Carbonyl compounds intermolecular hydrogen abstraction

The photoreaction investigated to test the above model is the well-known electron-transfer-initiated intermolecular hydrogen abstraction reaction of carbonyl compounds [277]. Under the conditions employed, one of the guest mole-... 

One of the earliest photoreactions to be studied was the photoreduction of benzophenone (Ciamician and Silber, 1900)—that is, the conversion of a carbonyl compound into an alcohol by an intermolecular hydrogen abstraction reaction. Intramolecular hydrogen abstraction by the carbonyl group, usually from the y site, is referred to as a Norrish type II reaction. Hydrogen abstraction by olefins and heterocycles has also been observed. 

Electronically excited carbonyl compounds serve as versatile intermediates in countless reactions. They not only operate as reactive substrates for intra- and intermolecular hydrogen abstraction and cycloaddition reactions as well as C-C cleavage steps, but many of them also are useful sensitizers for the generation of triplet excited compounds. This variety of reaction possibilities makes carbonyl photochemistry sometimes very complex,... 

Manganese(III) can oxidize carbonyl compounds and nitroalkanes to carboxy-methyl and nitromethyl radicals [186]. With Mn(III) as mediator, a tandem reaction consisting of an intermolecular radical addition followed by an intramolecular electrophilic aromatic substitution can be accomplished [186, 187). Further Mn(III)-mediated anodic additions of 1,3-dicarbonyl and l-keto-3-nitroalkyl compounds to alkenes and alkynes are reported in [110, 111, 188). Sorbic acid precursors have been obtained in larger scale and high current efficiency by a Mn(III)-mediated oxidation of acetic acid acetic anhydride in the presence of butadiene [189]. Also the nitromethylation of benzene can be performed in 78% yield with Mn(III) as electrocatalyst [190]. A N03 radical, generated by oxidation of a nitrate anion, can induce the 1,4-addition of aldehydes to activated olefins. NOj abstracts a hydrogen from the aldehyde to form an acyl radical, which undergoes addition to the olefin to afford a 1,4-diketone in 34-58% yield [191]. 

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