Nonconjugated aldehydes

Cyanohydrins of nonconjugated aldehydes are oxidized in high yield to carboxylic acids. 

Reduction of Conjugated Aldehydes In Preference to Nonconjugated Aldehydes... 

Selective reduction of aldehydes-1 Conjugated aldehydes are selectively reduced in the presence of nonconjugated ones by ErCl3 in aqueous ethanol. The effect is probably a result of preferential hydration of nonconjugated aldehydes. 

Reductive dimerization of a,p-unsaturated ketones is effected by either Cr" or V" chloride to give 1,6-diketones, but aliphatic a, -unsaturated aldehydes are dimerized to the allylic glycals. Interestingly, nonconjugated aldehydes are stable towards these reagents. Similar pinacolic couplings of aldehydes and ketones with Ti" reagents were developed by Corey. ... 

The exact mechanistic pathway of the classical J-L olefination is unknown. Deuterium-labeling studies showed that the nature of the reducing agent (sodium amalgam or Smb) determines what type of intermediate (vinyl radical or secondary alkyl radical) is involved. Both intermediates are able to equilibrate to the more stable isomer before conversion to the product. The high ( )-selectivity of the Kocienski-modified reaction is the result of kinetically controlled irreversible diastereoselective addition of metalated PT-sulfones to nonconjugated aldehydes to yield anti-P-alkoxysulfones which stereospecifically decompose to the ( )-alkenes. 

Nonconjugated aldehydes are not converted into esters by this procedure. 

In nonconjugated aldehydes and ketones, decomposition from the singlet state commonly results in carbon-carbon bond cleavage to produce free radicals (Schemes 9.23 and 9.24). 

Given the hypothesis that the formation of a geminal diol is critical to nonconjugated aldehyde function protection, it was subsequently shown by NMR study that cerium(III) enhances diol stability better than any other cation tested. This implies that the cerium ion is large enough to provide protection during reduction, but still allows ready recovery of the aldehyde during workup. The utility of the cerium ion is also fortuitous in that it is one of the least expensive of the lanthanides. 

Aldehydes are more readily oxidized than alcohols and thus react with the reagents given above. Nonconjugated aldehydes give acids in good yield with PDC in DME. Where selectivity is needed, very mild reagents such as freshly precipitated silver oxide [9] or sodium chlorite (Eq. 6.5) [10] serve well. 

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