Oxidation of allylic alcohols to α,β-unsaturated carbonyl compounds with aqueous hydrogen peroxide under organic solvent-free conditions

Article abstract of DOI:10.1039/b708612a

Allylic alcohols are chemoselectively oxidized to α,β- unsaturated carbonyl compounds in high yield with aqueous H₂O ₂ in the presence of Pt black catalyst under organic solvent-free conditions. The catalyst is easily recyclable and effective for at least 7 cycles. The Royal Society of Chemistry.

Full text of DOI:10.1039/b708612a

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Oxidation of allylic alcohols to a,b-unsaturated carbonyl compounds
with aqueous hydrogen peroxide under organic solvent-free conditions{
Yoshihiro Kon, Yoko Usui and Kazuhiko Sato*
Received (in Cambridge, UK) 6th June 2007, Accepted 8th August 2007
First published as an Advance Article on the web 20th August 2007
DOI: 10.1039/b708612a
Allylic alcohols are chemoselectively oxidized to a,b-unsatu-
rated carbonyl compounds in high yield with aqueous H O in
2
2
the presence of Pt black catalyst under organic solvent-free
conditions. The catalyst is easily recyclable and effective for at
least 7 cycles.
Oxidation of alcohols is one of the most frequently used synthetic
1
2
reactions in the laboratory and in chemical manufacturing.
Chemoselective oxidation is important in fine organic syntheses, as
3
well as regio- and stereo-selective oxidation. One of the central
Scheme 1 Hectogram-scale oxidation of cinnamyl alcohol.
issues in chemoselective oxidation is the discrimination between
olefinic double bonds and hydroxy groups. In particular, oxidation
of allylic alcohols to a,b-unsaturated carbonyl compounds has
long been of interest. Various oxidants with high chemoselectivity
(
under an air atmosphere), cinnamaldehyde was obtained in only
11,12
10% yield.
,
This chemoselective oxidation system is applicable to various
allylic alcohols to yield a,b-unsaturated carbonyl compounds.
These results are shown in Table 1. Primary allylic alcohols were
chemoselectively oxidized to form the corresponding a,b-unsatu-
rated aldehydes (Entries 1–8). Secondary allylic alcohol also
2 3
such as MnO and CrO have been developed, and they are
4
frequently used in organic synthesis. However, the atom efficiency
of these oxidants is low, and they form equimolar amounts of the
5,6
deoxygenated compounds as waste. Moreover, use of organic
solvents and toxic compounds should be decreased for environ-
underwent oxidation by H
2
O
2
to give the corresponding
2 2
ment conscious chemical processes. Hydrogen peroxide (H O ) is
a
2 2
Table 1 Oxidation of allylic and benzyl alcohols with aqueous H O
an ideal oxidant, because the atom efficiency is excellent and water
7
is theoretically the sole co-product. Therefore, we have developed
b
Entry Alcohol
Carbonyl compound
Yield (%)
various oxidation reactions with aqueous H O under organic
2
2
8
1
2
3
81
93
90
solvent-free conditions. The completely chemoselective alcohol
oxidation of allylic alcohols with H to generate carbonyl
compounds has been little reported, as far as we know. In general,
2 2
O
9
10
2
.
epoxidation of allylic alcohols easily proceeds with H
2
O
We
here report a practical method for the synthesis of a,b-unsaturated
c
d
4
94
92
carbonyl compounds from the selective oxidation of allylic
0
alcohols using aqueous H O catalyzed by easily reusable Pt
2 2
5
e
6
84
under organic solvent-free conditions with high yield and
selectivity. Although H is generally decomposed in the presence
2 2
O
1b
of trace transition metals, Pt black works surprisingly well as a
catalyst in the present method.
7
91
97
The operation is very simple, even on a hectogram-scale
synthesis as shown in Scheme 1. Cinnamyl alcohol (100 g) and a
f
8
0
.01 molar amount of Pt black were stirred in open air at 90 uC for
f,g
9
97
2 2
10 min, and then a 1.1 molar amount of aqueous 5% H O was
slowly added dropwise. The mixture was stirred at 90 uC for 3 h to
give cinnamaldehyde in a 94% yield (92.6 g). Epoxidation of
g
0
1
.99
2 2
cinnamyl alcohol was not observed. Without the use of H O
a
Unless otherwise stated, reaction was run using alcohol (10 mmol),
2 2
% H O , and Pt black in a 100 : 110 : 1 molar ratio at 90 uC for
b
National Institute of Advanced Industrial Science and Technology
AIST), Tsukuba Central 5 Higashi 1-1-1, Tsukuba, Ibaraki, Japan.
E-mail: k.sato@aist.go.jp; Fax: +81 29 861 4852; Tel: +81 29 861 4852
Electronic supplementary information (ESI) available: experimental
5
(
3
h. Determined by GC analysis. Based on alcohol charged.
c
d
Reaction was run using 100 g of alcohol (0.745 mol). Isolated
{
e
yield after distillation. Alcohol : H
:
f
:Pt = 33 : 100 : 1. Alcohol
H O : Pt = 33 : 67 : 1. 30% H O was used.
2 2 2 2
2
O
2
procedure and characterization data for compounds. See DOI: 10.1039/
b708612a
g
This journal is ß The Royal Society of Chemistry 2007
Chem. Commun., 2007, 4399–4400 | 4399

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3
R. A. Sheldon, CHEMTECH, 1991, 566.
4 For review of alcohol oxidation with MnO
Synthesis, 1976, 65. Oxidation of allylic alcohol with CrO
Table 2 Oxidation of cinnamyl alcohol with H
black
2
O
2
catalyzed by Pt
a
2
, see: (a) A. J. Fatiadi,
Cl , see: (b)
2
2
Reused number
1
2
3
4
5
6
7
K. B. Sharpless and K. Akashi, J. Am. Chem. Soc., 1975, 97, 5927.
Oxidation with DMSO–trifluoroacetic acid anhydride, see: (c)
K. Omura, A. K. Sharma and D. Swern, J. Org. Chem., 1976, 41,
b
%
Yield of cinnamaldehyde
96
92
90
90
91
97
97
a
957. Oxidation with (C
G. Schmidt, Tetrahedron Lett., 1979, 399.
5 (a) B. M. Trost, Science, 1991, 254, 1471; (b) R. A. Sheldon, Chem. Ind.,
992, 903.
5 5 2 2 7
H NH) Cr O , see: (d) E. J. Corey and
2 2
Reaction was run using cinnamyl alcohol (10 mmol), 5% H O ,
and Pt black in a 30 : 33 : 1 molar ratio at 90 uC for 5 h.
Determined by GC analysis. Based on alcohol charged.
b
1
6
(a) J. O. Metzger, Angew. Chem., Int. Ed., 1998, 37, 2975; (b)
P. T. Anastas and J. C. Warner, Green Chemistry, Theory and
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a,b-unsaturated ketone (Entry 9). Benzyl alcohol was easily
oxidized in this catalytic system (Entry 10). Interestingly, the
alcohol oxidation of allylic alcohols having a terminal double
bond, like 1-hexen-3-ol, did not proceed at all, nor did epoxidation.
While the oxidation of trans-2-hexen-1-ol with H
Pt black resulted in the formation of trans-2-hexenal in a 81% yield
Table 1, Entry 1), the addition of 1-hexen-3-ol or 1-hexene
retarded this oxidation of trans-2-hexen-1-ol (trans-2-hexenal in
3% yield with 1-hexen-3-ol and in 26% yield with 1-hexene). This
result indicates that the strong coordination of terminal olefin to
2 2
O catalyzed by
7
8
(a) G. Strukul, Catalytic Oxidations with Hydrogen Peroxide as Oxidant,
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Chem., 1996, 61, 8310; (b) K. Sato, M. Aoki, J. Takagi and R. Noyori,
J. Am. Chem. Soc., 1997, 119, 12386; (c) K. Sato, M. Aoki, M. Ogawa,
T. Hashimoto, D. Penyella and R. Noyori, Bull. Chem. Soc. Jpn., 1997,
(
4
0
13
7
(
3
0, 905; (d) K. Sato, M. Aoki and R. Noyori, Science, 1998, 281, 1646;
e) K. Sato, J. Takagi, M. Aoki and R. Noyori, Tetrahedron Lett., 1998,
9, 7549; (f) K. Sato, M. Aoki, J. Takagi, K. Zimmermann and
Pt largely retards the alcohol oxidation of allylic alcohols. The
oxidation of cinnamyl alcohol was completely stopped by the
removal of Pt black from the reaction solution. This result
indicates that any Pt species that may have leached into the
reaction solution were not active homogeneous catalysts.
R. Noyori, Bull. Chem. Soc. Jpn., 1999, 72, 2287; (g) K. Sato, M. Hyodo,
J. Takagi, M. Aoki and R. Noyori, Tetrahedron Lett., 2000, 1439; (h)
K. Sato, M. Hyodo, M. Aoki, X.-Q. Zheng and R. Noyori,
Tetrahedron, 2001, 57, 2469; (i) Y. Usui and K. Sato, Green Chem.,
2003, 5, 373; (j) Y. Usui, K. Sato and M. Tanaka, Angew. Chem., Int.
Ed., 2003, 42, 5623.
Pt black catalyst was easily reused in the oxidation of cinnamyl
9
alcohol. After the first alcohol oxidation, the catalyst was filtrated
and washed with water, then reused for the second reaction. Seven
cycles of oxidation could be catalyzed by reused Pt black without
decrease of its catalytic activity. Yields of each reaction were
mostly over 90%, as shown in Table 2.
9 R. Anderson, K. Griffin, P. Johnston and P. L. Alsters, Adv. Synth.
Catal., 2003, 345, 517.
1
0 (a) T. Hori and K. B. Sharpless, J. Org. Chem., 1978, 43, 1689; (b)
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11 A complex mixture containing benzaldehyde, benzoic acid, and other
carboxylic acids was formed.
This catalytic chemoselective oxidation of allylic alcohols to
form a,b-unsaturated carbonyl compounds is a green method
under organic solvent-free conditions. The catalyst is easily
reusable with simple manipulation. This green route is straightfor-
ward, effective, and environmentally conscious, meeting with the
requirements of modern organic synthesis.
1
2 Although the oxidation of cinnamyl alcohol to cinnamaldehyde with O
(or air) has been reported, organic solvents and/or base are necessary to
2
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Rev., 2004, 104, 3037; (b) M. Matsumoto and N. Watanabe, J. Org.
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2
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0
13 Coordination ability of terminal double bond to Ni complex, see:
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2
4
400 | Chem. Commun., 2007, 4399–4400
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