A Mild Photocatalytic Synthesis of Guanidine from Thiourea under Visible Light

In this work, we developed the catalytic guanylation of thiourea using Ru(bpy)(3)Cl-2 as a photocatalyst under irradiation by visible light. The conversion of various thioureas to the corresponding guanidines was achieved using 1-5 mol % of photocatalyst in a mixture of water and ethanol at room temperature. Key benefits of this reaction include the use of photoredox catalyst, low-toxicity solvents/base, ambient temperature, and an open-flask environment.