Synthesis and characterization of novel PEPPSI type bicyclic (alkyl)(amino)carbene (BICAAC)-Pd complexes
Márton Nagyházi, Balázs Almási, Ádám Lukács, Attila Bényei, Tibor Nagy, Sándor Kéki, Róbert Tuba
Abstract
A series of bicyclic alkylamino carbenes (BICAAC) (where N-aryl = dipp, mes, 2,6-dimethyl-4-(dimethylamino)phenyl, 5a–d) and their novel air- and moisture-resistant pyridine (pyridine, 4-dimethylaminopyridine) containing palladium Pd(II) complexes (6a–e) were synthetized and characterized. As novel examples of the PEPPSI (“pyridine enhanced precatalyst preparation stabilization and initiation”)-Pd compounds, the reported complexes have shown high activity in Mizoroki–Heck coupling reaction even at as low as 100 ppm loading (TON up to 10000). Kinetic studies revealed that reactions carried out in the presence of elemental mercury resulted decrease in activity. It indicates that the coupling reaction may have both molecular and Pd(0)-mediated catalytic paths.