[NH2:1][NH:2][C:3]([NH2:5])=[S:4].[CH3:6][O:7][CH2:8][C:9](O)=O.P(Cl)(Cl)(Cl)=O.[Na]>O1CCOCC1.O>[CH3:6][O:7][CH2:8][C:9]1[S:4][C:3]([NH2:5])=[N:2][N:1]=1To a suspension of thiosemicarbazide a24 (40 g, 0.44 mol, 1 eq) in dioxane (400 ml) at room temperature is added methoxyacetic acid (39.56 g, 0.44 mol, 1 eq) in one portion, and the reaction mixture is heated at 80° C. then phosphorous oxychloride (67.54 g, 0.44 mol, 1 eq) is carefully added over 1.5 hours. After reaction completion (4 hours), water is added and the solution is neutralised to pH=6-7 with sodium hydroxyde pellets. After extraction EtOAc/iPrOH (9/1) and evaporation under vacuum, the residue is recrystallized from MeTHF/iPrOH to afford 51 g of pure 5-(methoxymethyl)-1,3,4-thiadiazol-2-amine a25.
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