Silver-Mediated [2 + 2 + 1] Cyclization Reaction of Diynes with Elemental Selenium/Sulfur To Synthesize 3,4-Substituted Cyclopenta[c]selenophenes/Cyclopenta[c]thiophenes

Abstract

An efficient and atom-economical silver-mediated [2 + 2 + 1] cyclization protocol for the synthesis of 3,4-fused-ring-substituted and 2,5-unsubstituted selenophenes or thiophenes has been developed. Two C–Se/C–S bonds and one C–C bond were rapidly constructed in one step. Readily accessible substrates, commercially available elemental selenium/sulfur, and good functional group tolerance make this procedure attractive for the synthesis of π-conjugated material molecules.

Copper and Silver Catalysis in the (3 + 2) Cycloaddition of Neutral Three-Atom Components with Terminal Alkynes

“…The reaction was found efficient and selective providing selenophene ( 27 ) in very good yield (86%), without need of purification. 3 or 3,4-substituted selenophenes are of interest in material science, as their incorporation as building blocks in materials can be often beneficial in terms of optoelectronic properties. − Further studies on the application of this methodology to the synthesis of 3,4-fused selenophenes will be disclosed in due course …”

Silver-Mediated [2 + 2 + 1] Cyclization of ortho-Propioloylbenzonitriles with Elemental Selenium: Synthesis of 4H-indeno[1,2-c][1,2]selenazol-4-ones

“…We initially used 2-propynoylbenzonitrile 1a as a model substrate to test our ideas. According to our previous work, 10 we first chose to use 1.0 equiv of 1a and 3.0 equiv of elemental selenium in the presence of 1.0 equiv of AgOAc at 40 °C in DCM to carry out the reaction. At the same time, the reaction system was kept in a nitrogen atmosphere, and 4 Å molecular sieves were added.…”

“…However, this reaction mode has not been reported in the synthesis of nitrogen–selenium heterocyclic compounds, especially using a cyano functional group to construct N–Se bonds. Recently, we have developed an efficient silver-mediated [2 + 2 + 1] cyclization for the synthesis of 3,4-substituted selenophenes or thiophenes (Scheme d) . As part of our continued interest in selenium chemistry, we herein report a novel and atom-economical silver-mediated [2 + 2 + 1] cyclization reaction starting from ortho -propioloylbenzonitriles and elemental selenium to synthesize valuable 4 H -indeno­[1,2- c ]­[1,2]­selenazol-4-ones.…”

Synthesis of tetrasubstituted selenophenes by DBU-induced sequential three-component coupling and intramolecular cyclization

“…Roughly, these protocols can be divided into three categories. 14–17 The first pathway mainly relies on the Gewald process under the participation of elemental selenium (Scheme 1a). 14 These transformations typically require special energy supply methods such as ultrasonication (US) and focused microwave irradiation (MW) to increase the yield of selenophenes.…”