Ketocalixarenes: Versatile yet still Unexplored Macrocycles

Ketocalix[n]arenes can be prepared via oxidation of the methylene groups of protected calix[n]arenes. The presence of carbonyl groups at the bridges alters the preferred conformation and reactivity of the macrocycle and provides an entry point (via nucleophilic additions reactions) to a wide array of methylene-substituted derivatives as well as calix[n]radialenes. 1 Introduction 2 Synthesis of Ketocalix[n]arenes 2.1 Ketocalix[4]arene Derivatives 2.2 Systems Possessing both Carbonyl and Bromomethane Bridges 2.3 Pentaoxoketocalix[5]arene and Hexaoxoketocalix[6]arene Derivatives 2.4 Monooxo- and Dioxoketocalix[6]arenes 3 Conformation of Ketocalixarenes 4 Reactions of Ketocalixarenes 4.1 Alkylation of the OH Groups 4.2 Intramolecular Aromatic Nucleophilic Substitution 4.3 Reduction of the Carbonyl Groups 4.4 Reaction of 5c with PhLi 4.5 Reaction with tert-Butyllithium 5 From Ketocalix[n]arenes to Calix[n]radialenes and Calix[n]rotanes 6 Summary and Outlook