Tracking SF5I in the Iodopentafluorosulfanylation of Alkynes

The iodopentafluorosulfanylation of alkynes was made possible through formal manipulation of SF₅I. This method requires the combination SF₅Cl/KI/18-crown-6 in THF at low temperature. Mechanistic investigations by DFT revealed that a ionic pathway is not viable and a radical mechanism is preponderant.

Abstract

In the vibrant field of SF₅ chemistry, SF₅X reagents (X=F, Cl, Br) are at the heart of current investigations in radical pentafluorosulfanylation reactions. SF₅I is the missing link whose existence has not been reported despite its potential as SF₅ donor. This study reports the formal addition of the hitherto unknown SF₅I reagent to alkynes by means of a combination of SF₅Cl/KI/18-crown-6 ether. The exclusive regio- and stereoselective synthesis of unprecedented (E)-1-iodo-2-(pentafluoro-λ⁶-sulfanyl) alkenes was achieved. A consensus was reached through computational and mechanistic studies for the realistic formation of SF₅ ⁻ anion but not SF₅I in solution and the rational involvement of SF₅ ^⋅ and iodine radicals in the iodo pentafluorosulfanylation reaction.

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