Visible-Light-Triggered Difluoroacetylation/Cyclization of Chromone-Tethered Alkenes Enabling Synthesis of Tetrahydroxanthones.

Hydroxanthones have attracted considerable attention due to their significance in organic and biological chemistry, yet their synthesis remains a great challenge. In this study, a series of chromone-tethered alkenes are designed, and a radical cyclization reaction of these chromone derivatives has been achieved under photoredox conditions. The reaction uses bromodifluoroacetamides or bromodifluoroacetates as coupling partners, affording a broad range of functionalized tetrahydroxanthone products with up to 85% yields. The reaction is triggered via the generation of difluoroacetate radicals or alkene radical cations with -Ir(ppy) or 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene as a photocatalyst. This approach offers access to various tetrahydroxanthone derivatives from readily available starting materials and enriches the research content of heteroarene-tethered alkenes.