: Organoselenium chemistry has undergone extensive development during the past decades, mostly due to the unique chemical properties of organoselenium compounds that have been widely explored in a number of synthetic transformations, as well as due to the interesting biological properties of these compounds. Diselenides and selenocyanates constitute the promising classes of organoselenium compounds that possess interesting biological effects and that can be used in the preparation of other selenium compounds. The combination of diselenide and selenocyanate moieties with other biologically relevant molecules (such as heterocycles, steroids, etc.) is a way for the development of compounds with promising pharmaceutical potential. Therefore, the aim of this review is to highlight the recent achievements in the use of diselenides or selenocyanates as precursors for the synthesis of pharmaceutically relevant compounds, preferentially compounds with antitumor and antimicrobial activities.

Ligand design is a critical element in homogeneous catalysis. Over the past two decades, a variety of selenium-substituted compounds have been used as ligand scaffolds in the development of transition metal catalytic systems. Air and moisture stability, good solubility in various solvents, stability towards oxidation and excellent electron-donating properties of the selenium atom are some of the key features of organoselenium compounds that make them suitable candidates for application as ligands. The metal complexes of selenium ligands are widely known for their ability to catalyze various organic reactions, including but not limited to the Sonogashira coupling reaction, Heck coupling reaction, Suzuki–Miyaura coupling reaction, imidazole arylation, transfer hydrogenation reaction, oxidation of alcohols, and ortho-arylation of phenols. In some cases, exceptionally high catalytic efficiencies have been observed. In addition, catalysis often allows for a wide range of substrate in numerous scenarios, as it is tolerant of different functional groups. This review highlights the main synthetic methods used in the recent development of organoselenium compounds as ligands for the synthesis of transition metal complexes. It also considers their use in various preparative organic transformations. The bibliography includes 133 references.