Radical-Cascade Avenue to Access 1,2-Dithioles Employing Dithioesters and Edman’s Reagent

An operationally simple and efficient domino etiquette
has been
developed for the facile construction of 1,2-dithioles employing easily
accessible dithioesters as a three-atom CCS synthon and aryl isothiocyanates
as a two-atom CS unit in the absence of any catalyst and additive
at room temperature under open air. The reaction proceeded efficiently
affording the desired 1,2-dithioles in good yields having various
functional groups of a diverse electronic and steric nature. This
approach avoids possible toxicity and tiresome workup conditions and
features easy to handle, cheap, and readily accessible reagents, O2 as a green oxidant, and gram-scale ability. Notably, the
final S–S bond formation and cascade ring construction follow
a radical pathway, which has been recognized via a radical trapping
experiment with BHT during the course of the reaction. Notably, the
exocyclic CN bond at position 3 of 1,2-dithiole possesses Z stereochemistry.