1,3‐Diphenyl‐5‐imino‐2‐imidazolidinone‐4‐thione (II) was treated with diazomethanes to give (III‐V). Interaction of (II) with amino compounds furnished the corresponding 4‐substituted imino derivatives (VIa‐m). Imidazoquinoxaline derivatives (VIIIb, c) were obtained through interaction of (II) with o‐phenylenediamines. Condensation of (II) with hydrazines afforded the hydrazones (IX, Xa, b). Semicarbazone and thiosemicarbazone derivatives (XIIa‐d) were prepared from the reaction of (IX) with isocyanates and isothiocyanates. Again (II) was allowed to react with n‐butylmagnesium bromide and HgCl2 to give (XIII) and (XIV) respectively. Copyright © 1990 The Chemical Society Located in Taipei & Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany