Copper-free Sonogashira coupling of acid chlorides with terminal alkynes in the presence of a reusable palladium catalyst: An improved synthesis of 3-iodochromenones (=3-iodo-4H-1-benzopyran-4-ones)

摘要

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-4H-1-benzopyran-4-ones) in excellent yield (Table 4).