Zur Rhodium‐katalysierten Carbonylierung aromatischer Nitroverbindungen zu Isocyanaten. I. Katalysatoren und Reaktionsbedingungen

On the Rhodium‐catalyzed Carbonylation of Aromatic Nitrocompounds to Isocyanates The carbonylation of aromatic nitro compounds with carbon monoxide giving isocyanates at normal pressure and 100°C in the presence of rhodium complexes and a co‐catalyst has been studied. Isocyanates can be obtained in o‐dichlorbenzene with a selectivity of 50%. The main by‐product is the corresponding amine which destroys the co‐catalyst. Di‐μ‐chlorotetracarbonyldirhodium(I) is the active rhodium catalyst as the co‐catalyst reacts with the ligands of other rhodium complexes producing this complex in all cases. The most active co‐catalysts are MoCl5 and VCl4. Voluminous substituents in position 2 of the nitro compound increase the reaction rate, whereas substituents in position 4 have no unfluence. The reaction rate is independent of the carbon monoxide pressure.