Oxidation of Nitro Compounds

Because the nitrogen in nitro compounds is at the highest oxidation state, nitro compounds can be oxidized only in the carbon chain to which the nitro group is attached. The oxidation of primary and secondary nitro compounds in the form of their nitronic acids in alkaline medium by potassium permanganate represents a variation of the Nef reaction and gives the same products aldehydes from primary nitro compounds and ketones from secondary nitro compounds (equation 484) [867], 

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TABLE 13. Base catalyzed oxidation of nitro compounds by BTSP... 

Oxidation of nitro compounds to nitrophenols is another example of a nucleophilic reaction. Thus, m- dinitrobenzene and sym- trinitrobenzene were oxidized in an alkaline medium when boiled with potassium ferricyanide solution (Hepp[45]) ... 

The oxidation of nitrobenzene to o- nitrophenol (with traces of the p- isomer) when mixed with dry sodium hydroxide, and slightly heated, may be another example of the oxidation of nitro compounds by nucleophilic substitution (Wohl [46]) ... 

Although discovered in the eariy 19(X)s, the oxidation of nitro compounds with potassium permanganate has become a truly useful reaction only within the last 23 years. An alkoxide base is used to form the nitronate salt, and aqueous potassium permanganate gives the oxidized product in excellent yield. Even aldehydes can be obtained as in equation (9) without loss of the pivaloyl group. Cetyltri-... 

Oxidation of Nitro Compounds into Carbonyl Compounds Alkaline KMnO oxidises primary and secondary nitro groups into the corresponding carbonyl compounds (aldehydes and ketones respectively) (Scheme 85). 

Azo-compounds can be obtained by reduction of nitro-compounds, or by oxidation of hydrazo-compounds. They are usually prepared, however, by reacting a phenol or amine with a diazonium salt. The coupling usually takes place in the position para to the hydroxyl or amino group, but if this position is occupied it goes to the ortho position, e.g. 

Water. Based on the overall balanced equation for this reaction, a minimum of one mole of water per mole of nitro compound is required for the reduction to take place. In practice, however, 4 to 5 moles of water per mole of nitro compound are used to ensure that enough water is present to convert all of the iron to the intermediate ferrous and ferric hydroxides. In some cases, much larger amounts of water are used to dissolve the amino compound and help separate it from the iron oxide sludge after the reaction is complete. 

Cycloaddition reactions of nitro compounds, nitrones, and nitrile oxides 99JCS(P1)749. 

Aiiphadc md aromadc primary amines are rapidly md efficiently oxidized to nitro compounds by dimethyldioxirime. Dimethyldioxirime is prepared by teacdon of OXONE (Du-... 

Catalytic cleavage of the nitrogen-oxygen bond occurs very frequently as in reduction of nitro compounds, oximes, and various heterocyclics these reactions are discussed in separate chapters. Considered here are N-oxides, hydroxylamincs, and N- and C-nitroso compounds. 

Tertiary alkyl primary amines can be oxidized to nitro compounds in excellent yields A ith KMn04. This type of nitro compound is not easily prepared in other ways. 

All classes of primary amine (including primary, secondary, and tertiary alkyl as well as aryl) are oxidized to nitro compounds in high yields with dimethyl dioxirane." Other reagents that oxidize various types of primary amines to nitro compounds are dry ozone, various peroxyacids," MeRe03/H202,"" Oxone ," ° tcrt-butyl hydroperoxide in the presence of certain molybdenum and vanadium compounds, and sodium perborate." ... 

Aromatic nitro and nitroso compounds are easily reduced at carbon and mercury electrodes. Other nitro compounds such as nitrate esters, nitramines, and nitrosamines are also typically easily reduced. The complete reduction of a nitro compound consists of three two-electron steps (nitro-nitroso-hydroxylamine-amine). Since most organic oxidations are only two-electron processes, higher sensitivity is typically found for nitro compounds. Several LCEC based determination of nitro compounds have been reported... 

Recently, nitration of organolithiums and Grignards with N204 has been developed for the preparation of certain kinds of nitro compounds (Eqs. 2.14 and 2.15).31 The success of this process depends on the reaction conditions (low temperature) and the structure of substrates. For example, 3-nitrothiophene can be obtained in 70% overall yield from 3-bromothiophene this is far superior to the older method. 3-Nitroveratrole cannot be prepared usefully by classical electrophilic nitration of veratrole, but it can now be prepared by direct o>7/ o-lithiation followed by low-temperature N204 nitration. The mechanism is believed to proceed by dinitrogen tetroxide oxidation of the anion to a radical, followed by the radical s combination. 

SYNTHESIS OF NITRO COMPOUNDS BY OXIDATION 2.2.1 Oxidation of Amines... 

Aliphatic and aromatic primary amines are rapidly and efficiently oxidized to nitro compounds by dimethyldioxirane.111 Dimethyldioxirane is prepared by reaction of OXONE (DuPont trademark)-2KHS05-KHS04-K2S04 with buffered aqueous acetone.112... 

Conversion of carbonyl to nitro groups (retro Nef Reaction) is an important method for the preparation of nitro compounds. Such conversion is generally effected via oximes using strong oxidants such as CF3CO3H.120... 

Nitro compounds are versatile precursors for diverse functionalities. Their conversion into carbonyl compounds by the Nef reaction and into amines by reduction are the most widely used processes in organic synthesis using nitro compounds. In addition, dehydration of primary nitro compounds leads to nitrile oxides, a class of reactive 1,3-dipolar reagents. Nitro compounds are also good precursors for various nitrogen derivatives such as nitriles, oximes, hydroxylamines, and imines. These transformations of nitro compounds are well established and are used routinely in organic synthesis. 

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