Simple system for oxidation of alcohols in aqueous solution

Article abstract of DOI:10.1080/00397910802054255

A simple and mild system for conversion of primary and secondary alcohols to corresponding aldehydes and ketones has been developed using aqueous sodium dichloroiodate at room temperature in water. This novel application of aqueous sodium dichloroiodate gives high yield and offers a number of advantages in terms of safety and ease of use in comparison to other methods that often employ toxic and hazardous solvents and materials. Copyright Taylor & Francis Group, LLC.

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Simple System for Oxidation of
Alcohols in Aqueous Solution
a
a
Vikas N. Telvekar & Nikhil C. Jadhav
a
Department of Pharmaceutical Sciences and
Technology, University Institute of Chemical
Technology, University of Mumbai , Mumbai, India
Published online: 09 Sep 2008.
To cite this article: Vikas N. Telvekar & Nikhil C. Jadhav (2008) Simple System
for Oxidation of Alcohols in Aqueous Solution, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 38:18,
3107-3111
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Synthetic Communications , 38: 3107–3111, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802054255
Simple System for Oxidation of Alcohols in
Aqueous Solution
Vikas N. Telvekar and Nikhil C. Jadhav
Department of Pharmaceutical Sciences and Technology, University Institute of
Chemical Technology, University of Mumbai, Mumbai, India
Abstract: A simple and mild system for conversion of primary and secondary
alcohols to corresponding aldehydes and ketones has been developed using aque-
ous sodium dichloroiodate at room temperature in water. This novel application
of aqueous sodium dichloroiodate gives high yield and offers a number of advan-
tages in terms of safety and ease of use in comparison to other methods that often
employ toxic and hazardous solvents and materials.
Keywords: Alcohols, aldehydes, ketones, oxidation, sodium dichloroiodide
INTRODUCTION
There are a number of methods for the conversion of alcohols to
corresponding aldehydes and ketones. Iodine and iodine reagent sys-
tems have found widespread application in organic synthesis because
of their selectivity and simplicity of use. There are few examples of
[
1–3]
the oxidation of alcohols using iodine(III) reagents.
Existing
methods are limited to organic solvents and usually involve activation
by use of Ru or Yb catalyst or 2,2,6,6-tetramethyl-1-piperidinyloxyl;
also reaction with these reagents with the organic substrate leads to
iodobenzene as the by-product, which is difficult to recover and reuse
because of its high volatility and solubility in organic solvents. In our
laboratory, we are working on hypervalent iodine systems such as
Received February 13, 2008.
Address correspondence to Vikas N. Telvekar, Department of Pharmaceutical
Sciences and Technology, University Institute of Chemical Technology, Univer-
sity of Mumbai, Matunga, Mumbai, India. E-mail: vikastelvekar@rediffmail.com
3
107

3108
V. N. Telvekar and N. C. Jadhav
[
4]
Dess-Martin periodinane (DMP) and O-iodoxy benzoic acid (IBX).
DMP and IBX are potentially explosive and hazardous to stock.
Therefore, facile and efficient use of the readily available and relatively
stable iodine(III) reagents in place of iodine(V) reagents has long
been desired.
Sodium dichloroiodate is commercially available in a 50% water
solution, and recently we used this for conversion of aldehyde to corres-
[5]
ponding nitriles. While working on this reagent, we found that it can be
used for the oxidation of primary and secondary alcohols to corres-
ponding aldehydes and ketones in water.
RESULTS AND DISCUSSION
For the initial study, benzyl alcohol was chosen as substrate, and the
reaction with 50% aqueous solution of dichloroiodate in water was per-
formed (Scheme 1). The oxidation was carried out by simple addition of
an aqueous solution of dichloroiodate to a stirred suspension of the ben-
zyl alcohol in water at room temperature. The starting material was con-
sumed within 4 h as indicated by thin-layer chromatography (TLC)
analysis. After usual workup, almost pure benzaldehyde (entry 1) was
recovered by silica-gel column chromatography using hexane–EtOAc
(8:2) as eluents.
Encouraged by these results, further development work was underta-
ken. A variety of primary and secondary aromatic and aliphatic alcohols
were prepared as per the literature procedure and subjected to the reac-
tion, and the results are presented in Table 1.
The results clearly indicated that primary aliphatic alcohols do not
undergo oxidation reaction (entries 13, 14) even after 24 h. In this case,
aromatic alcohol reaction completed within 3 to 5 h, and protective
groups such as ester and ether remained unaffected (entries 4, 5, and
6
). Aromatic as well as aliphatic secondary alcohols easily underwent
oxidation reactions and converted into ketones (entries 7–11). In this
reaction condition, the double bond was not affected (entry 12), and
no iodination of the aromatic ring was observed. An advantage of this
Scheme 1. Oxidation of benzyl alcohol to benzylaldehyde using aqueous NalCl2.

Oxidation of Alcohols in Aqueous Solution
3109
a
Table 1. Oxidation of alcohols using aqueous sodium dichloroiodate
b
Entry
1
Alcohol
Product
Time (h) Yield (%)
4.0
87
2
3
4
3.0
88
3.0
3.5
88
86
5
4.0
89
6
7
3.5
3.0
91
92
8
6.0
91
(
Continued)

3110
V. N. Telvekar and N. C. Jadhav
Table 1. Continued
b
Entry
9
Alcohol
Product
Time (h) Yield (%)
6.0
90
10
3.0
89
1
1
1
2
5.0
5.0
88
89
1
3
4
—
—
24
NR
NR
1
24
a
All reactions were carried out at room temperature using 4.7 mmol of
substrate, 2 equiv. (2.0 M) of sodium dichloroiodate, and 15 mL of water at rt.
b
Isolated yields after column chromatography and structure confirmed by IR
1
and H NMR. NR: no reaction.
method is that the reaction takes place in the water. In conclusion, an
aqueous solution of NaICl has been found to be a versatile agent for
2
the oxidation of primary and secondary aromatic alcohols. In addition,
the use of aqueous NaICl for the oxidation of aromatic alcohols offers
2
a number of advantages in term of safety and ease of use in comparison
to other methods that often employ toxic and hazardous solvents and
materials.

Oxidation of Alcohols in Aqueous Solution
3111
GENERAL PROCEDURE
Preparation of Benzaldehyde
The NaICl solution (2.0 equiv, 2.0 M) was added to a stirred solution of
2
benzyl alcohol (1.0 equiv, 4.7 mmol) in water (15 mL). The resultant
mixture was stirred at rt until the starting material had been completely
consumed (TLC). The reaction mixture was diluted with water and
extracted with chloroform (2 Â 20 mL). The combined organic layer
was washed successively with 10% aq. sodium bisulfite solution
(
The organic layer was dried over Na SO and concentrated in vacuo. The
2 Â 15 mL), 10% aq. NaHCO (2 Â 15 mL), and finally H O (1 Â 20 mL).
3
2
2
4
residue obtained was purified by silica-gel column chromatography (10%
EtOAc–hexane) to afford pure benzaldehyde.
ACKNOWLEDGMENT
We gratefully acknowledge University Grants Commission India for
financial support.
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equivalent of 1-lithio-1,4-butanediol. Tetrahedron Lett. 1981, 22, 2361.
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oxidation of alcohols to aldehydes and ketones by means of iodosylbenzene.
Chem. Lett. 1993, 22, 571.
2
3
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