Acid hydrolysis of 5,6-dihydro-2-methyl-I,4-oxathiin-3-carboxanilide gives 2-(2-hydroxyethy1thio)-acetoacetanilide enol. 3-Carbonyl-substituted 5.6-dihydro-l,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 o n treatment with hydrazine gives 4-(2-hydroxyethylthi0)-3,5-dimethylpyrazole, instead of the hydrazone. The 1,4-oxathiins, N-(5,6-dihydro-2-methyl-1,4-oxathiin-3-ylcarbony1)-N'-phenylurea and 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxylic acid hydrazide rearrange to give 5-(2-hydroxyethy1thio)-6-methyl-I-phenylracil and 4-(2-hydroxyethy1thio)-3-methyl-2-pyrazolin-5-one, respectively. Finally, treatment of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl chloride with 2-aminopyridine and with 2-aminopyrimidine affords 4H-3-(2-hydroxyethy1thio)-2-methylpyrido[l,2-nlpyrimidin-4-one and 4H-3-(2-hydroxyethylthio)-2-methylpyrimido[l,2-a]pyrimidin-4-one, respectively, a s the predominant products.

A number of N,S-substituted α -thio- β-aminocrotonanilides have been synthesized. Their fungicidal activity on a number of organisms has been studied and in general it has been found that it is inferior to that of the 1,4-oxathiins to which these compounds bear some structural similarities.

Die Hydrolyse des Anilids (I) führt zu der Enolform des Ringspa1tungs‐Pro‐ dukts (II) (die mit 2,4‐Dinitrophenylhydrazon das Hydrazon der Acetylform gibt, beim Erhitzen mit Natronlauge deacetyliert und beim Wasserentzug mit Benzyl recyclisiert wird).

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