Isoselenocyanates: Synthesis and Their Use for Preparing Selenium-Based Heterocycles

Abstract Isoselenocyanates (ISCs) are a class of organoselenium compounds that have been recognized as potential chemotherapeutic and chemopreventative agents against cancer(s) and infectious diseases. ISC compounds are chemically analogous to their isosteric relatives, isothiocyanates (ITCs); however, they possess increased biological activity, such as enhanced cytotoxicity against cancer cells. ISCs not only serve as significant products, but also as precursors and essential intermediates for a variety of organoselenium compounds, such as selenium-containing heterocycles, which are biologically active. While syntheses of ISCs have become less difficult to accomplish, the syntheses of selenium-containing heterocycles are often difficult due to the use of highly toxic selenium reagents. Because of this, ISCs can serve as versatile reagents for the preparation of these heterocycles. In this review, the classical and recent syntheses of ISCs will be discussed, along with notable and recent synthetic work employing ISCs to access novel selenium-containing heterocycles. 1 Introduction 1.1 Selenium and Health 2 Isoselenocyanates 2.1 Preparation of Isoselenocyanates 3 Selenium-Containing Heterocycles 3.1 Notable Synthetic Work 3.2 Recent Synthetic Work 3.2.1 Synthesis of N-(3-Methyl-4-phenyl-3H-selenazol-2-ylidene)benzamide­ Derivatives 3.2.2 Synthesis and X-ray Studies of Diverse Selenourea Derivatives 3.2.3 Synthesis of Heteroarene-Fused [1,2,4]Thiadiazoles/Selenadiazoles via Iodine-Promoted [3+2] Oxidative Cyclization 3.2.4 2-Amino-1,3-selenazole Derivatives via Base-Promoted Multicomponent Reactions 4 Conclusion