A new coupled catalytic system for dihydroxylation of olefins by H2O2 [5]

Full text of DOI:10.1021/ja991710b

10424
J. Am. Chem. Soc. 1999, 121, 10424-10425
A New Coupled Catalytic System for
Dihydroxylation of Olefins by H2O2
Scheme 1. Upjohn Procedure for the Osmium-Catalyzed
Dihydroxylation9
†
‡
,‡
Katarina Bergstad, Sandra Y. Jonsson, and Jan-E. B a¨ ckvall*
Department of Organic Chemistry, Uppsala UniVersity
Box 531, SE-751 21 Uppsala, Sweden
Department of Organic Chemistry, Arrhenius Laboratory
Stockholm UniVersity, SE-106 91 Stockholm, Sweden
ReceiVed May 24, 1999
A number of oxidation reactions rely on the use of a substrate-
selective redox system (often Mn+2/M ) involving a two-electron
oxidation. For a catalytic reaction it is necessary to reoxidize the
reduced form of the redox system to its oxidized state. Attractive
n
Table 1. Cis-Selective Dihydroxylation of trans-5-Decene
as the Terminal Oxidanta
2 2
Employing H O
2 2 2
oxidants for this reoxidation are O and H O , since they are
1
NMMb
equiv
flavin (3)
% yield
of 2
inexpensive and environmentally friendly. Unfortunately, direct
reoxidation of the reduced form of the substrate-selective catalyst
by these oxidants is usually not viable due to a high-energy barrier
for electron transfer. This energy barrier may be lowered by a
relaying redox couple (electron-transfer mediator) between the
substrate-selective redox catalyst and the oxidant, a feature
common in biochemical processes.2 In industrial catalysis a
successful example of this principle is given by the palladium-
equivb
additive
c
entry
1d
2
3
10
16
72
95
0.27
0.27
0.05
0.05
4
2 equiv of TEAAe
a
The olefin (0.5 mmol), OsO4 (0.01 mmol, 0.02 equiv), and
additional catalysts/additives (according to the table) were dissolved
in acetone (1.88 mL) and H O (0.62 mL). To this mixture H (1.5
(
II)-catalyzed oxidation of ethylene to acetaldehyde (Wacker
2
2 2
O
3
equiv, 30% aqueous) was added over 9 h, unless otherwise noted. After
complete addition of the oxidant, the mixture was stirred for an
Process), where copper chloride catalyzes reoxidation of Pd(0)
to Pd(II) by O . We have recently designed and developed several
electron-transfer systems for selective aerobic oxidations employ-
2
b
c
d
additional 7-15 h. Equivalent to olefin. Isolated yields. In this case
e
2 2
the H O was added in one portion. Tetraethylammonium acetate.
4-6
ing Pd and Ru complexes as substrate-selective catalysts.
The osmium-catalyzed dihydroxylation of olefins involves an
Oxidation of trans-5-decene (1) was studied under different
reaction conditions employing H as the terminal oxidant (eq
), (Table 1). Stoichiometric amounts of NMO were employed
7
Os(VIII)/Os(VI) substrate-selective redox system. Viable catalytic
2
O
2
8,9
procedures for this reaction were reported in 1976, and in
1
9
particular the Upjohn procedure, in which N-methylmorpholine
N-oxide (NMO) is employed for the reoxidation of Os(VI) to
Os(VIII), was a major breakthrough (Scheme 1). The synthetic
utility of the reaction was dramatically enhanced when Sharpless
et al. developed an enantioselective version.1
0,11
In this communication we have designed an electron-transfer
2 2
system for H O oxidation of olefins to diols, in which NMM in
Scheme 1 is recycled to NMO by catalytic flavin/H O .
2 2
in a control experiment, which gave a 95% yield of diol 2. Direct
12
reoxidation of osmium(VI) by H
reaction where 2 was a minor product obtained in 10% yield
Table 1, entry 1). Slow addition of the oxidant did not change
2
O
2
led to a nonselective
†
Uppsala University.
‡
Stockholm University.
(
(
1) (a) Sim a´ ndi, L. I. Catalytic ActiVation of Dioxygen by Metal Complexes;
the outcome of the reaction much (entry 2).
We have recently shown that biomimetic flavin analogue 3
efficiently catalyzes H O oxidation of tertiary amines to amine
2 2
Kluwer: Dordrecht, The Netherlands, 1992. (b) Strukul, G. Catalytic
Oxidations with Hydrogen Peroxide as Oxidant; Kluwer: Dordrecht, The
Netherlands, 1992.
(
2) (a) Moser, C. C.; Keske, J. M.; Warncke, K.; Faird, R. S.; Dutton, P.
L. Nature 1992, 355, 796-802. (b) Nugent, J. H. A. Eur. J. Biochem. 1996,
37, 519-31. (c) Hughes, M. N. The Inorganic Chemistry of Biological
Processes; Wiley: Chichester, UK, 1981.
3) (a) Smidt, J.; Hafner, W.; Jira, R.; Sedlmeier, J.; Sieber, R.; R u¨ ttinger,
2
(
R.; Kojer, H. Angew. Chem. 1959, 71, 176. (b) Tsuji, J. Palladium Reagents
and Catalysts. InnoVations in Organic Synthesis; Wiley: Chichester, UK, 1995.
(
c) B a¨ ckvall, J. E.; Åkermark, B.; Ljunggren, S. O. J. Am. Chem. Soc. 1979,
1
01, 2411-2416.
(
4) (a) B a¨ ckvall, J. E.; Hopkins, R. B.; Grennberg, H.; Mader, M. M.;
Awasthi, A. K. J. Am. Chem. Soc. 1990, 112, 5160-5166. (b) Grennberg, H.;
Faizon, S.; B a¨ ckvall, J. E. Angew. Chem., Int. Ed. Engl. 1993, 32, 263-264.
oxides via a flavin hydroperoxide.13 It would be highly attractive
to apply this biomimetic N-oxidation to the recycling of NMM
(5) (a) B a¨ ckvall, J. E.; Chowdhury, R. L.; Karlsson, U. J. Chem. Soc., Chem.
Commun. 1991, 473-475. (b) Wang, G.-Z.; Andreasson, U.; B a¨ ckvall, J. E.
J. Chem. Soc., Chem. Commun. 1994, 1037-1038.
(11) (a) Wai, J. S. M.; Mark o´ , I.; Svendsen, J. S.; Finn, M. G.; Jacobsen,
E. N.; Sharpless, K. B. J. Am. Chem. Soc. 1989, 111, 1123. (b) Sharpless, K.
B.; Amberg, W.; Bennani, Y. L.; Crispino, G. A.; Hartung, J.; Jeong, K. S.;
Kwong, H.-L.; Morikawa, K.; Wang, Z.-M.; Xu, D.; Zhang, X.-L. J. Org.
Chem. 1992, 57, 2768. (c) Ahrgren, L.; Sutin, L. Org. Proc. Res. DeVelop.
1997, 1, 425-427.
(6) For aerobic electron transfer-based oxidations developed by others
see: (a) Bystr o¨ m, S. E.; Larsson, E. M.; Åkermark, B. J. Org. Chem. 1990,
5, 5674. (b) Yokota, T.; Sakurai, Y.; Sakaguchi, S.; Ishii, Y. Tetrahedron
5
Lett. 1997, 38, 3923-3926.
(
7) Schr o¨ der, M. Chem. ReV. 1980, 80, 187-213.
(
8) (a) Sharpless, K. B.; Akashi, K. J. Am. Chem. Soc. 1976, 98, 1986-
2 2
(12) H O as the terminal oxidant: (a) Milas, N. A.; Sussman, S. J. Am.
1
4
987. (b) Akashi, K.; Palermo, R. E.; Sharpless, K. B. J. Org. Chem. 1978,
3, 2063-2066.
Chem. Soc. 1936, 58, 1302-1305. (b) Milas, N. A.; Sussman, S. J. Am. Chem.
Soc. 1937, 59, 2345-2347. (c) Milas, N. A.; Sussman, S.; Mason, H. S. J.
Am. Chem. Soc. 1939, 61, 1844-1847. (d) Milas, N. A.; Trepagnier, J. H.;
Nolan, J. T.; Iliopulos, M. I. J. Am. Chem. Soc. 1959, 81, 4730-4733.
(13) The flavin hydroperoxide oxidizes NMM to NMO about 6300 times
(
9) (a) VanRheenen, V.; Kelly, R. C.; Cha, D. Y. Tetrahedron Lett. 1976,
1
1
973-1976. (b) VanRheenen, V.; Cha, D. Y.; Hartley, W. M. Org. Synth.
988, Collect. Vol. VI, 342-348.
(
10) Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem. ReV.
faster than H
2 2
O : Bergstad, K.; B a¨ ckvall, J. E. J. Org. Chem. 1998, 63, 6650-
1
994, 94, 2483-2547.
6655.
1
0.1021/ja991710b CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/23/1999

Communications to the Editor
J. Am. Chem. Soc., Vol. 121, No. 44, 1999 10425
Scheme 2. Triple Catalytic System for the Osmium-Catalyzed
Table 2. Cis-Dihydroxylation of Different Olefins Employing
H O
2 2
as the Terminal Oxidanta
Dihydroxylation of Olefins Using H
Oxidant
2
O
2
as the Terminal
yield of diolb
%
B. cat. OsO
cat. NMM/cat. 3
4
/
entry
substrate
A. cat. OsO
10
4
1
2
3
4
5
6
7
8
trans-5-decene
trans-stilbene
trans-2-octene
trans-4-octene
cyclohexene
1-methyl-1-cyclohexene
cis-stilbene
R-methylstyrene
95
74
95
92
91
77
72
93
c
c
10
18
34
50
25
c
c,d
62
79
a
Scheme 3. The Flavin Cycle in the Osmium-Catalyzed
Dihydroxylation Employing H as the Terminal Oxidant
2 2
Experimental conditions unless otherwise noted: (A) H O (1.5
O
2 2
equiv, 30% aqueous) was added all at once to a mixture of the olefin
1.0 mmol) and OsO (2 mol %) in acetone (3.8 mL) and H O (1.2
(
4
2
mL). The reaction mixture was stirred 20-26 h. (B) The olefin (0.5
mmol), N-methylmorpholine (27 mol %), TEAA (2 equiv), flavin 3 (5
mol %), and OsO
4
(2 mol %) were dissolved in acetone (1.88 mL) and
(1.5 equiv, 30% aqueous) was added to this
H
2
O (0.62 mL). H O
2 2
mixture over 9 h using a syringe pump. After complete addition of the
b
oxidant, the mixture was stirred for an additional 7-15 h. Isolated
c
yields of cis-addition product. 4.4:1 acetone/H
Addition time 14 h.
2
O was employed.
d
and flavin 3 (Table 2, A),17 and these experiments gave the
corresponding diols in low yields in nonselective reactions. For
example, the diols from trans-5-decene and trans-stilbene were
formed in only 10% yield in each case in the H
without NMM and flavin, whereas 95 and 74% yield, respectively,
were obtained in the corresponding triple catalytic H oxidations
2 2
O oxidation
to NMO in the osmium-catalyzed dihydroxylation, which would
provide a favorable reoxidation of Os(VI). Thus, in situ generation
of NMO from a catalytic amount of NMM by the use of catalytic
amounts of 3 (5 mol %) in the dihydroxylation of 1 (eq 1) afforded
diol 2 in a good isolated yield (72%, entry 3). It has previously
been observed that addition of tetraethylammonium acetate
2 2
O
(
entries 1 and 2). A substrate like R-methylstyrene (entry 8) works
12
well with the traditional OsO
case a significant improvement was observed with the triple
catalytic system. The turnover rate of this system is comparable
4
2 2
-H O system, but also in this
(
TEAA) improves the outcome of osmium-catalyzed dihydroxyla-
9,18
to standard osmium-catalyzed dihydroxylation.
8b,14
tions,
probably due to the increased rate of hydrolysis of the
An interesting question is if the system is compatible with the
intermediate osmate ester. Addition of TEAA to the reaction mix-
ture did indeed result in a significant improvement and 2 was
obtained in an excellent yield (95%, >99% cis-addition, entry
10,11b
use of Sharpless’ chiral ligands,
since one may suspect that
the tertiary amino groups of the ligands could be oxidized by the
flavin hydroperoxide. In a preliminary experiment H oxidation
of trans-stilbene employing the catalytic system OsO -NMM-
afforded the
corresponding diol in 87% yield and 88% ee. The triple catalytic
oxidation of styrene (in t-BuOH/H O) employing the same
2 2
O
4
).
The mechanism of the triple catalytic H
depicted in Scheme 2. The flavin hydroperoxide generated from
flavin and H is rapidly recycling the NMM to NMO, which
4
O
2 2
oxidation is
10,11b,19
2
flavin 3 and chiral ligand (DHQD) PHAL
2 2
O
H
O
2 2
2
in turn reoxidizes the OsO
3
to OsO
4
. The system leads to a mild
20
ligand gave the corresponding diol in 84% yield and 88% ee.
In the present work it was found that hydrogen peroxide can
be used as a selective oxidant in the osmium-catalyzed dihy-
droxylation of olefins by the use of N-methylmorpholine (NMM)
and flavin 3 as cocatalysts. The process does not require access
to an amine oxide but rather a tertiary amine in catalytic amounts.
This also allows a useful variation of the tertiary amine employed
if needed. The system is compatible with the use of Sharpless’
chiral ligands.
kinetically controlled4
a,15
electron transfer from the substrate
(olefin) to hydrogen peroxide at room temperature. The stepwise
electron transfer with falling redox potential is reminiscent of
electron-transfer processes occurring in biological systems.
The role of flavin 3 is most likely to act as a precursor of the
active catalyst. In the presence of molecular oxygen (air), an
intermediate flavin hydroperoxide 4 is easily generated (Scheme
13,16
3).
The latter is thought to be the actual oxidizing species,
which can transfer one of its oxygen atoms to NMM giving NMO
in a mild and fast reaction. During the reaction the cationic flavin
Acknowledgment. Financial support from the Swedish Natural
Science Research Council, the Swedish Research Council for Engineering
Sciences, and the Swedish Foundation for Strategic Research is gratefully
acknowledged.
5
is formed, which will react with hydrogen peroxide to regenerate
the flavin hydroperoxide 4.
Several other olefins were oxidized to diols in good to excellent
yields employing the mild triple catalytic system developed (Table
Supporting Information Available: Experimental details (PDF). This
material is available free of charge via the Internet at http://pubs.acs.org.
2, B). The use of hydrogen peroxide as oxidant without the
electron-transfer mediators (NMM, flavin) in osmium-catalyzed
JA991710B
12
dihydroxylation is inefficient and nonselective. In all cases
control experiments were carried out in the absence of NMM
(
17) These H
by Milas (see ref 12).
2 2
18) A shorter addition time of H O (2.5 h) in the oxidation of 1 did not
2 2
O oxidations were carried out according to the procedure
(
(
14) Bergstad, K.; Piet, J. J. N.; B a¨ ckvall, J. E. J. Org. Chem. 1999, 64,
545-2548.
15) This system contains four oxidants with falling redox potentials, and
result in any considerable change in the reaction outcome, and the diol 2 was
2
isolated in 83% yield.
(
(19) (a) Only the ligand (DHQD)
2
PHAL11b,19b has been tested so far. (b)
four species that can be oxidized. Therefore, there are ten redox reactions
that can occur but only four of these are involved due to the high kinetic
control.4a
2
(DHQD) PHAL ) hydroquinidine 1,4-phthalazinediyl diether.
(20) In this case it was necessary to change solvent to t-BuOH since the
oxidation in acetone gave a lower ee. Also, the olefin had to be added slowly
(over 9 h), since addition of all olefin at once gave only 74% ee. Optimization
of the enantioselectivity for different olefins with the present system will
require further studies (variation of solvent, addition time, temperature, etc).
(
16) For reaction of O
see: (a) Kemal, C.; Bruice, T. C. Proc. Natl. Acad. Sci. U.S.A. 1976, 73,
95. (b) Mager, H. I. X.; Berends, W. Tetrahedron 1976, 32, 2303.
2
with related flavins to give flavin hydroperoxides
9