Difluorinative Cyclopropene Rearrangement by I(I)/I(III) Catalysis: Regio- and Stereoselective Synthesis of Allyl Difluorides

Allyl difluorides are pervasive in the pharmaceutical arena, but synthetic challenges in the construction of highly substituted derivatives impede chemical space exploration. Consequently, efforts to develop general approaches that display high levels of regio- and stereo-selectivity continue to be intensively pursued. To contribute to this vibrant area of contemporary organofluorine chemistry, a highly efficient difluorinative rearrangement of densely substituted cyclopropenes is disclosed under the auspices of I(I)/I(III) catalysis. This platform leverages a highly intuitive ring opening model that enables di-, tri-, and tetra-substituted allyl difluorides to be generated with high levels of stereoselectivity where the transient I(III) center serves as a traceless directing group. X-ray crystal structural analysis is described together with facile post-reaction modifications that include expedient access to fluorinated indenes. Given the ubiquity of the allyl difluoride chemotype in drug discovery, it is envisaged that this operationally simple, organocatalytic platform will expedite bioisostere design.