Hydrogenation nitro reduction

See other catalytic nitro reduction processes, hydrogenation incidents See related nitroalkanes... 

See Other CATALYTIC NITRO REDUCTION PROCESSES, HYDROGENATION INCIDENTS, ORGANIC AZIDES... 

Catalytic hydrogenation on 400 g scale at 34 bar under excessively vigorous conditions (250°C, 12% catalyst, no solvent) caused the thin autoclave without bursting disk to rupture [1]. Under more appropriate conditions the hydrogenation is safe [2], See other catalytic nitro reduction processes... 

CATALYTIC NITRO REDUCTION PROCESSES HYDROGENATION CATALYSTS HYDROGENATION INCIDENTS... 

Amidine derivatives are effective dehalogenation inhibitors for the chemoselective hydrogenation of aromatic halonitro compounds with Raney nickel catalysts. The best modifiers are unsubstituted or N-alkyl substituted formamidine acetates and dicyandiamide which are able to prevent dehalogenation even of very sensitive substrates. Our results indicate that the dehalogenation occurs after the nitro group has been completely reduced i.e. as a consecutive reaction from the halogenated aniline. A possible explanation for these observations is the competitive adsorption between haloaniline, nitro compound, reaction intermediates and/or modifier. The measurement of the catalyst potential can be used to determine the endpoint of the desired nitro reduction very accurately. 

Catalytic hydrogenation of the title compound to the amine with hydrogen at 5—10 bar is described as hazardous, and an electrochemical reduction process is recommended. See other CATALYTIC NITRO REDUCTION PROCESSES, HYDROGENATION INCIDENTS See related NITROALKANES... 

Hydrogen peroxide, Hydrogen, Palladium catalyst, 4471 3-Methyl-2-penten-4-yn-l-ol, 2378 l,Ll-Tris(azidomethyl)ethane, 1931 Tris(hydroxymethyl)nitromethane, 1658 See CATALYTIC NITRO REDUCTION PROCESSES, HYDROGEN TRANSFER... 

The synthesis of the tetracyclic intermediate 49 was therefore studied in the hope that it might further cyclize to the desired lycorine skeleton. Birch reduction of o,p-dimethoxyphenethylamine led to the amine 50 which was converted into 51, giving rise in turn upon hydrolysis to 49. Its structure rests on physical data. Ordinary methods for nitro group reduction seemed to also destroy the 289-nm chromophore, but hydrogen transfer (a-phellandrene and Pd/C) gave a product which analyzed for the product of nitro reduction to amine in 49, the mass spectrometric data also being in agreement. The product was, however, not affected by diazotization, and, on the basis of spectral data, was... 

Crude N-methyl-5-nitrosophthalamic acid (11.2 g, 0.05 mole) was reduced with hydrogen in a low pressure hydrogenator. The solvent was anhydrous methanol (250 ml) and the catalyst was 5% palladium on charcoal slurried in 10 ml of water. After the theoretical quantity of hydrogen for reduction of the nitro group had been absorbed the solution was filtered to remove the catalyst and the solvent was evaporated under reduced pressure, leaving a white residue of crude 5-amino-N-methylisophthaIamic acid. M.p. 227°-230°C (corrected). 

Pd-C in both ethanol and DMF, little, if any, selectivity was obtained product ratios were 50 50 in ethanol and 60 40 in DMF. Palladium black in ethanol, which afforded 4-amino-5-nitroveratrole in 70-75% yield from 4,5-dinitroveratrole, provided no selectivity with 2,4-dinitroaniline, as well as with o- and m-dinitrobenzenes both nitro groups were hydrogenated.140 Reduction by sodium borohydride and Pd-C in methanol also does not appear to be selective, as 1,2,4-triaminobenzene is formed.141 It is of interest that over Pt-C in acidic alcohol 2,4-dinitroaniline is selectively hydrogenated at the 4-nitro group to give 4-amino-2-nitroaniline in 70% yield.142... 

For the synthesis of 13-hydroxysparteine the starting material was a-picoline iV-oxide (CXVIII) which was nitrated and the nitro group then replaced by benzyloxy. The action of acetic anhydride induced the Boekelheide rearrangement to the acetoxymethyl derivative CXIX. The latter, via the alcohol, the chloride, the cyanide, and the ester, was condensed with ethyl hydroxymethylenepyridylacetate to the quinol-izone CXX, hydrogenation and reduction of which with lithium aluminum hydride gave a separable mixture of hydroxysparteines. The... 

---