Microwave-assisted, palladium-catalyzed intramolecular direct arylation for the synthesis of novel fused heterocycles

An efficient synthesis of novel fused heterocycles has been established via microwave-assisted palladium-catalyzed intramolecular direct arylation. The acyclic aryl bromides are readily available from microwave-assisted one-pot annulation of N-(2-bromobenzyl)-2-aminophenois and ethyl 2-bromoalkanoates. The intramolecular direct arylation is then performed in the presence of palladium(II) acetate and dppf (10 mol% each) in toluene using potassium carbonate (2 equiv) as the base under microwave heating (150 degrees C, 1 h) to afford the products in 43-99% yields. Steric effect is observed for Ar-Ar bond formation, giving a substantial amount of the debromination byproduct.