Exploiting halogen bonding interactions in high-performance liquid chromatography enantioseparations

High-performance liquid chromatography (HPLC) on chiral stationary phases (CSPs) is a widely-known tool for producing pure enantiomers. Inside the chiral column, the enantioseparation is driven by the ability of the CSP to distinguish between two introduced enantiomers. The understanding of the chiral recognition mechanisms contributes to design successful enantioseparations. Recently, the enantioseparation results of 2,2’-dichloro-3-iodo-5-bromo-5’-halo-4,4’-bipyridines suggested that a halogen bonding (XB) interaction involving iodine as electrophilic XB donor and the carbamate carbonyl group of the polysaccharide-based selector as XB acceptor reasonably drives the recognition mechanism. With the aim to verify the effectiveness of the XB interaction in HPLC enantioseparation of compounds characterized by different topologies compared to the 4,4’-bipyridine derivatives, we also found that the enantioseparation of 2-halo and 2,3-dihalosubstituted benzonorbornadienes appears XB-dependent.