Ring Expansion Fluorination of Unactivated Cyclopropanes Mediated by a New Monofluoroiodane(III) Reagent

Abstract Herein, we report a new strategy for carbon−carbon bond scission and intramolecular ring expansion fluorination of unactivated cyclopropanes, which was accomplished with a new hypervalent fluoroiodane(III) reagent 1 . This novel method delivers medicinally relevant 4‐fully substituted fluoropiperidines in moderate to high yields with excellent regio‐ and diastereoselectivity. Reagent 1 , which has an N‐acetylbenziodazole framework, was readily synthesized via three steps in 76 % overall yield and was characterized by NMR spectroscopy and X‐ray crystallography. Owing to the presence of a secondary I⋅⋅⋅O bonding interaction between the λ 3 ‐iodane atom and the carbonyl oxygen of the acetyl group of the N‐acetylbenziodazole framework, 1 has excellent stability and can be stored at ambient temperature for 6 months without any detectable decomposition. Density functional theory calculations and experimental studies showed that the reaction proceeds via a carbocation intermediate that readily combines with a fluoride ion to generate the product.