Recent advances in organic synthesis applying elemental selenium

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

“…However, they have poor commercial availability and require complicated synthetic routes. Therefore, an alternative approach using the commercially available and easy-to-handle Se powder has attracted significant attention [15,[19][20][21][22][23][24][25][26]. This method involves a transition-metal-catalyzed one-pot, three-component reaction in which two functional groups are simultaneously introduced on the Se atom via double selenation.…”

Aerobic Copper-Catalyzed Four-Component Reaction of O-Phenylenediamines, Isocyanides, and Selenium Powder for the Assembly of Benzo[4,5]imidazo[2,1-c][1,2,4]selenadiazol-3-imine Derivatives

“…In the recent decade, growing efforts have been devoted to employing selenium powder as an ideal selenium source for the preparation of selenium-containing heterocycles, compared with unstable, smelly, and toxic previous selenium reagents (RSeH, KSeCN, PhSeCl, etc. ), and selenium powder is cheap, less toxic, stable, and easy to handle .…”

Synthesis of Benzoselenophenes via TMSCN-Enabled Radical-Mediated Tandem Reaction Involving Enamides and Elemental Selenium

“…However, only electron-rich styrenyl bromides with (multi) alkoxyl groups were found to be viable substrates for participating in the tandem cyclization reaction to yield benzoselenophenes, while styrenyl selenocyanates were obtained for electron-neutral, electron-deficient, and heteroarene (thiophene) vinyl bromides (Scheme b). More recently, the direct construction of benzoselenophenes using readily available and stable elemental selenium as a selenium source has emerged as a powerful approach, circumventing the unpleasant odors and air-/moisture-instability associated with unfavorable selenylation reagents. For instance, Zhou, Liu, and co-workers unveiled an elegant radical reaction involving arylboronic acids and elemental selenium for the synthesis of aryl selenocyanates and selenaheterocycles, including dibenzoselenophene and benzoselenophene, in the presence of AgNO 2 /K 2 S 2 O 8 or trimethylsilyl cyanide (TMSCN) (Scheme c).…”

“…Based on the previous literature − , and the obtained experimental results, a plausible reaction mechanism is proposed in Scheme . The reaction likely initiates with homolytic cleavage of the Se–Se bond, leading to the formation of biradical intermediate A .…”