Direct synthetic routes to functionalised crown ethers

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Macrocyclic Chemistry

Background:

• Crown ethers are versatile macrocyclic hosts capable of complexing various cations and neutral species.
• Their utility in chemistry relies heavily on functionalization for advanced applications.
• Traditional functionalization involves templated macrocyclization, which can be complex.

Purpose of the Study:

• To review methodologies for the direct functionalization of pre-formed aliphatic and aromatic crown ether frameworks.
• To highlight an underexplored alternative to conventional crown ether synthesis.
• To consolidate knowledge on direct functionalization strategies over four decades.

Main Methods:

• Review of literature methodologies for direct crown ether functionalization.
• Analysis of radical-mediated cross-dehydrogenative coupling for aliphatic crown ethers (photochemical/thermal/chemical activation).
• Analysis of electrophilic aromatic substitution for aromatic crown ethers.

Main Results:

• Direct functionalization of aliphatic crown ethers typically involves radical-mediated cross-dehydrogenative coupling.
• Aromatic crown ethers are commonly functionalized via electrophilic aromatic substitution.
• These direct routes offer reduced synthetic effort and enable late-stage modifications.

Conclusions:

• Direct functionalization provides efficient routes to modify crown ether architectures.
• These methods expand the synthetic toolkit for creating functionalized crown ethers.
• The review facilitates new applications of crown ethers in supramolecular science and technology.