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. A combination of fluorobenziodoxole (FBX) and BF3 ⋅ OEt2 in cyclopentyl methyl ether promotes regio‐ and stereoselective addition of benziodoxole (BX) and methoxy groups to alkynes. This trans‐difunctionalization reaction tolerates various internal and terminal alkynes to afford stereochemically well‐defined β‐methoxyvinyl‐BX derivatives. With this method, better or comparable yields can be generally achieved in comparison with an analogous method using benziodoxole triflate and methanol.