Synthesis of 2,3-bis-organochalcogenyl-benzo[b]chalcogenophenes promoted by Oxone®

Abstract

We report here an alternative and tunable metal-free synthesis of benzo[b]chalcogenophenes via the electrophilic cyclization of 2-functionalized chalcogenoalkynes promoted by Oxone®.

Dichalcogenides/Oxone®‐Mediated Cyclization of (Z)‐Chalcogenoenynes under Ultrasound Irradiation

“…Thus, based on the above observations and on previous reports involving electrophilic cyclization reactions, [70][71][72] the reactivity of Oxone ® [40,43,81] and reactions under ultrasonic irradiation, [77][78][79][80][81] a plausible mechanism for the formation of chalcogenophenes 7-9 from 1-3 is presented in Scheme 4.…”

“…Based on our previous studies using Oxone ® in reactions to prepare selenium-containing pyrazoles [40] and chalcogenophenes, [43] we started our studies by reacting (Z)-butyl(1,4-diphenylbut-1-en-3-yn-1-yl)selane 1 a (0.250 mmol) with diphenyl diselenide 4 a (0.125 mmol) in the presence of Oxone ® (0.250 mmol) and ethanol as the solvent (2.0 mL). The mixture was stirred at room temperature for 24 h, and no reaction was observed, with the starting materials being recovered almost quantitatively.…”

“…Once formed, intermediate B is activated in the acidic medium to form the strongest electrophile B'. [40,43,81] Then, enynes 1, 2 or 3 react with A or B to form the chalcogenironium intermediate C, that after an intramolecular attack by the electron pair of the chalcogen, gives the chalcogenonium intermediate D. Finally, D suffers a nucleophilic attack by one of the nucleophilic species present in the reaction medium (SO 4 2À , HSO 4 À ) to form the desired products 7-9 (Scheme 4).…”

“…[30][31][32][33][34][35][36] Recently, our group has explored the application of this oxidant in the synthesis of organoselenium and organotellurium compounds, [37][38][39][40][41][42] such as 2,3-bis-organochalcogenyl-benzo [b] chalcogenophenes, via the electrophilic cyclization of 2functionalized selanyl-and sulfanylalkynes (Scheme 1a). [43] In parallel, cyclization of enynes represents a versatile strategy for accessing cyclic compounds, specially due to the high atom-economy and excellent functional group tolerance. [44] This versatile and green strategy can proceed by radical-mediated oxidative annulations [45] or radical bicyclization of 1,n-enynes; [46] metal-free regioselective radical cyclization of 1,6-enynes [47] and in the synthesis of nitrogen-containing heterocycles in the presence of tert-butyl hydroperoxide (TBHP).…”

Selenocystine Peptides Performance in 5‐endo‐dig Reactions

“…Lewis acid (FeCl 3 ) mediated generation of selenium electrophile has been used for preparation of 3‐selanyl benzo[ b ]furans and indoles as well. Very recently, Perin et al reported the synthesis of 2,3‐dichalcogenyl‐substituted benzo[ b ]chalcogenophenes employing oxone induced generation of selenium electrophile . Another sulfur‐containing oxidant (persulfates) induced generation of selenium electrophile has been used for the direct selenylation of indole and arenofurans .…”