Iron-Mediated [3 + 2] or [3 + 3] Annulation of 2-(2-(Ethynyl)phenoxy)-1-arylethanones: Selective Synthesis of Indeno[1,2-<i>c</i>]chromenes and 5<i>H</i>-Naphtho[1,2-<i>c</i>]chromenes

Abstract

An iron-mediated tandem annulation strategy has been developed for the synthesis of numerous functional indeno[1,2-c]chromenes and 5H-naphtho[1,2-c]chromenes. This work is the first to disclose an iron-mediated method through sequential electrophilic addition of a ketone to an alkyne and annulation tandem reaction. Importantly, a halide is introduced into the products by a ring-opening process among the annulation of alkynylcyclopropanes, which makes the methodology more attractive for organic synthesis.