Selective oxidation of alcohols with a new reagent: Iron(III) nitrate supported on aluminum silicate

Article abstract of DOI:10.1080/00397910701771173

A selective and effective oxidation of alcohols, except aliphatic alcohols, such as 1-hexanol or 1-octyl alcohol, to the corresponding aldehydes and ketones using a new reagent, iron(III) nitrate supported on aluminum silicate, under heterogeneous conditions with reflux with 85-98% yield is described. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701771173

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Synthetic Communications , 38: 428–433, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701771173
Selective Oxidation of Alcohols with a New
Reagent: Iron(III) Nitrate Supported on
Aluminum Silicate
1
Ji-Dong Lou, Li-Hong Huang, Aizen J. Marrogi, Feng Li,
1
2
3
3
Li Li, and Chun-Ling Gao
4
1
College of Life Sciences, China Institute of Metrology, Hangzhou,
Zhejiang, China
2
Department of Pathology and Area Laboratory Medicine, Walter Reed
Army Medical Center, Washington, DC, USA
3
School of Chemistry, University of Sydney, NSW, Australia
Center for Prostate Disease Research, Uniformed Service University of
Health Science, Bethesda, Maryland, USA
4
Abstract: A selective and effective oxidation of alcohols, except aliphatic alcohols,
such as 1-hexanol or 1-octyl alcohol, to the corresponding aldehydes and ketones
using a new reagent, iron(III) nitrate supported on aluminum silicate, under hetero-
geneous conditions with reflux with 85–98% yield is described.
Keywords: alcohol, aluminum silicate, iron (III), nitrate nonahydrate, oxidation
INTRODUCTION
.
Iron(III) nitrate nonahydrate [Fe(NO3)3 9H O], a relatively nontoxic
2
chemical, has been widely used as a multipurpose reagent for the transform-
ation of a variety of organic functional groups. For example, the selective
oxidation of alcohols, oxidative coupling of thiols, carbonyl group depro-
tections, synthesis of azides and iminophosphoranes, aromatization of
Received in the USA August 2, 2007
Address correspondence to Chun-Ling Gao, Center for Prostate Disease Research,
Uniformed Service University of Health Science, 4301 Johns Bridge Road, Bethesda,
Maryland 20814, USA. E-mail: gao-cl@sohu.com
4
28

Selective Oxidation of Alcohols with a New Reagent
429
1
reported using this reagent.
,4-dihydropyridines, and regioselective nitration of phenols have all been
[
1]
So far, iron(III) nitrate nonahydrate supported on several inorganic
materials has been employed as an oxidizing reagent for the selective
oxidation of primary and secondary alcohols to the corresponding aldehydes
and ketones. Typical examples reported in the literature are iron(III) nitrate
[
2]
[3]
[4]
[5]
supported on K 10-clay, silica gel, graphite, and kieselguhr. These
supported reagents have achieved good selectivity under mild reaction con-
ditions and convenient isolation of the products. Although a diversity of
.
[Fe(NO3)3 9H O] supported reagents described previously are available
2
for the oxidation transformation, they have some common stability
problems. Therefore, to develop new methods or reagents is still an interested
topic for organic chemists, especially in the search of stable, versatile, and
selective oxidants such as iron(III) nitrate-based reagents.
RESULTS AND DISCUSSION
Previously, we have described that aluminum silicate is a good inorganic solid
[
6]
[7]
support of both chromic acid and potassium permanganate for the
selective oxidation of alcohols to carbonyl compounds. In connection with
[
6,7]
our previous studies,
we now report that iron(III) nitrate supported on
aluminum silicate is a new reagent suitable for the selective oxidation of
primary and secondary alcohols (1) into the corresponding aldehydes and
ketones (2) (Scheme 1).
The present reagent is easily prepared. First, the acetone solvate of iron(III)
nitrate nonahydrate is obtained by concentration under vacuum of an acetone
solution of iron(III) nitrate nonahydrate. It seems that the solvate is in a
viscous form with a brown color, to which aluminum silicate is added.
Rotary evaporation of the solvent under vacuum affords the desired powdered
reagent. In our cases, the temperature of the reaction procedure was kept
colder than 358C, since at higher temperatures it will lead to an unstable
[1]
reagent, which will decompose with evolution of nitrogen dioxide. The
process for the oxidation is very simple. After combining the alcohols with
the iron(III) nitrate hydrate supported on aluminum silicate, the mixture was
refluxed and the expected products were obtained. In our cases, a 1 to 1.2
molar ratio of the substrate to the oxidant was employed, and except
Scheme 1.

4
30
J.-D. Lou et al.
oxidation of cyclohexanol, the reactions were completed within 1 h with high
yield, for instance, 98% yield for the oxidation of benzyl alcohol to benzal-
dehyde. Meanwhile, we have observed that aliphatic alcohols, such as
1-hexanol or 1-octyl alcohol, were not efficiently oxidized under these con-
ditions, even though they had been performed at longer reaction time. The
mechanism of the present oxidation is the same as the well-known one
[1]
described previously in the literature. Our results are listed in Table 1.
Comparing with some of the other existing iron(III) nitrate hydrate –
supported reagents cited previously, the main advantage of the present
method is that the solid reagent is more stable, which means it can be
stored in a dark brown vacuum desiccator at room temperature at least 3
months without loss of activity. In addition, the reaction time of the present
oxidation is comparatively shorter.
CONCLUSION
In conclusion, the present iron(III) nitrate nonahydrate supported on
aluminum silicate reagent under heterogeneous conditions with reflux is a
new and efficient method for the oxidation of primary and secondary
alcohols to the corresponding aldehydes and ketones, except oxidation of
aliphatic alcohols, such as 1-hexanol or 1-octyl alcohol.
EXPERIMENTAL
Preparation of Iron(III) Nitrate Supported on Aluminum Silicate
Reagent
.
Fe(NO3)3 9H O (4 g, 10 mmol) is added to acetone (60 mL), and the mixture
2
is stirred vigorously for 10 min. Aluminum silicate (15 g; D50: ꢀ1.5 micron;
3
d: 2.1 g/cm ; Sasin Chemical New Material Co., Ltd.) is then added in small
amounts, and stirring is continued for another 10 min. The solid (18.3 g),
Fe(NO ) -aluminum silicate reagent, which can be directly used for
3
3
oxidation, is obtained by evaporation of the solvent from the resulting suspen-
sion in a rotary evaporator at temperatres less than 358C under vacuum. This
new Fe(NO ) -aluminum silicate reagent can be stored in a dark brown
3
3
vacuum desiccator without losing activities.
Oxidation of Benzyl Alcohol to Benzaldehyde
The Fe(NO ) -aluminum silicate reagent (2.2 g) is placed in a flask together
3
3
with CH Cl (15 mL), and the mixture is magnetically stirred. A solution of
2
2
benzyl alcohol (108 mg, 1 mmol) in CH Cl (3 mL) is added, and after 1 h
2
2

Table 1. Oxidation of alcohols with iron(III) nitrate supported on aluminum silicate reagent
Mp/8C of 2,4-DNP
Found Reported
237
Reaction time
(h)
a
b
c
Yield (%)
[8]
Substrate
Product
PhCH
2
OH
PhCH 55 CHCH OH
1
1
1
1
1
3
PhCHO
PhCH 55 CHCHO
p-H CO-C -CHO
CH 55 CHC(O)CH
CH CH C(O)CH
98
93
90
89
85
86
236–239
255–256
253–254
255
254
2
p-H
CH
CH CH CH(OH)CH
3
CO-C
6
H
4
-CH
2
OH
3
6
H
4
2
55 CHCH(OH)CH
3
2
3
139–140.5
113.5–115
160–163
139.5–140.5
115
161–162
3
2
3
3
2
3
d
d
PhCH(OH)Ph
1
PhC(O)Ph
98
47–49
48–49
a
All the substrates are commercially available.
b
All the aldehydes and ketones have been described previously in the literature and were identified by their IR spectra or by the IR spectra and
melting points of their 2,4-dinitrophenylhydrazones.
c
Yield of isolated product.
d
Mp of benzophenone.

4
32
J.-D. Lou et al.
at gentle reflux, the solid is filtered and washed with CH Cl (3 Â 5 mL). The
2
2
combined filtrates are evaporated to give crude product, which is purified by
preparative thin-layer chromatgraphy (TLC) with hexane–ethyl acetate (8:2)
to afford 104 mg (98%) of benzaldehyde.
Oxidation of 3-Phenyl-2-propentol to 3-Phenyl-2-propental
The Fe(NO ) -aluminum silicate reagent (2.2 g) is placed in a flask together
3
3
with CH Cl (15 mL), and the mixture is magnetically stirred. A solution of
2
2
3-phenyl-2-propentol (134 mg, 1 mmol) in CH Cl (3 mL) is added, and
after 1 h at gentle reflux, the solid is filtered and washed with CH Cl
2 2
2
2
(
3 Â 5 mL). The combined filtrates are evaporated to give crude product,
which is purified by preparative TLC with hexane–ethyl acetate (8:2) to
afford 123 mg (93%) of 3-phenyl-2-propental.
Oxidation of 4-Methoxybenzyl Alcohol to 4-Methoxybenzaldehyde
The Fe(NO ) -aluminum silicate reagent (2.2 g) is placed in a flask together
3
3
with CH Cl (15 mL) and the mixture is magnetically stirred. A solution of
2
2
4
and after 1 h at gentle reflux, the solid is filtered and washed with CH Cl
-methoxybenzyl alcohol (138 mg, 1 mmol) in CH Cl (3 mL) is added,
2 2
2
2
(
3 Â 5 mL). The combined filtrates are evaporated to give crude product,
which is purified by preparative TLC with hexane–ethyl acetate (8:2) to
afford 122 mg (90%) of 4-methoxybenzaldehyde.
Oxidation of 3-Buten-2-ol to 3-Buten-2-one
The Fe(NO ) -aluminum silicate reagent (4.4 g) is placed in a flask together
3
3
with CH Cl (15 mL), and the mixture is magnetically stirred. A solution of
2
2
3-buten-2-ol (144 mg, 2 mmol) in CH Cl (3 mL) is added, and after 1 h at
2 2
gentle reflux, the solid is filtered and washed with CH Cl (3 Â 5 mL). The
2
2
combined filtrates are evaporated to give crude product, which is purified
by preparative TLC with hexane–ethyl acetate (8:2) to afford 124 mg
(
89%) of 3-buten-2-one.
Oxidation of 2-Butanol to 2-Butanone
The Fe(NO ) -aluminum silicate reagent (4.4 g) is placed in a flask together
3
3
with CH Cl (15 mL), and the mixture is magnetically stirred. A solution of
2
2
2-butanol (148 mg, 2 mmol) in CH Cl (3 mL) is added, and after 1 h at
2 2
gentle reflux, the solid is filtered and washed with CH Cl (3 Â 5 mL). The
2
2

Selective Oxidation of Alcohols with a New Reagent
433
combined filtrates are evaporated to give crude product, which is purified by
preparative TLC with hexane–ethyl acetate (8:2) to afford 122 mg (85%) of
2
-butanone.
Oxidation of Cyclohexanol to Cyclohexanone
The Fe(NO ) -aluminum silicate reagent (2.2 g) is placed in a flask together
3
3
with CH Cl (15 mL), and the mixture is magnetically stirred. A solution of
2
2
cyclohexanol (100 mg, 1 mmol) in CH Cl (3 mL) is added, and after 3 h at
2
2
gentle reflux, the solid is filtered and washed with CH Cl (3 Â 5 mL). The
2
2
combined filtrates are evaporated to give crude product, which is purified
by preparative TLC with hexane–ethyl acetate (8:2) to afford 84 mg (86%)
of cyclohexanone.
Oxidation of Diphenylmethanol to Benzophenone
The Fe(NO ) -aluminum silicate reagent (2.2 g) is placed in a flask together
3
3
with CH Cl (15 mL), and the mixture is magnetically stirred. A solution of
2
2
diphenylmethanol (184 mg, 1 mmol) in CH Cl (3 mL) is added, and after
2
2
1
h at gentle reflux, the solid is filtered and washed with CH Cl2
2
(
3 Â 5 mL). The combined filtrates are evaporated to give crude product,
which is purified by preparative TLC with hexane–ethyl acetate (8:2) to
afford 178 mg (98%) of benzophenone.
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1
2
3
4
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