ABSTRACT

Reaction condition: mcatalyst=0.1g; Solvent: V=8ml; Substrate: 0.1g; P=10MPa; t=5h. Abbreviations: NaOH=2%NaOH-H2O, EtOAc=ethyl acetate, a0.4g substrate was used; only traces of by-products were detected. It is interesting to note that larger amount of 4-amino-cyclohexane carboxylic acid (ca. 10-15 g) was prepared using also 2%NaOH-H2O as a solvent. The reaction was carried out in a Parr reactor (V=300ml) at 100°C, 10MPa H2, for 5h. After filtering off the noble metal catalyst the liquid product was further reacted in the presence of Raney® nickel catalyst at 100°C, 10MPa H2, for 5h. After this reaction according to both 1H-NMR and TLC measurement the trans/cis isomer ratio in the reaction mixture was 3/7. As known the basic media is advantageous for the formation of trans isomer, therefore the B113W Raney® Ni was modified with potassium ions (2wt. %) using K2CO3 as precursor compound (13). However, the modification did not increase further the trans/cis ratio. Conversion data listed in Table 2 indicate that in the hydrogenation of 4-aminoethyl benzoate using cyclohexane as a solvent the Al2O3 supported Ru and Rh catalysts are more active than the carbon supported ones. In addition, the conversion of aromatic ester is smaller on Pd/C catalyst than on the carbon supported Ru and Rh. In ethyl acetate the hydrogenation proceeded slower than in cyclohexane, and Rh being more active than Ru. The trans/cis isomer ratio estimated from TLC results varied between 1/3 and 1/1. The UV active by-products were formed in coupling reactions.