A base‐catalyzed and elemental sulfur‐promoted decarboxylative insertion of a CN motif of isothiocyanates into an isatin ring to construct quinazoline‐2,4(1 H ,3 H )‐dithione has been described. This approach starts from easily available isatins, isothiocyanates, and sulfur, affording a series of structurally valuable heterocycles in satisfactory yields under mild conditions. Mechanism studies indicate that a base is essential to mediate the ring‐opening and thio‐Baeyer–Villiger rearrangement of isatin ring to pave the way for subsequent isothiocyanate insertion.
Nguyen et al. (Mon,) studied this question.