Tracking the Process of Domino Ring‐Opening and Coupling of Fused Imidazole and Direct Observation of Peroxide Intermediates

Comprehensive Summary A domino ring‐opening and coupling of imidazolyl annulated heterocycles 1 ( 1a : 4‐methyl‐1‐(1‐methyl‐1 H ‐benzo[ d ]imidazol‐2‐yl)‐4 H ‐ benzo[ d ]imidazo[1,5‐ a ]imidazole, 1b : 1‐(1,5‐dimethyl‐1 H ‐benzo[ d ]imidazol‐2‐yl)‐4,7‐dimethyl‐4 H ‐benzo[ d ]imidazo[1,5‐ a ]imidazole) with dioxygen was developed at solvothermal condition, leading to conjugated 1,2‐diamidoalkenes derivatives 2 (( E )‐ArCONHArC=CArNHCOAr (Ar: 1‐methyl‐1 H ‐benzo[ d ]imidazolyl ( 2a ), 1,5‐dimethyl‐1 H ‐benzo[ d ]imidazolyl ( 2b ))) as single crystals directly. The reaction process was tracked by electrospray ionization mass spectrometry (ESI‐HRMS) and a series of reaction intermediates are detected. 18 O 2 labeling experiment verified the source of oxygen in 2 . Combining evidence from control experiments, nuclear magnetic resonance (NMR) tracking, and crystallography, a seven‐step reaction pathway involving oxygen addition, ring opening, Friedel‐Crafts alkylation, oxidation, and dehydration was proposed and further supported by DFT calculation.