Chapter 17 - Supramolecular Chemistry of Benzoxazines: From Simple, Selective, Effective, and Efficient Macrocyclization Pathways to Host-Guest Properties

Abstract

This chapter discusses supermolecular chemistry, which has received much attention owing to the unique molecular recognition and the related inclusion phenomena from past few decades. Various kinds of molecules, not only in cyclic form but also in acyclic form, are clarified for supramolecular structure to create molecular assemblies based on noncovalent interactions or secondary forces between hosts and guests. The host molecules can either be acyclic molecules such as cholic acid or cyclic compounds whereas the guest species can be neutral molecules, cations, anions, or vinyl monomers depending on the host cavity. The specific interaction between host molecules and guest species have brought an inclusion phenomenon, which consequently relates to potential applications such as electrochemical sensors, luminescent probes, drug delivery systems, etc. Considering chemical structures of benzoxazine dimers, which contain the sites with electron-rich atoms of oxygen and nitrogen atoms, it is reasonable to expect benzoxazine dimmer as a host molecule with the unique property of metal ion interaction. To understand the interaction between benzoxazine dimers and metal ions, proton nuclear magnetic resonance (1H NMR) spectroscopic technique is applied. Many strategies are proposed to achieve the unique supramolecular compounds from fundamental molecular designs to synthesis pathways. Macrocyclic compounds are known as a traditional supramolecule based on the specific channel where molecular recognition is possible. Up to the present, various crown ethers and calixarene derivatives including their inclusion phenomena are reported. The macrocyclization of benzoxazine dimers was simple, effective, and efficient as it could be achieved in a simple condition.