4-Nitroacetophenone, hydrogenation

The hydrogenation of the three nitroacetophenone isomers was compared at 3 barg and 323 K. The results are shown in Table 8.1, where it can be seen that the 3-isomer is by far the most reactive with little difference between the 2- and 4-isomers. 

Figure 8.2. Reaction profile for 2-nitroacetophenone hydrogenation at 323 K and 5 barg hydrogen pressure.

Figure 8.3. Reaction of 3-nitroacetophenone with hydrogen and deuterium at 3 bar and 323 K.

The hydrogenation of nitroacetophenones has been studied and considerable kinetic and mechanistic information obtained. Differences in reaction rate, bonding and selectivity have been observed. The formation of 1-indolinone from 2-NAP was unexpected and revealed the presence of a surface nitrene. This intermediate has not been postulated in nitroaromatic hydrogenation previously. Hydrogenation in the presence of deuterium revealed, as well as a kinetic isotope effect, that it is likely that... 

Catalytic hydrogenation over palladium in acetic acid and sulfuric acid at room temperature and 2.5 atm reduced nitroacetophenones and their homologs and derivatives all the way through the alkyl anilines in yields of 78.5-95% [904]. 

Burney S, Niles JC, Dedon PC, Tannenbaum SR (1999) DNA damage in deoxynucleosides and oligonucleotides treated with peroxynitrite. Chem Res Toxicol 12 513-520 Burr JG, Wagner BO, Schulte-Frohlinde D (1976) The rates of electron transfer from ClUra " and CIUraH" top-nitroacetophenone. Int J Radiat Biol 29 433-438 Buxton GV, GreenstockCL, Helman WP, Ross AB (1988) Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals ( OH/ O-) in aqueous solution. J Phys Chem Ref Data 17 513-886... 

Fig. 14.62. Polar hydrogenation/ hydrogenolysis of an aromatic ketone (meta-nitroacetophenone). CF3COOH causes a reversible protonation of the ketone to the carboxonium ion A. The reducing agent triethylsilane then transfers a hydride ion onto A to form a benzylic alcohol. This alcohol presumably is silylated, protonated, and converted into the benzyl cation B. A second hydride transfer yields the final product.

Biotinamido-caproamide)methyl-2-nitroacetophenone hydrogen chloride... 

A solution of 295 g. (1.79 moles) of m-nitroacetophenone [Org. Syntheses Coll. Vol. 2, 434 (1943)] in 1.1 1. of absolute ethanol is shaken with 1.5 tablespoons of Raney nickel catalyst [Org. Syntheses, 21, 15 (1940)] at 50° under an initial hydrogen pressure of 1950 lb. After uptake of hydrogen has ceased, the solvent is evaporated and the residue triturated with 400 ml. of a mixture of cold water and excess concentrated hydrochloric acid. The undissolved portion after filtration is treated again with hydrochloric acid. The combined insoluble portions from four reduction batches are washed with water until free from acid and dried (170 g.) and subjected to reduction as before. The combined hydrochloric acid solutions are treated with solid sodium carbonate with stirring until the solution is alkaline, and the precipitated m-aminoacetophenone is removed by filtration. 

The reduction of o- and />-nitrotoluene and /7-ethylnitrobenzene in DMF in the presence of dioxygen to o- and />nitrobenzoic acid and / -nitroacetophenone plus - p-nitrophenyl)ethanol, respectively, has been suggested [128] to proceed via a proton or hydrogen atom abstraction from the side chain followed by reaction of this species with superoxide ion and/or dioxygen to the isolated products. 

Reduction of Nitro Compounds p-Nitroacetophenone A hydroxylamine intermediate is detected by the photo-induced reduction ofp-nitroacetophenone with high yields by the irradiation of suspensions of P25 Ti02 in ethanol. The photogenerated electrons reduce the nitro compound, whereas the holes oxidize ethanol to acetaldehyde with the formation of hydrogen. 

Preparation by catalytic hydrogenation of 5-bromo-2-hydroxy-3-nitroacetophenone in presence of Pd/C in solution of methanol and melhylaie chloride mixture at r.t. (99%) [1805]. 

Preparation by hydrogenation of 2-hydroxy-5-methyl-3-nitroacetophenone using 5% Pd/C catalyst in ethanol (68%) [1898], (48%) [1897]. 

Preparation by hydrogenation of 5-acetyl-2-hydroxy-3-nitroacetophenone using 5% Pd/C as a catalyst in ethanol (49%) [4699],... 

Preparation by catalytic hydrogenation of 3-acetyl-2-hydroxy-4,6-dimethyl-5-nitroacetophenone in ethanol in the presence of 10% Pd/C at 40° for 3 days (61%) [5809]. 

Table 1. Best conditions for production of specific compounds by hydrogenation of 4-nitroacetophenone.

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