The reactions between N, N'-disubstituted thioxamide and diamines (1,2-diaminoethane, 1,3-diaminopropane, trans-1,2-diaminocyclohexane) are studied. Various products are obtained from different diamines. The structures of the products are confirmed by IR, 1HNMR and x-ray diffraction study. There exist two kinds of reactions, one is that amino groups of diamines react with the same carbon atom of N,N'-disubstituted thioxamides, the other is that two amino groups react with different carbon of the thioxamides. E.g., reaction of thioxamide I with 1,3-diaminopropane at 20-30?gave 63% hydropyrimidine II, while reaction of I with 1,3-diaminopropane at 50?gave 54% hydrobipyrimidine III.

Key words: SULFOXIDE, INFRARED SPECTROPHOTOMETRY, PROTON MAGNETIC RESONANCE SPECTROMETRY, ETHANEDIAMINE, FOUR-CIRCLE DIFFRACTOMETER, PROPANEDIAMINE, RUBEANE (=RUBEANIC ACID)