Green synthesis of symmetrical N, N′-disubstituted thiourea derivatives in water using solar energy

Thioureas are of importance in medicinal chemistry due to their biological activities such as antituberculosis, anti-HIV, analgesic, anti-inflammatory, antimicrobial, antiarrhythmic, fungicide, herbicides, rodenticides and as phenoloxidase enzymatic inhibitors. Treatment of primary and secondary amines with thiophosgene is the common method of making symmetrical disubstituted thioureas. However, this method is hazardous due to the toxic properties of thiophosgene. Here, we report a green, operationally simple approach for the synthesis of 1, 3-disubstituted thiourea derivatives in moderate to excellent yields of 57–99 %. We use primary amines and CS₂ in water without any catalyst and solar thermal energy. This method is more environmentally benign and energy-saving compared with previously reported methods.