Silver-Catalyzed Synthesis of 3-Phosphorated Coumarins via Radical Cyclization of Alkynoates and Dialkyl H-Phosphonates

Ag2CO3-catalyzed difunctionalization of alkynes via a radical phosphonation and C–H functionalization tandem process was developed to synthesize various 3-phosphonated coumarins in moderate to high yields with high regioselectivity. A catalytic amount of cheap and nontoxic silver salt was employed in the domino C–P and C–C formation of alkynoates for the first time. Mechanistic studies indicate that the reaction pathway might proceed via the generation and cyclization of a phosphonated vinyl radical intermediate.