Preparation of Aldehydes and Ketones by Oxidation

Barton DHR, Hui RAHF, Lester DJ, Ley SV (1979) Preparation of aldehydes and ketones by oxidation of benzylic hydrocarbons with benzeneseleninic anhydride. Tetrahedron Lett 20 3331-3334... 

Hydroboration-oxidation of alkynes preparation of aldehydes and ketones Hydroboration-oxidation of terminal alkynes gives syn addition of water across the triple bond. The reaction is regioselective and follows anti-Markovnikov addition. Terminal alkynes are converted to aldehydes, and all other alkynes are converted to ketones. A sterically hindered dialkylborane must be used to prevent the addition of two borane molecules. A vinyl borane is produced with anU-Markovnikov orientation, which is oxidized by basic hydrogen peroxide to an enol. This enol tautomerizes readily to the more stable keto form. 

I Write equations for the preparation of aldehydes and ketones by the oxidation of alcohols. 

The most versatile method for preparing enamines involves the condensation of aldehydes and ketones with secondary amines [Eq. (1)]. Mannich and Davidsen (/) discovered that the reaction of secondary amines with aldehydes in the presence of potassium carbonate and at temperatures near 0° gave enamines, while calcium oxide and elevated temperatures were required to cause a reaction between ketones and secondary amines, although usually in poor yield. The introduction by Herr and Heyl 2-4) of the removal of the water produced in the condensation by azeotropic distillation with benzene made possible the facile preparation of enamines from ketones and disubstituted aldehydes. 

Ozonoiysis is a reaction used with unsaturated hydrocarbons when preparing aldehydes and ketones, by reducing intermediate ozonide or acids by oxidation. The reducing agents used include hydrogen in the presence of palladium, and zinc in acid medium. 

The carbonyl of aldehydes and ketones can be transformed into a gem-difluoro group. This transformation can be performed either directly with DAST or in an indirect manner by treating the corresponding thioacetal or hydrazone with an oxidant (NBS, dibromohydantoin, etc.) in the presence of a source of fluoride ions (e.g., HF-pyridin complex or TBABF prepared from TBAF and KHF2). ... 

Monosubstituted and 1,2-disubstituted olefins can be oxidized to aldehydes and ketones by palladium chloride and similar salts of noble metals.367 1,1-Disubstituted olefins generally give poor results. The reaction is used industrially to prepare acetaldehyde from ethylene... 

Aldehydes and ketones are usually prepared on insoluble supports by the acylation of arenes, C,H-acidic compounds, or organometallic reagents. Alcohols or other substrates can also be converted into carbonyl compounds by oxidation (Figure 12.1). Linkers that enable the generation of aldehydes and ketones upon cleavage from a support are considered in Section 3.14. 

The indium-mediated Barbier reaction has certainly become one of the most popular reactions for creating a carbon-carbon bond under aqueous conditions and has led to spectacular developments in recent years. Compared to other metals, indium is resistant to oxidation, hydrolysis, and has a very low first ionization potential (5.79 eV, in contrast to the second one which is quite normal) which confers on it a remarkable reactivity in Barbier-type reactions. In 1991, Li and co-workers reported the first allylation of aldehydes and ketones mediated by indium in water without any additives or special activation [133]. In particular, the use of indium allowed reactions with acid-sensitive compounds [134] or the preparation of complex carbohydrates such as deaminated... 

Alcohols can be prepared by the hydration of alkenes or reduction of aldehydes and ketones. Alcohols can undergo dehydration to )deld alkenes. Primary and secondary alcohols undergo oxidation reactions to yield aldehydes and ketones, respectively. Tertiary alcohols do not undergo oxidation. 

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