Principles and Synthetic Applications in Crown Ether Chemistry

The principles involved in macroheterocycle chemistry are discussed. Classes and types of macroheterocycles, synthetic approaches (including the template effect), complexation and complexes are mentioned. The utilization of crown ethers in synthetic organic chemistry is also surveyed. 1. Introduction 1.1. History 1.2. Nomenclature and Characteristics 1.3. Classes of Crowns and Related Molecules 2. Synthetic Access 2.1. Templated Syntheses 2.2. Non-Williamson Syntheses 3. Complexation 3.1. The Complexation Phenomenon 3.2. Types of Complexes 4. Synthetic Utility 4.1. Solubilization and Phase Transfer 4.2. Cation Effects 4.3. Crowns as Reagents and Catalysts 4.4. Complexation Specificity 5. Toxicity 6. Conclusions