Oxidation of vicinal diols

A. P. Rauter, F. Piedade, T. Almeida, R. Ramalho, M. J. Ferreira, R. Resende, J. Amado, H. Pereira, J. Justino, A. Neves, F. V. M. Silva, and T. Canda, Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols, Carbohydr. Res., 339 (2004) 1889-1897. 

Mechanisms involving glycol bond fission have been proposed for the oxidation of vicinal diols, and hydride transfer for other diols in the oxidation of diols by bromine in acid solution.The kinetics of oxidation of some five-ring heterocyclic aldehydes by acidic bromate have been studied. The reaction of phenothiazin-5-ium 3-amino-7-dimethylamino-2-methyl chloride (toluidine blue) with acidic bromate has been studied. Kinetic studies revealed an initial induction period before the rapid consumption of substrate and this is accounted for by a mechanism in which bromide ion is converted into the active bromate and hyperbromous acid during induction and the substrate is converted into the demethylated sulfoxide. 

T. R. Felthouse. P. B. Fraundorf, R. M. Friedman, C. L. Schosser, Expanded Lattiee Ruthenium Pyroehlore Oxide Catalysts. I. Liquid Phase Oxidations of Vicinal Diols, Primary alcohols, and related Substrates with Molecular Oxygen, J. Catal. 127 (1991)... 

Mechanisms have been proposed for ruthenium(III)-catalysed oxidation of leucine by acid bromate133 and for the chemoselective oxidation of vicinal diols to a-hydroxy ketones with NaBrC>3/NaHS03 reagent.134... 

Sodium bismuthate, NaBiOs, cleaves vicinal diols to dicarbonyl compounds [482, 483] but offers no advantage over the more common oxidants of vicinal diols, such as lead tetraacetate and periodic acid. 

While anodic oxidation of simple alcohols is of limited utility, direct oxidation of vicinal diols and related compounds is an excellent method for achieving oxidative cleavage to the corresponding carbonyl or carbonyl-acetal products, as in Eqs. (53) and (54). Unlike certain chemical glycol cleavage reactions, the anodic method is not limited by the stereochemistry of the substrate oxygens [132]. 

An interesting chemical characteristic of the hydroxymethylene group at C-2 of various branched penteno-y-lactones [108] can be observed during the oxidation of vicinal diols with periodate which proceeds with extremely high selectivity with the relative rates 100 1 3 100. Thus, the isomers with cis- and trans-2,3-diols can be readily identified. 

The catalytic oxidation of vicinal diols in water is a valuable target, for example, in the synthesis of glycolic acid and lactic acid via the... 

With the aim of exploring the activation of O2 toward the oxidation of vicinal diols we tested different supported-gold catalysts under mild conditions. By working in neutral aqueous solution of ethane-1,2-diol up to 100°C and 2 atm of O2 in the presence of 1% Au supported on active carbon there was no oxidation, whereas in alkaline solution a smooth oxygen uptake at 50-90°C was observed. HPLC and l C-NMR analyses of the reaction products showed quite good slectivity toward monooxygenation. 

Electrochemistry427 can be used to regenerate an expensive or toxic reagent in situ. An example is the electrical regeneration of periodate that is used for the oxidation of vicinal diols such as sugars. When used with osmium oxidations, it can keep the level of the toxic metal reagent quite low. In Chap. 4, an example of the conversion of a naphthoquinone to its epoxide by electrolysis of aqueous sodium iodide was given. The sodium hydroxide and iodine produced by electrolysis react to form hypoiodite that adds to the double bond to form the hydroxyiodide, which then eliminates sodium iodide by the action of the sodium hydroxide to re-form the sodium iodide.428 Electricity can be used in oxidations and... 

Catalytic oxidation of vicinal diols to a-hydroxy carboxylates was performed by Prati and Rossi [82] in alkaline aqueous solution with gold-based catalysts prepared by deposition-precipitation with sodium carbonate from HAUCI4 solutions on active carbon suspension. The 1 % Au/C catalysts had remarkable properties compared with conventional Pt/C and Pd/C catalysts in terms of selectivity and stability. Thus, Table 1 shows that at pH 8,1,2-propanediol was very selectively oxidized to lactic acid, which indicates that gold was more selective than platinum and palladium in the oxidation of the primary alcohol function. The activity of gold catalysts was also very stable as a function of conversion or after several recycles, indicating that gold is less sensitive to over-oxidation and/or self-poisoning than platinum and palladium. 

Table 13.3 Catalytic activity and selectivity of carbon dispersed metals in the oxidation of vicinal diols.

Carboxylic acids can be obtained from the oxidation of vicinal diols in the presence of cobalt complexes [320-322]. a-Ketols have been oxidized to a-diketones by Cu(II) in buffered aqueous pyridine and the reaction exhibits a rate-controlling enolization step [323]. The catalytic effect of Fe(III) and Fe(II) on the autoxidation of acetoin in aqueous HCIO4 showed that the formation of an iron(III) enolate was the slow step [324]. The oxidation of monosaccharides in the presence of catalysts such as copper phthalocyanine or cobalt glutamate in the presence of alkaline compounds gave oxidation products which were useful sequestering agents [325]. Thus cleavage to the acid salts occurred. 

Moreover, 2,3-dialdehyde xylan may be obtained in the well-known glycol cleavage oxidation of vicinal diol units with sodium periodate, which can be further oxidized to give 2,3-dicarboxyl xylan. Figure 3 summarizes the structures of the possible oxidized repeating units. 

Oxidation of secondary alcohols by hexamethylenetetramine-bromine (HABR) in acetic acid is first order with respect to HABR and Michaelis-Menten-type kinetics were observed with respect to alcohols. A mechanism involving transfer of a hydride ion from the alcohol to the oxidant has been proposed. The oxidation of vicinal diols by HABR proceeds by a glycol-bond fission via an intermediate complex, whereas non-vicinal diols behave like monohydric alcohols towards HABR. ... 

A reaction characteristic of vicinal diols is their oxidative cleavage on treatment with periodic acid (HIO4) The carbon-carbon bond of the vicinal diol unit is broken and two carbonyl groups result Periodic acid is reduced to iodic acid (HIO3)... 

The reaction is based, on the one hand, on the oxidative cleavage of vicinal diols by lead(IV) acetate and, on the other hand, on the reaction of dichlorofluorescein with lead(IV) acetate to yield a nonfluorescent oxidation product. The dichlorofluorescein only maintains its fluorescence in the chromatogram zones where the lead(IV) acetate has been consumed by the glycol cleavage reaction [1],... 

In theory, periodate oxidation could have given a clear-cut answer as to the composition of the isomeric mixture of deoxy ribose phosphates. The 4-phosphate (73), devoid of vicinal diol groups, should be resistant to periodate the 3-phosphate (74) should reduce one and only one molar equivalent of the oxidant and yield one molar equivalent of both formaldehyde and the phosphorylated dialdehyde (75), whereas the 5-phosphate (76) could be expected to reduce one molar equivalent of periodate relatively rapidly, followed by a slower overoxidation reaction owing to the oxidation of malonaldehyde, formed as a result of the glycol cleavage. 

We have developed an efficient and practical method for clean oxidation of starch (21-23) resulting in the oxidation of primary alcohol function in Ce position and the cleavage of vicinal diols in C2 and C3 position (Figure 30.2). We used small amounts of cheap iron tetrasulfophthalocyanine catalyst, pure water as reaction medium and H2O2 as clean oxidant to achieve a one-pot conversion of starch resulting in the introduction of aldehyde and carboxyl functions in polymer chains. The iron content... 

The nickel hydroxide electrode resembles in its applications and selectivity the chemical oxidant nickel peroxide. The nickel hydroxide electrode is, however, cheaper, easy to use and in scale-up, and produces no second streams/ waste- and by-products [196], Nickelhydroxide electrode has been applied to the oxidation of primary alcohols to acids or aldehydes, of secondary alcohols to ketones, as well as in the selective oxidation of steroid alcohols, cleavage of vicinal diols, in the oxidation of y-ketocarboxylic acids, of primary amines to nitriles, of 2,6-di-tert-butylphenol to 2,2, 6,6 -tetra-rert-butyldiphenoquinone, of 2-(benzylideneamino)-phenols to 2-phenyloxazols, of 1,1-dialkylhydrazines to tetraalkyltetrazenes. For details the reader is referred to Ref. [195]. 

There are fewer examples of this for such Ru-catalysed oxidations than for C-H activation, cleavage of the C-C bond in diols being the main example [111]. Optically pure D- and L-glyceric acids were made by cleavage of vicinal diols or of a-hydroxy acids by RuCl3/aq. Na(ClO) pH 8, e.g. l,2 5,6-di-0-isopropylidene-D-mannitol to 2,3-0-isopropylidene-D-glyceric acid (Fig. 4.6) [112],... 

Recently, heterogeneous catalytic systems were described41 that employ molecular oxygen for the liquid phase oxidative cleavage of vicinal diols. Although the catalysts appear to be mixed metal oxides rather than supported metals the method resembles closely the noble metal-catalyzed oxidations described above, hence their inclusion in this section. 

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