Radical Redox Cycloadditions: A General Light-Driven Meth-od for the Synthesis of Saturated Heterocycles



We introduce here a novel two-component annulation strategy that provides access to a diverse collection of five- and six-membered saturated heterocycles from aryl alkenes and a family of redox-active radical precursors bearing tethered nucleophiles. This transformation is mediated by a combination of an Ir(III) photocatalyst and a Brønsted acid under visible-light irradiation. A reductive proton-coupled electron transfer generates a reactive radical which undergoes addition to an alkene. Then, an oxidative radical-polar crossover step leading to carbocation formation is followed by ring closure through cyclization of the tethered nucleophile. A wide range of heterocycles are easily accessible, including pyrrolidines, piperidines, tetrahydrofurans, morpholines, δ-valerolactones, and dioxanones. We demonstrate the scope of this approach through broad structural variation of both reaction components. This method is amenable to gram-scale preparation and to complex fragment coupling.


Thumbnail image of Annulation_Manuscript_080422_SUBMIT.pdf

Supplementary material

Thumbnail image of Annulation_Supporting Information_080422_SUBMIT.pdf
Supporting Information
Experimental details, characterization data, and NMR spectra