Green synthesis of biologically active heterocycles of medicinal importance: a review

Heterocyclic moieties are basic skeletons for 80% of commercial medicines according to the US retail market in 2014–2015, yet many actual synthetic methods are not sustainable, calling for eco-friendly strategies. For instance, microwave-assisted synthesis produces molecules rapidly in excellent yields using less energy. Similarly, in nanoparticle-catalysed synthesis, the use of metal-impregnated nanoparticles provides benefits such as recyclability of catalysts, excellent yields and short reaction times. Other sustainable methods include solvent-free synthesis, ionic liquid-supported synthesis, organic synthesis in water, sonochemical synthesis and combinatorial synthesis. Here, we review the application of microwave irradiation for organic synthesis, organic synthesis in water and solvent-free synthesis in a combined manner. We present the synthesis of complex heterocyclic molecules using nanoparticles as catalysts. We emphasize green aspects of synthetic procedures.