Small aza cages as “fast proton sponges” and strong lithium binders

Abstract

The design and synthesis of new compounds in order to achieve expected or new chemical properties is one of the most fascinating aspects of modern synthetic chemistry. Among the many thousands of new compounds synthesized each year, macrocyclic compounds play an important role. The ever growing interest in this very active field stems from different points of view, including selective ion recognition, transport processes, reaction catalysis, industrial applications, model systems, and others [l-17]. Numerous books on macrocyclic chemistry have been published in the last few years [18-27]. Molecular topology and the nature of donor atoms are the two most important parameters influencing the chemical properties of macrocyclic compounds. Different classes of synthetic macrocyclic compounds have been developed and, in addition to the most studied crown-ether family, the aza-crowns are the next most studied class of synthetic macrocycles [ 19,251. These compounds could be considered to be derived from crown ethers by replacing the oxygen donor atoms with softer nitrogen donor atoms. The presence of this kind of donor atom makes these compounds water soluble bases and very prone to bind transition metal ions [28,29].