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

Abstract

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.