Lactamization of sp2 C−H Bonds with CO2: Transition‐Metal‐Free and Redox‐Neutral

The first direct use of carbon dioxide in the lactamization of alkenyl and heteroaryl C−H bonds to synthesize important 2‐quinolinones and polyheterocycles in moderate to excellent yields is reported. Carbon dioxide, a nontoxic, inexpensive, and readily available greenhouse gas, acts as an ideal carbonyl source. Importantly, this transition‐metal‐free and redox‐neutral process is eco‐friendly and desirable for the pharmaceutical industry. Moreover, these reactions feature a broad substrate scope, good functional group tolerance, facile scalability, and easy product derivatization.