Synthetic strategies for the functionalization of upper or lower rim of supramolecular calix[4]arene platform

Abstract

In the broad area of supramolecular chemistry, the calix[n]arene provides a congenial platform for synthetic modifications, and further has been a highly studied system and thereby occupies a unique position among the supramolecular scaffolds. This is attributable to its pre-organised hydrophobic cavity, amenability to synthetic modifications to generate derivatives, presence of pre-organised ion binding cores along with reporter moieties both at its lower and upper rims. Such derivatizations lead to well defined conformations, and tunable functionalization at both these rims. Among various possible derivatizations, the synthetic strategies of those leading to cone conformation have been rationalized in this review article. In addition, some insights into the synthesis of calix[4]arene dimers and tubes, and a variety of different macrocyclic derivatives of the calixarene have also been taken into consideration. All the conjugated derivatives of calix[4]arene platform reported in this article have been provided with a relevance to highlight their application potential.

Polyaromatic Calixarene Hosts: Calix[4]pyrenes

“…Most commonly, these modifications are introduced at the phenolic part of the molecule (lower rim) via the etherification or esterification reactions . Alternatively, direct aromatic substitution in the position para - to the phenolic oxygen (upper rim) was used to introduce various groups (Figure a) . These classical approaches to modify the calixarene cavities produced numerous structures with interesting properties for the chemosensory, biological, or materials applications.…”

“… 8 Alternatively, direct aromatic substitution in the position para - to the phenolic oxygen (upper rim) was used to introduce various groups ( Figure 1 a). 9 These classical approaches to modify the calixarene cavities produced numerous structures with interesting properties for the chemosensory, biological, or materials applications. The structures, however, only possess functional groups as pendants to the calixarene cavity with a high degree of flexibility.…”