The effect of substituents on the syn-anti conformer ratio in naphthyl-based imidazolinium salts and their corresponding N-heterocyclic carbenes

Eight new N-heterocyclic carbenes (NHCs) featuring substituted naphthyl side chains were synthesized. These molecules are present in solution as a stable mixture of anti and syn conformers. Through careful tuning of the substituents on position 2 and 2,7 of the naphthyl moieties, it was possible to synthesize molecules that display a strong preference for the anti conformation (up to 95: 5). This will greatly facilitate their optimized use as single isomeric ligands in metal-catalysis and as organocatalysts.