Controlling Calixarene Size with Metal Salts: The First Brønsted-Free Synthesis

Significance

The authors investigated the mechanism of calixarene formation from phenolic precursors, with a specific aim of elucidating the role of the cation in mediating cyclooligomerization. During the course of the study, it was found that calix[4-9]arenes were formed in high yield from tert-butyl phenol, formaldehyde, and a metal salt without the use of a Brønsted acid or base. Additionally, it was revealed that the size distribution of the calixarenes formed is reliant upon the identity and oxidation state of the cation, as well as the identity of the anion.