Advances in Unconventional and Sustainable Synthetic Approaches to Benzopyran Scaffolds

The benzopyran scaffold is a versatile family of heterocycles found in a wide range of bioactive natural products and functional molecules. In response to increasing environmental and regulatory demands, developing synthetic strategies focused on sustainability and low-impact conditions has become a central focus in modern heterocyclic chemistry. Therefore, this review provides a comprehensive and critical analysis of low-impact methods reported over the past 8 years for constructing benzopyran-derived structures, including coumarins, flavones, chromones, chromenes, and chromanes. We systematically integrated both enabling technologies (e.g., microwave irradiation, visible-light photocatalysis, continuous-flow systems, and ultrasound activation) and chemical strategies involving biocatalysis, multicomponent reactions, recyclable heterogeneous catalysis, and alternative solvents, including deep eutectic solvents and ionic liquids. Advances in selectivity, efficiency, and catalyst reusability are highlighted, as are certain limitations. By contextualizing these methods within the various benzopyran scaffolds, this review provides an important foundation for the rational integration of sustainable tools in benzopyran synthesis and highlights perspectives for future research, thereby enhancing their industrial and pharmaceutical relevance.