Diketones nitrations, nitric acid

Oxidation of benzoin with concentrated nitric acid or by catalytic amounts of cupric salts in acetic acid solution, which are regenerated continuously by ammonium nitrate, yields the diketone benzil ... 

Symmetrical and unsymmetrical benzoins have been rapidly oxidized to benzils in high yields using solid reagent systems, copper(II) sulfate-alumina [105] or Oxone-wet alumina [105, 106] under the influence of microwaves (Scheme 6.32). Conventionally, the oxidative transformation of a-hydroxy ketones to 1,2-diketones is accomplished by reagents such as nitric acid, Fehling s solution, thallium(III) nitrate (TTN), ytterbium(III) nitrate, ammonium chlorochromate-alumina and dayfen. In addition to the extended reaction time, most of these processes suffer from drawbacks such as the use of corrosive acids and toxic metals that generate undesirable waste products. 

Electrophilic nitrations of aliphatic nitriles, carboxylic acids,carboxylic esters, ° and /3-diketones have been reported. The nitration of 2-alkyl-substituted indane-l,3-diones with nitric acid, followed by alkaline hydrolysis, is a standard laboratory route to primary nitroalkanes. ... 

Dave and co-workers have reported a successful synthesis of 2,2,4,4-tetranitroadamantane (117) which uses the mono-protected diketone (113) as a key intermediate. In this synthesis (113) is converted to the oxime (114) and then treated with ammonium nitrate and nitric acid in methylene chloride to yield the em-dinitro derivative (115). This nitration-oxidation step also removes the acetal-protecting group to leave the second ketone group free. Formation of the oxime (116) from ketone (115), followed by a similar nitration-oxidation with nitric acid and ammonium nitrate, yields 2,2,4,4-tetranitroadamantane (117). In this synthesis the protection strategy enables each carbonyl group to be treated separately and thus prevents the problem of internal nitroso dimer formation. 

Figure 5-7. The direct nitration of a co-ordinated 2,4-diketonate ligand. The 2,4-diketonate complexes are not usually stable to nitric acid and the nitration is effected by milder reagents, such as a mixture of copper(n) nitrate and acetic anhydride (which generates N204). When tris(diketonate) complexes, such as [Co(acac)3] are nitrated, mixtures of mono-, bis- and tris- substituted products are obtained.

Nitration of Active Methylene Carbons. Active methylene carbons are nitrated by a number of reagents.With nitric acid the nitration of /S-diketones can be achieved (eq 7). Nitration of diethyl malonate provides diethyl nitromalonate in 92% yield. a-Nitro ketones are obtained by nitration of ketones or enol acetates with the reagent derived from nitric acid and acetic anhydride in moderate to good yields (eq 8). ... 

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