Blue Vitriol Catalyzed Decarboxylative C–C Cross-Coupling of α,β-Unsaturated Acids for C–H Functionalization of Unactivated Ethers

Herein, we introduce a visible-light-induced copper-catalyzed decarboxylative C(sp³)-C(sp³) cross-coupling of α,β-unsaturated carboxylic acids with unactivated cyclic ethers. The protocol employs an underexplored catalytic combination of CuSO₄·5H₂O/sodium L-(+)-ascorbate merged with an iridium photocatalyst for enabling direct C2-selective functionalization of cyclic ethers under ambient conditions. This transformation provides modular access to 2-oxyalkylated ketones via a rare anti-Giese-type radical addition. A wide range of cinnamic acid derivatives, including electron-rich, electron-deficient, heteroaryl, and sterically hindered substrates, as well as complex bioactive and natural product-derived motifs, have been tolerated with excellent yields. Detailed mechanistic investigations support a Cu/Ir dual-catalytic pathway involving oxygen-derived radical intermediates and copper-assisted decarboxylation.