ALKYLATION STUDIES ON 6-ETHYL-2,3-DIHYDROTHIAZOLO-[3,2-A]PYRIMIDINE-5,7-DIONES

The title compound 7b undergoes alkylation with ethyl iodide or ethyl sulfate at the 7‐position yielding the O‐ethylated product 10 rather than 6,6‐diethyl product 8 as reported previously. Reaction of 7b with mesyl chloride gives 13b which on reaction with potassium carbonate in absolute ethanol also gives 10. Treatment of 7b with phosphorus oxychloride gives 11b which on reaction with potassium carbonate or sodium ethoxide in ethanol produced a mixture from which no 10 was isolated. Authentic 8 was prepared by the reaction of 2‐amino‐thiazoline with ethyl diethylmalonyl chloride (20) in THF containing triethylamine or by the reaction of 5,5‐diethyl‐2‐thiouracil (18) with excess 1,2‐dibromoethane. Copyright © 1979 Journal of Heterocyclic Chemistry