Thiosemicarbazide → N-Ethyl-N-[3-(3-amino-1,2,4-triazolo[4,3-b]pyridazin-6-yl)phenyl]acetamide

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Reaction Steps

A solution of 2.0 g of N-ethyl-N-[3-(6-chloro-3-pyridazinyl)phenyl]acetamide and 1.32 g of thiosemicarbazide in 100 ml of ethanol was refluxed for 8 hours, then evaporated in vacuo. To the residue was added 100 ml of glacial acetic acid. This mixture was refluxed overnight, then the solvent was removed in vacuo, 150 ml of water added and aqueous sodium bicarbonate added to neutralize the solution. This mixture was extracted with dichloromethane:methanol (9:1). The extracts were dried and evaporated. The residue was chromatographed on a silica gel column eluting with dichloromethane:methanol (9:1). The fractions containing product were combined and evaporated. The residue was chromatographed on silica gel thick layer preparative plates with dichloromethane:methanol (95:5) to give yellow crystals. Recrystallization from dichloromethane-ether-hexane gave 0.3 g of the desired compound as yellow crystals, mp 192°-193° C.

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