Construction of C-S and C-Se Bonds Mediated by Hypervalent Iodine Reagents Under Metal-Free Conditions

Abstract

In the past few decades, the chemistry of hypervalent iodine reagents has undergone a flourishing development in synthetic organic chemistry owing to their mild oxidative, low toxicity, air and moisture stability and environmentally benign features. A plethora of oxidative coupling reactions have been conducted using hypervalent iodine reagents as a nonmetallic oxidant. In particular, the C-S and C-Se bond forming reactions mediated by hypervalent iodine reagents have emerged as a powerful approach in the construction of S-containing and Se-containing heterocycles or building blocks. In these reactions, hypervalent iodine reagents behave as strong oxidants or electrophiles and activate the S-containing or Se-containing species to form more electrophilic cationic or radical intermediates which participate in subsequent coupling reactions. It is anticipated that this review summarizes all C–S and C-Se bonds forming reactions enabled by hypervalent iodine reagents under metal-free conditions.

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

“…1). The carbon–chalcogen bond formation represents one of the most powerful methods for synthesizing organochalcogen compounds and it has been achieved mainly through cross-coupling, addition reactions and C–H chalcogenation, utilizing diverse chalcogen sources 14–19 under transition metal-catalyzed/mediated, 20–26 metal-free, 27–31 photocatalyzed, 32–36 electrochemical, 37 organocatalyzed 38,39 or enzymatic conditions. 40 As one of the most commonly employed protocols, transition-metal-catalyzed/mediated cross-couplings generally employ organic (pseudo)halides as reaction partners, 19,41–44 however, recent years have also witnessed the increasing use of other sources such as organic boronic acids, carboxylic acids, amines, phenols/alcohols, aldehydes, or esters as the coupling partners.…”