Fig. 2. Polar versus radical annulation approaches.

a Transition-metal-catalysed polar annulation approaches. b Transition-metal-free radical relay annulation approach, wherein an in situ generated iodanyl radical directly activates a C–H bond of an unactivated azine. c Reaction optimisation. ^aStandard reaction conditions: 1a (4.0 mmol, 20 equiv.), 2a (0.20 mmol, 1.0 equiv.), KOt-Bu (0.60 mmol, 3.0 equiv.) at 130 °C under Ar for 0.5 h. Isolated yields. ^bGC yields using n-dodecane as an internal standard. DG directing group; ⁻OTf triflate (CF₃SO₃⁻); KOt-Bu potassium tert-butoxide.