1,2,3-Thiadiazole derivatives with a nearly linear N-S…O grouping. X-ray crystal structure analysis of four methylated products of 4-phenyl-1,2,3-thiadiazole-5-carbaldoxime

The title oxime 6 was methylated under different conditions and yielded four monomethylated products 7-10 and two bismethylated products 11 and 12 which were easily distinguished by their ¹³C nmr spectra. In view of the potential thiapentalene character of 8, 9, 10 and 11 , their X-ray crystal structures were determined. The structural properties of the nitroso compound 9 are in accordance with a thiapentalene structure, whereas those of the other compounds deviate in the order 10 < 11 < < 8 .