Hydrogenation of Nitro-Substituted Acetophenones

Jackson, S. David; McEwan, Rebecca; Spence, Ron

doi:10.1201/9781420070774.ch8

Cited by 2 publications

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“…Formation of 4-aminophenol by a Pt-nitrenium intermediate explains the high yield obtained by nitrobenzene hydrogenation compared to the much lower yield observed when N-phenylhydroxylamine or nitrosobenzene are used instead of nitrobenzene. This is in agreement, with the research of Jackson and coworkers on substituted nitroacetophenones hydrogenation, in which Pd-nitrenium species has been identified as an intermediate [32]. As a matter of fact, homogeneous acid catalyzed Bamberger rearrangement is not the preferred reaction of N-phenylhydroxylamine if Pt catalysts are present, since its decomposition and condensation reactions are faster than the acid catalyzed rearrangement.…”

Section: Discussion On the Reaction Mechanismsupporting

confidence: 91%

“…The mechanism [27] has been generally accepted for long time but recently several authors have criticized some aspects, which do not explain the reactivity of the intermediates and of the specificity of different type of catalyst [31,32,[34][35][36][37][38]. In particular, Jackson and co-workers showed that the hydrogenation rate of nitrobenzene is higher than that of nitrosobenzene, and no nitrosobenzene accumulation is observed.…”

Section: Discussion On the Reaction Mechanismmentioning

confidence: 99%

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New insight on the mechanism of the catalytic hydrogenation of nitrobenzene to 4-aminophenol in CH3CN–H2O–CF3COOH as a reusable solvent system. Hydrogenation of nitrobenzene catalyzed by precious metals supported on carbon

Quartarone

Ronchin

Tosetto

et al. 2014

Applied Catalysis A: General

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a b s t r a c tThe preparation of 4-aminophenol via hydrogenation of nitrobenzene in a single liquid phase has been carried in the presence of different precious metal catalysts. The liquid phase is composed of CH 3 CN-H 2 O-CF 3 COOH, which can be easily distilled at low temperature, thus avoiding work-up operation. The yield of 4-aminophenol is in the range 45% and in the presence of sulfolane as promoter reaches almost 50%. The best result has been obtained in the presence of Pt/C as hydrogenation catalyst. The role of the solvent is strictly related to the selectivity to 4-aminophenol, since CH 3 CN decreases the hydrogenation activity compared to other solvent, CF 3 COOH promotes the formation of the desired product both via Bamberger rearrangement in solution as well by a surface catalyzed reaction, while H 2 O is responsible for 4-aminophenol formation in both reactions. Even though, nitrosobenzene and phenylhydroxylamine have not been observed, their reactivity suggest a complex pattern of reactions occurring either on the catalyst surface or in the solution. Indeed, formation of 4-aminophenol may occur both in solution, via acid catalyzed Bamberger rearrangement and on the catalyst surface by the formation of a surface Pt-nitrenium complex, which undergoes surface nucleophilic attack by H 2 O.

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Section: Discussion On the Reaction Mechanismsupporting

confidence: 91%