Microwaves and Multicomponent Reactions

The heating effect utilized in MAOS is based on MW dielectric heating, which depends on the ability of a specific material (solvent or reagent) to absorb MW energy and convert it into heat (Refs [20, 21] and Chapter 1 in this book). 

Two different kinds of MW reactor are currently emerging - multimode and monomode (also referred to as single mode) (Chapters 1 and 2 in this book). 

The development of monomode reactors, which focus the electromagnetic waves in an accurately dimensioned wave guide, enables homogeneous distribution of the electric field leading to increased efficiency and reliability. So, the current trend in MAOS is to move away from the multimode MW ovens and use the more dedicated monomode instruments, which have only become available in the last few years [22, 23]. 

In the early days of MAOS, solvent-free techniques were very popular. In these procedures, the reactants are either mixed directly without use of a solvent or the reactants are preabsorbed on to a solid support before irradiation with MW. The solvent free approach enabled safe use of domestic household microwave ovens and standard open-vessel technology (Refs [16, 19, 23] and Chapters 4 and 8 in this book). 

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