Synthesis of [1,3,2]dithiazolo[4,5-b][1,2,5]oxadiazolo[3,4-e]pyrazines

The reaction temperature has a strong impact on the results of chlorination of 5,6-bis(tert-butylthio)[1,2,5]oxadiazolo[3,4-b]pyrazine that is readily prepared from 5,6-dichloro[1,2,5]oxadiazolo[3,4-b]pyrazine and sodium tert-butylsulfide. Mono-and bis(sulfenylchlorides) were selectively obtained in high yield and their structure was confirmed by the reaction with morpholine. Treatment of [1,2,5]oxadiazolo[3,4-b]pyrazine-5,6-disulfenyl dichloride with primary aliphatic amines and benzylamine afforded N-substituted [1,3,2]dithiazolo[4,5-b][1,2,5]oxadiazolo[3,4-e]pyrazines in moderate yields. Novel pentacyclic [1,2,5]oxadiazolo[3 '',4 '':5',6']pyrazino[2',3':5,6][1,2,4]thiadiazino[3,4-b][1,3]benzothiazole, whose structure was confirmed by X-ray diffraction, was obtained by the reaction of this disulfenyl dichloride with 2-aminobenzothiazole.