Hexafluoroisopropanol-assisted selective intramolecular synthesis of heterocycles by single-electron transfer

Intramolecular amination of remote aliphatic C–H bonds via hydrogen atom transfer (HAT) reactions has become a powerful tool for accessing saturated N-containing heterocycles (SNHets). However, the formation of six-membered rings or oxa-heterocycles remains a formidable challenge for Hofmann-Löffler- Freytag (HLF) reactions. Herein, we show how by simply combining bench-stable PhI(OTFA)2 and HFIP we can switch from the well-established HLF mechanism to a new and versatile reaction pathway that enables the selective C(sp3)–H bonds functionalization. We have exploited the facile formation of radical cations via single electron transfer (SET), in the presence or absence of light, to synthesize pyrrolidines and piperidines, including drug-type molecules, along with O-heterocycles. Experimental and computational mechanistic studies support two different mechanistic pathways depending on the electron density of the substrate, where the HFIP plays a multifunctional role.