Efficient conversion of epoxides into β-hydroperoxy alcohols catalyzed by antimony trichloride/SiO2

Article abstract of DOI:10.1055/s-0028-1083147

Efficient ring-opening of various epoxides with hydrogen peroxide, catalyzed by antimony trichloride/SiO₂, afforded the corresponding β-hydroperoxy alcohols in good to excellent yields under mild reaction conditions. The reactions were efficien

Full text of DOI:10.1055/s-0028-1083147

3314
PAPER
Efficient Conversion of Epoxides into b-Hydroperoxy Alcohols Catalyzed by
Antimony Trichloride/SiO2
Conversion of
E
po
u
xide
s
into
b
-
-
H
ydrope
H
roxy Alcohols eng Liu, Zhan-Hui Zhang,* Tong-Shuang Li*
The College of Chemistry & Material Science, Hebei Normal University, Shijiazhuang 050016, P. R. of China
Fax +86(311)85208792; E-mail: zhanhui@126.com; E-mail: Tongshuang@hotmail.com
Received 26 May 2008; revised 30 June 2008
OOH
O
Abstract: Efficient ring-opening of various epoxides with hydro-
gen peroxide, catalyzed by antimony trichloride/SiO2, afforded the
corresponding b-hydroperoxy alcohols in good to excellent yields
under mild reaction conditions. The reactions were efficiently pro-
moted by ultrasound irradiation.
SbCl3/SiO2
H2O2
OH
R1
R2
R1
R2
1
2
Scheme 1
Key words: epoxides, b-hydroperoxy alcohols, antimony trichlo-
ride, ultrasound
of epoxides into b-hydroperoxy alcohols catalyzed by an-
timony trichloride/SiO2 (Scheme1).
Epoxides are versatile and important intermediates in or-
ganic synthesis that can undergo regio- and stereoselec-
tive ring-opening reactions to give b-substituted alcohols
with a variety of nucleophilic species.1 The opening of ep-
oxides with hydrogen peroxide is the easiest and most
straightforward synthetic procedure for the preparation of
b-hydroperoxy alcohols. Such alcohols are useful in the
field of pharmaceuticals and natural products,2–3 especial-
ly for the synthesis of 1,2,4-trioxanes,4 which are being
actively investigated as antimalarial agents.5 They can
also serve as effective tridentate oxygen donors for epoxi-
dation of ene diols.6 This ring-opening reaction can be
catalyzed by HClO4,7 CF3CO2H,8 molybdenyl acetylace-
tonate,9 and methyltriotylammonium tetrakis(oxodiper-
oxotungsto)phosphate.10 However, these procedures are
associated with disadvantages such as the use of strong
acid,7–8 or unsatisfactory yields,9 or require special efforts
to prepare the catalyst.10 Thus, an improved protocol for
the conversion of epoxides into the corresponding b-hy-
droperoxy alcohols is still actively pursued.
Initially, the catalytic activities of various catalysts such
as H3BO3, p-toluenesulfonic acid, InBr3, In(OTf)3, ZrCl4,
(NH4)2Ce(NO3)6, I2, SbCl3, HClO4/SiO2, HBF4/SiO2,
NaHSO4/SiO2 and SbCl3/SiO2 were investigated to pro-
Table 1 Synthesis of 2-Hydroperoxy-2-phenylethanol (2e) under
Different Conditionsa
Entry
Catalyst
Catalyst loading Time
Yield
(%)b
(mol%)
(h)
24
8
1
2
none
–
5
trace
51
68
43
38
46
52
42
41
53
62
68
80
82
85
79
85c
H3BO3
3
p-TsOH
5
12
36
24
48
15
15
5
4
InBr3
5
5
In(OTf)3
ZrCl4
5
6
5
7
(NH4)2Ce(NO3)6
I2
5
In recent years, antimony trichloride has been used as a
catalyst in organic synthesis because this compound is not
only commercially available and inexpensive, but is also
easier to handle than other metal halides such as InCl3,
GdCl3 and TiCl4.11 Antimony trichloride has been utilized
as a catalyst for many important organic transformations,
including selective cleavage of trityl ethers,12 Michael
addition,13 the ring opening of epoxides with anilines,14
synthesis of acylals,15 benzo[b]1,4-diazepines,16 and
bis(indolyl)methanes.17 Use of silica-supported reagents
as recoverable and reusable catalysts in organic synthesis
has received considerable attention. In a continuation of
our work to develop new synthetic methodologies,18 we
report herein a simple and practical method for conversion
8
5
9
SbCl3
5
10
11
12
13
14
15
16
17
HClO4/SiO2
HBF4/SiO2
NaHSO4/SiO2
SbCl3/SiO2
SbCl3/SiO2
SbCl3/SiO2
SbCl3/SiO2
SbCl3/SiO2
5
8
5
72
5
5
1
10
8
5
10
20
10
5
5
1.5
a The reaction was carried out according to the general experimental
procedure without sonication.
SYNTHESIS 2008, No. 20, pp 3314–3318
Advanced online publication: 25.09.2008
DOI: 10.1055/s-0028-1083147; Art ID: F11808SS
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x
.
2
0
0
8
b Isolated yield.
c With sonication.

PAPER
Conversion of Epoxides into b-Hydroperoxy Alcohols
3315
mote the model reaction of 2-phenyloxirane (1e) and hy- ence of 10 mol% of SbCl3/SiO2 with or without ultrasonic
drogen peroxide; the results are presented in Table 1. The conditions. The results, presented in Table 2, indicated
catalyst plays a crucial role in the success of the reaction that the SbCl3/SiO2-catalyzed ring-opening reaction of ep-
both in terms of the rate and yields. In the absence of cat- oxides proceeded smoothly and produced the correspond-
alyst, only traces of product were obtained, even after 24 ing b-hydroperoxy alcohols in good to excellent yields.
hours (Table 1, entry 1). Among the catalysts tested, The unsymmetrical alkyl oxiranes 1i and 1j afforded
SbCl3/SiO2 was found to be the most effective catalyst in b-hydroperoxy alcohols in a regioselective manner with
terms of both reaction time and yield. Next, we optimized preferential attack at the terminal position. For the styrene
the quantity of the catalyst (SbCl3/SiO2) used in this reac- oxide and substituted styrene oxides (1a–1h), the reaction
tion and it was observed that the use of just 10 mol% was occurred on the more substituted carbon, since the benzyl
sufficient to produce an excellent yield of the product position of the epoxides are more positive and thus more
(Table 1, entry 15). Higher amounts of the catalyst prone to attack by H2O2. With cyclohexene oxide, the ring
(20mol%) did not improve the result (Table 1, entry 16). opening took place completely via a trans-stereospecific
Lower catalyst loading could be used with only a marginal pathway and gave only the trans isomer (Table 2, entry k).
drop in reaction rate. When the same reaction was per-
formed under sonication in an ultrasonic bath, the reaction
time was strikingly shortened from 5 hours to 1.5 hours
In summary, we have reported a novel, mild and highly ef-
ficient procedure for the synthesis of b-hydroperoxy alco-
hols. The use of an inexpensive and easily available
(Table 1, entry 17). It is thus apparent that the reaction
catalyst, the high yields obtained, and the relatively short
could be efficiently promoted by ultrasound irradiation.
reaction times, together with the potential usefulness of
In light of these results, subsequent studies were carried the process for industrial applications are all attractive
out in order to evaluate the scope of the catalyst’s applica- features of this method.
tion under the optimized conditions. Various epoxides
were treated with an excess amount of H2O2 in the pres-
Table 2 Synthesis of b-Hydroperoxy Alcohols in the Presence of SbCl3/SiO2
Entry
Substrate 1
Product 2
Without sonication
With sonication
Time (h)
Time (h)
Yield (%)a
Yield (%)a
OOH
OOH
86
O
O
OH
OH
a
9
85
72
1.5
2.0
(95:5)b
Me
Me
Me
b
c
12
75
Me
Me
Me
OOH
O
OH
85
6
85
1.0
(96:4)b
OMe
OMe
OOH
MeO
MeO
O
MeO
OH
d
e
2
5
85
85
0.5
1.5
77
85
MeO
OMe
OMe
OOH
O
OH
Synthesis 2008, No. 20, 3314–3318 © Thieme Stuttgart · New York

3316
Y.-H. Liu et al.
PAPER
Table 2 Synthesis of b-Hydroperoxy Alcohols in the Presence of SbCl3/SiO2 (continued)
Entry
Substrate 1
Product 2
Without sonication
With sonication
Time (h)
Time (h)
Yield (%)a
Yield (%)a
85
OOH
OOH
O
O
f
5
86
78
1.0
OH
OH
Cl
Cl
78
g
5
1.0
(93:7)b
Cl
Cl
Cl
Cl
OOH
O
OH
h
10
8
81
82
2.0
1.5
85
Br
O
Br
O
OOH
82
OH
Me
O
Me
i
(94:6)b
OH
O
OOH
j
12
12
80
82
2.0
2.0
81
83
Me
Me
OOH
OH
k
O
a Isolated yield.
b Regioselectivity determined by 1H NMR.
IR spectra were obtained using a Shimadzu FTIR-8900 spectro-
meter. H NMR spectra were taken with Varian 400 or Bruker
Hydrogen peroxide (8.5 mL, 30% in H2O) was saturated with NaCl
and the solution was extracted with Et2O (4 × 30 mL). Behind a
safety shield, the ethereal solution was dried (MgSO4) and evapo-
rated in a rotavapor using a cold water bath until the solution vol-
ume reached 20 mL (~70 mmol H2O2). This solution was
introduced to a flask containing epoxide (7.5 mmol) at r.t., SbCl3/
SiO2 (2.25 g, 10 mol%) was added and the mixture was stirred or
irradiated in the ultrasonic bath (the progress of the reaction was
monitored by TLC). Upon completion of the reaction, the catalyst
was removed by filtration and the filtrate was diluted with Et2O
(100 mL), washed with H2O (2 × 50 mL) and brine (50 mL), dried
(MgSO4) and evaporated to give the crude b-hydroperoxy alcohol.
Further purification was achieved by silica gel chromatography
(EtOAc–cyclohexane) to afford the pure product.
1
DRX-500 spectrometers as CDCl3 solutions with TMS as internal
standard. Elemental analyses were performed on a Vario EL III
CHNOS elemental analyzer. Sonication was performed in a KQ-
250E ultrasonic clearer with a frequency of 40 kHz and an output
power of 250 W.
Preparation of Antimony Trichloride Adsorbed on Silica Gel
(SbCl3/SiO2)
The preparation of SbCl3/SiO2 was carried out following a reported
procedure.19 SbCl3 (2.28 g, 10 mmol) was added to a suspension of
SiO2 (300–400 mesh, 27.8 g) in EtOH (50.0 mL). The mixture was
stirred at r.t. for 1 h then the solvent was removed with a rotary
evaporator and the residue was heated at 100 °C under vacuum for
5 h to furnish SbCl3/SiO2 as a free-flowing powder.
2-Hydroperoxy-2-p-tolylethanol (2a)
Colorless needles; mp 81–82 °C.
Synthesis of b-Hydroperoxy Alcohols; General Procedure
Caution: Since organic peroxides are potentially hazardous com-
pounds, they must be handled with due care; avoid exposure to
strong heat or light, mechanical shock, oxidizable organic materials,
or transition-metal ions. A safety shield should be used for all reac-
tions involving hydrogen peroxide. No particular difficulties were
experienced in handling any of the hydroperoxy alcohols prepared
in this work using the reaction scales and procedures described be-
low together with the safeguards mentioned above.
IR (KBr): 3369, 2976, 2869, 1519, 1423, 1305, 1242, 1089, 1053,
1037, 908, 817, 767, 723 cm–1.
1H NMR (400 MHz, CDCl3): d = 2.36 (s, 3 H), 3.80 (dd, J = 12.8,
3.6 Hz, 1 H), 3.93 (dd, J = 12.8, 8.4 Hz, 1 H), 5.12 (dd, J = 8.4, 3.6
Hz, 1 H), 7.21 (d, J = 6.0 Hz, 2 H), 7.26 (d, J = 6.0 Hz, 2 H), 8.13
(br s, 1 H).
Anal. Calcd for C9H12O3: C, 64.27; H, 7.19. Found: C, 64.02; H,
7.42.
Synthesis 2008, No. 20, 3314–3318 © Thieme Stuttgart · New York

PAPER
Conversion of Epoxides into b-Hydroperoxy Alcohols
3317
2-(3,4-Dimethylphenyl)-2-hydroperoxyethanol (2b)
Colorless platelets; mp 82–84 °C.
1-Hydroperoxy-3-o-tolyloxypropan-2-ol (2i)
Colorless platelets; mp 67–68 °C.
IR (KBr): 3369, 3138, 2808, 1616, 1504, 1403, 1338, 1245, 1093,
1056, 1039, 954, 769 cm–1.
IR (KBr): 3489, 3203, 2979, 1602, 1496, 1458, 1402, 1244, 1126,
1049, 881, 752 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.26 (s, 3 H), 2.27 (s, 3 H), 3.79
(dd, J = 12.4, 3.6 Hz, 1 H), 3.91 (dd, J = 8.4, 12.4 Hz, 1 H), 5.08
(dd, J = 3.6, 8.4 Hz, 1 H), 7.08–7.18 (m, 3 H), 8.66 (br s, 1 H).
1H NMR (400 MHz, CDCl3): d = 2.23 (s, 3 H), 4.04–4.12 (m, 2 H),
4.20 (dd, J = 12.8, 6.4 Hz, 1 H), 4.30 (dd, J = 12.8, 3.6 Hz, 1 H),
4.39–4.45 (m, 1 H), 6.83 (d, J = 7.6 Hz, 1 H), 6.90 (t, J = 7.6 Hz,
1 H), 7.14–7.18 (m, 2 H), 8.78 (br s, 1 H).
Anal. Calcd for C10H14O3: C, 65.91; H, 7.74. Found: C, 66.02; H,
7.58.
Anal. Calcd for C10H14O4: C, 60.59; H, 7.12. Found: C, 60.80; H,
6.98.
2-Hydroperoxy-2-(3-methoxyphenyl)ethanol (2c)
Colorless needles; mp 66–68 °C.
1-Hydroperoxyoctadecan-2-ol (2j)
Colorless platelets; mp 74–75 °C.
IR (KBr): 3232, 2979, 1467, 1377, 1143, 1072, 993, 873, 721 cm–1.
IR (KBr): 3400, 2937, 2837, 1602, 1587, 1490, 1456, 1436, 1261,
1155, 1039, 873, 785, 698 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.78 (dd, J = 12.8, 3.6 Hz, 1 H),
3.82 (s, 3 H), 3.90 (dd, J = 12.8, 8.0 Hz, 1 H), 5.13 (dd, J = 8.0, 3.6
Hz, 1 H), 6.89–6.85 (m, 3 H), 7.32 (t, J = 5.7 Hz, 1 H).
1H NMR (500 MHz, CDCl3): d = 0.88 (t, J = 7.0 Hz, 3 H), 1.26–
1.45 (m, 30 H), 3.46 (dd, J = 11.0, 8.0 Hz, 1 H), 3.72–3.75 (m, 1 H),
3.73 (dd, J = 8.0, 3.0 Hz, 1 H).
Anal. Calcd for C9H12O4: C, 58.69; H, 6.57. Found: C, 58.90; H,
6.38.
Anal. Calcd for C18H38O3: C, 71.47; H, 12.66. Found: C, 71.68; H,
12.46.
2-Hydroperoxy-2-(3,4,5-trimethoxyphenyl)ethanol (2d)
Colorless cubics; mp 116–118 °C.
2-Hydroperoxycyclohexanol (2k)
Colorless viscous liquid.
IR (KBr): 3411, 3253, 2931, 2842, 1595, 1510, 1421, 1342, 1325,
1240, 1122, 1066, 981, 837, 785, 707 cm–1.
IR (film): 3379, 2937, 2860, 1452, 1234, 1124, 1070, 1026, 925,
835 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.80 (dd, J = 12.8, 3.6 Hz, 1 H),
3.85 (s, 3 H), 3.88 (s, 6 H), 3.92 (dd, J = 12.8, 8.4 Hz, 1 H), 5.09
(dd, J = 8.4, 3.6 Hz, 1 H), 6.59 (s, 2 H), 8.22 (br s, 1 H).
1H NMR (500 MHz, CDCl3): d = 1.15–1.34 (m, 4 H), 1.65–1.72 (m,
2 H), 1.98–2.09 (m, 2 H), 3.64 (td, J = 10.5, 5.0 Hz, 1 H), 3.73 (td,
J = 10.5, 5.0 Hz, 1 H), 7.42 (br s, 1 H).
Anal. Calcd for C11H16O6: C, 54.09; H, 6.60. Found: C, 54.26; H,
6.48.
Anal. Calcd for C6H12O3: C, 54.53; H, 9.15. Found: C, 54.72; H,
8.98.
2-Hydroperoxy-2-phenylethanol (2e)
Colorless platelets; mp 63–64 °C (Lit.8 60–61 °C).
Acknowledgment
IR (KBr): 3379, 3107, 2972, 1492, 1452, 1417, 1247, 1099, 1074,
1028, 916, 826, 756, 702 cm–1.
1H NMR (500 MHz, CDCl3): d = 3.83 (dd, J = 12.5, 3.5 Hz, 1 H),
3.92 (dd, J = 12.5, 8.0 Hz, 1 H), 5.16 (dd, J = 8.0, 3.5 Hz, 1 H),
7.24–7.43 (m, 5 H), 9.03 (br s, 1 H).
We are grateful for financial support from the Hebei Normal Uni-
versity (L20061314), the Nature Science Foundation of Hebei Pro-
vince (B2008000149) and the Natural Science Foundation of Hebei
Education Department (2006318).
Anal. Calcd for C8H10O3: C, 62.33; H, 6.54. Found: C, 62.55; H,
6.38.
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Synthesis 2008, No. 20, 3314–3318 © Thieme Stuttgart · New York