I₂/H₂O₂ Mediated Synthesis and Photophysical Properties of Imidazole‐Fused Heterocycles via [4+1] Cyclization Approach

An efficient I 2 (10 mmol %)/H 2 O 2 mediated oxidative formal [4+1] cyclization of 2‐pyridinemethylamine or o ‐phenylenediamine (2‐aminobenzenethiol) with benzaldehyde via C−N bond formation has been developed. This strategy provides a straightforward approach to imidazo[1,5‐ a ]pyridines, iodo‐substituted imidazo[1,5‐ a ]pyridines and benzimidazole (benzothiazole) derivatives in yields ranging from 60 % to 98 %, respectively. Several heterocyclic products exhibit promising blue luminous performance with satisfactory fluorescence quantum yields of up to 64 %, large Stokes shifts, and a longer lifetime (7.35 ns). The band gap energies obtained from DFT are also consistent with the absorption spectra.