One pot synthesis of ureas and carbamates via oxidative carbonylation of aniline-type substrates by CO/O2 mixture catalyzed by Pd-complexes

• One pot synthesis of ureas and carbamates from amines and CO/O2 is developed.
• Effects of substituent in the catalyst are studied.
• Kinetic studies resulted in the optimization of reaction conditions.
• High yield and selectivity are achieved under mild conditions.
• The mechanism of carbonylation of aniline catalyzed by Pd(II) complex is proposed.

Carbonylation of aromatic amines by direct insertion of carbon monoxide is catalyzed by PdCl2(XnPy)2 complexes (where Py = pyridine, X = −CH3, −Cl; n = 0–2) and gives, depending on the conditions, ethyl N-phenylcarbamates or N,N′‑diphenylureas. For carbonylation of aniline, a proper choice of XnPy ligands in PdCl2(XnPy)2 catalyst and application of molecular oxygen instead of nitrobenzene (conventionally used oxidant for carbonylations) allow to carry out the process under mild conditions with high yield and selectivity. The best results (75% yield of the main product with selectivity of catalyst above 90%) were obtained for the process catalyzed by PdCl2(2,4-Cl2Py)2 complex at 100 °C and they were greatly improved in comparison to 41% yield and 68% selectivity obtained for CO/nitrobenzene used at 180 °C.

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