Microwave Technology—Chemical Synthesis Applications

Abstract

Microwave‐accelerated chemical syntheses in various solvents as well as under solvent‐free conditions have witnessed an explosive growth. This technology, which is still in its growth phase, has found widespread application predominantly exploiting the inexpensive unmodified household microwave (MW) ovens although the use of dedicated MW equipment has been rapidly gaining ground. Of special interest is the environmentally friendlier solventless approach that often involves exposure of neat reactants to MW irradiation or employs supported reagents on recyclable inorganic oxides or catalysts and has been adequately demonstrated in several MW‐assisted condensation, deprotection, rearrangement, cyclization, reduction, and oxidation reactions. The rapid one‐pot preparation of heterocyclic compounds from in situ generated reactive intermediates and the general application to multicomponent reactions, that are adaptable for building a library of compounds, have been accomplished using this MW technique. More recently, the strategy has been extended to combinatorial chemistry and the synthesis of a newer class of solvents, ionic liquids that are essentially molten salts with barely measurable vapor pressure. The salient features of these high yield protocols, namely, the selectivity, experimental ease of manipulation, and the enhanced reaction rates are discussed.

Rapid Assembly of Functionalized 2H-Chromenes and 1,2-Dihydroquinolines via Microwave-Assisted Secondary Amine-Catalyzed Cascade Annulation of 2-O/N-Propargylarylaldehydes with 2,6-Dialkylphenols

“…The supply of energy to trigger the chemical reactions is one of the major concerns to access the desired products in a short span of time avoiding the formation of undesired byproducts and decomposition of the target molecules. Microwave heating is a fascinating and widely recognized non-conventional energy source for the execution of organic transformations . The key advantages of microwave-assisted reactions over conventional synthesis are spectacular accelerations of reactions, milder reaction conditions, high product yields, better regio- and diastereoselectivities, etc.…”

Effect of Microwave Radiation on the Synthesis of Ion Exchange Resins: A Comparative Study

“…Chemical reactions supported by microwaves meet with the rules of Green Chemistry [29] and allow one to obtain products characterized by high purity. [30] In many cases, microwave-assisted processing of materials has significant advantages over traditional techniques. [31−33] These include more precise and volumetric heating, lower energy consumption, and much shorter time required for completing the reactions.…”