Active cobalt catalyst for the cleavage of benzyl ether

Article abstract of DOI:10.1021/jo2018284

An improved method for the deprotection of benzyl ethers using a catalytic amount of Co₂(CO)₈ in the presence of Me₂PhSiH and CO (1 atm) is described. The deprotection reaction is compatible with double bond or sulfur-cont

Full text of DOI:10.1021/jo2018284

Note
pubs.acs.org/joc
Active Cobalt Catalyst for the Cleavage of Benzyl Ether
Bo Wang, Zhaojun Yin, Yangbing Li, Ting-Xiang Yang, Xiang-Bao Meng, and Zhong-Jun Li*
The State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, P.
R. China
S
* Supporting Information
ABSTRACT: An improved method for the deprotection of benzyl ethers using a catalytic amount of Co2(CO)8 in the presence
of Me2PhSiH and CO (1 atm) is described. The deprotection reaction is compatible with double bond or sulfur-containing
substrates. The method also tolerates other functional groups, such as Ac, Piv, and Bz, and shows potential selectivity in
perbenzylated monosaccharides.
Table 1. Screening of Hydrosilanes
he protection and deprotection of hydroxyl groups are
Tfrequently needed in the synthesis of bioactive complex
molecules. Among the many protective groups, benzyl ether is
one of the most often used protecting groups because of its
easy formation, inherent stability, and mild cleavage con-
ditions.1 A plethora of reagents and methods have been used to
remove benzyl ethers, including catalytic hydrogenolysis,2−6
reductive cleavage (lithium naphthalenide7,8 and TIBAL,9
etc.10,11), Lewis acid (TMSI12 and TiCl4,13 etc.14−16), or
oxidation-based cleavage (2,3-dichloro-5,6-dicyano-1,4-benzo-
quinone17,18 and 4-acetamido-2,2,6,6-tetramethylpiperidine-1-
oxoammonium tetrafluoroborate19). The triphenylphosphine
hydrobromide20 and the I2/Et3SiH system21 were also used to
cleave the benzyl ethers. However, most of the well-developed
methods are incompatible with double and triple bonds or
sulfur-containing substrates, which limit the application of
benzyl ethers. Recently, our laboratory reported a highly
efficient and thioglycoside compatible de-O-benzylation
method based on the Co2(CO)8−CO−Et3SiH system, in
which greater than stoichiometric amounts of Co2(CO)8 (1.5
or 3 equiv) were used for the selective cleavage of primary
benzyl ethers in complex saccharide.22 However, the excess use
of cobalt is not environmentally friendly, and the workup is
tedious. Herein, we disclose an improved cobalt-catalyzed
protocol for the efficient cleavage of benzyl ethers in a wide
range of substrates.
a
time
(h)
yield
entry
hydrosilane
product
(%)
1
2
3
EtMe2SiH
PhMe2SiH
Ph2MeSiH
CH3(CH2)11OSiMe2Et (1b)
CH3(CH2)11OSiMe2Ph (1c)
8
3
95
96
25
CH3(CH2)11OSiMePh2
(1d)
48
4
5
6
7
Et3SiH
CH3(CH2)11OSiEt3 (1e)
24
48
48
48
11
0
t-BuMe2SiH
Ph3SiH
0
(EtO)3SiH
0
a
Isolated yield.
was used in our previous report, provided a trace of desired
product. In contrast, the less steric EtMe2SiH and Me2PhSiH
afforded the desired products in excellent yield. Therefore,
Me2PhSiH was chosen for further studies owing to its lower
price and higher boiling point (156 °C compared with 46 °C
for EtMe2SiH).
The reaction conditions were further optimized (Table 2).
The catalyst loading can be reduced to 0.1 equiv without
compromising the product yield (entry 1). When the reaction
was carried out with 0.05 or 0.01 equiv of Co2(CO)8, poor
yields were obtained (entries 2 and 3). Decreasing the
temperature also led to low yield (entry 4). In addition,
when the reaction was carried out in DCM or 3 equiv of
hydrosilane was used, the yields decreased to some extent
(entries 5 and 6). Consequently, our optimal reaction
conditions were 0.1 equiv of Co2(CO)8, 6 equiv of Me2PhSiH,
and CO (1 atm) in refluxing benzene.
Our previous study indicated that the electric and steric
properties of substituents on the hydrosilane have great
influence on the reaction because the hydrosilane is involved
in the formation and activity of catalyst. It also participates in
the oxidative addition to alkyl carbonyl cobalt complex and
reduction of aldehyde. As a model study, benzyl ether 1a was
treated with Co2(CO)8 (0.2 equiv), various hydrosilanes (6.0
equiv), and CO (1 atm) under benzene reflux (Table 1). The
bulky hydrosilanes, such as t-BuMe2SiH, Ph3SiH, and
(EtO)3SiH, did not produce any products, and Et3SiH, which
Received: September 5, 2011
Published: October 14, 2011
© 2011 American Chemical Society
9531
dx.doi.org/10.1021/jo2018284|J. Org. Chem. 2011, 76, 9531−9535

The Journal of Organic Chemistry
Note
Table 2. Optimization Studies
a
entry
Co2(CO)8 (equiv)
Me2PhSiH (equiv)
solvent
T (°C)
time (h)
yield (%)
1
2
3
4
5
6
0.1
6
6
6
6
6
3
benzene
benzene
benzene
benzene
DCM
reflux
reflux
reflux
60
6
20
20
21
48
6.5
98
86
11
34
39
90
0.05
0.01
0.1
0.1
reflux
reflux
0.1
benzene
a
Isolated yield.
General Procedures for the Deprotection of Benzyl Ethers.
Co2(CO)8 (0.1 equiv or 0.2 equiv) was added to a flask under CO
atmosphere. Me2PhSiH (6 equiv or 20 equiv) was then added, and the
mixture was stirred for 30 min at room temperature. A solution of
benzyl ethers or perbenzylated saccharides in anhydrous benzene (1
mmol/5 mL) was degassed and added using a syringe. The mixture
was heated to reflux in an oil bath. The reaction was monitored by
TLC. After the disappearance of starting materials, the cobalt complex
was precipitated by the dropwise addition of pyridine and subsequent
bubbling of air through the solution for 20 min. The content of the
flask was filtered through 5 cm of silica gel and eluted with chloroform.
The filtrate was evaporated, and the residue was subjected to flash
chromatography.
Under the established optimal conditions, a wide spectrum of
structurally diverse benzyl ethers were subjected to depro-
tection by this procedure and the results are summarized in
Table 3. As shown, all of the primary benzyl ethers gave
satisfactory results within a short reaction time (entries 1−5).
However, the reaction rate for secondary benzyl ethers is slow,
and a longer reaction time (10−72 h) is needed under standard
conditions (entries 8−10). It should be emphasized that not
only esters but also a double bond can survive under the
deprotection conditions without any detected side products
(entries 3−5, 7). In addition, the alcohol benzyl ether can be
selectively cleaved in the presence of phenol benzyl ether (entry
6). The selectivity of this methodology was further illustrated in
carbohydrate substrates (entries 11−14). The primary benzyl
ethers can be selectively removed without affecting the
secondary benzyl ethers by using 20 equiv of hydrosilane.
The proposed mechanism for the cleavage of benzyl ethers is
shown in Scheme 1.23 The actual active catalyst Me2PhSiCo-
(CO)4, generated in situ by mixing Co2(CO)8 with Me2PhSiH,
reacts initially with benzyl ether and generates the desired
product and benzyl cobalt complex. After a series of
transformations with the cobalt complex, the catalyst is
regenerated. The well-known high affinity of the organosilyl
group for oxygen could be the driving force for the catalytic
cycle.
(Dodecyloxy)(ethyl)dimethylsilane (1b): colorless oil; 1H
NMR (400 MHz, CDCl3) δ 3.50 (t, 2H, J = 6.7 Hz), 1.40−1.50
(m, 2H), 1.15−1.28 (m, 18H), 0.88 (t, 3H, J = 7.9 Hz), 0.81 (t, 3H, J
= 6.8 Hz), 0.50 (q, 2H, J = 7.9 Hz), 0.01 (s, 6H); 13C NMR (100
MHz, CDCl3) δ 62.8, 32.8, 31.9, 29.7, 29.6, 29.6, 29.5, 29.4, 25.8, 22.7,
14.1, 8.0, 6.7, −2.7; HRMS (ESI) calcd for C16H36OSi [M + H]+
273.2614, found 273.2608.
(Dodecyloxy)dimethyl(phenyl)silane (1c): colorless oil; 1H
NMR (400 MHz, CDCl3) δ 7.42−7.54 (m, 2H), 7.22−7.34 (m,
3H), 3.51 (t, 2H, J = 6.7 Hz), 1.40−1.50 (m, 2H), 1.10−1.30 (m,
18H), 0.81 (t, 3H, J = 7.0 Hz), 0.30 (s, 6H); 13C NMR (100 MHz,
CDCl3) δ 138.2, 133.5, 129.5, 127.8, 63.2, 32.6, 31.9, 29.6, 29.4, 29.3,
25.8, 22.7, 14.1, −1.8; HRMS (ESI) calcd for C20H36OSi [M + H]+
321.2614, found 321.2614.
(Dodecyloxy)(methyl)diphenylsilane (1d): colorless oil; 1H
NMR (400 MHz, CDCl3) δ 7.48−7.56 (m, 4H), 7.26−7.36 (m,
6H), 3.61 (t, 2H, J = 6.7 Hz), 1.49 (m, 2H), 1.10−1.30 (m, 18H), 0.80
(t, 3H, J = 6.8 Hz), 0.56 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
136.3, 134.3, 129.7, 127.8, 63.6, 32.6, 31.9, 29.7, 29.6, 29.6, 29.4, 29.4,
25.8, 22.7, 14.1, −3.0; HRMS (ESI) calcd for C25H38OSi [M + H]+
383.2770, found 383.2766.
In conclusion, an efficient and selective method was
developed for the efficient cleavage of benzyl ethers with
cobalt catalyst, which is compatible with a wide range of
substrates. The compatibility and selectivity of the method will
present a valuable addition to the existing reagents. Studies to
extend its application in the area of carbohydrate synthesis are
underway.
(Dodecyloxy)triethylsilane (1e): colorless oil; 1H NMR (400
MHz, (CD3)2CO) δ 3.50 (t, 2H, J = 6.4 Hz), 1.38 (m, 2H), 1.30−1.10
(m, 18H), 0.83 (t, 9H, J = 7.9 Hz), 0.75 (t, 3H, J = 7.0 Hz), 0.47 (q,
6H, J = 7.9 Hz); 13C NMR (100 MHz, (CD3)2CO) δ 63.3, 33.7, 32.7,
30.4, 30.4, 30.2, 30.1, 26.6, 23.4, 14.4, 7.1, 5.1; HRMS (ESI) calcd for
C18H40OSi [M + H]+ 301.2927, found 301.2920.
Dimethyl(phenyl)(3-phenylpropoxy)silane (2b): colorless oil;
1H NMR (400 MHz, CDCl3) δ 7.42−7.52 (m, 2H), 7.2−7.3 (m, 3H),
7.08−7.18 (m, 2H), 6.98−7.08 (m, 3H), 3.52 (t, 2H, J = 6.3 Hz), 2.55
(t, 2H, J = 7.9 Hz), 1.74 (m, 2H), 0.28 (s, 6H); 13C NMR (100 MHz,
CDCl3) δ 142.0, 138.0, 133.4, 129.5, 128.4, 128.2, 127.8, 125.6, 62.3,
34.1, 32.0, −1.8; HRMS (ESI) calcd for C17H22OSi [M + H]+
271.1518, found 271.1517.
EXPERIMENTAL SECTION
■
General Experimental Methods. All chemicals were purchased
as reagent grade and used without further purification, unless
otherwise noted. Dichloromethane was distilled over calcium hydride.
Benzene was distilled from sodium. Analytical TLC was performed on
silica gel 60 F254 precoated on glass plates, with detection by
fluorescence and/or by staining with 5% concentrated sulfuric acid in
EtOH. Column chromatography was performed employing silica gel
(230−400 mesh). Optical rotations were recorded using an optical
activity polarimeter. 1H NMR spectra were recorded on advance
spectrometers at 25 °C. Chemical shifts (in ppm) were referenced
with tetramethylsilane (δ = 0 ppm) in deuterated chloroform,
deuterated acetone, or deuterated benzene. 13C NMR spectra were
obtained by using the same NMR spectrometers and were calibrated
with CDCl3 (δ = 77.00 ppm), (CD3)2CO (δ = 29.84, 206.26 ppm), or
C6D6 (δ = 128.00 ppm). High-resolution mass spectrometry was
performed on a mass spectrometer.
(4-Methoxyphenethoxy)dimethyl(phenyl)silane (3b): color-
1
less oil; H NMR (400 MHz, CDCl3) δ 7.40−7.47 (m, 2H), 7.23−
7.34 (m, 3H), 6.99 (d, 2H, J = 8.5 Hz), 6.73 (d, 2H, J = 8.5 Hz), 3.70
(s, 3H), 3.67 (t, 2H, J = 7.3 Hz), 2.69 (t, 2H, J = 7.2 Hz), 0.25 (s, 6H);
13C NMR (100 MHz, CDCl3) δ 158.1, 137.8, 133.4, 131.0, 130.0,
129.5, 127.8, 113.7, 64.5, 55.2, 38.4, −1.9; HRMS (ESI) calcd for
C17H22O2Si [M + Na]+ 309.1287, found 309.1288.
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The Journal of Organic Chemistry
Note
Table 3. Screening of Substrates
a
b
c
d
Isolated yield after chromatography on SiO2. Toluene, reflux. The yield could be increased to 81.6% when 0.2 equiv of Co2(CO)8 was used. The
yield would be decreased to 15.8% when the amount of Me2PhSiH was reduced to 10 equiv in 24 h.
1
4-(Benzyloxy)butyl pivalate (4a): colorless oil; H NMR (400
MHz, CDCl3) δ 7.17−7.31 (m, 5H), 4.44 (s, 2H), 4.00 (t, 2H, J = 6.3
Hz), 3.43 (t, 2H, J = 6.2 Hz), 1.64 (m, 4H), 1.12 (s, 9H); 13C NMR
(100 MHz, CDCl3) δ 178.6, 138.5, 128.4, 127.6, 127.6, 72.9, 69.8,
64.2, 38.7, 27.2, 26.3, 25.5; HRMS (ESI) calcd for C16H24O3 [M +
Na]+ 287.1623, found 287.1615.
178.5, 137.9, 133.4, 129.6, 127.8, 64.1, 62.5, 38.7, 29.1, 27.2, 25.2,
−1.8; HRMS (ESI) calcd for C17H28O3Si [M + Na]+ 331.1705, found
331.1702.
4-((Dimethyl(phenyl)silyl)oxy)butyl benzoate (5b): colorless
1
oil; H NMR (400 MHz, (CD3)2CO) δ 7.99−8.05 (m, 2H), 7.58−
7.66 (m, 3H), 7.48−7.54 (m, 2H), 7.34−7.41 (m, 3H), 4.32 (t, 2H, J =
6.4 Hz), 3.72 (t, 2H, J = 6.2 Hz), 1.76−1.89 (m, 2H), 1.65−1.73 (m,
2H), 0.36 (s, 6H); 13C NMR (100 MHz, (CD3)2CO) δ 166.7, 138.9,
134.2, 133.8, 131.5, 130.4, 130.1, 129.4, 128.6, 65.4, 63.1, 29.9, 26.1,
4-((Dimethyl(phenyl)silyl)oxy)butyl pivalate (4b): colorless
1
oil; H NMR (400 MHz, CDCl3) δ 7.46−7.52 (m, 2H), 7.26−7.34
(m, 3H), 3.96 (t, 2H, J = 6.3 Hz), 3.54 (t, 2H, J = 6.2 Hz), 1.46−1.65
(m, 4H), 1.11 (s, 9H), 0.30 (s, 6H); 13C NMR (100 MHz, CDCl3) δ
9533
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The Journal of Organic Chemistry
Note
((2,3-Dihydro-1H-inden-2-yl)oxy)dimethyl(phenyl)silane
Scheme 1. Proposed Mechanism
1
(11b): colorless oil. H NMR (400 MHz, CDCl3) δ 7.43−7.55 (m,
2H), 7.23−7.34 (m, 3H), 7.01−7.10 (m, 4H), 4.56 (m, 1H), 2.97 (dd,
2H, J = 6.6, 15.7 Hz), 2.82 (dd, 2H, J = 5.6, 15.7 Hz), 0.32 (s, 6H);
13C NMR (100 MHz, CDCl3) δ141.0, 138.1, 133.5, 129.6, 127.8,
126.4, 124.6, 74.0, 42.3, −1.2; HRMS (ESI) calcd for C17H20OSi [M +
Na]+ 291.1181, found 291.1172.
p-Methoxyphenyl 2,3,4-tri-O-benzyl-6-O-dimethylphenyl-
silyl-α-D-mannopyranoside (12b): colorless oil; [α]25 +42.7 (c
D
1
0.8, CHCl3); H NMR (400 MHz, CDCl3) δ 7.45−7.52 (m, 2H),
7.11−7.33 (m, 18H), 6.83−6.87 (m, 2H), 6.66−6.70 (m, 2H), 5.34 (d,
1H, J = 1.8 Hz), 4.82 (d, 1H, J = 10.9 Hz), 4.71 (d, 1H, J = 12.4 Hz),
4.65 (d, 1H, J = 12.4 Hz), 4.61 (d, 2H, J = 2.0 Hz), 4.49 (d, 1H, J =
10.9 Hz), 4.01 (dd, 1H, J = 3.0, 9.3 Hz), 3.94 (t, 1H, J = 9.4 Hz), 3.86
(dd, 1H, J = 2.2, 2.8 Hz), 3.79 (dd, 1H, J = 4.9, 11.4 Hz), 3.74 (dd, 1H,
J = 2.0, 11.3 Hz), 3.64−3.70 (m, 4H), 0.27 (s, 6H); 13C NMR (100
MHz, CDCl3) δ 154.9, 150.4, 138.6, 138.5, 138.3, 137.9, 133.6, 129.4,
128.3, 128.3, 127.8, 127.7, 127.7, 127.7, 127.6, 127.6, 127.5, 118.0,
114.4, 97.1, 79.9, 74.9, 74.9, 74.6, 73.4, 72.6, 72.3, 62.4, 55.6, −1.5,
−1.7; HRMS (ESI) calcd for C42H46O7Si [M + Na]+ 713.2905, found
713.2886.
−1.6; HRMS (ESI) calcd for C19H24O3Si [M + Na]+ 351.1392, found
351.1390.
4-((Dimethyl(phenyl)silyl)oxy)butyl acetate (6b): colorless
p-Methylphenyl 2,3,4-tri-O-benzyl-6-O-dimethylphenyl-
silyl-1-thio-β-D-glucopyranoside (13b): colorless oil; [α]25 −4.4
1
oil; H NMR (400 MHz, CDCl3) δ 7.54−7.60 (m, 2H), 7.35−7.42
D
1
(c 1.8, CHCl3); H NMR (400 MHz, C6D6) δ 7.34−7.41 (m, 4H),
(m, 3H), 4.04 (t, 2H, J = 6.5 Hz), 3.61 (t, 2H, J = 6.2 Hz), 2.02 (s,
3H), 1.62 (m, 4H), 0.37 (s, 6H); 13C NMR (100 MHz, CDCl3) δ
171.1, 137.8, 133.4, 129.6, 127.8, 64.3, 62.4, 29.0, 25.1, 21.0, −1.9;
HRMS (ESI) calcd for C14H22O3Si [M + Na]+ 289.1236; found
289.1231.
7.14−7.16 (m, 2H), 6.77−7.00 (m, 16H), 6.60 (d, 2H, J = 7.9 Hz),
4.68 (d, 1H, J = 10.7 Hz), 4.60 (d, 1H, J = 11.3 Hz), 4.53 (t, 2H, J =
11.8 Hz), 4.43 (d, 1H, J = 10.8 Hz), 4.32−4.35 (m, 2H), 3.57 (dd, 1H,
J = 1.9, 11.4 Hz), 3.52 (dd, 1H, J = 3.8, 11.4 Hz), 3.43 (t, 1H, J = 9.3
Hz), 3.32 (t, 1H, J = 8.7 Hz), 3.22 (t, 1H, J = 9.1 Hz), 2.82−2.86 (m,
1H), 1.73 (s, 3H), 0.15 (s, 3H), 0.15 (s, 3H); 13C NMR (100 MHz,
C6D6) δ 139.4, 139.2, 139.2, 138.2, 137.4, 134.1, 132.8, 131.4, 129.9,
129.8, 128.5, 128.2, 128.12, 127.9, 127.9, 127.7, 127.6, 88.4, 87.0, 81.5,
80.2, 77.6, 75.5, 75.4, 74.9, 62.6, 21.0, −1.3; HRMS (ESI) calcd for
C42H46O5SSi [M + Na]+ 713.2727, found 713.2719.
(4-(Benzyloxy)phenethoxy)dimethyl(phenyl)silane (7b): col-
1
orless oil; H NMR (400 MHz, (CD3)2CO) δ 7.27−7.57 (m, 10H),
7.12 (d, 2H, J = 8.4 Hz), 6.92 (d, 2H, J = 8.4 Hz), 5.08 (s, 2H), 3.78 (t,
2H, J = 7 Hz), 2.75 (t, 2H, J = 6.8 Hz), 0.30 (s, 6H); 13C NMR (100
MHz, (CD3)2CO) δ 158.3, 138.9, 138.6, 134.2, 132.3, 130.9, 130.3,
129.2, 128.6, 128.5, 128.3, 115.5, 70.4, 65.0, 39.1, −1.6; HRMS (ESI)
calcd for C23H26O2Si [M + Na]+ 385.1600, found 385.1599.
p-Methylphenyl 2,3,4-tri-O-benzyl-6-O-dimethylphenyl-
silyl-1-thio-α-D-mannopyranoside (14b): colorless oil; [α]25
+61.1 (c 1.1, CHCl3). H NMR (400 MHz, C6D6) δ 7.32−7.34 (m,
(((3S,8S,9S,10R,13R,14S,17R)-10,13-Dimethyl-17-((R)-6-
D
1
methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetra-
decahydro-1H-cyclopenta[a]phenanthren-3-yl)oxy)dimethyl-
2H), 7.26−7.28 (m, 2H), 6.96−7.03 (m, 6H), 6.75−6.93 (m, 12H),
6.62 (d, 2H, J = 7.9 Hz), 5.45 (d, 1H, J = 1.0 Hz), 4.69 (d, 1H, J = 11.4
Hz), 4.31 (d, 1H, J = 11.4 Hz), 4.19−4.23 (m, 1H), 4.15 (d, 1H, J =
12.2 Hz), 4.12 (s, 2H), 4.07 (d, 1H, J = 12.2 Hz), 4.01 (t, 1H, J = 9.5
Hz), 3.75−3.79 (m, 2H), 3.72 (dd, 1H, J = 4.9, 11.3 Hz), 3.67 (dd,
1H, J = 2.0, 11.3 Hz), 1.74 (s, 3H), 0.08 (s, 3H), 0.07 (s, 3H); 13C
NMR (100 MHz, C6D6) δ 139.5, 139.0, 138.8, 138.4, 137.5, 134.0,
132.6, 131.8, 130.0, 129.6, 128.5, 128.5, 128.4, 128.1, 127.9, 127.5,
86.7, 81.1, 77.4, 75.3, 75.1, 74.6, 72.2, 72.1, 63.0, 21.0, −1.2, −1.5;
HRMS (ESI) calcd for C42H46O5SSi [M + NH4]+ 708.3174, found
708.3166.
1
(phenyl)silane (8b): colorless oil; [α]25 −29.9 (c 1.1, CHCl3); H
D
NMR (400 MHz, CDCl3) δ 7.48−7.54 (m, 2H), 7.26−7.32 (m, 3H),
5.15−5.21 (m, 1H), 3.44 (m, 1H), 2.24 (m, 1H), 2.04−2.12 (m, 1H),
1.82−1.97 (m, 2H), 0.7−1.80 (m, 36H), 0.59 (s, 3H), 0.31 (s, 3H),
0.31 (s, 3H); 13C NMR (100 MHz, CDCl3) δ141.3, 138.5, 133.4,
129.4, 127.7, 121.4, 72.7, 56.8, 56.1, 50.2, 42.6, 42.3, 39.8, 39.5, 37.3,
36.5, 36.2, 35.8, 31.9, 31.9, 29.7, 28.2, 28.0, 24.3, 23.8, 22.8, 22.6, 21.0,
19.4, 18.7, 11.8, −0.1, −1.1; HRMS (ESI) calcd for C35H56OSi [M +
Na]+ 543.3998, found 543.4002.
(((1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl)oxy)dimethyl-
1
(phenyl)silane (9b): colorless oil; [α]25 −37.2 (c 1.1, CHCl3); H
D
p-Methylphenyl 2,3,4-tri-O-benzyl-6-O-dimethylphenyl-
silyl-1-thio-β-D-galactopyranoside (15b): colorless oil; [α]25
−5.6 (c 1.4, CHCl3); H NMR (400 MHz, C6D6) δ 7.38−7.41 (m,
NMR (400 MHz, CDCl3) δ 7.56−7.64 (m, 2H), 7.34−7.41 (m, 3H),
3.42 (m, 1H), 2.12−2.25 (m, 1H), 1.78−1.88 (m, 1H), 1.52−1.65 (m,
2H), 1.25−1.38 (m, 1H), 1.13−1.22 (m, 1H), 1.02 (m, 1H), 0.75−
D
1
2H), 7.26−7.29 (m, 2H), 7.13−7.15 (m, 2H), 7.03−7.05 (m, 2H),
6.78−6.97 (m, 14H), 6.53 (d, 2H, J = 8.0 Hz), 4.74 (d, 1H, J = 11.4
Hz), 4.58 (d, 1H, J = 10.8 Hz), 4.40 (d, 1H, J = 10.8 Hz), 4.31 (d, 1H,
J = 9.6 Hz), 4.28 (d, 1H, J = 11.4 Hz), 4.19 (d, 1H, J = 11.9 Hz), 4.13
(d, 1H, J = 11.9 Hz), 3.86 (t, 1H, J = 9.4 Hz), 3.62 (d, 2H, J = 6.6 Hz),
3.58 (d, 1H, J = 2.3 Hz), 3.04−3.07 (m, 2H), 1.71 (s, 3H), 0.05 (s,
3H), 0.04 (s, 3H); 13C NMR (100 MHz, C6D6) δ 139.5, 139.1, 137.9,
137.0, 133.8, 132.6, 131.3, 130.0, 129.8, 128.6, 128.4, 128.4, 128.1,
127.9, 127.7, 127.6, 127.5, 88.3, 84.8, 79.1, 77.7, 75.5, 74.8, 74.1, 72.8,
62.2, 21.0, −1.8, −1.9; HRMS (ESI) calcd for C42H46O5SSi [M + Na]+
713.2727, found 713.2728.
0.95 (m, 8H), 0.62 (d, 3H, J = 6.9 Hz), 0.39 (s, 3H), 0.39 (s, 3H); 13
C
NMR (100 MHz, CDCl3) δ138.6, 133.5, 129.4, 127.7, 72.8, 50.1, 45.4,
34.5, 31.6, 25.2, 22.8, 22.3, 21.3, 15.7, −0.7, −0.9; HRMS (ESI) calcd
for C18H30OSi [M + Na]+ 313.1964, found 313.1961.
((Tridecan-2-yloxy)methyl)benzene (10a): colorless oil; 1H
NMR (400 MHz, CDCl3) δ 7.13−7.32 (m, 5H), 4.34−4.51 (m,
2H), 3.36−3.47 (m, 1H), 1.45−1.57 (m, 1H), 1.06−1.42 (m, 22H),
0.80 (t, 3H, J = 6.7 Hz); 13C NMR (100 MHz, CDCl3) δ 139.2, 128.2,
127.6, 127.3, 74.9, 70.2, 36.7, 31.9, 29.7, 29.7, 29.6, 29.3, 25.5, 22.7,
19.6, 14.1; HRMS (ESI) calcd for C20H34O [M + Na]+ 313.2507,
found 313.2503.
Dimethyl(phenyl)(tridecan-2-yloxy)silane (10b): colorless oil;
1H NMR (400 MHz, CDCl3) δ 7.49−7.54 (m, 2H), 7.25−7.33 (m,
3H), 3.71 (m, 1H), 1.06−1.44 (m, 20H), 1.02 (d, 3H, J = 6.0 Hz),
0.81 (t, 3H, J = 6.8 Hz), 0.30 (s, 3H), 0.30 (s, 3H); 13C NMR (100
MHz, CDCl3) δ 138.6, 133.5, 129.4, 127.7, 69.0, 39.5, 31.9, 29.7, 29.6,
29.6, 29.4, 25.8, 23.7, 22.7, 14.1, −1.0, −1.1; HRMS (ESI) calcd for
C21H38OSi [M + Na]+ 357.2590, found 357.2583.
ASSOCIATED CONTENT
■
S
* Supporting Information
General procedures and characterization data (1H and 13C
NMR spectra). This material is available free of charge via the
Internet at http://pubs.acs.org.
9534
dx.doi.org/10.1021/jo2018284|J. Org. Chem. 2011, 76, 9531−9535

The Journal of Organic Chemistry
Note
AUTHOR INFORMATION
Corresponding Author
*E-mail: zjli@bjmu.edu.cn.
■
ACKNOWLEDGMENTS
■
This work was financially supported by the National Natural
Science Foundation of China (Nos. 20732001 and 21072016)
and the National Basic Research Program of China (No.
2012CB822100).
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