Ketones diimide

Diimide (N2H2, see p. 779) reduces aromatic aldehydes289 and ketones, but aliphatic carbonyl compounds react very poorly.290... 

Derivatives of hydrazine (R NH NH2) react with ketones to form substituted hydrazones of general formula (i). These compounds cannot suffer elimination of nitrogen because the intermediate diimides would be disubstituted, and therefore could not give anions. The effect of forming a substituted hydrazone from an a -substituted ketone is to promote... 

Similar reaction mechanisms involving a diimide intermediate (17) probably account for the conversion of the 5 a-hydroxy 6 ketone (16) into the A -steroid (18) xmder Wolff-Kishner conditions [14], and for the formation of choiest-2-ene (20) when 2a-bromocholestan-3-one (19) was treated with... 

Dimethyl sulfoxide (DMSO), which is successfully used to dehydrogenate primary alcohols to aldehydes, converts secondary alcohols into ketones in very high yields and under very gentle conditions. The mechanism is discussed in a previous section. Dehydrogenation and Oxidation of Primary Alcohols to Aldehydes (equation 217). The first oxidations were carried out in the presence of dicyclohexylcarbodiimide and an acid catalyst such as pyridinium trifluoroacetate [1016], which protonates the diimide and facilitates the attack by dimethyl sulfoxide (equation 259). 

The methods for generating acyl ketenes (Scheme 7-V) and their subsequent in situ participation in [4 + 2] cycloadditions with a wide range of hetero- or olefinic and acetylenic dienophiles (Scheme 7-VI), including acyl ketenes,185 186,197 carbonyl compounds, 86-188 nitriles,1874,189,191 isocyanates and isothiocyanates,1864,190,191 ketenes,191 imines,1864,1874,191,192 carbo-diimides,l87c 190,191,193 ynamines,194 ketene acetals,1864,195 enol ethers,1864,191,196 and V-sulfinylamines197 have been extensively reviewed.5,9,12 Two reports have detailed the 4-n- participation of allenic ketones in [4 + 2] cycloaddition reactions [Eq. (51)].198,199... 

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