Solvent-Driven Chirality Switching of a Pillar[4]arene[1]quinone Having a Chiral Amine-Substituted Quinone Subunit

Abstract

Several new chiral pillar[4]arene[1]quinone derivatives were synthesized by reacting pillar[4]arene[1]quinone (EtP4Q1), containing four 1,4-diethoxybenzene units and one benzoquinone unit, with various chiral amines via Michael addition. Due to the direct introduction of chiral substituents on the rim of pillar[n]arene and the close location of the chiral center to the rim of EtP4Q1, the newly prepared compounds showed unique chiroptical properties without complicated chiral resolution processes, and unprecedented high anisotropy factor of up to −0.018 at the charge transfer absorption band was observed. Intriguingly, the benzene sidearm attached pillar[4]arene[1]quinone derivative 1a showed solvent- and complexation-driven chirality inversion. This work provides a promising potential for absolute asymmetric synthesis of pillararene-based derivatives.

Alignment and Dynamic Inversion of Planar Chirality in Pillar[n]arenes

“…Moreover, host–guest interactions aggravate the population bias of the two diastereomers to a certain extent, because the binding ability to the guest molecule of the diastereomers is theoretically different. This study demonstrated the reversibility and controllability of the planar chirality of pillar[ n ]arenes with additional chiral sources, and this was widely observed in subsequent studies [62–66] …”

Functionalization of pillar[n]arenes towards optically responsive systems via host–guest interactions

“…Formation of diastereomeric pillar[n]arenes by introducing chiral side chains into pillar[n]arene scaffolds is another method that generates a bias in the population of planar chirality (i.e., pS/pR isomers). [113][114][115][116] In this system, the hostguest interaction with the achiral guest regulates the planar chirality of pillar[n]arenes and causes the CD signal. We demonstrated chiral regulation using a diastereomeric pillar [5]arene bearing ten 2-(S)-methylbutoxy groups (H22) (Fig.…”

“…, pS / pR isomers). 113–116 In this system, the host–guest interaction with the achiral guest regulates the planar chirality of pillar[ n ]arenes and causes the CD signal. We demonstrated chiral regulation using a diastereomeric pillar[5]arene bearing ten 2-( S )-methylbutoxy groups ( H22 ) (Fig.…”

Alignment and Dynamic Inversion of Planar Chirality in Pillar[n]arenes

“…This study demonstrated the reversibility and controllability of the planar chirality of pillar[n]arenes with additional chiral sources, and this was widely observed in subsequent studies. [62][63][64][65][66] More interestingly, external stimuli may even reverse the population bias of the two diastereomers. Both the Jung group [63] and the Yang group [64] reported the CD inversion of pillar [5]arenes with achiral guest molecules in which the guest length plays a critical role in the inversion.…”

“…[62][63][64][65][66] More interestingly, external stimuli may even reverse the population bias of the two diastereomers. Both the Jung group [63] and the Yang group [64] reported the CD inversion of pillar [5]arenes with achiral guest molecules in which the guest length plays a critical role in the inversion. In 2020, Ogoshi and co-workers screened the chiral properties of 24Me in various linear dihaloalkanes that acted as guest solvents.…”