Yield:3916-78-7 96%

Reaction Conditions:

Stage #1:3,6-dichlorpyridazine with sodium hydrogensulfide in ethanol for 1 h;Heating / reflux;
Stage #2: with sodium hydroxide in ethanol;water; pH=9
Stage #3: with hydrogenchloride;ethanol;water

Steps:

27
Reference Example 27 6-chloropyridazine-3-thiol; To a suspension (88 mL) of sodium hydrogensulfide (3.78 g) in ethanol was added 3,6-dichloropyridazine (5.0 g), and the mixture was refluxed for 1 hr. The solvent was evaporated under reduced pressure, and water (12.5 mL) was added. The mixture was adjusted to about pH 9 with 2 mol/L sodium hydroxide solution, and the precipitate was filtered off. The filtrate was adjusted to about pH 2 with 6 mol/L hydrochloric acid and the precipitate was collected by filtration to give the title compound as a yellow solid (yield 4.74 g, 96%). ¹H-NMR (CDCl₃) δ: 6.99 (1H, d, J=9.6 Hz), 7.60 (1H, d, J=9.6 Hz).

References:

Takeda Pharmaceutical Company Limited US2007/60623, 2007, A1 Location in patent:Page/Page column 23-24

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