A Simple and Efficient One‐Pot Synthesis of Substituted Benzo[b]furans by Sonogashira Coupling–5‐endo‐dig Cyclization Catalyzed by Palladium Nanoparticles in Water Under Ligand‐ and Copper‐Free Aerobic Conditions
A simple and efficient procedure for the synthesis of 2-substituted benzo[b]furan derivatives has been developed by the reaction of 2-iodophenols and arylacetylenes in water catalyzed by palladium nanoparticles generated in situ in open air. The reaction does not require any additive, ligand, or co-catalyst. The reaction occurs through Sonogashira coupling of 2-iodophenols with phenylacetylenes followed by 5-endo-dig cyclization. A series of functionalized benzo[b]furan derivatives was obtained in high yields by this procedure.