Nitrophenols, rearrangement

The Pd(0)-catalyzed rearrangement of the iV-allylenamine 800 in CF3CO2H affords the (5, -unsaturated imine 801, which is hydrolyzed to give the 7, 8-unsaturated aldehyde 802[498]. The vinyloxaspirohexane 803 undergoes rearrangement-ring expansion to give the cyclopentanone 804 in the presence of 1 equiv. of p-nitrophenol[499]. 

Production is by the acetylation of 4-aminophenol. This can be achieved with acetic acid and acetic anhydride at 80°C (191), with acetic acid anhydride in pyridine at 100°C (192), with acetyl chloride and pyridine in toluene at 60°C (193), or by the action of ketene in alcohoHc suspension. 4-Hydroxyacetanihde also may be synthesized directiy from 4-nitrophenol The available reduction—acetylation systems include tin with acetic acid, hydrogenation over Pd—C in acetic anhydride, and hydrogenation over platinum in acetic acid (194,195). Other routes include rearrangement of 4-hydroxyacetophenone hydrazone with sodium nitrite in sulfuric acid and the electrolytic hydroxylation of acetanilide [103-84-4] (196). 

The reaction products were shown to contain the expected product of rearrangement (XXXVI) together with the denitration product (XXXVII) and nitrophenol (XXXVIII). 

An attempt has been made to explain the strong colours of the salts of the nitrophenols as a rearrangement involving the formation of a... 

Under certain conditions the first products of the reaction, in the case of nitrophenols, are diazophenol ethers (diazohydroxy-compounds), which then very easily undergo rearrangement... 

The work of Coombes and coworkers20 on the formation of the 4-methyl-4-nitro intermediate has already been discussed above. Here the solvent was aqueous sulphuric acid with acid concentration ranging from 55% to 90%. The final product, 4-methyl-2-nitrophenol, was formed by the expected two routes about 40% via the ipso-intermediate and 60% directly. Their kinetic studies enabled the acidity dependence of the ipso-rearrangement to be examined they argued that this dependence demonstrated that the rate-limiting stage of the conversion involved the protonated /pso-intermediate (43). They... 

This compound ionizes to form four ions by cleavage and rearrangement. The loss of a methyl radical leads to the ion at ml z 248 the ion at ml z 154 amu is the p-nitrothio-phenolate ion the ion at mlz 158 is the p-nitrophenolate ion and the ion at mlz 141 is due to loss of the p-nitrophenyl radical. The carrier gas was argon/methane, and the source temperature was 240°C. A PZI79 column was used in the gas chromatograph. This mass spectrum was obtained while the compound was in the source, as indicated in Figure 4. Under these conditions, variations in the field in the source did not alter... 

Derivation The methyl ether of o-nitrophenol is reduced by zinc dust and caustic soda to the hydrazo compound, which is then rearranged with hydrochloric acid. 

A transformation called metallo-Fries rearrangement was described for lithiation of 0-substituted orf/zo-nitrophenols 260 (equation 120). Analogous migrations of SiRs groups were reported for reactions of the bromine-substituted 0-silylated phenols with f-BuLi. ... 

The 3-hydroxylaminophenol mutase from cells of R. eutropha JMP134 grown with 3-nitrophenol as N-source has been purified (Schenzle et al. 1999), and is able to catalyze the rearrangement of a number of substituted aromatic hydroxylamines, and the formation of both 2- and 4-hydroxyphenol from hydroxylaminobenzene that is formally comparable to the classic Bamberger rearrangement. 

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