Synthesis of phthalides from bis-propargyl ethers: use of Garratt–Braverman cyclization to construct the phthalans and IBX as a new reagent for subsequent oxidation

Abstract

An efficient route to phthalides is described starting from easily available bis-propargyl ethers. The method involves Garratt–Braverman cyclization of the ethers to phthalans which are then efficiently oxidized to the phthalides by iodoxy benzoic acid (IBX) which has been shown to be a superior reagent in terms of yield and reagent stoichiometry for such a transformation in comparison with more commonly used KMnO4/CuSO4 reagent.