Copper‐Free <i>Sonogashira</i> Coupling of Acid Chlorides with Terminal Alkynes in the Presence of a Reusable Palladium Catalyst: An Improved Synthesis of 3‐Iodochromenones (=3‐Iodo‐4<i>H</i>‐1‐benzopyran‐4‐ones)

Abstract

Abstract Pd/C is used as an efficient catalyst for the copper‐free Sonogashira coupling of acid chlorides and terminal alkynes to afford ynones in high yields ( Tables 1 and 3 ). Cyclization of (2‐methoxyaryl)‐substituted ynones induced by I 2 /ammonium cerium(IV) nitrate (CAN) at room temperature gave 3‐iodochromenones (=3‐iodo‐4 H ‐1‐benzopyran‐4‐ones) in excellent yield ( Table 4 ).