Direct Synthesis of Fluorescent 1,3a,6a-Triazapentalene Derivatives via Click-Cyclization-Aromatization Cascade Reaction

An efficient and versatile method was established for the preparation of 1,3a,6a-triazapentalenes. The 1,3a,6a-triazapentalene skeleton without an additional fused ring system was discovered to be a compact and highly fluorescent chromophore, which exhibited various interesting fluorescent properties such as a noteworthy correlation of luminescent wavelength with the Hammett sigma(P) value and a strongly positive solvatofluorochromism.