Preface

Since ethers and crown ethers are important structural parts of many manmade or natural organic materials with medicinal, agrochemical, or technological attributes, various protocols have been directed toward the synthesis of these valuable compounds during recent years. This book is a convenient, concise reference that summarizes the best and most reliable methods for the preparation of ethers and crown ethers. It also discusses their possible applications in various fields such as organic synthesis, ionic liquids, protecting groups, photoswitchable catalysis, phase transfer catalysis, usability as solvents, and biological functionality, especially for anticancer and antimicrobial effects, drug delivery, and biofuels. The book is organized into seven chapters that are very clearly presented and well-organized, in an effort to simplify the reader’s comprehension of various methods. It will probably be a reference book for undergraduates, postgraduates, and researchers either working in industry or university.

The first chapter describes the historical background of the synthetic methods and properties of ethers.

The second chapter illustrates recent advances in synthetic methods for dialkyl ethers. A concise overview is given of the electrophilic addition of alcohols to alkenes, the reaction of diazomethane with alcohols, dehydration of alcohols using acids, transition metal O-alkylative etherification reactions, transition-metal-free O-alkylative etherification reactions, and reductive etherification of aldehydes and ketones with alcohols. Also, this chapter contains selected examples of C–H functionalization methods, cross-coupling of aryl methyl sulfones with alcohols, α-tertiary dialkyl ether synthesis via reductive photocatalytic α-functionalization of alkyl enol ethers, decarboxylative etherification of benzylic carbonates, electrodecarboxylative etherification through the Hofer–Moest method using a radical C–O coupling strategy, hindered dialkyl ether synthesis with electrogenerated carbocations, programmable ether synthesis enabled by the oxa-Matteson reaction, and dimethyl ether synthesis.

The third chapter provides a rather brief discussion of the recent developments in synthetic methods for alkyl aryl ethers, such as the Williamson ether synthesis, cross-coupling of allyl alcohols with phenols, the addition of phenols to olefins using Brønsted acids, catalytic S_NAr hydroxylation, alkoxylation of aryl fluorides, etherification of fluoroarenes with alkoxyboronic acid pinacol esters via C–F bond cleavage, conversion of cyclohexanones to alkyl aryl ethers, and symmetrical or unsymmetrical dialkyl ether synthesis by oxidation–reduction.

The fourth chapter focuses on protocols for the synthesis of diaryl ethers through Ullmann-type diaryl ether synthesis, symmetrical or unsymmetrical diaryl ether synthesis by copper-catalyzed double arylation of a simple oxygen source, Buchwald–Hartwig, coupling of phenols with aryl reagents (such as nitroarenes, arylboronic acid, and Ph₃SnCl), arylation of arylboronic acids with nitroarenes, decarbonylative diaryl ether synthesis, metal-free synthesis of diaryl ethers with use of diaryliodonium salts, diaryl ether synthesis via a benzyne mechanism, S_NAr of activated nitroarenes via strong bases, microwave-assisted metal-free arylation of phenols with nitroarenes, radical C–O coupling reactions of phenols, and the benzannulation strategy. The substrate scope, limitations, reaction mechanisms, and chemoselectivity, as well as related control strategies of these reactions, are also discussed.

Inthe fifth chapter, the authors discuss the protocols involved in the synthesis of cyclic ethers using dehydrogenative coupling between an O–H bond and an inactivated sp³ C–H bond, selective C–H oxidation reactions, etherification of alcohols with transition metals, alkoxy radical generation, intramolecular exo-hydrofunctionalization of allenes with oxygen nucleophiles, the intramolecular hetero-Michael reaction of α,β-unsaturated carboxylic acids, Prins cyclization, the nucleophilic substitution of alkyl fluorides, cyclization of diols, treatment of tertiary 1,4- and 1,5-diols with cerium ammonium nitrate, and acylation-reductive cyclization reactions.

The sixth chapter provides a rather brief discussion of methods for the synthesis of aliphatic and aromatic crown ethers to access compounds that could carry out many functions and could be incorporated into sophisticated systems.

The seventh chapter describes the application of ethers and crown ethers in various fields such as organic synthesis, ionic liquids, protecting groups, photoswitchable catalysis, phase-transfer catalysis, usability as solvents, and biological functionality, especially for anticancer and antimicrobial effects, drug delivery, and biofuels.

Arash Ghorbani-Choghamarani, Bu-Ali Sina University, Iran

Maryam Hajjami, Bu-Ali Sina University, Iran

Zahra Taherinia, Ilam University, Iran