Sustainable Synthesis of 3-Acylmethylated Coumarins via Photoredox Catalytic Radical Addition/Cyclization in Aqueous Media

A photoredox catalytic cascade radical reaction for the addition/cyclization of arylalkynoates with α-bromoketones in water at room temperature has been developed, offering a green and efficient approach for synthesizing 3-acylmethylated coumarins. This method eliminates the need for conventional organic solvents, phase-transfer catalysts, and excess oxidants, ensuring operational simplicity and environmental sustainability. The reaction is scalable, accommodates a broad array of substrates with outstanding tolerance for functional groups, and offers a versatile route to biologically valuable coumarins.