Synthesis of 5-spiro (5'-methylisatin)-4-acetyl-2-(acetylamino)-Δ² -1,3,4-thiadiazoline and 5-spiro(5'-methylisatin)-4-acetyl-2-(5'-methylisatin-3'-hydrazino)-Δ² -1,3 ,4- thiadiazoline

240-242Condensation of 5-methylisatin 1 with thiosemicarbazide in glacial acetic acid gives 5-methylisatin-3-thiosemicarbazone 2,whereas with thiocarbohydrazide gives bis-5-methyli satin-3-thiocarbohydrazone 3. Acetylation of 2 and 3 with acetic anhydride affords 5-spiro (5' -methylisatin)-4-acetyl-2-(acetylamino)-Δ2-1,3,4-thiadiazoline 4 and 5-spiro(5'- methylisatin)-4-acetyl-2-(5'-methylisatin-3'-hydrazino)-Δ2-1,3,4-thiadiazoline 5 respectively. Methylation of 5 with methyliodide and sodium hydride furnishes 1,1'-N,N-dimethylated product 6