Sulfuric Acid → HCID 22605384, compound

Participants

Reaction Conditions

Reaction Steps

A solution of 4,4-dimethyl-3-thiosemicarbazide (2.0 g, 16.8 mmol) and ethyl chloro-oxo-acetate (2.3 g, 16.8 mmol) were mixed under an inert atmosphere and cooled to 0° C. in an ice bath. Sulfuric acid (2 mL) was added slowly. After the effervescence ceased, the ice bath was removed and the reaction was allowed to warm to room temperature and stirred for 3 hours. To the white heterogeneous mixture, ethyl acetate (100 mL) was added and the organic layer was washed twice with 2% sodium bicarbonate solution and brine. The organic layer was dried over anhydrous magnesium sulfate and evaporated. The residual solid was dissolved in ethyl acetate and the desired compound was precipitated with ether to yield the ethyl 5-(dimethylamino)-1,3,4-thiadiazole-2-carboxylate (IIIc) (1.9 g, 9.4 mmol). The ester, (IIIc) was dissolved in anhydrous methyl acetate (4 mL) and solution purged with an inert atmosphere. To this yellow solution sodium hydride (60% dispersion in mineral oil, 0.53 g, 13.25 mmol) was added providing a light yellow precipitate. The reaction mixture was then heated to 65° C. and it turned to a light green precipitate. Additional methyl acetate (4 mL) was added and in ten minutes the reaction mixture became a tan solid. The reaction was removed from the heat and an additional methyl acetate (20 mL) was added. The mixture was neutralized with acetic acid. The solid was filtered off and the filtrate was evaporated. The solid from the filtrate was washed with ether to yield the desired β-ketoester, ethyl 3-[5-(dimethylamino)(1,3,4-thiadiazol-2-yl)]-3-oxopropanoate, (Vd) (5.2 mmol) as a yellow solid. A mixture of the β-ketoester (Vd) (1.2 g, 1.31 mmol), ethanol (2 mL) and hydrazine hydrate (0.063 g, 1.96 mmol) was heated to 65° C. for two hours. The precipitate was filtered to obtain the pyrazolone (VIi) (0.075 g, 0.36mmol) as a light yellow solid.

Provenance & Evidence