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

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Reaction Steps

A 1.74 g (10 mmol) sample of 2-ethoxy-4-fluoro-6-hydrazinopyrimidine was dissolved in 20 mL of absolute ethanol and 2.84 g (37 mmol) of carbon disulfide and 3.20 g (10 mmol) of 21 percent by weight sodium ethoxide were added. The mixture was heated at reflux with stirring for 3 hours and then was cooled by adding 20 mL of ice water. The mixture was then acidified to a pH of about 2 by adding 2 mL of 6.25N hydrochloric acid diluted to 8 mL with water. The yellow precipitate that formed was recovered by filtration, washed with water, and dried to obtain 0.85 g (40 percent of theory) of 5-ethoxy-7-fluoro-1,2,4-triazolo[4,3-c]pyrimidine-3(2H)-thione. The proton and carbon NMR spectra of this material were consistent with its assigned structure.

Provenance & Evidence