Liquid-phase epoxidation of alkenes using molecular oxygen catalyzed by vanadium cation-exchanged montmorillonite

Article abstract of DOI:10.1246/cl.2005.1626

Vanadium cation-exchanged montmorillonite can efficiently catalyze the selective epoxidation of various alkenes and the oxygenation of adamantane using molecular oxygen as a sole oxidant. Copyright

Full text of DOI:10.1246/cl.2005.1626

1
626
Chemistry Letters Vol.34, No.12 (2005)
Liquid-phase Epoxidation of Alkenes Using Molecular Oxygen
Catalyzed by Vanadium Cation-exchanged Montmorillonite
ꢀ
Takato Mitsudome, Naoya Nosaka, Kohsuke Mori, Tomoo Mizugaki, Kohki Ebitani, and Kiyotomi Kaneda
Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University,
-3 Machikaneyama, Toyonaka, Osaka 560-8531
1
(Received August 10, 2005; CL-051040)
Vanadium cation-exchanged montmorillonite can efficient-
ly catalyze the selective epoxidation of various alkenes and the
oxygenation of adamantane using molecular oxygen as a sole
oxidant.
6
(c)
χ
(e)
(b)
Epoxidation is one of the most fundamental and important
1
V−O−V
reactions in organic synthesis. Various methods have been de-
veloped and exploited, and the search for new environmentally
friendly methods using molecular oxygen (O2) as the sole oxi-
dant has attracted much interest. However, there have been
few reports concerning the epoxidation of alkenes using 1 atm
(a)
(d)
(B)
(
A)
5465
5475
Photon energy (eV)
5485
0
1
2
3
4
5
6
Interatomic distance (Å)
2
of O2 without the use of reducing reagents.
Montmorillonites (monts) of smectite clays are composed of
negatively charged layers and an interlayer with cationic spe-
Figure 1. (A) V K-edge XANES spectra of (a) VOSO4, (b) V-
3
mont, and (c) Na3VO4. (B) Fourier transforms of k -weighted V
K-edge EXAFS for (d) V2O5, and (e) V-mont.
3
cies. The cationic species can easily be replaced by other metal
Table 1. Epoxidation of cyclooctene catalyzed by metal cation-
a
polycations using the cation exchange ability of the interlayer,
and the metal cation-exchanged monts have considerable poten-
tial as heterogeneous catalysts for various organic transforma-
exchanged monts and vanadium compounds using O2
O2, catalyst
O
4
tions. Here, we report the synthesis and characterization of va-
nadium cation-exchanged mont (V-mont) as well as its perform-
ance in catalyzing the epoxidation of various alkenes using 1 atm
of O2 as an oxidant. The V-mont-catalyzed aerobic oxygenation
of adamantane via C–H activation is also described.
V-mont was prepared as follows: Na -mont, Na0:66(OH)4-
Si7:7(Al3:34Mg0:66Fe0:19)O20 (6.0 g) (Kunipia F, Kunimine Indus-
try Co., Ltd.) was added to 100 mL of aqueous VCl3 solution
Yield of epoxide/%b
Entry
Catalyst
1c
2
3
4
5
6
7
8
9
V-montd
V-montd
V-montd,e
Fe-mont
Mn-mont
Mo-mont
Ru-mont
Na-mont
V2O5d
80
31
þ
trace
trace
trace
trace
trace
trace
4
(
ture was stirred at 60 C for 24 h. The resulting slurry was filtered
0.025 M). Aqueous HCl (1 mL, 10 M) was added, and the mix-
ꢁ
ꢁ
and washed with distilled water, then dried at 110 C and
ꢁ
calcined at 800 C for 18 h, giving 5.5 g of V-mont (V content:
0.97 wt %). XRD measurement showed that the lamellar
structure of the uncalcined V-mont with interlayer space of
d
10
11
12
V-X zeolite
d
1
V/Al2O3
trace
trace
d
VO(acac)2
ꢀ
.9 A was transformed into a card-house structure by the above
2
calcination process.
a
5
Substrate (3 mmol), catalyst (0.1 g), ꢀ,ꢀ,ꢀ-trifluorotoluene
b
ꢁ
5 mL), 90 C, 48 h, O2 atmosphere. Determined by GC analysis
(
The height of the pre-edge peak in V K-edge XANES spec-
trum of the calcined V-mont was similar to that of Na3VO4, but
c
using an internal standard technique. ꢀ,ꢀ,ꢀ-Trifluorotoluene
1 mL), 72 h. V (0.019 mmol). Uncalcined V-mont was used.
d
e
(
6
differed from that of VOSO4, as shown in Figure 1a. This result
showed that the vanadium species existed in a tetrahedral-like
geometry. Furthermore, the energy position of the pre-edge peak
and the absorption edge for the V-mont were higher than those of
ed on the mont.
Initially, epoxidations of cyclooctene were carried out using
various metal-exchanged monts under 1 atm of O2 in ꢀ,ꢀ,ꢀ-tri-
fluorotoluene solvent, as shown in Table 1. Among the cata-
6
8,9
VOSO4, suggesting that the oxidation state of the V-mont is 5þ.
3
In Fourier transform (FT) of k -weighted V K-edge EXAFS, no
peaks due to a V–O–V bond, detectable in the spectrum of V2O5
lysts examined, the calcined V-mont proved the most efficient
for the epoxidation of cyclooctene (Entry 2). Interestingly, the
uncalcined V-mont was found to be less effective (Entry 3). Oth-
er vanadium catalysts such as V2O5, V-X Zeolite, V-alumina,
and VO(acac)2 gave poor results (Entries 9–12). Under opti-
mized reaction conditions, the yield of cyclooctene oxide
reached up to 80% with >99% selectivity after 72 h (Entry 1).
To the best of our knowledge, this is the first example of selec-
ꢀ
at around 2.7 A, was observed for the V-mont (Figure 1b). The
ꢀ
inverse FT of the peak around 1–2 A was well fitted using two
ꢀ
ꢀ
short (1.59 A) and two long (1.70 A) V–O bonds. The short V–
7
O distance is associated with a V=O bond, as found in V2O5.
The above results suggest that a highly dispersed monomeric di-
5þ
oxo V species surrounded by four oxygen atoms can be creat-
Copyright Ó 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.12 (2005)
1627
Table 2. Epoxidation of various alkenes by V-mont in the
a
This work was supported by a Grant-in-Aid for Scientific
Research from JSPS. We thank the Center of Excellence
(21COE) program ‘‘Creation of Integrated Ecochemistry’’ of
Osaka University.
presence of O2
Yield of epoxide/%b
Entry
1
Substrate
Selectivity/%
Cyclooctene
Cyclooctene
Cyclooctene
Cyclododecene
Cyclopentene
2-Octene
80
79
78
40
35
21
11
>99
98
c
2
References and Notes
d
3
98
93
1
a) ‘‘Modern Oxidation Methods,’’ ed. by J.-E. B a¨ ckvall, Wiley-VCH,
Weinheim (2004). b) ‘‘The Activation of Dioxygen and Homogeneous
Catalytic Oxidation,’’ ed. by D. H. R. Barton, A. E. Martell, and D. T.
Sawyer, Plenum, New York (1993). c) R. A. Sheldon and J. K. Kochi,
4
5
e
54
80f
85g
6
‘‘Metal-Catalyzed Oxidation of Organic Compounds,’’ Academic Press,
New York (1981).
7
1-Octene
a
2
There is only one heterogeneous catalyst for liquid-phase epoxidation,
which has been applied only to styrene, see: a) Q. Tang, Y. Wang,
J. Liang, P. Wang, Q. Zhang, and H. Wan, Chem. Commun., 2004,
440. Homogeneous catalysts, see: b) Y. Nishiyama, Y. Nakagawa, and
N. Mizuno, Angew. Chem., Int. Ed., 40, 3639 (2001). c) R. Neumann
and M. Dahan, J. Am. Chem. Soc., 120, 11969 (1998). d) R. Neumann
and M. Dahan, Nature, 388, 353 (1997). e) A. S. Goldstein, R. H. Beer,
and R. S. Drago, J. Am. Chem. Soc., 116, 2424 (1994). f) M. M. T. Khan
and A. P. Rao, J. Mol. Catal., 39, 331 (1987). g) J. T. Groves and
R. Quinn, J. Am. Chem. Soc., 107, 5790 (1985).
Substrate (3 mmol), V-mont (0.1 g, V: 0.019 mmol), ꢀ,ꢀ,ꢀ-tri-
fluorotoluene (1 mL), 90 C, 72 h, O2 atmosphere. Determined
ꢁ
b
c
by GC analysis using an internal standard technique. Reuse-1.
f
d
e
Reuse-2. 2-Cyclopentene-1-ol was formed. Small amounts of
g
octanal was formed. Small amounts of decanal was formed.
OH
OH
O
V-mont (0.6 mol%)
+
+
tert-butyl acetate (10 mL),
OH
3
4
a) Y. Izumi and M. Onaka, Adv. Catal., 38, 245 (1992). b) P. Laszlo,
Acc. Chem. Res., 19, 121 (1986). c) T. J. Pinnavaia, Science, 220, 365
(
1)
(2)
(3)
9
6 h, 1 atm of O2, 100 °C
Total Yield 93%
(1983).
Selectivity; (1) : (2) : (3) = 41 : 44 : 15
a) T. Kawabata, M. Kato, T. Mizugaki, K. Ebitani, and K. Kaneda,
Chem.—Eur. J., 11, 288 (2005). b) T. Kawabata, T. Mizugaki, K.
Ebitani, and K. Kaneda, J. Am. Chem. Soc., 125, 10486 (2003). c) T.
Kawabata, T. Mizugaki, K. Ebitani, and K. Kaneda, Tetrahedron Lett.,
Scheme 1.
tive liquid-phase epoxidation of cyclooctene using a heterogene-
ous catalyst with an atmospheric pressure of O2 as the sole oxi-
dant.2
44, 9205 (2003). d) T. Kawabata, M. Kato, T. Mizugaki, K. Ebitani,
and K. Kaneda, Chem. Lett., 32, 648 (2003). e) K. Ebitani, M. Ide, T.
Mitsudome, T. Mizugaki, and K. Kaneda, Chem. Commun., 2002,
The scope for epoxidation using the V-mont catalyst is sum-
marized in Table 2. This V-mont selectively catalyzed the epox-
idation of various kinds of cyclic and linear alkenes with 1 atm of
O2, affording the corresponding epoxides as major products.
Upon completion of the epoxidation of cyclooctene, the V-mont
was separated from the reaction mixture by simple filtration, and
could be reused without any appreciable loss of its high catalytic
activity and selectivity (Entries 2 and 3).
Additionally, the above V-mont exhibited high catalytic ac-
tivity for the oxygenation of adamantane in tert-butyl acetate
solvent under an atmospheric O2 pressure, affording 1-adaman-
tanol (1), 1,3-adamantanediol (2), and 2-adamantanone (3); the
6
90. f) T. Kawabata, T. Mizugaki, K. Ebitani, and K. Kaneda, Tetra-
hedron Lett., 42, 8329 (2001). g) K. Ebitani, T. Kawabata, K.
Nagashima, T. Mizugaki, and K. Kaneda, Green Chem., 2, 157 (2000).
After calcination of the V-mont, the diminishing intensity of the (001)
diffraction and maintaining of the clay phase are indicative of the trans-
formation into a card-house structure.
The V ions in Na3VO4 and VOSO4 are known to exist in a tetrahedral
coordination and square-pyramidal coordination, respectively, see:
J. Wong, F. W. Lytle, R. P. Messmer, and D. H. Haylotte, Phys. Rev.
B, 30, 5596 (1984).
5
6
7
8
H. G. Bachmann, F. R. Ahmed, and W. H. Barnes, Z. Kristallogr.
Mineral., 115, 110 (1961).
Various metal cation-exchanged monts (M-monts) were prepared in a
similar way by treatment of Na-mont with aqueous solution of the cor-
responding metal chlorides. A general procedure for V-mont-catalyzed
epoxidation of cyclooctene is as follows: Into a reaction vessel equipped
with a reflux condenser and balloon were placed the V-mont (0.1 g, V:
total yield of oxygenated products reached 93% at 96 h, as
shown in Scheme 1.10 Oxidation did not proceed in the absence
of the V-mont under identical reaction conditions. This yield is
higher than those reported for other methods of adamantane
0.019 mmol), cyclooctene (3 mmol), and ꢀ,ꢀ,ꢀ-trifluorotoluene (1
mL). After vigorous stirring of the heterogeneous reaction mixture at
ꢁ
1
1
oxidation with O2 as a sole oxidant.
The above two oxidation reactions were inhibited by the
90 C for 72 h, the catalyst was separated by centrifugation. GC analysis
of the supernatant showed an 80% yield of epoxide.
9
With respect to solvents, the use of ꢀ,ꢀ,ꢀ-trifluorotoluene and tert-
butyl acetate afforded high yields of cyclooctene oxide (80%). The reac-
tion carried out in CH3CN gave a moderate yield (30%), while toluene,
and 1,2-dichloroethane were significantly less effective (<1%).
addition of radical scavengers such as p-tert-butylcatechol and
2,6-di-tert-butylphenol. Furthermore, the ratio of oxidation at
tertiary vs secondary positions in the oxygenation of adamantane
was 8.6:1, which is similar to the ratio observed for radical
oxidations.12 These facts suggest that the above oxidations by
10 1-Adamantanol was a major product at 48 h. The selectivities of (1), (2),
and (3) were 78:4:18, respectively.
1
1a,12
11 Product yields for oxygenation of adamantane: a) S. Shinachi, M.
Matsushita, K. Yamaguchi, and N. Mizuno, J. Catal., 233, 81 (2005),
vanadium-substituted phosphomolybdates catalyst (84%). b) K.
Yamaguchi and N. Mizuno, New J. Chem., 26, 972 (2002), Ru-substitut-
ed silicotungstate catalyst (42%). c) N. Mizuno, M. Tateishi, T. Hirose,
and M. Iwamoto, Chem. Lett., 1993, 2137, Ni and Fe-substituted hetero-
polyanion catalyst (29%). d) M. M. T. Khan, D. Chatterjee, S. Kumar,
and A. P. Rao, J. Mol. Catal., 75, L49 (1987), Ru-saloph complex
catalyst (13%). See: 2C) Ru-substituted polyoxometalate catalyst (57%).
the V-mont involve a radical oxidation mechanism.
In conclusion, we have developed a highly efficient hetero-
geneous catalyst system based on monts for the epoxidation with
molecular oxygen. This system has the following advantages: (a)
the use of 1 atm of molecular oxygen as an oxidant without the
need for reducing reagents or radical initiators, (b) high catalytic
activity and selectivity, (c) recyclable catalysts, and (d) applica-
tion to aerobic oxygenation of adamantane via C–H activation.
Further studies on mechanistic details and possible extension
to other organic syntheses are currently underway.
12
a) Y. Ishii, J. Mol. Catal. A: Chem., 117, 123 (1997). b) Y. Ishii, T.
Iwasawa, S. Sakaguchi, K. Nakayama, and Y. Nishiyama, J. Org.
Chem., 61, 4520 (1996).
Published on the web (Advance View) November 8, 2005; DOI 10.1246/cl.2005.1626