Fluorous osmium tetraoxide (FOsO4): A recoverable and reusable catalyst for dihydroxylation of olefins

Article abstract of DOI:10.1016/j.tetlet.2003.12.144

A fluorous osmium catalyst was firstly developed. It had been effectively used as recoverable and reusable catalyst in the dihydroxylation of olefins.

Full text of DOI:10.1016/j.tetlet.2003.12.144

b
Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 1965–1968
F
Fluorous osmium tetraoxide ( OsO ): a recoverable and reusable
4
catalyst for dihydroxylation of olefins
a
b
Yangen Huang, Wei-Dong Meng and Feng-Ling Qing
a,b,
*
a
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
54 Fenglin Lu, Shanghai 200032, China
3
b
College of Chemistry and Chemistry Engineering, Donghua University, 1882 West Yanan Lu, Shanghai 200051, China
Received 2 September 2003; revised 20 December 2003; accepted 22 December 2003
Abstract—A fluorous osmium catalyst was firstly developed. It had been effectively used as recoverable and reusable catalyst in the
dihydroxylation of olefins.
Ó 2004 Elsevier Ltd. All rights reserved.
Osmium tetraoxide (OsO
4
) is the most reliable reagent
to apply FBC on the toxic, volatile, and expensive cat-
alyst of osmium tetraoxide.
1
available for the production of cis-diols from olefins.
Although these reactions have been widely used in the
synthesis of pharmaceuticals, fine chemicals, etc., there
are few large-scale industrial applications due to the
high cost of osmium as well as the high toxicity and
Recently, Jacobs and co-workers have developed a new
approach to immobilize the osmium catalyst onto a
silica anchored tetrasubstituted olefin by the formation
2
3e;f
3f
volatility of the osmium component. Therefore, cata-
of stable Os-diolate esters. The basic idea was that
these tertiary diolate esters were not hydrolyzed during
the reaction, keeping the catalyst immobilized by the
support, if the reaction conditions were not too drastic.
The cis-dihydroxylation reaction could then take place
at the remaining free binding sites of the Os center.
lysts that could be readily separated from the reaction
mixture and used are the challenging in the osmium
community. A few attempts to address this issue have
been made by several groups, achieving varying levels of
success. Among these, various strategies to immobilize
the osmium tetraoxide on soluble and insoluble supports
According to JacobsÕ approach, we envisaged to use the
3
9
have been applied.
fluorous tetramethylethene 1 to anchor the OsO
4
and
make it suitable for fluorous biphase catalysis (FBC).
An ideal catalytic recycle was proposed in Scheme 1.
The added fluorous tetramethylethene 1 was reacted
4
ÔFluorous biphase catalysis (FBC)Õ, a new catalytic
procedure, has been developed by Horv ꢀa th and R ꢀa bai in
VI
1
994. Since then, this new protocol has been advanced
5
4
with OsO to form the Os monodiolate complex 2,
6
VIII
rapidly and a mass of fluorous catalysts and ligands
especially phosphines) are known. FBC is particularly
which could be reoxidized to cis-dioxo Os
the release of the diol. The catalytic reaction could then
3 without
(
suited for economical and green chemical processes due
to the reusable and recoverable of fluorous catalyst and
ligands. However, there are hitherto few reports about
the application of fluorous catalyst containing toxic
take place at the free coordination sites of Os in 3.
The fluorous osmium catalyst was prepared in the fol-
lowing procedure: OsO crystal (127 mg, 0.5 mmol) or in
4
7
metals. Curran and co-workers have developed several
8
4 wt % of aqueous solution (3.2 mL) was added in FC-77
(perfluoroalkane primarily with eight carbons) (4 mL) at
room temperature, and then a solution of fluorous
tetramethylethene 1 (576 mg, 0.5 mmol) in FC-77 (8 mL)
was added dropwise. After the addition, the reaction
mixture was stirred for another 18 h at room tempera-
ture. During the reaction, the solution turned black
fluorous tin reagents with similar reactivity to that of
the parent organic reagents. In this letter, we attempted
Keywords: Fluorous synthesis; Dihydroxylation; Osmium tetraoxide.
*
Corresponding author. Tel.: +86-21-64163300; fax: +86-21-
4166128; e-mail: flq@mail.sioc.ac.cn
indicating that OsO has been reduced to lower valence
4
osmate complex. The reaction mixture was thoroughly
6
0
040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2003.12.144

1966
Y. Huang et al. / Tetrahedron Letters 45 (2004) 1965–1968
(
Rfh) Si
3
1
no hydrolysis
OsO4
O
O
Os
O
O
Os
O
O
[O]
O
O
R
O
O
O
O
O
Os
O
(Rfh) Si
(Rfh)3Si
3
R
(
Rfh) Si
3
3
2
H2O
OH
[
O]
HO
R
O
Os
O
O
O
O
O
Rfh= C6F13CH2CH2
(Rfh)3Si
R
4
Scheme 1. A plausible reaction pathway of the fluorous osmium catalytic dihydroxylation of olefins.
washed twice with t-BuOH/CH Cl (v/v ¼ 2:1, 3 mL) to
fluorous osmium monodiolate underwent some hydro-
lysis to release the osmium during the reaction; sec-
2
2
remove trace of unbound OsO . Thus, the catalyst 2 in
FC-77 solution (calcd Os: 0.042 M in FC-77) was ready
for use.
4
F
ondly, the OsO
4
went into the organic phase during the
separation. In order to minimize the influence of these
two factors, the organic solvents used were varied. An
F
The performance of the fluorous osmium catalyst
F
addition, the partition of OsO between organic phase
and fluorous phase would be more favored at a lower
temperature of separation (from room temperature to
4
(
substrate (Table 1). Initially, the reaction was carried
OsO ) in FBC was investigated using styrene as a test
4
10
out under the standard Upjohn conditions (Table 1,
F
10 or 0 °C). As shown in Table 1, using t-BuOH/CH
O (v/v/v ¼ 10:5:1) and acetone/H O (v/v ¼ 10:1) as the
organic phase, the results were similar to those using
t-BuOH/H
2 2
Cl /
entry 1), using 2 mol % of the OsO
4
2 in a biphasic
H
2
2
solvent system: t-BuOH/H O (v/v ¼ 2:1, 3 mL) as
2
organic phase and FC-77 (2 mL) as fluorous phase with
N-methylmorpholine-N-oxide (1.2 equiv) as the second-
ary oxidizing agent. After stirring 36 h at room tem-
perature, the upper organic phase was removed by a
syringe and purified using standard method to afford the
pure diol product in a quantitative yield (Table 1, entry
2
O (v/v ¼ 2:1). The isolated yields of products
were also decreased significantly in the third run.
Fortunately, when the mixture of t-BuOH/acetone/H O
2
(v/v/v ¼ 10:5:1) was used as the organic phase, the diol
could be isolated in 80% yield even in the fifth run.
F
1
, run 1). A new batch of olefin and co-oxidant dissolved
Representative results of the OsO
4
-catalyzed dihydr-
oxylation reaction of a range of olefins are summarized
in organic solvent was added to the remaining FC-77
solution to carry out the second run of the dihydroxy-
lation. It was gratifying that the diol was isolated in 94%
yield (Table 1, entry 1, run 2), indicating that the flu-
orous catalyst was effective and reusable. However,
further runs with the remaining FC-77 solution resulted
11
in Table 2. Cyclic and acyclic, exo and internal olefins
including mono-, di-, and trisubstituted aliphatic as well
as aromatic underwent the dihydroxylation smoothly at
room temperature in the fluorous biphase catalytic sys-
tem, giving moderate to excellent yields of products over
five consecutive runs. In the case of a sterically hindered
substrate (entry 3), a moderately elevated temperature
was required to afford the product in an excellent yield.
in a dramatic decrease in the yield of the diol. The
F
OsO
the catalyst may be attributed to two factors. Firstly, the
4
catalyst leached significantly. The loss of
F
a
4
Table 1. Dihydroxylation of styrene using the fluorous osmium catalyst ( OsO ) in fluorous biphase system
catalyst 2 (2 mol%), NMO (1.2 eq.)
OH
OH
Ph
FC-77/organic phase, rt.
Ph
b
Entry
Organic phase
Yield (%)
Run 1
Run 2
Run 3
Run 4
Run 5
1
2
3
4
t-BuOH/H
t-BuOH/CH
Acetone/H O (10:1)
t-BuOH/acetone/H
2
O (2:1)
100
100
98
94
98
79
62
87
95
55
74
53
97
45
52
53
80
2
Cl /H
2
2
O (10:5:1)
2
92
2
O (10:5:1)
97
100
a
F
All reactions were carried out using OsO
4
(2 mol %) and NMO in FC-77 (2 mL)/organic solvent (3 mL) at room temperature for 36 h.
b
Isolated yield.

Y. Huang et al. / Tetrahedron Letters 45 (2004) 1965–1968
1967
a
Table 2. cis-Dihydroxylation of olefins using the reusable and recyclable catalyst
R1
R2
R3
R4
catalyst 2 (2.0 mol%), NMO (1.2 eq.)
FC-77, t-BuOH/acetone/H O (10:5:1), rt.
HO
OH
1
3
R
R
R2
R
4
2
b
Entry
1
Olefin
Diol
Yield (%)
Run 1
97
Run 2
Run 3
Run 4
97
Run 5
80
OH
Ph
100
95
94
OH
Ph
Ph
2
OH
100
99
100
99
OH
Ph
Ph
HO
Ph
OH
c
3
98
99
96
95
83
99
77
94
73
OH
OH
OH
4
5
100
HO
C H
C4H9
97
97
96
95
89
92
94
95
71
93
91
58
81
90
4
9
OH
OAc
6
7
OAc
OH
OH
Ph
d
Ph
72
Ph
Ph
OH
a
b
c
F
All reaction were carried out using OsO
4
(2 mol %) and NMO in FC-77 (2 mL)/organic solvent (3 mL) at room temperature for 36 h.
Isolated yield.
The reaction was run using t-BuOH/H
2
O as organic phase at 60 °C.
d
The reaction time was prolonged to 48 h.
It should be pointed out that prolonged reaction time in
the fifth run resulted in an improved yield (entry 7, runs
References and notes
4
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In summary, we have successfully developed a fluorous
osmium catalyst according to the JacobsÕ approach. This
was the first application of FBC with the toxic, volatile,
and expensive catalyst of OsO . The strategy exerted the
4
advantages of fluorous biphasic catalysis and was
demonstrated to be effective and easy to handle. Further
2
. Hammond, C. R. In CRC Handbook of Chemistry and
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We thank the National Natural Science Foundation of
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funding this work.
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9. Fluorous tetramethylethene 1 was prepared as follow:
Bromo-tris-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)sil-
ane (14 mmol) was added at 0 °C to a freshly prepared 2,3-
dimethyl-2-butenylmagnesium bromide (50 mmol) formed
from 1-bromo-2,3-dimethylbut-2-ene with magnesium in
THF at 0 °C. The reaction mixture was stirred at 0 °C for
4 h, and then was warmed to room temperature and stirred
for another 10 h. The reaction mixture was quenched with
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4
2
8, 37–41; (e) Horv ꢀa th, I. T. Acc. Chem. Soc. 1998, 31,
6
41–650.
aqueous NH
with ether, and the combined organic layer was dried over
MgSO , filtered, and concentrated in vacuo. The crude
product was purified by repeated extraction with FC-77/
CH Cl to afford the desired product as colorless oil
4
Cl. The aqueous phase was further extracted
5
. (a) Klement, I.; Lutjens, H.; Knochel, P. Angew. Chem.,
Int. Ed. 1997, 36, 1454–1456; (b) Vincent, J.-M.; Rabion,
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2
2
1
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C.; Glatz, H.; Bannwarth, W. Angew. Chem., Int. Ed.
(15.2 g, 94%). H NMR d: 1.95–2.13 (m, 6H), 1.69 (s, 3H),
1.66 (s, 3H), 1.63 (s, 3H), 1.58 (s, 2H), 0.86–0.92 (m, 6H);
1
9
F NMR d: )81.33 (t, J ¼ 11:3 Hz, 9F), )116.81
2002, 41, 4500–4503; (e) Lautens, M.; Yoshida, M. Org.
(t, J ¼ 15:2 Hz, 6F), )122.45 (s, 6F), )123.43 (s, 6F),
)123.89 (s, 6F), )126.68 (s, 6F); MS (EI, 70 eV, m=z): 1152
(M , 1), 497 (1), 289 (8), 83 (100); IR (thin film): 2929,
1443, 1362, 1240, 1209, 1145, 1070, 904 cm ; Anal. Calcd
for C30
2.27.
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H F39Si: C, 31.26; H, 2.01. Found: C, 31.52; H,
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11. General procedure for the dihydroxylation of olefin using
F
F
OsO
2 mol %) was added to a solution of olefin (1 mmol) and
4
:
OsO
4
solution (0.5 mL, 0.042 M in FC-77,
7
8
N-methylmorpholine-N-oxide (NMO) (1.2 mmol) in
t-BuOH/acetone/H O (10:5:1) (3 mL) and FC-77 (2 mL),
2
. (a) Curran, D. P.; Hadida, S. J. Am. Chem. Soc. 1996, 118,
the reaction mixture was stirred for 24–36 h at room
temperature and the extent was monitored by thin layer
chromatography. The reaction mixture was cooled to
20 °C and the upper organic phase was removed by a
syringe and purified by flash column chromatography on
silica (EtOAc/hexane 4:1). A new batch olefin and NMO
dissolved in organic solvents was then added to the
remaining fluorous solution in successive runs. All the
products in Table 2 were known compounds. The identity
2
531–2532; (b) Horner, J. H.; Martinez, F. N.; Newcomb,
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783–2786; (c) Hadida, S.; Super, M. S.; Beckman, E. J.;
2
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1
and purity of these diols were secured by H NMR and
MS data.