THE SYNTHESIS AND STRUCTURE OF 3-PHENYL-1,3,4-THIADIAZOL-2(3H)-ONE

A novel method for the synthesis of 3-phenyl 1,3,4-thiadiazo-2(3 H)-one 1 was investigated, and the structure was discussed in terms of resonance stabilization. The thiadiazole 1 was synthesized successfully by the reaction of N-phenyl-N'-thioformylhydrazine with 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) in the presence of triethylamine in acetonitrile. The structural investigation of 1 was carried out by use of spectral data such as H-1-NMR, C-13-NMR, IR and UV spectroscopies, and X-ray analysis. The structure of 1 is best interpreted by joining of two adjacent, resonance structures of 3 p-pi-2 p-pi-2 p-pi-2 p-pi (-S-C = N-N-) and 2 p-pi-2 p-pi (> C = O) in which each pi-electrons on the ring are drifted to oxygen atom of carbonyl group via the aromatic structure based on the resonance stabilized structure.