Aldehydes, oxidation reduction

Aldehydes can undergo an intermolecular oxidation—reduction (Canni22aro reaction) in the presence of base to produce an alcohol and a carboxyUc acid salt. Any aldehyde is capable of participating in such a reaction, however, it is more common for those containing no protons on the alpha carbon, for example... 

The reactions of n- and isobutyialdehyde are chaiactetistic aldehyde reactions of oxidation, reduction, and condensation. Aldehydes (qv) are intermediate in the sequence ... 

Methylthiomethyl p-tolyl sulfone 257 was shown to react with various esters in the presence of excess NaH, affording compounds 263 which, upon reduction with NaBH and further treatment with alkali, can be converted to the corresponding aldehydes ". Oxidation of 263 with hydrogen peroxide gives S-methyl a-ketocarbothioates 264. ... 

Some male arctiid moths produce their courtship pheromone from dietary pyrrolizidine alkaloids acquired during feeding by the larvae [ 126]. Conversion of monocrotaline to hydroxydanaidal by males is accomplished by aromatiza-tion, ester hydrolysis and oxidation of an alcohol to the aldehyde [7]. In the case of Utetheisa ornatirx the stereo-configuration at C7 of the dietary alkaloid is the same as the pheromone released (R). In contrast, another arctiid, Creatono-tos transiens, can convert a dietary precursor alkaloid with the (S) configuration at C7 (heliotrine) to (l )-hydroxydanaidal. The biosynthesis occurs by first oxidation-reduction at C7 to convert the stereochemistry and then proceeds through aromatization, hydrolysis, and oxidation [7]. 

Conversion of the A-ring aldehyde 50 to hydroxyallylsilane 57 is accomplished in a three-step sequence involving addition of allylstannane 49 followed by oxidation-reduction for diastereomeric enrichment at Cll. With both hydroxyallylsilane 57 and aldehyde 51 in hand, intermolecular Prins pyran annulation proceeds smoothly to furnish the tricyclic compound 58 in 61 % isolated yield. 

Aldehyde oxidation Aldehyde reduction Ketone reduction... 

Nitrocyclohexadiene 93a reacted with 4.0 equivalents of cyclopentadiene in toluene at 110°C for 96 h, producing the 10-glyco-l-nitrotricyclo[5.2.2.02,6]undeca-3,8-diene 96a in 70% yield. Subsequent treatment with potassium carbonate in a methanol-water (9 1) solution followed by oxidative cleavage of the sugar side chain with sodium metaperiodate afforded aldehyde 96c. Reduction of the aldehyde with sodium borohydride produced alcohol 96d. 

In contrast to oxidative dechlorination, the hydrolytic dechlorination of chloramphenicol replaces a Cl-atom with a OH group to yield a (monochlo-ro)hydroxyacetamido intermediate. The latter, like the dichloro analogue, also eliminates HC1, but the product is an aldehyde that is far less reactive than the oxamoyl chloride intermediate. Chloramphenicol-aldehyde undergoes the usual biotransformation of aldehydes, namely reduction to the primary alcohol 11.41 and dehydrogenation to the oxamic acid derivative 11.40 (Fig. 11.7). 

In a related study, the oxidation-reduction sequence was carried out in the presence of an olefin (Scheme 21). Two products were formed. The major product resulted from the net reduction of the carboxylic acid to an aldehyde. The minor product resulted from trapping of the radical anion intermediate generated from the reduction reaction by the olefin. It should be noted that, in the absence of a trapping group, the acid can be selectively reduced to the aldehyde without any over-reduction. Although not in the scope of this review, this is a very useful transformation in its own right [35]. At this time, the yields of the cyclized products from the cyclization reaction of the radical anion with the olefin remain low. 

Reductive coupling of 1,1-dimethylallene and 5-nitro-2-furancarboxaldehyde under a deuterium atmosphere provides the product of ferf-prenylation incorporating deuterium at the interior vinylic position (80% H). This result is consistent with a mechanism involving allene-aldehyde oxidative coupling. However, alternate pathways involving allene hydrometallation to furnish allyliridium species cannot be excluded on the basis of these data (Scheme 10). 

Chromium(III) catalyses the cerium(IV) oxidation of primary and secondary alcohols in a mixture of H2SO4 and HC104. Kinetic results have been interpreted in terms of the formation of chromium(IV) in a reversible equilibrium, which forms a complex with the alcohol. Internal oxidation-reduction occurs in a rate-determining step to give aldehyde or ketone and regenerate the catalyst in the +3 state. The oxidation of ethanol under similar conditions has also been studied. ... 

This enzyme [EC 1.1.99.8], also referred to as alcohol dehydrogenase (acceptor) and methanol dehydrogenase, catalyzes the oxidation-reduction reaction of a primary alcohol with an acceptor to generate an aldehyde and the reduced acceptor. The cofactor for this enzyme is pyrroloquinoline qutnone (PQQ). A wide variety of primary alcohols can act as the substrate. See also Alcohol Dehydrogenase... 

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