Visible-light photocatalytic synthesis of imidazole-2-thiones in water using cobalt phthalocyanine

A sustainable and efficient protocol for the synthesis of imidazole-2-thione derivatives is herein reported. The method relies on the reaction of imidazolium salts with sodium sulfide (Na₂S) in water at room temperature under visible-light irradiation. In this transformation, cobalt phthalocyanine (CoPc) serves as an inexpensive and robust catalyst, while ambient air acts as a clean and environmentally benign terminal oxidant. Operational simplicity, straightforward work-up, and excellent product yields highlight the practicality of this environmentally friendly methodology, making it an attractive approach for the green synthesis of imidazole-2-thiones.