An extended cavitand with an introverted carboxylic acid

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis

Background:

• Cavitands are molecular hosts with deep cavities.
• Designing cavitands with specific functionalities is crucial for molecular recognition and catalysis.

Purpose of the Study:

• To synthesize a novel cavitand with an exceptionally deep cavity and an inwardly-directed carboxylic acid.
• To investigate the binding capabilities of the new cavitand for various amines and isocyanides.
• To explore the reactivity within the cavitand's cavity.

Main Methods:

• Condensation reaction between a Kemp's triacid derivative and a diamino resorcinarene.
• Spectroscopic analysis (1H NMR, IR) to characterize the cavitand and detect reaction intermediates.

Main Results:

• A deep cavitand with a 6,7-diaminoquinoxaline wall and an inwardly-directed carboxylic acid was successfully synthesized.
• The cavitand effectively bound large (1-adamantanemethylamine) and small (triethylamine) amines.
• Adamantyl and cyclohexyl isocyanides were bound, positioning the isonitrile group near the carboxylic acid.
• Reactions within the cavity at ambient temperature yielded N-acylformamides from isocyanides.
• Transient O-acyl isoamide intermediates were detected spectroscopically.

Conclusions:

• The synthesized deep cavitand demonstrates significant molecular recognition capabilities for diverse guest molecules.
• The cavity environment promotes intramolecular reactions between bound guests.
• This work expands the scope of functional deep-cavity hosts for potential applications in catalysis and molecular encapsulation.