Fragmentation reaction via an ipso-attack in the multistep synthesis of regioselectively functionalized Calix

Abstract

The acid-catalyzed convergent synthesis of a calix[8]arene containing a regioselectively functionalized upper rim has been investigated through the isolation and identification of cyclic and acyclic byproducts. Theoretical calculations demonstrated that the synthetic process involves two types of reaction mechanisms, one of which leads to the favorably constructed framework, while the other causes undesirable fragmentation via ipso-substitution. A possible rationale is proposed to explain the overall reaction pathways which derive the calix[8]arene along with the byproducts.