(Z)-5-(2-thienylmethylene)-2,4-imidazolidinedione.

The major product formed in the thermolysis of 5-diazouracil in thiophene at 423-433 K has been identified as the unexpected compound (Z)-5-(2-thienylmethylene)-2,4-imidazolidinedione, C8H6N2O2S, by X-ray analysis. The molecule is a hydantoin derivative with a thienylmethylene group substituted at the 5-position. The structure is disordered in that the thiophene ring exists in two orientations which are related by an approximate 180 degree rotation about the C(6)-C(7) bond. All of the N and O atoms are involved in an intermolecular hydrogen-bonding network via N-H...O interactions. This network consists of an infinite chain along the a-axis direction and a cyclic trimer arrangement which branches from this chain. The molecules are arranged in the unit cell in pleated sheets which are approximately perpendicular to the c axis.