TEMPO-mediated environmentally benign oxidation of primary alcohols to carboxylic acids with poly[4-(diacetoxyiodo)styrene]

Article abstract of DOI:10.1055/s-2004-830881

An operationally simple and environmentally benign oxidation of primary alcohols to the corresponding carboxylic acids with a TEMPO-mediated poly[4-(diacetoxyiodo)styrene] system in acetone and water was carried out.

Full text of DOI:10.1055/s-2004-830881

2
010
LETTER
TEMPO-Mediated Environmentally Benign Oxidation of Primary Alcohols to
Carboxylic Acids with Poly[4-(diacetoxyiodo)styrene]
a
a,b
T
Y
EMPO-Mediated
o
E
nvironmen
u
tally Benign
s
O
xidation
u
of Primary
k
A
lcohols e Tashino, Hideo Togo*
a
Graduate School of Science and Technology, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522 Japan
b
Department of Chemistry, Faculty of Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522 Japan
E-mail: togo@faculty.chiba-u.jp
Received 9 April 2004
the other hand, oxidation of primary alcohols to carboxy-
lic acids with metal-free, less toxic reagents, instead of
Jones oxidation, is also important, therefore, the study of
Abstract: An operationally simple and environmentally benign ox-
idation of primary alcohols to the corresponding carboxylic acids
with a TEMPO-mediated poly[4-(diacetoxyiodo)styrene] system in
acetone and water was carried out.
6
TEMPO-mediated direct oxidation of primary alcohols to
the carboxylic acids with metal-free less toxic reagent has
been studied.2 However, study on a polymer-supported
reagent system for the oxidation of alcohols is rather lim-
ited.2 TEMPO-mediated oxidation of alcohols to the
Key words: oxidation, alcohol, carboxylic acid, aldehyde, TEMPO,
poly[4-(diacetoxyiodo)styrene], environmentally benign
c,d,j
l–q
corresponding carboxylic acids with NaOCl or NaClO is
2
Oxidation of hydroxyl groups to carbonyl groups are fun-
damental and important for functional group transforma-
tion in organic synthesis. One most useful approach is the
chemoselective oxidation of alcohols with N-oxoammoni-
um salts. Especially, oxidation of alcohols to ketones, al-
dehydes, and carboxylic acids using a catalytic amount of
rather complicated in experimental operation, i.e., such as
preparation of aqueous basic phosphate buffer solution,
1
7
etc. Recently, Widlanski reported the TEMPO-mediated
oxidation of 5¢-hydroxymethyl groups in 2¢,3¢-isopropyl-
idene protected purine- and pyrimidine-containing nu-
cleosides to the corresponding nucleoside-5¢-carboxylic
2
,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)
acids in good yields, with PhI(OAc) in a mixture of
2
and a stoichiometric amount of an oxidant is very attrac-
tive, because the reactions can be carried out under mild
and neutral reaction conditions, giving high yield of prod-
ucts with high chemoselectivity. Therefore, TEMPO-me-
diated oxidation of alcohols to aldehydes and ketones
together with a stoichiometric amount of a metal-free ox-
8
acetonitrile and water. Kita et al. reported the oxidation
of primary alcohols to the corresponding carboxylic acids
9a
and esters with PhIO–KBr, PSDIB–KBr in water and
9b
methanol , respectively. As a part of our study on envi-
ronmentally friendly organic synthesis with polymer-sup-
ported hypervalent iodines, we would like to report an
operationally simple and environmentally benign oxida-
tion of primary alcohols to the corresponding carboxylic
acids, using a TEMPO-mediated PSDIB system at room
temperature. Here, the reactive species, N-oxoammonium
salt, is formed in situ by the oxidation of TEMPO with
PSDIB.
2
idant has been extensively studied. Here, generally reac-
tive N-oxoammonium salt is generated in situ by the
oxidation of TEMPO with an oxidant. Hypervalent io-
dines also work as an oxidant for TEMPO-mediated oxi-
dation of alcohols to aldehydes or ketones. This system is
useful since hypervalent iodines are non-metallic, less
toxic, and easily handled oxidants. Recently, TEMPO-
mediated PhI(OAc) oxidation of alcohols to aldehydes As shown in Table 1, TEMPO-mediated oxidative con-
2
and ketones in high yields with high chemoselectivity un- version of primary alcohols with PSDIB proceeds
3
der mild reaction conditions was reported, especially by smoothly at room temperature, to provide the correspond-
3
a
Piancatelli, and 1,5-diols gave the corresponding g-lac- ing carboxylic acids in high yields. The oxidative conver-
3
c
tones under the same conditions. As a part of our study sion did not proceed at all without TEMPO (entry 1). The
4
on polymer-supported hypervalent iodines, we have re- reaction with 0.1 equiv of TEMPO was rather slow (entry
cently reported the TEMPO-mediated oxidation of alco- 2), and the reaction with 0.5 equiv of TEMPO was the
hols to the corresponding aldehydes and ketones with most effective (entry 3). When the present TEMPO-medi-
5
poly[4-(diacetoxyiodo)]styrene (PSDIB). Primary and ated oxidation was carried out in a mixture of acetone and
secondary alcohols were successfully oxidized to the cor- water, or a mixture of acetonitrile and water, the yield of
responding aldehydes and ketones in good yields in a carboxylic acid was decreased. This reason may come
small amount of an acetone solvent, and the products were from that the granular PSDIB becomes the paste by the
obtained by simple filtration of the reaction mixture, and, addition of water. Therefore, it is important that a small
moreover, the recovered poly(4-iodostyrene) could be re- amount of acetone (1 mL) alone is used in the initial oxi-
generated to PSDIB and reused for the same oxidation. On dation of alcohols to the aldehydes, and then, a small
amount of water (1–3 mL) is added to the reaction mixture
SYNLETT 2004, No. 11, pp 2010–2012
Advanced online publication: 04.08.2004
DOI: 10.1055/s-2004-830881; Art ID: U09704ST
0
6
.0
9
.2
0
0
4
for the formation of the corresponding carboxylic acids
effectively. Here, only a small amount of acetone and
subsequent water is required as a solvent, and carboxylic
©
Georg Thieme Verlag Stuttgart · New York

LETTER
TEMPO-Mediated Environmentally Benign Oxidation of Primary Alcohols
2011
Table 1 Oxidation of Alcohols to Carboxylic Acids with TEMPO-
Table 2 Oxidation of Aldhehyde to Carboxylic Acid with PSDIB
Mediated PSDIB System
PS
I(OAc)2 (1.2 equiv)
CHO
CO2H
PS
I(OAc)2 (2.0 equiv)
TEMPO
TEMPO (0.5 equiv)
acetone (1 mL), r.t.
acetone (1 mL),
H O (3 mL), r.t., 24 h
2
R
CH2OH
R
CHO
B1
C1
A
B
H2O (3 mL)
r.t., 24 h
TEMPO
Yields
R
CO2H
C
B
1
C
1
Entry Substrate
Time (A to B, h) Yield of C (%)
–
51
29
82
91
1
2
3
4a
4
0c,d
54
95
0.2 Equiv
0.5 Equiv
5
b
c,e
c
Trace
2 OH
4
4
3
92
3
4
OH
OH
erated by the oxidation with peracetic acid, prepared from
the reaction of hydrogen peroxide and acetic anhydride,
and the regenerated PSDIB can be reused without any loss
of activity for the same oxidation of alcohols to carboxylic
acids. Aldehydes can be also oxidized to the correspond-
ing carboxylic acids smoothly by the same treatment with
TEMPO and PSDIB, and a typical example is shown in
Table 2. Here again, addition of TEMPO promotes the
oxidation of aldehydes to the corresponding carboxylic
acids. Thus, the present method is an operationally simple
and environmentally benign oxidation of the primary al-
cohols to the corresponding carboxylic acids. Further
elaboration of the TEMPO-mediated PSDIB oxidation of
alcohols is now under way in this laboratory.
5
6
3
3
3
83
82
77
OH
O
7
OH
CH3
8
9
0
2
9
5
74
78
73
Cl
OH
OH
1
OH
CH (CH ) OH
Typical Procedures are as follows.
Oxidation of Alcohols to Carboxylic Acids: TEMPO (0.5
mmol) was added to a stirred mixture of 3-phenyl-1-propanol (1
mmol) and PSDIB (2.0 mmol, loading rate ca. 1.7 mmol/g) in ace-
tone (1 mL), and the mixture was stirred for 4 h at r.t. Water (1 mL)
was added to the mixture which solution was then stirred for 24 h.
1
1
1
1
2
3
5
6
4
81
82
85
10
3
2 7
CH (CH ) OH
3
2 12
OH
O
After the reaction, the mixture was diluted with Et O (5 mL), HCl
2
1
1
4
5
4
6
84
(1 N, 3 mL) was added, and then the obtained mixture was stirred
for 10 min. The mixture was filtered to remove the polymer species
and was washed with Et O. The filtrate was extracted with Et O
8
OH
58f
2
2
OH
three times. The combined organic layer was dried over Na SO and
2 4
filtered, and then the solvent was removed to give 3-phenylpropion-
ic acid as a crude state. Pure 3-phenylpropionic acid was obtained
by short column chromatography on silica gel (142 mg, 95%, mp
16
4
71
OH
4
8 °C).
a
b
c
d
e
f
Without TEMPO.
TEMPO (0.1 equiv).
mL of H O was used.
Alcohol was recovered in 88% yield.
Aldehyde was obtained in 31% yield.
Oxidation of Aldehydes to Carboxylic Acids:10 Water (3 mL) was
added to a stirred mixture of 3-phenylpropionaldehyde (1 mmol),
PSDIB (1.2 mmol), and TEMPO (0.5 mmol) in acetone (1 mL), and
the mixture was stirred for 24 h at r.t. After the reaction, the mixture
1
2
was diluted with Et O (5 mL), HCl (1 N, 3 mL) was added, and then
2
Reaction time (B to C) was 72 h, and 3.0 equiv of PSDIB were used,
the obtained mixture was stirred for 10 min. The mixture was fil-
and aldehyde was obtained in 27% yield.
tered to remove the polymer species and was washed with Et O. The
2
filtrate was extracted with Et O three times. The combined organic
2
layer was dried over Na SO and filtered, and then the solvent was
acids can be obtained by filtration of the reaction mixture,
followed by extraction from the filtrate with diethyl ether.
The used PSDIB is recovered quantitatively as poly(4-io-
dostyrene) by simple filtration, and PSDIB can be regen-
2
4
removed to give 3-phenylpropionic acid as a crude state. Pure 3-
phenylpropionic acid was obtained by short column chromatogra-
phy on silica gel (136 mg, 91%, mp 48 °C).
Synlett 2004, No. 11, 2010–2012 © Thieme Stuttgart · New York

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012
Y. Tashino, H. Togo
LETTER
Acknowledgment
Doren, H. R.; Gotlieb, K. F.; Bleeker, I. P. Carbohydr. Res.
1
1
997, 299, 221. (m) Bolm, C.; Fey, T. Chem. Commun.
999, 1795. (n) Dijksman, A.; Arends, I. W. C. E.; Sheldon,
Financial support from a Grant-in-Aid for Scientific Research (No.
1
3554028) from the Ministry of Education, Science, Sports and
R. A. Chem. Commun. 2000, 271. (o) Weik, S.; Nicholson,
G.; Jung, G.; Rademann, J. Angew. Chem. Int. Ed. 2001, 40,
Culture of Japan is gratefully acknowledged.
1436. (p) Tanyeli, C.; Gümüs, A. Tetrahedron Lett. 2003,
4
4, 1639. (q) Pozzi, G.; Cavazzini, M.; Quici, S.; Benaglia,
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Synlett 2004, No. 11, 2010–2012 © Thieme Stuttgart · New York