Acid hydrolysis of 5, 6-dihydro-2-methyl-1, 4-oxathiin-3-carboxanilide gives 2-(2- hydroxyethylthio)-acetoacetanilide enol. 3-Carbonyl-substituted 5, 6-dihydro-1, 4-oxathiins were found to undergo ring cleavage by nucleophilic nitrogen attack on C-2. Thus the following reactions were observed: 3-acetyl-5, 6-dihydro-2-methyl-1, 4-oxathiin on treatment with hydrazine gives 4-(2-hydroxyethylthio)-3, 5-di-methylpyrazole, instead of the ...
