Nitro-compounds, aliphatic from oximes

Aliphatic nitro compounds exhibit rather different behavior from nitroaromatic compounds. Secondary and primary nitro compounds tend to produce oximes because the intermediate nitroso compound quickly tautomerizes to the oxime (equation 1). Under aprotic conditions the radical anions of primary and secondary nitro compounds are relatively stable those derived from tertiary nitro compounds, on the other hand, eject nitrite ion relatively readily (equation 2)8. 

If we assume that it is possible to reduce an aliphatic nitro compound to the corresponding nitroso compound, the possibility of a simultaneous isomerisation to an oxime has to be kept in mind. It is known from the reduction of primary and secondary nitro paraffins by stannous chloride1121, that the reduction does not proceed to form amines, which could be explained by a rapid isomerisation of the adsorbed intermediate to an oxime. 

Removal of a proton from an aliphatic nitro compound gives a carbanion (R2C —NO2) that can be alkylated at oxygen or carbon. 0-Alkylation gives nitronic esters, which are generally unstable to heat but break down to give an oxime and an aldehyde or ketone. 

Aliphatic nitro compounds from oximes C NOH —> CHNOa... 

The nitrosation of aliphatic carbon atoms, particularly of carbon atoms activated by adjacent carbonyl, carboxyl, nitrile, or nitro groups, has been reviewed in great detail [2]. Judging from this review, with few exceptions, nitrosation of active methylene compounds leads to the formation of oximes (unfortunately termed isonitroso compounds in the older literature). The few exceptional cases cited in which true nitroso compounds (or their dimers) were formed involved tertiary carbon atoms in which no hydrogen atoms were available to permit tautomerism to the oxime or involved a reaction which was carried out under neither acidic nor basic conditions. 

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