Editorial [Hot Topic: Advances in Asymmetric Synthesis Using Organoselenium Chemistry (Guest Editor: Pete Silks)]

Organoselenium chemistry continues to attract the attention of many researchers. Perhaps the underlying reason for this is the broad interest in the unique applications of selenium to inorganic, biological, and organic chemistries. Inorganic selenium complexes range from metal complexes and new materials (organic semiconductors) to quantum dots. Since the discovery of selenium as an essential trace element, the role of selenium in biological systems has been actively investigated. There are many selenium- containing proteins that have been discovered. A large number of these are involved in redox reactions and the most commonly encountered proteins are glutathione peroxidase, selenoprotiens and selenophosphate synthetase 2. Incorporation of selenium into proteins can be accomplished with selenocysteine and selenomethionine. In fact, selenocysteine is the 21st proteinogenic amino acid. The special role that selenium plays in many of these biological systems can be directly linked to its unique chemical and physical properties. New developments in organoselenium chemistry are a reflection of the diversity of reactions that are accessible. Anionic, cationic, and radical behaviors have been well studied and are usually represented in the initial strategies researchers use when devising a chemical transformation. Other reactions, such as rearrangements and eliminations, are frequently employed. The recent discovery of non-bonded interactions of the divalent selenium atom with heteroatoms has been instrumental in the development of novel chemistry in which this interaction plays a critical role in the outcome of the reaction. Many of these processes are attractive because of the ease of selenium introduction, access to multiple oxidation states, and ease of removal at the end of the sequence, giving rise to predictable chemo, regio, and stereoselectivity. Logical extensions of many of these novel chemistries have led to the development of asymmetric methods which, in many cases, have provided chemical manifolds to gain access to chiral compounds with excellent enantiomeric excesses. This issue of Current Organic Chemistry presents specific examples of new advances in asymmetric methods that employ selenium as a chiral controller unit. The reports authored by Professor T. Wirth and D. M. Browne (New Developments with Chiral Electophilic Selenium Regents), Professor C. Zhu and Y. Huang (Asymmetric Synthesis of Chiral Organoselenium Compounds), Professor A. L. Braga, D. S. L udtke, and F. Vargas (Enantioselective Synthesis Mediated by Catalytic Chiral Organoselenium Compounds), and Professor Y. Guindon, B. Cardinal-David, J-F. Brazeau, I. A. Katsoulis (Phenylselenoethers as Precursors of Acylic Free Radicals. Creating Tertiary and Quaternary Centers Using Free Radical-Based Intermediates) are excellent examples of the level of science that is moving this field forward. Professor T. Murai and T. Kimura present recent advances in the “Syntheses and Properties of Phosphinoselenoic Chlorides, Acids and Their Salts.” In this manuscript the synthesis and characterization of optically active phosphinoselenoic acid derivatives is described. This important work enables the steric and electronic tuning of organophosphorus compounds to improve on catalytic processes. The manuscript by Dr. D. Kimball and L. A. “Pete” Silks reviews the literature on this segment of aldol reactions and briefly describes the use of a chiral selenocarbonyl controller unit to promote such reactions. Finally, the report of Professor M. P. Cole (“Utilization of Nonbonded Interactions Involving Organoselenium Compounds”) includes a review of the literature that pertains to weak interactions involving the selenium atom. With the advances in methods to directly observe these weak interactions a general realization has emerged that, indeed, these interactions can be quantified, physically described, and more importantly utilized to design molecular complexes with defined reactivities. The author has assimilated the most recent developments in this area of organoselenium chemistry and biochemistry, specifically where the role of non-bonded interactions have been implicated, studied or used. This manuscript describes a physical basis for these types of interactions, links a number of areas of science to a common theme, and clearly demonstrates that these interactions are more prevalent than once ever imagined.