Radical Dearomatising Spirocyclisation of Benzisoxazole‐Tethered Ynones

Abstract The dearomative spirocyclisation of benzisoxazoles through a radical chain mechanism is described. Densely functionalised spirocycles were prepared in high yields by reacting benzisoxazole‐tethered ynones with aryl thiols in 1,2‐dichloroethane (DCE) at 60 °C. The identification of stabilising three‐electron interactions was key to the development of this new radical cascade reaction. The obtained spirocyclic products were converted into other spirocyclic scaffolds through a two‐step hydrogenolysis‐cyclisation sequence.