Visible-Light-Mediated Cascade Arylcarboxylation/Cyclization of N-Aryl/Benzoyl Acrylamide with CO2.

A visible-light-mediated radical cascade arylcarboxylation/cyclization of N-alkyl-N-methacryloylbenzamides and N-alkyl-N-arylmethacrylamides with carbon dioxide (CO2) was established. The reactions employed economical CO2 as the carboxyl source, cesium carbonate as the base, triphenylsilane as the additive, and fac-Ir(ppy)3 as the photocatalyst. Novel 1,3-dioxo-1,2,3,4-tetrahydroisoquinolin-4-ylacetic acid derivatives and oxindole-3-acetic acid derivatives were obtained in moderate to good yields. This methodology shows a wide substrate scope, simple operation, excellent functional group compatibility, mild conditions, gram scale synthesis, and straightforward product derivatization. Detailed mechanistic insights reveal that CO2•- generated in situ was invovled as key a key active intermediate under conditions free of external hydrogen atom transfer (HAT) and reducing agents.