Photoredox-Catalyzed Site-Selective Intermolecular C(sp)-H Alkylation of Tetrahydrofurfuryl Alcohol Derivatives.

4'-Selective alkylation of nucleosides has been recognized as one of the ideal and straightforward approaches to chemically modified nucleosides, but such a transformation has been scarce and less explored. In this Letter, we combine a visible-light-mediated photoredox catalysis and hydrogen atom transfer (HAT) auxiliary to achieve β-C(sp)-H alkylation of alcohol on tetrahydrofurfuryl alcohol scaffolds and exploit it for 4'-selective alkylation of nucleosides. The reaction involves an intramolecular 1,5-HAT process and stereocontrolled Giese addition of the resultant radicals.