Synthesis of Heterocycles via Microwave-Assisted Cycloadditions and Cyclocondensations

Controlled microwave heating has found many important applications in the synthesis of heterocycles. Almost all kinds of heterocycles have been prepared (or their preparation attempted) with the aid of microwaves. Many examples of cyclocondensations, reactions where two or more functional groups combine with the loss of another small molecule (usually water), have been described. Moreover, microwave irradiation successfully induces cycloaddition reactions, especially in the cases where high temperatures are required. This review collects the most representative examples of the application of microwaves to these two kinds of transformations. Except for a few examples, all the reactions selected have been carried out under controlled microwave irradiation using dedicated instruments.