The potential of the aqueous system sodium tungstate‐hydrogen peroxide for glycol‐cleavage oxidation of maltodextrins, starch and trans‐1,2‐cyclohexanediol as a model compound has been evaluated. The peroxotungstate species formed in this medium effect oxidation of the glucose units via two major pathways: (i) glycol‐cleavage of the C2–C3 diol moieties in internal glucose units, followed by (undesired) hydrolysis of the ring‐opened intermediate and (ii) stepwise decarboxylation at the reducing terminal glucose unit until the glycosidic bond is reached. Both reaction types yield glucose oligomers terminated by erythronic acid at the former reducing end, which is an important fraction (up to 40%) of the oxidation product. Decomposition of hydrogen peroxide to oxygen and water is an inevitable side reaction.

A series of S 1-type reactions has been studied under various conditions to clarify the role of supercritical carbon dioxide (scCO ) as reaction medium for this kind of transformations. The application of scCO did not result in higher yields in any of the experiments in comparison to those under neat conditions or in the presence of other inert compressed gases. High-pressure UV/Vis spectroscopic measurements were carried out to quantify the degree of carbocation formation of a highly S 1-active alkyl halide as a function of the applied solvent. No measureable concentration of carbocations could be detected in scCO , just like in other low polarity solvents. Taken together, these results do not support the previously claimed activating effect via enhanced S 1 ionization due to the quadrupolar moment of the supercritical fluid.

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