Catalytic reductive carbonylation of aromatic nitro compounds to urethanes promoted by supported palladium activated with 1,10-phenanthroline derivatives

Abstract

A simple catalytic system, involving supported Pd and a phenanthroline in equimolar ratio, has been shown to be very active and selective in reductive carbonylation of nitroaromatic compounds to the corresponding urethanes when the reaction is conducted in anhydrous ethanol and in the presence of a catalytic amount of a weak non-esterifiable, Brönsted acid. The chelating nitrogen donor ligand plays the role taken in other systems by large amounts of Lewis acids involving activation of the supported metals, probably to favour a fragmentation process which gives active homogeneous species. The system works best at 170–190°C and CO pressures as low as 40 bars, with turnover numbers of up to 125 cycles per hour.