Ruthenium catalyzed oxidation of 1,2-diols to 1,2-diketones using bromamine-T as an oxidizing agent

Article abstract of DOI:10.1081/SCC-200048974

A variety of 1,2-diols were selectively oxidized to their corresponding 1,2-diketones with bromamine-T using RuCl₃ · xH₂O as catalyst in alkaline acetonitrile/ water (1:1) medium. The reaction was pH dependent (pH 8.4), and at higher pH the rate of the reaction decreased significantly. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200048974

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Ruthenium Catalyzed Oxidation
of 1,2‐Diols to 1,2‐Diketones
Using Bromamine‐T as an
Oxidizing Agent
Suman L. Jain a , Vishal B. Sharma a & Bir Sain a
a Chemical and Biosciences Division , Indian Institute
of Petroleum , Dehradun, 248005, India
Published online: 28 Jul 2007.
To cite this article: Suman L. Jain , Vishal B. Sharma & Bir Sain (2005) Ruthenium
Catalyzed Oxidation of 1,2‐Diols to 1,2‐Diketones Using Bromamine‐T as an Oxidizing
Agent, Synthetic Communications: An International Journal for Rapid Communication
of Synthetic Organic Chemistry, 35:3, 465-469, DOI: 10.1081/SCC-200048974
To link to this article: http://dx.doi.org/10.1081/SCC-200048974
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Synthetic Communicationsw, 35: 465–469, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200048974
Ruthenium Catalyzed Oxidation of 1,2-Diols
to 1,2-Diketones Using Bromamine-T
as an Oxidizing Agent
Suman L. Jain, Vishal B. Sharma, and Bir Sain
Chemical and Biosciences Division, Indian Institute of Petroleum,
Dehradun, India
Abstract: A variety of 1,2-diols were selectively oxidized to their corresponding 1,2-
.
diketones with bromamine-T using RuCl3 xH2O as catalyst in alkaline acetonitrile/
water (1 : 1) medium. The reaction was pH dependent (pH 8.4), and at higher pH the
rate of the reaction decreased significantly.
Keywords: Bromamine-T, 1,2-diketones, 1,2-diols, oxidation, ruthenium chloride
The oxidation of 1,2-diols to the corresponding 1,2-diketones has been
reported by RuCl2(PPh3)3 catalyzed hydrogen transfer,[1] 4-MeO-
TEMPO,[2]
4-PhCO2-TEMPO-electrolysis,[3]
(4-AcNH-TEMPO)-OTs-
TsOH,[4] H2O2-[C5H5N-(CH2)5 CH3[PO4(W(O)(O2)2]4],[5] and O2-
Co(acac)3-N-hydroxyphthalimide.[6] Recently Khurana et al.,[7] reported the
use of N-bromosuccinimide as an efficient reagent for this transformation,
but bromination as the side reaction particularly in substituted hydrobenzoins
was noticed. In continuation to our studies on oxidation,[8–12] herein we report
a simple and convenient method for the oxidation of 1,2-diols (1) to 1,2-
diketones (2) in near quantitative yields with bromamine-T as oxidant and
ruthenium trichloride as the catalyst (Scheme 1).
Received in India September 29, 2004
Address correspondence to Bir Sain, Chemical and Biosciences Division, Indian
Institute of Petroleum, Dehradun 248005, India. E-mail: birsain@iip.res.in

466
S. L. Jain, V. B. Sharma, and B. Sain
Scheme 1.
Oxidation of 1,2-diols (1) with catalytic amount of ruthenium tri-
chloride in acetonitrile/water (1 : 1) at 808C using bromamine-T with
substrate/bromamine-T under alkaline pH (8.4) provided a-diketones (2) in
almost quantitative yields. These results are summarized in Table 1. Hydro-
benzoins in general were found to be more reactive than aliphatic diols and
required lesser reaction time for their oxidation. Hydrobenzoins containing
electron-donating groups were by far the most reactive substrates (Table 1).
The reaction was found to be highly dependant upon the pH of the
reaction medium. At neutral pH, the oxidation of hydrobenzoin was found
to be very slow and the reaction completed in 6 h while at pH 8.4 the same
could be completed within 45 min. At higher pH (9–11), the rate of the
reaction slowed down,[13] and after 12 h the reaction was incomplete. After
several experimental investigations with respect to choice of solvents, 1 : 1
H3CN-H2O was found to be most efficient.
In the absence of the Ru-catalyst the oxidation of hydrobenzoin to benzil
did not take place after 12 h, however, with addition of 0.5 mol % ruthenium
trichloride to the reaction mixture the transformation occurred in 45 min.
We have developed a very simple and efficient method for the oxidation
of 1,2-diols to 1,2-diketones with bromamine-T/ruthenium system under mild
reaction conditions.
Typical Experimental Procedure
To a stirred solution of hydrobenzoin (1 mmol, 214 mg) in alkaline (pH 8.4)
.
acetonitrile/water (1 : 1) mixture (5 mL), RuCl3 xH2O (1 mg, 0.5 mol%)
was added and heated at 808C for 45 min. The progress of the reaction was
monitored by TLC (SiO2) using benzene/ethyl acetate (9 : 1) as eluent.
After completion of the reaction, solvent was evaporated under reduced
pressure and the residue dissolved in dichloromethane. The dichloromethane
layer was washed twice with water and dried over anhydrous sodium sulphate
followed by evaporation. The residue was purified on silica gel using ethyl
acetate/hexane (1 : 4) as eluent to yield benzil (199 mg, 95%) which was
identified by comparing the physical and spectral data with those of
authentic sample.

Ruthenium Catalyzed Oxidation of 1,2-Diols to 1,2-Diketones
467

468
S. L. Jain, V. B. Sharma, and B. Sain

Ruthenium Catalyzed Oxidation of 1,2-Diols to 1,2-Diketones
ACKNOWLEDGMENT
469
We are thankful to the director, IIP, for his kind permission to publish these
results. Suman L. Jain a‘nd Vishal B. Sharma are thankful to CSIR, New
Delhi, for the award of research fellowships.
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