Iodine-Catalyzed [5 + 1] Carbonylation of 2-Alkenyl/Pyrrolylanilines with CS₂ as the Carbonylating Reagent

Novel metal-free iodine (I₂)-catalyzed [5 + 1] carbonylation of 2-alkenyl/pyrrolylanilines with carbon disulfide (CS₂) as the carbonylating reagent has been developed. This innovative method allows for the synthesis of valuable derivatives such as 4-aryl-2-quinolinones and pyrrolyl-fused quinoxalinones. Notably, this work represents the first instance where CS₂ has been utilized as a carbonylating reagent source. The protocol demonstrates the utilization of various substrates, leading to diverse reactions that afford excellent yields under mild conditions. The method also shows good compatibility with functional groups present in the substrates, further enhancing its synthetic utility. Importantly, the developed reaction exhibits scalability, enabling gram-scale synthesis, and shows promise for the synthesis of druglike molecules. In this catalytic system, CS₂ serves as the carbonyl source, while dimethyl sulfoxide plays multiple roles, including acting as an oxidant and a solvent. Mechanistic studies have been conducted to elucidate the underlying processes, with the formation of quinolone-2-thiones identified as crucial intermediates, facilitating the carbonylation annulation process.