Thiazole as leaving group. Thermal elimination from thiazolylketoses

Heating thiazolylketofuranoses and -ketopyranoses in refluxing toluene resu lts in the elimination of thiazole and formation of the corresponding sugar lactones in nearly quantitative yield. The same reaction does not occur wi th 1-O-acetyl and 1-O-trimethylsilyl derivatives. Also model furyl- and thi enylketofuranoses and various thiazolyl alcohols proved to be stable under the above thermolysis conditions. A possible mechanism of the observed ther molysis of thiazolylketoses involves the thiazolium 2-ylide as the actual l eaving group.