Novel triazinium-imidothioate zwitterions: intermediates in the reaction of [1,3,4]thiadiazolo[2,3-d][1,2,4]triazolo[1,5-a][1,3,5]triazinium cations with amines

Starting with bis([1,3,4]thiadiazolo)[1,3,5]triazinium halides , a novel class of heterocyclic compounds, the [1,3,4]thiadiazolo[2,3-d][1,2,4]triazolo[1,5-a][1,3,5]triazinium halides were prepared. The reaction between and primary or secondary amines yielded highly substituted guanidines and fused tricyclic bis([1,2,4]triazolo)[1,5-a:1′,5′-d][1,3,5]triazinium halides . The formation of the reactive triazinium-imidothioate zwitterions , which is controlled by the influence of negative hyperconjugation, was proven by NMR data and the X-ray structure of . The subsequent ring-closure/ring-opening steps can be understood in terms of an SN(ANRORC) process accompanied by intramolecular proton-transfer reactions. The zwitterions were reacted with EtI forming cationic derivatives or hydrolyzed at pH 6–7 to give novel heterocyclic ethanethioamides .