Deconstructing the Catalytic, Vicinal Difluorination of Alkenes: HF-Free Synthesis and Structural Study of p-TolIF2

Recently, contemporaneous strategies to achieve the vicinal difluorination of alkenes via an I(I)/I(III) catalysis manifold were independently reported by this laboratory and by Jacobsen and co-workers. Both strategies proceed through a transient ArI(III)F2 species generated by oxidation of the ArI catalyst. Herein, an efficient synthesis of p-TolIF2 from p-TolI and Selectfluor is presented, together with a crystallographic and spectroscopic study. To mitigate safety concerns and simplify reaction execution, an HF-free protocol was devised employing CsF as a substitute fluoride source. The study provides insight into the initial I(I)→I(III) oxidation stage of the catalytic protocol using Selectfluor.