The dibenzo[b,d]azepin-6-one scaffold is widely present in natural products and pharmaceutically active molecules, and its efficient construction has long been a research hotspot in organic synthesis. Herein, we report a visible-light-catalyzed radical SO₂ insertion/cyclization cascade reaction for the rapid construction of β-sulfonylated dibenzo[b,d]azepin-6-ones. Under visible-light irradiation, using Ir(ppy)₃ as the photocatalyst, aryl diazonium salts, DABCO·(SO₂)₂, and N-aryl acrylamide substrates undergo a tandem sulfonylation/annulation process at room temperature to afford a series of target products in moderate to good yields. This protocol features mild conditions and simple operation, along with good functional group compatibility. Mechanistic studies indicate that the reaction proceeds through a radical pathway, involving key steps such as SO₂ insertion, radical addition, and intramolecular cyclization. This work provides a convenient and green route for the construction of β-sulfonylated dibenzo[b,d]azepin-6-one frameworks, which holds promise for applications in medicinal chemistry and functional materials. The general procedure for this visible-light-induced radical SO₂ insertion/annulation for the synthesis of β-sulfonylated dibenzo[b]azepin-6-ones is as follows: To a mixture of N-aryl acrylamide substrates (0.2 mmol), aryl diazonium salts (0.3 mmol), DABCO·(SO₂)₂ (0.3 mmol), Ir(ppy)₃ (2 mol%) in a 10 mL Schlenk tube was added acetonitrile (3.0 mL). The vessel was evacuated and backfilled with N₂ for three times. The tube was screw-capped and stirred at 35 ^oC under irradiation of 24V blue LEDs (distance app. 5 cm) for 24h. After completion of the reaction, the mixture was concentrated under reduced pressure. The residue was purified by flash column chromatography on silica gel using a mixture of petroleum ether and ethyl acetate (V_PE:V_EA = 3:1) as the eluent to afford the desired products.

Key words: Dibenzobenzo[b,d]azepin-6-ones, SO₂ insertion, β-sulfonylated, visible-light-induced, radical cascade cyclization