Phase-Transfer-Catalyzed Intramolecular Cyclization of ortho-Alkynyl Phenyl Ether Derivatives for Synthesis of 2,3-Disubstituted Benzo[b]furans

A variety of substituted benzo[b]furans are readily prepared in good to excellent yields under the mild reaction conditions from o-(1-alkynylphenoxy)-1-phenylethanone Under phase-transfer catalysis (PTC). This methodology accommodates simple experimental operations, inexpensive and environmentally benign catalysts, metal catalyst-free conditions, facile reagents and the possibility to conduct large-scale preparations. The development of carbon-carbon bond formation processes via an overall structural isomerization represents the most atom-economical approach.