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Metal-free synthesis of guanidine from thiourea under visible light irradiation in water was successfully developed. Using 1-5% mol of inexpensive and commercially available phenazine ethosulfate as a photocatalyst in the presence of 1% CTAB as surfactant with K2CO3 as an additive base, transformations of a variety of thiourea into corresponding guanidine under visible light irradiation were achieved in moderated to high yields. The advantages of this reaction included the use of metal-free photocatalyst, water as a non-toxic solvent and ease for operating at room temperature in open-flask manner.

In this work, we successfully prepared isothiocyanates in onepot manner from the corresponding amines using carbon tetrabromide as a desulfurizing agent. The in situ formation of dithiocarbamate salts from amines followed by desulfurization using carbon disulfide provided various isothiocyanates in good to excellent yields. Moreover, our method can be extended to prepare unsymmetrical thioureas in one-pot process. Both methods are applicable to large scale synthesis. The benefits of this reaction include one-pot synthesis, mild condition, simple operation, and metal-free process.