THE SYNTHESIS AND STRUCTURE OF 4,6-DIOXOPYRIMIDO-2,1,3-THIADIAZOLES

Article abstract of DOI:10.1007/BF00752701

Synthesis and spectral indices were reported for four 4,6-dioxopyrimido-2,1,3-thiadiazoles.An x-ray diffraction structural analysis carried out using an automatic diffractometer, λMoK_α radiation, 1433 reflections yielded the structure of 4,6-dioxo-5,7-dimethylpyrimido-2,1,3-thiadiazole (R = 4.7percent, R_w = 5.0percent).The molecule, with the exception of the methyl group hydrogen atoms, is planar.Bond delocalization is found within the heterocycles.A CNDO/2 calculation using the spd basis taking account of all the valence electrons showed that the sulfur 3d orbitals playa significant role in the formation of the S-N bonds.Anomalously short intermolecular S...O (3.033 Angstroem) and C...O contacts (2.914 Angstroem) were found in the crystal structure.