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.Cyanothioformanilides (thiooxanilonitriles) demonstrate herbicidal activity, 1 and have been used extensively for the preparation of various heterocycles including pyrroles, 2a,b imidazoles, 3 oxazoles, 4 1,3,4-thiadiazoles, 5 quinazolines, 6 and other fused heterocycles. 7 Furthermore, cyanothioformanilides participate in Diels-Alder 8 and ene-reactions, 9 they can be N-aroylated 10 and, upon addition of water, hydrogen sulfide or hydroxylamine to the nitrile, afford aminooxothioacetylanilines, aminothioxothioacetylanilines (N-aryldithioxamides) 3d,11 or amidinothioformylanilines, 4c,12 respectively. Cyanothioformanilides are traditionally prepared by the reaction of N-aryl isothiocyanates with cyanide, 3j,4c,6a,7f,g,8c,13 or bis(dialkylamino)acetonitriles 14 and also via dethiohydration of N-aryldithiooxamides, 13d,15 thionation-dethiohydration of N-arylthiooxalamides, 15 and thionation-dehydration of aryloxalamides. 15 More recent methods involve treating 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)benzenes with either the oxidizing agent m-chloroperoxybenzoic acid (MCPBA), 16 the reducing agent sodium cyanoborohydride (NaBH 3 CN), 17 or with nucleophilic (thiophilic) reagents such as aqueous sodium hydroxide, 18 hydroxylamine, 19 tert-butylamine, 20 tryptamine, 21 o-aminophenethylamine and o-phenylenediamine, 22 triphenylphosphoraneylidenes, 23 triphenylphosphine in moist dichloromethane, 24 and through the use of ethylmagnesium bromide (1 equiv). 24h,25While the use of triphenylphosphine (2 equiv) was reported to give good yields of the cyanothioformanilides, it was not possible to obtain 2-cyano-cyanothioformanilide (2a) from the reaction of 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)benzonitrile (1a) despite the preparation of the 4,5-dimethoxy analogue in high yield. 24c Nevertheless Kim et al. successfully isolated 2-cyano-cyanothioformanilide (2a) from the reaction of the dithiazolimine 1a with either NH 2 OH·HCl (4 equiv) in pyridine at ~20°C for 4 h (27%) 19 or as a by-product from reaction with phosphoraneylidenes in low yield (8%). 23 As part of our ongoing investigations of 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt) 26 and our desire to study the chemistry of 2-cyano-cyanothioformanilides 2, we required an efficient synt...