Nitrobenzenes, reductive coupling with

The highly oxophilic nature of the cobalt powder was readily demonstrated by its reaction with nitrobenzene at room temperature. Reductive coupling was quickly effected by 2 to give azo- and azoxy derivatives. Nitrobenzene reacted with 2 to give azobenzene in yields up to 37%. In some cases small amounts of azoxybenzene were also formed. With 1,4-diiodonitrobenzene, 2 reacted to give low yields of 4,4-diiodoazoxy-benzene and 4,4-diiodoazobenzene. 

In the sulphonation of aniline small amounts of the o-compound are produced along with sulphanilic acid. Aniline o-sulphonic acid, however, is of no further interest. Metanilic acid, on the other hand, is also manufactured as an intermediate in the azo-dye industry. It is obtained from nitrobenzene-m-sulphonic acid by reduction. The amino-(iand hydroxy-) sulphonic adds of the naphthalene series are of the greatest technical importance. They are either diazotised themselves or serve for coupling with other diazo-compounds. In this way the most important azo-dyes are produced. 

Electrochemical functionalization - reductive coupling of diazonium salts The electrochemical functionalization of SWCNTs, deposited on an Si/Si02 substrate, with 4-nitrophenyl groups succeeded by the reduction of 4-nitrobenzene-diazonium salt in a mini-electrochemical cell with platinum counter and (pseu-do-)reference electrodes. A probe needle was used to make contact with one of the Au-Pd bonding pads on the substrate and allowed the application of an electric potential to the electrode (-1.3 V vs. Pt for >30 s) and to any SWCNTs underneath the electrode [177b]. 

Nitro compounds are reduced to the corresponding amine. Unlike hydride reductions, both alkyl nitro compounds (2-methyl-2-nitro-1,3-propanediol was reduced to l-amino-2-methyl-1,3-propanediol in 95% yield)566 and aromatic nitro derivatives [nitrobenzene was reduced to aniline with Ti(S04)3 in sulfuric acid and cetyltrimethylammonium bromide] are electrolytically reduced. 7 jf conditions are modified, reductive coupling can give azoxy compounds such as 568 (from 569) or diazo compounds. A variety of acid derivatives are reduced under electrochemical conditions, including nitriles (to amines), acids (to alcohols),5 E572 estejs (jq alcohols), and amides (to alcohols). It is possible to selectively reduce a cyclic imide to a lactam.575... 

A novel attempt for the better utilization of the normal pulse polaro-graphic method in the study of follow-up reaction kinetics has been proposed by Kim [117], This technique is based on symmetry analysis of the first and higher-order derivative NP polarographic curves. Reversible electron transfer coupled with a first-order irreversible following reaction (ECirr mechanism) was assumed. Significant effects were expected for fast chemical steps. This supposition is true for benzidine rearrangement in the course of the reduction of nitrobenzene [18, 116, 117]. 

The feet that part of the starting perdeuteronitrobenzene is found at the end of the reaction as perdeuteroaniline, coupled with the other selectivity data, indicates that the nitrobenzene acting as an oxidant is at least in large part transformed into aniline (which may possibly reenter the catalytic cycle only at a later stage) and is not directly converted to carbonylated products (Some of the perdeuteroaniline may derive from a direct reduction of nitrobenzene by CO and the water formed in eq. 22 [51], a reaction which has not been considered in the... 

If the reduction of nitrobenzene takes place in neutral solution with zinc dust and water in presence of a little calcium or ammonium chloride, or with aluminium-mercury couple and watei, /d-phenylhydio. ylamme is formed (see Prep. 52, p. 14S). 

The use of a PTC, tetramethylammonium hydroxide, to carry out the coupling under aeration of nitrobenzene and aniline to give nitroso diphenylamine (which on catalytic reduction with H2 gives 4-aminodiphenylamine, required in the rubber industry) may be cited as a green chemistry route compared to the established process based on p-nitrochlorobenzene and aniline where Cl is wasted (Bashkin et al. 1999). 

The syntheses of these three compounds share a common route as described by Brickner et al. [53] and Barbachyn et al. [54]. Namely, the coupling reaction of 3,4-difluoronitrobenzene (82) with piperazine, morpholine, or thiomorpholine to yield the corresponding 4-substituted 3-fluoro-nitrobenzene (83), which upon reduction gives rise to the aniline derivative (84). Carbobenzoxy protection of the active nitrogen of 84 using benzyloxy-carbonyl chloride (CbzCl) results in the formation of carbamates 85a and 85b. Treatment of 85a,b with n-BuLi and (i -glycidyl butyrate yields a 5-(R)-... 

Interestingly, the photoreaction of indene with nitroarenes gives good yields of coupling products as shown in equation 62 (66% from 2-nitrothiophene and 52% from 2-nitrofurane). Nitrobenzene gives the reduction product. Strangely there is no reaction for p-nitrotoluene with indene. 

Coordination chemistry reveals how two ArN species can be coupled into one azobenzene molecule. In the case of the reaction of Fe3(CO)12 with aromatic nitro compounds in benzene1161, formation of derivatives such as in structure 111 has been proven by X-ray diffraction. Azoxybenzene can be formed by reaction of nitrene with nitrosobenzene, formed by reduction of nitrobenzene. 

It is postulated that the degree of polymerisation for [Si(0)Pc] (67) obtained by vacuum treatment is 3 and by heating in nitrobenzene 11. But surprisingly no reduction of intensity was observed when going from Ge(OH)2Pc to [Ge(0)Pc] This may be explained by vibronic coupling, which decreases with increasing distance between neighbouring Pc ". ... 

Nitrosobenzene may act as an electrophilic center, and in alkaline solution phenylhydroxylamine reacts with it with formation of azoxybenzene [130-132]. The reaaction may go through an initial, homogeneous one-electron transfer followed by a radical coupling [132]. This reaction occurs generally during the reduction of simple nitrobenzenes in alkaline solution and makes azo and hydrazobenzenes as well as benzidines easily available. Azoxybenzenes may, however, also be formed in acid solution [94,104,121] ... 

A mixture of products was produced in the case of 4-nitrobenzaldehyde due to competing reduction of the nitro group as observed by the reduction of nitrobenzene in an independent experiment and also with aliphatic aldehydes. No coupling of 4-chlorobenzaldehyde took place when methanol was replaced by THF, but when methanol was replaced by MeCN, a mixture of containing starting aldehyde, the corresponding alcohol and the diol was obtained. 

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