Regioselective lithiation/retro-Brook rearrangement via direct deprotonation

Article abstract of DOI:10.1016/j.tet.2012.11.024

A regioselective lithiation/retro-Brook rearrangement via direct deprotonation was developed. Varieties of benzyl silanes and vinyl silanes are obtained effectively up to 93% yields.

Full text of DOI:10.1016/j.tet.2012.11.024

Tetrahedron 69 (2013) 559e563
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Regioselective lithiation/retro-Brook rearrangement via direct
deprotonation
,b,
Yongping He a, Haitao Hu a, Xingang Xie a, Xuegong She a
*
a State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou 730000, People’s Republic of China
b State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A regioselective lithiation/retro-Brook rearrangement via direct deprotonation was developed. Varieties
of benzyl silanes and vinyl silanes are obtained effectively up to 93% yields.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 11 September 2012
Received in revised form 30 October 2012
Accepted 6 November 2012
Available online 14 November 2012
Keywords:
Retro-Brook rearrangement
Direct deprotonation
Benzyl silanes
Vinyl silanes
1. Introduction
2. Results and discussions
Functionalized organosilanes are attractive and potentially
useful reagents in organic chemistry.1 Vinyl silanes have potential
synthetic utility in silicon-based cross-couplings, providing an ef-
ficient protocol for accessing the configurationally pure multi-
substituted olefins.2 Desilylation of benzyl silanes is useful to
generate radicals or cationic species, providing a versatile route to
electrophilic synthetic equivalents.3 In general, the silanes were
prepared by several protocols: (1) direct installation of the silane
unit through metalelithium or halogenelithium exchange4 and
trapping with a silicon electrophile, (2) addition reaction of silicon
reagents, such as silylcuprate reagent with allenes or acetylenes,
etc. One of the powerful methods to prepare the functionally di-
verse organic silanes is the utilization of the retro-Brook rear-
rangement, which means trialkylsilyl group shift from the oxygen
atom to a carbanion terminus.5 The required carbanion terminus
was rarely obtained by direct deprotonation with organolithium
bases,6e9 although this method is the most direct way to prepare
carbanion termini, which has been well developed in the pioneer-
ing work of Witting and Gilman.7 In recent years, several ortho,
lateral, and vinyl lithiation have been reported.9 These results
prompted us to investigate its potential in retro-Brook rearrange-
ment. Herein we report a regioselective lithiation/retro-Brook
rearrangement via direct deprotonation.
To verify our hypothesis, tert-butyldimethyl(o-tolyloxy)silane
was chosen as a model substrate. Various strong bases, such as
n-BuLi, s-BuLi, t-BuLi, and LDA were utilized to promote this pro-
posed transformation. When LDA was used, the lateral lithiation did
happen, giving the desired 1,4-retro-Brook rearrangement prod-
uct.10 Further optimization showed that the product 2-((tert-butyl-
dimethylsilyl)methyl)phenol could be obtained in 93% yield when
4 equiv of LDA was used in THF from ꢀ78 ꢁC to rt and reflux for 24 h.
Having the optimized reaction conditions in hand, the scope and
limitation of the substrates were examined and the results were
shown in Table 1. When aryloxylsilanes containing ortho-, meta-,
and para-alkyl substituents were tested under the standard con-
dition, it was observed that the retro-Brook rearrangement pro-
ceeded smoothly to afford the desired products in high yields
(entries 1e4).11 In the case of substrates with different alkyl chains,
the desired products were also obtained in satisfied yields, which
were slightly lower compared with 1a, presumably due to the steric
hindrance of their alkyl chains (entries 5e8). Treatment of sub-
strate 9a (1-methylnaphthalen-2-yloxy)-(tert-butyl)dimethylsilane
gave the corresponding product 9b in 89% yield, while treatment of
tert-butyldimethyl((2-methylnaphthalen-1-yl)oxy)silane
didn’t
work under the standard condition.
Interestingly, treatment of substrates 10a and 11a with the
standard condition afforded a same trans-vinyl silane 10b, which
formationwas rationed in Scheme 1.8,12 Deprotonation of 10a or 11a,
the same compound A would be produced, followed the retro-Brook
* Corresponding author. Tel.: þ86 931 8912276; fax: þ86 931 8912583; e-mail
address: shexg@lzu.edu.cn (X. She).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.11.024

560
Y. He et al. / Tetrahedron 69 (2013) 559e563
Table 1
Lithiation/retro-Brook rearrangement of substrates
A
Entry
1
Substrate
Product
Yield (%)
93
2
3
91
90
B
Scheme 1. Plausible mechanism about lithiation/retro-Brook rearrangement of sub-
strates 10a and 11a.
4
91
5
6
7
8
83
78
61
82
Scheme 2. Cross reaction tests of retro-Brook rearrangement.
products 1b and 4d observed and neither of cross-migration
products 1b0 and 4d0 were detected. It was suggested that the
kind of retro-Brook rearrangement herein is intramolecular.
Based on the concept of anion relay chemistry (ARC),13 a lith-
iation/retro-Brook rearrangement/electrophile trapping reaction
sequence was also developed. A variety of electrophiles were used
to provide the corresponding protected benzyl silanes 1ee5e with
good to moderate yields in all cases (Table 2).
9
89
73
61
10
11
Table 2
Lithiation/retro-Brook rearrangement/electrophile trapping reaction of 1a
OTBS
OLi
OE
E+
LDA
TBS
TBS
1a
12
13
53
57
e
Entry
Electrophile
E
Product
Yield (%)
1
2
3
4
5
TESCl
MOMCl
Allyl bromide
Epoxide propyl chlorine
MeI
TES
MOM
Allyl
Epoxide propyl
Me
1e
2e
3e
4e
5e
71
67
63
59
70
rearrangement and deprotonation, compound B would be obtained,
which was stabilized by lithium-ion. Another factor in the formation
of trans-vinyl silane would be that 10b was thermodynamically
stable. Some trans-vinyl silanes were obtained in moderate yields
(entries 10e13).
3. Conclusion
In summary, a regioselective lithiation/retro-Brook rearrange-
ment via direct deprotonation has been developed. Many useful
benzyl silanes and trans-vinyl silanes can be prepared directly.
Further investigation and application of the methodology are under
way in our lab.
Cross reaction tests were done with substrates 1a and 4c (see
Scheme 2). The reactions proceeded successfully. There were only

Y. He et al. / Tetrahedron 69 (2013) 559e563
561
4. Experimental
4.1. General
HRMS (ESIMS) calcd for C14H28NOSiþ [MþNH4]þ 254.1935, found
254.1935.
4.2.5. 8-(tert-Butyldimethylsilyl)-5,6,7,8-tetrahydronaphthalen-1-ol
All commercially available reagents were used without further
purification unless otherwise noted. Solvents were purified and
dried by standard methods prior to use. Column chromatography
was generally performed on silica gel (200e300 mesh). Melting
points were determined with a digital Koffer apparatus and were
uncorrected. The 1H and 13C NMR data were recorded on a Mercury
Plus-300 MHz spectrometer or Bruker AM-400 MHz instrument
using CDCl3 as solvent at room temperature. Chemical shifts are
(5b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
6.92 (t, J¼7.6 Hz,
1H), 6.71 (d, J¼7.5 Hz, 1H), 6.54 (d, J¼7.8 Hz, 1H), 4.75e4.61 (m,
1H), 2.07 (s, 1H), 2.01e1.89 (m, 2H), 1.67 (d, J¼6.4 Hz, 1H),
1.05e1.01 (m, 9H), 0.09 (d, J¼1.1 Hz, 3H), ꢀ0.15 (d, J¼1.2 Hz, 3H);
13C NMR (100 MHz, CDCl3)
d 151.9, 138.8, 127.7, 124.1, 121.3, 111.8,
29.1, 27.3, 24.3, 21.7, 19.1, 18.1, ꢀ4.8, ꢀ5.6; IR (KBr) 3518, 2932,
2856, 1581, 1463, 1251, 1157, 1075, 1014, 828, 769, 679 cmꢀ1
;
HRMS (ESIMS) calcd for C16H30NOSiþ [MþNH4]þ 280.2091, found
reported as
d values relative to internal chloroform (d
7.27 for 1H
280.2085.
NMR and 77.0 for 13C NMR). High-resolution mass spectra (HRMS)
were obtained on a Bruker Daltonics APEXII47e FT-ICR mass
spectrometer.
4.2.6. 2-(1-(tert-Butyldimethylsilyl)hexyl)phenol (6b). Colorless oil.
1H NMR (400 MHz, CDCl3)
d
7.08 (d, J¼7.7 Hz, 1H), 6.99 (dd, J¼10.6,
4.5 Hz, 1H), 6.92e6.86 (m, 1H), 6.72 (d, J¼7.9 Hz, 1H), 4.76 (s, 1H),
2.68e2.57 (m, 1H), 1.79 (s, 2H), 1.25 (m, 6H), 0.91 (s, 9H), 0.86 (t,
J¼6.4 Hz, 3H), 0.07 (s, 3H), ꢀ0.22 (s, 3H); 13C NMR (100 MHz, CDCl3)
4.2. General procedure for lithiation/retro-Brook rearrange-
ment of 1a
d
152.9, 131.0, 127.0, 124.9, 120.7, 114.9, 31.7, 29.2, 27.1, 25.8, 22.6,
A solution of silane 1a (1 mmol) in anhydrous THF (10 mL) was
cooled to ꢀ78 ꢁC under Ar. LDA (4 mmol, 2 M) was added at ꢀ78 ꢁC
slowly under stirring. The mixture was allowed to warm up to room
temperature slowly, then heated to reflux and refluxed for 24 h and
monitored by TLC. When the starting material was consumed, the
resulting mixture was cooled to room temperature and quenched
with NH4Cl. The layers were separated and the aqueous layer was
extracted with ethyl acetate (three times). The combined organic
layers were washed with brine, dried over anhydrous Na2SO4, and
filtered. Concentration under reduced pressure gave a residue,
which was purified by flash column chromatography to afford the
product 1b.
22.5, 17.6, 14.1, ꢀ6.8, ꢀ7.2; IR (KBr) 3400, 2956, 2929, 2857, 1658,
1581, 1465, 1427, 1363, 1251, 1178, 1082, 945, 832, 748 cmꢀ1; HRMS
(ESIMS) calcd for
310.2565.
C
18H36NOSiþ [MþNH4]þ 310.2561, found
4.2.7. 2-((tert-Butyldimethylsilyl)(phenyl)methyl)phenol
(7b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.52 (dd, J¼7.6,
1.3 Hz, 1H), 7.41 (d, J¼7.3 Hz, 2H), 7.28 (dd, J¼9.3, 5.9 Hz, 2H), 7.16 (t,
J¼7.3 Hz, 1H), 7.04 (td, J¼7.8, 1.6 Hz, 1H), 6.92 (td, J¼7.5, 1.0 Hz, 1H),
6.74 (dd, J¼7.9, 1.0 Hz, 1H), 5.39 (d, J¼15.8 Hz, 1H), 4.24 (s, 1H), 0.86
(s, 9H), 0.15 (s, 3H), 0.11 (s, 3H); 13C NMR (100 MHz, CDCl3)
d 152.8,
143.3, 130.5, 130.2, 129.3, 128.2, 126.2, 125.0, 120.4, 115.5, 33.4, 27.2,
17.8, ꢀ5.3, ꢀ5.9; IR (KBr) 3428, 2928, 2856, 1598, 1490, 1453, 1256,
1080, 917, 836, 751, 700 cmꢀ1; HRMS (ESIMS) calcd for C19H30NOSiþ
[MþNH4]þ 316.2091, found 316.2093.
4.2.1. 2-((tert-Butyldimethylsilyl)methyl)phenol (1b). Colorless oil.
1H NMR (400 MHz, CDCl3)
d
6.98 (dd, J¼11.5, 4.4 Hz, 2H), 6.89e6.78
(m, 1H), 6.73 (d, J¼7.8 Hz, 1H), 4.57 (s, 1H), 2.09 (s, 2H), 0.96 (s, 9H),
ꢀ0.07 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 152.4,130.2, 126.9, 125.1,
120.6, 114.9, 26.5, 16.9, 15.7, ꢀ6.3; IR (KBr) 3533, 3448, 2953, 2929,
4.2.8. 2-(1-(tert-Butyldimethylsilyl)-2-phenylethyl)phenol
2856, 1588, 1499, 1455, 1361, 1249, 1159, 934, 831, 750, 699 cmꢀ1
;
(8b). Colorless oil.1H NMR (400 MHz, CDCl3)
d 7.25e7.17 (m,1H), 7.14
HRMS (ESIMS) calcd for C13H26NOSiþ [MþNH4]þ240.1778, found
(dd, J¼7.8, 6.5 Hz, 3H), 7.11e7.06 (m, 1H), 7.03 (d, J¼7.2 Hz, 2H), 6.92
(td, J¼7.7, 1.6 Hz, 1H), 6.86 (dd, J¼14.5, 4.1 Hz, 1H), 6.59 (d, J¼8.9 Hz,
1H), 4.37 (d, J¼18.3 Hz, 1H), 3.31e2.94 (m, 3H), 0.94 (s, 9H), 0.19 (s,
240.1772.
4.2.2. 2-((tert-Butyldimethylsilyl)methyl)-6-methylphenol
3H), ꢀ0.14 (s, 3H); 13C NMR (100 MHz, CDCl3)
d 152.7, 142.6, 130.2,
(2b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.01e6.96 (m, 2H),
6.86 (t, J¼7.5 Hz,1H), 4.65 (s,1H), 2.34 (s, 3H), 2.22 (s, 2H),1.10 (s, 9H),
0.07 (s, 6H); 13C NMR (100 MHz, CDCl3)
150.9, 127.9, 126.9, 126.2,
128.4, 128.2, 127.9, 125.5, 125.3, 120.8, 115.1, 32.5, 27.1, 25.9, 17.7, ꢀ6.6,
ꢀ6.9; IR (KBr) Vmax cmꢀ1: 3535, 3525, 2953, 2929, 2856, 1595, 1496,
1453, 1362, 1249, 1165, 1089, 828, 752, 699; HRMS (ESIMS) calcd for
d
122.5, 120.1, 26.5, 17.8, 16.0, 15.8, ꢀ6.3; IR (KBr) 3574, 2929, 2856,
1591, 1467, 1251, 1192, 1161, 1071, 920, 832, 744, 699 cmꢀ1; HRMS
(ESIMS) calcd for C14H28NOSiþ [MþNH4]þ 254.1935, found 254.1937.
C
20H32NOSiþ [MþNH4]þ330.2248, found 330.2240.
4.2.9. 1-((tert-Butyldimethylsilyl)methyl)naphthalen-2-ol
(9b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.94 (dd, J¼8.0,
4.2.3. 2-((tert-Butyldimethylsilyl)methyl)-5-isopropylphenol
(3b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
6.93 (d, J¼7.6 Hz,
3.5 Hz,1H), 7.88e7.80 (m,1H), 7.63e7.58 (m,1H), 7.56e7.49 (m,1H),
7.43e7.37 (m, 1H), 7.09 (dd, J¼8.7, 1.6 Hz, 1H), 5.27 (s, 1H), 2.63 (d,
J¼3.4 Hz, 2H), 1.14 (dd, J¼3.1, 2.3 Hz, 9H), ꢀ0.04 (dd, J¼3.5, 2.5 Hz,
1H), 6.72 (d, J¼7.6 Hz, 1H), 6.63 (s, 1H), 4.71 (m, 1H), 2.84 (m, 1H),
2.08 (s, 2H), 1.26 (dd, J¼0.8, 6.8 Hz, 6H), 0.99 (t, J¼1.6 Hz, 9H), ꢀ0.03
6H); 13C NMR (100 MHz, CDCl3)
d 149.3, 133.1, 129.4, 128.5, 125.5,
(t, J¼1.6 Hz, 6H); 13C NMR (100 MHz, CDCl3)
d 152.3, 146.3, 129.9,
123.8, 118.7, 113.1, 33.5, 26.5, 24.0, 16.8, 15.2, ꢀ6.3; IR (KBr) 3396,
123.8, 122.8, 119.2, 117.4, 26.6, 17.1, 10.7, ꢀ5.5; IR (KBr) 3546, 3428,
2952, 2928, 2856, 1624, 1600, 1513, 1467, 1353, 1259, 1150, 934, 829,
806, 745 cmꢀ1; HRMS (ESIMS) calcd for C17H28NOSiþ [MþNH4]þ
290.1935, found 290.1931.
2929, 2858, 1593, 1470, 1384, 1266, 1218, 1096, 919, 838, 774 cmꢀ1
;
HRMS (ESIMS) calcd for C16H32NOSiþ [MþNH4]þ282.2248, found
282.2246.
4.2.10. (E)-2-(1-(tert-Butyldimethylsilyl)prop-1-en-1-yl)phenol
4.2.4. 2-((tert-Butyldimethylsilyl)methyl)-4-methylphenol
(10b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.19e7.11 (m, 1H),
(4b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
6.78 (d, J¼10.6 Hz,
6.97e6.88 (m, 3H), 6.48 (q, J¼6.5 Hz,1H), 5.00 (d, J¼2.5 Hz,1H), 1.63
2H), 6.62 (d, J¼7.9 Hz,1H), 4.44 (s, 1H), 2.25 (s, 3H), 2.05 (s, 2H), 0.96
(d, J¼6.5 Hz, 3H), 0.87 (d, J¼1.3 Hz, 9H), 0.15 (s, 3H), 0.08 (s, 3H); 13
C
(s, 9H), ꢀ0.07 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 150.2, 130.8, 129.
NMR (100 MHz, CDCl3) d 151.0, 143.1, 138.1, 128.4, 127.9, 127.5, 120.1,
7, 126.6,125.5,114.8, 26.5, 20.6,16.9,15.6, ꢀ6.3; IR (KBr) 3443, 2952,
2929, 2857, 1715, 1605, 1507, 1466, 1255, 1166, 828, 747, 698 cmꢀ1
;
114.6, 26.9, 17.4, 16.4, ꢀ4.8, ꢀ5.7; IR (KBr) 3532, 2955, 2930, 2856,

562
Y. He et al. / Tetrahedron 69 (2013) 559e563
1595, 1577, 1481, 1460, 1338, 1248, 1205, 1034, 901, 829, 754 cmꢀ1
;
749 cmꢀ1
280.2091, found 280.2095.
;
HRMS (ESIMS) calcd for C16H30NOSiþ [MþNH4]þ
HRMS (ESIMS) calcd for C15H23OSiꢀ [MꢀH]ꢀ 247.1525, found
247.1525.
4.3.4. tert-Butyldimethyl(2-(oxiran-2-ylmethoxy)benzyl)silane
4.2.11. (E)-2-(1-(tert-Butyldimethylsilyl)hex-1-en-1-yl)phenol
(4e). Colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.11e7.01 (m, 2H),
(12b). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.13 (ddd, J¼12.5,
6.88 (t, J¼7.4 Hz, 1H), 6.79 (d, J¼8.1 Hz, 1H), 4.22e4.15 (m, 1H), 3.96
(dd, J¼10.9, 5.6 Hz, 1H), 3.43e3.35 (m, 1H), 2.96e2.89 (m, 1H), 2.77
(dd, J¼5.0, 2.6 Hz, 1H), 2.18 (s, 2H), 0.98 (s, 9H), ꢀ0.09 (d, J¼3.7 Hz,
6.3, 3.6 Hz, 1H), 6.94e6.86 (m, 3H), 6.35 (t, J¼6.9 Hz, 1H), 4.97 (s,
1H), 1.93 (ddd, J¼14.7, 7.0, 3.4 Hz, 2H), 1.46e1.35 (m, 2H), 1.10 (t,
J¼6.8 Hz, 2H), 0.88 (s, 9H), 0.85 (d, J¼7.4 Hz, 3H), 0.14 (s, 3H), 0.05 (s,
6H); 13C NMR (100 MHz, CDCl3)
d 155.2, 129.7, 124.9, 120.8, 110.8,
3H); 13C NMR (100 MHz, CDCl3)
d
151.0, 149.1, 137.0, 128.5, 128.3,
68.6, 50.2, 44.6, 26.5, 16.9, 15.9, ꢀ6.4; IR (KBr) 2928, 2856, 1591,
1492, 1454, 1242, 1159, 1048, 918, 830, 748 cmꢀ1; HRMS (ESIMS)
calcd for C16H30NO2Siþ [MþNH4]þ 296.2040, found 296.2047.
127.4, 120.0, 114.5, 32.5, 26.9, 25.9, 22.2, 17.4, 13.7, ꢀ4.7, ꢀ5.7; IR
(KBr) 3532, 2957, 2930, 2858, 1581, 1482, 1459, 1338, 1251, 1204,
1170, 1035, 922, 832, 754, 664 cmꢀ1; HRMS (ESIMS) calcd for
C
18H29OSiꢀ [MꢀH]ꢀ 289.1995, found 289.1993.
4.3.5. tert-Butyl(2-methoxybenzyl)dimethylsilane(5e). Colorless oil.
1H NMR (400 MHz, CDCl3)
d
7.14e7.09 (m, 1H), 7.04 (dd, J¼4.9,
4.2.12. (E)-2-(1-(tert-Butyldimethylsilyl)-3-phenylprop-1-en-1-yl)
phenol (13b). Colorless oil. 1H NMR (400 MHz, CDCl3)
7.30 (dd,
2.3 Hz, 1H), 6.92e6.81 (m, 2H), 3.83 (d, J¼2.3 Hz, 3H), 2.17 (d,
d
J¼3.5 Hz, 2H), 0.99 (d, J¼4.1 Hz, 9H), ꢀ0.08 (d, J¼4.1 Hz, 6H); 13C
J¼13.8, 6.2 Hz, 2H), 7.25e7.11 (m, 4H), 7.00e6.86 (m, 3H), 6.49 (dd,
NMR (100 MHz, CDCl3) d 156.4,129.5,129.5,124.9,120.2,109.7, 54.8,
J¼14.2, 6.8 Hz, 1H), 5.01 (s, 1H), 3.30 (qd, J¼15.5, 7.0 Hz, 2H), 0.89 (s,
26.5, 16.9, 16.1, ꢀ6.3; IR (KBr) 2928, 2856, 1593, 1492, 1469, 1240,
9H), 0.16 (s, 3H), 0.07 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
151.1,
1178, 1082, 1051, 839, 748, 698 cmꢀ1; HRMS (ESIMS) calcd for
146.6, 143.1, 139.7, 137.7, 128.5, 128.4, 127.9, 127.7, 126.1, 120.2, 114.8,
36.8, 26.9, 17.5, ꢀ4.8, ꢀ5.8. HRMS (ESIMS) calcd for C21H27OSiꢀ
[MꢀH]ꢀ 323.1837, found 323.1841.
C
15H30NOSiþ [MþNH4]þ 268.2091, found 268.2091.
4.3.6. 2-((tert-Butyldiphenylsilyl)methyl)-4-methylphenol
(4d). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.62e7.61 (d, J¼1.6,
4.3. General procedure for lithiation/retro-Brook rearrange-
ment/electrophile trapping reaction of 1a
4H), 7.45e7.42 (m, 2H), 7.38e7.35 (m, 4H), 6.72e6.69 (dd, J¼8.2,
2.0 Hz, 1H), 6.56e6.55 (d, J¼1.6 Hz, 1H), 6.51e6.49 (d, J¼8 Hz, 1H),
4.24 (s,1H), 2.73 (s, 2H), 2.07 (s, 3H),1.16 (s, 9H); 13C NMR (100 MHz,
A solution of silane 1a (1 mmol) in anhydrous THF (10 mL) was
cooled to ꢀ78 ꢁC under Ar. LDA (4 mmol, 2 M) was added at ꢀ78 ꢁC
slowly under stirring. The mixture was allowed to warm up to room
temperature slowly, then heated to reflux and refluxed for 24 h. The
resulting mixture was cooled to room temperature and then an
excess of the corresponding electrophile was added. The mixture
was stirred another 12 h and quenched with NH4Cl. The layers were
separated and the aqueous layer was extracted with ethyl acetate
(three times). The combined organic layers were washed with
brine, dried over anhydrous Na2SO4, and filtered. Concentration
under reduced pressure gave a residue, which was purified by flash
column chromatography to afford the product e.
CDCl3) d 150.4, 136.3, 134.6, 131.5, 129.5, 129.2, 127.4, 125.9, 125.5,
115.4, 27.8, 20.4, 18.6, 14.0; HRMS (ESIMS) calcd for C24H32NOSiþ
[MþNH4]þ 378.2248, found 378.2244.
Acknowledgements
We are grateful for the generous financial support by the MOST
(2010CB833200), the NSFC (21125207, 21072086, 21102062), Pro-
gram 111, and the Fundamental Research Funds for the Central
Universities (lzujbky-2011-76).
Supplementary data
NMR spectra (1H and 13C) for all products. This material is
available free of charge. Supplementary data related to this article
can be found online at http://dx.doi.org/10.1016/j.tet.2012.11.024.
4.3.1. tert-Butyldimethyl(2-((triethylsilyl)oxy)benzyl)silane
(1e). Colorless oil. 1H NMR (400 MHz, CDCl3)
d
6.99 (t, J¼5.2 Hz,
1H), 6.95 (d, J¼7.6 Hz, 1H), 6.83 (t, J¼7.3 Hz, 1H), 6.77 (d, J¼7.9 Hz,
1H), 2.11 (s, 2H), 1.03 (t, J¼7.9 Hz, 9H), 0.96 (s, 9H), 0.81 (q, J¼7.9 Hz,
6H), ꢀ0.09 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 152.7, 131.2, 129.9,
References and notes
124.7, 120.6, 117.8, 26.6, 16.86, 16.0, 6.8, 5.4, ꢀ6.4; IR (KBr) 2955,
2880, 1580, 1489, 1465, 1413, 1362, 1256, 921, 833, 747 cmꢀ1; HRMS
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(ESIMS) calcd for
354.2645.
C
19H40NOSiþ2 [MþNH4]þ354.2643, found
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7.13e7.03 (m, 3H),
d
6.93 (t, J¼7.1 Hz, 1H), 5.21 (s, 2H), 3.54 (d, J¼1.6 Hz, 3H), 2.19 (s, 2H),
1.06e0.98 (m, 9H), ꢀ0.02 to ꢀ0.09 (m, 6H); 13C NMR (100 MHz,
CDCl3)
d 154.5, 130.0, 129.7, 125.0, 121.4, 113.7, 94.7, 56.0, 26.5, 16.0,
ꢀ6.2; IR (KBr) 2952, 2930, 2856, 1585, 1491, 1466, 1235, 1158, 1077,
1009, 924, 838, 751 cmꢀ1; HRMS (ESIMS) calcd for C15H30NO2Siþ
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oil. 1H NMR (400 MHz, CDCl3)
d 7.10e6.97 (m, 2H), 6.93e6.77 (m,
2H), 6.17e6.00 (m, 1H), 5.45 (dd, J¼17.3, 1.3 Hz, 1H), 5.28 (dt, J¼9.2,
4.6 Hz, 1H), 4.51 (d, J¼5.1 Hz, 2H), 2.16 (s, 2H), 0.95 (s, 9H), ꢀ0.13 (s,
6H); 13C NMR (100 MHz, CDCl3)
d 155.4, 133.7, 129.6, 124.8, 120.3,
116.8, 110.9, 68.4, 26.5, 16.9, 15.9, ꢀ6.4; IR (KBr) 3402, 2927, 2855,
1700, 1640, 1461, 1408, 1243, 1090, 1024, 996, 916, 829, 806,

Y. He et al. / Tetrahedron 69 (2013) 559e563
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