Visible Light-Promoted Three-Component Tandem Annulation for the Synthesis of 2‑Iminothiazolidin-4-ones

Described is a visible light-promoted three-component tandem annulation of amines, aryl/alkyl isothiocyanates, and α-bromoesters to form 2-iminothiazolidin-4-ones in the absence of metal and photocatalyst at room temperature. This [1 + 2 + 2] cyclization strategy involves visible light-promoted C–S/C–N bond formation and features a powerful approach to the synthesis of 2-iminothiazolidin-4-ones with broad substrate scope, excellent functional group tolerance, mild reaction conditions, step-economy, and simple operation, which also has potential applications in the pharmaceutical industry. UV–vis spectroscopy indicates that an in situ-generated H-bonding electron donor–acceptor (EDA) complex probably acts as the photocatalyst, facilitating the reaction process.