Reduction of nitroaromatic compounds

A judicious combination of plural dihydroxyboryl and multiple hydroxyl components can lead to the formation of various boronate-based self-assemblies. Furthermore, the surfaces of such ensembles are composed of boronate esters with Lewis-acidic characteristics, and this opens up new possibilities for the use of scaffolds in various applications. In this context, we envisaged that such self-assemblies might have applications in the fabrication of organic-inorganic hybrid catalysts. The development of new types of catalyst for fine chemical synthesis is urgently required from the viewpoint of sustainable chemistry and green organic synthesis in particular, Au nanoparticle (Au NP)-catalysed fine chemical synthesis has the potential for practical use in industry.  

By replacing THB with pentaerythritol (PE), well-defined boronate self-assemblies (BP) were obtained by aging a THF solution of BDBA and PE at 

The deposition reduction (DR) method was used in an initial attempt to deposit nanogold on the surfaces of BP a solution of HAUCI4 in methanol was added to a turbid solution of BP in methanol, followed by filtration, dispersion in methanol, and reduction with NaBH4. However, nanogold was not deposited on the surface. The zeta potential of the support is negative (-33.24 mV), so AuCl4 hardly binds to the surface. To overcome this difficulty, we used polyethyleneimine (PEI) as a binder for nanogold deposition.  

HR-TEM image of lattice structure observed for ill facet of nanogold. 

The next stage was to assess the catalytic activity, via reduction of 4-nitro-phenol (4-NP) with NaBH. The reaction kinetics were simultaneously examined using absorption spectroscopy, enabling easy quantitative determination of the activity.  

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Two important examples of reductive metabolism of xenobiotics are the reductive dehalogenation of organohalogen compounds, and the reduction of nitroaromatic compounds. Examples of each are shown in Figure 2.13. Both types of reaction can take place in hepatic microsomal preparations at low oxygen tensions. Cytochrome P450 can catalyze both types of reduction. If a substrate is bound to P450 in the... 

Glaus M A, CG Heijman, RP Schwarzenbach, J Zeyer (1992) Reduction of nitroaromatic compounds mediated by Streptomyces sp. exudates. Appl Environ Microbiol 58 1945-1951. 

Schwarzenbach RP, R Stierliu, K Lanz, J Zeyer (1990) Quinone and iron porphyrin mediated reduction of nitroaromatic compounds in homogeneous aqueous solution. Environ. Sci. Technol. 24 1566-1574. 

Rafii F, W Franklin, RH Hetlich, CE Cerniglia (1991) Reduction of nitroaromatic compounds by anaerobic bacteria isolated from the human gastrointestinal tract. Appl Environ Microbiol 51 962-968. 

Schwarzenbach, R. P., R. Stierli, and J. Zeyer (1990), "Quinone and Iron Porphyrine Mediated Reduction of Nitroaromatic Compounds in Homogeneous Aqueous Solution , Env. Sci. Technol. 24/10, 1566-1574. 

Although most color tests for polynitroaromatic explosives are based on their reaction with bases, a completely different approach involves the reduction of nitroaromatic compound to the corresponding aromatic amine. Zn, SnCl2, and TiCls in acidic medium were used as reducing agents [23—26]. The aromatic amine is then identified by one of two methods ... 

Klupinski et al. (2004) conclude that the reduction of nitroaromatic compounds is a surface-mediated process and suggest that, with lack of an iron mineral, reductive transformation induced only by Fe(II) does not occur. However, when C Cl NO degradation was investigated in reaction media containing Fe(II) with no mineral phase added, a slow reductive transformation of the contaminant was observed. Because the loss of C Cl NO in this case was not described by a first-order kinetic model, as in the case of high concentration of Fe(II), but better by a zero-order kinetic description, Klupinski et al. (2004) suggest that degradation in these systems in fact is a surface-mediated reaction. They note that, in the reaction system, trace amounts of oxidize Fe(II), which form in situ suspended iron oxide... 

Sanders PF, Wolfe NL. 1985. Reduction of nitroaromatic compounds in anaerobic sediment/water systems. Amer Chem Soc 25 225-226. 

The required A-arylhydroxylamines may also be generated in situ by treatment of the corresponding nitrobenzenes with mild reductive metals in liquid hydrogen fluoride323 (former reports324-325). Examples of the reduction of nitroaromatic compounds 12 to fluoroaromatic amines 11 arc given below.323... 

Illustrative Example 14.5 Estimating Rates of Reduction of Nitroaromatic Compounds by DOM Components in the Presence of Hydrogen Sulfide... 

Haderlein, S. B., and R. P. Schwarzenbach, Environmental processes influencing the rate of abiotic reduction of nitroaromatic compounds in the subsurface . In Biodegradation of Nitroaromatic Compounds, J. C. Spain, Ed., Plenum Press, New York, 1995, pp. 199-225. 

Heijman, C. G., E. Grieder, C. Holliger, and R. P. Schwarzenbach, Reduction of nitroaromatic compounds coupled to microbial iron reduction in laboratory aquifer columns , Environ. Sci. Technol., 29, 775-783 (1995). 

Nivinskas, H., R. L. Koder, Z. Anusevicius, J. Sarlauskas, A.-F. Miller, and N. Cenas, Quantitative structure activity relationships in two-electron reduction of nitroaromatic compounds by Entrobacter cloacae NAD(P)H nitroreductase , Arch. Biochem. Biophys., 385, 170-178 (2001). 

Hofstetter T. B. Neumann A. Arnold W. A. Hartenbach A. E. Bolotin J. Cramer C. J. Schwarzenbach R. P. Substituent effects on nitrogen isotope fractionation during abiotic reduction of nitroaromatic compounds. Environ. Sci. Technol. 2008, 42, 1997-2003. 

Klausen J, Ranke J, Schwarzenbach RP. Influence of solution composition and column aging on the reduction of nitroaromatic compounds by zerovalent iron. Chemosphere 2001 44 511-517. 

Another type of intermediate has been observed following reduction of nitroaromatic compounds (Griinbein et al., 1970) and subsequent disproportionation of the radicals [reaction (84)]. These... 

Many xenobiotics, including a wide variety of quinones and nitro compounds, will accept an electron from almost any redox flavoenzyme. The microsomal reduction of nitroaromatic compounds, quinones, quinone-imines, some azoaromatic compounds, paraquat, and tetrazolium salts is catalyzed by NADPH-cytochrome P-450 reductase [44], One-electron transfer to these electron acceptors has been proved to be obligatory in the case of quinone and nitro compounds, and is probably obligatory in other cases as well. Therefore, a reduction of an aromatic compound by NADPH-cytochrome P-450 reductase can probably be assumed to form a free radical metabolite. In contrast, free radical formation by reductive dehalogenation is totally cytochrome P-450-dependent, with the reductase being inactive. 

From the rate law found for the reduction of nitroaromatic compounds with lawson, one may postulate that the transfer of the first electron from HLAW" to ArN02 is the rate-limiting step for transforming ArN02 to ArNO (which then r eacts in a fast reaction to yield ArNHOH) ... 

Schackmann, A. and R. Muller. 1991. Reduction of nitroaromatic compounds by different Pseudomonas species under aerobic conditions. Appl. Microbiol. Biotech-nol. 34 809-813. 

The reduction of nitroaromatic compounds is a very exothermic reaction (560 kJ mol ). When reaction control is lost, decomposition of the aromatic nitro compound or of partially hydrogenated intermediates could be triggered easily. 

The reduction of nitroaromatics in anaerobic systems has received considerable attention because of their importance as agrochemicals, munitions, textile dyes, and dye intermediates. The reaction products resulting from the reduction of nitroaromatic compounds are aromatic amines. The formation of aromatic amines occurs through a series of electron transfer reactions with nitroso compounds and hydrox-ylamines as even-electron intermediates (Equation 3.21). Typically, these intermediates are more reactive than the parent nitroaromatic compound, and do not persist to any great extent in reducing environments. 

Another related concept - reduction of nitroaromatic compounds -was elaborated by the Dijon School. The global four electron reduction is analyzed as an ECp E resp. ECproECpro mechanism in the framework of the theory of Nadjo and Saveant [51]. The formation of the intermediate (dihydroxylamine)... 

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