Novel synthesis and reactions of 5,7-dialkyl-4,6-dioxo-4,5,6,7-tetrahydro- isothiazolo[3,4,-d]pyrimidine-3-carbonitriles and 6-methyl-4-oxo-4H-1-aza-5-oxa-2- thiaindene-3-carbonitrile.

[reaction: see text] 5,7-Dialkyl-4,6-dioxo-4,5,6,7-tetrahydroisothiazolo[3,4-d]pyrimidine-3-carbonitriles 4, prepared from 6-amino-1,3-dialkyluracils 3 and 4,5-dichloro-5H-1,2,3-dithiazolium chloride (Appel's salt) 1, are utilized for the preparation of new derivatives of 4 bearing amino, alkylthio, amido, thioamido, tetrazolyl, and carboximidic acid ethyl ester groups at position 3. Similarly, the reactions of 6-methyl-4-oxo-4H-1-aza-5-oxa-2-thiaindene-3-carbonitrile 8, prepared from 4-amino-6-methyl-2-pyrone 6 and 1, with alkyl- and arylamines in DMF at 50 degrees C and reflux afforded different isothiazole derivatives 11 and 17, respectively. On the other hand, treatment of 8 with 1,3-diaminopropane in THF at room temperature, followed by chromatography on silica gel, gave 3-(2-oxopropyl)-6,7,8-trihydro-4H-1-thia-2,5,9-triazacyclopentacyclononene-4,10-dione 12 in 59% yield.