Synthesis of 2H-Chromenes via Green Catalytic Approaches: A Recent Update

: The synthesis of heterocyclic molecules is one of the fundamental areas of synthetic organic chemistry. Metal catalyzed synthesis is a widely used chemical tool for the preparation of important heterocycles. Chromene is one of the naturally occurring scaffolds that are highly valued, serving as the core structure for developing a variety of molecules withwith diverse applications. The aim of this study was to provide an effective method with several applications in the one-pot production of chromene derivatives with green methods and nanocatalyst. In the current compilation, synthetic methods, which have been cited to use exo and endo cyclization, produces chromene derivatives and provide a high yield of products in a straightforward onepot operation with mild reaction conditions. This review will serve as a guiding resource for the researchers in this field. The main benefits of the methodologies are short reaction time, low cost, high atom economy, solvent-free nature, and ease of work-up to give desired chromene derivatives in high yield.