Domino Synthesis of 2-Substituted Benzothiazoles by Base-Promoted Intramolecular C-S Bond Formation

A new, transition-metal-free, domino synthesis of 2-substituted benzothiazoles has been developed, involving base-promoted one-pot addition of active methylene compounds to o-iodoarylisothioacyanates and subsequent intramolecular C-S bond formation of the resulting thioamidate anion. The reaction proceeds at room temperature within 1-3 h, affording diversely substituted benzothiazoles in high yields. A possible radical intermediate pathway, via an S_RN1 mechanism, has been proposed for intramolecular C-S bond formation.