Silver-Mediated Intermolecular [2 + 2 + 1] Cyclization of Terminal Alkynones with Elemental Selenium: Regioselective Synthesis of 2,4- or 3,4-Dicarbonylselenophenes.

An efficient and atom-economical silver-mediated [2 + 2 + 1] cyclization protocol for the selective synthesis of 2,4- or 3,4-dicarbonylselenophenes has been developed. Readily accessible substrates, commercially available elemental selenium, and good functional group tolerance make this procedure attractive for the selective synthesis of dicarbonylselenophenes. Preliminary mechanistic investigations indicated that silver acetylene species are possible intermediates for the formation of 3,4-dicarbonylselenophenes.

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

An efficient silver-mediated [2 + 2 + 1] cyclization protocol of ortho-propioloylbenzonitriles with elemental selenium for the synthesis of 4H-indeno[1,2-c][1,2]selenazol-4-ones has been developed. One C-Se bond, one N-Se bond, and one C-C bond were rapidly constructed in one step. The reaction might proceed via the formation of a highly reactive selenoketene intermediate, followed by intramolecular cyclization.

Four-Component Ring-Opening Reaction of Pyrroles via C-N Bond Cleavage under Multiple Functions of Elemental Sulfur.

We report a four-component ring-opening reaction of pyrroles via C-N bond cleavage. In this process, elemental sulfur is used as the sulfur source of thiazole and thioamide and the reductant of olefin. A series of benzothiazoles functionalized with thiopropionamides at the C2 position were synthesized using this method. A plausible reaction mechanism is proposed based on the concise control experiments.

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

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.