Revisiting Fused‐Pyrrolo‐1,10‐Phenanthroline Derivatives: Novel Transformations and Stability Studies

In this study, new pyrrolo[3',4':3,4]pyrrolo[1,2-a][1,10]phenanthroline derivatives are developed and their stabilities and transformation pathways are investigated. The synthetic approach toward these novel derivatives include a pivotal [3 + 2] cycloaddition of in situ generated ylides, followed by cycloadducts oxidation and other unexpected transformations. The structures of the intermediate and final compounds are proposed based on information obtained from several spectral techniques. Stability study reveal that electron-donating groups in the para position of the phenyl ring promote easier oxidation, whereas electron-withdrawing substituents enhance the stability of the compounds. The acid–base titration of α-monosubstituted 1,10-phenanthroline 6a results in a reversible color change, which is preliminarily explored through spectral methods.