K-birnessite MnO2: A new selective oxidant for benzylic and allylic alcohols

Article abstract of DOI:10.1016/j.tetlet.2010.11.114

K-birnessite, which is readily prepared by the pyrolysis of KMnO ₄, acts as a convenient new oxidant for benzylic and allylic alcohols.

Full text of DOI:10.1016/j.tetlet.2010.11.114

Tetrahedron Letters 52 (2011) 538–540
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Tetrahedron Letters
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K-birnessite MnO2: a new selective oxidant for benzylic and allylic alcohols
Akio Kamimura a, , Yuichiro Nozaki a, Shingo Ishikawa a, Ryota Inoue b, Masaharu Nakayama b
⇑
a Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University, Ube 755-8611, Japan
b Department of Material Chemistry, Graduate School of Science and Engineering, Yamaguchi University, Ube 755-8611, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
K-birnessite, which is readily prepared by the pyrolysis of KMnO4, acts as a convenient new oxidant for
benzylic and allylic alcohols.
Received 9 November 2010
Accepted 19 November 2010
Available online 25 November 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Selective oxidation of alcohols to aldehydes is an important
transformation in organic synthesis. A number of useful methods
have been developed for the oxidation so far. For example, the
use of chromium oxide, such as pyridinium chlorochromate
(PCC)1 and pyridiunium dichromate (PDC),2 and Swern oxidation3
are typical strategies for the selective preparation of aldehydes
from primary alcohols. Tetrapropylammonium perruthenate
(TPAP)4 and Dess–Martin periodinane (DMP)5 are improved oxi-
dants for mild oxidation of alcohols. Recently some methods for
aerobic oxidation of alcohol by using gold cluster are reported.6
Among these oxidants, manganese oxide (MnO2) is a unique
class of oxidant owing to its capability to achieve selective and
mild oxidation of benzylic and allylic alcohols.7 For the oxidation,
MnO2 must be activated prior to use. Among the various activation
methods developed to date,8 Attenburrow’s method8a is the repre-
sentative one, in which KMnO4 and MnSO4 are treated in alkaline
solution and the precipitate is dried at 120 °C. The efficiency of
the oxidant depends on the activation processes of MnO2 which re-
quires special care for the treatment. For example, the water con-
tent of MnO2 critically affects the efficiency of the oxidation, that is
completely dried MnO2 is useless for the oxidation. The activated
MnO2 materials consist of an amorphous structure.9 Recently, an
interesting modification of aerobic oxidation by using catalytic
amounts of K-OMS was reported.10 Although several modern
methods are devised recently, MnO2 oxidation is still the most reli-
able and controllable method in organic synthesis for the conver-
sion of benzylic and allylic alcohols into the corresponding
aldehydes.
can be involved in the electron-transfer reactions. Birnessites have
been synthesized by a wide variety of chemical methods, including
oxidation of Mn2+ cations,11 reduction of KMnO4,12 and high-tem-
perature decomposition of KMnO4.13 However, very few studies re-
port the electrochemical synthesis of birnessite as a thin film.14
Thermolysis of KMnO4 is the simplest method to obtain highly-
crystallized birnessite, which may offer a peculiar oxidation reac-
tivity owing to its unique nanolayered structure. To the best of
our knowledge, however, no studies have been reported on the
use of birnessite in organic synthesis. In this paper, we report a
new selective oxidation of benzylic and allylic alcohols by birnes-
site-type MnO2 intercalated with potassium ions (K-birnessite),
that is very easily prepared by heat-treatment of commercially
available KMnO4.
K-birnessite was prepared by the reported method.13 KMnO4
was gradually heated in air to 800 °C over 13 h, then maintained
at that temperature for an additional 5 h. The crude K-birnessite
was cooled and washed thoroughly with water to remove the
remaining KMnO4. After that the product was dried at 80 °C over-
night. Peaks at 12.5° and 25.1° in 2h can be indexed to the 001
plane and its second (002) order diffractions from multilayers of
birnessite-type manganese oxide (Fig. 1).15 d-spacing of the 001
peak (d001) corresponds to the interlayer spacing and was mea-
sured to be 0.71 nm according to Bragg’s equation. Four small
peaks appearing between 36.4° and 44.6° are associated with the
intrasheet reflections,16 indicating that each manganese oxide
sheet is crystallized. All the above features are consistent with
those generally observed for K-birnessite. The full width at half-
maximum of the 001 peak was measured to be 0.173°, correspond-
ing to a crystallite size of 22 nm in the 001 direction, deduced by
the Scherrer equation (k = 0.89). Thus, there is no doubt that we
used highly-crystallized birnessite as the catalyst.
Birnessite, also called as d-type MnO2, has a two-dimensional
layered structure with an interlayer distance of ꢀ0.7 nm, and is
comprised of edge-sharing MnO6 octahedra. Small cations such
as potassium ions or protons are located in the interlayer space
to balance the negative charges on manganese oxide layers. In such
a layered structure, all of the material can be regarded as a surface.
This is different from bulk materials, in which not all of metal ions
Oxidation by K-birnessite was carried out in the following pro-
cedure. K-birnessite was added to a solution of alcohol 1 (1 mmol)
in CH2Cl2 (10 mL) at room temperature. The resulting suspension
was stirred for 2 h. After filtration of the mixture, the crude alde-
hyde or ketone 2 was isolated by concentration of the filtrate.
The results are summarized in Table 1.
⇑
Corresponding author. Tel.: +81 836 85 9231; fax: +81 836 85 9201.
E-mail address: ak10@yamaguchi-u.ac.jp (A. Kamimura).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.11.114

A. Kamimura et al. / Tetrahedron Letters 52 (2011) 538–540
539
CHO
CH2OH
2a; 91%
1a
K-birnessite
CH2Cl2/rt
+
+
OH
OH
1o; 90%
1o
Scheme 1.
K-birnessite
Ph
Ph
OH
OH
Ph
Ph
(2.98 g/mmol)
CH2Cl2/rt/4 h
O
3; 80%
Figure 1. XRD pattern of K-birnessite.
K-birnessite
(3.00 g/mmol)
CH2Cl2/rt/7 h
Table 1
O
Oxidation of benzyl alcohol by K-birnessite
4; 1%
OH
O
K-birnessite MnO2
CH2Cl2/rt
recovery of alcohol 97%
Ar
R
Ar
R
Bu3Sn
CHO
2
1; 1 mmol
CHO
Entry
Ar
R
Amounts (g/mmol)
Time (h)
2; yielda (%)
5a; 73%
5b; 95%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Ph
Ph
Ph
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
Et
iPr
0.45
1.73
3.03
2.86
2.95
2.92
2.99
3.00
2.68
2.91
3.03
3.03
3.00
3.00
3.00
3.03
2.86
2
2
2
3
2a; 20b
2a; 59b
2a; 89
2b; 88
2c; 90
2d; 85
2e; 78
2f; 80
2g; 99
2h; 67
2i; 71
2j; 86
2k; 85
2l; 82
2m; 89
2n; 79
2o; 70c
Ts
N
5c; 90%, 90%ee
CHO
m-ClC6H4
p-ClC6H4
p-O2NC6H4
o-O2NC6H4
m-O2NC6H4
p-MeOC6H4
m-MeOC6H4
o-MeC6H4
p-BrC6H4
2-Furanyl
2-Thienyl
Ph
(starting from 92% ee of
corresponding alcohol)
7
10
4.5
4
3
3
2
7
2
2
Scheme 2.
5–8, 12), while the yields of the aldehydes 2 were almost equally
high. Heteroaromatic compounds also underwent the smooth oxi-
dation to give corresponding aldehydes in good yield (entries 13
and 14). Thus, the present oxidation was compatible to these func-
tional groups.
The present method is useful for the oxidation of secondary
alcohols to give ketones (entries 15–17). For example, treatment
of a-phenethyl alcohol (1m) with K-birnessite resulted in the for-
2
3
9
Ph
Ph
a
b
c
Isolated yield.
GC yield.
mation of acetophenone (2m) in 89% yield. Propiophenone (2n)
was also prepared from the corresponding alcohol, but the steri-
cally demanded alcohol required longer reaction time to give ke-
tones in good yield. It should be noted that the present reaction
rate was much faster than the commercially available MnO2 which
could not oxidize 2-methyl-1-phenyl-1-propanol (1o) after 9 h of
treatment. Comparing with the oxidation of primary alcohol, the
reaction rate for the secondary alcohol was remarkably slow. For
example, a competitive reaction between benzyl alcohol (1a) and
The yield of 2o was 0% when treated with commercially available activated
MnO2 for 9 h.
The reaction occurred smoothly and desired benzaldehyde (2a)
was detected by GC analysis. Benzyl alcohol was consumed within
2 h when 0.45 g/mmol of K-birnessite was used, and the amounts
of benzaldehyde (2a) gradually increased. However, the reaction
stopped when the yield of 2a reached about 20% (entry 1). We
thought this was due to insufficient amounts of K-birnessite to
complete the reaction so we increased the amounts of K-birnessite
(entries 2 and 3). The yield of 2a was improved to about 89% when
3 g/mmol of K-birnessite was used for the oxidation (entry 3). The
necessary amount of manganese oxide is almost similar to that of
commercially available activated MnO2 to progress the practical
oxidation reaction.
With the optimized reaction conditions in hand, we examined
the oxidation of other benzyl alcohol derivatives. The oxidation
took place smoothly in 2 h and corresponding benzaldehyde 2
was isolated in good yield. The isolation procedure was simple;
just filtration and concentration gave aldehyde in good yield.17
Some alcohols required longer reaction time. For example, chloro-
and nitro-substituted benzyl alcohols were oxidized more slowly
and consumed 4–10 h until the completion of the reaction (entries
a-phenylethyl alcohol (1m) showed that the reaction rate of the
primary alcohol was about six times faster than the secondary
alcohol. It should be noted that selective oxidation of benzyl
alcohol was achieved from a mixture of benzyl alcohol (1a) and
2-methyl-1phyenyl-1-propanol (1o) (Scheme 1).
The present oxidative reagent is also effective toward the selec-
tive oxidation of allylic alcohol. For example, cinnamyl alcohol
readily gave cinnamaldehyde (3) in 80% yield (Scheme 2). It should
be mentioned that 3-phenyl-1-propanol, saturated derivative of
cinnamyl alcohol, was inert under the present reaction conditions
and the corresponding aldehyde 4 was detected only 1% after 7 h of
the reaction time; the starting alcohol was recovered in 97%. Other
allylic alcohols were successfully oxidized to give the correspond-
ing unsaturated aldehydes 5. For example, geraniol gave citral (5a)
in 73% yield. Stanny allylic alcohol was also converted into stannyl

540
A. Kamimura et al. / Tetrahedron Letters 52 (2011) 538–540
unsaturated aldehyde 5b18 in 95% yield. Chiral alcohol underwent
smooth oxidation within 3 h and gave unsaturated aldehyde 5c in
90% yield.19 The reaction occurred in a spot-to-spot manner and
purification of 5c was quite easy. It should be noted that no signif-
icant racemization at C3 chiral center was observed during the
reaction. Although the same oxidation was achieved by using com-
mercially available activated MnO2 under similar conditions (abt
3 g/mmol), it took more than 10 h until the completion of the reac-
tion. The yield of 5c was only 70% along with the formation of
small amounts of side products, and the purification of 5c was
not very easy. Thus, this birnessite is a much superior oxidant to
Burke, S. D., Danheiser, R. L., Eds.; Oxidizing and Reducing Agents; John
Wiley & Sons: Chichester, 1999; p 231.
8. (a) Attenburrow, J.; Cameron, A. F. B.; Chapman, J. H.; Evans, R. M.; Hems, B. A.;
Jansen, A. B. A.; Walker, T. J. Chem. Soc. 1952, 1094; (b) Mancera, O.;
Rosenkranz, G.; Sondheimer, F. J. Chem. Soc. 1954, 3271; (c) Mattock, A. R. J.
Chem. Res (S) 1977, 40; Harfenist, M.; Bavley, A.; Lazier, W. A. J. Org. Chem. 1954,
19, 1608; (d) Ball, S.; Goodwin, T. W.; Morton, R. A. Biochem. J. 1948, 42, 516; (e)
Carpino, L. A. J. Org. Chem. 1970, 35, 3971; (f) Goldman, I. M. J. Org. Chem. 1969,
34, 1979; (g) Belew, J. S.; Tek-Ling, C. Chem. Ind. 1967, 1958. see also Ref. 6.
9. Fatiadi, A. J. J. Chem. Soc. (B) 1971, 889.
10. Son, Y.-C.; Makwana, V. D.; Howell, A. R.; Suib, S. L. Angew. Chem., Int. Ed. 2001,
40, 4280.
11. (a) Luo, J.; Huang, A.; Park, S. H.; Suib, S. L.; Young, C.-L. O’. Chem. Mater. 1998,
10, 1561; (b) Pietro, O.; Del Arco, M.; Rives, V. J. Mater. Sci. 2003, 38, 2815; (c)
Cai, J.; Suib, S. L. Inorg. Chem. Commun. 2001, 4, 493.
12. (a) Frias, D.; Nousir, S.; Barrio, I.; Montes, M.; Centeno, M. A.; Odriozola, J. A.
Mater. Charact. 2007, 58, 776; (b) Yang, L.-X.; Zhu, Y.-J.; Cheng, G.-F. Mater. Res.
Bull. 2007, 42, 159; (c) Morales, J.; Sanchez, L.; Bach, S.; Pereira-Ramos, J. P.
Mater. Lett. 2002, 56, 653.
13. Komaba, S.; Kumagai, N.; Chiba, S. Electrochim. Acta 2000, 46, 31.
14. (a) Nakayama, M.; Konishi, S.; Tanaka, A.; Ogura, K. Chem. Lett. 2004, 33, 670;
(b) Nakayama, M.; Konishi, S.; Tagashira, H.; Ogura, K. Langmuir 2005, 21, 354.
15. Golden, D. C.; Chen, C. C.; Dixon, J. B. Clay Clay Mineral. 1987, 35, 271.
16. Julien, C.; Massot, M.; Baddour-Hadjean, R.; Franger, S.; Bach, S.; Pereira-
Ramos, J. P. Solid State Ionics 2003, 159, 345.
17. Oxidation of p-chlorobenzyl alcohol (Table 1, entry 5). Typical procedure: To a
solution of p-chlorobenzyl alcohol (143.4 mg, 1.01 mmol) in CH2Cl2 (10 mL)
was added K-birnessite (2.98 g). The reaction mixture was stirred at 30 °C for
7 h. Black precipitate was removed by filtration over celite. The filtrate was
concentrated to give crude p-benzaldehyde, which was purified through flash
chromatography (silica gel/hexane–EtOAc) to give 2c in 90% yield (129.1 mg).
18. Johnson, C. R.; Kadow, J. F. J. Org. Chem. 1987, 52, 1493.
commercially available MnO2 for the preparation of
rated aldehydes.
a,b-unsatu-
In conclusion, we have developed a new oxidizing reagent for
allylic and benzylic alcohols. K-birnessite is readily prepared from
commercially available KMnO4 by the thermal treatment at 800 °C
in a readily available electric muffle furnace. This is the first oxidiz-
ing reagent in crystalline state of MnO2. Optimum molar ratio for
the reaction is about 3 g of K-birnessite per 1 mmol of alcohol. Nei-
ther oxidation of aliphatic primary alcohol nor over-oxidation to
carboxylic acid was observed under the present conditions. Thus,
use of K-birnessite will provide a useful oxidizing method in organ-
ic synthesis.
References and notes
19. Preparation of (S)-3-(N-allyl-N-tosyl)amino-2-methylene-7-octenal 5c. To
a
solution of (S)-3-(N-allyl-N-tosyl)amino-2-methylene-7-octen-1-ol (2.727 g,
7.81 mmol, 92% ee) in CH2Cl2 (80 mL) was added K-birnessite (23.4398 g). The
reaction mixture was stirred at room temperature for 3 h. Black precipitate
was removed by filtration over celite. The filtrate was concentrated in vacuo
and then purified through flash chromatography (silica gel/hexane–EtOAc) to
give 5c in 90% yield (2.4419 g) as a pale yellow oil; enantiomeric purity was
determined by HPLC analysis (230 nm, 40 °C) tR 15.9 min (minor); tR 29.1 min
(major) [CHIRALPAK IC (0.46 cm  25 cm) hexane–iPrOH, 80/20, 1.00 mL/min]
1. Corey, E. J.; Suggs, J. W. Tetrahedron Lett. 1975, 16, 2647.
2. Corey, E. J.; Schmidt, G. Tetrahedron Lett. 1979, 20, 399.
3. Mancuso, A. J.; Swern, D. Synthesis 1981, 165.
4. (a) Griffith, W. P.; Ley, S. V. Aldrichim. Acta 1990, 23, 13; (b) Ley, S. V.; Norman,
J.; Griffith, W. P.; Marsden, S. P. Synthesis 1994, 639.
5. (a) Dess, D. B.; Martin, J. C. J. Org. Chem. 1983, 48, 4155; (b) Boeckman, R. K., Jr.;
Shao, P.; Mullins, J. J. Org. Synth. 2000, 77, 141.
as 90% ee. [
a]
D À54.8 (CHCl3, c 0.99); 1H NMR (CDCl3, 500 MHz) d 9.37 (s, 1H),
6. (a) Li, H.; Guan, B.; Wang, W.; Xing, D.; Fang, Z.; Wan, X.; Yang, L.; Shi, Z.
Tetrahedron 2007, 63, 8430; (b) Chaki, N. K.; Tsunoyama, H.; Negishi, Y.;
Sakurai, H.; Tsukuda, T. J. Phys. Chem. C 2007, 111, 4885; (c) Guan, B.; Xing, D.;
Cai, G.; Wan, X.; Yu, N.; Fang, Z.; Yang, L.; Shi, Z. J. Am. Chem. Soc. 2005, 127,
1800; (d) Tsunoyama, H.; Ichikuni, N.; Sakurai, H.; Tsukuda, T. J. Am. Chem. Soc.
2009, 131, 7086.
7.67 (d, J = 8.2 Hz, 2H), 7.25 (d, J = 8.1 Hz, 2H), 6.43 (s, 1H), 6.17 (s, 1H), 5.94–
5.52 (m, 2H), 5.24–5.02 (m, 2H), 4.96 (d, J = 15.5 Hz, 1H), 4.94 (d, J = 8.7 Hz, 1H),
4.69 (t, J = 7.6 Hz, 1H), 3.86 (d, J = 6.3 Hz, 2H), 2.40 (s, 3H), 2.01 (q, J = 7.2 Hz,
2H), 1.96–1.68 (m, 2H), 1.44–1.15 (m, 2H); 13C NMR (CDCl3, 126 MHz) d 193.4,
147.4, 143.1, 138.1, 138.0, 136.8, 135.4, 129.3, 127.5, 117.8, 114.9, 55.0, 48.6,
33.0, 31.0, 25.7, 21.4; IR (cmÀ1); 2926, 1689, 1332, 1153, 910; HRMS (ESI MS
M+1) m/z 348.1646. Calcd for C19H26NO3S 348.1633.
7. (a) Fatiadi, A. J. Synthesis 1976, 65; (b) Fatiadi, A. J. Synthesis 1976, 133;
(c) Caliez, G.; Alami, M. In Handbook of Reagents for Organic Synthesis;