth. Catal. 2015, 357, 1205ꢀ1210.
(28) Sawama, Y.; Yabe, Y.; Shigetsura, M.; Yamada, T.; Nagata S.; Fujiwara, Y.; Maegawa, T.;
Monguchi, Y.; Sajiki, H. Adv. Synth. Catal. 2012, 354, 777ꢀ782.
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(29) (a) Sawama, Y.; Yamada, T.; Yabe, Y.; Morita, K.; Shibata, K.; Shigetsura, M.; Monguchi, Y.;
Sajiki, H. Adv. Synth. Catal. 2013, 355, 1529ꢀ1534; (b) Yamada, T.; Sawama, Y.; Shibata, K.; Morita,
K.; Monguchi, Y.; Sajiki, H. RSC Adv. 2015, 5, 13727ꢀ13732.
(30) The reason why the isolated yields decreased in the reaction shown in Table 4 is unclear. Only
deuterated products were observed.
(31) Jorapur, Y. R.; Shimada, T. Synlett 2012, 29, 1633ꢀ1638.
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(35) Hamada, T.; Manabe, K.; Kobayashi, S. Chem. Eur. J. 2006, 12, 1205ꢀ1215.
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