Methyltrioxorhenium catalyzed oxidation of 1,2-diols to 1,2-diketones using hydrogen peroxide as oxidant

Article abstract of DOI:10.1016/j.tetlet.2003.11.131

A variety of 1,2-diols were oxidized selectively to the corresponding 1,2-diketones by the dropwise addition of 30% aqueous hydrogen peroxide using methyltrioxorhenium as catalyst.

Full text of DOI:10.1016/j.tetlet.2003.11.131

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 1233–1235
Methyltrioxorhenium catalyzed oxidation of 1,2-diols to
1,2-diketones using hydrogen peroxide as oxidant
Suman L. Jain, Vishal B. Sharma and Bir Sain*
Chemical and Biosciences Division, Indian Institute of Petroleum, Dehradun 248005, India
Received 17 October 2003; revised 21 November 2003; accepted 27 November 2003
Abstract—A variety of 1,2-diols were oxidized selectively to the corresponding 1,2-diketones by the dropwise addition of 30%
aqueous hydrogen peroxide using methyltrioxorhenium as catalyst.
Ó 2003 Elsevier Ltd. All rights reserved.
The methyltrioxorhenium (MTO)/hydrogen peroxide
oxidation system first reported by Herrmann and Kuhn1
in 1991 for the epoxidation of olefins has proved to be
an efficient and versatile system for various oxidation
reactions.2 The important features of the use of MTO as
a catalyst are its ease of synthesis, commercial avail-
ability, stability in air and efficiency in acting as a
homogeneous catalyst for oxidation using hydrogen
peroxide in both aqueous and organic solvents. The
oxidation of 1,2-diols is an important synthetic trans-
formation as 1,2-diketones find wide applications as
starting materials for the synthesis of heterocycles and
are extensively used as substrates for benzilic acid
rearrangements.3 Although a variety of oxidants have
been used to achieve this transformation, most are
associated with drawbacks such as the use of stoichio-
metric amounts of corrosive acids or toxic metallic
compounds that generate undesirable wastes.
on oxidation using eco-friendly oxidants10 we report
herein the first successful methyltrioxorhenium cata-
lyzed oxidation of 1,2-diols to the corresponding 1,2-
diketones using hydrogen peroxide as oxidant (Scheme
1). A variety of 1,2-diols were selectively oxidized to the
corresponding 1,2-diketones by the dropwise addition of
30% aqueous hydrogen peroxide to their solution in
refluxing acetonitrile using methyltrioxorhenium as
catalyst and MgSO4 as water trapping agent.11 These
results are presented in Table 1. Hydrobenzoins, in
general, were found to be more reactive than aliphatic
diols and required shorter reaction times for their oxi-
dation. Hydrobenzoins containing electron-donating
groups were found to be more reactive and could be
oxidized more easily. It was interesting to note that the
oxidation of hydrobenzoin with 5 equiv of 30% hydro-
gen peroxide, when added in one portion, gave a mix-
ture of benzil and benzoic acid along with unreacted
hydrobenzoin. In contrast, the same oxidation when
carried out by the dropwise addition of the hydrogen
peroxide afforded the benzil selectively in excellent yield.
The oxidation of 1,2-diols was found to be highly
dependent upon the reaction temperature, at room
temperature these oxidations were found to be very slow
and were not complete even after 20 h. Furthermore, the
presence of a water trapping agent (MgSO4) was found
In recent years the oxidation of 1,2-diols to 1,2-dike-
tones has been reported using 4-MeO-TEMPO,4
4-PhCO2-TEMPO-electrolysis,5 (4-AcNH-TEMPO)-OTs-
TsOH,6 H2O2–[C5H5N–(CH2)5 CH3[PO4(W(O)(O2)2]4],7
O2–Co(acac)3-N-hydroxyphthalimide8 and N-bromo-
succinimide.9 However these methods suffer from
drawbacks such as the use of expensive reagents, diffi-
cult experimental conditions, long reaction times and
low yields of products, leaving scope for further
improvement in this area. In continuation of our studies
Methyltrioxorhenium/H2O2 (aq)
'
R CH CH R
R C C R'
O O
Aceonitrile (Reflux), MgSO4
OH OH
Keywords: Methyltrioxorhenium; 1,2-Diols; 1,2-Diketones; Hydrogen
peroxide; Oxidation.
2
1
* Corresponding author. Tel.: +91-135-2660071; fax: +91-135-26602-
02; e-mail addresses: birsain@iip.res.in; birsain@hotmail.com
Scheme 1.
0040-4039/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2003.11.131

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S. L. Jain et al. / Tetrahedron Letters 45 (2004) 1233–1235
Table 1. Oxidation of 1,2-diols with the methyltrioxorhenium/H2O2 systema
Entry
1
Substrate
Reaction time (h)
7.50
Yieldb
92
CH CH
OH
OH
H3CO
H3C
H3CO
Cl
CH CH
OH
OCH3
CH3
2
5.50
5.75
6.25
8.00
7.00
4.00
8.75
9.25
10
95
94
92
92
94
97
90
85
80
75
70
OH
CH CH
OH
3
OH
CH CH
OH
4
OH
CH CH
OH
Cl
5
OH
CH CH
OH
N(CH3)2
(CH3)2N
6
OH
CH CH
OH
7
O
O
OH
Cl
CH CH
OH
8
OH
Cl
O2N
CH CH
OH
NO2
9
OH
Cl
Cl
CH CH
OH
10
11
12
OH
Cl
Cl
CH3(CH2)12CH CH(CH2)12CH3
OH OH
12.00
CH3(CH2)14CH CH(CH2)14CH3
OH OH
12.50
a Reaction conditions: substrate (1 mmol), catalyst (1 mol %), 30% aq. hydrogen peroxide (0.5 mL) in refluxing acetonitrile in the presence of MgSO4
as water trapping agent.
b Isolated yields.
to be essential and in the absence of MgSO4 only very
low yields of the 1,2-diketones were obtained.
oxide using methyltrioxorhenium as a catalyst under
mild reaction conditions.
The reactions involve the formation of a-hydroxycar-
bonyl compounds followed by their oxidation into the
corresponding diketones. The intermediacy of a-
hydroxycarbonyl compounds was confirmed in the case
of hydrobenzoin and hydroanisoin by quenching the
reactions after 2 h and isolating benzoin and anisoin,
respectively, from the reaction mixtures.
References and notes
1. Herrmann, W. A.; Kuhn, F. E. Acc. Chem. Res. 1997, 30,
169.
2. For reviews, see: (a) Romao, C. C.; Kuhn, F. E.;
Herrmann, W. A. Chem. Rev. 1997, 97, 3197; (b) Espen-
son, H. Chem. Commun. 1999, 479; (c) Owens, S.; Arias, J.;
Abu-Omar, M. M. Catal. Today 2000, 55, 317; (d)
Espenson, J. H.; Zhu, Z.; Zauche, T. H. J. Org. Chem.
1999, 64, 1191.
In conclusion, we have developed a very simple and
efficient method for the selective oxidation of 1,2-diols
to the corresponding diketones by 30% hydrogen per-

S. L. Jain et al. / Tetrahedron Letters 45 (2004) 1233–1235
1235
3. (a) Gill, G. B. In Comprehensive Organic Synthesis;
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11. Typical experimental procedure: To a stirred and refluxing
solution of hydrobenzoin (1 mmol, 214 mg) containing the
drying agent MgSO4 (100 mg) and methyltrioxorhenium
(2.5 mg, 1 mol %) in acetonitrile (5 mL), 30% aqueous
hydrogen peroxide (0.5 mL, 5 mmol) was added dropwise
over a period of 7.5 h. The progress of the reaction was
monitored by TLC (SiO2) using benzene/ethyl acetate (9:1)
as eluent. At the end of the reaction, the reaction mixture
was treated with excess MnO2 (for destruction of the
excess H2O2) followed by filtration. The solvent was
evaporated under reduced pressure and the residue was
dissolved in dichloromethane. The dichloromethane layer
was washed twice with water and dried over anhydrous
sodium sulfate followed by evaporation of the solvent. The
residue was purified by column chromatography on silica
gel using ethyl acetate/hexane (1:4) as eluent. Evaporation
of the solvent yielded benzil (190 mg, 92%), which was
identified by comparing physical and spectral data with
those of an authentic sample.
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42, 1265; (b) Sharma, V. B.; Jain, S. L.; Sain, B. Tetrahe-
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