Efficient synthesis of N,N '-disubstituted ureas/thioureas catalyzed by iodine

Iodine is an efficient catalyst for the synthesis of symmetrically N,N '-disubstituted ureas/thioureas by heating respective amines or phenyl hydrazine and urea/thiourea on a preheated hot plate at 90-95 degrees C, under solvent-free conditions. The yields are excellent, and the reactions go to complete within 5-10 min.