4-Nitroanilines, synthesis

Quinoxaline mono-N-oxides are also available by a direct synthesis from n-nitroaniline derivatives. Condensation of acetyl chloride derivatives with o-nitroaniline followed by treatment with sodium ethoxide in ethanol yields the mono-N-oxides in good yields (Scheme 20) (64JCS2666). 

The diffusion, location and interactions of guests in zeolite frameworks has been studied by in-situ Raman spectroscopy and Raman microscopy. For example, the location and orientation of crown ethers used as templates in the synthesis of faujasite polymorphs has been studied in the framework they helped to form [4.297]. Polarized Raman spectra of p-nitroaniline molecules adsorbed in the channels of AIPO4-5 molecular sieves revealed their physical state and orientation - molecules within the channels formed either a phase of head-to-tail chains similar to that in the solid crystalline substance, with a characteristic 0J3 band at 1282 cm , or a second phase, which is characterized by a similarly strong band around 1295 cm . This second phase consisted of weakly interacting molecules in a pseudo-quinonoid state similar to that of molten p-nitroaniline [4.298]. 

The corresponding reaction with 2-methylamino-5-nitroaniline affords an unambiguous synthesis of l-methyl-6-nitroquinoxaIin-2-one, the A -mcthyl derivative of (6) this product is also obtained by treatment of (6) with methyl iodide and methanolic sodium methoxided ... 

A neat synthesis of 4-nitroindole depends on an acyladon-deacyladon sequence from 2-methyl-3-nitroaniline, as shown in Eq. 10.53. On the other hand, treatment of iV-protected indoles v/ith acetyl nitrate generated in sini at bw temperanire gives the correspondmg... 

The synthesis can be carried out with most aromatic amines and is usually termed the Skraup reaction., The nitrobenzene is frequently replaced by arsenic acid, as in the preparation of 8-nltroquinoIine from o-nitroaniline ... 

A fused heterocyclic compound (146) distantly related to the antiinflammatory agent cintazone (Chapter 12), which itself can be viewed as a cyclized derivative of phenylbutazone, retains the activity of the prototype, in the synthesis of 146, reaction of the nitroaniline 139 with phosgene gives intermediate 140, which is then reacted with ammonia to afford the substituted urea (141). Cyclization of the ortho nitrourea function by means of sodium hydroxide leads to the N-oxide (142) this last reaction represents... 

A similar approach, synthesis of a selectively substituted benzotriazole from the corresponding ortfe-nitroaniline, is depicted in Scheme 212. The process starts from a microwave-assisted substitution of the fluorine atom in 4-fluoro-3-nitrobenzonitrile 1270 by isopropylamine to give ortfo-nitroaniline 1271 in 99% yield. Reduction of the nitro group provides ortfo-phenylenediamine 1272 that is directly converted to 5-cyano-l-isopropylbenzotriazole 1273, which is isolated in 83% yield <2006JME1227>. 

Benzofurazan oxide has also been prepared by the oxidation of o-nitroaniline with phenyl iodosoacetate.6 Other methods of preparation are given in reference 4. The hypochlorite oxidation method has been used in the synthesis of various substituted benzofurazan oxides.6... 

The synthesis of polyaniline and copolymers of aniline with o-nitroaniline is aimed at obtaining an electroactive material. This material can be used, for example, as an electrode in conjunction with the magnesium electrode to construct chemical power sources. The polymers were prepared by oxidation of aniline or its mixture with nitroaniline ammonium persulfate in aqueous hydrochloric... 

Apart from the chemistry of the 4-hydroxy derivative (see p. 126) relatively little investigation in this area has been conducted. Thiocoumarin-3-carbonyl compounds have proved to be effective precursors for the synthesis of the pharmaceutically useful 3-(2-benzimidazolyl) derivatives. Thus, on interaction of the 3-carboxamide with o-phenylenediamine or the 3-aldehyde with o-nitroanilines, the above benzimidazoles or their TV-oxides are formed. 

Urthophenylenediamine (OPDA) is an important intermediate of several biologically active compounds, including the benzimidazene--carbamate type fungicides [1]. There are different routes for the synthesis of OPUA. In the present work an attempt was done to prepare OPOA from 4-chloro-2-nitroaniline (CNA). CNA can be obtained by nitration and subsequent ammonolysis of para-dichloro-benzcne [ 1]. 

As part of an efficient, facile and practical liquid-phase combinatorial synthesis of benzimidazoles under microwave irradiation, the reduction of a polymer bound o -nitroaniline with zinc metal in methanol was completed in a very short time (2 min)61 (Scheme 4.33). However, no detailed reaction conditions were given. 

Once again the scientist chose to use the SNAr reaction to gain access to the key o-nitroaniline intermediate however, it is quite apparent from Table 8.7 that the use of microwave synthesis resulted in rapid optimization of this key reaction and significantly improved yields. The use of w-butanol as solvent for this substitution reaction gave high yields (88%) in only 15 min. It should also be pointed out that while in the thermal example DMSO was the optimal solvent, in the microwave example this solvent resulted in decomposed starting materials. 

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