Synthesis, structures, and conformational characteristics of pillararene-based Diels–Alder adducts with embedded chiral centres

Abstract

Functionalizing pillar[n]arenes through partial oxidation to form pillar[n-m]arene[m]quinones remains an important synthetic route. In this study, we demonstrate the subsequent [4 + 2] Diels–Alder (DA) cycloadditions between quinone-containing pillar[n]arene derivatives and linear dienes. Detailed NMR spectroscopic and X-ray crystallographic investigations reveal that the formation of new fused bicyclic rings from the DA reaction leads to distortion of the macrocycles. Moreover, the DA reactions introduce multiple chiral centres, resulting in the formation of a pair of enantiomers that can be resolved through chromatographic techniques and characterised using chiroptical spectroscopy. Our findings highlight a new method for producing pillararene derivatives with embedded chiral centres directly on the macrocyclic scaffold.