2-Alkyl-Δ2-thiazolines react with 2-phenyl-Δ2-oxazolin-5-one to give 4-[1 -(2-hippuroylamino-aikylthio)alkylidene]-2-phenyl-Δ2-oxazolin-5-ones and 4-[1-(2-hippuroyltnio-alkylarnino)alkylidene]-2-phenyl-Δ2-oxazolin-5-ones. 3-Phenylisoxazolin-5-one and 2-methylthio-1-azacycloalkanes react analogously to give 4-alkylidene compounds.