Nitro-azoxy reductive

Reduction of Nitro to Azoxy Compounds Nitro-azoxy reductive transformation... 

Ind 1954, 1355 (Thiourea as a reducing agent for aromatic nitro, azoxy, azo and hydrazo compds) CA 49, 13106 (1955) 20) S.JoAiewicz and H.Kuczynski, Zeszyty-NaukPolitechWroclaw (Poland) No 4, Chem No 1, 5-14 (1954) (Reduction of aromatic nitro compds by H2S in pyridine) CA 50, 214-5(1956) 21)S.Carboni G.Berti, Gazz... 

The alkaline reduction of an aromatic nitro-compound to give the azoxy... 

Nitro-compounds yield a series of reduction products accordmgto the nature of the reducing agent. Alkaline reducing agents sodium methylate, zinc dust and caustic soda, stannous chloride and caustic soda, produce azoxy, azo- and hydiazo-compounds. 

Azoxy compounds can be obtained from nitro compounds with certain reducing agents, notably sodium arsenite, sodium ethoxide, NaTeH, NaBH4—PhTeTePh, and glucose. The most probable mechanism with most reagents is that one molecule of nitro compound is reduced to a nitroso compound and another to a hydroxylamine 119-42), and these combine (12-51). The combination step is rapid compared to the reduction process. Nitroso compounds can be reduced to azoxy compounds with triethyl phosphite or triphenylphosphine or with an alkaline aqueous solution of an alcohol. ... 

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). 

The reduction of nitroarenes to azoxy compounds ArN=N(0)Ar is promoted by bismuth trichloride/powdered zinc427. Aromatic amines are formed in excellent yields in the reduction of nitroarenes with BH3/NiCl2428 or nickel boride429. Acyl, ester, amide and cyano groups are not affected. Reaction of the nitro compounds RCH2N02 (R = Ph, Bz... 

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]. 

Aromatic nitro compounds were among the first organic compounds ever reduced. The nitro group is readily converted to a series of functions of various degrees of reduction very exceptionally to a nitroso group, more often to a hydroxylamino group and most frequently to the amino group. In addition azoxy, azo and hydrazo compounds are formed by combination of two molecules of the reduction intermediates (Scheme 58). 

Chapter 11 - Reduction of Nitro, Nitroso, Azo and Azoxy Groups, Pages 371-396 Index, Pages 397-401... 

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 reductive methods of preparing azo compounds involve, as starting materials, aromatic nitro compounds, azoxy compounds, and azines. 

Historically this reaction developed from the assumption that the formation of azoxy compounds by the reduction of aromatic nitro compounds probably involved the intermediate formation of C-nitroso compounds and hydroxylamines. In the all-aliphatic series, this reaction appears to be quite general. Symmetrically and unsymmetrically substituted azoxy compounds have been prepared by it, the only major problems being the usual ones of developing procedures that afford good yields and of determining the exact position of the azoxy oxygen in unsymmetrically substituted products. 

The bimolecular reduction of aromatic nitro compounds, depending on reaction conditions, may proceed by way of azoxy and azo compounds to 1,2-diarylhydrazines (also referred to as hydrazo compounds). This may be... 

When sodium methylate or ethylate was prepared by direct reaction of sodium with an excess of alcohols and the resulting mixture was used as a dispersion in benzene to reduce aromatic nitro compounds, yields of azoxy compounds were quite low. With the higher alcohols, substantial production of azoxy compounds was observed. However, the reduction product mixture usually contained a 40 % yield of amino compounds. In a few examples, where benzyl alcohol was used to prepare sodium benzylate, only azoxy products and no amino by-products were formed. The scope of this preparation requires further study. 

The nature of the azo bond is such that only a very limited number of possible functional groups can be considered to have the necessary features to serve as starting materials for reductive methods of preparation. In a sense, the Bogo-slovskii reaction [17, 18] may be considered a reduction of a diazonium salt by copper(I) ions. However, because the reaction resembles the other condensations of diazonium salts, its classification among the condensation reactions seems appropriate. The direct reduction of azoxy compounds as such is of minor preparative importance except as a method of identification of an azoxy compound. However, in the various bimolecular reduction procedures of aromatic nitro compounds, it has been postulated that an azoxy intermediate forms in the course of the reaction. This intermediate azoxy compound is ultimately reduced to an azo compound. 

The reduction of aromatic nitro compounds is believed to proceed to an intermediate mixture of nitroso compounds and substituted hydroxylamines which are not isolated but condense to form an azoxy compound which, in turn, is reduced to an azo compound. Contributing evidence to substantiate this mechanism is that the reduction of a mixture of two aromatic nitro compounds leads to a mixture of azo compounds consistent with that predicted if each of the nitro compounds were reduced to a nitroso compound and a hydroxylamine and these, in turn, reacted with each other in all possible combinations. This observation also implies that the bimolecular reduction of nitro compounds is practical only from the preparative standpoint for the production of symmetrically substituted azo compounds. Spectrophotometric studies of the reaction kinetics of the reduction of variously substituted nitro compounds may, however, uncover reasonable procedures for the synthesis of unsymmetrical azo compounds. 

The bimolecular reduction of aromatic nitro compounds, depending on reaction conditions, may produce azoxy compounds, azo compounds, hydrazo compounds (1,2-diarylhydrazines), benzidines, or amines. Whereas the reduction with zinc and sodium hydroxide leads to azo compounds, zinc and acetic acid/acetic anhydride produces azoxy compounds. Other reducing agents suggested are stannous chloride, magnesium with anhydrous methanol, a sodium-lead alloy in ethanol, thallium in ethanol, and sodium arsenite. 

As indicated in the preceding chapter, the reduction of aromatic nitro compounds with zinc and sodium hydroxide solution leads to the azo product [39, 40]. On the other hand, in an acetic acid-acetic anhydride medium, reduction with zinc produces a symmetrical azoxy compound [41]. 

The reduction of aromatic nitro compounds to azoxy products with stannous chloride in a basic medium has also been reported however, the final purification of the product appears to be tedious [39],... 

The reduction to produce azoxy compounds appears to be successful for a wide range of aromatic nitro compounds. The following compounds, however, could not be reduced 1-nitronaphthalene, m-dinitrobenzene, 3,5-dinitroben-zoic acid (although o-, m-, and p-nitrobenzoic acids were reduced smoothly), compounds containing an amino group o-, orp- to a nitro group (except sodium... 

Substituted nitrobenzenes gave similar results on reduction of less than stoichiometric quantities in the absence of added alkali, hydrogen atom-substrate ratios of 3.0 to 4.1 being obtained while cessation of hydrogen absorption occurred at H/Co = 2.0 in all cases. Azoxy and azo compounds were isolated from o-nitrotoluene (H/substrate = 3.9) p-nitrotoluene (H/substrate = 3.2) yielded a mixture of azoxy and hydroxylamine derivatives, the latter believed to be the immediate precursor of the bimolecular product. Reduction of o-nitro-anisole in the presence of added alkali (NaOH, 3.3X cobalt concentration)... 

Oxidative cleavage of amines 9-39 Reduction of amides 9-47 Reduction of nitro compounds 9-50 Reduction of nitroso compounds or hydroxylamincs 9-51 Reduction of oximes 9-52 Reduction of azides 9-53 Reduction of isocyanates, isothiocyanates, or N-nitroso compounds 9-55 Reduction of amine oxides 9-59 Reduction of azo, azoxy, or hydrazo compounds... 

Reduction of azoxy compounds 9-67 Reduction of nitro compounds... 

The most common method of preparing azoxy compds is by the reduction of nitro compds ... 

Identification of azoxy compds) CA 45, 57K195D 10)H.W.Galbraith et al. JACS 73, 1323-4(1951) (Alkaline reduction of aromatic nitro compds with glucose to azoxy compds)... 

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