Efficient and Functional-Group-Tolerant Synthesis of Substituted Furans through the Pd-Catalyzed 5-exo-dig Cyclization/Coupling of γ-Acetylenic β-Keto Esters with (Hetero)Aryl Bromides

We report an efficient protocol for the synthesis of 2,3,5-trisubstituted furans through the reaction of readily available -acetylenic -keto esters with aryl and heteroaryl bromides. The reaction, which involves a 5-exo-dig cyclization, coupling, and isomerization of a double bond, proceeds smoothly with very low catalyst loading (0.1 mol-%), and shows excellent functional-group tolerance.