Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S N (ANRORC) Reaction Pathways

The formation of highly reactive zwitterionic triaziniumimidothioate intermediates 10 from bis(1,3,4‐thiadiazolo)‐1,3,5‐triazinium halides is reported. These intermediates are the first structures to be isolated from the reaction pathway between bis(1,3,4‐thiadiazolo)‐1,3,5‐triazinium halides 1 and benzylamines 2 . The reaction between 1 and 2 has a very complicated hypersurface and can yield unusual bis(1,2,4‐triazolo)‐1,3,5‐triazinium halides 6 , [1,2,4]triazolo[1,3,4]thiadiazolo[1,3,5]triazinium halides 7 or highly substituted guanidines 5 . The formation of 6 and 7 can be understood in terms of an S N (ANRORC) process. As could be demonstrated for the tricyclic cations 6 , these compounds, together with 7 , could be interesting in further synthetic applications. The salts 6 react with KOH/ t BuOK to give novel aminals 16 in good to excellent yields. Most of the important steps in the course of the transformation of 1 into 5 , 6 and 7 are supported by B3LYP/6−311++G(d,p) calculations and the X‐ray structures of 6a , 7b , 14b and 16c . From an electronic point of view, the more important reaction steps are governed by the conformation‐controlling effect of negative hyperconjugation, accompanied by intramolecular proton‐transfer reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)