Scope and Limitations of the Intermolecular Furan-Yne Cyclization

Different types of alkynes were reacted with 2,5‐disubstituted furans in order to evaluate the scope of the intermolecular furan‐yne reaction. With ethynyl aryl ethers as starting materials, 2‐phenoxy phenols were accessible in moderate to good yields. A different reaction mode was observed for alkynes bearing electron‐withdrawing substituents. For these starting materials a cis‐selective hydroarylation took place in an anti‐Markovnikov fashion in excellent yields. 1,2‐Diynes turned out to be suitable starting materials as well. Due to the second alkynyl moiety, after an initial phenol synthesis, a subsequent hydro‐alkoxylation by the newly formed phenolic oxygen gives access to benzofurans in a tandem process.