Nitro compounds with active hydrogen

Class II Other liquids composed of molecules containing both active hydrogen atoms and donor atoms (oxygen, nitrogen, and fluorine)—e.g., alcohols, acids, phenols, primary and secondary amines, oximes, nitro compounds with alpha-hydrogen atoms, nitriles with alpha hydrogen atoms, ammonia, hydrazine, HF, HCN (plus nitromethane, acetonitrile even though these form 3-dimensional networks they have weaker bonds than —OH and —NH bonds in class I)... 

Class 2 Other liqnids that have both active hydrogen atoms and donor atoms (O, N, F see Chapter. 3), but do not form three-dimensional networks (rather forming chainlike oligomers), e.g., primary alcohols, carboxylic acids, primary and secondary amines, nitro compounds with a-positioned hydrogen atoms, liqnified ammonia, etc. They are generally called protic or protogenic snbstances. 

In a reaction originating with Michael69 and Claisen,70 compounds containing active hydrogen add to, / -unsaturated aldehydes, ketones, esters, nitriles, sulfones, or nitro compounds, the C-C bond being formed to the vinyl carbon atom that is / to the carbonyl (or analogous) group ... 

The first chemists working in the area of the carbonylation of nitro compounds immediately noted many similarities between the products obtained from these reactions and the ones obtained from the reactions of organic azides (R-N3), which were known to be sources of free nitrenes when activated either photochemically or thermally (for some examples see [255, 256]). Similarities were especially found in the formation of coupled products such as azoarenes and in the formation of products derived from hydrogen-abstraction from the solvent or the nitro compound itself [255], a reaction typical for nitrenes in the triplet state [257]. It was also noted that high pressures were required to drive the reactions of both azides and nitro compounds with CO towards the synthesis of isocyanates rather than towards hydrogen-abstraction-derived products and this... 

Aliphatic nitro compounds 1035 with an a-hydrogen atom are readily O-silylated by N-trimethylsilyl-N,N -diphenylurea 23b to give a mixture of 1036 or 1037 [99]. This silylation works in particularly well if Ri and or R2 are activating nitro or car-... 

At an early stage it was found that the nitro group had the power of activating the hydrogen atom(s) on the carbon to which the NO2 is attached. Victor Meyer found that primary and secondary (but not tertiary) nitro compounds dissolve slowly in alkali and if alcohol is added an alkali metal salt of the nitro compound is precipitated. Thus the activation of CH by NO2 was associated with incipient acidity and the behaviour of the group in this way was similar to that of certain other groups such as CN, COMe and COOEt6. It was more than twenty years, however, before the incipient acidity of CH adjacent to NO2 was correctly formulated in terms of the tautomerism of nitro and isonitro or aci forms. 

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