Photocatalyst/metal-free sequential C–N/C–S bond formation: Synthesis of S-arylisothioureas via photoinduced EDA complex activation

A photocatalyst-free visible-light-promoted three-component reaction of thianthrenium salts, isothiocyanates, and amines is presented, which affords a rapid and efficient approach to S-arylisothioureas under mild conditions. This developed method exhibits the advantages of readily available raw materials, broad substrate scope, good functional tolerance, and operational simplicity. It is worth mentioning that the byproduct thianthrene can be recycled in quantity, ultimately maximizing the atomic economy of the reaction and avoiding chemical waste. Mechanism investigations support the strategy involving a photoinduced EDA complex.