Cyclopropene activation via I(I)/I(III) catalysis: Proof of principle and application in direct tetrafluorination

Abstract

Preliminary validation of cyclopropene activation by an I(I)/I(III) catalysis manifold is disclosed to enable the direct tetrafluorination of 3,3-diarylcyclopropenes. This transformation occurs through the in situ generation of ArI(III)F2, with inexpensive iodobenzene, amine·HF complexes and Selectfluor® serving as catalyst, fluoride source and oxidant, respectively. Leveraging this approach, it has been possible to generate four C(sp3)-F bonds in a single operation (up to 44%). A Hammett study revealed that the reaction has a very narrow tolerance window with respect to the p-substituent of the aryl groups. Through a process of reaction deconstruction, a mechanism involving two discrete catalytic processes is proposed. Whereas the first cycle results in the ring opening fluorination of the 3,3-diarylcyclopropene, the second proceeds via a fluorination/phenonium ion rearrangement to liberate a tetrafluorinated diarylethane. This study adds hypervalent iodine catalysis to the plenum of strategies that facilitate cyclopropene activation.