Synthesis of Thiadiazine, Imidazothiadiazole, Diazospiroundecatetraene and Spirothiadiazolopyrimidinocyclohexadiene Derivatives from 2,5-Dithiobiureas

Abstract

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