Cascade Reaction in the Synthesis of Heterocyclic Natural Products

Background: Cascade reactions, as an attractive branch of organic chemistry, have been the subject of intense research in the recent years. In these reactions numerous transformations occur in a single sequence, and the subsequent reactions are formed as a consequence of the functionality of the previous step. Cascade reactions are environmentally benign processes due to their one-pot procedure which accordingly proceed in a single reaction solvent, work-up, and purification step. Therefore, they are often associated with cost savings in terms of solvents, catalysts, and reagents in addition to time and effort. Objective: In the recent years, cascade reactions have been used for the construction of complicated molecular scaffolds, especially heterocyclic natural products. Different naturally occurring compounds were synthesized through cascade (tandem) reactions; this review has been focused on the use of cascade sequences for the synthesis of heterocyclic natural products.