EFFICIENT SELECTIVE REDUCTION OF AROMATIC NITRO-COMPOUNDS BY RUTHENIUM CATALYSIS UNDER CO/H2O CONDITIONS

Ruthenium-carbonyl complexes in the presence of small amounts of amines have exhibited both significant catalytic activities and remarkable selectivities of nitro group for reduction of aromatic nitro compounds under CO/H-2,O conditions. Notable increases of the catalytic activities were found upon the addition of a small amount of the specified amine, such as diisopropylamine, piperidine, dibutylamine, and triethylamine; the reaction rate increased at higher reaction temperatures, under higher CO pressures, The powerful importance of the present catalysis can be emphasized, because aromatic nitro group was reduced exclusively without the other unsaturated groups such as C=O, C=N, C=C, and C=C being reduced: the desired aromatic amines were, therefore, catalytically obtained in high yields. The reduction was also found to proceed without by-producing hydrogen gas generated from the water-gas shift reaction (WGSR). The role of amines in this catalysis was thus suggested to be different from that in the WGSR. Comparing the results here with those reported previously, an original reaction pathway in this catalysis, such as intramolecular hydrogen transfer between metal-nitrene and hydride, can be considered; the mechanism has also been discussed and presented in this paper.