5-Fluorouracil → 5-Fluoro-4-thiouracil

Participants

Reaction Steps

A mixture of 5-fluorouracil (26 g, 0.12 mole) and phosphorus pentasulfide (45 g, 0.2 mole) in 500 mL dioxane was heated under reflux for 3 hr. The hot reaction mixture was filtered and concentrated in vacuo. The residue was dissolved in 650 mL water, heated with 5 g charcoal and filtered. The solid which crystallized on cooling was collected by filtration to yield 25.4 g (88%) of 5-fluoro-4-thiouracil, m.p. 269°-272° C.

Provenance & Evidence