Abstract
An efficient ultrasound-promoted synthesis of 2,3-disubstituted benzo[b]furans in the ionic liquid [bmim]BF4 at room temperature is reported. 5-exo-dig carbanion-yne intramolecular cyclization is mediated using anhydrous K3PO4 as a mild, inexpensive base under atmospheric conditions giving the title benzo[b]furans in excellent yields. Ionic liquid [bmim]BF4 has been used both as a reaction medium, as well as a catalyst for the C-C bond formation.