Oxidation hydroxylated aldehyde

The use of silver (II) salts, particularly argentic picolinate, as reagents for hydroxyl oxidation has also been disclosed recently. The reaction may be run in acid, neutral or basic media in aqueous or polar organic solvents at room or slightly elevated temperatures. Primary alcohols may be oxidized to aldehydes or acids depending on the conditions used. Amines and trivalent phosphorous compounds are more sensitive to oxidation with this reagent than are hydroxyl groups. 

On the basis of the obtained results and the literature[17-18], we assume that during the oxidative decomposition of p-coumaric acid 1, three kind of reaction can happen before the opening of the aromatic ring (Scheme 1) cleavage of the very reactive exocyclic double bond to give p-hydroxybenzaldehyde 2, hydroxylation of the aromatic ring to yield 3,4-dihydroxycinnamic acid 3 and oxidation of aldehydes to carboxylic acids such as oxidation of 2 to p-hydroxybenzoic acid 4. Compound 2 can be hydroxylated to yield 3,4- dihydroxybenzaldehyde 6. and Compound 4 can also be hydroxylated to yield 3,4-dihydroxybenzoic acid 5. 

Oxidation of one molar proportion with sodium pieriodate produces two equivalents of formic acid, in accordance with the existence of hydroxyl groups attached to four contiguous carbon atoms. This oxidation (and also that carried out with lead tetraacetate) gives an aldehyde, whose semicar-bazone has an analysis corresponding to that of the semicarbazone of an ethyl formyl-methyl-furoate (XII). By oxidation of aldehyde XII with silver oxide in alkaline solution, 2-methyl-3,4-furandicarboxylic acid (XIV) was obtained this was identical with the compound described by Alder and Rickert.20 The identity was confirmed by preparation of the respective dianilides. The acid XIV has also been prepared by the reaction between the sodium salt of ethyl acetoacetate and ethyl bromopyruvate.9... 

Aromatic methyl group hydroxylation and oxidation to aldehyde and carboxylic acid Aspergillus sclerotiorum, Aspergillus sp.)... 

The treatment of an alkene by 5yn-hydroxylation, followed by periodic acid (HIO4) cleavage, is an alternative to the ozonolysis, followed by reductive work-up. 5yn-diols are oxidized to aldehydes and ketones by periodic acid (HIO4). This oxidation reaction divides the reactant into two pieces, thus it is called an oxidative cleavage. 

Oxidation of Aldehydes to Carboxylic Acids Hydroxylation or Hydroxy-de-hydrogenation... 

In addition to isomerization some of the epoxide groups could be oxidized to hydroxyl aldehyde and then carboxylic acid groups (7)57). These oxidation reactions would also be consistent with our FTIR observations. 

Aldehyde oxidase catalyzes the oxidation of aldehydes to carboxylic acids by dioxygen, but also catalyzes the hydroxylation of pyrimidines. Despite its rather broad specificity for substrates, it may well be that aldehyde oxidase should be regarded primarily as a pyrimidine hydroxylase. Thus, xanthine oxidase and aldehyde oxidase catalyze the hydroxylation of purines and pyrimidines respectively. The oxygen incorporated into the product comes from water, not 02. The dioxygen serves as the electron acceptor and other oxidizing agents may be used. 

Sodium periodate can be used to oxidize hydroxyl groups on adjacent carbon atoms, forming reactive aldehyde residues suitable for coupling with amine- or hydrazide-... 

Certain enzymes may be used to oxidize hydroxyl-containing carbohydrates to create aldehyde groups (Chapter 1, Section 4.4). For example, the reaction of galactose... 

It was also shown that the ratio of oxidized alcohol to oxidized Fe2+ could be greater then one. Baxendale and Wilson (1957) showed that hydroxyl radical initiating the chain polymerization of olefins by hydrogen peroxide was the same process as the rapid oxidation of glycolic acid. Merz and Waters (1947) confirmed that simple water-soluble alcohols are oxidized rapidly by Fenton s reagent. The primary alcohols are oxidized to aldehydes, which are further oxidized at comparable rates by exactly the same mechanism. Merz and Waters proposed a mechanism of chain oxidation of alcohols and aldehydes by sodium persulfate, hydrogen peroxide, and an excess of ferrous salt as follows ... 

CPO catalyzes the oxidation of 2-alkynes to aldehydes in the presence of H202 or tBuOOH via an alcoholic intermediate as depicted in Scheme 2.18 [242]. Propargylic alcohols are rapidly oxidized to the corresponding aldehydes [243] and there is a report about highly enantioselective propargylic hydroxylations catalyzed by CPO [244], In addition, a number of primary alcohols are selectively oxidized to aldehydes in a biphasic mixture of hexane and a buffer (Scheme 2.18) [245, 246]. 

The reactions of hydrogen peroxide with vanadate have been of interest for many years. Much of the early work was concerned with the function of peroxovanadates as oxygen transfer agents. Alkenes and similar compounds such as allyl alcohols can be hydroxylated or epoxidized. Even alkanes can be hydroxylated, whereas alcohols can be oxidized to aldehydes or ketones and thiols oxidized to sulphones or sulphoxides. Aromatic molecules, including benzene, can be hydroxylated. The rich chemistry associated with the peroxovanadates has, therefore, led to extensive studies of their reaction chemistry. To this end, x-ray diffraction studies have successfully provided details of a number of peroxovanadate structures. 

Phenol has been hydroxylated nearly quantitatively to hydroquinone 2 3 9 Most alkoxylations or hydroxylations of aromatics however either lead to anodic addition products (see Sect. 10.1) or to side chain substitution (see below). Specific side-chain hydroxylation is difficult to achieve because the alcohols formed as primary products are further oxidized to aldehydes, ketones and/or carboxylic acids. 

The initiation effect of ultrasound generating hydroxyl radicals in reaction medium as, e.g., during sonochemical oxidation of aldehydes has been widely studied but rarely utilized. 

MoOPh at 0° to the orf/to-hydroxylated aldehyde (4). Higher yields obtain if 3 is converted to the tributylboronic ester followed by oxidation with 30% H202. 

Alkylpyrazines may be oxidized to pyrazine aldehydes, ketones, or carboxylic acids. They may also undergo nuclear oxidation (covered piecemeal in most other chapters), oxidative hydroxylation, epoxidation, and so on. Such reactions are illustrated in the following examples ... 

Heat catalyzes free radical formation in cellulose. Aldehydes form from C2 and C3 hydroxyls. Aldehydes oxidize to carboxyls, and with dehydration, carbon monoxide (CO) and carbon dioxide (C02) form as well as conjugated carbonyl-ethylenic chromophoric groups that selectively absorb blue light and impart yellowness (35). During the induction stage of cellulose oxidation, yellowness may increase steadily with selective carbonyl and ethylene group formation. By artificially aging... 

---