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Updated: Aug 25, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
p-(1H-phenanthro[9,10-d]imidazol-2-yl)- substituted calix[4]arene, a deep cavity for guest inclusion
Enrique Botana1, Kalle Nättinen, Pilar Prados
1Universidad Autónoma de Madrid, Departamento de Química Orgánica, Cantoblanco, 28049-Madrid, Spain.
Abstract:
The reaction of tetra-p-formyltetra-O-propylcalix[4]arene with phenanthrenequinone in the presence of NH(4)OAc affords compound 2, a new class of calixarene with an expanded aromatic cavity, that could be stabilized by hydrogen-bonded bridges and/or ion pairing, thus preventing collapse into fully stacked pinched cone conformations as depicted. Two partially protonated calixarenes interdigitate in the solid state to give rise to a self-assembled face-to-face dimer, stabilized by pi-pi stacking interactions.
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