[CH3:1][C:2]1[O:6][C:5]([C:7]([NH:9][NH2:10])=[O:8])=[N:4][N:3]=1.[C:11](Cl)(Cl)=[S:12]>O1CCOCC1>[SH:12][C:11]1[O:8][C:7]([C:5]2[O:6][C:2]([CH3:1])=[N:3][N:4]=2)=[N:9][N:10]=13.6 g of 5-methyl-1,3,4-oxadiazole-2-carboxylic acid hydrazide of melting point 150°-151° C., prepared in the customary manner from the corresponding ethyl ester [Canad.J.Chem. 65, 166 (1987)], are stirred in 100 ml of dioxane with 2.9 g of thiophosgene at room temperature overnight and then at 55° C. for 5 hours. After cooling, undissolved solids are filtered off and 200 ml of hexane are added to the filtrate, the desired product (4 g of decomposition point 225°) crystallizing out.
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