Fluorobenziodoxole-BF3 Reagent for Iodo(III)etherification of Alkynes in Ethereal Solvent.

A combination of fluorobenziodoxole (FBX) and BF3  ⋅ OEt2 in cyclopentyl methyl ether promotes regio- and stereoselective addition of benziodoxole and methoxy groups to alkynes. This difunctionalization reaction tolerates a variety of functionalized internal and terminal alkynes to afford trans-β-alkoxyvinylbenziodoxoles, which represent versatile precursors to stereochemically well-defined multisubstituted vinyl ethers. The reaction is proposed to involve cleavage of the I-F bond of FBX by BF3 , followed by electrophilic activation of the alkyne by the resulting cationic IIII species that triggers the nucleophilic addition of the ethereal oxygen.