Systematic study on the catalytic synthesis of unsaturated 2-ketocarboxamides: palladium-catalyzed double carbonylation of 1-iodocyclohexene

1-Iodocyclohexene, a benchmark substrate, has been double carbonylated in the presence of palladium-phosphite precatalysts. Triarylphosphites with OR substituents, able to act both as P-monodentate and hemilabile P,O-heterobidentate ligands were used in this reaction. Systematic investigations have revealed that the chemoselectivity towards cyclohexenylglyoxylamides, i.e., the products obtained in aminocarbonylation by the insertion of two carbon monoxide, is strongly influenced by the amine nucleophile, temperature and carbon monoxide pressure. The highest yields of 2-ketocarboxamides were obtained at low temperature (30 °C) and high carbon monoxide pressure (110 bar). However, the structure of the phosphite ligand has practically no effect either on catalytic activity or chemoselectivity. This fact refers to the P-monodentate coordination of the ligands in catalytic intermediates or that palladium nanoparticles are the catalytically active species.

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