Aromatic compounds, nitro irradiation

A different mode of reaction, however, is observed in photoreductions of nitroaromatics by aromatic tertiary amines. Irradiation of benzene solutions of N-methylated anilines and either m-chloronitrobenzene or 1-nitronaphthalene results in oxidative demethylation of the amines accompanied with reduction of the nitro compound to the corresponding arylamine 49). The authors suggest that hydrogen abstraction from the methyl group takes place as the primary chemical event. 

Photolytic. Synthetic air containing gaseous nitrous acid and toluene exposed to artificial sunlight (Z = 300-450 nm) yielded methyl nitrate, peroxyacetal nitrate, and a nitro aromatic compound tentatively identified as a nitrophenol or nitrocresol (Cox et al., 1980). A n-hexane solution containing toluene and spread as a thin film (4 mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 26% of the toluene photooxidized into benzaldehyde. 

Water and methanol react in specially favourable systems only. Amines are much more effective as became clear at the beginning of the investigations by the possibility of photoamination in amine/ water and amine/methanol mixtures. Interestingly, nitroanisoles, like other aromatic nitro-compounds, when irradiated in pure diethyl-amine give only reduction products (Barltrop and Bunce, 1968). 

In certain cases, light promotes substitution reactions in aromatic compounds.34 One of the fascinating features of these reactions is an almost complete change in regioselectivity from that observed in the ground-state reactions. When the nitrocatechol ether 8.1 is irradiated in alkali or in methylamine, the nucleophilic substitution takes place meta to the nitro group. The nucleophilic substitution of p-nitroanisole 8.2, however, takes place para to the X-substituent. 

Sana et al. (2012) have carried out solvent-free and microwave-assisted nitration reactions, which underwent smoothly in the presence of group V and VI metal salts with high regio-selectivity for anilides, moderately and nonactivated aromatic compounds. Good to excellent yields were obtained under solvent-free conditions and the nitration was completed in few minutes under microwave irradiation. It was observed that when the ortho position was engaged, p-nitro derivatives were obtained, while o-nitro derivatives were obtained when para position was engaged. The nitration of aromatic carbonyl and related compounds was observed with good yield and the reaction times were about 3-5 min. 

Certain aromatic nitroso compounds (Ar—NO) can be obtained in good yields by irradiation of the corresponding nitro compounds in 0.1 M aqueous KCN with UV light. The reaction has also been performed electrochemically. " When nitro... 

Rapid reduction of aromatic nitro compounds into amines has been described using sodium hypophosphite and FeSC>4-7H20. The reactions showed best results in terms of yields and purity, when the substrates were pre-absorbed on alumina and irradiated by microwaves under solvent-free conditions. The reaction is chemoselective and does not affect functional groups such as CN, OH, COOH, CONH2 or halogens. In addition, oximes were not reduced under the given reaction conditions, but were dehydrated to the corresponding nitriles instead (Scheme 4.32)57. 

Vass, A., Dudas, J., T6th, J. and Varma, R.S., Solvent-free reduction of aromatic nitro compounds with alumina-supported hydrazine under microwave irradiation, Tetrahedron Lett., 2001, 42, 5347-5349. 

Keywords aromatic nitro compound, sodium hypophosphite, microwave irradiation, aromatic amine... 

Nitroalcohols 3a-j were isolated in good yields when a mixture of aromatic aldehydes 1 (10 mmol) and nitro compound 2 (10 mmol) adsorbed on Si02 (finer than 200 mesh, 5 g) and taken in a open Pyrex test tube was subjected to micro-wave irradiation in a domestic microwave oven (BPL, BMO 700T) at an out-put of about 600 W. After cooling the reaction mass to room temperature, the products were isolated by extracting with dichloromethane and evaporation of the sol-... 

Wardman P, Dennis MF, Everett SA, Patel KB, Stratford MRL, Tracy M (2003) Radicals from one-electron reduction of nitro compounds, aromatic N-oxides and quinones the kinetic basis for hypoxia-selective, bioreductive drugs. Biochem Soc Symp 61 171-194 Warman JM, de Haas MP, Hummel A, van Lith D, VerberneJB, Loman H (1980) A pulse radiolysis conductivity study of frozen aqueous solutions of DNA. Int J Radiat Biol 38 459-459 Warman JM, de Haas MP, Rupprecht A (1996) DNA a molecular wire Chem Phys Lett 249 319-322 Warters RL, Lyons BW (1992) Variation in radiation-induced formation of DNA double-strand breaks as a function of chromatin structure. Radiat Res 130 309-318 Warters RL, Hofer KG, Harris CR, Smith JM (1977) Radionuclide toxicity in cultured mammalian cells Elucidation of the primary site of radiation damage. Curr Top Radiat Res Q 12 389-407 Weiland B, Huttermann J (1998) Free radicals from X-irradiated, dry and hydrated lyophilized DNA as studies by electron spin resonance spectroscopy analysis of spectral components between 77 K and room temperature. Int J Radiat Biol 74 341-358 Weinfeld M, Soderlind K-JM (1991) 32P-Postlabeling detection of radiation-induced DNA-damage identification and estimation of thymine glycols and phosphoglycolate termini. Biochemistry 30 1091-1097... 

The effect of ultrasonic irradiation on hydrazine reductions in the presence of iron powder and activated carbon in ethanol has also been evaluated. The studies include graphite-catalyzed reductions of aromatic nitro compounds to the corresponding arylamines. The notable features of these reactions are the low cost, high yields and the simplicity of the work-up procedure. Significantly, nitro groups can be reduced in the presence of a variety of functional groups. 

Selective reduction of a halogenated aromatic nitro compound to the corresponding hydroxylamine or amine upon irradiation of Ti02 suspended in degassed alcohol has also been reported, as has the selective photoreduction of / -nitrobenzaldehyde to the corresponding aldehydic aniline (Eq. 30) [170], and alkyl azides can also be reduced to the corresponding amine. 

Alkoxynitroxyl radicals, isoelectronic with ketyls, are produced when aromatic nitro compounds trap other radicals [e.g., the nitroxyl 10 (R = tetrahydrofuran-2-yl)] when 2-nitrofuran is irradiated in THF a similar radical, 10 (R = EtjSi), is obtained when the solvent is triethylsilane. The latter radical exhibits separate rotamers in proportions of 7 3 at low temperatures, and at 60°C two well-resolved spectra were measured. They were not, however, assigned. ... 

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