Aliphatic Nitro Groups

Suitable halogen compounds are primary and secondary alkyl halides and benzyl or aryl halides, the last-mentioned provided that the halogen is activated by an o- or p-nitro group. Aliphatic sulfinates usually give lower yields than aromatic sulfinates. 

Table 3 (No. 16) shows that ( )-p-nitro-cmnamate or derivatives can be reduced by enoate reductase, too. However, this reaction can be performed only with isolated enoate reductase using NADH as electron donor. Reduced methylviologen spontaneously reacts with nitro groups. Aliphatic as well as aromatic nitro compounds are also reduced by ferredoxins present in clostridia (26).

Aromatic nitro groups (aliphatic nitro groups can yield... 

Some nitro-compounds are themselves coloured and can be used as dyestuffs, e.g. picric acid. In this case the nitro-group can be considered to be the chromophore. For aliphatic nitro-compounds see nitroparaffins. 

Formic acid is a good reducing agent in the presence of Pd on carbon as a catalyst. Aromatic nitro compounds are reduced to aniline with formic acid[100]. Selective reduction of one nitro group in 2,4-dinitrotoluene (112) with triethylammonium formate is possible[101]. o-Nitroacetophenone (113) is first reduced to o-aminoacetophenone, then to o-ethylaniline when an excess of formate is used[102]. Ammonium and potassium formate are also used for the reduction of aliphatic and aromatic nitro compounds. Pd on carbon is a good catalyst[103,104]. NaBH4 is also used for the Pd-catalyzed reduction of nitro compounds 105]. However, the ,/)-unsaturated nitroalkene 114 is partially reduced to the oxime 115 with ammonium formate[106]... 

Nitro C—NO2 Aliphatic ca 1560 (s) 1385-1350 (s) The two bands are due to asymmetrical and symmetrical stretching of the N=0 bond. Electron-withdrawing substituents adjacent to nitro group increase the frequency of the asymmetrical band and decrease that of the symmetrical frequency. 

In this method the nitro group in the aliphatic nitro compound is usually present on a carbon atom, which is also activated by CO-functioiiality (aldehyde, ester, arylketoiie). A successful application of this method is the Borsche modification of the Friedlander synthesis, involving condensation of A-(3-amino-4-picolylidene)-p-toluidine (17) with [Pg.289]

A similar reaction pathway is even described for an aliphatic nitro group nucleophilic displacement. Nitrohydrazones 126 with sodium hydride provide acceptable yields (40-60%) of tricyclic [l,2,4]triazolo[5,l-c][l,4]benzoxazines 128... 

S909). First, an addition of the cyano group takes place to give intermediate 127, in which nucleophilic substitution of aliphatic nitro group provides the final product 128 (Scheme 20). 

The 8-nitro group in intermediate quinolone 225 can be easily displaced even with aliphatic oxygen nucleophiles. Starting compound 224 under various conditions provided directly tricyclic compound 226 and all attempts to isolate the expected intermediate 225 failed (Scheme 34) (91CCC1937). 

Electrochemically generated nickel is very selective for the reduction of ai compounds into anilines, in which alkenyl, alkyhyl, halo, cytino, formyl, ind benzyloxy groups are not affected. Sodium snlfide has been used for the selective reduction of at group in the presence of aliphatic nitro groups (Tq. 6.44. ... 

Nitro-bakterien, n.pl. nitrobacteria, -benzol, -benzin, n. nitrobenzene, -chinon, n. nitro-quinone. -cocussaure, /. nitrocoeeic acid, -derivat, n. nitro derivative, -farbstoff, m. nitro dye. -fettkorper, m. aliphatic nitro compound, -fettsaure, /. nitro fatty acid, -gruppe, /. nitro group, -halogenbenzole,... 

The nitro group is reduced easily in preference to a nitrile (23,25,45,84) especially if the nitro group is aromatic and the groups are unable to interact, but the reverse preference has been seen (100) in certain aliphatic molecules. 

There is no problem of chemoselectivity here it is not possible to reduce the aliphatic NO group in (10) without reducing the aromatic NO group too. This is easily solved by introducing the aromatic nitro group after the reduction. 

As already discussed in Section 7.4, hexamethyidisiiane 857 (which is produced on a technical scale), in the presence of catalytic amounts of tetrabutylammonium fluoride di- or trihydrate in THF, reduces aromatic heterocyclic N-oxides such as pyridine N-oxide 860, quinoline N-oxide 877, or isoquinoline N-oxide 879 to the heterocycles [95] and nitrones to Schiff-bases. Aromatic nitro compounds such as nitrobenzene are reduced analogously to azo compounds such as azobenzene [96]. As mentioned in Section 7.5, secondary aliphatic nitro groups are reduced to oximes. 

Aromatic nitroso groups are as easily hydrogenated as nitro groups however such groups attached to aliphatic moieties are not so readily hydrogenated. 

Nitro Compounds. Under mild conditions, aromatic nitro compounds are hydrogenated easily to amines.518 The reaction may give partially reduced products, according to the circumstances. Palladium, platinum, and nickel are used frequently for this reaction. For example, nitro and benzyl ester functions are reduced on Pd(OH)2/C on THF and on Pd/C in EtOH.519 Aliphatic nitro groups are reduced more slowly. 

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