Electrochemical Cyclodesulfurization Strategy: Synthesis of 2‐Aminoquinazolines and 2‐Aminobenzimidazoles and Investigation of Reaction Mechanism Through Density functional Theory Calculations

A streamlined electrochemical protocol has been established that enables direct access to a diverse library of 2‐aminoquinazoline and 2‐aminobenzimidazole derivatives. This transformation proceeds via a tetrabutylammonium iodide (TBAI)‐mediated cyclodesulfurization reaction of various isothiocyanates with 2‐aminobenzylamine or o ‐phenylenediamine, forming intermolecular CN bonds in a single step and delivering the heterocycles in yields up to 86%. The reaction proceeds through a radical pathway in which iodine radicals play a pivotal role in promoting cyclization, while molecular iodine itself does not function as a conventional catalyst. This distinction highlights the unique redox behavior of iodide under electrochemical conditions, where anodic oxidation generates reactive iodine species that transiently drive bond formation without persisting as active catalytic species. The robustness of this methodology is underscored by its broad scope, compatibility with sensitive functional groups, and the absence of transition metals or external oxidants, which makes it operationally simple. Mechanistic understanding has been deepened through cyclic voltammetry, radical inhibition assays, HRMS, and electricity on/off control experiments, which confirm the radical nature and the crucial role of electricity in this process. Furthermore, density functional theory calculations provide strong computational support for the proposed intermediates and mechanistic pathways.