Synthesis of thiadiazine, imidazothiadiazole, diazospiroundecatetraeneand spirothiadiazolopyrimidinocyclohexadiene derivatives from2,5-dithiobiureas

摘要

Ethenetetracarbonitrile (2, in tetrahydrofuran solution), diethyl (E)-2,3-dicyanobutenedioate (10, in tetrahydrofuransolution), and 7,7',8,8'-tetracyanoquinodimethane (16, in pyridine solution) act on 1-substituted-2,5-dithiobiureas1a–c, forming the derivatives of imidazothiadiazole 5a–c, thiadiazine 11a–c and 12a–c, spiro(thiadiazolopyrimidino-cyclohexadiene)malononitrile 17a–c and diazospiroundecatetraene 18a–c. Rationales for these conversions involvingthe nucleophilic addition on diycanomethylene carbon atom are presented.