Iron-catalyzed fluoroalkylative alkylsulfonylation of alkenes via radical-anion relay.

Abstract

Transition metal-catalyzed reductive difunctionalization of alkenes with alkyl halides is a powerful method for upgrading commodity chemicals into densely functionalized molecules. However, super stoichiometric amounts of metal reductant and the requirement of installing a directing group into alkenes to suppress the inherent β-H elimination bring great limitations to this type of reaction. We demonstrate herein that the difunctionalization of alkenes with two different alkyl halides is accessible via a radical-anion relay with Na₂S₂O₄ as both reductant and sulfone-source. The Na₂S₂O₄ together with the electron-shuttle catalyst is crucial to divert the mechanistic pathway toward the formation of alkyl sulfone anion instead of the previously reported alkylmetal intermediates. Mechanistic studies allow the identification of carbon-centered alkyl radical and sulfur-centered alkyl sulfone radical, which are in equilibrium via capture or extrusion of SO₂ and could be converted to alkyl sulfone anion accelerated by iron electron-shuttle catalysis, leading to the observed high chemoselectivity.