Hybrid [n]arenes through thermodynamically driven macrocyclization reactions

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Macrocyclic Chemistry

Background:

• Hybrid [n]arenes are medium-sized macrocyclic compounds composed of diverse alkoxybenzene units.
• Their synthesis and properties are crucial for developing novel molecular architectures and host-guest systems.

Purpose of the Study:

• To develop a straightforward, one-pot synthesis for hybrid [n]arenes.
• To investigate the reaction's reversibility and the factors influencing product distribution.
• To explore the structural and recognition properties of the synthesized hybrid macrocycles.

Main Methods:

• One-pot condensation of alkoxybenzenes with formaldehyde catalyzed by trifluoroacetic acid.
• Scrambling experiments using pre-formed macrocycles to confirm reversibility.
• Structural characterization using NMR spectroscopy and X-ray crystallography.
• Evaluation of cation binding properties.

Main Results:

• Successful synthesis of hybrid [n]arenes with [2+2] and [3+1] stoichiometries.
• Isolation of an unusual [3+2] hybrid macrocycle as a major product under specific conditions.
• Confirmation of reaction reversibility and product stability through scrambling experiments.
• Identification of steric hindrance from 1,4-dialkoxybenzene units leading to isomers and chirality.
• Demonstration of selective N-methylpyridinium cation recognition by the [3+2] hybrid macrocycle.

Conclusions:

• A facile one-pot method for hybrid [n]arene synthesis has been established.
• The reaction is reversible and product distribution is governed by thermodynamic stability.
• Structural features, particularly steric hindrance, influence macrocycle formation and properties.
• The synthesized hybrid macrocycles exhibit potential in selective molecular recognition.