Visible-light-induced C–S bond formation of pyrazolin-5-ones with thioureas to pyrazol-4-yl carbamimidothioates

A simple, highly efficient and environmentally benign method for the synthesis of pyrazol-4-yl carbamimidothioates was reported. Under visible light irradiation and Eosin Y as photocatalyst, a variety of pyrazol-4-yl carbamimidothioates were obtained in good to excellent yields via C–S bond formation of pyrazolin-5-ones with thioureas in ethanol. The protocol features the advantages of easy performance, environmental friendliness, high yields, and good functional tolerance, showing potential value for the preparation of some biologically active compounds.