RUTHENIUM CARBONYL-CATALYZED DEOXYGENATION BY CARBON-MONOXIDE OF ORTHO-SUBSTITUTED NITROBENZENES - SYNTHESIS OF BENZIMIDAZOLES

Ru3(CO)12 is a very efficient catalyst for the deoxygenation of 2-nitro-N-(phenylmethylene) benzeneamine derivatives to give the corresponding 2-substituted benzimidazoles, at 220-degrees-C and 50 bar of carbon monoxide. Main byproducts are the corresponding amines. The same benzimidazoles are also obtained starting from o-nitroaniline and the corresponding aldehyde. When N-(2-nitrophenyl)methylene benzeneamine derivatives are used as substrates, the reaction changes dramatically and only traces of the corresponding heterocyclic compounds are obtained, although complete conversion of the starting nitro compounds is achieved.