Neighboring acetal-assisted bronsted-acid-catalyzed Si-H bond activation: Divergent synthesis of functional siloxanes through silylation and hydrolytic oxidation of organosilanes

Article abstract of DOI:10.1002/ejoc.201001532

A novel metal-free intramolecular Bronsted-acid-catalyzed domino deprotection-hydrosilylation with hydrosilanes has been developed, and the unexpected Bronsted-acid-catalyzed intermolecular hydrolytic oxidation to functional siloxanes was described for the divergent and facile synthesis of functionalized siloxanes containing aldehyde motifs. We propose that these reactions proceed via neighboring acetal-assisted Si-H bond activation. In addition, a related reaction is expected to open up further opportunities for the development and application of functional organosilicon compounds by organocatalysis. Copyright

Full text of DOI:10.1002/ejoc.201001532

FULL PAPER
DOI: 10.1002/ejoc.201001532
Neighboring Acetal-Assisted Brønsted-Acid-Catalyzed Si–H Bond Activation:
Divergent Synthesis of Functional Siloxanes through Silylation and Hydrolytic
Oxidation of Organosilanes
Xi-Huai Chen,[a] Yuan Deng,[a] Kezhi Jiang,[a] Guo-Qiao Lai,*[a] Yong Ni,[a]
Ke-Fang Yang,[a] Jian-Xiong Jiang,[a] and Li-Wen Xu*[a]
Keywords: Silicon / Organosilicon compounds / Silylation / Oxidation / Organocatalysis
A novel metal-free intramolecular Brønsted-acid-catalyzed
domino deprotection–hydrosilylation with hydrosilanes has
pose that these reactions proceed via neighboring acetal-
assisted Si–H bond activation. In addition, a related reaction
been developed, and the unexpected Brønsted-acid-cata- is expected to open up further opportunities for the develop-
lyzed intermolecular hydrolytic oxidation to functional silox-
anes was described for the divergent and facile synthesis of
functionalized siloxanes containing aldehyde motifs. We pro-
ment and application of functional organosilicon compounds
by organocatalysis.
silylations three decades ago,[7] efficient catalysts, including
metal salts (mainly transition metal complexes but also
main group metal complexes[8]) and metalloid Lewis acids[9]
and Lewis bases[10] have been described. Besides metal-cata-
lyzed hydrosilylation, two popular routes to siloxanes are
the silylation of alcohols from chlorosilane and the dehy-
drogenative coupling of hydrosilanes.[11] However, in most
cases of the silylation of alcohols, a long reaction time,
harsh reaction conditions, toxic catalysts or reagents, or te-
dious workup is needed. In dehydrogenative coupling reac-
tions of hydrosilanes, most metal-based catalytic processes
suffer from one or more disadvantages, including poor
functional group tolerance, slow rates with bulky silanes,
and strict reaction conditions.
We became interested in the acetal functional group for
its potential application as an “aldehyde store” within
metal-free, catalyst-initiated Si–H activation and transfor-
mation. Although various metal-based catalysts have been
investigated for the hydrosilylation of carbonyl compounds,
most synthetic methods only focus on the preparation of
alcohols but not siloxanes. In fact, the synthesis of siloxanes
or silyl ethers directly from hydrosilanes is not a trivial task.
Therefore, the development of highly efficient and environ-
mentally benign processes to synthesize functionalized
siloxanes is of considerable interest. In relation to this, we
set out to explore Brønsted-acid-catalyzed Si–H bond acti-
vation and related syntheses of aldehyde-functionalized
siloxanes. In this paper, we present a novel and simple
method to prepare functional siloxanes containing aldehyde
moieties through facile, one-pot, metal-free Brønsted-acid-
catalyzed domino deprotection–hydrosilylation. In ad-
dition, we report an unexpected and novel organocatalyzed
hydrolytic oxidation process for the synthesis of functional
Introduction
Organosilicon compounds are widely used in inorganic,
organic, organometallic, and polymeric chemistry, and the
field of research covered by organosilicon chemistry is very
broad.[1] In the past decades, the preparation and reactions
of novel types of organosilicon species are the most impor-
tant and fundamental topic for organosilicon chemistry,
and have been studied intensively.[2] Among them, silanes
and siloxanes are important as versatile building blocks that
have been prominently utilized in industry for the pro-
duction of silicon-based polymeric materials.[2b–2f] They are
also important in organic synthesis[3] as reducing reagents,
valuable protecting groups, privileged monomers, and rea-
gents, as well as intermediates and catalysts in a broad vari-
ety of organic transformations[4] including oxidation,[4f–4i]
cross-coupling,[4j–4o] and cycloadditions.[4p–4r] The prepara-
tion and use of functional siloxane compounds allows or-
ganosilanes to be installed onto a fragment at almost any
stage in an organic synthesis.
The activation of C–H bonds is important to synthetic
and catalytic processes involving the functionalization of
hydrocarbons.[5] Likewise, activation of Si–H bonds by dif-
ferent catalysts is important to industrial and academic re-
search in reactions such as hydrosilylation.[1,2,6] Since the
first application of Wilkinson’s catalyst in catalytic hydro-
[a] Key Laboratory of Organosilicon Chemistry and Material
Technology of Ministry of Education, Hangzhou Normal
University,
Hangzhou 310012, P. R. China
Fax: +86-571-28865135
E-mail: liwenxu@hznu.edu.cn
licpxulw@yahoo.com
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201001532.
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Hydrosilylation and Hydrolytic Oxidation of Organosilanes
siloxanes containing aldehydes. To the best of our knowl- Table 1. Brønsted-acid-catalyzed domino deprotection–hydro-
silylation.[a]
edge, there are no reports on the divergent synthesis alde-
hyde-functionalized siloxanes through Brønsted-acid-cata-
lyzed hydrolytic oxidation.
Entry
Cat. (mol-%) Solvent
Time [h] Additive Yield [%][b]
1
2
3
4
5
6
7
8
3a (1.5)
3a (1.5)
3b (10)
3b (10)
3b (10)
3b (10)
3c (10)
3c (10)
3c (10)
3c (10)
3c (10)
3c (10)
acetone
THF
acetone
THF
DCM/H2O
CH3NO2
acetone
DCM
0.5
20
24
24
24
24
24
24
48
48
48
24
–
–
–
–
–
–
–
–
70
Ͻ 10
0 [c]
0
0
0
Ͻ 10
0
0
0
0
Results and Discussion
Our initial evaluation of the proposed domino deprotec-
tion–intramolecular hydrosilylation began with the reaction
of dioxolane-protected aldehyde/acetal-based silane 1a
(Scheme 1). The bis[2-(1,3-dioxolan-2-yl)phenyl](methyl)-
silane (1a) was prepared via a simple two-step ap-
proach:[12,13] first, 2-(2-bromophenyl)-1,3-dioxolane was
obtained by TsOH-catalyzed protection of the aldehyde
group with 2-bromobenzaldehyde and ethane-1,2-diol; then
lithiation of 2-(2-bromophenyl)-1,3-dioxolane, followed by
reaction with methyldichlorosilane (MeSiHCl2), afforded
bis[2-(1,3-dioxolan-2-yl)phenyl](methyl)silane (1a) in good
yield (80%).
9
THF
–
–
–
10
11
12
EtOAc
toluene
DCM
PhCHO[d]
70
[a] Compound 1a (1.0 equiv., 0.2 m), catalyst 3 (1.5–10 mol-%), at
room temperature. [b] Isolated yields. [c] No reaction. [d] Addition
of 3.0 equiv. of benzaldehyde.
Scheme 2.
catalyzed deprotection of the acetal[14] and then the ad-
dition across the double bond of the aldehyde (Scheme 3).
The mechanism of this transformation is believed to involve
Scheme 1.
Fortunately, employing TsOH (3a) as catalyst in acetone the hypervalent intermediate i-2, in which intramolecular
gave the desired aldehyde-functionalized siloxane 2a in 70% oxygen coordination between silicon and aldehyde proved
isolated yield (Table 1, entry 1). Solvent screening revealed to be an effective factor in assisting the intramolecular
that acetone is a crucial solvent in this reaction because the hydrosilylation. When bis[2-(1,3-dioxolan-2-yl)-4-ethoxy-5-
first step is deprotection of the dioxolane moiety (Entry 2). methoxyphenyl](methyl)silane (1c) was used as the substrate
It is interesting that the functional siloxane 2a contains an in the presence of TsOH, a hypervalent silicon-based inter-
achiral silicon center, which inspired us to explore a method mediate was isolated. X-ray structural studies showed that
for the construction of silicon-stereogenic functional silox- this compound is a somewhat unusual hexacoordinate sili-
anes. Thus we screened a number of chiral catalysts, includ- con complex[15] (see Supporting Information, Figure S1).
ing l-proline (3b), under different conditions. Use of chiral The isolation of this hypervalent complex from the reaction
amino acids and BINOL-derived phosphoric acids did not mixture provides further evidence that the neighboring Si–
lead to the occurrence of the domino reaction, and no prod- H bond activated the aldehyde via a hexacoordinate inter-
uct was formed from the reaction.
mediate (or transition state), which resulted in intramolecu-
Scheme 2 presents a simple scope of the Brønsted-acid- lar hydrogen shifting to form the aldehyde-functionalized
atalyzed deprotection–hydrosilylation of acetal-based sil- siloxanes.
anes. As shown in Scheme 2, the substituted group in aro-
With these promising results (i.e., the novel reaction and
matic rings also gave good results. With these optimal reac- synthetic method for the preparation of functional silox-
tion conditions in hand, that is, TsOH as catalyst and ace- anes), we attempted to expand the range of substrates.
tone as solvent, we next explored the pyran-based acetals Interestingly, when the Brønsted-acid-catalyzed deprotec-
containing a hydrosilane moiety in this domino deprotec- tion–hydrosilylation of mono acetal-based hydrosilane 4a
tion–hydrosilylation reaction. However, the reaction of ace- was examined under the optimized conditions (Scheme 4),
tal deprotection is sluggish and many byproducts were de- no desired product 6a was obtained. Surprisingly, another
tected.
more relevant peculiarity we noticed in this series was that
On the basis of the aforementioned experimental results, an unexpected product, symmetrical disiloxane 5a was de-
we assumed that the mechanism of the domino deprotec- tected and isolated in good yield. It should be noted that
tion–hydrosilylation reaction involved the Brønsted-acid- the reaction is very fast – only 15 min could lead to the
Eur. J. Org. Chem. 2011, 1736–1742
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G.-Q. Lai, L.-W. Xu et. al
FULL PAPER
Table 2. Brønsted-acid-catalyzed oxidative coupling of hydrosilane-
containing acetals.[a]
Scheme 3. Proposed mechanism of deprotection–hydrosilylation.
completion of the reaction – and practical gram-scale syn-
thesis of functional symmetrical disiloxane-containing alde-
hydes was carried out easily.
Scheme 4.
An evaluation of the unexpected oxidation–coupling re-
action revealed that most acetal-containing hydrosilanes
with electron-neutral or electron-rich substituents pro-
ceeded equally well (Table 2, 4b–e). The structures of 5a–e
were assigned on the basis of 1H NMR, 13C NMR and
X-ray crystallographic analysis (Figure 1). Naphthyl and p-
trifluoromethyl substrates resulted in trace products (4f).
Interestingly, compound 4g, with its two phenyl groups,
only resulted in the deprotected product (5g, 76% yield).
Next, our attention was focused on the hydrolytic oxidation
of nonactivated hydrosilanes without any functional group
by using the same conditions. However, no reactions oc-
curred with simple hydrosilanes such as diphenylsilane and
phenylmethylsilane. This observation, taken together with
the inactivity of 4h in this reaction, suggest that the acetal
group may engage in facilitating the interaction between the
catalyst and the silicon in the hydrolytic oxidation.
[a] Compound 4 (1.0 equiv., 0.2 m), TsOH (10 mol-%), in acetone
at room temperature. [b] Isolated yields.
Figure 1. X-ray diffraction structure of compound 5b.
In the unexpected hydrolytic oxidation of organosilanes,
according to previous studies on metal complex- or Lewis
acid catalyzed hydrolytic oxidation of organosilanes,[16] we posed mechanism is different to that of intramolecular
postulated that the deprotection of the aldehyde occurred hydrosilylation (Scheme 3) due to the different reactivity of
quickly, and then the Brønsted-acid-catalyzed oxidation of pentacoordinate and hexacoordinate intermediates. In this
the hydrosilane happened smoothly in the presence of trace case, the rate-determining step involves nucleophilic attack
water because of little steric hindrance and a possible hyper- (trace water) on a pentacoordinate silicon (ii-1) via a hexa-
valent interaction between silicon and the neighboring alde- coordinate intermediate (or transition state ii-2).[15a] Sup-
hyde moiety (Scheme 5). As shown in Scheme 5, the pro- port for the mechanism in this hydrolytic oxidation is given
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Eur. J. Org. Chem. 2011, 1736–1742

Hydrosilylation and Hydrolytic Oxidation of Organosilanes
as follows: a) the reaction in water or aqueous acetone (con- bonds by using BiI3/Et3SiH system. The isolated yield of 6
taining 5 vol.-% of water), without catalyst, gave no desired derived from 5a at room temperature in only 5 h is good
product (5a) – only the deprotected product (minor com- (58%, Scheme 6).
pound ii-1) and starting material (major compound); b)
without the water and only in the presence of oxygen or air,
Conclusions
a high yield of deprotected aldehyde ii-1 was obtained,
along with several complicated and unidentified side-prod-
ucts and a trace of desired product; c) when the reaction
was carried out under simple conditions (i.e., without spe-
cial Schlenk technology or purification of solvents), the de-
sired product was formed smoothly with good yields, which
supported the proposed mechanism in Scheme 5. Therefore,
the presence of a trace of water is crucial to the hydrolytic
oxidation because it initiates the oxidative process. How-
ever, the true mechanism of Brønsted-acid-catalyzed oxi-
dation-coupling of hydrosilanes is still unclear. Although
further investigation on the Brønsted acid catalysis of oxi-
dation is needed, to the best of our knowledge, this is the
first successful and simple example of the use of a Brønsted
acid as a catalyst for the oxidative silylation of hydrosilanes
to symmetrical functional siloxanes containing aldehyde
moieties.
In summary, we have developed a novel and environmen-
tally benign Brønsted-acid-catalyzed one-pot domino de-
protection–hydrosilylation and hydrolytic oxidation to alde-
hyde-functionalized siloxanes. The present reaction repre-
sents the first example of a metal-free Brønsted-acid-cata-
lyzed intramolecular hydrosilylation of aldehydes and inter-
molecular hydrolytic oxidation of organosilanes, in which
the acetal group facilitated the corresponding oxidative si-
lylation. The activation of a Si–H bond through a hyperval-
ent transition state is observed, with neighboring interac-
tion between the aldehyde oxygen and the silicon atom.
These preliminary results encourage the development of
new organocatalysts for the functionalization of Si–H
bonds, and related reactions are expected to open up fur-
ther opportunities for the development and application of
functional organosilicon compounds. These studies are cur-
rently underway in our laboratory.
Experimental Section
General Remarks: All reagents and solvents were used directly with-
out purification. Flash column chromatography was performed
over silica (200–300 mesh). 1H and 13C NMR spectra were re-
corded at 400 and 100 MHz, respectively, with a Bruker Advance
400 MHz Nuclear Magnetic Resonance Spectromer, and were ref-
erenced to the internal solvent signals. Thin layer chromatography
was performed using silica gel F254 TLC plates and visualized with
ultraviolet light. HPLC was carried out with a Waters 2695 Millen-
nium system equipped with a photodiode array detector. EI and
CI mass spectra were performed with a Trace DSQ GC/MS spec-
trometer. The ESI-MS analysis of the samples was performed with
an LCQ advantage mass spectrometer (ThermoFisher Company,
USA), equipped with an ESI ion source in the positive ionization
mode, with data acquisition using the Xcalibur software (Version
1.4). X-ray diffraction data sets were collected with Bruker APEX
DUO and Bruker APEX-II CCD diffractometers. Programs used:
data collection with Bruker APEX2,[17a] data reduction with
Bruker SAINT, absorption correction for multi-scan, structure
solution with SHELX-97,[17b] structure refinement with SHELXL-
97,[17b] graphics with Bruker SHELXTL.[17b]
Scheme 5. Possible catalytic cycle of hydrolytic oxidation of organ-
osilanes.
In addition, the hydrolytic oxidation provided ready ac-
cess to different functionalized siloxanes for organosilicon
chemistry, the transformation of which merited exploration.
For example, a symmetrical disiloxane containing an alde-
hyde moiety could be converted to an unsymmetrical dis-
iloxane easily through reductive transformation of Si–O–Si
General Procedure for TsOH-Catalyzed Domino Deprotection–
Hydrosilylation and Oxidative Silylation: A catalytic amount of
TsOH (2–10 mol-%) was added to a vial containing 1 or 4 (1 mmol)
in acetone (5 mL). After vigorous stirring at room temperature
(times shown in the Table or Scheme), the reaction mixture was
poured into an extraction funnel containing EtOAc and brine di-
luted with distilled water. The aqueous phase was extracted with
EtOAc. The combined organic phases were dried with Na2SO4, and
the solvent was removed under reduced pressure. The crude prod-
uct was purified by silica gel column chromatography to furnish
the desired product. The products were confirmed by GC–MS and
NMR (see Supporting Information).
2-(1-Methyl-1,3-dihydrobenzo[c][1,2]oxasilol-1-yl)benzaldehyde (2a):
1
Scheme 6.
70% yield. H NMR (400 MHz, CDCl3, 25 °C): δ = 10.04 (s, 1 H),
Eur. J. Org. Chem. 2011, 1736–1742
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G.-Q. Lai, L.-W. Xu et. al
FULL PAPER
8.18 (d, J = 7.2 Hz, 1 H), 8.13 (d, J = 7.2 Hz, 1 H), 7.82 (d, J = 136.20, 134.64, 117.52, 114.93, 64.49, 55.93, 29.72, 14.69, 2.25 ppm.
7.6 Hz, 1 H); 7.70–7.66 (m, 1 H), 7.59–7.55 (m, 1 H), 7.44–7.40 (m, 29Si NMR (79.5 MHz, CDCl3, 25 °C): δ = –1.75 ppm. GC/MS: m/z
1 H), 7.34–7.26 (m, 2 H), 5.32 (dd, J = 11.2, 14.4 Hz, 2 H), 0.70
(s, 3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 194.56,
151.00, 140.18, 139.91, 135.88, 134.32, 134.15, 134.12, 133.34,
130.15, 129.98, 126.84, 121.62, 70.70, –0.31 ppm. 29Si NMR
(79.5 MHz, CDCl3, 25 °C): δ = 6.75 ppm. GC/MS: m/z = 254 (14)
[M+], 239 (100), 225 (9), 195 (1), 178 (31), 165 (33), 148 (23), 133
= 490 (16) [M+], 475 (73), 446 (21), 403 (9), 342 (7), 311 (58), 267
(19), 253 (63), 237 (100), 209 (52), 202 (70), 194 (54), 180 (21), 165
(31), 133 (51). IR (KBr): ν = 1687.8 cm–1. C H O Si (490.18):
˜
24 34
7
2
calcd. C 58.74, H 6.98, O 22.82, Si 11.45; found C 58.59, H 7.06.
1
5d: 37% yield. H NMR (400 MHz, CDCl3, 25 °C): δ = 10.03 (s 2
H), 7.91 (dd, J = 5.2, 8.4 Hz, 2 H), 7.57 (dd, J = 2.8, 9.2 Hz, 2 H),
7.25–7.21 (m, 2 H), 0.47 (s, 12 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C): δ = 191.81, 164.61, 146.18, 137.26, 135.89, 135.79,
(13), 105 (17), 89 (11), 77 (7). IR (KBr): ν = 1675.6 cm–1.
˜
C15H14O2Si (254.08): calcd. C 70.83, H 5.55, O 12.58, Si 11.04;
found C 70.73, H 5.49.
123.16, 122.93, 116.69, 116.49, 1.44 ppm. 29Si NMR:
(79.5 MHz, CDCl3): –1.88 ppm.
δ =
2-(5,6-Dimethoxy-1-methyl-1,3-dihydrobenzo[c][1,2]oxasilol-1-yl)-
4,5-dimethoxybenzaldehyde (2b): 54% yield. 1H NMR (400 MHz,
CDCl3, 25 °C): δ = 9.86 (s, 1 H), 7.58 (s, 1 H), 7.47 (s, 1 H), 7.31
(s, 1 H), 6.70 (s, 1 H), 5.16 (dd, J = 13.6, 22.0 Hz, 2 H), 3.99–3.85
(m, 12 H), 0.55 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C):
δ = 192.54, 154.29, 151.33, 150.07, 148.30, 143.99, 135.00, 133.19,
124.12, 117.53, 115.30, 115.22, 104.19, 70.49, 56.30, 56.13, 55.99,
55.77, –0.16 ppm. 29Si NMR (79.5 MHz, CDCl3, 25 °C): δ =
5.85 ppm. GC/MS: m/z = 374 (98) [M+], 359 (100), 343 (27), 329
(13), 315 (15), 298 (43), 283 (22), 271 (6), 255 (20), 240 (11), 225,
(9), 208 (46), 193 (27), 179 (14), 165 (23), 151 (28), 121 (9), 107 (7),
1
5e: 54% yield. H NMR (400 MHz, CDCl3, 25 °C): δ = 10.13 (d,
J = 3.2 Hz, 2 H), 7.76 (d, J = 8.0 Hz, 2 H), 7.43 (d, J = 2.4 Hz, 2
H), 7.13–7.10 (m, 2 H), 3.88 (d, J = 3.6 Hz, 6 H), 0.41 (d, J =
14.8 Hz, 12 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ =
193.25, 160.95, 142.61, 137.04, 133.40, 119.08, 116.59, 55.42,
2.09 ppm.
BiI3-Catalyzed Reductive Silylation of 5a: To a suspension of bis-
muth(III) iodide (0.1 mmol) and 5a (1.0 mmol) in acetonitrile
(3 mL) was added triethylsilane (2.0 mmol) at room temperature
under argon. After stirring for 5 h, the reaction mixture was
quenched with water. The organic materials were extracted with
dichloromethane, washed with brine, and dried with sodium sul-
91 (6), 77 (6). IR (KBr): ν = 1668.5 cm–1. C H O Si (374.12):
˜
19 22
6
calcd. C 60.94, H 5.92, O 25.64, Si 7.50; found C 60.62, H 5.82.
4-Ethoxy-2-(6-ethoxy-5-methoxy-1-methyl-1,3-dihydrobenzo[c][1,2]-
oxasilol-1-yl)-5-methoxybenzaldehyde (2c): 73% yield. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 9.85 (s, 1 H), 7.59 (s, 1 H), 7.49 (s,
1 H), 7.31 (s, 1 H), 6.71 (s, 1 H), 5.16 (dd, J = 13.6, 20.8 Hz, 2 H),
4.17 (dd, J = 6.8, 14.0 Hz, 2 H), 4.10–4.06 (m, 3 H), 3.89 (s, 3 H),
1.51–1.43 (m, 6 H), 0.56 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C): δ = 192.56, 154.58, 150.65, 149.33, 148.52, 143.96,
134.85, 133.19, 124.61, 117.74, 116.61, 115.66, 105.36, 70.48, 64.66,
64.10, 56.28, 56.08, 14.73, 14.69, –0.12 ppm. 29Si NMR (79.5 MHz,
CDCl3, 25 °C): δ = 5.85 ppm. GC/MS: m/z = 402 (00) [M+], 387
(99), 373 (27), 359 (13), 326 (26), 313 (12), 297 (23), 269 (12), 241
(15), 222 (39), 207 (25), 195 (12), 179 (21), 165 (30), 151 (25), 137
fate. The desired product
6 was isolated by flash column
1
chromatography on silica gel (58%). H NMR (400 MHz, CDCl3,
25 °C): δ = 10.16 (s, 1 H), 7.90–7.87 (m, 2 H), 7.63–7.53 (m, 2 H),
0.953 (t, J = 8.0 Hz, 9 H), 0.61 (q, J = 16.0 Hz, 6 H), 0.41 (s, 6 H)
ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 193.73, 142.80,
140.93, 135.47, 133.15, 132.03, 129.51, 6.87, 6.39, 1.72 ppm. 29Si
NMR (79.5 MHz, CDCl3): δ = 11.28, –3.09 ppm. GC/MS: m/z =
294 (2) [M+], 279 (33), 265 (25), 209 (100), 195 (16), 181 (14), 149
(22), 97 (85).
Supporting Information (see footnote on the first page of this arti-
cle): General remarks, spectroscopic data for the siloxanes, 29Si
NMR Spectra of siloxanes, and X-ray structures of 5b (CCDC-
787471) and intermediate i-2 (CCDC-803537, Scheme 3).
(16), 121 (7), 91 (6), 77 (8). IR (KBr): ν = 1675.6 cm–1. C H O Si
˜
21 26
6
(402.15): calcd. C 62.66, H 6.51, O 23.85, Si 6.98; found C 63.21,
H 6.59.
1
5a: 55% yield. H NMR (400 MHz, CDCl3, 25 °C): δ = 10.10 (d,
Acknowledgments
J = 8.0 Hz, 2 H), 7.93–7.88 (m, 4 H), 7.62–7.55 (m, 4 H), 0.57–
0.40 (m, 12 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ =
193.65, 142.10, 140.95, 135.69, 133.29, 132.66, 129.59, 1.58,
1.42 ppm. 29Si NMR (79.5 MHz, CDCl3, 25 °C): δ = –1.83 ppm.
GC/MS: m/z = 342 (0.4) [M+], 327 (77), 309 (61), 291 (7), 253 (2),
237 (12), 219 (6), 191 (41), 178 (22), 163 (100), 156 (68), 149 (54),
Financial support by the National Natural Science Foundation of
China (NSFC), grant number 20973051, the Zhejiang Provincial
Natural Science Foundation of China (ZPNSFC), grant number
Y4090139, and the Hangzhou Science and Technology Program,
grant number 20090231 T03 is appreciated.
104 (7), 91 (26), 89 (13), 73 (4). IR (KBr): ν = 1698.7 cm–1.
˜
C18H22O3Si2 (342.11): calcd. C 63.12, H 6.47, O 14.01, Si 16.40;
found C 62.87, H 6.52.
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1
5b: 60% yield. H NMR (400 MHz, CDCl3, 25 °C): δ = 10.06 (s, 2
H), 7.43 (s, 2 H), 7.34 (s, 2 H), 3.96 (s, 6 H), 3.82 (s, 6 H), 0.49 (s,
12 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 191.55,
152.93, 149.88, 136.42, 134.68, 117.25, 113.63, 56.03, 55.92,
2.23 ppm. 29Si NMR (79.5 MHz, CDCl3, 25 °C): δ = –1.71 ppm.
GC/MS: m/z = 462 (0.2) [M+], 429 (1), 329 (11), 209 (43), 165 (6),
151 (100), 85 (63). IR (KBr): ν = 1688.9, 1678.6 cm–1. C H O Si
˜
22 30
7
2
(462.15): calcd. C 57.11, H 6.54, O 24.21, Si 12.14; found C 57.16,
H 6.44.
1
5c: 71% yield. H NMR (400 MHz, CDCl3, 25 °C): δ = 10.03 (s, 2
H), 7.42 (s, 2 H), 7.34 (s, 2 H), 4.18 (dd, J = 6.8, 14.0 Hz, 4 H),
3.79 (s, 6 H), 1.50 (t, J = 7.2 Hz, 6 H), 0.48 (s, 12 H) ppm. 13C
NMR (100 MHz, CDCl3, 25 °C): δ = 191.61, 153.18, 149.19,
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FULL PAPER
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Received: November 15, 2010
Published Online: February 11, 2011
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