Selective catalytic hydrogenation of unsaturated derivatives of nitrobenzene in alcoholic media

The catalytic hydrogenation of nitrobenzylic ethers (4-nitrobenzylallylethe r and 4-nitrobenzylcrotylether) into the corresponding unsaturated amines, in ethanolic solutions containing different concentrations of KOH, was inve stigated. Platinum catalysts supported on graphite were used. Increasing se lectivities were obtained with increasing KOH concentrations, the basicity of the solution affecting more the hydrogenation rate of C=C bonds than tha t of the -NO2 group. However, the formation of dimer intermediates which ar e difficult to hydrogenate restricts the yields in unsaturated amines. The selectivity in 4-aminobenzylcrotylether is higher (64%) than the selectivit y in 4-aminobenzylallylether (50%). The steric effect and/or the electronic donor effect of the methyl group could account for this result. (C) 1999 E lsevier Science B.V. All rights reserved.