Selective Macrocycle Formation in Cavitands.

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Catalysis

Background:

• Macrocyclization via end-to-end cyclization of linear precursors is entropically unfavorable.
• Intermolecular reactions often compete with desired intramolecular cyclization, leading to low yields and unpredictability.
• Traditional templating methods can be inefficient, with templates acting as guests within the host structure.

Purpose of the Study:

• To develop a selective method for intramolecular aldol/dehydration reactions of long-chain α,ω-dialdehydes in aqueous solution.
• To utilize cavitands as hosts to control the conformation of linear precursors and favor macrocyclization.
• To reverse the conventional host-guest relationship seen in templated reactions, mimicking biological catalysis.

Main Methods:

• Application of cavitands to facilitate the aldol/dehydration reaction of long-chain α,ω-dialdehydes.
• Utilizing hydrophobic forces within cavitands to drive dialdehydes into folded conformations.
• Performing reactions in aqueous solution to promote macrocyclization over intermolecular side reactions.

Main Results:

• Selective intramolecular aldol/dehydration reactions were achieved using cavitands.
• Macrocyclic products were obtained in good yields, ranging from 30% to 85%.
• The method successfully formed macrocycles with ring sizes from 11 to 17 members.

Conclusions:

• Cavitands act as effective hosts, promoting selective macrocyclization by controlling precursor conformation.
• This cavitand-mediated approach overcomes the entropic barriers associated with traditional macrocyclization methods.
• The reversed host-guest dynamic in this system offers a novel strategy for templated synthesis, inspired by biological catalysis.