Overoxidation hydroxylation, direct

Enolate hydroxylation is a problem of long standing. Direct oxygenation succeeds with the fully substituted enolates of certain a,a-disubstituted ketones and a variety of carboxylic acid derivatives (ester anions, acid dianions, amide anions), but the reaction of enolates, RCH = C(0 )R or CH2 = C(0 )R, with oxygen results in complex products of overoxidation. The stable... 

Overoxidation by periodate may involve direct hydroxylation as the first step (as in the oxidation of hydrocarbons), with the resulting hydroxy-aldehyde (12 or 14) being cleaved in the conventional way however, hydroxylation... 

Direct hydroxylation is a probable step in the overoxidation phase observed during the periodate oxidation of glycals attack presumably occurs at the allylic position adjacent to the carbonyl group of the initial product formed by cleavage of the 3,4-diol grouping. 

Although the reactions implemented so far are limited to model systems, we believe that artificial metalloenzymes will reveal their full potential for transformations for which there exists to date no good homogeneous catalyst. In this context, onr current efforts are directed towards the hydroxylation of alkanes (where overoxidation is difficult to prevent with homogeneous systems) as well as highly sequence-specific DNA hydrolysis. 

Several catalytic technologies have been developed for direct hydroxylation of phenol to HQ and catechol (CAT) using HjOj as oxidant [106], More than 25,000tons/year of these important chemicals is produced using three main processes (Table 14.1), a common feature of which is the use of an excess of substrate to avoid overoxidation. 

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