Visible-Light-Induced ortho-Quinone Methides Formation in Situ Using ortho-Alkylarenols as Precursors for Tandem [4 + 2] Cycloaddition Reaction

Org Lett. 2024 Dec 26. doi: 10.1021/acs.orglett.4c04494. Online ahead of print.

Abstract

Reported herein is the generation of ortho-quinone methides (o-QMs) via metal-free visible-light-induced oxidation of ortho-alkylarenols, as well as their subsequent reaction with olefins to afford chromans in good to excellent yields (up to 91%). The key is the selective activation of the benzylic C(sp3)-H bond of ortho-alkylarenols via single electron transfer (SET) and the formation of o-QMs via hydrogen atom transfer (HAT).