TRIRUTHENIUM DODECACARBONYL-CATALYZED REDUCTIVE CARBONYLATION OF NITROARENES - CYCLIZATION, CARBON-MONOXIDE INSERTION AND REDUCTION - AN OVERVIEW

Several ortho-nitrobiarenes and dinitrobiarenes were submitted to Ru3(CO)12-catalyzed reductive carbonylation in acetonitrile and in cis-cyclooctene. The main reaction products were the corresponding amines and five-membered heterocycles such as indoles and imidazoles. Small amounts of six-membered cyclization products such as acridane dimers, phenothiazine, quinoxalines were also found. The cyclization to indole occurred also at room temperature under irradiation or with zinc. The use of cis-cyclooctene as the solvent also trapped the nitroso intermediates. Nitrones were formed in this reaction and were suggested to be intermediate in certain cyclizations. Force-field calculations allowed to suggest organoruthenium intermediates in these reactions.