Alkoxycarbonylating Reagents from Tetrahydroquinazoline: Enabling Photoredox Catalyst-Free Construction of C(sp ² )–C(sp ³ ) and C(sp ² )–C(sp ² ) Bonds

We designed and synthesized new alkoxycarbonylating reagents from tetrahydroquinazolinone through direct photoexcitation to generate alkoxycarbonyl radicals with varying alkyl chain lengths that can add to alkenes triggering cyclization to form a C(sp²)-C(sp³) bond or be trapped by 1,2,4-triazine-3,5(2H,4H)-diones to construct a C(sp²)-C(sp²) bond. These protocols accommodate a broad substrate scope under external photoredox catalyst-free conditions. Mechanistic studies (control reactions, radical trapping, UV-vis absorption, fluorescence emission, and cyclic voltammetry) elucidated the reaction pathway.