Microwave-Assisted Organic Synthesis: General Considerations and Transformations of Heterocyclic Compounds

In this review paper we present the most important features of microwave irradiation, their physical characteristics and the properties upon an interaction with matter. The heating mechanisms are described, followed by a description of the available microwave equipment, including the differences between single- and multi-mode microwave reactors, considerations on open vs. closed reaction vessels, the selection of the appropriate solvents (or possible uses of solvent-free reaction conditions), the problems connected with scale-up, as well as the continuous flow processes and automation of microwave-assisted synthesis. A series of transformations of organic compounds with the emphasis on the conversion of heterocycles is presented. In the last part we present some of the most interesting properties of 2H-pyran-2-ones, their fused derivatives and other systems, including the synthesis of natural and other compounds incorporating this structural fragment and further transformations with a special emphasis on Diels-Alder cycloadditions. The research conducted in domestic microwave ovens is, due to the well-known problems associated with reproducibility, only partially included.