Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:1342–1345, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.609216
Effective Oxidation of Alcohols under Heterogeneous
Conditions with a New Reagent: Manganese Dioxide
Supported on Graphite
1
,2
1
1
2
1
Ji-Dong Lou, Xiu Lian Lu, Li-Hong Huang, Qiang Wang, and Xiao-Nan Zou
1
College of Life Sciences, China Jiliang University, Hangzhou, Zhejiang, P. R. China
Sirnaomics, Inc., Gaithersburg, Maryland, USA
2
of organic products or solvents by solid materials. Other advan-
A new reagent, manganese dioxide supported on graphite, un- tages of solid-supported reagents in organic synthesis are mainly
der heterogeneous conditions at reflux is described for the oxidation that the reactions are normally carried out in common organic
of benzylic and allylic alcohols into the corresponding aldehydes
and ketones, respectively. The main advantage of the present ox-
volves decantation or filtration to remove the spent solid support
idation is that the insoluble solid support, graphite, provides a
solvents, and the isolation of the organic products simply in-
system, followed by evaporation of the solvent. Furthermore,
particular reaction environment capable of enhancing the reaction
selectivity and reactivity. Moreover, it turns out to be very prof- it should be possible in many cases involving solid-supported
itable in the workup, which becomes reduced to a mere filtration. reagents to regenerate the active reagent directly from the spent
The mechanism for this oxidation is also discussed.
support system by standard inorganic reactions. It is well known
that many reactions can be carried out cleanly, rapidly, and in
high yield under mild conditions using solid-supported reagents,
whereas attempts to carry out the same reactions with unsup-
Keywords benzylic and allylic alcohols, graphite, manganese diox-
ide, oxidation, supported reagent
ported reagents frequently either fail or result in the formation
of mixtures of products. In most cases, solid-supported reagents
have been found superior to the nonsupported reagents.
INTRODUCTION
Oxidation of alcohols to the corresponding carbonyl com-
pounds is a fundamental transformation in organic synthesis.
Because of its significant role, the development of newer meth- EXPERIMENTAL
ods or reagents is attracting much current interest in spite of the
Preparation of Active Manganese Dioxide Supported on
Graphite Reagent
availability of numerous procedures reported in the literature.
However, a drawback of most oxidants in the oxidation is their
Active manganese dioxide is prepared according to the pre-
lack of selectivity, for instance, overoxidation of aldehydes to
vious references.[
4–6]
Potassium permanganate (1.9 g) was dis-
carboxylic acids and degradation of unsaturated substrates are
often unavoidable side reactions. In addition to their lack of se-
lectivity, oxidants like chromium-based reagents are corrosive,
irritants, toxic, etc.
solved in water (50 mL) at room temperature, graphite (30 g)
◦
was added with stirring, and the water is evaporated at 60 C. The
residue was ground to fine powder and then added to a solution
of manganese sulfate monohydrate (4.7 g) in water (50 mL) with
vigorous stirring. After the resulting precipitate was filtered and
It has been found that reagents supported on insoluble solid
supports, such as inorganic and polymeric supports, are partic-
ularly convenient for solving many problems in organic synthe-
◦
dried at 100 C for 4 h, 32.1 g of manganese dioxide supported
[1–3]
on graphite reagent is obtained. Each gram of this supported
reagent contains around 0.78 mmol manganese dioxide.
sis.
One important aspect of reactions with solid supported
reagents is that in many cases both the reagent and the product
into which it is converted during reaction are strongly adsorbed
on the surface of the solid support or remain intercalated in
it; therefore, there is very little or probably no contamination
Oxidation of Benzyl Alcohol to Benzaldehyde, Typical
Procedure
The preceding manganese dioxide supported on graphite
reagent (2.4 g) is placed in a flask together with dichloromethane
(
25 mL) and the mixture is magnetically stirred. A solution of
Received 4 May 2011; accepted 26 July 2011.
Address correspondence to Ji-Dong Lou, College of Life Sciences,
China Jiliang University, Hangzhou, Zhejiang 310018, P. R. China.
E-mail: lou@cjlu.edu.cn
benzyl alcohol (108 mg, 1 mmol) in dichloromethane (5 mL) is
added and after 10 h at reflux the solid is filtered and washed
with dichloromethane (3 × 5 mL). The combined filtrates are
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