Catalytic synthesis of arylisocyanates from nitroaromatics. A computational study


Several conclusions of interest have emerged from a computational study of copper-catalyzed phenylisocyanate synthesis from nitrobenzene and carbon monoxide. Nitrobenzene complexes coordinate in a κ1-O fashion, while nitrosobenzene complexes generally coordinate in a κ1-N fashion. With regard to thermodynamics, differences were observed for neutral (amidate, amidinate, β-diketiminate) versus cationic (diimine, NHC) complexes, although discernible trends were less evident for calculated kinetic barriers. The deoxygenation of the nitroso oxygen of the nitrosobenzene complex to form a copper-nitrene intermediate is postulated to be the rate-determining step. For the mechanism assumed in eqs 2 through 5, each step is exothermic. These individual steps are also calculated to possess reasonable kinetic barriers. Hence, copper-based complexes deserve consideration as potential catalysts for the phosgene-free synthesis of arylisocyanates from nitroaromatics. © 2007 American Chemical Society.

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