Metal-free radical cascade cyclization/haloazidation of enynones to access functionalized 1-indanones

A novel three-component radical cyclization/haloazidation of enynones, employing TMSN₃ as the azide source and NIS (NBS or NCS) as the halogen source, has been developed under metal-free conditions for the efficient synthesis of various 1-indanones with moderate yields and acceptable <i>Z</i>/<i>E</i> ratio. The reaction progresses through a sequence involving radical addition, 5-<i>exo-dig</i> cyclization, and radical coupling, ultimately resulting in the formation of three new chemical bonds and a new ring in a single step. The synthetic benefits of this method have been proven by large-scale experiments and late-stage modification.