Thermodynamically Controlled Synthesis of a Chiral Tetra-cavitand Nanocapsule and Mechanism of Enantiomerization

摘要

The dynamic covalent synthesis, structure and conformational dynamics of a chiral polyimine nanocapsule la are reported. Reaction of four tetraformyl cavitands and eight H_2N(CH_2)_2NH_2 yields quantitatively la, which has a compact, asymmetrically folded, pseudo-C_2-symmetric structure, as determined by X-ray crystallography, and encapsulates four CHCl_3 and three CH_3OH guests in the solid state. In solution, la enantiomerizes bypassing over a barrier of ΔG_(298)* = 21.5 ± 0.7 kcal mo~(-1) via a refolding process.