Hydrochloric Acid → 5-ethoxy-7-fluoro-2H-(1,2,4)triazolo(4,3-c)pyrimidine-3-thione

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Reaction Steps

A mixture containing approximately 5.2 g (30 mmol) of 2-ethoxy-4-fluoro-6-hydrazinopyrimidine in a solvent composed of 50 mL of acetonitrile and 15 mL of water was prepared and to this was added 6.4 mL (107 mmol) of carbon disulfide at ambient temperature with stirring. The heterogeneous white mixture became a pale yellow solution after about 10 min and then 3.8 mL of 30 percent aqueous hydrogen peroxide (37 mmol) and 3.2 mL of water were added over a 30-min period with stirring and cooling to hold the temperature at about 25° C. The mixture was allowed to react another 10 min and then 3.22 g (32 mmol) of triethylamine was added and the resulting mixture filtered to remove sulfur. The filtrate was acidified with 10 mL of 3.75N hydrochloric acid (38 mmol). The resulting mixture was filtered to recover the precipitate that formed. This was washed with water and dried to obtain 4.4 g (66 percent of theory) of the title compound of 97 percent purity as a light beige solid melting at 170° C. Considerable product remained in the filtrate.

Provenance & Evidence