Synthesis of Medicinally Privileged Heterocycles through Dielectric Heating.

Abstract

Heterocyclic compounds are intriguing part of modern drug discovery research. Ecofriendly syntheses of heterocycles, following green techniques, are privileged routes to protect Mother nature. Microwave-assisted synthesis of chemical compounds is considered as a major greener pathway, both in academia and industry. A total of 106 publications (including a few authentic web links) have been reviewed mainly to discuss (i) mechanism of microwave irradiation, (ii) abundance of commercial heterocyclic drugs, (iii) various synthetic procedures, and (iv) medicinal activity of the synthesized molecules. This review summarizes the potential application of microwave irradiation (dielectric heating) to synthesize biologically important heterocyclic small molecules in the recent past. A huge number of heterocyclic compounds are present in various natural sources like plant, marine microbe or other organisms and many of them possess unique biological activity. In addition to nature-derived heterocyclic compounds, a large number of synthetic heterocycles are being used as medicines. This review describes the relevant recent examples of microwave irradiation to accomplish various chemical transformations accelerated by a variety of catalysts which include, but not limited to, Lewis acids, other metal containing catalysts, organocatalysts, heterogeneous catalysts, phase-transfer catalysts, solid-supported catalysts, inorganic catalysts (bases, acids and salts) and so on. Although there are an increasing number of reports on application of dielectric heating in various other fields, this review is focused on a large number of new and novel strategies related to synthetic organic chemistry. The discussion is mostly organized by the disease type although some reactions/molecules can certainly be placed in multiple sections. Since green chemistry is an extremely emerging and comparatively new field of research, attempts to stimulate more activities on green medicinal chemistry are provided. Discussion related to the concurrent effect of microwaves, catalysts and/or solvents, supports to constitute expeditious and general route for the syntheses of medicinally important heterocyclic compounds and pharmacophores has also been included. The dielectric heating procedure to produce novel medicinally privileged heterocyclic scaffolds/ compounds is extremely promising and challenging. As a result, this green technique has been gaining increasing interest from the pharmaceutical world. A recent update has been presented. While every effort has been made to include all pertinent reports in this field, any omission is unintentional.