Benzochalcogenodiazoles, Synthesis, and Applications in Medicinal Chemistry and Photomedicine

Benzochalcogenodiazoles (BXDs) (BOD: benzoxadiazole, BTD: benzothiadiazole, or BSD: benzoselenadiazole) are aromatic bicyclic compounds, containing chalcogen atoms, with applications ranging from material to medicinal chemistry. The recent developments in their preparation and functionalization are taking advantage of new methodologies such as CH activation and photocatalysis. After being almost restricted to organic semiconductor materials for optoelectronics applications, they are gaining more and more interest in medicinal chemistry as lipophilic aromatic fragments. Their unique optical properties make them attractive in biological imaging and in photomedicine, with emission up to the near‐infrared biological transparency window. The nature of the chalcogen atom influences their optical properties, with sulfur and selenium atoms favoring phototherapy over fluorescence. This review will not describe optoelectronic materials and fluorophores based on BXD but will focus on the preparation of BXD‐containing compounds, and their medicinal and photomedicinal applications.