Vanadium-catalyzed selective oxidation of alcohols to aldehydes and ketones with terf-butyl hydroperoxide

Article abstract of DOI:10.1002/adsc.200600397

The oxidation of alcohols to aldehydes and ketones has been described using silica-supported vanadium(IV) oxide (V/SiO₂,1) in the presence of terf-butyl hydroperoxide in tert-butyl alcohol at ambient temperature with quantitative yields. The procedure is simple, efficient and environmentally benign.

Full text of DOI:10.1002/adsc.200600397

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DOI: 10.1002/adsc.200600397
Vanadium-Catalyzed Selective Oxidation of Alcohols to
Aldehydes and Ketones with tert-Butyl Hydroperoxide
a
a
a,
Laxmidhar Rout, Pinku Nath, and Tharmalingam Punniyamurthy *
a
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India
Fax : (+91)-361-2690762; e-mail: tpunni@iitg.ernet.in
Received: August 7, 2006
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: The oxidation of alcohols to aldehydes
and ketones has been described using silica-sup-
ported vanadium(IV) oxide (V/SiO , 1) in the pres-
2
ence of tert-butyl hydroperoxide in tert-butyl alco-
hol at ambient temperature with quantitative yields.
The procedure is simple, efficient and environmen-
tally benign.
Scheme 1.
Keywords: alcohols; tert-butyl hydroperoxide; cata-
lyst; oxidation; vanadium
tions usually take place with 100% conversion, after
filtering the catalyst 1, the filtrate could be evaporat-
ed to provide the aldehydes or ketones as the only
products.
The oxidation of p-anisyl alcohol was first studied
The oxidation of alcohols to aldehydes and ketones is as a standard substrate using 1 in the presence of t-
one of the fundamental processes in organic synthe- BuOOH at ambient temperature (Table 1). We were
[
1,2]
sis.
The traditional methods for this purpose usual- pleased to find that the reaction occurred to afford p-
ly employ stoichiometric quantities of inorganic re- anisaldehyde in quantitative yield when it was al-
agents such as chromate and permanganate, which lowed to stir with 15 mg of 1 (5 mol% V) and
often generate significant amount of inorganic salt- 1.2 equivs. of t-BuOOH (5M in decane) for 3 h in t-
[
3]
containing effluent along with the target molecules.
Removal of traces of these effluents from the reaction
mixture is often difficult and demands laborious Table 1. Oxidation of anisyl alcohol.
work-up procedures. To circumvent this problem,
much attention has been recently focused on the
design and development of catalytic systems, especial-
ly without reducing agents in ecologically benign con-
ditions to reduce the environmental impact of the
[a]
[
4–13]
process (E factor).
During the course of our inves-
[
13]
tigation on the oxidation of organic compounds, we
found that the silica-supported vanadium(IV) oxide 1
catalyzed efficiently the oxidation of heteroatoms
[
14]
with 30% H O in high yields. Since the catalyst 1
2
2
is readily accessible, cheap and provides simplified
product isolation, we wanted to further explore its ap-
plication to other reactions. In this contribution, we
report the oxidation of alcohols to aldehydes and ke-
tones in the presence of tert-butyl hydroperoxide (t-
BuOOH) in tert-butyl alcohol (t-BuOH) at ambient
temperature (Scheme 1). It is a clean technological
process and no additive is involved. Since the reac-
[a]
Substrate (1 mmol), ROOH (1.2 mmol) and catalyst 1
15 mg, 5 mol% V) were stirred in t-BuOH (1 mL) at
ambient temperature for 3 h.
(
[
[
b]
c]
R=p-MeOC H -.
6
4
t-BuOOH was consumed in 1 h.
846
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2007, 349, 846 – 848

Vanadium-Catalyzed Selective Oxidation of Alcohols
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BuOH. Hydrogen peroxides [30–50% H O and urea Table 2. Vanadium-catalyzed oxidation of alcohols to alde-
2
2
hydes and ketones with t-BuOOH.
hydrogen peroxide (UHP)] were also investigated as
terminal oxidants, but they are less effective providing
either no reaction or a mixture of aldehyde and car-
[
15]
boxylic acid in moderate yield (entries 3–5). Also,
the reaction with VO(acac) was found to be efficient,
AHCTREUNG
2
but less selective giving a mixture of p-anisaldehyde
and p-anisic acid in 38% and 21% yields, respective-
ly.
To study the scope of the procedure, the oxidation
of other alcohols was next studied (Table 2). Benzyl
alcohols were oxidized to give the corresponding al-
dehydes with 100% conversion (entries 1–7). The sub-
strates having electron-donating and -withdrawing
substituents in the aromatic ring were compatible
with this protocol. 9-Anthracenemethanol, 2-furanme-
thanol and 2-pyridinemethanol were transformed to
the respective aldehydes in high yields (entries 8–10).
It is noteworthy that the reactions stopped at the al-
dehyde stage without overoxidation to the carboxylic
acid. Secondary alcohols, e.g., 1-phenylethanol and
benzoin, could be converted to the respective ketones
in >99% yields (entries 11 and 12). Aliphatic alco-
hols were less reactive in comparison to aromatic al-
cohols. The oxidations of cyclohexanol and cyclodode-
canol were studied (entries 13 and 14). They required
longer reaction times and were effective in the pres-
ence of 10 mol% of 1 and 2 equivs. of t-BuOOH to
afford the corresponding ketones. Similarly, allylic al-
cohols, such as cinnamyl alcohol and geraniol, under-
went oxidation to give a mixture of the corresponding
[
16]
epoxy alcohols and aldehydes.
The difference in the reactivity of 1 with t-BuOOH
and H O might be due to the pH and nature of the
2
2
[
17]
peroxide involved in the reaction process (Table 1).
Since the systems of 50% H O /1 and t-BuOOH/
VO(acac) are found to be more acidic (pH 2.03–3.83)
2
2
A
C
H
T
R
E
U
N
G
2
than t-BuOOH/1 (pH 5.23), the former may lead to
the formation of a hydrate which would undergo sub-
sequent oxidation to its carboxylic acid. Furthermore,
peroxo complexes formed in these reactions should
also be different since their formation depends on the
[a]
Substrate (1 mmol), t-BuOOH (1.2 mmol, 5M in decane)
and catalyst 1 (15 mg, 5 mol% V) were stirred in t-
[
17]
pH of the medium.
The reaction of 1 with 50%
H O generates brown-colored species while the com-
BuOH (1 mL) at ambient temperature.
Isolated yield.
Catalyst 1 (10 mol%, 30 mg) and t-BuOOH (2 mmol)
were used.
2
2
[
[
b]
c]
bination of 1 and t-BuOOH produces a yellowcom-
plex. Thus, the electrophilic character of the peroxo
oxygen atoms might also be different leading to varia-
tion in the reactivity toward aldehydes. When these
peroxo species are quenched with Na SO or con-
2
3
sumed during the oxidation processes, the color of the
catalyst changes to its initial green color [V(IV)] curred to afford p-anisaldehyde in 95% yield. This
[18,19]
(
Scheme 2).
The solid could be then filtered and result suggests that the present system could be used
the filtrate, after evaporation, provides the corre- for medium-scale syntheses.
sponding carbonyl compounds which usually do not
require further purification.
In conclusion, the vanadium catalyst 1 has been
found to catalyze efficiently the oxidation of alcohols
Finally, the oxidation of p-anisyl alcohol was stud- to aldehydes and ketones in the presence of t-
ied on a 100-mmol scale. As above, the reaction oc- BuOOH in t-BuOH at ambient temperature. It is a
Adv. Synth. Catal. 2007, 349, 846 – 848
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www.asc.wiley-vch.de
847

Laxmidhar Rout et al.
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[
[
clean technological process and no halogenated sol-
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2
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[
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[
2
3
3
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2
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[
[
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oxidation in the absence of t-BuOOH.
848
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Adv. Synth. Catal. 2007, 349, 846 – 848