Iron-Catalyzed Stereoselective Synthesis of Dihydrobenzofurans from O -Tethered Enynes and DDQ-Mediated Oxidative Annulation to Dibenzofurans

Iron-catalyzed stereoselective cyclization of O -tethered enynes has been developed for facile access of 2-methyl-2,3-dihydrobenzofurans in good to excellent yields. The transformation proceeds through an acetyl chloride-assisted intramolecular addition under mild conditions, generating alkenyl chloride intermediates with exclusive Z -selectivity. More than 99% deuterium incorporation was observed when D 2 O was used instead of H 2 O. Subsequent DDQ-mediated oxidative aromatization furnishes dibenzofuran-2,3-dicarbonitrile derivatives in excellent yields via a dehydrogenative annulation pathway. This operationally simple and ligand-free method offers a cost-effective general method to afford functionalized 2,3-dihydrobenzofurans and dibenzofuran-2,3-dicarbonitriles.