Friedel-Crafts Acylation for Accessing Multi-Bridge-Functionalized Large Pillar[n]arenes

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis

Background:

• Pillar[n]arenes are macrocycles typically synthesized via Friedel-Crafts alkylation.
• The reversible nature of alkylation leads to mixtures of macrocycle sizes, requiring extensive purification.
• Existing methods yield inert methylene bridges, limiting further functionalization.

Purpose of the Study:

• To develop a size-selective method for synthesizing pillar[n]arenes.
• To introduce reactive functional groups onto the pillar[n]arene bridges.
• To enable the synthesis of novel, laterally modified pillar[n]arenes.

Main Methods:

• Utilized an irreversible Friedel-Crafts acylation reaction.
• Employed precursors with carboxylic acids and electron-rich arene rings.
• Controlled macrocycle size by precursor length.

Main Results:

• Achieved exclusive formation of pillar[n]arenes with predictable ring sizes.
• Eliminated the need for laborious separation of undesired macrocycles.
• Introduced reactive carbonyl groups at bridge positions, allowing for versatile modifications.

Conclusions:

• Irreversible Friedel-Crafts acylation provides a superior route to size-defined pillar[n]arenes.
• The carbonyl bridges facilitate the creation of diverse, laterally functionalized pillar[n]arene derivatives.
• This method overcomes limitations of traditional alkylation strategies for pillar[n]arene synthesis.