Zur Existenzfähigkeit von 2‐Imino‐2H‐1,3‐thiazinen

Abstract

On the Existence of 2‐Imino‐2H‐1,3‐thiazines The title compounds 2 are readily liberated from the 2‐amino‐1,3‐thiazinium salts 1 by treatment with bases. Their stability depends sensitively on the substituents at the imino‐N. The imino‐N substituted 2a–i are isolable as well‐defined coloured substances. Reaction of the 2 as well 1 with nucleophilic agents affords pyrimidine‐2‐thiones (4, 9–11, 16–18). In these ring transformations a nucleophilic addition at ring position 6 as primary reaction step is preferred. The imino‐N unsubstituted representatives display a more complicated behaviour; the highly enhanced reactivity prevents or handicaps, respectively, any isolation. As exemplified in the base‐induced ring‐transformation of 1 m to the pyrimidine derivative 19, these 2 are able to react as nucleophiles too, and versatile intermolecular self‐reactions are increasingly favoured.