Microwave-Induced Synthesis of Aromatic Heterocycles

For more than a century heterocycles have constituted one of the largest areas of research in organic chemistry. Heterocycles have contributed to the development of the society from both biological and industrial view points. The heterocyclic moieties are of exceptional interest in the pharmaceutical industry as they make up a core part of several drugs. Many natural (quinine, atropine, codeine, morphine) and synthetic (diazepam, azidothymidine, captropril) drugs are heterocyclic in nature. They have also been used as anti-cancer agents, hypnotics, analgesics and vasopressor modifiers. Not only this, the heterocyclics have found certain miscellaneous applications including their use in dyestuffs, copolymers, anti-oxidant accelerators etc. The importance of heterocycles provides a significant basis for the development of new methods for their synthesis. The traditional methods used for the synthesis of these heterocycles are multistep processes and involve the use of hazardous reagents. However, due to the strengthing environmental regulations and safety concerns, the industries are in need of new innovative, environmental friendly alternate routes for synthesizing the therapeutic and pharmacological important heterocyclics. This environmentally benign synthesis can be easily designed using microwave methodology. Microwave irradiation is a non-conventional energy source whose popularity and synthetic utility has been considerably increasing. Microwave technology is versatile. The microwaves induce rapid heating and avoid the harsh classical conditions, resulting in the formation of cleaner products. §This book primarily focuses on the microwave-assisted synthesis of aromatic heterocycles and their application aspects. The first chapter is based on the microwave theory, latest developments in instrumentation technology, the various microwave technologies used for synthesis etc. The rest of the chapters are divided into two sections- Section A and Section B. The Section A deals with the five-membered heterocycles (pyrazoles, isoxazoles, triazoles, oxadiazoles, thiazoles, imidazoles, oxazoles, oxazolines etc.) and in Section B various six-membered heterocycles (triazines, benzoxazoles, benzimidazoles, benzothiazoles) are presented. In each section an elaborate description of a variety of examples from recent literature for the microwave assisted synthesis and applicability of various aromatic heterocyclics are included.