Nitro reduction, partial

Reduction of only one of several nitro groups (partial reduction) ... 

During catalytic hydrogenation of nitro derivatives, partial reduction of the nitro group yields azo, hydrazo, hydroxylamine, nitroso, or oxime functions, in side products, as a result of catalyst deactivation. Partial reduction may become synthetically useful under carefully chosen conditions, and in substrates where the new formed function cannot interact within the molecule. Nitrobenzene hydrogenation over platinum-on-carbon in a mixture alcohol-dimethyl sulfoxide (as promoter) produces high yields of phenylhydroxylamines ... 

With 41 in hand, a two-step nitro reduction and protection, followed by partial reduction of the lactam and resulting cyclization furnished aminal 42. Further treatment with cyanogen azide generated Wcyanoamidine 43. Hydrolysis and amide protection followed by alkylation with allyl iodide yielded olefin 44 as a single diastereomer. Conversion of 44 to aldehyde 45 was the followed reaction of the mesylate with azide, a cross-aldol reaction with acetone, lactam reprotection with Boc, and trimethylphosphine-mediated reductive rearrangement to provide spiro-y-lactam 46. Methyllithium addition to lactam 46 and similar chemistry as reported by Qin et al. gave communesin F (17) (Scheme 6). 

PL lifetimes were also examined at product concentrations and are shown in Figure 10. In pure buffer, the lifetime was measured to be 10 psec and, in the presence of j-nitro-phenol, the lifetime was measured to be 6 psec. This decrease indicates the presence of p-nitro-phenol partially quenching the fluorescence. Combining this observation with the PL reduction correlated with p-nitro-phenol build-up, as shown in Figures 9 and 10, indicates the PL is partially quenched by a reversible mechanism, most likely charge transfer between the p-nitro-phenol and the PSi surface. 

In a 500 ml. bolt-head flask, provided with a mechanical stirrer, place 70 ml. of oleum (20 per cent. SO3) and heat it in an oil bath to 70°. By means of a separatory funnel, supported so that the stem is just above the surface of the acid, introduce 41 g. (34 ml.) of nitrobenzene slowly and at such a rate that the temperature of the well-stirred mixture does not rise above 100-105°. When all the nitrobenzene has been introduced, continue the heating at 110-115° for 30 minutes. Remove a test portion and add it to the excess of water. If the odour of nitrobenzene is still apparent, add a further 10 ml. of fuming sulphuric acid, and heat at 110-115° for 15 minutes the reaction mixture should then be free from nitrobenzene. Allow the mixture to cool and pour it with good mechanical stirring on to 200 g. of finely-crushed ice contained in a beaker. AU the nitrobenzenesulphonic acid passes into solution if a little sulphone is present, remove this by filtration. Stir the solution mechanically and add 70 g. of sodium chloride in small portions the sodium salt of m-nitro-benzenesulphonic acid separates as a pasty mass. Continue the stirring for about 30 minutes, allow to stand overnight, filter and press the cake well. The latter will retain sufficient acid to render unnecessary the addition of acid in the subsequent reduction with iron. Spread upon filter paper to dry partially. 

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]... 

Amino-4-nitropheno1 is produced commercially by the partial reduction of 2,4-dinitrophenol This reduction may be achieved electrolyticaHy using vanadium (159) or chemically with polysulftde, sodium hydrosulftde, or hydrazine and copper (160). Alternatively, 2-acetamidophenol or 2-methylbenzoxazole may be nitrated in sulfuric acid to yield a mixture of 4- and 5-nitro derivatives that are then separated and hydrolyzed with sodium hydroxide (161). 

An alternative synthesis of (11) relies on the partial reduction of m-di-nitro groups (p T 38) but l hc-yield is poor. 

The N-labeled amines produced by partial and total reduction of the nitro groups in 2,4,6-trinitrotoluene reacted with carbonyl groups (quinones and ketones) in humic acid to produce a range of products (Thom and Kennedy 2002). 

Interactions may take place between metabolites at different levels of reduction. This may plausibly account for the dimerization of partially reduced intermediates to nitro-azoxytoluenes (Bayman and Radkar 1997), and the identification of azoxy componnds as biotransformation products of 2,4-dinitrotoluene by the fungus Mucrosporium sp. (Figure 9.49) (McCormick et al. 1978). 

Although the possibility of bioremediation of sites contaminated with nitrotoluene waste is clearly possible, important issues should be clearly appreciated. These include (a) additional carbon sources may be necessary to accomplish partial or complete reduction of nitro groups, (b) under aerobic conditions, dimeric azo compounds may be formed as terminal metabolites, and (c) aromatic amines may be incorporated into humic material by covalent bonding and thereby resist further degradation. 

MISCELLANEOUS BENZOHETEROCYCLES Partial reduction of lactone 166 (using for example diisobutylaluminum hydride in the cold) affords lactol 167. Condensation with nitromethane leads to the corresponding alkylated tetrahydrobenzopyran 170. The sequence probably starts by aldol reaction of the hydroxylactone form of the lactol (168) with nitrome thane to give the vinyl nitro intermediate 169 ... 

Partial reduction of the 3,3 -dinitro-4,4 -azoxyfurazan and 3,3 -dinitro-4,4 -azofurazan mixture 178 with Zn/HOAc (glacial) at room temperature gave the novel energetic material 3,3 -dinitro-4,4 -hydrazofurazan 179. The reduction also gives such by-products as 3-amino-3 -nitro-4,4 -azoxyfurazan 180 and 3,3 -diamino-4,4 -azoxyfurazan 181 (Equation 31) <2002USP6388087>. 

Selective reduction (e.g., partial reduction of one of two nitro groups) is carried out with an alkali sulfide, such as sodium hydrogen sulfide NaHS ( sodium sulfhy-drate ) or sodium sulfide Na2S, in an aqueous or alcoholic solution. Azo groups are not affected by this method. The reaction converts sodium hydrogen sulfide or sodium sulfide mainly to sodium thiosulfate. 

The complete reduction of nitro-compounds which contain several nitro-groups is carried out in the same way as in the case of mononitro-derivatives. If, however, only partial reduction is desired, the use of ammonium hydrosulphide is advantageous. 

A special use of sodium arsenite (applied in aqueous alkaline solutions) is partial reduction of trigeminal halides to geminal halides [220] and reduction of aromatic nitro compounds to azoxy compounds [221]. 

With the exception of the nitroso stage, all the intermediate stages of the reduction of nitro compounds can be obtained by controlled catalytic hydrogenation [572], and all reduction intermediates were prepared by reduction with appropriate hydrides or complex hydrides. However, the outcome of many hydride reductions is difficult to predict. Therefore more specific reagents are preferred for partial reductions of nitro compounds. 

Six derivatives of this system have been reported. Compound (113) was obtained by successive nitration of 3,4-dimethoxyphenyl tellurium trichloride (112) and partial reduction of the resulting 6-nitro derivative of (112) (Equation (10)). Compounds (47a)-(47c) were obtained by reaction of the oximes (114a)-(114c) with tellurium dioxide (Equation (11)) <86USP4607000,87USP4661438). 

Nitro compounds in presence of carbonyl group are selectively reduced to amines in the presence of Raney nickel catalyst. Hydrazine reduces nitrdes yielding hydrazones. Under controlled reaction conditions other functional groups, including nitroso and oxime, may be reduced. Many partially hydrogenated derivatives, such as azo-, hydrazo-, and azoxy compounds may be obtained by partial reduction with hydrazine. Reaction with chlorobenzene yields benzene. 

The reduction of carbazole nitro groups to the primary amines is straightforward stannous chloride, tin-hydrochloric acid, iron-hydrochloric acid" hydrogen-palladium/charcoal," hydrogen-nickel,hydrazine-palladium,and hydrazine-nickeP have all been employed. 3,6-Dichloro-l,8-dinitrocarbazole was partially reduced with sodium hydrogen sulfide to give l-amino-8-nitro-3,6-dichloro-carbazole. ... 

The replacement of one nitro group in w-dinitrobenzene by a chlorine atom by means of partial reduction and diazotization has been described by Griess.4... 

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