Base-Promoted 5-exo-dig Cyclization of o‑Alkynylamides or 2‑En-4-ynamides with CO2 toward Fully Substituted Acrylates

A base-promoted sequential cyclization and carboxylation of o-alkynylamides or 2-en-4-ynamides with CO2 has been achieved with high efficiency, stereoselectivity, and regioselectivity. This approach begins with 5-exo-dig cyclization followed by trapping the resulting vinyl anion with CO2 and MeI, which provides a convenient access to diverse cyclic and fully substituted acrylates with CO2 as the carboxylic source.