Solvent‐Switchable Regioselective Synthesis of Aurones and Flavones Using Palladium‐Supported Amine‐Functionalized Montmorillonite as a Heterogeneous Catalyst

Abstract

AbstractWe report the use of Pd0APTES@K10 (APTES=(3‐aminopropyl)triethoxysilane) as a heterogeneous catalyst for the regioselective synthesis of aurones and flavones from the carbonylative cyclization of 2‐iodophenol with terminal alkynes. This work emphasizes the role of the solvent on the mode of cyclization, that is, 5‐exo or 6‐endo. The 5‐exo products (aurones) were predominant over the 6‐endo products (flavones) in 1,2‐dimethoxyethane (DME), and a reversal of regioselectivity was observed in DMF to favor the 6‐endo product. This protocol provides a simple one‐pot access to a wide variety of aurone and flavone derivatives under mild reaction conditions. The heterogeneous Pd0APTES@K10 catalyst was characterized using several techniques. Furthermore, the catalyst could be reused in up to four consecutive cycles without a significant loss in catalytic activity.