Pyridazine-3-thione, 6-methyl

AIkyI-substituted pyridazine-3(2//)-thiones undergo reaction with methyl iodide at the sulfur atom. Methylation of 4,5-diaminopyridazine-3(2ff)-thione with excess methyl iodide produces 4,5-diamino-l-methyIthiopyridazinium iodide (81JOC2467). 

Alkylations of the 4-thione substituent of l-(2,3,5-tri-0-acetyl-/3-D-ribofuranosyl)triazolo[4,5- pyridazine-4-thione 29 were carried out using sodium hydride and various alkyl halides, and the reaction with methyl iodide to give methylthio derivative 48 is shown in Scheme 32 <1996BMC1725>. 

For thiones, the thione form is generally present (86JPR522), although it was claimed without proof that 4-arylmethyl-6-methyl-3-mercaptopy-ridazine exists in the thiol form (80S410). For pyridazine-3,4,6-trithiol, no firm conclusion could be reached about its preponderant tautomeric form, but it was concluded that it does not exist in the trithiol form nor as the 6(1//)- or 3(2//)-thione (78AJC389). 

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