Selenocarbonyl Synthetic Strategies, Molecular Diversification, and Applications of C═Se-Containing Compounds

Selenocarbonyl compounds are an important class of organoselenium compounds with unique reactivity, distinct electronic properties, and versatile biological activities. This review critically summarizes the main synthetic methods for C═Se derivatives, including selenoamides, selenoformamides, selenoureas, selenocarbamates, isoselenocyanates, and selenosemicarbazones. It covers both classical selenium-transfer reagents (Woollins' reagent, phosphorus pentaselenide, LiAlHSeH, metal selenides, selenium dioxide, potassium selenocyanate, and elemental selenium) and recent one-pot, multicomponent, and nucleophilic strategies. Rather than treating the literature as a chronological catalogue, the discussion is organized around shared selenium sources, reactive intermediates, and downstream functions, and explicitly compares reaction conditions, substrate scope, isolated yields, operational simplicity, product stability, safety, and scalability. The review further describes applications in selenium-containing heterocycles, metal complexes, bioactive molecules, supramolecular systems, and functional materials, highlighting reported anticancer, antimicrobial, antioxidant, anti-inflammatory, and enzyme-inhibitory activities. A dedicated discussion of ^{7 7}Se NMR spectroscopy clarifies how selenium chemical shifts connect molecular structure, electronic properties, and coordination behavior. Despite notable progress, many existing methods still rely on toxic or moisture-sensitive reagents, strong bases, elevated temperatures, or tedious purification, and biological and materials-related applications remain largely underexplored. Future research should focus on safer selenium sources, simpler scalable reactions, improved product stability, and better integration of molecular design with practical application.