Nitro oxidation catalysts

Oxidation of organonitrogen compounds is an important process from both industrial and synthetic viewpoints . N-oxides are obtained by oxidation of tertiary amines (equation 52), which in some cases may undergo further reactions like Cope elimination and Meisenheimer rearrangement . The oxygenation products of secondary amines are generally hydroxylamines, nitroxides and nitrones (equation 53), while oxidation of primary amines usually afforded oxime, nitro, nitroso derivatives and azo and azoxy compounds through coupling, as shown in Scheme 17. Product composition depends on the oxidant, catalyst and reaction conditions employed. 

Aromatic nitro compounds can be converted to the corresponding 4-fluoroanilines if the 4-position carries a hydrogen atom. Thus, nitrobenzene can be converted to 4-fluoroaniline with 100% conversion and 95% selectivity by heating with hydrogen under pressure [platinum(IV) oxide catalyst] in the presence of boron trifluoride-diethyl ether complex at 42°C for 12.5 hours. 3-Chloro-l-nitrobenzene can be similarly hydrogenated-fluorinated to 3-chloro-4-fluoroaniline.25,26... 

This ring closure takes place readily whenever the carbonyl and amino groups occur in the relative positions shown above. Reduction of o-nitro-phenylacetonitrile by stannous chloride produces indole rather than the corresponding amino aldehyde. The synthesis is most useful for the preparation of indole-2-carboxylic acid by reduction of o-nitrophenyl-pyruvic acid with ferrous sulfate and ammonia or with sodium hydrosulfite. The ethyl ester is obtained by a similar reduction with zinc and acetic acid or by catalytic hydrogenation of ethyl o-nitrophenyl-pyruvate over platinum oxide catalyst. ... 

Reduction of nitroquinazolines 1 using palladium oncharcoal, - palladium on calcium carbonate,Raney nickel,or platinum oxide catalysts, tin(II) chlo-ride, iron, sodium sulfide, or titaniuni(III) chloride is a facile route to quinazolinamines 2. Under conditions of catalytic reduction of the nitro group, chlorine in positions 2 and/or 4 is reductively removed (cf. Section 6.3.1.1.7.1.1.). 

Under suitable conditions it is possible to isolate the A-substituted hydroxylamines that are formed as intermediates in the reduction of nitro compounds. For this purpose it is essential in the reduction of aromatic nitro compounds to work with neutral or nearly neutral solutions suitable reducing agents are hydrogen and platinum oxide catalysts in glacial acetic acid,82,83 zinc dust in ammonium chloride solution,84 aluminum amalgam,85 and ammonium sulfide.86 Aliphatic nitro compounds may be reduced as their alkali salts (nitronates) by diborane in tetrahydrofuran, then giving A-alkylhydroxyl-amines 87 for instance, A-cyclohexylhydroxylamine is thus obtained from nitrocyclohexane in 53% yield. However, aliphatic nitro compounds are converted into A-alkylhydroxylamines more simply by catalytic hydrogenation in the presence of palladium-barium sulfate unlike aromatic nitro compounds, aliphatic nitro compounds require an acid medium for reduction to hydroxylamines an oxalic acid medium has proved the most suitable. 

We subsequently developed an efficient catalyst for oxidizing terminal olefins to ketones starting with a non-nitro based catalyst. This catalyst comprised PdCl2, CuCl, LiCl, CH3CN and CuCl2 in tetrahydrofuran or sulfolane solvent. No evidence of catalyst deactivation was observed even after >1(X) turnovers. 

A mixture of 6-nitro-5,8-dimethyl-l,3-benzodioxane and aq. Na-carbonate hydrogenated 2 hrs. at 270°/100 atm. with copper diromium oxide catalyst, whidi is then removed by filtration, the filtrate acidified with coned. HCl, treated with 40%-FeCl3, steam-distilled, and the distillate allowed to react at 40 with Na-dithionite trimethylhydroquinone. Y 78%. H. Otomasu, Chem. Pharm. Bull. 16, 378 (1968). 

In the context of heterogeneous asymmetric catalysis, Choudary et al. " reported a recyclable heterogeneous nanocrystalline magnesium oxide catalyst for the AH and AM reactions to afford chiral nitro alcohols and Michael adducts in good to excellent yields and enantioselectivities (ee s) (Scheme 5.1). 

More recently a process has been patented for preparing isocyanates by the reaction of nitro compounds with carbon monoxide in the presence of a rhodium oxide catalyst. 

The 4-hydroxy-1-alkene (homoallylic alcohol) 81 is oxidized to the hetni-acetal 82 of the aldehyde by the participation of the OH group when there is a substituent at C3. In the absence of the substituent, a ketone is obtained. The hemiacetal is converted into butyrolactone 83[117], When Pd nitro complex is used as a catalyst in /-BuOH under oxygen, acetals are obtained from homoallylic alcohols even in the absence of a substituent at C-3[l 18], /-Allylamine is oxidized to the acetal 84 of the aldehyde selectively by participation of the amino group[l 19],... 

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