Cyclopropenylidene Carbene Ligands in Palladium C−N Coupling Catalysis

Abstract

Palladium complexes supported by a 2,3-diphenylcyclopropenylidene carbene ligand are efficient and robust catalysts for C−N coupling reactions.

Carbocyclic carbene ligands in palladium-catalyzed C–N coupling reactions

“…However, quantification using 1 H NMR as suggested by Wass et al [14] for these substrates, particularly for the diphenylamine, turned out to be capricious, as such GC-FID quantification was employed [1]. As already shown, carbocyclic carbene palladium precatalysts do not suffer from an induction period [5, [12][13][14]. We could confirm these findings also for C-N coupling catalysis, even at room temperature (Fig.…”

“…However, we note that a similar stabilization for the threemembered ring system (2p-e À -aromaticity), as proposed inter alia by Wass et al [14], was recently ruled out by an experimental (7) 90.38 (11) For compound 3a X = Cl, for compound 4 X = Br.…”

“…However, employing only conversion as a measure for catalyst activity is in a way misleading and the importance of yield-based discussion should be emphasized [13]. Finally in this screening experiment for each run (except Table 2, entry 1) with the CHT system superior results could be realized in comparison with the preliminary data published by Wass et al for the 2,3-diphenylcyclopropenylidene system [14].…”

“…The three-membered ring systems yielded inferior catalytic activities in C-C coupling, especially for deactivated chloro arenes. Hence, we focused further work on the seven-membered ring system and now report on a new application of the CHT ligand, as well as on a comparison with the 2,3-diphenylcyclopropenylidene ligand [14].…”

Stabile cyclische Carbene und verwandte Spezies jenseits der Diaminocarbene

“…Mit Ausnahme einer kurzen Anmerkung von Tamm et al, [149] Mehrere gemischte Palladium(II)-Komplexe mit einem 2,3-Diarylcyclopropenyliden-und einem Phosphanliganden wurden von Wass et al [167,168] sowie Herrmann et al [169,170] als Katalysatoren in Suzuki-Miyaura-und Heck-Kupplungen und in der aromatischen Aminierung nach Hartwig und Buchwald untersucht. Wass et al fanden insbesondere in der Heck-Kupplung hohe Aktivitäten.…”