Arash GHORBANI-CHOGHAMARANI et al. / Chinese Journal of Catalysis, 2010, 31: 1103–1106
tion was then quenched with water (10 ml), and the organic
NMR (200 MHz, CDCl3) δ 6.70–6.84 (m, 3H), 3.87 (s, 3H),
2.36 (s, 3H), 0.34 (s, 9H); 13C NMR (50 MHz, CDCl3) δ 150.6,
142.2, 131.4, 121.1, 120.6, 113.1, 55.5, 21.1, 0.6.
Trimethyl(4-benzylphenoxy)silane (2s). 1H NMR (200
MHz, CDCl3) δ 6.95–7.59 (m, 9H), 4.18 (s, 2H), 0.57 (s, 9H);
13C NMR (50 MHz, CDCl3) δ 153.7, 141.7, 134.3, 130.2,
129.1, 128.8, 126.3, 120.2, 41.3, 0.53.
phase was dried over Na2SO4 (3 g) and filtered after 10 min.
Evaporation of dichloromethane gave 1,2-diphenyl-2-
(trimethylsilyloxy)ethanone (0.276 g, 97%) as a white crystal-
line solid; m.p. 119–122 ºC; 1H NMR (90 MHz, CDCl3) δ 8.00
(m, 2H), 7.36–7.51 (m, 8H), 5.92 (s, 1H), 0.15 (s, 9H); IR
(nujol, cm−1): v 1 687, 1 597, 1 578, 1 458, 1 377, 1 251, 1 109,
979, 888, 844, 698.
Trimethyl(phenethoxy)silane (2d). 1H NMR (90 MHz,
CDCl3) δ 7.29 (s, 5H), 3.85 (t, 2H), 2.90 (t, 2H), 0.14 (s, 9H);
IR (KBr, cm−1): v 3 029, 2 956, 1 605, 1 497, 1 454, 1 251,
1 095, 929, 883, 841, 748, 698.
2 Results and discussion
As a continuation of our previous studies on the application
of new reagents and catalysts in organic functional group
transformations [19–26], we now disclose a new, efficient, and
mild procedure for the trimethylsilyl protection of a wide range
of alcohols and phenols using HMDS in the presence of cata-
1
Trimethyl(cholesteroloxy)silane (2k). H NMR (90 MHz,
CDCl3) δ 5.34 (m, 1H), 3.49 (m, 1H), 0.67–2.17 (m, 43H);13C
NMR (25 MHz, CDCl3) δ 141.4, 121.3, 72.4, 56.9, 56.4, 50.4,
42.8, 42.4, 39.9, 39.6, 37.5, 36.6, 36.3, 35.9, 32.0, 28.3, 28.0,
24.4, 24.0, 22.8, 22.6, 21.2, 19.4, 18.8, 11.9, 0.36; IR (nujol,
cm−1): v 2 853, 1 464, 1 456, 1 378, 1 249, 1 085, 896, 840.
–
lytic amounts of PhMe3N+Br3 under mild and homogenous
conditions at room temperature.
Therefore, in this article, we report the efficient trimethyl-
silylation of different types of hydroxyl groups including pri-
mary, secondary, hindered secondary, and substituted phenols
using HMDS (I) in the presence of a catalytic amount of
1
Trimethyl(2-admantanoxy)silane (2l). H NMR (90 MHz,
CDCl3) δ 3.78 (m, 1H), 1.35–2.25 (m, 14H), 0.08 (s, 9H); IR
(nujol, cm−1): v 2 853, 1 450, 1 354, 1 249, 1 133, 1 093, 880,
839, 752.
–
PhMe3N+Br3 (II) in dichloromethane at room temperature
Trimethyl(4-chlorophenoxy)silane (2o). 1H NMR (200
MHz, CDCl3) δ 6.76–7.20 (dd, 71.5, 8.5, Hz, 4H), 0.02 (s, 9H);
13C NMR (50 MHz, CDCl3) δ 156.7, 129.5, 122.8, 117.3, 2.3.
Trimethyl(2-methoxy-4-methylphenoxy)silane (2r). 1H
with good to excellent yields (Scheme 1 and Table 1).
As is evident from Table 1 a good range of turnover number
(TON) and turnover frequency (TOF) for the catalyst is ob-
served. To investigate the role of PhMe3N+Br3– as the catalyst,
H
N
Me3Si
SiMe3
-
Ar–OH or R–OH
Ar–OTMS or R–OTMS
PhMe3N+Br3
1
2
OH
O2N
CH2OH
CH2OH
Cl
CH2OH
CH2CH2OH
1f
CH2OH
O
1b
1a
Cl
1d
1e
1c
OH
OH O
H
H
OH
H3C
CH3
1g
HO
H
H3C
1i
1j
1h
H
H
HO
1k
OH
OH
OH
Cl
OH
MeO
OH
CH2CCH3
CH3
1n
1p
1o
1l
1m
OH
Me
OH
CH2
OH
1q
1s
OMe
1r
Scheme 1. Trimethylsilylation of different types of hydroxyl groups.