A simple and straightforward methodology towards the synthesis of 2,4,5‐trisubstitutedpyrimidines has been developed by one‐step reaction of isoflavones with thiourea or guanidine. Ten 2‐mercapto‐4,5‐diphenylpyrimidines and eight 2‐amino‐4,5‐diphenylpyrimidines were reported. All of them were characterized by FT‐IR, NMR, and elemental analysis. A variety of substrates can participate in the process