Planar-Chiral Ferrocene-Based N-Heterocyclic Carbene Ligands.

In the last few decades, N-heterocyclic carbene (NHC) ligands, characterized by attractive features, have increased their presence in transition-metal catalysis. However, chiral NHC ligands still require further design enhancement to realize far more exciting synthetic applications. This review documents advances in chiral NHC ligands, focusing on planar-chiral ferrocene-based NHCs. As the basic shape of most classes of NHC rings is planar, it seems rational to employ a planar-chiral element in the design of chiral NHC ligands.