INTRAMOLECULAR REDUCTIVE CARBONYLATION OF O-NITROANILINE BY CARBON-MONOXIDE TO 2(3H)-BENZIMIDAZOLONE

o-Nitroaniline reacts with carbon monoxide under pressure in the prese nce of solvents (e.g. dioxane, tetrahydrofuran, N,N-dimethylformamide) and a catalytic system (sulfur or a low molecular sulfur compound - a basic medium - and optionally a vanadium(V) compound) at 370-445 K to give 2(3H)-benzimidazolone by intramolecular reductive carbonylation. Similarly to intermolecular carbonylation of nitroaromatic compounds also in the title reaction the efficiency of the sulfur component decr eases in the order: COS > H2S much greater than CS2 > S. The promotor action of NH4VO3 and V2O5 is, however, less pronounced. The rate of th e carbonylation increases with temperature, with optimal selectivity t o the 2(3H)-benzimidazolone (>82%) at 390-425 K. The basicity of o-nit roaniline was found to be insufficient. and inorganic or organic bases had to be added to effect the reaction. The above two-(or three-) com ponent system catalyze also the intramolecular oxidative carbonylation of o-phenylenediamine to 2(3H)-benzimidazolone.