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