Synthesis of Biologically Active Selenium-Containing Molecules From Greener Perspectives

Background: In this review we focus on the environmentally friendly processes used for the preparation of organoselenium compounds with biological and/or pharmacological properties. In this regard, the methods most commonly applied are alternative energy sources (microwave and ultrasound), reactions carried out under metal and solvent-free conditions, catalytic processes, and reactions that involve sustainable solvents (ionic liquids, glycerol, PEG-400, ethanol and water). The biological relevance of the compounds synthesized is also highlighted. Conclusions: In this review, we have highlighted the wide and growing interest in the development of new environmentally-friendly processes for the synthesis of biologically-active selenium-containing molecules. This interest is strongly correlated to the concept of sustainable chemistry, which encourages a reduction in the adverse effects of chemical synthesis through new approaches and careful planning. In this context, considerable progress has been made in relation to obtaining greener protocols for the synthesis of organoselenium compounds. Notable examples are the replacement of hazardous reagents and solvents with more sustainable chemicals, the use of renewable solvents obtained from biomass, the application of new catalytic processes, the introduction of new energy-saving sources and the use of metal- and solvent-free protocols. Although many important advances have been achieved in this field, further improvements are needed, particularly in relation to the increased use of bio-based solvents derived from renewable feedstock, due to the regulatory constraints that restrict the use of a large number of traditional organic solvents. This will lead to an increased number of new and sustainable methods for the synthesis of biologically-active organoselenium compounds. (AU)