Tomato Processing By-Products as a Sustainable Source of Lycopene and Other Bioactive Compounds for Animal Nutrition: A Circular-Economy Perspective.

Organic chemistry has elevated the development of sustainable and environmentally benign synthetic methodologies in response to the rising need to reduce the ecological footprint of chemical processes [,,]. In this context, organoselenium compounds have attracted sustained interest owing to their distinctive reactivity, redox behavior, and broad biological relevance, particularly in medicinal and synthetic chemistry [,,,,,]. Despite their importance, conventional routes to organoselenium compounds often rely on multistep protocols and toxic reagents, raising significant environmental and practical concerns [,,]. Recent advances in asymmetric synthesis, catalysis, and the adoption of green solvents have opened new opportunities for developing efficient, sustainable, and eco-friendly synthetic approaches to organoselenium compounds [,,]. The progress in the syntheses of organoselenium compounds is summarized in . The early 20th century marked the initial syntheses of simple organoselenium molecules, including selenophenes, selenobenzene, and diselenides. These compounds exhibited unique aromaticity, enhanced nucleophilicity, and distinctive redox properties relative to their sulfur and oxygen analogues, providing early insights into the bonding behavior of selenium within organic frameworks []. At this stage, research primarily focused on fundamental chemical properties, with limited attention to biological applications []. The biological significance of selenium became increasingly apparent in the mid-20th century through the synthesis of selenium-containing amino acids such as selenocysteine (SeCys) and selenomethionine (SeMet). These discoveries supported a role for selenium in enzymatic function and antioxidant defense mechanisms []. Since the 1970s, organoselenium synthesis has expanded rapidly with the introduction of new reagents and synthesis strategies, including selenenyl halides, nucleophilic substitutions, electrophilic additions, and oxidative cyclizations. These methodologies enabled the preparation of diverse selenium-functionalized structures, such as seleniranes, selenoepoxides, and heterocycles, including selenophenes and selenazoles. Additionally, selenium-specific reagents and radical-based strategies further broadened the scope of carbon–selenium bond formation [].