Organic Selenocyanates: Rapid Advancements and Applicationsin the Field of Organic Chemistry

Abstract

The incorporation of the cyanato‐chalcogen group (OCN, SCN, and SeCN) has piqued the interest of many researchers in the field of modern organic synthetic chemistry. Methodologies for selenocyanation are far less advanced than those for OCN and SCN chemistry due to the scarcity of SeCN transfer reagents and synthetic approaches. It has also been discovered that the selenocyanate precursor (SeCN) performs significantly better than the thiocyanate (SCN) precursor in terms of pharmacological properties of organic scaffolds. Recent years, new reagents (nucleophilic, electrophilic, radical) and techniques were introduced that allowed the creation of the selenocyanato group uncomplicatedly under gentle reaction conditions, particularly in transition metal catalysis and photo‐/electro‐chemically influenced reactions, which were seemingly unimaginable. In this review, we have categorized a variety of techniques using various types of selenocyanate regents and their applications in the last decades, focusing on multiple catalysts for the preparation of organic selenocyanates and their derivatives.

Recent progress of direct thiocyanation reactions

“…Similar selenocyanating reagents (nucleophilic, electrophilic, and radical) and selenocyanation reactions have been documented over the last few decades. 60 Recently, novel synthetic strategies, including electrochemical and photochemical-induced reactions are being increasingly developed for the synthesis of SeCN-containing compounds. Considering the significant pharmacological properties of selenocyanate precursors, it is still urgent to develop innovative selenocyanating reagents and techniques to efficiently transfer SeCN unit to parent molecules.…”

Recent advances in selective mono-/dichalcogenation and exclusive dichalcogenation of C(sp2)–H and C(sp3)–H bonds

“…Over the past two decades, the direct chalcogenation of C-H bonds has evolved as a straightforward, atom-and step-economical method for the preparation of chalcogenated compounds including organyl sulfides, selenides, sulfones, trifluoromethylthioethers, thiocyanates and selenocyanates. [57][58][59][60][61][62][63][64] A variety of transition-metal-catalyzed/mediated chelationassisted C-H chalcogenation, along with directing group-free C-H chalcogenation of electron-rich (hetero)arenes and deprotonative chalcogenation of electron-deficient (hetero)arenes 65 have been reported through transition-metal-catalyzed/ mediated, 58,59,[66][67][68][69] metal-free, 29,[70][71][72][73] photocatalytic or electrochemical 60,63 approaches. For instance, in 2017, Ackermann and coworkers disclosed a copper-catalyzed chelation-assisted C2-H chalcogenation (S, Se) of indoles and C7-H chalcogenation (S, Se) of indolines with diaryl dichalcogenides through an additive-free approach under aerobic reaction conditions.…”

Paired Electrolysis Enabled Cyanation of Diaryl Diselenides with KSCN Leading to Aryl Selenocyanates

“…They not only display a wide range of biological and pharmacological activities but also serve as highly versatile synthetic intermediates for the synthesis of various organic selenium compounds in organic synthesis [ 4 , 5 , 6 , 7 , 8 , 9 ]. As a consequence, considerable efforts have been devoted to constructing such molecules, and a series of synthetic protocols have been developed [ 10 , 11 ]. The traditional methods can be divided into two categories according to the reaction substrates ( Scheme 1 a): (1) the reaction of phenylselenol or its derivative (PhSeH and PhSeCl) with a cyanating agent [ 12 , 13 ]; and (2) the reaction of various selenium-free aryl substrates with in-situ-generated selenocyanating agent (selenium powder/ trimethylsilyl cyanide, [ 14 , 15 ] selenium dioxide/malononitrile [ 16 ]) or the harmful potassium selenocyanate (KSeCN) [ 17 , 18 , 19 , 20 , 21 ].…”