New Fused <i>as</i>‐Triazines with Bridgehead Nitrogen Synthesis and Reactivity

Abstract

Abstract Two synthetic pathways have been elaborated for the synthesis of pyrido[1,2‐b]‐as‐triazinium salts and were also extended to the linearly fused as‐triazino[2,3‐b]isoquinolinium and the angularly fused as‐triazino[3,2‐a]isoquinolinium systems. The ring closures were found to proceed in regioselective manner which was rationalized by assumption of the different charge distribution in acidic and basic conditions. Preparative route has also been worked out for the synthesis of pyrido[2,1‐f]‐as‐triazinium salts and its differently (linearly and angularly) fused benzologues. The new heteroaromatic ring systems easily formed covalent hydrate salts under acidic conditions and pseudo bases with nucleophiles under basic conditions.