Synthesis and cycloaddition reactions of 4,4-dimethyl-2,6-dioxocyclohexane-thiocarboxamides with nitrilimines

A new series of 4,4-dimethyl-2,6-dioxocyclohexane-thiocarboxamides were prepared by reaction of aryl isothiocyanate with dimedone.Reaction of N-aryl-4,4-dimethyl-2,6-dioxocyclohexanethiocarboxamides with hydrazonoyl halides led to the formation of the corresponding thiadiazoles.Treatment of 2-[5-acetyl-3-phenyl-1,3,4-thiadiazol-2(3H)-ylidene]-5,5dimethylcyclohexane-1,3-dione with dimethylformamide dimethylacetal (DMF-DMA) in refluxing dioxane afforded (E)-2-[5-(3-(dimethylamino)acryloyl)-3-phenyl-1,3,4-thiadiazol-2(3H)-ylidene]-5,5-dimethylcyclohexane-1,3-dione.Reaction of the latter enaminone with hydrazonoyl halides yielded the corresponding 2-(1-aryl-3-substituted-pyrazol-4-carbonyl)-5-[3phenyl-5-(5,5-dimethylcyclohexane-1,3-dione)-[1,3,4]-thiadiazole] derivatives.The structures of the new compounds were elucidated on the basis of their elemental analyses and spectral data.