Microwave-assisted synthesis of five-membered azaheterocyclic systems using nanocatalysts

Heterocycles form the largest and most important category of organic chemistry. They are the basic skeleton of more than 80% of drugs available on the market. Five-membered heterocyclic systems hold a prominent position among all heterocycle systems as they represent an integral part of natural compounds, antibiotics, vitamins, nucleic acids, hormones, and synthetic drugs. Most of the synthetic methods for synthesizing heterocyclic systems are not sustainable. In recent years, scientists have effectively investigated several organic reactions under microwave irradiation including the synthesis of nitrogen-containing five-membered heterocyclic systems. Microwave energy offers tremendous advantages relative to traditional heating methods, such as homogeneous heat distribution, cleaner chemistry, improved yields, reductions in reaction times, greater product quality, mild reaction conditions, and safety, as well as huge scope for automation. On another hand, in nanoparticle-catalyzed synthesis, the use of metal-impregnated nanoparticles also provides tremendous benefits such as atom economy, greener protocol, recyclability of catalysts, selectivity, excellent yields, and faster reaction. Here, we review the application of microwave irradiation for the synthesis of five-membered azaheterocycles in presence of nanoparticles as catalysts. We highlight the greener aspects of synthetic protocols as well as the medicinal application of the heterocycles.