The synthesis of 2-cyano-cyanothioformanilides from 2-(4-Chloro-5H-1,2,3- dithiazol-5-ylideneamino)benzonitriles using DBU

Abstract

A series of 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino) benzonitriles were prepared from the reaction of 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt) and the corresponding anthranilonitriles. Reaction of the 1,2,3-dithiazolimines with DBU (3 equiv) at -5 °C gave the corresponding 2-cyano-cyanothioformanilides in near quantitative yields. Treatment of 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)benzonitrile with DBU (4 equiv) at -5 to +20 °C gave 2-isothiocyanatobenzonitrile in 96% yield. The latter compound was also formed directly from 2-cyano-cyanothioformanilide on treatment with DBU (1 equiv) in 95% yield. A tentative mechanism for the DBU-mediated dithiazole to cyanothioformanilide transformation is proposed and all compounds were fully characterized. © Georg Thieme Verlag Stuttgart - New York.