Synthesis of quinoxaline cavitand baskets

Abstract

ABSTRACT The unique temperature, solvent and pH drivenvase to kite equilibrium in quinoxaline cavitands allows the reversible uptake and release of guests. However, the cavity breathing associated with this conformational switch reduces the strength of complexation. A limited number of solutions have been proposed for the cavity rigidification, using either H-bonding, metal coordination or covalent connections. Here we report the synthesis and structural characterisation of quinoxaline-based cavitand baskets, which present two distal quinoxaline walls linked together. Baskets A and B were obtained through a bridging reaction starting from an AC di-quinoxaline bridged cavitand using two different di-quinoxaline moieties. In both cases, two isomers were obtained: isomer C2, with the linking unit crossing the cavity mouth, and isomer Cs, having the linker sideways. The isomers were identified through 1H NMR analysis. In the case of basket A-Cs, the resolved molecular structure confirmed the Cs symmetry of the basket.