Rim-Differentiated C₅-Symmetric Tiara-Pillar[5]arenes

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis

Background:

• Synthesizing rim-differentiated pillar[5]arenes, featuring distinct chemical groups on opposing rims, presents significant challenges.
• The statistical cyclization of 1,4-disubstituted alkoxybenzenes typically yields a mixture of four constitutional isomers, with only a small fraction being rim-differentiated.

Purpose of the Study:

• To develop a novel synthetic strategy for efficiently producing C5-symmetric, rim-differentiated pillar[5]arenes.
• To overcome the limitations of statistical cyclization methods and improve selectivity for the desired isomer.

Main Methods:

• Employed a "preoriented" synthetic protocol utilizing FeCl3-catalyzed cyclization.
• Utilized asymmetrically substituted 2,5-dialkoxybenzyl alcohols as starting materials.

Main Results:

• Achieved an unprecedented 55% selectivity for the C5-symmetric tiara-like pillar[5]arene isomer among the four constitutional isomers.
• Successfully synthesized and characterized a series of functionalizable tiara-pillar[5]arene derivatives with C5-symmetry.

Conclusions:

• The developed "preoriented" synthetic method significantly enhances the selectivity for C5-symmetric tiara-pillar[5]arenes.
• This breakthrough enables the efficient preparation of functionalizable pillararene derivatives for diverse applications.