N-arylhydroxylamines

Aromatic compounds that do not contain meta-directing groups can be converted to diarylamines by treatment with aryl azides in the presence of phenol at — 60°C ArH -f- Ar N3 —> ArNHAr. Diarylamines are also obtained by the reaction of N-arylhydroxylamines with aromatic compounds (benzene, toluene, anisole) in the presence of F3CCOOH ArH -f Ar NHOH ArNHAr. ... 

In 1894 Bamberger began reporting on the rearrangement that bears his name. In its simplest form (Scheme 2) the Bamberger rearrangement is the conversion of an N-arylhydroxylamine (3) into the isomeric para-amino-... 

The decomposition of aryl azides in aqueous acid was known to produce para-aminophenols even before Bamberger began his work on the rearrangement of N-arylhydroxylamines. Bamberger recognized that N-arylhydroxyl-amines and aryl azides produced identical product mixtures when decomposed under the same conditions in aqueous acid, and he proposed a... 

Since differences were often reported in product yields from photochemical and thermal reactions, it was not clear that the same intermediate was generated in both cases. This issue was complicated by the fact that the temperatures under whieh the two experiments were run were usually quite different. The acid-base chemistry of nitrenium ions was largely unexplored so it was not known under what conditions these species could be protonated or deprotonated. It had also not been demonstrated that nitrenium ions played any role in the biological activity of mutagenic and carcinogenic esters of N-arylhydroxylamines or hydroxamic acids, particularly in their reactions with the DNA bases. Over the next decade these issues would be resolved but many questions about nitrenium ion chemistry would remain unanswered. 

The structures of the N-substitution products are reminiscent of the C-8 adduct that is the major product of the reaction of 2-fluorenyl-, 4-biphe-nylyl- and other N-arylhydroxylamine and hydroxamic acid esters with 2 -deoxyguanosine, (d-G) 2 deoxyguanosine-5 -phosphate (d-GMP), guano-sine, (G) or DNA in an aqueous environment." The mechanism of this reaction was not seriously investigated for many years because of the mistaken impression that the reaction was inefficient and could not compete with... 

Das et a/.78-80 have described the synthesis of a number of diorganobis(hydroxamato)tin(IV) complexes of the type R2SnL2 (R = Bun or Ph, HL = monohydroxamic acid) and 0-(triphenyl-stannyl)-7V-acyl-N-arylhydroxylamines. Attempts have been made to elucidate their structural features by a variety of physicochemical techniques like IR, NMR and Mossbauer spectroscopy. 

The asymmetric aziridination of a, P-unsaturated carboxylic acid derivatives is a direct route to optically active aza-cyclic a-amino acids, and this class of chiral aziridines can also be used as chiral building blocks for the preparation of other amino acids, P-lactams, and alkaloids. Prabhakar and coworkers carried out an asymmetric aziridination reaction of tert-butyl acrylate with O-pivaloyl-N-arylhydroxylamine 25 in the presence of cinchonine-derived chiral ammonium salt 2e under phase-transfer conditions, which furnished the corresponding chiral N-arylaziridine 26 with moderate enantioselectivity (Scheme 2.24) [46],... 

Tellurides (H2Te, NaTeH, PhTeH and Na2Te) are inexpensive and effective agents for reducing aromatic nitro compounds to hydroxylamines. Catalytic quantities of tellurium, in the presence of sodium borohydride, reduce p-substituted nitrobenzenes to N-arylhydroxylamines (equation 9). Mild reaction conditions, absence of side reactions and experimental simplicity are the main features of this reduction sequence. 

The iron sulfide complex (10) resembles the active sites of oxidized rubredoxins nonheme iron-sulfur proteins. The complex catalyzes the reductions of aromatic nitro compounds to A -arylhydroxylamines by thiol (equation 11 ). The method offers a facile, high yield approach to N-arylhydroxylamines. For example, p-dinitrobenzene was reduced to p-nitrophenylhydroxylamine in 92% yield. 

Significantly increased ee values were obtained by using the new chiral PTCs 31 and 32, which can be easily prepared starting from 2-hydroxy-3-chloromethyl-5-methyl benzaldehyde and cinchonine or cinchonidine, respectively [30]. By using 31 or 32, up to 95% ee was achieved in the reaction of electron-deficient olefins with N-acyl-N-arylhydroxylamines as nitrogen transfer reagents under biphasic conditions (toluene/aqueous NaOH) at room temperature (Scheme 5.24). 

In the presence of molten SbCls, anthracene and naphthacene are selectively hydrogenated by tetralin to give 9,10-dihydroanthracene and 5,12-dihydronaphtha-cene, respectively [31]. Both SbCls-Al and SbCls-Zn binary systems reduce a variety of aldehydes to the corresponding primary alcohols in DMF-H2O (Scheme 14.10) [32]. In the presence of a catalytic amount of SbCl3, acetophenones are reduced to 1-arylethanols by an electrochemical method [33]. Nitroarenes are reduced by Sb-NaBH4 in MeOH [34], and by Sb(.l, -Nal H4 in EtOH [35] to afford N-arylhydroxylamines (Scheme 14.11) and anilines (Scheme 14.12), respectively. 

Fishbein, J. C., McClelland, R. A., Halide Ion Trapping of Nitrenium Ions Formed in the Bamberger Rearrangement of N Arylhydroxylamines. Lifetime of the Parent Phenylnitrenium Ion in Water, Can. J. Chem. 1996, 74, 1321 1328. 

BAMBERGER Phenylhydroxylamine Rearrangement Rearrangement of N-arylhydroxylamine to aminoptienol. 

Systems Containing Two Different Heteroatoms 6.1 Oxazepines.- 2-Substituted triaryl-1,2-oxazepinium perchlorates, the first examples of seven-membered heterocyclic cations with eight n-electrons, have been prepared by the reaction of 2,4,6-triarylpyrylium salts with nitrones, or N-arylhydroxylamines,... 

Helmick, J. S., K. A. Martin, J. L. Heinrich and M. Novak. 1991. Mechanism of the reaction of carbon and nitrogen nucleophiles with the model carcinogens 0-pivaloyl-N-arylhydroxylamines competing Sn2 substitution and S l solvolysis. J. Amer. Chem. Soc. 113 3459-3466. 

Knight, G. T. and B. Saville. 1973. Hydrogen transfer from N-arylhydroxylamines to nitrosoarenes an accompaniment to azoxyarene formation. J. Chem. Soc. Perkin Trans. II 1973 1550-1553. 

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