A New Class of Stable, Saturated N-Heterocyclic Carbenes with N-Naphthyl Substituents: Synthesis, Dynamic Behavior, and Catalytic Potential

A new family of easily accessible and stable imidazolin‐2‐ylidenes has been synthesized, where the side chains are comprised of substituted naphthyl units. This generates C2‐symmetric (anti) and Cs‐symmetric (syn) atropisomers. The interconversion between the isomers is studied in detail both for the N‐heterocyclic carbene salts and the free carbenes through variable‐temperature 1H NMR spectroscopic studies; activation free energies are calculated and can be linked to the substitution pattern of the naphthyl moieties. Palladium complexes comprising the new N‐heterocyclic carbenes are synthesized and preliminary data show that these compounds behave well as precatalysts in the Buchwald–Hartwig amination reaction of aryl bromides and aryl chlorides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) A new family of saturated N‐heterocyclic carbenes (NHCs) has been synthesized, fully characterized, and used as ligands in palladium‐catalyzed Buchwald–Hartwig amination reactions. These carbenes represent rare examples of stable, saturated NHCs. The incorporation of naphthyl side chains leads to atropisomeric mixtures comprising C2‐symmetric (anti) and Cs‐symmetric (syn) conformers.