Transition‐Metal‐Free C−S, C−Se, and C−Te Bond Formation from Organoboron Compounds

Abstract

The present review describes the successful application of organoboron compounds in transition-metal-free CÀ S, CÀ Se, and CÀ Te bond formations. We presented studies regarding these C-Chalcogen bond formations using organoboron reagents, such as boronic acids, boronic esters, borate anions, and several sources of chalcogen atoms/moieties. Moreover, a broad range of transition-metal-free approaches to synthesize sulfides, selenides, and tellurides were described using conventional heating methods, which are sometimes green since they use green solvents, safe reagents, among others. Furthermore, protocols using alternative energy sources, including ultrasound, microwave irradiation, photocatalysis, and electrolytic processes, were also shown to be suitable. These protocols were applied to prepare a broad scope of functionalized chalcogenides with high molecular diversity. These studies and their proposed mechanisms were also reported herein in addition to the reuse of reaction promoters.

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

“…Triselenium dicyanide (TSD) or dicyanogen triselenide (Se(SeCN) 2 ) represents an alternative direct source of ideal selenocyanating reagent for the synthesis of aromatic and heteroaromatic selenocyanates, which has been well known for a long time [39a–c] . In particular, for the direct C−H bond, selenocyanation reactions that involve in situ generation of dicyanogen triselenide utilizing selenium dioxide (SeO 2 ) and malononitrile (CH 2 (CN) 2 ) have gained popularity because they are more economical and pragmatic, and in recent years, significant evolution has been ended in the synthesis of various types of selenocyanated molecules [39d–g] . Very recently, Maddani and coworkers established the first selenocyanation of ketene dithioacetals ( 102 / 102’ ) with SeO 2 and CH 2 (CN) 2 in situ generated triselenium dicyanide under transition metal free conditions [40] .…”

“…Organo‐selenocyanates (OSCs) have specifically been used to construct a number of organo‐selenium containing compounds. For a variety of purposes, selenocyanate‐containing organic compounds have gained considerable interest [39g,49] …”

Transition-Metal-Catalyzed C–S, C–Se, and C–Te Bond Formations via Cross-Coupling and Atom-Economic Addition Reactions. Achievements and Challenges

“…Of course, it should be mentioned that noncatalytic methods were successfully used for a long time for the preparation of organosulfur and other organochalcogen compounds and still are involved in organic synthesis. Just a few representative examples may be mentioned in this regard. ,,,,− We do not consider noncatalytic reactions in this review since we focus only on newly developed catalytic methodologies, which demonstrate a number of advantages and future potential.…”

Regioselective C–H chalcogenylation and halogenation of arenes and alkenes under metal-free conditions

“…14 A considerable number of methods to insert a phenylseleno group into (hetero)arenes or alkenes have been developed. [15][16][17][18][19] One of the most classic and common strategies is using various transition metals such as Pd, 20,21 Rh, [22][23][24][25] Cu, [26][27][28] Ni 29,30 etc. as catalysts (Scheme 1a).…”