The development of a visible-light mediated bromo radical addition/spirocyclization/ester migration cascade reaction to generate 3-bromocoumarins from alkynoates is reported.
Irradiation of 4-phenyl-3-arylcoumarins and 4-phenyl-3-alkenylcoumarins in EtOH with 313 nm UV light under an argon atmosphere at room temperature gave