Axially Chiral Catenanes and π‐Electron‐Deficient Receptors

Abstract

AbstractThe design of a new class of chiral [2]catenanes is reported. The self‐assembly of [2]catenanes comprising one or two 3,3′‐bitolyl spacers in the π‐electron‐deficient component, and bis‐p‐phenylene‐34‐crown‐10 (BPP 34 C 10) as the π‐electron‐rich component, is described. The X‐ray crystal structures, together with solution‐state dynamic 1H NMR spectroscopic studies, show that the degree of order characterizing the molecular structures is substantially different from that of the “parent” [2]‐catenane, comprising cyclobis(paraquat‐p‐phenylene) and BPP34C 10. When appropriately substituted in their ortho positions, bitolyl compounds can support axial chirality: the self‐assembly of axially chiral [2]catenanes, comprising one or two 3,3′‐disubstituted‐2,2′‐dihydroxy‐1,1′‐binaphthyl spacers, has been achieved in good yields, showing that the introduction of the bulky, axially chiral spacer and the consequent distortion of the cavity of the π‐electron‐deficient component still permits good molecular recognition between the components leading to efficient catenane production. X‐ray crystallography suggests that this recognition is driven by hydrogen bonding and π‐π stacking interactions between the complementary subunits. The hydroxyl groups on the chiral spacer were further functionalized as benzoyl esters in a [2]catenane as well as in the tetracationic cyclophanes; that is, chemistry can be done on these catenanes. The chiral tetracationic cyclophanes exhibit good enantiomeric differentiation toward the D‐ and L‐enantiomers of aromatic amino acids in water and their N‐acetylated derivatives in organic solvents.