Photochemical Access to Trifluoromethylated Benzofuranols via 1,6‐Hydrogen Atom Transfer

ABSTRACT Ortho‐alkoxy trifluoroacetophenones undergo efficient cyclization to benzofuranols under UV light irradiation (370 nm). Key to success is a 1,6‐hydrogen atom transfer (1,6‐HAT), which is enabled by the unique properties of the trifluoroacetophenone unit and strategic positioning of the methoxy group. The reaction proceeds best under dilute conditions, in polar aprotic solvents, and with high‐intensity irradiation. Although triplet quenching and intermolecular HAT limit certain aromatic substitution patterns, the reaction still accommodates a diverse set of substrates, providing access to tertiary benzofuranols, including spirocyclic compounds (12 examples, up to 92% yield, up to 90:10 diastereomeric ratios [dr]). Subsequent dehydration provides trifluoromethyl‐substituted benzofurans, offering a convenient route to these heterocycles.