Eco-friendly and sustainable synthetic approaches to biologically significant fused N-heterocycles

This review summarizes environmentally benign approaches for the synthesis of fused N-heterocycles since 2011. It is mainly focused on one-pot, multicomponent protocols for generating fused N-heterocyclic moieties with biological significance in atom-efficient manner. Several attractive and cost-effective approaches such as metal-, catalyst-, and solvent-free methods are discussed in this review. Electrochemical concept as green and environmentally optional strategy to produce fused N-heterocycles is also discussed. Synthesis of natural bioactive compounds like clausine V, glycoborine, and popular commercial drug alprazolam (Xanax) by utilizing such strategy is described.