Green Chemistry
COMMUNICATION
DOI: 10.1039/C C02362E
Jou4Grnal Name
our developed conditions contribute to converting this abundant
carbon source into alternative fuels.
Acknowledgements
The authors acknowledge Dr. Joo Ho Lee and Prasanna
Pullanikat for their initial efforts in this project and Richard Giles
for insightful discussions. We also acknowledge generous
financial support from the Hydrocarbon Research Foundation and
the National Institute of Health (S10 RR025432).
Notes and references
a
University of Southern California
Loker Hydrocarbon Research Institute & Department of Chemistry
Standard conditions: 100 ꢁmol of substrate, 5 ꢁmol of
NaOH were dissolved in 0.44 mL H O. 60 ꢁL 30% H
the mixture was stirred at 25 °C for 16 hours. 0.25 mL of D
1
, and 600 ꢁmol
was added and
O was then
2
2 2
O
2
added to the reaction mixture with a sealed capillary DMSO standard.
The solution was then analyzed using wet1D NMR.
Scheme 2. Proposed Pd(II) assisted αꢀoxidative degradation pathway
of Dꢀglucose with hydrogen peroxide.
†
Electronic Supplementary Information (ESI) available: formic acid
calibration curve, glycolic acid calibration curve, wet1D NMR spectra.
See DOI: 10.1039/c000000x/
Based on our results, we believe our procedure proceeds
primarily through an αꢀoxidation mechanism. Our primary source of
evidence is the nearly complete conversion of monosaccharides into
formic acid. Since the carbon turnover of the monosaccharides used
was 93% or higher, a mechanism entailing the loss of half of the
1
2
P. Gallezot, Chem. Soc. Rev. 2012, 41, 1538ꢀ1558.
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1
4
carbon mass by decarboxylation of oxalic acid would not be viable.
In addition, under alkaline aqueous conditions with catalyst 1 and
stoichiometric amounts of hydrogen peroxide, oxalic acid did not
produce formic acid. Lastly, only trace amounts of oxalic acid were
3
4
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13
detected by C NMR under our standard conditions after four hours,
corroborating that this route was minor and the αꢀoxidation pathway
11
would be predominant. As suggested in our previous work, catalyst
acts as a bidentate system, simultaneously activating an aldehyde
5
(a) L. Qi, Y. F. Mui, S. W. Lo, M. Y. Lui, G. R. Akien, I. T. Horváth,
1
ACS Catal. 2014,
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4
, 1470ꢀ1477; (b) Y. RománꢀLeshkov, M. E. Davis,
and alcohol in close proximity of each other, forming a fiveꢀ
membered heterocycle glucose adduct. This enhances the
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systematic sequential order. While other palladium salts may
activate saccharides in a similar fashion, catalyst 1 avoids the
overoxidation of formate into carbon dioxide, setting it apart from
other Pd(II) counterparts.
1
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In summary, we have discovered a set of efficient and
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7
8
H. S. Isbell, Carbohydr. Res. 1976, 49, C1ꢀC4.
amidate Pd(II) complex
1
catalyzed the reactions, likely acting
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as a Lewis acid and activating the aldehyde functional group in
the aldoses. Contrary to other procedures, this method did not
use excess amounts of oxidant and did not require the input of
heat for aldoses, while the catalyst was recyclable and
maintained its efficiency. This methodology can become of
great value since sugars comprise a majority of biomass. Thus,
9
H. van Bekkum, R. A. Sheldon, Synthesis 1996,
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1
,
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| J. Name., 2012, 00, 1-3
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